Sample records for einstein eddington timescale

  1. Sources of stellar energy, Einstein Eddington timescale of gravitational contraction and eternally collapsing objects

    NASA Astrophysics Data System (ADS)

    Mitra, Abhas

    2006-11-01

    We point out that although conventional stars are primarily fed by burning of nuclear fuel at their cores, in a strict sense, the process of release of stored gravitational energy, known as, Kelvin-Helmholtz (KH) process is either also operational albeit at an arbitrary slow rate, or lying in wait to take over at the disruption of the nuclear channel. In fact, the latter mode of energy release is the true feature of any self-gravity bound object including stars. We also highlight the almost forgotten fact that Eddington was the first physicist to introduce special relativity into the problem and correctly insist that, actually, total energy stored in a star is not the mere Newtonian energy but the total mass energy ( E = Mc2). Accordingly, Eddington defined an "Einstein time scale" of Evolution where the maximum age of the Sun turned out to be tE ? 1.4 × 10 13 yr. This concept has a fundamental importance though we know now that Sun in its present form cannot survive for more than 10 billion years. We extend this concept by introducing general relativity and show that the minimum value of depletion of total mass-energy is tE = ? not only for Sun but for and sufficiently massive or dense object. We propose that this time scale be known in the name of "Einstein-Eddington". We also point out that, recently, it has been shown that as massive stars undergo continued collapse to become a Black Hole, first they become extremely relativistic radiation pressure supported stars. And the life time of such relativistic radiation pressure supported compact stars is indeed dictated by this Einstein-Eddington time scale whose concept is formally developed here. Since this observed time scale of this radiation pressure supported quasistatic state turns out to be infinite, such objects are called eternally collapsing objects (ECO). Further since ECOs are expected to have strong intrinsic magnetic field, they are also known as "Magnetospheric ECO" or MECO.

  2. Penrose diagrams for the Einstein, Eddington--Lemaitre, Eddington--Lemaitre--Bondi, and anti-de Sitter universes

    SciTech Connect

    Tipler, F.J.

    1986-02-01

    Penrose diagrams including the c boundary at infinity and the singularities for the Einstein, Eddington--Lemaitre, Eddington--Lemaitre--Bondi, and anti-de Sitter universes are constructed. Penrose diagrams for the Einstein, Eddington--Lemaitre, and anti-de Sitter universes have been published before, but these diagrams are incomplete in that the published diagrams do not contain the c-boundary points of the universes they are supposed to represent.

  3. The Eddington CCD data simulator

    NASA Astrophysics Data System (ADS)

    Arentoft, T.; Kjeldsen, H.; De Ridder, J.; Stello, D.

    2004-01-01

    There are many open questions relating to the design and observing strategy for Eddington as well as to the data reduction methods that will be applied. The optimal solutions to these questions can only be found through extensive and realistic data simulations - simulations that will also help to assess and understand the expected final data quality. We have developed a CCD data simulator that can be used in detailed tests and verification of the Eddington data itself and in the development and optimisation of the on-board data reduction algorithms. The simulator can be used to characterise the instrumental noise profile to be included in the stellar time series simulations described by De Ridder et al. In this paper we present the simulator to the Eddington community and we demonstrate its capabilities and show examples of its performance.

  4. Surface singularities in Eddington-inspired Born-Infeld gravity.

    PubMed

    Pani, Paolo; Sotiriou, Thomas P

    2012-12-21

    Eddington-inspired Born-Infeld gravity was recently proposed as an alternative to general relativity that offers a resolution of spacetime singularities. The theory differs from Einstein's gravity only inside matter due to nondynamical degrees of freedom, and it is compatible with all current observations. We show that the theory is reminiscent of Palatini f(R) gravity and that it shares the same pathologies, such as curvature singularities at the surface of polytropic stars and unacceptable Newtonian limit. This casts serious doubt on its viability. PMID:23368444

  5. COSMOLOGICAL EVOLUTION OF MASSIVE BLACK HOLES: EFFECTS OF EDDINGTON RATIO DISTRIBUTION AND QUASAR LIFETIME

    SciTech Connect

    Cao Xinwu, E-mail: cxw@shao.ac.c [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030 (China)

