On the predictiveness of single-field inflationary models
NASA Astrophysics Data System (ADS)
Burgess, C. P.; Patil, Subodh P.; Trott, Michael
2014-06-01
We re-examine the predictiveness of single-field inflationary models and discuss how an unknown UV completion can complicate determining inflationary model parameters from observations, even from precision measurements. Besides the usual naturalness issues associated with having a shallow inflationary potential, we describe another issue for inflation, namely, unknown UV physics modifies the running of Standard Model (SM) parameters and thereby introduces uncertainty into the potential inflationary predictions. We illustrate this point using the minimal Higgs Inflationary scenario, which is arguably the most predictive single-field model on the market, because its predictions for A S , r and n s are made using only one new free parameter beyond those measured in particle physics experiments, and run up to the inflationary regime. We find that this issue can already have observable effects. At the same time, this UV-parameter dependence in the Renormalization Group allows Higgs Inflation to occur (in principle) for a slightly larger range of Higgs masses. We comment on the origin of the various UV scales that arise at large field values for the SM Higgs, clarifying cut off scale arguments by further developing the formalism of a non-linear realization of SU L (2) × U(1) in curved space. We discuss the interesting fact that, outside of Higgs Inflation, the effect of a non-minimal coupling to gravity, even in the SM, results in a non-linear EFT for the Higgs sector. Finally, we briefly comment on post BICEP2 attempts to modify the Higgs Inflation scenario.
Geometrical measures of non-Gaussianity generated from single field inflationary models
NASA Astrophysics Data System (ADS)
Junaid, M.; Pogosyan, D.
2015-08-01
We calculate the third-order moments of scalar curvature perturbations in configuration space for different inflationary models. We develop a robust numerical technique to compute the bispectrum for different models that have some features in the inflationary potential. From the bispectrum we evaluate moments analytically in the slow-roll regime while we devise a numerical mechanism to calculate these moments for non-slow-roll single-field inflationary models with a standard kinetic term that are minimally coupled to gravity. With the help of these third-order moments one can directly predict many non-Gaussian and geometrical measures of cosmic microwave background distributions in the configuration space. Thus, we devise a framework to calculate different third-order moments and geometrical measures, e.g. Minkowski functionals or the skeleton statistic, generated by different single-field models of inflation.
Reconstructing single-field inflationary actions from cosmic microwave background radiation data
Gauthier, Christopher S; Akhoury, Ratindranath E-mail: akhoury@umich.edu
2008-07-15
This paper describes a general program for deriving the action of single-field inflation models with non-standard kinetic energy terms using cosmic microwave background radiation power spectrum data. This method assumes that an action depends on a set of undetermined functions, each of which is a function of either the inflaton wavefunction or its time derivative. The scalar, tensor and non-Gaussianity of the curvature perturbation spectrum are used to derive a set of reconstruction equations whose solution set can specify up to three of the undetermined functions. The method is then used to find the undetermined functions in various types of action assuming power law type scalar and tensor spectra. In actions that contain only two unknown functions, the third reconstruction equation implies a consistency relation between the non-Gaussianity, sound speed and slow roll parameters. In particular we focus on reconstructing a generalized Dirac-Born-Infeld action with an unknown potential and warp factor. We find that for realistic scalar and tensor spectra, the reconstructed warp factor and potential are very similar to the theoretically derived result. Furthermore, physical consistency of the reconstructed warp factor and potential imposes strict constraints on the scalar and tensor spectral indices.
Inflationary field excursion in broad classes of scalar field models
NASA Astrophysics Data System (ADS)
Banerjee, Argha; Koley, Ratna
2016-12-01
In single-field slow-roll inflation models, the height and slope of the potential are made to satisfy certain conditions to match with observations. This in turn translates into bounds on the number of e -foldings and the excursion of the scalar field during inflation. In this work we consider broad classes of inflationary models to study how much the field excursion starting from the horizon exit to the end of inflation, Δ ϕ , can vary for the set of inflationary parameters given by Planck. We also derive an upper bound on the number of e -foldings between the horizon exit of a cosmologically interesting mode and the end of inflation. We comment on the possibility of having super-Planckian and sub-Planckian field excursions within the framework of single-field slow-roll inflation.
Can CMB data constrain the inflationary field range?
Garcia-Bellido, Juan
2014-09-01
We study to what extent the spectral index n{sub s} and the tensor-to-scalar ratio r determine the field excursion Δφ during inflation. We analyse the possible degeneracy of Δ φ by comparing three broad classes of inflationary models, with different dependence on the number of e-foldings N, to benchmark models of chaotic inflation with monomial potentials. The classes discussed cover a large set of inflationary single field models. We find that the field range is not uniquely determined for any value of (n{sub s}, r); one can have the same predictions as chaotic inflation and a very different Δ φ. Intriguingly, we find that the field range cannot exceed an upper bound that appears in different classes of models. Finally, Δ φ can even become sub-Planckian, but this requires to go beyond the single-field slow-roll paradigm.
Non-Gaussianity and Large Scale Structure in a two-field Inflationary model
Tseliakhovich, D.; Slosar, A.; Hirata, C.
2010-08-30
Single-field inflationary models predict nearly Gaussian initial conditions, and hence a detection of non-Gaussianity would be a signature of the more complex inflationary scenarios. In this paper we study the effect on the cosmic microwave background and on large-scale structure from primordial non-Gaussianity in a two-field inflationary model in which both the inflaton and curvaton contribute to the density perturbations. We show that in addition to the previously described enhancement of the galaxy bias on large scales, this setup results in large-scale stochasticity. We provide joint constraints on the local non-Gaussianity parameter f*{sub NL} and the ratio {zeta} of the amplitude of primordial perturbations due to the inflaton and curvaton using WMAP and Sloan Digital Sky Survey data.
Non-Gaussianity and large-scale structure in a two-field inflationary model
Tseliakhovich, Dmitriy; Hirata, Christopher
2010-08-15
Single-field inflationary models predict nearly Gaussian initial conditions, and hence a detection of non-Gaussianity would be a signature of the more complex inflationary scenarios. In this paper we study the effect on the cosmic microwave background and on large-scale structure from primordial non-Gaussianity in a two-field inflationary model in which both the inflaton and curvaton contribute to the density perturbations. We show that in addition to the previously described enhancement of the galaxy bias on large scales, this setup results in large-scale stochasticity. We provide joint constraints on the local non-Gaussianity parameter f-tilde{sub NL} and the ratio {xi} of the amplitude of primordial perturbations due to the inflaton and curvaton using WMAP and Sloan Digital Sky Survey data.
The inflationary bispectrum with curved field-space
Elliston, Joseph; Tavakol, Reza; Seery, David E-mail: d.seery@sussex.ac.uk
2012-11-01
We compute the covariant three-point function near horizon-crossing for a system of slowly-rolling scalar fields during an inflationary epoch, allowing for an arbitrary field-space metric. We show explicitly how to compute its subsequent evolution using a covariantized version of the separate universe or 'δN' expansion, which must be augmented by terms measuring curvature of the field-space manifold, and give the nonlinear gauge transformation to the comoving curvature perturbation. Nonlinearities induced by the field-space curvature terms are a new and potentially significant source of non-Gaussianity. We show how inflationary models with non-minimal coupling to the spacetime Ricci scalar can be accommodated within this framework. This yields a simple toolkit allowing the bispectrum to be computed in models with non-negligible field-space curvature.
Primordial magnetic fields from the post-inflationary universe
Kobayashi, Takeshi
2014-05-01
We explore cosmological magnetogenesis in the post-inflationary universe, when the inflaton oscillates around its potential minimum and the universe is effectively dominated by cold matter. During this epoch prior to reheating, large-scale magnetic fields can be significantly produced by the cosmological background. By considering magnetogenesis both during and after inflation, we demonstrate that magnetic fields stronger than 10{sup −15} G can be generated on Mpc scales without having strong couplings in the theory, or producing too large electric fields that would dominate the universe.
Can a spectator scalar field enhance inflationary tensor mode?
NASA Astrophysics Data System (ADS)
Fujita, Tomohiro; Yokoyama, Jun'ichi; Yokoyama, Shuichiro
2015-04-01
We consider the possibility of enhancing the inflationary tensor mode by introducing a spectator scalar field with a small sound speed which induces gravitational waves as a second-order effect. We analytically obtain the power spectra of gravitational waves and curvature perturbation induced by the spectator scalar field. We find that the small sound speed amplifies the curvature perturbation much more than the tensor mode and the current observational constraint forces the induced gravitational waves to be negligible compared with those from the vacuum fluctuation during inflation.
Inflationary dynamics of kinetically-coupled gauge fields
Ferreira, Ricardo Z.; Ganc, Jonathan E-mail: ganc@cp3.dias.sdu.dk
2015-04-01
We investigate the inflationary dynamics of two kinetically-coupled massless U(1) gauge fields with time-varying kinetic-term coefficients. Ensuring that the system does not have strongly coupled regimes shrinks the parameter space. Also, we further restrict ourselves to systems that can be quantized using the standard creation, annihilation operator algebra. This second constraint limits us to scenarios where the system can be diagonalized into the sum of two decoupled, massless, vector fields with a varying kinetic-term coefficient. Such a system might be interesting for magnetogenesis because of how the strong coupling problem generalizes. We explore this idea by assuming that one of the gauge fields is the Standard Model U(1) field and that the other dark gauge field has no particles charged under its gauge group. We consider whether it would be possible to transfer a magnetic field from the dark sector, generated perhaps before the coupling was turned on, to the visible sector. We also investigate whether the simple existence of the mixing provides more opportunities to generate magnetic fields. We find that neither possibility works efficiently, consistent with the well-known difficulties in inflationary magnetogenesis.
Effective field theory of dark matter from membrane inflationary paradigm
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan; Dasgupta, Arnab
2016-09-01
In this article, we have studied the cosmological and particle physics constraints on dark matter relic abundance from effective field theory of inflation from tensor-to-scalar ratio (r), in case of Randall-Sundrum single membrane (RSII) paradigm. Using semi-analytical approach we establish a direct connection between the dark matter relic abundance (ΩDMh2) and primordial gravity waves (r), which establishes a precise connection between inflation and generation of dark matter within the framework of effective field theory in RSII membrane. Further assuming the UV completeness of the effective field theory perfectly holds good in the prescribed framework, we have explicitly shown that the membrane tension, σ ≤ O(10-9) Mp4, bulk mass scale M5 ≤ O(0.04 - 0.05) Mp, and cosmological constant Λ˜5 ≥ - O(10-15) Mp5, in RSII membrane plays the most significant role to establish the connection between dark matter and inflation, using which we have studied the features of various mediator mass scale suppressed effective field theory "relevant operators" induced from the localized s, t and u channel interactions in RSII membrane. Taking a completely model independent approach, we have studied an exhaustive list of tree-level Feynman diagrams for dark matter annihilation within the prescribed setup and to check the consistency of the obtained results, further we apply the constraints as obtained from recently observed Planck 2015 data and Planck + BICEP2 + Keck Array joint data sets. Using all of these derived results we have shown that to satisfy the bound on, ΩDMh2 = 0.1199 ± 0.0027, as from Planck 2015 data, it is possible to put further stringent constraint on r within, 0.01 ≤ r ≤ 0.12, for thermally averaged annihilation cross-section of dark matter, < σv > ≈ O(10-28 - 10-27) cm3 / s, which are very useful to constrain various membrane inflationary models.
Effective field theory of weakly coupled inflationary models
Gwyn, Rhiannon; Palma, Gonzalo A.; Sakellariadou, Mairi; Sypsas, Spyros E-mail: gpalmaquilod@ing.uchile.cl E-mail: spyridon.sypsas@kcl.ac.uk
2013-04-01
The application of Effective Field Theory (EFT) methods to inflation has taken a central role in our current understanding of the very early universe. The EFT perspective has been particularly useful in analyzing the self-interactions determining the evolution of co-moving curvature perturbations (Goldstone boson modes) and their influence on low-energy observables. However, the standard EFT formalism, to lowest order in spacetime differential operators, does not provide the most general parametrization of a theory that remains weakly coupled throughout the entire low-energy regime. Here we study the EFT formulation by including spacetime differential operators implying a scale dependence of the Goldstone boson self-interactions and its dispersion relation. These operators are shown to arise naturally from the low-energy interaction of the Goldstone boson with heavy fields that have been integrated out. We find that the EFT then stays weakly coupled all the way up to the cutoff scale at which ultraviolet degrees of freedom become operative. This opens up a regime of new physics where the dispersion relation is dominated by a quadratic dependence on the momentum ω ∼ p{sup 2}. In addition, provided that modes crossed the Hubble scale within this energy range, the predictions of inflationary observables — including non-Gaussian signatures — are significantly affected by the new scales characterizing it.
Reconstruction of the Scalar Field Potential in Inflationary Models with a Gauss-Bonnet term
NASA Astrophysics Data System (ADS)
Koh, Seoktae; Lee, Bum-Hoon; Tumurtushaa, Gansukh
2017-06-01
We consider inflationary models with a Gauss-Bonnet term to reconstruct the scalar-field potentials and the Gauss-Bonnet coupling functions. Both expressions are derived from the observationally favored configurations of ns and r . Our result implies that, for the reconstructed potentials and coupling functions, the blue tilt of inflationary tensor fluctuations can be realized. To achieve a blue tilt for the inflationary tensor fluctuations, a scalar field must climb up its potential before rolling down. We further investigate the properties of propagation of the perturbation modes in Friedmann-Robertson-Walker spacetime. For the reconstructed configurations that give rise to the blue tilt for the inflationary tensor fluctuations, we show that the ghosts and instabilities are absent with the superluminal propagation speeds for the scalar perturbation modes, whereas the propagation speeds of the tensor perturbations are subluminal.
The behavior of the Higgs field in the new inflationary universe
NASA Technical Reports Server (NTRS)
Guth, Alan H.; Pi, So-Young
1986-01-01
Answers are provided to questions about the standard model of the new inflationary universe (NIU) which have raised concerns about the model's validity. A baby toy problem which consists of the study of a single particle moving in one dimension under the influence of a potential with the form of an upside-down harmonic oscillator is studied, showing that the quantum mechanical wave function at large times is accurately described by classical physics. Then, an exactly soluble toy model for the behavior of the Higgs field in the NIU is described which should provide a reasonable approximation to the behavior of the Higgs field in the NIU. The dynamics of the toy model is described, and calculative results are reviewed which, the authors claim, provide strong evidence that the basic features of the standard picture are correct.
The behavior of the Higgs field in the new inflationary universe
NASA Technical Reports Server (NTRS)
Guth, Alan H.; Pi, So-Young
1986-01-01
Answers are provided to questions about the standard model of the new inflationary universe (NIU) which have raised concerns about the model's validity. A baby toy problem which consists of the study of a single particle moving in one dimension under the influence of a potential with the form of an upside-down harmonic oscillator is studied, showing that the quantum mechanical wave function at large times is accurately described by classical physics. Then, an exactly soluble toy model for the behavior of the Higgs field in the NIU is described which should provide a reasonable approximation to the behavior of the Higgs field in the NIU. The dynamics of the toy model is described, and calculative results are reviewed which, the authors claim, provide strong evidence that the basic features of the standard picture are correct.
NASA Astrophysics Data System (ADS)
Ijjas, Anna; Steinhardt, Paul J.; Loeb, Abraham
2014-09-01
Classic inflation, the theory described in textbooks, is based on the idea that, beginning from typical initial conditions and assuming a simple inflaton potential with a minimum of fine-tuning, inflation can create exponentially large volumes of space that are generically homogeneous, isotropic and flat, with nearly scale-invariant spectra of density and gravitational wave fluctuations that are adiabatic, Gaussian and have generic predictable properties. In a recent paper, we showed that, in addition to having certain conceptual problems known for decades, classic inflation is for the first time also disfavored by data, specifically the most recent data from WMAP, ACT and Planck2013. Guth, Kaiser and Nomura and Linde have each recently published critiques of our paper, but, as made clear here, we all agree about one thing: the problematic state of classic inflation. Instead, they describe an alternative inflationary paradigm that revises the assumptions and goals of inflation, and perhaps of science generally. Assuming simple inflaton potentials with a single phase of inflation is “not at all realistic”, whereas highly complex potentials with many parameters, tunings, and fields are “very plausible according to recent ideas in high-energy physics” [GKN10-11]. The complex potentials inevitably lead to multiple stages of inflation and a multiverse in which anything can happen [GKN7]. The validity of the postmodern inflationary paradigm cannot be judged on whether it works for typical initial conditions since we do not know what those conditions are [GKN13]. Even if the initial conditions are determined some day they will not affect the validity of inflation; rather, the (yet unknown) measure will then be adjusted such that the observed properties of the universe are likely to emerge from those (yet unknown) initial conditions [GKN14]. The volume measure is rejected in favor of complex measures that are to be (re-)adjusted (a posteriori) to ensure that the
NASA Astrophysics Data System (ADS)
Blau, S. K.; Guth, A. H.
Contents: 1. Introduction. 2. Summary of the standard cosmological model. 3. Problems of the standard cosmological model. 4. The original inflationary universe. 5. Successes of the original inflationary model. 6. Problems of the original inflationary model. 7. The new inflationary universe. 8. Density perturbations in the new inflationary universe. 9. Quantum theory of the new inflationary universe phase transition. 10. Inflation in the minimal SU(5) grand unified theory. 11. False vacuum bubbles and child universes. 12. Conclusion.
NASA Astrophysics Data System (ADS)
Kohri, Kazunori; Matsui, Hiroki
2017-08-01
In this work, we investigated the electroweak vacuum instability during or after inflation. In the inflationary Universe, i.e., de Sitter space, the vacuum field fluctuations < δ phi 2 > enlarge in proportion to the Hubble scale H2. Therefore, the large inflationary vacuum fluctuations of the Higgs field < δ phi 2 > are potentially catastrophic to trigger the vacuum transition to the negative-energy Planck-scale vacuum state and cause an immediate collapse of the Universe. However, the vacuum field fluctuations < δ phi 2 >, i.e., the vacuum expectation values have an ultraviolet divergence, and therefore a renormalization is necessary to estimate the physical effects of the vacuum transition. Thus, in this paper, we revisit the electroweak vacuum instability from the perspective of quantum field theory (QFT) in curved space-time, and discuss the dynamical behavior of the homogeneous Higgs field phi determined by the effective potential V eff( phi ) in curved space-time and the renormalized vacuum fluctuations < δ phi 2 >ren via adiabatic regularization and point-splitting regularization. We simply suppose that the Higgs field only couples the gravity via the non-minimal Higgs-gravity coupling ξ(μ). In this scenario, the electroweak vacuum stability is inevitably threatened by the dynamical behavior of the homogeneous Higgs field phi, or the formations of AdS domains or bubbles unless the Hubble scale is small enough H< ΛI .
Scale and shape dependent non-Gaussianity in the presence of inflationary vector fields
NASA Astrophysics Data System (ADS)
Beltrán Almeida, Juan P.; Rodríguez, Yeinzon; Valenzuela-Toledo, César A.
2014-11-01
We consider cosmological inflationary models in which vector fields play some role in the generation of the primordial curvature perturbation ζ . Such models are interesting because the involved vector fields naturally seed statistical anisotropy in the primordial fluctuations which could eventually leave a measurable imprint on the cosmic microwave background fluctuations. In this article, we estimate the scale and shape dependent effects on the non-Gaussianity (NG) parameters due to the scale dependent statistical anisotropy in the distribution of the fluctuations. For concreteness, we use a power spectrum (PS) of the fluctuations of the quadrupolar form: Pζ(k → )≡Pζ(k )[1 +gζ(k )(n ^ .k ^ )2] , where gζ(k ) is the only quantity which parametrizes the level of statistical anisotropy and n ^ is a unitary vector which points towards the preferred direction. Then, we evaluate the contribution of the running of gζ(k ) on the NG parameters by means of the δ N formalism. We focus specifically on the details for the fNL NG parameter, associated with the bispectrum Bζ, but the structure of higher order NG parameters is straightforward to generalize. Although the level of statistical anisotropy in the power spectrum is severely constrained by recent observations, the importance of statistical anisotropy signals in higher order correlators remains to be determined, this being the main task that we address here. The precise measurement of the shape and scale dependence (or running) of statistical parameters such as the NG parameters and the statistical anisotropy level could provide relevant elements for model building and for the determination of the presence (or nonpresence) of inflationary vector fields and their role in the inflationary mechanism.
Cosmological backreaction for a test field observer in a chaotic inflationary model
Marozzi, Giovanni; Vacca, Gian Paolo; Brandenberger, Robert H. E-mail: vacca@bo.infn.it
2013-02-01
In an inhomogeneous universe, an observer associated with a particular matter field does not necessarily measure the same cosmological evolution as an observer in a homogeneous and isotropic universe. Here we consider, in the context of a chaotic inflationary background model, a class of observers associated with a ''clock field'' for which we use a light test field. We compute the effective expansion rate and fluid equation of state in a gauge invariant way, taking into account the quantum fluctuations of the long wavelength modes, and working up to second order in perturbation theory and in the slow-roll approximation. We find that the effective expansion rate is smaller than what would be measured in the absence of fluctuations. Within the stochastic approach we study the bounds for which the approximations we make are consistent.
NASA Astrophysics Data System (ADS)
Gilmore, James Brian
2010-12-01
General Relativity is the standard framework by which all gravitational systems are analyzed in modern research, and it provides the theme for all the investigations in this thesis. Beyond this common platform, very different gravitating problems are examined here, and several analytical approaches are used to investigate these systems. Effective field theory, a methodological approach prominent in quantum field theory, plays an important role in the analysis of two of the problems in this thesis. In the first instance, an effective field theory for bound gravitational states is used to compute the interaction Lagrangian of a binary system at the second post-Newtonian order. A metric parametrization based on a temporal Kaluza-Klein decomposition is also used. In this effective field theory calculation, the post-Newtonian results for the equations of motion are elegantly reproduced. In the next problem considered, effective field theory is used to investigate the thermodynamics of compactified charged black holes. The relevant thermodynamic quantities are all computed to second order in the perturbation parameter and finite size effects are incorporated through higher order worldline operators. Complete agreement is found with an exact extremal black hole solution constructed with traditional General Relativistic methods. The results indicate that the addition of charge to a compactified black hole may delay the phase transition to a black string. Finally, the third problem examined here concerns the evolution of perturbations at the end of early universe inflation. General Relativity enters this problem through cosmological perturbation theory. It is shown that the coherent oscillations in the inflaton break down at the comoving post-inflationary horizon size, about 14 e-folds after the end of inflation. This is many e-folds before any known constraints, leading to possible implications for the matching problem of inflation, and the generation of stochastic
Effective field theory and non-Gaussianity from general inflationary states
NASA Astrophysics Data System (ADS)
Agarwal, Nishant; Holman, R.; Tolley, Andrew J.; Lin, Jennifer
2013-05-01
We study the effects of non-trivial initial quantum states for inflationary fluctuations within the context of the effective field theory for inflation constructed by Cheung et al. which allows us to discriminate between different initial states in a model-independent way. We develop a Green's function/path integral based formulation that incorporates initial state effects and use it to address questions such as how state-dependent is the consistency relation for the bispectrum, how many e-folds beyond the minimum required to solve the cosmological fine tunings of the big bang are we allowed so that some information from the initial state survives until late times, among others. We find that the so-called consistency condition relating the local limit of the bispectrum and the slow-roll parameter is a state-dependent statement that can be avoided for physically consistent initial states either with or without initial non-Gaussianities.
NASA Astrophysics Data System (ADS)
Kinney, William H.
1996-01-01
Inflationary cosmology is an elegant and straightforward solution to two of the largest puzzles presented by the standard "Big Bang" cosmology: why is the universe so flat, and why is the cosmic microwave background in such excellent thermal equilibrium? However, models of inflation in particle physics typically suffer from the shortcoming that the fundamental energy scale for inflation is driven to nearly the Planck scale by observational constraints. In addition, models of inflation often require the "fine-tuning" of parameters to very small values in order to remain consistent with observation. This thesis investigates inflationary potentials in a general context, and shows that the difficulty of fundamental scales being forced to the Planck scale is in fact characteristic only of scalar field potentials V(phi) dominated near their maxima by terms of order phi^2. It is found that potentials dominated by terms of order phim with m > 2 can satisfy observational constraints at an essentially arbitrary symmetry breaking scale. Potentials characterized by m = 2 and m = 4 are illustrated in the context of several "natural inflation" models, with particular emphasis on questions of fine-tuning and fundamental scale. Natural inflation theories are a class of models in which inflation is driven by a pseudo Nambu-Goldstone boson, which acquires a mass as a result of radiative corrections. Two models characterized by m = 2 are evaluated, in which the potential for inflation is generated by loop effects from a fermion sector which explicitly breaks a global U(1) symmetry. The m = 4 case is implemented in a model with a broken SO(3) symmetry, in which the potential is generated by gauge boson loops. Constraints from the Cosmic Background Explorer (COBE) Differential Microwave Radiometer (DMR) measurement of the temperature anisotropy of the cosmic background radiation are used to limit the parameters of the models.
NASA Astrophysics Data System (ADS)
Guth, A. H.; Steinhardt, P. J.
1984-05-01
The theory of the inflationary universe is discussed. The problems facing the standard big-bang model are described, including the horizon problem, the smoothness problem, and the flatness problem. The combination of grand unified theories and the standard picture explains the asymmetry of matter and antimatter in the universe, but raises the problem of monopoles and domain walls. How the inflationary picture solves or avoids these problems is shown. The original inflationary theory is contrasted with the new inflationary theory, and the theoretical roles of supercooling, Higgs fields, symmetry-breaking, the false vacuum, the energy-density function, and the slow-rollover transition are discussed. The possibility that the actual creation of the universe is describable by physical laws is considered.
Sensitivity of inflationary predictions to pre-inflationary phases
Bahrami, Sina; Flanagan, Éanna É.
2016-01-15
How sensitive are the predictions of inflation to pre-inflationary conditions when the number of efolds of inflation is not too large? In an attempt to address this question, we consider a simple model where the inflationary era is preceded by an era dominated by a radiation fluid, which is coupled to the inflaton only gravitationally and which extends back to the Planck era. We show that there is a natural generalized Bunch-Davies vacuum state for perturbations to the coupled inflaton-gravity-fluid system at early times. With this choice of initial state the model predicts interesting deviations from the standard power spectrum of single field slow-roll inflation at large scales. However, the deviations are too small to be observable in near future CMB observations.
Sensitivity of inflationary predictions to pre-inflationary phases
Bahrami, Sina; Flanagan, Éanna É. E-mail: eef3@cornell.edu
2016-01-01
How sensitive are the predictions of inflation to pre-inflationary conditions when the number of efolds of inflation is not too large? In an attempt to address this question, we consider a simple model where the inflationary era is preceded by an era dominated by a radiation fluid, which is coupled to the inflaton only gravitationally and which extends back to the Planck era. We show that there is a natural generalized Bunch-Davies vacuum state for perturbations to the coupled inflaton-gravity-fluid system at early times. With this choice of initial state the model predicts interesting deviations from the standard power spectrum of single field slow-roll inflation at large scales. However, the deviations are too small to be observable in near future CMB observations.
Inflationary implications of supersymmetry breaking
Borghese, Andrea; Roest, Diederik; Zavala, Ivonne
2013-07-23
We discuss a general bound on the possibility to realise inflation in any minimal supergravity with F-terms. The derivation crucially depends on the sGoldstini, the scalar field directions that are singled out by spontaneous supersymmetry breaking. The resulting bound involves both slow-roll parameters and the geometry of the Kähler manifold of the chiral scalars. We analyse the inflationary implications of this bound, and in particular discuss to what extent the requirements of single field and slow-roll can both be met in F-term inflation.
Cirigliano, D.; Sanchez, N.G.; Vega, H.J. de
2005-05-15
We clarify inflaton models by considering them as effective field theories in the Ginzburg-Landau spirit. In this new approach, the precise form of the inflationary potential is constructed from the present WMAP data, and a useful scheme is prepared to confront with the forthcoming data. In this approach, the WMAP statement excluding the pure {phi}{sup 4} potential implies the presence of an inflaton mass term at the scale m{approx}10{sup 13} GeV. Chaotic, new and hybrid inflation models are studied in an unified way. In all cases the inflaton potential takes the form V({phi})=m{sup 2}M{sub Pl}{sup 2}v({phi}/M{sub Pl}), where all coefficients in the polynomial v({phi}) are of order one. If such potential corresponds to supersymmetry breaking, the corresponding susy breaking scale is {radical}(mM{sub Pl}){approx}10{sup 16} GeV which turns to coincide with the grand unification (GUT) scale. The inflaton mass is therefore given by a seesaw formula m{approx}M{sub GUT}{sup 2}/M{sub Pl}. The observables turn to be two-valued functions: one branch corresponds to new inflation and the other to chaotic inflation, the branch point being the pure quadratic potential. For red tilted spectrum, the potential which fits the best the present data (vertical bar 1-n{sub s} vertical bar < or approx. 0.1,r < or approx. 0.1) and which best prepares the way for the forthcoming data is a trinomial polynomial with negative quadratic term (new inflation). For blue tilted spectrum, hybrid inflation turns to be the best choice. In both cases we find an analytic formula relating the inflaton mass with the ratio r of tensor to scalar perturbations and the spectral index n{sub s} of scalar perturbations: 10{sup 6}(m/M{sub Pl})=127{radical}(r vertical bar 1-n{sub s} vertical bar) where the numerical coefficient is fixed by the WMAP amplitude of adiabatic perturbations. Implications for string theory are discussed.
On the consistency relation of the three-point function in single-field inflation
Cheung, Clifford; Fitzpatrick, A Liam; Kaplan, Jared; Senatore, Leonardo E-mail: fitzpatr@fas.harvard.edu E-mail: senatore@physics.harvard.edu
2008-02-15
The consistency relation for the three-point function of the cosmic microwave background is a very powerful observational signature which is believed to be true for every inflationary model in which there is only one dynamical degree of freedom. Its importance relies on the fact that deviations from it might be detected in next generation experiments, allowing us to rule out all single-field inflationary models. After making more precise the already existing proof of the consistency relation, we use a recently developed effective field theory for inflationary perturbations to provide an alternative and very explicit proof valid at leading non-trivial order in slow roll parameters.
Topics in inflationary cosmologies
Mahajan, S.
1986-04-01
Several aspects of inflationary cosmologies are discussed. An introduction to the standard hot big bang cosmological model is reviewed, and some of the problems associated with it are presented. A short review of the proposals for solving the cosmological conundrums of the big bang model is presented. Old and the new inflationary scenarios are discussed and shown to be unacceptable. Some alternative scenarios especially those using supersymmetry are reviewed briefly. A study is given of inflationary models where the same set of fields that breaks supersymmetry is also responsible for inflation. In these models, the scale of supersymmetry breaking is related to the slope of the potential near the origin and can thus be kept low. It is found that a supersymmetry breaking scale of the order of the weak breaking scale. The cosmology obtained from the simplest of such models is discussed in detail and it is shown that there are no particular problems except a low reheating temperature and a violation of the thermal constraint. A possible solution to the thermal constraint problem is given by introducing a second field, and the role played by this second field in the scenario is discussed. An alternative mechanism for the generation of baryon number within the framework of supergravity inflationary models is studied using the gravitational couplings of the heavy fields with the hidden sector (the sector which breaks supersymmetry). This mechanism is applied to two specific models - one with and one without supersymmetry breaking. The baryon to entropy ratio is found to be dependent on parameters which are model dependent. Finally, the effect of direct coupling between the two sectors on results is related, 88 refs., 6 figs.
Inflationary predictions and moduli masses
NASA Astrophysics Data System (ADS)
Das, Kumar; Dutta, Koushik; Maharana, Anshuman
2015-12-01
A generic feature of inflationary models in supergravity/string constructions is vacuum misalignment for the moduli fields. The associated production of moduli particles leads to an epoch in the post-inflationary history in which the energy density is dominated by cold moduli particles. This modification of the post-inflationary history implies that the preferred range for the number of e-foldings between horizon exit of the modes relevant for CMB observations and the end of inflation (Nk) depends on moduli masses. This in turn implies that the precision CMB observables ns and r are sensitive to moduli masses. We analyse this sensitivity for some representative models of inflation and find the effect to be highly relevant for confronting inflationary models with observations.
Renormalization-group improved inflationary scenarios
NASA Astrophysics Data System (ADS)
Pozdeeva, E. O.; Vernov, S. Yu.
2017-03-01
The possibility to construct an inflationary scenario for renormalization-group improved potentials corresponding to the Higgs sector of quantum field models is investigated. Taking into account quantum corrections to the renormalization-group potential which sums all leading logs of perturbation theory is essential for a successful realization of the inflationary scenario, with very reasonable parameters values. The scalar electrodynamics inflationary scenario thus obtained are seen to be in good agreement with the most recent observational data.
Enhanced Inflationary Trispectrum from a Non-Vacuum Initial State
NASA Astrophysics Data System (ADS)
Agullo, I.; Navarro-Salas, J.; Parker, L.
2015-01-01
We work out the primordial inflationary trispectrum for curvature perturbations in models with standard kinetic terms, when the initial quantum state is not necessarily the Bunch-Davies vacuum state. The presence of initial perturbations enhances the trispectrum amplitude for squeezed configurations, in parallel to the bispectrum enhancement. For those squeezed configurations the trispectrum acquires the so-called local form, with a scale dependent amplitude that can get values larger than the prediction of the so-called Maldacena consistency relation. The enhancement factor could be as large as 106, and could reach the sensitivity of forthcoming observations, even for single-field inflationary models.
K-inflationary power spectra at second order
Martin, Jérôme; Vennin, Vincent; Ringeval, Christophe E-mail: christophe.ringeval@uclouvain.be
2013-06-01
Within the class of inflationary models, k-inflation represents the most general single field framework that can be associated with an effective quadratic action for the curvature perturbations and a varying speed of sound. The incoming flow of high-precision cosmological data, such as those from the Planck satellite and small scale Cosmic Microwave Background (CMB) experiments, calls for greater accuracy in the inflationary predictions. In this work, we calculate for the first time the next-to-next-to-leading order scalar and tensor primordial power spectra in k-inflation needed in order to obtain robust constraints on the inflationary theory. The method used is the uniform approximation together with a second order expansion in the Hubble and sound flow functions. Our result is checked in various limits in which it reduces to already known situations.
The Quest for B Modes from Inflationary Gravitational Waves
NASA Astrophysics Data System (ADS)
Kamionkowski, Marc; Kovetz, Ely D.
2016-09-01
The search for the curl component (B mode) in the cosmic microwave background (CMB) polarization induced by inflationary gravitational waves is described. The canonical single-field slow-roll model of inflation is presented, and we explain the quantum production of primordial density perturbations and gravitational waves. It is shown how these gravitational waves then give rise to polarization in the CMB. We then describe the geometric decomposition of the CMB polarization pattern into a curl-free component (E mode) and curl component (B mode) and show explicitly that gravitational waves induce B modes. We discuss the B modes induced by gravitational lensing and by Galactic foregrounds and show how both are distinguished from those induced by inflationary gravitational waves. Issues involved in the experimental pursuit of these B modes are described, and we summarize some of the strategies being pursued. We close with a brief discussion of some other avenues toward detecting/characterizing the inflationary gravitational-wave background.
On soft limits of inflationary correlation functions
Assassi, Valentin; Baumann, Daniel; Green, Daniel E-mail: dbaumann@damtp.cam.ac.uk
2012-11-01
Soft limits of inflationary correlation functions are both observationally relevant and theoretically robust. Various theorems can be proven about them that are insensitive to detailed model-building assumptions. In this paper, we re-derive several of these theorems in a universal way. Our method makes manifest why soft limits are such an interesting probe of the spectrum of additional light fields during inflation. We illustrate these abstract results with a detailed case study of the soft limits of quasi-single-field inflation.
On soft limits of inflationary correlation functions
NASA Astrophysics Data System (ADS)
Assassi, Valentin; Baumann, Daniel; Green, Daniel
2012-11-01
Soft limits of inflationary correlation functions are both observationally relevant and theoretically robust. Various theorems can be proven about them that are insensitive to detailed model-building assumptions. In this paper, we re-derive several of these theorems in a universal way. Our method makes manifest why soft limits are such an interesting probe of the spectrum of additional light fields during inflation. We illustrate these abstract results with a detailed case study of the soft limits of quasi-single-field inflation.
Curvaton reheating in a logamediate inflationary model
Campo, Sergio del; Herrera, Ramon; Saavedra, Joel; Campuzano, Cuauhtemoc; Rojas, Efrain
2009-12-15
In a logamediate inflationary universe model we introduce the curvaton field in order to bring this inflationary model to an end. In this approach we determine the reheating temperature. We also outline some interesting constraints on the parameters that describe our models. Thus, we give the parameter space in this scenario.
Reheating predictions in single field inflation
Cook, Jessica L.; Dimastrogiovanni, Emanuela; Easson, Damien A.; Krauss, Lawrence M. E-mail: emad@asu.edu E-mail: krauss@asu.edu
2015-04-01
Reheating is a transition era after the end of inflation, during which the inflaton is converted into the particles that populate the Universe at later times. No direct cosmological observables are normally traceable to this period of reheating. Indirect bounds can however be derived. One possibility is to consider cosmological evolution for observable CMB scales from the time of Hubble crossing to the present time. Depending upon the model, the duration and final temperature after reheating, as well as its equation of state, may be directly linked to inflationary observables. For single-field inflationary models, if we approximate reheating by a constant equation of state, one can derive relations between the reheating duration (or final temperature), its equation of state parameter, and the scalar power spectrum amplitude and spectral index. While this is a simple approximation, by restricting the equation of state to lie within a broad physically allowed range, one can in turn bracket an allowed range of n{sub s} and r for these models. The added constraints can help break degeneracies between inflation models that otherwise overlap in their predictions for n{sub s} and r.
Moduli backreaction on inflationary attractors
NASA Astrophysics Data System (ADS)
Roest, Diederik; Scalisi, Marco; Werkman, Pelle
2016-12-01
We investigate the interplay between moduli dynamics and inflation, focusing on the Kachru-Kallosh-Linde-Trivedi scenario and cosmological α -attractors. General couplings between these sectors can induce a significant backreaction and potentially destroy the inflationary regime; however, we demonstrate that this generically does not happen for α -attractors. Depending on the details of the superpotential, the volume modulus can either be stable during the entire inflationary trajectory or become tachyonic at some point and act as a waterfall field, resulting in a sudden end of inflation. In the latter case there is a universal supersymmetric minimum where the scalars end up, preventing the decompactification scenario. The gravitino mass is independent from the inflationary scale with no fine-tuning of the parameters. The observational predictions conform to the universal value of attractors, fully compatible with the Planck data, with possibly a capped number of e -folds due to the interplay with moduli.
Inflationary buildup of a vector field condensate and its cosmological consequences
Sanchez, Juan C. Bueno; Dimopoulos, Konstantinos E-mail: k.dimopoulos1@lancaster.ac.uk
2014-01-01
Light vector fields during inflation obtain a superhorizon perturbation spectrum when their conformal invariance is appropriately broken. Such perturbations, by means of some suitable mechanism (e.g. the vector curvaton mechanism), can contribute to the curvatue perturbation in the Universe and produce characteristic signals, such as statistical anisotropy, on the microwave sky, most recently surveyed by the Planck satellite mission. The magnitude of such characteristic features crucially depends on the magnitude of the vector condensate generated during inflation. However, in the vast majority of the literature the expectation value of this condensate has so-far been taken as a free parameter, lacking a definite prediction or a physically motivated estimate. In this paper, we study the stochastic evolution of the vector condensate and obtain an estimate for its magnitude. Our study is mainly focused in the supergravity inspired case when the kinetic function and mass of the vector boson is time-varying during inflation, but other cases are also explored such as a parity violating axial theory or a non-minimal coupling between the vector field and gravity. As an example, we apply our findings in the context of the vector curvaton mechanism and contrast our results with current observations.
Massive fields as systematics for single field inflation
NASA Astrophysics Data System (ADS)
Jiang, Hongliang; Wang, Yi
2017-06-01
During inflation, massive fields can contribute to the power spectrum of curvature perturbation via a dimension-5 operator. This contribution can be considered as a bias for the program of using ns and r to select inflation models. Even the dimension-5 operator is suppressed by Λ = Mp, there is still a significant shift on the ns-r diagram if the massive fields have m ~ H. On the other hand, if the heavy degree of freedom appears only at the same energy scale as the suppression scale of the dimension-5 operator, then significant shift on the ns-r diagram takes place at m=Λ ~ 70H, which is around the inflationary time-translation symmetry breaking scale. Hence, the systematics from massive fields pose a greater challenge for future high precision experiments for inflationary model selection. This result can be thought of as the impact of UV sensitivity to inflationary observables.
Recovering the inflationary potential
Turner, Michael S.
1993-08-06
A procedure is developed for the recovery of the inflationary potential owl the interval that affects astrophysical scales. The amplitudes of the scalar and tensor metric perturbations and their power-spectrum indices, which can in principle be inferred from large-angle CBR anisotropy experiments and other cosmological data, determine the value of the inflationary potential and its first two derivatives. From these, the inflationary potential can be reconstructed in a Taylor series and the consistency of the inflationary hypothesis tested. A number of examples are presented, and the effect of observational uncertainties is discussed.
Recovering the inflationary potential
Turner, M.S. NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 )
1993-12-15
A procedure is developed for the recovery of the inflationary potential over the interval that affects astrophysical scales ([approx]1 Mpc to 10[sup 4] Mpc). The amplitudes of the scalar and tensor metric perturbations and their power-spectrum indices, which in principle can be inferred from large-angle CBR anisotropy and other cosmological data, determine the value of the inflationary potential and its first two derivatives. From these, the inflationary potential can be reconstructed in a Taylor series and the consistency of the inflationary hypothesis tested. Examples are presented, and the effect of observational uncertainties is discussed.
Constraints on single-field inflation
Pirtskhalava, David; Santoni, Luca; Trincherini, Enrico
2016-06-28
Many alternatives to canonical slow-roll inflation have been proposed over the years, one of the main motivations being to have a model, capable of generating observable values of non-Gaussianity. In this work, we (re-)explore the physical implications of a great majority of such models within a single, effective field theory framework (including novel models with large non-Gaussianity discussed for the first time below). The constraints we apply — both theoretical and experimental — are found to be rather robust, determined to a great extent by just three parameters: the coefficients of the quadratic EFT operators (δN){sup 2} and δNδE, and the slow-roll parameter ε. This allows to significantly limit the majority of single-field alternatives to canonical slow-roll inflation. While the existing data still leaves some room for most of the considered models, the situation would change dramatically if the current upper limit on the tensor-to-scalar ratio decreased down to r<10{sup −2}. Apart from inflationary models driven by plateau-like potentials, the single-field model that would have a chance of surviving this bound is the recently proposed slow-roll inflation with weakly-broken galileon symmetry. In contrast to canonical slow-roll inflation, the latter model can support r<10{sup −2} even if driven by a convex potential, as well as generate observable values for the amplitude of non-Gaussianity.
Constraints on single-field inflation
NASA Astrophysics Data System (ADS)
Pirtskhalava, David; Santoni, Luca; Trincherini, Enrico
2016-06-01
Many alternatives to canonical slow-roll inflation have been proposed over the years, one of the main motivations being to have a model, capable of generating observable values of non-Gaussianity. In this work, we (re-)explore the physical implications of a great majority of such models within a single, effective field theory framework (including novel models with large non-Gaussianity discussed for the first time below). The constraints we apply—both theoretical and experimental—are found to be rather robust, determined to a great extent by just three parameters: the coefficients of the quadratic EFT operators (δN)2 and δNδE, and the slow-roll parameter ɛ. This allows to significantly limit the majority of single-field alternatives to canonical slow-roll inflation. While the existing data still leaves some room for most of the considered models, the situation would change dramatically if the current upper limit on the tensor-to-scalar ratio decreased down to r < 10-2. Apart from inflationary models driven by plateau-like potentials, the single-field model that would have a chance of surviving this bound is the recently proposed slow-roll inflation with weakly-broken galileon symmetry. In contrast to canonical slow-roll inflation, the latter model can support r < 10-2 even if driven by a convex potential, as well as generate observable values for the amplitude of non-Gaussianity.
The best inflationary models after Planck
Martin, Jérôme; Vennin, Vincent; Ringeval, Christophe; Trotta, Roberto E-mail: christophe.ringeval@uclouvain.be E-mail: vennin@iap.fr
2014-03-01
We compute the Bayesian evidence and complexity of 193 slow-roll single-field models of inflation using the Planck 2013 Cosmic Microwave Background data, with the aim of establishing which models are favoured from a Bayesian perspective. Our calculations employ a new numerical pipeline interfacing an inflationary effective likelihood with the slow-roll library ASPIC and the nested sampling algorithm MultiNest. The models considered represent a complete and systematic scan of the entire landscape of inflationary scenarios proposed so far. Our analysis singles out the most probable models (from an Occam's razor point of view) that are compatible with Planck data, while ruling out with very strong evidence 34% of the models considered. We identify 26% of the models that are favoured by the Bayesian evidence, corresponding to 15 different potential shapes. If the Bayesian complexity is included in the analysis, only 9% of the models are preferred, corresponding to only 9 different potential shapes. These shapes are all of the plateau type.
Toward the inflationary paradigm: Lectures on inflationary cosmology
Turner, M.S.
1987-02-01
Guth's inflationary Universe scenario has revolutionized our thinking about the very early Universe. The inflationary scenario offers the possibility of explaining a handful of very fundamental cosmological facts - the homogeneity, isotropy, and flatness of the Universe, the origin of density inhomogeneities and the origin of the baryon asymmetry, while at the same time avoiding the monopole problem. It is based upon microphysical events which occurred early (t less than or equal to 10/sup -34/ sec) in the history of the Universe, but well after the planck epoc (t greater than or equal to 10/sup -43/ sec). While Guth's original model was fundamentally flawed, the variant based on the slow-rollover transition proposed by Linde, and Albrecht and Steinhardt (dubbed 'new inflation') appears viable. Although old inflation and the earliest models of new inflation were based upon first order phase transitions associated with spontaneous-symmetry breaking (SSB), it now appears that the inflationary transition is a much more generic phenomenon, being associated with the evolution of a weakly-coupled scalar field which for some reason or other was initially displaced from the minimum of its potential. Models now exist which are based on a wide variety of microphysics: SSB, SUSY/SUGR, compactification of extra dimensions, R/sup 2/ gravity, induced gravity, and some random, weakly-coupled scalar field. While there are several models which successfully implement the inflation, none is particularly compelling and all seem somewhat ad hoc. The common distasteful feature of all the successful models is the necessity of a small dimensionless number in the model - usually in the form of a dimensionless coupling of order 10/sup -15/. All inflationary scenarios rely upon the assumption that vacuum energy was once dynamically very significant, whereas today there exists every evidence that it is not. 133 refs., 17 figs.
Inflationary nonsingular quantum cosmological model
Falciano, Felipe T.; Pinto-Neto, Nelson; Santini, E. Sergio
2007-10-15
A stiff matter-dominated universe modeled by a free massless scalar field minimally coupled to gravity in a Friedmann-Lemaitre-Robertson-Walker (FLRW) geometry is quantized. Generalized complex-width Gaussian superpositions of the solutions of the Wheeler-DeWitt equation are constructed and the Bohm-de Broglie interpretation of quantum cosmology is applied. A planar dynamical system is found in which a diversity of quantum Bohmian trajectories are obtained and discussed. One class of solutions represents nonsingular inflationary models starting at infinity past from flat space-time with Planckian size spacelike hypersurfaces, which inflates without inflaton but due to a quantum cosmological effect, until it makes an analytical graceful exit from this inflationary epoch to a decelerated classical stiff matter expansion phase.
Simple inflationary quintessential model
NASA Astrophysics Data System (ADS)
de Haro, Jaume; Amorós, Jaume; Pan, Supriya
2016-04-01
In the framework of a flat Friedmann-Lemaître-Robertson-Walker geometry, we present a non-geodesically past complete model of our Universe without the big bang singularity at finite cosmic time, describing its evolution starting from its early inflationary era up to the present accelerating phase. We found that a hydrodynamical fluid with nonlinear equation of state could result in such scenario, which after the end of this inflationary stage, suffers a sudden phase transition and enters into the stiff matter dominated era, and the Universe becomes reheated due to a huge amount of particle production. Finally, it asymptotically enters into the de Sitter phase concluding the present accelerated expansion. Using the reconstruction technique, we also show that this background provides an extremely simple inflationary quintessential potential whose inflationary part is given by the well-known 1-dimensional Higgs potential, i.e., a double well inflationary potential, and the quintessential one by an exponential potential that leads to a deflationary regime after this inflation, and it can depict the current cosmic acceleration at late times. Moreover the Higgs potential leads to a power spectrum of the cosmological perturbations which fit well with the latest Planck estimations. Further, we compared our viable potential with some known inflationary quintessential potential, which shows that our quintessential model, that is, the Higgs potential combined with the exponential one, is an improved version of them because it contains an analytic solution that allows us to perform all analytic calculations. Finally, we have shown that the introduction of a nonzero cosmological constant simplifies the potential considerably with an analytic behavior of the background which again permits us to evaluate all the quantities analytically.
Critical constraint on inflationary magnetogenesis
Fujita, Tomohiro; Yokoyama, Shuichiro E-mail: shu@icrr.u-tokyo.ac.jp
2014-03-01
Recently, there are several reports that the cosmic magnetic fields on Mpc scale in void region is larger than ∼ 10{sup −15}G with an uncertainty of a few orders from the current blazar observations. On the other hand, in inflationary magnetogenesis models, additional primordial curvature perturbations are inevitably produced from iso-curvature perturbations due to generated electromagnetic fields. We explore such induced curvature perturbations in a model independent way and obtained a severe upper bound for the energy scale of inflation from the observed cosmic magnetic fields and the observed amplitude of the curvature perturbation , as ρ{sub inf}{sup 1/4} < 300MeV × (B{sub obs}/10{sup −15}G){sup −1} where B{sub obs} is the strength of the magnetic field at present. Therefore, without a dedicated low energy inflation model or an additional amplification of magnetic fields after inflation, inflationary magnetogenesis on Mpc scale is generally incompatible with CMB observations.
Transport equations for the inflationary trispectrum
Anderson, Gemma J.; Seery, David; Mulryne, David J. E-mail: D.Mulryne@qmul.ac.uk
2012-10-01
We use transport techniques to calculate the trispectrum produced in multiple-field inflationary models with canonical kinetic terms. Our method allows the time evolution of the local trispectrum parameters, τ{sub NL} and g{sub NL}, to be tracked throughout the inflationary phase. We illustrate our approach using examples. We give a simplified method to calculate the superhorizon part of the relation between field fluctuations on spatially flat hypersurfaces and the curvature perturbation on uniform density slices, ζ, and obtain its third-order part for the first time. We clarify how the 'backwards' formalism of Yokoyama et al. relates to our analysis and other recent work. We supply explicit formulae which enable each inflationary observable to be computed in any canonical model of interest, using a suitable first-order ODE solver.
Inflationary dynamics in f(𝒢) gravity
NASA Astrophysics Data System (ADS)
Sharif, M.; Ikram, Ayesha
This paper investigates inflationary dynamics for isotropic and homogeneous universe model in the background of f(𝒢) gravity. We construct Hubble-flow functions, slow-roll parameters, amplitude of scalar power spectrum, spectral index and tensor-scalar ratio for a particular form of equation of state which describes quasi-de Sitter expansion. The dynamics of inflationary epoch is analyzed for scalar field as well as fluid cosmology with viable power-law f(𝒢) model. We obtain different potential functions that correspond to chaotic inflation and Starobinsky type models. The graphical behavior of these parameters shows compatible results with observational Planck 2015 data in this gravity.
PLANCK and WMAP constraints on generalised Hubble flow inflationary trajectories
Contaldi, Carlo R.; Horner, Jonathan S. E-mail: j.horner11@imperial.ac.uk
2014-08-01
We use the Hamilton-Jacobi formalism to constrain the space of possible single field, inflationary Hubble flow trajectories when compared to the WMAP and PLANK satellites Cosmic Microwave Background (CMB) results. This method yields posteriors on the space of Hubble Slow Roll (HSR) parameters that uniquely determine the history of the Hubble parameter during the inflating epoch. The trajectories are used to numerically determine the observable primordial power spectrum and bispectra that can then be compared to observations. Our analysis is used to infer the most likely shape of the inflaton potential V(φ) and also yields a prediction for, B, the dimensionless amplitude of the non-Gaussian bispectrum.
PLANCK and WMAP constraints on generalised Hubble flow inflationary trajectories
NASA Astrophysics Data System (ADS)
Contaldi, Carlo R.; Horner, Jonathan S.
2014-08-01
We use the Hamilton-Jacobi formalism to constrain the space of possible single field, inflationary Hubble flow trajectories when compared to the WMAP and PLANK satellites Cosmic Microwave Background (CMB) results. This method yields posteriors on the space of Hubble Slow Roll (HSR) parameters that uniquely determine the history of the Hubble parameter during the inflating epoch. The trajectories are used to numerically determine the observable primordial power spectrum and bispectra that can then be compared to observations. Our analysis is used to infer the most likely shape of the inflaton potential V(phi) and also yields a prediction for, Script B, the dimensionless amplitude of the non-Gaussian bispectrum.
Quantum inflationary minisuperspace cosmological models
Kim Sangpyo.
1991-01-01
The Wheeler-DeWitt equations for the Friedmann-Robertson-Walker cosmology conformally and minimally coupled to scalar fields with power-lay potential are expanded in the eigenstates of the scalar field parts. The gravitational parts become a diagonal matrix-valued differential equation for a conformal scalar field, and a coupled matrix-valued differential equation for a minimally coupled scalar field. The Cauchy initial value problem is defined with respect to the intrinsic timelike coordinate, and the wavefunctions incorporating initial data are constructed using the product integral formulation. The packetlike wavefunctions around classical turning points are shown possible in the product integral formulation, and the returning wavepackets near the returning point of the classical Friedmann-Robertson-Walker cosmology are constructed. The wavefunctions to the Wheeler-DeWitt equation minimally coupled to the scaler field are constructed by two differential methods, the master equation and the enlarged matrix equation. The spectrum for the wavefunctions regular at the infinite size of universe is found, and these are interpreted as the Hawking-Page spectrum of wormholes connecting two asymptotically Euclidean regions. The quantum Friedmann-Robertson-Walker cosmology is extended to the minimal scalar field with the inflationary potential having a first order phase transition. The Wheeler-DeWitt equation is expanded in the eigenstates of the scalar field, and the gravitational part becomes a coupled matrix-valued differential equation.
Observational Signatures and Non-Gaussianities ofGeneral Single Field Inflation
Chen, Xingang; Huang, Min-xin; Kachru, Shamit; Shiu, Gary
2006-05-05
We perform a general study of primordial scalar non-Gaussianities in single field inflationary models. We consider models where the inflaton Lagrangian is an arbitrary function of the scalar field and its first derivative, and the sound speed is arbitrary. We find that under reasonable assumptions, the non-Gaussianity is completely determined by 5 parameters. In special limits of the parameter space, one finds distinctive ''shapes'' of the non-Gaussianity. In models with a small sound speed, several of these shapes would become potentially observable in the near future. Different limits of our formulae recover various previously known results.
Coupling the inflationary sector to matter
NASA Astrophysics Data System (ADS)
Kallosh, Renata; Linde, Andrei; Wrase, Timm
2016-04-01
We describe the coupling of matter fields to an inflationary sector of supergravity, the inflaton Φ and a stabilizer S, in models where the Kähler potential has a flat inflaton direction. Such models include, in particular, advanced versions of the hyperbolic α-attractor models with a flat inflaton direction Kähler potential, providing a good fit to the observational data. If the superpotential is at least quadratic in the matter fields U i , with restricted couplings to the inflaton sector, we prove that under certain conditions: i) The presence of the matter fields does not affect a successful inflationary evolution. ii) There are no tachyons in the matter sector during and after inflation. iii) The matter masses squared are higher than 3 H 2 during inflation. The simplest class of theories satisfying all required conditions is provided by models with a flat direction Kähler potential, and with the inflaton Φ and a stabilizer S belonging to a hidden sector, so that matter fields have no direct coupling to the inflationary sector in the Kähler potential and in the superpotential.
Single field double inflation and primordial black holes
NASA Astrophysics Data System (ADS)
Kannike, K.; Marzola, L.; Raidal, M.; Veermäe, H.
2017-09-01
Within the framework of scalar-tensor theories, we study the conditions that allow single field inflation dynamics on small cosmological scales to significantly differ from that of the large scales probed by the observations of cosmic microwave background. The resulting single field double inflation scenario is characterised by two consequent inflation eras, usually separated by a period where the slow-roll approximation fails. At large field values the dynamics of the inflaton is dominated by the interplay between its non-minimal coupling to gravity and the radiative corrections to the inflaton self-coupling. For small field values the potential is, instead, dominated by a polynomial that results in a hilltop inflation. Without relying on the slow-roll approximation, which is invalidated by the appearance of the intermediate stage, we propose a concrete model that matches the current measurements of inflationary observables and employs the freedom granted by the framework on small cosmological scales to give rise to a sizeable population of primordial black holes generated by large curvature fluctuations. We find that these features generally require a potential with a local minimum. We show that the associated primordial black hole mass function is only approximately lognormal.
