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Sample records for background power spectrum

  1. Fast cosmic microwave background power spectrum estimation of temperature and polarization with Gabor transforms

    NASA Astrophysics Data System (ADS)

    Hansen, Frode K.; Górski, Krzysztof M.

    2003-08-01

    We extend the analysis of Gabor transforms on a cosmic microwave background temperature map to polarization. We study the temperature and polarization power spectra on the cut sky, the so-called pseudo-power spectra. The transformation kernels relating the full-sky polarization power spectra and the polarization pseudo-power spectra are found to be similar to the kernel for the temperature power spectrum. This fact is used to construct a fast power spectrum estimation algorithm using the pseudo-power spectrum of temperature and polarization as data vectors in a maximum-likelihood approach. Using the pseudo-power spectra as input to the likelihood analysis solves the problem of having to invert huge matrices, which makes the standard likelihood approach infeasible.

  2. Angular power spectrum of the FASTICA cosmic microwave background component from Background Emission Anisotropy Scanning Telescope data

    NASA Astrophysics Data System (ADS)

    Donzelli, S.; Maino, D.; Bersanelli, M.; Childers, J.; Figueiredo, N.; Lubin, P. M.; Meinhold, P. R.; O'Dwyer, I. J.; Seiffert, M. D.; Villela, T.; Wandelt, B. D.; Wuensche, C. A.

    2006-06-01

    We present the angular power spectrum of the cosmic microwave background (CMB) component extracted with FASTICA from the Background Emission Anisotropy Scanning Telescope (BEAST) data. BEAST is a 2.2-m off-axis telescope with a focal plane comprising eight elements at Q (38-45 GHz) and Ka (26-36 GHz) bands. It operates from the UC (University of California) White Mountain Research Station at an altitude of 3800 m. The BEAST CMB angular power spectrum has already been calculated by O'Dwyer et al. using only the Q-band data. With two input channels, FASTICA returns two possible independent components. We found that one of these two has an unphysical spectral behaviour, while the other is a reasonable CMB component. After a detailed calibration procedure based on Monte Carlo (MC) simulations, we extracted the angular power spectrum for the identified CMB component and found a very good agreement with the already published BEAST CMB angular power spectrum and with the Wilkinson Microwave Anisotropy Probe (WMAP) data.

  3. What can be learned from the lensed cosmic microwave background B-mode polarization power spectrum?

    SciTech Connect

    Smith, Sarah; Challinor, Anthony; Rocha, Graca

    2006-01-15

    The effect of weak gravitational lensing on the cosmic microwave background (CMB) temperature anisotropies and polarization will provide access to cosmological information that cannot be obtained from the primary anisotropies alone. We compare the information content of the lensed B-mode polarization power spectrum, properly accounting for the non-Gaussian correlations between the power on different scales, with that of the unlensed CMB fields and the lensing potential. The latter represent the products of an (idealized) optimal analysis that exploits the lens-induced non-Gaussianity to reconstruct the fields. Compressing the non-Gaussian lensed CMB into power spectra is wasteful and leaves a tight degeneracy between the equation of state of dark energy and neutrino mass that is much stronger than in the more optimal analysis. Despite this, a power-spectrum analysis will be a useful first step in analyzing future B-mode polarization data. For this reason, we also consider how to extract accurate parameter constraints from the lensed B-mode power spectrum. We show with simulations that for cosmic-variance-limited measurements of the lensed B-mode power, including the non-Gaussian correlations in existing likelihood approximations gives biased parameter results. We develop a more refined likelihood approximation that performs significantly better. This new approximation should also be of more general interest in the wider context of parameter estimation from Gaussian CMB data.

  4. PROBING THE INFLATON: SMALL-SCALE POWER SPECTRUM CONSTRAINTS FROM MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND ENERGY SPECTRUM

    SciTech Connect

    Chluba, Jens; Erickcek, Adrienne L.; Ben-Dayan, Ido

    2012-10-20

    In the early universe, energy stored in small-scale density perturbations is quickly dissipated by Silk damping, a process that inevitably generates {mu}- and y-type spectral distortions of the cosmic microwave background (CMB). These spectral distortions depend on the shape and amplitude of the primordial power spectrum at wavenumbers k {approx}< 10{sup 4} Mpc{sup -1}. Here, we study constraints on the primordial power spectrum derived from COBE/FIRAS and forecasted for PIXIE. We show that measurements of {mu} and y impose strong bounds on the integrated small-scale power, and we demonstrate how to compute these constraints using k-space window functions that account for the effects of thermalization and dissipation physics. We show that COBE/FIRAS places a robust upper limit on the amplitude of the small-scale power spectrum. This limit is about three orders of magnitude stronger than the one derived from primordial black holes in the same scale range. Furthermore, this limit could be improved by another three orders of magnitude with PIXIE, potentially opening up a new window to early universe physics. To illustrate the power of these constraints, we consider several generic models for the small-scale power spectrum predicted by different inflation scenarios, including running-mass inflation models and inflation scenarios with episodes of particle production. PIXIE could place very tight constraints on these scenarios, potentially even ruling out running-mass inflation models if no distortion is detected. We also show that inflation models with sub-Planckian field excursion that generate detectable tensor perturbations should simultaneously produce a large CMB spectral distortion, a link that could potentially be established with PIXIE.

  5. Angular power spectrum of the microwave background anisotropy seen by the COBE differential microwave radiometer

    NASA Technical Reports Server (NTRS)

    Wright, E. L.; Smoot, G. F.; Bennett, C. L.; Lubin, P. M.

    1994-01-01

    The angular power spectrum estimator developed by Peebles (1973) and Hauser & Peebles (1973) has been modified and applied to the 2 yr maps produced by the Cosmic Background Explorer Satellite Differential Microwave Radiometer (COBE DMR)). The power spectrum of the real sky has been compared to the power spectra of a large number of simulated random skies produced with noise equal to the observed noise and primordial density fluctuation power spectra of power-law form, with P(k) proportional to k(exp n). Within the limited range of spatial scales covered by the COBE DMR, corresponding to spherical harmonic indices 3 less than or = l is less than or approximately = 30, the best-fitting value of the spectral index is n = 1.25(sup +0.39 sub -0.44) with the Harrisson-Zel'dovich value n = 1 approximately 0.5 sigma below the best fit. For 3 less than or = l less than or approximately = 19, the best fit is n = 1.46(sup +0.39 sub -0.44). Comparing the COBE DMR delta-T/T at small l to the delta-T/T at l approximately = 50 from degree scale anisotropy experiments gives a smaller range of acceptable spectral indices which includes n = 1.

  6. Bayesian Analysis of the Power Spectrum of the Cosmic Microwave Background

    NASA Technical Reports Server (NTRS)

    Jewell, Jeffrey B.; Eriksen, H. K.; O'Dwyer, I. J.; Wandelt, B. D.

    2005-01-01

    There is a wealth of cosmological information encoded in the spatial power spectrum of temperature anisotropies of the cosmic microwave background. The sky, when viewed in the microwave, is very uniform, with a nearly perfect blackbody spectrum at 2.7 degrees. Very small amplitude brightness fluctuations (to one part in a million!!) trace small density perturbations in the early universe (roughly 300,000 years after the Big Bang), which later grow through gravitational instability to the large-scale structure seen in redshift surveys... In this talk, I will discuss a Bayesian formulation of this problem; discuss a Gibbs sampling approach to numerically sampling from the Bayesian posterior, and the application of this approach to the first-year data from the Wilkinson Microwave Anisotropy Probe. I will also comment on recent algorithmic developments for this approach to be tractable for the even more massive data set to be returned from the Planck satellite.

  7. The Cosmic Microwave Background Anisotropy Power Spectrum from the BEAST Experiment

    NASA Astrophysics Data System (ADS)

    O'Dwyer, Ian J.; Bersanelli, Marco; Childers, Jeffrey; Figueiredo, Newton; Halevi, Doron; Huey, Greg; Lubin, Philip M.; Maino, Davide; Mandolesi, Nazzareno; Marvil, Joshua; Meinhold, Peter R.; Mejía, Jorge; Natoli, Paolo; O'Neill, Hugh; Pina, Agenor; Seiffert, Michael D.; Stebor, Nathan C.; Tello, Camilo; Villela, Thyrso; Wandelt, Benjamin D.; Williams, Brian; Wuensche, Carlos Alexandre

    2005-05-01

    The Background Emission Anisotropy Scanning Telescope (BEAST) is a 2.2 m off-axis telescope with an eight-element mixed Q-band (38-45 GHz) and Ka-band (26-36 GHz) focal plane, designed for balloon-borne and ground-based studies of the cosmic microwave background (CMB). Here we present the CMB angular power spectrum calculated from 682 hr of data observed with the BEAST instrument. We use a binned pseudo-Cl estimator (the MASTER method). We find results that are consistent with other determinations of the CMB anisotropy for angular wavenumbers l between 100 and 600. We also perform cosmological parameter estimation. The BEAST data alone produce a good constraint on Ωk≡1-Ωtot=-0.074+/-0.070, consistent with a flat universe. A joint parameter estimation analysis with a number of previous CMB experiments produces results consistent with previous determinations.

  8. Effect of background trends removal on noise power spectrum measurements in digital x-ray imaging

    NASA Astrophysics Data System (ADS)

    Zhou, Zhongxing; Gao, Feng; Zhao, Huijuan; Zhang, Lixin

    2011-03-01

    Noise characterization through estimation of the noise power spectrum (NPS) is a central component of the evaluation of digital X-ray systems. Extensive works have been conducted to achieve accurate and precise measurement of NPS. One approach to improve the accuracy of the NPS measurement is to reduce the statistical variance of the NPS results. However, this method is based on the assumption that the noise in a radiographic image is arising from stochastic (random) processes. In the practical data, the artifactuals always superimpose on the stochastic noise as low-frequency background trends and prevent us from achieving accurate NPS. In this study, NPS measurement was implemented and compared before and after background trends removal, the results showed that background detrending reduced the variance of the low-frequency spectral components, hence improving the accuracy of NPS measurement. Our results also showed that involving more samples for ensemble averaging had little effect in reducing the variance of the low-frequency spectral components. All results implied that it is necessary and feasible to get better NPS estimate by appropriate background detredning.

  9. SECOND SEASON QUIET OBSERVATIONS: MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRUM AT 95 GHz

    SciTech Connect

    Araujo, D.; Dumoulin, R. N.; Newburgh, L. B.; Zwart, J. T. L.; Bischoff, C.; Brizius, A.; Buder, I.; Kusaka, A.; Chinone, Y.; Cleary, K.; Reeves, R.; Naess, S. K.; Eriksen, H. K.; Wehus, I. K.; Bronfman, L.; Church, S. E.; Dickinson, C.; Gaier, T.; Collaboration: QUIET Collaboration; and others

    2012-12-01

    The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 {mu}K{radical}s. Four low-foreground fields were observed, covering a total of {approx}1000 deg{sup 2} with an effective angular resolution of 12.'8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C {sub l} (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with {Lambda}CDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1{sup +0.9} {sub -0.8} (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2{sup +0.9} {sub -0.8} (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

  10. Second Season QUIET Observations: Measurements of the Cosmic Microwave Background Polarization Power Spectrum at 95 GHz

    NASA Astrophysics Data System (ADS)

    QUIET Collaboration; Araujo, D.; Bischoff, C.; Brizius, A.; Buder, I.; Chinone, Y.; Cleary, K.; Dumoulin, R. N.; Kusaka, A.; Monsalve, R.; Næss, S. K.; Newburgh, L. B.; Reeves, R.; Wehus, I. K.; Zwart, J. T. L.; Bronfman, L.; Bustos, R.; Church, S. E.; Dickinson, C.; Eriksen, H. K.; Gaier, T.; Gundersen, J. O.; Hasegawa, M.; Hazumi, M.; Huffenberger, K. M.; Ishidoshiro, K.; Jones, M. E.; Kangaslahti, P.; Kapner, D. J.; Kubik, D.; Lawrence, C. R.; Limon, M.; McMahon, J. J.; Miller, A. D.; Nagai, M.; Nguyen, H.; Nixon, G.; Pearson, T. J.; Piccirillo, L.; Radford, S. J. E.; Readhead, A. C. S.; Richards, J. L.; Samtleben, D.; Seiffert, M.; Shepherd, M. C.; Smith, K. M.; Staggs, S. T.; Tajima, O.; Thompson, K. L.; Vanderlinde, K.; Williamson, R.

    2012-12-01

    The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 μK\\sqrt{s}. Four low-foreground fields were observed, covering a total of ~1000 deg2 with an effective angular resolution of 12farcm8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C l (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with ΛCDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1+0.9 - 0.8 (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2+0.9 - 0.8 (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

  11. A measurement by BOOMERANG of multiple peaks in the angular power spectrum of the cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Netterfield, C. B.; Ade, P. A. R.; Bock, J. J.; Bond, J. R.; Borrill, J.; Boscaleri, A.; Coble, K.; Contaldi, C. R.; Crill, B. P.; Bernardis, P. de; Farese, P.; Ganga, K.; Giacometti, M.; Hivon, E.; Hristov, V. V.; Iacoangeli, A.; Jaffe, A. H.; Jones, W. C.; Lange, A. E.; Martinis, L.; Masi, S.; Mason, P.; Mauskopf, P.; Melchiorri, A.; Montroy, T.

    2001-01-01

    This paper presents a measurement of the angular power spectrum of the Cosmic Microwave Background from l = 75 to l = 1025 (10' to 5 degrees) from a combined analysis of four 150 GHz channels in the BOOMERANG experiment. The spectrum contains multiple peaks and minima, as predicted by standard adiabatic-inflationary models in which the primordial plasma undergoes acoustic oscillations.

  12. Anatomical background noise power spectrum in differential phase contrast breast images

    NASA Astrophysics Data System (ADS)

    Garrett, John; Ge, Yongshuai; Li, Ke; Chen, Guang-Hong

    2015-03-01

    In x-ray breast imaging, the anatomical noise background of the breast has a significant impact on the detection of lesions and other features of interest. This anatomical noise is typically characterized by a parameter, β, which describes a power law dependence of anatomical noise on spatial frequency (the shape of the anatomical noise power spectrum). Large values of β have been shown to reduce human detection performance, and in conventional mammography typical values of β are around 3.2. Recently, x-ray differential phase contrast (DPC) and the associated dark field imaging methods have received considerable attention as possible supplements to absorption imaging for breast cancer diagnosis. However, the impact of these additional contrast mechanisms on lesion detection is not yet well understood. In order to better understand the utility of these new methods, we measured the β indices for absorption, DPC, and dark field images in 15 cadaver breast specimens using a benchtop DPC imaging system. We found that the measured β value for absorption was consistent with the literature for mammographic acquisitions (β = 3.61±0.49), but that both DPC and dark field images had much lower values of β (β = 2.54±0.75 for DPC and β = 1.44±0.49 for dark field). In addition, visual inspection showed greatly reduced anatomical background in both DPC and dark field images. These promising results suggest that DPC and dark field imaging may help provide improved lesion detection in breast imaging, particularly for those patients with dense breasts, in whom anatomical noise is a major limiting factor in identifying malignancies.

  13. Power spectrum constraints from spectral distortions in the cosmic microwave background

    NASA Technical Reports Server (NTRS)

    Hu, Wayne; Scott, Douglas; Silk, Joseph

    1994-01-01

    Using recent experimental limits on chemical potential distortions from Cosmic Background Explorer (COBE) Far Infrared Astronomy Satellite (FIRAS), and the large lever-arm spanning the damping of sub-Jeans scale fluctuations to the COBE DMR fluctuations, we set a constraint on the slope of the primordial power spectrum n. It is possible to analytically calculate the contribution over the full range of scales and redshifts, correctly taking into account fluctuation growth and damping as well as thermalization processes. Assuming conservatively that mu is less than 1.76 x 10(exp -4), we find that the 95% upper limit on n is only weakly dependent on other cosmological parameters, e.g., n is less than 1.60 (h=0.5) and n is less than 1.63 (h=1.0) for Omega(sub 0) = 1, with marginally weaker constraints for Omega(sub 0) is less than 1 in a flat model with a cosmological constant.

  14. DIRECT MEASUREMENT OF THE ANGULAR POWER SPECTRUM OF COSMIC MICROWAVE BACKGROUND TEMPERATURE ANISOTROPIES IN THE WMAP DATA

    SciTech Connect

    Chiang, Lung-Yih; Chen, Fei-Fan

    2012-05-20

    The angular power spectrum of the cosmic microwave background temperature anisotropies is one of the most important characteristics in cosmology that can shed light on the properties of the universe such as its geometry and total density. Using flat sky approximation and Fourier analysis, we estimate the angular power spectrum from an ensemble of the least foreground-contaminated square patches from the Wilkinson Microwave Anisotropy Probe W and V frequency band map. This method circumvents the issue of foreground cleaning and that of breaking orthogonality in spherical harmonic analysis because we are able to mask out the bright Galactic plane region, thereby rendering a direct measurement of the angular power spectrum. We test and confirm the Gaussian statistical characteristic of the selected patches, from which the first and second acoustic peaks of the power spectrum are reproduced, and the third peak is clearly visible, albeit with some noise residual at the tail.

  15. Probing reionization with the cross-power spectrum of 21 cm and near-infrared radiation backgrounds

    SciTech Connect

    Mao, Xiao-Chun

    2014-08-01

    The cross-correlation between the 21 cm emission from the high-redshift intergalactic medium and the near-infrared (NIR) background light from high-redshift galaxies promises to be a powerful probe of cosmic reionization. In this paper, we investigate the cross-power spectrum during the epoch of reionization. We employ an improved halo approach to derive the distribution of the density field and consider two stellar populations in the star formation model: metal-free stars and metal-poor stars. The reionization history is further generated to be consistent with the electron-scattering optical depth from cosmic microwave background measurements. Then, the intensity of the NIR background is estimated by collecting emission from stars in first-light galaxies. On large scales, we find that the 21 cm and NIR radiation backgrounds are positively correlated during the very early stages of reionization. However, these two radiation backgrounds quickly become anti-correlated as reionization proceeds. The maximum absolute value of the cross-power spectrum is |Δ{sub 21,NIR}{sup 2}|∼10{sup −4} mK nW m{sup –2} sr{sup –1}, reached at ℓ ∼ 1000 when the mean fraction of ionized hydrogen is x-bar{sub i}∼0.9. We find that Square Kilometer Array can measure the 21 cm-NIR cross-power spectrum in conjunction with mild extensions to the existing CIBER survey, provided that the integration time independently adds up to 1000 and 1 hr for 21 cm and NIR observations, and that the sky coverage fraction of the CIBER survey is extended from 4 × 10{sup –4} to 0.1. Measuring the cross-correlation signal as a function of redshift provides valuable information on reionization and helps confirm the origin of the 'missing' NIR background.

  16. EVOLUTION OF THE COSMIC MICROWAVE BACKGROUND POWER SPECTRUM ACROSS WILKINSON MICROWAVE ANISOTROPY PROBE DATA RELEASES: A NONPARAMETRIC ANALYSIS

    SciTech Connect

    Aghamousa, Amir; Arjunwadkar, Mihir; Souradeep, Tarun E-mail: mihir@ncra.tifr.res.in

    2012-02-01

    Using a nonparametric function estimation methodology, we present a comparative analysis of the Wilkinson Microwave Anisotropy Probe (WMAP) 1-, 3-, 5-, and 7-year data releases for the cosmic microwave background (CMB) angular power spectrum with respect to the following key questions. (1) How well is the power spectrum determined by the data alone? (2) How well is the {Lambda}CDM model supported by a model-independent, data-driven analysis? (3) What are the realistic uncertainties on peak/dip locations and heights? Our results show that the height of the power spectrum is well determined by data alone for multipole l approximately less than 546 (1-year), 667 (3-year), 804 (5-year), and 842 (7-year data). We show that parametric fits based on the {Lambda}CDM model are remarkably close to our nonparametric fits in l-regions where data are sufficiently precise. In contrast, the power spectrum for an H{Lambda}CDM model is progressively pushed away from our nonparametric fit as data quality improves with successive data realizations, suggesting incompatibility of this particular cosmological model with respect to the WMAP data sets. We present uncertainties on peak/dip locations and heights at the 95% (2{sigma}) level of confidence and show how these uncertainties translate into hyperbolic 'bands' on the acoustic scale (l{sub A} ) and peak shift ({phi}{sub m}) parameters. Based on the confidence set for the 7-year data, we argue that the low-l upturn in the CMB power spectrum cannot be ruled out at any confidence level in excess of about 10% ( Almost-Equal-To 0.12{sigma}). Additional outcomes of this work are a numerical formulation for minimization of a noise-weighted risk function subject to monotonicity constraints, a prescription for obtaining nonparametric fits that are closer to cosmological expectations on smoothness, and a method for sampling cosmologically meaningful power spectrum variations from the confidence set of a nonparametric fit.

  17. THE ATACAMA COSMOLOGY TELESCOPE: A MEASUREMENT OF THE 600 < l < 8000 COSMIC MICROWAVE BACKGROUND POWER SPECTRUM AT 148 GHz

    SciTech Connect

    Fowler, J. W.; Appel, J. W.; Das, S.; Dunkley, J.; Essinger-Hileman, T.; Fisher, R. P.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Barrientos, L. F.; Duenner, R.; Amiri, M.; Battistelli, E. S.; Burger, B.; Bond, J. R.; Brown, B.; Chervenak, J.; Doriese, W. B.

    2010-10-20

    We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.'4 angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg{sup 2} of the southern sky, in a 4.{sup 0}2 wide strip centered on declination 53{sup 0} south. The CMB at arcminute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy clusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 < l < 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 < l < 1150. The power beyond the Silk damping tail of the CMB (l {approx} 5000) is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized to {sigma}{sub 8} = 0.8. We constrain the model's amplitude A{sub SZ} < 1.63 (95% CL). If interpreted as a measurement of {sigma}{sub 8}, this implies {sigma}{sup SZ}{sub 8} < 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a six-parameter {Lambda}CDM model plus point sources and the SZ effect is consistent with these results.

  18. A Measurement of the Damping Tail of the Cosmic Microwave Background Power Spectrum with the South Pole Telescope

    NASA Astrophysics Data System (ADS)

    Keisler, R.; Reichardt, C. L.; Aird, K. A.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Dudley, J.; George, E. M.; Halverson, N. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hou, Z.; Hrubes, J. D.; Joy, M.; Knox, L.; Lee, A. T.; Leitch, E. M.; Lueker, M.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Millea, M.; Mohr, J. J.; Montroy, T. E.; Natoli, T.; Padin, S.; Plagge, T.; Pryke, C.; Ruhl, J. E.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Spieler, H. G.; Staniszewski, Z.; Stark, A. A.; Story, K.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.; Zahn, O.

    2011-12-01

    We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) using data from the South Pole Telescope (SPT). The data consist of 790 deg2 of sky observed at 150 GHz during 2008 and 2009. Here we present the power spectrum over the multipole range 650 < l < 3000, where it is dominated by primary CMB anisotropy. We combine this power spectrum with the power spectra from the seven-year Wilkinson Microwave Anisotropy Probe (WMAP) data release to constrain cosmological models. We find that the SPT and WMAP data are consistent with each other and, when combined, are well fit by a spatially flat, ΛCDM cosmological model. The SPT+WMAP constraint on the spectral index of scalar fluctuations is ns = 0.9663 ± 0.0112. We detect, at ~5σ significance, the effect of gravitational lensing on the CMB power spectrum, and find its amplitude to be consistent with the ΛCDM cosmological model. We explore a number of extensions beyond the ΛCDM model. Each extension is tested independently, although there are degeneracies between some of the extension parameters. We constrain the tensor-to-scalar ratio to be r < 0.21 (95% CL) and constrain the running of the scalar spectral index to be dns /dln k = -0.024 ± 0.013. We strongly detect the effects of primordial helium and neutrinos on the CMB; a model without helium is rejected at 7.7σ, while a model without neutrinos is rejected at 7.5σ. The primordial helium abundance is measured to be Yp = 0.296 ± 0.030, and the effective number of relativistic species is measured to be N eff = 3.85 ± 0.62. The constraints on these models are strengthened when the CMB data are combined with measurements of the Hubble constant and the baryon acoustic oscillation feature. Notable improvements include ns = 0.9668 ± 0.0093, r < 0.17 (95% CL), and N eff = 3.86 ± 0.42. The SPT+WMAP data show a mild preference for low power in the CMB damping tail, and while this preference may be accommodated by models that have a

  19. SMALL ANGULAR SCALE MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND TEMPERATURE POWER SPECTRUM FROM QUaD

    SciTech Connect

    Friedman, R. B.; Culverhouse, T.; Ade, P.; Bowden, M.; Gear, W. K.; Gupta, S.; Orlando, A.; Bock, J.; Leitch, E.; Brown, M. L.; Cahill, G.; Murphy, J. A.; Castro, P. G.; Memari, Y.; Church, S.; Hinderks, J.; Ganga, K.; Melhuish, S. J.

    2009-08-01

    We present measurements of the cosmic microwave background (CMB) radiation temperature anisotropy in the multipole range 2000 < l < 3000 from the QUaD telescope's second and third observing seasons. After masking the brightest point sources our results are consistent with the primary {lambda}CDM expectation alone. We estimate the contribution of residual (un-masked) radio point sources using a model calibrated to our own bright source observations, and a full simulation of the source finding and masking procedure. Including this contribution slightly improves the {chi}{sup 2}. We also fit a standard Sunyaev-Zel'dovich (SZ) template to the bandpowers and see no strong evidence of an SZ contribution, which is as expected for {sigma}{sub 8} {approx} 0.8.

  20. A CONSTRAINT ON THE INTEGRATED MASS POWER SPECTRUM OUT TO z = 1100 FROM LENSING OF THE COSMIC MICROWAVE BACKGROUND

    SciTech Connect

    Smidt, Joseph; Cooray, Asantha; Amblard, Alexandre; Joudaki, Shahab; Serra, Paolo; Munshi, Dipak; Santos, Mario G.

    2011-02-10

    The temperature fluctuations and polarization of the cosmic microwave background (CMB) are now a well-known probe of the universe at an infant age of 400,000 years. During the transit to us from the surface of last scattering, the CMB photons are expected to undergo modifications induced by the intervening large-scale structure. Among the expected secondary effects is the weak gravitational lensing of the CMB by the foreground dark matter distribution. We derive a quadratic estimator that uses the non-Gaussianities generated by the lensing effect at the four-point function level to extract the power spectrum of lensing potential fluctuations integrated out to z {approx} 1100 with peak contributions from potential fluctuations at z of 2-3. Using Wilkinson Microwave Anisotropy Probe seven-year temperature maps, we report the first direct constraints of this lensing potential power spectrum and find that it has an amplitude of A{sub L} = 0.96 {+-} 0.60, 1.06 {+-} 0.69, and 0.97 {+-} 0.47 using the W, V, and W + V bands, respectively.

  1. Measurement of the cosmic microwave background polarization lensing power spectrum with the POLARBEAR experiment.

    PubMed

    Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Linder, E; Leitch, E M; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Schanning, I; Schenck, D E; Sherwin, B; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tomaru, T; Wilson, B; Yadav, A; Zahn, O

    2014-07-11

    Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ∼30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat+sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves. PMID:25062161

  2. Measurement of the Cosmic Microwave Background Polarization Lensing Power Spectrum with the POLARBEAR Experiment

    NASA Astrophysics Data System (ADS)

    Ade, P. A. R.; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Linder, E.; Leitch, E. M.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Paar, H.; Peloton, J.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Schanning, I.; Schenck, D. E.; Sherwin, B.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.; Polarbear Collaboration

    2014-07-01

    Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ˜30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat +sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves.

  3. A measurement of the cosmic microwave background B-mode polarization power spectrum at sub-degree scales with POLARBEAR

    SciTech Connect

    Ade, P. A. R.; Akiba, Y.; Hasegawa, M.; Anthony, A. E.; Halverson, N. W.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Elleflot, T.; Feng, C.; Borrill, J.; Errard, J.; Chapman, S.; Chinone, Y.; Flanigan, D.; Dobbs, M.; Gilbert, A.; Fabbian, G.; Collaboration: Polarbear Collaboration; and others

    2014-10-20

    We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the POLARBEAR experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < ℓ < 2100 and is based on observations of an effective sky area of 25 deg{sup 2} with 3.'5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter A{sub BB} to the measured band powers, A{sub BB}=1.12±0.61(stat){sub −0.12}{sup +0.04}(sys)±0.07(multi), where A{sub BB} = 1 is the fiducial WMAP-9 ΛCDM value. In this expression, 'stat' refers to the statistical uncertainty, 'sys' to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and 'multi' to the calibration uncertainties that have a multiplicative effect on the measured amplitude A{sub BB}.

  4. A Measurement of the Cosmic Microwave Background B-mode Polarization Power Spectrum at Sub-degree Scales with POLARBEAR

    NASA Astrophysics Data System (ADS)

    The Polarbear Collaboration: P. A. R. Ade; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A. H.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Leitch, E. M.; Linder, E.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Orlando, A.; Paar, H.; Peloton, J.; Poletti, D.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Schanning, I.; Schenck, D. E.; Sherwin, B. D.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.

    2014-10-01

    We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the POLARBEAR experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < l < 2100 and is based on observations of an effective sky area of 25 \\deg ^2 with 3.'5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter ABB to the measured band powers, ABB = 1.12 +/- 0.61 (stat) +0.04-0.12(sys) +/- 0.07 (multi), where ABB = 1 is the fiducial WMAP-9 ΛCDM value. In this expression, "stat" refers to the statistical uncertainty, "sys" to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and "multi" to the calibration uncertainties that have a multiplicative effect on the measured amplitude ABB .

  5. The Atacama Cosmology Telescope: A Measurement of the Cosmic Microwave Background Power Spectrum at 148 AND 218 GHz from the 2008 Southern Survey

    NASA Technical Reports Server (NTRS)

    Das, Sudeep; Marriage, Tobias A.; Ade, Peter A. R.; Aguirre, Paula; Amiri, Mandana; Appel, John W.; Barrientos, L. Felipe; Battistelli, Elia A.; Bond, J. Richard; Brown, Ben; Burger, Bryce; Chervenak, Jay; Devlin, Mark J.; Dicker, Simon R.; Doriese, W. Bertrand; Dunkley, Joanna; Duenner, Rolando; Essinger-Hileman, Thomas; Fisher, Ryan P.; Fowler, Joseph W.; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hernandez-Monteagudo, Carlos; Wollack, Ed

    2010-01-01

    We present measurements of the cosmic microwave background (CMB) power spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. Our results dearly show the second through the seventh acoustic peaks in the CMB power spectrum. The measurements of these higher-order peaks provide an additional test of the ACDM cosmological model. At l > 3000, we detect power in excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 < l < 3000, we find evidence for gravitational lensing of the CMB in the power spectrum at the 2.8(sigma) level. We also detect a low level of Galactic dust in our maps, which demonstrates that we can recover known faint, diffuse signals.

  6. Multiple Peaks in the Angular Power Spectrum of the CosmicMicrowave Background: Significance and Consequences for Cosmology

    SciTech Connect

    de Bernardis, P.; Ade, P.A.R.; Bock, J.J.; Bond, J.R.; Borrill,J.; Boscaleri, A.; Coble, K.; Contaldi, C.R.; Crill, B.P.; De Troia, G.; Farese, P.; Ganga, K.; Giacometti, M.; Hivon, E.; Hristov, V.V.; Iacoangeli, A.; Jaffe, A.H.; Jones, W.C.; Lange, A.E.; Martinis, L.; Masi, S.; Mason, P.; Mauskopf, P.D.; Melchiorri, A.; Montroy, T.; Netterfield, C.B.; Pascale, E.; Piacentini, F.; Pogosyan, D.; Polenta,G.; Pongetti, F.; Prunet, S.; Romeo, G.; Ruhl, J.E.; Scaramuzzi, F.

    2001-05-17

    Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at {ell} {approx} 210, 540, 840 and {ell} {approx} 420, 750, respectively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflationary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a second 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: {Omega}{sub tot} = 1.02{sub -0.05}{sup +0.06} vs. 1.04 {+-} 0.05, {Omega}{sub b}h{sup 2} = 0.022{sub -0.003}{sup +0.004} vs. 0.019{sub -0.004}{sup +0.005}, and n{sub s} = 0.96{sub -0.09}{sup +0.10} vs. 0.90 {+-} 0.08. The deviation in primordial spectral index n{sub s} is a consequence of the strong correlation with the optical depth.

  7. Constraints on Cosmology from the Cosmic Microwave Background Power Spectrum of the 2500 deg2 SPT-SZ Survey

    NASA Astrophysics Data System (ADS)

    Hou, Z.; Reichardt, C. L.; Story, K. T.; Follin, B.; Keisler, R.; Aird, K. A.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H.-M.; Crawford, T. M.; Crites, A. T.; de Haan, T.; de Putter, R.; Dobbs, M. A.; Dodelson, S.; Dudley, J.; George, E. M.; Halverson, N. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hrubes, J. D.; Joy, M.; Knox, L.; Lee, A. T.; Leitch, E. M.; Lueker, M.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Millea, M.; Mohr, J. J.; Montroy, T. E.; Padin, S.; Plagge, T.; Pryke, C.; Ruhl, J. E.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Spieler, H. G.; Staniszewski, Z.; Stark, A. A.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.; Zahn, O.

    2014-02-01

    We explore extensions to the ΛCDM cosmology using measurements of the cosmic microwave background (CMB) from the recent SPT-SZ survey, along with data from WMAP7 and measurements of H 0 and baryon acoustic oscillation (BAO). We check for consistency within ΛCDM between these data sets, and find some tension. The CMB alone gives weak support to physics beyond ΛCDM, due to a slight trend relative to ΛCDM of decreasing power toward smaller angular scales. While it may be due to statistical fluctuation, this trend could also be explained by several extensions. We consider running of the primordial spectral index (dns /dln k), as well as two extensions that modify the damping tail power (the primordial helium abundance Yp and the effective number of neutrino species N eff) and one that modifies the large-scale power due to the integrated Sachs-Wolfe effect (the sum of neutrino masses ∑m ν). These extensions have similar observational consequences and are partially degenerate when considered simultaneously. Of the six one-parameter extensions considered, we find CMB to have the largest preference for dns /dln k with -0.046 < dns /dln k < -0.003 at 95% confidence, which strengthens to a 2.7σ indication of dns /dln k < 0 from CMB+BAO+H 0. Detectable dns /dln k ≠ 0 is difficult to explain in the context of single-field, slow-roll inflation models. We find N eff = 3.62 ± 0.48 for the CMB, which tightens to N eff = 3.71 ± 0.35 from CMB+BAO+H 0. Larger values of N eff relieve the mild tension between CMB, BAO, and H 0. When the Sunyaev-Zel'dovich selected galaxy cluster abundances (SPT_{CL}) data are also included, we obtain N eff = 3.29 ± 0.31. Allowing for ∑m ν gives a 3.0σ detection of ∑m ν > 0 from CMB+BAO+H 0 +SPT_{CL}. The median value is (0.32 ± 0.11) eV, a factor of six above the lower bound set by neutrino oscillation observations. All data sets except H 0 show some preference for massive neutrinos; data combinations including H 0 favor nonzero

  8. The Atacama Cosmology Telescope: A Measurement of the 600 less than l less than 8000 Cosmic Microwave Background Power Spectrum at 148 GHz

    NASA Technical Reports Server (NTRS)

    Fowler, J. W.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Bassistelli, E. S.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Doriese, W. B.; Dunkley, J.; Duenner, R.; Essinger-Hileman, T.; Fisher, R. P.; Hajian, A.; Halpern, M.; Hasselfield, M.; Moseley, H.; Wollack, Ed

    2010-01-01

    We present a measurement of the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz. The measurement uses maps with 1.4' angular resolution made with data from the Atacama Cosmology Telescope (ACT). The observations cover 228 deg(sup 2) of the southern sky, in a 4 deg. 2-wide strip centered on declination 53 deg. South. The CMB at arc minute angular scales is particularly sensitive to the Silk damping scale, to the Sunyaev-Zel'dovich (SZ) effect from galaxy dusters, and to emission by radio sources and dusty galaxies. After masking the 108 brightest point sources in our maps, we estimate the power spectrum between 600 less than l less than 8000 using the adaptive multi-taper method to minimize spectral leakage and maximize use of the full data set. Our absolute calibration is based on observations of Uranus. To verify the calibration and test the fidelity of our map at large angular scales, we cross-correlate the ACT map to the WMAP map and recover the WMAP power spectrum from 250 less than l less than 1150. The power beyond the Silk damping tail of the CMB (l approximately 5000) is consistent with models of the emission from point sources. We quantify the contribution of SZ clusters to the power spectrum by fitting to a model normalized to sigma 8 = 0.8. We constrain the model's amplitude A(sub sz) less than 1.63 (95% CL). If interpreted as a measurement of as, this implies sigma (sup SZ) (sub 8) less than 0.86 (95% CL) given our SZ model. A fit of ACT and WMAP five-year data jointly to a 6-parameter ACDM model plus point sources and the SZ effect is consistent with these results.

  9. Can the cosmic x ray and gamma ray background be due to reflection of a steep power law spectrum and Compton scattering by relativistic electrons?

    NASA Technical Reports Server (NTRS)

    Zycki, Piotr T.; Zdziarski, Andrzej A.; Svensson, Roland

    1991-01-01

    We reconsider the recent model for the origin in the cosmic X-ray and gamma-ray background by Rogers and Field. The background in the model is due to an unresolved population of AGNs. An individual AGN spectrum contains three components: a power law with the energy index of alpha = 1.1, an enhanced reflection component, and a component from Compton scattering by relativistic electrons with a low energy cutoff at some minimum Lorentz factor, gamma(sub min) much greater than 1. The MeV bump seen in the gamma-ray background is then explained by inverse Compton emission by the electrons. We show that the model does not reproduce the shape of the observed X-ray and gamma-ray background below 10 MeV and that it overproduces the background at larger energies. Furthermore, we find the assumptions made for the Compton component to be physically inconsistent. Relaxing the inconsistent assumptions leads to model spectra even more different from that of the observed cosmic background. Thus, we can reject the hypothesis that the high-energy cosmic background is due to the described model.

  10. Primordial power spectrum from Planck

    NASA Astrophysics Data System (ADS)

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun

    2014-11-01

    Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near l ~ 750-850 represents the most prominent feature in the data. Feature near l ~ 1800-2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ~ 2.5%. In this context low-l and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.

  11. Primordial power spectrum from Planck

    SciTech Connect

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun E-mail: arman@apctp.org

    2014-11-01

    Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near ℓ ∼ 750–850 represents the most prominent feature in the data. Feature near ℓ ∼ 1800–2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ∼ 2.5%. In this context low-ℓ and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.

  12. Spectrum of the microwave background radiation

    SciTech Connect

    Richards, P.L.

    1982-04-01

    A review is given of the present status of measurements of the spectrum of the microwave background. Factors which limit experimental accuracy are discussed with particular reference to high frequency measurements. A selection of the available measurements yields a data set which is reasonably consistent with the blackbody spectrum for a temperature of 2.9 K. A simple statistical analysis suggests either that there are errors in the data set, or that deviations from a blackbody spectrum exist. The difficulties inherent in property averaging the results from different observers are described. Prospects for improved measurements will be summarized.

  13. Spectrum of the microwave background radiation

    NASA Technical Reports Server (NTRS)

    Richards, P. L.

    1982-01-01

    A review is given of the present status of measurements of the spectrum of the microwave background. Factors that limit experimental accuracy are discussed with particular reference to high-frequency measurements. A selection of the available measurements yields a data set that is reasonably consistent with the black-body spectrum for a temperature of 2.9 K. A simple statistical analysis suggests either that there are errors in the data set, or that deviations from a black-body spectrum exist. The difficulties inherent in properly averaging the results from different observers are described. Prospects for improved measurements are summarized.

  14. Power Spectrum Estimation. I. Basics

    NASA Astrophysics Data System (ADS)

    Hamilton, A. J. S.

    This chapter and its companion form an extended version of notes provided to participants in the Valencia September 2004 summer school on Data Analysis in Cosmology. The lectures offer a pedagogical introduction to the problem of estimating the power spectrum from galaxy surveys. The intention is to focus on concepts rather than on technical detail, but enough mathematics is provided to point the student in the right direction. This first lecture presents background material. It collects some essential definitions, discusses traditional methods for measuring power, notably the Feldman-Kaiser-Peacock [2] method, and introduces Bayesian analysis, Fisher matrices, and maximum likelihood. For pedagogy and brevity, several derivations are set as exercises for the reader. At the summer school, multiple choice questions, included herein, were used to convey some didactic ideas, and provoked a little lively debate.

  15. Constraints on the power spectrum of the primordial density field from large-scale data - Microwave background and predictions of inflation

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.

    1992-01-01

    It is shown here that, by using galaxy catalog correlation data as input, measurements of microwave background radiation (MBR) anisotropies should soon be able to test two of the inflationary scenario's most basic predictions: (1) that the primordial density fluctuations produced were scale-invariant and (2) that the universe is flat. They should also be able to detect anisotropies of large-scale structure formed by gravitational evolution of density fluctuations present at the last scattering epoch. Computations of MBR anisotropies corresponding to the minimum of the large-scale variance of the MBR anisotropy are presented which favor an open universe with P(k) significantly different from the Harrison-Zeldovich spectrum predicted by most inflationary models.

  16. Reduced shear power spectrum

    SciTech Connect

    Dodelson, Scott; Shapiro, Charles; White, Martin J.; /UC, Berkeley, Astron. Dept. /UC, Berkeley

    2005-08-01

    Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.

  17. Constraints on cosmology from the cosmic microwave background power spectrum of the 2500 deg{sup 2} SPT-SZ survey

    SciTech Connect

    Hou, Z.; Follin, B.; Reichardt, C. L.; George, E. M.; Story, K. T.; Keisler, R.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Dodelson, S.; Aird, K. A.; Cho, H.-M.; De Haan, T.; Dobbs, M. A.; Dudley, J.; De Putter, R.; Halverson, N. W.; and others

    2014-02-20

    We explore extensions to the ΛCDM cosmology using measurements of the cosmic microwave background (CMB) from the recent SPT-SZ survey, along with data from WMAP7 and measurements of H {sub 0} and baryon acoustic oscillation (BAO). We check for consistency within ΛCDM between these data sets, and find some tension. The CMB alone gives weak support to physics beyond ΛCDM, due to a slight trend relative to ΛCDM of decreasing power toward smaller angular scales. While it may be due to statistical fluctuation, this trend could also be explained by several extensions. We consider running of the primordial spectral index (dn{sub s} /dln k), as well as two extensions that modify the damping tail power (the primordial helium abundance Y{sub p} and the effective number of neutrino species N {sub eff}) and one that modifies the large-scale power due to the integrated Sachs-Wolfe effect (the sum of neutrino masses ∑m {sub ν}). These extensions have similar observational consequences and are partially degenerate when considered simultaneously. Of the six one-parameter extensions considered, we find CMB to have the largest preference for dn{sub s} /dln k with –0.046 < dn{sub s} /dln k < –0.003 at 95% confidence, which strengthens to a 2.7σ indication of dn{sub s} /dln k < 0 from CMB+BAO+H {sub 0}. Detectable dn{sub s} /dln k ≠ 0 is difficult to explain in the context of single-field, slow-roll inflation models. We find N {sub eff} = 3.62 ± 0.48 for the CMB, which tightens to N {sub eff} = 3.71 ± 0.35 from CMB+BAO+H {sub 0}. Larger values of N {sub eff} relieve the mild tension between CMB, BAO, and H {sub 0}. When the Sunyaev-Zel'dovich selected galaxy cluster abundances (SPT{sub CL}) data are also included, we obtain N {sub eff} = 3.29 ± 0.31. Allowing for ∑m {sub ν} gives a 3.0σ detection of ∑m {sub ν} > 0 from CMB+BAO+H {sub 0} +SPT{sub CL}. The median value is (0.32 ± 0.11) eV, a factor of six above the lower bound set by neutrino oscillation

  18. Distortions of the cosmic microwave background spectrum by dust

    NASA Technical Reports Server (NTRS)

    Rowan-Robinson, M.; Negroponte, J.; Silk, J.

    1979-01-01

    The effects of dust in the early universe on the spectrum of the cosmic microwave background are considered, taking into account the effects of a pregalactic generation of stars. It is shown that observed distortions of the background spectrum from that of a black body at 3 K could be due to emission by silicate dust grains at a metal abundance of 0.00001 by mass and with a substantial energy input, which represent the remnants of population III stars. Attempts to fit the microwave background spectrum to the model of Rees (1978) in which the entire cosmic background is accounted for by grain emission are shown to require an implausible value for the metal abundance at early epochs, and not to agree with the millimeter and submillimeter spectrum observed by Woody and Richards (1979).

  19. Modelling the TSZ power spectrum

    SciTech Connect

    Bhattacharya, Suman; Shaw, Laurie D; Nagai, Daisuke

    2010-01-01

    The structure formation in university is a hierarchical process. As universe evolves, tiny density fluctuations that existed in the early universe grows under gravitational instability to form massive large scale structures. The galaxy clusters are the massive viralized objects that forms by accreting smaller clumps of mass until they collapse under their self-gravity. As such galaxy clusters are the youngest objects in the universe which makes their abundance as a function of mass and redshift, very sensitive to dark energy. Galaxy clusters can be detected by measuring the richness in optical waveband, by measuring the X-ray flux, and in the microwave sky using Sunyaev-Zel'dovich (SZ) effect. The Sunyaev-Zel'dovich (SZ) effect has long been recognized as a powerful tool for detecting clusters and probing the physics of the intra-cluster medium. Ongoing and future experiments like Atacama Cosmology Telescope, the South Pole Telescope and Planck survey are currently surveying the microwave sky to develop large catalogs of galaxy clusters that are uniformly selected by the SZ flux. However one major systematic uncertainties that cluster abundance is prone to is the connection between the cluster mass and the SZ flux. As shown by several simulation studies, the scatter and bias in the SZ flux-mass relation can be a potential source of systematic error to using clusters as a cosmology probe. In this study they take a semi-analytic approach for modeling the intra-cluster medium in order to predict the tSZ power spectrum. The advantage of this approach is, being analytic, one can vary the parameters describing gas physics and cosmology simultaneously. The model can be calibrated against X-ray observations of massive, low-z clusters, and using the SZ power spectrum which is sourced by high-z lower mass galaxy groups. This approach allows us to include the uncertainty in gas physics, as dictated by the current observational uncertainties, while measuring the cosmological

  20. Pregalactic dust and distortions of the cosmic-background spectrum

    NASA Astrophysics Data System (ADS)

    Aiello, S.; Melchiorri, F.; Cecchini, S.; Mandolesi, N.

    1980-04-01

    The paper focuses on a comparison between the cosmic-background spectrum and the emission by a dust cloud of silicate grains. The similarity between the emission from a cloud of silicate grains and the observed cosmic-background spectrum is clearly shown schematically. However, for a quantitative comparison a more detailed computation is required. An expression is written for the observed cosmic-background spectrum in terms of the deceleration parameter, the grain extinction cross section, the number density of grains at the present epoch, and the rate of grain production in the pregalactic epoch /f(z)/. A complete analysis of the problem requires the computation of the optical depth for different values of f(z), for different grain materials, and for various distributions of grain radii. All these computations are reported by Aiello et al. (1979). The paper presents only preliminary results.

  1. The EPIC-MOS Particle-Induced Background Spectrum

    NASA Technical Reports Server (NTRS)

    Kuntz, K. D.; Snowden, S. L.

    2006-01-01

    We have developed a method for constructing a spectrum of the particle-induced instrumental background of the XMM-Newton EPIC MOS detectors that can be used for observations of the diffuse background and extended sources that fill a significant fraction of the instrument field of view. The strength and spectrum of the particle-induced background, that is, the background due to the interaction of particles with the detector and the detector surroundings, is temporally variable as well as spatially variable over individual chips. Our method uses a combination of the filter-wheel-closed data and a database of unexposed-region data to construct a spectrum of the "quiescent" background. We show that, using this method of background subtraction, the differences between independent observations of the same region of "blank sky" are consistent with the statistical uncertainties except when there is clear evidence of solar wind charge exchange emission. We use the blank sky observations to show that contamination by SWCX emission is a strong function of the solar wind proton flux, and that observations through the flanks of the magnetosheath appear to be contaminated only at much higher solar wind fluxes. We have also developed a spectral model of the residual soft proton flares, which allows their effects to be removed to a substantial degree during spectral fitting.

  2. Near-millimeter spectrum of the microwave background

    NASA Technical Reports Server (NTRS)

    Woody, D. P.; Richards, P. L.

    1981-01-01

    A description is given of a method for the measurement of the cosmic microwave background (CMB) spectrum. A helium-cooled, balloon-borne spectrophotometer was used to measure the emission spectrum of the night sky over the frequency range 1.7-40/cm. The apparatus was calibrated using a blackbody source at a variety of temperatures both before and after the flight. It is shown that the spectrum of the CMB peaks at 6/cm and is approximately that of a blackbody out to several times that frequency. The measured flux is also found to be equivalent to that from a blackbody in the temperature range from 2.88 to 3.09 K. The data set resulting from the combination of these measurements with previous observations of the CMB covers three decades in frequency, and is compared with various CMB models.

  3. A preliminary measurement of the cosmic microwave background spectrum by the Cosmic Background Explorer (COBE) satellite

    NASA Technical Reports Server (NTRS)

    Mather, J. C.; Cheng, E. S.; Shafer, R. A.; Bennett, C. L.; Boggess, N. W.; Dwek, E.; Hauser, M. G.; Kelsall, T.; Moseley, S. H., Jr.; Silverberg, R. F.

    1990-01-01

    A preliminary spectrum is presented of the background radiation between 1 and 20/cm from regions near the north Galactic pole, as observed by the FIRAS instrument on the COBE satellite. The spectral resolution is 1/cm. The spectrum is well fitted by a blackbody with a temperature of 2.735 + or - 0.06 K, and the deviation from a blackbody is less than 1 percent of the peak intensity over the range 1-20/cm. These new data show no evidence for the submillimeter excess previously reported by Matsumoto et al. (1988) in the cosmic microwave background. Further analysis and additional data are expected to improve the sensitivity to deviations from a blackbody spectrum by an order of magnitude.

  4. Near-millimeter spectrum of the microwave background

    SciTech Connect

    Woody, D.P.; Richards, P.L.

    1981-08-15

    A complete description is given of a measurement of the spectrum of the cosmic microwave background (CMB). A fully calibrated, liquid helium cooled, ballon borne spectrophotometer was used to measure the emission spectrum of the night sky over the frequency range from 1.7 to 40 cm/sup -1/. Great care was taken with the instrumental design to avoid radiation from the Earth or the apparatus. The apparatus was calibrated using a blackbody source with a variety of temperatures before and after the flight. The atmospheric emission was subtracted by fitting the data to the spectrum computed from an atmospheric model. The resulting spectral measurements have a flux accuracy of better than 10% of the peak flux of a 3 K blackbody and extend over the frequency range from 2.5 to 24 cm/sup -1/. They show that the spectrum of the CMB peaks at 6 cm/sup -1/ and is approximately that of a blackbody out to several times that frequency. Some deviations from blackbody shape are observed. The measured flux is equivalent to that from a blackbody in the temperature range from 2.88 to 3.09 K. These measurements are combined with previous observations of the CMB to produce a set of data covering three decades in frequency. This data set is compared with various models of the CMB.

  5. Feature selection using Haar wavelet power spectrum

    PubMed Central

    Subramani, Prabakaran; Sahu, Rajendra; Verma, Shekhar

    2006-01-01

    Background Feature selection is an approach to overcome the 'curse of dimensionality' in complex researches like disease classification using microarrays. Statistical methods are utilized more in this domain. Most of them do not fit for a wide range of datasets. The transform oriented signal processing domains are not probed much when other fields like image and video processing utilize them well. Wavelets, one of such techniques, have the potential to be utilized in feature selection method. The aim of this paper is to assess the capability of Haar wavelet power spectrum in the problem of clustering and gene selection based on expression data in the context of disease classification and to propose a method based on Haar wavelet power spectrum. Results Haar wavelet power spectra of genes were analysed and it was observed to be different in different diagnostic categories. This difference in trend and magnitude of the spectrum may be utilized in gene selection. Most of the genes selected by earlier complex methods were selected by the very simple present method. Each earlier works proved only few genes are quite enough to approach the classification problem [1]. Hence the present method may be tried in conjunction with other classification methods. The technique was applied without removing the noise in data to validate the robustness of the method against the noise or outliers in the data. No special softwares or complex implementation is needed. The qualities of the genes selected by the present method were analysed through their gene expression data. Most of them were observed to be related to solve the classification issue since they were dominant in the diagnostic category of the dataset for which they were selected as features. Conclusion In the present paper, the problem of feature selection of microarray gene expression data was considered. We analyzed the wavelet power spectrum of genes and proposed a clustering and feature selection method useful for

  6. Precise measurements of primordial power spectrum with 21 cm fluctuations

    SciTech Connect

    Kohri, Kazunori; Oyama, Yoshihiko; Sekiguchi, Toyokazu; Takahashi, Tomo E-mail: oyamayo@post.kek.jp E-mail: tomot@cc.saga-u.ac.jp

    2013-10-01

    We discuss the issue of how precisely we can measure the primordial power spectrum by using future observations of 21 cm fluctuations and cosmic microwave background (CMB). For this purpose, we investigate projected constraints on the quantities characterizing primordial power spectrum: the spectral index n{sub s}, its running α{sub s} and even its higher order running β{sub s}. We show that future 21 cm observations in combinations with CMB would accurately measure above mentioned observables of primordial power spectrum. We also discuss its implications to some explicit inflationary models.

  7. Hierarchical cosmic shear power spectrum inference

    NASA Astrophysics Data System (ADS)

    Alsing, Justin; Heavens, Alan; Jaffe, Andrew H.; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till

    2016-02-01

    We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models a posteriori without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear E-mode, B-mode and EB-cross power spectra from a simulated galaxy shear catalogue with a number of important features; galaxies distributed on the sky and in redshift with photometric redshift uncertainties, realistic random ellipticity noise for every galaxy and a complicated survey mask. The obtained posterior distributions for the tomographic power spectrum coefficients recover the underlying simulated power spectra for both E- and B-modes.

  8. Reconstruction of the primordial power spectrum from CMB data

    SciTech Connect

    Guo, Zong-Kuan; Zhang, Yuan-Zhong; Schwarz, Dominik J. E-mail: dschwarz@physik.uni-bielefeld.de

    2011-08-01

    Measuring the deviation from scale invariance of the primordial power spectrum is a critical test of inflation. In this paper we reconstruct the shape of the primordial power spectrum of curvature perturbations from the cosmic microwave background data, including the 7-year Wilkinson Microwave Anisotropy Probe data and the Atacama Cosmology Telescope 148 GHz data, by using a binning method of a cubic spline interpolation in log-log space. We find that the power-law spectrum is preferred by the data and that the Harrison-Zel'dovich spectrum is disfavored at 95% confidence level. These conclusions hold with and without allowing for tensor modes, however the simpler model without tensors is preferred by the data. We do not find evidence for a feature in the primordial power spectrum — in full agreement with generic predictions from cosmological inflation.

  9. Ultraviolet spectrum of the sky background at different galactic latitudes

    NASA Astrophysics Data System (ADS)

    Zvereva, A. M.; Severnyi, A. B.; Granitskii, L. V.; Hua, C. T.; Cruvellier, P.; Courtes, G.

    1982-12-01

    The intensity distributions of the sky background radiation in the 1100-1850 A range were measured in deep space (70,000-200,000 km from the earth) by the Prognoz-6 photoelectric spectrometer. Spectral distributions of UV background Ilambda, after subtraction of the stellar component, vary with galactic latitude in the range bII equals minus 58 to plus 27 deg. Ilambda decreases with increasing wavelength at high latitudes; the spectrum then becomes flat at intermediate latitudes, and there is a rapid decrease of Ilambda with lambda near and inside the Milky Way. The intensity I(lambda equals 1600) in the higher latitude range (the absolute value of bII higher than 30 deg) shows good correlation with soft X-ray brightness and neutral hydrogen (21-cm) density N(H I). However, there is appreciable UV emission near the galactic poles where N(H I) is approximately zero

  10. Log-transforming the matter power spectrum

    NASA Astrophysics Data System (ADS)

    Greiner, M.; Enßlin, T. A.

    2015-02-01

    We investigate whether non-linear effects on the large-scale power spectrum of dark matter, namely the increase in small-scale power and the smearing of baryon acoustic oscillations, can be decreased by a log-transformation or emulated by an exponential transformation of the linear spectrum. To that end we present a formalism to convert the power spectrum of a log-normal field to the power spectrum of the logarithmic Gaussian field and vice versa. All ingredients of our derivation can already be found in various publications in cosmology and other fields. We follow a more pedagogical approach providing a detailed derivation, application examples, and a discussion of implementation subtleties in one text. We use the formalism to show that the non-linear increase in small-scale power in the matter power spectrum is significantly smaller for the log-transformed spectrum which fits the linear spectrum (with less than 20% error) for redshifts down to 1 and k ≤ 1.0 h Mpc. For lower redshifts the fit to the linear spectrum is not as good, but the reduction of non-linear effects is still significant. Similarly, we show that applying the linear growth factor to the logarithmic density leads to an automatic increase in small-scale power for low redshifts fitting to third-order perturbation spectra and Cosmic Emulator spectra with an error of less than 20%. Smearing of baryon acoustic oscillations is at least three times weaker, but still present.

  11. The microlocal spectrum condition, initial value formulations, and background independence

    NASA Astrophysics Data System (ADS)

    Stottmeister, Alexander; Thiemann, Thomas

    2016-02-01

    We analyze implications of the microlocal spectrum/Hadamard condition for states in a (linear) quantum field theory on a globally hyperbolic spacetime M in the context of a (distributional) initial value formulation. More specifically, we work in 3+1-split M ≅ ℝ × Σ and give a bound, independent of the spacetime metric, on the wave front sets of the initial data for a quasi-free Hadamard state in a quantum field theory defined by a normally hyperbolic differential operator P acting in a vector bundle E → π M . This aims at a possible way to apply the concept of Hadamard states within approaches to quantum field theory/gravity relying on a Hamiltonian formulation, potentially without a (classical) background metric g.

  12. Towards optimal cluster power spectrum analysis

    NASA Astrophysics Data System (ADS)

    Smith, Robert E.; Marian, Laura

    2016-04-01

    The power spectrum of galaxy clusters is an important probe of the cosmological model. In this paper, we develop a formalism to compute the optimal weights for the estimation of the matter power spectrum from cluster power spectrum measurements. We find a closed-form analytic expression for the optimal weights, which takes into account: the cluster mass, finite survey volume effects, survey masking, and a flux limit. The optimal weights are w(M,χ ) ∝ b(M,χ )/[1+bar{n}_h(χ ) overline{b^2}(χ )overline{P}(k)], where b(M, χ) is the bias of clusters of mass M at radial position χ(z), bar{n}_h(χ ) and overline{b^2}(χ ) are the expected space density and bias squared of all clusters, and overline{P}(k) is the matter power spectrum at wavenumber k. This result is analogous to that of Percival et al. We compare our optimal weighting scheme with mass weighting and also with the original power spectrum scheme of Feldman et al. We show that our optimal weighting scheme outperforms these approaches for both volume- and flux-limited cluster surveys. Finally, we present a new expression for the Fisher information matrix for cluster power spectrum analysis. Our expression shows that for an optimally weighted cluster survey the cosmological information content is boosted, relative to the standard approach of Tegmark.

  13. Another look at distortions of the Cosmic Microwave Background spectrum

    NASA Astrophysics Data System (ADS)

    De Zotti, G.; Negrello, M.; Castex, G.; Lapi, A.; Bonato, M.

    2016-03-01

    We review aspects of Cosmic Microwave Background (CMB) spectral distortions which do not appear to have been fully explored in the literature. In particular, implications of recent evidences of heating of the intergalactic medium (IGM) by feedback from active galactic nuclei are investigated. Taking also into account the IGM heating associated to structure formation, we argue that values of the y parameter of several × 10-6, i.e. a factor of a few below the COBE/FIRAS upper limit, are to be expected. The Compton scattering by the re-ionized plasma also re-processes primordial distortions, adding a y-type contribution. Hence no pure Bose-Einstein-like distortions are to be expected. An assessment of Galactic and extragalactic foregrounds, taking into account the latest results from the Planck satellite as well as the contributions from the strong CII and CO lines from star-forming galaxies, demonstrates that a foreground subtraction accurate enough to fully exploit the PIXIE sensitivity will be extremely challenging. Motivated by this fact we also discuss methods to detect spectral distortions not requiring absolute measurements and show that accurate determinations of the frequency spectrum of the CMB dipole amplitude may substantially improve over COBE/FIRAS limits on distortion parameters. Such improvements may be at reach of next generation CMB anisotropy experiments. The estimated amplitude of the Cosmic Infrared Background (CIB) dipole might be detectable by careful analyses of Planck maps at the highest frequencies. Thus Planck might provide interesting constraints on the CIB intensity, currently known with a simeq 30% uncertainty.

  14. Probing the primordial power spectrum with cluster number counts

    SciTech Connect

    Chantavat, Teeraparb; Gordon, Christopher; Silk, Joseph

    2009-04-15

    We investigate how well galaxy cluster number counts can constrain the primordial power spectrum. Measurements of the primary anisotropies in the cosmic microwave background may be limited, by the presence of foregrounds from secondary sources, to probing the primordial power spectrum at wave numbers less than about 0.30h Mpc{sup -1}. We break up the primordial power spectrum into a number of nodes and interpolate linearly between each node. This allows us to show that cluster number counts could then extend the constraints on the form of the primordial power spectrum up to wave numbers of about 0.45h Mpc{sup -1}. We estimate combinations of constraints from PLANCK and SPT primary cosmic microwave background and their respective Sunyaev-Zeldovich surveys. We find that their constraining ability is limited by uncertainties in the mass-scaling relations. We also estimate the constraint from clusters detected from a SNAP-like gravitational lensing survey. As there is an unambiguous and simple relationship between the filtered shear of the lensing survey and the cluster mass, it may be possible to obtain much tighter constraints on the primordial power spectrum in this case.

  15. Primordial power spectrum features and fNL constraints

    NASA Astrophysics Data System (ADS)

    Gariazzo, Stefano; Lopez-Honorez, Laura; Mena, Olga

    2015-09-01

    The simplest models of inflation predict small non-Gaussianities and a featureless power spectrum. However, there exist a large number of well-motivated theoretical scenarios in which large non-Gaussianties could be generated. In general, in these scenarios the primordial power spectrum will deviate from its standard power law shape. We study, in a model-independent manner, the constraints from future large-scale structure surveys on the local non-Gaussianity parameter fNL when the standard power law assumption for the primordial power spectrum is relaxed. If the analyses are restricted to the large-scale-dependent bias induced in the linear matter power spectrum by non-Gaussianites, the errors on the fNL parameter could be increased by 60% when exploiting data from the future DESI survey, if dealing with only one possible dark matter tracer. In the same context, a nontrivial bias |δ fNL|˜2.5 could be induced if future data are fitted to the wrong primordial power spectrum. Combining all the possible DESI objects slightly ameliorates the problem, as the forecasted errors on fNL would be degraded by 40% when relaxing the assumptions concerning the primordial power spectrum shape. Also, the shift on the non-Gaussianity parameter is reduced in this case, |δ fNL|˜1.6 . The addition of cosmic microwave background priors ensures robust future fNL bounds, as the forecasted errors obtained including these measurements are almost independent on the primordial power spectrum features, and |δ fNL|˜0.2 , close to the standard single-field slow-roll paradigm prediction.

  16. A measurement of the low frequency spectrum of the cosmic microwave background radiation

    SciTech Connect

    Levin, S.M.

    1987-04-01

    As part of a larger effort to measure the spectrum of the Cosmic Background Radiation (CBR) at low frequencies, the intensity of the CBR has been measured at a frequency of 1.410 GHz. The measurement was made by comparing the power received from the sky with the power received from a specially designed cooled calibration target with known properties. Sources of radiation other than the CBR were then identified and subtracted to calculate the antenna temperature of the CBR at 1.410 GHz. The instrument used to measure the CBR was a total-power microwave radiometer with a 25 MHz bandwidth centered at 1.410 GHz. The radiometer had a noise temperature of 80 K, and sufficient data were taken that radiometer noise did not contribute significantly to the total measurement error. The sources of error were predominantly systematic in nature, and the largest error was due to uncertainty in the reflection characteristics of the cold-load calibrator. Identification and subtraction of signals from the Galaxy (0.7 K) and the Earth's atmosphere (0.8 K) were also significant parts of the data reduction and error analysis. The brightness temperature of the Cosmic Background Radiation at 1.410 GHz is 222. +- 0.55 Kelvin. The spectrum of the CBR, as determined by this measurement and other published results, is consistent with a blackbody spectrum of temperature 2.741 +- 0.016. Constraints on the amount by which the CBR spectrum deviates from Planck spectrum are used to place limits on energy releases early in the history of the universe. 55 refs., 25 figs., 8 tabs.

  17. The Spectrum of the Cosmic X-ray Background Observed by RTXE/PCA

    NASA Technical Reports Server (NTRS)

    Revnivtsev, M.; Gilfanov, M.; Sunyaev, R.; Jahoda, K.; Markwardt, C.

    2004-01-01

    We have analyzed a large set of Rossi X-ray Timing Explorer/Proportional Counter Array (RXTE/PCA) scanning and slewing observations performed between April 1996 and March 1999. We obtained the 3-20 keV spectrum of the cosmic X-ray background (CXB) by subtracting Earth-occulted observations from observations of the X-ray sky at high galactic latitude and far away from sources. The sky coverage is approximately 22.6 x 10(exp 3) square degrees. The PCA spectrum of CXB in 3-20 keV energy band is adequately approximated by a single power law with photon index GAMMA approximately 1.4 and normalization at 1 keV approximately 9.5 phot/s/square centimeter/keV/sr. Instrumental background uncertainty precludes accurate RXTE/PCA measurements of the spectrum of cosmic X-ray background at energies above 15 keV and therefore we cannot detect the high energy cutoff observed by the High Energy Astronomical Observatory (HEAO)-1 A2 experiment. Deep observations of the 6 high latitude points used to model the PCA background provide a coarse measure of the spatial variation of the CXB. The CXB variations are consistent with a fixed spectral shape and variable normalization characterized by a fractional rms amplitude of approximately 7% on angular scales of approximately 1 square deg.

  18. Background neutron spectrum at 2420 m above sea level

    NASA Astrophysics Data System (ADS)

    Vega-Carrillo, Hector Rene; Manzanares-Acuña, Eduardo

    2004-05-01

    The ambient neutron spectrum was measured in-doors at ground level in Zacatecas Mexico at 2420 m above sea level. A Bonner sphere spectrometer with a 6LiI(Eu) scintillator was used to obtain the neutron spectrum. With the spectrum the ambient dose equivalent was calculated using the ICRP 74 neutron fluence-to-dose conversion factors. The neutron fluence rate was 65±3 cm -2 h -1, producing 13.7±0.6 nSv h -1 due to ambient dose equivalent.

  19. LIKELIHOOD OF THE POWER SPECTRUM IN COSMOLOGICAL PARAMETER ESTIMATION

    SciTech Connect

    Sun, Lei; Wang, Qiao; Zhan, Hu

    2013-11-01

    The likelihood function is a crucial element of parameter estimation. In analyses of galaxy overdensities and weak lensing shear, one often approximates the likelihood of the power spectrum with a Gaussian distribution. The posterior probability derived from such a likelihood deviates considerably from the exact posterior on the largest scales probed by any survey, where the central limit theorem does not apply. We show that various forms of Gaussian likelihoods can have a significant impact on the estimation of the primordial non-Gaussianity parameter f{sub NL} from the galaxy angular power spectrum. The Gaussian plus log-normal likelihood, which has been applied successfully in analyses of the cosmic microwave background, outperforms the Gaussian likelihoods. Nevertheless, even if the exact likelihood of the power spectrum is used, the estimated parameters may be still biased. As such, the likelihoods and estimators need to be thoroughly examined for potential systematic errors.

  20. Deconstructing the Spectrum of the Soft X-ray Background

    NASA Technical Reports Server (NTRS)

    Kuntz, K. D.; Snowden, S. L.

    2000-01-01

    The soft X-ray background in the 0.1-1.0 keV band is known to be produced by at least three sources; the Local Hot Bubble (LHB), the extragalactic power law (EPL), and a seemingly galactic component that lies outside the bulk of the absorption that is due to the ISM of the galactic disk. This last component, which we call the Trans-Absorption Emission (TAE), has been modeled by a number of groups who have derived disparate measures of its temperature. The differences have arisen from differing assumptions about the structure of the emitting gas and unrecognized methodological difficulties. In particular, spectral fitting methods do not uniquely separate the TAE from the foreground emission that is due the LHB. This "degeneracy" can be resolved using the angular variation of the absorption of the TAE. We show that the TAE cannot be characterized by a single thermal component; no single-component model can be consistent with both the spectral energy distribution of the TAE emission and the angular variation due to absorption by the galactic disk. We use the angular anticorrelation of the ROSAT All-Sky Survey with the galactic absorption to separate local from distant emission components, and to fit the spectral energy distribution of the resulting distant emission. We find that the emission is best described by a two-thermal-component model with logT(sub S) = 6.06(sup +0.14, sub -0.12) and log T(sub H) = 6.42(sup +0.14, sub -0.12). This two-thermal-component TAE fits the ROSAT spectral energy distribution significantly better than single-component models, and is consistent with both angular variation and spectral constraints.

  1. computePk: Power spectrum computation

    NASA Astrophysics Data System (ADS)

    L'Huillier, Benjamin

    2014-03-01

    ComputePk computes the power spectrum in cosmological simulations. It is MPI parallel and has been tested up to a 4096^3 mesh. It uses the FFTW library. It can read Gadget-3 and GOTPM outputs, and computes the dark matter component. The user may choose between NGP, CIC, and TSC for the mass assignment scheme.

  2. Generalized slow roll approximation for large power spectrum features

    SciTech Connect

    Dvorkin, Cora; Hu, Wayne

    2010-01-15

    We develop a variant of the generalized slow roll approach for calculating the curvature power spectrum that is well suited for order unity deviations in power caused by sharp features in the inflaton potential. As an example, we show that predictions for a step function potential, which has been proposed to explain order unity glitches in the cosmic microwave background temperature power spectrum at multipoles l=20-40, are accurate at the percent level. Our analysis shows that to good approximation there is a single source function that is responsible for observable features and that this function is simply related to the local slope and curvature of the inflaton potential. These properties should make the generalized slow roll approximation useful for inflation-model-independent studies of features, both large and small, in the observable power spectra.