    2010-12-10

    A power-law time-dependent light curve for active galactic nuclei (AGNs) is expected by the self-regulated black hole growth scenario, in which the feedback of AGNs expels gas and shut down accretion. This is also supported by the observed power-law Eddington ratio distribution of AGNs. At high redshifts, the AGN life timescale is comparable with (or even shorter than) the age of the universe, which sets a constraint on the minimal Eddington ratio for AGNs on the assumption of a power-law AGN light curve. The black hole mass function (BHMF) of AGN relics is calculated by integrating the continuity equation of massive black hole number density on the assumption of the growth of massive black holes being dominated by mass accretion with a power-law Eddington ratio distribution for AGNs. The derived BHMF of AGN relics at z = 0 can fit the measured local mass function of the massive black holes in galaxies quite well, provided the radiative efficiency {approx}0.1 and a suitable power-law index for the Eddington ratio distribution are adopted. In our calculations of the black hole evolution, the duty cycle of AGN should be less than unity, which requires the quasar life timescale {tau}{sub Q} {approx}> 5 x 10{sup 8} years.

  6. An expedition to heal the wounds of war. The 1919 eclipse and Eddington as Quaker adventurer

    NASA Astrophysics Data System (ADS)

    Stanley, Matthew

    2003-03-01

    The 1919 eclipse expedition's confirmation of general relativity is often celebrated as a triumph of scientific internationalism. However, British scientific opinion during World War I leaned toward the permanent severance of intellectual ties with Germany. That the expedition came to be remembered as a progressive moment of internationalsm was largely the result of the efforts of A. S. Eddington. A devout Quaker, Eddington imported into the scientific community the strategies being used by his coreligionists in the national dialogue: humanize the enemy through personal contact and dramatic projects that highlight the value of peace and cooperation. The essay also addresses the common misconception that Eddington's sympathy for Einstein led him intentionally to misinterpret the expedition's results. The evidence gives no reason to think that Eddington or his coworkers were anything but rigorous. Eddington's pacifism is reflected not in manipulated data but in the meaning of the expedition and the way it entered the collective memory as a celebration of international cooperation in the wake of war.

  7. Chandrasekhar vs. Eddington - An Unanticipated Confrontation.

    ERIC Educational Resources Information Center

    Wali, Kameshwar C.

    1982-01-01

    In the 1930s, Subrahmanyan Chandrasekhar found a fundamental parameter that determines the density of stars. Although recognized as a major discovery, it was generally unaccepted by astronomers because the work was ridiculed by a preeminent astronomer (Arthur Eddington). The controversy and current understanding of stellar evolution are discussed.…

  8. Eddington's theory of gravity and its progeny.

    PubMed

    Bañados, Máximo; Ferreira, Pedro G

    2010-07-01

    We resurrect Eddington's proposal for the gravitational action in the presence of a cosmological constant and extend it to include matter fields. We show that the Newton-Poisson equation is modified in the presence of sources and that charged black holes show great similarities with those arising in Born-Infeld electrodynamics coupled to gravity. When we consider homogeneous and isotropic space-times, we find that there is a minimum length (and maximum density) at early times, clearly pointing to an alternative theory of the big bang. We thus argue that the modern formulation of Eddington's theory, Born-Infeld gravity, presents us with a novel, nonsingular description of the Universe. PMID:20867432

  9. Eddington's Theory of Gravity and Its Progeny

    Microsoft Academic Search

    Máximo Bañados; Pedro G. Ferreira

    2010-01-01

    We resurrect Eddington's proposal for the gravitational action in the presence of a cosmological constant and extend it to include matter fields. We show that the Newton-Poisson equation is modified in the presence of sources and that charged black holes show great similarities with those arising in Born-Infeld electrodynamics coupled to gravity. When we consider homogeneous and isotropic space-times, we

  10. Software for timescale applications

    Microsoft Academic Search

    P. T. Wallace

    2011-01-01

    This paper describes some of the design considerations behind the timescale transformation software provided by the International Astronomical Union's SOFA collaboration. The solution adopted by SOFA includes two-part Julian dates, to safeguard precision, and individual treatment of specific transformations, rather than a single general-purpose routine. Correct handling of UTC leap seconds was a particular challenge.