Closed inflationary universe in patch cosmology
Campo, Sergio del Herrera, Ramon Saavedra, Joel Labrana, Pedro
2009-09-15
In this paper, we study closed inflationary universe models using the Gauss-Bonnet Brane. We determine and characterize the existence of a universe with {omega}>1, with an appropriate period of inflation. We have found that this model is less restrictive in comparison with the standard approach where a scalar field is considered. We use recent astronomical observations to constrain the parameters appearing in the model.
Single-field inflation constraints from CMB and SDSS data
NASA Astrophysics Data System (ADS)
Finelli, Fabio; Hamann, Jan; Leach, Samuel M.; Lesgourgues, Julien
2010-04-01
We present constraints on canonical single-field inflation derived from WMAP five year, ACBAR, QUAD, BICEP data combined with the halo power spectrum from SDSS LRG7. Models with a non-scale-invariant spectrum and a red tilt nS < 1 are now preferred over the Harrison-Zel'dovich model (nS = 1, tensor-to-scalar ratio r = 0) at high significance. Assuming no running of the spectral indices, we derive constraints on the parameters (nS, r) and compare our results with the predictions of simple inflationary models. The marginalised credible intervals read nS = 0.962+0.028-0.026 and r < 0.17 (95% confidence level). With respect to previous analyses, the portion of the 68% c.l. contours compatible with potentials which are concave in the observable region becomes even smaller, but the quadratic potential model remains inside the 95% c.l. contours. We demonstrate that these results are robust to changes in the datasets considered and in the theoretical assumptions made. We then consider a non-vanishing running of the spectral indices by employing different methods, non-parametric but approximate, or parametric but exact. With our combination of CMB and LSS data, running models are preferred over power-law models only by a Δχ2 simeq 5.8, allowing inflationary stages producing a sizable negative running -0.063+0.061-0.049 and larger tensor-scalar ratio r < 0.33 at the 95% c.l. This requires large values of the third derivative of the inflaton potential within the observable range. We derive bounds on this derivative under the assumption that the inflaton potential can be approximated as a third order polynomial within the observable range.
Inflationary predictions in scalar-tensor DBI inflation
Weller, Joel M.; Bruck, Carsten van de; Mota, David F. E-mail: c.vandebruck@sheffield.ac.uk
2012-06-01
The scalar-tensor Dirac-Born-Infeld (DBI) inflation scenario provides a simple mechanism to reduce the large values of the boost factor associated with single field models with DBI action, whilst still being able to drive 60 efolds of inflation. Using a slow-roll approach, we obtain an analytical expression for the spectral index of the perturbations and, moreover, determine numerically the regions of the parameter space of the model capable of giving rise to a power spectrum with amplitude and spectral index within the observed bounds. We find that regions that exhibit significant DBI effects throughout the inflationary period can be discarded by virtue of a blue-tilted spectral index, however, there are a number of viable cases — associated with a more red-tilted spectral index — for which the boost factor is initially suppressed by the effect of the coupling between the fields, but increases later to moderate values.
Observing inflationary reheating.
Martin, Jérôme; Ringeval, Christophe; Vennin, Vincent
2015-02-27
Reheating is the epoch which connects inflation to the subsequent hot big-bang phase. Conceptually very important, this era is, however, observationally poorly known. We show that the current Planck satellite measurements of the cosmic microwave background (CMB) anisotropies constrain the kinematic properties of the reheating era for most of the inflationary models. This result is obtained by deriving the marginalized posterior distributions of the reheating parameter for about 200 models of slow-roll inflation. Weighted by the statistical evidence of each model to explain the data, we show that the Planck 2013 measurements induce an average reduction of the posterior-to-prior volume by 40%. Making some additional assumptions on reheating, such as specifying a mean equation of state parameter, or focusing the analysis on peculiar scenarios, can enhance or reduce this constraint. Our study also indicates that the Bayesian evidence of a model can substantially be affected by the reheating properties. The precision of the current CMB data is therefore such that estimating the observational performance of a model now requires incorporating information about its reheating history.
Einstein Inflationary Probe (EIP)
NASA Technical Reports Server (NTRS)
Hinshaw, Gary
2004-01-01
I will discuss plans to develop a concept for the Einstein Inflation Probe: a mission to detect gravity waves from inflation via the unique signature they impart to the cosmic microwave background (CMB) polarization. A sensitive CMB polarization satellite may be the only way to probe physics at the grand-unified theory (GUT) scale, exceeding by 12 orders of magnitude the energies studied at the Large Hadron Collider. A detection of gravity waves would represent a remarkable confirmation of the inflationary paradigm and set the energy scale at which inflation occurred when the universe was a fraction of a second old. Even a strong upper limit to the gravity wave amplitude would be significant, ruling out many common models of inflation, and pointing to inflation occurring at much lower energy, if at all. Measuring gravity waves via the CMB polarization will be challenging. We will undertake a comprehensive study to identify the critical scientific requirements for the mission and their derived instrumental performance requirements. At the core of the study will be an assessment of what is scientifically and experimentally optimal within the scope and purpose of the Einstein Inflation Probe.
Primordial black holes, eternal inflation, and the inflationary parameter space after WMAP5
Peiris, Hiranya V; Easther, Richard E-mail: richard.easther@yale.edu
2008-07-15
We consider constraints on inflation driven by a single, minimally coupled scalar field in the light of the WMAP5 (WMAP: Wilkinson Microwave Anisotropy Probe) data set, as well as ACBAR (Arcminute Cosmology Bolometer Array Receiver) and the SuperNova Legacy Survey. We use the slow roll reconstruction algorithm to derive optimal constraints on the inflationary parameter space. The scale dependence in the slope of the scalar spectrum permitted by WMAP5 is large enough to lead to viable models where the small scale perturbations have a substantial amplitude when extrapolated to the end of inflation. We find that excluding parameter values which would cause the overproduction of primordial black holes or even the onset of eternal inflation leads to potentially significant constraints on the slow roll parameters. Finally, we present a more sophisticated approach to including priors based on the total duration of inflation, and discuss the resulting restrictions on the inflationary parameter space.
Higgs vacuum stability and inflationary dynamics after BICEP2 and PLANCK dust polarisation data
Bhattacharya, Kaushik; Chakrabortty, Joydeep; Das, Suratna; Mondal, Tanmoy E-mail: joydeep@iitk.ac.in E-mail: tanmoym@prl.res.in
2014-12-01
If the recent detection of B-mode polarization of the Cosmic Microwave Background by BICEP2 observations, withstand the test of time after the release of recent PLANCK dust polarisation data, then it would surprisingly put the inflationary scale near Grand Unification scale if one considers single-field inflationary models. On the other hand, Large Hadron Collider has observed the elusive Higgs particle whose presently observed mass can lead to electroweak vacuum instability at high scale (∼ O(10{sup 10}) GeV). In this article, we seek for a simple particle physics model which can simultaneously keep the vacuum of the theory stable and yield high-scale inflation successfully. To serve our purpose, we extend the Standard Model of particle physics with a U(1){sub B-L} gauged symmetry which spontaneously breaks down just above the inflationary scale. Such a scenario provides a constrained parameter space where both the issues of vacuum stability and high-scale inflation can be successfully accommodated. The threshold effect on the Higgs quartic coupling due to the presence of the heavy inflaton field plays an important role in keeping the electroweak vacuum stable. Furthermore, this scenario is also capable of reheating the universe at the end of inflation. Though the issues of Dark Matter and Dark Energy, which dominate the late-time evolution of our universe, cannot be addressed within this framework, this model successfully describes the early universe dynamics according to the Big Bang model.
WMAP normalization of inflationary cosmologies
Liddle, Andrew R.; Parkinson, David; Mukherjee, Pia; Leach, Samuel M.
2006-10-15
We use the three-year WMAP observations to determine the normalization of the matter power spectrum in inflationary cosmologies. In this context, the quantity of interest is not the normalization marginalized over all parameters, but rather the normalization as a function of the inflationary parameters n{sub S} and r with marginalization over the remaining cosmological parameters. We compute this normalization and provide an accurate fitting function. The statistical uncertainty in the normalization is 3%, roughly half that achieved by COBE. We use the k-l relation for the standard cosmological model to identify the pivot scale for the WMAP normalization. We also quote the inflationary energy scale corresponding to the WMAP normalization.
Graviton production in inflationary cosmology
NASA Astrophysics Data System (ADS)
Abbott, L. F.; Harari, D. D.
1986-01-01
We provide a completely quantum-mechanical derivation of the spectrum of gravitational waves producedin any inflationary cosmology. The gravitational waves result from a sequence of Bogoliubov transformations between creation and annihilation operators defined in de Sitter space and in radiation- and matter-dominated Robertson-Walker spacetimes. We discuss how the results depend on the initial state at the beginning of the inflationary period. Supported by a Fellowship from the Consejo Nacional de Investigaciones Científicas y Técnicas, República Argentina.
Designing and testing inflationary models with Bayesian networks
Price, Layne C.; Peiris, Hiranya V.; Frazer, Jonathan; Easther, Richard E-mail: h.peiris@ucl.ac.uk E-mail: r.easther@auckland.ac.nz
2016-02-01
Even simple inflationary scenarios have many free parameters. Beyond the variables appearing in the inflationary action, these include dynamical initial conditions, the number of fields, and couplings to other sectors. These quantities are often ignored but cosmological observables can depend on the unknown parameters. We use Bayesian networks to account for a large set of inflationary parameters, deriving generative models for the primordial spectra that are conditioned on a hierarchical set of prior probabilities describing the initial conditions, reheating physics, and other free parameters. We use N{sub f}-quadratic inflation as an illustrative example, finding that the number of e-folds N{sub *} between horizon exit for the pivot scale and the end of inflation is typically the most important parameter, even when the number of fields, their masses and initial conditions are unknown, along with possible conditional dependencies between these parameters.
Causality implies inflationary back-reaction
NASA Astrophysics Data System (ADS)
Basu, S.; Tsamis, N. C.; Woodard, R. P.
2017-07-01
There is a widespread belief among inflationary cosmologists that a local observer cannot sense super-horizon gravitons. The argument goes that a local observer would subsume super-horizon gravitons into a redefinition of his coordinate system. We show that adopting this view for pure gravity on de Sitter background leads to time variation in the Hubble parameter measured by a local observer. It also leads to a violation of the gravitational field equation R = 4Λ because that equation is obeyed by the full metric, rather than the one which has been cleansed of super-horizon modes.
CMB cold spot from inflationary feature scattering
NASA Astrophysics Data System (ADS)
Wang, Yi; Ma, Yin-Zhe
2016-05-01
We propose a ;feature-scattering; mechanism to explain the cosmic microwave background cold spot seen from WMAP and Planck maps. If there are hidden features in the potential of multi-field inflation, the inflationary trajectory can be scattered by such features. The scattering is controlled by the amount of isocurvature fluctuations, and thus can be considered as a mechanism to convert isocurvature fluctuations into curvature fluctuations. This mechanism predicts localized cold spots (instead of hot ones) on the CMB. In addition, it may also bridge a connection between the cold spot and a dip on the CMB power spectrum at ℓ ∼ 20.
Quantum gravity extension of the inflationary scenario.
Agullo, Ivan; Ashtekar, Abhay; Nelson, William
2012-12-21
Since the standard inflationary paradigm is based on quantum field theory on classical space-times, it excludes the Planck era. Using techniques from loop quantum gravity, the paradigm is extended to a self-consistent theory from the Planck scale to the onset of slow roll inflation, covering some 11 orders of magnitude in energy density and curvature. This preinflationary dynamics also opens a small window for novel effects, e.g., a source for non-Gaussianities, which could extend the reach of cosmological observations to the deep Planck regime of the early Universe.
Bootstrapping from inflationary magnetogenesis to CMB initial conditions
NASA Astrophysics Data System (ADS)
Giovannini, Massimo
2013-10-01
The temperature and polarization anisotropies of the cosmic microwave background are analyzed under the hypothesis that the same inflationary seed accounting for protogalactic magnetism also affects the Einstein-Boltzmann hierarchy whose initial conditions are assigned for typical correlation scales larger than the Hubble radius after matter-radiation equality but before decoupling. Since the primordial gauge spectrum depends on a combination of pivotal parameters of the concordance model, the angular power spectra of the temperature and of the polarization are computed, for the first time, in the presence of a putative large-scale magnetic field of inflationary origin and without supplementary hypotheses.
Friedman, Brett C.; Cooray, Asantha; Melchiorri, Alessandro
2006-12-15
In addition to density perturbations, inflationary models of the early Universe generally predict a stochastic background of gravitational waves or tensor fluctuations. By making use of the inflationary flow approach for single field models and fitting the models with Monte Carlo techniques to cosmic microwave background (CMB) data from the Wilkinson Microwave Anisotropy Probe (WMAP), we discuss the expected properties of the gravitational wave background from inflation at scales corresponding to direct detection experiments with laser interferometers in space. We complement the Monte Carlo numerical calculations by including predictions expected under several classes of analytical inflationary models. We find that an improved version of big bang observer (BBO-grand) can be used to detect a gravitational wave background at 0.1 Hz with a corresponding CMB tensor-to-scalar ratio above 10{sup -4}. Even if the CMB tensor-to-scalar ratio were to be above 10{sup -2}, we suggest that BBO-grand will be useful to study inflationary models as the standard version of BBO, with a sensitivity to a stochastic gravitational wave background {omega}{sub GW}h{sup 2}>10{sup -17}, will only allow a marginal detection of the amplitude while leaving the tensor spectral index at 0.1 Hz unconstrained. Also, inflationary models with a large tensor-to-scalar ratio predict a substantial negative tensor spectral index such that the gravitational wave amplitude is damped at direct detection frequencies. We also discuss the extent to which CMB measurements can be used to predict the gravitational wave background amplitude in a direct detection experiment and how any measurement of the amplitude and the spectral tilt of the gravitational wave background at direct detection frequencies together with the CMB tensor-to-scalar ratio can be used to establish slow-roll inflation.
Particle production and reheating of the inflationary universe
Moss, Ian G.; Graham, Chris
2008-12-15
Thermal field theory is applied to particle production rates in inflationary models, leading to new results for catalyzed or two-stage decay, where massive fields act as decay channels for the production of light fields. A numerical investigation of the Boltzmann equation in an expanding universe shows that the particle distributions produced during small amplitude inflaton oscillations or even alongside slowly moving inflaton fields can thermalize.
Inflationary perturbations and precision cosmology
Habib, Salman; Heinen, Andreas; Heitmann, Katrin; Jungman, Gerard
2005-02-15
Inflationary cosmology provides a natural mechanism for the generation of primordial perturbations which seed the formation of observed cosmic structure and lead to specific signals of anisotropy in the cosmic microwave background radiation. In order to test the broad inflationary paradigm as well as particular models against precision observations, it is crucial to be able to make accurate predictions for the power spectrum of both scalar and tensor fluctuations. We present detailed calculations of these quantities utilizing direct numerical approaches as well as error-controlled uniform approximations, comparing with the (uncontrolled) traditional slow-roll approach. A simple extension of the leading-order uniform approximation yields results for the power spectra amplitudes, the spectral indices, and the running of spectral indices, with accuracy of the order of 0.1%--approximately the same level at which the transfer functions are known. Several representative examples are used to demonstrate these results.
Inflationary imprints on dark matter
NASA Astrophysics Data System (ADS)
Nurmi, Sami; Tenkanen, Tommi; Tuominen, Kimmo
2015-11-01
We show that dark matter abundance and the inflationary scale H could be intimately related. Standard Model extensions with Higgs mediated couplings to new physics typically contain extra scalars displaced from vacuum during inflation. If their coupling to Standard Model is weak, they will not thermalize and may easily constitute too much dark matter reminiscent to the moduli problem. As an example we consider Standard Model extended by a Z2 symmetric singlet s coupled to the Standard Model Higgs Φ via λ Φ†Φ s2. Dark matter relic density is generated non-thermally for λ lesssim 10-7. We show that the dark matter yield crucially depends on the inflationary scale. For H~ 1010 GeV we find that the singlet self-coupling and mass should lie in the regime λsgtrsim 10-9 and mslesssim 50 GeV to avoid dark matter overproduction.
NASA Astrophysics Data System (ADS)
Amorós, Jaume; de Haro, Jaume
2016-12-01
The PLANCK collaboration has determined, or greatly constrained, values for the spectral parameters of the CMB radiation, namely the spectral index n s , its running α s , the running of the running β s , using a growing body of measurements of CMB anisotropies by the Planck satellite and other missions. These values do not follow the hierarchy of sizes predicted by single field, slow roll inflationary theory, and are thus difficult to fit for such inflation models. In this work we present first a study of 49 single field, slow roll inflationary potentials in which we assess the likelyhood of these models fitting the spectral parameters to their currently most accurate determination given by the PLANCK collaboration. We check numerically with a MATLAB program the spectral parameters that each model can yield for a very broad, comprehensive list of possible parameter and field values. The comparison of spectral parameter values supported by the models with their determinations by the PLANCK collaboration leads to the conclusion that the data provided by PLANCK2015 TT+lowP and PLANCK2015 TT,TE,EE+lowP taking into account the running of the running disfavours 40 of the 49 models with confidence level at least 92.8 %. Next, we discuss the reliability of the current computations of these spectral parameters. We identify a bias in the method of determination of the spectral parameters by least residue parameter fitting (using MCMC or any other scheme) currently used to reconstruct the power spectrum of scalar perturbations. This bias can explain the observed contradiction between theory and observations. Its removal is computationally costly, but necessary in order to compare the forecasts of single field, slow roll theories with observations.
Pre-inflationary clues from String Theory?
Kitazawa, N.; Sagnotti, A. E-mail: sagnotti@sns.it
2014-04-01
''Brane supersymmetry breaking'' occurs in String Theory when the only available combinations of D-branes and orientifolds are not mutually BPS and yet do not introduce tree-level tachyon instabilities. It is characterized by the emergence of a steep exponential potential, and thus by the absence of maximally symmetric vacua. The corresponding low-energy supergravity admits intriguing spatially-flat cosmological solutions where a scalar field is forced to climb up toward the steep potential after an initial singularity, and additional milder terms can inject an inflationary phase during the ensuing descent. We show that, in the resulting power spectra of scalar perturbations, an infrared suppression is typically followed by a pre-inflationary peak that reflects the end of the climbing phase and can lie well apart from the approximately scale invariant profile. A first look at WMAP9 raw data shows that, while the χ{sup 2} fits for the low-ℓ CMB angular power spectrum are clearly compatible with an almost scale invariant behavior, they display nonetheless an eye-catching preference for this type of setting within a perturbative string regime.
A scenario for inflationary magnetogenesis without strong coupling problem
Tasinato, Gianmassimo
2015-03-01
Cosmological magnetic fields pervade the entire universe, from small to large scales. Since they apparently extend into the intergalactic medium, it is tantalizing to believe that they have a primordial origin, possibly being produced during inflation. However, finding consistent scenarios for inflationary magnetogenesis is a challenging theoretical problem. The requirements to avoid an excessive production of electromagnetic energy, and to avoid entering a strong coupling regime characterized by large values for the electromagnetic coupling constant, typically allow one to generate only a tiny amplitude of magnetic field during inflation. We propose a scenario for building gauge-invariant models of inflationary magnetogenesis potentially free from these issues. The idea is to derivatively couple a dynamical scalar, not necessarily the inflaton, to fermionic and electromagnetic fields during the inflationary era. Such couplings give additional freedom to control the time-dependence of the electromagnetic coupling constant during inflation. This fact allows us to find conditions to avoid the strong coupling problems that affect many of the existing models of magnetogenesis. We do not need to rely on a particular inflationary set-up for developing our scenario, that might be applied to different realizations of inflation. On the other hand, specific requirements have to be imposed on the dynamics of the scalar derivatively coupled to fermions and electromagnetism, that we are able to satisfy in an explicit realization of our proposal.
A scenario for inflationary magnetogenesis without strong coupling problem
Tasinato, Gianmassimo
2015-03-23
Cosmological magnetic fields pervade the entire universe, from small to large scales. Since they apparently extend into the intergalactic medium, it is tantalizing to believe that they have a primordial origin, possibly being produced during inflation. However, finding consistent scenarios for inflationary magnetogenesis is a challenging theoretical problem. The requirements to avoid an excessive production of electromagnetic energy, and to avoid entering a strong coupling regime characterized by large values for the electromagnetic coupling constant, typically allow one to generate only a tiny amplitude of magnetic field during inflation. We propose a scenario for building gauge-invariant models of inflationary magnetogenesis potentially free from these issues. The idea is to derivatively couple a dynamical scalar, not necessarily the inflaton, to fermionic and electromagnetic fields during the inflationary era. Such couplings give additional freedom to control the time-dependence of the electromagnetic coupling constant during inflation. This fact allows us to find conditions to avoid the strong coupling problems that affect many of the existing models of magnetogenesis. We do not need to rely on a particular inflationary set-up for developing our scenario, that might be applied to different realizations of inflation. On the other hand, specific requirements have to be imposed on the dynamics of the scalar derivatively coupled to fermions and electromagnetism, that we are able to satisfy in an explicit realization of our proposal.
Exploring Inflationary Braneworld Models
Leeper, Emily
2006-11-03
We demonstrate that a two brane system with a bulk scalar field driving power-law inflation on the branes has an instability in the radion. We solve for the resulting trajectory of the brane, and find that the instability can lead to collision. Brane quantities such as the scale factor are shown to be regular at this collision. In addition we describe the system using a low energy expansion. The low energy expansion accurately reproduces the known exact solution, but also identifies an alternative solution for the bulk metric and brane trajectory. This article, and the talk it accompanies are based on work first published in Physical Review D73 043506 (2006000.
Popa, L. A.; Caramete, A.; Mandolesi, N.; Burigana, C.
2009-12-01
We make a more general determination of the inflationary observables in the standard four-dimensional (4D) and five-dimensional (5D) single-field inflationary scenarios by the exact reconstruction of the dynamics of the inflation potential during the observable inflation with a minimal number of assumptions: the computation does not assume the slow-roll approximation and is valid in all regimes if the field is monotonically rolling down its potential. We address higher order effects in the standard and braneworld single-field inflation scenarios by fitting the Hubbble expansion rate and subsequently the inflationary potential directly to WMAP5+SN+BAO and Planck-like simulated data sets. Making use of the Hamilton-Jacobi formalism developed for the 5D single-field inflation model, we compute the scale dependence of the amplitudes of the scalar and tensor perturbations by integrating the exact mode equation. The solutions in 4D and 5D inflation scenarios differ through the dynamics of the background scalar field and the number of e-folds assumed to be compatible with the observational window of inflation. We analyze the implications of the theoretical uncertainty in the determination of the reheating temperature after inflation on the observable predictions of inflation and evaluate its impact on the degeneracy of the standard inflation consistency relation. We find that the detection of tensor perturbations and the theoretical uncertainties in the inflationary observable represents a significant challenge for the future Planck cosmic microwave background measurements: distinguishing between the observational signatures of the standard and braneworld single-field inflation scenarios. This work has been done in the frame of Planck Core Team activities.
Hybrid quantization of an inflationary universe
NASA Astrophysics Data System (ADS)
Fernández-Méndez, Mikel; Mena Marugán, Guillermo A.; Olmedo, Javier
2012-07-01
We quantize to completion an inflationary universe with small inhomogeneities in the framework of loop quantum cosmology. The homogeneous setting consists of a massive scalar field propagating in a closed, homogeneous scenario. We provide a complete quantum description of the system employing loop quantization techniques. After introducing small inhomogeneities as scalar perturbations, we identify the true physical degrees of freedom by means of a partial gauge fixing, removing all the local degrees of freedom except the matter perturbations. We finally combine a Fock description for the inhomogeneities with the polymeric quantization of the homogeneous background, providing the quantum Hamiltonian constraint of the composed system. Its solutions are then completely characterized, owing to the suitable choice of quantum constraint, and the physical Hilbert space is constructed. Finally, we consider the analog description for an alternate gauge and, moreover, in terms of gauge-invariant quantities. In the deparametrized model, all these descriptions are unitarily equivalent at the quantum level.
Gao, Xian; Kobayashi, Tsutomu; Yamaguchi, Masahide; Yokoyama, Jun'ichi
2011-11-18
We completely clarify the feature of primordial non-Gaussianities of tensor perturbations in the most general single-field inflation model with second-order field equations. It is shown that the most general cubic action for the tensor perturbation h(ij) is composed only of two contributions, one with two spacial derivatives and the other with one time derivative on each h(ij). The former is essentially identical to the cubic term that appears in Einstein gravity and predicts a squeezed shape, while the latter newly appears in the presence of the kinetic coupling to the Einstein tensor and predicts an equilateral shape. Thus, only two shapes appear in the graviton bispectrum of the most general single-field inflation model, which could open a new clue to the identification of inflationary gravitational waves in observations of cosmic microwave background anisotropies as well as direct detection experiments.
Inflationary imprints on dark matter
Nurmi, Sami; Tenkanen, Tommi; Tuominen, Kimmo E-mail: tommi.tenkanen@helsinki.fi
2015-11-01
We show that dark matter abundance and the inflationary scale H could be intimately related. Standard Model extensions with Higgs mediated couplings to new physics typically contain extra scalars displaced from vacuum during inflation. If their coupling to Standard Model is weak, they will not thermalize and may easily constitute too much dark matter reminiscent to the moduli problem. As an example we consider Standard Model extended by a Z{sub 2} symmetric singlet s coupled to the Standard Model Higgs Φ via λ Φ{sup †}Φ s{sup 2}. Dark matter relic density is generated non-thermally for λ ∼< 10{sup −7}. We show that the dark matter yield crucially depends on the inflationary scale. For H∼ 10{sup 10} GeV we find that the singlet self-coupling and mass should lie in the regime λ{sub s}∼> 10{sup −9} and m{sub s}∼< 50 GeV to avoid dark matter overproduction.
Modified Chaplygin gas inspired inflationary model in braneworld scenario
NASA Astrophysics Data System (ADS)
Jawad, Abdul; Rani, Shamaila; Mohsaneen, Sidra
2016-05-01
We investigate the modified Chaplygin gas inspired inflationary regime in the brane-world framework in the presence of standard and tachyon scalar fields. We consider the intermediate inflationary scenario and construct the slow-roll parameters, e-folding numbers, spectral index, scalar and tensor power spectra, tensor to scalar ratio for both scalar field models. We develop the ns - N and r - N planes and concluded that ns˜eq96^{+0.5}_{-0.5} and r≤0.0016 for N˜eq60^{+5}_{-5} in both cases of scalar field models as well as for all values of m. These constraints are consistent with observational data such as WMAP7, WMAP9 and Planck data.
Relaxing the limits on inflationary magnetogenesis
NASA Astrophysics Data System (ADS)
Tsagas, Christos G.
2015-11-01
Inflation has long been considered the best way to produce primordial large-scale magnetic fields. To achieve fields strong enough to seed the galactic dynamo, most of the mechanisms operate outside conventional electromagnetic theory. The latter is typically restored after the end of the de Sitter phase. Breaking away from standard electromagnetism can lead to substantially stronger magnetic fields by the end of inflation, thus compensating for their subsequent adiabatic depletion. We argue that the drastic magnetic enhancement during the de Sitter era may no longer be necessary because, contrary to the widespread perception, superhorizon-sized magnetic fields decay at a slower pace after inflation. The principle behind this claim is causality, which confines the postinflationary electric currents inside the horizon. Without the currents there can be no magnetic-flux freezing on super-Hubble lengths. There, the magnetic decay rate slows down, thus making it much easier to produce primordial fields of astrophysical interest. To quantify this qualitative statement, one can start from the current galactic-dynamo requirements and "reverse engineer" the magnetic strengths needed at the end of inflation in order to produce astrophysically relevant residual seeds today. Our numerical estimates suggest that, depending on the magnetic scale, mechanisms of inflationary magnetogenesis generating fields stronger than 1017 G by the end of the de Sitter phase could successfully seed the galactic dynamo at present.
Near-field single molecule spectroscopy
Xie, X.S.; Dunn, R.C.
1995-02-01
The high spatial resolution and sensitivity of near-field fluorescence microscopy allows one to study spectroscopic and dynamical properties of individual molecules at room temperature. Time-resolved experiments which probe the dynamical behavior of single molecules are discussed. Ground rules for applying near-field spectroscopy and the effect of the aluminum coated near-field probe on spectroscopic measurements are presented.
Inflationary magnetogenesis without the strong coupling problem
Ferreira, Ricardo J.Z.; Jain, Rajeev Kumar; Sloth, Martin S. E-mail: jain@cp3.dias.sdu.dk
2013-10-01
The simplest gauge invariant models of inflationary magnetogenesis are known to suffer from the problems of either large backreaction or strong coupling, which make it difficult to self-consistently achieve cosmic magnetic fields from inflation with a field strength larger than 10{sup −32}G today on the Mpc scale. Such a strength is insufficient to act as seed for the galactic dynamo effect, which requires a magnetic field larger than 10{sup −20}G. In this paper we analyze simple extensions of the minimal model, which avoid both the strong coupling and back reaction problems, in order to generate sufficiently large magnetic fields on the Mpc scale today. First we study the possibility that the coupling function which breaks the conformal invariance of electromagnetism is non-monotonic with sharp features. Subsequently, we consider the effect of lowering the energy scale of inflation jointly with a scenario of prolonged reheating where the universe is dominated by a stiff fluid for a short period after inflation. In the latter case, a systematic study shows upper bounds for the magnetic field strength today on the Mpc scale of 10{sup −13}G for low scale inflation and 10{sup −25}G for high scale inflation, thus improving on the previous result by 7-19 orders of magnitude. These results are consistent with the strong coupling and backreaction constraints.
Loop Quantum Cosmology: holonomy corrections to inflationary models
Artymowski, Michal; Lalak, Zygmunt; Szulc, Lukasz
2009-01-15
In the recent years the quantization methods of Loop Quantum Gravity have been successfully applied to the homogeneous and isotropic Friedmann-Robertson-Walker space-times. The resulting theory, called Loop Quantum Cosmology (LQC), resolves the Big Bang singularity by replacing it with the Big Bounce. We argue that the LQC holonomy corrections generate also certain corrections to field theoretical inflationary scenarios. These corrections imply that in the LQC the effective sonic horizon becomes infinite at some point after the bounce and that the scale of the inflationary potential implied by the COBE normalisation increases. The evolution of scalar fields immediately after the Bounce becomes modified in an interesting way. We point out that one can use COBE normalisation to establish an upper bound on the quantum of length of LQG. LQC corrections other than the holonomy one are assumed to be subdominant.
Probing Inflationary Cosmology: The Atacama B-Mode Search (ABS)
NASA Astrophysics Data System (ADS)
Essinger-Hileman, Thomas
Observations of the Cosmic Microwave Background (CMB) have provided compelling evidence for the Standard Model of Cosmology and have led to the most precise estimates of cosmological parameters to date. Through its sensitivity to gravitational waves, the CMB provides a glimpse into the state of the universe just 10-35 seconds after the Big Bang and of physics on grand-unification-theory (GUT) energy scales around 1016 GeV, some 13 orders of magnitude above the energies achievable by current terrestrial particle accelerators. A gravitational-wave background (GWB) in the early universe would leave a unique, odd-parity pattern of polarization in the CMB called B modes, the magnitude of which is characterized by the tensor-to-scalar ratio, r. A GWB is generically predicted to exist by inflationary theories, and the current generation of CMB polarization experiments will probe the interesting parameter space of r < 0.05 corresponding to single-field inflationary models at GUT scales. I detail the design and construction of the Atacama B-Mode Search (ABS), which aims to measure the polarization of the CMB at degree angular scales where the primordial B-mode signal is expected to peak. ABS is a 145-GHz polarimeter that will operate from a high-altitude site in the Atacama Desert of Chile, consisting of a 60-cm crossed-Dragone telescope with cryogenic primary and secondary reflectors; an array of 240 feedhorn-coupled, transition-edge-sensor, bolometric polarimeters; and, a continuously-rotating, warm, sapphire half-wave plate (HWP) that will provide modulation of the incoming polarization of light. In this thesis, I describe the optical, mechanical, and cryogenic design of the receiver, including the reflector design, focal-plane layout, HWP design, and free-space lowpass filters. I describe physical-optics modeling of the reflector and feedhorn to validate the optical design. A matrix model that allows the calculation of the Mueller matrix of the anti
Single-layer high field dipole magnets
Vadim V. Kashikhin and Alexander V. Zlobin
2001-07-30
Fermilab is developing high field dipole magnets for post-LHC hadron colliders. Several designs with a nominal field of 10-12 T, coil bore size of 40-50 mm based on both shell-type and block-type coil geometry are currently under consideration. This paper presents a new approach to magnet design, based on simple and robust single-layer coils optimized for the maximum field, good field quality and minimum number of turns.
Inflationary Magnetogenesis with On-shell Local U(1) Symmetry
NASA Astrophysics Data System (ADS)
Domènech, Guillem; Lin, Chunshan; Sasaki, Misao
2017-08-01
We propose a new mechanism for inflationary magnetogenesis in which the local U(1) symmetry is broken during inflation. Nevertheless it is shown that the U(1) symmetry is recovered on-shell. We find that it is free from both the strong coupling and back reaction problems, and can explain the origin of cosmic magnetic fields on intergalactic scales, whose existence has been strongly suggested by recent observations.
Electric field imaging of single atoms
NASA Astrophysics Data System (ADS)
Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi
2017-05-01
In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures.
Electric field imaging of single atoms
Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D.; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi
2017-01-01
In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures. PMID:28555629
Electric field imaging of single atoms.
Shibata, Naoya; Seki, Takehito; Sánchez-Santolino, Gabriel; Findlay, Scott D; Kohno, Yuji; Matsumoto, Takao; Ishikawa, Ryo; Ikuhara, Yuichi
2017-05-30
In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures.
Fine-tuning in DBI inflationary mechanism
Chen, Xingang
2008-12-15
We show a model-independent fine-tuning issue in the DBI inflationary mechanism. DBI inflation requires a warp factor h small enough to sufficiently slow down the inflation. On the other hand, the Einstein equation in extra dimensions under the inflationary background deforms the warp space on the IR side. Generically these two locations coincide with each other, spoiling the DBI inflation. The origin and tuning of this 'h problem' is closely related, through the AdS/CFT duality, to those of the well-known '{eta} problem' in the slow-roll inflationary mechanism.
Inflationary potentials from the exact renormalisation group
NASA Astrophysics Data System (ADS)
Grozdanov, Sašo; Kraljić, David; Svanes, Eirik Eik
2016-08-01
We show that an inflationary slow-roll potential can be derived as an IR limit of the non-perturbative exact renormalisation group equation for a scalar field within the mean-field approximation. The result follows without having to specify a Lagrangian in the UV, which we take to be somewhere below the Planck scale to avoid discussing quantum gravity effects. We assume that the theory contains a scalar mode with suppressed coupling to other fields, and that higher derivative couplings are suppressed. In this framework the exact RG equation becomes a one-dimensional Schrödinger equation, which we solve. The effective IR potential is then dominated by the eigen-states of the RG Hamiltonian with the highest eigenvalues. We find that these potentials can generically give rise to slow-roll inflation, which is fully consistent with recent observations. As an example of how the proposed renormalisation group procedure works, we perform an explicit calculation in the ϕ4 theory in an appendix.
Surprising phenomena in a rich new class of inflationary models
Vaudrevange, Pascal M.; Podolsky, Dmitry I.; Starkman, Glenn D. E-mail: podolsky@phys.cwru.edu
2010-04-01
We report on a new class of fast-roll inflationary models. In a huge part of its parameter space, inflationary perturbations exhibit quite unusual phenomena such as scalar and tensor modes freezing out at widely different times, as well as scalar modes reentering the horizon during inflation. One specific point in parameter space is characterized by extraordinary behavior of the scalar perturbations. Freeze-out of scalar perturbations as well as particle production at horizon crossing are absent. Also the behavior of the perturbations around this quasi-de Sitter background is dual to a quantum field theory in flat space-time. Finally, the form of the primordial power spectrum is determined by the interaction between different modes of scalar perturbations.
Initial conditions for anisotropic extended-type inflationary universes
del Campo, S. )
1992-05-15
Recently, extended-type inflationary universe models have been proposed as an appealing approach for solving most of the cosmological puzzles'' that, in contrast with previous models, do not require a fine-tuning'' for the microphysical parameters present in the effective potential. These scenarios rest on a Brans-Dicke-type theory, where a nonminimal coupling of the form {ital f}({ital cphi}){ital R} is assumed, and it may or may not include a potential for the Brans-Dicke field. In its classical description, different extended inflationary universe scenarios are described, where anisotropy is taken into account. By using the Hartle-Hawking and the Vilenkin boundary conditions for the wave function of the Universe, the probability distributions for the initial states of these extended models in the case of a small anisotropy are determined and discussed.
Galilean creation of the inflationary universe
Kobayashi, Tsutomu; Yamaguchi, Masahide; Yokoyama, Jun'ichi E-mail: gucci@phys.titech.ac.jp
2015-07-01
It has been pointed out that the null energy condition can be violated stably in some non-canonical scalar-field theories. This allows us to consider the Galilean Genesis scenario in which the universe starts expanding from Minkowski spacetime and hence is free from the initial singularity. We use this scenario to study the early-time completion of inflation, pushing forward the recent idea of Pirtskhalava et al. We present a generic form of the Lagrangian governing the background and perturbation dynamics in the Genesis phase, the subsequent inflationary phase, and the graceful exit from inflation, as opposed to employing the effective field theory approach. Our Lagrangian belongs to a more general class of scalar-tensor theories than the Horndeski theory and Gleyzes-Langlois-Piazza-Vernizzi generalization, but still has the same number of the propagating degrees of freedom, and thus can avoid Ostrogradski instabilities. We investigate the generation and evolution of primordial perturbations in this scenario and show that one can indeed construct a stable model of inflation preceded by (generalized) Galilean Genesis.
Narrowing the window of inflationary magnetogenesis
NASA Astrophysics Data System (ADS)
Markkanen, Tommi; Nurmi, Sami; Räsänen, Syksy; Vennin, Vincent
2017-06-01
We consider inflationary magnetogenesis where the conformal symmetry is broken by the term f2(phi) Fαβ Fαβ. We assume that the magnetic field power spectrum today between 0.1 and 104 Mpc is a power law, with upper and lower limits from observation. This fixes f to be close to a power law in conformal time in the window during inflation when the modes observed today are generated. In contrast to previous work, we do not make any assumptions about the form of f outside these scales. We cover all possible reheating histories, described by an average equation of state -1/3 < bar w < 1. Requiring that strong coupling and large backreaction are avoided both at the background and perturbative level, we find the bound δB0 < 5 ×10-15 (r/0.07)1/2 κG for the magnetic field generated by inflation, where r is the tensor-to-scalar ratio and κ is a constant related to the form of f. This estimate has an uncertainty of one order of magnitude related to our approximations. The parameter κ is < 100, and values gtrsim 1 require a highly fine-tuned form of f; typical values are orders of magnitude smaller.
Galilean creation of the inflationary universe
Kobayashi, Tsutomu; Yamaguchi, Masahide; Yokoyama, Jun’ichi
2015-07-13
It has been pointed out that the null energy condition can be violated stably in some non-canonical scalar-field theories. This allows us to consider the Galilean Genesis scenario in which the universe starts expanding from Minkowski spacetime and hence is free from the initial singularity. We use this scenario to study the early-time completion of inflation, pushing forward the recent idea of Pirtskhalava et al. We present a generic form of the Lagrangian governing the background and perturbation dynamics in the Genesis phase, the subsequent inflationary phase, and the graceful exit from inflation, as opposed to employing the effective field theory approach. Our Lagrangian belongs to a more general class of scalar-tensor theories than the Horndeski theory and Gleyzes-Langlois-Piazza-Vernizzi generalization, but still has the same number of the propagating degrees of freedom, and thus can avoid Ostrogradski instabilities. We investigate the generation and evolution of primordial perturbations in this scenario and show that one can indeed construct a stable model of inflation preceded by (generalized) Galilean Genesis.
Loops in inflationary correlation functions
NASA Astrophysics Data System (ADS)
Tanaka, Takahiro; Urakawa, Yuko
2013-12-01
We review the recent progress regarding the loop corrections to the correlation functions in the inflationary universe. A naive perturbation theory predicts that the loop corrections generated during inflation suffer from various infrared (IR) pathologies. Introducing an IR cutoff by hand is neither satisfactory nor enough to fix the problem of a secular growth, which may ruin the predictive power of inflation models if the inflation lasts sufficiently long. We discuss the origin of the IR divergences and explore the regularity conditions of the loop corrections for the adiabatic perturbation, the iso-curvature perturbation, and the tensor perturbation, in turn. These three kinds of perturbations have qualitative differences, but in discussing the IR regularity there is a feature common to all cases, which is the importance of the proper identification of observable quantities. Genuinely, observable quantities should respect the gauge invariance from the view point of a local observer. Interestingly, we find that the requirement of the IR regularity restricts the allowed quantum states.
Single cell sequencing: a distinct new field.
Wang, Jian; Song, Yuanlin
2017-12-01
Single cell sequencing (SCS) has become a new approach to study biological heterogeneity. The advancement in technologies for single cell isolation, amplification of genome/transcriptome and next-generation sequencing enables SCS to reveal the inherent properties of a single cell from the large scale of the genome, transcriptome or epigenome at high resolution. Recently, SCS has been widely applied in various clinical and research fields, such as cancer biology and oncology, immunology, microbiology, neurobiology and prenatal diagnosis. In this review, we will discuss the development of SCS methods and focus on the latest clinical and research applications of SCS.
Linde, Andrei
2015-05-05
I describe a simple class of α-attractors, generalizing the single-field GL model of inflation in supergravity. The new class of models is defined for 0<α≲1, providing a good match to the present cosmological data. I also present a generalized version of these models which can describe not only inflation but also dark energy and supersymmetry breaking.
Short distance physics of the inflationary de Sitter universe
Ali, Ahmed Farag; Faizal, Mir; Khalil, Mohammed M. E-mail: f2mir@uwaterloo.ca
2015-09-01
In this work, we investigate inflationary cosmology using scalar field theory deformed by the generalized uncertainty principle (GUP) containing a linear momentum term. Apart from being consistent with the existence of a minimum measurable length scale, this GUP is also consistent with doubly special relativity and hence with the existence of maximum measurable momentum. We use this deformed scalar field theory to analyze the tensor and scalar mode equations in a de Sitter background, and to calculate modifications to the tensor-to-scalar ratio. Finally, we compare our results for the tensor-to-scalar ratio with the Planck data to constrain the minimum length parameter in the GUP.
Inflationary perturbations in bimetric gravity
Cusin, Giulia; Durrer, Ruth; Guarato, Pietro; Motta, Mariele E-mail: ruth.durrer@unige.ch E-mail: mariele.motta@unige.ch
2015-09-01
In this paper we study the generation of primordial perturbations in a cosmological setting of bigravity during inflation. We consider a model of bigravity which can reproduce the ΛCDM background and large scale structure and a simple model of inflation with a single scalar field and a quadratic potential. Reheating is implemented with a toy-model in which the energy density of the inflaton is entirely dissipated into radiation. We present analytic and numerical results for the evolution of primordial perturbations in this cosmological setting. We find that the amplitude of tensor perturbations generated during inflation is sufficiently suppressed to avoid the effects of the tensor instability discovered in refs. [1,2] which develops during the cosmological evolution in the physical sector. We argue that from a pure analysis of the tensor perturbations this bigravity model is compatible with present observations. However, we derive rather stringent limits on inflation from the vector and scalar sectors.
Single-electron solitons in magnetic field
NASA Astrophysics Data System (ADS)
Rudenko, M.; Svintsov, D.; Filippov, S.; Vyurkov, V.
2016-12-01
Single-electron solitons (or movable polarons) can originate near a metal surface owing to interaction with image charges. Image charges (really, surface charges) appear in response to the `instant' electron density (probability density). Interaction with metal electrodes (as well as any polarization of the environment) much affects a charge qubits functioning. To verify this theory we propose a crucial experiment based on the motion of electrons in a magnetic field in presence of weak and strong polarization.
Inflationary quasiscale-invariant attractors
NASA Astrophysics Data System (ADS)
Rinaldi, Massimiliano; Vanzo, Luciano; Zerbini, Sergio; Venturi, Giovanni
2016-01-01
In a series of recent papers Kallosh, Linde, and collaborators provide a unified description of single-field inflation with several types of potentials ranging from power law to supergravity, in terms of just one parameter α . These so-called α attractors predict a spectral index ns and a tensor-to-scalar ratio r , which are fully compatible with the latest Planck data. The only common feature of all α attractors is a noncanonical kinetic term with a pole, and a potential analytic around the pole. In this paper, starting from the same Einstein frame with a noncanonical scalar kinetic energy, we explore the case of nonanalytic potentials. We find the functional form that corresponds to quasiscale-invariant gravitational models in the Jordan frame characterized by a universal relation between r and ns that fits the observational data but is clearly distinct from the one of the α attractors. It is known that the breaking of the exact classical scale invariance in the Jordan frame can be attributed to one-loop corrections. Therefore we conclude that there exists a class of nonanalytic potentials in the noncanonical Einstein frame that is physically equivalent to a class of models in the Jordan frame, with scale invariance softly broken by one-loop quantum corrections.
A field range bound for general single-field inflation
Baumann, Daniel; Green, Daniel E-mail: drgreen@ias.edu
2012-05-01
We explore the consequences of a detection of primordial tensor fluctuations for general single-field models of inflation. Using the effective theory of inflation, we propose a generalization of the Lyth bound that applies to models of inflation coupled to Einstein gravity. Our strongest bound applies to all single-field models with two-derivative kinetic terms for the scalar fluctuations and is always stronger than the corresponding bound for slow-roll models. This shows that non-trivial dynamics of the inflaton can't evade the Lyth bound. We also present a weaker, but more universal bound that holds when the Null Energy Condition (NEC) is satisfied at horizon crossing.
Observational signatures of anisotropic inflationary models
Ohashi, Junko; Tsujikawa, Shinji; Soda, Jiro E-mail: jiro@phys.sci.kobe-u.ac.jp
2013-12-01
We study observational signatures of two classes of anisotropic inflationary models in which an inflaton field couples to (i) a vector kinetic term F{sub μν}F{sup μν} and (ii) a two-form kinetic term H{sub μνλ}H{sup μνλ}. We compute the corrections from the anisotropic sources to the power spectrum of gravitational waves as well as the two-point cross correlation between scalar and tensor perturbations. The signs of the anisotropic parameter g{sub *} are different depending on the vector and the two-form models, but the statistical anisotropies generally lead to a suppressed tensor-to-scalar ratio r and a smaller scalar spectral index n{sub s} in both models. In the light of the recent Planck bounds of n{sub s} and r, we place observational constraints on several different inflaton potentials such as those in chaotic and natural inflation in the presence of anisotropic interactions. In the two-form model we also find that there is no cross correlation between scalar and tensor perturbations, while in the vector model the cross correlation does not vanish. The non-linear estimator f{sub NL} of scalar non-Gaussianities in the two-form model is generally smaller than that in the vector model for the same orders of |g{sub *}|, so that the former is easier to be compatible with observational bounds of non-Gaussianities than the latter.
Warm inflationary model in loop quantum cosmology
Herrera, Ramon
2010-06-15
A warm inflationary universe model in loop quantum cosmology is studied. In general we discuss the condition of inflation in this framework. By using a chaotic potential, V({phi}){proportional_to}{phi}{sup 2}, we develop a model where the dissipation coefficient {Gamma}={Gamma}{sub 0}=constant. We use recent astronomical observations for constraining the parameters appearing in our model.
About the isocurvature tension between axion and high scale inflationary models
NASA Astrophysics Data System (ADS)
Estevez, M.; Santillán, O.
2016-07-01
The present work suggests that the isocurvature tension between axion and high energy inflationary scenarios may be avoided by considering a double field inflationary model involving the hidden Peccei-Quinn Higgs and the Standard Model one. Some terms in the lagrangian we propose explicitly violate the Peccei-Quinn symmetry but, at the present era, their effect is completely negligible. The resulting mechanism allows for a large value for the axion constant, of the order f_a˜ M_p, thus the axion isocurvature fluctuations are suppressed even when the scale of inflation H_{inf} is very high, of the order of H_{inf}˜ M_{gut}. This numerical value is typical in Higgs inflationary models. An analysis about topological defect formation in this scenario is also performed, and it is suggested that, under certain assumptions, their effect is not catastrophic from the cosmological point of view.
Simple inflationary quintessential model. II. Power law potentials
NASA Astrophysics Data System (ADS)
de Haro, Jaume; Amorós, Jaume; Pan, Supriya
2016-09-01
The present work is a sequel of our previous work [Phys. Rev. D 93, 084018 (2016)] which depicted a simple version of an inflationary quintessential model whose inflationary stage was described by a Higgs-type potential and the quintessential phase was responsible due to an exponential potential. Additionally, the model predicted a nonsingular universe in past which was geodesically past incomplete. Further, it was also found that the model is in agreement with the Planck 2013 data when running is allowed. But, this model provides a theoretical value of the running which is far smaller than the central value of the best fit in ns , r , αs≡d ns/d l n k parameter space where ns, r , αs respectively denote the spectral index, tensor-to-scalar ratio and the running of the spectral index associated with any inflationary model, and consequently to analyze the viability of the model one has to focus in the two-dimensional marginalized confidence level in the allowed domain of the plane (ns,r ) without taking into account the running. Unfortunately, such analysis shows that this model does not pass this test. However, in this sequel we propose a family of models runs by a single parameter α ∈[0 ,1 ] which proposes another "inflationary quintessential model" where the inflation and the quintessence regimes are respectively described by a power law potential and a cosmological constant. The model is also nonsingular although geodesically past incomplete as in the cited model. Moreover, the present one is found to be more simple compared to the previous model and it is in excellent agreement with the observational data. In fact, we note that, unlike the previous model, a large number of the models of this family with α ∈[0 ,1/2 ) match with both Planck 2013 and Planck 2015 data without allowing the running. Thus, the properties in the current family of models compared to its past companion justify its need for a better cosmological model with the successive
Cosmic inflation in a landscape of heavy-fields
Céspedes, Sebastián; Palma, Gonzalo A. E-mail: gpalmaquilod@ing.uchile.cl
2013-10-01
Heavy isocurvature fields may have a strong influence on the low energy dynamics of curvature perturbations during inflation, as long as the inflationary trajectory becomes non-geodesic in the multi-field target space (the landscape). If fields orthogonal to the inflationary trajectory are sufficiently heavy, one expects a reliable effective field theory describing the low energy dynamics of curvature perturbations, with self-interactions determined by the shape of the inflationary trajectory. Previous work analyzing the role of heavy-fields during inflation have mostly focused in the effects on curvature perturbations due to a single heavy-field. In this article we extend the results of these works by studying models of inflation in which curvature perturbations interact with two heavy-fields. We show that the second heavy-field (orthogonal to both tangent and normal directions of the inflationary trajectory) may significantly affect the evolution of curvature modes. We compute the effective field theory for the low energy curvature perturbations obtained by integrating out the two heavy-fields and show that the presence of the second heavy-field implies the existence of additional self-interactions not accounted for in the single heavy-field case. We conclude that future observations will be able to constrain the number of heavy fields interacting with curvature perturbations.
Density perturbations and the cosmological constant from inflationary landscapes
Feldstein, Brian; Hall, Lawrence J.; Watari, Taizan
2005-12-15
An anthropic understanding of the cosmological constant requires that the vacuum energy at late time scans from one patch of the universe to another. If the vacuum energy during inflation also scans, the various patches of the universe acquire exponentially differing volumes. In a generic landscape with slow-roll inflation, we find that this gives a steeply varying probability distribution for the normalization of the primordial density perturbations, resulting in an exponentially small fraction of observers measuring the Cosmic Background Explorer value of 10{sup -5}. Inflationary landscapes should avoid this ''{sigma} problem,'' and we explore features that can allow them to do that. One possibility is that, prior to slow-roll inflation, the probability distribution for vacua is extremely sharply peaked, selecting essentially a single anthropically allowed vacuum. Such a selection could occur in theories of eternal inflation. A second possibility is that the inflationary landscape has a special property: although scanning leads to patches with volumes that differ exponentially, the value of the density perturbation does not vary under this scanning. This second case is preferred over the first, partly because a flat inflaton potential can result from anthropic selection, and partly because the anthropic selection of a small cosmological constant is more successful.
SU(1,1) Lie algebraic approach for the evolution of the quantum inflationary universe
NASA Astrophysics Data System (ADS)
Choi, Jeong Ryeol
2013-03-01
Quantum behavior of scalar fields and vacuum energy density in the inflationary universe are investigated using SU(1,1) Lie algebraic approach. Wave functions describing the evolution of scalar fields that have been thought to have driven cosmic inflation are identified in several possible quantum states at the early stage of the universe, such as the Fock state, the Glauber coherent state, and the SU(1,1) coherent states. In particular, we focus in this research on two important classes of the SU(1,1) coherent states, which are the so-called even and odd coherent states and the Perelomov coherent state. It is shown in the spatially flat universe driven by a single scalar field that the probability densities in all these states have converged to the origin (ϕ = 0, where ϕ is the scalar field) as time goes by. This outcome implies that the vacuum energy density characterized by the scalar field dissipates with time. The probability density in the matter-dominated era converged more rapidly than that in the radiation-dominated era. Hence, we can confirm that the progress of dissipation for the vacuum energy density became faster as the matter era began after the end of the early dominance of radiation. This consequence is, indeed, in agreement with the results of our previous researches in cosmology (for example, see [Chin. Phys. C 35 (2011) 233] and references there in).
On the initial condition of inflationary fluctuations
Jiang, Hongliang; Wang, Yi; Zhou, Siyi
2016-04-21
It is usually assumed that the inflationary fluctuations start from the Bunch-Davies (BD) vacuum and the iε prescription is used when interactions are calculated. We show that those assumptions can be verified explicitly by calculating the loop corrections to the inflationary two-point and three-point correlation functions. Those loop corrections can be resummed to exponential factors, which suppress non-BD coefficients and behave as the iε factor for the case of the BD initial condition. A new technique of loop chain diagram resummation is developed for this purpose. For the non-BD initial conditions which is setup at finite time and has not fully decayed, explicit correction to the two-point and three-point correlation functions are calculated. Especially, non-Gaussianity in the folded limit is regularized due to the interactions.
Dependence of inflationary reconstruction upon cosmological parameters
Turner, M.S. |
1996-06-01
The inflationary potential and its derivatives determine the spectrum of scalar and tensor metric perturbations that arise from quantum fluctuations during inflation. The CBR anisotropy offers a promising means of determining the spectra of metric perturbations and thereby a means of constraining the inflationary potential. The relation between the metric perturbations and CBR anisotropy depends upon cosmological parameters{emdash}most notably the possibility of a cosmological constant. Motivated by some observational evidence for a cosmological constant (large-scale structure, cluster-baryon fraction, measurements of the Hubble constant, and age of the Universe) we derive the reconstruction equations and consistency relation to second order in the presence of a cosmological constant. We also clarify previous notation and discuss alternative schemes for reconstruction. {copyright} {ital 1996 The American Physical Society.}
Inflation after COBE: Lectures on inflationary cosmology
Turner, M.S. . Enrico Fermi Inst. Fermi National Accelerator Lab., Batavia, IL )
1992-01-01
In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the initial data'' for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models.
Inflation after COBE: Lectures on inflationary cosmology
Turner, M.S. |
1992-12-31
In these lectures I review the standard hot big-bang cosmology, emphasizing its successes, its shortcomings, and its major challenge-a detailed understanding of the formation of structure in the Universe. I then discuss the motivations for and the fundamentals of inflationary cosmology, particularly emphasizing the quantum origin of metric (density and gravity-wave) perturbations. Inflation addresses the shortcomings of the standard cosmology and provides the ``initial data`` for structure formation. I conclude by addressing the implications of inflation for structure formation, evaluating the various cold dark matter models in the light of the recent detection of temperature anisotropies in the cosmic background radiation by COBE. In the near term, the study of structure formation offers a powerful probe of inflation, as well as specific inflationary models.
Inflationary magnetogenesis and non-local actions: the conformal anomaly
El-Menoufi, Basem Kamal
2016-02-01
We discuss the possibility of successful magnetogenesis during inflation by employing the one-loop effective action of massless QED. The action is strictly non-local and results from the long distance fluctuations of massless charged particles present at the inflationary scale. Most importantly, it encodes the conformal anomaly of QED which is crucial to avoid the vacuum preservation in classical electromagnetism. In particular, we find a blue spectrum for the magnetic field with spectral index n{sub B} ≅ 2 − α{sub e} where α{sub e} depends on both the number of e-folds during inflation as well as the coefficient of the one-loop beta function. In particular, the sign of the beta function has important bearing on the final result. A low reheating temperature is required for the present day magnetic field to be consistent with the lower bound inferred on the field in the intergalactic medium.