  3. Enhancing the cosmic shear power spectrum

    NASA Astrophysics Data System (ADS)

    Simpson, Fergus; Harnois-Déraps, Joachim; Heymans, Catherine; Jimenez, Raul; Joachimi, Benjamin; Verde, Licia

    2016-02-01

    Applying a transformation to a non-Gaussian field can enhance the information content of the resulting power spectrum, by reducing the correlations between Fourier modes. In the context of weak gravitational lensing, it has been shown that this gain in information content is significantly compromised by the presence of shape noise. We apply clipping to mock convergence fields, a technique which is known to be robust in the presence of noise and has been successfully applied to galaxy number density fields. When analysed in isolation the resulting convergence power spectrum returns degraded constraints on cosmological parameters. However, substantial gains can be achieved by performing a combined analysis of the power spectra derived from both the original and transformed fields. Even in the presence of realistic levels of shape noise, we demonstrate that this approach is capable of reducing the area of likelihood contours within the Ωm - σ8 plane by more than a factor of 3.

  4. COPSS: The CO Power Spectrum Survey

    NASA Astrophysics Data System (ADS)

    Keating, Garrett K.; Bower, Geoffrey C.; Marrone, Daniel P.; Heiles, Carl E.; SZA, CARMA, COPSS

    2016-01-01

    Molecular gas is a vital component of galactic evolution and star formation, but its abundance in normal star-forming galaxies in the early Universe is poorly understood. Direct detection methods have been able to probe only the most luminous of galaxies at z˜3, missing the vast population of Milky Way progenitors and "building block" galaxies that are expected to bear the bulk of the molecular gas of the early Universe. Using the technique of "intensity mapping", where measurements of different 3D Fourier modes are used to construct a power spectrum, these smaller galaxies can be detectable as an integrated ensemble.We present results from the CO Power Spectrum Survey (COPSS), an intensity mapping experiment performed with the Sunyaev-Zel'dovich Array (SZA). The SZA, a 3.5m × 8-element subset of the Combined Array for Research in Millimeter-wave Astronomy, is capable of observing CO (J=1→0) at z=2.3-3.3. We present final results from of the first phase of this project, utilizing an archival dataset (covering 44 fields in 1400 hours observing time). With these data, we constrain the CO power spectrum to PCO < 2.6×104 μK2 (Mpc/h)3 at z˜3, excluding the model of Lidz et al. (2011) and putting significant constraints on one of two models from Pullen et al. (2013) at this redshift. With this limit, we are able to constrain the cosmic molecular gas density to ρH2(z˜3) < 2.8×108 M⊙ Mpc-3. We also present current results from the second phase of this project, a 5000-hour observing campaign with the SZA, which increases our sensitivity by more than an order of magnitude.

  5. Gabor transforms on the sphere with applications to CMB power spectrum estimation

    NASA Astrophysics Data System (ADS)

    Hansen, Frode K.; Górski, Krzysztof M.; Hivon, Eric

    2002-11-01

    The Fourier transform of a data set apodized with a window function is known as the Gabor transform. In this paper we extend the Gabor transform formalism to the sphere with the intention of applying it to cosmic microwave background (CMB) data analysis. The Gabor coefficients on the sphere known as the pseudo power spectrum is studied for windows of different size. By assuming that the pseudo power spectrum coefficients are Gaussian distributed, we formulate a likelihood ansatz using these as input parameters to estimate the full-sky power spectrum from a patch on the sky. As this likelihood can be calculated quickly without having to invert huge matrices, this allows for fast power spectrum estimation. By using the pseudo power spectrum from several patches on the sky together, the full-sky power spectrum can be estimated from full-sky or nearly full-sky observations.

  6. FLUKA: Predictive power for cosmogenic backgrounds

    SciTech Connect

    Empl, A. Hungerford, E. V.; Ferrari, A.; Smirnov, G. I.

    2015-08-17

    The next generation of experiments searching for rare physics events with increased sensitivity will require precise predictions of cosmogenic backgrounds. Recent high quality deep underground measurements for cosmogenic neutrons in large liquid scintillator targets were used to study the FLUKA simulation package for this purpose. The results and conclusions drawn from a detailed benchmark comparison with data from the Borexino experiment were reported recently. In general, good agreement between data and simulation results were found with some identified discrepancies. Improved physics models already implemented in the current version of the FLUKA code, which will be publicly available with the upcoming code release, address the more important identified issues. A careful evaluation of the improved predictions is ongoing. However, the agreement between preliminary FLUKA simulation results and the Borexino experimental data are excellent. The preliminary findings will be discussed.

  7. FLUKA: Predictive power for cosmogenic backgrounds

    NASA Astrophysics Data System (ADS)

    Empl, A.; Ferrari, A.; Hungerford, E. V.; Smirnov, G. I.

    2015-08-01

    The next generation of experiments searching for rare physics events with increased sensitivity will require precise predictions of cosmogenic backgrounds. Recent high quality deep underground measurements for cosmogenic neutrons in large liquid scintillator targets were used to study the FLUKA simulation package for this purpose. The results and conclusions drawn from a detailed benchmark comparison with data from the Borexino experiment were reported recently. In general, good agreement between data and simulation results were found with some identified discrepancies. Improved physics models already implemented in the current version of the FLUKA code, which will be publicly available with the upcoming code release, address the more important identified issues. A careful evaluation of the improved predictions is ongoing. However, the agreement between preliminary FLUKA simulation results and the Borexino experimental data are excellent. The preliminary findings will be discussed.

  8. Cosmic string power spectrum, bispectrum, and trispectrum

    SciTech Connect

    Regan, D. M.; Shellard, E. P. S.

    2010-09-15

    We use analytic calculations of the post-recombination gravitational effects of cosmic strings to estimate the resulting CMB power spectrum, bispectrum and trispectrum. We place a particular emphasis on multipole regimes relevant for forthcoming CMB experiments, notably the Planck satellite. These calculations use a flat-sky approximation, generalizing previous work by integrating string contributions from last scattering to the present day, finding the dominant contributions to the correlators for multipoles l>50. We find a well-behaved shape for the string bispectrum (without divergences) which is easily distinguishable from the inflationary bispectra which possess significant acoustic peaks. We estimate that the nonlinearity parameter characterizing the bispectrum is approximately 0 > or approx. f{sub NL} > or approx. -40 (given present string constraints from the CMB power spectrum). We also apply these unequal time correlator methods to calculate the trispectrum for parrallelogram configurations, again valid over a large range of angular scales relevant for WMAP and Planck, as well as on very small angular scales. We find that, unlike the bispectrum which is suppressed by symmetry considerations, the trispectrum for cosmic strings is large. Our current estimate for the trispectrum parameter is {tau}{sub NL{approx}}10{sup 5}, which may provide one of the strongest constraints on the string model in future analysis.

  9. Cosmological parameter estimation with free-form primordial power spectrum

    NASA Astrophysics Data System (ADS)

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun

    2013-06-01

    Constraints on the main cosmological parameters using cosmic microwave background (CMB) or large scale structure data are usually based on the power-law assumption of the primordial power spectrum (PPS). However, in the absence of a preferred model for the early Universe, this raises a concern that current cosmological parameter estimates are strongly prejudiced by the assumed power-law form of PPS. In this paper, for the first time, we perform cosmological parameter estimation allowing the free form of the primordial spectrum. This is in fact the most general approach to estimate cosmological parameters without assuming any particular form for the primordial spectrum. We use a direct reconstruction of the PPS for any point in the cosmological parameter space using the recently modified Richardson-Lucy algorithm; however, other alternative reconstruction methods could be used for this purpose as well. We use WMAP 9 year data in our analysis considering the CMB lensing effect, and we report, for the first time, that the flat spatial universe with no cosmological constant is ruled out by more than a 4σ confidence limit without assuming any particular form of the primordial spectrum. This would be probably the most robust indication for dark energy using CMB data alone. Our results on the estimated cosmological parameters show that higher values of the baryonic and matter density and a lower value of the Hubble parameter (in comparison to the estimated values by assuming power-law PPS) is preferred by the data. However, the estimated cosmological parameters by assuming a free form of the PPS have an overlap at 1σ confidence level with the estimated values assuming the power-law form of PPS.

  10. Primordial power spectrum of tensor perturbations in Finsler spacetime

    NASA Astrophysics Data System (ADS)

    Li, Xin; Wang, Sai

    2016-02-01

    We first investigate the gravitational wave in the flat Finsler spacetime. In the Finslerian universe, we derive the perturbed gravitational field equation with tensor perturbations. The Finslerian background spacetime breaks rotational symmetry and induces parity violation. Then we obtain the modified primordial power spectrum of the tensor perturbations. The parity violation feature requires that the anisotropic effect contributes to the TT, TE, EE, BB angular correlation coefficients with l'=l+1 and TB, EB with l'=l. The numerical results show that the anisotropic contributions to the angular correlation coefficients depend on m, and TE and ET angular correlation coefficients are different.

  11. Power spectrum analysis for defect screening in integrated circuit devices

    DOEpatents

    Tangyunyong, Paiboon; Cole Jr., Edward I.; Stein, David J.

    2011-12-01

    A device sample is screened for defects using its power spectrum in response to a dynamic stimulus. The device sample receives a time-varying electrical signal. The power spectrum of the device sample is measured at one of the pins of the device sample. A defect in the device sample can be identified based on results of comparing the power spectrum with one or more power spectra of the device that have a known defect status.

  12. Halo Substructure and the Power Spectrum

    NASA Astrophysics Data System (ADS)

    Zentner, Andrew R.; Bullock, James S.

    2003-11-01

    We present a semianalytic model to investigate the merger history, destruction rate, and survival probability of substructure in hierarchically formed dark matter halos and use it to study the substructure content of halos as a function of input primordial power spectrum. For a standard cold dark matter ``concordance'' cosmology (ΛCDM n=1, σ8=0.95) we successfully reproduce the subhalo velocity function and radial distribution profile seen in N-body simulations and determine that the rate of merging and disruption peaks ~10-12 Gyr in the past for Milky Way-like halos, while surviving substructures are typically accreted within the last ~0-8 Gyr. We explore power spectra with normalizations and spectral ``tilts'' spanning the ranges σ8~=1-0.65 and n~=1-0.8, and include a ``running-index'' model with dn/dlnk=-0.03 similar to the best-fit model discussed in the first-year Wilkinson Microwave Anisotropy Probe (WMAP) report. We investigate spectra with truncated small-scale power, including a broken-scale inflation model and three warm dark matter cases with mW=0.75-3.0 keV. We find that the mass fraction in substructure is relatively insensitive to the tilt and overall normalization of the primordial power spectrum. All of the CDM-type models yield projected substructure mass fractions that are consistent with, but on the low side, of published estimates from strong lens systems: f9=0.4%-1.5% (64th percentile) for subhalos smaller than 109 Msolar within projected cylinders of radius r<10 kpc. Truncated models produce significantly smaller fractions, f9=0.02%-0.2% for mW~=1 keV, and are disfavored by lensing estimates. This suggests that lensing and similar probes can provide a robust test of the CDM paradigm and a powerful constraint on broken-scale inflation/warm particle masses, including masses larger than the ~1 keV upper limits of previous studies. We compare our predicted subhalo velocity functions with the dwarf satellite population of the Milky Way. Assuming

  13. On minimally parametric primordial power spectrum reconstruction and the evidence for a red tilt

    SciTech Connect

    Verde, Licia; Peiris, Hiranya E-mail: lverde@astro.princeton.edu

    2008-07-15

    The latest cosmological data seem to indicate a significant deviation from scale invariance of the primordial power spectrum when parameterized either by a power law or by a spectral index with non-zero 'running'. This deviation, by itself, serves as a powerful tool for discriminating among theories for the origin of cosmological structures such as inflationary models. Here, we use a minimally parametric smoothing spline technique to reconstruct the shape of the primordial power spectrum. This technique is well suited to searching for smooth features in the primordial power spectrum such as deviations from scale invariance or a running spectral index, although it would recover sharp features of high statistical significance. We use the WMAP three-year results in combination with data from a suite of higher resolution cosmic microwave background experiments (including the latest ACBAR 2008 release), as well as large-scale structure data from SDSS and 2dFGRS. We employ cross-validation to assess, using the data themselves, the optimal amount of smoothness in the primordial power spectrum consistent with the data. This minimally parametric reconstruction supports the evidence for a power law primordial power spectrum with a red tilt, but not for deviations from a power law power spectrum. Smooth variations in the primordial power spectrum are not significantly degenerate with the other cosmological parameters.

  14. Power spectrum of the fluctuation of Chebyshev's prime counting function

    NASA Astrophysics Data System (ADS)

    Lan, Boon Leong; Yong, Shaohen

    2006-02-01

    The one-sided power spectrum of the fluctuation of Chebyshev's weighted prime counting function is numerically estimated based on samples of the fluctuating function of different sizes. The power spectrum is also estimated analytically for large frequency based on Riemann hypothesis and the exact formula for the fluctuating function in terms of all the non-trivial Riemann zeroes. Our analytical estimate is consistent with our numerical estimate of a 1/f2 power spectrum.

  15. Review of Cosmic Background Radiation Spectrum Measurements:Limits on Distortions, Energy Release, and Cosmological Processes

    SciTech Connect

    Smoot, G.F.

    1986-01-01

    This paper reviews the three major cosmic microwave background radiation (CMBR) spectrum measurement programs conducted and published since the last (XVII) IAU General Assembly. The results are consistent with a Planckian spectrum with temperature 2.72 {+-} 0.03 K spanning a wavelength range of 0.1 to 12 cm. Limits on possible distortions and implications are outlined. Ongoing and future measurements are discussed.

  16. Review of cosmic background radiation spectrum measurements: limits on distortions, energy release, and cosmological processes

    SciTech Connect

    Smoot, G.F.

    1986-01-01

    This paper reviews the three major cosmic microwave background radiation (CMBR) spectrum measurement programs conducted and published since the last (XVII) IAU General Assembly. The results are consistent with a Planckian spectrum with temperature 2.72 +- 0.03 K spanning a wavelength range of 0.1 to 12 cm. Limits on possible distortions and implications are outlined. Ongoing and future measurements are discussed.

  17. Just enough inflation: power spectrum modifications at large scales

    SciTech Connect

    Cicoli, Michele; Downes, Sean; Dutta, Bhaskar; Pedro, Francisco G.; Westphal, Alexander E-mail: ssdownes@phys.ntu.edu.tw E-mail: francisco.pedro@desy.de

    2014-12-01

    We show that models of 'just enough' inflation, where the slow-roll evolution lasted only 50- 60 e-foldings, feature modifications of the CMB power spectrum at large angular scales. We perform a systematic analytic analysis in the limit of a sudden transition between any possible non-slow-roll background evolution and the final stage of slow-roll inflation. We find a high degree of universality since most common backgrounds like fast-roll evolution, matter or radiation-dominance give rise to a power loss at large angular scales and a peak together with an oscillatory behaviour at scales around the value of the Hubble parameter at the beginning of slow-roll inflation. Depending on the value of the equation of state parameter, different pre-inflationary epochs lead instead to an enhancement of power at low ℓ, and so seem disfavoured by recent observational hints for a lack of CMB power at ℓ∼< 40. We also comment on the importance of initial conditions and the possibility to have multiple pre-inflationary stages.

  18. THE ATACAMA COSMOLOGY TELESCOPE: A MEASUREMENT OF THE PRIMORDIAL POWER SPECTRUM

    SciTech Connect

    Hlozek, Renee; Dunkley, Joanna; Addison, Graeme; Appel, John William; Das, Sudeep; Essinger-Hileman, Thomas; Fowler, Joseph W.; Hajian, Amir; Hincks, Adam D.; Bond, J. Richard; Carvalho, C. Sofia; Devlin, Mark J.; Klein, Jeff; Duenner, Rolando; Gallardo, Patricio; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hughes, John P.; Irwin, Kent D.; and others

    2012-04-10

    We present constraints on the primordial power spectrum of adiabatic fluctuations using data from the 2008 Southern Survey of the Atacama Cosmology Telescope (ACT) in combination with measurements from the Wilkinson Microwave Anisotropy Probe and a prior on the Hubble constant. The angular resolution of ACT provides sensitivity to scales beyond l = 1000 for resolution of multiple peaks in the primordial temperature power spectrum, which enables us to probe the primordial power spectrum of adiabatic scalar perturbations with wavenumbers up to k {approx_equal} 0.2 Mpc{sup -1}. We find no evidence for deviation from power-law fluctuations over two decades in scale. Matter fluctuations inferred from the primordial temperature power spectrum evolve over cosmic time and can be used to predict the matter power spectrum at late times; we illustrate the overlap of the matter power inferred from cosmic microwave background measurements (which probe the power spectrum in the linear regime) with existing probes of galaxy clustering, cluster abundances, and weak-lensing constraints on the primordial power. This highlights the range of scales probed by current measurements of the matter power spectrum.

  19. Geometric biases in power-spectrum measurements

    NASA Astrophysics Data System (ADS)

    Samushia, L.; Branchini, E.; Percival, W. J.

    2015-10-01

    The observed distribution of galaxies has local transverse isotropy around the line of sight (LOS) with respect to the observer. The difference in the statistical clustering signal along and across the LOS encodes important information about the geometry of the Universe, its expansion rate and the rate of growth of structure within it. Because the LOS varies across a survey, the standard fast Fourier transform (FFT) based methods of measuring the anisotropic power spectrum (APS) cannot be used for surveys with wide observational footprint, other than to measure the monopole moment. We derive a simple analytic formula to quantify the bias for higher order Legendre moments, and we demonstrate that it is scale independent for a simple survey model, and depends only on the observed area. We derive a similar numerical correction formula for recently proposed alternative estimators of the APS that are based on summing over galaxies rather than using an FFT, and can therefore incorporate a varying LOS. We demonstrate that their bias depends on scale but not on the observed area. For a quadrupole the bias is always less than 1 per cent for k > 0.01 h Mpc^{-1} at z > 0.32. For a hexadecapole the bias is below 5 per cent for k > 0.05 h Mpc^{-1} at z > 0.32.

  20. Low-Frequency Measurments of the Cosmic Background RadiationSpectrum

    SciTech Connect

    Smoot, G.F.; De Amici, G.; Friedman, S.D.; Witebsky, C.; Sironi,G.; Bonelli, G.; Mandolesi, N.; Cortiglioni, S.; Morigi, G.; Partridge,R.B.; Danese, L.; De Zotti, G.

    1984-11-01

    The long-wavelength spectrum of the cosmic background radiation has been measured at five wavelengths (0.33, 0.9, 3.0, 6.3, and 12.0 cm). These measurements represent a continuation of the work reported by Smoot et al. (1983). The combine results have a weighted average of 2.73 {+-} 0.05 K and are consistent with past measurements. They limit the possible Compton distortion of the Cosmic Background Radiation spectrum to less than 8%.

  1. Angular power spectrum of the FastICA CMB component from BEAST data

    NASA Astrophysics Data System (ADS)

    Donzelli, Simona

    We present the angular power spectrum of the CMB component extracted with FASTICA from the data of the Background Emission Anisotropy Scanning Telescope (BEAST), operating in Q two input channels FASTICA returns two possible independent components. We found that one of them has an unphysical spectral behaviour, due to the poor S/N ratio, while the other is a reasonable CMB component. After a detailed calibration procedure based on Monte-Carlo (MC) simulations we extracted the angular power spectrum for the identified CMB component and found a very good agreement with the already published BEAST CMB angular power spectrum

  2. Estimating the angular power spectrum of z > 2 BOSS QSOs using the MASTER method

    NASA Astrophysics Data System (ADS)

    Maldonado, Felipe; Huffenberger, Kevin; Rotti, Aditya

    2016-01-01

    We implement the MASTER method for angular power spectrum estimation and apply it to z > 2 quasars selected by the SDSS-III BOSS survey. Quasars are filtered for completeness and bad spectra, and include ~100,000 QSOs in the CORE sample and ~75,000 in the non-uniform BONUS sample. We estimate the angular power spectrum in redshift shells to constrain the matter power spectrum and quasar properties. In the future, we will jointly analyze overlapping Cosmic Microwave Background lensing maps from the Atacama Cosmology Telescope to place further constraints.

  3. Wind speed power spectrum analysis for Bushland, Texas

    SciTech Connect

    Eggleston, E.D.

    1996-12-31

    Numerous papers and publications on wind turbulence have referenced the wind speed spectrum presented by Isaac Van der Hoven in his article entitled Power Spectrum of Horizontal Wind Speed Spectrum in the Frequency Range from 0.0007 to 900 Cycles per Hour. Van der Hoven used data measured at different heights between 91 and 125 meters above the ground, and represented the high frequency end of the spectrum with data from the peak hour of hurricane Connie. These facts suggest we should question the use of his power spectrum in the wind industry. During the USDA - Agricultural Research Service`s investigation of wind/diesel system power storage, using the appropriate wind speed power spectrum became a significant issue. We developed a power spectrum from 13 years of hourly average data, 1 year of 5 minute average data, and 2 particularly gusty day`s 1 second average data all collected at a height of 10 meters. While the general shape is similar to the Van der Hoven spectrum, few of his peaks were found in the Bushland spectrum. While higher average wind speeds tend to suggest higher amplitudes in the high frequency end of the spectrum, this is not always true. Also, the high frequency end of the spectrum is not accurately described by simple wind statistics such as standard deviation and turbulence intensity. 2 refs., 5 figs., 1 tab.

  4. Estimating the Crustal Power Spectrum From Vector Magsat Data: Crustal Power Spectrum

    NASA Technical Reports Server (NTRS)

    Lowe, David A. J.; Parker, Robert L.; Purucker, Michael E.; Constable, Catherine G.

    2000-01-01

    The Earth's magnetic field can be subdivided into core and crustal components and we seek to characterize the crustal part through its spatial power spectrum (R(sub l)). We process vector Magsat data to isolate the crustal field and then invert power spectral densities of flight-local components along-track for R(sub l) following O'Brien et al. [1999]. Our model (LPPC) is accurate up to approximately degree 45 (lambda=900 km) - this is the resolution limit of our data and suggests that global crustal anomaly maps constructed from vector Magsat data should not contain features with wavelengths less than 900 km. We find continental power spectra to be greater than oceanic ones and attribute this to the relative thicknesses of continental and oceanic crust.

  5. EEG Power Spectrum Analysis in Children with ADHD

    PubMed Central

    Kamida, Akira; Shimabayashi, Kenta; Oguri, Masayoshi; Takamori, Toshihiro; Ueda, Naoyuki; Koyanagi, Yuki; Sannomiya, Naoko; Nagira, Haruki; Ikunishi, Saeko; Hattori, Yuiko; Sato, Kengo; Fukuda, Chisako; Hirooka, Yasuaki; Maegaki, Yoshihiro

    2016-01-01

    Background Attention deficit disorder/hyperactivity disorder (ADHD) is a pathological condition that is not fully understood. In this study, we investigated electroencephalographic (EEG) power differences between children with ADHD and healthy control children. Methods EEGs were recorded as part of routine medical care received by 80 children with ADHD aged 4–15 years at the Department of Pediatric Neurology in Tottori University Hospital. Additionally, we recorded in 59 control children aged 4–15 years after obtaining informed consent. Specifically, awake EEG signals were recorded from each child using the international 10–20 system, and we used ten 3-s epochs on the EEG power spectrum to calculate the powers of individual EEG frequency bands. Results The powers of different EEG bands were significantly higher in the frontal brain region of those in the ADHD group compared with the control group. In addition, the power of the beta band in the ADHD group was significantly higher in all brain regions, except for the occipital region, compared with control children. With regard to developmental changes, the power of the alpha band in the occipital region showed an age-dependent decrease in both groups, with slightly lower power in the ADHD group. Additionally, the intergroup difference decreased in children aged 11 years or older. As with the alpha band in the occipital region, the beta band in the frontal region showed an age-dependent decrease in both groups. Unlike the alpha band, the power of the beta band was higher in the ADHD group than in the control group for children of all ages. Conclusion The observed intergroup differences in EEG power may provide insight into the brain function of children with ADHD. PMID:27493489

  6. Effects of Background Noise on Cortical Encoding of Speech in Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Russo, Nicole; Zecker, Steven; Trommer, Barbara; Chen, Julia; Kraus, Nina

    2009-01-01

    This study provides new evidence of deficient auditory cortical processing of speech in noise in autism spectrum disorders (ASD). Speech-evoked responses (approximately 100-300 ms) in quiet and background noise were evaluated in typically-developing (TD) children and children with ASD. ASD responses showed delayed timing (both conditions) and…

  7. Power spectrum and non-Gaussianities in anisotropic inflation

    SciTech Connect

    Dey, Anindya; Kovetz, Ely D.; Paban, Sonia E-mail: elykovetz@gmail.com

    2014-06-01

    We study the planar regime of curvature perturbations for single field inflationary models in an axially symmetric Bianchi I background. In a theory with standard scalar field action, the power spectrum for such modes has a pole as the planarity parameter goes to zero. We show that constraints from back reaction lead to a strong lower bound on the planarity parameter for high-momentum planar modes and use this bound to calculate the signal-to-noise ratio of the anisotropic power spectrum in the CMB, which in turn places an upper bound on the Hubble scale during inflation allowed in our model. We find that non-Gaussianities for these planar modes are enhanced for the flattened triangle and the squeezed triangle configurations, but show that the estimated values of the f{sub NL} parameters remain well below the experimental bounds from the CMB for generic planar modes (other, more promising signatures are also discussed). For a standard action, f{sub NL} from the squeezed configuration turns out to be larger compared to that from the flattened triangle configuration in the planar regime. However, in a theory with higher derivative operators, non-Gaussianities from the flattened triangle can become larger than the squeezed configuration in a certain limit of the planarity parameter.

  8. Terahertz spectrum analyzer based on frequency and power measurement.

    PubMed

    Yee, Dae-Su; Jang, Yudong; Kim, Youngchan; Seo, Dae-Cheol

    2010-08-01

    We demonstrate a terahertz (THz) spectrum analyzer based on frequency and power measurement. A power spectrum of a continuous THz wave is measured through optical heterodyne detection using an electromagnetic THz frequency comb and a bolometer and power measurement using a bolometer with a calibrated responsivity. The THz spectrum analyzer has a frequency precision of 1x10(-11), a frequency resolution of 1Hz, a frequency band up to 1.7THz, and an optical noise equivalent power of approximately 1 pW/Hz(1/2). PMID:20680048

  9. Background radiation measurements at high power research reactors

    NASA Astrophysics Data System (ADS)

    Ashenfelter, J.; Balantekin, B.; Baldenegro, C. X.; Band, H. R.; Barclay, G.; Bass, C. D.; Berish, D.; Bowden, N. S.; Bryan, C. D.; Cherwinka, J. J.; Chu, R.; Classen, T.; Davee, D.; Dean, D.; Deichert, G.; Dolinski, M. J.; Dolph, J.; Dwyer, D. A.; Fan, S.; Gaison, J. K.; Galindo-Uribarri, A.; Gilje, K.; Glenn, A.; Green, M.; Han, K.; Hans, S.; Heeger, K. M.; Heffron, B.; Jaffe, D. E.; Kettell, S.; Langford, T. J.; Littlejohn, B. R.; Martinez, D.; McKeown, R. D.; Morrell, S.; Mueller, P. E.; Mumm, H. P.; Napolitano, J.; Norcini, D.; Pushin, D.; Romero, E.; Rosero, R.; Saldana, L.; Seilhan, B. S.; Sharma, R.; Stemen, N. T.; Surukuchi, P. T.; Thompson, S. J.; Varner, R. L.; Wang, W.; Watson, S. M.; White, B.; White, C.; Wilhelmi, J.; Williams, C.; Wise, T.; Yao, H.; Yeh, M.; Yen, Y.-R.; Zhang, C.; Zhang, X.

    2016-01-01

    Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the background fields encountered. The general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.

  10. Background radiation measurements at high power research reactors

    SciTech Connect

    Ashenfelter, J.; Yeh, M.; Balantekin, B.; Baldenegro, C. X.; Band, H. R.; Barclay, G.; Bass, C. D.; Berish, D.; Bowden, N. S.; Bryan, C. D.; Cherwinka, J. J.; Chu, R.; Classen, T.; Davee, D.; Dean, D.; Deichert, G.; Dolinski, M. J.; Dolph, J.; Dwyer, D. A.; Fan, S.; Gaison, J. K.; Galindo-Uribarri, A.; Gilje, K.; Glenn, A.; Green, M.; Han, K.; Hans, S.; Heeger, K. M.; Heffron, B.; Jaffe, D. E.; Kettell, S.; Langford, T. J.; Littlejohn, B. R.; Martinez, D.; McKeown, R. D.; Morrell, S.; Mueller, P. E.; Mumm, H. P.; Napolitano, J.; Norcini, D.; Pushin, D.; Romero, E.; Rosero, R.; Saldana, L.; Seilhan, B. S.; Sharma, R.; Stemen, N. T.; Surukuchi, P. T.; Thompson, S. J.; Varner, R. L.; Wang, W.; Watson, S. M.; White, B.; White, C.; Wilhelmi, J.; Williams, C.; Wise, T.; Yao, H.; Yen, Y. -R.; Zhang, C.; Zhang, X.

    2015-10-23

    Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the background fields encountered. Furthermore, the general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.

  11. Power spectrum, correlation function, and tests for luminosity bias in the CfA redshift survey

    NASA Technical Reports Server (NTRS)

    Park, Changbom; Vogeley, Michael S.; Geller, Margaret J.; Huchra, John P.

    1994-01-01

    We describe and apply a method for directly computing the power spectrum for the galaxy distribution in the extension of the Center for Astrophysics Redshift Survey. Tests show that our technique accurately reproduces the true power spectrum for k greater than 0.03 h Mpc(exp -1). The dense sampling and large spatial coverage of this survey allow accurate measurement of the redshift-space power spectrum on scales from 5 to approximately 200 h(exp -1) Mpc. The power spectrum has slope n approximately equal -2.1 on small scales (lambda less than or equal 25 h(exp -1) Mpc) and n approximately -1.1 on scales 30 less than lambda less than 120 h(exp -1) Mpc. On larger scales the power spectrum flattens somewhat, but we do not detect a turnover. Comparison with N-body simulations of cosmological models shows that an unbiased, open universe CDM model (OMEGA h = 0.2) and a nonzero cosmological constant (CDM) model (OMEGA h = 0.24, lambda(sub zero) = 0.6, b = 1.3) match the CfA power spectrum over the wavelength range we explore. The standard biased CDM model (OMEGA h = 0.5, b = 1.5) fails (99% significance level) because it has insufficient power on scales lambda greater than 30 h(exp -1) Mpc. Biased CDM with a normalization that matches the Cosmic Microwave Background (CMB) anisotropy (OMEGA h = 0.5, b = 1.4, sigma(sub 8) (mass) = 1) has too much power on small scales to match the observed galaxy power spectrum. This model with b = 1 matches both Cosmic Background Explorer Satellite (COBE) and the small-scale power spect rum but has insufficient power on scales lambda approximately 100 h(exp -1) Mpc. We derive a formula for the effect of small-scale peculiar velocities on the power spectrum and combine this formula with the linear-regime amplification described by Kaiser to compute an estimate of the real-space power spectrum. Two tests reveal luminosity bias in the galaxy distribution: First, the amplitude of the pwer spectrum is approximately 40% larger for the brightest

  12. MEASUREMENT OF COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRA FROM TWO YEARS OF BICEP DATA

    SciTech Connect

    Chiang, H. C.; Barkats, D.; Bock, J. J.; Hristov, V. V.; Jones, W. C.; Kovac, J. M.; Lange, A. E.; Mason, P. V.; Matsumura, T.; Ade, P. A. R.; Battle, J. O.; Dowell, C. D.; Nguyen, H. T.; Bierman, E. M.; Keating, B. G.; Duband, L.; Hivon, E. F.; Holzapfel, W. L.; Kuo, C. L.; Leitch, E. M.

    2010-03-10

    Background Imaging of Cosmic Extragalactic Polarization (BICEP) is a bolometric polarimeter designed to measure the inflationary B-mode polarization of the cosmic microwave background (CMB) at degree angular scales. During three seasons of observing at the South Pole (2006 through 2008), BICEP mapped {approx}2% of the sky chosen to be uniquely clean of polarized foreground emission. Here, we present initial results derived from a subset of the data acquired during the first two years. We present maps of temperature, Stokes Q and U, E and B modes, and associated angular power spectra. We demonstrate that the polarization data are self-consistent by performing a series of jackknife tests. We study potential systematic errors in detail and show that they are sub-dominant to the statistical errors. We measure the E-mode angular power spectrum with high precision at 21 <= l <= 335, detecting for the first time the peak expected at l {approx} 140. The measured E-mode spectrum is consistent with expectations from a LAMBDACDM model, and the B-mode spectrum is consistent with zero. The tensor-to-scalar ratio derived from the B-mode spectrum is r = 0.02{sup +0.31}{sub -0.26}, or r < 0.72 at 95% confidence, the first meaningful constraint on the inflationary gravitational wave background to come directly from CMB B-mode polarization.

  13. The REFLEX II galaxy cluster survey: power spectrum analysis

    NASA Astrophysics Data System (ADS)

    Balaguera-Antolínez, A.; Sánchez, Ariel G.; Böhringer, H.; Collins, C.; Guzzo, L.; Phleps, S.

    2011-05-01

    We present the power spectrum of galaxy clusters measured from the new ROSAT-ESO Flux-Limited X-Ray (REFLEX II) galaxy cluster catalogue. This new sample extends the flux limit of the original REFLEX catalogue to 1.8 × 10-12 erg s-1 cm-2, yielding a total of 911 clusters with ≥94 per cent completeness in redshift follow-up. The analysis of the data is improved by creating a set of 100 REFLEX II-catalogue-like mock galaxy cluster catalogues built from a suite of large-volume Λ cold dark matter (ΛCDM) N-body simulations (L-BASICC II). The measured power spectrum is in agreement with the predictions from a ΛCDM cosmological model. The measurements show the expected increase in the amplitude of the power spectrum with increasing X-ray luminosity. On large scales, we show that the shape of the measured power spectrum is compatible with a scale-independent bias and provide a model for the amplitude that allows us to connect our measurements with a cosmological model. By implementing a luminosity-dependent power-spectrum estimator, we observe that the power spectrum measured from the REFLEX II sample is weakly affected by flux-selection effects. The shape of the measured power spectrum is compatible with a featureless power spectrum on scales k > 0.01 h Mpc-1 and hence no statistically significant signal of baryonic acoustic oscillations can be detected. We show that the measured REFLEX II power spectrum displays signatures of non-linear evolution.

  14. Reference MWA EoR Power Spectrum analysis

    NASA Astrophysics Data System (ADS)

    Hazelton, Bryna; Pober, Jonathan; Beardsley, Adam; Morales, Miguel F.; Sullivan, Ian S.; MWA Collaboration

    2015-01-01

    Observations of the Epoch of Reionization using redshifted 21cm HI emission promise to provide sensitive new cosmological constraints in the next few years. The current generation of HI EoR telescopes are targeting a statistical detection of the EoR in the power spectrum of the 21cm emission. The principal challenge lies in extracting the faint cosmological signal in the face of bright foregrounds and instrumental systematics that threaten to overwhelm it.We present the UW EoR power spectrum code, the reference code for the MWA and the first power spectrum analysis to analytically propagate the error bars through the full data analysis pipeline. We demonstrate the sensitivity of the power spectrum as a diagnostic tool for identifying subtle systematics and show power spectra of the first season of MWA observations.

  15. The Murchison Widefield Array 21 cm Power Spectrum Analysis Methodology

    NASA Astrophysics Data System (ADS)

    Jacobs, Daniel C.; Hazelton, B. J.; Trott, C. M.; Dillon, Joshua S.; Pindor, B.; Sullivan, I. S.; Pober, J. C.; Barry, N.; Beardsley, A. P.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Carroll, P.; Corey, B. E.; de Oliveira-Costa, A.; Emrich, D.; Ewall-Wice, A.; Feng, L.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hewitt, J. N.; Hurley-Walker, N.; Johnston-Hollitt, M.; Kaplan, D. L.; Kasper, J. C.; Kim, HS; Kratzenberg, E.; Lenc, E.; Line, J.; Loeb, A.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Neben, A. R.; Thyagarajan, N.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Paul, S.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Udaya Shankar, N.; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Tegmark, M.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S. B.

    2016-07-01

    We present the 21 cm power spectrum analysis approach of the Murchison Widefield Array Epoch of Reionization project. In this paper, we compare the outputs of multiple pipelines for the purpose of validating statistical limits cosmological hydrogen at redshifts between 6 and 12. Multiple independent data calibration and reduction pipelines are used to make power spectrum limits on a fiducial night of data. Comparing the outputs of imaging and power spectrum stages highlights differences in calibration, foreground subtraction, and power spectrum calculation. The power spectra found using these different methods span a space defined by the various tradeoffs between speed, accuracy, and systematic control. Lessons learned from comparing the pipelines range from the algorithmic to the prosaically mundane; all demonstrate the many pitfalls of neglecting reproducibility. We briefly discuss the way these different methods attempt to handle the question of evaluating a significant detection in the presence of foregrounds.

  16. Is natural background or radiation from nuclear power plants leukemogenic

    SciTech Connect

    Cronkite, E.P.

    1989-01-01

    The objective in this review is to provide some facts about normal hemopoietic cell proliferation relevant to leukemogenesis, physical, chemical, and biological facts about radiation effects with the hope that each person will be able to decide for themselves whether background radiation or emissions from nuclear power plants and facilities significantly add to the spontaneous leukemia incidence. 23 refs., 1 tab.

  17. The grand unified photon spectrum: A coherent view of the diffuse extragalactic background radiation

    NASA Technical Reports Server (NTRS)

    Ressell, M. Ted; Turner, Michael S.

    1989-01-01

    The spectrum of diffuse extragalactic background radiation (DEBRA) at wavelengths from 10(exp 5) to 10(exp -24) cm is presented in a coherent fashion. Each wavelength region, from the radio to ultra-high energy photons and cosmic rays, is treated both separately and as part of the grand unified photon spectrum (GUPS). A discussion of, and references to, the relevant literature for each wavelength region is included. This review should provide a useful tool for those interested in diffuse backgrounds, the epoch of galaxy formation, astrophysical/cosmological constraints to particle properties, exotic early Universe processes, and many other astrophysical and cosmological enterprises. As a worked example, researchers derive the cosmological constraints to an unstable-neutrino spies (with arbitrary branching ratio to a radiative decay mode) that follow from the GUPS.

  18. Cosmic microwave background dipole spectrum measured by the COBE FIRAS instrument

    NASA Technical Reports Server (NTRS)

    Fixsen, D. J.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Isaacman, R. B.; Mather, J. C.; Meyer, S. S.; Noerdlinger, P. D.; Shafer, R. A.; Weiss, R.

    1994-01-01

    The Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on the Cosmic Background Explorer (COBE) has determined the dipole spectrum of the cosmic microwave background radiation (CMBR) from 2 to 20/cm. For each frequency the signal is decomposed by fitting to a monopole, a dipole, and a Galactic template for approximately 60% of the sky. The overall dipole spectrum fits the derivative of a Planck function with an amplitude of 3.343 +/- 0.016 mK (95% confidence level), a temperature of 2.714 +/- 0.022 K (95% confidence level), and an rms deviation of 6 x 10(exp -9) ergs/sq cm/s/sr cm limited by a detector and cosmic-ray noise. The monopole temperature is consistent with that determined by direct measurement in the accompanying article by Mather et al.

  19. Spectrum management considerations of adaptive power control in satellite networks

    NASA Technical Reports Server (NTRS)

    Sawitz, P.; Sullivan, T.

    1983-01-01

    Adaptive power control concepts for the compensation of rain attenuation are considered for uplinks and downlinks. The performance of example power-controlled and fixed-EIRP uplinks is compared in terms of C/Ns and C/Is. Provisional conclusions are drawn with regard to the efficacy of uplink and downlink power control orbit/spectrum utilization efficiency.

  20. Monte-Carlo Simulations of the Suzaku-XRS Residual Background Spectrum

    NASA Technical Reports Server (NTRS)

    Perinati, E.; Kilbourne, Caroline Anne; Colasanti, L.; Lotti, S.; Macculi, C.; Piro, L.; Mineo, T.; Mitsuda, K.; Bonardi, A.; Santangelo, A.

    2012-01-01

    Cryogenic micro-calorimeters are suitable to detect small amounts of energy deposited by electromagnetic and nuclear interactions, which makes them attractive in a variety of applications on ground and in space. The only X-ray microcalorimeter that operated in orbit to date is the X-Ray Spectrometer on-board of the Japanese Suzaku satellite. We discuss the analysis of the components of its residual background spectrum with the support of Monte-Carlo simulations.

  1. Low Frequency Measurement of the Spectrum of the Cosmic Background Radiation

    DOE R&D Accomplishments Database

    Smoot, G. F.; De Amici, G.; Friedman, S. D.; Witebsky, C.; Mandolesi, N.; Partridge, R. B.; Sironi, G.; Danese, L.; De Zotti, G.

    1983-06-01

    We have made measurements of the cosmic background radiation spectrum at 5 wavelengths (0.33, 0.9, 3, 6.3, and 12 cm) using radiometers with wavelength-scaled corrugated horn antennas having very low sidelobes. A single large-mouth (0.7 m diameter) liquid-helium-cooled absolute reference load was used for all five radiometers. The results of the observations are consistent with previous measurements and represent a significant improvement in accuracy.

  2. Background radiation measurements at high power research reactors

    DOE PAGESBeta

    Ashenfelter, J.; Yeh, M.; Balantekin, B.; Baldenegro, C. X.; Band, H. R.; Barclay, G.; Bass, C. D.; Berish, D.; Bowden, N. S.; Bryan, C. D.; et al

    2015-10-23

    Research reactors host a wide range of activities that make use of the intense neutron fluxes generated at these facilities. Recent interest in performing measurements with relatively low event rates, e.g. reactor antineutrino detection, at these facilities necessitates a detailed understanding of background radiation fields. Both reactor-correlated and naturally occurring background sources are potentially important, even at levels well below those of importance for typical activities. Here we describe a comprehensive series of background assessments at three high-power research reactors, including γ-ray, neutron, and muon measurements. For each facility we describe the characteristics and identify the sources of the backgroundmore » fields encountered. Furthermore, the general understanding gained of background production mechanisms and their relationship to facility features will prove valuable for the planning of any sensitive measurement conducted therein.« less

  3. MEASURING THE JET POWER OF FLAT-SPECTRUM RADIO QUASARS

    SciTech Connect

    Shabala, S. S.; Santoso, J. S.; Godfrey, L. E. H.

    2012-09-10

    We use frequency-dependent position shifts of flat-spectrum radio cores to estimate the kinetic power of active galactic nucleus (AGN) jets. We find a correlation between the derived jet powers and AGN narrow-line luminosity, consistent with the well-known relation for radio galaxies and steep spectrum quasars. This technique can be applied to intrinsically weak jets even at high redshift.

  4. Spline-based Study of the Extragalactic Background Light Spectrum using Gamma-Ray Observations

    NASA Astrophysics Data System (ADS)

    Bose, Anoushka; Rathmann-Bloch, Julia; Biteau, Jonathan; Williams, David A.

    2016-01-01

    The extragalactic background light (EBL) is made of all the light emitted by stars and galaxies throughout cosmic history. Expanding on the work of Biteau & Williams 2015, we develop a novel natural cubic spline model of the local EBL spectrum and constrain its parameters using the gamma-ray spectra of 38 blazars measured in the high-energy (HE, 0.1 to 100 GeV) and very-high-energy (VHE, 0.1 to 20 TeV) bands. Starting from this best-fit model, we then study the so-called "delta gamma" (ΔΓ) observable, defined as the difference between the VHE and HE photon indices. This second study is focused on a subset of nine BL Lac objects. The application of a scaling factor to the cosmic optical background (0.1 - 10 nm) significantly impacts the predicted ΔΓ as a function of redshift, whereas a similar modification of the cosmic infrared background (10 - 1000 nm) has no impact. We conclude that the simple delta gamma approach can only constrain part of the EBL spectrum, while a detailed study of the spectra, such as presented in the first part of this research, is needed to constrain the cosmic infrared background.

  5. On Removing Interloper Contamination from Intensity Mapping Power Spectrum Measurements

    NASA Astrophysics Data System (ADS)

    Lidz, Adam; Taylor, Jessie

    2016-07-01

    Line intensity mapping experiments seek to trace large-scale structures by measuring the spatial fluctuations in the combined emission, in some convenient spectral line, from individually unresolved galaxies. An important systematic concern for these surveys is line confusion from foreground or background galaxies emitting in other lines that happen to lie at the same observed frequency as the “target” emission line of interest. We develop an approach to separate this “interloper” emission at the power spectrum level. If one adopts the redshift of the target emission line in mapping from observed frequency and angle on the sky to co-moving units, the interloper emission is mapped to the wrong co-moving coordinates. Because the mapping is different in the line of sight and transverse directions, the interloper contribution to the power spectrum becomes anisotropic, especially if the interloper and target emission are at widely separated redshifts. This distortion is analogous to the Alcock–Paczynski test, but here the warping arises from assuming the wrong redshift rather than an incorrect cosmological model. We apply this to the case of a hypothetical [C ii] emission survey at z∼ 7 and find that the distinctive interloper anisotropy can, in principle, be used to separate strong foreground CO emission fluctuations. In our models, however, a significantly more sensitive instrument than currently planned is required, although there are large uncertainties in forecasting the high-redshift [C ii] emission signal. With upcoming surveys, it may nevertheless be useful to apply this approach after first masking pixels suspected of containing strong interloper contamination.

  6. On Removing Interloper Contamination from Intensity Mapping Power Spectrum Measurements

    NASA Astrophysics Data System (ADS)

    Lidz, Adam; Taylor, Jessie

    2016-07-01

    Line intensity mapping experiments seek to trace large-scale structures by measuring the spatial fluctuations in the combined emission, in some convenient spectral line, from individually unresolved galaxies. An important systematic concern for these surveys is line confusion from foreground or background galaxies emitting in other lines that happen to lie at the same observed frequency as the “target” emission line of interest. We develop an approach to separate this “interloper” emission at the power spectrum level. If one adopts the redshift of the target emission line in mapping from observed frequency and angle on the sky to co-moving units, the interloper emission is mapped to the wrong co-moving coordinates. Because the mapping is different in the line of sight and transverse directions, the interloper contribution to the power spectrum becomes anisotropic, especially if the interloper and target emission are at widely separated redshifts. This distortion is analogous to the Alcock–Paczynski test, but here the warping arises from assuming the wrong redshift rather than an incorrect cosmological model. We apply this to the case of a hypothetical [C ii] emission survey at z˜ 7 and find that the distinctive interloper anisotropy can, in principle, be used to separate strong foreground CO emission fluctuations. In our models, however, a significantly more sensitive instrument than currently planned is required, although there are large uncertainties in forecasting the high-redshift [C ii] emission signal. With upcoming surveys, it may nevertheless be useful to apply this approach after first masking pixels suspected of containing strong interloper contamination.

  7. Primordial black holes under the double inflationary power spectrum

    NASA Astrophysics Data System (ADS)

    Kim, Hee Il

    2000-09-01

    Recently, it has been shown that the primordial black holes (PBHs) produced by near critical collapse in the expanding universe have a scaling mass relation similar to that of black holes produced in asymptotically flat spacetime. Distinct from PBHs formed with a mass about the size of the horizon mass (type I), the PBHs with the scaling relation (type II) can be created with a range of masses at a given formation time. In general, only the case in which the PBH formation is concentrated at one epoch has been considered. However, it is expected that PBH formation is possible over a broad range of epochs if the density fluctuation has a rather large amplitude and smooth scale dependence. In this paper, we study the PBH formation for both types assuming the power spectrum of double inflationary models in which the small scale fluctuations could have large amplitudes independent of the CMBR anisotropy. The mass spectrum of type II PBHs is newly constructed without limiting the PBH formation period. The double inflationary power spectrum is assumed to be of double simple power law which are smoothly connected. Under the assumed power spectrum, the accumulation of small PBHs formed at later times is important and the mass range is significantly broadened for both types. The PBH mass spectra are far smoother than the observed MACHO spectrum due to our assumption of a smooth spectrum. In order to fit the observation, a more spiky spectrum is required.

  8. The matter power spectrum of dark energy models and the Harrison-Zel'dovich prescription

    SciTech Connect

    Duran, Ivan; Pavón, Diego; Atrio-Barandela, Fernando E-mail: atrio@usal.es

    2012-04-01

    According to the Harrison-Zel'dovich prescription, the amplitude of matter density perturbations at horizon crossing is the same at all scales. Based on this prescription, we show how to construct the matter power spectrum of generic dark energy models from the power spectrum of a ΛCDM model without the need of solving in full the dynamical equations describing the evolution of all energy density perturbations. Our approach allows to make model predictions of observables that can be expressed in terms of the matter power spectrum alone, such as the amplitude of matter fluctuations, peculiar velocities, cosmic microwave background temperature anisotropies on large angular scales or the weak lensing convergence spectrum. Then, models that have been tested only at the background level using the rate of the expansion of the Universe can now be tested using data on gravitational clustering and on large scale structure. This method can save a lot of effort in checking the validity of dark energy models. As an example of the accurateness of the approximation used, we compute the power spectrum of different dark energy models with constant equation of state parameter (w{sub DE} = −0.1, -0.5 and -0.8, ruled out by observations but easy to compare to numerical solutions) using our methodology and discuss the constraints imposed by the low multipoles of the cosmic microwave background.

  9. CMB anisotropy power spectrum using linear combinations of WMAP maps

    SciTech Connect

    Saha, Rajib; Prunet, Simon; Jain, Pankaj; Souradeep, Tarun

    2008-07-15

    In recent years the goal of estimating different cosmological parameters precisely has set new challenges in the effort to accurately measure the angular power spectrum of the CMB. This has required removal of foreground contamination as well as detector noise bias with reliability and precision. Recently, a novel, model-independent method for the estimation of the CMB angular power spectrum solely from multifrequency observations has been proposed and implemented on the first year WMAP data by Saha et al. 2006. All previous estimates of the power spectrum of the CMB are based upon foreground templates using data sets from different experiments. However, our methodology demonstrates that the CMB angular spectrum can be reliably estimated with precision from a self-contained analysis of the WMAP data. In this work we provide a detailed description of this method. We also study and identify the biases present in our power spectrum estimate. We apply our methodology to extract the power spectrum from the WMAP data.

  10. The wedge bias in reionization 21-cm power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Jensen, Hannes; Majumdar, Suman; Mellema, Garrelt; Lidz, Adam; Iliev, Ilian T.; Dixon, Keri L.

    2016-02-01

    A proposed method for dealing with foreground emission in upcoming 21-cm observations from the epoch of reionization is to limit observations to an uncontaminated window in Fourier space. Foreground emission can be avoided in this way, since it is limited to a wedge-shaped region in k∥, k⊥ space. However, the power spectrum is anisotropic owing to redshift-space distortions from peculiar velocities. Consequently, the 21-cm power spectrum measured in the foreground avoidance window - which samples only a limited range of angles close to the line-of-sight direction - differs from the full redshift-space spherically averaged power spectrum which requires an average over all angles. In this paper, we calculate the magnitude of this `wedge bias' for the first time. We find that the bias amplifies the difference between the real-space and redshift-space power spectra. The bias is strongest at high redshifts, where measurements using foreground avoidance will overestimate the redshift-space power spectrum by around 100 per cent, possibly obscuring the distinctive rise and fall signature that is anticipated for the spherically averaged 21-cm power spectrum. In the later stages of reionization, the bias becomes negative, and smaller in magnitude (≲20 per cent).

  11. IMPACT OF CLUSTER PHYSICS ON THE SUNYAEV-ZEL'DOVICH POWER SPECTRUM

    SciTech Connect

    Shaw, Laurie D.; Nagai, Daisuke; Bhattacharya, Suman; Lau, Erwin T.

    2010-12-20

    We use an analytic model to investigate the theoretical uncertainty on the thermal Sunyaev-Zel'dovich (SZ) power spectrum due to astrophysical uncertainties in the thermal structure of the intracluster medium. Our model accounts for star formation and energy feedback (from supernovae and active galactic nuclei) as well as radially dependent non-thermal pressure support due to random gas motions, the latter calibrated by recent hydrodynamical simulations. We compare the model against X-ray observations of low-redshift clusters, finding excellent agreement with observed pressure profiles. Varying the levels of feedback and non-thermal pressure support can significantly change both the amplitude and shape of the thermal SZ power spectrum. Increasing the feedback suppresses power at small angular scales, shifting the peak of the power spectrum to lower l. On the other hand, increasing the non-thermal pressure support has the opposite effect, significantly reducing power at large angular scales. In general, including non-thermal pressure at the level measured in simulations has a large effect on the power spectrum, reducing the amplitude by 50% at angular scales of a few arcminutes compared to a model without a non-thermal component. Our results demonstrate that measurements of the shape of the power spectrum can reveal useful information on important physical processes in groups and clusters, especially at high redshift where there exists little observational data. Comparing with the recent South Pole Telescope measurements of the small-scale cosmic microwave background power spectrum, we find our model reduces the tension between the values of {sigma}{sub 8} measured from the SZ power spectrum and from cluster abundances.

  12. Analytical model for CMB temperature angular power spectrum from cosmic (super-)strings

    SciTech Connect

    Yamauchi, Daisuke; Yoo, Chul-Moon; Sasaki, Misao; Takahashi, Keitaro; Sendouda, Yuuiti

    2010-09-15

    We present a new analytical method to calculate the small angle cosmic microwave background (CMB) temperature angular power spectrum due to cosmic (super-)string segments. In particular, using our method, we clarify the dependence on the intercommuting probability P. We find that the power spectrum is dominated by Poisson-distributed string segments. The power spectrum for a general value of P has a plateau on large angular scales and shows a power-law decrease on small angular scales. The resulting spectrum in the case of conventional cosmic strings is in very good agreement with the numerical result obtained by Fraisse et al.. Then we estimate the upper bound on the dimensionless tension of the string for various values of P by assuming that the fraction of the CMB power spectrum due to cosmic (super-)strings is less than ten percent at various angular scales up to l=2000. We find that the amplitude of the spectrum increases as the intercommuting probability. As a consequence, strings with smaller intercommuting probabilities are found to be more tightly constrained.

  13. The power spectrum of galaxies in the nearby universe

    NASA Technical Reports Server (NTRS)

    Da Costa, L. Nicolaci; Vogeley, Michael S.; Geller, Margaret J.; Huchra, John P.; Park, Changbom

    1994-01-01

    We compute the power spectrum of galaxy density fluctuations in a recently completed Southern Sky Redshift Survey of optically selected galaxies (SSRS2). The amplitude and shape of the SSRS2 power spectrum are consistent with results of the Center for Astrophysics redshift survey of the northern hemisphere (CfA2), including the abrupt change of slope on a scale of 30-50/h Mpc; these results are reproducible for independent volumes of space, and variations are consistent with the errors estimated from mock surveys. Taken together, the SSRS2 and the CfA2 form a complete sample of 14,383 galaxies which covers one-third of the sky. The power spectrum of this larger sample continues to rise on scales up to approximately 200/h Mpc, with weak evidence for flattening on the largest scales. The SSRS2 + CfA2 power spectrum and the power spectrum constraints implied by COBE are well matched by an Omega(h) is approximately 0.2, Omega + lambda(sub 0) = 1 cold dark matter model with minimal biasing of optically selected galaxies.

  14. On the information content of the matter power spectrum

    NASA Astrophysics Data System (ADS)

    Carron, J.; Wolk, M.; Szapudi, I.

    2015-10-01

    We discuss an analytical approximation for the matter power spectrum covariance matrix and its inverse on translinear scales, k ˜ 0.1h - 0.8 h Mpc-1 at z = 0. We proceed to give an analytical expression for the Fisher information matrix of the non-linear density-field spectrum, and derive implications for its cosmological information content. We find that the spectrum information is characterized by a pair of upper bounds, `plateaux', caused by the trispectrum, and a `knee' in the presence of white noise. The effective number of Fourier modes, normally growing as a power law, is bounded from above by these plateaux, explaining naturally earlier findings from N-body simulations. These plateaux limit best possible measurements of the non-linear power at the per cent level in an h-3 Gpc3 volume; the extraction of model parameters from the spectrum is limited explicitly by their degeneracy to the non-linear amplitude. The value of the first, supersurvey (SS) plateau depends on the characteristic survey volume and the large-scale power; the second, intra-survey plateau is set by the small-scale power. While both have simple interpretations within the hierarchical Ansatz, the SS plateau can be predicted and generalized to still smaller scales within Takada and Hu's spectrum response formalism. Finally, the noise knee is naturally set by the density of tracers.

  15. Measurement of the cosmic microwave background spectrum by the COBE FIRAS instrument

    NASA Technical Reports Server (NTRS)

    Mather, J. C.; Cheng, E. S.; Cottingham, D. A.; Eplee, R. E., Jr.; Fixsen, D. J.; Hewagama, T.; Isaacman, R. B.; Jensen, K. A.; Meyer, S. S.; Noerdlinger, P. D.

    1994-01-01

    The cosmic microwave background radiation (CMBR) has a blackbody spectrum within 3.4 x 10(exp -8) ergs/sq cm/s/sr cm over the frequency range from 2 to 20/cm (5-0.5 mm). These measurements, derived from the Far-Infrared Absolute Spectrophotomer (FIRAS) instrument on the Cosmic Background Explorer (COBE) satellite, imply stringent limits on energy release in the early universe after t approximately 1 year and redshift z approximately 3 x 10(exp 6). The deviations are less than 0.30% of the peak brightness, with an rms value of 0.01%, and the dimensionless cosmological distortion parameters are limited to the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) (95% confidence level). The temperature of the CMBR is 2.726 +/- 0.010 K (95% confidence level systematic).

  16. Visibility moments and power spectrum of turbulence velocity

    NASA Astrophysics Data System (ADS)

    Dutta, Prasun

    2016-02-01

    Here we introduce moments of visibility function and discuss how those can be used to estimate the power spectrum of the turbulent velocity of external spiral galaxies. We perform numerical simulation to confirm the credibility of this method and found that for galaxies with lower inclination angles it works fine. The estimator outlined here is unbiased and has the potential to recover the turbulent velocity spectrum completely from radio interferometric observations.

  17. The small scale power asymmetry in the cosmic microwave background

    SciTech Connect

    Flender, Samuel; Hotchkiss, Shaun E-mail: shaun.hotchkiss@helsinki.fi

    2013-09-01

    We investigate the hemispherical power asymmetry in the cosmic microwave background on small angular scales. We find an anomalously high asymmetry in the multipole range l = 601−2048, with a naive statistical significance of 6.5σ. However, we show that this extreme anomaly is simply a coincidence of three other effects, relativistic power modulation, edge effects from the mask applied, and inter-scale correlations. After correcting for all of these effects, the significance level drops to ∼ 1σ, i.e., there is no anomalous intrinsic asymmetry in the small angular scales. Using this null result, we derive a constraint on a potential dipolar modulation amplitude, A(k) < 0.0045 on the ∼ 10 Mpc-scale, at 95% C.L. This new constraint must be satisfied by any theoretical model attempting to explain the hemispherical asymmetry at large angular scales.

  18. The millimeter and submillimeter wavelength diffuse backgrounds: Measurements of the spectrum and anisotropy

    NASA Astrophysics Data System (ADS)

    Alsop, David Charles

    The results of two experiments to study the diffuse background at millimeter and submillimeter wavelengths are reported. The first experiment was a rocket-borne photometer designed to measure the spectrum of the background. The background was observed in six bands centered at 7, 13, 20, 30, 40, and 50 cm-1. After the flight, a systematic error was detected in the flight data. A model for the error was developed and an attempt at correction was made, but indications that the correction was not complete were found. The second experiment was a search for anisotropy in the Cosmic Microwave Background at one degree angular scales. The search employed a multiband, bolometric receiver mounted on a balloon-borne telescope. The search achieved the highest statistical sensitivity at this angular scale, which is of crucial importance for constraining theories of structure formation in the universe. Signals in excess of random were detected but concern over possible systematic error sources prevents the interpretation of the signals as uniquely cosmological in origin.

  19. Prediction of background in low-energy spectrum of Phoswich detector.

    PubMed

    Arun, B; Manohari, M; Mathiyarasu, R; Rajagopal, V; Jose, M T

    2014-12-01

    In vivo monitoring of actinides in occupational workers is done using Phoswich detector by measuring the low-energy X ray and gamma rays. Quantification of actinides like plutonium and americium in the lungs is extremely difficult due to higher background in the low-energy regions, which is from ambient background as well as from the subject. In the latter case, it is mainly due to the Compton scattering of body potassium, which varies person-to-person. Hence, an accurate prediction of subject-specific background counts in the lower-energy regions is an essential element in the in vivo measurement of plutonium and americium. Empirical equations are established for the prediction of background count rate in (239)Pu and (241)Am lower-energy regions, called 'target regions', as a function of count rate in the monitoring region (97-130 keV)/(40)K region in the high-energy spectrum, weight-to-height ratio of the subject (scattering parameter) and the gender. PMID:24300341

  20. THE COYOTE UNIVERSE. II. COSMOLOGICAL MODELS AND PRECISION EMULATION OF THE NONLINEAR MATTER POWER SPECTRUM

    SciTech Connect

    Heitmann, Katrin; Higdon, David; Williams, Brian J.; Lawrence, Earl; White, Martin; Habib, Salman; Wagner, Christian

    2009-11-01

    The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the 1% level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state, 'wCDM', cosmologies. In this paper, we demonstrate that a limited set of only 37 cosmological models-the 'Coyote Universe' suite-can be used to predict the nonlinear matter power spectrum to 1% over a prior parameter range set by current cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

  1. The Coyote Universe. II. Cosmological Models and Precision Emulation of the Nonlinear Matter Power Spectrum

    NASA Astrophysics Data System (ADS)

    Heitmann, Katrin; Higdon, David; White, Martin; Habib, Salman; Williams, Brian J.; Lawrence, Earl; Wagner, Christian

    2009-11-01

    The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the 1% level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state, "wCDM", cosmologies. In this paper, we demonstrate that a limited set of only 37 cosmological models—the "Coyote Universe" suite—can be used to predict the nonlinear matter power spectrum to 1% over a prior parameter range set by current cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

  2. The Coyote Universe II: Cosmological Models and Precision Emulation of the Nonlinear Matter Power Spectrum

    SciTech Connect

    Heitmann, Katrin; Habib, Salman; Higdon, David; Williams, Brian J; White, Martin; Wagner, Christian

    2008-01-01

    The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the one percent level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state 'wCDM' cosmologies. In this paper we demonstrate that a limited set of only 37 cosmological models -- the 'Coyote Universe' suite -- can be used to predict the nonlinear matter power spectrum at the required accuracy over a prior parameter range set by cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

  3. Universal power law for the spectrum of breaking Riemann waves

    NASA Astrophysics Data System (ADS)

    Pelinovsky, Dmitry; Pelinovsky, Efim; Kartashova, Elena; Talipova, Tatiana

    2014-05-01

    The universal power law for the spectrum of one-dimensional breaking Riemann waves is justified for the simple wave equation with arbitrary nonlinearity. This equation describe the long surface and internal wave in the coastal zone. The spectrum of spatial amplitudes at the breaking time has an power asymptotic decay with exponent - 4/3. This spectrum is formed by the singularity of the form like x1/3 in the wave shape at the breaking time. In addition, we demonstrate numerically that the universal power law is observed for long time in the range of small wave numbers if small dissipation or dispersion is accounted in the viscous Burgers or Korteweg-de Vries equations.

  4. Noise power spectrum measurements under nonuniform gains and their compensations

    NASA Astrophysics Data System (ADS)

    Kim, Dong Sik; Kim, Eun; Shin, Choul Woo

    2016-03-01

    The fixed pattern noise, which is due to the nonuniform amplifier gains and scintillator sensitivities, should be alleviated in radiography imaging and should have less influence on measuring the noise power spectrum (NPS) of the radiography detector. In order to reduce the influence, background trend removing methods, which are based on low-pass filtering, polynomial fitting, and subtracting the average image of the uniform exposure images, are traditionally employed in the literature. In terms of removing the fixed pattern noise, the subtraction method shows a good performance. However, the number of images to be averaged is practically finite and thus the noise contained in the average image contaminates the image difference and inflates the NPS curve. In this paper, an image formation model considering the nonuniform gain is constructed and two measuring methods, which are based on the subtraction and gain correction, respectively, are considered. In order to accurately measure a normalized NPS (NNPS) in the measuring methods, the number of images to be averaged is considered for NNPS compensations. For several flat-panel radiography detectors, the NNPS measurements are conducted and compared with conventional approaches, which have no compensation stages. Through experiments it is shown that the compensation can provide accurate NNPS measurements less influenced by the fixed pattern noise.

  5. Methods for Bayesian Power Spectrum Inference with Galaxy Surveys

    NASA Astrophysics Data System (ADS)

    Jasche, Jens; Wandelt, Benjamin D.

    2013-12-01

    We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves upon previous Bayesian methods by performing a joint inference of the three-dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases, and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate subsamples. This method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal-to-noise regimes by using a deterministic reversible jump algorithm. This approach reduces the correlation length of the sampler by several orders of magnitude, turning the otherwise numerically unfeasible problem of joint parameter exploration into a numerically manageable task. We test our method on an artificial mock galaxy survey, emulating characteristic features of the Sloan Digital Sky Survey data release 7, such as its survey geometry and luminosity-dependent biases. These tests demonstrate the numerical feasibility of our large scale Bayesian inference frame work when the parameter space has millions of dimensions. This method reveals and correctly treats the anti-correlation between bias amplitudes and power spectrum, which are not taken into account in current approaches to power spectrum estimation, a 20% effect across large ranges in k space. In addition, this method results in constrained realizations of density fields obtained without assuming the power spectrum or bias parameters

  6. Methods for Bayesian power spectrum inference with galaxy surveys

    SciTech Connect

    Jasche, Jens; Wandelt, Benjamin D.

    2013-12-10

    We derive and implement a full Bayesian large scale structure inference method aiming at precision recovery of the cosmological power spectrum from galaxy redshift surveys. Our approach improves upon previous Bayesian methods by performing a joint inference of the three-dimensional density field, the cosmological power spectrum, luminosity dependent galaxy biases, and corresponding normalizations. We account for all joint and correlated uncertainties between all inferred quantities. Classes of galaxies with different biases are treated as separate subsamples. This method therefore also allows the combined analysis of more than one galaxy survey. In particular, it solves the problem of inferring the power spectrum from galaxy surveys with non-trivial survey geometries by exploring the joint posterior distribution with efficient implementations of multiple block Markov chain and Hybrid Monte Carlo methods. Our Markov sampler achieves high statistical efficiency in low signal-to-noise regimes by using a deterministic reversible jump algorithm. This approach reduces the correlation length of the sampler by several orders of magnitude, turning the otherwise numerically unfeasible problem of joint parameter exploration into a numerically manageable task. We test our method on an artificial mock galaxy survey, emulating characteristic features of the Sloan Digital Sky Survey data release 7, such as its survey geometry and luminosity-dependent biases. These tests demonstrate the numerical feasibility of our large scale Bayesian inference frame work when the parameter space has millions of dimensions. This method reveals and correctly treats the anti-correlation between bias amplitudes and power spectrum, which are not taken into account in current approaches to power spectrum estimation, a 20% effect across large ranges in k space. In addition, this method results in constrained realizations of density fields obtained without assuming the power spectrum or bias parameters

  7. Statistical analysis of the cosmic microwave background: Power spectra and foregrounds

    NASA Astrophysics Data System (ADS)

    O'Dwyer, Ian J.

    2005-11-01

    In this thesis I examine some of the challenges associated with analyzing Cosmic Microwave Background (CMB) data and present a novel approach to solving the problem of power spectrum estimation, which is called MAGIC (MAGIC Allows Global Inference of Covariance). In light of the computational difficulty of a brute force approach to power spectrum estimation, I review several approaches which have been applied to the problem and show an example application of such an approximate method to experimental CMB data from the Background Emission Anisotropy Scanning Telescope (BEAST). I then introduce MAGIC, a new approach to power spectrum estimation; based on a Bayesian statistical analysis of the data utilizing Gibbs Sampling. I demonstrate application of this method to the all-sky Wilkinson Microwave Anistropy Probe WMAP data. The results are in broad agreement with those obtained originally by the WMAP team. Since MAGIC generates a full description of each C l it is possible to examine several issues raised by the best-fit WMAP power spectrum, for example the perceived lack of power at low ℓ. It is found that the distribution of C ℓ's at low l are significantly non-Gaussian and, based on the exact analysis presented here, the "low quadrupole issue" can be attributed to a statistical fluctuation. Finally, I examine the effect of Galactic foreground contamination on CMB experiments and describe the principle foregrounds. I show that it is possible to include the foreground components in a self-consistent fashion within the statistical framework of MAGIC and give explicit examples of how this might be achieved. Foreground contamination will become an increasingly important issue in CMB data analysis and the ability of this new algorithm to produce an exact power spectrum in a computationally feasible time, coupled with the foreground component separation and removal is an exciting development in CMB data analysis. When considered with current algorithmic developments

  8. Effect of curvaton decay on the primordial power spectrum

    NASA Astrophysics Data System (ADS)

    Firouzjahi, Hassan; Green, Anne M.; Malik, Karim A.; Zarei, Moslem

    2013-05-01

    We study the effect of curvaton decay on the primordial power spectrum. Using analytical approximations and also numerical calculations, we find that the power spectrum is enhanced during the radiation dominated era after the curvaton decay. The amplitude of the Bardeen potential is controlled by the fraction of the energy density in the curvaton at the time of curvaton decay. We show that the enhancement in the amplitude of the primordial curvature perturbation is, however, not large enough to lead to primordial black hole overproduction on scales which reenter the horizon after the time of curvaton decay.

  9. Reexamination of the Power Spectrum in De Sitter Inflation

    NASA Astrophysics Data System (ADS)

    Agulló, Iván; Navarro-Salas, José; Olmo, Gonzalo J.; Parker, Leonard

    2008-10-01

    We find that the amplitude of quantum fluctuations of the invariant de Sitter vacuum coincides exactly with that of the vacuum of a comoving observer for a massless scalar (inflaton) field. We propose redefining the actual physical power spectrum as the difference between the amplitudes of the above vacua. An inertial particle detector continues to observe the Gibbons-Hawking temperature. However, although the resulting power spectrum is still scale-free, its amplitude can be drastically reduced since now, instead of the Hubble’s scale at the inflationary period, it is determined by the square of the mass of the inflaton fluctuation field.