  11. Software for timescale applications

    NASA Astrophysics Data System (ADS)

    Wallace, P. T.

    2011-08-01

    This paper describes some of the design considerations behind the timescale transformation software provided by the International Astronomical Union's SOFA collaboration. The solution adopted by SOFA includes two-part Julian dates, to safeguard precision, and individual treatment of specific transformations, rather than a single general-purpose routine. Correct handling of UTC leap seconds was a particular challenge.

  12. Optical intra-day variability timescales and black hole mass of the blazars

    NASA Astrophysics Data System (ADS)

    Gupta, S. P.; Pandey, U. S.; Singh, K.; Rani, B.; Pan, J.; Fan, J. H.; Gupta, A. C.

    2012-01-01

    In this paper, we have used optical intra-day variability archive data to calculate the central black hole masses and Eddington luminosities for nine blazars: 3C 66A, AO 0235+164, S5 0716+714, PKS 0735+178, OJ 287, 1215+303, 1216-010, 1308+326, PKS 1510-089, Mrk 501 and BL Lac using intra-day variability timescales and periodicity (if present). The calculated central black hole mass of these nine blazars using intra-day variability timescales are found to be in the range of 1.22-25.30 × 10 7 M ? and corresponding Eddington luminosity in the range of 1.58-32.88 × 10 45 erg s -1. The black hole mass and Eddington luminosity are in the range of 0.32-31.23 × 10 8 M ? and 1.23-31.20 × 10 46 erg s -1, respectively when optical Doppler factor is taken into account. The comparison show, our estimated values of black hole mass are consistent with earlier reported values. Periodicity were present in two blazars OJ 287 and 1216-010 which give the central black hole mass of these blazars in the range of 1.32-14.6 × 10 7 M ? and corresponding Eddington luminosity in the range of 1.60-19.0 × 10 45 erg s -1, respectively.

  13. The Eddington Limit and Soft Gamma Repeaters

    NASA Astrophysics Data System (ADS)

    Katz, J. I.

    1996-05-01

    Observed intensities and inferred distances of soft gamma repeaters (SGRs) imply luminosities in excess of the nominal (electron scattering opacity) Eddington limit by 4-6 orders of magnitude. I review the physical basis of this limit. Accretional luminosities may exceed it if energy is hydrodynamically coupled from accreting matter to closed field lines where it forms a pair gas. This magnetically confined pair gas radiates roughly a blackbody spectrum with kB Te ? 23 keV, consistent with observations, at a luminosity up to ˜3 x 1044 ergs s-1 for a surface field of 1013 G. Magnetic transparency is not required. I discuss the minutes-long continuing emission of 1979 March 5, steady counterparts to SGRs and their spin periods.

  14. Compact stars in Eddington inspired gravity.

    PubMed

    Pani, Paolo; Cardoso, Vitor; Delsate, Térence

    2011-07-15

    A new, Eddington inspired theory of gravity was recently proposed by Bañados and Ferreira. It is equivalent to general relativity in vacuum, but differs from it inside matter. This viable, one-parameter theory was shown to avoid cosmological singularities and turns out to lead to many other exciting new features that we report here. First, for a positive coupling parameter, the field equations have a dramatic impact on the collapse of dust, and do not lead to singularities. We further find that the theory supports stable, compact pressureless stars made of perfect fluid, which provide interesting models of self-gravitating dark matter. Finally, we show that the mere existence of relativistic stars imposes a strong, near optimal constraint on the coupling parameter, which can even be improved by observations of the moment of inertia of the double pulsar. PMID:21838345

  15. Eddington limit for a gaseous stratus with finite optical depth

    NASA Astrophysics Data System (ADS)