Getting inflationary models using the deformation method
NASA Astrophysics Data System (ADS)
Rodrigues, J. J.; Souza, M. A. M.
2015-04-01
In this paper we show that the dynamics associated with slow-roll models of inflation can be investigated through a method called the deformation procedure. Using the latter, we explicitly derive an expression linking two slow-roll inflationary potentials, applying the resulting framework to show how to construct an eternal inflation from chaotic inflation, or even, a natural inflation from hilltop inflation, easily.
Anisotropic higher derivative gravity and inflationary universe
Kao, W. F.
2006-08-15
Stability analysis of the Kantowski-Sachs type universe in pure higher derivative gravity theory is studied in detail. The nonredundant generalized Friedmann equation of the system is derived by introducing a reduced one-dimensional generalized Kantowski-Sachs type action. Existence and stability of inflationary solution in the presence of higher derivative terms are also studied in detail. Implications to the choice of physical theories are discussed in detail in this paper.
Warm-intermediate inflationary universe model
Campo, Sergio del; Herrera, Ramon E-mail: ramon.herrera@ucv.cl
2009-04-15
Warm inflationary universe models in the context of intermediate expansion, between power law and exponential, are studied. General conditions required for these models to be realizable are derived and discussed. This study is done in the weak and strong dissipative regimes. The inflaton potentials considered in this study are negative-power-law and powers of logarithms, respectively. The parameters of our models are constrained from the WMAP three and five year data.
Production of scalar and tensor perturbations in inflationary models
Turner, M.S. NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 )
1993-10-15
Scalar (density) and tensor (gravity-wave) perturbations provide the basis for the fundamental observable consequences of inflation, including CBR anisotropy and the formation of structure in the Universe. These perturbations are nearly scale invariant (Harrison-Zel'dovich spectrum), though a slight deviation from scale invariance ( tilt'') can have significant consequences for both CBR anisotropy and structure formation. In particular, a slightly tilted spectrum of scalar perturbations may improve the agreement of the cold dark matter scenario with the observational data. The amplitude and spectrum of the scalar and tensor perturbations depend upon the shape of the inflationary potential in the small interval where the scalar field responsible for inflation was between about 46 and 54 [ital e]-folds before the end of inflation. By expanding the inflationary potential in a Taylor series over this interval we show that the amplitudes of the perturbations and the power-law slopes of their spectra can be expressed in terms of the value of the potential 50 [ital e]-folds before the end of inflation, [ital V][sub 50], its steepness [ital x][sub 50][equivalent to][ital m][sub Pl][ital V50][sup [prime
Last stand of single small field inflation
NASA Astrophysics Data System (ADS)
Bramante, Joseph; Lehman, Landon; Martin, Adam; Downes, Sean
2014-07-01
By incorporating both the tensor-to-scalar ratio and the measured value of the spectral index, we set a bound on solo small field inflation of Δϕ/mPl≥1.00√r/0.1 . Unlike previous bounds which require monotonic ɛV, |ηV|<1, and 60 e-folds of inflation, the bound remains valid for nonmonotonic ɛV, |ηV|≳1, and for inflation which occurs only over the eight e-folds which have been observed on the cosmic microwave background. The negative value of the spectral index over the observed eight e-folds is what makes the bound strong; we illustrate this by surveying single field models and finding that for r ≳0.1 and eight e-folds of inflation, there is no simple potential which reproduces observed cosmic microwave background perturbations and remains sub-Planckian. Models that are sub-Planckian after eight e-folds must be patched together with a second epoch of inflation that fills out the remaining ˜50 e-folds. This second, post-cosmic microwave background epoch is characterized by extremely small ɛV and therefore an increasing scalar power spectrum. Using the fact that large power can overabundantly produce primordial black holes, we bound the maximum energy level of the second phase of inflation.
Inflationary paradigm after Planck 2013
NASA Astrophysics Data System (ADS)
Guth, Alan H.; Kaiser, David I.; Nomura, Yasunori
2014-06-01
Models of cosmic inflation posit an early phase of accelerated expansion of the universe, driven by the dynamics of one or more scalar fields in curved spacetime. Though detailed assumptions about fields and couplings vary across models, inflation makes specific, quantitative predictions for several observable quantities, such as the flatness parameter (Ωk = 1 - Ω) and the spectral tilt of primordial curvature perturbations (ns - 1 = dln PR / dln k), among others-predictions that match the latest observations from the Planck satellite to very good precision. In the light of data from Planck as well as recent theoretical developments in the study of eternal inflation and the multiverse, we address recent criticisms of inflation by Ijjas, Steinhardt, and Loeb. We argue that their conclusions rest on several problematic assumptions, and we conclude that cosmic inflation is on a stronger footing than ever before.
Discrete spectrum of inflationary fluctuations
Hogan, Craig J.
2004-10-15
It is conjectured that inflation, taking account of quantum gravity, leads to a discrete spectrum of cosmological perturbations, instead of the continuous Gaussian spectrum predicted by standard field theory in an unquantized background. Heuristic models of discrete spectra are discussed, based on an inflaton mode with self-gravity, a lattice of amplitude states, an entangled ensemble of modes, and the holographic or covariant entropy bound. Estimates are given for the discreteness observable in cosmic background anisotropy, galaxy clustering, and gravitational wave backgrounds.
Hamilton-Jacobi formalism to warm inflationary scenario
NASA Astrophysics Data System (ADS)
Sayar, K.; Mohammadi, A.; Akhtari, L.; Saaidi, Kh.
2017-01-01
The Hamilton-Jacobi formalism as a powerful method is being utilized to reconsider the warm inflationary scenario, where the scalar field as the main component driving inflation interacts with other fields. Separating the context into strong and weak dissipative regimes, the goal is followed for two popular functions of Γ . Applying slow-rolling approximation, the required perturbation parameters are extracted and, by comparing to the latest Planck data, the free parameters are restricted. The possibility of producing an acceptable inflation is studied where the result shows that for all cases the model could successfully suggest the amplitude of scalar perturbation, scalar spectral index, its running, and the tensor-to-scalar ratio.
Spectrum of perturbations in anisotropic inflationary universe with vector hair
Himmetoglu, Burak
2010-03-01
We study both the background evolution and cosmological perturbations of anisotropic inflationary models supported by coupled scalar and vector fields. The models we study preserve the U(1) gauge symmetry associated with the vector field, and therefore do not possess instabilities associated with longitudinal modes (which instead plague some recently proposed models of vector inflation and curvaton). We first intoduce a model in which the background anisotropy slowly decreases during inflation; we then confirm the stability of the background solution by studying the quadratic action for all the perturbations of the model. We then compute the spectrum of the h{sub ×} gravitational wave polarization. The spectrum we find breaks statistical isotropy at the largest scales and reduces to the standard nearly scale invariant form at small scales. We finally discuss the possible relevance of our results to the large scale CMB anomalies.
Inflationary dynamics reconstruction via inverse-scattering theory
NASA Astrophysics Data System (ADS)
Mastache, Jorge; Zago, Fernando; Kosowsky, Arthur
2017-03-01
The evolution of inflationary fluctuations can be recast as an inverse scattering problem. In this context, we employ the Gel'fand-Levitan method from inverse-scattering theory to reconstruct the evolution of both the inflaton field freeze-out horizon and the Hubble parameter during inflation. We demonstrate this reconstruction procedure numerically for a scenario of slow-roll inflation, as well as for a scenario which temporarily departs from slow-roll. The field freeze-out horizon is reconstructed from the accessible primordial scalar power spectrum alone, while the reconstruction of the Hubble parameter requires additional information from the tensor power spectrum. We briefly discuss the application of this technique to more realistic cases incorporating estimates of the primordial power spectra over limited ranges of scales and with specified uncertainties.
The origin of density fluctuations in the 'new inflationary universe'
NASA Technical Reports Server (NTRS)
Turner, M. S.
1983-01-01
Cosmological mysteries which are not explained by the Big Bang hypothesis but may be approached by a revamped inflationary universe model are discussed. Attention is focused on the isotropy, the large-scale homogeneity, small-scale inhomogeneity, the oldness/flatness of the universe, and the baryon asymmetry. The universe is assumed to start in the lowest energy state, be initially dominated by false vacuum energy, enter a de Sitter phase, and then cross a barrier which is followed by the formation of fluctuation regions that lead to structure. The scalar fields (perturbation regions) experience quantum fluctuations which produce spontaneous symmetry breaking on a large scale. The scalar field value would need to be much greater than the expansion rate during the de Sitter epoch. A supersymmetric (flat) potential which satisfies the requirement, yields fluctuations of the right magnitude, and allows inflation to occur is described.
The origin of density fluctuations in the 'new inflationary universe'
NASA Technical Reports Server (NTRS)
Turner, M. S.
1983-01-01
Cosmological mysteries which are not explained by the Big Bang hypothesis but may be approached by a revamped inflationary universe model are discussed. Attention is focused on the isotropy, the large-scale homogeneity, small-scale inhomogeneity, the oldness/flatness of the universe, and the baryon asymmetry. The universe is assumed to start in the lowest energy state, be initially dominated by false vacuum energy, enter a de Sitter phase, and then cross a barrier which is followed by the formation of fluctuation regions that lead to structure. The scalar fields (perturbation regions) experience quantum fluctuations which produce spontaneous symmetry breaking on a large scale. The scalar field value would need to be much greater than the expansion rate during the de Sitter epoch. A supersymmetric (flat) potential which satisfies the requirement, yields fluctuations of the right magnitude, and allows inflation to occur is described.
The origin of density fluctuations in the 'new inflationary universe'
NASA Astrophysics Data System (ADS)
Turner, M. S.
Cosmological mysteries which are not explained by the Big Bang hypothesis but may be approached by a revamped inflationary universe model are discussed. Attention is focused on the isotropy, the large-scale homogeneity, small-scale inhomogeneity, the oldness/flatness of the universe, and the baryon asymmetry. The universe is assumed to start in the lowest energy state, be initially dominated by false vacuum energy, enter a de Sitter phase, and then cross a barrier which is followed by the formation of fluctuation regions that lead to structure. The scalar fields (perturbation regions) experience quantum fluctuations which produce spontaneous symmetry breaking on a large scale. The scalar field value would need to be much greater than the expansion rate during the de Sitter epoch. A supersymmetric (flat) potential which satisfies the requirement, yields fluctuations of the right magnitude, and allows inflation to occur is described.
Multiple fields in stochastic inflation
Assadullahi, Hooshyar; Firouzjahi, Hassan; Noorbala, Mahdiyar; Vennin, Vincent; Wands, David
2016-06-24
Stochastic effects in multi-field inflationary scenarios are investigated. A hierarchy of diffusion equations is derived, the solutions of which yield moments of the numbers of inflationary e-folds. Solving the resulting partial differential equations in multi-dimensional field space is more challenging than the single-field case. A few tractable examples are discussed, which show that the number of fields is, in general, a critical parameter. When more than two fields are present for instance, the probability to explore arbitrarily large-field regions of the potential, otherwise inaccessible to single-field dynamics, becomes non-zero. In some configurations, this gives rise to an infinite mean number of e-folds, regardless of the initial conditions. Another difference with respect to single-field scenarios is that multi-field stochastic effects can be large even at sub-Planckian energy. This opens interesting new possibilities for probing quantum effects in inflationary dynamics, since the moments of the numbers of e-folds can be used to calculate the distribution of primordial density perturbations in the stochastic-δN formalism.
Particle decay in inflationary cosmology
Boyanovsky, D.; Vega, H.J. de
2004-09-15
We investigate the relaxation and decay of a particle during inflation by implementing the dynamical renormalization group. This investigation allows us to give a meaningful definition for the decay rate in an expanding universe. As a prelude to a more general scenario, the method is applied here to study the decay of a particle in de Sitter inflation via a trilinear coupling to massless conformally coupled particles, both for wavelengths much larger and much smaller than the Hubble radius. For superhorizon modes we find that the decay is of the form {eta}{sup {gamma}{sub 1}} with {eta} being conformal time and we give an explicit expression for {gamma}{sub 1} to leading order in the coupling which has a noteworthy interpretation in terms of the Hawking temperature of de Sitter space-time. We show that if the mass M of the decaying field is <
Particle decay in inflationary cosmology
NASA Astrophysics Data System (ADS)
Boyanovsky, D.; de Vega, H. J.
2004-09-01
We investigate the relaxation and decay of a particle during inflation by implementing the dynamical renormalization group. This investigation allows us to give a meaningful definition for the decay rate in an expanding universe. As a prelude to a more general scenario, the method is applied here to study the decay of a particle in de Sitter inflation via a trilinear coupling to massless conformally coupled particles, both for wavelengths much larger and much smaller than the Hubble radius. For superhorizon modes we find that the decay is of the form ηΓ1 with η being conformal time and we give an explicit expression for Γ1 to leading order in the coupling which has a noteworthy interpretation in terms of the Hawking temperature of de Sitter space-time. We show that if the mass M of the decaying field is ≪H then the decay rate during inflation is enhanced over the Minkowski space-time result by a factor 2H/πM. For wavelengths much smaller than the Hubble radius we find that the decay law is e with C(η) the scale factor and α determined by the strength of the trilinear coupling. In all cases we find a substantial enhancement in the decay law as compared to Minkowski space-time. These results suggest potential implications for the spectrum of scalar density fluctuations as well as non-Gaussianities.
Multiple inflationary stages with varying equation of state
Namjoo, Mohammad Hossein; Firouzjahi, Hassan; Sasaki, Misao E-mail: firouz@mail.ipm.ir
2012-12-01
We consider a model of inflation consisting a single fluid with a time-dependent equation of state. In this phenomenological picture, two periods of inflation are separated by an intermediate non-inflationary stage which can be either a radiation dominated, matter dominated or kinetic energy dominated universe, respectively, with the equation of state w = 1/3, 0 or 1. We consider the toy model in which the change in w happens instantaneously. Depending on whether the mode of interest leaves the horizon before or after or between the phase transitions, the curvature power spectrum can have non-trivial sinusoidal modulations. This can have interesting observational implications for CMB anisotropies and for primordial black-hole formation.
Evolution of perturbations in an inflationary universe
NASA Technical Reports Server (NTRS)
Frieman, J. A.; Will, C. M.
1982-01-01
The evolution of inhomogeneous density perturbations in a model of the very early universe that is dominated for a time by a constant energy density of a false quantum-mechanical vacuum is analyzed. During this period, the universe inflates exponentially and supercools exponentially, until a phase transition back to the true vacuum reheats the matter and radiation. Focus is on the physically measurable, coordinate-independent modes of inhomogeneous perturbations of this model and it is found that all modes either are constant or are exponentially damped during the inflationary era.
Quantum cosmology and the evolution of inflationary spectra
NASA Astrophysics Data System (ADS)
Kamenshchik, Alexander Y.; Tronconi, Alessandro; Venturi, Giovanni
2016-12-01
We illustrate how it is possible to calculate the quantum gravitational effects on the spectra of primordial scalar/tensor perturbations starting from the canonical, Wheeler-De Witt, approach to quantum cosmology. The composite matter-gravity system is analyzed through a Born-Oppenheimer approach in which gravitation is associated with the heavy degrees of freedom and matter (here represented by a scalar field) with the light ones. Once the independent degrees of freedom are identified, the system is canonically quantized and a semiclassical approximation is used for the scale factor. The differential equation governing the dynamics of the primordial spectra with their quantum-gravitational corrections is then obtained and is applied to diverse inflationary evolutions. Finally, the analytical results are compared to observations through a Monte Carlo Markov chain technique and an estimate of the free parameters of our approach is finally presented and the results obtained are compared with previous ones.
Inflationary scenarios in Starobinsky model with higher order corrections
NASA Astrophysics Data System (ADS)
Artymowski, Michał; Lalak, Zygmunt; Lewicki, Marek
2015-06-01
We consider the Starobinsky inflation with a set of higher order corrections parametrised by two real coefficients λ1 , λ2. In the Einstein frame we have found a potential with the Starobinsky plateau, steep slope and possibly with an additional minimum, local maximum or a saddle point. We have identified three types of inflationary behaviour that may be generated in this model: i) inflation on the plateau, ii) at the local maximum (topological inflation), iii) at the saddle point. We have found limits on parameters λi and initial conditions at the Planck scale which enable successful inflation and disable eternal inflation at the plateau. We have checked that the local minimum away from the GR vacuum is stable and that the field cannot leave it neither via quantum tunnelling nor via thermal corrections.
Inflationary scenarios in Starobinsky model with higher order corrections
Artymowski, Michał; Lalak, Zygmunt; Lewicki, Marek
2015-06-17
We consider the Starobinsky inflation with a set of higher order corrections parametrised by two real coefficients λ{sub 1} ,λ{sub 2}. In the Einstein frame we have found a potential with the Starobinsky plateau, steep slope and possibly with an additional minimum, local maximum or a saddle point. We have identified three types of inflationary behaviour that may be generated in this model: i) inflation on the plateau, ii) at the local maximum (topological inflation), iii) at the saddle point. We have found limits on parameters λ{sub i} and initial conditions at the Planck scale which enable successful inflation and disable eternal inflation at the plateau. We have checked that the local minimum away from the GR vacuum is stable and that the field cannot leave it neither via quantum tunnelling nor via thermal corrections.
Inflationary scenarios in Starobinsky model with higher order corrections
Artymowski, Michał; Lalak, Zygmunt; Lewicki, Marek E-mail: Zygmunt.Lalak@fuw.edu.pl
2015-06-01
We consider the Starobinsky inflation with a set of higher order corrections parametrised by two real coefficients λ{sub 1} , λ{sub 2}. In the Einstein frame we have found a potential with the Starobinsky plateau, steep slope and possibly with an additional minimum, local maximum or a saddle point. We have identified three types of inflationary behaviour that may be generated in this model: i) inflation on the plateau, ii) at the local maximum (topological inflation), iii) at the saddle point. We have found limits on parameters λ{sub i} and initial conditions at the Planck scale which enable successful inflation and disable eternal inflation at the plateau. We have checked that the local minimum away from the GR vacuum is stable and that the field cannot leave it neither via quantum tunnelling nor via thermal corrections.
49 CFR 578.5 - Inflationary adjustment of civil penalties.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 49 Transportation 7 2012-10-01 2012-10-01 false Inflationary adjustment of civil penalties. 578.5 Section 578.5 Transportation Other Regulations Relating to Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) CIVIL AND CRIMINAL PENALTIES § 578.5 Inflationary adjustment of civil...
Inflationary perturbations in no-scale theories
NASA Astrophysics Data System (ADS)
Salvio, Alberto
2017-04-01
We study the inflationary perturbations in general (classically) scale-invariant theories. Such scenario is motivated by the hierarchy problem and provides natural inflationary potentials and dark matter candidates. We analyse in detail all sectors (the scalar, vector and tensor perturbations) giving general formulae for the potentially observable power spectra, as well as for the curvature spectral index n_s and the tensor-to-scalar ratio r. We show that the conserved Hamiltonian for all perturbations does not feature negative energies even in the presence of the Weyl-squared term if the appropriate quantisation is performed and argue that this term does not lead to phenomenological problems at least in some relevant setups. The general formulae are then applied to a concrete no-scale model, which includes the Higgs and a scalar, "the planckion", whose vacuum expectation value generates the Planck mass. Inflation can be triggered by a combination of the planckion and the Starobinsky scalar and we show that no tension with observations is present even in the case of pure planckion inflation, if the coefficient of the Weyl-squared term is large enough. In general, even quadratic inflation is allowed in this case. Moreover, the Weyl-squared term leads to an isocurvature mode, which currently satisfies the observational bounds, but it may be detectable with future experiments.
Post-inflationary gravitino production revisited
Ellis, John; Garcia, Marcos A.G.; Olive, Keith A.; Nanopoulos, Dimitri V.; Peloso, Marco E-mail: garciagarcia@physics.umn.edu E-mail: olive@physics.umn.edu
2016-03-01
We revisit gravitino production following inflation. As a first step, we review the standard calculation of gravitino production in the thermal plasma formed at the end of post-inflationary reheating when the inflaton has completely decayed. Next we consider gravitino production prior to the completion of reheating, assuming that the inflaton decay products thermalize instantaneously while they are still dilute. We then argue that instantaneous thermalization is in general a good approximation, and also show that the contribution of non-thermal gravitino production via the collisions of inflaton decay products prior to thermalization is relatively small. Our final estimate of the gravitino-to-entropy ratio is approximated well by a standard calculation of gravitino production in the post-inflationary thermal plasma assuming total instantaneous decay and thermalization at a time t ≅ 1.2/Γ{sub φ}. Finally, in light of our calculations, we consider potential implications of upper limits on the gravitino abundance for models of inflation, with particular attention to scenarios for inflaton decays in supersymmetric Starobinsky-like models.
Modification of single molecule fluorescence using external fields
NASA Astrophysics Data System (ADS)
Chen, Rui-Yun; Zhang, Guo-Feng; Qin, Cheng-Bin; Gao, Yan; Xiao, Lian-Tuan; Jia, Suo-Tang
2017-10-01
Controlling and manipulating the fluorescence of single fluorophores is of great interest in recent years for its potential uses in improving the performance of molecular photonics and molecular electronics, such as in organic light-emitting devices, single photon sources, organic field-effect transistors, and probes or sensors based on single molecules. This review shows how the fluorescence emission of single organic molecules can be modified using local electromagnetic fields of metallic nanostructures and electric-field-induced electron transfer. Electric-field-induced fluorescence modulation, hysteresis, and the achievement of fluorescence switch are discussed in detail.
Behavior of a Single Langmuir Probe in a Magnetic Field.
ERIC Educational Resources Information Center
Pytlinski, J. T.; And Others
1978-01-01
Describes an experiment to demonstrate the influence of a magnetic field on the behavior of a single Langmuir probe. The experiment introduces the student to magnetically supported plasma and particle behavior in a magnetic field. (GA)
Electric field dependent spectroscopy of single nanocrystal systems
NASA Astrophysics Data System (ADS)
LeBlanc, Sharonda L. Johnson
A suite of single molecule spectroscopic techniques and data analysis methods were implemented to explore the complex role of electric fields in single semiconductor nanocrystal photophysics. This dissertation spans the synthesis, characterization, biological applications, and photophysics of semiconductor nanocrystals. The core single molecule techniques employed in the current work include time-resolved fluorescence, time-correlated single photon counting, single molecule spectroscopy, and photon correlation spectroscopy. Various electrode devices were patterned to investigate the optical properties of single nanocrystal systems under an applied electric field. Electric field dependent spectroscopy and data analysis have revealed distributed kinetics and multiple charging of nanocrystals. In addition, interactions of nanocrystal excited states with plasmonic gold films have revealed strong enhancement of multiple exciton emission from single nanocrystals, and control by an applied electric field. The broader implications of this work can be extended to bioimaging, light harvesting, electro-optics, and lasing technologies.
Constraints on tachyon inflationary models with an AdS/CFT correspondence
NASA Astrophysics Data System (ADS)
Bouabdallaoui, Zahra; Errahmani, Ahmed; Bouhmadi-López, Mariam; Ouali, Taoufik
2016-12-01
To study the effect of the anti-de Sitter/conformal field theory correspondence (AdS/CFT) on the primordial inflationary era, we consider a universe filled with a tachyon field in a slow-roll regime. In this context, the background and perturbative parameters characterizing the inflationary era are related to the standard one by correction terms. We show a clear agreement between the theoretical prediction and the observational data for the above-mentioned model. The main results of our work are illustrated for an exponential potential. We show that, for a suitable conformal anomaly coefficient, AdS/CFT correspondence might leave its imprints on the spectrum of the gravitational waves amplitude with a tensor to scalar ratio, r , of the perturbations compatible with Planck data.
Inflationary α -attractors from F (R ) gravity
NASA Astrophysics Data System (ADS)
Odintsov, S. D.; Oikonomou, V. K.
2016-12-01
In this paper, we study some classes of α -attractor models in the Jordan frame, and we find the corresponding F (R ) gravity theory. We study analytically the problem at leading order, and we investigate whether the attractor picture persists in the F (R ) gravity equivalent theory. As we show, if the slow-roll conditions are assumed in the Jordan frame, the spectral index of primordial curvature perturbations and the scalar-to-tensor ratio are identical to the corresponding observational indices of the R2 model, a result which indicates that the attractor property is also found in the corresponding F (R ) gravity theories of the α -attractor models. Moreover, implicit and approximate forms of the F (R ) gravity inflationary attractors are found.
Non-Gaussianities and the stimulated creation of quanta in the inflationary universe
Agullo, Ivan; Parker, Leonard
2011-03-15
Cosmological inflation generates a spectrum of density perturbations that can seed the cosmic structures we observe today. These perturbations are usually computed as the result of the gravitationally induced spontaneous creation of perturbations from an initial vacuum state. In this paper, we compute the perturbations arising from gravitationally induced stimulated creation when perturbations are already present in the initial state. The effect of these initial perturbations is not diluted by inflation and survives to its end, and beyond. We consider a generic statistical density operator {rho} describing an initial mixed state that includes probabilities for nonzero numbers of scalar perturbations to be present at early times during inflation. We analyze the primordial bispectrum for general configurations of the three different momentum vectors in its arguments. We find that the initial presence of quanta can significantly enhance non-Gaussianities in the so-called squeezed limit. Our results show that an observation of non-Gaussianities in the squeezed limit can occur for single-field inflation when the state in the very early inflationary Universe is not the vacuum, but instead contains early-time perturbations. Valuable information about the initial state can then be obtained from observations of those non-Gaussianities.
Non-Gaussian and loop effects of inflationary correlation functions in BRST formalism
NASA Astrophysics Data System (ADS)
Kitamoto, Hiroyuki; Kitazawa, Yoshihisa; Kojima, Ryota
2017-07-01
We investigate inflationary correlation functions in single-field inflation models. We adopt a BRST formalism where locality and covariance at the subhorizon scale are manifest. The scalar and tensor perturbations are identified with those in the comoving gauge which become constant outside the cosmological horizon. Our construction reproduces the identical non-Gaussianity with the standard comoving gauge. The accumulation of almost scale-invariant fluctuations could give rise to IR logarithmic corrections at the loop level. We investigate the influence of this effect on the subhorizon dynamics. Since such an effect must respect covariance, our BRST gauge has an advantage over the standard comoving gauge. We estimate IR logarithmic effects to the slow-roll parameters at the one-loop level. We show that ɛ receives IR logarithmic corrections, while this is not the case for η . We point out that IR logarithmic effects provide the shift-symmetry-breaking mechanism. This scenario may lead to an inflation model with a linear potential.
Inflationary universe in the presence of a minimal measurable length
NASA Astrophysics Data System (ADS)
Mohammadi, A.; Ali, Ahmed Farag; Golanbari, T.; Aghamohammadi, A.; Saaidi, Kh.; Faizal, Mir
2017-10-01
In this paper, we will study the effect of having a minimum measurable length on inflationary cosmology. We will analyze the inflationary cosmology in the Jacobson approach. In this approach, gravity is viewed as an emergent thermodynamical phenomena. We will demonstrate that the existence of a minimum measurable length will modify the Friedmann equations in the Jacobson approach. We will use this modified Friedmann equation to analyze the effect of minimum measurable length scale on inflationary cosmology. This analysis will be performed using the Hamiltonian-Jacobi approach. We compare our results to recent data, and find that our model may agree with the recent data.
NASA Astrophysics Data System (ADS)
Chä, Seok-Yeong; Fischer, Uwe R.
2017-03-01
We consider an analogue de Sitter cosmos in an expanding quasi-two-dimensional Bose-Einstein condensate with dominant dipole-dipole interactions between the atoms or molecules in the ultracold gas. It is demonstrated that a hallmark signature of inflationary cosmology, the scale invariance of the power spectrum of inflaton field correlations, experiences strong modifications when, at the initial stage of expansion, the excitation spectrum displays a roton minimum. Dipolar quantum gases thus furnish a viable laboratory tool to experimentally investigate, with well-defined and controllable initial conditions, whether primordial oscillation spectra deviating from Lorentz invariance at trans-Planckian momenta violate standard predictions of inflationary cosmology.
Simple brane-world inflationary models — An update
NASA Astrophysics Data System (ADS)
Okada, Nobuchika; Okada, Satomi
2016-05-01
In the light of the Planck 2015 results, we update simple inflationary models based on the quadratic, quartic, Higgs and Coleman-Weinberg potentials in the context of the Randall-Sundrum brane-world cosmology. Brane-world cosmological effect alters the inflationary predictions of the spectral index (ns) and the tensor-to-scalar ratio (r) from those obtained in the standard cosmology. In particular, the tensor-to-scalar ratio is enhanced in the presence of the 5th dimension. In order to maintain the consistency with the Planck 2015 results for the inflationary predictions in the standard cosmology, we find a lower bound on the five-dimensional Planck mass (M5). On the other hand, the inflationary predictions laying outside of the Planck allowed region can be pushed into the allowed region by the brane-world cosmological effect with a suitable choice of M5.
Cosmology with many light scalar fields: Stochastic inflation and loop corrections
Adshead, Peter; Easther, Richard; Lim, Eugene A.
2009-03-15
We explore the consequences of the existence of a very large number of light scalar degrees of freedom in the early universe. We distinguish between participator and spectator fields. The former have a small mass, and can contribute to the inflationary dynamics; the latter are either strictly massless or have a negligible VEV. In N-flation and generic assisted inflation scenarios, inflation is a cooperative phenomenon driven by N participator fields, none of which could drive inflation on its own. We review upper bounds on N, as a function of the inflationary Hubble scale H. We then consider stochastic and eternal inflation in models with N participator fields showing that individual fields may evolve stochastically while the whole ensemble behaves deterministically, and that a wide range of eternal inflationary scenarios are possible in this regime. We then compute one-loop quantum corrections to the inflationary power spectrum. These are largest with N spectator fields and a single participator field, and the resulting bound on N is always weaker than those obtained in other ways. We find that loop corrections to the N-flation power spectrum do not scale with N, and thus place no upper bound on the number of participator fields. This result also implies that, at least to leading order, the theory behaves like a composite single scalar field. In order to perform this calculation, we address a number of issues associated with loop calculations in the Schwinger-Keldysh ''in-in'' formalism.
Inflationary gravitational waves and the evolution of the early universe
Jinno, Ryusuke; Moroi, Takeo; Nakayama, Kazunori E-mail: moroi@hep-th.phys.s.u-tokyo.ac.jp
2014-01-01
We study the effects of various phenomena which may have happened in the early universe on the spectrum of inflationary gravitational waves. The phenomena include phase transitions, entropy productions from non-relativistic matter, the production of dark radiation, and decoupling of dark matter/radiation from thermal bath. These events can create several characteristic signatures in the inflationary gravitational wave spectrum, which may be direct probes of the history of the early universe and the nature of high-energy physics.
Single-phase-field model of stepped surfaces.
Castro, M; Hernández-Machado, A; Cuerno, R
2009-02-01
We formulate a phase-field description of step dynamics on vicinal surfaces that makes use of a single dynamical field, at variance with previous analogous works in which two coupled fields are employed, namely, a phase-field proper plus the physical adatom concentration. Within an asymptotic sharp interface limit, our formulation is shown to retrieve the standard Burton-Cabrera-Frank model in the general case of asymmetric attachment coefficients (Ehrlich-Schwoebel effect). We confirm our analytical results by means of numerical simulations of our phase-field model. Our present formulation seems particularly well adapted to generalization when additional physical fields are required.
Consistency of the tachyon warm inflationary universe models
Zhang, Xiao-Min; Zhu, Jian-Yang E-mail: zhujy@bnu.edu.cn
2014-02-01
This study concerns the consistency of the tachyon warm inflationary models. A linear stability analysis is performed to find the slow-roll conditions, characterized by the potential slow-roll (PSR) parameters, for the existence of a tachyon warm inflationary attractor in the system. The PSR parameters in the tachyon warm inflationary models are redefined. Two cases, an exponential potential and an inverse power-law potential, are studied, when the dissipative coefficient Γ = Γ{sub 0} and Γ = Γ(φ), respectively. A crucial condition is obtained for a tachyon warm inflationary model characterized by the Hubble slow-roll (HSR) parameter ε{sub H}, and the condition is extendable to some other inflationary models as well. A proper number of e-folds is obtained in both cases of the tachyon warm inflation, in contrast to existing works. It is also found that a constant dissipative coefficient (Γ = Γ{sub 0}) is usually not a suitable assumption for a warm inflationary model.
Rojas, Clara
2009-05-15
The phase-integral approximation devised by Froeman and Froeman is used for computing cosmological perturbations in the quadratic chaotic inflationary model. The phase-integral formulas for the scalar and tensor power spectra are explicitly obtained up to fifth order of the phase-integral approximation. We show that the phase integral gives a very good approximation for the shape of the power spectra associated with scalar and tensor perturbations as well as the spectral indices. We find 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.
Single event burnout sensitivity of embedded field effect transistors
Koga, R.; Crain, S.H.; Crawford, K.B.; Yu, P.; Gordon, M.J.
1999-12-01
Observations of single event burnout (SEB) in embedded field effect transistors are reported. Both SEB and other single event effects are presented for several pulse width modulation and high frequency devices. The microscope has been employed to locate and to investigate the damaged areas. A model of the damage mechanism based on the results so obtained is described.
Taming the Runaway Problem of Inflationary Landscapes
Hall, Lawrence J.; Watari, Taizan; Yanagida, T. T.
2006-03-15
A wide variety of vacua, and their cosmological realization, may provide an explanation for the apparently anthropic choices of some parameters of particle physics and cosmology. If the probability on various parameters is weighted by volume, a flat potential for slow-roll inflation is also naturally understood, since the flatter the potential the larger the volume of the sub-universe. However, such inflationary landscapes have a serious problem, predicting an environment that makes it exponentially hard for observers to exist and giving an exponentially small probability for a moderate universe like ours. A general solution to this problem is proposed, and is illustrated in the context of inflaton decay and leptogenesis, leading to an upper bound on the reheating temperature in our sub-universe. In a particular scenario of chaotic inflation and non-thermal leptogenesis, predictions can be made for the size of CP violating phases, the rate of neutrinoless double beta decay and, in the case of theories with gauge-mediated weak scale supersymmetry, for the fundamental scale of supersymmetry breaking.
Signatures of spontaneous collapse-dynamics-modified single-field inflation
NASA Astrophysics Data System (ADS)
Banerjee, Shreya; Das, Suratna; Kumar, K. Sravan; Singh, T. P.
2017-05-01
The observed classicality of primordial perturbations, despite their quantum origin during inflation, calls for a mechanism for a quantum-to-classical transition of these initial fluctuations. As the literature suggests a number of plausible mechanisms which try to address this issue, it is of importance to seek concrete observational signatures of the various approaches in order to have a better understanding of the early Universe dynamics. Among these several approaches, it is the spontaneous collapse dynamics of quantum mechanics which is most viable for leaving discrete observational signatures as the collapse mechanism inherently changes the generic quantum dynamics. We observe in this study that the observables from the scalar sector, i.e., scalar tilt ns, running of scalar tilt αs, and running of running of scalar tilt βs, cannot potentially distinguish a collapse-modified inflationary dynamics in the realm of canonical scalar field and k -inflationary scenarios. The only distinguishable imprint of the collapse mechanism lies in the observables of the tensor sector in the form of a modified consistency relation and a blue-tilted tensor spectrum only when the collapse parameter δ is nonzero and positive.
Electric-field sensing using single diamond spins
NASA Astrophysics Data System (ADS)
Dolde, F.; Fedder, H.; Doherty, M. W.; Nöbauer, T.; Rempp, F.; Balasubramanian, G.; Wolf, T.; Reinhard, F.; Hollenberg, L. C. L.; Jelezko, F.; Wrachtrup, J.
2011-06-01
The ability to sensitively detect individual charges under ambient conditions would benefit a wide range of applications across disciplines. However, most current techniques are limited to low-temperature methods such as single-electron transistors, single-electron electrostatic force microscopy and scanning tunnelling microscopy. Here we introduce a quantum-metrology technique demonstrating precision three-dimensional electric-field measurement using a single nitrogen-vacancy defect centre spin in diamond. An a.c. electric-field sensitivity reaching 202+/-6Vcm-1Hz-1/2 has been achieved. This corresponds to the electric field produced by a single elementary charge located at a distance of ~150nm from our spin sensor with averaging for one second. The analysis of the electronic structure of the defect centre reveals how an applied magnetic field influences the electric-field-sensing properties. We also demonstrate that diamond-defect-centre spins can be switched between electric- and magnetic-field sensing modes and identify suitable parameter ranges for both detector schemes. By combining magnetic- and electric-field sensitivity, nanoscale detection and ambient operation, our study should open up new frontiers in imaging and sensing applications ranging from materials science to bioimaging.
Chambers, Alex; Rajantie, Arttu
2008-02-01
If light scalar fields are present at the end of inflation, their nonequilibrium dynamics such as parametric resonance or a phase transition can produce non-Gaussian density perturbations. We show how these perturbations can be calculated using nonlinear lattice field theory simulations and the separate universe approximation. In the massless preheating model, we find that some parameter values are excluded while others lead to acceptable but observable levels of non-Gaussianity. This shows that preheating can be an important factor in assessing the viability of inflationary models.
Optical singularities in plasmonic fields near single subwavelength holes
NASA Astrophysics Data System (ADS)
de Hoogh, A.; Rotenberg, N.; Kuipers, L.
2014-11-01
We identify phase and polarization singularities in near-field measurements and theoretical modeling of the electric near-field distributions that result from the scattering of surface plasmon polaritons from single subwavelength holes in optically thick gold films. We discuss properties of the singularities, such as their topological charge or the field amplitudes at their locations. We show that it is possible to tune the in-plane field amplitude at the positions of the polarization singularities by three orders of magnitude simply by varying the hole or incident plasmon beam size.
On the divergences of inflationary superhorizon perturbations
Enqvist, K; Nurmi, S; Podolsky, D; Rigopoulos, G I E-mail: sami.nurmi@helsinki.fi E-mail: gerasimos.rigopoulos@helsinki.fi
2008-04-15
We discuss the infrared divergences that appear to plague cosmological perturbation theory. We show that, within the stochastic framework, they are regulated by eternal inflation so that the theory predicts finite fluctuations. Using the {Delta}N formalism to one loop, we demonstrate that the infrared modes can be absorbed into additive constants and the coefficients of the diagrammatic expansion for the connected parts of two-and three-point functions of the curvature perturbation. As a result, the use of any infrared cutoff below the scale of eternal inflation is permitted, provided that the background fields are appropriately redefined. The natural choice for the infrared cutoff would, of course, be the present horizon; other choices manifest themselves in the running of the correlators. We also demonstrate that it is possible to define observables that are renormalization-group-invariant. As an example, we derive a non-perturbative, infrared finite and renormalization point-independent relation between the two-point correlators of the curvature perturbation for the case of the free single field.
Modeling Single Particle Transport in Stochastic Magnetic Fields
NASA Astrophysics Data System (ADS)
Hudson, Ben; Fiksel, Gennady; Prager, Stewart
2001-10-01
Single particle transport in a stochastic magnetic field is simulated via code ION and RIO. Developed in collaboration with a group in Novosibirsk, Russia, they simulate both single ion and multiple ion trajectories in a stochastic magnetic field. A sharp decrease in the relative diffusion of ions to magnetic field lines is seen in two gyro-radii regimes. One is explainable from the unbroken flux surfaces near the edge of the plasma. The other is thought to be due to a "gyro-averaging" effect that occurs when the gyro-radius exceeds the radial correlation length of the field lines. The simulations indicate a decrease in expected transport, most strongly as a function of gyro-radius, which will be tested experimentally with the MST neutral beam injector.
Strongly enhanced field-dependent single-molecule electroluminescence
NASA Astrophysics Data System (ADS)
Lee, Tae-Hee; Gonzalez, Jose I.; Dickson, Robert M.
2002-08-01
Individual, strongly electroluminescent Agn molecules (n = 28 atoms) have been electrically written within otherwise nonemissive silver oxide films. Exhibiting characteristic single-molecule behavior, these individual room-temperature molecules exhibit extreme electroluminescence enhancements (>104 vs. bulk and dc excitation on a per molecule basis) when excited with specific ac frequencies. Occurring through field extraction of electrons with subsequent reinjection and radiative recombination, single-molecule electroluminescence is enhanced by a general mechanism that avoids slow bulk material response. Thus, while we detail strong electroluminescence from single, highly fluorescent Agn molecules, this mechanism also yields strong ac-excited electroluminescence from similarly prepared, but otherwise nonemissive, individual Cu nanoclusters.
Single-ion microwave near-field quantum sensor
NASA Astrophysics Data System (ADS)
Wahnschaffe, M.; Hahn, H.; Zarantonello, G.; Dubielzig, T.; Grondkowski, S.; Bautista-Salvador, A.; Kohnen, M.; Ospelkaus, C.
2017-01-01
We develop an intuitive model of 2D microwave near-fields in the unusual regime of centimeter waves localized to tens of microns. Close to an intensity minimum, a simple effective description emerges with five parameters that characterize the strength and spatial orientation of the zero and first order terms of the near-field, as well as the field polarization. Such a field configuration is realized in a microfabricated planar structure with an integrated microwave conductor operating near 1 GHz. We use a single 9 Be+ ion as a high-resolution quantum sensor to measure the field distribution through energy shifts in its hyperfine structure. We find agreement with simulations at the sub-micron and few-degree level. Our findings give a clear and general picture of the basic properties of oscillatory 2D near-fields with applications in quantum information processing, neutral atom trapping and manipulation, chip-scale atomic clocks, and integrated microwave circuits.
High-scale axions without isocurvature from inflationary dynamics
NASA Astrophysics Data System (ADS)
Kearney, John; Orlofsky, Nicholas; Pierce, Aaron
2016-05-01
Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation HI . If the scale of Peccei-Quinn (PQ) breaking fa is greater than H/I 2 π , CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation fI require either late-time dilution of the axion abundance or highly super-Planckian fI that somehow does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow fa close to the Planck scale. Avoiding disruption of inflationary dynamics provides important limits on the parameter space.
High-scale axions without isocurvature from inflationary dynamics
Kearney, John; Orlofsky, Nicholas; Pierce, Aaron
2016-05-31
Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation HI. If the scale of Peccei-Quinn (PQ) breaking fa is greater than HI/2π, CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation fI require either late-time dilution of the axion abundance or highly super-Planckian fI that somehowmore » does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow fa close to the Planck scale. Lastly, avoiding disruption of inflationary dynamics provides important limits on the parameter space.« less
Wavefunction of anisotropic inflationary universes with no-boundary conditions
NASA Astrophysics Data System (ADS)
Bramberger, Sebastian F.; Farnsworth, Shane; Lehners, Jean-Luc
2017-04-01
We study the emergence of anisotropic (Bianchi IX) inflationary universes with no-boundary conditions in the path integral approach to quantum gravity. In contrast to previous work, we find no evidence for any limit to how large the anisotropies can become, although for increasing anisotropies the shape of the instantons becomes significantly different from Hawking's original no-boundary instanton. In all cases an inflationary phase is reached, with the anisotropies decaying away. Larger anisotropies are associated with a much larger imaginary part of the action, implying that the highly anisotropic branches of the wavefunction are heavily suppressed. Interestingly, the presence of anisotropies causes the wavefunction to become classical much more slowly than for isotropic inflationary universes. We derive the associated scaling of the WKB classicality conditions both numerically and analytically.
Field emission properties of single crystal chromium disilicide nanowires
Valentin, L. A.; Carpena-Nunez, J.; Yang, D.; Fonseca, L. F.
2013-01-07
The composition, crystal structure, and field emission properties of high-crystallinity chromium disilicide (CrSi{sub 2}) nanowires synthesized by a vapor deposition method have been studied. High resolution transmission electron microscopy, energy dispersive spectroscopy, and selected area electron diffraction studies confirm the single-crystalline structure and composition of the CrSi{sub 2} nanowires. Field emission measurements show that an emission current density of 0.1 {mu}A/cm{sup 2} was obtained at a turn-on electric field intensity of 2.80 V/{mu}m. The maximum emission current measured was 1.86 mA/cm{sup 2} at 3.6 V/{mu}m. The relation between the emission current density and the electric field obtained follows the Fowler-Nordheim equation, with an enhancement coefficient of 1140. The electrical conductivity of single nanowires was measured by using four-point-probe specialized microdevices at different temperatures, and the calculated values are close to those reported in previous studies for highly conductive single crystal bulk CrSi{sub 2}. The thermal tolerance of the nanowires was studied up to a temperature of 1100 Degree-Sign C. The stability of the field emission current, the I-E values, their thermal tolerance, and high electrical conductivity make CrSi{sub 2} nanowires a promising material for field emission applications.
Cosmological constraints on nonstandard inflationary quantum collapse models
NASA Astrophysics Data System (ADS)
Landau, Susana J.; Scóccola, Claudia G.; Sudarsky, Daniel
2012-06-01
We briefly review an important shortcoming—unearthed in previous works—of the standard version of the inflationary model for the emergence of the seeds of cosmic structure. We consider here some consequences emerging from a proposal inspired on ideas of Penrose and Diósi [R. Penrose, The Emperor’s New Mind. Concerning Computers, Minds and Laws of Physics (1989).][R. Penrose, in Physics meets Philosophy at the Planck Scale: Contemporary Theories in Quantum Gravity, edited by C. Callendar and N. Huggett (2001), pp. 290-+.][L. Diósi, Phys. Lett. A 120, 377 (1987).PYLAAG0375-960110.1016/0375-9601(87)90681-5][L. Diósi, Phys. Rev. A 40, 1165 (1989).PLRAAN0556-279110.1103/PhysRevA.40.1165] about a quantum-gravity induced reduction of the wave function, which has been put forward to address the shortcomings, arguing that its effect on the inflaton field is what can lead to the emergence of the seeds of cosmic structure [A. Perez, H. Sahlmann, and D. Sudarsky, Classical Quantum Gravity 23, 2317 (2006).CQGRDG0264-938110.1088/0264-9381/23/7/008]. The proposal leads to a deviation of the primordial spectrum from the scale-invariant Harrison-Zel’dovich one, and consequently, to a different CMB power spectrum. We perform statistical analyses to test two quantum collapse schemes with recent data from the CMB, including the 7-yr release of WMAP and the matter power spectrum measured using LRGs by the Sloan Digital Sky Survey. Results from the statistical analyses indicate that several collapse models are compatible with CMB and LRG data, and establish constraints on the free parameters of the models. The data put no restriction on the timescale for the collapse of the scalar field modes.
Constraining = 1 supergravity inflationary framework with non-minimal Kähler operators
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan; Mazumdar, Anupam; Pukartas, Ernestas
2014-04-01
In this paper we will illustrate how to constrain unavoidable Kähler corrections for = 1 supergravity (SUGRA) inflation from the recent Planck data. We will show that the non-renormalizable Kähler operators will induce in general non-minimal kinetic term for the inflaton field, and two types of SUGRA corrections in the potential — the Hubble-induced mass ( c H ), and the Hubble-induced A-term ( a H ) correction. The entire SUGRA inflationary framework can now be constrained from (i) the speed of sound, c s , and (ii) from the upper bound on the tensor to scalar ratio, r ⋆. We will illustrate this by considering a heavy scalar degree of freedom at a scale, M s , and a light inflationary field which is responsible for a slow-roll inflation. We will compute the corrections to the kinetic term and the potential for the light field explicitly. As an example, we will consider a visible sector inflationary model of inflation where inflation occurs at the point of inflection, which can match the density perturbations for the cosmic microwave background radiation, and also explain why the universe is filled with the Standard Model degrees of freedom. We will scan the parameter space of the non-renormalizable Kähler operators, which we find them to be order (1), consistent with physical arguments. While the scale of heavy physics is found to be bounded by the tensor-to scalar ratio, and the speed of sound, (1011 ≤ M s ≤ 1016) GeV, for 0 .02 ≤ c s ≤ 1 and 10-22 ≤ r ⋆ ≤ 0 .12.
Field emission from single-crystalline HfC nanowires
Yuan, Jinshi; Tang, Jie; Zhang Han; Shinya, Norio; Nakajima, Kiyomi; Qin, Lu-Chang
2012-03-12
Single HfC nanowire field emitter/electrode structures have been fabricated using nano-assembling and electron beam induced deposition. Field ion microscopy has been applied to study the atomic arrangement of facets formed on a field evaporation-modified HfC nanowire tip. Field evaporation and crystal form studies suggest that the {l_brace}111{r_brace} and {l_brace}110{r_brace} crystal planes have lower work functions, while the {l_brace}100{r_brace}, {l_brace}210{r_brace}, and {l_brace}311{r_brace} planes have higher work functions. Field emission measurement permits us to obtain that the work function of the {l_brace}111{r_brace} crystal plane is about 3.4 eV.
Tachyon warm-intermediate inflationary universe model in high dissipative regime
Setare, M.R.; Kamali, V. E-mail: vkamali1362@gmail.com
2012-08-01
We consider tachyonic warm-inflationary models in the context of intermediate inflation. We derive the characteristics of this model in slow-roll approximation and develop our model in two cases, 1- For a constant dissipative parameter Γ. 2- Γ as a function of tachyon field φ. We also describe scalar and tensor perturbations for this scenario. The parameters appearing in our model are constrained by recent observational data. We find that the level of non-Gaussianity for this model is comparable with non-tachyonic model.
TOPICAL REVIEW: Organic field-effect transistors using single crystals
NASA Astrophysics Data System (ADS)
Hasegawa, Tatsuo; Takeya, Jun
2009-04-01
Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm2 Vs-1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.
Organic field-effect transistors using single crystals.
Hasegawa, Tatsuo; Takeya, Jun
2009-04-01
Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm(2) Vs(-1), achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.
Organic field-effect transistors using single crystals
Hasegawa, Tatsuo; Takeya, Jun
2009-01-01
Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for ‘plastic electronics’. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20–40 cm2 Vs−1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps. PMID:27877287
Radiation burst from a single {gamma}-photon field
Shakhmuratov, R. N.; Vagizov, F.; Kocharovskaya, O.
2011-10-15
The radiation burst from a single {gamma}-photon field interacting with a dense resonant absorber is studied theoretically and experimentally. This effect was discovered for the fist time by P. Helisto et al.[Phys. Rev. Lett. 66, 2037 (1991)] and it was named the ''gamma echo''. The echo is generated by a 180 Degree-Sign phase shift of the incident radiation field, attained by an abrupt change of the position of the absorber with respect to the radiation source during the coherence time of the photon wave packet. Three distinguishing cases of the gamma echo are considered; i.e., the photon is in exact resonance with the absorber, close to resonance (on the slope of the absorption line), and far from resonance (on the far wings of the resonance line). In resonance the amplitude of the radiation burst is two times larger than the amplitude of the input radiation field just before its phase shift. This burst was explained by Helisto et al. as a result of constructive interference of the coherently scattered field with the phase-shifted input field, both having almost the same amplitude. We found that out of resonance the scattered radiation field acquires an additional component with almost the same amplitude as the amplitude of the incident radiation field. The phase of the additional field depends on the optical thickness of the absorber and resonant detuning. Far from resonance this field interferes destructively with the phase-shifted incident radiation field and radiation quenching is observed. Close to resonance the three fields interfere constructively and the amplitude of the radiation burst is three times larger than the amplitude of the input radiation field.
Large slow roll parameters in single field inflation
Cook, Jessica L.; Krauss, Lawrence M. E-mail: krauss@asu.edu
2016-03-01
We initially consider two simple situations where inflationary slow roll parameters are large and modes no longer freeze out shortly after exiting the horizon, treating both cases analytically. By modes, we refer to the comoving curvature perturbation R. We then consider applications to transient phases where the slow roll parameters can become large, especially in the context of the common 'fast-roll' inflation frequently used as a mechanism to explain the anomalously low scalar power at low l in the CMB. These transient cases we treat numerically. We find when ε, the first slow roll parameter, and only ε is large, modes decay outside the horizon, and when δ, the second slow roll parameter, is large, modes grow outside the horizon. When multiple slow roll parameters are large the behavior in general is more complicated, but we nevertheless show in the 'fast-roll' inflation case, modes grow outside the horizon.
Inflationary Cosmology: Is Our Universe Part of a Multiverse?
Guth, Alan
2008-11-06
In this talk, Guth explains the inflationary theory and reviews the features that make it scientifically plausible. In addition, he discusses the biggest mystery in cosmology: Why is the value of the cosmological constant, sometimes called the "anti-gravity" effect, so remarkably small compared to theoretical expectations?
Nonisotropy in the CMB power spectrum in single field inflation
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.
Single-field inflation à la generalized Chaplygin gas
Campo, Sergio del
2013-11-01
In the simplest scenario for inflation, i.e. in the single-field inflation, it is presented an inflaton field with properties equivalent to a generalized Chaplygin gas. Their study is performed using the Hamilton-Jacobi approach to cosmology. The main results are contrasted with the measurements recently released by the Planck data, combined with the WMAP large-angle polarization. If the measurements released by Planck for the scalar spectral index together with its running are taken into account it is found a value for the α-parameter associated to the generalized Chaplygin gas given by α = 0.2578±0.0009.
Optimal bispectrum constraints on single-field models of inflation
Anderson, Gemma J.; Regan, Donough; Seery, David E-mail: D.Regan@sussex.ac.uk
2014-07-01
We use WMAP 9-year bispectrum data to constrain the free parameters of an 'effective field theory' describing fluctuations in single-field inflation. The Lagrangian of the theory contains a finite number of operators associated with unknown mass scales. Each operator produces a fixed bispectrum shape, which we decompose into partial waves in order to construct a likelihood function. Based on this likelihood we are able to constrain four linearly independent combinations of the mass scales. As an example of our framework we specialize our results to the case of 'Dirac-Born-Infeld' and 'ghost' inflation and obtain the posterior probability for each model, which in Bayesian schemes is a useful tool for model comparison. Our results suggest that DBI-like models with two or more free parameters are disfavoured by the data by comparison with single-parameter models in the same class.
Single shot line-field optical coherence elastography
NASA Astrophysics Data System (ADS)
Liu, Chih-Hao; Schill, Alexander; Singh, Manmohan; Wu, Chen; Li, Jiasong; Han, Zhaolong; Raghunathan, Raksha; Kazemi, Tina; Nair, Achuth; Hsu, Thomas; Larin, Kirill V.
2016-03-01
Elastic wave imaging optical coherence elastography (EWI-OCE) is an emerging technique that can quantify local biomechanical properties of tissues. However, long acquisition times make this technique unfeasible for clinical use. Here, we demonstrate a noncontact single shot line-field OCE technique using a line-field interferometer and an air-pulse delivery system. The spatial-temporal elastic wave propagation profile was acquired in a single shot and used to quantify the elastic wave group velocity in tissue. Results on tissue-mimicking phantoms and chicken breast muscle agreed well with mechanical compression testing, demonstrating that the presented method can effectively reduce the OCE acquisition time to a few milliseconds in biological application.
Quantitative annular dark field electron microscopy using single electron signals.
Ishikawa, Ryo; Lupini, Andrew R; Findlay, Scott D; Pennycook, Stephen J
2014-02-01
One of the difficulties in analyzing atomic resolution electron microscope images is that the sample thickness is usually unknown or has to be fitted from parameters that are not precisely known. An accurate measure of thickness, ideally on a column-by-column basis, parameter free, and with single atom accuracy, would be of great value for many applications, such as matching to simulations. Here we propose such a quantification method for annular dark field scanning transmission electron microscopy by using the single electron intensity level of the detector. This method has the advantage that we can routinely quantify annular dark field images operating at both low and high beam currents, and under high dynamic range conditions, which is useful for the quantification of ultra-thin or light-element materials. To facilitate atom counting at the atomic scale we use the mean intensity in an annular dark field image averaged over a primitive cell, with no free parameters to be fitted. To illustrate the potential of our method, we demonstrate counting the number of Al (or N) atoms in a wurtzite-type aluminum nitride single crystal at each primitive cell over the range of 3-99 atoms.
Single-point inversion of the coronal magnetic field
Plowman, Joseph
2014-09-01
The Fe XIII 10747 and 10798 Å lines observed in the solar corona are sensitive to the coronal magnetic field in such a way that, in principle, the full vector field at a point on the line of sight can be inferred from their combined polarization signals. This paper presents analytical inversion formulae for the field parameters and analyzes the uncertainty of magnetic field measurements made from such observations, assuming emission dominated by a single region along the line of sight. We consider the case of the current Coronal Multi-channel Polarimeter (CoMP) instrument as well as the future Coronal Solar Magnetism Observatory (COSMO) and Advanced Technology Solar Telescope (ATST) instruments. Uncertainties are estimated with a direct analytic inverse and with a Markov Chain Monte Carlo algorithm. We find that (in effect) two components of the vector field can be recovered with CoMP, and well recovered with COSMO or ATST, but that the third component can only be recovered when the solar magnetic field is strong and optimally oriented.