  10. Kolmogorov spectrum of renewable wind and solar power fluctuations

    NASA Astrophysics Data System (ADS)

    Tabar, M. Reza Rahimi; Anvari, M.; Lohmann, G.; Heinemann, D.; Wächter, M.; Milan, P.; Lorenz, E.; Peinke, Joachim

    2014-10-01

    With increasing the contribution of renewable energies in power production, the task of reducing dynamic instability in power grids must also be addressed from the generation side, because the power delivered from such sources is spatiotemporally stochastic in nature. Here we characterize the stochastic properties of the wind and solar energy sources by studying their spectrum and multifractal exponents. The computed power spectrum from high frequency time series of solar irradiance and wind power reveals a power-law behaviour with an exponent ˜ 5/3 (Kolmogorov exponent) for the frequency domain 0.001 Hz < f < 0.05 Hz, which means that the power grid is being fed by turbulent-like sources. Our results bring important evidence on the stochastic and turbulent-like behaviour of renewable power production from wind and solar energies, which can cause instability in power grids. Our statistical analysis also provides important information that must be used as a guideline for an optimal design of power grids that operate under intermittent renewable sources of power.

  11. Red, Straight, no bends: primordial power spectrum reconstruction from CMB and large-scale structure

    NASA Astrophysics Data System (ADS)

    Ravenni, Andrea; Verde, Licia; Cuesta, Antonio J.

    2016-08-01

    We present a minimally parametric, model independent reconstruction of the shape of the primordial power spectrum. Our smoothing spline technique is well-suited to search for smooth features such as deviations from scale invariance, and deviations from a power law such as running of the spectral index or small-scale power suppression. We use a comprehensive set of the state-of the art cosmological data: Planck observations of the temperature and polarisation anisotropies of the cosmic microwave background, WiggleZ and Sloan Digital Sky Survey Data Release 7 galaxy power spectra and the Canada-France-Hawaii Lensing Survey correlation function. This reconstruction strongly supports the evidence for a power law primordial power spectrum with a red tilt and disfavours deviations from a power law power spectrum including small-scale power suppression such as that induced by significantly massive neutrinos. This offers a powerful confirmation of the inflationary paradigm, justifying the adoption of the inflationary prior in cosmological analyses.

  12. Primordial power spectrum: a complete analysis with the WMAP nine-year data

    NASA Astrophysics Data System (ADS)

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun

    2013-07-01

    We have improved further the error sensitive Richardson-Lucy deconvolution algorithm making it applicable directly on the un-binned measured angular power spectrum of Cosmic Microwave Background observations to reconstruct the form of the primordial power spectrum. This improvement makes the application of the method significantly more straight forward by removing some intermediate stages of analysis allowing a reconstruction of the primordial spectrum with higher efficiency and precision and with lower computational expenses. Applying the modified algorithm we fit the WMAP 9 year data using the optimized reconstructed form of the primordial spectrum with more than 300 improvement in χ2eff with respect to the best fit power-law. This is clearly beyond the reach of other alternative approaches and reflects the efficiency of the proposed method in the reconstruction process and allow us to look for any possible feature in the primordial spectrum projected in the CMB data. Though the proposed method allow us to look at various possibilities for the form of the primordial spectrum, all having good fit to the data, proper error-analysis is needed to test for consistency of theoretical models since, along with possible physical artefacts, most of the features in the reconstructed spectrum might be arising from fitting noises in the CMB data. Reconstructed error-band for the form of the primordial spectrum using many realizations of the data, all bootstrapped and based on WMAP 9 year data, shows proper consistency of power-law form of the primordial spectrum with the WMAP 9 data at all wave numbers. Including WMAP polarization data in to the analysis have not improved much our results due to its low quality but we expect Planck data will allow us to make a full analysis on CMB observations on both temperature and polarization separately and in combination.

  13. Primordial power spectrum: a complete analysis with the WMAP nine-year data

    SciTech Connect

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun E-mail: arman@apctp.org

    2013-07-01

    We have improved further the error sensitive Richardson-Lucy deconvolution algorithm making it applicable directly on the un-binned measured angular power spectrum of Cosmic Microwave Background observations to reconstruct the form of the primordial power spectrum. This improvement makes the application of the method significantly more straight forward by removing some intermediate stages of analysis allowing a reconstruction of the primordial spectrum with higher efficiency and precision and with lower computational expenses. Applying the modified algorithm we fit the WMAP 9 year data using the optimized reconstructed form of the primordial spectrum with more than 300 improvement in χ{sup 2}{sub eff} with respect to the best fit power-law. This is clearly beyond the reach of other alternative approaches and reflects the efficiency of the proposed method in the reconstruction process and allow us to look for any possible feature in the primordial spectrum projected in the CMB data. Though the proposed method allow us to look at various possibilities for the form of the primordial spectrum, all having good fit to the data, proper error-analysis is needed to test for consistency of theoretical models since, along with possible physical artefacts, most of the features in the reconstructed spectrum might be arising from fitting noises in the CMB data. Reconstructed error-band for the form of the primordial spectrum using many realizations of the data, all bootstrapped and based on WMAP 9 year data, shows proper consistency of power-law form of the primordial spectrum with the WMAP 9 data at all wave numbers. Including WMAP polarization data in to the analysis have not improved much our results due to its low quality but we expect Planck data will allow us to make a full analysis on CMB observations on both temperature and polarization separately and in combination.

  14. Reconstruction of the primordial power spectrum using temperature and polarisation data from multiple experiments

    SciTech Connect

    Nicholson, Gavin; Contaldi, Carlo R. E-mail: c.contaldi@imperial.ac.uk

    2009-07-01

    We develop a method to reconstruct the primordial power spectrum, P(k), using both temperature and polarisation data from the joint analysis of a number of Cosmic Microwave Background (CMB) observations. The method is an extension of the Richardson-Lucy algorithm, first applied in this context by Shafieloo and Souradeep [1]. We show how the inclusion of polarisation measurements can decrease the uncertainty in the reconstructed power spectrum. In particular, the polarisation data can constrain oscillations in the spectrum more effectively than total intensity only measurements. We apply the estimator to a compilation of current CMB results. The reconstructed spectrum is consistent with the best-fit power spectrum although we find evidence for a 'dip' in the power on scales k ≈ 0.002 Mpc{sup −1}. This feature appears to be associated with the WMAP power in the region 18 ≤ l ≤ 26 which is consistently below best-fit models. We also forecast the reconstruction for a simulated, Planck-like [2] survey including sample variance limited polarisation data.

  15. Reconstruction of the primordial power spectrum using temperature and polarisation data from multiple experiments

    NASA Astrophysics Data System (ADS)

    Nicholson, Gavin; Contaldi, Carlo R.

    2009-07-01

    We develop a method to reconstruct the primordial power spectrum, P(k), using both temperature and polarisation data from the joint analysis of a number of Cosmic Microwave Background (CMB) observations. The method is an extension of the Richardson-Lucy algorithm, first applied in this context by Shafieloo & Souradeep [1]. We show how the inclusion of polarisation measurements can decrease the uncertainty in the reconstructed power spectrum. In particular, the polarisation data can constrain oscillations in the spectrum more effectively than total intensity only measurements. We apply the estimator to a compilation of current CMB results. The reconstructed spectrum is consistent with the best-fit power spectrum although we find evidence for a `dip' in the power on scales k approx 0.002 Mpc-1. This feature appears to be associated with the WMAP power in the region 18 <= ell <= 26 which is consistently below best-fit models. We also forecast the reconstruction for a simulated, Planck-like [2] survey including sample variance limited polarisation data.

  16. A robust power spectrum split cancellation-based spectrum sensing method for cognitive radio systems

    NASA Astrophysics Data System (ADS)

    Qi, Pei-Han; Li, Zan; Si, Jiang-Bo; Gao, Rui

    2014-12-01

    Spectrum sensing is an essential component to realize the cognitive radio, and the requirement for real-time spectrum sensing in the case of lacking prior information, fading channel, and noise uncertainty, indeed poses a major challenge to the classical spectrum sensing algorithms. Based on the stochastic properties of scalar transformation of power spectral density (PSD), a novel spectrum sensing algorithm, referred to as the power spectral density split cancellation method (PSC), is proposed in this paper. The PSC makes use of a scalar value as a test statistic, which is the ratio of each subband power to the full band power. Besides, by exploiting the asymptotic normality and independence of Fourier transform, the distribution of the ratio and the mathematical expressions for the probabilities of false alarm and detection in different channel models are derived. Further, the exact closed-form expression of decision threshold is calculated in accordance with Neyman—Pearson criterion. Analytical and simulation results show that the PSC is invulnerable to noise uncertainty, and can achive excellent detection performance without prior knowledge in additive white Gaussian noise and flat slow fading channels. In addition, the PSC benefits from a low computational cost, which can be completed in microseconds.

  17. The X-ray variability of NGC 6814 - Power spectrum

    NASA Technical Reports Server (NTRS)

    Done, C.; Madejski, G. M.; Mushotzky, R. F.; Turner, T. J.; Koyama, K.; Kunieda, H.

    1992-01-01

    The existence of the periodic component seen in NGC 6814 with Exosat at 12,000 +/- 100 s is confirmed by a power spectrum and folded light curve analysis of unevenly sampled Ginga data. A comparison of the power spectra produced from simulated light curves with that observed enables the intrinsic shape of the power spectrum of the source to be determined despite the distortions introduced by the window function. The best estimate for the period is 12,132 +/- 3 s, where the error is that derived from simulations. An upper limit to the rate of change of period of about 10 exp -9 is inferred if the light curves are truly phase-coherent, but as this is not required by the data, the conservative upper limit is not greater than 5 x 10 exp -7. The large amount of power in the periodic component and its stability both suggest occultation of the source as its origin.

  18. The Spectrum of 1ES0229 + 200 and the Cosmic Infrared Background

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Scully, S. T.

    2008-01-01

    Aims. We reexamine the implications of the recent HESS observations of the blazar 1ES0229+200 for constraining the extragalactic mid-infrared background radiation. Methods. We examine the effect of gamma-ray absorption by the extragalactic infrared radiation on predicted intrinsic spectra for this blazar and compare our results with the observational data. Results. We find agreement with our previous results on the shape of the infrared spectral energy distribution, contrary to the recent assertion of the HESS group. Our analysis indicates that 1ES0229+200 has a very hard intrinsic spectrum with a spectral index between 1.1 +/- 0.3 and 1.5 0.3 in the energy range between 0.5 TeV and 15 TeV. Conclusions. Under the assumptions that (1) the models of Stecker et al. as derived from numerous detailed infrared observations are reasonable, and (2) spectral indexes in the range 1 < Gamma < 1.5 are obtainable from relativistic shock acceleration under the astrophysical conditions extant in blazar flares, the fits to the observations of 1ES0229+200 using our previous infrared spectral energy distributions are consistent with both the infrared and -ray observations. Our analysis presents evidence indicating that the energy spectrum of relativistic particles in 1ES0229+200 is produced by relativistic shock acceleration, producing an intrinsic gamma-ray spectrum with index 1 < Gamma < 1.5 and with no evidence of a peak in the spectral energy distribution up to energies approximately 15 TeV.

  19. Do clusters of galaxies affect the spectrum of the microwave background?

    NASA Technical Reports Server (NTRS)

    Markevitch, M.; Blumenthal, G. R.; Forman, W.; Jones, C.; Suniaev, R. A.

    1991-01-01

    The distortion, averaged over the sky, due to the Compton scattering of background photons with electrons in the hot gas in clusters of galaxies is calculated. Using an existing sample of X-ray clusters, various values of the density parameter Omega, and plausible models for cluster evolution, Monte Carlo realizations of the microwave sky are generated. The spatial structure of these simulations shows a network of discrete sources whose properties can be a strong function of both evolution and Omega. The amount of spectral distortion in the models is greatest for models characterized by self-similar cluster evolution in an open universe and is within an order of magnitude of the current upper limits. Thus, improved observational sensitivity must inevitably detect some deviation from a blackbody spectrum.

  20. Joint resonant CMB power spectrum and bispectrum estimation

    NASA Astrophysics Data System (ADS)

    Meerburg, P. Daniel; Münchmeyer, Moritz; Wandelt, Benjamin

    2016-02-01

    We develop the tools necessary to assess the statistical significance of resonant features in the CMB correlation functions, combining power spectrum and bispectrum measurements. This significance is typically addressed by running a large number of simulations to derive the probability density function (PDF) of the feature-amplitude in the Gaussian case. Although these simulations are tractable for the power spectrum, for the bispectrum they require significant computational resources. We show that, by assuming that the PDF is given by a multivariate Gaussian where the covariance is determined by the Fisher matrix of the sine and cosine terms, we can efficiently produce spectra that are statistically close to those derived from full simulations. By drawing a large number of spectra from this PDF, both for the power spectrum and the bispectrum, we can quickly determine the statistical significance of candidate signatures in the CMB, considering both single frequency and multifrequency estimators. We show that for resonance models, cosmology and foreground parameters have little influence on the estimated amplitude, which allows us to simplify the analysis considerably. A more precise likelihood treatment can then be applied to candidate signatures only. We also discuss a modal expansion approach for the power spectrum, aimed at quickly scanning through large families of oscillating models.

  1. Cosmic Emulation: Fast Predictions for the Galaxy Power Spectrum

    NASA Astrophysics Data System (ADS)

    Kwan, Juliana; Heitmann, Katrin; Habib, Salman; Padmanabhan, Nikhil; Lawrence, Earl; Finkel, Hal; Frontiere, Nicholas; Pope, Adrian

    2015-09-01

    The halo occupation distribution (HOD) approach has proven to be an effective method for modeling galaxy clustering and bias. In this approach, galaxies of a given type are probabilistically assigned to individual halos in N-body simulations. In this paper, we present a fast emulator for predicting the fully nonlinear galaxy-galaxy auto and galaxy-dark matter cross power spectrum and correlation function over a range of freely specifiable HOD modeling parameters. The emulator is constructed using results from 100 HOD models run on a large ΛCDM N-body simulation, with Gaussian Process interpolation applied to a PCA-based representation of the galaxy power spectrum. The total error is currently ˜1% in the auto correlations and ˜2% in the cross correlations from z = 1 to z = 0, over the considered parameter range. We use the emulator to investigate the accuracy of various analytic prescriptions for the galaxy power spectrum, parametric dependencies in the HOD model, and the behavior of galaxy bias as a function of HOD parameters. Additionally, we obtain fully nonlinear predictions for tangential shear correlations induced by galaxy-galaxy lensing from our galaxy-dark matter cross power spectrum emulator. All emulation products are publicly available at http://www.hep.anl.gov/cosmology/CosmicEmu/emu.html.

  2. A high resolution spectrum of the diffuse soft X-ray background

    NASA Astrophysics Data System (ADS)

    Crowder, S. Gwynne

    Galactic contributions to the diffuse X-ray background were believed to largely come from thermal emission of hot gas and models of the Galactic neighborhood within ˜ 100 pc reflected this belief. However, recent observations led to the realization that emission from charge exchange within the Solar System might produce comparable intensities to that of thermal emission. A high resolution spectrum of the diffuse X-ray background from 0.1 to 1 keV was obtained for a ˜ 1 sr region of the sky centered at l = 90°, b = +60° in May 2008 using a 36 pixel array of microcalorimeters flown on a sounding rocket. With an energy resolution of 11 eV FWHM below 1 keV, the spectrum can be used to separate charge exchange contributions originating within the heliosphere from thermal emission of hot gas in the interstellar medium. The X-ray sensitivity below 1 keV was reduced about a factor of four by contamination that occurred early in the flight, limiting the significance of the results. The observed ratio of helium-like O VII forbidden plus intercombination to resonance lines is 1.2 +/- 1.2 at 90% confidence. This indicates that at least 67% of the emission is thermal. On the other hand, the observed ratio of C VI Lygamma to Lyalpha is 0.3+0.3-0.2 , requiring at least a 33% contribution from charge exchange. In addition to these astrophysical results, I present experimental improvements from the addition of a gold coating to the detector array substrate which greatly reduces extraneous signals and from the use of silicon support meshes which improves blocking filter robustness. I also detail a new optimal filtering analysis technique that preserves spectral resolution and live time in the presence of pulse overlap.

  3. Galactic antiproton spectrum at high energies: Background expectation versus exotic contributions

    SciTech Connect

    Bringmann, Torsten; Salati, Pierre

    2007-04-15

    A new generation of upcoming space-based experiments will soon start to probe the spectrum of cosmic-ray antiparticles with an unprecedented accuracy and, in particular, will open up a window to energies much higher than those accessible so far. It is thus timely to carefully investigate the expected antiparticle fluxes at high energies. Here, we perform such an analysis for the case of antiprotons. We consider both standard sources as the collision of other cosmic rays with interstellar matter, as well as exotic contributions from dark matter annihilations in the galactic halo. Up to energies well above 100 GeV, we find that the background flux in antiprotons is almost uniquely determined by the existing low-energy data on various cosmic-ray species; for even higher energies, however, the uncertainties in the parameters of the underlying propagation model eventually become significant. We also show that if the dark matter is composed of particles with masses at the TeV scale, which is naturally expected in extra-dimensional models as well as in certain parameter regions of supersymmetric models, the annihilation flux can become comparable to--or even dominate--the antiproton background at the high energies considered here.

  4. Primordial scalar power spectrum from the Euclidean big bounce

    NASA Astrophysics Data System (ADS)

    Schander, Susanne; Barrau, Aurélien; Bolliet, Boris; Linsefors, Linda; Mielczarek, Jakub; Grain, Julien

    2016-01-01

    In effective models of loop quantum cosmology, the holonomy corrections are associated with deformations of space-time symmetries. The most evident manifestation of the deformations is the emergence of a Euclidean phase accompanying the nonsingular bouncing dynamics of the scale factor. In this article, we compute the power spectrum of scalar perturbations generated in this model, with a massive scalar field as the matter content. Instantaneous and adiabatic vacuum-type initial conditions for scalar perturbations are imposed in the contracting phase. The evolution through the Euclidean region is calculated based on the extrapolation of the time direction pointed by the vectors normal to the Cauchy hypersurface in the Lorentzian domains. The obtained power spectrum is characterized by a suppression in the IR regime and oscillations in the intermediate energy range. Furthermore, the speculative extension of the analysis in the UV reveals a specific rise of the power leading to results incompatible with the data.

  5. The very low frequency power spectrum of Centaurus X-3

    NASA Technical Reports Server (NTRS)

    Gruber, D. E.

    1988-01-01

    The long-term variability of Cen X-3 on time scales ranging from days to years has been examined by combining data obtained by the HEAO 1 A-4 instrument with data from Vela 5B. A simple interpretation of the data is made in terms of the standard alpha-disk model of accretion disk structure and dynamics. Assuming that the low-frequency variance represents the inherent variability of the mass transfer from the companion, the decline in power at higher frequencies results from the leveling of radial structure in the accretion disk through viscous mixing. The shape of the observed power spectrum is shown to be in excellent agreement with a calculation based on a simplified form of this model. The observed low-frequency power spectrum of Cen X-3 is consistent with a disk in which viscous mixing occurs about as rapidly as possible and on the largest scale possible.

  6. Multiredshift Limits on the 21 cm Power Spectrum from PAPER

    NASA Astrophysics Data System (ADS)

    Jacobs, Daniel C.; Pober, Jonathan C.; Parsons, Aaron R.; Aguirre, James E.; Ali, Zaki S.; Bowman, Judd; Bradley, Richard F.; Carilli, Chris L.; DeBoer, David R.; Dexter, Matthew R.; Gugliucci, Nicole E.; Klima, Pat; Liu, Adrian; MacMahon, David H. E.; Manley, Jason R.; Moore, David F.; Stefan, Irina I.; Walbrugh, William P.

    2015-03-01

    The epoch of the reionization (EoR) power spectrum is expected to evolve strongly with redshift, and it is this variation with cosmic history that will allow us to begin to place constraints on the physics of reionization. The primary obstacle to the measurement of the EoR power spectrum is bright foreground emission. We present an analysis of observations from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) telescope, which place new limits on the H i power spectrum over the redshift range of 7.5\\lt z\\lt 10.5, extending previously published single-redshift results to cover the full range accessible to the instrument. To suppress foregrounds, we use filtering techniques that take advantage of the large instrumental bandwidth to isolate and suppress foreground leakage into the interesting regions of k-space. Our 500 hr integration is the longest such yet recorded and demonstrates this method to a dynamic range of 104. Power spectra at different points across the redshift range reveal the variable efficacy of the foreground isolation. Noise-limited measurements of Δ2 at k = 0.2 hr Mpc-1 and z = 7.55 reach as low as (48 mK)2 (1σ). We demonstrate that the size of the error bars in our power spectrum measurement as generated by a bootstrap method is consistent with the fluctuations due to thermal noise. Relative to this thermal noise, most spectra exhibit an excess of power at a few sigma. The likely sources of this excess include residual foreground leakage, particularly at the highest redshift, unflagged radio frequency interference, and calibration errors. We conclude by discussing data reduction improvements that promise to remove much of this excess.

  7. Thermal power spectrum in the CFT driven cosmology

    SciTech Connect

    Barvinsky, A.O.

    2013-10-01

    We present an overview of the recently suggested cosmological model driven by conformal field theory (CFT) with the initial conditions in the form of the microcanonical density matrix. In particular, we discuss the origin of inflationary stage in this model and a novel feature — the thermal nature of the primordial power spectrum of the CMB anisotropy. The relevant effect of ''temperature of the relic temperature anisotropy'' can be responsible for a thermal contribution to the red tilt of this spectrum, additional to its conventional vacuum component. The amplification of this effect due to recently established a-theorem in CFT is briefly discussed.

  8. On syntheses of the X-ray background with power-law sources

    NASA Technical Reports Server (NTRS)

    De Zotti, G.; Boldt, E. A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.; Cavaliere, A.; Danese, L.; Franceschini, A.

    1982-01-01

    The conditions under which the combined emission from power-law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low-luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit steeper spectra at higher energies.

  9. On syntheses of the X-ray background with power-law sources

    NASA Technical Reports Server (NTRS)

    Dezotti, G.; Boldt, E. A.; Cavaliere, A.; Danese, L.; Franceschini, A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.

    1981-01-01

    The conditions under which the combined emission from power law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit sleeper spectra at higher energies.

  10. On syntheses of the X-ray background with power-law sources

    NASA Astrophysics Data System (ADS)

    De Zotti, G.; Boldt, E. A.; Cavaliere, A.; Danese, L.; Franceschini, A.; Marshall, F. E.; Swank, J. H.; Szymkowiak, A. E.

    1981-08-01

    The conditions under which the combined emission from power law sources can mimic the X-ray background (XRB) spectrum in the 3-50 keV range are considered in view of HEAO 1 A-2 experiment measurements, and it is confirmed that a good fit may be obtained. The required spectral properties of the component sources differ, however, from those observed for local active galactic nuclei. Constraints are deduced for both the low luminosity extension and evolution of such local objects, and it is shown that any other class of sources contributing to the X-ray background must be characterized by an energy spectral index lower than about 0.4, which is the mean index of the XRB, and exhibit sleeper spectra at higher energies.

  11. Decomposition of Heart Rate Variability Spectrum into a Power-Law Function and a Residual Spectrum

    PubMed Central

    Kuo, Jane; Kuo, Cheng-Deng

    2016-01-01

    The power spectral density (PSD) of heart rate variability (HRV) contains a power-law relationship that can be obtained by plotting the logarithm of PSD against the logarithm of frequency. The PSD of HRV can be decomposed mathematically into a power-law function and a residual HRV (rHRV) spectrum. Almost all rHRV measures are significantly smaller than their corresponding HRV measures except the normalized high-frequency power (nrHFP). The power-law function can be characterized by the slope and Y-intercept of linear regression. Almost all HRV measures except the normalized low-frequency power have significant correlations with the Y-intercept, while almost all rHRV measures except the total power [residual total power (rTP)] do not. Though some rHRV measures still correlate significantly with the age of the subjects, the rTP, high-frequency power (rHFP), nrHFP, and low-/high-frequency power ratio (rLHR) do not. In conclusion, the clinical significances of rHRV measures might be different from those of traditional HRV measures. The Y-intercept might be a better HRV measure for clinical use because it is independent of almost all rHRV measures. The rTP, rHFP, nrHFP, and rLHR might be more suitable for the study of age-independent autonomic nervous modulation of the subjects. PMID:27314001

  12. The Atacama Cosmology Telescope: temperature and gravitational lensing power spectrum measurements from three seasons of data

    NASA Astrophysics Data System (ADS)

    Das, Sudeep; Louis, Thibaut; Nolta, Michael R.; Addison, Graeme E.; Battistelli, Elia S.; Bond, J. Richard; Calabrese, Erminia; Crichton, Devin; Devlin, Mark J.; Dicker, Simon; Dunkley, Joanna; Dünner, Rolando; Fowler, Joseph W.; Gralla, Megan; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renée; Huffenberger, Kevin M.; Hughes, John P.; Irwin, Kent D.; Kosowsky, Arthur; Lupton, Robert H.; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D.; Page, Lyman A.; Partridge, Bruce; Reese, Erik D.; Schmitt, Benjamin L.; Sehgal, Neelima; Sherwin, Blake D.; Sievers, Jonathan L.; Spergel, David N.; Staggs, Suzanne T.; Swetz, Daniel S.; Switzer, Eric R.; Thornton, Robert; Trac, Hy; Wollack, Ed

    2014-04-01

    We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ΛCDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6σ detection significance.

  13. The Atacama Cosmology Telescope: Temperature and Gravitational Lensing Power Spectrum Measurements from Three Seasons of Data

    NASA Technical Reports Server (NTRS)

    Das, Sudeep; Louis, Thibaut; Nolta, Michael R.; Addison, Graeme E.; Battisetti, Elia S.; Bond, J. Richard; Calabrese, Erminia; Crichton, Devin; Devlin, Mark J.; Dicker, Simon; Dunkley, Joanna; Dunner, Rolando; Fowler, Joseph W.; Gralla, Megan; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Huffenberger, Kevin M.; Hughes, John P.; Irwin, Kent D; Kosowsky, Arthur; Wollack, Ed

    2014-01-01

    We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ?CDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6s detection significance.

  14. Automated FMV image quality assessment based on power spectrum statistics

    NASA Astrophysics Data System (ADS)

    Kalukin, Andrew

    2015-05-01

    Factors that degrade image quality in video and other sensor collections, such as noise, blurring, and poor resolution, also affect the spatial power spectrum of imagery. Prior research in human vision and image science from the last few decades has shown that the image power spectrum can be useful for assessing the quality of static images. The research in this article explores the possibility of using the image power spectrum to automatically evaluate full-motion video (FMV) imagery frame by frame. This procedure makes it possible to identify anomalous images and scene changes, and to keep track of gradual changes in quality as collection progresses. This article will describe a method to apply power spectral image quality metrics for images subjected to simulated blurring, blocking, and noise. As a preliminary test on videos from multiple sources, image quality measurements for image frames from 185 videos are compared to analyst ratings based on ground sampling distance. The goal of the research is to develop an automated system for tracking image quality during real-time collection, and to assign ratings to video clips for long-term storage, calibrated to standards such as the National Imagery Interpretability Rating System (NIIRS).

  15. Rejuvenating the Matter Power Spectrum. III. The Cosmology Sensitivity of Gaussianized Power Spectra

    NASA Astrophysics Data System (ADS)

    Neyrinck, Mark C.

    2011-12-01

    It was recently shown that applying a Gaussianizing transform, such as a logarithm, to the nonlinear matter density field extends the range of useful applicability of the power spectrum by a factor of a few smaller. Such a transform dramatically reduces nonlinearities in both the covariance and the shape of the power spectrum. Here, analyzing Coyote Universe real-space dark-matter density fields, we investigate the consequences of these transforms for cosmological parameter estimation. The power spectrum of the log-density provides the tightest cosmological parameter error bars (marginalized or not), giving a factor of 2-3 improvement over the conventional power spectrum in all five parameters tested. For the tilt, ns , the improvement reaches a factor of five. Similar constraints are achieved if the log-density power spectrum and conventional power spectrum are analyzed together. Rank-order Gaussianization seems just as useful as a log transform to constrain ns , but not other parameters. Dividing the overdensity by its dispersion in few-Mpc cells, while it diagonalizes the covariance matrix, does not seem to help with parameter constraints. We also provide a code that emulates these power spectra over a range of concordance cosmological models.

  16. REJUVENATING THE MATTER POWER SPECTRUM. III. THE COSMOLOGY SENSITIVITY OF GAUSSIANIZED POWER SPECTRA

    SciTech Connect

    Neyrinck, Mark C.

    2011-12-01

    It was recently shown that applying a Gaussianizing transform, such as a logarithm, to the nonlinear matter density field extends the range of useful applicability of the power spectrum by a factor of a few smaller. Such a transform dramatically reduces nonlinearities in both the covariance and the shape of the power spectrum. Here, analyzing Coyote Universe real-space dark-matter density fields, we investigate the consequences of these transforms for cosmological parameter estimation. The power spectrum of the log-density provides the tightest cosmological parameter error bars (marginalized or not), giving a factor of 2-3 improvement over the conventional power spectrum in all five parameters tested. For the tilt, n{sub s} , the improvement reaches a factor of five. Similar constraints are achieved if the log-density power spectrum and conventional power spectrum are analyzed together. Rank-order Gaussianization seems just as useful as a log transform to constrain n{sub s} , but not other parameters. Dividing the overdensity by its dispersion in few-Mpc cells, while it diagonalizes the covariance matrix, does not seem to help with parameter constraints. We also provide a code that emulates these power spectra over a range of concordance cosmological models.

  17. COSMIC MICROWAVE BACKGROUND POLARIZATION AND TEMPERATURE POWER SPECTRA ESTIMATION USING LINEAR COMBINATION OF WMAP 5 YEAR MAPS

    SciTech Connect

    Samal, Pramoda Kumar; Jain, Pankaj; Saha, Rajib; Prunet, Simon; Souradeep, Tarun

    2010-05-01

    We estimate cosmic microwave background (CMB) polarization and temperature power spectra using Wilkinson Microwave Anisotropy Probe (WMAP) 5 year foreground contaminated maps. The power spectrum is estimated by using a model-independent method, which does not utilize directly the diffuse foreground templates nor the detector noise model. The method essentially consists of two steps: (1) removal of diffuse foregrounds contamination by making linear combination of individual maps in harmonic space and (2) cross-correlation of foreground cleaned maps to minimize detector noise bias. For the temperature power spectrum we also estimate and subtract residual unresolved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our TT, TE, and EE power spectra are in good agreement with the published results of the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We find that the bias is small in almost all cases. A negative bias at low l in TT power spectrum has been pointed out in an earlier publication. We find that the bias-corrected quadrupole power (l(l + 1)C{sub l} /2{pi}) is 532 {mu}K{sup 2}, approximately 2.5 times the estimate (213.4 {mu}K{sup 2}) made by the WMAP team.

  18. Electron density power spectrum in the local interstellar medium

    NASA Technical Reports Server (NTRS)

    Armstrong, J. W.; Rickett, B. J.; Spangler, S. R.

    1995-01-01

    Interstellar scintillation (ISS), fluctuations in the amplitude and phase of radio waves caused by scattering in the interstellar medium, is important as a diagnostic of interstellar plasma turbulence. ISS is also of interest because it is noise for other radio astronomical observations. The unifying concern is the power spectrum of the interstellar electron density. Here we use ISS observations through the nearby (less than or approximately =1 kpc) (ISM) to estimate the spectrum. From measurements of angular broadening of pulsars and extragalactic sources, decorrelation bandwidth of pulsars, refractive steering of features in pulsar dynamic spectra, dispersion measured fluctuations of pulsars, and refractive scintillation index measurements, we construct a composite structure function that is approximately power law over 2 x 10(exp 6) m less than scale less than 10(exp 13) m. The data are consistent with the structure function having a logarithmic slope versus baseline less than 2; thus there is a meaningful connection between scales in the radiowave fluctuation field and the scales in the electron density field causing the scattering. The data give an upper limit to the inner scale, l(sub o) less than or approximately 10(exp 8) m and are consistent with much smaller values. We construct a composite electron density spectrum that is approximately power law over at least the approximately = 5 decade wavenumber range 10(exp -13)/m less than wavenumber less than 10(exp -8)/m and that may extend to higher wavenumbers. The average spectral index of electron density over this wavenumber range is approximately = 3.7, very close to the value expected for a Kolmogorov process. The outer scale size, L(sub o), must be greater than or approximately = 10(exp 13) m (determined from dispersion measure fluctuations). When the ISS data are combined with measurements of differential Faraday rotation angle, and gradients in the average electron density, constraints can be put on the

  19. 21 cm Power Spectrum Upper Limits from PAPER-64

    NASA Astrophysics Data System (ADS)

    Shiraz Ali, Zaki; Parsons, Aaron; Pober, Jonathan; Team PAPER

    2016-01-01

    We present power spectrum results from the 64 antenna deployment of the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER-64). We find an upper limit of Δ2≤(22.4 mK)2 over the range 0.15power spectrum constraints to date. In addition, we use these results to place lower limits on the spin temperature at a redshift of 8.4. We find that the spin temperature is at least 10K for a neutral fraction between 15% and 80%. This further suggests that there was heating in the early universe through various sources such as x-ray binaries.

  20. Normalized Noise Power Spectrum of Full Field Digital Mammography System

    SciTech Connect

    Isa, Norriza Mohd; Wan Hassan, Wan Muhamad Saridan

    2010-01-05

    A method to measure noise power spectrum of a full field digital mammography system is presented. The effect of X-ray radiation dose, size and configuration of region of interest on normalized noise power spectrum (NNPS) was investigated. Flat field images were acquired using RQA-M2 beam quality technique (Mo/Mo anode-filter, 28 kV, 2 mm Al) with different clinical radiation doses. The images were cropped at about 4 cm from the edge of the breast wall and then divided into different size of non-overlapping or overlapping segments. NNPS was determined through detrending, 2-D fast Fourier transformation and normalization. Our measurement shows that high radiation dose gave lower NNPS at a specific beam quality.

  1. Nonisotropy in the CMB power spectrum in single field inflation

    SciTech Connect

    Donoghue, John F.; Dutta, Koushik; Ross, Andreas

    2009-07-15

    Contaldi et al.[C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys. 07 (2003) 002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of l. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low l.

  2. Measurement of primordial non-Gaussianity using the WMAP 5-year temperature skewness power spectrum

    SciTech Connect

    Smidt, Joseph; Amblard, Alexandre; Serra, Paolo; Cooray, Asantha

    2009-12-15

    We constrain the primordial non-Gaussianity parameter of the local model f{sub NL} using the skewness power spectrum associated with the two-to-one cumulant correlator of cosmic microwave background temperature anisotropies. This bispectrum-related power spectrum was constructed after weighting the temperature map with the appropriate window functions to form an estimator that probes the multipolar dependence of the underlying bispectrum associated with the primordial non-Gaussianity. We also estimate a separate skewness power spectrum sensitive more strongly to unresolved point sources. When compared to previous attempts at measuring the primordial non-Gaussianity with WMAP data, our estimators have the main advantage that we do not collapse information to a single number. When model fitting the two-to-one skewness power spectrum, we make use of bispectra generated by the primordial non-Gaussianity, radio point sources, and lensing-secondary correlation. We analyze Q, V, and W-band WMAP 5-year data using the KQ75 mask out to l{sub max}=600. Using V and W-band data and marginalizing over model parameters related to point sources and lensing-secondary bispectrum, our overall and preferred constraint on f{sub NL} is 11.0{+-}23.7 at the 68% confidence level (-36.4

  3. Reproducing neutrino effects on the matter power spectrum through a degenerate Fermi gas approach

    NASA Astrophysics Data System (ADS)

    Perico, E. L. D.; Bernardini, A. E.

    2011-06-01

    Modifications on the predictions about the matter power spectrum based on the hypothesis of a tiny contribution from a degenerate Fermi gas (DFG) test-fluid to some dominant cosmological scenario are investigated. Reporting about the systematic way of accounting for all the cosmological perturbations, through the Boltzmann equation we obtain the analytical results for density fluctuation, δ, and fluid velocity divergence, θ, of the DFG. Small contributions to the matter power spectrum are analytically obtained for the radiation-dominated background, through an ultra-relativistic approximation, and for the matter-dominated and Λ-dominated eras, through a non-relativistic approximation. The results can be numerically reproduced and compared with those of considering non-relativistic and ultra-relativistic neutrinos into the computation of the matter power spectrum. Lessons concerning the formation of large scale structures of a DFG are depicted, and consequent deviations from standard ΛCDM predictions for the matter power spectrum (with and without neutrinos) are quantified.

  4. REVISING THE HALOFIT MODEL FOR THE NONLINEAR MATTER POWER SPECTRUM

    SciTech Connect

    Takahashi, Ryuichi; Sato, Masanori; Nishimichi, Takahiro; Taruya, Atsushi; Oguri, Masamune

    2012-12-20

    Based on a suite of state-of-the-art high-resolution N-body simulations, we revisit the so-called halofit model as an accurate fitting formula for the nonlinear matter power spectrum. While the halofit model has frequently been used as a standard cosmological tool to predict the nonlinear matter power spectrum in a universe dominated by cold dark matter, its precision has been limited by the low resolution of N-body simulations used to determine the fitting parameters, suggesting the necessity of an improved fitting formula at small scales for future cosmological studies. We run high-resolution N-body simulations for 16 cosmological models around the Wilkinson Microwave Anisotropy Probe best-fit cosmological parameters (one-, three-, five-, and seven-year results), including dark energy models with a constant equation of state. The simulation results are used to re-calibrate the fitting parameters of the halofit model so as to reproduce small-scale power spectra of the N-body simulations, while keeping the precision at large scales. The revised fitting formula provides an accurate prediction of the nonlinear matter power spectrum in a wide range of wavenumbers (k {<=} 30 h Mpc{sup -1}) at redshifts 0 {<=} z {<=} 10, with 5% precision for k {<=} 1 h Mpc{sup -1} at 0 {<=} z {<=} 10 and 10% for 1 {<=} k {<=} 10 h Mpc{sup -1} at 0 {<=} z {<=} 3. We discuss the impact of the improved halofit model on weak-lensing power spectra and correlation functions, and show that the improved model better reproduces ray-tracing simulation results.

  5. Gamma-ray Background Spectrum and Annihilation Rate in the Baryon-symmetric Big-bang Cosmology

    NASA Technical Reports Server (NTRS)

    Puget, J. L.

    1973-01-01

    An attempt was made to acquire experimental information on the problem of baryon symmetry on a large cosmological scale by observing the annihilation products. Data cover absorption cross sections and background radiation due to other sources for the two main products of annihilation, gamma rays and neutrinos. Test results show that the best direct experimental test for the presence of large scale antimatter lies in the gamma ray background spectrum between 1 and 70 MeV.

  6. Influence of DBT reconstruction algorithm on power law spectrum coefficient

    NASA Astrophysics Data System (ADS)

    Vancamberg, Laurence; Carton, Ann-Katherine; Abderrahmane, Ilyes H.; Palma, Giovanni; Milioni de Carvalho, Pablo; Iordache, Rǎzvan; Muller, Serge

    2015-03-01

    In breast X-ray images, texture has been characterized by a noise power spectrum (NPS) that has an inverse power-law shape described by its slope β in the log-log domain. It has been suggested that the magnitude of the power-law spectrum coefficient β is related to mass lesion detection performance. We assessed β in reconstructed digital breast tomosynthesis (DBT) images to evaluate its sensitivity to different typical reconstruction algorithms including simple back projection (SBP), filtered back projection (FBP) and a simultaneous iterative reconstruction algorithm (SIRT 30 iterations). Results were further compared to the β coefficient estimated from 2D central DBT projections. The calculations were performed on 31 unilateral clinical DBT data sets and simulated DBT images from 31 anthropomorphic software breast phantoms. Our results show that β highly depends on the reconstruction algorithm; the highest β values were found for SBP, followed by reconstruction with FBP, while the lowest β values were found for SIRT. In contrast to previous studies, we found that β is not always lower in reconstructed DBT slices, compared to 2D projections and this depends on the reconstruction algorithm. All β values estimated in DBT slices reconstructed with SBP were larger than β values from 2D central projections. Our study also shows that the reconstruction algorithm affects the symmetry of the breast texture NPS; the NPS of clinical cases reconstructed with SBP exhibit the highest symmetry, while the NPS of cases reconstructed with SIRT exhibit the highest asymmetry.

  7. CHIPS: The Cosmological H i Power Spectrum Estimator

    NASA Astrophysics Data System (ADS)

    Trott, C. M.; Pindor, B.; Procopio, P.; Wayth, R. B.; Mitchell, D. A.; McKinley, B.; Tingay, S. J.; Barry, N.; Beardsley, A. P.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Carroll, P.; de Oliveira-Costa, A.; Dillon, Joshua S.; Ewall-Wice, A.; Feng, L.; Greenhill, L. J.; Hazelton, B. J.; Hewitt, J. N.; Hurley-Walker, N.; Johnston-Hollitt, M.; Jacobs, Daniel C.; Kaplan, D. L.; Kim, H. S.; Lenc, E.; Line, J.; Loeb, A.; Lonsdale, C. J.; Morales, M. F.; Morgan, E.; Neben, A. R.; Thyagarajan, Nithyanandan; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Paul, S.; Pober, J. C.; Prabu, T.; Riding, J.; Udaya Shankar, N.; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Sullivan, I. S.; Tegmark, M.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S. B.

    2016-02-01

    Detection of the cosmological neutral hydrogen signal from the Epoch of Reionization (EoR) and estimation of its basic physical parameters are principal scientific aims of many current low-frequency radio telescopes. Here we describe the Cosmological H i Power Spectrum Estimator (CHIPS), an algorithm developed and implemented with data from the Murchison Widefield Array, to compute the two-dimensional and spherically-averaged power spectrum of brightness temperature fluctuations. The principal motivations for CHIPS are the application of realistic instrumental and foreground models to form the optimal estimator, thereby maximizing the likelihood of unbiased signal estimation, and allowing a full covariant understanding of the outputs. CHIPS employs an inverse-covariance weighting of the data through the maximum likelihood estimator, thereby allowing use of the full parameter space for signal estimation (“foreground suppression”). We describe the motivation for the algorithm, implementation, application to real and simulated data, and early outputs. Upon application to a set of 3 hr of data, we set a 2σ upper limit on the EoR dimensionless power at k=0.05 {{h}} Mpc-1 of {{{Δ }}}k2\\lt 7.6× {10}4 mK2 in the redshift range z = [6.2-6.6], consistent with previous estimates.

  8. Distributed Energy Resources, Power Quality and Reliability - Background

    SciTech Connect

    Schienbein, Lawrence A.; DeSteese, John G.

    2002-01-31

    Power quality [PQ] and power reliability [PR] gained importance in the industrialized world as the pace of installation of sensitive appliances and other electrical loads by utility customers accelerated, beginning in the mid 1980s. Utility-grid-connected customers rapidly discovered that this equipment was increasingly sensitive to various abnormalities in the electricity supply.

  9. IONOSPHERIC POWER-SPECTRUM TOMOGRAPHY IN RADIO INTERFEROMETRY

    SciTech Connect

    Koopmans, L. V. E.

    2010-08-01

    A tomographic method is described to quantify the three-dimensional power spectrum of the ionospheric electron-density fluctuations based on radio-interferometric observations by a two-dimensional planar array. The method is valid for the first-order Born approximation and might be applicable in correcting observed visibilities for phase variations due to the imprint of the full three-dimensional ionosphere. It is shown that the ionospheric electron-density distribution is not the primary structure to model in interferometry, but rather its autocorrelation function or equivalently its power spectrum. An exact mathematical expression is derived that provides the three-dimensional power spectrum of the ionospheric electron-density fluctuations directly from a rescaled scattered intensity field and an incident intensity field convolved with a complex unit phasor that depends on the w-term and is defined on the full sky pupil plane. In the limit of a small field of view, the method reduces to the single phase-screen approximation. Tomographic self-calibration can become important in high-dynamic range observations at low radio frequencies with wide-field antenna interferometers because a three-dimensional ionosphere causes a spatially varying convolution of the sky, whereas a single phase screen results in a spatially invariant convolution. A thick ionosphere can therefore not be approximated by a single phase screen without introducing errors in the calibration process. By applying a Radon projection and the Fourier projection-slice theorem, it is shown that the phase-screen approach in three dimensions is identical to the tomographic method. Finally, we suggest that residual speckle can cause a diffuse intensity halo around sources due to uncorrectable ionospheric phase fluctuations in the short integrations, which could pose a fundamental limit on the dynamic range in long-integration images.

  10. Matter power spectrum and the challenge of percent accuracy

    NASA Astrophysics Data System (ADS)

    Schneider, Aurel; Teyssier, Romain; Potter, Doug; Stadel, Joachim; Onions, Julian; Reed, Darren S.; Smith, Robert E.; Springel, Volker; Pearce, Frazer R.; Scoccimarro, Roman

    2016-04-01

    Future galaxy surveys require one percent precision in the theoretical knowledge of the power spectrum over a large range including very nonlinear scales. While this level of accuracy is easily obtained in the linear regime with perturbation theory, it represents a serious challenge for small scales where numerical simulations are required. In this paper we quantify the precision of present-day N-body methods, identifying main potential error sources from the set-up of initial conditions to the measurement of the final power spectrum. We directly compare three widely used N-body codes, Ramses, Pkdgrav3, and Gadget3 which represent three main discretisation techniques: the particle-mesh method, the tree method, and a hybrid combination of the two. For standard run parameters, the codes agree to within one percent at k<=1 h Mpc‑1 and to within three percent at k<=10 h Mpc‑1. We also consider the bispectrum and show that the reduced bispectra agree at the sub-percent level for k<= 2 h Mpc‑1. In a second step, we quantify potential errors due to initial conditions, box size, and resolution using an extended suite of simulations performed with our fastest code Pkdgrav3. We demonstrate that the simulation box size should not be smaller than L=0.5 h‑1Gpc to avoid systematic finite-volume effects (while much larger boxes are required to beat down the statistical sample variance). Furthermore, a maximum particle mass of Mp=109 h‑1Msolar is required to conservatively obtain one percent precision of the matter power spectrum. As a consequence, numerical simulations covering large survey volumes of upcoming missions such as DES, LSST, and Euclid will need more than a trillion particles to reproduce clustering properties at the targeted accuracy.

  11. Constraints on massive neutrinos from the CFHTLS angular power spectrum

    SciTech Connect

    Xia, Jun-Qing; Granett, Benjamin R.; Guzzo, Luigi; Viel, Matteo; Bird, Simeon; Haehnelt, Martin G.; Coupon, Jean; McCracken, Henry Joy; Mellier, Yannick E-mail: ben.granett@brera.inaf.it E-mail: spb@ias.edu E-mail: haehnelt@ast.cam.ac.uk E-mail: hjmcc@iap.fr

    2012-06-01

    We use the galaxy angular power spectrum at z ∼ 0.5–1.2 from the Canada-France-Hawaii-Telescope Legacy Survey Wide fields (CFHTLS-Wide) to constrain separately the total neutrino mass Σm{sub ν} and the effective number of neutrino species N{sub eff}. This survey has recently benefited from an accurate calibration of the redshift distribution, allowing new measurements of the (non-linear) matter power spectrum in a unique range of scales and redshifts sensitive to neutrino free streaming. Our analysis makes use of a recent model for the effect of neutrinos on the weakly non-linear matter power spectrum derived from accurate N-body simulations. We show that CFHTLS, combined with WMAP7 and a prior on the Hubble constant provides an upper limit of Σm{sub ν} < 0.29 eV and N{sub eff} = 4.17{sup +1.62}{sub −1.26} (2 σ confidence levels). If we omit smaller scales which may be affected by non-linearities, these constraints become Σm{sub ν} < 0.41 eV and N{sub eff} = 3.98{sup +2.02}{sub −1.20} (2 σ confidence levels). Finally we show that the addition of other large scale structures probes can further improve these constraints, demonstrating that high redshift large volumes surveys such as CFHTLS are complementary to other cosmological probes of the neutrino mass.

  12. Imprint of inhomogeneous and anisotropic primordial power spectrum on CMB polarization

    NASA Astrophysics Data System (ADS)

    Kothari, Rahul; Ghosh, Shamik; Rath, Pranati K.; Kashyap, Gopal; Jain, Pankaj

    2016-08-01

    We consider an inhomogeneous model and independently an anisotropic model of primordial power spectrum in order to describe the observed hemispherical anisotropy in cosmic microwave background radiation (CMBR). This anisotropy can be parametrized in terms of the dipole modulation model of the temperature field. Both the models lead to correlations between spherical harmonic coefficients corresponding to multipoles, l and l ± 1. We obtain the model parameters by making a fit to TT correlations in CMBR data. Using these parameters we predict the signature of our models for correlations among different multipoles for the case of the TE and EE modes. These predictions can be used to test whether the observed hemispherical anisotropy can be correctly described in terms of a primordial power spectrum. Furthermore these may also allow us to distinguish between an inhomogeneous and an anisotropic model.

  13. Imprint of Inhomogeneous and Anisotropic Primordial Power Spectrum on CMB Polarization

    NASA Astrophysics Data System (ADS)

    Kothari, Rahul; Ghosh, Shamik; Rath, Pranati K.; Kashyap, Gopal; Jain, Pankaj

    2016-05-01

    We consider an inhomogeneous model and independently an anisotropic model of primordial power spectrum in order to describe the observed hemispherical anisotropy in Cosmic Microwave Background Radiation. This anisotropy can be parametrized in terms of the dipole modulation model of the temperature field. Both the models lead to correlations between spherical harmonic coefficients corresponding to multipoles, l and l ± 1. We obtain the model parameters by making a fit to TT correlations in CMBR data. Using these parameters we predict the signature of our models for correlations among different multipoles for the case of the TE and EE modes. These predictions can be used to test whether the observed hemispherical anisotropy can be correctly described in terms of a primordial power spectrum. Furthermore these may also allow us to distinguish between an inhomogeneous and an anisotropic model.

  14. HMcode: Halo-model matter power spectrum computation

    NASA Astrophysics Data System (ADS)

    Mead, Alexander

    2015-08-01

    HMcode computes the halo-model matter power spectrum. It is written in Fortran90 and has been designed to quickly (~0.5s for 200 k-values across 16 redshifts on a single core) produce matter spectra for a wide range of cosmological models. In testing it was shown to match spectra produced by the 'Coyote Emulator' to an accuracy of 5 per cent for k less than 10h Mpc^-1. However, it can also produce spectra well outside of the parameter space of the emulator.

  15. Ultrasonic Inspection With Angular-Power-Spectrum Scanning

    NASA Technical Reports Server (NTRS)

    Generazio, Edward R.

    1994-01-01

    Principal advantage of angular-power-spectrum scanning (APSS) is that, unlike x-radiography and prior ultrasonic techniques, it reveals subtle distributions of microstructural features; e.g., variations in densities of micropores or regions in which fibers and matrices are poorly bonded to each other. Potential applications include development and characterization of composite-material components of large structures, such as buildings and bridges; determination of quality and detection of damage in fiberglass hulls, surfboards, ladders, and scaffolds; and development of porous prosthetic skins and complicated "smart" materials. Superposed diffraction patterns give clues to internal structural features of ceramic composites.

  16. Spectrum of power laws for curved hand movements

    PubMed Central

    Huh, Dongsung; Sejnowski, Terrence J.

    2015-01-01

    In a planar free-hand drawing of an ellipse, the speed of movement is proportional to the −1/3 power of the local curvature, which is widely thought to hold for general curved shapes. We investigated this phenomenon for general curved hand movements by analyzing an optimal control model that maximizes a smoothness cost and exhibits the −1/3 power for ellipses. For the analysis, we introduced a new representation for curved movements based on a moving reference frame and a dimensionless angle coordinate that revealed scale-invariant features of curved movements. The analysis confirmed the power law for drawing ellipses but also predicted a spectrum of power laws with exponents ranging between 0 and −2/3 for simple movements that can be characterized by a single angular frequency. Moreover, it predicted mixtures of power laws for more complex, multifrequency movements that were confirmed with human drawing experiments. The speed profiles of arbitrary doodling movements that exhibit broadband curvature profiles were accurately predicted as well. These findings have implications for motor planning and predict that movements only depend on one radian of angle coordinate in the past and only need to be planned one radian ahead. PMID:26150514

  17. Peaks in the CMBR Power Spectrum II: Physical Interpretation for any Cosmological Scenario

    NASA Astrophysics Data System (ADS)

    López-Corredoira, Martín

    2013-06-01

    In a previous paper (part I), the mathematical properties of the cosmic microwave background radiation (CMBR) power spectrum which presents oscillations were discussed. Here, we discuss the physical interpretation: a power spectrum with oscillations is a rather normal characteristic expected from any fluid with clouds of overdensities that emit/absorb radiation or interact gravitationally with the photons, and with a finite range of sizes and distances for those clouds. The standard cosmological interpretation of "acoustic" peaks is just a particular case; peaks in the power spectrum might be generated in scenarios within some alternative cosmological model that have nothing to do with oscillations due to gravitational compression in a fluid. We also calculate the angular correlation function of the anisotropies from the Wilkinson Microwave Anisotropy Probe (WMAP)-7 yr and ACT data, in an attempt to derive the minimum number of parameters a polynomial function should have to fit it: a set of polynomial functions with a total of ≈ 6 free parameters, apart from the amplitude, is enough to reproduce the first two peaks. However, the standard model with six tunable free parameters also reproduces higher-order peaks, giving the standard model a higher confidence. At present, while no simple function with six free parameters is found to give a fit as good as the one given by the standard cosmological model, we may consider the predictive power of the standard model beyond an instrumentalist approach (such as the Ptolemaic astronomy model of the orbits of the planets).

  18. Effective field theory during inflation. II. Stochastic dynamics and power spectrum suppression

    NASA Astrophysics Data System (ADS)

    Boyanovsky, D.

    2016-02-01

    We obtain the nonequilibrium effective action of an inflatonlike scalar field—the system—by tracing over sub-Hubble degrees of freedom of "environmental" light scalar fields. The effective action is stochastic leading to effective Langevin equations of motion for the fluctuations of the inflatonlike field, with self-energy corrections and stochastic noise correlators that obey a de Sitter space-time analog of a fluctuation dissipation relation. We solve the Langevin equation implementing a dynamical renormalization group resummation of the leading secular terms and obtain the corrections to the power spectrum of super-Hubble fluctuations of the inflaton field, P (k ;η )=P0(k )e-γ (k ;η ) where P0(k ) is the nearly scale invariant power spectrum in absence of coupling. γ (k ;η )>0 describes the suppression of the power spectrum; it features Sudakov-type double logarithms and entails violations of scale invariance. We also obtain the effective action for the case of a heavy scalar field of mass M ≫H ; this case yields a local "Fermi" limit with a very weak self-interaction of the inflatonlike field and dissipative terms that are suppressed by powers of H /M . We conjecture on the possibility that the large scale anomalies in the cosmic microwave background may originate in dissipative processes from inflaton coupling to sub-Hubble degrees of freedom.

  19. Nonisotropy in the CMB power spectrum in single field inflation

    NASA Astrophysics Data System (ADS)

    Donoghue, John F.; Dutta, Koushik; Ross, Andreas

    2009-07-01

    Contaldi et al. [C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys.1475-7516 07 (2003) 00210.1088/1475-7516/2003/07/002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of ℓ. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low ℓ.

  20. Power Spectrum Density of Stochastic Oscillating Accretion Disk

    NASA Astrophysics Data System (ADS)

    Long, G. B.; Ou, J. W.; Zheng, Y. G.

    2016-06-01

    In this paper, we employ a stochastic oscillating accretion disk model for the power spectral index and variability of BL Lac object S5 0716+714. In the model, we assume that there is a relativistic oscillation of thin accretion disks and it interacts with an external thermal bath through a friction force and a random force. We simulate the light curve and the power spectrum density (PSD) at (i) over-damped, (ii) critically damped and (iii) under-damped cases, respectively. Our results show that the simulated PSD curves depend on the intrinsic property of the accretion disk, and it could be produced in a wide interval ranging from 0.94 to 2.05 by changing the friction coefficient in a stochastic oscillating accretion disk model. We argue that accretion disk stochastic oscillating could be a possible interpretation for observed PSD variability.

  1. Unbiased contaminant removal for 3D galaxy power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Kalus, B.; Percival, W. J.; Bacon, D. J.; Samushia, L.

    2016-08-01

    We assess and develop techniques to remove contaminants when calculating the 3D galaxy power spectrum. We separate the process into three separate stages: (i) removing the contaminant signal, (ii) estimating the uncontaminated cosmological power spectrum, (iii) debiasing the resulting estimates. For (i), we show that removing the best-fit contaminant (mode subtraction), and setting the contaminated components of the covariance to be infinite (mode deprojection) are mathematically equivalent. For (ii), performing a Quadratic Maximum Likelihood (QML) estimate after mode deprojection gives an optimal unbiased solution, although it requires the manipulation of large N_mode^2 matrices (Nmode being the total number of modes), which is unfeasible for recent 3D galaxy surveys. Measuring a binned average of the modes for (ii) as proposed by Feldman, Kaiser & Peacock (1994, FKP) is faster and simpler, but is sub-optimal and gives rise to a biased solution. We present a method to debias the resulting FKP measurements that does not require any large matrix calculations. We argue that the sub-optimality of the FKP estimator compared with the QML estimator, caused by contaminants is less severe than that commonly ignored due to the survey window.

  2. Joint Bayesian Component Separation and CMB Power Spectrum Estimation

    NASA Technical Reports Server (NTRS)

    Eriksen, H. K.; Jewell, J. B.; Dickinson, C.; Banday, A. J.; Gorski, K. M.; Lawrence, C. R.

    2008-01-01

    We describe and implement an exact, flexible, and computationally efficient algorithm for joint component separation and CMB power spectrum estimation, building on a Gibbs sampling framework. Two essential new features are (1) conditional sampling of foreground spectral parameters and (2) joint sampling of all amplitude-type degrees of freedom (e.g., CMB, foreground pixel amplitudes, and global template amplitudes) given spectral parameters. Given a parametric model of the foreground signals, we estimate efficiently and accurately the exact joint foreground- CMB posterior distribution and, therefore, all marginal distributions such as the CMB power spectrum or foreground spectral index posteriors. The main limitation of the current implementation is the requirement of identical beam responses at all frequencies, which restricts the analysis to the lowest resolution of a given experiment. We outline a future generalization to multiresolution observations. To verify the method, we analyze simple models and compare the results to analytical predictions. We then analyze a realistic simulation with properties similar to the 3 yr WMAP data, downgraded to a common resolution of 3 deg FWHM. The results from the actual 3 yr WMAP temperature analysis are presented in a companion Letter.

  3. Power spectrum for inflation models with quantum and thermal noises

    SciTech Connect

    Ramos, Rudnei O.; Silva, L.A. da E-mail: las.leandro@gmail.com

    2013-03-01

    We determine the power spectrum for inflation models covering all regimes from cold (isentropic) to warm (nonisentropic) inflation. We work in the context of the stochastic inflation approach, which can nicely describe both types of inflationary regimes concomitantly. A throughout analysis is carried out to determine the allowed parameter space for simple single field polynomial chaotic inflation models that is consistent with the most recent cosmological data from the nine-year Wilkinson Microwave Anisotropy Probe (WMAP) and in conjunction with other observational cosmological sources. We present the results for both the amplitude of the power spectrum, the spectral index and for the tensor to scalar curvature perturbation amplitude ratio. We briefly discuss cases when running is present. Despite single field polynomial-type inflaton potential models be strongly disfavored, or even be already ruled out in their simplest versions in the case of cold inflation, this is not the case for nonisentropic inflation models in general (warm inflation in particular), though higher order polynomial potentials (higher than quartic order) tend to become less favorable also in this case, presenting a much smaller region of parameter space compatible with the recent observational cosmological data.

  4. State regulation and power plant productivity: background and recommendations

    SciTech Connect

    Not Available

    1980-09-01

    This report was prepared by representatives of several state regulatory agencies. It is a guide to some of the activities currently under way in state agencies to promote increased availability of electrical generating power plants. Standard measures of plant performance are defined and the nature of data bases that report such measures is discussed. It includes reviews of current state, federal, and industry programs to enhance power plant productivity and provides detailed outlines of programs in effect in California, Illinois, Michigan, New York, North Carolina, Ohio, and Texas. A number of actions are presented that could be adopted by state regulatory agencies, depending on local conditions. They include: develop a commission position or policy statement to encourage productivity improvements by utilities; coordinate state efforts with ongoing industry and government programs to improve the acquisition of power plant performance data and the maintenance of quality information systems; acquire the capability to perform independent analyses of power plant productivity; direct the establishment of productivity improvement programs, including explicit performance objectives for both existing and planned power plants, and a performance program; establish a program of incentives to motivate productivity improvement activities; and participate in ongoing efforts at all levels and initiate new actions to promote productivity improvements.

  5. Power spectrum sensitivity of raster-scanned CMB experiments in the presence of 1/f noise

    SciTech Connect

    Crawford, Tom

    2007-09-15

    We investigate the effects of 1/f noise on the ability of a particular class of cosmic microwave background experiments to measure the angular power spectrum of temperature anisotropy. We concentrate on experiments that operate primarily in raster-scan mode and develop formalism that allows us to calculate analytically the effect of 1/f noise on power-spectrum sensitivity for this class of experiments and determine the benefits of raster-scanning at different angles relative to the sky field versus scanning at only a single angle (cross-linking versus not cross-linking). We find that the sensitivity of such experiments in the presence of 1/f noise is not significantly degraded at moderate spatial scales (l{approx}100) for reasonable values of scan speed and 1/f knee. We further find that the difference between cross-linked and non-cross-linked experiments is small in all cases and that the non-cross-linked experiments are preferred from a raw sensitivity standpoint in the noise-dominated regime - i.e., in experiments in which the instrument noise is greater than the sample variance of the target power spectrum at the scales of interest. This analysis does not take into account systematic effects.

  6. Violation of statistical isotropy and homogeneity in the 21-cm power spectrum

    NASA Astrophysics Data System (ADS)

    Shiraishi, Maresuke; Muñoz, Julian B.; Kamionkowski, Marc; Raccanelli, Alvise

    2016-05-01

    Most inflationary models predict primordial perturbations to be statistically isotropic and homogeneous. Cosmic microwave background (CMB) observations, however, indicate a possible departure from statistical isotropy in the form of a dipolar power modulation at large angular scales. Alternative models of inflation, beyond the simplest single-field slow-roll models, can generate a small power asymmetry, consistent with these observations. Observations of clustering of quasars show, however, agreement with statistical isotropy at much smaller angular scales. Here, we propose to use off-diagonal components of the angular power spectrum of the 21-cm fluctuations during the dark ages to test this power asymmetry. We forecast results for the planned SKA radio array, a future radio array, and the cosmic-variance-limited case as a theoretical proof of principle. Our results show that the 21-cm line power spectrum will enable access to information at very small scales and at different redshift slices, thus improving upon the current CMB constraints by ˜2 orders of magnitude for a dipolar asymmetry and by ˜1 - 3 orders of magnitude for a quadrupolar asymmetry case.

  7. Updating constraints on inflationary features in the primordial power spectrum with the Planck data

    NASA Astrophysics Data System (ADS)

    Benetti, Micol

    2013-10-01

    We present new constraints on possible features in the primordial inflationary density perturbation power spectrum in light of the recent cosmic microwave background anisotropy measurements from the Planck satellite. We found that the Planck data hints for the presence of features in two different ranges of angular scales, corresponding to multipoles 10<ℓ<60 and 150<ℓ<300, with a decrease in the best-fit χ2 value with respect to the featureless “vanilla” ΛCDM model of Δχ2≃9 in both cases.

  8. Increased photovoltaic power output via diffractive spectrum separation.

    PubMed

    Kim, Ganghun; Dominguez-Caballero, Jose A; Lee, Howard; Friedman, Daniel J; Menon, Rajesh

    2013-03-22

    In this Letter, we report the preliminary demonstration of a new paradigm for photovoltaic power generation that utilizes a broadband diffractive-optical element (BDOE) to efficiently separate sunlight into laterally spaced spectral bands. These bands are then absorbed by single-junction photovoltaic cells, whose band gaps correspond to the incident spectral bands. We designed such BDOEs by utilizing a modified version of the direct-binary-search algorithm. Gray scale lithography was used to fabricate these multilevel optics. They were experimentally characterized with an overall optical efficiency of 70% over a wavelength range of 350-1100 nm, which was in excellent agreement with simulation predictions. Finally, two prototype devices were assembled: one with a pair of copper indium gallium selenide based photovoltaic devices, and another with GaAs and c-Si photovoltaic devices. These devices demonstrated an increase in output peak electrical power of ∼ 42% and ∼ 22%, respectively, under white-light illumination. Because of the optical versatility and manufacturability of the proposed BDOEs, the reported spectrum-splitting approach provides a new approach toward low-cost solar power. PMID:25166805

  9. Power Spectrum Density of Long-Term MAXI Data

    NASA Astrophysics Data System (ADS)

    Sugimoto, Juri; Mihara, Tatehiro; Sugizaki, Mutsumi; Serino, Motoko; Kitamoto, Shunji; Sato, Ryousuke; Ueda, Yoshihiro; Ueno, Shiro

    Monitor of All-sky X-ray Image (MAXI) on the International Space Station has been observing the X-ray sky since 2009 August 15. It has accumulated the X-ray data for about four years, so far. X-ray objects are usually variable and their variability can be studied by the power spectrum density (PSD) of the X-ray light curves. We applied our method to calculate PSDs of several kinds of objects observed with MAXI. We obtained significant PSDs from 16 Seyfert galaxies. For blackhole binary Cygnus X-1 there was a difference in the shape of PSD between the hard state and the soft state. For high mass X-ray binaries, Cen X-3, SMC X-1, and LMC X-4, there were several peaks in the PSD corresponding to the orbital period and the superorbital period.

  10. Fermi-bounce cosmology and scale-invariant power spectrum

    NASA Astrophysics Data System (ADS)

    Alexander, Stephon; Bambi, Cosimo; Marcianò, Antonino; Modesto, Leonardo

    2014-12-01

    We develop a nonsingular bouncing cosmology using a nontrivial coupling of general relativity to fermionic fields. The usual big bang singularity is avoided thanks to a negative energy density contribution from the fermions. Our theory is ghost free since the fermionic operator that generates the bounce is equivalent to torsion, which has no kinetic terms. The physical system consists of standard general relativity plus a topological sector for gravity and fermionic matter described by Dirac fields with a nonminimal coupling. We show that a scale-invariant power spectrum generated in the contracting phase can be recovered by suitable choices of fermion number density and bare mass, thus providing a possible alternative to the inflationary scenario.

  11. Contribution of domain wall networks to the CMB power spectrum

    NASA Astrophysics Data System (ADS)

    Lazanu, A.; Martins, C. J. A. P.; Shellard, E. P. S.

    2015-07-01

    We use three domain wall simulations from the radiation era to the late-time dark energy domination era based on the PRS algorithm to calculate the energy-momentum tensor components of domain wall networks in an expanding universe. Unequal time correlators in the radiation, matter and cosmological constant epochs are calculated using the scaling regime of each of the simulations. The CMB power spectrum of a network of domain walls is determined. The first ever quantitative constraint for the domain wall surface tension is obtained using a Markov chain Monte Carlo method; an energy scale of domain walls of 0.93 MeV, which is close but below the Zel'dovich bound, is determined.

  12. Neutrino mass limits: Robust information from the power spectrum of galaxy surveys

    NASA Astrophysics Data System (ADS)

    Cuesta, Antonio J.; Niro, Viviana; Verde, Licia

    2016-09-01

    We present cosmological upper limits on the sum of active neutrino masses using large-scale power spectrum data from the WiggleZ Dark Energy Survey and from the Sloan Digital Sky Survey - Data Release 7 (SDSS-DR7) sample of Luminous Red Galaxies (LRG). Combining measurements on the Cosmic Microwave Background temperature and polarisation anisotropies by the Planck satellite together with WiggleZ power spectrum results in a neutrino mass bound of 0.37 eV at 95% C.L., while replacing WiggleZ by the SDSS-DR7 LRG power spectrum, the 95% C.L. bound on the sum of neutrino masses is 0.38 eV. Adding Baryon Acoustic Oscillation (BAO) distance scale measurements, the neutrino mass upper limits greatly improve, since BAO data break degeneracies in parameter space. Within a ΛCDM model, we find an upper limit of 0.13 eV (0.14 eV) at 95% C.L., when using SDSS-DR7 LRG (WiggleZ) together with BAO and Planck. The addition of BAO data makes the neutrino mass upper limit robust, showing only a weak dependence on the power spectrum used. We also quantify the dependence of neutrino mass limit reported here on the CMB lensing information. The tighter upper limit (0.13 eV) obtained with SDSS-DR7 LRG is very close to that recently obtained using Lyman-alpha clustering data, yet uses a completely different probe and redshift range, further supporting the robustness of the constraint. This constraint puts under some pressure the inverted mass hierarchy and favours the normal hierarchy.

  13. AlphaSpectrum ASPECT analysis code for background correction & peak integration

    Energy Science and Technology Software Center (ESTSC)

    2005-04-13

    The ASPECT code provides a means for rapid analysis of energy-resolved spectra obtained by multi-channel pulse-height analysis (MCA) during (or after) counting of alpha-emissions from a filter air sample (or other suitably prepared sample) utilizing a solid-state detector, or other detector having sufficient energy resolution indiviual radioisotope peaks indentified in a spectrum are fitted using a peak shape algorithm by non-linear least-square fitting procedures that minimize Chi-square differences between the data and a fitted peakmore » function. The code accomplishes the identification of all significant peaks present in the spectrum with automatic recalibration to the 7.68 Po-214 alpha peak from the Radon-222 decay chain, the subtraction of all radon progeny interference overlaps with lower energy peaks in the energy range of Pu-238, Am-241, Pu-239, and U-234/Th-232, and the integration of the counts in any peak identified for these transuranic radionuclides. The output is therefore in the form of isotope specific net transuranic CPM, DPM or concentration, available in near real-time during air sampling. In this "copyright" version, the assumption is made that the alpha spectra to be analyzed have been stored by unique name in sequential form: "FileName(i)", where "FileName" can be any name and i is the index number of the file saved (e.g., i = 1,2, ..., n). this format is one automatically generated by the alpha Environmental Continuous Air Monitor (ECAM), developed by Los Alamos National Laboratory, and manufactured by Canberra Industries, a Laboratory Industrial Partner for this technology. It is assumed in this version of the code that the alpha spectrum data are stored in a 256 channel spectrum, although a larger num ber of channels could be easily accommodated by small code changes. The ECAM data output format is RADNET compliant (an inidustry standard developed at Los Alamos), and include, in addition to a 256-channel alpha spectrum, data on the

  14. AlphaSpectrum ASPECT analysis code for background correction & peak integration

    SciTech Connect

    Rodgers, John C.