    Fukue, Jun

    2015-06-01

    The Eddington luminosity of a spherical source is usually defined for a uniformly extending normal plasma. We usually suppose that the gas can accrete to the central object at the sub-Eddington luminosity, while it would be blown off from the central luminous source in the super-Eddington case. We reconsider this central dogma of the Eddington limit under the radiative transfer effect for the purely scattering case, using analytical and numerical methods. For the translucent isolated gas cloud (stratus) with finite optical depth, the concept of the Eddington luminosity is drastically changed. In an heuristic way, we find that the critical condition is approximately expressed as ? = (1 + ?* + ?c)/2, where ? (=L/LE) is the central luminosity L normalized by the Eddington luminosity LE, ?c is the optical depth of the stratus, and ?* (=?{1-R_*^2/R^2}) is the direction cosine of the central object, R* being the radius of the central object, and R the distance from the central object. When the optical depth of the stratus is around unity, the classical Eddington limit roughly holds for the stratus; ? ˜ 1. However, when the optical depth is greater than unity, the critical condition becomes roughly ? ˜ ?c/2, and the stratus would infall on to the central source even at the highly super-Eddington luminosity. When the optical depth is less than unity, on the other hand, the critical condition reduces to ? ? (1 + ?*)/2, and the stratus could be blown off in some limited ranges, depending on ?*. This new concept of the Eddington limit for the isolated stratus could drastically change the accretion and outflow physics of highly inhomegeneous plasmas, with relevance for astrophysical jets and winds and supermassive black hole formation.

  16. Non-linear Oscillations of Massive Stars Near the Eddington Limit

    NASA Astrophysics Data System (ADS)

    Sanyal, Debashis; Langer, Norbert

    2013-06-01

    The physics of massive star evolution, even on the main sequence is marred by uncertainties and hence, poorly understood. The focus of our work lies on the evolution of very massive stars on the main sequence when they approach the Eddington limit. Massive stars evolving near the Eddington limit are characterized by pronounced core-halo structures (Ishii et al. 1999) with extended low density envelopes accounting for even ~ 70% of the stellar radius, and density inversions (Petrovic et al. 2006, Graefener et al. 2011). These are ideal conditions or radial oscillations called ``strange modes'' (Glatzel 2004) which have very small growth times (~ dynamical timescale). We present non-linear calculations of these pulsations using a state-of-the-art one-dimensional hydrodynamic stellar evolution code (BEC) and latest input physics. The brightness perturbations caused as a result may relate to the microvariations observed in LBVs like AG Car (Lamers et al. 2004) or in supergiants like Deneb. Moreover, the feature of inflated envelopes coupled with the dynamic pulsations can play a major role in the modelling of mass transfer in very massive binary systems. We investigate how mass loss (through RLOF or wind) from such inflated stars may affect the envelope structure.

  17. FOREWORD: Modern Applications of Timescales Modern Applications of Timescales

    Microsoft Academic Search

    E. F. Arias; W. Lewandowski

    2011-01-01

    The development of the first atomic frequency standard by Louis Essen in the 1950s is at the origin of the adoption of the atomic definition of the SI second by the 13th General Conference on Weights and Measures in 1967 and the consequent adoption of the atomic timescale. After the short reign of ephemeris time as the world's reference timescale

  18. The Mythical Snake which Swallows its Tail: Einstein's matter world

    E-print Network

    Weinstein, Galina

    2013-01-01

    In 1917 Einstein introduced into his field equations a cosmological term having the cosmological constant as a coefficient, in order that the theory should yield a static universe. Einstein desired to eliminate absolute space from physics according to "Mach's ideas". De Sitter objected to the "world-matter" in Einstein's world, and proposed a vacuum solution of Einstein's field equations with the cosmological constant and with no "world-matter". In 1920 the world-matter of Einstein's world was equivalent to "Mach's Ether", a carrier of the effects of inertia. De Sitter's 1917 solution predicted a spectral shift effect. In 1923 Eddington and Weyl adopted De Sitter's model and studied this effect. Einstein objected to this "cosmological problem". This paper is a new interpretation to Einstein's cosmological considerations over the period 1917-1923.

  19. Riemann-Eddington theory: Incorporating matter, degravitating the cosmological constant

    E-print Network

    Durmus A. Demir

    2014-09-09

    Here we show that, Eddington's pure affine gravity, when extended with Riemann curvature, leads to gravitational field equations that incorporate matter. This Riemanned Eddington gravity outfits a setup in which matter gravitates normally with Newton's constant but vacuum gravitates differently with an independent gravitational constant. This novel setup enables degravitation of the vacuum to observed level not by any fine-tuning but by a large hierarchy between its gravitational constant and its energy density. Remarkably, degravitation of the cosmological constant is local, causal and natural yet only empirical because the requisite degravitation condition is not predicted by the theory.