Field Regulation of Single Molecule Conductivity by a Charged Atom
NASA Astrophysics Data System (ADS)
Wolkow, Robert
2006-03-01
A new concept for a single molecule transistor is demonstrated [1]. A single chargeable atom adjacent to a molecule shifts molecular energy levels into alignment with electrode levels, thereby gating current through the molecule. Seemingly paradoxically, the silicon substrate to which the molecule is covalently attached provides 2, not 1, effective contacts to the molecule. This is achieved because the single charged silicon atom is at a substantially different potential than the remainder of the substrate. Charge localization at one dangling bond is ensured by covalently capping all other surface atoms. Dopant level control and local Fermi level control can change the charge state of that atom. The same configuration is shown to be an effective transducer to an electrical signal of a single molecule detection event. Because the charged atom induced shifting results in conductivity changes of substantial magnitude, these effects are easily observed at room temperature. [1] Paul G. Piva1,Gino A. DiLabio, Jason L. Pitters, Janik Zikovsky, Moh'd Rezeq, Stanislav Dogel, Werner A. Hofer & Robert A. Wolkow, Field regulation of single-molecule conductivity by a charged surface atom, NATURE 435, 658-661 (2005)
Relaxation models for single helical reversed field pinch plasmas
NASA Astrophysics Data System (ADS)
Paccagnella, Roberto
2016-09-01
In this paper, a relaxation theory for plasmas where a single dominant mode is present [Bhattacharjee et al., Phys. Rev. Lett. 45, 347 (1980)], is revisited. The solutions of a related eigenvalue problem are numerically calculated and discussed. Although these solutions can reproduce well, the magnetic fields measured in experiments, there is no way within the theory to determine the dominant mode, whose pitch is a free parameter in the model. To find the preferred helical perturbation, a procedure is proposed that minimizes the "distance" of the relaxed state from a state which is constructed as a two region generalization of the Taylor's relaxation model [Taylor, Phys. Rev. Lett. 33, 1139 (1974); Rev. Mod. Phys. 58, 751 (1986)] and that allows current discontinuities. It is found that this comparison is able to predict the observed scaling with the aspect ratio and reversal parameter for the dominant mode in the Single Helical states. The aspect ratio scaling alone is discussed in a previous paper [Paccagnella, Nucl. Fusion 56, 046010 (2016)] in terms of the efficient response of a toroidal shell to specific modes (leaving a sign undetermined), showing that the ideal wall boundary condition, a key ingredient in relaxation theories, is particularly well matched for them. Therefore, the present paper altogether [Paccagnella, Nucl. Fusion 56, 046010 (2016)] can give a new and satisfactory explanation of some robust and reproducible experimental facts observed in the Single Helical Reversed Field Pinch plasmas and never explained before.
On squeezed limits in single-field inflation. Part I
Flauger, Raphael; Green, Daniel; Porto, Rafael A. E-mail: dgreen@stanford.edu
2013-08-01
The n-point correlation functions in single-field inflation obey a set of consistency conditions in the exact squeezed limit which are not present in multi-field models, and thus are powerful tools to distinguish between the two. However, these consistency conditions may be violated for a finite range of scales in single-field models, for example by departures from the Bunch-Davies state. These excited states may be the consequence of interactions during inflation, or may be a remnant of the era that preceded inflation. In this paper we analyze the bispectrum, and show that in the regime of theoretical control the resulting signal in the squeezed limit remains undetectably small in all known models which continuously excite the state. We also show that the signal remains undetectably small if the initial state is related to the Bunch-Davies state by a Bogoliubov transformation and the energy density in the state is small enough so that the usual slow-roll conditions are obeyed. Bogoliubov states that lead to violations of the slow-roll conditions, as well as more general excited states, require more careful treatment and will be discussed in a separate publication.
[Striate receptive fields mapped with single and bipartite stimuli].
Lazareva, N A; Shevelev, I A; Saltykov, K A; Novikova, R V; Tikhomirov, A S; Sharaev, G A; Tsutskiridze, D Iu; Eĭdeland, P V
2008-01-01
In 22 acute experiments with anesthetized and immobilized adult cats, 364 maps of receptive fields (RF) of 47 striate neurons were obtained by means of single local stimuli flashed at different parts of the visual field, or with additional asynchronous activation of the RF excitatory center with oscillating bar of the optimal orientation. Under bipartite stimulation, considerable and significant decrease in the square and weight of the central excitatory RF zone was revealed in more then 75% of the studied cells. Additional excitatory zones appeared in 54% of cases, or the square and weight of the excitatory zones substantially increased, and inhibitory zones developed in 90% of cases. These effects were correlated with the degree of increase in the background firing during transition from the mode of mapping with single stimulation to that with bipartite stimulation. The mechanism and possible functional role of cooperative excitatory and inhibitory intracortical interactions in organization of receptive fields and detection of features of a visual image are discussed.
Measuring the complex field scattered by single submicron particles
Potenza, Marco A. C. Sanvito, Tiziano
2015-11-15
We describe a method for simultaneous measurements of the real and imaginary parts of the field scattered by single nanoparticles illuminated by a laser beam, exploiting a self-reference interferometric scheme relying on the fundamentals of the Optical Theorem. Results obtained with calibrated spheres of different materials are compared to the expected values obtained through a simplified analytical model without any free parameters, and the method is applied to a highly polydisperse water suspension of Poly(D,L-lactide-co-glycolide) nanoparticles. Advantages with respect to existing methods and possible applications are discussed.
Quasi-single field inflation with large mass
Chen, Xingang; Wang, Yi E-mail: tririverwangyi@gmail.com
2012-09-01
We study the effect of massive isocurvaton on density perturbations in quasi-single field inflation models, when the mass of the isocurvaton M becomes larger than the order of the Hubble parameter H. We analytically compute the correction to the power spectrum, leading order in coupling but exact for all values of mass. This verifies the previous numerical results for the range 0 < M < 3H/2 and shows that, in the large mass limit, the correction is of order H{sup 2}/M{sup 2}.
Inflationary effect of crude oil prices in Turkey
NASA Astrophysics Data System (ADS)
Berument, Hakan; Taşçı, Hakan
2002-12-01
It is generally acknowledged that changes in oil prices affect economic welfare in ways that are not entirely reflected in transactions in the oil market. In this article, by using the 1990 input-output table, the inflationary effects of crude oil prices are investigated for Turkey. Under fixed nominal wages, profits, interest and rent earnings, the effect of increasing prices of oil on inflation is limited. However, when wages and the other three factors of income (profit, interest and rent) are adjusted to the general price level that includes the oil price increases, the inflationary effect of oil prices becomes significant. Hence, indexation could have very severe effects on an economy when oil prices increase and, in some cases, could even lead to hyperinflation.
Inflationary Cosmology: Is Our Universe Part of a Multiverse
Guth, Alan
2008-11-06
In 1981, Guth proposed the theory of the inflationary universe, a modification of the Big Bang theory, which is generally accepted by scientists to explain how the universe began. Nevertheless, the Big Bang theory leaves some questions, and the theory of inflation attempts to answer them. Guth states that a repulsive gravitational force generated by an exotic form of matter brought about the expansion of the universe. He postulates that the universe underwent an expansion of astronomical proportions within the first trillionth of a second of its existence, during which the seeds for its large-scale structure were generated. Guth and colleagues have further explored the possibility of mimicking inflation in a hypothetical laboratory, thereby creating a new universe, and they concluded that it might be theoretically possible. If it happened, the new universe would not endanger our own universe. Instead, it would slip through a wormhole, a hypothetical space-time travel shortcut, and rapidly disconnect from our universe. In this talk, Guth will explain the inflationary theory and review the features that make it scientifically plausible. In addition, he will discuss the biggest mystery in cosmology: Why is the value of the cosmological constant, sometimes called the "anti-gravity" effect, so remarkably small compared to theoretical expectations? Guth will explain how the inflationary theory, combined with other ideas from elementary particle physics and cosmology, can provide a possible explanation for this discrepancy.
High-scale axions without isocurvature from inflationary dynamics
Kearney, John; Orlofsky, Nicholas; Pierce, Aaron
2016-05-31
Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation H_{I}. If the scale of Peccei-Quinn (PQ) breaking f_{a} is greater than H_{I}/2π, CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation f_{I} require either late-time dilution of the axion abundance or highly super-Planckian f_{I} that somehow does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow f_{a} close to the Planck scale. Lastly, avoiding disruption of inflationary dynamics provides important limits on the parameter space.
High-scale axions without isocurvature from inflationary dynamics
Kearney, John; Orlofsky, Nicholas; Pierce, Aaron
2016-05-31
Observable primordial tensor modes in the cosmic microwave background (CMB) would point to a high scale of inflation H_{I}. If the scale of Peccei-Quinn (PQ) breaking f_{a} is greater than H_{I}/2π, CMB constraints on isocurvature naively rule out QCD axion dark matter. This assumes the potential of the axion is unmodified during inflation. We revisit models where inflationary dynamics modify the axion potential and discuss how isocurvature bounds can be relaxed. We find that models that rely solely on a larger PQ-breaking scale during inflation f_{I} require either late-time dilution of the axion abundance or highly super-Planckian f_{I} that somehow does not dominate the inflationary energy density. Models that have enhanced explicit breaking of the PQ symmetry during inflation may allow f_{a} close to the Planck scale. Lastly, avoiding disruption of inflationary dynamics provides important limits on the parameter space.
Low reheating temperatures in monomial and binomial inflationary models
NASA Astrophysics Data System (ADS)
Rehagen, Thomas; Gelmini, Graciela B.
2015-06-01
We investigate the allowed range of reheating temperature values in light of the Planck 2015 results and the recent joint analysis of Cosmic Microwave Background (CMB) data from the BICEP2/Keck Array and Planck experiments, using monomial and binomial inflationary potentials. While the well studied phi2 inflationary potential is no longer favored by current CMB data, as well as phip with p>2, a phi1 potential and canonical reheating (0wre=) provide a good fit to the CMB measurements. In this last case, we find that the Planck 2015 68% confidence limit upper bound on the spectral index, ns, implies an upper bound on the reheating temperature of Trelesssim 6× 1010 GeV, and excludes instantaneous reheating. The low reheating temperatures allowed by this model open the possibility that dark matter could be produced during the reheating period instead of when the Universe is radiation dominated, which could lead to very different predictions for the relic density and momentum distribution of WIMPs, sterile neutrinos, and axions. We also study binomial inflationary potentials and show the effects of a small departure from a phi1 potential. We find that as a subdominant phi2 term in the potential increases, first instantaneous reheating becomes allowed, and then the lowest possible reheating temperature of Tre=4 MeV is excluded by the Planck 2015 68% confidence limit.
Single crystal growth of organic semiconductors for field effect applications
NASA Astrophysics Data System (ADS)
Kloc, Christian
2006-08-01
Organic semiconductors attract considerable attention due to promising applications in organic light emitting diodes, field effect transistors, and organic solar cells. Moreover, solubility of some organic semiconductors in organic solvents favors them for printed large area OLED displays and inexpensive printed microelectronics. However, low mobility of carriers in organic semiconductors limits usability of organic semiconductors in integrated circuits and need to be overcome. For this reason, the knowledge of intrinsic properties achievable in very pure and perfect crystals is important. Therefore, we have carried out a program to grow high quality single crystals of organics. Solution growth, melt growth, solvothermal method and vapor transport crystal growth have been applied and will be reported. For research purpose, using a gas phase transport method, we have produced millimeter - sized crystals of numerous organic semiconductors with higher quality and purity. Structure quality has been evaluated by x-ray topography methods. Field effect transistors have been prepared on surfaces of single crystals. Some of organic semiconductors like rubrene, pentacene, copper phthalocyanine exhibit carrier mobilities comparable or even higher than amorphous silicon. However, characterization of starting materials, crystals, thin films and resulting devices remains the crucial issue. The relation between organic semiconductor properties, used device fabrication technologies and resulting device characteristics is the object of presented here studies.
Subsurface Stress Fields in Single Crystal (Anisotropic) Contacts
NASA Technical Reports Server (NTRS)
Arakere, Nagaraj K.
2003-01-01
Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and fatigue stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. Techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts are presented in this report. Figure 1 shows typical damper contact locations in a turbine blade. The subsurface stress results are used for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades.
Subsurface Stress Fields In Single Crystal (Anisotropic) Contacts
NASA Technical Reports Server (NTRS)
Arakere, Nagaraj K.; Knudsen, Erik C.; Duke, Greg; Battista, Gilda; Swanson, Greg
2004-01-01
Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent HCF failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and noncrystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is , presented, for evaluating the subsurface stresses in the elastic half-space, using a complex potential method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis. Effects of crystal orientation on stress response and fatigue life are examined.
Hyperspectral Dark Field Optical Microscopy of Single Silver Nanospheres
El-Khoury, Patrick Z.; Joly, Alan G.; Hess, Wayne P.
2016-04-07
We record spectrally (400 nm ≤ λ ≤ 675 nm, Δλ < 4.69 nm) and spatially (diffraction-limited, sampled at 85 nm2/pixel) resolved dark field (DF) scattering from single silver nanospheres of 100 nm in diameter. Hyperspectral DF optical microscopy is achieved by coupling a hyperspectral detector to an optical microscope, whereby spectrally resolved diffraction-limited images of hundreds of silver nanoparticles can be recorded in ~30 seconds. We demonstrate how the centers and edges of individual particles can be localized in 2D to within a single pixel (85 nm2), using a statistical method for examining texture based on a co-occurrence matrix. Subsequently, spatial averaging of the spectral response in a 3x3 pixel area around the particle centers affords ample signal-to-noise to resolve the plasmon resonance of a single silver nanosphere. A close inspection of the scattering spectra of 31 different nanospheres reveals that each particle has its unique (i) relative scattering efficiency, and (ii) plasmon resonance maximum and dephasing time. These observations are suggestive of nanometric structural variations over length scales much finer than the spatial resolution attainable using the all-optical technique described herein.
Dark energy from primordial inflationary quantum fluctuations.
Ringeval, Christophe; Suyama, Teruaki; Takahashi, Tomo; Yamaguchi, Masahide; Yokoyama, Shuichiro
2010-09-17
We show that current cosmic acceleration can be explained by an almost massless scalar field experiencing quantum fluctuations during primordial inflation. Provided its mass does not exceed the Hubble parameter today, this field has been frozen during the cosmological ages to start dominating the Universe only recently. By using supernovae data, completed with baryonic acoustic oscillations from galaxy surveys and cosmic microwave background anisotropies, we infer the energy scale of primordial inflation to be around a few TeV, which implies a negligible tensor-to-scalar ratio of the primordial fluctuations. Moreover, our model suggests that inflation lasted for an extremely long period. Dark energy could therefore be a natural consequence of cosmic inflation close to the electroweak energy scale.
Subsurface Stress Fields in FCC Single Crystal Anisotropic Contacts
NASA Technical Reports Server (NTRS)
Arakere, Nagaraj K.; Knudsen, Erik; Swanson, Gregory R.; Duke, Gregory; Ham-Battista, Gilda
2004-01-01
Single crystal superalloy turbine blades used in high pressure turbomachinery are subject to conditions of high temperature, triaxial steady and alternating stresses, fretting stresses in the blade attachment and damper contact locations, and exposure to high-pressure hydrogen. The blades are also subjected to extreme variations in temperature during start-up and shutdown transients. The most prevalent high cycle fatigue (HCF) failure modes observed in these blades during operation include crystallographic crack initiation/propagation on octahedral planes, and non-crystallographic initiation with crystallographic growth. Numerous cases of crack initiation and crack propagation at the blade leading edge tip, blade attachment regions, and damper contact locations have been documented. Understanding crack initiation/propagation under mixed-mode loading conditions is critical for establishing a systematic procedure for evaluating HCF life of single crystal turbine blades. This paper presents analytical and numerical techniques for evaluating two and three dimensional subsurface stress fields in anisotropic contacts. The subsurface stress results are required for evaluating contact fatigue life at damper contacts and dovetail attachment regions in single crystal nickel-base superalloy turbine blades. An analytical procedure is presented for evaluating the subsurface stresses in the elastic half-space, based on the adaptation of a stress function method outlined by Lekhnitskii. Numerical results are presented for cylindrical and spherical anisotropic contacts, using finite element analysis (FEA). Effects of crystal orientation on stress response and fatigue life are examined. Obtaining accurate subsurface stress results for anisotropic single crystal contact problems require extremely refined three-dimensional (3-D) finite element grids, especially in the edge of contact region. Obtaining resolved shear stresses (RSS) on the principal slip planes also involves
The field-space metric in spiral inflation and related models
NASA Astrophysics Data System (ADS)
Erlich, Joshua; Olsen, Jackson; Wang, Zhen
2016-09-01
Multi-field inflation models include a variety of scenarios for how inflation proceeds and ends. Models with the same potential but different kinetic terms are common in the literature. We compare spiral inflation and Dante's inferno-type models, which differ only in their field-space metric. We justify a single-field effective description in these models and relate the single-field description to a mass-matrix formalism. We note the effects of the nontrivial field-space metric on inflationary observables, and consequently on the viability of these models. We also note a duality between spiral inflation and Dante's inferno models with different potentials.
The reconstruction of tachyon inflationary potentials
NASA Astrophysics Data System (ADS)
Fei, Qin; Gong, Yungui; Lin, Jiong; Yi, Zhu
2017-08-01
We derive a lower bound on the field excursion for the tachyon inflation, which is determined by the amplitude of the scalar perturbation and the number of e-folds before the end of inflation. Using the relation between the observables like ns and r with the slow-roll parameters, we reconstruct three classes of tachyon potentials. The model parameters are determined from the observations before the potentials are reconstructed, and the observations prefer the concave potential. We also discuss the constraints from the reheating phase preceding the radiation domination for the three classes of models by assuming the equation of state parameter wre during reheating is a constant. Depending on the model parameters and the value of wre, the constraints on Nre and Tre are different. As ns increases, the allowed reheating epoch becomes longer for wre=-1/3, 0 and 1/6 while the allowed reheating epoch becomes shorter for wre=2/3.
Conformal consistency relations for single-field inflation
Creminelli, Paolo; Noreña, Jorge; Simonović, Marko E-mail: jorge.norena@gmail.com
2012-07-01
We generalize the single-field consistency relations to capture not only the leading term in the squeezed limit — going as 1/q{sup 3}, where q is the small wavevector — but also the subleading one, going as 1/q{sup 2}. This term, for an (n+1)-point function, is fixed in terms of the variation of the n-point function under a special conformal transformation; this parallels the fact that the 1/q{sup 3} term is related with the scale dependence of the n-point function. For the squeezed limit of the 3-point function, this conformal consistency relation implies that there are no terms going as 1/q{sup 2}. We verify that the squeezed limit of the 4-point function is related to the conformal variation of the 3-point function both in the case of canonical slow-roll inflation and in models with reduced speed of sound. In the second case the conformal consistency conditions capture, at the level of observables, the relation among operators induced by the non-linear realization of Lorentz invariance in the Lagrangian. These results mean that, in any single-field model, primordial correlation functions of ζ are endowed with an SO(4,1) symmetry, with dilations and special conformal transformations non-linearly realized by ζ. We also verify the conformal consistency relations for any n-point function in models with a modulation of the inflaton potential, where the scale dependence is not negligible. Finally, we generalize (some of) the consistency relations involving tensors and soft internal momenta.
Directed Assembly of Single Wall Carbon Nanotube Field Effect Transistors.
Penzo, Erika; Palma, Matteo; Chenet, Daniel A; Ao, Geyou; Zheng, Ming; Hone, James C; Wind, Shalom J
2016-02-23
The outstanding electronic properties of single wall carbon nanotubes (SWCNTs) have made them prime candidates for future nanoelectronics technologies. One of the main obstacles to the implementation of advanced SWCNT electronics to date is the inability to arrange them in a manner suitable for complex circuits. Directed assembly of SWCNT segments onto lithographically patterned and chemically functionalized substrates is a promising way to organize SWCNTs in topologies that are amenable to integration for advanced applications, but the placement and orientational control required have not yet been demonstrated. We have developed a technique for assembling length sorted and chirality monodisperse DNA-wrapped SWCNT segments on hydrophilic lines patterned on a passivated oxidized silicon substrate. Placement of individual SWCNT segments at predetermined locations was achieved with nanometer accuracy. Three terminal electronic devices, consisting of a single SWCNT segment placed either beneath or on top of metallic source/drain electrodes were fabricated. Devices made with semiconducting nanotubes behaved as typical p-type field effect transistors (FETs), whereas devices made with metallic nanotubes had a finite resistance with little or no gate modulation. This scalable, high resolution approach represents an important step forward toward the potential implementation of complex SWCNT devices and circuits.
CMOS Integration of Single-Molecule Field-Effect Transistors
NASA Astrophysics Data System (ADS)
Warren, Steven Benjamin
Point functionalized carbon nanotubes have recently demonstrated the ability to serve as single-molecule biosensors. Operating as single-molecule Field-Effect Transistors (smFET), the sensors have been used to explore activity ranging in scope from DNA hybridization kinetics to DNA polymerase functionality. High signal levels and an all-electronic label-free transduction mechanism make the smFET an attractive candidate for next-generation medical diagnostics platforms and high-bandwidth basic science research studies. In this work, carbon nanotubes are integrated onto a custom designed CMOS chip. Integration enables arraying many devices for measurement, providing the requisite scale-up for any commercial application of smFETs. Integration also provides substantial benefits towards achieving high bandwidths through the reduction of electrical parasitics. In a first exploitation of these high-bandwidth measurement capabilities, integrated devices are electrically characterized over a 1-MHz bandwidth. Functionalization through electrochemical oxidation of the devices is observed with microsecond temporal resolution, revealing complex reaction pathways with resolvable scattering signatures. High rate random telegraph noise (RTN) is observed in certain oxidized devices, further illustrating the temporal resolution of the integrated sensing platform.
Low reheating temperatures in monomial and binomial inflationary models
Rehagen, Thomas; Gelmini, Graciela B.
2015-06-23
We investigate the allowed range of reheating temperature values in light of the Planck 2015 results and the recent joint analysis of Cosmic Microwave Background (CMB) data from the BICEP2/Keck Array and Planck experiments, using monomial and binomial inflationary potentials. While the well studied ϕ{sup 2} inflationary potential is no longer favored by current CMB data, as well as ϕ{sup p} with p>2, a ϕ{sup 1} potential and canonical reheating (w{sub re}=0) provide a good fit to the CMB measurements. In this last case, we find that the Planck 2015 68% confidence limit upper bound on the spectral index, n{sub s}, implies an upper bound on the reheating temperature of T{sub re}≲6×10{sup 10} GeV, and excludes instantaneous reheating. The low reheating temperatures allowed by this model open the possibility that dark matter could be produced during the reheating period instead of when the Universe is radiation dominated, which could lead to very different predictions for the relic density and momentum distribution of WIMPs, sterile neutrinos, and axions. We also study binomial inflationary potentials and show the effects of a small departure from a ϕ{sup 1} potential. We find that as a subdominant ϕ{sup 2} term in the potential increases, first instantaneous reheating becomes allowed, and then the lowest possible reheating temperature of T{sub re}=4 MeV is excluded by the Planck 2015 68% confidence limit.
Inflationary cosmology with Chaplygin gas in Palatini formalism
Borowiec, Andrzej; Wojnar, Aneta; Stachowski, Aleksander; Szydłowski, Marek E-mail: aleksander.stachowski@uj.edu.pl E-mail: aneta.wojnar@ift.uni.wroc.pl
2016-01-01
We present a simple generalisation of the ΛCDM model which on the one hand reaches very good agreement with the present day experimental data and provides an internal inflationary mechanism on the other hand. It is based on Palatini modified gravity with quadratic Starobinsky term and generalized Chaplygin gas as a matter source providing, besides a current accelerated expansion, the epoch of endogenous inflation driven by type III freeze singularity. It follows from our statistical analysis that astronomical data favors negative value of the parameter coupling quadratic term into Einstein-Hilbert Lagrangian and as a consequence the bounce instead of initial Big-Bang singularity is preferred.
Inflationary α-attractors and F(R)-gravity
NASA Astrophysics Data System (ADS)
Kuiroukidis, A.
2017-09-01
We consider a generic class of the so-called inflationary α-attractor models and compute the cosmological observables in the Einstein and Jordan frames of the corresponding F(R)-gravity theory. We find that the two sets coincide (to within errors from the use of the slow-roll approximation) for moderate and large values of the number of e-foldings N, which is the novel result of this paper, generalizing previous results on the subject (see e.g. Ref. 24). We briefly comment on the possible generalizations of these results.
Gao, Xian; Langlois, David; Mizuno, Shuntaro E-mail: langlois@apc.univ-paris7.fr
2013-10-01
In the context of two-field inflation characterized by a light direction and a heavy direction, we revisit the question of the impact of the massive modes on the power spectrum produced after a turn in the inflationary trajectory. We consider in particular the resonant effect due to the background oscillations following a sharp turn. Working in the mass basis, i.e. in the basis spanned by the eigenvectors of the effective mass matrix for the perturbations, we provide an analytical estimate of the resonant effect, using the in-in formalism. In comparison with earlier estimates, we find the same the spectral dependence but a smaller amplitude. We also compute, again via the in-in formalism, the effect of the direct coupling between the light and heavy modes at the instant of the turn and confirm our previous results obtained via a different method.
Multi-field conformal cosmological attractors
Kallosh, Renata; Linde, Andrei E-mail: alinde@stanford.edu
2013-12-01
We describe a broad class of multi-field inflationary models with spontaneously broken conformal invariance. It generalizes the recently discovered class of cosmological attractors with a single inflaton field [1]. In the new multi-field theories, just as in the single-field models of [1], the moduli space has a boundary (Kähler cone) in terms of the original homogeneous conformal variables. Upon spontaneous breaking of the conformal invariance and switching to the Einstein frame, this boundary moves to infinity in terms of the canonically normalized inflaton field. This results in the exponential stretching and flattening of scalar potentials in the vicinity of the boundary of the moduli space, which makes even very steep potentials perfectly suitable for the slow-roll inflation. These theories, just like their single-field versions, typically lead to inflationary perturbations with n{sub s} = 1−2/N and r = 12/N{sup 2}, where N is the number of e-foldings.
Structured dark-field imaging for single nano-particles
NASA Astrophysics Data System (ADS)
Chen, Jian; Gao, Kun; Wang, Zhi-Li; Yun, Wen-Bing; Wu, Zi-Yu
2015-08-01
In this work, we extensively describe and demonstrate the structured dark-field imaging (SDFI). SDFI is a newly proposed x-ray microscopy designed for revealing the fine features below Rayleigh resolution, in which different orders of scattered x-ray photons are collected by changing the numerical aperture of the condenser. Here, the samples of single particles are discussed to extend the scope of the SDFI technique reported in a previous work (Chen J, Gao K, Ge X, et al. 2013 Opt. Lett. 38 2068). In addition, the details of the newly invented algorithm are explained, which is able to calculate the intensity of any pixel on the image plane rapidly and reliably. Project supported by the National Basic Research Program of China (Grant No. 2012CB825800), the Science Fund for Creative Research Groups, the National Natural Science Foundation of China (Grant No. 11321503), the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KJCX2-YW-N42), and the National Natural Science Foundation of China (Grant Nos. 11475170, 11205157, and 11305173).
Single-field consistency relations of large scale structure
Creminelli, Paolo; Noreña, Jorge; Simonović, Marko; Vernizzi, Filippo E-mail: jorge.norena@icc.ub.edu E-mail: filippo.vernizzi@cea.fr
2013-12-01
We derive consistency relations for the late universe (CDM and ΛCDM): relations between an n-point function of the density contrast δ and an (n+1)-point function in the limit in which one of the (n+1) momenta becomes much smaller than the others. These are based on the observation that a long mode, in single-field models of inflation, reduces to a diffeomorphism since its freezing during inflation all the way until the late universe, even when the long mode is inside the horizon (but out of the sound horizon). These results are derived in Newtonian gauge, at first and second order in the small momentum q of the long mode and they are valid non-perturbatively in the short-scale δ. In the non-relativistic limit our results match with [1]. These relations are a consequence of diffeomorphism invariance; they are not satisfied in the presence of extra degrees of freedom during inflation or violation of the Equivalence Principle (extra forces) in the late universe.
Rojas, Clara; Villalba, Victor M.
2007-03-15
The phase-integral approximation devised by Froeman and Froeman, is used for computing cosmological perturbations in the power-law inflationary model. The phase-integral formulas for the scalar and tensor power spectra are explicitly obtained up to ninth-order of the phase-integral approximation. We show that, the phase-integral approximation exactly reproduces the shape of the power spectra for scalar and tensor perturbations as well as the spectral indices. We compare the accuracy of the phase-integral approximation with the results for the power spectrum obtained with the slow-roll and uniform-approximation methods.
Emergence of inflationary perturbations in the CSL model
NASA Astrophysics Data System (ADS)
León, Gabriel; Bengochea, Gabriel R.
2016-01-01
The inflationary paradigm is the most successful model that explains the observed spectrum of primordial perturbations. However, the precise emergence of such inhomogeneities and the quantum-to-classical transition of the perturbations has not yet reached a consensus among the community. The continuous spontaneous localization model (CSL), in the cosmological context, might be used to provide a solution to the mentioned issues by considering a dynamical reduction of the wave function. The CSL model has been applied to the inflationary universe before and different conclusions have been obtained. In this letter, we use a different approach to implement the CSL model during inflation. In particular, in addition to accounting for the quantum-to-classical transition, we use the CSL model to generate the primordial perturbations, that is, the dynamical evolution provided by the CSL model is responsible for the transition from a homogeneous and isotropic initial state to a final one lacking such symmetries. Our approach leads to results that can be clearly distinguished from preceding works. Specifically, the scalar and tensor power spectra are not time-dependent, and one retains the amplification mechanism of the CSL model. Moreover, our framework depends only on one parameter (the CSL parameter) and its value is consistent with cosmological and laboratory observations.
Inflationary cosmology in unimodular F(T) gravity
NASA Astrophysics Data System (ADS)
Bamba, Kazuharu; Odintsov, Sergei D.; Saridakis, Emmanuel N.
2017-07-01
We investigate the inflationary realization in the context of unimodular F(T) gravity, which is based on the F(T) modification of teleparallel gravity, in which one imposes the unimodular condition through the use of Lagrange multipliers. We develop the general reconstruction procedure of the F(T) form that can give rise to a given scale-factor evolution, and then we apply it in the inflationary regime. We extract the Hubble slow-roll parameters that allow us to calculate various inflation-related observables, such as the scalar spectral index and its running, the tensor-to-scalar ratio, and the tensor spectral index. Then, we examine the particular cases of de Sitter and power-law inflation, of Starobinsky inflation, as well as inflation in a specific model of unimodular F(T) gravity. As we show, in all cases the predictions of our scenarios are in a very good agreement with Planck observational data. Finally, inflation in unimodular F(T) gravity has the additional advantage that it always allows for a graceful exit for specific regions of the model parameters.
Tensor perturbations in inflationary models as a probe of cosmology
Turner, M.S.; White, M.; Lidsey, J.E. NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 Center for Particle Astrophysics, University of California, Berkeley, California 94720 )
1993-11-15
In principle, the tensor metric (gravity-wave) perturbations that arise in inflationary models can, beyond probing the underlying inflationary model, provide information about the Universe: ionization history, presence of a cosmological constant, and epoch of matter-radiation equality. Because tensor perturbations give rise to the anisotropy of the cosmic background radiation (CBR) solely through the Sachs-Wolfe effect we are able to calculate analytically their contribution to the variance of the multipole moments of the CBR temperature anisotropy. In so doing, we carefully take account of the effect of tensor perturbations that entered the Hubble radius during both the matter-dominated and radiation-dominated epochs by means of a transfer function. (Previously, only those modes that entered during the matter era were properly taken into account.) The striking feature in the spectrum of multipole amplitudes is a dramatic falloff for [ital l][approx gt] [radical]1+[ital z][sub LSS] , where [ital z][sub LSS] is the redshift of the last-scattering surface, which depends upon the ionization history of the Universe. Finally, using our transfer function we provide a more precise formula for the energy density in stochastic gravitational waves from inflation, and, using the Cosmic Background Explorer Differential Microwave Radiometer (COBE DMR) quadrupole normalization, we express this energy density in terms of the tilt'' of the spectrum of tensor perturbations alone and show that it is unlikely that the stochastic background of gravity waves can be detected directly in the foreseeable future.
Second-order reconstruction of the inflationary potential
NASA Technical Reports Server (NTRS)
Liddle, Andrew R.; Turner, Michael S.
1994-01-01
To first order in the deviation from scale invariance the inflationary potential and its first two derivatives can be expressed in terms of the spectral indices of the scalar and tensor perturbations, n and n(sub T), and their contributions to the variance of the quadrupole CBR temperature anisotropy, S and T. In addition, there is a 'consistency relation' between these quantities: n(sub T) = (-1/ 7)(T/S). We derive the second-order expressions for the inflationary potential and its first two derivatives and the first-order expression for its third derivative, in terms, of n, n(sub T), S, T, and dn/d ln gamma. We also obtain the second-order consistency relation, n(sub T) = (-1/7)(T/S)(1 + 0.11(T/S) + 0.15(n-1)). As an example we consider the exponential potential, the only known case where exact analytic solutions for the perturbation spectra exist. We reconstruct the potential via Taylor expansion (with coefficients calculated at both first and second order), and introduce the Pade approximate as a greatly improved alternative.
NASA Astrophysics Data System (ADS)
Das, Suratna; Lochan, Kinjalk; Sahu, Satyabrata; Singh, T. P.
2013-10-01
The inflationary paradigm provides a mechanism to generate the primordial perturbations needed to explain the observed large-scale structures in the Universe. Inflation traces back all the inhomogeneities to quantum fluctuations although the structures look classical today. The squeezing of primordial quantum fluctuations along with the mechanism of decoherence accounts for many aspects of this quantum-to-classical transition, although it remains a matter of debate as to whether this is sufficient to explain the issue of the realization of a single outcome (i.e. the issue of macro-objectification) from a quantum ensemble given that the Universe is a closed system. A similar question of the emergence of classical behavior of macroscopic objects exists also for laboratory systems and apart from decoherence there have been attempts to resolve this issue through continuous spontaneous localization (CSL), which is a stochastic nonlinear modification of the nonrelativistic Schrödinger equation. Recently, Martin et al. have investigated whether a CSL-like mechanism with a constant strength parameter—when the Mukhanov-Sasaki variable is taken as the “collapse operator”—can explain how the primordial quantum perturbations generated during inflation become classical. Within the scope of their assumptions they essentially come to a negative conclusion. In the present work, we generalize their analysis by allowing the CSL strength parameter to depend on physical scales so as to capture the CSL amplification mechanism. We show that such a generalization provides a mechanism for the macro-objectification (i.e. classicalization) of the inflationary quantum perturbations, while also preserving the scale invariance of the power spectrum and the phase coherence of superhorizon perturbation modes in a particular class of these models.
Single-Plane Magnetically Focused Elongated Small Field Proton Beams.
McAuley, Grant A; Slater, James M; Wroe, Andrew J
2015-08-01
We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams. © The Author(s) 2014.
HARMONI: a single-field wide-band integral-field spectrograph for the European ELT
NASA Astrophysics Data System (ADS)
Thatte, Niranjan; Tecza, Mathias; Clarke, Fraser; Davies, Roger L.; Remillieux, Alban; Bacon, Roland; Lunney, David; Arribas, Santiago; Mediavilla, Evencio; Gago, Fernando; Bezawada, Naidu; Ferruit, Pierre; Fragoso, Ana; Freeman, David; Fuentes, Javier; Fusco, Thierry; Gallie, Angus; Garcia, Adolfo; Goodsall, Timothy; Gracia, Felix; Jarno, Aurelien; Kosmalski, Johan; Lynn, James; McLay, Stuart; Montgomery, David; Pecontal, Arlette; Schnetler, Hermine; Smith, Harry; Sosa, Dario; Battaglia, Giuseppina; Bowles, Neil; Colina, Luis; Emsellem, Eric; Garcia-Perez, Ana; Gladysz, Szymon; Hook, Isobel; Irwin, Patrick; Jarvis, Matt; Kennicutt, Robert; Levan, Andrew; Longmore, Andy; Magorrian, John; McCaughrean, Mark; Origlia, Livia; Rebolo, Rafael; Rigopoulou, Dimitra; Ryan, Sean; Swinbank, Mark; Tanvir, Nial; Tolstoy, Eline; Verma, Aprajita
2010-07-01
We describe the results of a Phase A study for a single field, wide band, near-infrared integral field spectrograph for the European Extremely Large Telescope (E-ELT). HARMONI, the High Angular Resolution Monolithic Optical & Nearinfrared Integral field spectrograph, provides the E-ELT's core spectroscopic requirement. It is a work-horse instrument, with four different spatial scales, ranging from seeing to diffraction-limited, and spectral resolving powers of 4000, 10000 & 20000 covering the 0.47 to 2.45 μm wavelength range. It is optimally suited to carry out a wide range of observing programs, focusing on detailed, spatially resolved studies of extended objects to unravel their morphology, kinematics and chemical composition, whilst also enabling ultra-sensitive observations of point sources. We present a synopsis of the key science cases motivating the instrument, the top level specifications, a description of the opto-mechanical concept, operation and calibration plan, and image quality and throughput budgets. Issues of expected performance, complementarity and synergies, as well as simulated observations are presented elsewhere in these proceedings[1].
TOPICAL REVIEW: String cosmology versus standard and inflationary cosmology
NASA Astrophysics Data System (ADS)
Gasperini, M.
2000-06-01
This paper presents a review of the basic, model-independent differences between the pre-big-bang scenario, arising naturally in a string cosmology context, and the standard inflationary scenario. We use an unconventional approach in which the introduction of technical details is avoided as much as possible, trying to focus the reader's attention on the main conceptual aspects of both scenarios. The aim of the paper is not to conclude either in favour of one or other of the scenarios, but to raise questions that are left to the reader's meditation. Warning: the paper does not contain equations, and is not intended as a complete review of all aspects of string cosmology.
Loop quantum cosmology: from pre-inflationary dynamics to observations
NASA Astrophysics Data System (ADS)
Ashtekar, Abhay; Barrau, Aurélien
2015-12-01
The Planck collaboration has provided us rich information about the early Universe, and a host of new observational missions will soon shed further light on the ‘anomalies’ that appear to exist on the largest angular scales. From a quantum gravity perspective, it is natural to inquire if one can trace back the origin of such puzzling features to Planck scale physics. Loop quantum cosmology provides a promising avenue to explore this issue because of its natural resolution of the big bang singularity. Thanks to advances over the last decade, the theory has matured sufficiently to allow concrete calculations of the phenomenological consequences of its pre-inflationary dynamics. In this article we summarize the current status of the ensuing two-way dialog between quantum gravity and observations.
Testing and extending the inflationary consistency relation for tensor modes
NASA Astrophysics Data System (ADS)
Boyle, Latham; Smith, Kendrick M.; Dvorkin, Cora; Turok, Neil
2015-08-01
If observations confirm BICEP2's claim of a tensor-scalar ratio r ≈0.2 on CMB scales, then the inflationary consistency relation nt=-r /8 predicts a small negative value for the tensor spectral index nt. We show that future CMB polarization experiments should be able to confirm this prediction at several sigma. We also show how to properly extend the consistency relation to solar system scales, where the primordial gravitational wave density Ωgw could be measured by proposed experiments such as the Big Bang Observer. This would provide a far more stringent test of the consistency relation and access much more detailed information about the early Universe.
The Strength of PIN-PMN-PT Single Crystals under Bending with a Longitudinal Electric Field
2011-04-06
The strength of PIN– PMN – PT single crystals under bending with a longitudinal electric field This article has been downloaded from IOPscience. Please...COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE The Strength Of PIN- PMN - PT Single Crystals Under Bending With A Longitudinal Electric Field... PMN ? PT ) single crystals was measured using a four point bending apparatus with a longitudinal electric field applied to the bar during bending. The
Ballesteros, G; Casas, J A; Espinosa, J R; Ruiz de Austri, R
2008-03-15
We use cosmic microwave background (CMB) and large scale structure (LSS) data to test a broad and physically well-motivated class of inflationary models: those with flat tree-level potentials (typical in supersymmetry). The non-trivial features of the potential arise from radiative corrections which give a simple logarithmic dependence on the inflaton field, making the models very predictive. We also consider a modified scenario with new physics beyond a certain high energy cut-off showing up as non-renormalizable operators (NRO) in the inflaton field. We find that both kinds of models fit CMB and LSS data remarkably well, with very few free parameters. Besides, many of these models naturally predict a reasonable number of e-folds. A robust feature of these scenarios is the smallness of tensor perturbations (r{approx}<10{sup -3}). The NRO case can give a sizable running of the spectral index while achieving a sufficient number of e-folds. We use Bayesian model comparison tools to assess the relative performance of the models. We believe that these scenarios can be considered as a standard physical class of inflationary models, on a similar footing to monomial potentials.
Hernandez, V; Sempau, J
2011-03-01
To study the influence of the field setup on the dosimetry at the junction in single-isocenter half-beam techniques. The dosimetry at the junction for a two-field setup with the gantry at zero was first evaluated with radiochromic films. A three-field setup, with an anterior field and two opposed lateral fields, was also analyzed for two different relative positions of the fields involved. In all cases, the dose increase at the central axis, called the junction dose, was measured. Junction doses varied greatly with the setup. For the three-field setup, the junction dose differed from that obtained with the two-field setup, and it greatly depended on the relative position of the fields. When the anterior field was closer to the gantry than the lateral fields, a field gap occurred and the junction dose was negative. When the anterior field was farther from the gantry than the lateral fields, a field overlap was obtained and the junction dose was positive. The difference in the junction dose between the three-field setups was around 18% for the three accelerators evaluated. Having a uniform dose distribution for two fields at gantry 0 degrees does not guarantee a uniform distribution at other gantry angles. Junction doses are largely affected by the relative position of the radiation fields, which may have an impact in clinical practice. Therefore, any method aiming to assess or to optimize the dose homogeneity at the junction should take this effect into account.
Testud, Frederik; Gallichan, Daniel; Layton, Kelvin J; Barmet, Christoph; Welz, Anna M; Dewdney, Andrew; Cocosco, Chris A; Pruessmann, Klaas P; Hennig, Jürgen; Zaitsev, Maxim
2015-03-01
PatLoc (Parallel Imaging Technique using Localized Gradients) accelerates imaging and introduces a resolution variation across the field-of-view. Higher-dimensional encoding employs more spatial encoding magnetic fields (SEMs) than the corresponding image dimensionality requires, e.g. by applying two quadratic and two linear spatial encoding magnetic fields to reconstruct a 2D image. Images acquired with higher-dimensional single-shot trajectories can exhibit strong artifacts and geometric distortions. In this work, the source of these artifacts is analyzed and a reliable correction strategy is derived. A dynamic field camera was built for encoding field calibration. Concomitant fields of linear and nonlinear spatial encoding magnetic fields were analyzed. A combined basis consisting of spherical harmonics and concomitant terms was proposed and used for encoding field calibration and image reconstruction. A good agreement between the analytical solution for the concomitant fields and the magnetic field simulations of the custom-built PatLoc SEM coil was observed. Substantial image quality improvements were obtained using a dynamic field camera for encoding field calibration combined with the proposed combined basis. The importance of trajectory calibration for single-shot higher-dimensional encoding is demonstrated using the combined basis including spherical harmonics and concomitant terms, which treats the concomitant fields as an integral part of the encoding. © 2014 Wiley Periodicals, Inc.
Mass spectroscopy of single aerosols from field measurements
Thomson, D.S.; Murphy, D.M.
1995-12-31
We are developing an aircraft instrument for the chemical analysis of individual ambient aerosols in real time. In order to test the laboratory version of this instrument, we participated in a field campaign near the continental divide in Colorado in September, 1993. During this campaign, over 5000 mass spectra of ambient aerosols were collected. Analysis of the negative ion spectra shows that sulfate was the most commonly seen component of smaller particles, while nitrate was more common in larger particles. Organic compounds are present in most particles, and we believe we can distinguish inorganic carbon in some particles. Although numerous distinct classes of particles were observed, indicating external mixtures, almost all of these particle types were themselves mixtures of several compounds. Finally, we note that although the field site experienced distinct polluted and unpolluted episodes, aerosol composition did not correlate with gas phase chemistry.
Analysis of electric field stimulation of single cardiac muscle cells.
Tung, L; Borderies, J R
1992-01-01
Electrical stimulation of cardiac cells by imposed extracellular electric fields results in a transmembrane potential which is highly nonuniform, with one end of the cell depolarized and the other end hyperpolarized along the field direction. To date, the implications of the close proximity of oppositely polarized membranes on excitability have not been explored. In this work we compare the biophysical basis for field stimulation of cells at rest with that for intracellular current injection, using three Luo-Rudy type membrane patches coupled together as a lumped model to represent the cell membrane. Our model shows that cell excitation is a function of the temporal and spatial distribution of ionic currents and transmembrane potential. The extracellular and intracellular forms of stimulation were compared in greater detail for monophasic and symmetric biphasic rectangular pulses, with duration ranging from 0.5 to 10 ms. Strength-duration curves derived for field stimulation show that over a wide range of pulse durations, biphasic waveforms can recruit and activate membrane patches about as effectively as can monophasic waveforms having the same total pulse duration. We find that excitation with biphasic stimulation results from a synergistic, temporal summation of inward currents through the sodium channel in membrane patches at opposite ends of the cell. Furthermore, with both waveform types, a net inward current through the inwardly rectifying potassium channel contributes to initial membrane depolarization. In contrast, models of stimulation by intracellular current injection do not account for the nonuniformity of transmembrane potential and produce substantially different (even contradictory) results for the case of stimulation from rest. PMID:1420884
Infrared light field imaging using single carbon nanotube detector
NASA Astrophysics Data System (ADS)
Xi, Ning; Chen, Liangliang; Zhou, Zhanxin; Yang, Ruiguo; Song, Bo; Sun, Zhiyong
2014-06-01
The conventional photographs only record the sum total of light rays of each point on image plane so that they tell little about the amount of light traveling along individual rays. The focus and lens aberration problems have challenged photographers since the very beginning therefore light field photography was proposed to solve these problems. Lens array and multiple camera systems are used to capture 4D light rays, by reordering the different views of scene from multiple directions. The coded aperture is another method to encode the angular information in frequency domain. However, infrared light field sensing is still widely opening to research. In the paper, we will propose micro plane mirror optics together with compressive sensing algorithm to record light field in infrared spectrum. The micro mirror reflects objects irradiation and forms a virtual image behind the plane in which the mirror lies. The Digital Micromirror (DMD) consists of millions microscale mirrors which work as CCD array in the camera and it is controlled separately so as to project linear combination of object image onto lens. Coded aperture could be utilized to control angular resolution of infrared light rays. The carbon nanotube based infrared detector, which has ultra high signal to noise ratio and ultra fast responsibility, will sum up all image information on it without image distortion. Based on a number of measurements, compressive sensing algorithm was used to recover images from distinct angles, which could compute different views of scene to reconstruct infrared light field scence. Two innovative applications of full image recovery using nano scale photodetector and DMD based synthetic aperture photography will also be discussed in this paper.
Inflationary dynamics with a smooth slow-roll to constant-roll era transition
NASA Astrophysics Data System (ADS)
Odintsov, S. D.; Oikonomou, V. K.
2017-04-01
In this paper we investigate the implications of having a varying second slow-roll index on the canonical scalar field inflationary dynamics. We shall be interested in cases that the second slow-roll can take small values and correspondingly large values, for limiting cases of the function that quantifies the variation of the second slow-roll index. As we demonstrate, this can naturally introduce a smooth transition between slow-roll and constant-roll eras. We discuss the theoretical implications of the mechanism we introduce and we use various illustrative examples in order to better understand the new features that the varying second slow-roll index introduces. In the examples we will present, the second slow-roll index has exponential dependence on the scalar field, and in one of these cases, the slow-roll era corresponds to a type of α-attractor inflation. Finally, we briefly discuss how the combination of slow-roll and constant-roll may lead to non-Gaussianities in the primordial perturbations.
Inflationary cosmology leading to a soft type singularity
NASA Astrophysics Data System (ADS)
Brevik, I.; Obukhov, V. V.; Timoshkin, A. V.
2016-06-01
A remarkable property of modern cosmology is that it allows for a special case of symmetry, consisting in the possibility of describing the early-time acceleration (inflation) and the late-time acceleration using the same theoretical framework. In this paper, we consider various cosmological models corresponding to a generalized form for the equation of state for the fluid in a flat Friedmann-Robertson-Walker (FRW) universe, emphasizing cases where the so-called type IV singular inflation is encountered in the future. This is a soft (non-crushing) kind of singularity. Parameter values for an inhomogeneous equation of state leading to singular inflation are obtained. We present models for which there are two type IV singularities, the first corresponding to the end of the inflationary era and the second to a late-time event. We also study the correspondence between the theoretical slow-roll parameters leading to type IV singular inflation and the recent results observed by the Planck satellite.
Dynamics of warm Chaplygin gas inflationary models with quartic potential
NASA Astrophysics Data System (ADS)
Jawad, Abdul; Butt, Sadaf; Rani, Shamaila
2016-05-01
Warm inflationary universe models in the context of the generalized Chaplygin gas, the modified Chaplygin gas, and the generalized cosmic Chaplygin gas are being studied. The dissipative coefficient of the form Γ ∝ T, and the weak and the strong dissipative regimes are being considered. We use the quartic potential, λ _{*}φ 4/4, which is ruled out by current data in cold inflation but in our models by analysis it is seen to be in agreement with the WMAP9 and the latest Planck data. In these scenarios, the power spectrum, the spectral index, and the tensor-to-scalar ratio are being examined in the slow-roll approximation. We show the dependence of the tensor-scalar ratio r on the spectral index ns and observe that the range of the tensor-scalar ratio is r<0.05 in the generalized Chaplygin gas, r<0.15 in the modified Chaplygin gas, and r<0.12 in the generalized cosmic Chaplygin gas models. Our results are in agreement with recent observational data like WMAP9 and the latest Planck data.
Uniformity of CMB as a non-inflationary geometrical effect
NASA Astrophysics Data System (ADS)
Vlahovic, Branislav; Ilie, Cosmin; Eingorn, Maxim
2014-03-01
The conventional LambdaCDM cosmological model supplemented by the inflation concept explains the Universe evolution well. However, there are still a few concerns: New Planck data impose a non-trivial constraint on the shape of the inflation potential, which excludes many inflationary models; the dark matter is not detected directly; and the dark energy is not described theoretically on a satisfactory level. Within the FLRW formalism we consider a model of the closed Universe (with the spherical spatial topology), filled with the additional perfect fluid with the constant parameter -1/3 in the linear equation of state (which may be called quintessence). We compare this model with the standard LambdaCDM and answer the following question: can this additional fluid lead to light traveling between the antipodal points during the current age of the Universe? This possibility could strongly affect the inflation scenario which may completely lose its necessity. This work is supported by NSF CREST (HRD-0833184) and NASA (NNX09AV07A).
Bayesian analysis of inflationary features in Planck and SDSS data
NASA Astrophysics Data System (ADS)
Benetti, Micol; Alcaniz, Jailson S.
2016-07-01
We perform a Bayesian analysis to study possible features in the primordial inflationary power spectrum of scalar perturbations. In particular, we analyze the possibility of detecting the imprint of these primordial features in the anisotropy temperature power spectrum of the cosmic microwave background (CMB) and also in the matter power spectrum P (k ) . We use the most recent CMB data provided by the Planck Collaboration and P (k ) measurements from the 11th data release of the Sloan Digital Sky Survey. We focus our analysis on a class of potentials whose features are localized at different intervals of angular scales, corresponding to multipoles in the ranges 10 <ℓ<60 (Oscill-1) and 150 <ℓ<300 (Oscill-2). Our results show that one of the step potentials (Oscill-1) provides a better fit to the CMB data than does the featureless Λ CDM scenario, with moderate Bayesian evidence in favor of the former. Adding the P (k ) data to the analysis weakens the evidence of the Oscill-1 potential relative to the standard model and strengthens the evidence of this latter scenario with respect to the Oscill-2 model.
Perturbative instability of inflationary cosmology from quantum potentials
NASA Astrophysics Data System (ADS)
Tawfik, A.; Diab, A.; Abou El Dahab, E.
2017-09-01
It was argued that the Raychaudhuri equation with a quantum correction term seems to avoid the Big Bang singularity and to characterize an everlasting Universe (Ali and Das in Phys Lett B 741:276, 2015). Critical comments on both conclusions and on the correctness of the key expressions of this work were discussed in literature (Lashin in Mod Phys Lett 31:1650044, 2016). In the present work, we have analyzed the perturbative (in)stability conditions in the inflationary era of the early Universe. We conclude that both unstable and stable modes are incompatible with the corresponding ones obtained in the standard FLRW Universe. We have shown that unstable modes do exist at small (an)isotropic perturbation and for different equations of state. Inequalities for both unstable and stable solutions with the standard FLRW space were derived. They reveal that in the FLRW flat Universe both perturbative instability and stability are likely. While negative stability modes have been obtained for radiation- and matter-dominated eras, merely, instability modes exist in case of a finite cosmological constant and also if the vacuum energy dominates the cosmic background geometry.
Dark radiation and inflationary freedom after Planck 2015
NASA Astrophysics Data System (ADS)
Di Valentino, Eleonora; Gariazzo, Stefano; Gerbino, Martina; Giusarma, Elena; Mena, Olga
2016-04-01
The simplest inflationary models predict a primordial power spectrum (PPS) of the curvature fluctuations that can be described by a power-law function that is nearly scale invariant. It has been shown, however, that the low-multipole spectrum of the cosmic microwave background anisotropies may hint at the presence of some features in the shape of the scalar PPS, which could deviate from its canonical power-law form. We study the possible degeneracies of this nonstandard PPS with the active neutrino masses, the effective number of relativistic species, and a sterile neutrino or a thermal axion mass. The limits on these additional parameters are less constraining in a model with a nonstandard PPS when including only the temperature autocorrelation spectrum measurements in the data analyses. The inclusion of the polarization spectra noticeably helps in reducing the degeneracies, leading to results that typically show no deviation from the Λ CDM model with a standard power-law PPS. These findings are robust against changes in the function describing the noncanonical PPS. Albeit current cosmological measurements seem to prefer the simple power-law PPS description, the statistical significance to rule out other possible parametrizations is still very poor. Future cosmological measurements are crucial to improve the present PPS uncertainties.
Creation and recovery of a W(111) single atom gas field ion source.
Pitters, Jason L; Urban, Radovan; Wolkow, Robert A
2012-04-21
Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.
Single-acquisition wide-field superresolution for telescopes.
Wereley, Steve; Zhang, Yuxing; Khor, Jian-Wei; Snoeyink, Craig
2016-12-10
A simple optical setup is introduced here that is capable of improving the diffraction-limited angular resolution of a telescope at minimal cost to image quality. The system consists of, at minimum, an axicon and a convex lens located in the optical path of the telescope, which can increase the angular resolution by up to 38%. Analytical results for this resolution gain along with the Strehl ratio of this system are presented along with experimental results, which show a 30% improvement in single-acquisition image resolution with a Strehl ratio of 0.07, agreeing well with predicted values. With an ultrashallow axicon, large increases in Strehl ratio are possible, up to and beyond unity making higher angular resolution measurements possible with little cost to image quality or experimental complexity.
NASA Astrophysics Data System (ADS)
Rodriguez, Alvar; Singh, Simranjeet; Haque, Firoze; Del Barco, Enrique; Nguyen, Tu; Christou, George
2012-02-01
Dependence of magnetic field and electronic transport of Mn4 Single-molecule magnet in a Single-Electron Transistor A. Rodriguez, S. Singh, F. Haque and E. del Barco Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816 USA T. Nguyen and G. Christou Department of Chemistry, University of Florida, Gainesville, Florida 32611 USA Abstract We have performed single-electron transport measurements on a series of Mn-based low-nuclearity single-molecule magnets (SMM) observing Coulomb blockade. SMMs with well isolated and low ground spin states, i.e. S = 9/2 (Mn4) and S = 6 (Mn3) were chosen for these studies, such that the ground spin multiplet does not mix with levels of other excited spin states for the magnetic fields (H = 0-8 T) employed in the experiments. Different functionalization groups were employed to change the mechanical, geometrical and transport characteristics of the molecules when deposited from liquid solution on the transistors. Electromigration-broken three-terminal single-electron transistors were used. Results obtained at temperatures down to 240 mK and in the presence of high magnetic fields will be shown.