    2005-04-13

    The ASPECT code provides a means for rapid analysis of energy-resolved spectra obtained by multi-channel pulse-height analysis (MCA) during (or after) counting of alpha-emissions from a filter air sample (or other suitably prepared sample) utilizing a solid-state detector, or other detector having sufficient energy resolution indiviual radioisotope peaks indentified in a spectrum are fitted using a peak shape algorithm by non-linear least-square fitting procedures that minimize Chi-square differences between the data and a fitted peak function. The code accomplishes the identification of all significant peaks present in the spectrum with automatic recalibration to the 7.68 Po-214 alpha peak from the Radon-222 decay chain, the subtraction of all radon progeny interference overlaps with lower energy peaks in the energy range of Pu-238, Am-241, Pu-239, and U-234/Th-232, and the integration of the counts in any peak identified for these transuranic radionuclides. The output is therefore in the form of isotope specific net transuranic CPM, DPM or concentration, available in near real-time during air sampling. In this "copyright" version, the assumption is made that the alpha spectra to be analyzed have been stored by unique name in sequential form: "FileName(i)", where "FileName" can be any name and i is the index number of the file saved (e.g., i = 1,2, ..., n). this format is one automatically generated by the alpha Environmental Continuous Air Monitor (ECAM), developed by Los Alamos National Laboratory, and manufactured by Canberra Industries, a Laboratory Industrial Partner for this technology. It is assumed in this version of the code that the alpha spectrum data are stored in a 256 channel spectrum, although a larger num ber of channels could be easily accommodated by small code changes. The ECAM data output format is RADNET compliant (an inidustry standard developed at Los Alamos), and include, in addition to a 256-channel alpha spectrum, data on the count time

  15. Planck 2013 results. XXI. Power spectrum and high-order statistics of the Planck all-sky Compton parameter map

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Carvalho, P.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Comis, B.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Da Silva, A.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Flores-Cacho, I.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Génova-Santos, R. T.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lacasa, F.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; León-Tavares, J.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Marcos-Caballero, A.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Melchiorri, A.; Melin, J.-B.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-11-01

    We have constructed the first all-sky map of the thermal Sunyaev-Zeldovich (tSZ) effect by applying specifically tailored component separation algorithms to the 100 to 857 GHz frequency channel maps from the Planck survey. This map shows an obvious galaxy cluster tSZ signal that is well matched with blindly detected clusters in the Planck SZ catalogue. To characterize the signal in the tSZ map we have computed its angular power spectrum. At large angular scales (ℓ < 60), the major foreground contaminant is the diffuse thermal dust emission. At small angular scales (ℓ > 500) the clustered cosmic infrared background and residual point sources are the major contaminants. These foregrounds are carefully modelled and subtracted. We thus measure the tSZ power spectrum over angular scales 0.17° ≲ θ ≲ 3.0° that were previously unexplored. The measured tSZ power spectrum is consistent with that expected from the Planck catalogue of SZ sources, with clear evidence of additional signal from unresolved clusters and, potentially, diffuse warm baryons. Marginalized band-powers of the Planck tSZ power spectrum and the best-fit model are given. The non-Gaussianity of the Compton parameter map is further characterized by computing its 1D probability distribution function and its bispectrum. The measured tSZ power spectrum and high order statistics are used to place constraints on σ8.

  16. Unscreening Modified Gravity in the Matter Power Spectrum.

    PubMed

    Lombriser, Lucas; Simpson, Fergus; Mead, Alexander

    2015-06-26

    Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k<0.3h/Mpc can yield constraints on chameleon models that are more stringent than what is inferred from Solar System tests or distance indicators in unscreened dwarf galaxies. Finally, we verify that our method is also applicable to the Vainshtein mechanism. PMID:26197114

  17. The Distortion of the Cosmic Microwave Background Spectrum Due to Intergalactic Dust

    NASA Astrophysics Data System (ADS)

    Imara, Nia; Loeb, Abraham

    2016-07-01

    Infrared emission from intergalactic dust might compromise the ability of future experiments to detect subtle spectral distortions in the Cosmic Microwave Background (CMB) from the early universe. We provide the first estimate of foreground contamination of the CMB signal due to diffuse dust emission in the intergalactic medium. We use models of the extragalactic background light to calculate the intensity of intergalactic dust emission and find that emission by intergalactic dust at z ≲ 0.5 exceeds the sensitivity of the planned Primordial Inflation Explorer to CMB spectral distortions by 1–3 orders of magnitude. In the frequency range ν = 150–2400 GHz, we place an upper limit of 0.06% on the contribution to the far-infrared background from intergalactic dust emission.

  18. The Knotted Sky II: does BICEP2 require a nontrivial primordial power spectrum?

    SciTech Connect

    Abazajian, Kevork N.; Aslanyan, Grigor; Easther, Richard; Price, Layne C. E-mail: g.aslanyan@auckland.ac.nz E-mail: lpri691@aucklanduni.ac.nz

    2014-08-01

    An inflationary gravitational wave background consistent with BICEP2 is difficult to reconcile with a simple power-law spectrum of primordial scalar perturbations. Tensor modes contribute to the temperature anisotropies at multipoles with l∼< 100, and this effect — together with a prior on the form of the scalar perturbations — was the source of previous bounds on the tensor-to-scalar ratio. We compute Bayesian evidence for combined fits to BICEP2 and Planck for three nontrivial primordial spectra: a) a running spectral index, b) a cutoff at fixed wavenumber, and c) a spectrum described by a linear spline with a single internal knot. We find no evidence for a cutoff, weak evidence for a running index, and significant evidence for a ''broken'' spectrum. Taken at face-value, the BICEP2 results require two new inflationary parameters in order to describe both the broken scale invariance in the perturbation spectrum and the observed tensor-to-scalar ratio. Alternatively, this tension may be resolved by additional data and more detailed analyses.

  19. The thermal Sunyaev-Zel'dovich effect power spectrum in light of Planck

    NASA Astrophysics Data System (ADS)

    McCarthy, I. G.; Le Brun, A. M. C.; Schaye, J.; Holder, G. P.

    2014-06-01

    The amplitude of the thermal Sunyaev-Zel'dovich effect (tSZ) power spectrum is extremely sensitive to the abundance of the most massive dark matter haloes (galaxy clusters) and therefore to fundamental cosmological parameters that control their growth, such as σ8 and Ωm. Here we explore the sensitivity of the tSZ power spectrum to important non-gravitational (`subgrid') physics by employing the cosmo-OWLS suite of large-volume cosmological hydrodynamical simulations, run in both the Planck and 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) best-fitting cosmologies. On intermediate and small angular scales (ℓ ≳ 1000, or θ≲10 arcmin), accessible with the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT), the predicted tSZ power spectrum is highly model dependent, with gas ejection due to active galactic nuclei (AGN) feedback having a particularly large effect. However, at large scales, observable with the Planck telescope, the effects of subgrid physics are minor. Comparing the simulated tSZ power spectra with observations, we find a significant amplitude offset on all measured angular scales (including large scales), if the Planck best-fitting cosmology is assumed by the simulations. This is shown to be a generic result for all current models of the tSZ power spectrum. By contrast, if the WMAP7 cosmology is adopted, there is full consistency with the Planck tSZ power spectrum measurements on large scales and agreement at the 2σ level with the SPT and ACT measurements at intermediate scales for our fiducial AGN model, which Le Brun et al. have shown reproduces the `resolved' properties of the Local Group and cluster population remarkably well. These findings strongly suggest that there are significantly fewer massive galaxy clusters than expected for the Planck best-fitting cosmology, which is consistent with recent measurements of the tSZ number counts. Our findings therefore pose a significant challenge to the cosmological

  20. Spectrum of the cosmic background radiation: early and recent measurements from the White Mountain Research Station

    SciTech Connect

    Smoot, G.F.

    1985-09-01

    The White Mountain Research Station has provided a support facility at a high, dry, radio-quiet site for measurements that have established the blackbody character of the cosmic microwave background radiation. This finding has confirmed the interpretation of the radiation as a relic of the primeval fireball and helped to establish the hot Big Bang theory as the standard cosmological model.

  1. Analysis of noise power spectrum of gamma rays camera

    NASA Astrophysics Data System (ADS)

    Xie, Hongwei; Zhang, Faqiang; Zhang, Jianhua; Chen, Jinchuan; Chen, Dingyang; Li, Linbo

    2014-01-01

    Gamma rays camera is widely used in many studies, including the image diagnostics of the radiation sources, flash photography, and nondestructive assessment (NDA), etc. As a major component of the high sensitivity gamma rays camera, the MCP image intensifier is characterized in the intensified image, tunable shutter time and gain. The gamma rays camera is consisting with rays-fluorescence convertor, the optical imaging system, the MCP image intensifier, CCD and other devices. The performance of the gamma rays camera is mainly dependent on such parameters as the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE), etc. All of the parameters are somewhat limited by the noise characteristics of the system. Compared with the standard derivative noise distribution, the NPS, which can reflect the evolution characteristics of the noise of the imaging system with the change of the spatial frequency, could convey more information on the noise distribution in the system. In this paper, theoretical analysis is presented on the major sources of the noise in the gamma rays camera. Based on the analysis, the noise power spectra of the gamma rays camera were calibrated under various radiation dosages respectively with the visible light and gamma rays radiation sources (0.2MeV and 1.25MeV in energy, respectively). As indicated by the experimental results, the noise is majorly induced by the fluctuations of the gain of the MCP image intensifier. And the remarkable noise peak occurs nearby the spatial frequency of about 0.633 Hz/mm. And almost the same phenomena were found with both the 0.2MeV and 1.25MeV radiation energy. Besides, the noise power spectra are in circular symmetrical distribution, whose intensities are rapidly decreased with the increasing spatial frequencies.

  2. Tissue type characterization using photoacoustic power spectrum, a feasibility study

    NASA Astrophysics Data System (ADS)

    Tavakoli, Behnoosh; Goldstein, Seth D.; Kang, Jin U.; Choti, Michaal; Boctor, Emad M.

    2015-03-01

    The development of technologies capable of non-invasive characterization of tissue has the potential to significantly improve diagnostic and therapeutic medical interventions. In this study we investigated the feasibility of a noninvasive photoacoustic (PA) approach for characterizing biological tissues. The measurement was performed in the transmission mode with a wideband hydrophone while a tunable Q-switched Nd:YAG pulsed laser was used for illumination. The power spectrum of photoacoustic signal induced by a pulsed laser light from tissue was analyzed and features were extracted to study their correlation with tissue biomechanical properties. For a controlled study, tissue mimicking gelatin phantoms with different densities and equivalent optical absorptions were used as targets. The correlation between gelatin concentration of such phantoms and their mechanical properties were validated independently with a dynamic mechanical analyzer capable of calculating complex loss and storage moduli between two compression plates. It was shown that PA spectrums were shifted towards higher frequencies by increasing gelatin concentration. In order to quantify this effect, signal energy in two intervals of low and high frequency ranges were calculated. Gelatin concentration was correlated with PA energy in high frequency range with R2=0.94. Subsequently, PA signals generated from freshly resected human thyroid specimens were measured and analyzed in a similar fashion. We found that in aggregate, malignant thyroid tissue contains approximately 1.6 times lower energy in the high frequency range in comparison to normal thyroid tissue (p<0.01). This ratio increased with increasing illumination wavelength from 700 nm to 900nm. In summary, this study demonstrated the feasibility of using photoacoustic technique for characterizing tissue on the basis of viscoelastic properties of the tissue.

  3. Increasing the quantitative credibility of open-path FT-IR spectroscopic data with focus on several properties of the background spectrum

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The choice of the type of background spectrum affects the credibility of open-path Fourier transform infrared (OP/FT-IR) spectroscopic data, and consequently the quality of data analysis. We systematically investigated several properties of the background spectrum. The results show that a short-pa...

  4. Angular power spectrum of sterile neutrino decay lines: the role of eROSITA

    NASA Astrophysics Data System (ADS)

    Zandanel, Fabio; Weniger, Christoph; Ando, Shin’ichiro

    2016-05-01

    We study the potential of the angular auto and cross-correlation power spectrum of the cosmic X-ray background in identifying sterile neutrino dark matter taking as reference the performances of the soon-to-be-launched eROSITA satellite. The main astrophysical background sources in this case are active galactic nuclei, galaxies powered by X-ray binaries, and clusters of galaxies. We show that while sterile neutrino decays are always subdominant in the autocorrelation power spectra, they can be efficiently enhanced when cross-correlating with tracers of the dark matter distribution. We estimate that the four-years eROSITA all-sky survey will potentially provide very stringent constraints on the sterile neutrino decay lifetime by cross-correlating the cosmic X-ray background with the 2MASS galaxy catalogue. This will allow to firmly test the recently claimed 3.56-keV X-ray line found towards several clusters and galaxies and its decaying dark matter interpretation. We finally stress that the main limitation of this approach is due to the shot noise of the galaxy catalogues used as tracers for the dark matter distribution, a limitation that we need to overcome to fully exploit the potential of the eROSITA satellite in this context.

  5. Infrared divergence of pure Einstein gravity contributions to the cosmological density power spectrum.

    PubMed

    Noh, Hyerim; Jeong, Donghui; Hwang, Jai-Chan

    2009-07-10

    We probe the pure Einstein gravity contributions to the second-order density power spectrum. On the small scale, we discover that Einstein's gravity contribution is negligibly small. This guarantees that Newton's gravity is currently sufficient to handle the baryon acoustic oscillation scale. On the large scale, however, we discover that Einstein's gavity contribution to the second-order power spectrum dominates the linear-order power spectrum. Thus, the pure Einstein gravity contribution appearing in the third-order perturbation leads to an infrared divergence in the power spectrum. PMID:19659195

  6. Monte Carlo simulations to estimate the background spectrum in a shielded NaI(Tl) gamma-spectrometric system.

    PubMed

    Sengupta Mitra, Mausumi; Sarkar, P K

    2005-10-01

    The paper describes a Monte Carlo simulation technique to estimate the background gamma-radiation for a low-level counting setup with NaI(Tl) detector inside an iron shield box. With monoenergetic gamma-sources ranging from 300 to 2000 keV at intervals of 100 keV we have got a matrix of transmitted flux data calculated using a general purpose Monte Carlo code. The intrinsic efficiency of the detector is also calculated. This matrix of data is folded with the measured spectrum outside the setup to estimate the observed spectrum in the NaI(Tl) detector. We have studied various combinations of splitting and Russian roulette to arrive at an optimal combination based on the figure of merit of the Monte Carlo results. The observed discrepancy between the measured and calculated spectra is mainly due to porosity of the iron shield box. PMID:15998590

  7. Semi-blind Bayesian inference of CMB map and power spectrum

    NASA Astrophysics Data System (ADS)

    Vansyngel, Flavien; Wandelt, Benjamin D.; Cardoso, Jean-François; Benabed, Karim

    2016-04-01

    We present a new blind formulation of the cosmic microwave background (CMB) inference problem. The approach relies on a phenomenological model of the multifrequency microwave sky without the need for physical models of the individual components. For all-sky and high resolution data, it unifies parts of the analysis that had previously been treated separately such as component separation and power spectrum inference. We describe an efficient sampling scheme that fully explores the component separation uncertainties on the inferred CMB products such as maps and/or power spectra. External information about individual components can be incorporated as a prior giving a flexible way to progressively and continuously introduce physical component separation from a maximally blind approach. We connect our Bayesian formalism to existing approaches such as Commander, spectral mismatch independent component analysis (SMICA), and internal linear combination (ILC), and discuss possible future extensions.

  8. Estimating the power spectrum covariance matrix with fewer mock samples

    NASA Astrophysics Data System (ADS)

    Pearson, David W.; Samushia, Lado

    2016-03-01

    The covariance matrices of power-spectrum (P(k)) measurements from galaxy surveys are difficult to compute theoretically. The current best practice is to estimate covariance matrices by computing a sample covariance of a large number of mock catalogues. The next generation of galaxy surveys will require thousands of large volume mocks to determine the covariance matrices to desired accuracy. The errors in the inverse covariance matrix are larger and scale with the number of P(k) bins, making the problem even more acute. We develop a method of estimating covariance matrices using a theoretically justified, few-parameter model, calibrated with mock catalogues. Using a set of 600 BOSS DR11 mock catalogues, we show that a seven parameter model is sufficient to fit the covariance matrix of BOSS DR11 P(k) measurements. The covariance computed with this method is better than the sample covariance at any number of mocks and only ˜100 mocks are required for it to fully converge and the inverse covariance matrix converges at the same rate. This method should work equally well for the next generation of galaxy surveys, although a demand for higher accuracy may require adding extra parameters to the fitting function.

  9. Parameterizing the power spectrum: Beyond the truncated Taylor expansion

    SciTech Connect

    Abazajian, Kevork; Kadota, Kenji; Stewart, Ewan D.; /KAIST, Taejon /Canadian Inst. Theor. Astrophys.

    2005-07-01

    The power spectrum is traditionally parameterized by a truncated Taylor series: ln P(k) = ln P{sub *} + (n{sub *} - 1) ln(k/k{sub *}) + 1/2 n'{sub *} ln{sup 2} (k/k{sub *}). It is reasonable to truncate the Taylor series if |n'{sub *} ln(k/k{sub *})| << |n{sub *} - 1|, but it is not if |n'{sub *} ln(k/k{sub *})| {approx}> |n{sub *} - 1|. We argue that there is no good theoretical reason to prefer |n'{sub *}| << |n{sub *} - 1|, and show that current observations are consistent with |n*{sub *} ln(k/k{sub *})| {approx} |n{sub *} - 1| even for |ln(k/k{sub *})| {approx} 1. Thus, there are regions of parameter space, which are both theoretically and observationally relevant, for which the traditional truncated Taylor series parameterization is inconsistent, and hence it can lead to incorrect parameter estimations. Motivated by this, we propose a simple extension of the traditional parameterization, which uses no extra parameters, but that, unlike the traditional approach, covers well motivated inflationary spectra with |n'{sub *}| {approx} |n{sub *} - 1|. Our parameterization therefore covers not only standard-slow-roll inflation models but also a much wider class of inflation models. We use this parameterization to perform a likelihood analysis for the cosmological parameters.

  10. Roundoff noise analysis for digital signal power processors using Welch's power spectrum estimation

    NASA Technical Reports Server (NTRS)

    Chi, Chong-Yung; Long, David; Li, Fuk-Kwok

    1987-01-01

    The noise due to finite-word-length effects is analyzed for digital-signal power processors using Welch's power-spectrum estimation technique to measure the power of Gaussian random signals over a frequency band of interest. The input of the digital signal processor contains a finite-length time interval in which the true Gaussian signal is contaminated by Gaussian noise. The roundoff noise-to-signal ratio in the measurement of the signal power is derived, and computer simulations which validate the analytical results are presented. These results can be used in tradeoff studies of hardware design, such as the number of bits required at each processing stage. The results presented in this paper are currently being used in the design of a digital Doppler processor (Chi et al., 1986) for a radar scatterometer.

  11. Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field

    NASA Technical Reports Server (NTRS)

    Voorhies, C.

    1998-01-01

    The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic null-hypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.

  12. The Atacama Cosmology Telescope: A Measurement of the Primordial Power Spectrum

    NASA Technical Reports Server (NTRS)

    Hlozek, Renee; Dunkley, Joanna; Addison, Graeme; Appel, John William; Bond, J. Richard; Carvalho, C. Sofia; Das, Sudeep; Devlin, Mark J.; Duenner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W.; Gallardo, Patricio; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hughes, John P.; Irwin, Kent D.; Klein, Jeff; Kosowsky, Arthur; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Wollack, Ed

    2011-01-01

    We present constraints on the primordial power spectrum of adiabatic fluctuations using data from the 2008 Southern Survey of the Atacama Cosmology Telescope (ACT). The angular resolution of ACT provides sensitivity to scales beyond l = 1000 for resolution of multiple peaks in the primordial temperature power spectrum, which enables us to probe the primordial power spectrum of adiabatic scalar perturbations with wavenumbers up to k approx. = 0.2 Mp/c. We find no evidence for deviation from power-law fluctuations over two decades in scale. Matter fluctuations inferred from the primordial temperature power spectrum evolve over cosmic time and can be used to predict the matter power spectrum at late times; we illustrate the overlap of the matter power inferred from CMB measurements (which probe the power spectrum in thc linear regime) with existing probes of galaxy clustering, cluster abundances and weak lensing constraints on the primordial power. This highlights the range of scales probed by current measurement.s of the matter power spectrum.

  13. [Restoration filtering based on projection power spectrum for single-photon emission computed tomography].

    PubMed

    Kubo, N

    1995-04-01

    To improve the quality of single-photon emission computed tomographic (SPECT) images, a restoration filter has been developed. This filter was designed according to practical "least squares filter" theory. It is necessary to know the object power spectrum and the noise power spectrum. The power spectrum is estimated from the power spectrum of a projection, when the high-frequency power spectrum of a projection is adequately approximated as a polynomial exponential expression. A study of the restoration with the filter based on a projection power spectrum was conducted, and compared with that of the "Butterworth" filtering method (cut-off frequency of 0.15 cycles/pixel), and "Wiener" filtering (signal-to-noise power spectrum ratio was a constant). Normalized mean-squared errors (NMSE) of the phantom, two line sources located in a 99mTc filled cylinder, were used. NMSE of the "Butterworth" filter, "Wiener" filter, and filtering based on a power spectrum were 0.77, 0.83, and 0.76 respectively. Clinically, brain SPECT images utilizing this new restoration filter improved the contrast. Thus, this filter may be useful in diagnosis of SPECT images. PMID:7776546

  14. Power spectrum scale invariance identifies prefrontal dysregulation in paranoid schizophrenia.

    PubMed

    Radulescu, Anca R; Rubin, Denis; Strey, Helmut H; Mujica-Parodi, Lilianne R

    2012-07-01

    Theory and experimental evidence suggest that complex living systems function close to the boundary of chaos, with erroneous organization to an improper dynamical range (too stiff or chaotic) underlying system-wide dysregulation and disease. We hypothesized that erroneous organization might therefore also characterize paranoid schizophrenia, via optimization abnormalities in the prefrontal-limbic circuit regulating emotion. To test this, we acquired fMRI scans from 35 subjects (N = 9 patients with paranoid schizophrenia and N = 26 healthy controls), while they viewed affect-valent stimuli. To quantify dynamic regulation, we analyzed the power spectrum scale invariance (PSSI) of fMRI time-courses and computed the geometry of time-delay (Poincaré) maps, a measure of variability. Patients and controls showed distinct PSSI in two clusters (k(1) : Z = 4.3215, P = 0.00002 and k(2) : Z = 3.9441, P = 0.00008), localized to the orbitofrontal/medial prefrontal cortex (Brodmann Area 10), represented by β close to white noise in patients (β ≈ 0) and in the pink noise range in controls (β ≈ -1). Interpreting the meaning of PSSI differences, the Poincaré maps indicated less variability in patients than controls (Z = -1.9437, P = 0.05 for k(1) ; Z = -2.5099, P = 0.01 for k(2) ). That the dynamics identified Brodmann Area 10 is consistent with previous schizophrenia research, which implicates this area in deficits of working memory, executive functioning, emotional regulation and underlying biological abnormalities in synaptic (glutamatergic) transmission. Our results additionally cohere with a large body of work finding pink noise to be the normal range of central function at the synaptic, cellular, and small network levels, and suggest that patients show less supple responsivity of this region. PMID:21567663

  15. THE ATACAMA COSMOLOGY TELESCOPE: COSMOLOGICAL PARAMETERS FROM THE 2008 POWER SPECTRUM

    SciTech Connect

    Dunkley, J.; Hlozek, R.; Sievers, J.; Bond, J. R.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Barrientos, L. F.; Duenner, R.; Amiri, M.; Battistelli, E. S.; Burger, B.; Appel, J. W.; Das, S.; Essinger-Hileman, T.; Brown, B.; Chervenak, J.; Doriese, W. Bertrand

    2011-09-20

    We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg{sup 2} with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 < l < 10, 000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be B{sub 3000} = 6.8 {+-} 2.9 {mu}K{sup 2}, where B{sub l}{identical_to}l(l + 1)C{sub l}/2{pi}. The IR Poisson power at 148 GHz is B{sub 3000} = 7.8 {+-} 0.7 {mu}K{sup 2} (C{sub l} = 5.5 {+-} 0.5 nK{sup 2}), and a clustered IR component is required with B{sub 3000} = 4.6 {+-} 0.9 {mu}K{sup 2}, assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 {mu}K{sup 2}, is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index {alpha} = 3.69 {+-} 0.14 for flux scaling as S({nu}){proportional_to}{nu}{sup {alpha}}. We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The {Lambda}CDM cosmological model is a good fit to the data ({chi}{sup 2}/dof = 29/46), and {Lambda}CDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n{sub s} = 1 excluded at 99.7% confidence level (CL) (3{sigma}). A model with no CMB lensing is disfavored at 2.8{sigma}. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on

  16. The Atacama Cosmology Telescope: Cosmological Parameters from the 2008 Power Spectrum

    NASA Technical Reports Server (NTRS)

    Dunkley, J.; Hlozek, R.; Sievers, J.; Acquaviva, V.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Bertrand Doriese, W.; Dunner, R.; Essinger-Hileman, T.; Fisher, R. P.; Fowler, J. W.; Hajian, A.; Moseley, H.; Wollack, E.

    2011-01-01

    We present cosmological parameters derived from the angular power spectrum of the cosmic microwave background (CMB) radiation observed at 148 GHz and 218 GHz over 296 deg(exp 2) with the Atacama Cosmology Telescope (ACT) during its 2008 season. ACT measures fluctuations at scales 500 < l < 10,000. We fit a model for the lensed CMB, Sunyaev-Zel'dovich (SZ), and foreground contribution to the 148 GHz and 218 GHz power spectra, including thermal and kinetic SZ, Poisson power from radio and infrared point sources, and clustered power from infrared point sources. At l = 3000, about half the power at 148 GHz comes from primary CMB after masking bright radio sources. The power from thermal and kinetic SZ is estimated to be Beta(sub 3000) is identical to 6.8 +/- 2.9 mu K (exp 2), where Beta (sub l) is identical to l(l + 1) C(sub l)/2pi. The IR Poisson power at 148 GHz is Bewta(sub 3000) 7.8 +/- 0.7 muK(exp 2) (C(sub l) = 5.5 +/- 0.5 nK(exp 2)), and a clustered IR component is required with Beta (sub 3000) = 4.6 +/- 0.9 muK(exp 2), assuming an analytic model for its power spectrum shape. At 218 GHz only about 15% of the power, approximately 27 mu K(exp 2), is CMB anisotropy at l = 3000. The remaining 85% is attributed to IR sources (approximately 50% Poisson and 35% clustered), with spectral index alpha = 3.69 +/- 0.14 for flux scaling as S(nu) varies as nu(sup alpha). We estimate primary cosmological parameters from the less contaminated 148 GHz spectrum, marginalizing over SZ and source power. The ACDM cosmological model is a good fit to the data (chi square/dof = 29/46), and ACDM parameters estimated from ACT+Wilkinson Microwave Anisotropy Probe (WMAP) are consistent with the seven-year WMAP limits, with scale invariant n(sub s) = 1 excluded at 99.7% confidence level (CL) (3 sigma). A model with no CMB lensing is disfavored at 2.8 sigma. By measuring the third to seventh acoustic peaks, and probing the Silk damping regime, the ACT data improve limits on cosmological

  17. Anisotropic power spectrum and bispectrum in the f(Φ)F² mechanism

    DOE PAGESBeta

    Bartolo, Nicola; Matarrese, Sabino; Peloso, Marco; Ricciardone, Angelo

    2013-01-04

    A suitable coupling of the inflaton φ to a vector kinetic term F² gives frozen and scale invariant vector perturbations. We compute the cosmological perturbations ζ that result from such coupling by taking into account the classical vector field that unavoidably gets generated at large scales during inflation. This generically results in a too-anisotropic power spectrum of ζ. Specifically, the anisotropy exceeds the 1% level (10% level) if inflation lasts ~5 e-folds (~50 e-folds) more than the minimal amount required to produce the cosmic microwave background modes. This conclusion applies, among others, to the application of this mechanism for magnetogenesis,more » for anisotropic inflation, and for the generation of anisotropic perturbations at the end of inflation through a waterfall field coupled to the vector (in this case, the unavoidable contribution that we obtain is effective all throughout inflation, and it is independent of the waterfall field). For a tuned duration of inflation, a 1% (10%) anisotropy in the power spectrum corresponds to an anisotropic bispectrum which is enhanced like the local one in the squeezed limit, and with an effective local fNL~3(~30). More in general, a significant anisotropy of the perturbations may be a natural outcome of all models that sustain higher than 0 spin fields during inflation.« less

  18. Anisotropic power spectrum and bispectrum in the f(Φ)F² mechanism

    SciTech Connect

    Bartolo, Nicola; Matarrese, Sabino; Peloso, Marco; Ricciardone, Angelo

    2013-01-04

    A suitable coupling of the inflaton φ to a vector kinetic term F² gives frozen and scale invariant vector perturbations. We compute the cosmological perturbations ζ that result from such coupling by taking into account the classical vector field that unavoidably gets generated at large scales during inflation. This generically results in a too-anisotropic power spectrum of ζ. Specifically, the anisotropy exceeds the 1% level (10% level) if inflation lasts ~5 e-folds (~50 e-folds) more than the minimal amount required to produce the cosmic microwave background modes. This conclusion applies, among others, to the application of this mechanism for magnetogenesis, for anisotropic inflation, and for the generation of anisotropic perturbations at the end of inflation through a waterfall field coupled to the vector (in this case, the unavoidable contribution that we obtain is effective all throughout inflation, and it is independent of the waterfall field). For a tuned duration of inflation, a 1% (10%) anisotropy in the power spectrum corresponds to an anisotropic bispectrum which is enhanced like the local one in the squeezed limit, and with an effective local fNL~3(~30). More in general, a significant anisotropy of the perturbations may be a natural outcome of all models that sustain higher than 0 spin fields during inflation.

  19. Tension between the power spectrum of density perturbations measured on large and small scales

    NASA Astrophysics Data System (ADS)

    Battye, Richard A.; Charnock, Tom; Moss, Adam

    2015-05-01

    There is a tension between measurements of the amplitude of the power spectrum of density perturbations inferred using the cosmic microwave background (CMB) and directly measured by large-scale structure (LSS) on smaller scales. We show that this tension exists, and is robust, for a range of LSS indicators including clusters, lensing and redshift space distortions and using CMB data from either Planck or WMAP +SPT /ACT . One obvious way to try to reconcile this is the inclusion of a massive neutrino which could be either active or sterile. Using Planck and a combination of all the LSS data we find that (i) for an active neutrino ∑mν=(0.357 ±0.099 ) eV and (ii) for a sterile neutrino msterileeff=(0.67 ±0.18 ) eV and Δ Neff=0.32 ±0.20 . This is, however, at the expense of a degraded fit to Planck temperature data, and we quantify the residual tension at 2.5 σ and 1.6 σ for massive and sterile neutrinos, respectively. We also consider alternative explanations including a lower redshift for reionization that would be in conflict with polarization measurements made by WMAP and ad hoc modifications to the primordial power spectrum.

  20. Anisotropic power spectrum and bispectrum in the f(ϕ)F2 mechanism

    NASA Astrophysics Data System (ADS)

    Bartolo, Nicola; Matarrese, Sabino; Peloso, Marco; Ricciardone, Angelo

    2013-01-01

    A suitable coupling of the inflaton φ to a vector kinetic term F2 gives frozen and scale invariant vector perturbations. We compute the cosmological perturbations ζ that result from such coupling by taking into account the classical vector field that unavoidably gets generated at large scales during inflation. This generically results in a too-anisotropic power spectrum of ζ. Specifically, the anisotropy exceeds the 1% level (10% level) if inflation lasts ˜5 e-folds (˜50 e-folds) more than the minimal amount required to produce the cosmic microwave background modes. This conclusion applies, among others, to the application of this mechanism for magnetogenesis, for anisotropic inflation, and for the generation of anisotropic perturbations at the end of inflation through a waterfall field coupled to the vector (in this case, the unavoidable contribution that we obtain is effective all throughout inflation, and it is independent of the waterfall field). For a tuned duration of inflation, a 1% (10%) anisotropy in the power spectrum corresponds to an anisotropic bispectrum which is enhanced like the local one in the squeezed limit, and with an effective local fNL˜3(˜30). More in general, a significant anisotropy of the perturbations may be a natural outcome of all models that sustain higher than 0 spin fields during inflation.

  1. Application of power spectrum, cepstrum, higher order spectrum and neural network analyses for induction motor fault diagnosis

    NASA Astrophysics Data System (ADS)

    Liang, B.; Iwnicki, S. D.; Zhao, Y.

    2013-08-01

    The power spectrum is defined as the square of the magnitude of the Fourier transform (FT) of a signal. The advantage of FT analysis is that it allows the decomposition of a signal into individual periodic frequency components and establishes the relative intensity of each component. It is the most commonly used signal processing technique today. If the same principle is applied for the detection of periodicity components in a Fourier spectrum, the process is called the cepstrum analysis. Cepstrum analysis is a very useful tool for detection families of harmonics with uniform spacing or the families of sidebands commonly found in gearbox, bearing and engine vibration fault spectra. Higher order spectra (HOS) (also known as polyspectra) consist of higher order moment of spectra which are able to detect non-linear interactions between frequency components. For HOS, the most commonly used is the bispectrum. The bispectrum is the third-order frequency domain measure, which contains information that standard power spectral analysis techniques cannot provide. It is well known that neural networks can represent complex non-linear relationships, and therefore they are extremely useful for fault identification and classification. This paper presents an application of power spectrum, cepstrum, bispectrum and neural network for fault pattern extraction of induction motors. The potential for using the power spectrum, cepstrum, bispectrum and neural network as a means for differentiating between healthy and faulty induction motor operation is examined. A series of experiments is done and the advantages and disadvantages between them are discussed. It has been found that a combination of power spectrum, cepstrum and bispectrum plus neural network analyses could be a very useful tool for condition monitoring and fault diagnosis of induction motors.

  2. The Knotted Sky I: Planck constraints on the primordial power spectrum

    SciTech Connect

    Aslanyan, Grigor; Price, Layne C.; Easther, Richard; Abazajian, Kevork N. E-mail: lpri691@aucklanduni.ac.nz E-mail: r.easther@auckland.ac.nz

    2014-08-01

    Using the temperature data from Planck we search for departures from a power-law primordial power spectrum, employing Bayesian model-selection and posterior probabilities. We parametrize the spectrum with n knots located at arbitrary values of logk, with both linear and cubic splines. This formulation recovers both slow modulations and sharp transitions in the primordial spectrum. The power spectrum is well-fit by a featureless, power-law at wavenumbers k>10{sup -3} Mpc{sup -1}. A modulated primordial spectrum yields a better fit relative to ΛCDM at large scales, but there is no strong evidence for a departure from a power-law spectrum. Moreover, using simulated maps we show that a local feature at k ∼ 10{sup -3} Mpc{sup -1} can mimic the suppression of large-scale power. With multi-knot spectra we see only small changes in the posterior distributions for the other free parameters in the standard ΛCDM universe. Lastly, we investigate whether the hemispherical power asymmetry is explained by independent features in the primordial power spectrum in each ecliptic hemisphere, but find no significant differences between them.

  3. Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Stutz, R. A.; Rosolowsky, E. W.; Kothes, R.; Landecker, T. L.

    2014-05-01

    Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization data set at 1.4 GHz covering an area of 1060 deg2. The data analyzed are a combination of data from the 100 m Effelsberg Telescope, the 26 m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from l ≈ 60 to l ≈ 104 and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at b = 9°, associated with the disk-halo transition in a 15° region around l = 108°. Localized variations in the index are found toward H II regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by Hα emission) indicating that the thermal emission depolarizes background synchrotron emission.

  4. Power spectrum analysis of polarized emission from the Canadian galactic plane survey

    SciTech Connect

    Stutz, R. A.; Rosolowsky, E. W.; Kothes, R.; Landecker, T. L.

    2014-05-20

    Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization data set at 1.4 GHz covering an area of 1060 deg{sup 2}. The data analyzed are a combination of data from the 100 m Effelsberg Telescope, the 26 m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from ℓ ≈ 60 to ℓ ≈ 10{sup 4} and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at b = 9°, associated with the disk-halo transition in a 15° region around l = 108°. Localized variations in the index are found toward H II regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by Hα emission) indicating that the thermal emission depolarizes background synchrotron emission.

  5. First Year Wilkinson Microwave Anisotropy Probe(WMAP)Observations: The Angular Power Spectrum

    NASA Technical Reports Server (NTRS)

    Hinshaw, G.; Spergel, D. N.; Verde, L.; Hill, R. S.; Meyer, S. S.; Barnes, C.; Bennett, C. L.; Halpern, M.; Jarosik, N.; Kogut, A.

    2003-01-01

    We present the angular power spectrum derived from the first-year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps. We study a variety of power spectrum estimation methods and data combinations and demonstrate that the results are robust. The data are modestly contaminated by diffuse Galactic foreground emission, but we show that a simple Galactic template model is sufficient to remove the signal. Point sources produce a modest contamination in the low frequency data. After masking approximately 700 known bright sources from the maps, we estimate residual sources contribute approximately 3500 mu sq Kappa at 41 GHz, and approximately 130 mu sq Kappa at 94 GHz, to the power spectrum [iota(iota + 1)C(sub iota)/2pi] at iota = 1000. Systematic errors are negligible compared to the (modest) level of foreground emission. Our best estimate of the power spectrum is derived from 28 cross-power spectra of statistically independent channels. The final spectrum is essentially independent of the noise properties of an individual radiometer. The resulting spectrum provides a definitive measurement of the CMB power spectrum, with uncertainties limited by cosmic variance, up to iota approximately 350. The spectrum clearly exhibits a first acoustic peak at iota = 220 and a second acoustic peak at iota approximately 540, and it provides strong support for adiabatic initial conditions. Researchers have analyzed the CT(sup Epsilon) power spectrum, and present evidence for a relatively high optical depth, and an early period of cosmic reionization. Among other things, this implies that the temperature power spectrum has been suppressed by approximately 30% on degree angular scales, due to secondary scattering.

  6. Reconstruction of the primordial fluctuation spectrum from the five-year WMAP data by the cosmic inversion method with band-power decorrelation analysis

    SciTech Connect

    Nagata, Ryo; Yokoyama, Jun'ichi

    2008-12-15

    The primordial curvature fluctuation spectrum is reconstructed by the cosmic inversion method using the five-year Wilkinson Microwave Anisotropy Probe data of the cosmic microwave background temperature anisotropy. We apply the covariance matrix analysis and decompose the reconstructed spectrum into statistically independent band-powers. The statistically significant deviation from a simple power-law spectrum suggested by the analysis of the first-year data is not found in the five-year data except possibly at one point near the border of the wave number domain where accurate reconstruction is possible.

  7. THE EXTRAGALACTIC BACKGROUND LIGHT FROM THE MEASUREMENTS OF THE ATTENUATION OF HIGH-ENERGY GAMMA-RAY SPECTRUM

    SciTech Connect

    Gong Yan; Cooray, Asantha

    2013-07-20

    The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features of the gamma-rays from blazars as seen by the Fermi Gamma-ray Space Telescope to explore the EBL flux density and constrain the EBL spectrum, star formation rate density (SFRD), and photon escape fraction from galaxies out to z = 6. Our results are basically consistent with the existing determinations of the quantities. We find a larger photon escape fraction at high redshifts, especially at z = 3, compared to the result from recent Ly{alpha} measurements. Our SFRD result is consistent with the data from both gamma-ray burst and ultraviolet (UV) observations in the 1{sigma} level. However, the average SFRD we obtain at z {approx}> 3 matches the gamma-ray data better than the UV data. Thus our SFRD result at z {approx}> 6 favors the fact that star formation alone is sufficiently high enough to reionize the universe.

  8. Unveiling acoustic physics of the CMB using nonparametric estimation of the temperature angular power spectrum for Planck

    SciTech Connect

    Aghamousa, Amir; Shafieloo, Arman; Arjunwadkar, Mihir; Souradeep, Tarun E-mail: shafieloo@kasi.re.kr E-mail: tarun@iucaa.ernet.in

    2015-02-01

    Estimation of the angular power spectrum is one of the important steps in Cosmic Microwave Background (CMB) data analysis. Here, we present a nonparametric estimate of the temperature angular power spectrum for the Planck 2013 CMB data. The method implemented in this work is model-independent, and allows the data, rather than the model, to dictate the fit. Since one of the main targets of our analysis is to test the consistency of the ΛCDM model with Planck 2013 data, we use the nuisance parameters associated with the best-fit ΛCDM angular power spectrum to remove foreground contributions from the data at multipoles ℓ ≥50. We thus obtain a combined angular power spectrum data set together with the full covariance matrix, appropriately weighted over frequency channels. Our subsequent nonparametric analysis resolves six peaks (and five dips) up to ℓ ∼1850 in the temperature angular power spectrum. We present uncertainties in the peak/dip locations and heights at the 95% confidence level. We further show how these reflect the harmonicity of acoustic peaks, and can be used for acoustic scale estimation. Based on this nonparametric formalism, we found the best-fit ΛCDM model to be at 36% confidence distance from the center of the nonparametric confidence set—this is considerably larger than the confidence distance (9%) derived earlier from a similar analysis of the WMAP 7-year data. Another interesting result of our analysis is that at low multipoles, the Planck data do not suggest any upturn, contrary to the expectation based on the integrated Sachs-Wolfe contribution in the best-fit ΛCDM cosmology.

  9. Elimination of threshold-induced distortion in the power spectrum of narrow-band laser speckle

    NASA Astrophysics Data System (ADS)

    Ducharme, Alfred D.; Boreman, Glenn D.; Yang, Sidney S.

    1995-10-01

    The distortion in the power spectrum of narrow-band laser speckle that results from irradiance thresholding is quantified. A method for compensation of this distortion is presented. An optimal threshold level is presented that simplifies the compensation method.

  10. The BaR-SPOrt experiment: measuring the CMBP E-mode power spectrum from Dome C

    NASA Astrophysics Data System (ADS)

    Carretti, E.; Cortiglioni, S.; Bernardi, G.; Casarini, L.; Cecchini, S.; Macculi, C.; Ramponi, M.; Sbarra, C.; Ventura, G.; Monari, J.; Poloni, M.; Poppi, S.; Baralis, M.; Peverini, O. A.; Tascone, R.; Virone, G.; Zannoni, M.; Bonometto, S.; Colombo, L.; Gervasi, M.; Sironi, G.; Fabbri, R.; Natale, V.; Nesti, R.; Nicastro, L.; de Bernardis, P.; Masi, S.; de Petris, M.; Boscaleri, A.; Sazhin, M.; Vinyajkin, E.

    The BaR-SPOrt experiment is designed to measure the E-mode power spectrum of the Cosmic Microwave Background Polarization (CMBP) in the multipole range 50 < ℓ < 1000. In the current configuration at 32 GHz it can explore up to ℓ = 400. Recent low frequency observations of the target region show that the synchrotron emission should not contamine the CMBP already at 32 GHz. A 6-month observation of a 6° × 6° sky area during the polar night, in ideal environmental conditions, will allow the Italian-French collaboration to both measure the E mode power spectrum with appropriate sensitivity and perform important tests of the anomalous dust emission. The BaR-SPOrt 32 GHz instrument, now under test and ready for operations by Spring 2005, is proposed for 1 2 years Winter operations at Dome C.

  11. Reconstruction of the primordial power spectrum of curvature perturbations using multiple data sets

    SciTech Connect

    Hunt, Paul; Sarkar, Subir E-mail: s.sarkar@physics.ox.ac.uk

    2014-01-01

    Detailed knowledge of the primordial power spectrum of curvature perturbations is essential both in order to elucidate the physical mechanism ('inflation') which generated it, and for estimating the cosmological parameters from observations of the cosmic microwave background and large-scale structure. Hence it ought to be extracted from such data in a model-independent manner, however this is difficult because relevant cosmological observables are given by a convolution of the primordial perturbations with some smoothing kernel which depends on both the assumed world model and the matter content of the universe. Moreover the deconvolution problem is ill-conditioned so a regularisation scheme must be employed to control error propagation. We demonstrate that 'Tikhonov regularisation' can robustly reconstruct the primordial spectrum from multiple cosmological data sets, a significant advantage being that both its uncertainty and resolution are then quantified. Using Monte Carlo simulations we investigate several regularisation parameter selection methods and find that generalised cross-validation and Mallow's C{sub p} method give optimal results. We apply our inversion procedure to data from the Wilkinson Microwave Anisotropy Probe, other ground-based small angular scale CMB experiments, and the Sloan Digital Sky Survey. The reconstructed spectrum (assuming the standard ΛCDM cosmology) is not scale-free but has an infrared cutoff at k∼<5 × 10{sup −4} Mpc{sup −1} (due to the anomalously low CMB quadrupole) and several features with ∼ 2σ significance at k/Mpc{sup −1} ∼ 0.0013–0.0025, 0.0362–0.0402 and 0.051–0.056, reflecting the 'WMAP glitches'. To test whether these are indeed real will require more accurate data, such as from the Planck satellite and new ground-based experiments.

  12. Reconstruction of the primordial power spectrum of curvature perturbations using multiple data sets

    NASA Astrophysics Data System (ADS)

    Hunt, Paul; Sarkar, Subir

    2014-01-01

    Detailed knowledge of the primordial power spectrum of curvature perturbations is essential both in order to elucidate the physical mechanism (`inflation') which generated it, and for estimating the cosmological parameters from observations of the cosmic microwave background and large-scale structure. Hence it ought to be extracted from such data in a model-independent manner, however this is difficult because relevant cosmological observables are given by a convolution of the primordial perturbations with some smoothing kernel which depends on both the assumed world model and the matter content of the universe. Moreover the deconvolution problem is ill-conditioned so a regularisation scheme must be employed to control error propagation. We demonstrate that `Tikhonov regularisation' can robustly reconstruct the primordial spectrum from multiple cosmological data sets, a significant advantage being that both its uncertainty and resolution are then quantified. Using Monte Carlo simulations we investigate several regularisation parameter selection methods and find that generalised cross-validation and Mallow's Cp method give optimal results. We apply our inversion procedure to data from the Wilkinson Microwave Anisotropy Probe, other ground-based small angular scale CMB experiments, and the Sloan Digital Sky Survey. The reconstructed spectrum (assuming the standard ΛCDM cosmology) is not scale-free but has an infrared cutoff at klesssim5 × 10-4 Mpc-1 (due to the anomalously low CMB quadrupole) and several features with ~ 2σ significance at k/Mpc-1 ~ 0.0013-0.0025, 0.0362-0.0402 and 0.051-0.056, reflecting the `WMAP glitches'. To test whether these are indeed real will require more accurate data, such as from the Planck satellite and new ground-based experiments.

  13. Fourier Power Spectrum Characteristics of Face Photographs: Attractiveness Perception Depends on Low-Level Image Properties

    PubMed Central

    Langner, Oliver; Wiese, Holger; Redies, Christoph

    2015-01-01

    We investigated whether low-level processed image properties that are shared by natural scenes and artworks – but not veridical face photographs – affect the perception of facial attractiveness and age. Specifically, we considered the slope of the radially averaged Fourier power spectrum in a log-log plot. This slope is a measure of the distribution of special frequency power in an image. Images of natural scenes and artworks possess – compared to face images – a relatively shallow slope (i.e., increased high spatial frequency power). Since aesthetic perception might be based on the efficient processing of images with natural scene statistics, we assumed that the perception of facial attractiveness might also be affected by these properties. We calculated Fourier slope and other beauty-associated measurements in face images and correlated them with ratings of attractiveness and age of the depicted persons (Study 1). We found that Fourier slope – in contrast to the other tested image properties – did not predict attractiveness ratings when we controlled for age. In Study 2A, we overlaid face images with random-phase patterns with different statistics. Patterns with a slope similar to those in natural scenes and artworks resulted in lower attractiveness and higher age ratings. In Studies 2B and 2C, we directly manipulated the Fourier slope of face images and found that images with shallower slopes were rated as more attractive. Additionally, attractiveness of unaltered faces was affected by the Fourier slope of a random-phase background (Study 3). Faces in front of backgrounds with statistics similar to natural scenes and faces were rated as more attractive. We conclude that facial attractiveness ratings are affected by specific image properties. An explanation might be the efficient coding hypothesis. PMID:25835539

  14. High frequency formulation for the acoustic power spectrum due to cascade-turbulence interaction.

    PubMed

    Cheong, Cheolung; Joseph, Phillip; Lee, Soogab

    2006-01-01

    This paper investigates the noise radiated by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. An analytic formulation for the spectrum of acoustic power of a two-dimensional flat-plate is derived. The main finding of this paper is that the acoustic power spectrum from the cascade of flat airfoils may be split into two distinct frequency regions of low frequency and high frequency, separated by a critical frequency. Below this frequency, cascade effects due to the interaction between neighboring airfoils are shown to be important. At frequencies above the critical frequency, cascade effects are shown to be relatively weak. In this frequency range, acoustic power is shown to be approximately proportional to the number of blades. Based on this finding at high frequencies, an approximate expression is derived for the power spectrum that is valid above the critical frequency and which is in excellent agreement with the exact expression for the broadband power spectrum. The formulation is used to perform a parametric study on the effects on the power spectrum of the blade number, stagger angle, gap-chord ratio, and Mach number. The theory is also shown to provide a close fit to the measured spectrum of rotor-stator interaction. PMID:16454269

  15. Optimized Large-scale CMB Likelihood and Quadratic Maximum Likelihood Power Spectrum Estimation

    NASA Astrophysics Data System (ADS)

    Gjerløw, E.; Colombo, L. P. L.; Eriksen, H. K.; Górski, K. M.; Gruppuso, A.; Jewell, J. B.; Plaszczynski, S.; Wehus, I. K.

    2015-11-01

    We revisit the problem of exact cosmic microwave background (CMB) likelihood and power spectrum estimation with the goal of minimizing computational costs through linear compression. This idea was originally proposed for CMB purposes by Tegmark et al., and here we develop it into a fully functioning computational framework for large-scale polarization analysis, adopting WMAP as a working example. We compare five different linear bases (pixel space, harmonic space, noise covariance eigenvectors, signal-to-noise covariance eigenvectors, and signal-plus-noise covariance eigenvectors) in terms of compression efficiency, and find that the computationally most efficient basis is the signal-to-noise eigenvector basis, which is closely related to the Karhunen-Loeve and Principal Component transforms, in agreement with previous suggestions. For this basis, the information in 6836 unmasked WMAP sky map pixels can be compressed into a smaller set of 3102 modes, with a maximum error increase of any single multipole of 3.8% at ℓ ≤ 32 and a maximum shift in the mean values of a joint distribution of an amplitude-tilt model of 0.006σ. This compression reduces the computational cost of a single likelihood evaluation by a factor of 5, from 38 to 7.5 CPU seconds, and it also results in a more robust likelihood by implicitly regularizing nearly degenerate modes. Finally, we use the same compression framework to formulate a numerically stable and computationally efficient variation of the Quadratic Maximum Likelihood implementation, which requires less than 3 GB of memory and 2 CPU minutes per iteration for ℓ ≤ 32, rendering low-ℓ QML CMB power spectrum analysis fully tractable on a standard laptop.

  16. The power spectrum and bispectrum of SDSS DR11 BOSS galaxies - II. Cosmological interpretation

    NASA Astrophysics Data System (ADS)

    Gil-Marín, Héctor; Verde, Licia; Noreña, Jorge; Cuesta, Antonio J.; Samushia, Lado; Percival, Will J.; Wagner, Christian; Manera, Marc; Schneider, Donald P.

    2015-09-01

    We examine the cosmological implications of the measurements of the linear growth rate of cosmological structure obtained in a companion paper from the power spectrum and bispectrum monopoles of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey Data Release 11, CMASS galaxies. This measurement was of f 0.43σ8, where σ8 is the amplitude of dark matter density fluctuations, and f is the linear growth rate, at the effective redshift of the survey, zeff = 0.57. In conjunction with cosmic microwave background (CMB) data, interesting constraints can be placed on models with non-standard neutrino properties and models where gravity deviates from General Relativity on cosmological scales. In particular, the sum of the masses of the three species of the neutrinos is constrained to mν < 0.49 eV (at 95 per cent confidence level) when the f 0.43σ8 measurement is combined with state-of-the-art CMB measurements. Allowing the effective number of neutrinos to vary as a free parameter does not significantly change these results. When we combine the measurement of f 0.43σ8 with the complementary measurement of fσ8 from the monopole and quadrupole of the two-point correlation function, we are able to obtain an independent measurements of f and σ8. We obtain f = 0.63 ± 0.16 and σ8 = 0.710 ± 0.086 (68 per cent confidence level). This is the first time when these parameters have been able to be measured independently using the redshift-space power spectrum and bispectrum measurements from galaxy clustering data only.

  17. Neutrino masses and cosmology with Lyman-alpha forest power spectrum

    NASA Astrophysics Data System (ADS)

    Palanque-Delabrouille, Nathalie; Yèche, Christophe; Baur, Julien; Magneville, Christophe; Rossi, Graziano; Lesgourgues, Julien; Borde, Arnaud; Burtin, Etienne; LeGoff, Jean-Marc; Rich, James; Viel, Matteo; Weinberg, David

    2015-11-01

    We present constraints on neutrino masses, the primordial fluctuation spectrum from inflation, and other parameters of the ΛCDM model, using the one-dimensional Lyα-forest power spectrum measured by [1] from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III), complemented by Planck 2015 cosmic microwave background (CMB) data and other cosmological probes. This paper improves on the previous analysis by [2] by using a more powerful set of calibrating hydrodynamical simulations that reduces uncertainties associated with resolution and box size, by adopting a more flexible set of nuisance parameters for describing the evolution of the intergalactic medium, by including additional freedom to account for systematic uncertainties, and by using Planck 2015 constraints in place of Planck 2013. Fitting Lyα data alone leads to cosmological parameters in excellent agreement with the values derived independently from CMB data, except for a weak tension on the scalar index ns. Combining BOSS Lyα with Planck CMB constrains the sum of neutrino masses to ∑ mν < 0.12 eV (95% C.L.) including all identified systematic uncertainties, tighter than our previous limit (0.15 eV) and more robust. Adding Lyα data to CMB data reduces the uncertainties on the optical depth to reionization τ, through the correlation of τ with σ8. Similarly, correlations between cosmological parameters help in constraining the tensor-to-scalar ratio of primordial fluctuations r. The tension on ns can be accommodated by allowing for a running dns/d ln k. Allowing running as a free parameter in the fits does not change the limit on ∑ mν. We discuss possible interpretations of these results in the context of slow-roll inflation.

  18. Power spectrum tomography of dark matter annihilation with local galaxy distribution

    SciTech Connect

    Ando, Shin'ichiro

    2014-10-01

    Cross-correlating the gamma-ray background with local galaxy catalogs potentially gives stringent constraints on dark matter annihilation. We provide updated theoretical estimates of sensitivities to the annihilation cross section from gamma-ray data with Fermi telescope and 2MASS galaxy catalogs, by elaborating the galaxy power spectrum and astrophysical backgrounds, and adopting the Markov-Chain Monte Carlo simulations. In particular, we show that taking tomographic approach by dividing the galaxy catalogs into more than one redshift slice will improve the sensitivity by a factor of a few to several. If dark matter halos contain lots of bright substructures, yielding a large annihilation boost (e.g., a factor of ∼100 for galaxy-size halos), then one may be able to probe the canonical annihilation cross section for thermal production mechanism up to masses of ∼700 GeV. Even with modest substructure boost (e.g., a factor of ∼10 for galaxy-size halos), on the other hand, the sensitivities could still reach a factor of three larger than the canonical cross section for dark matter masses of tens to a few hundreds of GeV.

  19. Spectrum sensing and resource allocation for multicarrier cognitive radio systems under interference and power constraints

    NASA Astrophysics Data System (ADS)

    Dikmese, Sener; Srinivasan, Sudharsan; Shaat, Musbah; Bader, Faouzi; Renfors, Markku

    2014-12-01

    Multicarrier waveforms have been commonly recognized as strong candidates for cognitive radio. In this paper, we study the dynamics of spectrum sensing and spectrum allocation functions in cognitive radio context using very practical signal models for the primary users (PUs), including the effects of power amplifier nonlinearities. We start by sensing the spectrum with energy detection-based wideband multichannel spectrum sensing algorithm and continue by investigating optimal resource allocation methods. Along the way, we examine the effects of spectral regrowth due to the inevitable power amplifier nonlinearities of the PU transmitters. The signal model includes frequency selective block-fading channel models for both secondary and primary transmissions. Filter bank-based wideband spectrum sensing techniques are applied for detecting spectral holes and filter bank-based multicarrier (FBMC) modulation is selected for transmission as an alternative multicarrier waveform to avoid the disadvantage of limited spectral containment of orthogonal frequency-division multiplexing (OFDM)-based multicarrier systems. The optimization technique used for the resource allocation approach considered in this study utilizes the information obtained through spectrum sensing and knowledge of spectrum leakage effects of the underlying waveforms, including a practical power amplifier model for the PU transmitter. This study utilizes a computationally efficient algorithm to maximize the SU link capacity with power and interference constraints. It is seen that the SU transmission capacity depends critically on the spectral containment of the PU waveform, and these effects are quantified in a case study using an 802.11-g WLAN scenario.

  20. Contribution of strong discontinuities to the power spectrum of the solar wind.

    PubMed

    Borovsky, Joseph E

    2010-09-10

    Eight and a half years of magnetic field measurements (2(22) samples) from the ACE spacecraft in the solar wind at 1 A.U. are analyzed. Strong (large-rotation-angle) discontinuities in the solar wind are collected and measured. An artificial time series is created that preserves the timing and amplitudes of the discontinuities. The power spectral density of the discontinuity series is calculated and compared with the power spectral density of the solar-wind magnetic field. The strong discontinuities produce a power-law spectrum in the "inertial subrange" with a spectral index near the Kolmogorov -5/3 index. The discontinuity spectrum contains about half of the power of the full solar-wind magnetic field over this "inertial subrange." Warnings are issued about the significant contribution of discontinuities to the spectrum of the solar wind, complicating interpretation of spectral power and spectral indices. PMID:20867562

  1. Conservative constraints on dark matter from the Fermi-LAT isotropic diffuse gamma-ray background spectrum

    SciTech Connect

    Abazajian, Kevork N.; Agrawal, Prateek; Chacko, Zackaria; Kilic, Can E-mail: apr@umd.edu E-mail: kilic@physics.rutgers.edu

    2010-11-01

    We examine the constraints on final state radiation from Weakly Interacting Massive Particle (WIMP) dark matter candidates annihilating into various standard model final states, as imposed by the measurement of the isotropic diffuse gamma-ray background by the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope. The expected isotropic diffuse signal from dark matter annihilation has contributions from the local Milky Way (MW) as well as from extragalactic dark matter. The signal from the MW is very insensitive to the adopted dark matter profile of the halos, and dominates the signal from extragalactic halos, which is sensitive to the low mass cut-off of the halo mass function. We adopt a conservative model for both the low halo mass survival cut-off and the substructure boost factor of the Galactic and extragalactic components, and only consider the primary final state radiation. This provides robust constraints which reach the thermal production cross-section for low mass WIMPs annihilating into hadronic modes. We also reanalyze limits from HESS observations of the Galactic Ridge region using a conservative model for the dark matter halo profile. When combined with the HESS constraint, the isotropic diffuse spectrum rules out all interpretations of the PAMELA positron excess based on dark matter annihilation into two lepton final states. Annihilation into four leptons through new intermediate states, although constrained by the data, is not excluded.

  2. Power Versus Spectrum 2-D Sensing in Energy Harvesting Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    Zhang, Yanyan; Han, Weijia; Li, Di; Zhang, Ping; Cui, Shuguang

    2015-12-01

    Energy harvester based cognitive radio is a promising solution to address the shortage of both spectrum and energy. Since the spectrum access and power consumption patterns are interdependent, and the power value harvested from certain environmental sources are spatially correlated, the new power dimension could provide additional information to enhance the spectrum sensing accuracy. In this paper, the Markovian behavior of the primary users is considered, based on which we adopt a hidden input Markov model to specify the primary vs. secondary dynamics in the system. Accordingly, we propose a 2-D spectrum and power (harvested) sensing scheme to improve the primary user detection performance, which is also capable of estimating the primary transmit power level. Theoretical and simulated results demonstrate the effectiveness of the proposed scheme, in term of the performance gain achieved by considering the new power dimension. To the best of our knowledge, this is the first work to jointly consider the spectrum and power dimensions for the cognitive primary user detection problem.

  3. An automatic method to determine cutoff frequency based on image power spectrum

    SciTech Connect

    Beis, J.S.; Celler, A.; Barney, J.S.

    1995-12-01

    The authors present an algorithm for automatically choosing filter cutoff frequency (F{sub c}) using the power spectrum of the projections. The method is based on the assumption that the expectation of the image power spectrum is the sum of the expectation of the blurred object power spectrum (dominant at low frequencies) plus a constant value due to Poisson noise. By considering the discrete components of the noise-dominated high-frequency spectrum as a Gaussian distribution N({mu},{sigma}), the Student t-test determines F{sub c} as the highest frequency for which the image frequency components are unlikely to be drawn from N ({mu},{sigma}). The method is general and can be applied to any filter. In this work, the authors tested the approach using the Metz restoration filter on simulated, phantom, and patient data with good results. Quantitative performance of the technique was evaluated by plotting recovery coefficient (RC) versus NMSE of reconstructed images.

  4. CMB lensing power spectrum biases from galaxies and clusters using high-angular resolution temperature maps

    SciTech Connect

    Van Engelen, A.; Sehgal, N.; Bhattacharya, S.; Holder, G. P.; Zahn, O.; Nagai, D.

    2014-05-01

    The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to the Atacama Cosmology Telescope and the South Pole Telescope. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on σ{sub 8} and an uncertainty on the total neutrino mass of ∼50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M {sub vir} = 10{sup 14} M {sub ☉}. To achieve such percent level bias, we find that only modes up to a maximum multipole of l {sub max} ∼ 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.

  5. Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study

    NASA Technical Reports Server (NTRS)

    Szabo, A.; Koval, A.; Merka, J.; Narock, T.

    2011-01-01

    The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the 2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

  6. Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study

    NASA Technical Reports Server (NTRS)

    Szabo, A.; Koval, A.; Merka, J.; Narock, T.

    2010-01-01

    The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions . The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed

  7. Multi-redshift limits on the Epoch of Reionization 21cm power spectrum from PAPER

    NASA Astrophysics Data System (ADS)

    Jacobs, Danny; Pober, Jonathan; Parsons, Aaron; Paper Team

    2015-01-01

    The epoch of reionization hydrogen power spectrum is expected to vary strongly with redshift with cosmic history as star formation progressively ionizes the pervasive intergalactic hydrogen. We present an analysis of observations from the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) telescope which place new limits on the HI power spectrum over the redshift range of 7.5power spectrum is bright foreground emission, which varies slowly with redshift. To suppress these foregrounds, we use filtering techniques adopted from digital signal processing to isolate foreground in power spectrum k-space. This 500 hour integration demonstrates a spectral rejection dynamic range of 10^4. The measured power spectrum uncertainty compares well with the expected thermal noise. Relative to this thermal noise, most spectra exhibit an excess of power at a few sigma. The possible sources of this modest excess include residual foreground leakage, particularly at the highest redshift, and unflagged RFI.

  8. Angular Power Spectrum in Modular Invariant Inflation Model

    SciTech Connect

    Hayashi, Mitsuo J.; Okame, Y.; Takagi, K.; Watanabe, T.; Hirai, S.; Takami, T.

    2008-05-29

    A scalar potential of inflation is proposed and the angular power spectra of the adiabatic density perturbations are computed. The potential consists of three scalar fields, S, Y and T, together with two free parameters. By fitting the parameters to cosmological data at the fixed point T = 1, we find that the potential behaves like the single-field potential of S, which slowly rolls down. We further show that the inflation predictions corresponding to this potential provide a good fit to the recent three-year WMAP data, e.g. the spectral index n{sub s} = 0.951.The TT and TE angular power spectra obtained from our model almost completely coincide with the corresponding results obtained from the {lambda}CDM model. We conclude that our model is considered to be an adequate theory of inflation that explains the present data.

  9. Constraints on primordial non-Gaussianity from WMAP7 and luminous red galaxies power spectrum and forecast for future surveys

    SciTech Connect

    De Bernardis, Francesco; Serra, Paolo; Cooray, Asantha; Melchiorri, Alessandro

    2010-10-15

    We place new constraints on the primordial local non-Gaussianity parameter f{sub NL} using recent cosmic microwave background anisotropy and galaxy clustering data. We model the galaxy power spectrum according to the halo model, accounting for a scale-dependent bias correction proportional to f{sub NL}/k{sup 2}. We first constrain f{sub NL} in a full 13 parameters analysis that includes 5 parameters of the halo model and 7 cosmological parameters. Using the WMAP7 CMB data and the SDSS DR4 galaxy power spectrum, we find f{sub NL}=171{sub -139}{sup +140} at 68% C.L. and -69power spectrum data finding, for a {Lambda}CDM+f{sub NL} model, f{sub NL}=-93{+-}128 at 68% C.L. and -327

  10. Cosmology from the thermal Sunyaev-Zel'dovich power spectrum: Primordial non-Gaussianity and massive neutrinos

    NASA Astrophysics Data System (ADS)

    Hill, J. Colin; Pajer, Enrico

    2013-09-01

    We carry out a comprehensive analysis of the possible constraints on cosmological and astrophysical parameters achievable with measurements of the thermal Sunyaev-Zel’dovich (tSZ) power spectrum from upcoming full-sky cosmic microwave background observations, with a particular focus on one-parameter extensions to the ΛCDM standard model involving local primordial non-Gaussianity (described by fNL) and massive neutrinos (described by Mν). We include all of the relevant physical effects due to these additional parameters, including the change to the halo mass function and the scale-dependent halo bias induced by local primordial non-Gaussianity. We use the halo model to compute the tSZ power spectrum and provide a pedagogical derivation of the one- and two-halo terms in an Appendix. We model the pressure profile of the intracluster medium (ICM) using a parametrized fit that agrees well with existing observations, and include uncertainty in the ICM modeling by including the overall normalization and outer logarithmic slope of the profile as free parameters. We compute forecasts for Planck, Primordial Inflation Explorer (PIXIE), and a cosmic variance (CV)-limited experiment, using multifrequency subtraction to remove foregrounds and implementing two masking criteria based on the ROSAT and eROSITA cluster catalogs to reduce the significant CV errors at low multipoles. We find that Planck can detect the tSZ power spectrum with >30σ significance, regardless of the masking scenario. However, neither Planck or PIXIE is likely to provide competitive constraints on fNL from the tSZ power spectrum due to CV noise at low ℓ overwhelming the unique signature of the scale-dependent bias. A future CV-limited experiment could provide a 3σ detection of fNL≃37, which is the WMAP9 maximum-likelihood result. The outlook for neutrino masses is more optimistic: Planck can reach levels comparable to the current upper bounds ≲0.3eV with conservative assumptions about the ICM

  11. Calculated power distribution of a thermionic, beryllium oxide reflected, fast-spectrum reactor

    NASA Technical Reports Server (NTRS)

    Mayo, W.; Lantz, E.

    1973-01-01

    A procedure is developed and used to calculate the detailed power distribution in the fuel elements next to a beryllium oxide reflector of a fast-spectrum, thermionic reactor. The results of the calculations show that, although the average power density in these outer fuel elements is not far from the core average, the power density at the very edge of the fuel closest to the beryllium oxide is about 1.8 times the core avearge.

  12. Generic inference of inflation models by non-Gaussianity and primordial power spectrum reconstruction

    SciTech Connect

    Dorn, Sebastian; Enßlin, Torsten A.; Ramirez, Erandy; Kunze, Kerstin E.

    2014-06-01

    We present a generic inference method for inflation models from observational data by the usage of higher-order statistics of the curvature perturbation on uniform density hypersurfaces. This method is based on the calculation of the posterior for the primordial non-Gaussianity parameters f{sub NL} and g{sub NL}, which in general depend on specific parameters of inflation and reheating models, and enables to discriminate among the still viable inflation models. To keep analyticity as far as possible to dispense with numerically expensive sampling techniques a saddle-point approximation is introduced, whose precision is validated for a numerical toy example. The mathematical formulation is done in a generic way so that the approach remains applicable to cosmic microwave background data as well as to large scale structure data. Additionally, we review a few currently interesting inflation models and present numerical toy examples thereof in two and three dimensions to demonstrate the efficiency of the higher-order statistics method. A second quantity of interest is the primordial power spectrum. Here, we present two Bayesian methods to infer it from observational data, the so called critical filter and an extension thereof with smoothness prior, both allowing for a non-parametric spectrum reconstruction. These methods are able to reconstruct the spectra of the observed perturbations and the primordial ones of curvature perturbation even in case of non-Gaussianity and partial sky coverage. We argue that observables like T- and B-modes permit to measure both spectra. This also allows to infer the level of non-Gaussianity generated since inflation.

  13. PkANN: Non-Linear Matter Power Spectrum Interpolation through Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Agarwal, Shankar

    We investigate the interpolation of power spectra of matter fluctuations using artificial neural networks (ANNs). We present a new approach to confront small-scale non-linearities in the matter power spectrum. This ever-present and pernicious uncertainty is often the Achilles' heel in cosmological studies and must be reduced if we are to see the advent of precision cosmology in the late-time Universe. We detail how an accurate interpolation of the matter power spectrum is achievable with only a sparsely sampled grid of cosmological parameters. We show that an optimally trained ANN, when presented with a set of cosmological parameters (Omh2 , Obh2, ns, w0, sigma8, sum mnu and z), can provide a worst-case error ≤ 1 per cent (for redshift z ≤ 2) fit to the non-linear matter power spectrum deduced through large-scale N-body simulations, for modes up to k ≤ 0.9 hMpc-1 . Our power spectrum interpolator, which we label 'PkANN', is designed to simulate a range of cosmological models including massive neutrinos and dark energy equation of state w 0 ≠ -1. PkANN is accurate in the quasi-non-linear regime (0.1 hMpc-1 ≤ k ≤ 0.9 hMpc -1) over the entire parameter space and marks a significant improvement over some of the current power spectrum calculators. The response of the power spectrum to variations in the cosmological parameters is explored using PkANN. Using a compilation of existing peculiar velocity surveys, we investigate the cosmic Mach number statistic and show that PkANN not only successfully accounts for the non-linear motions on small scales, but also, unlike N-body simulations which are computationally expensive and/or infeasible, it can be an extremely quick and reliable tool in interpreting cosmological observations and testing theories of structure-formation.

  14. Power spectrum of electrical discharges seen on earth and at Saturn

    NASA Astrophysics Data System (ADS)

    Warwick, J. W.

    1989-07-01

    A technique is described for deriving the radio spectrum of electrical discharges by using the properties of the time series of charges crossing the discharge gap. The method was applied to the spectrum of lightning and to the Saturn's electrical discharges (SEDs). It is shown that the occurrence and the power density of SEDs have subtle, but important, differences from these observables described in the last five years. The reasons for these differences are discussed.

  15. DOAS evaluation of volcanic SO2 using a modeled background spectrum: Examples from the NOVAC stations at Nevado del Ruiz (Colombia) and Tungurahua (Ecuador)

    NASA Astrophysics Data System (ADS)

    Lübcke, Peter; Lampel, Johannes; Bobrowski, Nicole; Arellano, Santiago; Galle, Bo; Garzón, Gustavo; Hidalgo, Silvana; Vogel, Leif; Warnach, Simon; Platt, Ulrich

    2015-04-01

    SO2 emission rates are monitored using Differential Optical Absorption Spectroscopy (DOAS) in the UV at an increasing number of volcano observatories. The Network for Observation of Volcanic and Atmospheric Change (NOVAC) has currently installed 80 scanning DOAS instruments at 30 volcanoes world-wide. One important question for the evaluation of spectra using DOAS is the availability of background spectra that are not influenced by volcanic gas emissions. An SO2 contaminated background spectrum would lead to a negative offset of the retrieved SO2 column densities, and thus to an underestimation of the volcanic SO2 emission rate. In NOVAC this problem is approached by performing a scan, e.g. through a plane from one horizon to the other horizon, and defining the average of the 20% spectra with the lowest SO2 content as the zero-baseline value, which is assumed to be gas free. To verify this assumption we revisit the idea of evaluating spectra using the DOAS method with a modeled background spectrum based on a high-resolution solar atlas. One challenge when evaluating spectra with a modeled background spectrum is properly accounting for instrumental effects that are usually removed when calculating the measured optical density relative to a measured background spectrum. We present our approach to handle these instrumental effects, showing that we gain a similar fit quality to the method using a measured reference spectrum. For example, wavelength dependent structures in the spectrum due to the spectrometer (e.g., quantum efficiency of the detector and grating efficiency) were identified with help of a principal component analysis of an SO2 free subset of the residual spectra. These structures were included in a second iteration of the fit in order to improve the evaluation. We further discuss influences like strong ozone absorption and the instrument temperature on the quality of the SO2 fit using a modeled background spectrum. The new evaluation scheme was applied

  16. Power spectrum nulls due to nonstandard inflationary evolution

    NASA Astrophysics Data System (ADS)

    Goswami, Gaurav; Souradeep, Tarun

    2011-01-01

    The simplest models of inflation based on slow roll produce nearly scale invariant primordial power spectra (PPS). But there are also numerous models that predict radically broken scale invariant PPS. In particular, markedly cuspy dips in the PPS correspond to nulls where the perturbation amplitude, hence PPS, goes through a zero at a specific wave number. Near this wave number, the true quantum nature of the generation mechanism of the primordial fluctuations may be revealed. Naively these features may appear to arise from fine-tuned initial conditions. However, we show that this behavior arises under fairly generic set of conditions involving super-Hubble scale evolution of perturbation modes during inflation. We illustrate this with the well-studied examples of punctuated inflation and the Starobinsky-break model.

  17. ON THE CLUSTER PHYSICS OF SUNYAEV-ZEL'DOVICH AND X-RAY SURVEYS. II. DECONSTRUCTING THE THERMAL SZ POWER SPECTRUM

    SciTech Connect

    Battaglia, N.; Bond, J. R.; Pfrommer, C.; Sievers, J. L.

    2012-10-20

    Secondary anisotropies in the cosmic microwave background are a treasure-trove of cosmological information. Interpreting current experiments probing them are limited by theoretical uncertainties rather than by measurement errors. Here we focus on the secondary anisotropies resulting from the thermal Sunyaev-Zel'dovich (tSZ) effect; the amplitude of which depends critically on the average thermal pressure profile of galaxy groups and clusters. To this end, we use a suite of hydrodynamical TreePM-SPH simulations that include radiative cooling, star formation, supernova feedback, and energetic feedback from active galactic nuclei. We examine in detail how the pressure profile depends on cluster radius, mass, and redshift and provide an empirical fitting function. We employ three different approaches for calculating the tSZ power spectrum: an analytical approach that uses our pressure profile fit, a semianalytical method of pasting our pressure fit onto simulated clusters, and a direct numerical integration of our simulated volumes. We demonstrate that the detailed structure of the intracluster medium and cosmic web affect the tSZ power spectrum. In particular, the substructure and asphericity of clusters increase the tSZ power spectrum by 10%-20% at l {approx} 2000-8000, with most of the additional power being contributed by substructures. The contributions to the power spectrum from radii larger than R {sub 500} is {approx}20% at l = 3000, thus clusters interiors (r < R {sub 500}) dominate the power spectrum amplitude at these angular scales.

  18. On the Cluster Physics of Sunyaev-Zel'dovich and X-Ray Surveys. II. Deconstructing the Thermal SZ Power Spectrum

    NASA Astrophysics Data System (ADS)

    Battaglia, N.; Bond, J. R.; Pfrommer, C.; Sievers, J. L.

    2012-10-01

    Secondary anisotropies in the cosmic microwave background are a treasure-trove of cosmological information. Interpreting current experiments probing them are limited by theoretical uncertainties rather than by measurement errors. Here we focus on the secondary anisotropies resulting from the thermal Sunyaev-Zel'dovich (tSZ) effect; the amplitude of which depends critically on the average thermal pressure profile of galaxy groups and clusters. To this end, we use a suite of hydrodynamical TreePM-SPH simulations that include radiative cooling, star formation, supernova feedback, and energetic feedback from active galactic nuclei. We examine in detail how the pressure profile depends on cluster radius, mass, and redshift and provide an empirical fitting function. We employ three different approaches for calculating the tSZ power spectrum: an analytical approach that uses our pressure profile fit, a semianalytical method of pasting our pressure fit onto simulated clusters, and a direct numerical integration of our simulated volumes. We demonstrate that the detailed structure of the intracluster medium and cosmic web affect the tSZ power spectrum. In particular, the substructure and asphericity of clusters increase the tSZ power spectrum by 10%-20% at l ~ 2000-8000, with most of the additional power being contributed by substructures. The contributions to the power spectrum from radii larger than R 500 is ~20% at l = 3000, thus clusters interiors (r < R 500) dominate the power spectrum amplitude at these angular scales.

  19. Sensitivity of neutrinos to the supernova turbulence power spectrum: Point source statistics

    NASA Astrophysics Data System (ADS)

    Kneller, James P.; Kabadi, Neel V.

    2015-07-01

    The neutrinos emitted from the proto-neutron star created in a core-collapse supernova must run through a significant amount of turbulence before exiting the star. Turbulence can modify the flavor evolution of the neutrinos imprinting itself upon the signal detected here at Earth. The turbulence effect upon individual neutrinos, and the correlation between pairs of neutrinos, might exhibit sensitivity to the power spectrum of the turbulence, and recent analysis of the turbulence in a two-dimensional hydrodynamical simulation of a core-collapse supernova indicates the power spectrum may not be the Kolmogorov 5 /3 inverse power law as has been previously assumed. In this paper we study the effect of non-Kolmogorov turbulence power spectra upon neutrinos from a point source as a function of neutrino energy and turbulence amplitude at a fixed postbounce epoch. We find the two effects of turbulence upon the neutrinos—the distorted phase effect and the stimulated transitions—both possess strong and weak limits in which dependence upon the power spectrum is absent or evident, respectively. Since neutrinos of a given energy will exhibit these two effects at different epochs of the supernova each with evolving strength, we find there is sensitivity to the power spectrum present in the neutrino burst signal from a Galactic supernova.

  20. Power spectrum extraction for redshifted 21-cm Epoch of Reionization experiments: the LOFAR case

    NASA Astrophysics Data System (ADS)

    Harker, Geraint; Zaroubi, Saleem; Bernardi, Gianni; Brentjens, Michiel A.; de Bruyn, A. G.; Ciardi, Benedetta; Jelić, Vibor; Koopmans, Leon V. E.; Labropoulos, Panagiotis; Mellema, Garrelt; Offringa, André; Pandey, V. N.; Pawlik, Andreas H.; Schaye, Joop; Thomas, Rajat M.; Yatawatta, Sarod

    2010-07-01

    One of the aims of the Low Frequency Array (LOFAR) Epoch of Reionization (EoR) project is to measure the power spectrum of variations in the intensity of redshifted 21-cm radiation from the EoR. The sensitivity with which this power spectrum can be estimated depends on the level of thermal noise and sample variance, and also on the systematic errors arising from the extraction process, in particular from the subtraction of foreground contamination. We model the extraction process using realistic simulations of the cosmological signal, the foregrounds and noise, and so estimate the sensitivity of the LOFAR EoR experiment to the redshifted 21-cm power spectrum. Detection of emission from the EoR should be possible within 360 h of observation with a single station beam. Integrating for longer, and synthesizing multiple station beams within the primary (tile) beam, then enables us to extract progressively more accurate estimates of the power at a greater range of scales and redshifts. We discuss different observational strategies which compromise between depth of observation, sky coverage and frequency coverage. A plan in which lower frequencies receive a larger fraction of the time appears to be promising. We also study the nature of the bias which foreground fitting errors induce on the inferred power spectrum and discuss how to reduce and correct for this bias. The angular and line-of-sight power spectra have different merits in this respect, and we suggest considering them separately in the analysis of LOFAR data.

  1. PkANN - I. Non-linear matter power spectrum interpolation through artificial neural networks

    NASA Astrophysics Data System (ADS)

    Agarwal, Shankar; Abdalla, Filipe B.; Feldman, Hume A.; Lahav, Ofer; Thomas, Shaun A.

    2012-08-01

    We investigate the interpolation of power spectra of matter fluctuations using artificial neural networks (PkANN). We present a new approach to confront small-scale non-linearities in the power spectrum of matter fluctuations. This ever-present and pernicious uncertainty is often the Achilles heel in cosmological studies and must be reduced if we are to see the advent of precision cosmology in the late-time Universe. We show that an optimally trained artificial neural network (ANN), when presented with a set of cosmological parameters (? and redshift z), can provide a worst-case error ≤1 per cent (for z≤ 2) fit to the non-linear matter power spectrum deduced through N-body simulations, for modes up to k≤ 0.7 h Mpc-1. Our power spectrum interpolator is accurate over the entire parameter space. This is a significant improvement over some of the current matter power spectrum calculators. In this paper, we detail how an accurate interpolation of the matter power spectrum is achievable with only a sparsely sampled grid of cosmological parameters. Unlike large-scale N-body simulations which are computationally expensive and/or infeasible, a well-trained ANN can be an extremely quick and reliable tool in interpreting cosmological observations and parameter estimation. This paper is the first in a series. In this method paper, we generate the non-linear matter power spectra using HALOFIT and use them as mock observations to train the ANN. This work sets the foundation for Paper II, where a suite of N-body simulations will be used to compute the non-linear matter power spectra at sub-per cent accuracy, in the quasi-non-linear regime (0.1 ≤k≤ 0.9 h Mpc-1). A trained ANN based on this N-body suite will be released for the scientific community.

  2. The non-linear power spectrum of the Lyman alpha forest

    NASA Astrophysics Data System (ADS)

    Arinyo-i-Prats, Andreu; Miralda-Escudé, Jordi; Viel, Matteo; Cen, Renyue

    2015-12-01

    The Lyman alpha forest power spectrum has been measured on large scales by the BOSS survey in SDSS-III at z~ 2.3, has been shown to agree well with linear theory predictions, and has provided the first measurement of Baryon Acoustic Oscillations at this redshift. However, the power at small scales, affected by non-linearities, has not been well examined so far. We present results from a variety of hydrodynamic simulations to predict the redshift space non-linear power spectrum of the Lyα transmission for several models, testing the dependence on resolution and box size. A new fitting formula is introduced to facilitate the comparison of our simulation results with observations and other simulations. The non-linear power spectrum has a generic shape determined by a transition scale from linear to non-linear anisotropy, and a Jeans scale below which the power drops rapidly. In addition, we predict the two linear bias factors of the Lyα forest and provide a better physical interpretation of their values and redshift evolution. The dependence of these bias factors and the non-linear power on the amplitude and slope of the primordial fluctuations power spectrum, the temperature-density relation of the intergalactic medium, and the mean Lyα transmission, as well as the redshift evolution, is investigated and discussed in detail. A preliminary comparison to the observations shows that the predicted redshift distortion parameter is in good agreement with the recent determination of Blomqvist et al., but the density bias factor is lower than observed. We make all our results publicly available in the form of tables of the non-linear power spectrum that is directly obtained from all our simulations, and parameters of our fitting formula.

  3. Calculation of power spectrums from digital time series with missing data points

    NASA Technical Reports Server (NTRS)

    Murray, C. W., Jr.

    1980-01-01

    Two algorithms are developed for calculating power spectrums from the autocorrelation function when there are missing data points in the time series. Both methods use an average sampling interval to compute lagged products. One method, the correlation function power spectrum, takes the discrete Fourier transform of the lagged products directly to obtain the spectrum, while the other, the modified Blackman-Tukey power spectrum, takes the Fourier transform of the mean lagged products. Both techniques require fewer calculations than other procedures since only 50% to 80% of the maximum lags need be calculated. The algorithms are compared with the Fourier transform power spectrum and two least squares procedures (all for an arbitrary data spacing). Examples are given showing recovery of frequency components from simulated periodic data where portions of the time series are missing and random noise has been added to both the time points and to values of the function. In addition the methods are compared using real data. All procedures performed equally well in detecting periodicities in the data.

  4. Possible Evidence for Planck-Scale Resonant Particle Production during Inflation from the CMB Power Spectrum

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Mayukh; Mathews, Grant; Ichiki, Kiyotomo; Kajino, Toshitaka

    2016-03-01

    The power spectrum of the cosmic microwave background from both the Planck and WMAP data exhibits a slight dip for multipoles in the range of l = 10 - 30 . We show that such a dip could be the result of the resonant creation of massive particles that couple to the inflaton field. For our best-fit models, the epoch of resonant particle creation reenters the horizon at a wave number of k* ~ 0 . 00011 +/- 0 . 0004 (h Mpc-1). The amplitude and location of this feature corresponds to the creation of a number of degenerate fermion species of mass ~ (8 - 11) /λ 3 / 2 mpl during inflation where λ ~ (1 . 0 +/- 0 . 5) N - 2 / 5 is the coupling constant between the inflaton field and the created fermion species, while N is the number of degenerate species. Although the evidence is of marginal statistical significance, this could constitute new observational hints of unexplored physics beyond the Planck scale. Work at the University of Notre Dame is supported by the U.S. Department of Energy under Nuclear Theory Grant DE-FG02-95-ER40934. Work at NAOJ was supported in part by Grants-in-Aid for Scientific Research of JSPS (26105517, 24340060). Work at Nagoya Uni.

  5. Matter power spectrum for the generalized Chaplygin gas model: The Newtonian approach

    SciTech Connect

    Fabris, J. C.; Goncalves, S. V. B.; Velten, H. E. S.; Zimdahl, W.

    2008-11-15

    We model the cosmic medium as the mixture of a generalized Chaplygin gas and a pressureless matter component. Within a neo-Newtonian approach (in which, different from standard Newtonian cosmology, the pressure enters the homogeneous and isotropic background dynamics) we compute the matter power spectrum. The 2dFGRS data are used to discriminate between unified models of the dark sector (a purely baryonic matter component of roughly 5% of the total energy content and roughly 95% generalized Chaplygin gas) and different models, for which there is separate dark matter, in addition to that accounted for by the generalized Chaplygin gas. Leaving the corresponding density parameters free, we find that the unified models are strongly disfavored. On the other hand, using unified model priors, the observational data are also well described, in particular, for small and large values of the generalized Chaplygin gas parameter {alpha}. The latter result is in agreement with a recent, more qualitative but fully relativistic, perturbation analysis in [V. Gorini, A. Y. Kamenshchik, U. Moschella, O. F. Piatella, and A. A. Starobinsky, J. Cosmol. Astropart. Phys. 02 (2008) 016.].

  6. Constraining models of f(R) gravity with Planck and WiggleZ power spectrum data

    SciTech Connect

    Dossett, Jason; Parkinson, David; Hu, Bin E-mail: hu@lorentz.leidenuniv.nl

    2014-03-01

    In order to explain cosmic acceleration without invoking ''dark'' physics, we consider f(R) modified gravity models, which replace the standard Einstein-Hilbert action in General Relativity with a higher derivative theory. We use data from the WiggleZ Dark Energy survey to probe the formation of structure on large scales which can place tight constraints on these models. We combine the large-scale structure data with measurements of the cosmic microwave background from the Planck surveyor. After parameterizing the modification of the action using the Compton wavelength parameter B{sub 0}, we constrain this parameter using ISiTGR, assuming an initial non-informative log prior probability distribution of this cross-over scale. We find that the addition of the WiggleZ power spectrum provides the tightest constraints to date on B{sub 0} by an order of magnitude, giving log{sub 10}(B{sub 0}) < −4.07 at 95% confidence limit. Finally, we test whether the effect of adding the lensing amplitude A{sub Lens} and the sum of the neutrino mass ∑m{sub ν} is able to reconcile current tensions present in these parameters, but find f(R) gravity an inadequate explanation.

  7. The 21cm power spectrum and the shapes of non-Gaussianity

    SciTech Connect

    Chongchitnan, Sirichai

    2013-03-01

    We consider how measurements of the 21cm radiation from the epoch of reionization (z = 8−12) can constrain the amplitudes of various 'shapes' of primordial non-Gaussianity. The limits on these shapes, each parametrized by the non-linear parameter f{sub NL}, can reveal whether the physics of inflation is more complex than the standard single-field, slow-roll scenario. In this work, we quantify the effects of the well-known local, equilateral, orthogonal and folded types of non-Gaussianities on the 21cm power spectrum, which is expected to be measured by upcoming radio arrays such as the Square-Kilometre Array (SKA). We also assess the prospects of the SKA in constraining these non-Gaussianities, and found constraints that are comparable with those from cosmic-microwave-background experiments such as Planck. We show that the limits on various f{sub NL} can be tightened to O(1) using a radio array with a futuristic but realistic set of specifications.

  8. The non-linear redshift-space power spectrum: Omega from redshift surveys

    NASA Astrophysics Data System (ADS)

    Fisher, Karl B.; Nusser, Adi

    1996-03-01

    We examine the anisotropies in the power spectrum by the mapping of real space to redshift space. Using the Zel'dovich approximation, we obtain an analytic expression for the non-linear redshift-space power spectrum in the distant observer limit. For a given unbiased galaxy distribution in redshift space, the anisotropies in the power spectrum depend on the parameter f(Omega)~=Omega^0.6, where Omega is the density parameter. We quantify these anisotropies by the ratio, R, of the quadrupole and monopole angular moments of the power spectrum. In contrast to linear theory, the Zel'dovich approximation predicts a decline in R with decreasing scale. This departure from linear theory is due to non-linear dynamics and is not a result of incoherent random velocities. The rate of decline depends strongly on Omega and the initial power spectrum. However, we find a scaling relation between the quantity R/R_lin (where R_lin is the linear theory value of R) and the dimensionless variable k/k_nl, where k_nl is a wavenumber determined by the scale of non-linear structures. The scaling is weakly dependent on the initial power spectrum and is in good agreement with a large N-body simulation. This universal scaling relation greatly extends the scales over which redshift distortions can be used as a probe of Omega. The scaling relation is in agreement with the observed quadrupole-to-monopole ratio from the 1.2-Jy IRAS survey, with a best estimate of Omega^0.6/b_lin=0.6+/-0.2 where b_lin is the linear bias parameter.

  9. Scaling-law for the energy dependence of anatomic power spectrum in dedicated breast CT

    SciTech Connect

    Vedantham, Srinivasan; Shi, Linxi; Glick, Stephen J.; Karellas, Andrew

    2013-01-15

    Purpose: To determine the x-ray photon energy dependence of the anatomic power spectrum of the breast when imaged with dedicated breast computed tomography (CT). Methods: A theoretical framework for scaling the empirically determined anatomic power spectrum at one x-ray photon energy to that at any given x-ray photon energy when imaged with dedicated breast CT was developed. Theory predicted that when the anatomic power spectrum is fitted with a power curve of the form k f{sup -{beta}}, where k and {beta} are fit coefficients and f is spatial frequency, the exponent {beta} would be independent of x-ray photon energy (E), and the amplitude k scales with the square of the difference in energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues. Twenty mastectomy specimens based numerical phantoms that were previously imaged with a benchtop flat-panel cone-beam CT system were converted to 3D distribution of glandular weight fraction (f{sub g}) and were used to verify the theoretical findings. The 3D power spectrum was computed in terms of f{sub g} and after converting to linear attenuation coefficients at monoenergetic x-ray photon energies of 20-80 keV in 5 keV intervals. The 1D power spectra along the axes were extracted and fitted with a power curve of the form k f{sup -{beta}}. The energy dependence of k and {beta} were analyzed. Results: For the 20 mastectomy specimen based numerical phantoms used in the study, the exponent {beta} was found to be in the range of 2.34-2.42, depending on the axis of measurement. Numerical simulations agreed with the theoretical predictions that for a power-law anatomic spectrum of the form k f{sup -{beta}}, {beta} was independent of E and k(E) =k{sub 1}[{mu}{sub g}(E) -{mu}{sub a}(E)]{sup 2}, where k{sub 1} is a constant, and {mu}{sub g}(E) and {mu}{sub a}(E) represent the energy-dependent linear attenuation coefficients of fibroglandular and adipose tissues, respectively. Conclusions: Numerical

  10. General requirements on matter power spectrum predictions for cosmology with weak lensing tomography

    SciTech Connect

    Hearin, Andrew P.; Zentner, Andrew R.; Ma, Zhaoming E-mail: zentner@pitt.edu

    2012-04-01

    Forthcoming projects such as DES, LSST, WFIRST, and Euclid aim to measure weak lensing shear correlations with unprecedented precision, constraining the dark energy equation of state at the percent level. Reliance on photometrically-determined redshifts constitutes a major source of uncertainty for these surveys. Additionally, interpreting the weak lensing signal requires a detailed understanding of the nonlinear physics of gravitational collapse. We present a new analysis of the stringent calibration requirements for weak lensing analyses of future imaging surveys that addresses both photo-z uncertainty and errors in the calibration of the matter power spectrum. We find that when photo-z uncertainty is taken into account the requirements on the level of precision in the prediction for the matter power spectrum are more stringent than previously thought. Including degree-scale galaxy clustering statistics in a joint analysis with weak lensing not only strengthens the survey's constraining power by ∼ 20%, but can also have a profound impact on the calibration demands, decreasing the degradation in dark energy constraints with matter power spectrum uncertainty by a factor of 2-5. Similarly, using galaxy clustering information significantly relaxes the demands on photo-z calibration. We compare these calibration requirements to the contemporary state-of-the-art in photometric redshift estimation and predictions of the power spectrum and suggest strategies to utilize forthcoming data optimally.

  11. Ruling out the power-law form of the scalar primordial spectrum

    SciTech Connect

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Smoot, George F.; Starobinsky, Alexei A. E-mail: arman@apctp.org E-mail: alstar@landau.ac.ru

    2014-06-01

    Combining Planck CMB temperature [1] and BICEP2 B-mode polarization data [2,3] we show qualitatively that, assuming inflationary consistency relation, the power-law form of the scalar primordial spectrum is ruled out at more than 3σ CL. This is an important finding, since the power-law form of the scalar primordial spectrum is one of the main assumptions of concordance model of cosmology and also a direct prediction of many inflationary scenarios. We show that a break or step in the form of the primordial scalar perturbation spectrum, similar to what we studied recently analyzing Planck data [4], can address both Planck and BICEP2 results simultaneously. Our findings also indicate that the data may require more flexibilities than what running of scalar spectral index can provide. Finally we show that an inflaton potential, originally appeared in [5], can generate both the step and the break model of scalar primordial spectrum in two different limits. The discussed potential is found to be favored by Planck data but marginally disfavored by BICEP2 results as it produces slightly lower amplitude of tensor primordial spectrum. Hence, if the tensor-to-scalar ratio (r) quoted by BICEP2 persists, it is of importance that we generate inflationary models with large r and at the same time provide suppression in scalar primordial spectrum at large scales.

  12. Contamination cannot explain the lack of large-scale power in the cosmic microwave background radiation

    SciTech Connect

    Bunn, Emory F.; Bourdon, Austin

    2008-12-15

    Several anomalies appear to be present in the large-angle cosmic microwave background (CMB) anisotropy maps of the Wilkinson Microwave Anisotropy Probe. One of these is a lack of large-scale power. Because the data otherwise match standard models extremely well, it is natural to consider perturbations of the standard model as possible explanations. We show that, as long as the source of the perturbation is statistically independent of the source of the primary CMB anisotropy, no such model can explain this large-scale power deficit. On the contrary, any such perturbation always reduces the probability of obtaining any given low value of large-scale power. We rigorously prove this result when the lack of large-scale power is quantified with a quadratic statistic, such as the quadrupole moment. When a statistic based on the integrated square of the correlation function is used instead, we present strong numerical evidence in support of the result. The result applies to models in which the geometry of spacetime is perturbed (e.g., an ellipsoidal universe) as well as explanations involving local contaminants, undiagnosed foregrounds, or systematic errors. Because the large-scale power deficit is arguably the most significant of the observed anomalies, explanations that worsen this discrepancy should be regarded with great skepticism, even if they help in explaining other anomalies such as multipole alignments.

  13. The Impact of Nonlinear Structure Formation on the Power Spectrum of Transverse Momentum Fluctuations and the Kinetic Sunyaev-Zel'dovich Effect

    NASA Astrophysics Data System (ADS)

    Park, Hyunbae; Komatsu, Eiichiro; Shapiro, Paul R.; Koda, Jun; Mao, Yi

    2016-02-01

    Cosmological transverse momentum fields, whose directions are perpendicular to Fourier wave vectors, induce temperature anisotropies in the cosmic microwave background via the kinetic Sunyaev-Zel’dovich (kSZ) effect. The transverse momentum power spectrum contains the four-point function of density and velocity fields, < δ δ {vv}> . In the post-reionization epoch, nonlinear effects dominate in the power spectrum. We use perturbation theory and cosmological N-body simulations to calculate this nonlinearity. We derive the next-to-leading order expression for the power spectrum with a particular emphasis on the connected term that has been ignored in the literature. While the contribution from the connected term on small scales (k\\gt 0.1 h {{{Mpc}}}-1) is subdominant relative to the unconnected term, we find that its contribution to the kSZ power spectrum at {\\ell }=3000 at z\\lt 6 can be as large as ten percent of the unconnected term, which would reduce the allowed contribution from the reionization epoch (z\\gt 6) by twenty percent. The power spectrum of transverse momentum on large scales is expected to scale as k2 as a consequence of momentum conservation. We show that both the leading and the next-to-leading order terms satisfy this scaling. In particular, we find that both of the unconnected and connected terms are necessary to reproduce k2.

  14. High power diode laser array development using completely indium free packaging technology with narrow spectrum

    NASA Astrophysics Data System (ADS)

    Hou, Dong; Wang, Jingwei; Gao, Lijun; Liang, Xuejie; Li, Xiaoning; Liu, Xingsheng

    2016-03-01

    The high power diode lasers have been widely used in many fields. In this work, a sophisticated high power and high performance horizontal array of diode laser stacks have been developed and fabricated with high duty cycle using hard solder bonding technology. CTE-matched submount and Gold Tin (AuSn) hard solder are used for bonding the diode laser bar to achieve the performances of anti-thermal fatigue, higher reliability and longer lifetime. This array consists of 30 bars with the expected optical output peak power of 6000W. By means of numerical simulation and analytical results, the diode laser bars are aligned on suitable positions along the water cooled cooler in order to achieve the uniform wavelength with narrow spectrum and accurate central wavelength. The performance of the horizontal array, such as output power, spectrum, thermal resistance, life time, etc., is characterized and analyzed.

  15. A statistical spatial power spectrum of the Earth's lithospheric magnetic field

    NASA Astrophysics Data System (ADS)

    Thébault, E.; Vervelidou, F.

    2015-05-01

    The magnetic field of the Earth's lithosphere arises from rock magnetization contrasts that were shaped over geological times. The field can be described mathematically in spherical harmonics or with distributions of magnetization. We exploit this dual representation and assume that the lithospheric field is induced by spatially varying susceptibility values within a shell of constant thickness. By introducing a statistical assumption about the power spectrum of the susceptibility, we then derive a statistical expression for the spatial power spectrum of the crustal magnetic field for the spatial scales ranging from 60 to 2500 km. This expression depends on the mean induced magnetization, the thickness of the shell, and a power law exponent for the power spectrum of the susceptibility. We test the relevance of this form with a misfit analysis to the observational NGDC-720 lithospheric magnetic field model power spectrum. This allows us to estimate a mean global apparent induced magnetization value between 0.3 and 0.6 A m-1, a mean magnetic crustal thickness value between 23 and 30 km, and a root mean square for the field value between 190 and 205 nT at 95 per cent. These estimates are in good agreement with independent models of the crustal magnetization and of the seismic crustal thickness. We carry out the same analysis in the continental and oceanic domains separately. We complement the misfit analyses with a Kolmogorov-Smirnov goodness-of-fit test and we conclude that the observed power spectrum can be each time a sample of the statistical one.

  16. The Effects of Polarized Foregrounds on 21 cm Epoch of Reionization Power Spectrum Measurements

    NASA Astrophysics Data System (ADS)

    Moore, David F.; Aguirre, James E.; Parsons, Aaron R.; Jacobs, Daniel C.; Pober, Jonathan C.

    2013-06-01

    Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using the delay spectrum approach presented in Parsons et al. Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21 cm EoR signal.

  17. THE EFFECTS OF POLARIZED FOREGROUNDS ON 21 cm EPOCH OF REIONIZATION POWER SPECTRUM MEASUREMENTS

    SciTech Connect

    Moore, David F.; Aguirre, James E.; Parsons, Aaron R.; Pober, Jonathan C.; Jacobs, Daniel C.

    2013-06-01

    Experiments aimed at detecting highly-redshifted 21 cm emission from the epoch of reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using the delay spectrum approach presented in Parsons et al. Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21 cm EoR signal.

  18. Slow-roll inflation and BB-mode angular power spectrum of CMB

    NASA Astrophysics Data System (ADS)

    Malsawmtluangi, N.; Suresh, P. K.

    2016-05-01

    The BB-mode correlation angular power spectrum of CMB is obtained by considering the primordial gravitational waves in the squeezed vacuum state for various inflationary models and results are compared with the joint analysis of the BICEP2/Keck Array and Planck 353 GHz data. The present results may constrain several models of inflation.

  19. Effect of features on the functional form of the scalar power spectrum

    NASA Astrophysics Data System (ADS)

    Brooker, D. J.; Tsamis, N. C.; Woodard, R. P.

    2016-08-01

    We study how the scalar power spectrum of single-scalar inflation depends functionally on models with features which have been proposed to explain anomalies in the data. We exploit a new formalism based on evolving the norm-squared of the scalar mode functions, rather than the mode functions themselves.

  20. Angular 21 cm power spectrum of a scaling distribution of cosmic string wakes

    SciTech Connect

    Hernández, Oscar F.; Wang, Yi; Brandenberger, Robert; Fong, José E-mail: wangyi@physics.mcgill.ca E-mail: jose.fong@ens-lyon.fr

    2011-08-01

    Cosmic string wakes lead to a large signal in 21 cm redshift maps at redshifts larger than that corresponding to reionization. Here, we compute the angular power spectrum of 21 cm radiation as predicted by a scaling distribution of cosmic strings whose wakes have undergone shock heating.

  1. Constraining cosmology and ionization history with combined 21 cm power spectrum and global signal measurements

    NASA Astrophysics Data System (ADS)

    Liu, Adrian; Parsons, Aaron R.

    2016-04-01

    Improvements in current instruments and the advent of next-generation instruments will soon push observational 21 cm cosmology into a new era, with high significance measurements of both the power spectrum and the mean (`global') signal of the 21 cm brightness temperature. In this paper, we use the recently commenced Hydrogen Epoch of Reionization Array (HERA) as a worked example to provide forecasts on astrophysical and cosmological parameter constraints. In doing so, we improve upon previous forecasts in a number of ways. First, we provide updated forecasts using the latest best-fitting cosmological parameters from the Planck satellite, exploring the impact of different Planck data sets on 21 cm experiments. We also show that despite the exquisite constraints that other probes have placed on cosmological parameters, the remaining uncertainties are still large enough to have a non-negligible impact on upcoming 21 cm data analyses. While this complicates high-precision constraints on reionization models, it provides an avenue for 21 cm reionization measurements to constrain cosmology. We additionally forecast HERA's ability to measure the ionization history using a combination of power spectrum measurements and semi-analytic simulations. Finally, we consider ways in which 21 cm global signal and power spectrum measurements can be combined, and propose a method by which power spectrum results can be used to train a compact parametrization of the global signal. This parametrization reduces the number of parameters needed to describe the global signal, increasing the likelihood of a high significance measurement.

  2. Interference detection and correction applied to incoherent-scatter radar power spectrum measurement

    NASA Technical Reports Server (NTRS)

    Ying, W. P.; Mathews, J. D.; Rastogi, P. K.

    1986-01-01

    A median filter based interference detection and correction technique is evaluated and the method applied to the Arecibo incoherent scatter radar D-region ionospheric power spectrum is discussed. The method can be extended to other kinds of data when the statistics involved in the process are still valid.

  3. Scattering of energetic particles by anisotropic magnetohydrodynamic turbulence with a goldreich-sridhar power spectrum

    PubMed

    Chandran

    2000-11-27

    Scattering rates for a Goldreich-Sridhar (GS) spectrum of anisotropic, incompressible, magnetohydrodynamic turbulence are calculated in the quasilinear approximation. Because the small-scale fluctuations are constrained to have wave vectors nearly perpendicular to the background magnetic field, scattering is too weak to provide either the mean-free paths commonly used in Galactic cosmic-ray propagation models or the mean-free paths required for acceleration of cosmic rays at quasiparallel shocks. Where strong pitch-angle scattering occurs, it is due to fluctuations not described by the GS spectrum, such as fluctuations generated by streaming cosmic rays. PMID:11082620

  4. Cosmology Constraints from the Weak Lensing Peak Counts and the Power Spectrum in CFHTLenS

    DOE PAGESBeta

    Liu, Jia; May, Morgan; Petri, Andrea; Haiman, Zoltan; Hui, Lam; Kratochvil, Jan M.

    2015-03-04

    Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters Ωm, σ8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator thatmore » interpolates the power spectrum and the peak counts to an accuracy of ≤ 5%, and compute the likelihood in the three-dimensional parameter space (Ωm, σ8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (Ωm, σ8) plane reduces by a factor of ≈ two, compared to using the power spectrum alone. For a flat Λ cold dark matter model, combining both statistics, we obtain the constraint σ8(Ωm/0.27)0.63 = 0.85+0.03-0.03.« less

  5. Power-density spectrum of non-stationary short-lived light curves

    NASA Astrophysics Data System (ADS)

    Guidorzi, Cristiano

    2011-08-01

    The power-density spectrum of a light curve is often calculated as the average of a number of spectra derived on individual time intervals the light curve is divided into. This procedure implicitly assumes that each time interval is a different sample function of the same stochastic ergodic process. While this assumption can be applied to many astrophysical sources, there remains a class of transient, highly non-stationary and short-lived events, such as gamma-ray bursts, for which this approach is often inadequate. The power spectrum statistics of a constant signal affected by statistical (Poisson) noise are known to be a χ22 in the Leahy normalization. However, this is no more the case when a non-stationary signal is also present. As a consequence, the uncertainties on the power spectrum cannot be calculated on the basis of the χ22 properties, as assumed by tools such as XRONOS POWSPEC. We generalize the result in the case of a non-stationary signal affected by uncorrelated white noise and show that the new distribution is a non-central χ22(λ), whose non-central value λ is the power spectrum of the deterministic function describing the non-stationary signal. Finally, we test these results in the case of synthetic curves of gamma-ray bursts. We end up with a new formula for calculating the power spectrum uncertainties. This is crucial in the case of non-stationary short-lived processes affected by uncorrelated statistical noise, for which ensemble averaging does not make any physical sense.

  6. Cosmology Constraints from the Weak Lensing Peak Counts and the Power Spectrum in CFHTLenS

    SciTech Connect

    Liu, Jia; May, Morgan; Petri, Andrea; Haiman, Zoltan; Hui, Lam; Kratochvil, Jan M.

    2015-03-04

    Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters Ωm, σ8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator that interpolates the power spectrum and the peak counts to an accuracy of ≤ 5%, and compute the likelihood in the three-dimensional parameter space (Ωm, σ8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (Ωm, σ8) plane reduces by a factor of ≈ two, compared to using the power spectrum alone. For a flat Λ cold dark matter model, combining both statistics, we obtain the constraint σ8m/0.27)0.63 = 0.85+0.03-0.03.

  7. Predictions for the 21 cm-galaxy cross-power spectrum observable with LOFAR and Subaru

    NASA Astrophysics Data System (ADS)

    Vrbanec, Dijana; Ciardi, Benedetta; Jelić, Vibor; Jensen, Hannes; Zaroubi, Saleem; Fernandez, Elizabeth R.; Ghosh, Abhik; Iliev, Ilian T.; Kakiichi, Koki; Koopmans, Léon V. E.; Mellema, Garrelt

    2016-03-01

    The 21 cm-galaxy cross-power spectrum is expected to be one of the promising probes of the Epoch of Reionization (EoR), as it could offer information about the progress of reionization and the typical scale of ionized regions at different redshifts. With upcoming observations of 21 cm emission from the EoR with the Low Frequency Array (LOFAR), and of high-redshift Ly α emitters with Subaru's Hyper Suprime-Cam (HSC), we investigate the observability of such cross-power spectrum with these two instruments, which are both planning to observe the ELAIS-N1 field at z = 6.6. In this paper, we use N-body + radiative transfer (both for continuum and Ly α photons) simulations at redshift 6.68, 7.06 and 7.3 to compute the 3D theoretical 21 cm-galaxy cross-power spectrum and cross-correlation function, as well as to predict the 2D 21 cm-galaxy cross-power spectrum and cross-correlation function expected to be observed by LOFAR and HSC. Once noise and projection effects are accounted for, our predictions of the 21 cm-galaxy cross-power spectrum show clear anti-correlation on scales larger than ˜60 h-1 Mpc (corresponding to k ˜ 0.1 h Mpc-1), with levels of significance p = 0.003 at z = 6.6 and p = 0.08 at z = 7.3. On smaller scales, instead, the signal is completely contaminated. On the other hand, our 21 cm-galaxy cross-correlation function is strongly contaminated by noise on all scales, since the noise is no longer being separated by its k modes.

  8. The Trial Software version for DEMETER power spectrum files visualization and mapping

    NASA Astrophysics Data System (ADS)

    Lozbin, Anatoliy; Inchin, Alexander; Shpadi, Maxim

    2010-05-01

    In the frame of Kazakhstan's Scientific Space System creation for earthquakes precursors research, the hardware and software of DEMETER satellite was investigated. The data processing Software of DEMETER is based on package SWAN under IDL Virtual machine and realizes many features, but we can't find an important tool for the spectrograms analysis - space-time visualization of power spectrum files from electromagnetic devices as ICE and IMSC. For elimination of this problem we have developed Software which is offered to use. The DeSS (DEMETER Spectrogram Software) - it is Software for visualization, analysis and a mapping of power spectrum data from electromagnetic devices ICE and IMSC. The Software primary goal is to give the researcher friendly tool for the analysis of electromagnetic data from DEMETER Satellite for earthquake precursors and other ionosphere events researches. The Input data for DeSS Software is a power spectrum files: - Power spectrum of 1 component of the electric field in the VLF range (APID 1132); - Power spectrum of 1 component of the electric field in the HF range (APID 1134); - Power spectrum of 1 component of the magnetic field in the VLF range (APID 1137). The main features and operations of the software is possible: - various time and frequency filtration; - visualization of time dependence of signal intensity on fixed frequency; - spectral density visualization for fixed frequency range; - spectrogram autosize and smooth spectrogram; - the information in each point of the spectrogram: time, frequency and intensity; - the spectrum information in the separate window, consisting of 4 blocks; - data mapping with 6 range scale. On the map we can browse next information: - satellite orbit; - conjugate point at the satellite altitude; - north conjugate point at the altitude 110 km; - south conjugate point at the altitude 110 km. This is only trial software version to help the researchers and we always ready collaborate with scientists for

  9. NOx lifetimes and emissions of cities and power plants in polluted background estimated by satellite observations

    NASA Astrophysics Data System (ADS)

    Liu, Fei; Beirle, Steffen; Zhang, Qiang; Dörner, Steffen; He, Kebin; Wagner, Thomas

    2016-04-01

    We present a new method to quantify NOx emissions and corresponding atmospheric lifetimes from OMI NO2 observations together with ECMWF wind fields without further model input for sources located in a polluted background. NO2 patterns under calm wind conditions are used as proxy for the spatial patterns of NOx emissions, and the effective atmospheric NOx lifetime is determined from the change of spatial patterns measured at larger wind speeds. Emissions are subsequently derived from the NO2 mass above the background, integrated around the source of interest. Lifetimes and emissions are estimated for 17 power plants and 53 cities located in non-mountainous regions across China and the USA. The derived lifetimes for the ozone season (May-September) are 3.8 ± 1.0 h (mean ± standard deviation) with a range of 1.8 to 7.5 h. The derived NOx emissions show generally good agreement with bottom-up inventories for power plants and cities. Regional inventory shows better agreement with top-down estimates for Chinese cities compared to global inventory, most likely due to different downscaling approaches adopted in the two inventories.

  10. The Power Spectrum of Ionic Nanopore Currents: The Role of Ion Correlations.

    PubMed

    Zorkot, Mira; Golestanian, Ramin; Bonthuis, Douwe Jan

    2016-04-13

    We calculate the power spectrum of electric-field-driven ion transport through nanometer-scale membrane pores using both linearized mean-field theory and Langevin dynamics simulations. Remarkably, the linearized mean-field theory predicts a plateau in the power spectral density at low frequency ω, which is confirmed by the simulations at low ion concentration. At high ion concentration, however, the power spectral density follows a power law that is reminiscent of the 1/ω(α) dependence found experimentally at low frequency. On the basis of simulations with and without ion-ion interactions, we attribute the low-frequency power-law dependence to ion-ion correlations. We show that neither a static surface charge density, nor an increased pore length, nor an increased ion valency have a significant effect on the shape of the power spectral density at low frequency. PMID:26977905

  11. Sunyaev-Zel'dovich power spectrum with decaying cold dark matter

    NASA Astrophysics Data System (ADS)

    Takahashi, Keitaro; Oguri, Masamune; Ichiki, Kiyotomo

    2004-07-01

    Recent studies of the structures of galaxies and clusters imply that dark matter might be unstable and may decay with lifetime Γ-1, about the age of the Universe. We study the effects of the decay of cold dark matter on the Sunyaev-Zel'dovich (SZ) power spectrum. We analytically calculate the SZ power spectrum taking the finite lifetime of cold dark matter into account. We find the finite lifetime of dark matter decreases the power at large scale (l < 4000) and increases the power at small scale (l > 4000). This is in marked contrast with the dependence of other cosmological parameters such as the amplitude of mass fluctuations σ8 and the cosmological constant Ωλ (under the assumption of a flat Universe) which mainly change the normalization of the angular power spectrum. This difference allows one to determine the lifetime and other cosmological parameters separately. We also investigate the sensitivity of future SZ surveys to the cosmological parameters including the lifetime, assuming a fiducial model Γ-1 = 10 h-1 Gyr, σ8 = 1.0 and Ωλ = 0.7. We show that future SZ surveys such as ACT, AMIBA and BOLOCAM can determine the lifetime within a factor of 2 even if σ8 and Ωλ are marginalized.

  12. Design of a personnel TLD badge for a power reactor beta/gamma spectrum

    SciTech Connect

    Quinn, D.M.; Labenski, T. )

    1983-10-01

    This paper reports that three basic challenges are inherent in the design of a thermoluminescent dosimeter for a power reactor beta/gamma spectrum: the dosimeter must meet the current standard for performance in laboratory testing, the dosimeter must properly respond to a power reactor spectrum that is different from that specified in the standard, and the dosimeter must function under field conditions. These challenges were met at the Indian Point 3 Nuclear Power Station by modifying the case of a commercial multi-element TLD to include varying thicknesses of tissue equivalent plastic absorbers over the elements. An algorithm was developed to correct the TLD responses for laboratory testing: however, in field use, shallow and deep dose are read directly from the TLD without the use of an algorithm.

  13. Higher order corrections to the large scale matter power spectrum in the presence of massive neutrinos

    SciTech Connect

    Wong, Yvonne Y Y

    2008-10-15

    We present the first systematic derivation of the one-loop correction to the large scale matter power spectrum in a mixed cold + hot dark matter cosmology with subdominant massive neutrino hot dark matter. Starting with the equations of motion for the density and velocity fields, we derive perturbative solutions to these quantities and construct recursion relations for the interaction kernels, noting and justifying all approximations along the way. We find interaction kernels similar to those for a cold dark matter only universe, but with additional dependences on the neutrino energy density fraction f{sub {nu}} and the linear growth functions of the incoming wavevectors. Compared with the f{sub {nu}} = 0 case, the one-loop corrected matter power spectrum for a mixed dark matter cosmology exhibits a decrease in small scale power exceeding the canonical {approx}8f{sub {nu}} suppression predicted by linear theory, a feature also seen in multi-component N-body simulations.

  14. Spectrum Analysis of the Wind Farm Power based on the Spatial Structures of Wind

    NASA Astrophysics Data System (ADS)

    Kawamoto, Teru; Yamashita, Masaru

    Spectrum analysis has been carried out based on the spatial structure model of wind. Power fluctuation from nine wind turbines arranged in 3 × 3 manner is less than that from a single turbine, regardless of wind direction. The increased distance between two turbines slightly reduces power fluctuation. In case of an inline arrangement, power fluctuation caused by the wind perpendicular to the turbine line is lower than that by the wind parallel to the turbine line, because the coherence of wind perpendicular to the wind direction decays sharply. For double line arrangement, fluctuation will be almost the same for the 3 × 3 arrangement.

  15. Increasing the quantitative credibility of open-path Fourier transform infrared (FT-IR) spectroscopic data, with focus on several properties of the background spectrum.

    PubMed

    Shao, Limin; Wang, Wanping; Griffiths, Peter R; Leytem, April B

    2013-03-01

    The choice of the type of background spectrum affects the credibility of open-path Fourier transform infrared spectroscopy (OP/FT-IR) data, and consequently, the quality of data analysis. We systematically investigated several properties of the background spectrum. The results show that a short-path background measured with the lowest amplifier gain could significantly reduce noise in the calculated absorbance spectrum, by at least 30% in our case. We demonstrated that by using a short-path background, data analysis is more resistant to interferences such as wavenumber shift or resolution alteration that occurs as a consequence of aging hardware or misalignment. We discussed a systematic error introduced into quantitative analyses by the short-path background and developed a procedure to correct that error. With this correction approach, a short-path background established five years ago was still found to be valid. By incorporating these findings into the protocol for quantitative analysis, we processed the measurements with two OP/FT-IR instruments set up side by side in the vicinity of a large dairy farm, to monitor NH3, CH4, and N2O. The two sets of calculated concentrations showed high agreement with each other. The findings of our investigations are helpful to atmospheric monitoring practitioners of OP/FT-IR spectroscopy and could also be a reference for future amendments to the protocols outlined in the guidelines of the U.S. Environmental Protection Agency, the American Society for Testing and Materials, and the European Committee for Standardization. PMID:23452499

  16. Ultrasound characterization of the infertile male testis with rf power spectrum analysis

    NASA Astrophysics Data System (ADS)

    Coleman, Jonathan A.; Silverman, Ronald H.; Rondeau, Mark; Coleman, D. J.; Schlegel, Peter

    2002-04-01

    Objective: To investigate and diagnose testicular pathology in patients with testicular dysfunction using the technique of ultrasound power spectrum analysis. Methods: Testicular ultrasound studies with power spectrum tissue characterization analysis were performed on men with testicular abnormalities as well as normal controls. Semen analysis, biopsy data, microscopic intra-operative findings and data pertaining to testicular function were collected for each surgically evaluated subject. Ultrasound data were analyzed for power spectrum characteristics of microscopic scatterer size and concentration within discrete areas of testicular tissue. Results: Patients with varicoceles and greater than 2x106 sperm/ml on semen analysis had larger average scatterer size (107.7 micrometers ) and lower scatterer concentration (-15.02 dB) than non-obstructed, azoospermic patients with varicoceles (92.4 micrometers and -11.41 dB, respectively). Subjects with obstructed azoospermia had slightly larger average tissue scatterer size (108.1 micrometers ) and lower concentration (-15.73 dB) while normal control data revealed intermediate values of size (102.3 micrometers ) and concentration (-13.1 dB) of scatterers. Spectral data from pure testicular seminoma lesions had the lowest average scatterer size (82.3 micrometers ) with low relative concentration (-14.7 dB). Summary: Ultrasound tissue characterization based on RF spectrum analysis may distinguish different types of testicular pathology including obstructed and non-obstructed azoospermia and tissue changes due to varicocele and tumor.

  17. JPL 2-to-the-20th-power channel 300 MHz bandwidth digital spectrum analyzer

    NASA Technical Reports Server (NTRS)

    Morris, G. A., Jr.; Wilck, H. C.

    1978-01-01

    A million (two to the 20th power) channel, 300 MHz bandwidth, digital spectrum analyzer was considered. The design, fabrication, and maintenance philosophy of the modular, pipelined, fast fourier transform (FFT) hardware are described. The spectrum analyzer will be used to examine the region from 1.4 GHz to 26 GHz for radio frequency interference which may be harmful to present and future tracking missions of the Deep Space Network. The design has application to the search for extraterrestrial intelligence signals and radio science phenomena.

  18. Investigation of Pulser-transducer Matching Networks for Power Delivery Efficiency of Spread Spectrum Signals

    NASA Astrophysics Data System (ADS)

    Kybartas, Darius; Rodriguez, Alberto; Svilainis, Linas; Chaziachmetovas, Andrius

    Replacement of a single ultrasonic pulse to the spread spectrum signals allows higher energy without losing the bandwidth and it also means higher requirements for energy delivery to test object. Pulser efficiency for single pulse is not essential comparing to high energy signals. Pulser stress is large if power delivery efficiency to transducer is low. In narrowband case the solution is to use the matching network, but matching circuit effect will be different in case of wideband excitation. Aim of the investigation was to evaluate the matching techniques for spread spectrum signals.

  19. Inferring the IGM thermal history during reionisation with the Lyman-α forest power spectrum at redshift z ≃ 5

    NASA Astrophysics Data System (ADS)

    Nasir, Fahad; Bolton, James S.; Becker, George D.

    2016-08-01

    We use cosmological hydrodynamical simulations to assess the feasibility of constraining the thermal history of the intergalactic medium during reionisation with the Ly{α } forest at z ≃ 5 . The integrated thermal history has a measureable impact on the transmitted flux power spectrum that can be isolated from Doppler broadening at this redshift. We parameterise this using the cumulative energy per proton, u0, deposited into a gas parcel at the mean background density, a quantity that is tightly linked with the gas density power spectrum in the simulations. We construct mock observations of the line of sight Ly{α } forest power spectrum and use a Markov Chain Monte Carlo approach to recover u0 at redshifts 5 ⪉ z ⪉ 12. A statistical uncertainty of ˜20 per cent is expected (at 68 per cent confidence) at z ≃ 5 using high resolution spectra with a total redshift path length of Δz = 4 and a typical signal-to-noise ratio of S/N=15 per pixel. Estimates for the expected systematic uncertainties are comparable, such that existing data should enable a measurement of u0 to within ˜30 per cent. This translates to distinguishing between reionisation scenarios with similar instantaneous temperatures at z ≃ 5, but with an energy deposited per proton that differs by 2-3 eV over the redshift interval 5⪉ z ⪉ 12. For an initial temperature of T˜ 104 K following reionisation, this corresponds to the difference between early (zre = 12) and late (zre = 7) reionisation in our models.

  20. Baryon acoustic oscillations in 2D: Modeling redshift-space power spectrum from perturbation theory

    SciTech Connect

    Taruya, Atsushi; Nishimichi, Takahiro; Saito, Shun

    2010-09-15

    We present an improved prescription for the matter power spectrum in redshift space taking proper account of both nonlinear gravitational clustering and redshift distortion, which are of particular importance for accurately modeling baryon acoustic oscillations (BAOs). Contrary to the models of redshift distortion phenomenologically introduced but frequently used in the literature, the new model includes the corrections arising from the nonlinear coupling between the density and velocity fields associated with two competitive effects of redshift distortion, i.e., Kaiser and Finger-of-God effects. Based on the improved treatment of perturbation theory for gravitational clustering, we compare our model predictions with the monopole and quadrupole power spectra of N-body simulations, and an excellent agreement is achieved over the scales of BAOs. Potential impacts on constraining dark energy and modified gravity from the redshift-space power spectrum are also investigated based on the Fisher-matrix formalism, particularly focusing on the measurements of the Hubble parameter, angular diameter distance, and growth rate for structure formation. We find that the existing phenomenological models of redshift distortion produce a systematic error on measurements of the angular diameter distance and Hubble parameter by 1%-2%, and the growth-rate parameter by {approx}5%, which would become non-negligible for future galaxy surveys. Correctly modeling redshift distortion is thus essential, and the new prescription for the redshift-space power spectrum including the nonlinear corrections can be used as an accurate theoretical template for anisotropic BAOs.

  1. What is the optimal way to measure the galaxy power spectrum?

    NASA Astrophysics Data System (ADS)

    Smith, Robert E.; Marian, Laura

    2016-04-01

    Measurements of the galaxy power spectrum contain a wealth of cosmological information. In Smith & Marian, we generalized the power spectrum methodology of Feldman et al. to take into account the key tenets of galaxy formation: galaxies form and reside exclusively in dark matter haloes; a given dark matter halo may host galaxies of various luminosities; galaxies inherit the large-scale bias of their host halo. In this paradigm, we derived the optimal weighting scheme for maximizing the signal-to-noise ({S}/{N}) on a given band power estimate. For a future all-sky flux-limited galaxy redshift survey of depth bJ > 22, we demonstrate that the optimal weighting scheme does indeed provide improved {S}/{N} at the level of ˜20 per cent when compared to Feldman et al. and ˜60 per cent relative to Percival et al., for scales of the order of k ˜ 0.5 h Mpc-1. Using a Fisher matrix approach, we show the cosmological information yield is also increased relative to these alternate methods - especially the primordial power spectrum amplitude and dark energy equation of state. Caveats: uncertainties in cluster masses, non-linear halo bias and redshift distortions may reduce information gains.

  2. First Limits on the 21 cm Power Spectrum during the Epoch of X-ray heating.

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, A.; Dillon, Joshua S.; Hewitt, J. N.; Loeb, A.; Mesinger, A.; Neben, A. R.; Offringa, A. R.; Tegmark, M.; Barry, N.; Beardsley, A. P.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Carroll, P.; Corey, B. E.; de Oliveira-Costa, A.; Emrich, D.; Feng, L.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hurley-Walker, N.; Johnston-Hollitt, M.; Jacobs, Daniel C.; Kaplan, D. L.; Kasper, J. C.; Kim, HS; Kratzenberg, E.; Lenc, E.; Line, J.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Thyagarajan, Nithyanandan; Oberoi, D.; Ord, S. M.; Paul, S.; Pindor, B.; Pober, J. C.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Sullivan, I. S.; Tingay, S. J.; Trott, C. M.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S. B.

    2016-05-01

    We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 and 17.9 (113 and 75 MHz). Three hours of observations were conducted over two nights with significantly different levels of ionospheric activity. We use these data to assess the impact of systematic errors at low frequency, including the ionosphere and radio-frequency interference, on a power spectrum measurement. We find that after the 1-3 hours of integration presented here, our measurements at the Murchison Radio Observatory are not limited by RFI, even within the FM band, and that the ionosphere does not appear to affect the level of power in the modes that we expect to be sensitive to cosmology. Power spectrum detections, inconsistent with noise, due to fine spectral structure imprinted on the foregrounds by reflections in the signal-chain, occupy the spatial Fourier modes where we would otherwise be most sensitive to the cosmological signal. We are able to reduce this contamination using calibration solutions derived from autocorrelations so that we achieve an sensitivity of 104 mK on comoving scales k ≲ 0.5 hMpc-1. This represents the first upper limits on the 21 cm power spectrum fluctuations at redshifts 12 ≲ z ≲ 18 but is still limited by calibration systematics. While calibration improvements may allow us to further remove this contamination, our results emphasize that future experiments should consider carefully the existence of and their ability to calibrate out any spectral structure within the EoR window.

  3. First limits on the 21 cm power spectrum during the Epoch of X-ray heating

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, A.; Dillon, Joshua S.; Hewitt, J. N.; Loeb, A.; Mesinger, A.; Neben, A. R.; Offringa, A. R.; Tegmark, M.; Barry, N.; Beardsley, A. P.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Carroll, P.; Corey, B. E.; de Oliveira-Costa, A.; Emrich, D.; Feng, L.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hurley-Walker, N.; Johnston-Hollitt, M.; Jacobs, Daniel C.; Kaplan, D. L.; Kasper, J. C.; Kim, HS; Kratzenberg, E.; Lenc, E.; Line, J.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Thyagarajan, Nithyanandan; Oberoi, D.; Ord, S. M.; Paul, S.; Pindor, B.; Pober, J. C.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Sullivan, I. S.; Tingay, S. J.; Trott, C. M.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S. B.

    2016-08-01

    We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 and 17.9 (113 and 75 MHz). Three hours of observations were conducted over two nights with significantly different levels of ionospheric activity. We use these data to assess the impact of systematic errors at low frequency, including the ionosphere and radio-frequency interference, on a power spectrum measurement. We find that after the 1-3 hours of integration presented here, our measurements at the Murchison Radio Observatory are not limited by RFI, even within the FM band, and that the ionosphere does not appear to affect the level of power in the modes that we expect to be sensitive to cosmology. Power spectrum detections, inconsistent with noise, due to fine spectral structure imprinted on the foregrounds by reflections in the signal-chain, occupy the spatial Fourier modes where we would otherwise be most sensitive to the cosmological signal. We are able to reduce this contamination using calibration solutions derived from autocorrelations so that we achieve an sensitivity of $10^4$ mK on comoving scales $k\\lesssim 0.5 h$Mpc$^{-1}$. This represents the first upper limits on the $21$ cm power spectrum fluctuations at redshifts $12\\lesssim z \\lesssim 18$ but is still limited by calibration systematics. While calibration improvements may allow us to further remove this contamination, our results emphasize that future experiments should consider carefully the existence of and their ability to calibrate out any spectral structure within the EoR window.

  4. First limits on the 21 cm power spectrum during the Epoch of X-ray heating

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, A.; Dillon, Joshua S.; Hewitt, J. N.; Loeb, A.; Mesinger, A.; Neben, A. R.; Offringa, A. R.; Tegmark, M.; Barry, N.; Beardsley, A. P.; Bernardi, G.; Bowman, Judd D.; Briggs, F.; Cappallo, R. J.; Carroll, P.; Corey, B. E.; de Oliveira-Costa, A.; Emrich, D.; Feng, L.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hurley-Walker, N.; Johnston-Hollitt, M.; Jacobs, Daniel C.; Kaplan, D. L.; Kasper, J. C.; Kim, HS; Kratzenberg, E.; Lenc, E.; Line, J.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Thyagarajan, Nithyanandan; Oberoi, D.; Ord, S. M.; Paul, S.; Pindor, B.; Pober, J. C.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Sethi, Shiv K.; Srivani, K. S.; Subrahmanyan, R.; Sullivan, I. S.; Tingay, S. J.; Trott, C. M.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.; Wu, C.; Wyithe, J. S. B.

    2016-08-01

    We present first results from radio observations with the Murchison Widefield Array seeking to constrain the power spectrum of 21 cm brightness temperature fluctuations between the redshifts of 11.6 and 17.9 (113 and 75 MHz). 3 h of observations were conducted over two nights with significantly different levels of ionospheric activity. We use these data to assess the impact of systematic errors at low frequency, including the ionosphere and radio-frequency interference, on a power spectrum measurement. We find that after the 1-3 h of integration presented here, our measurements at the Murchison Radio Observatory are not limited by RFI, even within the FM band, and that the ionosphere does not appear to affect the level of power in the modes that we expect to be sensitive to cosmology. Power spectrum detections, inconsistent with noise, due to fine spectral structure imprinted on the foregrounds by reflections in the signal-chain, occupy the spatial Fourier modes where we would otherwise be most sensitive to the cosmological signal. We are able to reduce this contamination using calibration solutions derived from autocorrelations so that we achieve an sensitivity of 104 mK on comoving scales k ≲ 0.5 h Mpc-1. This represents the first upper limits on the 21 cm power spectrum fluctuations at redshifts 12 ≲ z ≲ 18 but is still limited by calibration systematics. While calibration improvements may allow us to further remove this contamination, our results emphasize that future experiments should consider carefully the existence of and their ability to calibrate out any spectral structure within the EoR window.

  5. The matter power spectrum from the Lyα forest: an optical depth estimate

    NASA Astrophysics Data System (ADS)

    Zaroubi, S.; Viel, M.; Nusser, A.; Haehnelt, M.; Kim, T.-S.

    2006-06-01

    We measure the matter power spectrum from 31 Lyα spectra spanning the redshift range of 1.6-3.6. The optical depth, τ, for Lyα absorption of the intergalactic medium is obtained from the flux using the inversion method of Nusser & Haehnelt. The optical depth is converted to density by using a simple power-law relation, τ ~ (1 + δ)α. The non-linear 1D power spectrum of the gas density is then inferred with a method that makes simultaneous use of the one- and two-point statistics of the flux and compared against theoretical models with a likelihood analysis. A cold dark matter model with standard cosmological parameters fits the data well. The power-spectrum amplitude is measured to be (assuming a flat Universe), σ8 = (0.92 +/- 0.09) × (Ωm/0.3)-0.3, with α varying in the range of 1.56-1.8 with redshift. Enforcing the same cosmological parameters in all four redshift bins, the likelihood analysis suggests some evolution in the temperature-density relation and the thermal smoothing length of the gas. The inferred evolution is consistent with that expected if reionization of HeII occurred at z ~ 3.2. A joint analysis with the Wilkinson Microwave Anisotropy Probe results together with a prior on the Hubble constant as suggested by the Hubble Space Telescope key project data, yields values of Ωm and σ8 that are consistent with the cosmological concordance model. We also perform a further inversion to obtain the linear 3D power spectrum of the matter density fluctuations.

  6. Fiber laser strain sensor based in the measurement of a Sagnac interferometer optical power spectrum

    NASA Astrophysics Data System (ADS)

    Durán Sánchez, M.; Álvarez Tamayo, R. I.; Pottiez, O.; Kuzin, E. A.; Ibarra-Escamilla, B.; Barcelata Pinzón, A.

    2014-06-01

    In this paper a linear cavity Erbium doped fiber (EDF) laser based in a fiber Bragg grating (FBG) and a fiber optical loop mirror with a high birefringence fiber in the loop (Hi-Bi FOLM) is used as a strain sensor. The Fabry-Perot cavity is formed by the FBG and the Hi-Bi FOLM, used as a measurement system of strain variations produced on the FBG, used as a strain sensor device. Usually, fiber laser sensor experimental setups determine the measured variable magnitude by using of an optical spectrum analyzer (OSA). Hi-Bi FOLM transmission spectrum wavelength displacement by fiber loop temperature variations measurement can be an attractive application exploiting the characteristics of FOLM transmission spectrum behavior due to Hi-Bi fiber loop temperature variations to determine the FBG strain applied through the maximal optical power monitoring by simple use of a photodetector and a temperature meter.

  7. CROSS-POWER SPECTRUM AND ITS APPLICATION ON WINDOW FUNCTIONS IN THE WILKINSON MICROWAVE ANISOTROPY PROBE DATA

    SciTech Connect

    Chiang, Lung-Yih; Chen, Fei-Fan

    2011-09-10

    The cross-power spectrum is a quadratic estimator between two maps that can provide unbiased estimate of the underlying power spectrum of the correlated signals, which is therefore used for extracting the power spectrum in the Wilkinson Microwave Anisotropy Probe (WMAP) data. In this paper, we discuss the limit of the cross-power spectrum and derive the residual from the uncorrelated signal, which is the source of error in power spectrum extraction. We employ the estimator to extract window functions by crossing pairs of extragalactic point sources. We demonstrate its usefulness in WMAP difference assembly maps where the window functions are measured via Jupiter and then extract the window functions of the five WMAP frequency band maps.

  8. Sound power spectrum and wave drag of a propeller in flight

    NASA Technical Reports Server (NTRS)

    Hanson, D. B.

    1989-01-01

    Theory is presented for the sound power and sound power spectrum of a single rotation propeller in forward flight. Calculations are based on the linear wave equation with sources distributed over helicoidal surfaces to represent effects of blade thickness and steady loading. Sound power is distributed continuously over frequecy, as would be expected from Doppler effects, rather than in discrete harmonics. The theory is applied to study effects of sweep and Mach number in propfans. An acoustic efficiency is defined as the ratio of radiated sound power to shaft input power. This value is the linear estimate of the effect of wave drag due to the supersonic blade section speeds. It is shown that the acoustic efficiency is somewhat less than 1 percent for a well designed propfan.

  9. Constraining primordial magnetic fields with distortions of the black-body spectrum of the cosmic microwave background: pre- and post-decoupling contributions

    SciTech Connect

    Kunze, Kerstin E.

    2014-01-01

    Primordial magnetic fields that exist before the photon-baryon decoupling epoch are damped on length scales below the photon diffusion and free-streaming scales. The energy injected into the plasma by dissipation of magnetosonic and Alfv and apos;en waves heats photons, creating a y-type distortion of the black-body spectrum of the cosmic microwave background. This y-type distortion is converted into a μ-type distortion when elastic Compton scattering is efficient. Therefore, we can use observational limits on y- and μ-type distortions to constrain properties of magnetic fields in the early universe. Assuming a Gaussian, random, and non-helical field, we calculate μ and y as a function of the present-day strength of the field, B{sub 0}, smoothed over a certain Gaussian width, k{sub c}{sup −1}, as well as of the spectral index of the power spectrum of fields, n{sub B}, defined by P{sub B}(k)∝k{sup n{sub B}}. For a nearly scale-invariant spectrum with n{sub B} = −2.9 and a Gaussian smoothing width of k{sub c}{sup −1} = 1Mpc, the existing COBE/FIRAS limit on μ yields B{sub 0} < 40 nG, whereas the projected PIXIE limit on μ would yield B{sub 0} < 0.8 nG. For non-scale-invariant spectra, constraints can be stronger. For example, for B{sub 0} = 1 nG with k{sub c}{sup −1} = 1Mpc, the COBE/FIRAS limit on μ excludes a wide range of spectral indices given by n{sub B} > −2.6. After decoupling, energy dissipation is due to ambipolar diffusion and decaying MHD turbulence, creating a y-type distortion. The distortion is completely dominated by decaying MHD turbulence, and is of order y ≈ 10{sup −7} for a few nG field smoothed over the damping scale at the decoupling epoch, k{sub d,} {sub dec} ≈ 290(B{sub 0}/1nG){sup −1}Mpc{sup −1}. The projected PIXIE limit on y would exclude B{sub 0} > 1.0 and 0.6 nG for n{sub B} = −2.9 and -2.3, respectively, and B{sub 0} > 0.6 nG for n{sub B} ≥ 2. Finally, we find that the current limits on the optical depth to

  10. BAYESIAN INFERENCE OF POLARIZED COSMIC MICROWAVE BACKGROUND POWER SPECTRA FROM INTERFEROMETRIC DATA

    SciTech Connect

    Karakci, Ata; Korotkov, Andrei; Tucker, Gregory S.; Sutter, P. M.; Wandelt, Benjamin D.; Zhang, Le; Timbie, Peter; Bunn, Emory F.

    2013-01-15

    Detection of B-mode polarization of the cosmic microwave background (CMB) radiation is one of the frontiers of observational cosmology. Because they are an order of magnitude fainter than E-modes, it is quite a challenge to detect B-modes. Having more manageable systematics, interferometers prove to have a substantial advantage over imagers in detecting such faint signals. Here, we present a method for Bayesian inference of power spectra and signal reconstruction from interferometric data of the CMB polarization signal by using the technique of Gibbs sampling. We demonstrate the validity of the method in the flat-sky approximation for a simulation of an interferometric observation on a finite patch with incomplete uv-plane coverage, a finite beam size, and a realistic noise model. With a computational complexity of O(n {sup 3/2}), n being the data size, Gibbs sampling provides an efficient method for analyzing upcoming cosmology observations.

  11. Power spectrum of the rectified EMG: when and why is rectification beneficial for identifying neural connectivity?

    NASA Astrophysics Data System (ADS)

    Negro, Francesco; Keenan, Kevin; Farina, Dario

    2015-06-01

    Objective. The identification of common oscillatory inputs to motor neurons in the electromyographic (EMG) signal power spectrum is often preceded by EMG rectification for enhancing the low-frequency oscillatory components. However, rectification is a nonlinear operator and its influence on the EMG signal spectrum is not fully understood. In this study, we aim at determining when EMG rectification is beneficial in the study of oscillatory inputs to motor neurons. Approach. We provide a full mathematical description of the power spectrum of the rectified EMG signal and the influence of the average shape of the motor unit action potentials on it. We also provide a validation of these theoretical results with both simulated and experimental EMG signals. Main results. Simulations using an advanced computational model and experimental results demonstrated the accuracy of the theoretical derivations on the effect of rectification on the EMG spectrum. These derivations proved that rectification is beneficial when assessing the strength of low-frequency (delta and alpha bands) common synaptic inputs to the motor neurons, when the duration of the action potentials is short, and when the level of cancellation is relatively low. On the other hand, rectification may distort the estimation of common synaptic inputs when studying higher frequencies (beta and gamma), in a way dependent on the duration of the action potentials, and may introduce peaks in the coherence function that do not correspond to physiological shared inputs. Significance. This study clarifies the conditions when rectifying the surface EMG is appropriate for studying neural connectivity.