Effects of Gases on Field Emission from Single and Multi-Wall Carbon Nanotubes
NASA Astrophysics Data System (ADS)
Wadhawan, A.; Stephens, K.; Stallcup, R., II; Perez, J.; Physics Department Collaboration
2001-03-01
We report the effects of O_2, H_2, and Ar exposure on the field emission properties of single and multi-wall carbon nanotubes. The field emission current vs. voltage curves and field emission current vs. time were measured as a function of gas exposure at 10-8 Torr over a period of approximately 8 hours. The data were collected using an automated system running under Labview. We find that H2 and Ar exposure do not significantly affect the field emission properties of either single or multi-walled carbon nanotubes. However, O2 exposure degrades the field emission properties of multi-wall tubes more than those of single-wall tubes. After O2 exposure, the turn-on voltage for multi-wall tubes increased fromm 300 to 500 volts, while the turn-on voltage for single-wall tubes increased from 200 to 250 volts. An explanation of these results will be discussed.
Case history of the Cormorant field single satellite well
Brommer, J.J.; Fernandinho, C.M.M.S.; Liles, J.R.
1982-01-01
A case history of the development of specifically tailor-made equipment and the experience gained from the installation and production from the first subsea well in the central area of the Cormorant field is presented. Emphasis is placed on development concepts and the equipment uniquely manufactured to meet special needs. A one-year onshore integrated system test of the equipment is described along with the interface problems identified and resolved prior to going offshore. Actual installation and commissioning activities are fully covered including drilling, completion, and production from the well. The study describes the major reasons for the success of the subsea well to date as being extensive onshore testing, detailed planning, and the early involvement of operating personnel.
Field-induced rectification in rutile single crystals.
NASA Astrophysics Data System (ADS)
Jameson, John R.; Fukuzumi, Yoshiaki; Tsunoda, Koji; Wang, Zheng; Griffin, Peter B.; Nishi, Yoshio
2007-03-01
A previously unknown resistive memory effect is reported in rutile titanium dioxide. Two Pt electrodes were placed on the surface of a rutile crystal, and a large voltage was applied between them. Afterwards, the device allowed current to pass in the direction of the voltage, but not in the other direction. The orientation of this rectification could then be switched by applying a large voltage of opposite sign. The effect was observed with electrodes on the (100) or (110) surfaces, but not the (001) surface. A plausible explanation is the field-induced motion of oxygen vacancies, which the large voltage might cause to pile up under the negative electrode, eliminating a Schottky barrier at that interface, but leaving a Schottky at the positive electrode intact. Parallels are drawn to other memory effects in titanium dioxide.
Research on single-chip microcomputer controlled rotating magnetic field mineralization model
NASA Astrophysics Data System (ADS)
Li, Yang; Qi, Yulin; Yang, Junxiao; Li, Na
2017-08-01
As one of the method of selecting ore, the magnetic separation method has the advantages of stable operation, simple process flow, high beneficiation efficiency and no chemical environment pollution. But the existing magnetic separator are more mechanical, the operation is not flexible, and can not change the magnetic field parameters according to the precision of the ore needed. Based on the existing magnetic separator is mechanical, the rotating magnetic field can be used for single chip microcomputer control as the research object, design and trial a rotating magnetic field processing prototype, and through the single-chip PWM pulse output to control the rotation of the magnetic field strength and rotating magnetic field speed. This method of using pure software to generate PWM pulse to control rotary magnetic field beneficiation, with higher flexibility, accuracy and lower cost, can give full play to the performance of single-chip.
Quality improvement: single-field sterile scrub, prep, and dwell for laparoscopic hysterectomy.
O'Hanlan, Katherine A; McCutcheon, Stacey Paris; McCutcheon, John G; Charvonia, Beth E
2013-05-01
The vulva and vaginal interior are considered a contaminated surgical area, and current OR guidelines require surgeons who are gloved and gowned at the abdominal field to avoid contact with the urethral catheter, the uterine manipulator, and the introitus or to change their gloves and even regown if contact occurs. It is our belief that the perception of the vaginal field as contaminated reflects a lack of specific standards for the preoperative cleansing of the deeper vagina and a lack of preoperative prep instructions for the combined fields. We developed a comprehensive single-field prep technique designed to improve surgical efficiency and prevent contamination of the sterile field. Combining a methodical scrub, prep, and dwell, this technique allows the entire abdomino-perineovaginal field to be treated as a single sterile field for laparoscopic procedures. Our surgical site infection rate of 1.8% when using this single-field prep technique and the subsequent surgical treatment of the abdominal, vaginal, and perineal fields as a single sterile field is well within reported norms.
Single-shot spatiotemporal measurements of high-field terahertz pulses
van Tilborg, Jeroen; Schroeder, Carl; Toth, Csaba; Geddes, Cameron; Esarey, Eric; Leemans, Wim
2011-06-17
The electric field profiles of broad-bandwidth coherent terahertz (THz) pulses, emitted by laser-wakefield-accelerated electron bunches, are studied. The near-single-cycle THz pulses are measured with two single-shot techniques in the temporal and spatial domains. Spectra of 0-6 THz and peak fields up to {approx_equal} 0.4 MV cm{sup -1} are observed. The measured field substructure demonstrates the manifestation of spatiotemporal coupling at focus, which affects the interpretation of THz radiation as a bunch diagnostic and in high-field pump-probe experiments.
Electric-field-assisted position and orientation control of organic single crystals.
Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro
2014-12-02
We have investigated the motion of growing pentacene single crystals in solution under various electric fields. The pentacene single crystals in 1,2,4-trichlorobenzene responded to the electric field as if they were positively charged. By optimizing the strength and frequency of an alternating electric field, the pentacene crystals automatically bridged the electrodes on SiO2. The pentacene crystal with a large aspect ratio tended to direct the [1̅10] orientation parallel to the conduction direction, which will be suitable from a viewpoint of anisotropy in mobility. The present result shows a possibility of controlling the position and orientation of organic single crystals by the use of an electric field, which leads to high throughput and low cost industrial manufacturing of the single crystal array from solution.
Bayesian evidence and predictivity of the inflationary paradigm
NASA Astrophysics Data System (ADS)
Gubitosi, Giulia; Lagos, Macarena; Magueijo, João; Allison, Rupert
2016-06-01
In this paper we consider the issue of paradigm evaluation by applying Bayes' theorem along the following nested hierarchy of progressively more complex structures: i) parameter estimation (within a model), ii) model selection and comparison (within a paradigm), iii) paradigm evaluation. In such a hierarchy the Bayesian evidence works both as the posterior's normalization at a given level and as the likelihood function at the next level up. Whilst raising no objections to the standard application of the procedure at the two lowest levels, we argue that it should receive a considerable modification when evaluating paradigms, when testability and fitting data are equally important. By considering toy models we illustrate how models and paradigms that are difficult to falsify are always favoured by the Bayes factor. We argue that the evidence for a paradigm should not only be high for a given dataset, but exceptional with respect to what it would have been, had the data been different. With this motivation we propose a measure which we term predictivity, as well as a prior to be incorporated into the Bayesian framework, penalising unpredictivity as much as not fitting data. We apply this measure to inflation seen as a whole, and to a scenario where a specific inflationary model is hypothetically deemed as the only one viable as a result of information alien to cosmology (e.g. Solar System gravity experiments, or particle physics input). We conclude that cosmic inflation is currently hard to falsify, but that this could change were external/additional information to cosmology to select one of its many models. We also compare this state of affairs to bimetric varying speed of light cosmology.
NASA Astrophysics Data System (ADS)
Jaggi, Chandra K.; Mittal, Mandeep; Khanna, Aditi
2013-09-01
In this article, an Economic Order Quantity (EOQ) model has been developed with unreliable supply, where each received lot may have random fraction of defective items with known distribution. Thus, the inspection of lot becomes essential in almost all the situations. Moreover, its role becomes more significant when the items are deteriorating in nature. It is assumed that defective items are salvaged as a single batch after the screening process. Further, it has been observed that the demand as well as price for certain consumer items increases linearly with time, especially under inflationary conditions. Owing to this fact, this article investigates the impact of defective items on retailer's ordering policy for deteriorating items under inflation when both demand and price vary with the passage of time. The proposed model optimises the order quantity by maximising the retailer's expected profit. Results are demonstrated with the help of a numerical example and the sensitivity analysis is also presented to provide managerial insights into practice.
Chen, Yaofei; Han, Qun; Liu, Tiegen; Lan, Xinwei; Xiao, Hai
2013-10-15
An optical fiber magnetic field sensor based on the single-mode-multimode-single-mode (SMS) structure and magnetic fluid (MF) is proposed and demonstrated. By using a piece of no-core fiber as the multimode waveguide in the SMS structure and MF sealed in a capillary tube as the magnetic sensitive media, which totally immersing the no-core fiber, an all-fiber magnetic sensor was fabricated. Interrogation of the magnetic field strength can be achieved either by measuring the dip wavelength shift of the transmission spectrum or by detecting the transmission loss at a specific wavelength. A demonstration sensor with sensitivities up to 905 pm/mT and 0.748 dB/mT was fabricated and investigated. A theoretical model for the design of the proposed device was developed and numerical simulations were performed.
Renema, J. J.; Rengelink, R. J.; Komen, I.; Wang, Q.; Kes, P.; Aarts, J.; Exter, M. P. van; Dood, M. J. A. de; Gaudio, R.; Hoog, K. P. M. op 't; Zhou, Z.; Fiore, A.; Sahin, D.; Driessen, E. F. C.
2015-03-02
We experimentally investigate the effect of a magnetic field on photon detection in superconducting single-photon detectors (SSPDs). At low fields, the effect of a magnetic field is through the direct modification of the quasiparticle density of states of the superconductor, and magnetic field and bias current are interchangeable, as is expected for homogeneous dirty-limit superconductors. At the field where a first vortex enters the detector, the effect of the magnetic field is reduced, up until the point where the critical current of the detector starts to be determined by flux flow. From this field on, increasing the magnetic field does not alter the detection of photons anymore, whereas it does still change the rate of dark counts. This result points at an intrinsic difference in dark and photon counts, and also shows that no enhancement of the intrinsic detection efficiency of a straight SSPD wire is achievable in a magnetic field.
NASA Astrophysics Data System (ADS)
Renema, J. J.; Rengelink, R. J.; Komen, I.; Wang, Q.; Gaudio, R.; op't Hoog, K. P. M.; Zhou, Z.; Sahin, D.; Fiore, A.; Kes, P.; Aarts, J.; van Exter, M. P.; de Dood, M. J. A.; Driessen, E. F. C.
2015-03-01
We experimentally investigate the effect of a magnetic field on photon detection in superconducting single-photon detectors (SSPDs). At low fields, the effect of a magnetic field is through the direct modification of the quasiparticle density of states of the superconductor, and magnetic field and bias current are interchangeable, as is expected for homogeneous dirty-limit superconductors. At the field where a first vortex enters the detector, the effect of the magnetic field is reduced, up until the point where the critical current of the detector starts to be determined by flux flow. From this field on, increasing the magnetic field does not alter the detection of photons anymore, whereas it does still change the rate of dark counts. This result points at an intrinsic difference in dark and photon counts, and also shows that no enhancement of the intrinsic detection efficiency of a straight SSPD wire is achievable in a magnetic field.
NASA Astrophysics Data System (ADS)
Jamonneau, P.; Lesik, M.; Tetienne, J. P.; Alvizu, I.; Mayer, L.; Dréau, A.; Kosen, S.; Roch, J.-F.; Pezzagna, S.; Meijer, J.; Teraji, T.; Kubo, Y.; Bertet, P.; Maze, J. R.; Jacques, V.
2016-01-01
We analyze the impact of electric field and magnetic field fluctuations in the decoherence of the electronic spin associated with a single nitrogen-vacancy (NV) defect in diamond. To this end, we tune the amplitude of a magnetic field in order to engineer spin eigenstates protected either against magnetic noise or against electric noise. The competition between these noise sources is analyzed quantitatively by changing their relative strength through modifications of the host diamond material. This study provides significant insights into the decoherence of the NV electronic spin, which is valuable for quantum metrology and sensing applications.
Quantum teleportation of the angular spectrum of a single-photon field
Walborn, S. P.; Ether, D. S.; Matos Filho, R. L. de; Zagury, N.
2007-09-15
We propose a quantum teleportation scheme for the angular spectrum of a single-photon field, which allows for the transmission of a large amount of information. Our proposal also provides a method to tune the frequencies of spatially entangled fields, which is useful for interactions with stationary qubits.
Optical Field-Strength Polarization of Two-Mode Single-Photon States
ERIC Educational Resources Information Center
Linares, J.; Nistal, M. C.; Barral, D.; Moreno, V.
2010-01-01
We present a quantum analysis of two-mode single-photon states based on the probability distributions of the optical field strength (or position quadrature) in order to describe their quantum polarization characteristics, where polarization is understood as a significative confinement of the optical field-strength values on determined regions of…
Optical Field-Strength Polarization of Two-Mode Single-Photon States
ERIC Educational Resources Information Center
Linares, J.; Nistal, M. C.; Barral, D.; Moreno, V.
2010-01-01
We present a quantum analysis of two-mode single-photon states based on the probability distributions of the optical field strength (or position quadrature) in order to describe their quantum polarization characteristics, where polarization is understood as a significative confinement of the optical field-strength values on determined regions of…
Single Event Effects (SEE) for Power Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs)
NASA Technical Reports Server (NTRS)
Lauenstein, Jean-Marie
2011-01-01
Single-event gate rupture (SEGR) continues to be a key failure mode in power MOSFETs. (1) SEGR is complex, making rate prediction difficult SEGR mechanism has two main components: (1) Oxide damage-- Reduces field required for rupture (2) Epilayer response -- Creates transient high field across the oxide.
Trapping and injecting single domain walls in magnetic wire by local fields.
Vázquez, Manuel; Basheed, G A; Infante, Germán; Del Real, Rafael P
2012-01-20
A single domain wall (DW) moves at linearly increasing velocity under an increasing homogeneous drive magnetic field. Present experiments show that the DW is braked and finally trapped at a given position when an additional antiparallel local magnetic field is applied. That position and its velocity are further controlled by suitable tuning of the local field. In turn, the parallel local field of small amplitude does not significantly affect the effective wall speed at long distance, although it generates tail-to-tail and head-to-head pairs of walls moving along opposite directions when that field is strong enough.
Testing predictions of the quantum landscape multiverse 1: the Starobinsky inflationary potential
NASA Astrophysics Data System (ADS)
Di Valentino, Eleonora; Mersini-Houghton, Laura
2017-03-01
The 2015 Planck data release has placed tight constraints on the allowed class of inflationary models. The current data favors concave downwards inflationary potentials while offering interesting hints on possible deviations from the standard picture of CMB perturbations. We here test the predictions of the theory of the origin of the universe from the landscape multiverse, against the most recent Planck data, for the case of concave downwards inflationary potentials, such as the Starobinsky model of inflation. By considering the quantum entanglement correction of the multiverse, we can place a lower limit on the local `SUSY breaking' scale b > 1.2 × 107 GeV at 95% c.l. from Planck TT+lowTEB. We find that this limit is consistent with the range for b that allows the landscape multiverse to explain a serie of anomalies present in the current data.
Unusually large shielding fields in single-grain YBa2Cu3O7 - delta
NASA Astrophysics Data System (ADS)
Gao, L.; Xue, Y. Y.; Meng, R. L.; Chu, C. W.; Hannahs, S.; Thang, V.; Rubin, L.
1994-08-01
Magnetic field trapping and shielding by several unirradiated single-grain YBa2Cu3O7-δ disks have been investigated between 4.2 and 71 K up to 20 T. Flux avalanches due to thermal instabilities limited the trapping field to ˜5 T below 45 K and often caused microcracks in the disks. However, a shielding field greater than 19 T was detected at 4.2 K in the same sample assembly even after it was damaged by flux avalanches. This violates the expected symmetry between shielding and trapping fields. The shielding field of ≳19 T exceeds the total quench field of 10 T predicted by the Swartz-Bean model. The observations suggest that thermomechanical properties play an important role in field shielding and trapping and mechanical stress may be effectively used to enhance the field trapped by disks of high temperature superconductors.
Single-field sterile-scrub, preparation, and dwell for laparoscopic hysterectomy.
O'Hanlan, Katherine A; McCutcheon, Stacey Paris; McCutcheon, John G; Charvonia, Beth E
2012-01-01
Type VII laparoscopic hysterectomy is classified as a "clean-contaminated" procedure because the surgery involves contact with both the abdominal and vaginal fields. Because the vulva has traditionally been perceived as a separate but contaminated field, operating room guidelines have evolved to require that surgeons gloved and gowned at the abdominal field either avoid contact with the urethral catheter, the uterine manipulator, and the introitus or change their gloves and even re-gown after any contact with those fields. In the belief that the perception of the vaginal field as contaminated stems from inadequate preoperative preparation instructions, we have developed a rigorous abdomino-perineo-vaginal field preparation technique to improve surgical efficiency and prevent surgical site infections. This thorough scrub, preparation, and dwell technique enables the entire abdomino-perineo-vaginal field to be safely treated as a single sterile field while maintaining a low rate of surgical site infection, and should be further investigated in randomized studies.
Improved field emission stability from single-walled carbon nanotubes chemically attached to silicon
2012-01-01
Here, we demonstrate the simple fabrication of a single-walled carbon nanotube (SWCNT) field emission electrode which shows excellent field emission characteristics and remarkable field emission stability without requiring posttreatment. Chemically functionalized SWCNTs were chemically attached to a silicon substrate. The chemical attachment led to vertical alignment of SWCNTs on the surface. Field emission sweeps and Fowler-Nordheim plots showed that the Si-SWCNT electrodes field emit with a low turn-on electric field of 1.5 V μm−1 and high electric field enhancement factor of 3,965. The Si-SWCNT electrodes were shown to maintain a current density of >740 μA cm−2 for 15 h with negligible change in applied voltage. The results indicate that adhesion strength between the SWCNTs and substrate is a much greater factor in field emission stability than previously reported. PMID:22853557
Shearer, Cameron J; Fahy, Adam; Barr, Matthew; Dastoor, Paul C; Shapter, Joseph G
2012-08-01
Here, we demonstrate the simple fabrication of a single-walled carbon nanotube (SWCNT) field emission electrode which shows excellent field emission characteristics and remarkable field emission stability without requiring posttreatment. Chemically functionalized SWCNTs were chemically attached to a silicon substrate. The chemical attachment led to vertical alignment of SWCNTs on the surface. Field emission sweeps and Fowler-Nordheim plots showed that the Si-SWCNT electrodes field emit with a low turn-on electric field of 1.5 V μm-1 and high electric field enhancement factor of 3,965. The Si-SWCNT electrodes were shown to maintain a current density of >740 μA cm-2 for 15 h with negligible change in applied voltage. The results indicate that adhesion strength between the SWCNTs and substrate is a much greater factor in field emission stability than previously reported.
Non-gaussian inflationary shapes in G{sup 3} theories beyond Horndeski
Fasiello, Matteo; Renaux-Petel, Sébastien E-mail: srenaux@lpthe.jussieu.fr
2014-10-01
We consider the possible signatures of a recently introduced class of healthy theories beyond Horndeski models on higher-order correlators of the inflationary curvature fluctuation. Despite the apparent large number and complexity of the cubic interactions, we show that the leading-order bispectrum generated by the Generalized Horndeski (also called G{sup 3}) interactions can be reduced to a linear combination of two well known k-inflationary shapes. We conjecture that said behavior is not an accident of the cubic order but a consequence dictated by the requirements on the absence of Ostrogradski instability, the general covariance and the linear dispersion relation in these theories.
The inflationary universe scenario - in 10-35sec after the big-bang.
NASA Astrophysics Data System (ADS)
Liu, Liao; Jiang, Yuan-Fang; Zhen-Hua, Qiao
1989-06-01
According to the inflationary universe scenario, the universe in 10-35sec after the big-bang was expanded exponentially in the unstable false vacuum state. At the end of the exponential expansion (inflation) the energy of the false vacuum transforms into the energy of hot dense matter, and the subsequent evolution of the universe is described by the usual hot universe theory. The inflationary universe scenario makes it possible to obtain a simple solution to many longstanding cosmological problems in the hot universe theory and occurs naturally in a wide class of realistic theories of elementary particles.
Testing non-standard inflationary models with the cosmic microwave background
NASA Astrophysics Data System (ADS)
Landau, Susana J.
2015-03-01
The emergence of the seeds of cosmic structure from an isotropic and homogeneuous universe has not been clearly explained by the standard version of inflationary models. We review a proposal that attempts to deal with this problem by introducing "the self induced collapse hypothesis". As a consequence of this modification of standard inflationary scenarios, the predicted primordial power spectrum and the CMB spectrum are modified. We show the results of statistical analyses comparing the predictions of these models with recent CMB observations and the matter power spectrum from galaxy surveys.
Basics of quantum field theory of electromagnetic interaction processes in single-layer graphene
NASA Astrophysics Data System (ADS)
Hieu Nguyen, Van
2016-09-01
The content of this work is the study of electromagnetic interaction in single-layer graphene by means of the perturbation theory. The interaction of electromagnetic field with Dirac fermions in single-layer graphene has a peculiarity: Dirac fermions in graphene interact not only with the electromagnetic wave propagating within the graphene sheet, but also with electromagnetic field propagating from a location outside the graphene sheet and illuminating this sheet. The interaction Hamiltonian of the system comprising electromagnetic field and Dirac fermions fields contains the limits at graphene plane of electromagnetic field vector and scalar potentials which can be shortly called boundary electromagnetic field. The study of S-matrix requires knowing the limits at graphene plane of 2-point Green functions of electromagnetic field which also can be shortly called boundary 2-point Green functions of electromagnetic field. As the first example of the application of perturbation theory, the second order terms in the perturbative expansions of boundary 2-point Green functions of electromagnetic field as well as of 2-point Green functions of Dirac fermion fields are explicitly derived. Further extension of the application of perturbation theory is also discussed.
Electric-field-induced domain intersection in BaTiO3 single crystal
NASA Astrophysics Data System (ADS)
He, Ming; Wang, Mengxia; Zhang, Zhihua
2017-03-01
Large-angle convergent beam electron diffraction was used to determine the directions of polarization vectors in a BaTiO3 single crystal. Domain intersections driven by an electric field were investigated by in situ transmission electron microscopy. The dark triangles observed in the domain intersection region can be accounted for by dislocations and the strain field. Domains nucleate at the domain tip depending on the dislocations and strain field to relieve the accumulated stress. Schematic representations of the intersecting domains and the microscopic structure are given, clarifying the special electric-field-induced domain structure.
Deformation of doubly clamped single-walled carbon nanotubes in an electrostatic field.
Wang, Zhao; Philippe, Laetitia
2009-05-29
In this Letter, we demonstrate a strong dependence of the electrostatic deformation of doubly clamped single-walled carbon nanotubes on both the field strength and the tube length, using molecular simulations. Metallic nanotubes are found to be more sensitive to an electric field than semiconducting ones of the same size. For a given electric field, the induced deformation increases with tube length but decreases with tube radius. Furthermore, it is found that nanotubes can be more efficiently bent in a center-oriented transverse electric field.
Determination of optimal ionic liquid for organic single-crystal field-effect transistors
NASA Astrophysics Data System (ADS)
Ono, S.; Miwa, K.; Seki, S.
2016-02-01
We investigate organic single-crystal field-effect transistors with various ionic liquids as gate dielectric. We find that the mobility of the field-effect transistors for both p-type and n-type organic semiconductors increases with decreasing total capacitance of the ionic liquid. However, it does not depend on the ion species at the interface between the organic semiconductor and the ionic liquid. By choosing an appropriate ionic liquid, a high carrier mobility of 12.4 cm2/V s in rubrene single crystals (p-type) and 0.13 cm2/V s in 7.7.8.8-Tetracyanoquinodimethane single crystals (n-type) are achieved. This study clarifies the influence of ionic liquids on the device performance of organic field-effect transistors and shows a way to maximize carrier mobility at the solid/liquid interface.
Non-Gaussianity in single field models without slow-roll conditions
NASA Astrophysics Data System (ADS)
Noller, Johannes; Magueijo, João
2011-05-01
We investigate non-Gaussianity in general single field models without assuming slow-roll conditions or the exact scale invariance of the scalar power spectrum. The models considered include general single field inflation (e.g. Dirac-Born-Infeld and canonical inflation) as well as bimetric models. We compute the full non-Gaussian amplitude A, its size fNL, its shape, and the running with scale nNG. In doing so we show that observational constraints allow significant violations of slow-roll conditions and we derive explicit bounds on slow-roll parameters for fast-roll single field scenarios. A variety of new observational signatures is found for models respecting these bounds. We also explicitly construct concrete model implementations giving rise to this new phenomenology.
Single-field inflation and the local ansatz: Distinguishability and consistency
NASA Astrophysics Data System (ADS)
de Putter, Roland; Doré, Olivier; Green, Daniel; Meyers, Joel
2017-03-01
The single-field consistency conditions and the local ansatz have played separate but important roles in characterizing the non-Gaussian signatures of single- and multifield inflation respectively. We explore the precise relationship between these two approaches and their predictions. We demonstrate that the predictions of the single-field consistency conditions can never be satisfied by a general local ansatz with deviations necessarily arising at order (ns-1 )2 . This implies that there is, in principle, a minimum difference between single- and (fully local) multifield inflation in observables sensitive to the squeezed limit such as scale-dependent halo bias. We also explore some potential observational implications of the consistency conditions and its relationship to the local ansatz. In particular, we propose a new scheme to test the consistency relations. In analogy with delensing of the cosmic microwave background, one can deproject the coupling of the long wavelength modes with the short wavelength modes and test for residual anomalous coupling.
NEPP Update of Independent Single Event Upset Field Programmable Gate Array Testing
NASA Technical Reports Server (NTRS)
Berg, Melanie; Label, Kenneth; Campola, Michael; Pellish, Jonathan
2017-01-01
This presentation provides a NASA Electronic Parts and Packaging (NEPP) Program update of independent Single Event Upset (SEU) Field Programmable Gate Array (FPGA) testing including FPGA test guidelines, Microsemi RTG4 heavy-ion results, Xilinx Kintex-UltraScale heavy-ion results, Xilinx UltraScale+ single event effect (SEE) test plans, development of a new methodology for characterizing SEU system response, and NEPP involvement with FPGA security and trust.
SINGLE CRYSTAL CADMIUM SULFIDE AND CADMIUM SELENIDE INSULATED-GATE FIELD-EFFECT TRIODES.
Insulated-gate field-effect triodes were fabricated on single crystal cadmium sulfide and cadmium selenide . Both bulk crystals and platelets were...used for single crystal samples. Chromium and aluminum were found to make low impedance contacts to cadmium sulfide and cadmium selenide . The...polycrystalline cadmium sulfide and cadmium selenide IGFET’s. The characteristics of the fabricated devices were unstable with respect to time and temperature
NASA Astrophysics Data System (ADS)
Thirion, C.; Wernsdorfer, W.; Jamet, M.; Dupuis, V.; Mélinon, P.; Pérez, A.; Mailly, D.
2002-04-01
An improved micro-SQUID technique is presented allowing us to measure the temperature dependence of the magnetisation switching fields of single nanoparticles well above the critical superconducting temperature of the SQUID. Our first measurements on 3 nm cobalt nanoparticle embedded in a niobium matrix are compared to the Néel Brown model describing the magnetisation reversal by thermal activation over a single anisotropy barrier.
Temperature dependence of switching fields of single 3 nm cobalt nanoparticles
NASA Astrophysics Data System (ADS)
Thirion, C.; Wernsdorfer, W.; Jamet, M.; Dupuis, V.; Mélinon, P.; Pérez, A.; Mailly, D.
2002-05-01
We study the temperature dependence of the magnetization switching fields of single nanoparticles with an improved micro-superconducting quantum interference device (SQUID) technique, that allows us to perform measurements independently of the critical superconducting temperature of the SQUID. A simplified Néel-Brown model that describes the magnetization reversal by thermal activation over a single anisotropy barrier is compared to measurements on a 3 nm cobalt nanoparticle embedded in a niobium matrix.
NASA Astrophysics Data System (ADS)
Yoshioka, Katsumasa; Katayama, Ikufumi; Minami, Yasuo; Kitajima, Masahiro; Yoshida, Shoji; Shigekawa, Hidemi; Takeda, Jun
2016-12-01
The ultrafast coherent manipulation of electrons using waveform-controlled laser pulses is a key issue in the development of modern electronics. Developing such an approach for a tunnel junction will provide a new platform for governing ultrafast currents on an even smaller scale, which will be indispensable for the advancement of next-generation quantum nanocircuits and plasmonic devices. Here, we demonstrate that carrier-envelope-phase-controlled single-cycle terahertz electric fields can coherently drive electron tunnelling either from a nanotip to a sample or vice versa. Spatially confined electric fields of more than 10 V nm-1 strongly modulate the potential barrier at a nanogap in a scanning tunnelling microscope (STM) on the subpicosecond timescale and can steer a large number of electrons in an extremely nonlinear regime, which is not possible using a conventional STM. Our results are expected to pave the way for the future development of nanoscale science and technologies.
A single-atom sharp iridium tip as an emitter of gas field ion sources
NASA Astrophysics Data System (ADS)
Kuo, Hong-Shi; Hwang, Ing-Shouh; Fu, Tsu-Yi; Hwang, Ying-Siang; Lu, Yi-Hsien; Lin, Chun-Yueh; Hou, Jin-Long; Tsong, Tien T.
2009-08-01
We report a reliable method for preparing a pure Ir single-atom tip by thermal treatment in oxygen. The atomic structure of the tip apex and its ion emission characteristics are investigated with field ion microscopy. We have shown that the Ir single-atom tip can be a good field ion emitter, capable of emitting a variety of gas ion beams, such as He+, H2+, N2+, and O2+, with high brightness and stability. In addition, this tip can easily be maintained and regenerated in vacuum, ensuring it has sufficient lifetime for practical applications.
The four fixed points of scale invariant single field cosmological models
Xue, BingKan
2012-10-01
We introduce a new set of flow parameters to describe the time dependence of the equation of state and the speed of sound in single field cosmological models. A scale invariant power spectrum is produced if these flow parameters satisfy specific dynamical equations. We analyze the flow of these parameters and find four types of fixed points that encompass all known single field models. Moreover, near each fixed point we uncover new models where the scale invariance of the power spectrum relies on having simultaneously time varying speed of sound and equation of state. We describe several distinctive new models and discuss constraints from strong coupling and superluminality.
Measurements of the MHD dynamo in the quasi-single-helicity reversed-field pinch.
Piovesan, P; Craig, D; Marrelli, L; Cappello, S; Martin, P
2004-12-03
The first experimental study of the MHD dynamo in a quasi-single-helicity (QSH) reversed-field pinch toroidal plasma is presented. In QSH plasmas, a dominant wave number appears in the velocity fluctuation spectrum. This velocity component extends throughout the plasma volume and couples with magnetic fluctuations to produce a significant MHD dynamo electric field. The narrowing of the velocity fluctuation spectrum and the single-mode character of the dynamo are features predicted by theory and computation, but only now are observed in experiment.
Fast phase manipulation of the single nuclear spin in solids by rotating fields
NASA Astrophysics Data System (ADS)
Shimo-Oka, T.; Tokura, Y.; Suzuki, Y.; Mizuochi, N.
2017-03-01
We propose fast phase gates of single nuclear spins interacting with single electron spins. The gate operation utilizes geometric phase shifts of the electron spin induced by fast and slow rotating fields; the path difference depending on nuclear-spin states enables nuclear phase shifts. The gate time is inversely proportional to the frequency of the slow rotating field. As an example, we use nitrogen-vacancy centers in diamond, and show, in principle, the phase-gate time orders of magnitude to be shorter than previously reported. We also confirmed the robustness of the gate against decoherence and systematic errors.
Longitudinal wave function control in single quantum dots with an applied magnetic field
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
2015-01-01
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. PMID:25624018
Longitudinal wave function control in single quantum dots with an applied magnetic field
NASA Astrophysics Data System (ADS)
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
2015-01-01
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.
Pulsed field actuation of Ni-Mn-Ga ferromagnetic shape memory alloy single crystal
NASA Astrophysics Data System (ADS)
Marioni, M.; Bono, D.; Banful, A. B.; del Rosario, M.; Rodriguez, E.; Peterson, B. W.; Allen, S. M.; O'Handley, R. C.
2003-10-01
Ferromagnetic Shape Memory Alloy Ni-Mn-Ga has twin boundaries in the martensitic phase that move when a suitable magnetic field is applied. In this fashion strains of up to 6% have been observed for static fields in single crystals [1]. Recently 2.5% strain has been demonstrated [2] in Ni-Mn-Ga single crystals for oscillating fields up to frequencies of 75 Hz (150 Hz actuation). This work studies the actuation of single crystals when pulsed fields are applied. Fields in the 0.4-1.5MA/m-range were generated in an air coil with rise times of the order of 1ms and below. The elongation of the samples is measured with a light beam reflected off the tip of the crystal. Single twin boundaries have been observed to advance 0.16 mm during 600 μsec-ong pulses. Actuation has been shown to be possible at least up to frequencies of 1700 Hz.
Longitudinal wave function control in single quantum dots with an applied magnetic field.
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
2015-01-27
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.
Magnetic-field-induced quantum criticality in a planar ferromagnet with single-ion anisotropy
NASA Astrophysics Data System (ADS)
Mercaldo, M. T.; Rabuffo, I.; De Cesare, L.; Caramico D'Auria, A.
2014-08-01
We analyze the effects induced by single-ion anisotropy on quantum criticality in a d-dimensional spin-3/2 planar ferromagnet. To tackle this problem we employ the two-time Green's function method, using the Tyablikov decoupling for exchange interactions and the Anderson-Callen decoupling for single-ion anisotropy. In our analysis the role of non-thermal control parameter which drives the quantum phase transition is played by a longitudinal external magnetic field. We find that the single-ion anisotropy has substantial effects on the structure of the phase diagram close to the quantum critical point.
Gas field ion source current stability for trimer and single atom terminated W(111) tips
Urban, Radovan; Wolkow, Robert A.; Pitters, Jason L.
2012-06-25
Tungsten W(111) oriented trimer-terminated tips as well as single atom tips, fabricated by a gas and field assisted etching and evaporation process, were investigated with a view to scanning ion microscopy and ion beam writing applications. In particular, ion current stability was studied for helium and neon imaging gases. Large ion current fluctuations from individual atomic sites were observed when a trimer-terminated tip was used for the creation of neon ion beam. However, neon ion current was stable when a single atom tip was employed. No such current oscillations were observed for either a trimer or a single atom tip when imaged with helium.
Design of a surgical robot with dynamic vision field control for Single Port Endoscopic Surgery.
Kobayashi, Yo; Sekiguchi, Yuta; Tomono, Yu; Watanabe, Hiroki; Toyoda, Kazutaka; Konishi, Kozo; Tomikawa, Morimasa; Ieiri, Satoshi; Tanoue, Kazuo; Hashizume, Makoto; Fujie, Masaktsu G
2010-01-01
Recently, a robotic system was developed to assist Single Port Endoscopic Surgery (SPS). However, the existing system required a manual change of vision field, hindering the surgical task and increasing the degrees of freedom (DOFs) of the manipulator. We proposed a surgical robot for SPS with dynamic vision field control, the endoscope view being manipulated by a master controller. The prototype robot consisted of a positioning and sheath manipulator (6 DOF) for vision field control, and dual tool tissue manipulators (gripping: 5DOF, cautery: 3DOF). Feasibility of the robot was demonstrated in vitro. The "cut and vision field control" (using tool manipulators) is suitable for precise cutting tasks in risky areas while a "cut by vision field control" (using a vision field control manipulator) is effective for rapid macro cutting of tissues. A resection task was accomplished using a combination of both methods.
Longitudinally polarized single-cycle terahertz pulses generated with high electric field strengths
NASA Astrophysics Data System (ADS)
Cliffe, M. J.; Graham, D. M.; Jamison, S. P.
2016-05-01
We demonstrate the generation of single-cycle longitudinally polarized terahertz pulses with field amplitudes in excess of 11 kV/cm using the interferometric recombination of two linearly polarized terahertz beams. High field strength transversely polarized pulses were generated by optical rectification in a matched pair of magnesium-oxide doped stoichiometric lithium niobate (MgO:SLN) crystals with a reversal in the χ333 ( 2 ) orientation. The discontinuity in χ333 ( 2 ) produces a polarity flip in the transverse field; the longitudinal field produced as a consequence of the transverse field discontinuity was measured in the far-field. Both the spatial and temporal profiles of the measured longitudinally polarized terahertz radiation were consistent with the propagation of the transverse discontinuity.
Controlling field-emission patterns of isolated single-walled carbon nanotube rope
NASA Astrophysics Data System (ADS)
Tong, Yu; Lim, Seong Chu; Park, Kyung Ah; Jeong, Hee Jin; Jeong, Seung Yoi; Lee, Young Hee; Liu, Chang; Cheng, Hui-Ming; Choi, Yoon
2005-07-01
We report a method of controlling field-emission patterns from an isolated single-walled carbon nanotube (SWCNT) rope. By positioning two soda-lime glass flakes on both sides of a SWCNT rope, we found an anomalous current jump, enlarging the field emission current above the threshold bias voltage. The electron trajectories were systematically controlled with different configurations of glass flakes. This was explained by the induced charges on the surface of the dielectric that modified the electric field distribution near the cathode and anode, and hence, the electron trajectories and the field emission patterns as well. This opens a possibility of tuning electron beam trajectories in field emission that can be applied to various electron sources such as field emission displays and cold cathode lamps.
Smartphone Microscopy of Parasite Eggs Accumulated into a Single Field of View.
Sowerby, Stephen J; Crump, John A; Johnstone, Maree C; Krause, Kurt L; Hill, Philip C
2016-01-01
A Nokia Lumia 1020 cellular phone (Microsoft Corp., Auckland, New Zealand) was configured to image the ova of Ascaris lumbricoides converged into a single field of view but on different focal planes. The phone was programmed to acquire images at different distances and, using public domain computer software, composite images were created that brought all the eggs into sharp focus. This proof of concept informs a framework for field-deployable, point of care monitoring of soil-transmitted helminths.
Smartphone Microscopy of Parasite Eggs Accumulated into a Single Field of View
Sowerby, Stephen J.; Crump, John A.; Johnstone, Maree C.; Krause, Kurt L.; Hill, Philip C.
2016-01-01
A Nokia Lumia 1020 cellular phone (Microsoft Corp., Auckland, New Zealand) was configured to image the ova of Ascaris lumbricoides converged into a single field of view but on different focal planes. The phone was programmed to acquire images at different distances and, using public domain computer software, composite images were created that brought all the eggs into sharp focus. This proof of concept informs a framework for field-deployable, point of care monitoring of soil-transmitted helminths. PMID:26572870
Single-sided lateral-field and phototransistor-based optoelectronic tweezers
NASA Technical Reports Server (NTRS)
Ohta, Aaron (Inventor); Chiou, Pei-Yu (Inventor); Hsu, Hsan-Yin (Inventor); Jamshidi, Arash (Inventor); Wu, Ming-Chiang (Inventor); Neale, Steven L. (Inventor)
2011-01-01
Described herein are single-sided lateral-field optoelectronic tweezers (LOET) devices which use photosensitive electrode arrays to create optically-induced dielectrophoretic forces in an electric field that is parallel to the plane of the device. In addition, phototransistor-based optoelectronic tweezers (PhOET) devices are described that allow for optoelectronic tweezers (OET) operation in high-conductivity physiological buffer and cell culture media.
NASA Astrophysics Data System (ADS)
Gallagher, John A.; Liu, Tieqi; Lynch, Christopher S.
2013-02-01
The effect of a bias stress induced phase transformation on the large field dielectric loss in [001] cut and poled single crystal stack actuators of (1 - x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT, x = 32) was experimentally characterized. Dielectric loss was observed to increase with compressive preload and electric field amplitude. The dielectric loss was determined by measuring the area within electric displacement vs. electric field hysteresis loops and the measured area was expressed in terms of an effective loss tangent. This approach matches the measured area within the hysteresis loop to an equivalent area ellipse in which the electric displacement lags the electric field by an amount, delta, under sinusoidal loading. The results collapse the measured loss as a function of bias stress and electric field amplitude reasonably close to a single curve. The measured dielectric loss behavior was attributed to the compressive stress preload driving a partial phase transformation from rhombohedral to orthorhombic and the electric field driving the reverse phase transformation from the stress induced orthorhombic phase to the zero stress rhombohedral phase. When the compressive bias stress partially or fully drives this phase transformation, the dielectric loss under unipolar electric field loading increases. This work is focused on quasi-static measurements. The large field dielectric loss is anticipated to be a function of frequency and temperature.
Gilding the Outcome by Tarnishing the Past: Inflationary Biases in Retrospective Pretests
ERIC Educational Resources Information Center
Taylor, Paul J.; Russ-Eft, Darlene F.; Taylor, Hazel
2009-01-01
We tested for inflationary bias introduced through retrospective pretests by analyzing traditional pretest, retrospective pretest, and posttest evaluation data collected on a first-line supervisory leadership training program, involving 196 supervisors and their subordinates, across 17 organizational settings. Retrospective pretest ratings by both…
Inflationary generalized Chaplygin gas and dark energy in light of the Planck and BICEP2 experiments
NASA Astrophysics Data System (ADS)
Dinda, Bikash R.; Kumar, Sumit; Sen, Anjan A.
2014-10-01
In this work, we study an inflationary scenario in the presence of generalized Chaplygin gas (GCG). We show that in Einstein gravity, GCG is not a suitable candidate for inflation; but in a five-dimensional brane-world scenario, it can work as a viable inflationary model. We calculate the relevant quantities such as ns, r, and As related to the primordial scalar and tensor fluctuations, and using their recent bounds from Planck and BICEP2, we constrain the model parameters as well as the five-dimensional Planck mass. But as a slow-roll inflationary model with a power-law type scalar primordial power spectrum, GCG as an inflationary model cannot resolve the tension between results from BICEP2 and Planck with a concordance ΛCDM Universe. We show that by going beyond the concordance ΛCDM model and incorporating more general dark energy behavior, we may ease this tension. We also obtain the constraints on the ns and r and the GCG model parameters using Planck+WP +BICEP2 data considering the CPL dark energy behavior.
Electrically controlling single-spin qubits in a continuous microwave field
Laucht, Arne; Muhonen, Juha T.; Mohiyaddin, Fahd A.; Kalra, Rachpon; Dehollain, Juan P.; Freer, Solomon; Hudson, Fay E.; Veldhorst, Menno; Rahman, Rajib; Klimeck, Gerhard; Itoh, Kohei M.; Jamieson, David N.; McCallum, Jeffrey C.; Dzurak, Andrew S.; Morello, Andrea
2015-01-01
Large-scale quantum computers must be built upon quantum bits that are both highly coherent and locally controllable. We demonstrate the quantum control of the electron and the nuclear spin of a single 31P atom in silicon, using a continuous microwave magnetic field together with nanoscale electrostatic gates. The qubits are tuned into resonance with the microwave field by a local change in electric field, which induces a Stark shift of the qubit energies. This method, known as A-gate control, preserves the excellent coherence times and gate fidelities of isolated spins, and can be extended to arbitrarily many qubits without requiring multiple microwave sources. PMID:26601166
A Novel Prediction Method about Single Components of Analog Circuits Based on Complex Field Modeling
Tian, Shulin; Yang, Chenglin
2014-01-01
Few researches pay attention to prediction about analog circuits. The few methods lack the correlation with circuit analysis during extracting and calculating features so that FI (fault indicator) calculation often lack rationality, thus affecting prognostic performance. To solve the above problem, this paper proposes a novel prediction method about single components of analog circuits based on complex field modeling. Aiming at the feature that faults of single components hold the largest number in analog circuits, the method starts with circuit structure, analyzes transfer function of circuits, and implements complex field modeling. Then, by an established parameter scanning model related to complex field, it analyzes the relationship between parameter variation and degeneration of single components in the model in order to obtain a more reasonable FI feature set via calculation. According to the obtained FI feature set, it establishes a novel model about degeneration trend of analog circuits' single components. At last, it uses particle filter (PF) to update parameters for the model and predicts remaining useful performance (RUP) of analog circuits' single components. Since calculation about the FI feature set is more reasonable, accuracy of prediction is improved to some extent. Finally, the foregoing conclusions are verified by experiments. PMID:25147853
Zhou, Jingyu; Tian, Shulin; Yang, Chenglin
2014-01-01
Few researches pay attention to prediction about analog circuits. The few methods lack the correlation with circuit analysis during extracting and calculating features so that FI (fault indicator) calculation often lack rationality, thus affecting prognostic performance. To solve the above problem, this paper proposes a novel prediction method about single components of analog circuits based on complex field modeling. Aiming at the feature that faults of single components hold the largest number in analog circuits, the method starts with circuit structure, analyzes transfer function of circuits, and implements complex field modeling. Then, by an established parameter scanning model related to complex field, it analyzes the relationship between parameter variation and degeneration of single components in the model in order to obtain a more reasonable FI feature set via calculation. According to the obtained FI feature set, it establishes a novel model about degeneration trend of analog circuits' single components. At last, it uses particle filter (PF) to update parameters for the model and predicts remaining useful performance (RUP) of analog circuits' single components. Since calculation about the FI feature set is more reasonable, accuracy of prediction is improved to some extent. Finally, the foregoing conclusions are verified by experiments.
Aircraft measurements made downwind from specific coal fired power plants during the 2013 Southeast Nexus field campaign provide a unique opportunity to evaluate single source photochemical model predictions of both O3 and secondary PM2.5 species. The model did well at predicting...
Is there scale-dependent bias in single-field inflation?
De Putter, Roland; Doré, Olivier; Green, Daniel E-mail: Olivier.P.Dore@jpl.nasa.gov
2015-10-01
Scale-dependent halo bias due to local primordial non-Gaussianity provides a strong test of single-field inflation. While it is universally understood that single-field inflation predicts negligible scale-dependent bias compared to current observational uncertainties, there is still disagreement on the exact level of scale-dependent bias at a level that could strongly impact inferences made from future surveys. In this paper, we clarify this confusion and derive in various ways that there is exactly zero scale-dependent bias in single-field inflation. Much of the current confusion follows from the fact that single-field inflation does predict a mode coupling of matter perturbations at the level of f{sub NL}{sup local}; ≈ −5/3, which naively would lead to scale-dependent bias. However, we show explicitly that this mode coupling cancels out when perturbations are evaluated at a fixed physical scale rather than fixed coordinate scale. Furthermore, we show how the absence of scale-dependent bias can be derived easily in any gauge. This result can then be incorporated into a complete description of the observed galaxy clustering, including the previously studied general relativistic terms, which are important at the same level as scale-dependent bias of order f{sub NL}{sup local} ∼ 1. This description will allow us to draw unbiased conclusions about inflation from future galaxy clustering data.
Iwasaki, Takayuki; Naruki, Wataru; Tahara, Kosuke; Makino, Toshiharu; Kato, Hiromitsu; Ogura, Masahiko; Takeuchi, Daisuke; Yamasaki, Satoshi; Hatano, Mutsuko
2017-02-28
The electric field inside semiconductor devices is a key physical parameter that determines the properties of the devices. However, techniques based on scanning probe microscopy are limited to sensing at the surface only. Here, we demonstrate the direct sensing of the internal electric field in diamond power devices using single nitrogen-vacancy (NV) centers. The NV center embedded inside the device acts as a nanoscale electric field sensor. We fabricated vertical diamond p-i-n diodes containing the single NV centers. By performing optically detected magnetic resonance measurements under reverse-biased conditions with an applied voltage of up to 150 V, we found a large splitting in the magnetic resonance frequencies. This indicated that the NV center senses the transverse electric field in the space-charge region formed in the i-layer. The experimentally obtained electric field values are in good agreement with those calculated by a device simulator. Furthermore, we demonstrate the sensing of the electric field in different directions by utilizing NV centers with different N-V axes. This direct and quantitative sensing method using an electron spin in a wide-band-gap material provides a way to monitor the electric field in operating semiconductor devices.
Quantum Otto engine of a two-level atom with single-mode fields.
Wang, Jianhui; Wu, Zhaoqi; He, Jizhou
2012-04-01
We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent θ but is independent of the energy spectrum index σ.
Quantum Otto engine of a two-level atom with single-mode fields
NASA Astrophysics Data System (ADS)
Wang, Jianhui; Wu, Zhaoqi; He, Jizhou
2012-04-01
We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent θ but is independent of the energy spectrum index σ.
Detection of the spatiotemporal field of a single-shot terahertz pulse based on spectral holography
NASA Astrophysics Data System (ADS)
Wang, Xiao-Lei; Fei, Yang; Li, Lu-Jie; Wang, Qiang; Zhu, Zhu-Qing
2014-06-01
According to electro-optical sampling theory, we propose a new method to detect the spatiotemporal field of a single-shot terahertz pulse by spectral holography for the first time. The single-shot terahertz pulse is coupled into a broadened chirped femtosecond pulse according to electro-optical sampling theory in the detecting system. Then the reference wave and the signal wave are split by Dammann grating and spread into the interference band-pass filter. The filtered sub-waves are at different central-frequencies because of the different incident angles. These sub-waves at different central-frequencies interfere to form sub-holograms, which are recorded in a single frame of a charge coupled device (CCD). The sub-holograms are numerically processed, and the spatiotemporal field distribution of the original terahertz pulse is reconstructed. The computer simulations verify the feasibility of the proposed method.
Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.
Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro
2016-01-19
We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process.
Communication: Multiple atomistic force fields in a single enhanced sampling simulation
Hoang Viet, Man; Derreumaux, Philippe; Nguyen, Phuong H.
2015-07-14
The main concerns of biomolecular dynamics simulations are the convergence of the conformational sampling and the dependence of the results on the force fields. While the first issue can be addressed by employing enhanced sampling techniques such as simulated tempering or replica exchange molecular dynamics, repeating these simulations with different force fields is very time consuming. Here, we propose an automatic method that includes different force fields into a single advanced sampling simulation. Conformational sampling using three all-atom force fields is enhanced by simulated tempering and by formulating the weight parameters of the simulated tempering method in terms of the energy fluctuations, the system is able to perform random walk in both temperature and force field spaces. The method is first demonstrated on a 1D system and then validated by the folding of the 10-residue chignolin peptide in explicit water.
Bowtie nano-aperture as interface between near-fields and a single-mode fiber.
Mivelle, M; Ibrahim, I A; Baida, F; Burr, G W; Nedeljkovic, D; Charraut, D; Rauch, J-Y; Salut, R; Grosjean, T
2010-07-19
We present the development and study of a single bowtie nano-aperture (BNA) at the end of a monomode optical fiber as an interface between near-fields/nano-optical objects and the fiber mode. To optimize energy conversion between BNA and the single fiber mode, the BNA is opened at the apex of a specially designed polymer fiber tip which acts as an efficient mediator (like a horn optical antenna) between the two systems. As a first application, we propose to use our device as polarizing electric-field nanocollector for scanning near-field optical microscopy (SNOM). However, this BNA-on-fiber probe may also find applications in nanolithography, addressing and telecommunications as well as in situ biological and chemical probing and trapping.
Field emission from a single carbon nanofiber at sub 100 nm gap
NASA Astrophysics Data System (ADS)
Sim, H. S.; Lau, S. P.; Ang, L. K.; You, G. F.; Tanemura, M.; Yamaguchi, K.; Zamri, M.; Yusop, M.
2008-07-01
The authors report the electron field emission from a single carbon nanofiber (CNF) over a range of anode to CNF tip separations of 20-5500nm. Our results show that the field enhancement factor γ is associated with the electrode separation (S). The modified Miller equation is a reasonable empirical model to describe the behavior of γ, which varies with S over a large range of values. The γ approaches to an asymptotic value of 415 or 1 when S is very large or very small as compared to the length of the CNF, respectively. The maximum field emission current sustained by the single CNF without causing damage was estimated to be as high as 15μA.
Inflammable gas mixture detection with a single catalytic sensor based on the electric field effect.
Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng
2014-04-08
This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%.
Petrovic, C.; Lei, H.; Hu, R.
2011-07-27
We present critical fields, thermally activated flux flow (TAFF), and critical current density of tetragonal phase {beta}-FeSe single crystals. The upper critical fields H{sub c2}(T) for H {parallel} (101) and H {perpendicular} (101) are nearly isotropic and are likely governed by the Pauli limiting process. The large Ginzburg-Landau parameter {Kappa} {approx} 72.3(2) indicates that {beta}-FeSe is a type-II superconductor with a smaller penetration depth than in Fe(Te, Se). The resistivity below T{sub c} follows Arrhenius TAFF behavior. For both field directions below 30 kOe, single-vortex pinning is dominant, whereas collective creep becomes important above 30 kOe. The critical current density J{sub c} from M-H loops for H {parallel} (101) is about five times larger than for H {perpendicular} (101), yet much smaller than in other iron-based superconductors.
Fluorescence modulation in single CdSe quantum dots by moderate applied electric fields
LeBlanc, Sharonda J.; McClanahan, Mason R.; Moyer, Tully; Moyer, Patrick J.; Jones, Marcus
2014-01-21
Single molecule time-resolved fluorescence spectroscopy of CdSe/ZnS core-shell quantum dots (QDs) under the influence of moderate applied electric fields reveals distributed emission from states which are neither fully on nor off and pronounced changes in the excited state decay. The data suggest that a 54 kV/cm applied electric field causes small perturbations to the QD surface charge distribution, effectively increasing the surface trapping probability and resulting in the appearance of gray states. We present simultaneous blinking and fluorescence decay results for two sets of QDs, with and without an applied electric field. Further kinetic modeling analysis suggests that a single trapped charged cannot be responsible for a blinking off event.
Single-molecule near-field optical energy transfer microscopy with dielectric tips.
Trabesinger, W; Kramer, A; Kreiter, M; Hecht, B; Wild, U P
2003-03-01
The fluorescence lifetime and the fluorescence rate of single molecules are recorded as a function of the position of a Si3N4 atomic force microscopy tip with respect to the molecule. We observe a decrease of the excited state lifetime and the fluorescence rate when the tip apex is in close proximity to the molecule. These effects are attributed to the fact that the dielectric tip converts non-propagating near-fields to propagating fields within the dielectric tip effectively quenching the fluorescence. The spatial extension of the quenching area is of subwavelength dimensions. The results are discussed in terms of molecular fluorescence in a system of stratified media. The experiment provides surprising new insights into the interactions between a fluorescent molecule and a dielectric tip. The methodology holds promise for applications in ultra high-resolution near-field optical imaging at the level of single fluorophores.
Field-effect modulation of Seebeck coefficient in single PbSe nanowires.
Liang, Wenjie; Hochbaum, Allon I; Fardy, Melissa; Rabin, Oded; Zhang, Minjuan; Yang, Peidong
2009-04-01
In this Letter, we present a novel strategy to control the thermoelectric properties of individual PbSe nanowires. Using a field-effect gated device, we were able to tune the Seebeck coefficient of single PbSe nanowires from 64 to 193 microV x K(-1). This direct electrical field control of sigma and S suggests a powerful strategy for optimizing ZT in thermoelectric devices. These results represent the first demonstration of field-effect modulation of the thermoelectric figure of merit in a single semiconductor nanowire. This novel strategy for thermoelectric property modulation could prove especially important in optimizing the thermoelectric properties of semiconductors where reproducible doping is difficult to achieve.
Inflammable Gas Mixture Detection with a Single Catalytic Sensor Based on the Electric Field Effect
Tong, Ziyuan; Tong, Min-Ming; Meng, Wen; Li, Meng
2014-01-01
This paper introduces a new way to analyze mixtures of inflammable gases with a single catalytic sensor. The analysis technology was based on a new finding that an electric field on the catalytic sensor can change the output sensitivity of the sensor. The analysis of mixed inflammable gases results from processing the output signals obtained by adjusting the electric field parameter of the catalytic sensor. For the signal process, we designed a group of equations based on the heat balance of catalytic sensor expressing the relationship between the output signals and the concentration of gases. With these equations and the outputs of different electric fields, the gas concentration in a mixture could be calculated. In experiments, a mixture of methane, butane and ethane was analyzed by this new method, and the results showed that the concentration of each gas in the mixture could be detected with a single catalytic sensor, and the maximum relative error was less than 5%. PMID:24717635
Space of non-Gaussian fields with single-clock bispectra
NASA Astrophysics Data System (ADS)
Baytaş, Bekir; Shandera, Sarah
2016-08-01
We develop a mathematical construction of non-Gaussian fields whose bispectra satisfy the single-clock inflation consistency relation. At the same order that our basis for bispectra recovers the two simplest single-clock templates, we also find a third orthogonal template which has the single-clock squeezed limit, peaks in folded configurations, and has very small coupling in the equilateral limit. We explore the map between templates and operators in a very general Lagrangian for single-clock fluctuations and find no significant overlap between the new template and models in the literature. We comment on the physical implications of this conclusion. Our findings add support for the idea that both theory- and data-driven considerations will be best served if next-generation non-Gaussianity constraints are made in a basis that uses the degree of coupling between long- and short-wavelength modes as an organizing principle.