  12. Spectrum Resolving Power of Hearing: Measurements, Baselines, and Influence of Maskers

    PubMed Central

    Supin, Alexander Ya.

    2011-01-01

    Contemporary methods of measurement of frequency resolving power in the auditory system are reviewed. Majority of classical methods are based on the frequency-selective masking paradigm and require multi-point measurements (a number of masked thresholds should be measured to obtain a single frequency-tuning estimate). Therefore, they are rarely used for practical needs. As an alternative approach, frequency-selective properties of the auditory system may be investigated using probes with complex frequency spectrum patterns, in particular, rippled noise that is characterized by a spectrum with periodically alternating maxima and minima. The maximal ripple density discriminated by the auditory system is a convenient measure of the spectrum resolving power (SRP). To find the highest resolvable ripple density, a phase-reversal test has been suggested. Using this technique, normal SRP, its dependence on probe center frequency, spectrum contrast, and probe level were measured. The results were not entirely predictable by frequency-tuning data obtained by masking methods. SRP is influenced by maskers, with on- and off-frequency maskers influencing SRP very differently. Dichotic separation of the probe and masker results in almost complete release of SRP from influence of maskers. PMID:26557320

  13. Spectrum Resolving Power of Hearing: Measurements, Baselines, and Influence of Maskers.

    PubMed

    Supin, Alexander Ya

    2011-07-01

    Contemporary methods of measurement of frequency resolving power in the auditory system are reviewed. Majority of classical methods are based on the frequency-selective masking paradigm and require multi-point measurements (a number of masked thresholds should be measured to obtain a single frequency-tuning estimate). Therefore, they are rarely used for practical needs. As an alternative approach, frequency-selective properties of the auditory system may be investigated using probes with complex frequency spectrum patterns, in particular, rippled noise that is characterized by a spectrum with periodically alternating maxima and minima. The maximal ripple density discriminated by the auditory system is a convenient measure of the spectrum resolving power (SRP). To find the highest resolvable ripple density, a phase-reversal test has been suggested. Using this technique, normal SRP, its dependence on probe center frequency, spectrum contrast, and probe level were measured. The results were not entirely predictable by frequency-tuning data obtained by masking methods. SRP is influenced by maskers, with on- and off-frequency maskers influencing SRP very differently. Dichotic separation of the probe and masker results in almost complete release of SRP from influence of maskers. PMID:26557320

  14. A perturbative approach to the redshift space power spectrum: beyond the Standard Model

    NASA Astrophysics Data System (ADS)

    Bose, Benjamin; Koyama, Kazuya

    2016-08-01

    We develop a code to produce the power spectrum in redshift space based on standard perturbation theory (SPT) at 1-loop order. The code can be applied to a wide range of modified gravity and dark energy models using a recently proposed numerical method by A.Taruya to find the SPT kernels. This includes Horndeski's theory with a general potential, which accommodates both chameleon and Vainshtein screening mechanisms and provides a non-linear extension of the effective theory of dark energy up to the third order. Focus is on a recent non-linear model of the redshift space power spectrum which has been shown to model the anisotropy very well at relevant scales for the SPT framework, as well as capturing relevant non-linear effects typical of modified gravity theories. We provide consistency checks of the code against established results and elucidate its application within the light of upcoming high precision RSD data.

  15. Nonlinear relativistic single-electron Thomson scattering power spectrum for incoming laser of arbitrary intensity

    SciTech Connect

    Alvarez-Estrada, R. F.; Pastor, I.; Guasp, J.; Castejon, F.

    2012-06-15

    The classical nonlinear incoherent Thomson scattering power spectrum from a single relativistic electron with incoming laser radiation of any intensity, investigated numerically by the present authors in a previous publication, displayed both an approximate quadratic behavior in frequency and a redshift of the power spectrum for high intensity incoming radiation. The present work is devoted to justify, in a more general setup, those numerical findings. Those justifications are reinforced by extending suitably analytical approaches, as developed by other authors. Moreover, our analytical treatment exhibits differences between the Doppler-like frequencies for linear and circular polarization of the incoming radiation. Those differences depend nonlinearly on the laser intensity and on the electron initial velocity and do not appear to have been displayed by previous authors. Those Doppler-like frequencies and their differences are validated by new Monte Carlo computations beyond our previuos ones and reported here.

  16. Reconstruction of a nonminimal coupling theory with scale-invariant power spectrum

    SciTech Connect

    Qiu, Taotao

    2012-06-01

    A nonminimal coupling single scalar field theory, when transformed from Jordan frame to Einstein frame, can act like a minimal coupling one. Making use of this property, we investigate how a nonminimal coupling theory with scale-invariant power spectrum could be reconstructed from its minimal coupling counterpart, which can be applied in the early universe. Thanks to the coupling to gravity, the equation of state of our universe for a scale-invariant power spectrum can be relaxed, and the relation between the parameters in the action can be obtained. This approach also provides a means to address the Big-Bang puzzles and anisotropy problem in the nonminimal coupling model within Jordan frame. Due to the equivalence between the two frames, one may be able to find models that are free of the horizon, flatness, singularity as well as anisotropy problems.

  17. The Coyote Universe. I. Precision Determination of the Nonlinear Matter Power Spectrum

    NASA Astrophysics Data System (ADS)

    Heitmann, Katrin; White, Martin; Wagner, Christian; Habib, Salman; Higdon, David

    2010-05-01

    Near-future cosmological observations targeted at investigations of dark energy pose stringent requirements on the accuracy of theoretical predictions for the nonlinear clustering of matter. Currently, N-body simulations comprise the only viable approach to this problem. In this paper, we study various sources of computational error and methods to control them. By applying our methodology to a large suite of cosmological simulations we show that results for the (gravity-only) nonlinear matter power spectrum can be obtained at 1% accuracy out to k ~ 1 h Mpc-1. The key components of these high accuracy simulations are precise initial conditions, very large simulation volumes, sufficient mass resolution, and accurate time stepping. This paper is the first in a series of three; the final aim is a high-accuracy prediction scheme for the nonlinear matter power spectrum that improves current fitting formulae by an order of magnitude.

  18. CosmicEmu: Cosmic Emulator for the Dark Matter Power Spectrum

    NASA Astrophysics Data System (ADS)

    Lawrence, Earl; Heitmann, Katrin; White, Martin; Higdon, David; Wagner, Christian; Habib, Salman; Williams, Brian

    2010-10-01

    Many of the most exciting questions in astrophysics and cosmology, including the majority of observational probes of dark energy, rely on an understanding of the nonlinear regime of structure formation. In order to fully exploit the information available from this regime and to extract cosmological constraints, accurate theoretical predictions are needed. Currently such predictions can only be obtained from costly, precision numerical simulations. The "Coyote Universe'' simulation suite comprises nearly 1,000 N-body simulations at different force and mass resolutions, spanning 38 wCDM cosmologies. This large simulation suite enabled construct of a prediction scheme, or emulator, for the nonlinear matter power spectrum accurate at the percent level out to k~1 h/Mpc. This is the first cosmic emulator for the dark matter power spectrum.

  19. THE COYOTE UNIVERSE. I. PRECISION DETERMINATION OF THE NONLINEAR MATTER POWER SPECTRUM

    SciTech Connect

    Heitmann, Katrin; White, Martin; Wagner, Christian; Habib, Salman; Higdon, David

    2010-05-20

    Near-future cosmological observations targeted at investigations of dark energy pose stringent requirements on the accuracy of theoretical predictions for the nonlinear clustering of matter. Currently, N-body simulations comprise the only viable approach to this problem. In this paper, we study various sources of computational error and methods to control them. By applying our methodology to a large suite of cosmological simulations we show that results for the (gravity-only) nonlinear matter power spectrum can be obtained at 1% accuracy out to k {approx} 1 h Mpc{sup -1}. The key components of these high accuracy simulations are precise initial conditions, very large simulation volumes, sufficient mass resolution, and accurate time stepping. This paper is the first in a series of three; the final aim is a high-accuracy prediction scheme for the nonlinear matter power spectrum that improves current fitting formulae by an order of magnitude.

  20. Comparison of Two Methods of Noise Power Spectrum Determinations of Medical Radiography Systems

    SciTech Connect

    Hassan, Wan Muhamad Saridan Wan; Ahmed Darwish, Zeki

    2011-03-30

    Noise in medical images is recognized as an important factor that determines the image quality. Image noise is characterized by noise power spectrum (NPS). We compared two methods of NPS determination namely the methods of Wagner and Dobbins on Lanex Regular TMG screen-film system and Hologic Lorad Selenia full field digital mammography system, with the aim of choosing the better method to use. The methods differ in terms of various parametric choices and algorithm implementations. These parameters include the low pass filtering, low frequency filtering, windowing, smoothing, aperture correction, overlapping of region of interest (ROI), length of fast Fourier transform, ROI size, method of ROI normalization, and slice selection of the NPS. Overall, the two methods agreed to the practical value of noise power spectrum between 10{sup -3}-10{sup -6} mm{sup 2} over spatial frequency range 0-10 mm{sup -1}.

  1. Analyses of DNA Base Sequences for Eukaryotes in Terms of Power Spectrum Method

    NASA Astrophysics Data System (ADS)

    Isohata, Yasuhiko; Hayashi, Masaki

    2005-02-01

    By adopting a power spectrum method we have analyzed long-range correlations in the gene base sequences, exons and introns for five or six eukaryote species. As a measure of the long-range correlations, we have used an exponent α in 1/fα, which is an approximation of a power spectrum in a low-frequency region. We have analyzed frequency distributions of α and the dependence of its average values <α> on the sequence length for the five or six species, paying particular attention to the species dependence. We have shown that long-range correlations have been formed mainly due to the intron's elongation as well as by the sequence structures of introns acquired over the course of evolution.

  2. Spacecraft radio scattering observations of the power spectrum of electron density fluctuations in the solar wind

    NASA Technical Reports Server (NTRS)

    Woo, R.; Armstrong, J. W.

    1979-01-01

    Solar wind electron density power spectra in the solar equatorial region are inferred from observations of phase scintillations and spectral broadening made with the Viking, Helios, and Pioneer spacecraft. The heliocentric distance range covered is 2-215 solar radii and for some observations close to the sun the spectra extend to fluctuation frequencies as high as 100 Hz. For heliocentric distances of about 20 solar radii the equivalent spacecraft-measured one-dimensional density spectrum is well modeled by a single power law in the frequency range 0.0001-0.05 Hz. The flattening of the density spectrum within 20 solar radii is presumably associated with energy deposition in the near-sun region and acceleration of the solar wind.

  3. Comparison of Two Methods of Noise Power Spectrum Determinations of Medical Radiography Systems

    NASA Astrophysics Data System (ADS)

    Hassan, Wan Muhamad Saridan Wan; Ahmed Darwish, Zeki

    2011-03-01

    Noise in medical images is recognized as an important factor that determines the image quality. Image noise is characterized by noise power spectrum (NPS). We compared two methods of NPS determination namely the methods of Wagner and Dobbins on Lanex Regular TMG screen-film system and Hologic Lorad Selenia full field digital mammography system, with the aim of choosing the better method to use. The methods differ in terms of various parametric choices and algorithm implementations. These parameters include the low pass filtering, low frequency filtering, windowing, smoothing, aperture correction, overlapping of region of interest (ROI), length of fast Fourier transform, ROI size, method of ROI normalization, and slice selection of the NPS. Overall, the two methods agreed to the practical value of noise power spectrum between 10-3-10-6 mm2 over spatial frequency range 0-10 mm-1.

  4. Imprints of dark energy on cosmic structure formation - I. Realistic quintessence models and the non-linear matter power spectrum

    NASA Astrophysics Data System (ADS)

    Alimi, J.-M.; Füzfa, A.; Boucher, V.; Rasera, Y.; Courtin, J.; Corasaniti, P.-S.

    2010-01-01

    Quintessence has been proposed to account for dark energy (DE) in the Universe. This component causes a typical modification of the background cosmic expansion, which, in addition to its clustering properties, can leave a potentially distinctive signature on large-scale structures. Many previous studies have investigated this topic, particularly in relation to the non-linear regime of structure formation. However, no careful pre-selection of viable quintessence models with high precision cosmological data was performed. Here we show that this has led to a misinterpretation (and underestimation) of the imprint of quintessence on the distribution of large-scale structures. To this purpose, we perform a likelihood analysis of the combined Supernova Ia UNION data set and Wilkinson Microwave Anisotropy Probe 5-yr data to identify realistic quintessence models. These are specified by different model parameter values, but still statistically indistinguishable from the vanilla Λ cold dark matter (ΛCDM). Differences are especially manifest in the predicted amplitude and shape of the linear matter power spectrum though these remain within the uncertainties of the Sloan Digital Sky Survey data. We use these models as a benchmark for studying the clustering properties of dark matter haloes by performing a series of high-resolution N-body simulations. In this first paper, we specifically focus on the non-linear matter power spectrum. We find that realistic quintessence models allow for relevant differences of the dark matter distribution with respect to the ΛCDM scenario well into the non-linear regime, with deviations of up to 40 per cent in the non-linear power spectrum. Such differences are shown to depend on the nature of DE, as well as the scale and epoch considered. At small scales (k ~ 1-5hMpc-1, depending on the redshift), the structure formation process is about 20 per cent more efficient than in ΛCDM. We show that these imprints are a specific record of the cosmic

  5. Gamma-Ray background spectrum and annihilation rate in the baryon-symmetric big-bang cosmology

    NASA Technical Reports Server (NTRS)

    Puget, J. L.

    1973-01-01

    An attempt was made to extract experimental data on baryon symmetry by observing annihilation products. Specifically, gamma rays and neutrons with long mean free paths were analyzed. Data cover absorption cross sections and radiation background of the 0.511 MeV gamma rays from positron annihilations and the 70 MeV gamma rays from neutral pion decay.

  6. Noise-induced synchronization in a system with a 1 / f power spectrum

    NASA Astrophysics Data System (ADS)

    Koverda, V. P.; Skokov, V. N.

    2016-06-01

    A spatially distributed system with 1/ f fluctuations at coupled nonequilibrium phase transitions have been simulated by two nonlinear stochastic equations. It is shown numerically that at sufficiently high intensity of white noise in the system there arises noise-induced synchronization, which is a nonequilibrium phase transition. To the critical point of the nonequilibrium phase transition corresponds the 1/ f power spectrum and the maximum of informational entropy.

  7. Detecting the 21 cm forest in the 21 cm power spectrum

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, Aaron; Dillon, Joshua S.; Mesinger, Andrei; Hewitt, Jacqueline

    2014-07-01

    We describe a new technique for constraining the radio-loud population of active galactic nuclei at high redshift by measuring the imprint of 21 cm spectral absorption features (the 21 cm forest) on the 21 cm power spectrum. Using semi-numerical simulations of the intergalactic medium and a semi-empirical source population, we show that the 21 cm forest dominates a distinctive region of k-space, k ≳ 0.5 Mpc- 1. By simulating foregrounds and noise for current and potential radio arrays, we find that a next-generation instrument with a collecting area of the order of ˜ 0.1 km2 (such as the Hydrogen Epoch of Reionization Array) may separately constrain the X-ray heating history at large spatial scales and radio-loud active galactic nuclei of the model we study at small ones. We extrapolate our detectability predictions for a single radio-loud active galactic nuclei population to arbitrary source scenarios by analytically relating the 21 cm forest power spectrum to the optical depth power spectrum and an integral over the radio luminosity function.

  8. The coyote universe III: simulation suite and precision emulator for the nonlinear matter power spectrum

    SciTech Connect

    Heitmann, Katrin; White, Martin; Higdon, David; Wagner, Christian; Lawrence, Earl; Habib, Salman; Williams, Brian

    2009-01-01

    Ongoing and future large scale structure surveys targeted at the investigation of dark energy will enter the nonlinear regime of structure formation. In order to fully exploit the newly available information from this regime and to extract cosmological constraints. very accurate theoretical predictions are needed. Such predictions can currently only be obtained from costly precision N-body simulations. We have recently shown that it is possible to obtain predictions for the nonlinear matter power spectrum at the level of one-percent accuracy and that we can build a precise prediction scheme for the nonlinear power spectrum from a small set of cosmological models. In this paper we introduce the 'Coyote Universe' simulation suite which comprises more than 800 N-body simulations at different force and mass resolutions, spanning 38 wCDM cosmologies. This large simulation suite enables us to construct a prediction scheme for the nonlinear matter power spectrum accurate at the 1% level out to k {approx_equal} 1 hMpc{sup -1}.

  9. The Coyote Universe. III. Simulation Suite and Precision Emulator for the Nonlinear Matter Power Spectrum

    NASA Astrophysics Data System (ADS)

    Lawrence, Earl; Heitmann, Katrin; White, Martin; Higdon, David; Wagner, Christian; Habib, Salman; Williams, Brian

    2010-04-01

    Many of the most exciting questions in astrophysics and cosmology, including the majority of observational probes of dark energy, rely on an understanding of the nonlinear regime of structure formation. In order to fully exploit the information available from this regime and to extract cosmological constraints, accurate theoretical predictions are needed. Currently, such predictions can only be obtained from costly, precision numerical simulations. This paper is the third in a series aimed at constructing an accurate calibration of the nonlinear mass power spectrum on Mpc scales for a wide range of currently viable cosmological models, including dark energy models with w ≠ -1. The first two papers addressed the numerical challenges and the scheme by which an interpolator was built from a carefully chosen set of cosmological models. In this paper, we introduce the "Coyote Universe" simulation suite which comprises nearly 1000 N-body simulations at different force and mass resolutions, spanning 38 w CDM cosmologies. This large simulation suite enables us to construct a prediction scheme, or emulator, for the nonlinear matter power spectrum accurate at the percent level out to k ~= 1 h Mpc-1. We describe the construction of the emulator, explain the tests performed to ensure its accuracy, and discuss how the central ideas may be extended to a wider range of cosmological models and applications. A power spectrum emulator code is released publicly as part of this paper.

  10. Constraining high-redshift X-ray sources with next generation 21-cm power spectrum measurements

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, Aaron; Hewitt, Jacqueline; Mesinger, Andrei; Dillon, Joshua S.; Liu, Adrian; Pober, Jonathan

    2016-05-01

    We use the Fisher matrix formalism and seminumerical simulations to derive quantitative predictions of the constraints that power spectrum measurements on next-generation interferometers, such as the Hydrogen Epoch of Reionization Array (HERA) and the Square Kilometre Array (SKA), will place on the characteristics of the X-ray sources that heated the high-redshift intergalactic medium. Incorporating observations between z = 5 and 25, we find that the proposed 331 element HERA and SKA phase 1 will be capable of placing ≲ 10 per cent constraints on the spectral properties of these first X-ray sources, even if one is unable to perform measurements within the foreground contaminated `wedge' or the FM band. When accounting for the enhancement in power spectrum amplitude from spin temperature fluctuations, we find that the observable signatures of reionization extend well beyond the peak in the power spectrum usually associated with it. We also find that lower redshift degeneracies between the signatures of heating and reionization physics lead to errors on reionization parameters that are significantly greater than previously predicted. Observations over the heating epoch are able to break these degeneracies and improve our constraints considerably. For these two reasons, 21-cm observations during the heating epoch significantly enhance our understanding of reionization as well.

  11. A fast method for power spectrum and foreground analysis for 21 cm cosmology

    NASA Astrophysics Data System (ADS)

    Dillon, Joshua S.; Liu, Adrian; Tegmark, Max

    2013-02-01

    We develop and demonstrate an acceleration of the Liu and Tegmark quadratic estimator formalism for inverse variance foreground subtraction and power spectrum estimation in 21 cm tomography from O(N3) to O(Nlog⁡N), where N is the number of voxels of data. This technique makes feasible the megavoxel scale analysis necessary for current and upcoming radio interferometers by making only moderately restrictive assumptions about foreground models and survey geometry. We exploit iterative and Monte Carlo techniques and the symmetries of the foreground covariance matrices to quickly estimate the 21 cm brightness temperature power spectrum, P(k∥,k⊥), the Fisher information matrix, the error bars, the window functions, and the bias. We also extend the Liu and Tegmark foreground model to include bright point sources with known positions in a way that scales as O[(Nlog⁡N)×(Npointsources)]≤O(N5/3). As a first application of our method, we forecast error bars and window functions for the upcoming 128-tile deployment of the Murchinson Widefield Array, showing that 1000 hours of observation should prove sufficiently sensitive to detect the power spectrum signal from the Epoch of Reionization.

  12. Electromyographic power spectrum of jaw muscles during clenching in unilateral temporomandibular joint osteoarthritis patients.

    PubMed

    Park, I H; McCall, W D; Chung, J W

    2012-09-01

    The relationship between temporomandibular joints (TMJ) osteoarthritis and masticatory muscle disorders is poorly understood. The data are sparse, the results are conflicting, and electromyographic (EMG) power spectrum analysis has not been used. The aims of this study were to compare the differences in EMG power spectrum during, and pressure pain thresholds (PPTs) before and after, sustained clenching in patients with unilateral TMJ osteoarthritis and healthy control subjects. Nineteen patients with unilateral TMJ osteoarthritis without masticatory muscle pain and 20 control subjects were evaluated. We measured EMG amplitudes at maximum voluntary contraction, median frequency from the EMG power spectrum during sustained clenching at 70% and PPTs before and after the clenching in both temporalis and masseter muscles. There were no significant differences in PPT decrease between muscles or between groups during sustained clenching. There were no significant differences in maximum voluntary contraction EMG activity ratios of affected to unaffected sides between groups, or of masseter to temporalis muscles between affected and unaffected side of patients with TMJ osteoarthritis. Median frequencies decreased from the beginning to the end of the sustained clench, and the interaction between group and clench was significant: the median frequency decrease was larger in the osteoarthritis group. Our results suggested that masticatory muscles of patients with unilateral TMJ osteoarthritis are more easily fatigued during sustained clenching than normal subjects. PMID:22672238

  13. NON-GAUSSIAN ERROR CONTRIBUTION TO LIKELIHOOD ANALYSIS OF THE MATTER POWER SPECTRUM

    SciTech Connect

    Takahashi, Ryuichi; Yoshida, Naoki; Takada, Masahiro; Sugiyama, Naoshi; Kayo, Issha; Nishimichi, Takahiro; Taruya, Atsushi; Matsubara, Takahiko; Saito, Shun

    2011-01-01

    We study the sample variance of the matter power spectrum for the standard {Lambda} cold dark matter universe. We use a total of 5000 cosmological N-body simulations to study in detail the distribution of best-fit cosmological parameters and the baryon acoustic peak positions. The obtained distribution is compared with the results from the Fisher matrix analysis with and without including non-Gaussian errors. For the Fisher matrix analysis, we compute the derivatives of the matter power spectrum with respect to cosmological parameters using directly full nonlinear simulations. We show that the non-Gaussian errors increase the unmarginalized errors by up to a factor of five for k{sub max} = 0.4 h Mpc{sup -1} if there is only one free parameter, provided other parameters are well determined by external information. On the other hand, for multi-parameter fitting, the impact of the non-Gaussian errors is significantly mitigated due to severe parameter degeneracies in the power spectrum. The distribution of the acoustic peak positions is well described by a Gaussian distribution, with its width being consistent with the statistical interval predicted from the Fisher matrix. We also examine systematic bias in the best-fit parameter due to the non-Gaussian errors. The bias is found to be smaller than the 1{sigma} statistical error for both the cosmological parameters and the acoustic scale positions.

  14. Effects of intensity thresholding on the power spectrum of laser speckle.

    PubMed

    Ducharme, A D; Boreman, G D; Snyder, D R

    1994-05-01

    Spatial-frequency filtering of laser-speckle patterns has proved to be a useful tool in the measurement of the modulation transfer function for focal plane arrays. Intensity thresholding of the laser-speckle patterns offers nearly an order of magnitude savings in digital storage space. The effect of this thresholding on the spatial-frequency power spectral density of the speckle pattern is investigated. An optimum threshold level is found that minimizes distortion of the power spectrum for the classes of speckle data used for modulation transfer function testing. PMID:20885628

  15. ANOMALOUS PARITY ASYMMETRY OF THE WILKINSON MICROWAVE ANISOTROPY PROBE POWER SPECTRUM DATA AT LOW MULTIPOLES

    SciTech Connect

    Kim, Jaiseung; Naselsky, Pavel

    2010-05-10

    We have investigated non-Gaussianity of our early universe by comparing the parity asymmetry of the Wilkinson Microwave Anisotropy Probe (WMAP) power spectrum with simulations. We find that odd-parity preference of the WMAP data (2 {<=} l {<=} 18) is anomalous at 4-in-1000 level. We find it likely that low quadrupole power is part of this parity asymmetry rather than an isolated anomaly. Further investigation is required to find out whether the origin of this anomaly is a cosmological or a systematic effect. The data from Planck Surveyor, which has systematics distinct from WMAP, will help us to resolve the origin of the anomalous odd-parity preference.

  16. Study and parametrization of the night sky background radiation spectrum in the range 3000-6000 Å, for use with air fluorescence detectors of UHECR

    NASA Astrophysics Data System (ADS)

    Moyssides, P. G.; Maltezos, S.; Fokitis, E.

    2005-01-01

    The fluorescence light, induced by showers of the extremely high energy cosmic rays, is produced through the excitation of, mainly, nitrogen molecules, atoms, and ions, in the atmosphere. The fluorescence telescopes of the Auger Project record this nitrogen radiation under the variable night sky optical noise (background radiation) and, therefore, the study of the latter is crucial. In this paper we present a parametrization of an experimental night sky background radiation spectrum that, to our knowledge, is being carried out for the first time, recorded in the range 3000-6000 Å. Although the parametrization described here refers to a particular spectrum, our results are generally applicable, and could be adapted to those prevailing in particular locations, where EAS fluorescence telescopes are operating if, in addition, the gradual time variations of the spectrum are taken into account. They could be useful in data analysis for the event reconstruction, during the operation of the fluorescence detector of the Auger Observatory, since they could be used for the experimental emulation of the optical noise. In addition, they could be used in the designing of air fluorescence observatory components, such as photomultipliers and their spectral sensitivity, as well as in the corresponding optical filters.

  17. Double Power Laws in the Event-integrated Solar Energetic Particle Spectrum

    NASA Astrophysics Data System (ADS)

    Zhao, Lulu; Zhang, Ming; Rassoul, Hamid K.

    2016-04-01

    A double power law or a power law with exponential rollover at a few to tens of MeV nucleon‑1 of the event-integrated differential spectra has been reported in many solar energetic particle (SEP) events. The rollover energies per nucleon of different elements correlate with a particle's charge-to-mass ratio (Q/A). The probable causes are suggested as residing in shock finite lifetimes, shock finite sizes, shock geometry, and an adiabatic cooling effect. In this work, we conduct a numerical simulation to investigate a particle's transport process in the inner heliosphere. We solve the focused transport equation using a time-backward Markov stochastic approach. The convection, magnetic focusing, adiabatic cooling effect, and pitch-angle scattering are included. The effects that the interplanetary turbulence imposes on the shape of the resulting SEP spectra are examined. By assuming a pure power-law differential spectrum at the Sun, a perfect double-power-law feature with a break energy ranging from 10 to 120 MeV nucleon‑1 is obtained at 1 au. We found that the double power law of the differential energy spectrum is a robust result of SEP interplanetary propagation. It works for many assumptions of interplanetary turbulence spectra that give various forms of momentum dependence of a particle's mean free path. The different spectral shapes in low-energy and high-energy ends are not just a transition from the convection-dominated propagation to diffusion-dominated propagation.

  18. Fourier-analytic technique for the separation of the signature of atmospheric ClO absorption from the solar background spectrum in the near ultraviolet

    SciTech Connect

    Burnett, E.B.

    1989-02-01

    The high-resolution ClO absorption signature in the region of 308.1 nm has a very low absorption fraction, of the order of 6 x 10/sup -5/, and linewidths comparable with those of the solar background spectrum. Because of the need for reliable absorption measurements of the abundance of this species, which is important in ozone photochemistry, a Fourier-analysis-based technique for the deconvolution of atmospheric solar absorption spectra in this region has been developed. The technique utilizes the regularity of the ClO spectrum and results in a significant reduction in the minimum signal-to-noise required for the retrieval of ClO abundances from absorption spectra.

  19. Power Spectrum of Atmospheric Scintillation for the Deep Space Network Goldstone Ka-Band Downlink

    NASA Technical Reports Server (NTRS)

    Ho, C.; Wheelon, A.

    2004-01-01

    Dynamic signal fluctuations due to atmospheric scintillations may impair the Ka-band (around 32-GHz) link sensitivities for a low-margin Deep Space Network (DSN) receiving system. The ranges of frequency and power of the fast fluctuating signals (time scale less than 1 min) are theoretically investigated using the spatial covariance and turbulence theory. Scintillation power spectrum solutions are derived for both a point receiver and a finite-aperture receiver. The aperture-smoothing frequency ((omega(sub s)), corner frequency ((omega(sub c)), and damping rate are introduced to define the shape of the spectrum for a finite-aperture antenna. The emphasis is put on quantitatively describing the aperture-smoothing effects and graphically estimating the corner frequency for a large aperture receiver. Power spectral shapes are analyzed parametrically in detail through both low- and high-frequency approximations. It is found that aperture-averaging effects become significant when the transverse correlation length of the scintillation is smaller than the antenna radius. The upper frequency or corner frequency for a finite-aperture receiver is controlled by both the Fresnel frequency and aperture-smoothing frequency. Above the aperture-smoothing frequency, the spectrum rolls off at a much faster rate of exp (-omega(sup 2)/omega(sup 2, sub s), rather than omega(sup -8/3), which is customary for a point receiver. However, a relatively higher receiver noise level can mask the fast falling-off shape and make it hard to be identified. We also predict that when the effective antenna radius a(sub r) less than or = 6 m, the corner frequency of its power spectrum becomes the same as that for a point receiver. The aperture-smoothing effects are not obvious. We have applied these solutions to the scenario of a DSN Goldstone 34-m-diameter antenna and predicted the power spectrum shape for the receiving station. The maximum corner frequency for the receiver (with omega(sub s) = 0

  20. New approach for precise computation of Lyman-α forest power spectrum with hydrodynamical simulations

    NASA Astrophysics Data System (ADS)

    Borde, Arnaud; Palanque-Delabrouille, Nathalie; Rossi, Graziano; Viel, Matteo; Bolton, James S.; Yèche, Christophe; LeGoff, Jean-Marc; Rich, Jim

    2014-07-01

    Current experiments are providing measurements of the flux power spectrum from the Lyman-α forests observed in quasar spectra with unprecedented accuracy. Their interpretation in terms of cosmological constraints requires specific simulations of at least equivalent precision. In this paper, we present a suite of cosmological N-body simulations with cold dark matter and baryons, specifically aiming at modeling the low-density regions of the inter-galactic medium as probed by the Lyman-α forests at high redshift. The simulations were run using the GADGET-3 code and were designed to match the requirements imposed by the quality of the current SDSS-III/BOSS or forthcoming SDSS-IV/eBOSS data. They are made using either 2 × 7683 simeq 1 billion or 2 × 1923 simeq 14 million particles, spanning volumes ranging from (25 Mpc h-1)3 for high-resolution simulations to (100 Mpc h-1)3 for large-volume ones. Using a splicing technique, the resolution is further enhanced to reach the equivalent of simulations with 2 × 30723 simeq 58 billion particles in a (100 Mpc h-1)3 box size, i.e. a mean mass per gas particle of 1.2 × 105Msolar h-1. We show that the resulting power spectrum is accurate at the 2% level over the full range from a few Mpc to several tens of Mpc. We explore the effect on the one-dimensional transmitted-flux power spectrum of four cosmological parameters (ns, σ8, Ωm and H0) and two astrophysical parameters (T0 and γ) that are related to the heating rate of the intergalactic medium. By varying the input parameters around a central model chosen to be in agreement with the latest Planck results, we built a grid of simulations that allows the study of the impact on the flux power spectrum of these six relevant parameters. We improve upon previous studies by not only measuring the effect of each parameter individually, but also probing the impact of the simultaneous variation of each pair of parameters. We thus provide a full second-order expansion, including

  1. Hemispherical power asymmetry: parameter estimation from cosmic microwave background WMAP5 data

    SciTech Connect

    Lew, Bartosz

    2008-09-15

    We re-examine the evidence for hemispherical power asymmetry, detected in the cosmic microwave background (CMB) WMAP (Wilkinson Microwave Anisotropy Probe) data using a new method. We use a data filtering, preprocessing, and a statistical approach different from those used previously, and pursue an independent method of parameter estimation. First, we analyze the hemispherical variance ratios and compare these with simulated distributions. Secondly, working within a previously proposed CMB bipolar modulation model, we constrain model parameters: the amplitude and the orientation of the modulation field, as a function of various multipole bins. Finally, we select three ranges of multipoles leading to the most anomalous signals, and we process a hundred corresponding Gaussian random field (GRF) simulations, treated as observational data, to further test the statistical significance and robustness of the hemispherical power asymmetry. For our analysis we use the Internally Linearly Coadded (ILC) full sky map, and the KQ75 cut sky V channel foreground reduced map of the WMAP five-year data (V5). We constrain the modulation parameters using a generic maximum a posteriori method. In particular, we find differences in hemispherical power distribution, which when described in terms of a model with a bipolar modulation field, exclude the field amplitude value of the isotropic model, A = 0, at the confidence level of {approx}99.5% ({approx}99.4%) in the multipole range l element of [7,19] (l element of [7,79]) for the V5 data, and at the confidence level of {approx}99.9% in the multipole range l element of [7,39] for the ILC5 data, with best-fit (modal probability distribution function) values in these particular multipole ranges of A = 0.21 (A = 0.21) and A = 0.15 respectively. However, we also point out that similar or larger significances (in terms of rejecting the isotropic model) and large best-fit modulation amplitudes are obtained in GRF simulations as well, which

  2. Diamond tool wear detection method using cutting force and its power spectrum analysis in ultra-precision fly cutting

    NASA Astrophysics Data System (ADS)

    Zhang, G. Q.; To, S.

    2014-08-01

    Cutting force and its power spectrum analysis was thought to be an effective method monitoring tool wear in many cutting processes and a significant body of research has been conducted on this research area. However, relative little similar research was found in ultra-precision fly cutting. In this paper, a group of experiments were carried out to investigate the cutting forces and its power spectrum characteristics under different tool wear stages. Result reveals that the cutting force increases with the progress of tool wear. The cutting force signals under different tool wear stages were analyzed using power spectrum analysis. The analysis indicates that a characteristic frequency does exist in the power spectrum of the cutting force, whose power spectral density increases with the increasing of tool wear level, this characteristic frequency could be adopted to monitor diamond tool wear in ultra-precision fly cutting.

  3. Background dust emission following grassland fire: a snapshot across the particle-size spectrum highlights how high-resolution measurements enhance detection

    SciTech Connect

    Whicker, Jeffrey J; Martin, Luis M; Field, Jason P; Villegas, Juan C; Brehsears, David D; Law, Darin J; Urgeghe, Anna M

    2009-01-01

    Dust emission rates vary temporally and with particle size. Many studies of dust emission focus on a particular temporal scale and the portion of the particle-size spectrum associated with a single instrument; fewer studies have assessed dust emission across the particle-size spectrum and associated temporal scales using multiple instruments. Particularly lacking are measurements following disturbances such as fire that are high-resolution and focused on finer particles - those with direct implications for human health and potential for long-distance biogeochemical transport - during less windy but more commonly occurring background conditions. We measured dust emissions in unburned and burned semiarid grassland using four different instruments spanning different combinations of temporal resolution and particle-size spectrum: Big Springs Number Eight (BSNE) and Sensit instruments for larger saltating particles, DustTrak instruments for smaller suspended particles, and Total Suspended Particulate (TSP) samplers for measuring the entire range of particle sizes. Unburned and burned sites differed in vegetation cover and aerodynamic roughness, yet surprisingly differences in dust emission rates were only detectable for saltation using BSNE and for smaller aerosols using DustTrak. Our results, surprising in the lack of consistently detected differences, indicate that high-resolution DustTrak measurements offered the greatest promise for detecting differences in background emission rates and that BSNE samplers, which integrate across height, were effective for longer intervals. More generally, our results suggest that interplay between particle size, temporal resolution, and integration across time and height can be complex and may need to be considered more explicitly for effective sampling for background dust emissions.

  4. Quantitative Estimation of the Amount of Fibrosis in the Rat Liver Using Fractal Dimension of the Shape of Power Spectrum

    NASA Astrophysics Data System (ADS)

    Kikuchi, Tsuneo; Nakazawa, Toshihiro; Furukawa, Tetsuo; Higuchi, Toshiyuki; Maruyama, Yukio; Sato, Sojun

    1995-05-01

    This paper describes the quantitative measurement of the amount of fibrosis in the rat liver using the fractal dimension of the shape of power spectrum. The shape of the power spectrum of the scattered echo from biotissues is strongly affected by its internal structure. The fractal dimension, which is one of the important parameters of the fractal theory, is useful to express the complexity of shape of figures such as the power spectrum. From in vitro experiments using rat liver, it was found that this method can be used to quantitatively measure the amount of fibrosis in the liver, and has the possibility for use in the diagnosis of human liver cirrhosis.

  5. So You Think the Crab is Described by a Power-Law Spectrum

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.

    2008-01-01

    X-ray observations of the Crab Nebula and its pulsar have played a prominent role in the history of X-ray astronomy. Discoveries range from the detection of the X-ray Nebula and pulsar and the measurement of the Nebula-averaged X-ray polarization, to the observation of complex X-ray morphology, including jets emanating from the pulsar and the ring defining the shocked pulsar wind. The synchrotron origin of much of the radiation has been deduced by detailed studies across the electromagnetic spectrum, yet has fooled many X-ray astronomers into believing that the integrated spectrum from this system ought to be a power law. In many cases, this assumption has led observers to adjust the experiment response function(s) to guarantee such a result. We shall discuss why one should not observe a power-law spectrum, and present simulations using the latest available response matrices showing what should have been observed for a number of representative cases including the ROSAT IPC, XMM-Newton, and RXTE. We then discuss the implications, if any, for current calibrations.

  6. Perturbation theory, effective field theory, and oscillations in the power spectrum

    NASA Astrophysics Data System (ADS)

    Vlah, Zvonimir; Seljak, Uroš; Yat Chu, Man; Feng, Yu

    2016-03-01

    We explore the relationship between the nonlinear matter power spectrum and the various Lagrangian and Standard Perturbation Theories (LPT and SPT). We first look at it in the context of one dimensional (1-d) dynamics, where 1LPT is exact at the perturbative level and one can exactly resum the SPT series into the 1LPT power spectrum. Shell crossings lead to non-perturbative effects, and the PT ignorance can be quantified in terms of their ratio, which is also the transfer function squared in the absence of stochasticity. At the order of PT we work, this parametrization is equivalent to the results of effective field theory (EFT), and can thus be expanded in terms of the same parameters. We find that its radius of convergence is larger than the SPT loop expansion. The same EFT parametrization applies to all SPT loop terms and if stochasticity can be ignored, to all N-point correlators. In 3-d, the LPT structure is considerably more complicated, and we find that LPT models with parametrization motivated by the EFT exhibit running with k and that SPT is generally a better choice. Since these transfer function expansions contain free parameters that change with cosmological model their usefulness for broadband power is unclear. For this reason we test the predictions of these models on baryonic acoustic oscillations (BAO) and other primordial oscillations, including string monodromy models, for which we ran a series of simulations with and without oscillations. Most models are successful in predicting oscillations beyond their corresponding PT versions, confirming the basic validity of the model. We show that if primordial oscillations are localized to a scale q, the wiggles in power spectrum are approximately suppressed as exp[-k2Σ2(q)/2], where Σ(q) is rms displacement of particles separated by q, which saturates on large scales, and decreases as q is reduced. No oscillatory features survive past k ~ 0.5h/Mpc at z = 0.

  7. Low-Power Direct-Sequence Spread-Spectrum Modem Architecture for Distributed Wireless Sensor Networks

    SciTech Connect

    Chien, C; Elgorriaga, I; McConaghy, C

    2001-07-03

    Emerging CMOS and MEMS technologies enable the implementation of a large number of wireless distributed microsensors that can be easily and rapidly deployed to form highly redundant, self-configuring, and ad hoc sensor networks. To facilitate ease of deployment, these sensors should operate on battery for extended periods of time. A particular challenge in maintaining extended battery lifetime lies in achieving communications with low power. This paper presents a direct-sequence spread-spectrum modem architecture that provides robust communications for wireless sensor networks while dissipating very low power. The modem architecture has been verified in an FPGA implementation that dissipates only 33 mW for both transmission and reception. The implementation can be easily mapped to an ASIC technology, with an estimated power performance of less than 1 mW.

  8. The power spectrum of the solar wind speed for periods greater than 10 days

    NASA Technical Reports Server (NTRS)

    Fenimore, E. E.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.

    1978-01-01

    The use of the more than 11 years of solar wind speed data obtained by Vela 2-6 and Imp 6-8 to study the power spectrum of speed variations in the range near the solar rotational frequency is discussed. The broad bands of power near periods of 27 days (corresponding to the rotational period of the sun), 13.5 days, and higher harmonics are characterized, and it is suggested that the described individual peaks in both the solar wind and the geomagnetic spectra are probably not due to differential rotation. The alternate explanation is that the multipeak nature of the power spectra are explained by a wave packet concept in which recurring highspeed streams are described as a series of pulses (separated by a constant period) that last for a varying number of solar rotations.

  9. Galaxy power spectrum in redshift space: Combining perturbation theory with the halo model

    SciTech Connect

    Okumura, Teppei; Hand, Nick; Seljak, Uros; Vlah, Zvonimir; Desjacques, Vincent

    2015-11-19

    Theoretical modeling of the redshift-space power spectrum of galaxies is crucially important to correctly extract cosmological information from galaxy redshift surveys. The task is complicated by the nonlinear biasing and redshift space distortion (RSD) effects, which change with halo mass, and by the wide distribution of halo masses and their occupations by galaxies. One of the main modeling challenges is the existence of satellite galaxies that have both radial distribution inside the halos and large virial velocities inside halos, a phenomenon known as the Finger-of-God (FoG) effect. We present a model for the redshift-space power spectrum of galaxies in which we decompose a given galaxy sample into central and satellite galaxies and relate different contributions to the power spectrum to 1-halo and 2-halo terms in a halo model. Our primary goal is to ensure that any parameters that we introduce have physically meaningful values, and are not just fitting parameters. For the lowest order 2-halo terms we use the previously developed RSD modeling of halos in the context of distribution function and perturbation theory approach. This term needs to be multiplied by the effect of radial distances and velocities of satellites inside the halo. To this one needs to add the 1-halo terms, which are nonperturbative. We show that the real space 1-halo terms can be modeled as almost constant, with the finite extent of the satellites inside the halo inducing a small k2R2 term over the range of scales of interest, where R is related to the size of the halo given by its halo mass. Furthermore, we adopt a similar model for FoG in redshift space, ensuring that FoG velocity dispersion is related to the halo mass. For FoG k2 type expansions do not work over the range of scales of interest and FoG resummation must be used instead. We test several simple damping functions to model the velocity dispersion FoG effect. Applying the formalism to mock

  10. Galaxy power spectrum in redshift space: Combining perturbation theory with the halo model

    NASA Astrophysics Data System (ADS)

    Okumura, Teppei; Hand, Nick; Seljak, Uroš; Vlah, Zvonimir; Desjacques, Vincent

    2015-11-01

    Theoretical modeling of the redshift-space power spectrum of galaxies is crucially important to correctly extract cosmological information from galaxy redshift surveys. The task is complicated by the nonlinear biasing and redshift space distortion (RSD) effects, which change with halo mass, and by the wide distribution of halo masses and their occupations by galaxies. One of the main modeling challenges is the existence of satellite galaxies that have both radial distribution inside the halos and large virial velocities inside halos, a phenomenon known as the Finger-of-God (FoG) effect. We present a model for the redshift-space power spectrum of galaxies in which we decompose a given galaxy sample into central and satellite galaxies and relate different contributions to the power spectrum to 1-halo and 2-halo terms in a halo model. Our primary goal is to ensure that any parameters that we introduce have physically meaningful values, and are not just fitting parameters. For the lowest order 2-halo terms we use the previously developed RSD modeling of halos in the context of distribution function and perturbation theory approach. This term needs to be multiplied by the effect of radial distances and velocities of satellites inside the halo. To this one needs to add the 1-halo terms, which are nonperturbative. We show that the real space 1-halo terms can be modeled as almost constant, with the finite extent of the satellites inside the halo inducing a small k2R2 term over the range of scales of interest, where R is related to the size of the halo given by its halo mass. We adopt a similar model for FoG in redshift space, ensuring that FoG velocity dispersion is related to the halo mass. For FoG k2 type expansions do not work over the range of scales of interest and FoG resummation must be used instead. We test several simple damping functions to model the velocity dispersion FoG effect. Applying the formalism to mock galaxies modeled after the "CMASS" sample of the

  11. Galaxy power spectrum in redshift space: Combining perturbation theory with the halo model

    DOE PAGESBeta

    Okumura, Teppei; Hand, Nick; Seljak, Uros; Vlah, Zvonimir; Desjacques, Vincent

    2015-11-19

    Theoretical modeling of the redshift-space power spectrum of galaxies is crucially important to correctly extract cosmological information from galaxy redshift surveys. The task is complicated by the nonlinear biasing and redshift space distortion (RSD) effects, which change with halo mass, and by the wide distribution of halo masses and their occupations by galaxies. One of the main modeling challenges is the existence of satellite galaxies that have both radial distribution inside the halos and large virial velocities inside halos, a phenomenon known as the Finger-of-God (FoG) effect. We present a model for the redshift-space power spectrum of galaxies in whichmore » we decompose a given galaxy sample into central and satellite galaxies and relate different contributions to the power spectrum to 1-halo and 2-halo terms in a halo model. Our primary goal is to ensure that any parameters that we introduce have physically meaningful values, and are not just fitting parameters. For the lowest order 2-halo terms we use the previously developed RSD modeling of halos in the context of distribution function and perturbation theory approach. This term needs to be multiplied by the effect of radial distances and velocities of satellites inside the halo. To this one needs to add the 1-halo terms, which are nonperturbative. We show that the real space 1-halo terms can be modeled as almost constant, with the finite extent of the satellites inside the halo inducing a small k2R2 term over the range of scales of interest, where R is related to the size of the halo given by its halo mass. Furthermore, we adopt a similar model for FoG in redshift space, ensuring that FoG velocity dispersion is related to the halo mass. For FoG k2 type expansions do not work over the range of scales of interest and FoG resummation must be used instead. We test several simple damping functions to model the velocity dispersion FoG effect. Applying the formalism to mock galaxies modeled after the

  12. VizieR Online Data Catalog: The cosmic TeV gamma-ray background spectrum (Inoue+, 2016)

    NASA Astrophysics Data System (ADS)

    Inoue, Y.; Tanaka, Y. T.

    2016-05-01

    We select 35 known extragalactic TeV sources which are located at Galactic latitude |b|>=10° and whose low activity state flux is available, since our aim is to give conservative constraints on the total cosmic gamma-ray background (CGB) in the TeV band. For each source, we select the lowest fluxes among several TeV measurements by modern imaging atmospheric Cherenkov telescopes (IACTs; H.E.S.S., MAGIC, and VERITAS) and further restrict samples showing no significant variability in the TeV band during observations. The sample contains 30 blazars, 3 radio galaxies, and 2 starburst galaxies from the default TeVcat catalog (Wakely & Horan 2008ICRC....3.1341W) which include published sources only. We also include the Fermi third source (3FGL) catalog data (Acero et al. 2015, J/ApJS/218/23) to cover GeV gamma-ray spectra. The 3FGL catalog is based on its first 48 months of survey data. All of our sample have counterparts in the 3FGL catalog. (2 data files).

  13. Tore Supra LH transmitter upgrade, a new RF driver for the power spectrum

    SciTech Connect

    Berger-By, G.; Achard, J.; Armitano, A.; Bouquey, F.; Corbel, E.; Delpech, L.; Ekedahl, A.; Lombard, G.; Magne, R.; Mollard, P.; Pagano, M.; Prou, M.; Samaille, F.; Volpe, D.; Volpe, R.

    2011-12-23

    New real time tools have been developed for testing new 700kW/3.7GHz/CW klystrons and for the operations on very long plasma shots. After the commissioning of the 18 series tubes on the high power test bed facility, the installation of the first 8 klystrons in the Tore Supra transmitter and the adjustment tests on load, this upgrade work has been materialized during the last 2010 campaign by a successful operation on the Full Active Multijunction (FAM) C3 antenna, with new performances: 3.5MW/40s on plasma. The RF output power control in amplitude and phase has been improved for a better control of the wave spectrum launched into the plasma. The new klystrons have no modulating anode and the high cathode voltage must be adjusted with the RF input power in order to optimize the RF output power with a minimization of the thermal power losses in the collector. A new phase correction, depending on the 3 RF output power ranges used, has been introduced. The improvements made in 2009 and 2010 on the generic phase loop and the procedures used during the real time tests of the RF transfer functions in amplitude and phase are detailed below. All RF measurements systems, RF safety systems and the RF calibration procedures have been revised in order to have the best consistency, reproducibility and with a measurement error against the calorimetry measurement lower than 10%.

  14. Scintillation noise power spectrum and its impact on high-redshift 21-cm observations

    NASA Astrophysics Data System (ADS)

    Vedantham, H. K.; Koopmans, L. V. E.

    2016-05-01

    Visibility scintillation resulting from wave propagation through the turbulent ionosphere can be an important source of noise at low radio frequencies (ν ≲ 200 MHz). Many low-frequency experiments are underway to detect the power spectrum of brightness temperature fluctuations of the neutral-hydrogen 21-cm signal from the Epoch of Reionization (EoR: 12 ≳ z ≳ 7, 100 ≲ ν ≲ 175 MHz). In this paper, we derive scintillation noise power spectra in such experiments while taking into account the effects of typical data processing operations such as self-calibration and Fourier synthesis. We find that for minimally redundant arrays such as LOFAR and MWA, scintillation noise is of the same order of magnitude as thermal noise, has a spectral coherence dictated by stretching of the snapshot uv-coverage with frequency, and thus is confined to the well-known wedge-like structure in the cylindrical (two-dimensional) power spectrum space. Compact, fully redundant (dcore ≲ rF ≈ 300 m at 150 MHz) arrays such as HERA and SKA-LOW (core) will be scintillation noise dominated at all baselines, but the spatial and frequency coherence of this noise will allow it to be removed along with spectrally smooth foregrounds.

  15. Temporal power spectrum of irradiance fluctuations for a Gaussian-beam wave propagating through non-Kolmogorov turbulence.

    PubMed

    Tan, Liying; Zhai, Chao; Yu, Siyuan; Ma, Jing; Lu, Gaoyuan

    2015-05-01

    In the past decades, both the increasing experimental evidence and some results of theoretical investigation on non-Kolmogorov turbulence have been reported. This has prompted the study of optical propagation in non-Kolmogorov atmospheric turbulence. In this paper, based on the thin phase screen model and a non-Kolmogorov power spectrum which owns a generalized power law instead of standard Kolmogorov power law value 11/3 and a generalized amplitude factor instead of constant value 0.033, the temporal power spectrum of irradiance fluctuations for a Gaussian-beam wave is derived in the weak fluctuation regime for a horizontal path. The analytic expressions are obtained and then used to analyze the influence of spectral power law variations on the temporal power spectrum of irradiance fluctuations. PMID:25969221

  16. EEG Beta Power but Not Background Music Predicts the Recall Scores in a Foreign-Vocabulary Learning Task.

    PubMed

    Küssner, Mats B; de Groot, Annette M B; Hofman, Winni F; Hillen, Marij A

    2016-01-01

    As tantalizing as the idea that background music beneficially affects foreign vocabulary learning may seem, there is-partly due to a lack of theory-driven research-no consistent evidence to support this notion. We investigated inter-individual differences in the effects of background music on foreign vocabulary learning. Based on Eysenck's theory of personality we predicted that individuals with a high level of cortical arousal should perform worse when learning with background music compared to silence, whereas individuals with a low level of cortical arousal should be unaffected by background music or benefit from it. Participants were tested in a paired-associate learning paradigm consisting of three immediate word recall tasks, as well as a delayed recall task one week later. Baseline cortical arousal assessed with spontaneous EEG measurement in silence prior to the learning rounds was used for the analyses. Results revealed no interaction between cortical arousal and the learning condition (background music vs. silence). Instead, we found an unexpected main effect of cortical arousal in the beta band on recall, indicating that individuals with high beta power learned more vocabulary than those with low beta power. To substantiate this finding we conducted an exact replication of the experiment. Whereas the main effect of cortical arousal was only present in a subsample of participants, a beneficial main effect of background music appeared. A combined analysis of both experiments suggests that beta power predicts the performance in the word recall task, but that there is no effect of background music on foreign vocabulary learning. In light of these findings, we discuss whether searching for effects of background music on foreign vocabulary learning, independent of factors such as inter-individual differences and task complexity, might be a red herring. Importantly, our findings emphasize the need for sufficiently powered research designs and exact replications

  17. EEG Beta Power but Not Background Music Predicts the Recall Scores in a Foreign-Vocabulary Learning Task

    PubMed Central

    de Groot, Annette M. B.; Hofman, Winni F.; Hillen, Marij A.

    2016-01-01

    As tantalizing as the idea that background music beneficially affects foreign vocabulary learning may seem, there is—partly due to a lack of theory-driven research—no consistent evidence to support this notion. We investigated inter-individual differences in the effects of background music on foreign vocabulary learning. Based on Eysenck’s theory of personality we predicted that individuals with a high level of cortical arousal should perform worse when learning with background music compared to silence, whereas individuals with a low level of cortical arousal should be unaffected by background music or benefit from it. Participants were tested in a paired-associate learning paradigm consisting of three immediate word recall tasks, as well as a delayed recall task one week later. Baseline cortical arousal assessed with spontaneous EEG measurement in silence prior to the learning rounds was used for the analyses. Results revealed no interaction between cortical arousal and the learning condition (background music vs. silence). Instead, we found an unexpected main effect of cortical arousal in the beta band on recall, indicating that individuals with high beta power learned more vocabulary than those with low beta power. To substantiate this finding we conducted an exact replication of the experiment. Whereas the main effect of cortical arousal was only present in a subsample of participants, a beneficial main effect of background music appeared. A combined analysis of both experiments suggests that beta power predicts the performance in the word recall task, but that there is no effect of background music on foreign vocabulary learning. In light of these findings, we discuss whether searching for effects of background music on foreign vocabulary learning, independent of factors such as inter-individual differences and task complexity, might be a red herring. Importantly, our findings emphasize the need for sufficiently powered research designs and exact

  18. Nearly scale-invariant power spectrum and quantum cosmological perturbations in the gravity's rainbow scenario

    NASA Astrophysics Data System (ADS)

    Wang, Sai; Chang, Zhe

    2015-06-01

    We propose the gravity's rainbow scenario as a possible alternative of the inflation paradigm to account for the flatness and horizon problems. We focus on studying the cosmological scalar perturbations which are seeded by the quantum fluctuations in the very early universe. The scalar power spectrum is expected to be nearly scale-invariant. We estimate the rainbow index and energy scale M in the gravity's rainbow scenario by analyzing the Planck temperature and WMAP polarization datasets. The constraints on them are given by and at the confidence level.

  19. Matter Power Spectrum in f(R) Gravity with Massive Neutrinos

    NASA Astrophysics Data System (ADS)

    Motohashi, H.; Starobinsky, A. A.; Yokoyama, J.

    2010-09-01

    The effect of massive neutrinos on matter power spectrum is discussed in the context of f(R) gravity. It is shown that the anomalous growth of density fluctuations on small scales due to the scalaron force can be compensated by the free streaming of neutrinos. As a result, models that predict observable deviation of the equation-of-state parameter w_{DE} from w_{DE} = -1 can be reconciled with observations of matter clustering if the total neutrino mass is O (0.5 eV).

  20. Short distance physics and initial state effects on the CMB power spectrum

    SciTech Connect

    Zarei, M.

    2008-12-15

    We investigate a modification in the action of inflaton due to noncommutativity leads to a nonstandard initial vacuum and oscillatory corrections in the initial power spectrum. We show that the presence of these oscillations causes a drop in the WMAP {chi}{sup 2} about {delta}{chi}{sup 2}{approx}8.5. As a bonus, from the parameter estimation done in this work, we show that the noncommutative parameters can be precisely bound to 10{sup 16} GeV or 10{sup 4} GeV depending on the inflation scale.

  1. Computation of the power spectrum in chaotic ¼λφ{sup 4} inflation

    SciTech Connect

    Rojas, Clara; Villalba, Víctor M. E-mail: Victor.Villalba@monash.edu

    2012-01-01

    The phase-integral approximation devised by Fröman and Fröman, is used for computing cosmological perturbations in the quartic chaotic inflationary model. The phase-integral formulas for the scalar power spectrum are explicitly obtained up to fifth order of the phase-integral approximation. As in previous reports (Rojas 2007b, 2007c and 2009), we point out that the accuracy of the phase-integral approximation compares favorably with the numerical results and those obtained using the slow-roll and uniform approximation methods.

  2. Cosmological constraints from the observed angular cross-power spectrum between Sunyaev-Zel'dovich and X-ray surveys

    NASA Astrophysics Data System (ADS)

    Hurier, G.; Douspis, M.; Aghanim, N.; Pointecouteau, E.; Diego, J. M.; Macias-Perez, J. F.

    2015-04-01

    We present the first detection of the cross-correlation angular power spectrum between the thermal Sunyaev-Zel'dovich (tSZ) effect and the X-ray emission over the full sky. The tSZ effect and X-rays are produced by the same hot gas within groups and clusters of galaxies, which creates a naturally strong correlation between them that can be used to boost the joint signal and derive cosmological parameters. We computed the correlation between the ROSAT All Sky Survey in the 0.5-2 keV energy band and the tSZ effect reconstructed from six Planck all-sky frequency maps between 70 and 545 GHz. We detect a significant correlation over a wide range of angular scales. In the range 50 <ℓ< 2000, the cross-correlation of X-rays to tSZ is detected at an overall significance of 28σ. As part of our systematic study, we performed a multi-frequency modelling of the AGN contamination and the correlation between cosmic infra-red background and X-rays. Taking advantage of the strong dependence of the cross-correlation signal on the amplitude of the power spectrum, we constrained σ8 = 0.804 ± 0.037, where modelling uncertainties dominate statistical and systematic uncertainties. We also derived constraints on the mass indices of scaling relations between the halo mass and X-ray luminosity, L500 - M500, and SZ signal, Y500 - M500, asz + ax = 3.37 ± 0.09, and on the indices of the extra-redshift evolution, βsz + βx = 0.4+0.4_{-0.5}.

  3. Self-consistent determination of the spike-train power spectrum in a neural network with sparse connectivity

    PubMed Central

    Dummer, Benjamin; Wieland, Stefan; Lindner, Benjamin

    2014-01-01

    A major source of random variability in cortical networks is the quasi-random arrival of presynaptic action potentials from many other cells. In network studies as well as in the study of the response properties of single cells embedded in a network, synaptic background input is often approximated by Poissonian spike trains. However, the output statistics of the cells is in most cases far from being Poisson. This is inconsistent with the assumption of similar spike-train statistics for pre- and postsynaptic cells in a recurrent network. Here we tackle this problem for the popular class of integrate-and-fire neurons and study a self-consistent statistics of input and output spectra of neural spike trains. Instead of actually using a large network, we use an iterative scheme, in which we simulate a single neuron over several generations. In each of these generations, the neuron is stimulated with surrogate stochastic input that has a similar statistics as the output of the previous generation. For the surrogate input, we employ two distinct approximations: (i) a superposition of renewal spike trains with the same interspike interval density as observed in the previous generation and (ii) a Gaussian current with a power spectrum proportional to that observed in the previous generation. For input parameters that correspond to balanced input in the network, both the renewal and the Gaussian iteration procedure converge quickly and yield comparable results for the self-consistent spike-train power spectrum. We compare our results to large-scale simulations of a random sparsely connected network of leaky integrate-and-fire neurons (Brunel, 2000) and show that in the asynchronous regime close to a state of balanced synaptic input from the network, our iterative schemes provide an excellent approximations to the autocorrelation of spike trains in the recurrent network. PMID:25278869

  4. Maximum entropy in a nonlinear system with a 1/f power spectrum

    NASA Astrophysics Data System (ADS)

    Koverda, V. P.; Skokov, V. N.

    2012-01-01

    An analysis of master-slave hierarchy has been made in a system of nonlinear stochastic equations describing fluctuations with a 1/f spectrum at coupled nonequilibrium phase transitions. It is shown that for a system of stochastic equations there exist different probability distribution functions with power-law (non-Gaussian) and Gaussian tails. The governing equation of a system has a probability distribution function with Gaussian tails. Therefore, distribution functions for governing equations may be used for finding the Gibbs-Shannon entropy. The local maximum of this entropy has been found. It corresponds to the tuning of the parameters of the equations to criticality and points to the stability of fluctuations with a 1/f spectrum. The Tsallis entropy and the Renyi entropy for the probability distribution functions with power-law tails have been calculated. The parameter q, which is included in the determination of these entropies has been found from the condition that the coordinates of the maximum Gibbs-Shannon entropy coincide with the maxima of the Tsallis and Renyi entropies.

  5. On the soft limit of the large scale structure power spectrum: UV dependence

    NASA Astrophysics Data System (ADS)

    Garny, Mathias; Konstandin, Thomas; Porto, Rafael A.; Sagunski, Laura

    2015-11-01

    We derive a non-perturbative equation for the large scale structure power spectrum of long-wavelength modes. Thereby, we use an operator product expansion together with relations between the three-point function and power spectrum in the soft limit. The resulting equation encodes the coupling to ultraviolet (UV) modes in two time-dependent coefficients, which may be obtained from response functions to (anisotropic) parameters, such as spatial curvature, in a modified cosmology. We argue that both depend weakly on fluctuations deep in the UV. As a byproduct, this implies that the renormalized leading order coefficient(s) in the effective field theory (EFT) of large scale structures receive most of their contribution from modes close to the non-linear scale. Consequently, the UV dependence found in explicit computations within standard perturbation theory stems mostly from counter-term(s). We confront a simplified version of our non-perturbative equation against existent numerical simulations, and find good agreement within the expected uncertainties. Our approach can in principle be used to precisely infer the relevance of the leading order EFT coefficient(s) using small volume simulations in an `anisotropic separate universe' framework. Our results suggest that the importance of these coefficient(s) is a ~ 10% effect, and plausibly smaller.

  6. More on loops in reheating: non-gaussianities and tensor power spectrum

    SciTech Connect

    Katirci, Nihan; Kaya, Ali; Tarman, Merve E-mail: ali.kaya@boun.edu.tr

    2014-06-01

    We consider the single field chaotic m{sup 2}φ{sup 2} inflationary model with a period of preheating, where the inflaton decays to another scalar field χ in the parametric resonance regime. In a recent work, one of us has shown that the χ modes circulating in the loops during preheating notably modify the (ζζ) correlation function. We first rederive this result using a different gauge condition hence reconfirm that superhorizon ζ modes are affected by the loops in preheating. Further, we examine how χ loops give rise to non-gaussianity and affect the tensor perturbations. For that, all cubic and some higher order interactions involving two χ fields are determined and their contribution to the non-gaussianity parameter f{sub NL} and the tensor power spectrum are calculated at one loop. Our estimates for these corrections show that while a large amount of non-gaussianity can be produced during reheating, the tensor power spectrum receive moderate corrections. We observe that the loop quantum effects increase with more χ fields circulating in the loops indicating that the perturbation theory might be broken down. These findings demonstrate that the loop corrections during reheating are significant and they must be taken into account for precision inflationary cosmology.

  7. More on loops in reheating: non-gaussianities and tensor power spectrum

    SciTech Connect

    Katırcı, Nihan; Kaya, Ali; Tarman, Merve

    2014-06-11

    We consider the single field chaotic m{sup 2}ϕ{sup 2} inflationary model with a period of preheating, where the inflaton decays to another scalar field χ in the parametric resonance regime. In a recent work, one of us has shown that the χ modes circulating in the loops during preheating notably modify the <ζζ> correlation function. We first rederive this result using a different gauge condition hence reconfirm that superhorizon ζ modes are affected by the loops in preheating. Further, we examine how χ loops give rise to non-gaussianity and affect the tensor perturbations. For that, all cubic and some higher order interactions involving two χ fields are determined and their contribution to the non-gaussianity parameter f{sub NL} and the tensor power spectrum are calculated at one loop. Our estimates for these corrections show that while a large amount of non-gaussianity can be produced during reheating, the tensor power spectrum receive moderate corrections. We observe that the loop quantum effects increase with more χ fields circulating in the loops indicating that the perturbation theory might be broken down. These findings demonstrate that the loop corrections during reheating are significant and they must be taken into account for precision inflationary cosmology.

  8. The one-dimensional Lyα forest power spectrum from BOSS

    NASA Astrophysics Data System (ADS)

    Palanque-Delabrouille, Nathalie; Yèche, Christophe; Borde, Arnaud; Le Goff, Jean-Marc; Rossi, Graziano; Viel, Matteo; Aubourg, Éric; Bailey, Stephen; Bautista, Julian; Blomqvist, Michael; Bolton, Adam; Bolton, James S.; Busca, Nicolás G.; Carithers, Bill; Croft, Rupert A. C.; Dawson, Kyle S.; Delubac, Timothée; Font-Ribera, Andreu; Ho, Shirley; Kirkby, David; Lee, Khee-Gan; Margala, Daniel; Miralda-Escudé, Jordi; Muna, Demitri; Myers, Adam D.; Noterdaeme, Pasquier; Pâris, Isabelle; Petitjean, Patrick; Pieri, Matthew M.; Rich, James; Rollinde, Emmanuel; Ross, Nicholas P.; Schlegel, David J.; Schneider, Donald P.; Slosar, Anže; Weinberg, David H.

    2013-11-01

    We have developed two independent methods for measuring the one-dimensional power spectrum of the transmitted flux in the Lyman-α forest. The first method is based on a Fourier transform and the second on a maximum-likelihood estimator. The two methods are independent and have different systematic uncertainties. Determination of the noise level in the data spectra was subject to a new treatment, because of its significant impact on the derived power spectrum. We applied the two methods to 13 821 quasar spectra from SDSS-III/BOSS DR9 selected from a larger sample of over 60 000 spectra on the basis of their high quality, high signal-to-noise ratio (S/N), and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from ⟨z⟩ = 2.2 to ⟨z⟩ = 4.4, and scales from 0.001 km s-1 to 0.02 km s-1. We determined the methodological andinstrumental systematic uncertainties of our measurements. We provide a preliminary cosmological interpretation of our measurements using available hydrodynamical simulations. The improvement in precision over previously published results from SDSS is a factor 2-3 for constraints on relevant cosmological parameters. For a ΛCDM model and using a constraint on H0 that encompasses measurements based on the local distance ladder and on CMB anisotropies, we infer σ8 = 0.83 ± 0.03 and ns = 0.97 ± 0.02 based on H i absorption in the range 2.1 < z < 3.7. The measured values of the power spectrum and correlation matrices for all scales and all redshifts (full Tables 4 and 5) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/559/A85

  9. Power Spectrum of Cerenkov Radiation from Laser Wakefield in Magnetized Plasma

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Higashiguchi, Takeshi; Yugami, Noboru; Ito, Hiroaki; Nishida, Yasushi

    2000-10-01

    An angle and radiation frequecy distribution of the output power of the electromagnetic wave radiation from the laser wakefield in a magnetized plasma (Cerenkov wakes radiaiton) have been calculated. The magnetic field here is applied for the far field electromagnetic wave radiation = requirement. The radiation frequency is confined from ωp to = ω_h. The electromagnetic wave generation originates from the coupling between the DC perpendicular magnetic field and the plasma electron longitudinal = disturbance caused by the laser ponderomotive force. Under Coulomb gauge condition, the wave equation can be completely partitioned for the scale potential = and the vector field, so it can be easily obtained from the near zone static = field and far zone radiation field. The former has well been studied as the = static wakefield acceleration. Here we wish to present the detailed study on = the feature of the radiated electromagnetic field for the later case. The radiation = power spectrum which depends on the magnetic field, the laser pulse length, = the radiation frequency and the corresponding refraction index have been = given. The analysis shows that at the direction of \\cos θ= c=3D1/β n, where n is the refraction index of the magnetized plasma, the output = power has the maximum which satisfies the Cerenkov radiation angle condition, = so that the output power for the radiation frequency of ωp = is mainly located at the forward direction.

  10. THE POWER SPECTRUM OF THE MILKY WAY: VELOCITY FLUCTUATIONS IN THE GALACTIC DISK

    SciTech Connect

    Bovy, Jo; Bird, Jonathan C.; Pérez, Ana E. García; Majewski, Steven R.; Nidever, David L.; Zasowski, Gail

    2015-02-20

    We investigate the kinematics of stars in the mid-plane of the Milky Way (MW) on scales between 25 pc and 10 kpc with data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE), the Radial Velocity Experiment (RAVE), and the Geneva-Copenhagen survey (GCS). Using red-clump (RC) stars in APOGEE, we determine the large-scale line-of-sight velocity field out to 5 kpc from the Sun in (0.75 kpc){sup 2} bins. The solar motion V{sub ☉} {sub –} {sub c} with respect to the circular velocity V{sub c} is the largest contribution to the power on large scales after subtracting an axisymmetric rotation field; we determine the solar motion by minimizing the large-scale power to be V{sub ☉} {sub –} {sub c} = 24 ± 1 (ran.) ± 2 (syst. [V{sub c} ]) ± 5 (syst.[large-scale]) km s{sup –1}, where the systematic uncertainty is due to (1) a conservative 20 km s{sup –1} uncertainty in V{sub c} and (2) the estimated power on unobserved larger scales. Combining the APOGEE peculiar-velocity field with RC stars in RAVE out to 2 kpc from the Sun and with local GCS stars, we determine the power spectrum of residual velocity fluctuations in the MW's disk on scales between 0.2 kpc{sup –1} ≤ k ≤ 40 kpc{sup –1}. Most of the power is contained in a broad peak between 0.2 kpc{sup –1} < k < 0.9 kpc{sup –1}. We investigate the expected power spectrum for various non-axisymmetric perturbations and demonstrate that the central bar with commonly used parameters but of relatively high mass can explain the bulk of velocity fluctuations in the plane of the Galactic disk near the Sun. Streaming motions ≈10 km s{sup –1} on ≳ 3 kpc scales in the MW are in good agreement with observations of external galaxies and directly explain why local determinations of the solar motion are inconsistent with global measurements.

  11. OPTIMAL CAPTURE OF NON-GAUSSIANITY IN WEAK-LENSING SURVEYS: POWER SPECTRUM, BISPECTRUM, AND HALO COUNTS

    SciTech Connect

    Berge, Joel; Refregier, Alexandre

    2010-04-01

    We compare the efficiency of weak-lensing-selected galaxy cluster counts and of the weak-lensing bispectrum at capturing non-Gaussian features in the dark matter distribution. We use the halo model to compute the weak-lensing power spectrum, the bispectrum, and the expected number of detected clusters, and derive constraints on cosmological parameters for a large, low systematic weak-lensing survey, by focusing on the OMEGA{sub m}-sigma{sub 8} plane and on the dark energy equation of state. We separate the power spectrum into the resolved and the unresolved parts of the data, the resolved part being defined as detected clusters, and the unresolved part as the rest of the field. We consider four kinds of clusters counts, taking into account different amount of information: signal-to-noise ratio peak counts, counts as a function of clusters' mass, counts as a function of clusters' redshift, and counts as a function of clusters' mass and redshift. We show that when combined with the power spectrum, those four kinds of counts provide similar constraints, thus allowing one to perform the most direct counts, signal-to-noise peak counts, and get percent level constraints on cosmological parameters. We show that the weak-lensing bispectrum gives constraints comparable to those given by the power spectrum and captures non-Gaussian features as well as cluster counts, its combination with the power spectrum giving errors on cosmological parameters that are similar to, if not marginally smaller than, those obtained when combining the power spectrum with cluster counts. We finally note that in order to reach its potential, the weak-lensing bispectrum must be computed using all triangle configurations, as equilateral triangles alone do not provide useful information. The appendices summarize the halo model, and the way the power spectrum and bispectrum are computed in this framework.

  12. Constraining the intracluster pressure profile from the thermal SZ power spectrum

    NASA Astrophysics Data System (ADS)

    Ramos-Ceja, M. E.; Basu, K.; Pacaud, F.; Bertoldi, F.

    2015-11-01

    The angular power spectrum of the thermal Sunyaev-Zel'dovich (tSZ) effect is highly sensitive to cosmological parameters such as σ8 and Ωm, but its use as a precision cosmological probe is hindered by the astrophysical uncertainties in modeling the gas pressure profile in galaxy groups and clusters. In this paper we assume that the relevant cosmological parameters are accurately known and explore the ability of current and future tSZ power spectrum measurements to constrain the intracluster gas pressure or the evolution of the gas mass fraction, fgas. We use the CMB bandpower measurements from the South Pole Telescope and a Bayesian Markov chain Monte Carlo (MCMC) method to quantify deviations from the standard, universal gas pressure model. We explore analytical model extensions that bring the predictions for the tSZ power into agreement with experimental data. We find that a steeper pressure profile in the cluster outskirts or an evolving fgas have mild-to-severe conflicts with experimental data or simulations. Varying more than one parameter in the pressure model leads to strong degeneracies that cannot be broken with current observational constraints. We use simulated bandpowers from future tSZ survey experiments, in particular a possible 2000 deg2 CCAT survey, to show that future observations can provide almost an order of magnitude better precision on the same model parameters. This will allow us to break the current parameter degeneracies and place simultaneous constraints on the gas pressure profile and its redshift evolution, for example.

  13. The Power Card Strategy: Strength-Based Intervention to Increase Direction Following of Children with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Campbell, Abbi; Tincani, Matt

    2011-01-01

    The Power Card strategy is a strength-based intervention to promote social skills of children with autism spectrum disorders (ASD) by capitalizing on their special interests. Although preliminary studies have shown that the Power Card strategy is a promising approach to teach social skills, additional research is needed. The purpose of this study…

  14. Shift-invariant, DWT-based "projection" method for estimation of ultrasound pulse power spectrum.

    PubMed

    Michailovich, Oleg; Adam, Dan

    2002-08-01

    An approach to computing estimates of the ultrasound pulse spectrum from echo-ultrasound RF sequences, measured from biological tissues, is proposed. It is computed by a "projection" algorithm based on the Discrete Wavelet Transform (DWT) using averaging over a range of linear shifts. It is shown that the robust, shift invariant estimate of the ultrasound pulse power spectrum can be obtained by the projection of RF line log spectrum on an appropriately chosen subspace of L2(R) (i.e., the space of square-integrable functions) that is spanned by a redundant collection of compactly supported, scaling functions. This redundant set is formed from the traditional (in Wavelet analysis) orthogonal set of scaling functions and also by all its linear (discrete) shifts. A proof is given that the estimate, so obtained, could be viewed as the average of the orthogonal projections of the RF line log spectrum, computed for all significant linear shifts of the RF line log spectrum in frequency domain. It implies that the estimate is shift-invariant. A computationally efficient scheme is presented for calculating the estimate. Proof is given that the averaged, shift-invariant estimate can be obtained simply by a convolution with a kernel, which can be viewed as the discretized auto-correlation function of the scaling function, appropriate to the particular subspace being considered. It implies that the computational burden is at most O(n log2 n), where n is the problem size, making the estimate quite suitable for real-time processing. Because of the property of the wavelet transform to suppress polynomials of orders lower than the number of the vanishing moments of the wavelet used, the presented approach can be considered as a local polynomial fitting. This locality plays a crucial role in the performance of the algorithm, improving the robustness of the estimation. Moreover, it is shown that the "averaging" nature of the proposed estimation allows using (relatively) poorly

  15. Association between power law coefficients of the anatomical noise power spectrum and lesion detectability in breast imaging modalities

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Abbey, Craig K.; Boone, John M.

    2013-03-01

    Previous research has demonstrated that a parameter extracted from a power function fit to the anatomical noise power spectrum, β, may be predictive of breast mass lesion detectability in x-ray based medical images of the breast. In this investigation, the value of β was compared with a number of other more widely used parameters, in order to determine the relationship between β and these other parameters. This study made use of breast CT data sets, acquired on two breast CT systems developed in our laboratory. A total of 185 breast data sets in 183 women were used, and only the unaffected breast was used (where no lesion was suspected). The anatomical noise power spectrum computed from two-dimensional region of interests (ROIs), was fit to a power function (NPS(f) = α f-β), and the exponent parameter (β) was determined using log/log linear regression. Breast density for each of the volume data sets was characterized in previous work. The breast CT data sets analyzed in this study were part of a previous study which evaluated the receiver operating characteristic (ROC) curve performance using simulated spherical lesions and a pre-whitened matched filter computer observer. This ROC information was used to compute the detectability index as well as the sensitivity at 95% specificity. The fractal dimension was computed from the same ROIs which were used for the assessment of β. The value of β was compared to breast density, detectability index, sensitivity, and fractal dimension, and the slope of these relationships was investigated to assess statistical significance from zero slope. A statistically significant non-zero slope was considered to be a positive association in this investigation. All comparisons between β and breast density, detectability index, sensitivity at 95% specificity, and fractal dimension demonstrated statistically significant association with p < 0.001 in all cases. The value of β was also found to be associated with patient age and

  16. PARAMETRIC TENSION BETWEEN EVEN AND ODD MULTIPOLE DATA OF THE WMAP POWER SPECTRUM: UNACCOUNTED CONTAMINATION OR MISSING PARAMETERS?

    SciTech Connect

    Kim, Jaiseung; Naselsky, Pavel

    2010-12-01

    There exists power contrast in even and odd multipoles of the WMAP power spectrum at low and intermediate multipole ranges. This anomaly is explicitly associated with the angular power spectrum, which is heavily used for cosmological model fitting. Having noted this, we have investigated whether even (odd) multipole data set is individually consistent with the WMAP concordance model. Our investigation shows that the WMAP concordance model does not make a good fit for even (odd) multipole data set, which indicates parametric tension between even and odd multipole data set. Noting that tension is highest in primordial power spectrum parameters, we have additionally considered a running spectral index, but found that tension increases to even a higher level. We believe these parametric tensions may be indications of unaccounted contamination or imperfection of the model.

  17. Power spectrum analysis of the x-ray scatter signal in mammography and breast tomosynthesis projections

    PubMed Central

    Sechopoulos, Ioannis; Bliznakova, Kristina; Fei, Baowei

    2013-01-01

    Purpose: To analyze the frequency domain characteristics of the signal in mammography images and breast tomosynthesis projections with patient tissue texture due to detected scattered x-rays. Methods: Acquisitions of x-ray projection images of 19 different patient breasts were simulated using previously acquired volumetric patient images. Acquisition of these images was performed with a dedicated breast CT prototype system, and the images were classified into voxels representing skin, adipose, and glandular tissue with a previously validated automated algorithm. The classified three dimensional images then underwent simulated mechanical compression representing that which is performed during acquisition of mammography and breast tomosynthesis images. The acquisition of projection images of each patient breast was simulated using Monte Carlo methods with each simulation resulting in two images: one of the primary (non-scattered) signal and one of the scatter signal. To analyze the scatter signal for both mammography and breast tomosynthesis, two projections images of each patient breast were simulated, one with the x-ray source positioned at 0° (mammography and central tomosynthesis projection) and at 30° (wide tomosynthesis projection). The noise power spectra (NPS) for both the scatter signal alone and the total signal (primary + scatter) for all images were obtained and the combined results of all patients analyzed. The total NPS was fit to the expected power-law relationship NPS(f) = k/f^β and the results were compared with those previously published on the power spectrum characteristics of mammographic texture. The scatter signal alone was analyzed qualitatively and a power-law fit was also performed. Results: The mammography and tomosynthesis projections of three patient breasts were too small to analyze, so a total of 16 patient breasts were analyzed. The values of β for the total signal of the 0° projections agreed well with previously published results

  18. CMB power spectrum parameter degeneracies in the era of precision cosmology

    SciTech Connect

    Howlett, Cullan; Lewis, Antony; Hall, Alex; Challinor, Anthony E-mail: antony@cosmologist.info E-mail: adc1000@ast.cam.ac.uk

    2012-04-01

    Cosmological parameter constraints from the CMB power spectra alone suffer several well-known degeneracies. These degeneracies can be broken by numerical artefacts and also a variety of physical effects that become quantitatively important with high-accuracy data e.g. from the Planck satellite. We study degeneracies in models with flat and non-flat spatial sections, non-trivial dark energy and massive neutrinos, and investigate the importance of various physical degeneracy-breaking effects. We test the CAMB power spectrum code for numerical accuracy, and demonstrate that the numerical calculations are accurate enough for degeneracies to be broken mainly by true physical effects (the integrated Sachs-Wolfe effect, CMB lensing and geometrical and other effects through recombination) rather than numerical artefacts. We quantify the impact of CMB lensing on the power spectra, which inevitably provides degeneracy-breaking information even without using information in the non-Gaussianity. Finally we check the numerical accuracy of sample-based parameter constraints using CAMB and COSMOMC. In an appendix we document recent changes to CAMB's numerical treatment of massive neutrino perturbations, which are tested along with other recent improvements by our degeneracy exploration results.

  19. Analysis of the Helioseismic Power-Spectrum Diagram of a Sunspot

    NASA Astrophysics Data System (ADS)

    Zhao, Junwei; Chou, Dean-Yi

    2013-10-01

    The continuous high spatial resolution Doppler observation of the Sun by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager allows us to compute a helioseismic k- ω power-spectrum diagram using only oscillations inside a sunspot. Individual modal ridges can be clearly seen with reduced power in the k- ω diagram that is constructed from a 40-hour observation of a stable and round sunspot. Comparing this with the k- ω diagram obtained from a quiet-Sun region, one sees that inside the sunspot the f-mode ridge is more reduced in power than the p-mode ridges, especially at high wavenumbers. The p-mode ridges all shift toward lower wavenumber (or higher frequency) for a given frequency (or wavenumber), implying an increase of phase velocity beneath the sunspot. This is probably because the acoustic waves travel across the inclined magnetic field of the sunspot penumbra. Line-profile asymmetries exhibited in the p-mode ridges are more significant in the sunspot than in the quiet Sun. Convection inside the sunspot is also highly suppressed, and its characteristic spatial scale is substantially larger than the typical convection scale of the quiet Sun. These observational facts demand a better understanding of magnetoconvection and interactions of helioseismic waves with magnetic field.

  20. Cosmology constraints from the weak lensing peak counts and the power spectrum in CFHTLenS data

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Petri, Andrea; Haiman, Zoltán; Hui, Lam; Kratochvil, Jan M.; May, Morgan

    2015-03-01

    Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models covering broad ranges of the three parameters Ωm, σ8, and w , and replicating the Galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator that interpolates the power spectrum and the peak counts to an accuracy of ≤5 %, and compute the likelihood in the three-dimensional parameter space (Ωm, σ8, w ) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error "banana" in the (Ωm, σ8) plane reduces by a factor of ≈2 , compared to using the power spectrum alone. For a flat Λ cold dark matter model, combining both statistics, we obtain the constraint σ8(Ωm/0.27 )0.63=0.85-0.03+0.03 .

  1. Intercomparison of methods for image quality characterization. II. Noise power spectrum

    SciTech Connect

    Dobbins, James T. III; Samei, Ehsan; Ranger, Nicole T.; Chen Ying

    2006-05-15

    Second in a two-part series comparing measurement techniques for the assessment of basic image quality metrics in digital radiography, in this paper we focus on the measurement of the image noise power spectrum (NPS). Three methods were considered: (1) a method published by Dobbins et al. [Med. Phys. 22, 1581-1593 (1995)] (2) a method published by Samei et al. [Med. Phys. 30, 608-622 (2003)], and (3) a new method sanctioned by the International Electrotechnical Commission (IEC 62220-1, 2003), developed as part of an international standard for the measurement of detective quantum efficiency. In addition to an overall comparison of the estimated NPS between the three techniques, the following factors were also evaluated for their effect on the measured NPS: horizontal versus vertical directional dependence, the use of beam-limiting apertures, beam spectrum, and computational methods of NPS analysis, including the region-of-interest (ROI) size and the method of ROI normalization. Of these factors, none was found to demonstrate a substantial impact on the amplitude of the NPS estimates ({<=}3.1% relative difference in NPS averaged over frequency, for each factor considered separately). Overall, the three methods agreed to within 1.6%{+-}0.8% when averaged over frequencies >0.15 mm{sup -1}.

  2. Fiber-distributed Ultra-wideband noise radar with steerable power spectrum and colorless base station.

    PubMed

    Zheng, Jianyu; Wang, Hui; Fu, Jianbin; Wei, Li; Pan, Shilong; Wang, Lixian; Liu, Jianguo; Zhu, Ninghua

    2014-03-10

    A fiber-distributed Ultra-wideband (UWB) noise radar was achieved, which consists of a chaotic UWB noise source based on optoelectronic oscillator (OEO), a fiber-distributed transmission link, a colorless base station (BS), and a cross-correlation processing module. Due to a polarization modulation based microwave photonic filter and an electrical UWB pass-band filter embedded in the feedback loop of the OEO, the power spectrum of chaotic UWB signal could be shaped and notch-filtered to avoid the spectrum-overlay-induced interference to the narrow band signals. Meanwhile, the wavelength-reusing could be implemented in the BS by means of the distributed polarization modulation-to-intensity modulation conversion. The experimental comparison for range finding was carried out as the chaotic UWB signal was notch-filtered at 5.2 GHz and 7.8 GHz or not. Measured results indicate that space resolution with cm-level could be realized after 3-km fiber transmission thanks to the excellent self-correlation property of the UWB noise signal provided by the OEO. The performance deterioration of the radar raised by the energy loss of the notch-filtered noise signal was negligible. PMID:24663829

  3. Reconstruction of crystal band structure from the power spectrum of strong-field generated high harmonics

    NASA Astrophysics Data System (ADS)

    Wang, Chang-Ming; Ho, Tak-San; Chu, Shih-I.

    2016-05-01

    The study of high harmonic generation in solid driven by intense laser fields is a subject of much current interest. Recently we introduce a new optimization method to directly reconstruct the band structure of the crystal from the power spectrum of strong-field generated high harmonics. Without loss of generality, the reconstruction is formulated for a one-dimensional single band model as a minimization problem and solved by a derivative-free unconstrained optimization algorithm-NEWUOA. The method can be readily generalized to treat multi-band problems. Numerical simulations are presented to demonstrate the applicability of the method, and the reconstructed band structure is found to be in excellent agreement with the exact one. It is also shown that our optimization method remains robust and efficient even starting from the poorly guessed band structure.

  4. Power spectrum oscillations from Planck-suppressed operators in effective field theory motivated monodromy inflation

    NASA Astrophysics Data System (ADS)

    Price, Layne C.

    2015-11-01

    We consider a phenomenological model of inflation where the inflaton is the phase of a complex scalar field Φ . Planck-suppressed operators of O (f5/Mpl) modify the geometry of the vev ⟨Φ ⟩ at first order in the decay constant f , which adds a first-order periodic term to the definition of the canonically normalized inflaton ϕ . This correction to the inflaton induces a fixed number of extra oscillatory terms in the potential V ˜θp. We derive the same result in a toy scenario where the vacuum ⟨Φ ⟩ is an ellipse with an arbitrarily large eccentricity. These extra oscillations change the form of the power spectrum as a function of scale k and provide a possible mechanism for differentiating effective field theory motivated inflation from models where the angular shift symmetry is a gauge symmetry.

  5. Noise power spectrum studies of CT systems with off-centered image object and bowtie filter

    NASA Astrophysics Data System (ADS)

    Gomez-Cardona, Daniel; Cruz-Bastida, Juan P.; Li, Ke; Budde, Adam; Hsieh, Jiang; Chen, Guang-Hong

    2016-03-01

    In previous studies of the noise power spectrum (NPS) of multi-detector CT (MDCT) systems, the image object was usually placed at the iso-center of the CT system; therefore, the bowtie filter had negligible impact on the shape of the two-dimensional (2D) NPS of MDCT. This work characterized the NPS of off-centered objects when a bowtie filter is present. It was found that the interplay between the bowtie filter and object position has significant impact on the rotational symmetry of the 2D NPS. Depending on the size of the bowtie filter, the degree of object off-centering, and the location of the region of interest (ROI) used for the NPS measurements, the symmetry of the 2D NPS can be classified as circular, dumbbell, and a peculiar cloverleaf symmetry. An anisotropic NPS corresponds to structured noise texture, which may directly influence the detection performance of certain low contrast detection tasks.

  6. Constraining halo occupation distribution and cosmic growth rate using multipole power spectrum

    NASA Astrophysics Data System (ADS)

    Hikage, Chiaki

    2014-06-01

    We propose a new method of measuring halo occupation distribution (HOD) together with cosmic growth rate using multipole components of galaxy power spectrum Pl(k). The non-linear redshift-space distortion due to the random motion of satellite galaxies, i.e. Fingers-of-God, generates high-l multipole anisotropy in galaxy clustering, such as the hexadecapole (l = 4) and tetra-hexadecapole (l = 6), which are sensitive to the fraction and the velocity dispersion of satellite galaxies. Using simulated samples following the HOD of luminous red galaxies, we find that the input HOD parameters are successfully reproduced from Pl(k), and that high-l multipole information help to break the degeneracy among HOD parameters. We also show that the measurements of the cosmic growth rate as well as the satellite fraction and velocity dispersions are significantly improved by adding the small-scale information of high-l multipoles.

  7. Disentangling Redshift-Space Distortions and Nonlinear Bias using the 2D Power Spectrum

    SciTech Connect

    Jennings, Elise; Wechsler, Risa H.

    2015-08-07

    We present the nonlinear 2D galaxy power spectrum, P(k, µ), in redshift space, measured from the Dark Sky simulations, using galaxy catalogs constructed with both halo occupation distribution and subhalo abundance matching methods, chosen to represent an intermediate redshift sample of luminous red galaxies. We find that the information content in individual µ (cosine of the angle to the line of sight) bins is substantially richer then multipole moments, and show that this can be used to isolate the impact of nonlinear growth and redshift space distortion (RSD) effects. Using the µ < 0.2 simulation data, which we show is not impacted by RSD effects, we can successfully measure the nonlinear bias to an accuracy of ~ 5% at k < 0.6hMpc-1 . This use of individual µ bins to extract the nonlinear bias successfully removes a large parameter degeneracy when constraining the linear growth rate of structure. We carry out a joint parameter estimation, using the low µ simulation data to constrain the nonlinear bias, and µ > 0.2 to constrain the growth rate and show that f can be constrained to ~ 26(22)% to a kmax < 0.4(0.6)hMpc-1 from clustering alone using a simple dispersion model, for a range of galaxy models. Our analysis of individual µ bins also reveals interesting physical effects which arise simply from different methods of populating halos with galaxies. We also find a prominent turnaround scale, at which RSD damping effects are greater then the nonlinear growth, which differs not only for each µ bin but also for each galaxy model. These features may provide unique signatures which could be used to shed light on the galaxy–dark matter connection. Furthermore, the idea of separating nonlinear growth and RSD effects making use of the full information in the 2D galaxy power spectrum yields significant improvements in constraining cosmological parameters and may be a promising probe of galaxy formation models.

  8. Weak lensing statistics as a probe of {OMEGA} and power spectrum.

    NASA Astrophysics Data System (ADS)

    Bernardeau, F.; van Waerbeke, L.; Mellier, Y.

    1997-06-01

    The possibility of detecting weak lensing effects from deep wide field imaging surveys has opened new means of probing the large-scale structure of the Universe and measuring cosmological parameters. In this paper we present a systematic study of the expected dependence of the low order moments of the filtered gravitational local convergence on the power spectrum of the density fluctuations and on the cosmological parameters {OMEGA}_0_ and {LAMBDA}. The results show a significant dependence on all these parameters. Though we note that this degeneracy could be partially raised by considering two populations of sources, at different redshifts, computing the third moment is more promising since it is expected, in the quasi-linear regime and for Gaussian initial conditions, to be only {OMEGA}_0_ dependent (with a slight degeneracy with {LAMBDA}) when it is correctly expressed in terms of the second moment. More precisely we show that the variance of the convergence varies approximately as P(k){OMEGA}_0_^1.5^z_s_^1.5^, whereas the skewness varies as {OMEGA}_0_^-0.8^z_s_^-1.35^, where P(k) is the projected power spectrum and z_s_ the redshift of the sources. Thus, used jointly they can provide both P(k) and {OMEGA}_0_. However, the dependence on the redshift of the sources is large and could be a major concern for a practical implementation. We have estimated the errors expected for these parameters in a realistic scenario and sketched what would be the observational requirements for doing such measurements. A more detailed study of an observational strategy is left for a second paper.

  9. Disentangling redshift-space distortions and non-linear bias using the 2D power spectrum

    NASA Astrophysics Data System (ADS)

    Jennings, Elise; Wechsler, Risa H.; Skillman, Samuel W.; Warren, Michael S.

    2016-03-01

    We present the 2D redshift-space galaxy power spectrum, P(k, μ), measured from the Dark Sky simulations, using catalogues constructed with halo occupation distribution and subhalo abundance matching methods, chosen to represent an intermediate redshift sample of luminous red galaxies. We find that the information content in individual μ (cosine of the angle to the line of sight) bins is substantially richer then multipole moments, and show that this can be used to isolate the impact of non-linear growth and redshift-space distortion (RSD) effects. Using the μ < 0.2 simulation data, which is not impacted by RSD, we can successfully measure the non-linear bias to ˜5 per cent at k < 0.6 h Mpc-1. Using the low μ simulation data to constrain the non-linear bias, and μ ≥ 0.2 to constrain the growth rate, we show that f can be constrained to ˜26(22) per cent to a kmax < 0.4(0.6) h Mpc-1 from clustering alone using a dispersion model, for a range of galaxy models. Our analysis of individual μ bins reveals interesting physical effects which arise from different methods of populating haloes with galaxies. We find a prominent turnaround scale, at which RSD damping effects are greater than the non-linear growth, which differs for each galaxy model. The idea of separating non-linear growth and RSD effects making use of the full information in the 2D galaxy power spectrum yields significant improvements in constraining cosmological parameters and may be a promising probe of galaxy formation models.

  10. Galaxy formation from annihilation-generated supersonic turbulence in the baryon-symmetric big-bang cosmology and the gamma ray background spectrum

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Puget, J. L.

    1972-01-01

    Following the big-bang baryon symmetric cosmology of Omnes, the redshift was calculated to be on the order of 500-600. It is show that, at these redshifts, annihilation pressure at the boundaries between regions of matter and antimatter drives large scale supersonic turbulence which can trigger galaxy formation. This picture is consistent with the gamma-ray background observations discussed previously. Gravitational binding of galaxies then occurs at a redshift of about 70, at which time vortical turbulent velocities of about 3 x 10 to the 7th power cm/s lead to angular momenta for galaxies comparable with measured values.

  11. Limits on the Polarized Power Spectrum at 126 and 164 MHz from PAPER South Africa 32-Element Data

    NASA Astrophysics Data System (ADS)

    Aguirre, James E.; Moore, David; Paper Collaboration

    2015-01-01

    Faraday-rotated, polarized emission represents a potential contaminating foreground for measurements of the highly redshifted 21 cm power spectrum. There are few existing measurements of polarized foreground emission at meter wavelengths (e.g. Bernardi et al 2013, Jelic et al 2014) and its actual effect on the measured Stokes I spectrum from reionization is unclear. We present new limits on the power spectrum of Stokes Q, U, and V emission at 126 and 164 MHz using PAPER South Africa 32-element data, to supplement existing results for Stokes I (Parsons et al 2014, Jacobs et al 2014). We use upper limits on the Q power spectra to place upper limits on the average polarization fraction of point sources.

  12. New transient absorption observed in the spectrum of colloidal CdSe nanoparticles pumped with high-power femtosecond pulses

    SciTech Connect

    Burda, C.; Link, S.; Green, T.C.; El-Sayed, M.A.

    1999-12-09

    The power dependence of the transient absorption spectrum of CdSe nanoparticle colloids with size distribution of 4.0 {+-} 0.4 nm diameter is studied with femtosecond pump-probe techniques. At the lowest pump laser power, the absorption bleaching (negative spectrum) characteristic of the exciton spectrum is observed with maxima at 560 and 480 nm. As the pump laser power increases, two new transient absorptions at 510 and 590 nm with unresolved fast rise (<100 fs) and long decay times ({much{underscore}gt}150 ps) are observed. The energy of each of the positive absorption is red shifted from that of the bleach bands by {approximately}120 MeV. The origin of this shift is discussed in terms of the effect of the internal electric field of the many electron-hole pairs formed within the quantum dot at the high pump intensity, absorption from a metastable excited state or the formation of biexcitons.

  13. An experimental investigation of the power spectrum of phase modulation induced on a satellite radio signal by the ionosphere

    NASA Technical Reports Server (NTRS)

    Moser, D. T.

    1972-01-01

    The power spectrum of phase modulation imposed upon satellite radio signals by the inhomogeneous F-region of the ionosphere (100 - 500 km) was studied. Tapes of the S-66 Beacon B Satellite recorded during the period 1964 - 1966 were processed to yield or record the frequency of modulation induced on the signals by ionospheric dispersion. This modulation is produced from the sweeping across the receiving station as the satellite transits of the two dimensional spatial phase pattern are produced on the ground. From this a power spectrum of structure sizes comprising the diffracting mechanism was determined using digital techniques. Fresnel oscillations were observed and analyzed along with some comments on the statistical stationarity of the shape of the power spectrum observed.

  14. Polarization observations with the Cosmic Background Imager.

    PubMed

    Readhead, A C S; Myers, S T; Pearson, T J; Sievers, J L; Mason, B S; Contaldi, C R; Bond, J R; Bustos, R; Altamirano, P; Achermann, C; Bronfman, L; Carlstrom, J E; Cartwright, J K; Casassus, S; Dickinson, C; Holzapfel, W L; Kovac, J M; Leitch, E M; May, J; Padin, S; Pogosyan, D; Pospieszalski, M; Pryke, C; Reeves, R; Shepherd, M C; Torres, S

    2004-10-29

    Polarization observations of the cosmic microwave background with the Cosmic Background Imager from September 2002 to May 2004 provide a significant detection of the E-mode polarization and reveal an angular power spectrum of polarized emission showing peaks and valleys that are shifted in phase by half a cycle relative to those of the total intensity spectrum. This key agreement between the phase of the observed polarization spectrum and that predicted on the basis of the total intensity spectrum provides support for the standard model of cosmology, in which dark matter and dark energy are the dominant constituents, the geometry is close to flat, and primordial density fluctuations are predominantly adiabatic with a matter power spectrum commensurate with inflationary cosmological models. PMID:15472038

  15. Anomalous parity asymmetry of WMAP 7-year power spectrum data at low multipoles: Is it cosmological or systematics?

    SciTech Connect

    Kim, Jaiseung; Naselsky, Pavel

    2010-09-15

    It is natural to assume a parity-neutral Universe and accordingly no particular parity preference in the cosmic microwave background sky. However, our investigation based on the WMAP 7-year power spectrum shows there exists a large-scale odd-parity preference with high statistical significance. We also find that the odd-parity preference in WMAP7 data is slightly higher than earlier releases. We have investigated possible origins, and ruled out various noncosmological origins. We also find that the primordial origin requires |Re[{Phi}(k)]|<<|Im[{Phi}(k)]| for k < or approx. 22/{eta}{sub 0}, where {eta}{sub 0} is the present conformal time. In other words, it requires translational invariance in the primordial Universe to be violated on scales larger than 4 Gpc. The Planck surveyor, which possesses wide frequency coverage and systematics distinct from the WMAP, may allow us to resolve the mystery of the anomalous odd-parity preference. Furthermore, polarization maps of large-sky coverage will reduce degeneracy in cosmological origins.

  16. CMB power spectrum contribution from cosmic strings using field-evolution simulations of the Abelian Higgs model

    SciTech Connect

    Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Urrestilla, Jon

    2007-03-15

    We present the first field-theoretic calculations of the contribution made by cosmic strings to the temperature power spectrum of the cosmic microwave background (CMB). Unlike previous work, in which strings were modeled as idealized one-dimensional objects, we evolve the simplest example of an underlying field theory containing local U(1) strings, the Abelian Higgs model. Limitations imposed by finite computational volumes are overcome using the scaling property of string networks and a further extrapolation related to the lessening of the string width in comoving coordinates. The strings and their decay products, which are automatically included in the field theory approach, source metric perturbations via their energy-momentum tensor, the unequal-time correlation functions of which are used as input into the CMB calculation phase. These calculations involve the use of a modified version of CMBEASY, with results provided over the full range of relevant scales. We find that the string tension {mu} required to normalize to the WMAP 3-year data at multipole l=10 is G{mu}=[2.04{+-}0.06(stat.){+-}0.12(sys.)]x10{sup -6}, where we have quoted statistical and systematic errors separately, and G is Newton's constant. This is a factor 2-3 higher than values in current circulation.

  17. Robust multipixel matched subspace detection with signal-dependent background power

    NASA Astrophysics Data System (ADS)

    Golikov, Victor; Rodriguez-Blanco, Marco; Lebedeva, Olga

    2016-01-01

    A modified matched subspace detector (MSD) has been recently proposed for detecting a barely discernible object in an additive Gaussian background clutter using a single pixel in a sequence of digital images. In contrast to this detector designed for the subpixel object, we developed a generalized likelihood ratio approach to the detection of a multipixel object of unknown shape, size, and position in an additive signal-dependent Gaussian background and noise. The proposed detector modifies the MSD by adding the additional term proportional to the square of the difference between the background variances under two statistical hypotheses. The performances of these detectors are evaluated for the example scenario of two multipixel floating objects on the agitated sea surface. The crucial characteristic of the proposed detector is that prior knowledge of the target size, shape, and position is not required. Computer simulation and experimental results have shown that the proposed detector outperforms the MSD, especially in the case of weak and poorly contrasted objects of unknown shape, size, and position.

  18. A power line data communication interface using spread spectrum technology in home automation

    SciTech Connect

    Shwehdi, M.H.; Khan, A.Z.

    1996-07-01

    Building automation technology is rapidly developing towards more reliable communication systems, devices that control electronic equipments. These equipment if controlled leads to efficient energy management, and savings on the monthly electricity bill. Power Line communication (PLC) has been one of the dreams of the electronics industry for decades, especially for building automation. It is the purpose of this paper to demonstrate communication methods among electronic control devices through an AC power line carrier within the buildings for more efficient energy control. The paper outlines methods of communication over a powerline, namely the X-10 and CE bus. It also introduces the spread spectrum technology as to increase speed to 100--150 times faster than the X-10 system. The powerline carrier has tremendous applications in the field of building automation. The paper presents an attempt to realize a smart house concept, so called, in which all home electronic devices from a coffee maker to a water heater microwave to chaos robots will be utilized by an intelligent network whenever one wishes to do so. The designed system may be applied very profitably to help in energy management for both customer and utility.

  19. X-Ray Ccds for Space Applications: Calibration, Radiation Hardness, and Use for Measuring the Spectrum of the Cosmic X-Ray Background

    NASA Astrophysics Data System (ADS)

    Gendreau, Keith Charles

    1995-01-01

    This thesis has two distinct components. One concerns the physics of the high energy resolution X-ray charge coupled devices (CCD) detectors used to measure the cosmic X-ray background (XRB) spectrum. The other involves the measurements and analysis of the XRB spectrum and instrumental background with these detectors on board the advanced satellite for cosmology and astrophysics (ASCA). The XRB has a soft component and a hard component divided at ~2 keV. The hard component is extremely isotropic, suggesting a cosmological origin. The soft component is extremely anisotropic. A galactic component most likely dominates the soft band with X-ray line emission due to a hot plasma surrounding the solar system. ASCA is one of the first of a class of missions designed to overlap the hard and soft X-ray bands. The X-ray CCD's energy resolution allows us to spectrally separate the galactic and cosmological components. Also, the resolution offers the ability to test several specific cosmological models which would make up the XRB. I have concentrated on models for the XRB origin which include active galactic nuclei (AGN) as principal components. I use ASCA data to put spectral constraints on the AGN synthesis model for the XRB. The instrumental portion of this thesis concerns the development and calibration of the X-ray CCDs. I designed, built and operated an X-ray calibration facility for these detectors. It makes use of a reflection grating spectrometer to measure absolute detection efficiency, characteristic absorption edge strengths, and spectral redistribution in the CCD response function. Part of my thesis research includes a study of radiation damage mechanisms in CCDs. This work revealed radiation damage-induced degradation in the spectral response to X-rays. It also uncovered systematic effects which affect both data analysis and CCD design. I have developed a model involving trap energy levels in the CCD band gap structure. These traps reduce the efficiency in which

  20. On the determination of the cosmic infrared background radiation from the high-energy spectrum of extragalactic gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Slavin, Jonathan

    1994-01-01

    In a recent paper Stecker, De Jager, & Salamon have suggested using the observed approximately MeV to TeV spectra of extragalactic gamma-ray sources as probes of the local density of the cosmic infrared background radiation (CIBR) and have subsequently claimed a first possible measurement of the CIBR from the analysis of the gamma-ray spectrum of Mrk 421 (De Jager, Stecker, & Salamon). The CIBR from normal galaxies consists of two components: a stellar emission component (CIBRs), and a thermal dust emission component (CIBRd). Photons with energies in the approximately 0.1-2 TeV range interact primarily with the CIBRs, whereas interactions with CIBRd dominate the absorption of photons in the approximately 2-100 TeV energy range. SDS 92 and DSS94 considered only the interaction of the gamma-rays with the dust emission component of the CIBR. We present here an improved analysis of the absorption of extragalactic TeV gamma rays by the CIBR, taking the dual nature of its origin into account. Applying the analysis to the observed gamma-ray spectrum of Mrk 421, a BL Lac object at z = 0.031, we find agreement with DSS94 tentative evidence for absorption by the CINRs. Our analysis therefore limits the detection of the CIBR to the approximately 15-40 micron wavelength regime which, considering the uncertainties in the highest energy (greater than 4 TeV) data and ion the possibility of absorption inside the source, many turn out to be an upper limit on its energy density. At shorter wavelengths (lambda approximately = 1-15 microns), where the gamma-ray interactions are dominated by the CIBRs, our analysis definitely yields only an upper limit on the energy density of the CIBR. In contrast, DSS94 have claimed a possible first measurement of the CIBR over the entire 1-120 micron wavelength region. The upper limit on the CIBRs and tentative detection of the CIBRd are consistent with normal galaxies contributing most of the energy to the CIBR, and constrain the contribution of

  1. New 21 cm Power Spectrum Upper Limits From PAPER II: Constraints on IGM Properties at z = 7.7

    NASA Astrophysics Data System (ADS)

    Pober, Jonathan; Ali, Zaki; Parsons, Aaron; Paper Team

    2015-01-01

    Using a simulation-based framework, we interpret the power spectrum measurements from PAPER of Ali et al. in the context of IGM physics at z = 7.7. A cold IGM will result in strong 21 cm absorption relative to the CMB and leads to a 21 cm fluctuation power spectrum that can exceed 3000 mK^2. The new PAPER measurements allow us to rule out extreme cold IGM models, placing a lower limit on the physical temperature of the IGM. We also compare this limit with a calculation for the predicted heating from the currently observed galaxy population at z = 8.

  2. Large-scale power spectrum and structures from the ENEAR galaxy peculiar velocity catalogue

    NASA Astrophysics Data System (ADS)

    Zaroubi, S.; Bernardi, M.; da Costa, L. N.; Hoffman, Y.; Alonso, M. V.; Wegner, G.; Willmer, C. N. A.; Pellegrini, P. S.

    2001-09-01

    We estimate the mass density fluctuations power spectrum (PS) on large scales by applying a maximum likelihood technique to the peculiar velocity data of the recently completed redshift-distance survey of early-type galaxies (hereafter ENEAR). Parametric cold dark matter (CDM)-like models for the PS are assumed, and the best-fitting parameters are determined by maximizing the probability of the model given the measured peculiar velocities of the galaxies, their distances and estimated errors. The method has been applied to CDM models with and without COBE normalization. The general results are in agreement with the high-amplitude power spectra found from similar analyses of other independent all-sky catalogue of peculiar velocity data such as MARK III and SFI, in spite of the differences in the way these samples were selected, the fact that they probe different regions of space and galaxy distances are computed using different distance relations. For example, at k=0.1hMpc-1 the power spectrum value is P(k)Ω1.2=(6.5+/-3)×103(h- 1Mpc)3 and η8≡σ8Ω0.6=1.1- 0.35+0.2 the quoted uncertainties refer to 3σ error level. We also find that, for ΛCDM and OCDM COBE-normalized models, the best-fitting parameters are confined by a contour approximately defined by Ωh1.3=0.377+/-0.08 and Ωh0.88=0.517+/-0.083 respectively. Γ-shape models, free of COBE normalization, result in the weak constraint of Γ>=0.17 and in the rather stringent constraint of η8=1.0+/-0.25. All quoted uncertainties refer to 3σ confidence level (c.l.). The calculated PS has been used as a prior for Wiener reconstruction of the density field at different resolutions and the three-dimensional velocity field within a volume of radius ~80h-1Mpc. All major structures in the nearby Universe are recovered and are well matched to those predicted from all-sky redshift surveys. The robustness of these features has been tested with constrained realizations (CR). Analysis of the reconstructed three

  3. Power-law spectrum and small-world structure emerge from coupled evolution of neuronal activity and synaptic dynamics

    NASA Astrophysics Data System (ADS)

    Zeng, Hong-Li; Zhu, Chen-Ping; Guo, Yan-Dong; Teng, Ao; Jia, Jing; Kong, Hui; Zhou, Rui; Yang, Juan-Ping; Li, Su-Quan

    2015-04-01

    A co-evolutionary neuronal network model based on previous ones is proposed, and both functional and structural properties are numerically calculated. Recent experiments have revealed power-law behavior in electrocorticogram (ECoG) spectrum related with synaptic plasticity and reorganization. In the present neuronal network model, the network starts its evolution from the initial configuration of random network which is the least biased and without special structure, and the interaction rules among neurons are modified from both models by Bornholdt's and Arcangelis' groups to simulate the process of synaptic development and maturation. The system exhibits dynamic small-world structure which is the result of evolution instead of the assumption beforehand. Meanwhile, the power spectrum of electrical signals reproduces the power-law behavior with the exponent 2.0 just as what is experimentally measured in ECoG spectrum. Moreover, the power spectrum of the average degree per neuron over time also exhibits power-law behavior, with the exponent 2.0 again over more than 5 orders of magnitude. Different from previous results, our network exhibits assortative degree-degree correlation which is expected to be checked by experiments.

  4. Primary cosmic ray spectrum in the 10 to the 12th power - 10 to the 16th power eV energy range from the NUSEX experiment

    NASA Technical Reports Server (NTRS)

    Battistoni, G.; Bellotti, E.; Bloise, C.; Bologna, G.; Campana, P.; Castagnoli, C.; Castellina, A.; Chiarella, V.; Ciocio, A.; Cundy, D.

    1985-01-01

    A primary cosmic ray spectrum was derived which fits both experimental multiple muon rates and the all-nucleon flux derived from the single muon intensities underground. In the frame of the interaction model developed by Gaisser, Elbert and Stanev, it is possible to reproduce NUSEX muon data with a primary composition in which the iron spectrum is only slightly flatter than the proton one. This result rules out the popular idea that the primary composition varies drastically with increasing energy, leading to the dominance of heavier nuclei at energies 10 to the 15th power to 10 to the 16th power eV.

  5. Implications of the cosmic microwave background power asymmetry for the early universe

    NASA Astrophysics Data System (ADS)

    Byrnes, Christian T.; Regan, Donough; Seery, David; Tarrant, Ewan R. M.

    2016-06-01

    Observations of the microwave background fluctuations suggest a scale-dependent amplitude asymmetry of roughly 2.5 σ significance. Inflationary explanations for this "anomaly" require non-Gaussian fluctuations which couple observable modes to those on much larger scales. In this paper, we describe an analysis of such scenarios which significantly extends previous treatments. We identify the non-Gaussian "response function" which characterizes the asymmetry and show that it is nontrivial to construct a model which yields a sufficient amplitude; many independent fine-tunings are required, often making such models appear less likely than the anomaly they seek to explain. We present an explicit model satisfying observational constraints and determine for the first time how large its bispectrum would appear to a Planck-like experiment. Although this model is merely illustrative, we expect it is a good proxy for the bispectrum in a sizeable class of models which generate a scale-dependent response using a large η parameter.

  6. Disentangling Redshift-Space Distortions and Nonlinear Bias using the 2D Power Spectrum

    DOE PAGESBeta

    Jennings, Elise; Wechsler, Risa H.

    2015-08-07

    We present the nonlinear 2D galaxy power spectrum, P(k, µ), in redshift space, measured from the Dark Sky simulations, using galaxy catalogs constructed with both halo occupation distribution and subhalo abundance matching methods, chosen to represent an intermediate redshift sample of luminous red galaxies. We find that the information content in individual µ (cosine of the angle to the line of sight) bins is substantially richer then multipole moments, and show that this can be used to isolate the impact of nonlinear growth and redshift space distortion (RSD) effects. Using the µ < 0.2 simulation data, which we show ismore » not impacted by RSD effects, we can successfully measure the nonlinear bias to an accuracy of ~ 5% at k < 0.6hMpc-1 . This use of individual µ bins to extract the nonlinear bias successfully removes a large parameter degeneracy when constraining the linear growth rate of structure. We carry out a joint parameter estimation, using the low µ simulation data to constrain the nonlinear bias, and µ > 0.2 to constrain the growth rate and show that f can be constrained to ~ 26(22)% to a kmax < 0.4(0.6)hMpc-1 from clustering alone using a simple dispersion model, for a range of galaxy models. Our analysis of individual µ bins also reveals interesting physical effects which arise simply from different methods of populating halos with galaxies. We also find a prominent turnaround scale, at which RSD damping effects are greater then the nonlinear growth, which differs not only for each µ bin but also for each galaxy model. These features may provide unique signatures which could be used to shed light on the galaxy–dark matter connection. Furthermore, the idea of separating nonlinear growth and RSD effects making use of the full information in the 2D galaxy power spectrum yields significant improvements in constraining cosmological parameters and may be a promising probe of galaxy formation models.« less

  7. Small-Scale Power Spectrum and Correlations in Lambda + Cold Dark Matter Models

    NASA Astrophysics Data System (ADS)

    Klypin, Anatoly; Primack, Joel; Holtzman, Jon

    1996-07-01

    Cosmological models with a positive cosmological constant ({LAMBDA} > 0) and {OMEGA}_0_ < 1 have a number of attractive features. A larger Hubble constant H_0_, which can be compatible with the recent Hubble Space Telescope (HST) estimate, and a large fraction of baryon density in galaxy clusters make them current favorites. Early galaxy formation also is considered as a welcome feature of these models. But early galaxy formation implies that fluctuations on scales of a few megaparsecs spent more time in the nonlinear regime, as compared With standard cold dark matter (CDM) or cold + hot dark matter (CHDM) models. As has been known for a long time, this results in excessive clustering on small scales. We show that a typical {LAMBDA}CDM model with H_0_ = 70 km s^-1^ Mpc^-1^, {OMEGA}_0_ = 0.3, and cosmological constant {LAMBDA} such that {OMEGA}LAMBDA_ = {LAMBDA}/(3H_0_^2^) = 1 - {OMEGA}_0_, normalized to COBE on large scales and compatible with the number density of galaxy clusters, predicts a power spectrum of galaxy clustering in real space which is too high: at least twice larger than CfA estimates and 3 times larger than estimates for the APM Galaxy Survey for wavenumbers k = (0.4- 1)h Mpc^-1^. This conclusion holds if we assume either that galaxies trace the dark matter (σ_8_ ~ 1.1 for this model) or just that a region with higher density produces more galaxies than a region with lower density. The only way to reconcile the model with the observed power spectrum P(k) is to assume that regions with high dark matter density produce fewer galaxies than regions with low density. Theoretically this is possible, but it seems very unlikely: X-ray emission from groups and clusters indicates that places with a large density of dark matter produce a large number of galaxies. Since it follows that the low-{OMEGA} {LAMBDA}CDM models are in serious trouble, we discuss which ACDM models have the best hope of surviving the confrontation with all available observational data.

  8. Correlation between peak energy and Fourier power density spectrum slope in gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Dichiara, S.; Guidorzi, C.; Amati, L.; Frontera, F.; Margutti, R.

    2016-05-01

    Context. The origin of the gamma-ray burst (GRB) prompt emission still defies explanation, in spite of recent progress made, for example, on the occasional presence of a thermal component in the spectrum along with the ubiquitous non-thermal component that is modelled with a Band function. The combination of finite duration and aperiodic modulations make GRBs hard to characterise temporally. Although correlations between GRB luminosity and spectral hardness on one side and time variability on the other side have long been known, the loose and often arbitrary definition of the latter makes the interpretation uncertain. Aims: We characterise the temporal variability in an objective way and search for a connection with rest-frame spectral properties for a number of well-observed GRBs. Methods: We studied the individual power density spectra (PDS) of 123 long GRBs with measured redshift, rest-frame peak energy Ep,i of the time-averaged ν Fν spectrum, and well-constrained PDS slope α detected with Swift, Fermi and past spacecraft. The PDS were modelled with a power law either with or without a break adopting a Bayesian Markov chain Monte Carlo technique. Results: We find a highly significant Ep,i-α anti-correlation. The null hypothesis probability is ~10-9. Conclusions: In the framework of the internal shock synchrotron model, the Ep,i-α anti-correlation can hardly be reconciled with the predicted Ep,i ∝ Γ-2, unless either variable microphysical parameters of the shocks or continual electron acceleration are assumed. Alternatively, in the context of models based on magnetic reconnection, the PDS slope and Ep,i are linked to the ejecta magnetisation at the dissipation site, so that more magnetised outflows would produce more variable GRB light curves at short timescales (≲1 s), shallower PDS, and higher values of Ep,i. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  9. Correlation between peak energy and Fourier power density spectrum slope in gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Dichiara, S.; Guidorzi, C.; Amati, L.; Frontera, F.; Margutti, R.

    2016-04-01

    Context. The origin of the gamma-ray burst (GRB) prompt emission still defies explanation, in spite of recent progress made, for example, on the occasional presence of a thermal component in the spectrum along with the ubiquitous non-thermal component that is modelled with a Band function. The combination of finite duration and aperiodic modulations make GRBs hard to characterise temporally. Although correlations between GRB luminosity and spectral hardness on one side and time variability on the other side have long been known, the loose and often arbitrary definition of the latter makes the interpretation uncertain. Aims: We characterise the temporal variability in an objective way and search for a connection with rest-frame spectral properties for a number of well-observed GRBs. Methods: We studied the individual power density spectra (PDS) of 123 long GRBs with measured redshift, rest-frame peak energy Ep,i of the time-averaged ν Fν spectrum, and well-constrained PDS slope α detected with Swift, Fermi and past spacecraft. The PDS were modelled with a power law either with or without a break adopting a Bayesian Markov chain Monte Carlo technique. Results: We find a highly significant Ep,i-α anti-correlation. The null hypothesis probability is ~10-9. Conclusions: In the framework of the internal shock synchrotron model, the Ep,i-α anti-correlation can hardly be reconciled with the predicted Ep,i ∝ Γ-2, unless either variable microphysical parameters of the shocks or continual electron acceleration are assumed. Alternatively, in the context of models based on magnetic reconnection, the PDS slope and Ep,i are linked to the ejecta magnetisation at the dissipation site, so that more magnetised outflows would produce more variable GRB light curves at short timescales (≲1 s), shallower PDS, and higher values of Ep,i. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc

  10. LOFAR insights into the epoch of reionization from the cross-power spectrum of 21 cm emission and galaxies

    NASA Astrophysics Data System (ADS)

    Wiersma, R. P. C.; Ciardi, B.; Thomas, R. M.; Harker, G. J. A.; Zaroubi, S.; Bernardi, G.; Brentjens, M.; de Bruyn, A. G.; Daiboo, S.; Jelic, V.; Kazemi, S.; Koopmans, L. V. E.; Labropoulos, P.; Martinez, O.; Mellema, G.; Offringa, A.; Pandey, V. N.; Schaye, J.; Veligatla, V.; Vedantham, H.; Yatawatta, S.

    2013-07-01

    Using a combination of N-body simulations, semi-analytic models and radiative transfer calculations, we have estimated the theoretical cross-power spectrum between galaxies and the 21 cm emission from neutral hydrogen during the epoch of reionization. In accordance with previous studies, we find that the 21 cm emission is initially correlated with haloes on large scales (≳30 Mpc), anticorrelated on intermediate (˜5 Mpc) and uncorrelated on small (≲3 Mpc) scales. This picture quickly changes as reionization proceeds and the two fields become anticorrelated on large scales. The normalization of the cross-power spectrum can be used to set constraints on the average neutral fraction in the intergalactic medium and its shape can be a powerful tool to study the topology of reionization. When we apply a drop-out technique to select galaxies and add to the 21 cm signal the noise expected from the LOw Frequency ARray (LOFAR) telescope, we find that while the normalization of the cross-power spectrum remains a useful tool for probing reionization, its shape becomes too noisy to be informative. On the other hand, for an Lyα Emitter (LAE) survey both the normalization and the shape of the cross-power spectrum are suitable probes of reionization. A closer look at a specific planned LAE observing program using Subaru Hyper-Suprime Cam reveals concerns about the strength of the 21 cm signal at the planned redshifts. If the ionized fraction at z ˜ 7 is lower than the one estimated here, then using the cross-power spectrum may be a useful exercise given that at higher redshifts and neutral fractions it is able to distinguish between two toy models with different topologies.

  11. The scale invariant power spectrum of the primordial curvature perturbations from the coupled scalar tachyon bounce cosmos

    SciTech Connect

    Li, Changhong; Cheung, Yeuk-Kwan E. E-mail: cheung@nju.edu.cn

    2014-07-01

    We investigate the spectrum of cosmological perturbations in a bounce cosmos modeled by a scalar field coupled to the string tachyon field (CSTB cosmos). By explicit computation of its primordial spectral index we show the power spectrum of curvature perturbations, generated during the tachyon matter dominated contraction phase, to be nearly scale invariant. We propose a unified parameter space for a systematic study of inflationary and bounce cosmologies. The CSTB cosmos is dual-in Wands's sense-to slow-roll inflation as can be visualized with the aid of this parameter space. Guaranteed by the dynamical attractor behavior of the CSTB Cosmos, the scale invariance of its power spectrum is free of the fine-tuning problem, in contrast to the slow-roll inflation model.

  12. The resemblance of an autocorrelation function to a power spectrum density for a spike train of an auditory model

    NASA Astrophysics Data System (ADS)

    Ushakov, Y. V.; Dubkov, A. A.; Spagnolo, B.

    2013-01-01

    In this work we develop an analytical approach for calculation of the all-order interspike interval density (AOISID), show its connection with the autocorrelation function, and try to explain the discovered resemblance of AOISID to the power spectrum of the same spike train.

  13. Non-linear matter power spectrum covariance matrix errors and cosmological parameter uncertainties

    NASA Astrophysics Data System (ADS)

    Blot, L.; Corasaniti, P. S.; Amendola, L.; Kitching, T. D.

    2016-06-01

    The covariance of the matter power spectrum is a key element of the analysis of galaxy clustering data. Independent realizations of observational measurements can be used to sample the covariance, nevertheless statistical sampling errors will propagate into the cosmological parameter inference potentially limiting the capabilities of the upcoming generation of galaxy surveys. The impact of these errors as function of the number of realizations has been previously evaluated for Gaussian distributed data. However, non-linearities in the late-time clustering of matter cause departures from Gaussian statistics. Here, we address the impact of non-Gaussian errors on the sample covariance and precision matrix errors using a large ensemble of N-body simulations. In the range of modes where finite volume effects are negligible (0.1 ≲ k [h Mpc-1] ≲ 1.2), we find deviations of the variance of the sample covariance with respect to Gaussian predictions above ˜10 per cent at k > 0.3 h Mpc-1. Over the entire range these reduce to about ˜5 per cent for the precision matrix. Finally, we perform a Fisher analysis to estimate the effect of covariance errors on the cosmological parameter constraints. In particular, assuming Euclid-like survey characteristics we find that a number of independent realizations larger than 5000 is necessary to reduce the contribution of sampling errors to the cosmological parameter uncertainties at subpercent level. We also show that restricting the analysis to large scales k ≲ 0.2 h Mpc-1 results in a considerable loss in constraining power, while using the linear covariance to include smaller scales leads to an underestimation of the errors on the cosmological parameters.

  14. Reheating effects in the matter power spectrum and implications for substructure

    SciTech Connect

    Erickcek, Adrienne L.; Sigurdson, Kris

    2011-10-15

    The thermal and expansion history of the Universe before big bang nucleosynthesis is unknown. We investigate the evolution of cosmological perturbations through the transition from an early matter era to radiation domination. We treat reheating as the perturbative decay of an oscillating scalar field into relativistic plasma and cold dark matter. After reheating, we find that subhorizon perturbations in the decay-produced dark matter density are significantly enhanced, while subhorizon radiation perturbations are instead suppressed. If dark matter originates in the radiation bath after reheating, this suppression may be the primary cutoff in the matter power spectrum. Conversely, for dark matter produced nonthermally from scalar decay, enhanced perturbations can drive structure formation during the cosmic dark ages and dramatically increase the abundance of compact substructures. For low reheat temperatures, we find that as much as 50% of all dark matter is in microhalos with M > or approx. 0.1M{sub +} at z{approx_equal}100, compared to a fraction of {approx}10{sup -10} in the standard case. In this scenario, ultradense substructures may constitute a large fraction of dark matter in galaxies today.

  15. Intrinsic noise power spectrum for the electronic noise in radiography image detectors

    NASA Astrophysics Data System (ADS)

    Kim, Dong Sik; Kim, Eun; Shin, Choul Woo

    2015-03-01

    In order to design low-dose imaging systems, the radiography detector should have a good noise performance especially at low incident exposures. The signal-to-noise ratio (SNR) performance at low incident exposures is influenced by the electronic noise of readout circuits as well as the quantum noise of x-rays. Hence, analyzing the electronic noise of a detector is of importance in developing good detectors. However, the SNR value for electronic noise is zero and does not provide any useful information. Observing the standard deviation of the acquired image without exposure may confuse the analysis due to the inconsistent electronic gains of the readout circuits. Hence, it is required to find an appropriate evaluation scheme for the electronic noise. A blind electronic noise evaluation approach, which uses a set of acquired images at various incident exposures, is considered in this paper. We calculate the electronic gain and then derive an intrinsic noise power spectrum (NPS), which is independent of the electronic gain. Furthermore, we can obtain the intrinsic NPS only for the electronic noise. The proposed evaluation schemes are experimentally tested for digital x-ray images, which are obtained from various development prototypes of direct and indirect detectors. It is shown that the proposed schemes can efficiently provide an evaluation for the electronic noise performance.

  16. A new probe of the magnetic field power spectrum in cosmic web filaments

    NASA Astrophysics Data System (ADS)

    Hales, Christopher A.; Greiner, Maksim; Ensslin, Torsten A.

    2015-08-01

    Establishing the properties of magnetic fields on scales larger than galaxy clusters is critical for resolving the unknown origin and evolution of galactic and cluster magnetism. More generally, observations of magnetic fields on cosmic scales are needed for assessing the impacts of magnetism on cosmology, particle physics, and structure formation over the full history of the Universe. However, firm observational evidence for magnetic fields in large scale structure remains elusive. In an effort to address this problem, we have developed a novel statistical method to infer the magnetic field power spectrum in cosmic web filaments using observation of the two-point correlation of Faraday rotation measures from a dense grid of extragalactic radio sources. Here we describe our approach, which embeds and extends the pioneering work of Kolatt (1998) within the context of Information Field Theory (a statistical theory for Bayesian inference on spatially distributed signals; Enfllin et al., 2009). We describe prospects for observation, for example with forthcoming data from the ultra-deep JVLA CHILES Con Pol survey and future surveys with the SKA.

  17. Diesel engine noise source identification based on EEMD, coherent power spectrum analysis and improved AHP

    NASA Astrophysics Data System (ADS)

    Zhang, Junhong; Wang, Jian; Lin, Jiewei; Bi, Fengrong; Guo, Qian; Chen, Kongwu; Ma, Liang

    2015-09-01

    As the essential foundation of noise reduction, many noise source identification methods have been developed and applied to engineering practice. To identify the noise source in the board-band frequency of different engine parts at various typical speeds, this paper presents an integrated noise source identification method based on the ensemble empirical mode decomposition (EEMD), the coherent power spectrum analysis, and the improved analytic hierarchy process (AHP). The measured noise is decomposed into several IMFs with physical meaning, which ensures the coherence analysis of the IMFs and the vibration signals are meaningful. An improved AHP is developed by introducing an objective weighting function to replace the traditional subjective evaluation, which makes the results no longer dependent on the subject performances and provides a better consistency in the meantime. The proposed noise identification model is applied to identifying a diesel engine surface radiated noise. As a result, the frequency-dependent contributions of different engine parts to different test points at different speeds are obtained, and an overall weight order is obtained as oil pan  >  left body  >  valve chamber cover  >  gear chamber casing  >  right body  >  flywheel housing, which provides an effectual guidance for the noise reduction.

  18. Power Spectrum and Mutual Information Analyses of DNA Base (Nucleotide) Sequences

    NASA Astrophysics Data System (ADS)

    Isohata, Yasuhiko; Hayashi, Masaki

    2003-03-01

    On the basis of the power spectrum analyses for the base (nucleotide) sequences of various genes, we have studied long-range correlations in total base sequences which are expressed as 1/fα, behaviour of the exponent α for the accumulated base sequences as well as periodicities at short range. In particular from the analysis of content rate distributions of α we have obtained the average value \\barα=0.40± 0.01 and \\barα=0.20± 0.01 for the human genes and S. cerevisiae genes, respectively. We have also performed the analyses using the mutual information function. We show that there exists a clear difference between the content rate distributions of correlation lengths for the sample human genes and the S. cerevisiae genes. We are led to a conjecture that the elongation of the correlation length in the base sequences of genes from the early eukaryote (S. cerevisiae) to the late eukaryote (human) should be the definite reflection of the evolutionary process.

  19. Gas density fluctuations in the Perseus Cluster: clumping factor and velocity power spectrum

    NASA Astrophysics Data System (ADS)

    Zhuravleva, I.; Churazov, E.; Arévalo, P.; Schekochihin, A. A.; Allen, S. W.; Fabian, A. C.; Forman, W. R.; Sanders, J. S.; Simionescu, A.; Sunyaev, R.; Vikhlinin, A.; Werner, N.

    2015-07-01

    X-ray surface brightness fluctuations in the core of the Perseus Cluster are analysed, using deep observations with the Chandra observatory. The amplitude of gas density fluctuations on different scales is measured in a set of radial annuli. It varies from 7 to 12 per cent on scales of ˜10-30 kpc within radii of 30-220 kpc from the cluster centre. Using a statistical linear relation between the observed amplitude of density fluctuations and predicted velocity, the characteristic velocity of gas motions on each scale is calculated. The typical amplitudes of the velocity outside the central 30 kpc region are 90-140 km s-1 on ˜20-30 kpc scales and 70-100 km s-1 on smaller scales ˜7-10 kpc. The velocity power spectrum (PS) is consistent with cascade of turbulence and its slope is in a broad agreement with the slope for canonical Kolmogorov turbulence. The gas clumping factor estimated from the PS of the density fluctuations is lower than 7-8 per cent for radii ˜30-220 kpc from the centre, leading to a density bias of less than 3-4 per cent in the cluster core. Uncertainties of the analysis are examined and discussed. Future measurements of the gas velocities with the Astro-H, Athena and Smart-X observatories will directly measure the gas density-velocity perturbation relation and further reduce systematic uncertainties in this analysis.

  20. VizieR Online Data Catalog: 1D Lya forest power spectrum (Palanque-Delabrouille+, 2013)

    NASA Astrophysics Data System (ADS)

    Palanque-Delabrouille, N.; Yeche, C.; Borde, A.; Le Goff, J.-M.; Rossi, G.; Viel, M.; Aubourg, E.; Bailey, S.; Bautista, J.; Blomqvist, M.; Bolton, A.; Bolton, J. S.; Busca, N. G.; Carithers, B.; Croft, R. A. C.; Dawson, K. S.; Delubac, T.; Font-Ribera, A.; Ho, S.; Kirkby, D.; Lee, K.-G.; Margala, D.; Miralda-Escude, J.; Muna, D.; Myers, A. D.; Noterdaeme, P.; Paris, I.; Petitjean, P.; Pieri, M. M.; Rich, J.; Rollinde, E.; Ross, N. P.; Schlegel, D. J.; Schneider, D. P.; Slosar, A.; Weinberg, D. H.

    2013-09-01

    The files contain the data describing the measured 1D power spectrum and the correlations between bins from the BOSS Lyman-alpha data. table4a.dat and table5a.dat: P1D results obtained with the Fourier transform and the likelihood method respectively, for each k and z bin. cct4b*.dat and cct5b*.dat: Correlation matrices between k bins for each z bin, for the Fourier transform and the likelihood method respectively. There are 12 HDUs, one for each redshift bin from =2.2 (HDU 1, table[45]b1.dat) to =4.4 (HDU 12, table[45]b12.dat). Each HDU contains a binary table with 35 bins x 35 entries for the Fourier transform method, and 32 bins x 32 entries for the likelihood method. The tables contain the correlation coefficients. The scale ki corresponding to entry (or bin) i can be read in the corresponding entry of table4a.dat or table5a.dat. (30 data files).

  1. Forecasting sensitivity on tilt of power spectrum of primordial gravitational waves after Planck satellite

    NASA Astrophysics Data System (ADS)

    Huang, Qing-Guo; Wang, Sai; Zhao, Wen

    2015-10-01

    By taking into account the contamination of foreground radiations, we employ the Fisher matrix to forecast the future sensitivity on the tilt of power spectrum of primordial tensor perturbations for several ground-based (AdvACT, CLASS, Keck/BICEP3, Simons Array, SPT-3G), balloon-borne (EBEX, Spider) and satellite (CMBPol, COrE, LiteBIRD) experiments of B-mode polarizations. For the fiducial model nt=0, our results show that the satellite experiments give good sensitivity on the tensor tilt nt to the level σntlesssim0.1 for rgtrsim2×10-3, while the ground-based and balloon-borne experiments give worse sensitivity. By considering the BICEP2/Keck Array and Planck (BKP) constraint on the tensor-to-scalar ratio r, we see that it is impossible for these experiments to test the consistency relation nt=-r/8 in the canonical single-field slow-roll inflation models.

  2. Nonlinear power spectrum from resummed perturbation theory: a leap beyond the BAO scale

    SciTech Connect

    Anselmi, Stefano; Pietroni, Massimo E-mail: massimo.pietroni@pd.infn.it

    2012-12-01

    A new computational scheme for the nonlinear cosmological matter power spectrum (PS) is presented. Our method is based on evolution equations in time, which can be cast in a form extremely convenient for fast numerical evaluations. A nonlinear PS is obtained in a time comparable to that needed for a simple 1-loop computation, and the numerical implementation is very simple. Our results agree with N-body simulations at the percent level in the BAO range of scales, and at the few-percent level up to k ≅ 1 h/Mpc at z∼>0.5, thereby opening the possibility of applying this tool to scales interesting for weak lensing. We clarify the approximations inherent to this approach as well as its relations to previous ones, such as the Time Renormalization Group, and the multi-point propagator expansion. We discuss possible lines of improvements of the method and its intrinsic limitations by multi streaming at small scales and low redshifts.

  3. The Angular Power Spectrum of BATSE 3B Gamma-Ray Bursts

    NASA Technical Reports Server (NTRS)

    Tegmark, Max; Hartmann, Dieter H.; Briggs, Michael S.; Meegan, Charles A.

    1996-01-01

    We compute the angular power spectrum C(sub l) from the BATSE 3B catalog of 1122 gamma-ray bursts and find no evidence for clustering on any scale. These constraints bridge the entire range from small scales (which probe source clustering and burst repetition) to the largest scales (which constrain possible anisotropics from the Galactic halo or from nearby cosmological large-scale structures). We develop an analysis technique that takes the angular position errors into account. For specific clustering or repetition models, strong upper limits can be obtained down to scales l approx. equal to 30, corresponding to a couple of degrees on the sky. The minimum-variance burst weighting that we employ is visualized graphically as an all-sky map in which each burst is smeared out by an amount corresponding to its position uncertainty. We also present separate bandpass-filtered sky maps for the quadrupole term and for the multipole ranges l = 3-10 and l = 11-30, so that the fluctuations on different angular scales can be inspected separately for visual features such as localized 'hot spots' or structures aligned with the Galactic plane. These filtered maps reveal no apparent deviations from isotropy.

  4. Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Trott, Cathryn M.; Murphy, Tara; Cairns, Iver H.; Bell, Martin; Hurley-Walker, Natasha; Morgan, John; Lenc, Emil; Offringa, A. R.; Feng, L.; Hancock, P. J.; Kaplan, D. L.; Kudryavtseva, N.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Emrich, D.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Johnston-Hollitt, M.; Kasper, J. C.; Kratzenberg, E.; Lonsdale, C. J.; Lynch, M. J.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Rogers, A. E. E.; Roshi, A.; Shankar, N. Udaya; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

    2015-07-01

    Low-frequency, wide field-of-view (FOV) radio telescopes such as the Murchison Widefield Array (MWA) enable the ionosphere to be sampled at high spatial completeness. We present the results of the first power spectrum analysis of ionospheric fluctuations in MWA data, where we examined the position offsets of radio sources appearing in two data sets. The refractive shifts in the positions of celestial sources are proportional to spatial gradients in the electron column density transverse to the line of sight. These can be used to probe plasma structures and waves in the ionosphere. The regional (10-100 km) scales probed by the MWA, determined by the size of its FOV and the spatial density of radio sources (typically thousands in a single FOV), complement the global (100-1000 km) scales of GPS studies and local (0.01-1 km) scales of radar scattering measurements. Our data exhibit a range of complex structures and waves. Some fluctuations have the characteristics of traveling ionospheric disturbances, while others take the form of narrow, slowly drifting bands aligned along the Earth's magnetic field.

  5. MASKING VERSUS REMOVING POINT SOURCES IN CMB DATA: THE SOURCE-CORRECTED WMAP POWER SPECTRUM FROM NEW EXTENDED CATALOG

    SciTech Connect

    Scodeller, Sandro; Hansen, Frode K. E-mail: frodekh@astro.uio.no

    2012-12-20

    In Scodeller et al., a new and extended point source catalog obtained from the Wilkinson Microwave Anisotropy Probe (WMAP) seven-year data was presented. It includes most of the sources included in the standard WMAP seven-year point source catalogs as well as a large number of new detections. Here, we study the effects on the estimated CMB power spectrum when taking the newly detected point sources into consideration. We create point source masks for all the 2102 sources that we detected as well as a smaller one for the 665 sources detected in the Q, V, and W bands. We also create WMAP7 maps with point sources subtracted in order to compare with the spectrum obtained with source masks. The extended point source masks and point source cleaned WMAP7 maps are made publicly available. Using the proper residual correction, we find that the CMB power spectrum obtained from the point source cleaned map without any source mask is fully consistent with the spectrum obtained from the masked map. We further find that the spectrum obtained masking all 2102 sources is consistent with the results obtained using the standard WMAP seven-year point source mask (KQ85y7). We also verify that the removal of point sources does not introduce any skewness.

  6. Tunable high-power narrow-spectrum external-cavity diode laser based on tapered amplifier at 668 nm.

    PubMed

    Chi, Mingjun; Erbert, G; Sumpf, B; Petersen, Paul Michael

    2010-05-15

    A 668 nm tunable high-power narrow-spectrum diode laser system based on a tapered semiconductor optical amplifier in external cavity is demonstrated. The laser system is tunable from 659to675 nm. As high as 1.38 W output power is obtained at 668.35 nm. The emission spectral bandwidth is less than 0.07 nm throughout the tuning range, and the beam quality factor M(2) is 2.0 with the output power of 1.27 W. PMID:20479803

  7. Background rhythm frequency and theta power of quantitative EEG analysis: predictive biomarkers for cognitive impairment post-cerebral infarcts.