Single-molecule imaging of cell surfaces using near-field nanoscopy.
Hinterdorfer, Peter; Garcia-Parajo, Maria F; Dufrêne, Yves F
2012-03-20
Living cells use surface molecules such as receptors and sensors to acquire information about and to respond to their environments. The cell surface machinery regulates many essential cellular processes, including cell adhesion, tissue development, cellular communication, inflammation, tumor metastasis, and microbial infection. These events often involve multimolecular interactions occurring on a nanometer scale and at very high molecular concentrations. Therefore, understanding how single-molecules localize, assemble, and interact on the surface of living cells is an important challenge and a difficult one to address because of the lack of high-resolution single-molecule imaging techniques. In this Account, we show that atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) provide unprecedented possibilities for mapping the distribution of single molecules on the surfaces of cells with nanometer spatial resolution, thereby shedding new light on their highly sophisticated functions. For single-molecule recognition imaging by AFM, researchers label the tip with specific antibodies or ligands and detect molecular recognition signals on the cell surface using either adhesion force or dynamic recognition force mapping. In single-molecule NSOM, the tip is replaced by an optical fiber with a nanoscale aperture. As a result, topographic and optical images are simultaneously generated, revealing the spatial distribution of fluorescently labeled molecules. Recently, researchers have made remarkable progress in the application of near-field nanoscopy to image the distribution of cell surface molecules. Those results have led to key breakthroughs: deciphering the nanoscale architecture of bacterial cell walls; understanding how cells assemble surface receptors into nanodomains and modulate their functional state; and understanding how different components of the cell membrane (lipids, proteins) assemble and communicate to confer efficient functional
Excitons and trions in single and vertically coupled quantum dots under an electric field
NASA Astrophysics Data System (ADS)
Zhai, Li-Xue; Wang, Yan; An, Zhong
2017-08-01
We present a theoretical study of the exciton (X0), the positive and negative trions (X+ and X-) in single and vertically coupled configurations of self-assembled InGaAs quantum dots under an electric field. The quantum states of X0, X+ and X- have been investigated using a quasi-one-dimensional (Q1D) model within the effective-mass approximation. For the single quantum dots, the electric-field dependent energy levels and the average inter-particle distances for the exciton and trions have been calculated. For the coupled quantum dots, the ground and the excited states for X0, X+ and X- have also been calculated and discussed. It is found that either the hole or the electron can be tuned into resonance states by the electric field and that the transition energy spectra for both trions consequently show crossing and anticrossing patterns. The recombination probabilities of the exciton and trion optical transitions are also calculated. The theoretical results have been compared with previously reported photoluminescence data and qualitative agreement is obtained. The trion conditional wave functions are also plotted under different electric field intensities, and it is found that a molecular orbital can be formed at a critical electric field intensity. The evolution of the energy levels of the trions in coupled quantum dots can be explained by the interplay of particle transfer and the electric field.
NASA Astrophysics Data System (ADS)
AL-Baradi, Ateyyah M.; Mykhaylyk, Oleksandr O.; Blythe, Harry J.; Geoghegan, Mark
2011-03-01
We consider the effect of applied magnetic fields on the diffusion of single dextran molecules labeled with fluorescein isothiocyanate within a ferrogel [a composite of magnetite nanoparticles in a poly(methacrylic acid) hydrogel] using fluorescence correlation spectroscopy. We show that the mesh size of the ferrogel is controlled by the applied magnetic field, B, and scales as exp ( { - √[4]{{ξ ^3 B^2 /2μ _0 k_B T}}}), where ξ is a correlation length, μ0 the magnetic constant, kB the Boltzmann constant, and T is the absolute temperature. The diffusion coefficient of the dextran can be modeled with a simple Stokes-Einstein law, containing the same scaling behavior with magnetic field as the swelling of the hydrogel. Furthermore, the magnetic field-dependent release of dextran from the hydrogel is also controlled by the same relationship. The samples were characterized by small angle x-ray scattering (SAXS) and magnetometry experiments. Magnetic hysteresis loops from these ferrogels and zero field cooled/field cooled measurements reveal single domain ferromagnetic behavior at room temperature with a similar coercivity for both as-prepared and fully swollen ferrogels, and for increasing magnetic nanoparticle concentration. SAXS experiments, such as the hysteresis loops, show that magnetite does not aggregate in these gels.
Al-Baradi, Ateyyah M; Mykhaylyk, Oleksandr O; Blythe, Harry J; Geoghegan, Mark
2011-03-07
We consider the effect of applied magnetic fields on the diffusion of single dextran molecules labeled with fluorescein isothiocyanate within a ferrogel [a composite of magnetite nanoparticles in a poly(methacrylic acid) hydrogel] using fluorescence correlation spectroscopy. We show that the mesh size of the ferrogel is controlled by the applied magnetic field, B, and scales as exp(-(4)√ξ(3)B(2)/2μ(0)k(B)T), where ξ is a correlation length, μ(0) the magnetic constant, k(B) the Boltzmann constant, and T is the absolute temperature. The diffusion coefficient of the dextran can be modeled with a simple Stokes-Einstein law, containing the same scaling behavior with magnetic field as the swelling of the hydrogel. Furthermore, the magnetic field-dependent release of dextran from the hydrogel is also controlled by the same relationship. The samples were characterized by small angle x-ray scattering (SAXS) and magnetometry experiments. Magnetic hysteresis loops from these ferrogels and zero field cooled∕field cooled measurements reveal single domain ferromagnetic behavior at room temperature with a similar coercivity for both as-prepared and fully swollen ferrogels, and for increasing magnetic nanoparticle concentration. SAXS experiments, such as the hysteresis loops, show that magnetite does not aggregate in these gels.
Vectorial nanoscale mapping of optical antenna fields by single molecule dipoles.
Singh, Anshuman; Calbris, Gaëtan; van Hulst, Niek F
2014-08-13
Optical nanoantennas confine light on the nanoscale, enabling strong light-matter interactions and ultracompact optical devices. Such confined nanovolumes of light have nonzero field components in all directions (x, y, and z). Unfortunately mapping of the actual nanoscale field vectors has so far remained elusive, though antenna hotspots have been explored by several techniques. In this paper, we present a novel method to probe all three components of the local antenna field. To this end a resonant nanoantenna is fabricated at the vertex of a scanning tip. Next, the nanoantenna is deterministically scanned in close proximity to single fluorescent molecules, whose fixed excitation dipole moment reads out the local field vector. With nanometer molecular resolution, we distinctly map x-, y-, and z-field components of the dipole antenna, i.e. a full vectorial mode map, and show good agreement with full 3D FDTD simulations. Moreover, the fluorescence polarization maps the localized coupling, with emission through the longitudinal antenna mode. Finally, the resonant antenna probe is used for single molecule imaging with 40 nm fwhm response function. The total fluorescence enhancement is 7.6 times, while out-of-plane molecules, almost undetectable in far-field, are made visible by the strong antenna z-field with a fluorescence enhancement up to 100 times. Interestingly, the apparent position of molecules shifts up to 20 nm depending on their orientation. The capability to resolve orientational information on the single molecule level makes the scanning resonant antenna an ideal tool for extreme resolution bioimaging.
Direct simulation of single bubble motion under vertical magnetic field: Paths and wakes
NASA Astrophysics Data System (ADS)
Zhang, Jie; Ni, Ming-Jiu
2014-10-01
Motion of single Ar bubbles rising in GaInSn under vertical magnetic fields is studied numerically using a volume-of-fluid method and adaptive mesh refinement technique for two-phase interface treatment; a consistent and conservative scheme calculates induced current density and Lorentz force. Numerical results are compared with published experimental data [C. Zhang, S. Eckert, and G. Gerbeth, "Experimental study of single bubble motion in a liquid metal column exposed to a DC magnetic field," Int. J. Multiphase Flow 31, 824-842 (2005)], where bubble diameters range from 2.5 to 6.4 mm, producing Reynolds numbers that vary between 2000 and 4000. Maximum experimental magnetic field strength was set to 0.3 T because of experimental restrictions, although we increased it to 0.5 T for firm conclusions. Apart from terminal rising velocity comparisons, we focused on variations in bubble motion paths and wake structures under magnetic fields, which cannot be observed experimentally because liquid metal is opaque. Magnetic field effects on bubble trajectory are exerted through vortex structure modification, which reinforced the conjecture that path instability is mainly attributed to wake instability. In bubble motion without magnetic fields, vortex threads in the bubble wake wrap around each other while vortex filaments incline parallel to the field with increasing magnetic intensity. Additionally, high magnetic fields will induce secondary bubble path instabilities, which contribute to the high Reynolds number flow that instabilities develop around the bubble, producing an asymmetrical Lorentz force distribution. This instability vanishes under higher magnetic intensities because flow instability is suppressed. Rising bubble aspect ratios decrease considerably under magnetic fields and may also contribute to smaller vorticities at the bubble surface. A close relationship between fluctuations in rising velocity and shape variations is found.
NASA Astrophysics Data System (ADS)
Maleknejad, A.; Sheikh-Jabbari, M. M.; Soda, J.
2013-07-01
small field models also have a potential minimum at φ≠0 which the system falls in at the end of inflation. A typical property of small field models is that a sufficient number of e-folds, requires a sub-Planckian inflaton initial value. For this reason they are called small field models. Natural inflation is an example of this type [12]. Hybrid inflation models: These models involve more than one scalar field while inflation is mainly driven by a single inflaton field ϕ. Inflaton starts from a large value rolling down until it reaches a bifurcation point, ϕ=ϕe, after which the field becomes unstable and undergoes a waterfall transition toward its global minimum. Its prime example is the Linde’s hybrid inflation model with the following potential [13] V(ϕ,χ)={λ}/{4}(+{1}/{2}g2ϕ2χ2+{1}/{2}m2ϕ2. During the initial inflationary phase the potential of the hybrid inflation is effectively described by a single field ϕ while inflation ends by a phase transition triggered by the presence of the second scalar field, the waterfall field χ. In other words, when the effective mass squared of a waterfall field becomes negative, the tachyonic instability makes waterfall field roll down toward the true vacuum state and the inflation suddenly ends.Number of e-folds Ne is given as Ne≃{M4}/{4λm2}ln({ϕ0}/{ϕe}), where ϕe={M}/{g} is the critical value of the inflaton below which, due to tachyonic instability, χ=0 becomes unstable and mχ2 gets negative. K-inflation: This is the prime example of models with non-canonical Kinetic term we discuss here. They are described by the action [14] S=∫d4x√{-g}({R}/{2}+P(φ,X)), where φ is a scalar field and X≔-{1}/{2}(. Here, P plays the rule of the effective pressure, while the energy density is given by ρ=2XP-P. Thus, the slow-roll parameter is given as ɛ={3XP}/{2XP-P}. The characteristic feature of these models is that in general they have a non-trivial sound speed cs2 for the propagation of perturbations (cf. our
Xia Changlong; Zhang Gangtai; Wu Jie; Liu Xueshen
2010-04-15
We investigate theoretic high-order harmonic generation and single attosecond pulse generation in an orthogonally polarized two-color laser field, which is synthesized by a mid-infrared (IR) pulse (12.5 fs, 2000 nm) in the y component and a much weaker (12 fs, 800 nm) pulse in the x component. We find that the width of the harmonic plateau can be extended when a static electric field is added in the y component. We also investigate emission time of harmonics in terms of a time-frequency analysis to illustrate the physical mechanism of high-order harmonic generation. We calculate the ionization rate using the Ammosov-Delone-Krainov model and interpret the variation of harmonic intensity for different static electric field strengths. When the ratio of strengths of the static and the y-component laser fields is 0.1, a continuous harmonic spectrum is formed from 220 to 420 eV. By superposing a properly selected range of the harmonic spectrum from 300 to 350 eV, an isolated attosecond pulse with a duration of about 75 as is obtained, which is near linearly polarized.
Chen, Quan; Marble, Andrew E; Colpitts, Bruce G; Balcom, Bruce J
2005-08-01
When fluid saturated porous media are subjected to an applied uniform magnetic field, an internal magnetic field, inside the pore space, is induced due to magnetic susceptibility differences between the pore-filling fluid and the solid matrix. The microscopic distribution of the internal magnetic field, and its gradients, was simulated based on the thin-section pore structure of a sedimentary rock. The simulation results were verified experimentally. We show that the 'decay due to diffusion in internal field' magnetic resonance technique may be applied to measure the pore size distribution in partially saturated porous media. For the first time, we have observed that the internal magnetic field and its gradients in porous rocks have a Lorentzian distribution, with an average gradient value of zero. The Lorentzian distribution of internal magnetic field arises from the large susceptibility contrast and an intrinsic disordered pore structure in these porous media. We confirm that the single exponential magnetic resonance free induction decay commonly observed in fluid saturated porous media arises from a Lorentzian internal field distribution. A linear relationship between the magnetic resonance linewidth, and the product of the susceptibility difference in the porous media and the applied magnetic field, is observed through simulation and experiment.
Electric field effect on (6,0) zigzag single-walled aluminum nitride nanotube.
Baei, Mohammad T; Peyghan, Ali Ahmadi; Moghimi, Masoumeh
2012-09-01
Structural, electronic, and electrical responses of the H-capped (6,0) zigzag single-walled aluminum nitride nanotube was studied under the parallel and transverse electric fields with strengths 0-140 × 10(-4) a.u. by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using a locally modified version of the GAMESS electronic structure program. The dipole moments, atomic charge variations, and total energy of the (6,0) zigzag AlNNT show increases with increase in the applied external electric field strengths. The length, tip diameters, electronic spatial extent, and molecular volume of the nanotube do not significantly change with increasing electric field strength. The energy gap of the nanotube decreases with increases of the electric field strength and its reactivity is increased. Increase of the ionization potential, electron affinity, chemical potential, electrophilicity, and HOMO and LUMO in the nanotube with increase of the applied parallel electric field strengths shows that the parallel field has a much stronger interaction with the nanotube with respect to the transverse electric field strengths. Analysis of the parameters indicates that the properties of AlNNTs can be controlled by the proper external electric field.
NASA Technical Reports Server (NTRS)
Lawton, R. M.
1976-01-01
An analysis of magnetic fields in the Orbiter Payload Bay resulting from the present grounding configuration (structure return) was presented and the amount of improvement that would result from installing wire returns for the three dc power buses was determined. Ac and dc magnetic fields at five points in a cross-section of the bay are calculated for both grounding configurations. Y and Z components of the field at each point are derived in terms of a constant coefficient and the current amplitude of each bus. The dc loads assumed are 100 Amperes for each bus. The ac noise current used is a spectrum 6 db higher than the Orbiter equipment limit for narrowband conducted emissions. It was concluded that installing return wiring to provide a single point ground for the dc Buses in the Payload Bay would reduce the ac and dc magnetic field intensity by approximately 30 db.
NASA Astrophysics Data System (ADS)
Barseghyan, M. G.
2016-11-01
The intraband optical absorption in GaAs/Ga0.7Al0.3As two-dimensional single quantum ring is investigated. Considering the combined effects of hydrostatic pressure and intense laser field the energy of the ground and few excited states has been found using the effective mass approximation and exact diagonalization technique. The energies of these states and the corresponding threshold energy of the intraband optical transitions are examined as a function of hydrostatic pressure for the different values of the laser field parameter. We also investigated the dependencies of the intraband optical absorption coefficient as a function of incident photon energy for different values of hydrostatic pressure and laser field parameter. It is found that the effects of hydrostatic pressure and intense laser field lead to redshift and blueshift of the intraband optical spectrum respectively.
Field emission of carbon quantum dots synthesized from a single organic solvent.
Liu, Xiahui; Yang, Bingjun; Yang, Juan; Yu, Shengxue; Chen, Jiangtao
2016-11-04
In this paper, a facile synthesis of carbon quantum dots (CQDs) and its field emission performance are reported. The CQDs are prepared from a single N, N-dimethylformamide acting as carbon and nitrogen-doping sources simultaneously. The CQDs are investigated by photoluminescence, transmission electron microscopy and x-ray photoelectron spectroscopy. The CQDs have an average size of 3 nm and are doped with N atoms. CQD dispersion shows strong fluorescence under UV illumination. For the first time, the field emission behavior of CQDs coated on Si substrate is studied. As a candidate of cold cathode, the CQDs display good field emission performance. The CQD emitter reaches the current density of 1.1 mA cm(-2) at 7.0 V μm(-1) and exhibits good long-term emission stability, suggesting promising application in field emission devices.
The field-space metric in spiral inflation and related models
Erlich, Joshua; Olsen, Jackson; Wang, Zhen
2016-09-22
Multi-field inflation models include a variety of scenarios for how inflation proceeds and ends. Models with the same potential but different kinetic terms are common in the literature. We compare spiral inflation and Dante’s inferno-type models, which differ only in their field-space metric. We justify a single-field effective description in these models and relate the single-field description to a mass-matrix formalism. We note the effects of the nontrivial field-space metric on inflationary observables, and consequently on the viability of these models. We also note a duality between spiral inflation and Dante’s inferno models with different potentials.
Extending the GRACE Data Record with Gravity Field Solutions Based on a Single GRACE Satellite
NASA Astrophysics Data System (ADS)
McCullough, C.; Bettadpur, S. V.; Cheng, M.; Ries, J. C.
2015-12-01
Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has enabled unprecedented scientific discovery in a variety of physical Earth sciences. However, with the launch of GRACE Follow-On not taking place until 2017 and the declining health of the current GRACE satellites, it is necessary to cultivate the ability to estimate the Earth's gravity field without the full suite of GRACE measurements. Using a single GRACE satellite, equipped with an accelerometer and a GPS receiver, as well as a compliment of SLR satellites, large-scale features of the Earth's gravity field can be determined. While the accuracy of such solutions are noticeably degraded relative to the nominal GRACE product and smaller-scale features of the Earth's gravity field are impossible to discern without the use of GRACE's satellite-to-satellite (SST) tracking measurements, single satellite solutions do capture continental scale variations in the Earth's gravitational field. These large-scale variations can be used to track global trends such as polar ice loss and water storage, in the event of a gap between GRACE and GRACE Follow-On. In addition, the lessons learned from gravity field solutions computed using only GRACE GPS data provide valuable insight into the optimal combination of GPS data with SST for GRACE Follow-On and other future missions.
Layton, Kelvin J; Gallichan, Daniel; Testud, Frederik; Cocosco, Chris A; Welz, Anna M; Barmet, Christoph; Pruessmann, Klaas P; Hennig, Jürgen; Zaitsev, Maxim
2013-09-01
It has recently been demonstrated that nonlinear encoding fields result in a spatially varying resolution. This work develops an automated procedure to design single-shot trajectories that create a local resolution improvement in a region of interest. The technique is based on the design of optimized local k-space trajectories and can be applied to arbitrary hardware configurations that employ any number of linear and nonlinear encoding fields. The trajectories designed in this work are tested with the currently available hardware setup consisting of three standard linear gradients and two quadrupolar encoding fields generated from a custom-built gradient insert. A field camera is used to measure the actual encoding trajectories up to third-order terms, enabling accurate reconstructions of these demanding single-shot trajectories, although the eddy current and concomitant field terms of the gradient insert have not been completely characterized. The local resolution improvement is demonstrated in phantom and in vivo experiments. Copyright © 2012 Wiley Periodicals, Inc.
Comparing Hall Effect and Field Effect Measurements on the Same Single Nanowire.
Hultin, Olof; Otnes, Gaute; Borgström, Magnus T; Björk, Mikael; Samuelson, Lars; Storm, Kristian
2016-01-13
We compare and discuss the two most commonly used electrical characterization techniques for nanowires (NWs). In a novel single-NW device, we combine Hall effect and back-gated and top-gated field effect measurements and quantify the carrier concentrations in a series of sulfur-doped InP NWs. The carrier concentrations from Hall effect and field effect measurements are found to correlate well when using the analysis methods described in this work. This shows that NWs can be accurately characterized with available electrical methods, an important result toward better understanding of semiconductor NW doping.
Single-cycle multiterahertz transients with peak fields above 10 MV/cm.
Junginger, F; Sell, A; Schubert, O; Mayer, B; Brida, D; Marangoni, M; Cerullo, G; Leitenstorfer, A; Huber, R
2010-08-01
Phase-locked single-cycle transients with frequency components between 1 and 60THz and peak fields of up to 12MV/cm are generated as the idler wave of a parametric amplifier. To achieve broadband conversion in GaSe nonlinear crystals, we match the group velocities of signal and idler components. The influence of group-velocity dispersion is minimized by long-wavelength pumping at 1.18mum. Free-space electro-optic sampling monitors the multiterahertz waveforms with direct field resolution.
Nanoscale magnetic field mapping with a single spin scanning probe magnetometer
Rondin, L.; Tetienne, J.-P.; Spinicelli, P.; Roch, J.-F.; Jacques, V.; Dal Savio, C.; Karrai, K.; Dantelle, G.; Thiaville, A.; Rohart, S.
2012-04-09
We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.
Triple unification of inflation, dark matter, and dark energy using a single field
Liddle, Andrew R.; Pahud, Cedric; Urena-Lopez, L. Arturo
2008-06-15
We construct an explicit scenario whereby the same material driving inflation in the early universe can comprise dark matter in the present universe, using a simple quadratic potential. Following inflation and preheating, the density of inflaton/dark matter particles is reduced to the observed level by a period of thermal inflation, of a duration already invoked in the literature for other reasons. Within the context of the string landscape, one can further argue for a nonzero vacuum energy of this field, thus unifying inflation, dark matter, and dark energy into a single fundamental field.
A single-step method for RNA isolation from tropical crops in the field
Breitler, J.-C.; Campa, C.; Georget, F.; Bertrand, B.; Etienne, H.
2016-01-01
The RNAzol RT reagent was used to provide pure RNA from human cells. We develop a protocol using RNAzol RT reagent to extract pure RNA from plants tissues and demonstrate that this RNA extraction method works not only at room temperature but also at elevated temperatures and provides the simplest and most effective single-step method to extract pure and undegraded RNA directly from tropical plants in the field. RNA extraction directly in a complex field environment opens up the way for studying gene-environment interactions at transcriptome level to decipher the complex regulatory network involved in multiple-stress responses. PMID:27922073
NASA Astrophysics Data System (ADS)
Wu, Chen-Wu; Shu, Yong-Hua; Xie, Ji-Jia; Jiang, Jian-Zheng; Fan, Jing
2017-02-01
A concept was developed to inversely estimate the near-field temperature as well as the surface heat flux for the transient heat conduction problem with boundary condition of the unknown heat flux. The mathematical formula was derived for the inverse estimation of the near-field temperature and surface heat flux via a single point temperature measurement. The experiments were carried out in a vacuum chamber and the theoretically predicted temperatures were justified in specific positions. The inverse estimation principle was validated and the estimation deviation was evaluated for the present configuration.
Ferromagnetic resonance and high field ESR in a TDAE-C60 single crystal
NASA Astrophysics Data System (ADS)
Arčon, D.; Cevc, P.; Omerzu, A.; Blinc, R.; Mehring, M.; Knorr, S.; Grupp, A.; Barra, A.-L.; Chouteau, G.
1998-08-01
Frequency variable ESR measurements have been performed on well annealed TDAE-C60 single crystals between 40 MHz and 245 GHz. A non-linear variation of the electron resonance frequency with the magnetic field has been observed below TC=16 K in the radio-frequency region. The observed ferromagnetic resonance data are characteristic for a three-dimensional Heisenberg ferromagnet with a small positive uniaxial anisotropy field. The easy axis coincides with the crystal c-direction which is the direction of closest approach of the C60- ions.
Formation of a ''child'' universe in an inflationary cosmological model
Holcomb, K.A.; Park, S.J.; Vishniac, E.T.
1989-02-15
The evolution of a flat, spherically symmetric cosmological model, containing radiation and an inhomogeneous scalar field, is simulated numerically to determine whether the inhomogeneity could cause a ''child'' universe, connected by a wormhole to the external universe, to form. The gravitational and field quantities were computed self-consistently by means of the techniques of numerical relativity. Although we were unable to follow the process to its completion, preliminary indications are that the ''budding'' phenomenon could occur under very general initial conditions, as long as the scalar field is sufficiently inhomogeneous that the wormhole forms before the inflation is damped by the expansion of the background spacetime.
Microfluidic Device for Electric Field-Driven Single-Cell Captureand Activation
Toriello, Nicholas M.; Douglas, Erik S.; Mathies, Richard A.
2005-09-20
A microchip that performs directed capture and chemical activation of surface-modified single-cells has been developed. The cell-capture system is comprised of interdigitated gold electrodes microfabricated on a glass substrate within PDMS channels. The cell surface is labeled with thiol functional groups using endogenous RGD receptors and adhesion to exposed gold pads on the electrodes is directed by applying a driving electric potential. Multiple cell types can thus be sequentially and selectively captured on desired electrodes. Single-cell capture efficiency is optimized by varying the duration of field application. Maximum single-cell capture is attained for the 10 min trial, with 63+-9 percent (n=30) of the electrode pad rows having a single cell. In activation studies, single M1WT3 CHO cells loaded with the calcium-sensitive dye fluo-4 AM were captured; exposure to the muscarinic agonist carbachol increased the fluorescence to 220+-74percent (n=79) of the original intensity. These results demonstrate the ability to direct the adhesion of selected living single cells on electrodes in a microfluidic device and to analyze their response to chemical stimuli.
Magnetic-field-induced diameter-selective synthesis of single-walled carbon nanotubes
NASA Astrophysics Data System (ADS)
Su, Yanjie; Zhang, Yaozhong; Wei, Hao; Zhang, Liling; Zhao, Jiang; Yang, Zhi; Zhang, Yafei
2012-02-01
We report a facile and scalable approach to synthesize single-walled carbon nanotubes (SWNTs) with selected diameter distribution by applying a magnetic field perpendicular to the electric field in the arc plasma region. It is found that this magnetic field-induced diameter-selectivity strategy enables the control of the SWNTs with different diameter distributions in different regions, and the diameter-selective efficiency could be enhanced by modifying the direction of magnetic field. Our results indicate that the motions of the catalysts with different particle sizes, positive carbon ions and electrons are significantly influenced by the magnetic field and electromagnetic force, resulting in the different nucleation and growth processes of SWNTs due to the collective interactions between the magnetic field and arc plasma. This approach would enable a viable route towards the synthesis of SWNTs with desired diameter through the tuning of arc parameters in the arc discharge process.We report a facile and scalable approach to synthesize single-walled carbon nanotubes (SWNTs) with selected diameter distribution by applying a magnetic field perpendicular to the electric field in the arc plasma region. It is found that this magnetic field-induced diameter-selectivity strategy enables the control of the SWNTs with different diameter distributions in different regions, and the diameter-selective efficiency could be enhanced by modifying the direction of magnetic field. Our results indicate that the motions of the catalysts with different particle sizes, positive carbon ions and electrons are significantly influenced by the magnetic field and electromagnetic force, resulting in the different nucleation and growth processes of SWNTs due to the collective interactions between the magnetic field and arc plasma. This approach would enable a viable route towards the synthesis of SWNTs with desired diameter through the tuning of arc parameters in the arc discharge process
Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields
NASA Astrophysics Data System (ADS)
Noe, G. Timothy; Katayama, Ikufumi; Katsutani, Fumiya; Allred, James J.; Horowitz, Jeffrey A.; Sullivan, David M.; Zhang, Qi; Sekiguchi, Fumiya; Woods, Gary L.; Hoffmann, Matthias C.; Nojiri, Hiroyuki; Takeda, Jun; Kono, Junichiro
2016-12-01
We have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective echelon to create time-delayed beamlets across the intensity profile of the optical gate beam before it spatially and temporally overlaps with the terahertz radiation in a ZnTe detection crystal. After imaging the gate beam onto a camera, we can retrieve the terahertz time-domain waveform by analyzing the resulting image. To demonstrate the utility of our technique, we measured cyclotron resonance absorption of optically excited carriers in the terahertz frequency range in intrinsic silicon at high magnetic fields, with results that agree well with published values.
Single and dual-Gregorian reflector antenna shaped beam far-field synthesis
NASA Astrophysics Data System (ADS)
Mehler, M. J.
The direct far-field G.O. synthesis of shaped beam reflector antennas has recently been treated by Mehler, Tun and Adatia (1986). These authors use a synthesis technique which exploits complex coordinates and which is based on a method originally considered by Norris and Westcott (1976). They describe the synthesis of single reflector antennas which radiate both elliptical beams and European coverage patterns. Here this technique is extended to consider a class of dual reflector antennas which possess shaped main reflectors and conic subreflectors. An example is given of a Gregorian duel reflector antenna which radiates a cross-polar field significantly smaller than that radiated by single shaped reflector antennas. In addition, the behavior of the radiation pattern as a function of the reflector diameter is investigated.
Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields
Noe, II, G. Timothy; Katayama, Ikufumi; Katsutani, Fumiya; Allred, James J.; Horowitz, Jeffrey A.; Sullivan, David M.; Zhang, Qi; Sekiguchi, Fumiya; Woods, Gary L.; Hoffmann, Matthias C.; Nojiri, Hiroyuki; Takeda, Jun; Kono, Junichiro
2016-12-22
Here, we have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective echelon to create time-delayed beamlets across the intensity profile of the optical gate beam before it spatially and temporally overlaps with the terahertz radiation in a ZnTe detection crystal. After imaging the gate beam onto a camera, we can retrieve the terahertz time-domain waveform by analyzing the resulting image. To demonstrate the utility of our technique, we measured cyclotron resonance absorption of optically excited carriers in the terahertz frequency range in intrinsic silicon at high magnetic fields, with results that agree well with published values.
Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields
Noe, II, G. Timothy; Katayama, Ikufumi; Katsutani, Fumiya; ...
2016-12-22
Here, we have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective echelon to create time-delayed beamlets across the intensity profile of the optical gate beam before it spatially and temporally overlaps with the terahertz radiation in a ZnTe detection crystal. After imaging the gate beam onto a camera, we can retrieve the terahertz time-domain waveform by analyzing the resulting image. To demonstrate the utility of our technique, we measured cyclotron resonance absorption of optically excited carriers inmore » the terahertz frequency range in intrinsic silicon at high magnetic fields, with results that agree well with published values.« less
Aligned Single Wall Carbon Nanotube Polymer Composites Using an Electric Field
NASA Technical Reports Server (NTRS)
Park, Cheol; Wiklinson, John; Banda, Sumanth; Ounaies, Zoubeida; Wise, Kristopher E.; Sauti, Godfrey; Lillehei, Peter T.; Harrison, Joycelyn S.
2005-01-01
While high shear alignment has been shown to improve the mechanical properties of single wall carbon nanotubes (SWNT)-polymer composites, it is difficult to control and often results in degradation of the electrical and dielectric properties of the composite. Here, we report a novel method to actively align SWNTs in a polymer matrix, which allows for control over the degree of alignment of SWNTs without the side effects of shear alignment. In this process, SWNTs are aligned via field-induced dipolar interactions among the nanotubes under an AC electric field in a liquid matrix followed by immobilization by photopolymerization while maintaining the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy and the morphology of the aligned nanocomposites was investigated by high resolution scanning electron microscopy. The structure of the field induced aligned SWNTs is intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties in addition to improving the mechanical properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field conditions.
NASA Astrophysics Data System (ADS)
Liu, Shuhong
The search for low-cost, large area, flexible devices has led to a remarkable increase in the research and development of organic semiconductors. Single-crystal organic field-effect transistors (OFETs) are ideal device structures for studying fundamental science associated with charge transport in organic materials and have demonstrated high mobility and outstanding electrical characteristics. For example, an exceptionally high carrier mobility of 20 cm2/Vs has been demonstrated for rubrene single crystal field effect transistors. However, it remains a technical challenge to integrate single-crystal devices into practical electronic applications. A key difficulty is that organic single-crystal devices are usually fabricated one device at a time by handpicking a single crystal and placing it onto the device substrate. This makes it impossible to mass-produce at high density with reasonable throughput. Therefore, there is a great need for a high-throughput method for depositing large arrays of organic semiconductor single crystals directly onto device structures. In this dissertation, I develop several approaches towards realizing this goal. The first approach is a solution-processing technique, which relies on solvent wetting and de-wetting on substrates with patterned wettability to selectively direct the deposition or removal of organic crystals. The assembly of different organic crystals over centimeter-squared areas on Au, SiO 2 and flexible plastic substrates is demonstrated. By designing line features on the substrate, alignment of needle-like crystals is also achieved. As a demonstration of the potential application of this approach, arrays of organic single crystal FETs are fabricated by patterning organic single crystals directly onto and between transistor source and drain electrodes. Besides organic single crystals, this self-assembly strategy is also applicable for patterning other objects such as metallic nanowires. In the second technique, organic
NASA Astrophysics Data System (ADS)
Marks, Michael; Kroupa, Pavel
2011-11-01
The galactic field's late-type stellar single and binary populations are calculated on the observationally well-constrained supposition that all stars form as binaries with invariant properties in discrete star formation events. A recently developed tool (Marks, Kroupa & Oh) is used to evolve the binary star distributions in star clusters for a few million years until an equilibrium situation is achieved which has a particular mixture of single and binary stars. On cluster dissolution the population enters the galactic field with these characteristics. The different contributions of single stars and binaries from individual star clusters, which are selected from a power-law-embedded star cluster mass function, are then added up. This gives rise to integrated galactic field binary distribution functions (IGBDFs), resembling a galactic field's stellar content (dynamical population synthesis). It is found that the binary proportion in the galactic field of a galaxy is larger the lower the minimum cluster mass, Mecl, min, the lower the star formation rate, SFR, the steeper the embedded star cluster mass function (described by index β) and the larger the typical size of forming star clusters in the considered galaxy. In particular, period, mass ratio and eccentricity IGBDFs for the Milky Way (MW) are modelled using Mecl, min= 5 M⊙, SFR = 3 M⊙ yr-1 and β= 2 which are justified by observations. For rh≈ 0.1-0.3 pc, the half-mass radius of an embedded cluster, the aforementioned theoretical IGBDFs agree with independently observed distributions, suggesting that the individual discrete star formation events in the MW generally formed compact star clusters. Of all late-type binaries, 50 per cent stem from Mecl≲ 300 M⊙ clusters, while 50 per cent of all single stars were born in Mecl≳ 104 M⊙ clusters. Comparison of the G-dwarf and M-dwarf binary populations indicates that the stars are formed in mass-segregated clusters. In particular, it is pointed out that
Phase retrieval from a single near-field diffraction pattern with a large Fresnel number.
Li, Enrong; Liu, Yijin; Liu, Xiaosong; Zhang, Kai; Wang, Zhili; Hong, Youli; Yuan, Qingxi; Huang, Wanxia; Marcelli, Augusto; Zhu, Peiping; Wu, Ziyu
2008-11-01
A new method of phase retrieval from a single near-field diffraction image with a large Fresnel number is presented and discussed. This method requires only the oversampled diffraction pattern without any other information such as the object envelope. Moreover, we show that the combination with a fast computational method is possible when the linear oversampling ratio is an integer. Numerical simulations are also presented, showing that the method works well with noisy data.
Near-field acoustic characteristics of a single-rotor propfan
NASA Technical Reports Server (NTRS)
Bartel, H. W.; Swift, G.
1989-01-01
The near-field noise characteristics of the SR-7L, an eight-blade, single-rotor, wing-mounted, tractor propfan have been determined. It is found that the noise is dominated by discrete tones, usually at the first order (and occasionally at the second or third order) of the blade-passage frequency. The highest noise levels were noted at conditions of high tip helical speeds and high dynamic pressures.
Single-particle dynamics of a free-electron laser with axial field
Pandya, T.P.; Bali, L.M.; Bakshi, U.; Jha, P.
1987-06-15
Single-particle dynamics of electron motion through a free-electron-laser cavity with axial guide field is presented. Equations governing the trajectories in the absence of radiation are obtained, and significant departures from the results of earlier work are discussed. Linearized gain in the presence of radiation is derived. Comparison with previous studies reveals (i) good agreement with results and (ii) gain enhancements at hitherto unreported frequencies.
NASA Astrophysics Data System (ADS)
Durach, Maxim; Rusina, Anastasia; Kling, Matthias F.; Stockman, Mark I.
2011-08-01
We predict a dynamic metallization effect where an ultrafast (single-cycle) optical pulse with a ≲1V/Å field causes plasmonic metal-like behavior of a dielectric film with a few-nm thickness. This manifests itself in plasmonic oscillations of polarization and a significant population of the conduction band evolving on a ˜1fs time scale. These phenomena are due to a combination of both adiabatic (reversible) and diabatic (for practical purposes irreversible) pathways.
Durach, Maxim; Rusina, Anastasia; Kling, Matthias F; Stockman, Mark I
2011-08-19
We predict a dynamic metallization effect where an ultrafast (single-cycle) optical pulse with a ≲1 V/Å field causes plasmonic metal-like behavior of a dielectric film with a few-nm thickness. This manifests itself in plasmonic oscillations of polarization and a significant population of the conduction band evolving on a ~1 fs time scale. These phenomena are due to a combination of both adiabatic (reversible) and diabatic (for practical purposes irreversible) pathways.
Single molecule fluorescence resonance energy transfer scanning near-field optical microscopy
NASA Astrophysics Data System (ADS)
Sekatskii, S. K.; Dietler, G.; Letokhov, V. S.
2008-02-01
The first single molecule fluorescence resonant energy transfer scanning near-field optical microscope (FRET SNOM) images of CdSe nanocrystal (donor) deposited onto the glass slide surface are presented. Images were obtained using the earlier proposed FRET SNOM probes which are 30-100 nm thick polymer layers stained with the acceptor dye molecules coated onto the apex of the standard sharp aperture SNOM tip. An original SNOM construction enabling very fast scanning was used to overcome the photostability problem.
Gao, Qing Dong, Daoyi Petersen, Ian R.; Rabitz, Herschel
2016-06-15
The purpose of this paper is to solve the fault tolerant filtering and fault detection problem for a class of open quantum systems driven by a continuous-mode bosonic input field in single photon states when the systems are subject to stochastic faults. Optimal estimates of both the system observables and the fault process are simultaneously calculated and characterized by a set of coupled recursive quantum stochastic differential equations.
ELF-magnetic field induced effects on the bioelectric activity of single neurone cells
NASA Astrophysics Data System (ADS)
Azanza, Maria J.; del Moral, A.
1998-01-01
The membrane bioelectric activity recorded from single neurones is dramatically modified under applied extremely low frequency magnetic fields (ELF-MF) of 50 Hz and 1-15 mT peak intensity. In ≌27% of the neurones studied a firing rhythm is generated for ≌7 mT, which resembles synchronous oscillations activity. The possibility that ELF-MF could generate neuronal networks synchrony firing does exist as an explanatory physical model shows.
Shaped and Feedback-Controlled Excitation of Single Molecules in the Weak-Field Limit
2015-01-01
Coherent control uses tailored femtosecond pulse shapes to influence quantum pathways and drive a light-induced process toward a specific outcome. There has been a long-standing debate whether the absorption properties or the probability for population to remain in an excited state of a molecule can be influenced by the pulse shape, even if only a single photon is absorbed. Most such experiments are performed on many molecules simultaneously, so that ensemble averaging reduces the access to quantum effects. Here, we demonstrate systematic coherent control experiments on the fluorescence intensity of a single molecule in the weak-field limit. We demonstrate that a delay scan of interfering pulses reproduces the excitation spectrum of the molecule upon Fourier transformation, but that the spectral phase of a pulse sequence does not affect the transition probability. We generalize this result to arbitrary pulse shapes by performing the first closed-loop coherent control experiments on a single molecule. PMID:26706166
Nanopore extended field-effect transistor for selective single-molecule biosensing.
Ren, Ren; Zhang, Yanjun; Nadappuram, Binoy Paulose; Akpinar, Bernice; Klenerman, David; Ivanov, Aleksandar P; Edel, Joshua B; Korchev, Yuri
2017-09-19
There has been a significant drive to deliver nanotechnological solutions to biosensing, yet there remains an unmet need in the development of biosensors that are affordable, integrated, fast, capable of multiplexed detection, and offer high selectivity for trace analyte detection in biological fluids. Herein, some of these challenges are addressed by designing a new class of nanoscale sensors dubbed nanopore extended field-effect transistor (nexFET) that combine the advantages of nanopore single-molecule sensing, field-effect transistors, and recognition chemistry. We report on a polypyrrole functionalized nexFET, with controllable gate voltage that can be used to switch on/off, and slow down single-molecule DNA transport through a nanopore. This strategy enables higher molecular throughput, enhanced signal-to-noise, and even heightened selectivity via functionalization with an embedded receptor. This is shown for selective sensing of an anti-insulin antibody in the presence of its IgG isotype.Efficient detection of single molecules is vital to many biosensing technologies, which require analytical platforms with high selectivity and sensitivity. Ren et al. combine a nanopore sensor and a field-effect transistor, whereby gate voltage mediates DNA and protein transport through the nanopore.
Attentional modulation of MT neurons with single or multiple stimuli in their receptive fields
Lee, Joonyeol; Maunsell, John H.R.
2010-01-01
Descriptions of how attention modulates neuronal responses suggest that the strength of its effects depends on stimulus conditions. Attention to an isolated stimulus in the receptive field of an individual neuron typically produces a moderate enhancement of the cell's response, but neuronal responses are often strongly modulated when attention is shifted between multiple stimuli that lie within the receptive field. However, previous reports have not compared these stimulus effects under equivalent conditions, so differences in task difficulty could have been responsible for much of the difference. Consequently, the quantitative effects of stimulus conditions have remained unknown, and it has not been possible to address the question of whether the differences that have been observed could be explained by a single mechanism. We measured the attentional modulation of the responses of 70 single neurons in area MT of two rhesus monkeys using a task design that kept attention stable across different stimulus configurations. We found that attentional modulation was indeed much stronger when more than one stimulus was within the receptive field. Nevertheless, the broad range of attentional modulations seen across the different conditions could be readily explained by single mechanism. The neurophysiological data from all stimulus conditions were well fit by a model in which attention acts through a response normalization mechanism (Lee and Maunsell, 2009). Collectively, these results validate previous impressions of the effects of stimulus configuration on attentional modulation, and add support to hypothesis that attention modulation depends on a response normalization mechanism. PMID:20181602
Magnetic field variations in the umbra of single sunspots during their passage across the solar disk
NASA Astrophysics Data System (ADS)
Zagainova, Iu. S.; Fainshtein, V. G.; Obridko, V. N.; Rudenko, G. V.
2016-12-01
Temporal variations of the maximum ( B max) and average (< B>) magnetic inductions, minimum ( α min) and average (< α>) inclination angles of the field lines to the radial direction from the center of the Sun, and areas of the sunspot umbra S in the umbra of single sunspots during their passage across the solar disk are investigated. The variation of the properties of single sunspots has been considered at different stages of their existence, i.e., during formation, the "quiet" period, and the disappearance stage. It has been found that, for the majority of the selected single sunspots, there is a positive correlation between B max and S and between and S defined at different times during the passage of sunspots across the solar disk. It is shown in this case that the nature of the dependence between the parameters α min and B max, α min and S, as well as between < α> and < B>, < α> and S, can vary from sunspot to sunspot, but for many sunspots the inclination angle of the field lines decreases on average with the growth of the sunspot umbra area and the field strength.
The present and future of the most favoured inflationary models after Planck 2015
NASA Astrophysics Data System (ADS)
Escudero, Miguel; Ramírez, Héctor; Boubekeur, Lotfi; Giusarma, Elena; Mena, Olga
2016-02-01
The value of the tensor-to-scalar ratio r in the region allowed by the latest Planck 2015 measurements can be associated to a large variety of inflationary models. We discuss here the potential of future Cosmic Microwave Background cosmological observations in disentangling among the possible theoretical scenarios allowed by our analyses of current Planck temperature and polarization data. Rather than focusing only on r, we focus as well on the running of the primordial power spectrum, αs and the running thereof, βs. If future cosmological measurements, as those from the COrE mission, confirm the current best-fit value for βs gtrsim 10-2 as the preferred one, it will be possible to rule-out the most favoured inflationary models.
Inflationary Dilatonic de Sitter Universe from { N} = 4 Super-Yang Mills Theory Perturbed by Scalars
NASA Astrophysics Data System (ADS)
Hurtado, John Quiroga
In this paper a quantum { N} = 4 super-Yang Mills theory perturbed by dilaton-coupled scalars, is considered. The induced effective action for such a theory is calculated on a dilaton-gravitational background using the conformal anomaly found via AdS/CFT correspondence. Considering such an effective action (using the large N method) as a quantum correction to the classical gravity action with cosmological constant we study the effect from dilaton to the scale factor (which corresponds to the inflationary universe without dilaton). It is shown that, depending on the initial conditions for the dilaton, the dilaton may slow down, or accelerate, the inflation process. At late times, the dilaton is decaying exponentially. At the end of this work, we consider the question how the perturbation of the solution for the scale factor affects the stability of the solution for the equations of motion and therefore the stability of the Inflationary Universe, which could be eternal.
The present and future of the most favoured inflationary models after Planck 2015
Escudero, Miguel; Ramírez, Héctor; Boubekeur, Lotfi; Mena, Olga; Giusarma, Elena E-mail: hector.ramirez@ific.uv.es E-mail: elena.giusarma@roma1.infn.it
2016-02-01
The value of the tensor-to-scalar ratio r in the region allowed by the latest Planck 2015 measurements can be associated to a large variety of inflationary models. We discuss here the potential of future Cosmic Microwave Background cosmological observations in disentangling among the possible theoretical scenarios allowed by our analyses of current Planck temperature and polarization data. Rather than focusing only on r, we focus as well on the running of the primordial power spectrum, α{sub s} and the running thereof, β{sub s}. If future cosmological measurements, as those from the COrE mission, confirm the current best-fit value for β{sub s} ∼> 10{sup −2} as the preferred one, it will be possible to rule-out the most favoured inflationary models.
Can inflationary models of cosmic perturbations evade the secondary oscillation test?
Lewin, Alex; Albrecht, Andreas
2001-07-15
We consider the consequences of an observed cosmic microwave background (CMB) temperature anisotropy spectrum containing no secondary oscillations. While such a spectrum is generally considered to be a robust signature of active structure formation, we show that such a spectrum can be produced by (very unusual) inflationary models or other passive evolution models. However, we show that for all these passive models the characteristic oscillations would show up in other observable spectra. Our work shows that when CMB polarization and matter power spectra are taken into account secondary oscillations are indeed a signature of even these very exotic passive models. We construct a measure of the observability of secondary oscillations in a given experiment, and show that even with foregrounds both the MAP and Planck satellites should be able to distinguish between models with and without oscillations. Thus we conclude that inflationary and other passive models cannot evade the secondary oscillation test.
Revisiting a pre-inflationary radiation era and its effect on the CMB power spectrum
Das, Suratna; Goswami, Gaurav; Rangarajan, Raghavan; Prasad, Jayanti E-mail: gaugo@prl.res.in E-mail: raghavan@prl.res.in
2015-06-01
We revisit the scenario where inflation is preceded by a radiation era by considering that the inflaton too could have been in thermal equilibrium early in the radiation era. Hence we take into account not only the effect of a pre-inflationary era on the inflaton mode functions but also that of a frozen thermal distribution of inflaton quanta. We initially discuss in detail the issues relevant to our scenario of a pre-inflationary radiation dominated era and then obtain the scalar power spectrum for this scenario. We find that the power spectrum is free from infrared divergences. We then use the WMAP and Planck data to determine the constraints on the inflaton comoving 'temperature' and on the duration of inflation. We find that the best fit value of the duration of inflation is less than 1 e-folding more than what is required to solve cosmological problems, while only an upper bound on the inflaton temperature can be obtained.
NASA Technical Reports Server (NTRS)
Yokoyama, Jun'ichi; Suto, Yasushi
1991-01-01
A phenomenological model to produce isocurvature baryon-number fluctuations is proposed in the framework of inflationary cosmology. The resulting spectrum of density fluctuation is very different from the conventional Harrison-Zel'dovich shape. The model, with the parameters satisfying several requirements from particle physics and cosmology, provides an appropriate initial condition for the minimal baryon isocurvature scenario of galaxy formation discussed by Peebles.
NASA Technical Reports Server (NTRS)
Yokoyama, Jun'ichi; Suto, Yasushi
1991-01-01
A phenomenological model to produce isocurvature baryon-number fluctuations is proposed in the framework of inflationary cosmology. The resulting spectrum of density fluctuation is very different from the conventional Harrison-Zel'dovich shape. The model, with the parameters satisfying several requirements from particle physics and cosmology, provides an appropriate initial condition for the minimal baryon isocurvature scenario of galaxy formation discussed by Peebles.
Quantitative 3D electromagnetic field determination of 1D nanostructures from single projection
Phatak, C.; Knoop, L. de; Houdellier, F.; ...
2016-05-01
One-dimensional (1D) nanostructures have been regarded as the most promising building blocks for nanoelectronics and nanocomposite material systems as well as for alternative energy applications. Although they result in confinement of a material, their properties and interactions with other nanostructures are still very much three-dimensional (3D) in nature. In this work, we present a novel method for quantitative determination of the 3D electromagnetic fields in and around 1D nanostructures using a single electron wave phase image, thereby eliminating the cumbersome acquisition of tomographic data. Using symmetry arguments, we have reconstructed the 3D magnetic field of a nickel nanowire as wellmore » as the 3D electric field around a carbon nanotube field emitter, from one single projection. The accuracy of quantitative values determined here is shown to be a better fit to the physics at play than the value obtained by conventional analysis. Moreover the 3D reconstructions can then directly be visualized and used in the design of functional 3D architectures built using 1D nanostructures.« less
Quantitative 3D electromagnetic field determination of 1D nanostructures from single projection
Phatak, C.; Knoop, L. de; Houdellier, F.; Gatel, C.; Hÿtch, M. J.; Masseboeuf, A.
2016-05-01
One-dimensional (1D) nanostructures have been regarded as the most promising building blocks for nanoelectronics and nanocomposite material systems as well as for alternative energy applications. Although they result in confinement of a material, their properties and interactions with other nanostructures are still very much three-dimensional (3D) in nature. In this work, we present a novel method for quantitative determination of the 3D electromagnetic fields in and around 1D nanostructures using a single electron wave phase image, thereby eliminating the cumbersome acquisition of tomographic data. Using symmetry arguments, we have reconstructed the 3D magnetic field of a nickel nanowire as well as the 3D electric field around a carbon nanotube field emitter, from one single projection. The accuracy of quantitative values determined here is shown to be a better fit to the physics at play than the value obtained by conventional analysis. Moreover the 3D reconstructions can then directly be visualized and used in the design of functional 3D architectures built using 1D nanostructures.
Noise in single-wall carbon nanotubes under high electric field stress
NASA Astrophysics Data System (ADS)
Richter, Curt; Jurchescu, Oana; Liang, Xuelei; Gundlach, David; Liao, Albert; Pop, Eric
2010-03-01
We characterized the noise properties of field effect transistors made from individual semiconducting single-walled carbon nanotubes (CNTs) under high electric field stress to probe scattering mechanisms during avalanche and self-heating conditions. Single-walled CNTs were grown from patterned Fe catalyst by CVD on oxidized p-doped Si wafers which serve as a back gate. Pd source/drain (S/D) contacts were used to form devices ranging in length from 1 μm to 4μm. 1/ f noise measured at room temperature in air shows conventional changes in amplitude as a function of gate voltage and low S/D voltages. As the S/D bias on the CNTs increases, we observe an unexpected increase in noise at 3 V. This change occurs at fields and voltages below those necessary to induce avalanche generation of free electrons and holes. Thermal modeling reveals that the average temperature of the CNTs reaches 370 K when the noise behavior increases, which is consistent with oxygen desorption. Thus, our measurements and modeling provide insight into noise at high field in CNTs, uncovering the role of changes in doping and threshold voltage at high operating temperature.
Quantitative 3D electromagnetic field determination of 1D nanostructures from single projection
Phatak, C.; Knoop, L. de; Houdellier, F.; Gatel, C.; Hÿtch, M. J.; Masseboeuf, A.
2016-05-01
One-dimensional (1D) nanostructures have been regarded as the most promising building blocks for nanoelectronics and nanocomposite material systems as well as for alternative energy applications. Although they result in confinement of a material, their properties and interactions with other nanostructures are still very much three-dimensional (3D) in nature. In this work, we present a novel method for quantitative determination of the 3D electromagnetic fields in and around 1D nanostructures using a single electron wave phase image, thereby eliminating the cumbersome acquisition of tomographic data. Using symmetry arguments, we have reconstructed the 3D magnetic field of a nickel nanowire as well as the 3D electric field around a carbon nanotube field emitter, from one single projection. The accuracy of quantitative values determined here is shown to be a better fit to the physics at play than the value obtained by conventional analysis. Moreover the 3D reconstructions can then directly be visualized and used in the design of functional 3D architectures built using 1D nanostructures.
Zhang, Liang; Balzano, Leandro; Resasco, Daniel E
2005-08-04
Field emission studies were conducted on as-produced CoMoCAT single-walled carbon nanotube/silica composites with controlled nanotube diameter and bundle size. It has been observed that the as-produced nanotube material does not need to be separated from the high-surface area catalyst to be an effective electron emitter. By adjusting the catalytic synthesis conditions, single-walled carbon nanotubes (SWNT) of different diameters and bundle sizes were synthesized. A detailed characterization involving Raman spectroscopy, optical absorption (vis-NIR), SEM, and TEM was conducted to identify the nanotube species present in the different samples. The synthesis reaction temperature was found to affect the nanotube diameter and bundle size in opposite ways; that is, as the synthesis temperature increased the nanotube average diameter became larger, but the bundle size became smaller. A gradual and consistent reduction in the emission onset field was observed as the synthesis temperature increased. It is suggested that the bundle size, more than the nanotube diameter or chirality, determines the field emission characteristics of these composites. This is a clear demonstration that field emission characteristics of SWNT can be controlled by the nanotube synthesis conditions.
NASA Astrophysics Data System (ADS)
Kumar, Avshish; Khan, Sunny; Zulfequar, M.; Harsh; Husain, Mushahid
2017-04-01
In this work, high-quality graphene has successfully been synthesized on copper (Cu) coated Silicon (Si) substrate at very large-area by plasma enhanced chemical vapor deposition system. This method is low cost and highly effective for synthesizing graphene relatively at low temperature of 600 °C. Electron microscopy images have shown that surface morphology of the grown samples is quite uniform consisting of single layered graphene (SLG) to few layered graphene (FLG). Raman spectra reveal that graphene has been grown with high-quality having negligible defects and the observation of G and G' peaks is also an indicative of stokes phonon energy shift caused due to laser excitation. Scanning probe microscopy image also depicts the synthesis of single to few layered graphene. The field emission characteristics of as-grown graphene samples were studied in a planar diode configuration at room temperature. The graphene samples were observed to be a good field emitter having low turn-on field, higher field amplification factor and long term emission current stability.
Anomalous Kondo transport in a single-electron transistor driven by microwave field
NASA Astrophysics Data System (ADS)
Cao, Zhan; Chen, Cheng; Chen, Fu-Zhou; Luo, Hong-Gang
2014-03-01
The Kondo transport in a single-electron transistor continues to provide unexpected physics due to the interplay between magnetic field and microwave applied, as shown in a recent experiment(B. Hemingway et al., arXiv:1304.0037). For a given microwave frequency, the Kondo differential conductance shows an anomalous magnetic field dependence, and a very sharp peak is observed for certain field applied. Additionally, the microwave frequency is found to be larger of about one order than the corresponding Zeeman energy. These two features are not understood in the current theory. Here we propose a phenomenological mechanism to explain these observations. When both magnetic field and microwave are applied in the SET, if the frequency matches the (renormalized) Zeeman energy, it is assumed that the microwave is able to induce spin-ip in the single-electron transistor, which leads to two consequences. One is the dot level shifts down and the other is the renormalization of the Zeeman energy. This picture can not only explain qualitatively the main findings in the experiment but also further stimulate the related experimental study of the Kondo transport. Additional microwave modulation may provide a novel way to explore the functional of the SET in nanotechnology and quantum information processing.
Enhanced electrocaloric cooling in ferroelectric single crystals by electric field reversal
NASA Astrophysics Data System (ADS)
Ma, Yang-Bin; Novak, Nikola; Koruza, Jurij; Yang, Tongqing; Albe, Karsten; Xu, Bai-Xiang
2016-09-01
An improved thermodynamic cycle is validated in ferroelectric single crystals, where the cooling effect of an electrocaloric refrigerant is enhanced by applying a reversed electric field. In contrast to the conventional adiabatic heating or cooling by on-off cycles of the external electric field, applying a reversed field is significantly improving the cooling efficiency, since the variation in configurational entropy is increased. By comparing results from computer simulations using Monte Carlo algorithms and experiments using direct electrocaloric measurements, we show that the electrocaloric cooling efficiency can be enhanced by more than 20% in standard ferroelectrics and also relaxor ferroelectrics, like Pb (Mg1 /3 /Nb2 /3)0.71Ti0.29O3 .