    PubMed

    Song, Yang; Zang, Da-Wei; Jin, Yan-Yu; Wang, Zhi-Jun; Ni, Hong-Yan; Yin, Jian-Zhong; Ji, Dong-Xu

    2015-04-01

    In clinical settings, cerebral infarct is a common disease of older adults, which usually increases the risk of cognitive impairment. This study aims to assess the quantitative electroencephalography (qEEG) as a predictive biomarker for the development of cognitive impairment, post-cerebral infarcts, in subjects from the Department of Neurology. They underwent biennial EEG recording. Cerebral infarct subjects, with follow-up cognitive evaluation, were analyzed for qEEG measures of background rhythm frequency (BRF) and relative δ, θ, α, and β band power. The relationship between cognitive impairment and qEEG, and other possible predictors, was assessed by Cox regression. The results showed that the risk hazard of developing cognitive impairment was 14 times higher for those with low BRF than for those with high BRF (P < .001). Hazard ratio (HR) was also significant for more than median θ band power (HR = 5, P = .002) compared with less than median θ band power. The HRs for δ, α, and β bands were equal to the baseline demographic, and clinical characteristics were not significantly different. In conclusion, qEEG measures of BRF, and relative power in θ band, are potential predictive biomarkers for cognitive impairment in patients with cerebral infarcts. These biomarkers might be valuable in early prediction of cognitive impairment in patients with cerebral infarcts. PMID:24699438

  8. The Coyote Universe Extended: Precision Emulation of the Matter Power Spectrum

    NASA Astrophysics Data System (ADS)

    Heitmann, Katrin; Lawrence, Earl; Kwan, Juliana; Habib, Salman; Higdon, David

    2014-01-01

    Modern sky surveys are returning precision measurements of cosmological statistics such as weak lensing shear correlations, the distribution of galaxies, and cluster abundance. To fully exploit these observations, theorists must provide predictions that are at least as accurate as the measurements, as well as robust estimates of systematic errors that are inherent to the modeling process. In the nonlinear regime of structure formation, this challenge can only be overcome by developing a large-scale, multi-physics simulation capability covering a range of cosmological models and astrophysical processes. As a first step to achieving this goal, we have recently developed a prediction scheme for the matter power spectrum (a so-called emulator), accurate at the 1% level out to k ~ 1 Mpc-1 and z = 1 for wCDM cosmologies based on a set of high-accuracy N-body simulations. It is highly desirable to increase the range in both redshift and wavenumber and to extend the reach in cosmological parameter space. To make progress in this direction, while minimizing computational cost, we present a strategy that maximally reuses the original simulations. We demonstrate improvement over the original spatial dynamic range by an order of magnitude, reaching k ~ 10 h Mpc-1, a four-fold increase in redshift coverage, to z = 4, and now include the Hubble parameter as a new independent variable. To further the range in k and z, a new set of nested simulations run at modest cost is added to the original set. The extension in h is performed by including perturbation theory results within a multi-scale procedure for building the emulator. This economical methodology still gives excellent error control, ~5% near the edges of the domain of applicability of the emulator. A public domain code for the new emulator is released as part of the work presented in this paper.

  9. The coyote universe extended: Precision emulation of the matter power spectrum

    SciTech Connect

    Heitmann, Katrin; Kwan, Juliana; Habib, Salman; Lawrence, Earl; Higdon, David

    2014-01-01

    Modern sky surveys are returning precision measurements of cosmological statistics such as weak lensing shear correlations, the distribution of galaxies, and cluster abundance. To fully exploit these observations, theorists must provide predictions that are at least as accurate as the measurements, as well as robust estimates of systematic errors that are inherent to the modeling process. In the nonlinear regime of structure formation, this challenge can only be overcome by developing a large-scale, multi-physics simulation capability covering a range of cosmological models and astrophysical processes. As a first step to achieving this goal, we have recently developed a prediction scheme for the matter power spectrum (a so-called emulator), accurate at the 1% level out to k ∼ 1 Mpc{sup –1} and z = 1 for wCDM cosmologies based on a set of high-accuracy N-body simulations. It is highly desirable to increase the range in both redshift and wavenumber and to extend the reach in cosmological parameter space. To make progress in this direction, while minimizing computational cost, we present a strategy that maximally reuses the original simulations. We demonstrate improvement over the original spatial dynamic range by an order of magnitude, reaching k ∼ 10 h Mpc{sup –1}, a four-fold increase in redshift coverage, to z = 4, and now include the Hubble parameter as a new independent variable. To further the range in k and z, a new set of nested simulations run at modest cost is added to the original set. The extension in h is performed by including perturbation theory results within a multi-scale procedure for building the emulator. This economical methodology still gives excellent error control, ∼5% near the edges of the domain of applicability of the emulator. A public domain code for the new emulator is released as part of the work presented in this paper.

  10. Precision comparison of the power spectrum in the EFTofLSS with simulations

    NASA Astrophysics Data System (ADS)

    Foreman, Simon; Perrier, Hideki; Senatore, Leonardo

    2016-05-01

    We study the prediction of the dark matter power spectrum at two-loop order in the Effective Field Theory of Large Scale Structures (EFTofLSS) using high precision numerical simulations. In our universe, short distance non-linear fluctuations, not under perturbative control, affect long distance fluctuations through an effective stress tensor that needs to be parametrized in terms of counterterms that are functions of the long distance fluctuating fields. We find that at two-loop order it is necessary to include three counterterms: a linear term in the overdensity, δ, a quadratic term, δ2, and a higher derivative term, ∂2δ. After the inclusion of these three terms, the EFTofLSS at two-loop order matches simulation data up to k simeq 0.34 h Mpc‑1 at redshift z = 0, up to k simeq 0.55 h Mpc‑1 at z = 1, and up to k simeq 1.1 h Mpc‑1 at z = 2. At these wavenumbers, the cosmic variance of the simulation is at least as small as 10‑3, providing for the first time a high precision comparison between theory and data. The actual reach of the theory is affected by theoretical uncertainties associated to not having included higher order terms in perturbation theory, for which we provide an estimate, and by potentially overfitting the data, which we also try to address. Since in the EFTofLSS the coupling constants associated with the counterterms are unknown functions of time, we show how a simple parametrization gives a sensible description of their time-dependence. Overall, the k-reach of the EFTofLSS is much larger than previous analytical techniques, showing that the amount of cosmological information amenable to high-precision analytical control might be much larger than previously believed.

  11. Noise Power Spectrum Measurements in Digital Imaging With Gain Nonuniformity Correction.

    PubMed

    Kim, Dong Sik

    2016-08-01

    The noise power spectrum (NPS) of an image sensor provides the spectral noise properties needed to evaluate sensor performance. Hence, measuring an accurate NPS is important. However, the fixed pattern noise from the sensor's nonuniform gain inflates the NPS, which is measured from images acquired by the sensor. Detrending the low-frequency fixed pattern is traditionally used to accurately measure NPS. However, detrending methods cannot remove high-frequency fixed patterns. In order to efficiently correct the fixed pattern noise, a gain-correction technique based on the gain map can be used. The gain map is generated using the average of uniformly illuminated images without any objects. Increasing the number of images n for averaging can reduce the remaining photon noise in the gain map and yield accurate NPS values. However, for practical finite n , the photon noise also significantly inflates NPS. In this paper, a nonuniform-gain image formation model is proposed and the performance of the gain correction is theoretically analyzed in terms of the signal-to-noise ratio (SNR). It is shown that the SNR is O(√n) . An NPS measurement algorithm based on the gain map is then proposed for any given n . Under a weak nonuniform gain assumption, another measurement algorithm based on the image difference is also proposed. For real radiography image detectors, the proposed algorithms are compared with traditional detrending and subtraction methods, and it is shown that as few as two images ( n=1 ) can provide an accurate NPS because of the compensation constant (1+1/n) . PMID:27254867

  12. Constraints on CDM cosmology from galaxy power spectrum, CMB and SNIa evolution

    NASA Astrophysics Data System (ADS)

    Ferramacho, L. D.; Blanchard, A.; Zolnierowski, Y.

    2009-05-01

    Aims: We examine the constraints that can be obtained on standard cold dark matter models from the most currently used data set: CMB anisotropies, type Ia supernovae and the SDSS luminous red galaxies. We also examine how these constraints are widened when the equation of state parameter w and the curvature parameter Ωk are left as free parameters. Finally, we investigate the impact on these constraints of a possible form of evolution in SNIa intrinsic luminosity. Methods: We obtained our results from MCMC analysis using the full likelihood of each data set. Results: For the ΛCDM model, our “vanilla” model, cosmological parameters are tightly constrained and consistent with current estimates from various methods. When the dark energy parameter w is free we find that the constraints remain mostly unchanged, i.e. changes are smaller than the 1 sigma uncertainties. Similarly, relaxing the assumption of a flat universe leads to nearly identical constraints on the dark energy density parameter of the universe Ω_Λ , baryon density of the universe Ω_b, the optical depth τ, the index of the power spectrum of primordial fluctuations n_S, with most one sigma uncertainties better than 5%. More significant changes appear on other parameters: while preferred values are almost unchanged, uncertainties for the physical dark matter density Ω_ch^2, Hubble constant H0 and σ8 are typically twice as large. The constraint on the age of the Universe, which is very accurate for the vanilla model, is the most degraded. We found that different methodological approaches on large scale structure estimates lead to appreciable differences in preferred values and uncertainty widths. We found that possible evolution in SNIa intrinsic luminosity does not alter these constraints by much, except for w, for which the uncertainty is twice as large. At the same time, this possible evolution is severely constrained. Conclusions: We conclude that systematic uncertainties for some estimated

  13. Statistics of the epoch of reionization 21-cm signal - I. Power spectrum error-covariance

    NASA Astrophysics Data System (ADS)

    Mondal, Rajesh; Bharadwaj, Somnath; Majumdar, Suman

    2016-02-01

    The non-Gaussian nature of the epoch of reionization (EoR) 21-cm signal has a significant impact on the error variance of its power spectrum P(k). We have used a large ensemble of seminumerical simulations and an analytical model to estimate the effect of this non-Gaussianity on the entire error-covariance matrix {C}ij. Our analytical model shows that {C}ij has contributions from two sources. One is the usual variance for a Gaussian random field which scales inversely of the number of modes that goes into the estimation of P(k). The other is the trispectrum of the signal. Using the simulated 21-cm Signal Ensemble, an ensemble of the Randomized Signal and Ensembles of Gaussian Random Ensembles we have quantified the effect of the trispectrum on the error variance {C}ii. We find that its relative contribution is comparable to or larger than that of the Gaussian term for the k range 0.3 ≤ k ≤ 1.0 Mpc-1, and can be even ˜200 times larger at k ˜ 5 Mpc-1. We also establish that the off-diagonal terms of {C}ij have statistically significant non-zero values which arise purely from the trispectrum. This further signifies that the error in different k modes are not independent. We find a strong correlation between the errors at large k values (≥0.5 Mpc-1), and a weak correlation between the smallest and largest k values. There is also a small anticorrelation between the errors in the smallest and intermediate k values. These results are relevant for the k range that will be probed by the current and upcoming EoR 21-cm experiments.

  14. Systematic Observation of Time-Dependent Phenomena in the RF Output Spectrum of High Power Gyrotrons

    NASA Astrophysics Data System (ADS)

    Schlaich, Andreas; Gantenbein, Gerd; Kern, Stefan; Thumm, Manfred

    2012-09-01

    At IHM/KIT, high power gyrotrons with conventional cavity (e.g. 1 MW CW at 140 GHz for the stellarator Wendelstein 7-X) and coaxial cavity (2 MW shortpulse at 170 GHz for ITER) for fusion applications are being developed and verified experimentally. Especially with respect to the problem of parasitic RF oscillations in the beam tunnel of some W7-X tubes, investigations of the gyrotron RF output spectrum have proved to be a valuable source of diagnostic information. Signs of transient effects in millisecond pulses, like frequency switching or intermittent low-frequency modulation, have indicated that truly time-dependent measurements with high frequency resolution and dynamic range could give deeper insight into these phenomena. In this paper, an improved measurement system is presented, which employs a fast oscilloscope as receiver. Shorttime Fourier transform (STFT) is applied to the time-domain signal, yielding time-variant spectra with frequency resolutions only limited by acquisition length and STFT segmentation choice. Typical reasonable resolutions are in the range of 100 kHz to 10 MHz with a currently memory-limited maximum acquisition length of 4 ms. A key feature of the system consists in the unambiguity of frequency measurement: The system receives through two parallel channels, each using a harmonic mixer (h = 9 - 12) to convert the signal from RF millimeter wave frequencies (full D-Band, 110 - 170 GHz) to IF (0 - 3 GHz). For each IF output signal of each individual mixer, injection side and receiving harmonic are initially not known. Using accordingly determined LO frequencies, this information is retrieved from the redundancy of the channels, yielding unambiguously reconstructed RF spectra with a total span of twice the usable receiver IF bandwidth, up to ≈ 6 GHz in our case. Using the system, which is still being improved continuously, various transient effects like cavity mode switching, parasitic oscillation frequency variation, and lowfrequency

  15. Impact of Baryonic Processes on Weak-lensing Cosmology: Power Spectrum, Nonlocal Statistics, and Parameter Bias

    NASA Astrophysics Data System (ADS)

    Osato, Ken; Shirasaki, Masato; Yoshida, Naoki

    2015-06-01

    We study the impact of baryonic physics on cosmological parameter estimation with weak-lensing surveys. We run a set of cosmological hydrodynamics simulations with different galaxy formation models. We then perform ray-tracing simulations through the total matter density field to generate 100 independent convergence maps with a field of view of 25 {{deg }2}, and we use them to examine the ability of the following three lensing statistics as cosmological probes: power spectrum (PS), peak counts, and Minkowski functionals (MFs). For the upcoming wide-field observations, such as the Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of 1400 {{deg }2}, these three statistics provide tight constraints on the matter density, density fluctuation amplitude, and dark energy equation of state, but parameter bias is induced by baryonic processes such as gas cooling and stellar feedback. When we use PS, peak counts, and MFs, the magnitude of relative bias in the dark energy equation of state parameter w is at a level of, respectively, δ w∼ 0.017, 0.061, and 0.0011. For the HSC survey, these values are smaller than the statistical errors estimated from Fisher analysis. The bias could be significant when the statistical errors become small in future observations with a much larger survey area. We find that the bias is induced in different directions in the parameter space depending on the statistics employed. While the two-point statistic, i.e., PS, yields robust results against baryonic effects, the overall constraining power is weak compared with peak counts and MFs. On the other hand, using one of peak counts or MFs, or combined analysis with multiple statistics, results in a biased parameter estimate. The bias can be as large as 1σ for the HSC survey and will be more significant for upcoming wider-area surveys. We suggest to use an optimized combination so that the baryonic effects on parameter estimation are mitigated. Such a “calibrated” combination can

  16. FIRST SEASON QUIET OBSERVATIONS: MEASUREMENTS OF COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRA AT 43 GHz IN THE MULTIPOLE RANGE 25 {<=} l {<=} 475

    SciTech Connect

    Bischoff, C.; Brizius, A.; Buder, I.; Kusaka, A.; Smith, K. M.; Chinone, Y.; Cleary, K.; Reeves, R.; Dumoulin, R. N.; Newburgh, L. B.; Zwart, J. T. L.; Monsalve, R.; Bustos, R.; Naess, S. K.; Eriksen, H. K.; Wehus, I. K.; Zuntz, J. A.; Bronfman, L.; Church, S. E.; Dickinson, C.

    2011-11-10

    The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43 GHz and 94 GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the cosmic microwave background (CMB). QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, over 10,000 hr of data were collected, first with the 19 element 43 GHz array (3458 hr) and then with the 90 element 94 GHz array. Each array observes the same four fields, selected for low foregrounds, together covering Almost-Equal-To 1000 deg{sup 2}. This paper reports initial results from the 43 GHz receiver, which has an array sensitivity to CMB fluctuations of 69 {mu}K{radical}s. The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross-correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB, and EB power spectra in the multipole range l = 25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3{sigma} significance, the E-mode spectrum is consistent with the {Lambda}CDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r = 0.35{sup +1.06}{sub -0.87}. The combination of a new time-stream 'double-demodulation' technique, side-fed Dragonian optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r

  17. First Season QUIET Observations: Measurements of Cosmic Microwave Background Polarization Power Spectra at 43 GHz in the Multipole Range 25 <= ℓ <= 475

    NASA Astrophysics Data System (ADS)

    QUIET Collaboration; Bischoff, C.; Brizius, A.; Buder, I.; Chinone, Y.; Cleary, K.; Dumoulin, R. N.; Kusaka, A.; Monsalve, R.; Næss, S. K.; Newburgh, L. B.; Reeves, R.; Smith, K. M.; Wehus, I. K.; Zuntz, J. A.; Zwart, J. T. L.; Bronfman, L.; Bustos, R.; Church, S. E.; Dickinson, C.; Eriksen, H. K.; Ferreira, P. G.; Gaier, T.; Gundersen, J. O.; Hasegawa, M.; Hazumi, M.; Huffenberger, K. M.; Jones, M. E.; Kangaslahti, P.; Kapner, D. J.; Lawrence, C. R.; Limon, M.; May, J.; McMahon, J. J.; Miller, A. D.; Nguyen, H.; Nixon, G. W.; Pearson, T. J.; Piccirillo, L.; Radford, S. J. E.; Readhead, A. C. S.; Richards, J. L.; Samtleben, D.; Seiffert, M.; Shepherd, M. C.; Staggs, S. T.; Tajima, O.; Thompson, K. L.; Vanderlinde, K.; Williamson, R.; Winstein, B.

    2011-11-01

    The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43 GHz and 94 GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the cosmic microwave background (CMB). QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, over 10,000 hr of data were collected, first with the 19 element 43 GHz array (3458 hr) and then with the 90 element 94 GHz array. Each array observes the same four fields, selected for low foregrounds, together covering ≈1000 deg2. This paper reports initial results from the 43 GHz receiver, which has an array sensitivity to CMB fluctuations of 69 μK\\sqrt{s}. The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross-correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB, and EB power spectra in the multipole range \\ell = 25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3σ significance, the E-mode spectrum is consistent with the ΛCDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r = 0.35+1.06 -0.87. The combination of a new time-stream "double-demodulation" technique, side-fed Dragonian optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r = 0.1.

  18. Enhancing photovoltaic output power by 3-band spectrum-splitting and concentration using a diffractive micro-optic.

    PubMed

    Mohammad, Nabil; Wang, Peng; Friedman, Daniel J; Menon, Rajesh

    2014-10-20

    We report the enhancement of photovoltaic output power by separating the incident spectrum into 3 bands, and concentrating these bands onto 3 different photovoltaic cells. The spectrum-splitting and concentration is achieved via a thin, planar micro-optical element that demonstrates high optical efficiency over the entire spectrum of interest. The optic (which we call a polychromat) was designed using a modified version of the direct-binary-search algorithm. The polychromat was fabricated using grayscale lithography. Rigorous optical characterization demonstrates excellent agreement with simulation results. Electrical characterization of the solar cells made from GaInP, GaAs and Si indicate increase in the peak output power density of 43.63%, 30.84% and 30.86%, respectively when compared to normal operation without the polychromat. This represents an overall increase of 35.52% in output power density. The potential for cost-effective large-area manufacturing and for high system efficiencies makes our approach a strong candidate for low cost solar power. PMID:25607308

  19. Enhancing photovoltaic output power by 3-band spectrum-splitting and concentration using a diffractive micro-optic

    SciTech Connect

    Mohammad, Nabil; Wang, Peng; Friedman, Daniel J.; Menon, Rajesh

    2014-09-17

    We report the enhancement of photovoltaic output power by separating the incident spectrum into 3 bands, and concentrating these bands onto 3 different photovoltaic cells. The spectrum-splitting and concentration is achieved via a thin, planar micro-optical element that demonstrates high optical efficiency over the entire spectrum of interest. The optic (which we call a polychromat) was designed using a modified version of the direct-binary-search algorithm. The polychromat was fabricated using grayscale lithography. Rigorous optical characterization demonstrates excellent agreement with simulation results. Electrical characterization of the solar cells made from GaInP, GaAs and Si indicate increase in the peak output power density of 43.63%, 30.84% and 30.86%, respectively when compared to normal operation without the polychromat. This represents an overall increase of 35.52% in output power density. As a result, the potential for cost-effective large-area manufacturing and for high system efficiencies makes our approach a strong candidate for low cost solar power.

  20. Empirical covariance modeling for 21 cm power spectrum estimation: A method demonstration and new limits from early Murchison Widefield Array 128-tile data

    NASA Astrophysics Data System (ADS)

    Dillon, Joshua S.; Neben, Abraham R.; Hewitt, Jacqueline N.; Tegmark, Max; Barry, N.; Beardsley, A. P.; Bowman, J. D.; Briggs, F.; Carroll, P.; de Oliveira-Costa, A.; Ewall-Wice, A.; Feng, L.; Greenhill, L. J.; Hazelton, B. J.; Hernquist, L.; Hurley-Walker, N.; Jacobs, D. C.; Kim, H. S.; Kittiwisit, P.; Lenc, E.; Line, J.; Loeb, A.; McKinley, B.; Mitchell, D. A.; Morales, M. F.; Offringa, A. R.; Paul, S.; Pindor, B.; Pober, J. C.; Procopio, P.; Riding, J.; Sethi, S.; Shankar, N. Udaya; Subrahmanyan, R.; Sullivan, I.; Thyagarajan, Nithyanandan; Tingay, S. J.; Trott, C.; Wayth, R. B.; Webster, R. L.; Wyithe, S.; Bernardi, G.; Cappallo, R. J.; Deshpande, A. A.; Johnston-Hollitt, M.; Kaplan, D. L.; Lonsdale, C. J.; McWhirter, S. R.; Morgan, E.; Oberoi, D.; Ord, S. M.; Prabu, T.; Srivani, K. S.; Williams, A.; Williams, C. L.

    2015-06-01

    The separation of the faint cosmological background signal from bright astrophysical foregrounds remains one of the most daunting challenges of mapping the high-redshift intergalactic medium with the redshifted 21 cm line of neutral hydrogen. Advances in mapping and modeling of diffuse and point source foregrounds have improved subtraction accuracy, but no subtraction scheme is perfect. Precisely quantifying the errors and error correlations due to missubtracted foregrounds allows for both the rigorous analysis of the 21 cm power spectrum and for the maximal isolation of the "EoR window" from foreground contamination. We present a method to infer the covariance of foreground residuals from the data itself in contrast to previous attempts at a priori modeling. We demonstrate our method by setting limits on the power spectrum using a 3 h integration from the 128-tile Murchison Widefield Array. Observing between 167 and 198 MHz, we find at 95% confidence a best limit of Δ2(k )<3.7 ×104 mK2 at comoving scale k =0.18 h Mpc-1 and at z =6.8 , consistent with existing limits.

  1. A Novel Wireless Power Transfer-Based Weighed Clustering Cooperative Spectrum Sensing Method for Cognitive Sensor Networks

    PubMed Central

    Liu, Xin

    2015-01-01

    In a cognitive sensor network (CSN), the wastage of sensing time and energy is a challenge to cooperative spectrum sensing, when the number of cooperative cognitive nodes (CNs) becomes very large. In this paper, a novel wireless power transfer (WPT)-based weighed clustering cooperative spectrum sensing model is proposed, which divides all the CNs into several clusters, and then selects the most favorable CNs as the cluster heads and allows the common CNs to transfer the received radio frequency (RF) energy of the primary node (PN) to the cluster heads, in order to supply the electrical energy needed for sensing and cooperation. A joint resource optimization is formulated to maximize the spectrum access probability of the CSN, through jointly allocating sensing time and clustering number. According to the resource optimization results, a clustering algorithm is proposed. The simulation results have shown that compared to the traditional model, the cluster heads of the proposed model can achieve more transmission power and there exists optimal sensing time and clustering number to maximize the spectrum access probability. PMID:26528987

  2. A Novel Wireless Power Transfer-Based Weighed Clustering Cooperative Spectrum Sensing Method for Cognitive Sensor Networks.

    PubMed

    Liu, Xin

    2015-01-01

    In a cognitive sensor network (CSN), the wastage of sensing time and energy is a challenge to cooperative spectrum sensing, when the number of cooperative cognitive nodes (CNs) becomes very large. In this paper, a novel wireless power transfer (WPT)-based weighed clustering cooperative spectrum sensing model is proposed, which divides all the CNs into several clusters, and then selects the most favorable CNs as the cluster heads and allows the common CNs to transfer the received radio frequency (RF) energy of the primary node (PN) to the cluster heads, in order to supply the electrical energy needed for sensing and cooperation. A joint resource optimization is formulated to maximize the spectrum access probability of the CSN, through jointly allocating sensing time and clustering number. According to the resource optimization results, a clustering algorithm is proposed. The simulation results have shown that compared to the traditional model, the cluster heads of the proposed model can achieve more transmission power and there exists optimal sensing time and clustering number to maximize the spectrum access probability. PMID:26528987

  3. POWER ASYMMETRY IN COSMIC MICROWAVE BACKGROUND FLUCTUATIONS FROM FULL SKY TO SUB-DEGREE SCALES: IS THE UNIVERSE ISOTROPIC?

    SciTech Connect

    Hansen, F. K.; Eriksen, H. K.; Lilje, P. B.; Banday, A. J.; Gorski, K. M. E-mail: h.k.k.eriksen@astro.uio.n E-mail: banday@MPA-Garching.MPG.D

    2009-10-20

    We repeat and extend the analysis of Eriksen et al. and Hansen et al., testing the isotropy of the cosmic microwave background fluctuations. We find that the hemispherical power asymmetry previously reported for the largest scales l = 2-40 extends to much smaller scales. In fact, for the full multipole range l = 2-600, significantly more power is found in the hemisphere centered at (theta = 107{sup 0} +- 10{sup 0}, phi = 226{sup 0} +- 10{sup 0}) in galactic co-latitude and longitude than in the opposite hemisphere, consistent with the previously detected direction of asymmetry for l = 2-40. We adopt a model selection test where the direction and amplitude of asymmetry, as well as the multipole range, are free parameters. A model with an asymmetric distribution of power for l = 2-600 is found to be preferred over the isotropic model at the 0.4% significance level, taking into account the additional parameters required to describe it. A similar direction of asymmetry is found independently in all six subranges of 100 multipoles between l = 2-600. None of our 9800 isotropic simulated maps show a similarly consistent direction of asymmetry over such a large multipole range. No known systematic effects or foregrounds are found to be able to explain the asymmetry.

  4. Measuring the 21 cm Power Spectrum from the Epoch of Reionization with the Giant Metrewave Radio Telescope

    NASA Astrophysics Data System (ADS)

    Paciga, Gregory

    The Epoch of Reionization (EoR) is the transitional period in the universe's evolution which starts when the first luminous sources begin to ionize the intergalactic medium for the first time since recombination, and ends when the most of the hydrogen is ionized by about a redshift of 6. Observations of the 21cm emission from hyperfine splitting of the hydrogen atom can carry a wealth of cosmological information from this epoch since the redshifted line can probe the entire volume. The GMRT-EoR experiment is an ongoing effort to make a statistical detection of the power spectrum of 21cm neutral hydrogen emission due to the patchwork of neutral and ionized regions present during the transition. In this work we detail approximately five years of observations at the GMRT, comprising over 900 hours, and an in-depth analysis of about 50 hours which have lead to the first upper limits on the 21cm power spectrum in the range z = 8.1 to 9.2. This includes a concentrated radio frequency interference (RFI) mitigation campaign around the GMRT area, a novel method for removing broadband RFI with a singular value decomposition, and calibration with a pulsar as both a phase and polarization calibrator. Preliminary results from 2011 showed a 2-sigma upper limit to the power spectrum of (70 mK). 2. However, we find that foreground removalstrategies tend to reduce the cosmological signal significantly, and modeling this signal loss is crucial for interpretation of power spectrum measurements. Using a simulated signal to estimate the transfer function of the real 21cm signal through the foreground removal procedure, we are able to find the optimal level of foreground removal and correct for the signal loss. Using this correction, we report a 2-sigma upper limit of (248 mK)2 at k = 0.5 h Mpc-1.

  5. What next-generation 21 cm power spectrum measurements can teach us about the epoch of reionization

    SciTech Connect

    Pober, Jonathan C.; Morales, Miguel F.; Liu, Adrian; McQuinn, Matthew; Parsons, Aaron R.; Dillon, Joshua S.; Hewitt, Jacqueline N.; Tegmark, Max; Aguirre, James E.; Bowman, Judd D.; Jacobs, Daniel C.; Bradley, Richard F.; Carilli, Chris L.; DeBoer, David R.; Werthimer, Dan J.

    2014-02-20

    A number of experiments are currently working toward a measurement of the 21 cm signal from the epoch of reionization (EoR). Whether or not these experiments deliver a detection of cosmological emission, their limited sensitivity will prevent them from providing detailed information about the astrophysics of reionization. In this work, we consider what types of measurements will be enabled by the next generation of larger 21 cm EoR telescopes. To calculate the type of constraints that will be possible with such arrays, we use simple models for the instrument, foreground emission, and the reionization history. We focus primarily on an instrument modeled after the ∼0.1 km{sup 2} collecting area Hydrogen Epoch of Reionization Array concept design and parameterize the uncertainties with regard to foreground emission by considering different limits to the recently described 'wedge' footprint in k space. Uncertainties in the reionization history are accounted for using a series of simulations that vary the ionizing efficiency and minimum virial temperature of the galaxies responsible for reionization, as well as the mean free path of ionizing photons through the intergalactic medium. Given various combinations of models, we consider the significance of the possible power spectrum detections, the ability to trace the power spectrum evolution versus redshift, the detectability of salient power spectrum features, and the achievable level of quantitative constraints on astrophysical parameters. Ultimately, we find that 0.1 km{sup 2} of collecting area is enough to ensure a very high significance (≳ 30σ) detection of the reionization power spectrum in even the most pessimistic scenarios. This sensitivity should allow for meaningful constraints on the reionization history and astrophysical parameters, especially if foreground subtraction techniques can be improved and successfully implemented.

  6. A computer program for estimating the power-density spectrum of advanced continuous simulation language generated time histories

    NASA Technical Reports Server (NTRS)

    Dunn, H. J.

    1981-01-01

    A computer program for performing frequency analysis of time history data is presented. The program uses circular convolution and the fast Fourier transform to calculate power density spectrum (PDS) of time history data. The program interfaces with the advanced continuous simulation language (ACSL) so that a frequency analysis may be performed on ACSL generated simulation variables. An example of the calculation of the PDS of a Van de Pol oscillator is presented.

  7. Enhancing photovoltaic output power by 3-band spectrum-splitting and concentration using a diffractive micro-optic

    DOE PAGESBeta

    Mohammad, Nabil; Wang, Peng; Friedman, Daniel J.; Menon, Rajesh

    2014-09-17

    We report the enhancement of photovoltaic output power by separating the incident spectrum into 3 bands, and concentrating these bands onto 3 different photovoltaic cells. The spectrum-splitting and concentration is achieved via a thin, planar micro-optical element that demonstrates high optical efficiency over the entire spectrum of interest. The optic (which we call a polychromat) was designed using a modified version of the direct-binary-search algorithm. The polychromat was fabricated using grayscale lithography. Rigorous optical characterization demonstrates excellent agreement with simulation results. Electrical characterization of the solar cells made from GaInP, GaAs and Si indicate increase in the peak output powermore » density of 43.63%, 30.84% and 30.86%, respectively when compared to normal operation without the polychromat. This represents an overall increase of 35.52% in output power density. As a result, the potential for cost-effective large-area manufacturing and for high system efficiencies makes our approach a strong candidate for low cost solar power.« less

  8. A method for evaluating the expectation value of a power spectrum using the probability density function of phases

    SciTech Connect

    Caliandro, G.A.; Torres, D.F.; Rea, N. E-mail: dtorres@aliga.ieec.uab.es

    2013-07-01

    Here, we present a new method to evaluate the expectation value of the power spectrum of a time series. A statistical approach is adopted to define the method. After its demonstration, it is validated showing that it leads to the known properties of the power spectrum when the time series contains a periodic signal. The approach is also validated in general with numerical simulations. The method puts into evidence the importance that is played by the probability density function of the phases associated to each time stamp for a given frequency, and how this distribution can be perturbed by the uncertainties of the parameters in the pulsar ephemeris. We applied this method to solve the power spectrum in the case the first derivative of the pulsar frequency is unknown and not negligible. We also undertook the study of the most general case of a blind search, in which both the frequency and its first derivative are uncertain. We found the analytical solutions of the above cases invoking the sum of Fresnel's integrals squared.

  9. The cosmic microwave background radiation

    NASA Technical Reports Server (NTRS)

    Silk, Joseph

    1992-01-01

    A review the implications of the spectrum and anisotropy of the cosmic microwave background for cosmology. Thermalization and processes generating spectral distortions are discussed. Anisotropy predictions are described and compared with observational constraints. If the evidence for large-scale power in the galaxy distribution in excess of that predicted by the cold dark matter model is vindicated, and the observed structure originated via gravitational instabilities of primordial density fluctuations, the predicted amplitude of microwave background anisotropies on angular scales of a degree and larger must be at least several parts in 10 exp 6.

  10. Gravitino decay and the cosmic gamma-ray background

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1986-01-01

    It is argued that the cosmic gamma-ray background (CGB) spectrum does not exhibit evidence for the decay of light gravitinos, in contradiction to the suggestion by Olive and Silk (1985), who observed a bump near 1 MeV in the CGB radiation spectrum. It is suggested that better fits to the CGB spectrum would be provided by mechanisms generating a power-law spectrum which is flattened below about 2 MeV. Olive and Silk maintain that the decays of a long-lived particle such as the gravitino may be responsible for features in the gamma-ray spectrum near 1 MeV.

  11. A new measurement of the cosmic ray energy spectrum between 3 x 10 to the 15th power eV and 3 x 10 to the 16th power eV

    NASA Technical Reports Server (NTRS)

    Gregory, A. G.; Patterson, J. R.; Protheroe, R. J.

    1985-01-01

    A new Cerenkov photon density spectrum measurement is reported. The derivation of the primary cosmic ray energy spectrum for energies from 3x10 to the 15th power eV to 3x10 to the 16th power eV are presented.

  12. Inflation with primordial broken power law spectrum as an alternative to the concordance cosmological model

    SciTech Connect

    Pandolfi, Stefania; Giusarma, Elena; Lattanzi, Massimiliano; Melchiorri, Alessandro

    2010-05-15

    We consider cosmological models with a non-scale-invariant spectrum of primordial perturbations and assess whether they represent a viable alternative to the concordance {Lambda}CDM model. We find that in the framework of a model selection analysis, the WMAP and 2dF data do not provide any conclusive evidence in favor of one or the other kind of model. However, when a marginalization over the entire space of nuisance parameters is performed, models with a modified primordial spectrum and {Omega}{sub {Lambda}=}0 are strongly disfavored.

  13. High-z objects and cold dark matter cosmogonies - Constraints on the primordial power spectrum on small scales

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.

    1993-01-01

    Modified cold dark matter (CDM) models were recently suggested to account for large-scale optical data, which fix the power spectrum on large scales, and the COBE results, which would then fix the bias parameter, b. We point out that all such models have deficit of small-scale power where density fluctuations are presently nonlinear, and should then lead to late epochs of collapse of scales M between 10 exp 9 - 10 exp 10 solar masses and (1-5) x 10 exp 14 solar masses. We compute the probabilities and comoving space densities of various scale objects at high redshifts according to the CDM models and compare these with observations of high-z QSOs, high-z galaxies and the protocluster-size object found recently by Uson et al. (1992) at z = 3.4. We show that the modified CDM models are inconsistent with the observational data on these objects. We thus suggest that in order to account for the high-z objects, as well as the large-scale and COBE data, one needs a power spectrum with more power on small scales than CDM models allow and an open universe.

  14. Temperature and strain measurements using the power, line-width, shape, and frequency shift of the Brillouin loss spectrum

    NASA Astrophysics Data System (ADS)

    Bao, Xiaoyi; Smith, Jeffrey; Brown, Anthony W.

    2002-09-01

    A Brillouin scattering based fiber sensor system has been developed by our Fiber Optics Group for the structural monitoring and civil engineering related applications. In this paper, the Brillouin loss spectrum has been characterized in terms of its center frequency, peak power, line-width and shape. These parameters have been considered as a function of the input pump and probe laser powers, the pump pulse duration, strain and temperature. The measurement accuracy has been studied at different Brillouin frequency steps to study the uncertainty of the Brillouin frequency, line-width, peak power and shape factor vs. signal to noise ratio, so that we can optimize the system performance. Characterization of the Brillouin loss spectrum led to the development of an innovative technique to measure the strain and temperature simultaneously using the strain and temperature dependence on the peak power in conjunction with the Brillouin frequency for the single mode fiber with 3m spatial resolution, 3°C temperature resolution and 200 me (mm/m) strain accuracy.

  15. Advanced Condenser Boosts Geothermal Power Plant Output (Fact Sheet), The Spectrum of Clean Energy Innovation

    SciTech Connect

    Not Available

    2010-12-01

    When power production at The Geysers geothermal power complex began to falter, the National Renewable Energy Laboratory (NREL) stepped in, developing advanced condensing technology that dramatically boosted production efficiency - and making a major contribution to the effective use of geothermal power. NREL developed advanced direct-contact condenser (ADCC) technology to condense spent steam more effectively, improving power production efficiency in Unit 11 by 5%.

  16. Sensitivity of Cosmic-Ray Proton Spectra to the Low-wavenumber Behavior of the 2D Turbulence Power Spectrum

    NASA Astrophysics Data System (ADS)

    Engelbrecht, N. E.; Burger, R. A.

    2015-12-01

    In this study, a novel ab initio cosmic ray (CR) modulation code that solves a set of stochastic transport equations equivalent to the Parker transport equation, and that uses output from a turbulence transport code as input for the diffusion tensor, is introduced. This code is benchmarked with a previous approach to ab initio modulation. The sensitivity of computed galactic CR proton spectra at Earth to assumptions made as to the low-wavenumber behavior of the two-dimensional (2D) turbulence power spectrum is investigated using perpendicular mean free path expressions derived from two different scattering theories. Constraints on the low-wavenumber behavior of the 2D power spectrum are inferred from the qualitative comparison of computed CR spectra with spacecraft observations at Earth. Another key difference from previous studies is that observed and inferred CR intensity spectra at 73 AU are used as boundary spectra instead of the usual local interstellar spectrum. Furthermore, the results presented here provide a tentative explanation as to the reason behind the unusually high galactic proton intensity spectra observed in 2009 during the recent unusual solar minimum.

  17. The Power of Positivity: Predictors of Relationship Satisfaction for Parents of Children with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Ekas, Naomi V.; Timmons, Lisa; Pruitt, Megan; Ghilain, Christine; Alessandri, Michael

    2015-01-01

    The current study uses the actor-partner interdependence model to examine the predictors of relationship satisfaction for mothers and fathers of children with autism spectrum disorder. Sixty-seven couples completed measures of optimism, benefit finding, coping strategies, social support, and relationship satisfaction. Results indicated that…

  18. Harnessing the Power of Play: Opportunities for Children with Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Mastrangelo, Sonia

    2009-01-01

    Play is a complex phenomenon that occurs naturally for most children; they move through the various stages of play development and are able to add complexity, imagination, and creativity to their thought processes and actions. However, for many children with autism spectrum disorders (ASD), the various stages of play never truly develop, or occur…

  19. Oscillation in power spectrum of primordial gravitational wave as a signature of higher-order stringy corrections

    NASA Astrophysics Data System (ADS)

    Cai, Yong; Wang, Yu-Tong; Piao, Yun-Song

    2016-02-01

    In low-energy effective string theory, α' corrections involve the coupling of the dilaton field to Gauss-Bonnet term. We assume that the dilaton potential is fine tuned so that the dilaton field may oscillate rapidly for a while around the minimum of its potential but the inflation background is not affected. By numerical method, we find that if the dilaton starts to oscillate at the time of about ˜ 60 e-folds before the end of inflation, α' correction may bring unusual oscillations to the inflationary gravitational wave spectrum, which might be measurably imprinted in the CMB B-mode polarization.

  20. Featuring the primordial power spectrum: New constraints on interrupted slow-roll from CMB and LRG data

    NASA Astrophysics Data System (ADS)

    Benetti, Micol; Pandolfi, Stefania; Lattanzi, Massimiliano; Martinelli, Matteo; Melchiorri, Alessandro

    2013-01-01

    Using the most recent data from the WMAP, ACT and SPT experiments, we update the constraints on models with oscillatory features in the primordial power spectrum of scalar perturbations. This kind of features can appear in models of inflation where slow-roll is interrupted, like multifield models. We also derive constraints for the case in which, in addition to cosmic microwave observations, we also consider the data on the spectrum of luminous red galaxies from the 7th SDSS catalog, and the SNIa Union Compilation 2 data. We have found that: (i) considering a model with features in the primordial power spectrum increases the agreement with data compared to the featureless “vanilla” ΛCDM model by Δχ2=6.7, representing an improvement with respect to the expected value Δχ2=3 for an equivalent model with three additional parameters; (ii) the uncertainty on the determination of the standard parameters is not degraded when features are included; (iii) the best fit for the features model locates the step in the primordial spectrum at a scale k≃0.005Mpc-1, corresponding to the scale where the outliers in the WMAP7 data at ℓ=22 and ℓ=40 are located.; (iv) a distinct, albeit less statistically significant peak is present in the likelihood at smaller scales, whose presence might be related to the WMAP7 preference for a negative value of the running of the scalar spectral index parameter; (v) the inclusion of the LRG-7 data does not change significantly the best fit model, but allows to better constrain the amplitude of the oscillations.

  1. Murder on the mind: tyranical power and other points along the perverse spectrum.

    PubMed

    Tuch, Richard

    2010-02-01

    This paper illustrates the breadth and depth of the spectrum of perversion and perversity as currently represented in the psychoanalytic literature, raises questions about recent tendencies to include a host of diverse-seeming phenomena under the same conceptual umbrella, and strives to demonstrate what these phenomena have in common that justifies lumping them together under the same rubric. One end of this spectrum is represented by the employment of simple fetishes introduced into a sexual scene in order to promote sexual arousal. Moving along the continuum, one encounters increasing complex behavioral patterns including the enactment of scripts that actualize one's perverse fantasies, including the assumption of complementary roles (e.g. sadomasochism) that equally serve the needs, and represent the desires, of both parties involved. A unique clinical entity, 'perverse modes of relatedness,' lies on the extreme end of the spectrum, representing the reification of the relationship as it becomes little more than a vehicle to take possession and control one's object for the gratification of one's sole needs and desires. What each of these phenomena share in common is both the insertion of a thing or condition - ranging from a simple fetishistic object to an elaborate style of relating that reduces the other into pawn played upon the pervert's chessboard, between the two 'relating' objects as well as a less than honest relationship with reality. PMID:20433479

  2. Signatures of modified gravity on the 21 cm power spectrum at reionisation

    SciTech Connect

    Brax, Philippe

    2013-01-01

    Scalar modifications of gravity have an impact on the growth of structure. Baryon and Cold Dark Matter (CDM) perturbations grow anomalously for scales within the Compton wavelength of the scalar field. In the late time Universe when reionisation occurs, the spectrum of the 21 cm brightness temperature is thus affected. We study this effect for chameleon-f(R) models, dilatons and symmetrons. Although the f(R) models are more tightly constrained by solar system bounds, and effects on dilaton models are negligible, we find that symmetrons where the phase transition occurs before z{sub *} ∼ 12 could be detectable for a scalar field range as low as 5kpc. For all these models, the detection prospects of modified gravity effects are higher when considering modes parallel to the line of sight where very small scales can be probed. The study of the 21 cm spectrum thus offers a complementary approach to testing modified gravity with large scale structure surveys. Short scales, which would be highly non-linear in the very late time Universe when structure forms and where modified gravity effects are screened, appear in the linear spectrum of 21 cm physics, hence deviating from General Relativity in a maximal way.

  3. A SENSITIVITY AND ARRAY-CONFIGURATION STUDY FOR MEASURING THE POWER SPECTRUM OF 21 cm EMISSION FROM REIONIZATION

    SciTech Connect

    Parsons, Aaron; Pober, Jonathan; McQuinn, Matthew; Jacobs, Daniel; Aguirre, James

    2012-07-01

    Telescopes aiming to measure 21 cm emission from the Epoch of Reionization must toe a careful line, balancing the need for raw sensitivity against the stringent calibration requirements for removing bright foregrounds. It is unclear what the optimal design is for achieving both of these goals. Via a pedagogical derivation of an interferometer's response to the power spectrum of 21 cm reionization fluctuations, we show that even under optimistic scenarios first-generation arrays will yield low-signal-to-noise detections, and that different compact array configurations can substantially alter sensitivity. We explore the sensitivity gains of array configurations that yield high redundancy in the uv-plane-configurations that have been largely ignored since the advent of self-calibration for high-dynamic-range imaging. We first introduce a mathematical framework to generate optimal minimum-redundancy configurations for imaging. We contrast the sensitivity of such configurations with high-redundancy configurations, finding that high-redundancy configurations can improve power-spectrum sensitivity by more than an order of magnitude. We explore how high-redundancy array configurations can be tuned to various angular scales, enabling array sensitivity to be directed away from regions of the uv-plane (such as the origin) where foregrounds are brighter and instrumental systematics are more problematic. We demonstrate that a 132 antenna deployment of the Precision Array for Probing the Epoch of Reionization observing for 120 days in a high-redundancy configuration will, under ideal conditions, have the requisite sensitivity to detect the power spectrum of the 21 cm signal from reionization at a 3{sigma} level at k < 0.25 h Mpc{sup -1} in a bin of {Delta}ln k = 1. We discuss the tradeoffs of low- versus high-redundancy configurations.

  4. Relative Power of Specific EEG Bands and Their Ratios during Neurofeedback Training in Children with Autism Spectrum Disorder

    PubMed Central

    Wang, Yao; Sokhadze, Estate M.; El-Baz, Ayman S.; Li, Xiaoli; Sears, Lonnie; Casanova, Manuel F.; Tasman, Allan

    2016-01-01

    Neurofeedback is a mode of treatment that is potentially useful for improving self-regulation skills in persons with autism spectrum disorder. We proposed that operant conditioning of EEG in neurofeedback mode can be accompanied by changes in the relative power of EEG bands. However, the details on the change of the relative power of EEG bands during neurofeedback training course in autism are not yet well explored. In this study, we analyzed the EEG recordings of children diagnosed with autism and enrolled in a prefrontal neurofeedback treatment course. The protocol used in this training was aimed at increasing the ability to focus attention, and the procedure represented the wide band EEG amplitude suppression training along with upregulation of the relative power of gamma activity. Quantitative EEG analysis was completed for each session of neurofeedback using wavelet transform to determine the relative power of gamma and theta/beta ratio, and further to detect the statistical changes within and between sessions. We found a linear decrease of theta/beta ratio and a liner increase of relative power of gamma activity over 18 weekly sessions of neurofeedback in 18 high functioning children with autism. The study indicates that neurofeedback is an effective method for altering EEG characteristics associated with the autism spectrum disorder. Also, it provides information about specific changes of EEG activities and details the correlation between changes of EEG and neurofeedback indexes during the course of neurofeedback. This pilot study contributes to the development of more effective approaches to EEG data analysis during prefrontal neurofeedback training in autism. PMID:26834615

  5. Possibility of precise measurement of the cosmological power spectrum with a dedicated survey of 21 cm emission after reionization.

    PubMed

    Loeb, Abraham; Wyithe, J Stuart B

    2008-04-25

    Measurements of the 21 cm line emission by residual cosmic hydrogen after reionization can be used to trace the power spectrum of density perturbations through a significant fraction of the observable volume of the Universe. We show that a dedicated 21 cm observatory could probe a number of independent modes that is 2 orders of magnitude larger than currently available, and enable a cosmic-variance limited detection of the signature of a neutrino mass approximately 0.05 eV. The evolution of the linear growth factor with redshift could also constrain exotic theories of gravity or dark energy to an unprecedented precision. PMID:18518181

  6. Power spectrum and fractal dimension of laser backscattering from the ocean.

    PubMed

    Churnside, James H; Wilson, James J

    2006-11-01

    We flew an airborne lidar perpendicular to the coastline along straight-line transects that varied in length between 230 and 280 km. The sample spacing was approximately 3 m, so we sampled almost five decades of spatial scales. Except for the return from right at the surface, the power spectra of backscattered power had a power-law dependence on spatial frequency, with a slope of approximately 1.49. This corresponds to a fractal dimension of 1.76. This implies that the distribution is not as patchy as that of a purely turbulent process. PMID:17047710

  7. Self-organized perturbations enhance class IV behavior and 1/f power spectrum in elementary cellular automata.

    PubMed

    Nakajima, Kohei; Haruna, Taichi

    2011-09-01

    In this paper, we propose a new class of cellular automata based on the modification of its state space. It is introduced to model a computation which is exposed to an environment. We formalized the computation as extension and projection processes of its state space and resulting misidentifications of the state. This is motivated to embed the role of an environment into the system itself, which naturally induces self-organized internal perturbations rather than the usual external perturbations. Implementing this structure into the elementary cellular automata, we characterized its effect by means of input entropy and power spectral analysis. As a result, the cellular automata with this structure showed robust class IV behavior and a 1/f power spectrum in a wide range of rule space comparative to the notion of the edge of chaos. PMID:21600265

  8. Components Makeover Gives Concentrating Solar Power a Boost (Fact Sheet), The Spectrum of Clean Energy Innovation

    SciTech Connect

    Not Available

    2010-12-01

    Parabolic trough technology is the most mature of the various concentrating solar power (CSP) options. But scientists at the National Renewable Energy Laboratory (NREL) continue to make advances on trough systems through innovative research on various components in industrial partnerships with Acciona Solar Power, SkyFuel, Schott Solar, and others. The results are leading to improved system efficiencies and lower costs for CSP plants.

  9. Sample Entropy Tracks Changes in EEG Power Spectrum With Sleep State and Aging

    PubMed Central

    Bruce, Eugene N.; Bruce, Margaret C.; Vennelaganti, Swetha

    2009-01-01

    The regularity of EEG signals was compared between middle-aged (47.2 ± 2.0 yrs) and elderly (78.4 ± 3.8 yrs) female subjects in Wake (W), NREM stages 2 and 3 (S2, S3), and REM. Signals from C3A2 leads of healthy normal subjects, acquired from polysomnograms obtained from the Sleep Heart Health Study, were analyzed using both Sample Entropy (SaEn) and power spectral analysis (delta, theta, alpha, and beta frequency band powers). SaEn changed systematically and significantly (p<0.001) with sleep state in both age groups, following the relationships W > REM > S2 > S3. SaEn was found to be negatively correlated with delta power and positively correlated with beta power. Small changes in SaEn appear to reflect changes in spectral content rather than changes in regularity of the signal. A better predictor of SaEn than the frequency band powers was the logarithm of the power ratio (alpha+beta)/(delta+theta). Thus, SaEn appears to reflect the balance between sleep-promoting and alertness-promoting mechanisms. SaEn of the elderly was larger than that of middle-aged subjects in S2 (p=0.029) and REM (p=0.001), suggesting that cortical state is shifted towards alertness in elderly subjects in these sleep states compared to middle-aged. PMID:19590434

  10. Imprints of spherical nontrivial topologies on the cosmic microwave background.

    PubMed

    Niarchou, Anastasia; Jaffe, Andrew

    2007-08-24

    The apparent low power in the cosmic microwave background (CMB) temperature anisotropy power spectrum derived from the Wilkinson Microwave Anisotropy Probe motivated us to consider the possibility of a nontrivial topology. We focus on simple spherical multiconnected manifolds and discuss their implications for the CMB in terms of the power spectrum, maps, and the correlation matrix. We perform a Bayesian model comparison against the fiducial best-fit cold dark matter model with a cosmological constant based both on the power spectrum and the correlation matrix to assess their statistical significance. We find that the first-year power spectrum shows a slight preference for the truncated cube space, but the three-year data show no evidence for any of these spaces. PMID:17930937

  11. Tapering the sky response for angular power spectrum estimation from low-frequency radio-interferometric data

    PubMed Central

    Choudhuri, Samir; Bharadwaj, Somnath; Roy, Nirupam; Ghosh, Abhik; Ali, Sk. Saiyad

    2016-01-01

    It is important to correctly subtract point sources from radio-interferometric data in order to measure the power spectrum of diffuse radiation like the Galactic synchrotron or the Epoch of Reionization 21-cm signal. It is computationally very expensive and challenging to image a very large area and accurately subtract all the point sources from the image. The problem is particularly severe at the sidelobes and the outer parts of the main lobe where the antenna response is highly frequency dependent and the calibration also differs from that of the phase centre. Here, we show that it is possible to overcome this problem by tapering the sky response. Using simulated 150 MHz observations, we demonstrate that it is possible to suppress the contribution due to point sources from the outer parts by using the Tapered Gridded Estimator to measure the angular power spectrum Cℓ of the sky signal. We also show from the simulation that this method can self-consistently compute the noise bias and accurately subtract it to provide an unbiased estimation of Cℓ. PMID:27274703

  12. Non-Gaussian covariance of the matter power spectrum in the effective field theory of large scale structure

    NASA Astrophysics Data System (ADS)

    Bertolini, Daniele; Schutz, Katelin; Solon, Mikhail P.; Walsh, Jonathan R.; Zurek, Kathryn M.

    2016-06-01

    We compute the non-Gaussian contribution to the covariance of the matter power spectrum at one-loop order in standard perturbation theory (SPT), using the framework of the effective field theory (EFT) of large scale structure (LSS). The complete one-loop contributions are evaluated for the first time, including the leading EFT corrections that involve seven independent operators, of which four appear in the power spectrum and bispectrum. We compare the non-Gaussian part of the one-loop covariance computed with both SPT and EFT of LSS to two separate simulations. In one simulation, we find that the one-loop prediction from SPT reproduces the simulation well to ki+kj˜0.25 h /Mpc , while in the other simulation we find a substantial improvement of EFT of LSS (with one free parameter) over SPT, more than doubling the range of k where the theory accurately reproduces the simulation. The disagreement between these two simulations points to unaccounted for systematics, highlighting the need for improved numerical and analytic understanding of the covariance.

  13. Calibration Requirements for Detecting the 21 cm Epoch of Reionization Power Spectrum and Implications for the SKA

    NASA Astrophysics Data System (ADS)

    Barry, N.; Hazelton, B.; Sullivan, I.; Morales, M. F.; Pober, J. C.

    2016-06-01

    21 cm Epoch of Reionization observations promise to transform our understanding of galaxy formation, but these observations are impossible without unprecedented levels of instrument calibration. We present end-to-end simulations of a full EoR power spectrum analysis including all of the major components of a real data processing pipeline: models of astrophysical foregrounds and EoR signal, frequency-dependent instrument effects, sky-based antenna calibration, and the full PS analysis. This study reveals that traditional sky-based per-frequency antenna calibration can only be implemented in EoR measurement analyses if the calibration model is unrealistically accurate. For reasonable levels of catalogue completeness, the calibration introduces contamination in otherwise foreground-free power spectrum modes, precluding a PS measurement. We explore the origin of this contamination and potential mitigation techniques. We show that there is a strong joint constraint on the precision of the calibration catalogue and the inherent spectral smoothness of antennae, and that this has significant implications for the instrumental design of the SKA and other future EoR observatories.

  14. Tapering the sky response for angular power spectrum estimation from low-frequency radio-interferometric data

    NASA Astrophysics Data System (ADS)

    Choudhuri, Samir; Bharadwaj, Somnath; Roy, Nirupam; Ghosh, Abhik; Ali, Sk. Saiyad

    2016-06-01

    It is important to correctly subtract point sources from radio-interferometric data in order to measure the power spectrum of diffuse radiation like the Galactic synchrotron or the Epoch of Reionization 21-cm signal. It is computationally very expensive and challenging to image a very large area and accurately subtract all the point sources from the image. The problem is particularly severe at the sidelobes and the outer parts of the main lobe where the antenna response is highly frequency dependent and the calibration also differs from that of the phase centre. Here, we show that it is possible to overcome this problem by tapering the sky response. Using simulated 150 MHz observations, we demonstrate that it is possible to suppress the contribution due to point sources from the outer parts by using the Tapered Gridded Estimator to measure the angular power spectrum Cℓ of the sky signal. We also show from the simulation that this method can self-consistently compute the noise bias and accurately subtract it to provide an unbiased estimation of Cℓ.

  15. Participation Weight Estimation in Power Oscillation Mode based on Synchronized Phasor Measurements and Auto-spectrum Analysis

    NASA Astrophysics Data System (ADS)

    Li, Changsong; Watanabe, Masayuki; Mitani, Yasunori; Monchusi, Bessie

    In order to effectively monitor and control the interarea oscillations in a power system, it is crucial to obtain the full knowledge about the oscillation mode, such as participation level, mode distribution, frequency and damping. The paper presents an approach to estimate the participation weight of a generator in an oscillation mode based on synchronized phasor measurements and auto-spectrum analysis. The participation weight is a quantity defined in this paper to indicate the relative participation of one generator in one oscillation mode of interest. Compared to traditional participation factor computed from model-based modal analysis, the participation weight is directly defined and estimated based on the measurements of system output signals. The input-output relationship for a constant-parameter linear system when subjected to a stationary white noise disturbance is introduced to establish connection between measureable power system response quantities and participation weight. The auto-spectrum analysis is adopted to estimate participation weight with demonstrative examples, which include simulation examples as well as practical examples using measured phasor data from the CampusWAMS.

  16. Crater shape and size-frequency distribution in determining the topographic power spectrum of a cratered surface

    NASA Astrophysics Data System (ADS)

    Rosenburg, M. A.; Aharonson, O.; Smith, D. E.; Zuber, M. T.; Zhang, X.

    2010-12-01

    The statistical properties of a heavily cratered planetary surface reflect several factors that govern its formation and subsequent modification: the size-frequency distribution of impactors, the corresponding distribution of crater sizes, crater morphology, and downslope movement of material on steep slopes. We develop and apply a new cratered terrain-generating model to study the relative contributions of the crater size-frequency distribution and crater shape to the power spectral density of a surface that accumulates impacts. By monitoring surviving rim fragments through time, we derive the relationship between the size-frequency distribution of observable craters and its production function, whose slope we vary. This permits us to explore the criteria for equilibrium. Further, we examine the effects of changes in crater morphology with size—the transition from simple to complex crater shapes, as well as the appearance of complex features such as central peaks, peak rings, and wall terraces—on the slope of the power spectrum, utilizing the new global topography dataset provided by the Lunar Orbiter Laser Altimeter (LOLA) to characterize the power spectra of several lunar craters. Finally, we compare our findings on the dependencies of the power spectral slope to the observed roughness properties at several length scales of lunar terrains in various stages of saturation, from young maria to ancient highlands.

  17. [Slow alpha in the EEG power spectrum as an indicator for conceptual arousal].

    PubMed

    Bösel, R

    1992-01-01

    Based on previous findings (Bösel et al., 1990) it was assumed that in concept learning tasks generating on hypotheses on a concept which has to be developed is accompanied by increases of the Alpha 1 power (7.5-10 Hz) in the spontaneous EEG activity. In this study 16 subjects performed five problem solving tasks with similar processing requirements. EEG data were analyzed by means of post hoc comparisons of subjects differing in performance quality. Additionally, four control tasks were employed in which, based on previous studies, variations in the Theta frequency range were expected. An effect in the Alpha 1 frequency band was observed in tasks requiring reconstructive recall or testing the usefulness of an mathematical algorithm. The creation of a rank order or mental map is accompanied by power increases in the lower portions of the Alpha 1 frequency band (7.5-8.5 Hz). Moreover a high amount of controlled variance (eta2 up to 34%) was obtained for this effect. Increases in EEG Theta power, which presumably indicate subjects' component analysis, were found before the subjects recognized parts of geometric figures or before relevant features in the "buddhist monk problem" were discriminated. The dynamics of EEG power over time is in examples of frequency/time plots in a figure, illustrated. PMID:1441650

  18. EAS spectrum in the primary energy region above 10 to the 15th power eV by the Akeno and Yakutsk array data

    NASA Technical Reports Server (NTRS)

    Krasilnikov, D. D.; Krasilnikov, A. D.; Knurenko, S. P.; Pavlov, V. N.; Sleptsov, I. Y.; Yegorova, V. P.

    1985-01-01

    The extensive air showers spectrum on scintillation desity Rko in primary energy region E sub approx. 10 to the 15th power - 10 to the 20th power eV on the Yakutsk array data and recent results of the Akeno is given.

  19. A TWO-COMPONENT POWER LAW COVERING NEARLY FOUR ORDERS OF MAGNITUDE IN THE POWER SPECTRUM OF SPITZER FAR-INFRARED EMISSION FROM THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Block, David L.; Puerari, Ivanio; Elmegreen, Bruce G.; Bournaud, Frederic

    2010-07-20

    Power spectra of Large Magellanic Cloud (LMC) emission at 24, 70, and 160 {mu}m observed with the Spitzer Space Telescope have a two-component power-law structure with a shallow slope of -1.6 at low wavenumber, k, and a steep slope of -2.9 at high k. The break occurs at k {sup -1} {approx} 100-200 pc, which is interpreted as the line-of-sight thickness of the LMC disk. The slopes are slightly steeper for longer wavelengths, suggesting the cooler dust emission is smoother than the hot emission. The power spectrum (PS) covers {approx}3.5 orders of magnitude, and the break in the slope is in the middle of this range on a logarithmic scale. Large-scale driving from galactic and extragalactic processes, including disk self-gravity, spiral waves, and bars, presumably causes the low-k structure in what is effectively a two-dimensional geometry. Small-scale driving from stellar processes and shocks causes the high-k structure in a three-dimensional geometry. This transition in dimensionality corresponds to the observed change in PS slope. A companion paper models the observed power law with a self-gravitating hydrodynamics simulation of a galaxy like the LMC.

  20. Learning to modulate the partial powers of a single sEMG power spectrum through a novel human-computer interface.

    PubMed

    Skavhaug, Ida-Maria; Lyons, Kenneth R; Nemchuk, Anna; Muroff, Shira D; Joshi, Sanjay S

    2016-06-01

    New human-computer interfaces that use bioelectrical signals as input are allowing study of the flexibility of the human neuromuscular system. We have developed a myoelectric human-computer interface which enables users to navigate a cursor to targets through manipulations of partial powers within a single surface electromyography (sEMG) signal. Users obtain two-dimensional control through simultaneous adjustments of powers in two frequency bands within the sEMG spectrum, creating power profiles corresponding to cursor positions. It is unlikely that these types of bioelectrical manipulations are required during routine muscle contractions. Here, we formally establish the neuromuscular ability to voluntarily modulate single-site sEMG power profiles in a group of naïve subjects under restricted and controlled conditions using a wrist muscle. All subjects used the same pre-selected frequency bands for control and underwent the same training, allowing a description of the average learning progress throughout eight sessions. We show that subjects steadily increased target hit rates from 48% to 71% and exhibited greater control of the cursor's trajectories following practice. Our results point towards an adaptable neuromuscular skill, which may allow humans to utilize single muscle sites as limited general-purpose signal generators. Ultimately, the goal is to translate this neuromuscular ability to practical interfaces for the disabled by using a spared muscle to control external machines. PMID:26874751

  1. High background photon counting lidar

    NASA Technical Reports Server (NTRS)

    Lentz, W. J.

    1992-01-01

    Photon counting with lidar returns is usually limited to low light levels, while wide dynamic range is achieved by counting for long times. The broad emission spectrum of inexpensive high-power semiconductor lasers makes receiver filters pass too much background light for traditional photon counting in daylight. Very high speed photon counting is possible, however, at more than 500 MHz which allows the construction of eyesafe lidar operating in the presence of bright clouds. Detector improvements are possible to count to 20 GHz producing a single shot dynamic range of ten decades.

  2. High-power fiber-coupled 100W visible spectrum diode lasers for display applications

    NASA Astrophysics Data System (ADS)

    Unger, Andreas; Küster, Matthias; Köhler, Bernd; Biesenbach, Jens

    2013-02-01

    Diode lasers in the blue and red spectral range are the most promising light sources for upcoming high-brightness digital projectors in cinemas and large venue displays. They combine improved efficiency, longer lifetime and a greatly improved color space compared to traditional xenon light sources. In this paper we report on high-power visible diode laser sources to serve the demands of this emerging market. A unique electro-optical platform enables scalable fiber coupled sources at 638 nm with an output power of up to 100 W from a 400 μm NA0.22 fiber. For the blue diode laser we demonstrate scalable sources from 5 W to 100 W from a 400 μm NA0.22 fiber.

  3. Emotion classification in Parkinson's disease by higher-order spectra and power spectrum features using EEG signals: a comparative study.

    PubMed

    Yuvaraj, R; Murugappan, M; Ibrahim, Norlinah Mohamed; Omar, Mohd Iqbal; Sundaraj, Kenneth; Mohamad, Khairiyah; Palaniappan, R; Satiyan, M

    2014-03-01

    Deficits in the ability to process emotions characterize several neuropsychiatric disorders and are traits of Parkinson's disease (PD), and there is need for a method of quantifying emotion, which is currently performed by clinical diagnosis. Electroencephalogram (EEG) signals, being an activity of central nervous system (CNS), can reflect the underlying true emotional state of a person. This study applied machine-learning algorithms to categorize EEG emotional states in PD patients that would classify six basic emotions (happiness and sadness, fear, anger, surprise and disgust) in comparison with healthy controls (HC). Emotional EEG data were recorded from 20 PD patients and 20 healthy age-, education level- and sex-matched controls using multimodal (audio-visual) stimuli. The use of nonlinear features motivated by the higher-order spectra (HOS) has been reported to be a promising approach to classify the emotional states. In this work, we made the comparative study of the performance of k-nearest neighbor (kNN) and support vector machine (SVM) classifiers using the features derived from HOS and from the power spectrum. Analysis of variance (ANOVA) showed that power spectrum and HOS based features were statistically significant among the six emotional states (p < 0.0001). Classification results shows that using the selected HOS based features instead of power spectrum based features provided comparatively better accuracy for all the six classes with an overall accuracy of 70.10% ± 2.83% and 77.29% ± 1.73% for PD patients and HC in beta (13-30 Hz) band using SVM classifier. Besides, PD patients achieved less accuracy in the processing of negative emotions (sadness, fear, anger and disgust) than in processing of positive emotions (happiness, surprise) compared with HC. These results demonstrate the effectiveness of applying machine learning techniques to the classification of emotional states in PD patients in a user independent manner using EEG signals. The

  4. Interplanetary Magnetic Field Power Spectrum Variations in the Inner Heliosphere: A Wind and MESSENGER Study

    NASA Technical Reports Server (NTRS)

    Szabo, Adam; Koval, A.

    2011-01-01

    The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the similar observations made by the MESSENGER spacecraft in the inner heliosphere affords an opportunity to compare magnetic field power spectral density variations as a function of radial distance from the Sun under different solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The powe'r spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. Wind and MESSENGER magnetic fluctuations are compared for times when the two spacecraft are close to radial and Parker field alignment. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed.

  5. Position-dependent power spectrum of the large-scale structure: a novel method to measure the squeezed-limit bispectrum

    SciTech Connect

    Chiang, Chi-Ting; Wagner, Christian; Schmidt, Fabian; Komatsu, Eiichiro E-mail: cwagner@mpa-garching.mpg.de E-mail: komatsu@mpa-garching.mpg.de

    2014-05-01

    The influence of large-scale density fluctuations on structure formation on small scales is described by the three-point correlation function (bispectrum) in the so-called ''squeezed configurations,'' in which one wavenumber, say k{sub 3}, is much smaller than the other two, i.e., k{sub 3} << k{sub 1} ≈ k{sub 2}. This bispectrum is generated by non-linear gravitational evolution and possibly also by inflationary physics. In this paper, we use this fact to show that the bispectrum in the squeezed configurations can be measured without employing three-point function estimators. Specifically, we use the ''position-dependent power spectrum,'' i.e., the power spectrum measured in smaller subvolumes of the survey (or simulation box), and correlate it with the mean overdensity of the corresponding subvolume. This correlation directly measures an integral of the bispectrum dominated by the squeezed configurations. Measuring this correlation is only slightly more complex than measuring the power spectrum itself, and sidesteps the considerable complexity of the full bispectrum estimation. We use cosmological N-body simulations of collisionless particles with Gaussian initial conditions to show that the measured correlation between the position-dependent power spectrum and the long-wavelength overdensity agrees with the theoretical expectation. The position-dependent power spectrum thus provides a new, efficient, and promising way to measure the squeezed-limit bispectrum from large-scale structure observations such as galaxy redshift surveys.

  6. [Contribution of 210Bi beta-ray induced bremsstrahlung to the emission of Pb-KX-rays observed in the lead shielded gamma-ray background spectrum (author's transl)].

    PubMed

    Shima, K; Mihara, T; Umetani, K; Mikumo, T

    1980-08-01

    Observation of gamma-ray background has been done by using a Ge(Li) semiconductor detector when it was placed inside the lead shielding material. With the aid of a very simple model calculation, the concentration of 210Pb radioisotope embedded in the lead material has been estimated to be 0.1-0.4 (Bq/Pb-g) (3-12 (pCi/Pb-g). The origin of Pb-KX-ray emission, the highest peak in the background spectrum, has been investigated by comparing the 210Pb-47 keV gamma-ray and Pb-KX-ray peak counts. As the results, about 50 +/- 30% of Pb-KX-ray production is estimated to be due to the Pb-K shell photoionization which is induced by the bremsstrahlung of 210Bi beta-ray. PMID:7208990

  7. Entropy information of heart rate variability and its power spectrum during day and night

    NASA Astrophysics Data System (ADS)

    Jin, Li; Jun, Wang

    2013-07-01

    Physiologic systems generate complex fluctuations in their output signals that reflect the underlying dynamics. We employed the base-scale entropy method and the power spectral analysis to study the 24 hours heart rate variability (HRV) signals. The results show that such profound circadian-, age- and pathologic-dependent changes are accompanied by changes in base-scale entropy and power spectral distribution. Moreover, the base-scale entropy changes reflect the corresponding changes in the autonomic nerve outflow. With the suppression of the vagal tone and dominance of the sympathetic tone in congestive heart failure (CHF) subjects, there is more variability in the date fluctuation mode. So the higher base-scale entropy belongs to CHF subjects. With the decrease of the sympathetic tone and the respiratory frequency (RSA) becoming more pronounced with slower breathing during sleeping, the base-scale entropy drops in CHF subjects. The HRV series of the two healthy groups have the same diurnal/nocturnal trend as the CHF series. The fluctuation dynamics trend of data in the three groups can be described as “HF effect”.

  8. Observing trans-Planckian ripples in the primordial power spectrum with future large scale structure probes</