Fabrication and characterization of single-grain organic field-effect transistor of pentacene
NASA Astrophysics Data System (ADS)
Minari, Takeo; Nemoto, Takashi; Isoda, Seiji
2004-07-01
A single-grain pentacene field-effect transistor with ordinary top-contact structure is fabricated, and its electrical properties are characterized at various temperatures. The device exhibits field-effect mobility as high as 2 cm2/V s at 300 K, although mobility is dependent on gate voltage. This value for field-effect mobility is about one order of magnitude higher than that of a polycrystalline device made from the same pentacene film. The activation energy obtained from an Arrhenius plot of mobility is nearly constant with varying gate voltage, whereas the activation energy of the polycrystalline device decreases as gate voltage increases. Such behavior of the activation energy suggests that intrinsic carrier transport in an organic grain can be described by thermally activated hopping of molecular polarons while extrinsic transport across grain boundaries can be described by the trap model.
Effective realization of random magnetic fields in compounds with large single-ion anisotropy
NASA Astrophysics Data System (ADS)
Herbrych, J.; Kokalj, J.
2017-03-01
We show that spin S =1 system with large and random single-ion anisotropy can be at low energies mapped to a S =1 /2 system with random magnetic fields. This is, for example, realized in Ni (Cl1 -xBrx)2-4 SC (NH2)2 compound (DTNX) and therefore it represents a long-sought realization of random local (on-site) magnetic fields in antiferromagnetic systems. We support the mapping by numerical study of S =1 and effective S =1 /2 anisotropic Heisenberg chains and find excellent agreement for static quantities and also for the spin conductivity. Such systems can therefore be used to study the effects of local random magnetic fields on transport properties.
Optical wide field monitor AROMA-W using multiple digital single-lens reflex cameras
NASA Astrophysics Data System (ADS)
Takahashi, Ichiro; Tsunashima, Kosuke; Tatsuhito, Takeda; Saori, Ono; Kazutaka, Yamaoka; Yoshida, Atsumasa
2010-12-01
We have developed and operated the automatic optical observation device Aoyama Gakuin University Robotic Optical Monitor for Astrophysical objects - Wide field (AROMA-W). It covers a large field of view of about 45 degrees W 30 degrees at a time by the multiple digital single-lens reflex cameras, and provides photometric data in four bands with a limiting V magnitude of about 12-13 magnitude (20 seconds, 3 sigma level). The automatic analysis pipeline which can analyze in parallel with observation has been constructed so far. It can draw the light curves of all stars in the field of view of AROMA-W. We are aiming at the simultaneous observation of the transients (e.g., X-ray nova, Supernova, GRB) that MAXI discovered by using the AROMA-W. We report the developmental status, the observational results of AROMA-W and a possibility of the simultaneous observation to the X-ray transients discovered with MAXI.
Yan, Shihai; Lee, Jin Yong; Hahn, Jae Ryang
2008-04-17
A low-temperature scanning tunneling microscope (STM) and ab initio calculations were used to study the electric field effect on the vibration of single CO molecules in an STM junction at 13 K. The vibrational energy of CO molecules adsorbed on silver atoms, measured by STM-based inelastic electron tunneling spectroscopy, depends on the direction of the electric field applied between the STM tip and the silver species. This characteristic can be explained by the charge separation model. The electric field modifies the binding characteristics of CO on silver as a result of a change in the charged states of the species, which leads to an increase (or a decrease) of the energies of the hindered rotation and the CO stretch on silver.
NASA Astrophysics Data System (ADS)
Fujieda, Tadashi; Okai, Makoto; Tokumoto, Hiroshi
2008-04-01
We investigated the dependence of tip radius on the field emission energy spread of electrons emitted from clean single pentagons in individual multi-walled carbon nanotubes (MWNTs) in a wide range of total emission currents (10-2000 nA). We found that the full width at half maximum of the field emission energy distribution decreases in inverse proportion to the involution of the radius of curvature at a constant total emission current. This is because as the radius of curvature increases, the space between adjoining pentagons becomes wider, and therefore the stochastic Coulomb interactions between electrons emitted from adjoining pentagons become weaker. The full widths at half maximum of the field emission energy distributions of MWNTs with tip radii of 1.8-45.0 nm were 0.38-0.60 eV at a total emission current of 2000 nA.
NASA Astrophysics Data System (ADS)
Jung, Myung-Sup; Ko, Young Koan; Jung, Dae-Hwan; Choi, Do Hwan; Jung, Hee-Tae; Heo, Jung Na; Sohn, Byung Hee; Jin, Yong Wan; Kim, Jongmin
2005-07-01
Well-defined and high-density single-walled carbon nanotube (SWNT) patterns were fabricated using a combination of photolithographic and chemical assembling processes. Unlike the patterned SWNT arrays reported thus far, these SWNT patterned layers have high-density multilayer structures and excellent surface adhesion due to their direct chemical bonding to their substrates, which results in high electrical conductivity. We found that the high-density multilayer SWNT patterns emit electrons under an applied electrical field. The electrical resistivities of the SWNT layers were found to be 5-10Ωcm, with a turn-on electric field of about 3V/μm at an emission current density of 10μA/cm2. This technique for fabricating SWNT patterns can be used in the production of field-emission displays and in future device integration requiring carbon nanotubes (CNTs), because it provides large-area patterning of SWNTs with high stability and uniformity.
Growth of carbon nanotube field emitters on single strand carbon fiber: a linear electron source
NASA Astrophysics Data System (ADS)
Kim, Ha Jin; Jong Bae, Min; Kim, Yong C.; Cho, Eun S.; Sohn, Y. C.; Kim, D. Y.; Lee, S. E.; Kang, H. S.; Han, In T.; Kim, Young H.; Patole, Shashikant P.; Yoo, Ji Beom
2011-03-01
The multi-stage effect has been revisited through growing carbon nanotube field emitters on single strand carbon fiber with a thickness of 11 µm. A prepared linear electron source exhibits a turn-on field as low as 0.4 V µm - 1 and an extremely high field enhancement factor of 19 300, when compared with those results from reference nanotube emitters grown on flat silicone wafer; 3.0 V µm - 1 and 2500, respectively. In addition, we introduce a novel method to grow nanotubes uniformly around the circumference of carbon fibers by using direct resistive heating on the continuously feeding carbon threads. These results open up not only a new path for synthesizing nanocomposites, but also offer an excellent linear electron source for special applications such as backlight units for liquid crystal displays and multi-array x-ray sources.
Electric field dependence of photoluminescence from individual single-walled carbon nanotubes
NASA Astrophysics Data System (ADS)
Yasukochi, S.; Murai, T.; Shimada, T.; Chiashi, S.; Maruyama, S.; Kato, Y. K.
2011-03-01
Using suspended single-walled carbon nanotubes, we investigate electric field effects on photoluminescence. Trenches are fabricated on Si O2 /Si substrates, and Pt is deposited for electrical contacts. Carbon nanotubes are grown by patterned chemical vapor deposition. These devices operate as back-gate field effect transistors, allowing application of electric fields on as-grown ultraclean nanotubes. Individual suspended carbon nanotubes are identified by taking photoluminescence images using a home-built laser-scanning confocal microscope. After determining the chirality by photoluminescence excitation spectra, we measure gate voltage dependence of photoluminescence. We observe quenching of photoluminescence intensity and shifts of emission wavelength as gate voltages are applied. This work is supported by KAKENHI, Mizuho Foundation for the Promotion of Sciences, Research Foundation for Opto-Science and Technology, TEPCO Research Foundation, SCAT, SCOPE, and Photon Frontier Network Program of MEXT, Japan.
Core magnetic field enhancement in single X line, multiple X line and patchy reconnection
NASA Technical Reports Server (NTRS)
Ma, Z. W.; Otto, A.; Lee, L. C.
1994-01-01
Magnetic flux transfer events often show a significant increase of the magnetic field strength at the center of the events. Similar magnetic field observations have been reported for structures in or near the plasma sheet of the magnetotail at about 20 R(sub E). We have carried out two-dimensional (2D) and three-dimensional (3D) and simulations of single X line reconnection (SXR), multiple X line reconnection (MXR), and patchy reconnection to determine and compare the amplification of the magnetic field in the center of the developing flux tubes. The various processes are achieved by appropriate choices of 2D or 3D resistivity models. The simulations show that the increase in magnetic field strength depends on both the property of the initial configuration and the particular reconnection geometry. For the chosen initial conditions the MXR process leads to a larger increase in the core magnetic field than the patchy reconnection and SXR caused by larger magnetic tensions in the MXR process. The 3D processes always lead to a larger amplification than the corresponding 2D processes. In the 3D cases, force imbalance in the y direction will accelerate plasma out of the flux tube. This process reduces the thermal pressure and leads to a further compression of the flux rope, which yields an additional increase in the interior magnetic field strength.
Anisotropic physical properties of single-crystal U2Rh2Sn in high magnetic fields
NASA Astrophysics Data System (ADS)
Prokeš, K.; Gorbunov, D. I.; Reehuis, M.; Klemke, B.; Gukasov, A.; Uhlířová, K.; Fabrèges, X.; Skourski, Y.; Yokaichiya, F.; Hartwig, S.; Andreev, A. V.
2017-05-01
We report on the crystal and magnetic structures, magnetic, transport, and thermal properties of U2Rh2Sn single crystals studied in part in high magnetic fields up to 58 T. The material adopts a U3Si2 -related tetragonal crystal structure and orders antiferromagnetically below TN=25 K. The antiferromagnetic structure is characterized by a propagation vector k =(00 1/2 ) . The magnetism in U2Rh2Sn is found to be associated mainly with 5 f states. However, both unpolarized and polarized neutron experiments reveal at low temperatures in zero field non-negligible magnetic moments also on Rh sites. U moments of 0.50(2) μB are directed along the tetragonal axis while Rh moments of 0.06(4) μB form a noncollinear arrangement confined to the basal plane. The response to applied magnetic field is highly anisotropic. Above ˜15 K the easy magnetization direction is along the tetragonal axis. At lower temperatures, however, a stronger response is found perpendicular to the c axis. While for the a axis no magnetic phase transition is observed up to 58 T, for the field applied at 1.8 K along the tetragonal axis we observe above 22.5 T a field-polarized state. A magnetic phase diagram for the field applied along the c axis is presented.
High field magneto-optical spectroscopy of semiconducting single-walled carbon nanotubes
NASA Astrophysics Data System (ADS)
Shaver, Jonah
Single-walled carbon nanotubes (SWNTs) present an ideal system for study of one dimensional physics. Classically speaking, their long persistence lengths, i.e. the length over which they do not bend, result in rigid-rod-like behavior in the solution-phase. Quantum mechanically speaking, extreme confinement in the radial direction result in interesting properties for optically excited correlated electron-hole pairs, or excitons. In addition, their hollow crystalline structure presents a controllable way to modify the circumferential boundary conditions on their electronic wavefunctions resulting in changes to the electronic band structure via threading a magnetic field through the diameter. An applied magnetic field also aligns SWNTs due to their magnetic susceptibility anisotropy. We have measured the dynamic alignment properties of single-walled carbon nanotube (SWNT) suspensions in pulsed high magnetic fields through linear dichroism spectroscopy. Millisecond-duration pulsed high magnetic fields up to 55 T as well as microsecond-duration pulsed ultrahigh magnetic fields up to 166 T were used. Due to their anisotropic magnetic properties, SWNTs align in an applied magnetic field, and due to their anisotropic optical properties, aligned SWNTs show linear dichroism. The characteristics of their overall alignment depend on several factors, including the viscosity and temperature of the suspending solvent, the degree of anisotropy of nanotube magnetic susceptibilities, the nanotube length distribution, the degree of nanotube bundling, and the strength and duration of the applied magnetic field. In order to explain our data, we have developed a theoretical model based on the time-dependent Smoluchowski equation for rigid rods that accurately reproduces the salient features of the experimental data. We have also investigated excitons in SWNTs in stretch aligned polyacrylic acid films, direction of stretch (n̂), through optical spectroscopy at low temperature (1.5 K
Implications of Planck2015 for inflationary, ekpyrotic and anamorphic bouncing cosmologies
NASA Astrophysics Data System (ADS)
Ijjas, Anna; Steinhardt, Paul J.
2016-02-01
The results from Planck2015, when combined with earlier observations from the Wilkinson Microwave Anisotropy Probe, Atacama Cosmology Telescope, South Pole Telescope and other experiments, were the first observations to disfavor the ‘classic’ inflationary paradigm. To satisfy the observational constraints, inflationary theorists have been forced to consider plateau-like inflaton potentials that introduce more parameters and more fine-tuning, problematic initial conditions, multiverse-unpredictability issues, and a new ‘unlikeliness problem’. Some propose turning instead to a ‘postmodern’ inflationary paradigm in which the cosmological properties in our observable Universe are only locally valid and set randomly, with completely different properties (and perhaps even different physical laws) existing in most regions outside our horizon. By contrast, the new results are consistent with the simplest versions of ekpyrotic cyclic models in which the Universe is smoothed and flattened during a period of slow contraction followed by a bounce, and another promising bouncing theory, anamorphic cosmology, has been proposed that can produce distinctive predictions.
Testing predictions of the quantum landscape multiverse 2: the exponential inflationary potential
NASA Astrophysics Data System (ADS)
Di Valentino, Eleonora; Mersini-Houghton, Laura
2017-03-01
The 2015 Planck data release tightened the region of the allowed inflationary models. Inflationary models with convex potentials have now been ruled out since they produce a large tensor to scalar ratio. Meanwhile the same data offers interesting hints on possible deviations from the standard picture of CMB perturbations. Here we revisit the predictions of the theory of the origin of the universe from the landscape multiverse for the case of exponential inflation, for two reasons: firstly to check the status of the anomalies associated with this theory, in the light of the recent Planck data; secondly, to search for a counterexample whereby new physics modifications may bring convex inflationary potentials, thought to have been ruled out, back into the region of potentials allowed by data. Using the exponential inflation as an example of convex potentials, we find that the answer to both tests is positive: modifications to the perturbation spectrum and to the Newtonian potential of the universe originating from the quantum entanglement, bring the exponential potential, back within the allowed region of current data; and, the series of anomalies previously predicted in this theory, is still in good agreement with current data. Hence our finding for this convex potential comes at the price of allowing for additional thermal relic particles, equivalently dark radiation, in the early universe.
Thermal gravitational-wave background in the general pre-inflationary scenario
NASA Astrophysics Data System (ADS)
Wang, Kai; Santos, Larissa; Xia, Jun-Qing; Zhao, Wen
2017-01-01
We investigate the primordial gravitational waves (PGWs) in the general scenario where the inflation is preceded by a pre-inflationary stage with the effective equation of state w. Comparing with the results in the usual inflationary models, the power spectrum of PGWs is modified in two aspects: one is the mixture of the perturbation modes caused by he presence of the pre-inflationary period, and the other is the thermal initial state formed at the Planck era of the early Universe. By investigating the observational imprints of these modifications on the B-mode polarization of cosmic microwave background (CMB) radiation, we obtain the constraints on the conformal temperature of the thermal gravitational-wave background T<5.01× 10‑4 Mpc‑1 and a tensor-to-scalar ratio r<0.084 (95% confident level), which follows the bounds on total number of e-folds N>63.5 for the model with w=1/3, and N>65.7 for that with w=1. By taking into account various noises and the foreground radiations, we forecast the detection possibility of the thermal gravitational-wave background by the future CMBPol mission, and find that if r>0.01, the detection is possible as long as T>1.5× 10‑4 Mpc‑1. However, the effect of different w is quite small, and it seems impossible to determine its value from the potential observations of CMBPol mission.
NASA Astrophysics Data System (ADS)
Vernick, Sefi; Trocchia, Scott M.; Warren, Steven B.; Young, Erik F.; Bouilly, Delphine; Gonzalez, Ruben L.; Nuckolls, Colin; Shepard, Kenneth L.
2017-05-01
The study of biomolecular interactions at the single-molecule level holds great potential for both basic science and biotechnology applications. Single-molecule studies often rely on fluorescence-based reporting, with signal levels limited by photon emission from single optical reporters. The point-functionalized carbon nanotube transistor, known as the single-molecule field-effect transistor, is a bioelectronics alternative based on intrinsic molecular charge that offers significantly higher signal levels for detection. Such devices are effective for characterizing DNA hybridization kinetics and thermodynamics and enabling emerging applications in genomic identification. In this work, we show that hybridization kinetics can be directly controlled by electrostatic bias applied between the device and the surrounding electrolyte. We perform the first single-molecule experiments demonstrating the use of electrostatics to control molecular binding. Using bias as a proxy for temperature, we demonstrate the feasibility of detecting various concentrations of 20-nt target sequences from the Ebolavirus nucleoprotein gene in a constant-temperature environment.
Electric field modulation of thermovoltage in single-layer MoS{sub 2}
Dobusch, Lukas; Furchi, Marco M.; Pospischil, Andreas; Mueller, Thomas; Bertagnolli, Emmerich; Lugstein, Alois
2014-12-22
We study electric field modulation of the thermovoltage in single-layer MoS{sub 2}. The Seebeck coefficient generally increases for a diminishing free carrier concentration, and in the case of single-layer MoS{sub 2} reaches considerable large values of about S = −5160 μV/K at a resistivity of 490 Ω m. Further, we observe time dependent degradation of the conductivity in single layer MoS{sub 2}, resulting in variations of the Seebeck coefficient. The degradation is attributable to adsorbates from ambient air, acting as p-dopants and additional Coulomb potentials, resulting in carrier scattering increase, and thus decrease of the electron mobility. The corresponding power factors remain at moderate levels, due to the low conductivity of single layer MoS{sub 2}. However, as single-layer MoS{sub 2} has a short intrinsic phonon mean free path, resulting in low thermal conductivity, MoS{sub 2} holds great promise as high-performance 2D thermoelectric material.
Houshyari, Mohammad; Kashi, Amir Shahram Yousefi; Varaki, Sakineh Soleimani; Rakhsha, Afshin; Blookat, Eftekhar Rajab
2015-01-01
Background: The treatment of lymph nodes engaged in breast cancer with radiotherapy leads to improved locoregional control and enhanced survival rates in patients after surgery. The aim of this study was to compare two treatment techniques, namely single anterior posterior (AP) supraclavicular field with plan depth and two anterior and posterior opposed (AP/PA) supraclavicular fields. In the study, we also examined the relationships between the depth of supraclavicular lymph nodes (SCLNs) and the diameter of the wall of the chest and body mass index (BMI). Methods: Forty patients with breast cancer were analyzed using computed tomography (CT) scans. In planning target volume (PTV), the SCLNs and axillary lymph nodes (AXLNs) were contoured, and, with the attention to PTV, supraclavicular (SC) depth was measured. The dosage that reached the aforementioned lymph nodes and the level of hot spots were investigated using two treatment methods, i.e., 1) AP/PA and 2) AP with three-dimensional (3D) planning. Each of these methods was analyzed using the program Isogray for the 6 MV compact accelerator, and the diameter of the wall of the chest was measured using the CT scan at the center of the SC field. Results: Placing the plan such that 95% of the target volume with 95% or greater of the prescribed dose of 50 Gy (V95) had ≥95% concordance in both treatment techniques. According to the PTV, the depth of SCLNs and the diameter of the wall of the chest were 3–7 and 12–21cm, respectively. Regression analysis showed that the mean SC depth (the mean Plan depth) and the mean diameter of the wall of the chest were related directly to BMI (p<0.0001, adjusted R2=0.67) and (p<0.0001, adjusted R2=0.71), respectively. Conclusion: The AP/PA treatment technique was a more suitable choice of treatment than the AP field, especially for overweight and obese breast cancer patients. However, in the AP/PA technique, the use of a single-photon, low energy (6 MV) caused more hot spots
Houshyari, Mohammad; Kashi, Amir Shahram Yousefi; Varaki, Sakineh Soleimani; Rakhsha, Afshin; Blookat, Eftekhar Rajab
2015-01-01
The treatment of lymph nodes engaged in breast cancer with radiotherapy leads to improved locoregional control and enhanced survival rates in patients after surgery. The aim of this study was to compare two treatment techniques, namely single anterior posterior (AP) supraclavicular field with plan depth and two anterior and posterior opposed (AP/PA) supraclavicular fields. In the study, we also examined the relationships between the depth of supraclavicular lymph nodes (SCLNs) and the diameter of the wall of the chest and body mass index (BMI). Forty patients with breast cancer were analyzed using computed tomography (CT) scans. In planning target volume (PTV), the SCLNs and axillary lymph nodes (AXLNs) were contoured, and, with the attention to PTV, supraclavicular (SC) depth was measured. The dosage that reached the aforementioned lymph nodes and the level of hot spots were investigated using two treatment methods, i.e., 1) AP/PA and 2) AP with three-dimensional (3D) planning. Each of these methods was analyzed using the program Isogray for the 6 MV compact accelerator, and the diameter of the wall of the chest was measured using the CT scan at the center of the SC field. Placing the plan such that 95% of the target volume with 95% or greater of the prescribed dose of 50 Gy (V95) had ≥95% concordance in both treatment techniques. According to the PTV, the depth of SCLNs and the diameter of the wall of the chest were 3-7 and 12-21cm, respectively. Regression analysis showed that the mean SC depth (the mean Plan depth) and the mean diameter of the wall of the chest were related directly to BMI (p<0.0001, adjusted R(2)=0.67) and (p<0.0001, adjusted R(2)=0.71), respectively. The AP/PA treatment technique was a more suitable choice of treatment than the AP field, especially for overweight and obese breast cancer patients. However, in the AP/PA technique, the use of a single-photon, low energy (6 MV) caused more hot spots than usual.
Warm inflation in presence of magnetic fields
Piccinelli, Gabriella; Ayala, Alejandro; Mizher, Ana Julia
2013-07-23
We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales which rises de possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger's proper time method.
Charting an Inflationary Landscape with Random Matrix Theory
Marsh, M.C. David; McAllister, Liam; Pajer, Enrico; Wrase, Timm E-mail: mcallister@cornell.edu E-mail: timm.wrase@stanford.edu
2013-11-01
We construct a class of random potentials for N >> 1 scalar fields using non-equilibrium random matrix theory, and then characterize multifield inflation in this setting. By stipulating that the Hessian matrices in adjacent coordinate patches are related by Dyson Brownian motion, we define the potential in the vicinity of a trajectory. This method remains computationally efficient at large N, permitting us to study much larger systems than has been possible with other constructions. We illustrate the utility of our approach with a numerical study of inflation in systems with up to 100 coupled scalar fields. A significant finding is that eigenvalue repulsion sharply reduces the duration of inflation near a critical point of the potential: even if the curvature of the potential is fine-tuned to be small at the critical point, small cross-couplings in the Hessian cause the curvature to grow in the neighborhood of the critical point.
Precision single mode fibre integral field spectroscopy with the RHEA spectrograph
NASA Astrophysics Data System (ADS)
Rains, Adam D.; Ireland, Michael J.; Jovanovic, Nemanja; Feger, Tobias; Bento, Joao; Schwab, Christian; Coutts, David W.; Guyon, Olivier; Arriola, Alexander; Gross, Simon
2016-08-01
The RHEA Spectrograph is a single-mode echelle spectrograph designed to be a replicable and cost effective method of undertaking precision radial velocity measurements. Two versions of RHEA currently exist, one located at the Australian National University in Canberra, Australia (450 - 600nm wavelength range), and another located at the Subaru Telescope in Hawaii, USA (600 - 800 nm wavelength range). Both instruments have a novel fibre feed consisting of an integral field unit injecting light into a 2D grid of single mode fibres. This grid of fibres is then reformatted into a 1D array at the input of the spectrograph (consisting of the science fibres and a reference fibre capable of receiving a white-light or xenon reference source for simultaneous calibration). The use of single mode fibres frees RHEA from the issue of modal noise and significantly reduces the size of the optics used. In addition to increasing the overall light throughput of the system, the integral field unit allows for cutting edge science goals to be achieved when operating behind the 8.2m Subaru Telescope and the SCExAO adaptive optics system. These include, but are not limited to: resolved stellar photospheres; resolved protoplanetary disk structures; resolved Mira shocks, dust and winds; and sub-arcsecond companions. We present details and results of early tests of RHEA@Subaru and progress towards the stated science goals.
NASA Astrophysics Data System (ADS)
Hermann, Regina; Uhlemann, Margitta; Wendrock, Horst; Gerbeth, Gunter; Büchner, Bernd
2011-03-01
The aim of this work is growth and characterisation of Ti55Nb45 (wt%) single crystals by floating-zone single crystal growth of intermetallic compounds using two-phase radio-frequency (RF) electromagnetic heating. Thereby, the process and, in particular, the flow field in the molten zone is influenced by additional magnetic fields. The growth of massive intermetallic single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. It is generally known that the crystallization process stability is enhanced if the crystallization interface is convex. For this, a tailored magnetic two-phase stirrer system has been developed, which enables a controlled influence on the melt ranging from intensive inwards to outwards flows. Since Ti is favourably light, strong and biocompatible, it is one of the few materials that naturally match the requirements for implantation in the human body. Therefore, the magnetic system was applied to crystal growth of Ti alloys. The grown crystals were oriented and cut to cubes with the desired crystallographic orientations [1 0 0] and [1 0 1] normally on a plane. The electron backscatter diffraction (EBSD) technique was applied to clearly determine crystal orientation and to localize grain boundaries. The formation of oxidic nanotubes on Ti surfaces in dependence of the grain orientation was investigated, performed electrochemically by anodic oxidation from fluoride containing electrolyte.
Phase-field modeling on morphological landscape of isotactic polystyrene single crystals.
Xu, Haijun; Matkar, Rushikesh; Kyu, Thein
2005-07-01
Spatio-temporal growth of isotactic polystyrene single crystals during isothermal crystallization has been investigated theoretically based on the phase field model by solving temporal evolution of a nonconserved phase order parameter coupled with a heat conduction equation. In the description of the total free energy, an asymmetric double-well local free energy density has been adopted to represent the metastable melt and the stable solid crystal. Unlike the small molecule systems, polymer crystallization rarely reaches thermodynamic equilibrium; most polymer crystals are kinetically stabilized in some metastable states. To capture various metastable polymer crystals, the phase field crystal order parameter at the solidification potential has been treated to be supercooling dependent such that it can assume an intermediate value between zero (melt) and unity (perfect crystal), reflecting imperfect polycrystalline nature of polymer crystals. Two-dimensional simulations exhibit various single crystal morphologies of isotactic polystyrene crystals such as faceted hexagonal patterns transforming to nonfaceted snowflakes with increasing supercooling. Of particular interest is that heat liberation from the crystallizing front influences the curvature of the crystal-melt interface, leading to directional growth of lamellar tips and side branches. The landscape of these morphological textures has been established as a function of anisotropy of surface energy and supercooling. With increasing supercooling and decreasing anisotropy, the hexagonal single crystal transforms to the dense lamellar branching morphology in conformity with the experimental findings.
Transport studies of quantum dots sensitized single Mn-ZnO nanowire field effect transistors
NASA Astrophysics Data System (ADS)
Sapkota, Keshab R.; Maloney, Francis Scott; Rimal, Gaurab; Poudyal, Uma; Tang, Jinke; Wang, Wenyong
We present opto-electrical transport properties of Mn-CdSe quantum dots (QDs) sensitized single Mn-ZnO nanowire (NW) field effect transistors (FET). The ZnO NWs with 2 atomic % of Mn doping are grown by chemical vapor deposition. The NWs are ferromagnetic at low temperature. The as grown nanowires are transferred to clean SiO2/Si substrate and single nanowire field effect transistors (FET) are fabricated by standard e-beam lithography. Mobility and carrier concentration of Mn-ZnO NWs are estimated from FET device measurement which shows NWs are n-type semiconductors. Pulse laser deposition of Mn-CdSe QDs on the single NW FET significantly increases carrier concentration of the QD-NW system in dark where the QD monolayer conduction is negligibly small. The photoconductivity study of QD sensitized NW FET enlightens the conduction spectrum of QD-NW system and QD to NW carrier transfer mechanism. This work has been supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-FG02-10ER46728.
Blumrosen, Gadi; Abazari, Alireza; Golberg, Alexander; Yarmush, Martin L.; Toner, Mehmet
2017-01-01
The design of effective electroporation protocols for molecular delivery applications requires the determination of transport parameters including diffusion coefficient, membrane resealing, and critical electric field strength for electroporation. The use of existing technologies to determine these parameters is time-consuming and labor-intensive, and often results in large inconsistencies in parameter estimation due to variations in the protocols and setups. In this work, we suggest using a set of concentric electrodes to screen a full range of electric field strengths in a single test to determine the electroporation-induced transmembrane transport parameters. Using Calcein as a fluorescent probe, we developed analytical methodology to determine the transport parameters based on the electroporation-induced pattern of fluorescence loss from cells. A monolayer of normal human dermal fibroblast (NHDF) cells were pre-loaded with Calcein and electroporated with an applied voltage of 750 V with 10 and 50 square pulses with 50 μs duration. Using our analytical model, the critical electric field strength for electroporation was found for the 10 and 50 pulses experiments. An inverse correlation between the field strength and the molecular transport time decay constant, and a direct correlation between field strength and the membrane permeability were observed. The results of this work can simplify the development of electroporation-assisted technologies for research and therapies. PMID:27263825
Near-field Electrical Detection of Optical Surface Plasmons and Single Plasmon Sources
NASA Astrophysics Data System (ADS)
Koppens, Frank; Falk, A.; Yu, C.; Kang, K.; de Leon, N.; Akimov, A.; Jo, M.; Lukin, M.; Park, H.
2009-05-01
Surface plasmon polaritons (SPs) are a promising basis for nanoscale photonic circuits and allow for strong coupling between single photon emitters and propagating plasmon modes. However, there is a general tradeoff between the localization of an SP and the efficiency with which it can be detected with conventional far-field optics. In this talk, I will discus a nanoscale all-electrical SP detection technique based on the near-field coupling between propagating surface plasmons and a nanowire field-effect transistor. The detection scheme consists of an Ag nanowire (NW) crossing a Ge NW field-effect transistor. The Ag NW guides SPs to the Ag/Ge junction, where they are converted to electron-hole (e-h) pairs and detected as current through the Ge NW. We use our detectors to electrically detect the plasmon emission from an individual colloidal quantum dot coupled to a SP waveguide. The detectors are highly efficient (0.1 electrons/plasmon), and a plasmonic gating effect can be used to amplify the signal even higher (up to 50 electrons/plasmon). These results enable new and efficient on-chip optical sensing applications and fulfill a key requirement for 'dark' optical frequency nanocircuits in which SPs can be generated, manipulated, and detected without involving far-field radiation.
Blumrosen, Gadi; Abazari, Alireza; Golberg, Alexander; Yarmush, Martin L; Toner, Mehmet
2016-09-01
The design of effective electroporation protocols for molecular delivery applications requires the determination of transport parameters including diffusion coefficient, membrane resealing, and critical electric field strength for electroporation. The use of existing technologies to determine these parameters is time-consuming and labor-intensive, and often results in large inconsistencies in parameter estimation due to variations in the protocols and setups. In this work, we suggest using a set of concentric electrodes to screen a full range of electric field strengths in a single test to determine the electroporation-induced transmembrane transport parameters. Using Calcein as a fluorescent probe, we developed analytical methodology to determine the transport parameters based on the electroporation-induced pattern of fluorescence loss from cells. A monolayer of normal human dermal fibroblast (NHDF) cells were pre-loaded with Calcein and electroporated with an applied voltage of 750V with 10 and 50 square pulses with 50μs duration. Using our analytical model, the critical electric field strength for electroporation was found for the 10 and 50 pulses experiments. An inverse correlation between the field strength and the molecular transport time decay constant, and a direct correlation between field strength and the membrane permeability were observed. The results of this work can simplify the development of electroporation-assisted technologies for research and therapies.
Relic vector field and CMB large scale anomalies
Chen, Xingang; Wang, Yi E-mail: yw366@cam.ac.uk
2014-10-01
We study the most general effects of relic vector fields on the inflationary background and density perturbations. Such effects are observable if the number of inflationary e-folds is close to the minimum requirement to solve the horizon problem. We show that this can potentially explain two CMB large scale anomalies: the quadrupole-octopole alignment and the quadrupole power suppression. We discuss its effect on the parity anomaly. We also provide analytical template for more detailed data comparison.
Post-Inflationary Higgs Relaxation and the Origin of Matter
NASA Astrophysics Data System (ADS)
Yang, Louis
The recent measurement of the Higgs boson mass implies a relatively slow rise of the Standard Model Higgs potential at large scales, and a possible second minimum at even larger scales. Consequently, the Higgs field may develop a large vacuum expectation value during inflation. The relaxation of the Higgs field from its large postinflationary value to the minimum of the effective potential represents an important stage in the evolution of the Universe. During this epoch, the time-dependent Higgs condensate can create an effective chemical potential for the lepton number, leading to a generation of the lepton asymmetry in the presence of some large right-handed Majorana neutrino masses. The electroweak sphalerons redistribute this asymmetry between leptons and baryons. This Higgs relaxation leptogenesis can explain the observed matter-antimatter asymmetry of the Universe even if the Standard Model is valid up to the scale of inflation, and any new physics is suppressed by that high scale. The baryonic isocurvature perturbations generated by the relaxation leptogenesis can also explain the excess found in the cosmic infrared background (CIB) anisotropy. We begin this dissertation by reviewing the development of the large vacuum expectation value (VEV) of the Higgs and other scalar fields during inflation. We then discuss the postinflationary relaxation of the Higgs field in full detail, and present the relaxation leptogenesis framework using the Standard Model Higgs field as an example. Next, we extend the relaxation leptogenesis to the elementary Goldstone Higgs (EGH) framework and the pseudoscalar scenario. In the EGH paradigm, the electroweak (EW) scale is not fundamental but radiatively generated. This allows one to disentangle the EW scale from the vacuum expectation of the elementary Higgs field, and construct a very flat scalar potential directions along which the relaxation leptogenesis mechanism can be implemented with larger parameter space. In December
NASA Astrophysics Data System (ADS)
Sánchez, S. F.; Rosales-Ortega, F. F.; Kennicutt, R. C.; Johnson, B. D.; Diaz, A. I.; Pasquali, A.; Hao, C. N.
2011-01-01
We present a wide-field Integral Field Spectroscopy (IFS) survey on the nearby face-on Sbc galaxy NGC 628, comprising 11094 individual spectra, covering a nearly circular field-of-view of ˜6 arcmin in diameter, with a sampling of ˜2.7 arcsec per spectrum in the optical wavelength range (3700-7000 Å). This galaxy is part of the PPAK IFS Nearby Galaxies Survey (PINGS). To our knowledge, this is the widest spectroscopic survey ever made in a single nearby galaxy. A detailed flux calibration was applied, granting a spectrophotometric accuracy of ˜0.2 mag. The spectroscopic data were analysed both as a single integrated spectrum that characterizes the global properties of the galaxy and using each individual spectrum to determine the spatial variation of the stellar and ionized gas components. The spatial distribution of the luminosity-weighted ages and metallicities of the stellar populations was analysed. Using typical strong emission-line ratios we derived the integrated and 2D spatial distribution of the ionized gas, the dust content, star formation rate (SFR) and oxygen abundance. The age of the stellar populations shows a negative gradient from the inner (older) to the outer (younger) regions. We found an inversion of this gradient in the central ˜1 kpc region, where a somewhat younger stellar population is present within a ring at this radius. This structure is associated with a circumnuclear star-forming region at ˜500 pc, also found in similar spiral galaxies. From the study of the integrated and spatially resolved ionized gas, we found a moderate SFR of ˜2.4 M⊙ yr-1. The oxygen abundance shows a clear gradient of higher metallicity values from the inner part to the outer part of the galaxy, with a mean value of 12 + log(O/H) ˜ 8.7. At some specific regions of the galaxy, the spatially resolved distribution of the physical properties shows some level of structure, suggesting real point-to-point variations within an individual H II region. Our results
Coupled acoustic-gravity field for dynamic evaluation of ion exchange with a single resin bead.
Kanazaki, Takahiro; Hirawa, Shungo; Harada, Makoto; Okada, Tetsuo
2010-06-01
A coupled acoustic-gravity field is efficient for entrapping a particle at the position determined by its acoustic properties rather than its size. This field has been applied to the dynamic observation of ion-exchange reactions occurring in a single resin bead. The replacement of counterions in an ion-exchange resin induces changes in its acoustic properties, such as density and compressibility. Therefore, we can visually trace the advancement of an ion-exchange reaction as a time change in the levitation position of a resin bead entrapped in the field. Cation-exchange reactions occurring in resin beads with diameters of 40-120 microm are typically completed within 100-200 s. Ion-exchange equilibrium or kinetics is often evaluated with off-line chemical analyses, which require a batch amount of ion exchangers. Measurements with a single resin particle allow us to evaluate ion-exchange dynamics and kinetics of ions including those that are difficult to measure by usual off-line analyses. The diffusion properties of ions in resins have been successfully evaluated from the time change in the levitation positions of resin beads.
Ambrose, W.P.; Affleck, R.L.; Goodwin, P.M.; Keller, R.A.; Martin, J.C.; Petty, J.T.; Schecker, J.A.; Wu, Ming
1995-12-01
We have developed a near-field scanning optical microscope with the sensitivity to detect single fluorescent molecules. Our microscope is based on scanning a sample under a tapered and metal coated fiber optic probe and has an illumination-aperture diameter as small as 100 nm. The microscope simultaneously acquires a shear force image with a height noise of {approximately} 1 nm. We have used this system to demonstrate the detection of single molecules of Rhodamine-6G on silica. In this paper, we explore the use of NSOM for investigations of biological molecules. We have prepared and imaged double-stranded DNA intercalated with thiazole orange homodimer (TOTO); single chromosomes stained with propidium iodide; and {beta}-phycoerythrin proteins on dry, borosilicate-glass surfaces. At very dilute coverages, isolated fluorescent spots are observed for the un-intercalated TOTO dye and for {beta}-phycoerythrin. These fluorescent spots exhibit-emission intensity fluctuations and abrupt bleaching transitions, similar to the intensity behavior observed previously for single Rhodamine 6G molecules on silica.
Single trap dynamics in electrolyte-gated Si-nanowire field effect transistors
Pud, S.; Li, J.; Offenhäusser, A.; Vitusevich, S. A.; Gasparyan, F.; Petrychuk, M.
2014-06-21
Liquid-gated silicon nanowire (NW) field effect transistors (FETs) are fabricated and their transport and dynamic properties are investigated experimentally and theoretically. Random telegraph signal (RTS) fluctuations were registered in the nanolength channel FETs and used for the experimental and theoretical analysis of transport properties. The drain current and the carrier interaction processes with a single trap are analyzed using a quantum-mechanical evaluation of carrier distribution in the channel and also a classical evaluation. Both approaches are applied to treat the experimental data and to define an appropriate solution for describing the drain current behavior influenced by single trap resulting in RTS fluctuations in the Si NW FETs. It is shown that quantization and tunneling effects explain the behavior of the electron capture time on the single trap. Based on the experimental data, parameters of the single trap were determined. The trap is located at a distance of about 2 nm from the interface Si/SiO{sub 2} and has a repulsive character. The theory of dynamic processes in liquid-gated Si NW FET put forward here is in good agreement with experimental observations of transport in the structures and highlights the importance of quantization in carrier distribution for analyzing dynamic processes in the nanostructures.
Single-shot velocity-map imaging of attosecond light-field control at kilohertz rate.
Süssmann, F; Zherebtsov, S; Plenge, J; Johnson, Nora G; Kübel, M; Sayler, A M; Mondes, V; Graf, C; Rühl, E; Paulus, G G; Schmischke, D; Swrschek, P; Kling, M F
2011-09-01
High-speed, single-shot velocity-map imaging (VMI) is combined with carrier-envelope phase (CEP) tagging by a single-shot stereographic above-threshold ionization (ATI) phase-meter. The experimental setup provides a versatile tool for angle-resolved studies of the attosecond control of electrons in atoms, molecules, and nanostructures. Single-shot VMI at kHz repetition rate is realized with a highly sensitive megapixel complementary metal-oxide semiconductor camera omitting the need for additional image intensifiers. The developed camera software allows for efficient background suppression and the storage of up to 1024 events for each image in real time. The approach is demonstrated by measuring the CEP-dependence of the electron emission from ATI of Xe in strong (≈10(13) W/cm(2)) near single-cycle (4 fs) laser fields. Efficient background signal suppression with the system is illustrated for the electron emission from SiO(2) nanospheres. © 2011 American Institute of Physics
Matlis, Nicholas; Plateau, Guillaume; van Tilborg, Jeroen; Leemans, Wim
2011-06-17
A new single-shot technique based on linear spectral interferometry between a temporally short reader pulse and a temporally long probe pulse is demonstrated for measuring the spatiotemporal phase and amplitude of an optical probe for use as an ultrafast diagnostic. The probe spatiotemporal field information is recovered, with a resolution set by the duration of the reader pulse, by applying a single Fourier transform operation to the interferogram image, without need of any reference data. The technique was used in conjunction with electro-optic sampling to measure waveforms of coherent, ultrashort THz pulses emitted by electron bunches from a laser-plasma accelerator with sub-50fs resolution. The presence of strong spatiotemporal coupling in the THz waveforms and of complex temporal electron-bunch structure was determined.
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-17
We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. Asmore » a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.« less
3D position estimation using a single coil and two magnetic field sensors.
Tadayon, P; Staude, G; Felderhoff, T
2015-01-01
This paper presents an algorithm which enables the estimation of relative 3D position of a sensor module with two magnetic sensors with respect to a magnetic field source using a single transmitting coil. Starting with the description of the ambiguity problem caused by using a single coil, a system concept comprising two sensors having a fixed spatial relation to each other is introduced which enables the unique determination of the sensors' position in 3D space. For this purpose, an iterative two-step algorithm is presented: In a first step, the data of one sensor is used to limit the number of possible position solutions. In a second step, the spatial relation between the sensors is used to determine the correct sensor position.
Non-contact single shot elastography using line field low coherence holography
Liu, Chih-Hao; Schill, Alexander; Wu, Chen; Singh, Manmohan; Larin, Kirill V.
2016-01-01
Optical elastic wave imaging is a powerful technique that can quantify local biomechanical properties of tissues. However, typically long acquisition times make this technique unfeasible for clinical use. Here, we demonstrate non-contact single shot elastographic holography using a line-field interferometer integrated with an air-pulse delivery system. The propagation of the air-pulse induced elastic wave was imaged in real time, and required a single excitation for a line-scan measurement. Results on tissue-mimicking phantoms and chicken breast muscle demonstrated the feasibility of this technique for accurate assessment of tissue biomechanical properties with an acquisition time of a few milliseconds using parallel acquisition. PMID:27570694
Electrical coupling of single cardiac rat myocytes to field-effect and bipolar transistors.
Kind, Thomas; Issing, Matthias; Arnold, Rüdiger; Müller, Bernt
2002-12-01
A novel bipolar transistor for extracellular recording the electrical activity of biological cells is presented, and the electrical behavior compared with the field-effect transistor (FET). Electrical coupling is examined between single cells separated from the heart of adults rats (cardiac myocytes) and both types of transistors. To initiate a local extracellular voltage, the cells are periodically stimulated by a patch pipette in voltage clamp and current clamp mode. The local extracellular voltage is measured by the planar integrated electronic sensors: the bipolar and the FET. The small signal transistor currents correspond to the local extracellular voltage. The two types of sensor transistors used here were developed and manufactured in the laboratory of our institute. The manufacturing process and the interfaces between myocytes and transistors are described. The recordings are interpreted by way of simulation based on the point-contact model and the single cardiac myocyte model.
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-17
We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. As a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.
Temperature and Field Induced Strain Measurements in Single Crystal Gd5Si2Ge2
NASA Astrophysics Data System (ADS)
McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.
2016-06-01
The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of -8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of -8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.
Near-field imaging of single walled carbon nanotubes emitting in the telecom wavelength range
NASA Astrophysics Data System (ADS)
La China, F.; Caselli, N.; Sarti, F.; Biccari, F.; Torrini, U.; Intonti, F.; Vinattieri, A.; Durán-Valdeiglesias, E.; Alonso Ramos, C.; Le Roux, X.; Balestrieri, M.; Filoramo, A.; Vivien, L.; Gurioli, M.
2016-09-01
Hybrid systems based on carbon nanotubes emitting in the telecom wavelength range and Si-photonic platforms are promising candidates for developing integrated photonic circuits. Here, we consider semiconducting single walled carbon nanotubes (s-SWNTs) emitting around 1300 nm or 1550 nm wavelength. The nanotubes are deposited on quartz substrate for mapping their photoluminescence in hyperspectral near-field microscopy. This method allows for a sub-wavelength resolution in detecting the spatial distribution of the emission of single s-SWNTs at room temperature. Optical signature delocalized over several micrometers is observed, thus denoting the high quality of the produced carbon nanotubes on a wide range of tube diameters. Noteworthy, the presence of both nanotube bundles and distinct s-SWNT chiralities is uncovered.
NASA Astrophysics Data System (ADS)
Bugoslavsky, Yu. V.; Minakov, A. A.; Vasyurin, S. I.
1996-02-01
Dependence of the remanent magnetization (Mr) anisotropy on the structure and shape of the superconductor and on the magnetizing procedure was studied for a number of high-Tc superconductor ceramics and single crystals. The experiments were done by means of a vibrating-sample magnetometer with a rotatable sample holder. It was found that the main contribution to the anisotropic behavior of Mr is due to the surface screening currents, and therefore the anisotropy is subject to variation when sample shape is changed. The question is resolved, why the effective demagnetization factors for decoupled ceramic samples are different from those calculated in the inscribed-ellipsoid approximation. Influence of inhomogeneous grain magnetization and global bulk currents on the angular dependencies of Mr in ceramic samples is investigated. The evolution of remanence in YBCO single crystals with an increase of the magnetizing field is described within an extended Bean model.
Electric-field gradient characterization at 181Ta impurities in sapphire single crystals
NASA Astrophysics Data System (ADS)
Rentería, M.; Darriba, G. N.; Errico, L. A.; Muñoz, E. L.; Eversheim, P. D.
2005-07-01
We report Perturbed-Angular-Correlation (PAC) experiments on corundum Al2O3 single crystals implanted with 181Hf/181Ta ions at the ISKP at Bonn and measured at La Plata with high efficiency and time-resolution. The magnitude, asymmetry, and orientation (with respect to the crystalline axes) of the electric-field gradient (EFG) tensor were determined measuring the spin-rotation curves as a function of different orientations of the single crystals relative to the detector system. These results are analyzed in the framework of point-charge model and ab initio Full-Potential Linearized-Augmented Plane Wave calculations, and compared with EFG results coming from PAC experiments with 111In/111Cd impurities. This combined study enables the determination of lattice relaxations induced by the presence of the impurity and the state of charge of a deep impurity donor level in the band gap of the semiconductor.
NASA Astrophysics Data System (ADS)
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
2015-02-01
We demonstrate that a nonperturbative framework for the treatment of the excitations of single-walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. We test this theory explicitly on the data reported by Dukovic et al. [Nano Lett. 5, 2314 (2005), 10.1021/nl0518122] and Sfeir et al. [Phys. Rev. B 82, 195424 (2010), 10.1103/PhysRevB.82.195424] and so demonstrate the method works over a wide range of reported excitonic spectra.
DOE and JAEA Field Trial of the Single Chip Shift Register (SCSR)
Newell, Matthew R.
2016-03-23
Los Alamos National Laboratories (LANL) has recently developed a new data acquisition system for multiplicity analysis of neutron detector pulse streams. This new technology, the Single Chip Shift Register (SCSR), places the entire data acquisition system along with the communications hardware onto a single chip. This greatly simplifies the instrument and reduces the size. The SCSR is designed to be mounted into the neutron detector head alongside the instrument amplifiers. The user’s computer connects via USB directly to the neutron detector eliminating the external data acquisition electronics entirely. JAEA, through the INSEP program, asked LANL to demonstrate the functionality of the SCSR in Tokai using the JAEA Epithermal Neutron Multiplicity Counter, ENMC. In late September of 2015 LANL traveled to Tokai to install, demonstrate and uninstall the SCSR in the ENMC. This report documents the results of that field trial.
NASA Technical Reports Server (NTRS)
Ng, Tak-kwong (Inventor); Herath, Jeffrey A. (Inventor)
2010-01-01
An integrated system mitigates the effects of a single event upset (SEU) on a reprogrammable field programmable gate array (RFPGA). The system includes (i) a RFPGA having an internal configuration memory, and (ii) a memory for storing a configuration associated with the RFPGA. Logic circuitry programmed into the RFPGA and coupled to the memory reloads a portion of the configuration from the memory into the RFPGA's internal configuration memory at predetermined times. Additional SEU mitigation can be provided by logic circuitry on the RFPGA that monitors and maintains synchronized operation of the RFPGA's digital clock managers.
The cosmological Slavnov-Taylor identity from BRST symmetry in single-field inflation
Binosi, D.; Quadri, A. E-mail: andrea.quadri@mi.infn.it
2016-03-01
The cosmological Slavnov-Taylor (ST) identity of the Einstein-Hilbert action coupled to a single inflaton field is obtained from the Becchi-Rouet-Stora-Tyutin (BRST) symmetry associated with diffeomorphism invariance in the Arnowitt-Deser-Misner (ADM) formalism. The consistency conditions between the correlators of the scalar and tensor modes in the squeezed limit are then derived from the ST identity, together with the softly broken conformal symmetry. Maldacena's original relations connecting the 2- and 3-point correlators at horizon crossing are recovered, as well as the next-to-leading corrections, controlled by the special conformal transformations.
(AASERT-93) Field-Effect-Controlled, Coulomb-BlocKage Single-Electron Transistor in Silicon.
2007-11-02
imludCigdibei m , f lei reviewingI Ifistrctflnfl iiv thing~ rIUrmg Ol a m"su’e. gi~wr~ng LrIs fl Ifanil fbe data needed, and c~fO atingbl aw~d...AASERT-93) Field-Effect-Controlled, Coulomb -Blockage Single-Electron Transistor in Silicon .61103D 1-. AUTHO-R(S) 3484/TS Professor Dimitri.Antoniadis...limits of X-ray nanolithography for real devices was found. Novel I coulomb -blockade devices have been fabricated using this modified process
A single-channel SQUID magnetometer for measuring magnetic field of human fetal heart
NASA Astrophysics Data System (ADS)
Bachir, Wesam; Grot, Przemyslaw; Dunajski, Zbigniew
2004-07-01
A non-invasive single-channel SQUID magnetometer for fetal magnetocardiography has been developed. The signal is picked-up with a wire wound third order gradiometer. The optimal configuration of the flux transformer is a trade-off between sufficient sensitivity for the magnetic field originated in fetal heart and effective immunity against the ambient magnetic noise. The over all system performance together with the measuring probe and SQUID electronics is described. The balancing of the third order flux transformer is discussed as well as the signal processing of fetal magnetocardiogram recordings.
Analysis of menisci formed on cones for single field of view parasite egg microscopy.
Cooke, I R; Laing, C J; White, L V; Wakes, S J; Sowerby, S J
2015-02-01
Parasite ova caused to accumulate in a single microscopic field simplifies monitoring soil-transmitted helminthiasis by optical microscopy. Here we demonstrate new egg-accumulating geometries based on annular menisci formed on the surface of a wetted cone. Fluidic features extracted from profile images of the system provided mathematical representations of the meniscus gradient that were compared quantitatively to numerical solutions of an axisymmetric Young-Laplace equation. Our results show that the governing dynamics of these systems is dominated by the surface tension of the fluid. These image analysis and mathematical tools provide simple quantitative methods for system analysis and optimization.
Detection in near-field domain of biomolecules adsorbed on a single metallic nanoparticle.
Barbillon, G; Bijeon, J-L; Bouillard, J-S; Plain, J; Lamy De la Chapelle, M; Adam, P-M; Royer, P
2008-02-01
In this paper, we study the performances of nanosensors based on Localized Surface Plasmon Resonance in the context of biological sensing. We demonstrate the sensitivity and the selectivity of our designed nanosensors by studying the influence of the concentration of Streptavidin on the shift of Localized Surface Plasmon Resonance wavelength. In addition, to study the detection of biomolecules on a single Au nanoparticle, we used a Scanning Near-field Optical Microscope. These results represent new steps for applications in biological research and medical diagnostics.
STARE Results on a Single Field: Tens of New Pulsating Stars
NASA Astrophysics Data System (ADS)
Alonso, Roi; Belmonte, Juan Antonio; Brown, Tim
We present preliminary results on variable stars of a STARE's three month observational run centered at the Cygnus constellation. A total amount of aprox. 14000 stars with 9
Advances in the field of single-particle cryo-electron microscopy over the last decade.
Frank, Joachim
2017-02-01
In single-particle cryo-electron microscopy (cryo-EM), molecules suspended in a thin aqueous layer are rapidly frozen and imaged at cryogenic temperature in the transmission electron microscope. From the random projection views, a three-dimensional image is reconstructed, enabling the structure of the molecule to be obtained. In this article I discuss technological progress over the past decade, which has, in my own field of study, culminated in the determination of ribosome structure at 2.5-Å resolution. I also discuss likely future improvements in methodology.
Single field inflation in supergravity with a U(1) gauge symmetry
Heurtier, L.; Khalil, S.; Moursy, A. E-mail: skhalil@zewailcity.edu.eg
2015-10-01
A single field inflation based on a supergravity model with a shift symmetry and U(1) extension of the MSSM is analyzed. We show that one of the real components of the two U(1) charged scalar fields plays the role of inflaton with an effective scalar potential similar to the ''new chaotic inflation'' scenario. Both non-anomalous and anomalous (with Fayet-Iliopoulos term) U(1) are studied. We show that the non-anomalous U(1) scenario is consistent with data of the cosmic microwave background and recent astrophysical measurements. A possible kinetic mixing between U(1) and U(1){sub B−L} is considered in order to allow for natural decay channels of the inflaton, leading to a reheating epoch. Upper limits on the reheating temperature thus turn out to favour an intermediate (∼ O(10{sup 13}) GeV) scale B−L symmetry breaking.
Characteristics of krypton ion emission from a gas field ionization source with a single atom tip
NASA Astrophysics Data System (ADS)
Shichi, Hiroyasu; Matsubara, Shinichi; Hashizume, Tomihiro
2017-06-01
A scanning ion beam instrument equipped with a gas field ionization source (GFIS) has been commercialized, but only helium and neon are currently available as GFISs. The characteristics of krypton ion emission from a single atom tip (SAT) have not been reported yet. In this study, the characteristics of krypton ion emission were investigated by field ion microscopy. At 65 K, the krypton ion emission current reached approximately 40 pA, which is 1 order of magnitude higher than that at 130 K. As the krypton gas pressure was increased, the krypton ion current increased. At a pressure of 0.3 Pa, the emission current was anticipated to reach 200 pA, which may be high enough for nanofabrication. The variation of the krypton ion current was as low as 5% in one hour. We concluded that a krypton ion beam instrument equipped with a GFIS will be a powerful tool for nanofabrication.
Single field inflation in supergravity with a U(1) gauge symmetry
Heurtier, L.; Khalil, S.; Moursy, A.
2015-10-19
A single field inflation based on a supergravity model with a shift symmetry and U(1) extension of the MSSM is analyzed. We show that one of the real components of the two U(1) charged scalar fields plays the role of inflaton with an effective scalar potential similar to the “new chaotic inflation” scenario. Both non-anomalous and anomalous (with Fayet-Iliopoulos term) U(1) are studied. We show that the non-anomalous U(1) scenario is consistent with data of the cosmic microwave background and recent astrophysical measurements. A possible kinetic mixing between U(1) and U(1){sub B−L} is considered in order to allow for natural decay channels of the inflaton, leading to a reheating epoch. Upper limits on the reheating temperature thus turn out to favour an intermediate (∼O(10{sup 13}) GeV) scale B−L symmetry breaking.
Synthesis of 3D Model of a Magnetic Field-Influenced Body from a Single Image
NASA Technical Reports Server (NTRS)
Wang, Cuilan; Newman, Timothy; Gallagher, Dennis
2006-01-01
A method for recovery of a 3D model of a cloud-like structure that is in motion and deforming but approximately governed by magnetic field properties is described. The method allows recovery of the model from a single intensity image in which the structure's silhouette can be observed. The method exploits envelope theory and a magnetic field model. Given one intensity image and the segmented silhouette in the image, the method proceeds without human intervention to produce the 3D model. In addition to allowing 3D model synthesis, the method's capability to yield a very compact description offers further utility. Application of the method to several real-world images is demonstrated.
Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe
TonThat, D.M.; Augustine, M.P.; Pines, A.; Clarke, J. |
1997-03-01
We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 {Omega}. Low-field, {sup 1}H nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies {lt}1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200. {copyright} {ital 1997 American Institute of Physics.}
Steep switching characteristics of single-gated feedback field-effect transistors
NASA Astrophysics Data System (ADS)
Kim, Minsuk; Kim, Yoonjoong; Lim, Doohyeok; Woo, Sola; Cho, Kyoungah; Kim, Sangsig
2017-02-01
In this study, we propose newly designed feedback field-effect transistors that utilize the positive feedback of charge carriers in single-gated silicon channels to achieve steep switching behaviors. The band diagram, I-V characteristics, subthreshold swing, and on/off current ratio are analyzed using a commercial device simulator. Our proposed feedback field-effect transistors exhibit subthreshold swings of less than 0.1 mV dec-1, an on/off current ratio of approximately 1011, and an on-current of approximately 10-4 A at room temperature, demonstrating that the switching characteristics are superior to those of other silicon-based devices. In addition, the device parameters that affect the device performance, hysteresis characteristics, and temperature-dependent device characteristics are discussed in detail.
A Single Polyaniline Nanofiber Field Effect Transistor and Its Gas Sensing Mechanisms
Chen, Dajing; Lei, Sheng; Chen, Yuquan
2011-01-01
A single polyaniline nanofiber field effect transistor (FET) gas sensor fabricated by means of electrospinning was investigated to understand its sensing mechanisms and optimize its performance. We studied the morphology, field effect characteristics and gas sensitivity of conductive nanofibers. The fibers showed Schottky and Ohmic contacts based on different electrode materials. Higher applied gate voltage contributes to an increase in gas sensitivity. The nanofiber transistor showed a 7% reversible resistance change to 1 ppm NH3 with 10 V gate voltage. The FET characteristics of the sensor when exposed to different gas concentrations indicate that adsorption of NH3 molecules reduces the carrier mobility in the polyaniline nanofiber. As such, nanofiber-based sensors could be promising for environmental and industrial applications. PMID:22163969
Photon Energy Deposition in Strong-Field Single Ionization of Multielectron Molecules.
Zhang, Wenbin; Li, Zhichao; Lu, Peifen; Gong, Xiaochun; Song, Qiying; Ji, Qinying; Lin, Kang; Ma, Junyang; He, Feng; Zeng, Heping; Wu, Jian
2016-09-02
Molecules exposed to strong laser fields may coherently absorb multiple photons and deposit the energy into electrons and nuclei, triggering the succeeding dynamics as the primary stage of the light-molecule interaction. We experimentally explore the electron-nuclear sharing of the absorbed photon energy in above-threshold multiphoton single ionization of multielectron molecules. Using CO as a prototype, vibrational and orbital resolved electron-nuclear sharing of the photon energy is observed. Different from the simplest one- or two-electron systems, the participation of the multiple orbitals and the coupling of various electronic states in the strong-field ionization and dissociation processes alter the photon energy deposition dynamics of the multielectron molecule. The population of numerous vibrational states of the molecular cation as the energy reservoir in the ionization process plays an important role in photon energy sharing between the emitted electron and the nuclear fragments.
Low magnetic field dynamic nuclear polarization using a single-coil two-channel probe
NASA Astrophysics Data System (ADS)
TonThat, Dinh M.; Augustine, Matthew P.; Pines, Alexander; Clarke, John
1997-03-01
We describe the design and construction of a single-coil, two-channel probe for the detection of low-field magnetic resonance using dynamic nuclear polarization (DNP). The high-frequency channel of the probe, which is used to saturate the electron spins, is tuned to the electron Larmor frequency, 75 MHz at 2.7 mT, and matched to 50 Ω. Low-field, 1H nuclear magnetic resonance (NMR) is detected through the second, low-frequency channel at frequencies <1 MHz. The performance of the probe was tested by measuring the DNP of protons in a manganese (II) chloride solution at 2.7 mT. At the proton NMR frequency of 120 kHz, the signal amplitude was enhanced over the value without DNP by a factor of about 200.
NASA Astrophysics Data System (ADS)
Radusovska, M.; Diko, P.; Piovarci, S.; Park, S.-D.; Jun, B.-H.; Kim, C.-J.
2017-10-01
The microstructural analyses of YBCO bulk single-grain superconductors grown by interior seeding with taller and shorter upper pellets have shown that a suitable upper pellet height can lower the porosity in the upper part of the sample, produce a more appropriate distribution of pinning centres in the form of Y-211 particles and suppress subgrain formation with a higher crystal misalignment in the c-growth sector (c-GS), which can lead to a higher measured trapped magnetic field and a more uniform cone of the trapped-field profile. The observed bulging of the sample surface at the c-GS can be explained by the edge melt distribution model, which shows that macroscopic mass transport to the growth sector occurs with higher growth rates.
Synthesis of 3D Model of a Magnetic Field-Influenced Body from a Single Image
NASA Technical Reports Server (NTRS)
Wang, Cuilan; Newman, Timothy; Gallagher, Dennis
2006-01-01
A method for recovery of a 3D model of a cloud-like structure that is in motion and deforming but approximately governed by magnetic field properties is described. The method allows recovery of the model from a single intensity image in which the structure's silhouette can be observed. The method exploits envelope theory and a magnetic field model. Given one intensity image and the segmented silhouette in the image, the method proceeds without human intervention to produce the 3D model. In addition to allowing 3D model synthesis, the method's capability to yield a very compact description offers further utility. Application of the method to several real-world images is demonstrated.
Bispectrum signatures of a modified vacuum in single field inflation with a small speed of sound
Meerburg, P. Daniel; Schaar, Jan Pieter van der; Jackson, Mark G. E-mail: j.p.vanderschaar@uva.nl
2010-02-01
Deviations from the Bunch-Davies vacuum during an inflationary period can leave a testable imprint on the higher-order correlations of the CMB and large scale structures in the Universe. The effect is particularly pronounced if the statistical non-Gaussianity is inherently large, such as in models of inflation with a small speed of sound, e.g. DBI. First reviewing the motivations for a modified vacuum, we calculate the non-Gaussianity for a general action with a small speed of sound. The shape of its bispectrum is found to most resemble the 'orthogonal' or 'local' templates depending on the phase of the Bogolyubov parameter. In particular, for DBI models of inflation the bispectrum can have a profound 'local' template feature, in contrast to previous results. Determining the projection into the observational templates allows us to derive constraints on the absolute value of the Bogolyubov parameter. In the small sound speed limit, the derived constraints are generally stronger than the constraint obtainable from the power spectrum. The bound on the absolute value of the Bogolyubov parameter ranges from the 10{sup −6} to the 10{sup −3} level for H/Λ{sub c} = 10{sup −3}, depending on the specific details of the model, the sound speed and the phase of the Bogolyubov parameter.
Orientation effect on the giant stress field induced in a single Ni nanowire by mechanical strain
NASA Astrophysics Data System (ADS)
Melilli, G.; Madon, B.; Clochard, M.-C.; Wegrowe, J.-E.
2015-09-01
The change of magnetization (i.e. using the inverse magnetostriction effect) allows to investigate at the nanoscale the effects of thermoelastic and piezoelectric strain of an active track-etched β-PVDF polymer matrix on an electrodeposited single-contacted Ni nanowire (NW). The magnetization state is measured locally by anisotropic magnetoresitance (AMR). The ferromagnetic NW plays thus the role of a mechanical probe that allows the effects of mechanical strain to be characterized and described qualitatively and quantitatively. Due to the inverse magnetostriction, a quasi-disappearance of the AMR signal for a variation of the order of ΔT ≍ 10 K has been evidenced. The coplanarity of the vectors between the magnetization and the magnetic field is broken. A way of studying the effect of the geometry on such a system, is to fabricate oriented polymer templates. Track-etched polymer membranes were thus irradiated at various angles (αirrad) leading, after electrodeposition, to embedded Ni NWs of different orientations. With cylindrical Ni NW oriented normally to the template surface, the induced stress field in a single Ni NW was found 1000 time higher than the bulk stress field (due to thermal expansion measured on the PVDF). This amplification results in three nanoscopic effects: (1) a stress mismatch between the Ni NW and the membrane, (2) a non-negligible role of the surface tension on Ni NW Young modulus, and (3) the possibility of non-linear stress-strain law. When the Ni NWs are tilted from the polymer template surface normality, the induced stress field is reduced and the amplification phenomenon is less important.
Axonal and dendritic density field estimation from incomplete single-slice neuronal reconstructions
van Pelt, Jaap; van Ooyen, Arjen; Uylings, Harry B. M.
2014-01-01
Neuronal information processing in cortical networks critically depends on the organization of synaptic connectivity. Synaptic connections can form when axons and dendrites come in close proximity of each other. The spatial innervation of neuronal arborizations can be described by their axonal and dendritic density fields. Recently we showed that potential locations of synapses between neurons can be estimated from their overlapping axonal and dendritic density fields. However, deriving density fields from single-slice neuronal reconstructions is hampered by incompleteness because of cut branches. Here, we describe a method for recovering the lost axonal and dendritic mass. This so-called completion method is based on an estimation of the mass inside the slice and an extrapolation to the space outside the slice, assuming axial symmetry in the mass distribution. We validated the method using a set of neurons generated with our NETMORPH simulator. The model-generated neurons were artificially sliced and subsequently recovered by the completion method. Depending on slice thickness and arbor extent, branches that have lost their outside parents (orphan branches) may occur inside the slice. Not connected anymore to the contiguous structure of the sliced neuron, orphan branches result in an underestimation of neurite mass. For 300 μm thick slices, however, the validation showed a full recovery of dendritic and an almost full recovery of axonal mass. The completion method was applied to three experimental data sets of reconstructed rat cortical L2/3 pyramidal neurons. The results showed that in 300 μm thick slices intracortical axons lost about 50% and dendrites about 16% of their mass. The completion method can be applied to single-slice reconstructions as long as axial symmetry can be assumed in the mass distribution. This opens up the possibility of using incomplete neuronal reconstructions from open-access data bases to determine population mean mass density fields
Single and multiple light scattering studies of PDLC films in the presence of electric fields
NASA Astrophysics Data System (ADS)
Wu, Wei
Light scattering from Polymer Dispersed Liquid Crystal (PDLC) films is studied in four major respects: the differential scattering cross-section of a single liquid crystal droplet; the total scattering cross-section and film transmittance; multiple scattering effects; and scattering by absorbing droplets (PDLC doped with dichroic dye). The effects of applied electric field, light wavelength and the liquid crystal droplet size on the scattering behavior are examined. PDLC scattering properties under electric field are described by combining the Anomalous Diffraction Approach (ADA) with PDLC electro-optical response theory. Numerical computation results directly demonstrate how the total scattering cross section relates to the incident light wavelength, the droplet size and the applied electric field. Transmittance measurements are used to study the total scattering cross-section. Analyses of the transmittance characteristics show good agreement with the theoretical predictions. PDLC samples with a practical contrast ratio exhibit strong multiple scattering effects. Studies of the single scattering differential cross section provide a foundation for the modeling and experimental work on the multiple scattering effects. Single scattering characteristics of a bipolar droplet director configuration are derived for a highly symmetric situation. The results offer qualitative explanations for some experimental observations, such as the presence of off-normal maxima and breakdown of rotational symmetry in the scattering pattern. As a novel approach, we propose a multiple scattering model for PDLC based on successive order and Monte Carlo methods. This model, along with ADA and electro-optical response theories, was used to calculate the angular distribution of scattered light and electric field switching response. The predictions demonstrate close quantitative agreement with experimental results. Incorporating complex refractive indices to treat dye- doped PDLC
A no-scale inflationary model to fit them all
Ellis, John; García, Marcos A.G.; Olive, Keith A.; Nanopoulos, Dimitri V. E-mail: garciagarcia@physics.umn.edu E-mail: olive@physics.umn.edu
2014-08-01
The magnitude of B-mode polarization in the cosmic microwave background as measured by BICEP2 favours models of chaotic inflation with a quadratic m{sup 2} φ{sup 2}/2 potential, whereas data from the Planck satellite favour a small value of the tensor-to-scalar perturbation ratio r that is highly consistent with the Starobinsky R +R{sup 2} model. Reality may lie somewhere between these two scenarios. In this paper we propose a minimal two-field no-scale supergravity model that interpolates between quadratic and Starobinsky-like inflation as limiting cases, while retaining the successful prediction n{sub s} ≅ 0.96.
Implications of purely classical gravity for inflationary tensor modes
NASA Astrophysics Data System (ADS)
Ashoorioon, Amjad; Dev, P. S. Bhupal; Mazumdar, Anupam
2014-09-01
We discuss the implications of a purely classical (instead of quantum) theory of gravity for the primordial gravitational wave spectrum generated during inflation. We argue that for a scalar field driven inflation in a classical gravity the amplitude of the gravitational wave will be too small, irrespective of its primordial seed, to be detected in any forthcoming experiments. Therefore, a positive detection of the B-mode polarizations in the Cosmic Microwave Background (CMB) spectrum will naturally confirm the quantum nature of gravity itself. Furthermore there will be no upper limit on the scale of inflation in the case of classical gravity, and a high-scale model of inflation can easily bypass the observational constraints.
Running spectral index and formation of primordial black hole in single field inflation models
Drees, Manuel; Erfani, Encieh E-mail: erfani@th.physik.uni-bonn.de
2012-01-01
A broad range of single field models of inflation are analyzed in light of all relevant recent cosmological data, checking whether they can lead to the formation of long-lived Primordial Black Holes (PBHs). To that end we calculate the spectral index of the power spectrum of primordial perturbations as well as its first and second derivatives. PBH formation is possible only if the spectral index increases significantly at small scales, i.e. large wave number k. Since current data indicate that the first derivative α{sub S} of the spectral index n{sub S}(k{sub 0}) is negative at the pivot scale k{sub 0}, PBH formation is only possible in the presence of a sizable and positive second derivative (''running of the running'') β{sub S}. Among the three small-field and five large-field models we analyze, only one small-field model, the ''running mass'' model, allows PBH formation, for a narrow range of parameters. We also note that none of the models we analyze can accord for a large and negative value of α{sub S}, which is weakly preferred by current data.
Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.
Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok
2015-11-24
The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.
Terahertz probes of magnetic field induced spin reorientation in YFeO{sub 3} single crystal
Lin, Xian; Jiang, Junjie; Ma, Guohong; Jin, Zuanming; Wang, Dongyang; Tian, Zhen; Han, Jiaguang; Cheng, Zhenxiang
2015-03-02
Using the terahertz time-domain spectroscopy, we demonstrate the spin reorientation of a canted antiferromagnetic YFeO{sub 3} single crystal, by evaluating the temperature and magnetic field dependence of resonant frequency and amplitude for the quasi-ferromagnetic (FM) and quasi-antiferromagnetic modes (AFM), a deeper insight into the dynamics of spin reorientation in rare-earth orthoferrites is established. Due to the absence of 4f-electrons in Y ion, the spin reorientation of Fe sublattices can only be induced by the applied magnetic field, rather than temperature. In agreement with the theoretical predication, the frequency of FM mode decreases with magnetic field. In addition, an obvious step of spin reorientation phase transition occurs with a relatively large applied magnetic field of 4 T. By comparison with the family members of RFeO{sub 3} (R = Y{sup 3+} or rare-earth ions), our results suggest that the chosen of R would tailor the dynamical rotation properties of Fe ions, leading to the designable spin switching in the orthoferrite antiferromagnetic systems.
Evaluation of debonding strength of single lap joint by the intensity of singular stress field
NASA Astrophysics Data System (ADS)
Miyazaki, Tatsujiro; Noda, Nao-Aki
2017-05-01
In this paper, the similarity of the singular stress field of the single lap joint (SLJ) is discussed to evaluate the debonding fracture by the intensity of the singular stress field (ISSF). The practical method is proposed for analyzing the ISSF for the SLJ. The analysis method focuses on the FEM stress at the interface end by applying the same mesh pattern to the unknown and reference models. It is found that the independent technique useful for the bonded plate and butt joint cannot be applied to the SLJ because the singular stress field of the SLJ consists of two singular stress terms. The FEM stress is divided to two FEM stresses by applying the unknown and reference models to different minimum element sizes. Then, the practicality of the present method is examined by applying to the previous tensile test results of the SLJ composed of the aluminum alloy and the epoxy resin. The ISSFs for the SLJ were calculated by changing the adhesive thickness t 2 and the overlap length l 2. In the case of the SLJ with 225 mm in total length and 7 mm in adherend thickness, it was found that the similar singular stress fields are formed in the range of 0.15 mm ≤ t 2 ≤ 0.9mm and 15 mm ≤ l 2 ≤ 50 mm. It is shown that the critical ISSFs at the fracture are constant in the range.
Retrieving three-dimensional displacement fields of mining areas from a single InSAR pair
NASA Astrophysics Data System (ADS)
Li, Zhi Wei; Yang, Ze Fa; Zhu, Jian Jun; Hu, Jun; Wang, Yun Jia; Li, Pei Xian; Chen, Guo Liang
2015-01-01
This paper presents a novel method for retrieving three-dimensional (3-D) displacement fields of mining areas from a single interferometric synthetic aperture radar (InSAR) pair. This method fully exploits the mechanism of mining subsidence, specifically the proportional relationship between the horizontal displacement and horizontal gradient of vertical displacements caused by underground mining. This method overcomes the limitations of conventional InSAR techniques that can only measure one-dimensional (1-D) deformation of mining area along the radar line-of-sight direction. The proposed method is first validated with simulated 3-D displacement fields, which are obtained by the FLAC software. The root mean square errors of the 3-D displacements retrieved by the proposed method are 13.7, 27.6 and 3.6 mm for the West-East, North-South, and Up-Down components, respectively. We then apply the proposed method to estimate the 3-D displacements of the Qianyingzi and the Xuzhou coal mines in China, respectively, each along with two Advanced Land Observing Satellite (ALOS) Phased Array Type L-band Synthetic Aperture Radar images. Results show that the estimated 3-D displacement is highly consistent with that of the field surveying. This demonstrates that the proposed method is an effective approach for retrieving 3-D mining displacement fields and will play an important role in mining-related hazard prevention and environment assessment under limited InSAR acquisitions.
Malace, Simona P.; Sawatzky, Bradley D.; Gao, Haiyan
2013-09-01
We studied the single-photoelectron detection capabilities of a multianode photomultiplier tube H8500C-03 and its performance in high magnetic field. Our results show that the device can readily resolve signals at the single photoelectron level making it suitable for photon detection in both threshold and ring imaging Cherenkov detectors. We also found that a large longitudinal magnetic field, up to 300 Gauss, induces a change in the relative output of at most 55% for an edge pixel, and of at most 15% for a central pixel. The H8500C-03 signal loss in transverse magnetic fields it is significantly more pronounced than for the longitudinal case. Our studies of single photoelectron reduction in magnetic fields point to the field induced misfocusing of the photoelectron extracted from the photocathode as primary cause of signal loss. With appropriate shielding this PMT could function in high magnetic field environments.
Inflationary tensor fossils in large-scale structure
Dimastrogiovanni, Emanuela; Fasiello, Matteo; Jeong, Donghui; Kamionkowski, Marc E-mail: mrf65@case.edu E-mail: kamion@jhu.edu
2014-12-01
Inflation models make specific predictions for a tensor-scalar-scalar three-point correlation, or bispectrum, between one gravitational-wave (tensor) mode and two density-perturbation (scalar) modes. This tensor-scalar-scalar correlation leads to a local power quadrupole, an apparent departure from statistical isotropy in our Universe, as well as characteristic four-point correlations in the current mass distribution in the Universe. So far, the predictions for these observables have been worked out only for single-clock models in which certain consistency conditions between the tensor-scalar-scalar correlation and tensor and scalar power spectra are satisfied. Here we review the requirements on inflation models for these consistency conditions to be satisfied. We then consider several examples of inflation models, such as non-attractor and solid-inflation models, in which these conditions are put to the test. In solid inflation the simplest consistency conditions are already violated whilst in the non-attractor model we find that, contrary to the standard scenario, the tensor-scalar-scalar correlator probes directly relevant model-dependent information. We work out the predictions for observables in these models. For non-attractor inflation we find an apparent local quadrupolar departure from statistical isotropy in large-scale structure but that this power quadrupole decreases very rapidly at smaller scales. The consistency of the CMB quadrupole with statistical isotropy then constrains the distance scale that corresponds to the transition from the non-attractor to attractor phase of inflation to be larger than the currently observable horizon. Solid inflation predicts clustering fossils signatures in the current galaxy distribution that may be large enough to be detectable with forthcoming, and possibly even current, galaxy surveys.
Separation of non-stationary sound fields with single layer pressure-velocity measurements.
Bi, Chuan-Xing; Geng, Lin; Zhang, Xiao-Zheng
2016-02-01
This paper examines the feasibility of extracting the non-stationary sound field generated by a target source in the presence of disturbing source from single layer pressure-velocity measurements. Unlike the method described in a previous paper [Bi, Geng, and Zhang, J. Acoust. Soc. Am. 135(6), 3474-3482 (2014)], the proposed method allows measurements of pressure and particle velocity signals on a single plane instead of pressure signals on two planes, and the time-dependent pressure generated by the target source is extracted by a simple superposition of the measured pressure and the convolution between the measured particle velocity and the corresponding impulse response function. Because the particle velocity here is measured directly, the error caused by the finite difference approximation can be avoided, which makes it possible to perform the separation better than the previous method. In this paper, a Microflown pressure-velocity probe is used to perform the experimental measurements, and the calibration procedure of the probe in the time domain is given. The experimental results demonstrate that the proposed method is effective in extracting the desired non-stationary sound field generated by the target source from the mixed one in both time and space domains, and it obtains more accurate results than the previous method.
Wang, Feng; Karan, Niladri S.; Minh Nguyen, Hue; ...
2015-09-23
Through single dot spectroscopy and numerical simulation studies, we demonstrate that the fundamental mode of gold patch nanoantennas have fringe-field resonance capable of enhancing the nano-emitters coupled around the edge of the patch antenna. This fringe-field coupling is used to enhance the radiative rates of core/thick-shell nanocrystal quantum dots (g-NQDs) that cannot be embedded into the ultra-thin dielectric gap of patch nanoantennas due to their large sizes. We attain 14 and 3 times enhancements in single exciton radiative decay rate and bi-exciton emission efficiencies of g-NQDs respectively, with no detectable metal quenching. Our numerical studies confirmed our experimental results andmore » further reveal that patch nanoantennas can provide strong emission enhancement for dipoles lying not only in radial direction of the circular patches but also in the direction normal to the antennas surface. Finally, this provides a distinct advantage over the parallel gap-bar antennas that can provide enhancement only for the dipoles oriented across the gap.« less
Wang, Feng; Karan, Niladri S.; Minh Nguyen, Hue; Ghosh, Yagnaseni; Hollingsworth, Jennifer A.; Htoon, Han
2015-09-23
Through single dot spectroscopy and numerical simulation studies, we demonstrate that the fundamental mode of gold patch nanoantennas have fringe-field resonance capable of enhancing the nano-emitters coupled around the edge of the patch antenna. This fringe-field coupling is used to enhance the radiative rates of core/thick-shell nanocrystal quantum dots (g-NQDs) that cannot be embedded into the ultra-thin dielectric gap of patch nanoantennas due to their large sizes. We attain 14 and 3 times enhancements in single exciton radiative decay rate and bi-exciton emission efficiencies of g-NQDs respectively, with no detectable metal quenching. Our numerical studies confirmed our experimental results and further reveal that patch nanoantennas can provide strong emission enhancement for dipoles lying not only in radial direction of the circular patches but also in the direction normal to the antennas surface. Finally, this provides a distinct advantage over the parallel gap-bar antennas that can provide enhancement only for the dipoles oriented across the gap.
Wang, Feng; Karan, Niladri S.; Minh Nguyen, Hue; Ghosh, Yagnaseni; Hollingsworth, Jennifer A.; Htoon, Han
2015-01-01
Through single dot spectroscopy and numerical simulation studies, we demonstrate that the fundamental mode of gold patch nanoantennas have fringe-field resonance capable of enhancing the nano-emitters coupled around the edge of the patch antenna. This fringe-field coupling is used to enhance the radiative rates of core/thick-shell nanocrystal quantum dots (g-NQDs) that cannot be embedded into the ultra-thin dielectric gap of patch nanoantennas due to their large sizes. We attain 14 and 3 times enhancements in single exciton radiative decay rate and bi-exciton emission efficiencies of g-NQDs respectively, with no detectable metal quenching. Our numerical studies confirmed our experimental results and further reveal that patch nanoantennas can provide strong emission enhancement for dipoles lying not only in radial direction of the circular patches but also in the direction normal to the antennas surface. This provides a distinct advantage over the parallel gap-bar antennas that can provide enhancement only for the dipoles oriented across the gap. PMID:26394763
Magnetic field of a single muscle fiber. First measurements and a core conductor model.
van Egeraat, J M; Friedman, R N; Wikswo, J P
1990-01-01
We present the first measurements of the magnetic field from a single muscle fiber of the frog gastrocnemius, obtained by using a toroidal pickup coil coupled to a room-temperature, low-noise amplifier. The axial currents associated with the magnetic fields of single fibers were biphasic and had peak-to-peak amplitudes ranging between 50 and 100 nA, depending primarily on the fiber radius. With an intracellular microelectrode, we measured the action potential of the same fiber, which allowed us to determine that the intracellular conductivity of the muscle fiber in the core conductor approximation was 0.20 +/- 0.09 S/m. Similarly, we found that the effective membrane capacitance was 0.030 +/- 0.011 F/m2. These results were not significantly affected by the anisotropic conductivity of the muscle bundle. We demonstrate how our magnetic technique can be used to determine the transmembrane action potential without penetrating the membrane with a microelectrode, thereby offering a reliable, stable, and atraumatic method for studying contracting muscle fibers. PMID:2306511
Single-field consistency relations of large scale structure part II: resummation and redshift space
Creminelli, Paolo; Gleyzes, Jérôme; Vernizzi, Filippo; Simonović, Marko E-mail: jerome.gleyzes@cea.fr E-mail: filippo.vernizzi@cea.fr
2014-02-01
We generalize the recently derived single-field consistency relations of Large Scale Structure in two directions. First, we treat the effect of the long modes (with momentum q) on the short ones (with momentum k) non-perturbatively, by writing resummed consistency relations which do not require k/q⋅δ{sub q} << 1. These relations do not make any assumptions on the short-scales physics and are extended to include (an arbitrary number of) multiple long modes, internal lines with soft momenta and soft loops. We do several checks of these relations in perturbation theory and we verify that the effect of soft modes always cancels out in equal-time correlators. Second, we write the relations directly in redshift space, without assuming the single-stream approximation: not only the long mode affects the short scales as a homogeneous gravitational field, but it also displaces them by its velocity along the line-of-sight. Redshift space consistency relations still vanish when short modes are taken at equal time: an observation of a signal in the squeezed limit would point towards multifield inflation or a violation of the equivalence principle.
Linear magnetoresistance and zero-field anomalies in HfNiSn single crystals
NASA Astrophysics Data System (ADS)
Steinke, Lucia; Kistner-Morris, Jedediah J.; Deng, Haiming; Geschwind, Gayle; Aronson, Meigan C.
The Half-Heusler compound HfNiSn is probably best known as a candidate material for thermoelectric applications, and studies of its properties have mainly focused on polycrystalline samples and thin films. However, magnetotransport studies of HfNiSn show unusual transport properties like linear magnetoresistance (LMR), where single-crystalline samples of HfNiSn exhibit unexpected LMR at very low fields. In this work, we optimized the solution growth of HfNiSn to obtain high-quality single crystals, where electrical transport measurements show that it is a compensated semimetal below ~ 200 K, where the Hall voltage is zero. At higher temperatures, we see a finite Hall contribution from activated excess carriers. In the semimetallic regime, we observe transport anomalies like resistive signals that strongly depend on contact configuration, and LMR below 5 K. Both low-field DC and low frequency AC magntization measurements show pronounced diamagnetic behavior and the onset of paramagnetism below 4 K. High-frequency diamagnetic screening may be attributed to a decreased skin depth with decreased resistance, but this scenario seems unlikely in HfNiSn since the measured resistance increases steeply at the lowest temperatures This research was supported by the Army Research Office.
IR near-field spectroscopy and imaging of single Li(x)FePO4 microcrystals.
Lucas, I T; McLeod, A S; Syzdek, J S; Middlemiss, D S; Grey, C P; Basov, D N; Kostecki, R
2015-01-14
This study demonstrates the unique capability of infrared near-field nanoscopy combined with Fourier transform infrared spectroscopy to map phase distributions in microcrystals of Li(x)FePO4, a positive electrode material for Li-ion batteries. Ex situ nanoscale IR imaging provides direct evidence for the coexistence of LiFePO4 and FePO4 phases in partially delithiated single-crystal microparticles. A quantitative three-dimensional tomographic reconstruction of the phase distribution within a single microcrystal provides new insights into the phase transformation and/or relaxation mechanism, revealing a FePO4 shell surrounding a diamond-shaped LiFePO4 inner core, gradually shrinking in size and vanishing upon delithiation of the crystal. The observed phase propagation pattern supports recent functional models of LiFePO4 operation relating electrochemical performance to material design. This work demonstrates the remarkable potential of near-field optical techniques for the characterization of electrochemical materials and interfaces.
Wang, Feng; Karan, Niladri S; Minh Nguyen, Hue; Ghosh, Yagnaseni; Hollingsworth, Jennifer A; Htoon, Han
2015-09-23
Through single dot spectroscopy and numerical simulation studies, we demonstrate that the fundamental mode of gold patch nanoantennas have fringe-field resonance capable of enhancing the nano-emitters coupled around the edge of the patch antenna. This fringe-field coupling is used to enhance the radiative rates of core/thick-shell nanocrystal quantum dots (g-NQDs) that cannot be embedded into the ultra-thin dielectric gap of patch nanoantennas due to their large sizes. We attain 14 and 3 times enhancements in single exciton radiative decay rate and bi-exciton emission efficiencies of g-NQDs respectively, with no detectable metal quenching. Our numerical studies confirmed our experimental results and further reveal that patch nanoantennas can provide strong emission enhancement for dipoles lying not only in radial direction of the circular patches but also in the direction normal to the antennas surface. This provides a distinct advantage over the parallel gap-bar antennas that can provide enhancement only for the dipoles oriented across the gap.
Modeling of anomalous Wtb interactions in single top quark events using subsidiary fields
NASA Astrophysics Data System (ADS)
Boos, E.; Bunichev, V.; Dudko, L.; Perfilov, M.
2017-01-01
A method to simulate anomalous fermion-boson interactions in Wtb vertex is presented with a minimal set of simulated samples of single top quark events at the LHC energies. In the proposed method, additional subsidiary vector fields corresponding to the Standard Model gauge fields are implemented for each type of the anomalous vertex structure. The method allows to simulate a manifestation of anomalous gauge couplings in two approaches used in experimental analyses either keeping only the linear order contributions in the anomalous couplings or keeping all contributions in numerators and denominators as appeared in matrix elements. For the processes with several anomalous couplings contributing simultaneously to the production and to the decay as well as to various interference terms the method allows to model correctly the dependence of kinematic distributions on anomalous couplings. The method shows how to generate a minimum set of event samples needed for a concrete analysis. All the single top quark production mechanisms, t-, s- and associative tW-channels, are considered. The correctness of the proposed method is demonstrated.
Baker, Kirk R; Woody, Matthew C
2017-03-15
Aircraft measurements made downwind from specific coal fired power plants during the 2013 Southeast Nexus field campaign provide a unique opportunity to evaluate single source photochemical model predictions of both O3 and secondary PM2.5 species. The model did well at predicting downwind plume placement. The model shows similar patterns of an increasing fraction of PM2.5 sulfate ion to the sum of SO2 and PM2.5 sulfate ion by distance from the source compared with ambient based estimates. The model was less consistent in capturing downwind ambient based trends in conversion of NOX to NOY from these sources. Source sensitivity approaches capture near-source O3 titration by fresh NO emissions, in particular subgrid plume treatment. However, capturing this near-source chemical feature did not translate into better downwind peak estimates of single source O3 impacts. The model estimated O3 production from these sources but often was lower than ambient based source production. The downwind transect ambient measurements, in particular secondary PM2.5 and O3, have some level of contribution from other sources which makes direct comparison with model source contribution challenging. Model source attribution results suggest contribution to secondary pollutants from multiple sources even where primary pollutants indicate the presence of a single source.
Wang, Dongxing; Zhu, Wenqi; Best, Michael D; Camden, Jon P; Crozier, Kenneth B
2013-10-04
The ability to detect molecules at low concentrations is highly desired for applications that range from basic science to healthcare. Considerable interest also exists for ultrathin materials with high optical absorption, e.g. for microbolometers and thermal emitters. Metal nanostructures present opportunities to achieve both purposes. Metal nanoparticles can generate gigantic field enhancements, sufficient for the Raman spectroscopy of single molecules. Thin layers containing metal nanostructures ("metasurfaces") can achieve near-total power absorption at visible and near-infrared wavelengths. Thus far, however, both aims (i.e. single molecule Raman and total power absorption) have only been achieved using metal nanostructures produced by techniques (high resolution lithography or colloidal synthesis) that are complex and/or difficult to implement over large areas. Here, we demonstrate a metasurface that achieves the near-perfect absorption of visible-wavelength light and enables the Raman spectroscopy of single molecules. Our metasurface is fabricated using thin film depositions, and is of unprecedented (wafer-scale) extent.
Florica, Camelia; Costas, Andreea; Boni, Andra Georgia; Negrea, Raluca; Preda, Nicoleta E-mail: encu@infim.ro; Pintilie, Lucian; Enculescu, Ionut E-mail: encu@infim.ro; Ion, Lucian
2015-06-01
High aspect ratio CuO nanowires are synthesized by a simple and scalable method, thermal oxidation in air. The structural, morphological, optical, and electrical properties of the semiconducting nanowires were studied. Au-Ti/CuO nanowire and Pt/CuO nanowire electrical contacts were investigated. A dominant Schottky mechanism was evidenced in the Au-Ti/CuO nanowire junction and an ohmic behavior was observed for the Pt/CuO nanowire junction. The Pt/CuO nanowire/Pt structure allows the measurements of the intrinsic transport properties of the single CuO nanowires. It was found that an activation mechanism describes the behavior at higher temperatures, while a nearest neighbor hopping transport mechanism is characteristic at low temperatures. This was also confirmed by four-probe resistivity measurements on the single CuO nanowires. By changing the metal/semiconductor interface, devices such as Schottky diodes and field effect transistors based on single CuO p-type nanowire semiconductor channel are obtained. These devices are suitable for being used in various electronic circuits where their size related properties can be exploited.
Effect of high SARs produced by cell phone like radiofrequency fields on mollusk single neuron.
Partsvania, B; Sulaberidze, T; Shoshiashvili, L
2013-03-01
During exposure to the cell phone electromagnetic field (EMF), some neurons in the brain at areas of peak specific absorption rate (SAR) absorb more electromagnetic energy than is permitted by existing guidelines. The goal of the present work was to investigate the influence of cell phone-like EMF signal on excitability and memory processes in single neurons. A Transverse Electromagnetic Cell (TEM Cell) was used to expose single neurons of mollusk to the EMF. Finite-Difference Time-Domain (FDTD) method was used for modeling the TEM Cell and the EMF interactions with living nerve ganglion and neurons. Neuron electrophysiology was investigated using standard microelectrode technique. SAR deposited into the single neuron was calculated to be 8.2 W/kg with a temperature increment of 1.21°C. After acute exposure, the threshold of firing of action potentials (AP) was significantly decreased (p ≈ 0.001). Time of habituation to stimulation with the intracellular current injection was increased (p ≈ 0.003). These results indicate that acute exposure to EMF at high SARs impairs the ability of neurons to store information.
NASA Astrophysics Data System (ADS)
Hollars, Christopher W.; Dunn, Robert C.
2000-05-01
Single molecule near-field fluorescence measurements are utilized to characterize the molecular level structure in Langmuir-Blodgett monolayers of L-α-dipalmitoylphosphatidylcholine (DPPC). Monolayers incorporating 3×10-4 mol % of the fluorescent lipid analog N-(6-tetramethylrhodaminethiocarbamoyl)-1,2-dihexadecanoyl-sn- glycero-3-phosphoethanolamine, triethylammonium salt (TRITC-DHPE) are transferred onto a freshly cleaved mica surface at low (π=8 mN/m) and high (π=30 mN/m) surface pressures. The near-field fluorescence images exhibit shapes in the single molecule images that are indicative of the lipid analog probe orientation within the films. Modeling the fluorescence patterns yields the single molecule tilt angle distribution in the monolayers which indicates that the majority of the molecules are aligned with their absorption dipole moment pointed approximately normal to the membrane plane. Histograms of the data indicate that the average orientation of the absorption dipole moment is 2.2° (σ=4.8°) in monolayers transferred at π=8 mN/m and 2.4° (σ=5.0°) for monolayers transferred at π=30 mN/m. There is no statistical difference in the mean tilt angle or distribution for the two monolayer conditions studied. The insensitivity of tilt angle to film surface pressure may arise from small chromophore doped domains of trapped liquid-expanded lipid phase remaining at high surface pressure. There is no evidence in the near-field fluorescence images for probe molecules oriented with their dipole moment aligned parallel with the membrane plane. We do, however, find a small but significant population of probe molecules (˜13%) with tilt angles greater than 16°. Comparison of the simultaneously collected near-field fluorescence and force images suggests that these large angle orientations are not the result of significant defects in the films. Instead, this small population may represent a secondary insertion geometry for the probe molecule into the lipid
Experimental measurement of the near tip strain field in an iron-silicon single crystal
NASA Astrophysics Data System (ADS)
Shield, T. W.; Kim, K.-S.
1994-05-01
EXPERIMENTAL RESULTS are presented for the plastic deformation field near a crack (200 μm wide notch) tip in an iron-3% silicon single crystal. The specimen was loaded in four point bending and the measurements were made at zero load after extensive plastic deformation had occurred. Results are given for a crack on the (011) plane with its tip along the [01|T] direction. The surface deformation field was measured using moire microscopy and a grating on the specimen surface. The in-plane Almansi strain components have been obtained by digitally processing the moire fringes. A well-structured asymptotic field has been found at a distance of 350-500 μm from the notch tip, where the maximum plastic strain is about 9%. The asymptotic field is observed to be composed of many distinct angular sectors. Three (six symmetric) of these sectors are found to have approximately constant strains. In a fourth (two symmetric) sector, the surface strains are approximately 1/ r singular. Between these sectors there are interconnecting transition sectors. The location of the stress state on the yield surface and the active slip systems in each sector are identified by assuming that the plastic strain rates are normal to a Schmid law yield surface. The slip systems identified in this manner show excellent agreement with direct observations of the slip texture on the surface and dislocation etch pits in the interior of the specimen. The experimental strain measurements also show that the constant strain sectors are regions in which unloading occurs. Because of this unloading, the crack tip stress and deformation state is substantially different from an HRR type field which assumes proportional loading. This strong nonproportional loading is thought to be caused by the presence of material anisotropy. The nonproportional loading also provides a large amount of crack tip shielding that is evidence of a toughening mechanism that results from the presence of material anisotropy.
AC field-induced polymer electroluminescence with single wall carbon nanotubes.
Sung, Jinwoo; Choi, Yeon Sik; Kang, Seok Ju; Cho, Sung Hwan; Lee, Tae-Woo; Park, Cheolmin
2011-03-09
We developed a high-performance field-induced polymer electroluminescence (FPEL) device consisting of four stacked layers: a top metal electrode/thin solution-processed nanocomposite film of single wall carbon nanotubes (SWNTs) and a fluorescent polymer/insulator/transparent bottom electrode working under an alternating current (AC) electric field. A small amount of SWNTs that were highly dispersed in the fluorescent polymer matrix by a conjugate block copolymer dispersant significantly enhanced EL, and we were able to realize an SWNT-FPEL device with a light emission of approximately 350 cd/m(2) at an applied voltage of ±25 V and an AC frequency of 300 kHz. The brightness of the SWNT-FPEL device is much greater than those of other AC-based organic or even inorganic ELs that generally require at least a few hundred volts. Light is emitted from our SWNT-FPEL device because of the sequential injection of field-induced holes and then electron carriers through ambipolar carbon nanotubes under an AC field, followed by exciton formation in the conjugated organic layer. Field-induced bipolar charge injection provides great material design freedom for our devices; the energy level does not have to be aligned between the electrode and the emission layer, and the balance of the carrier injected and transported can be altered in contrast to that in conventional organic light-emitting diodes, leading to an extremely cost-effective and unified device architecture that is applicable to all red-green-blue fluorescent polymers.
NASA Technical Reports Server (NTRS)
Larsson, A.; Muttelstein, M.; Arakawa, Y.; Yariv, A.
1986-01-01
Broad-area single-quantum-well graded-index waveguide separate-confinement heterostructure lasers were fabricated by molecular beam epitaxy. A high external quantum efficiency of 79 percent and stable, single-lobed far-field patterns with a beam divergence as narrow as 0.8 deg (1.9 times diffraction limit) for a 100 micron-wide laser were obtained under pulsed conditions.
Butter, J Y P; Hecht, B
2006-03-28
Single-molecule imaging and spectroscopy using an aperture scanning near-field optical microscope operating at 1.8 K in a helium bath cryostat is demonstrated. From near-field images at constant excitation frequency, the orientation of single molecules can be deduced. Spectral information is obtained using both near-field and confocal excitation schemes by scanning the excitation frequency at a fixed sample position. Differences between near-field and confocal spectra are discussed in terms of the position with respect to the aperture and the molecular orientation.
Noninvasive, near-field terahertz imaging of hidden objects using a single-pixel detector
Stantchev, Rayko Ivanov; Sun, Baoqing; Hornett, Sam M.; Hobson, Peter A.; Gibson, Graham M.; Padgett, Miles J.; Hendry, Euan
2016-01-01
Terahertz (THz) imaging can see through otherwise opaque materials. However, because of the long wavelengths of THz radiation (λ = 400 μm at 0.75 THz), far-field THz imaging techniques suffer from low resolution compared to visible wavelengths. We demonstrate noninvasive, near-field THz imaging with subwavelength resolution. We project a time-varying, intense (>100 μJ/cm2) optical pattern onto a silicon wafer, which spatially modulates the transmission of synchronous pulse of THz radiation. An unknown object is placed on the hidden side of the silicon, and the far-field THz transmission corresponding to each mask is recorded by a single-element detector. Knowledge of the patterns and of the corresponding detector signal are combined to give an image of the object. Using this technique, we image a printed circuit board on the underside of a 115-μm-thick silicon wafer with ~100-μm (λ/4) resolution. With subwavelength resolution and the inherent sensitivity to local conductivity, it is possible to detect fissures in the circuitry wiring of a few micrometers in size. THz imaging systems of this type will have other uses too, where noninvasive measurement or imaging of concealed structures is necessary, such as in semiconductor manufacturing or in ex vivo bioimaging. PMID:27386577
Reversible control of magnetic interactions by electric field in a single-phase material
NASA Astrophysics Data System (ADS)
Ryan, P. J.; Kim, J.-W.; Birol, T.; Thompson, P.; Lee, J.-H.; Ke, X.; Normile, P. S.; Karapetrova, E.; Schiffer, P.; Brown, S. D.; Fennie, C. J.; Schlom, D. G.
2013-01-01
Intrinsic magnetoelectric coupling describes the interaction between magnetic and electric polarization through an inherent microscopic mechanism in a single-phase material. This phenomenon has the potential to control the magnetic state of a material with an electric field, an enticing prospect for device engineering. Here, we demonstrate ‘giant’ magnetoelectric cross-field control in a tetravalent titanate film. In bulk form, EuTiO3, is antiferromagnetic. However, both anti and ferromagnetic interactions coexist between different nearest europium neighbours. In thin epitaxial films, strain was used to alter the relative strength of the magnetic exchange constants. We not only show that moderate biaxial compression precipitates local magnetic competition, but also demonstrate that the application of an electric field at this strain condition switches the magnetic ground state. Using first-principles density functional theory, we resolve the underlying microscopic mechanism resulting in G-type magnetic order and illustrate how it is responsible for the ‘giant’ magnetoelectric effect.
Geomagnetic field strength 3.2 billion years ago recorded by single silicate crystals.
Tarduno, John A; Cottrell, Rory D; Watkeys, Michael K; Bauch, Dorothy
2007-04-05
The strength of the Earth's early geomagnetic field is of importance for understanding the evolution of the Earth's deep interior, surface environment and atmosphere. Palaeomagnetic and palaeointensity data from rocks formed near the boundary of the Proterozoic and Archaean eons, some 2.5 Gyr ago, show many hallmarks of the more recent geomagnetic field. Reversals are recorded, palaeosecular variation data indicate a dipole-dominated morphology and available palaeointensity values are similar to those from younger rocks. The picture before 2.8 Gyr ago is much less clear. Rocks of the Archaean Kaapvaal craton (South Africa) are among the best-preserved, but even they have experienced low-grade metamorphism. The variable acquisition of later magnetizations by these rocks is therefore expected, precluding use of conventional palaeointensity methods. Silicate crystals from igneous rocks, however, can contain minute magnetic inclusions capable of preserving Archaean-age magnetizations. Here we use a CO2 laser heating approach and direct-current SQUID magnetometer measurements to obtain palaeodirections and intensities from single silicate crystals that host magnetite inclusions. We find 3.2-Gyr-old field strengths that are within 50 per cent of the present-day value, indicating that a viable magnetosphere sheltered the early Earth's atmosphere from solar wind erosion.
Theoretical investigation of single dopant in core/shell nanocrystal in magnetic field
NASA Astrophysics Data System (ADS)
Talbi, A.; Feddi, E.; Oukerroum, A.; Assaid, E.; Dujardin, F.; Addou, M.
2015-09-01
The control of single dopant or "solitary dopant" in semiconductors constitute a challenge to achieve new range of tunable optoelectronic devices. Knowing that the properties of doped monocrystals are very sensitive to different external perturbations, the aim of this study is to understand the effect of a magnetic field on the ground state energy of an off-center ionized donor in a core/shell quantum dot (CSQD). The binding energies with and without an applied magnetic field are determined by the Ritz variational method taking into account the electron-impurity correlation in the trial wave function deduced from the second-order perturbation. It has been found that the external magnetic field affects strongly the binding energy, and its effect varies as a function of the core radius and the shell thickness. We have shown the existence of a threshold ratio (a / b) crit which represents the limit between the tridimensional and the spherical surface confinement. In addition our analysis demonstrates the important influence of the position of ionized donor in the shell material.
NASA Astrophysics Data System (ADS)
Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Wang, Di; Hahn, Horst; Dasgupta, Subho
2016-10-01
Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm2 V-1 s-1.
Noninvasive, near-field terahertz imaging of hidden objects using a single-pixel detector.
Stantchev, Rayko Ivanov; Sun, Baoqing; Hornett, Sam M; Hobson, Peter A; Gibson, Graham M; Padgett, Miles J; Hendry, Euan
2016-06-01
Terahertz (THz) imaging can see through otherwise opaque materials. However, because of the long wavelengths of THz radiation (λ = 400 μm at 0.75 THz), far-field THz imaging techniques suffer from low resolution compared to visible wavelengths. We demonstrate noninvasive, near-field THz imaging with subwavelength resolution. We project a time-varying, intense (>100 μJ/cm(2)) optical pattern onto a silicon wafer, which spatially modulates the transmission of synchronous pulse of THz radiation. An unknown object is placed on the hidden side of the silicon, and the far-field THz transmission corresponding to each mask is recorded by a single-element detector. Knowledge of the patterns and of the corresponding detector signal are combined to give an image of the object. Using this technique, we image a printed circuit board on the underside of a 115-μm-thick silicon wafer with ~100-μm (λ/4) resolution. With subwavelength resolution and the inherent sensitivity to local conductivity, it is possible to detect fissures in the circuitry wiring of a few micrometers in size. THz imaging systems of this type will have other uses too, where noninvasive measurement or imaging of concealed structures is necessary, such as in semiconductor manufacturing or in ex vivo bioimaging.
Independent complexity patterns in single neuron activity induced by static magnetic field.
Spasić, S; Nikolić, Lj; Mutavdžić, D; Saponjić, J
2011-11-01
We applied a combination of fractal analysis and Independent Component Analysis (ICA) method to detect the sources of fractal complexity in snail Br neuron activity induced by static magnetic field of 2.7 mT. The fractal complexity of Br neuron activity was analyzed before (Control), during (MF), and after (AMF) exposure to the static magnetic field in six experimental animals. We estimated the fractal dimension (FD) of electrophysiological signals using Higuchi's algorithm, and empirical FD distributions. By using the Principal Component Analysis (PCA) and FastICA algorithm we determined the number of components, and defined the statistically independent components (ICs) in the fractal complexity of signal waveforms. We have isolated two independent components of the empirical FD distributions for each of three groups of data by using FastICA algorithm. ICs represent the sources of fractal waveforms complexity of Br neuron activity in particular experimental conditions. Our main results have shown that there could be two opposite intrinsic mechanisms in single snail Br neuron response to static magnetic field stimulation. We named identified ICs that correspond to those mechanisms - the component of plasticity and the component of elasticity. We have shown that combination of fractal analysis with ICA method could be very useful for the decomposition and identification of the sources of fractal complexity of bursting neuronal activity waveforms.
Modelling inflation with a power-law approach to the inflationary plateau
NASA Astrophysics Data System (ADS)
Dimopoulos, Konstantinos; Owen, Charlotte
2016-09-01
A new family of inflationary models is introduced and analyzed. The behavior of the parameters characterizing the models suggest preferred values, which generate the most interesting testable predictions. Results are further improved if late reheating and/or a subsequent period of thermal inflation is taken into account. Specific model realizations consider a sub-Planckian inflaton variation or a potential without fine-tuning of mass scales, based on the Planck and grand unified theory scales. A toy model realization in the context of global and local supersymmetry is examined, and results fitting the Planck observations are determined.
NASA Astrophysics Data System (ADS)
Orlofsky, Nicholas; Pierce, Aaron; Wells, James D.
2017-03-01
The gravitational waves measured at LIGO are presumed here to come from merging primordial black holes. We ask how these primordial black holes could arise through inflationary models while not conflicting with current experiments. Among the approaches that work, we investigate the opportunity for corroboration through experimental probes of gravitational waves at pulsar timing arrays. We provide examples of theories that are already ruled out, theories that will soon be probed, and theories that will not be tested in the foreseeable future. The models that are most strongly constrained are those with a relatively broad primordial power spectrum.
Inflationary cosmology: exploring the universe from the smallest to the largest scales.
Guth, Alan H; Kaiser, David I
2005-02-11
Understanding the behavior of the universe at large depends critically on insights about the smallest units of matter and their fundamental interactions. Inflationary cosmology is a highly successful framework for exploring these interconnections between particle physics and gravitation. Inflation makes several predictions about the present state of the universe-such as its overall shape, large-scale smoothness, and smaller scale structure-which are being tested to unprecedented accuracy by a new generation of astronomical measurements. The agreement between these predictions and the latest observations is extremely promising. Meanwhile, physicists are busy trying to understand inflation's ultimate implications for the nature of matter, energy, and spacetime.
Testing Inflationary Cosmology with the Bicep1 and Bicep2 Experiments
NASA Astrophysics Data System (ADS)
Aikin, Randol Wallace
Recent observations of the temperature anisotropies of the cosmic microwave background (CMB) favor an inflationary paradigm in which the scale factor of the universe inflated by many orders of magnitude at some very early time. Such a scenario would produce the observed large-scale isotropy and homogeneity of the universe, as well as the scale-invariant perturbations responsible for the observed (10 parts per million) anisotropies in the CMB. An inflationary epoch is also theorized to produce a background of gravitational waves (or tensor perturbations), the effects of which can be observed in the polarization of the CMB. The E-mode (or parity even) polarization of the CMB, which is produced by scalar perturbations, has now been measured with high significance. Con- trastingly, today the B-mode (or parity odd) polarization, which is sourced by tensor perturbations, has yet to be observed. A detection of the B-mode polarization of the CMB would provide strong evidence for an inflationary epoch early in the universe's history. In this work, we explore experimental techniques and analysis methods used to probe the B- mode polarization of the CMB. These experimental techniques have been used to build the Bicep2 telescope, which was deployed to the South Pole in 2009. After three years of observations, Bicep2 has acquired one of the deepest observations of the degree-scale polarization of the CMB to date. Similarly, this work describes analysis methods developed for the Bicep1 three-year data analysis, which includes the full data set acquired by Bicep1. This analysis has produced the tightest constraint on the B-mode polarization of the CMB to date, corresponding to a tensor-to-scalar ratio estimate of r = 0.04+/-0.32, or a Bayesian 95% credible interval of r < 0.70. These analysis methods, in addition to producing this new constraint, are directly applicable to future analyses of Bicep2 data. Taken together, the experimental techniques and analysis methods described
A general theorem on indeterminism in classical particle dynamics: inflationary scenarios
NASA Astrophysics Data System (ADS)
Pérez Laraudogoitia, Jon
2017-01-01
In the study of systems with an infinite number of particles, the results of indeterminism through deterministic collisions have until now usually made use of the temporal symmetry of mechanics. In this paper we take a more general path. This path furnishes proof that (in such systems) indeterminism based on deterministic collisions is rather more common than is suggested in studies published to date. A detailed analysis is made of what are known as inflationary scenarios, an interesting type of very general situations that display indeterminism.
A strong-field driver in the single-cycle regime based on self-compression in a kagome fibre
Balciunas, T.; Fourcade-Dutin, C.; Fan, G.; Witting, T.; Voronin, A. A.; Zheltikov, A. M.; Gerome, F.; Paulus, G. G.; Baltuska, A.; Benabid, F.
2015-01-01
Over the past decade intense laser fields with a single-cycle duration and even shorter, subcycle multicolour field transients have been generated and applied to drive attosecond phenomena in strong-field physics. Because of their extensive bandwidth, single-cycle fields cannot be emitted or amplified by laser sources directly and, as a rule, are produced by external pulse compression—a combination of nonlinear optical spectral broadening followed up by dispersion compensation. Here we demonstrate a simple robust driver for high-field applications based on this Kagome fibre approach that ensures pulse self-compression down to the ultimate single-cycle limit and provides phase-controlled pulses with up to a 100 μJ energy level, depending on the filling gas, pressure and the waveguide length. PMID:25625549
A strong-field driver in the single-cycle regime based on self-compression in a kagome fibre.
Balciunas, T; Fourcade-Dutin, C; Fan, G; Witting, T; Voronin, A A; Zheltikov, A M; Gerome, F; Paulus, G G; Baltuska, A; Benabid, F
2015-01-27
Over the past decade intense laser fields with a single-cycle duration and even shorter, subcycle multicolour field transients have been generated and applied to drive attosecond phenomena in strong-field physics. Because of their extensive bandwidth, single-cycle fields cannot be emitted or amplified by laser sources directly and, as a rule, are produced by external pulse compression-a combination of nonlinear optical spectral broadening followed up by dispersion compensation. Here we demonstrate a simple robust driver for high-field applications based on this Kagome fibre approach that ensures pulse self-compression down to the ultimate single-cycle limit and provides phase-controlled pulses with up to a 100 μJ energy level, depending on the filling gas, pressure and the waveguide length.
NASA Astrophysics Data System (ADS)
Tarduno, J. A.; Cottrell, R. D.
2012-04-01
Pioneering studies of meteorites and recent investigations have presented paleomagnetic data suggesting some parent bodies had dynamos. With this background, meteorites of the Howardite-Eucrite-Diogenite (HED) group of anchondrites, linked to the differentiated asteroid 4 Vesta, represent promising targets for magnetic investigation. Prior studies of HED meteorites have yielded contrasting results. Cisowski [1] reported low paleofields (1-5 μT) from two unbrecciated eucrites, whereas Morden [2] reported paleointensities of up to 37 μT from Thellier analyses of the brecciated Millbillillie eucrite; the latter were interpreted as indicative of a past dynamo. The age of the Millbillillie magnetization might be approximately 3.55 Ga [3] when the meteorite was heated by impact. Fu and Weiss [4-5] have recently reported a study of fusion crust of the Millibillie eucrite, supporting the conclusion that the meteorite preserves an ancient magnetization, but with very low (2-3 μT) paleointensity values. Here we discuss results from Northwest Africa (NWA) 5480, which is a olivine-diogenite (or harzburgite), 57 vol% olivine and 42 vol% orthopyroxene. Olivine is found in bands that have been interpreted as magmatic flow within the Vestan mantle [6-7]. We use single crystal paleointensity analyses [8]. Olivine grains 1-2 mm in size were separated for analyses. We specifically exclude grains with large visible inclusions as these may be multidomain magnetic minerals which relax on relatively short timescales. Magnetic hysteresis measurements suggest that olivine hosts single to pseudo-single domain magnetic inclusions suitable for paleointensity analyses. Thermal demagnetization reveals removal of several scattered magnetizations at low unblocking temperatures, followed by stable decay at higher temperatures. Thellier-Coe paleointensity data suggest a field of approximately 36 μT. These preliminary data, if confirmed, imply a Vestan dynamo because alternative primary magnetic