  20. Not Only Because of Theory: Dyson, Eddington and the Competing Myths of the 1919 Eclipse Expedition

    E-print Network

    Daniel Kennefick

    2007-09-05

    The 1919 Eclipse Expedition to test the light-bending prediction of General Relativity remains one of the most famous physics experiments of the 20th century. However, in recent decades it has been increasingly often alleged that the data-analysis of the expedition's leaders was faulty and biased in favor of Einstein's theory. Arthur Stanley Eddington is particularly alleged to have been prejudiced in favor of general relativity. Specifically it is claimed that some of the data, which would have favored the so-called Newtonian prediction, was thrown out on dubious grounds. This paper argues that a close examination of the views of the expedition's organizers, and of their data analysis, suggests that they had good grounds for acting as they did, and that the key people involved, in particular the astronomer Frank Watson Dyson, were not biased in favor of Einstein. It also draws attention to a modern re-analysis of the most important eclipse plates which, though overlooked until now, tends to strongly support the thesis of this paper.

  1. Timescale Analysis of Spectral Lags

    E-print Network

    T. P. Li; J. L. Qu; H. Feng; L. M. Song; G. Q. Ding; L. Chen

    2004-07-21

    A technique for timescale analysis of spectral lags performed directly in the time domain is developed. Simulation studies are made to compare the time domain technique with the Fourier frequency analysis for spectral time lags. The time domain technique is applied to studying rapid variabilities of X-ray binaries and $\\gamma$-ray bursts. The results indicate that in comparison with the Fourier analysis the timescale analysis technique is more powerful for the study of spectral lags in rapid variabilities on short time scales and short duration flaring phenomena.

  2. FOREWORD: Modern Applications of Timescales Modern Applications of Timescales

    NASA Astrophysics Data System (ADS)

    Arias, E. F.; Lewandowski, W.

    2011-08-01

    The development of the first atomic frequency standard by Louis Essen in the 1950s is at the origin of the adoption of the atomic definition of the SI second by the 13th General Conference on Weights and Measures in 1967 and the consequent adoption of the atomic timescale. After the short reign of ephemeris time as the world's reference timescale from 1954 until 1967, Coordinated Universal Time (UTC), synchronized to universal time UT1, appeared as the best compromise for satisfying the requests of all users. At the moment of the discussion on the adoption of an atomic timescale to replace ephemeris time, the possibility of having both an astronomical time and an atomic time to serve different purposes was discussed. In the words of Essen [1], this 'would cause endless confusion as well as involving duplication of equipment'. Forty years after the adoption of the definition of Coordinated Universal Time at the International Telecommunication Union (ITU), we are close to the moment of making a decision on whether or not to decouple UTC from its tight link to the rotation of the Earth embodied in UT1. It has been a ten-year process of discussion, mainly at the ITU with the input of the International Astronomical Union, the BIPM, the Consultative Committee for Time and Frequency and other organizations. The majority opinion supported the change based on developers and users of systems that need time synchronization to a stable and continuous reference timescale; others insist on the necessity of keeping the leap-second strategy for serving some applications or just for tradition. It is our hope that, as happened in the seventies, the most appropriate definition to serve all modern applications will be adopted with the consensus of the different sectors. The redirection of international timekeeping from astronomy to metrology can be considered the benchmark that started the era of modern timescales, all based on atomic properties. The aim of this special issue of Metrologia is to review timescales in use today, either the internationally recognized references or those adapted to some specific applications, to discuss new and future developments and to present the sometimes complex procedures for making international recommendations. We are grateful to our colleagues who, without exception, accepted our invitation to contribute to this special issue. Reference Henderson D 2005 Metrologia 42 S4-29 The pdf file contains an appendix: "Glossary of acronyms related to timescales used in this issue".

  3. Massive main sequence stars evolving at the Eddington limit

    E-print Network

    Sanyal, Debashis; Langer, Norbert; Bestenlehner, Joachim M

    2015-01-01

    The evolution of massive stars even on the main sequence is not yet well understood. Due to the steep mass-luminosity relation, massive main sequence stars become very luminous. This brings their envelopes very close to the Eddington limit. We are analysing stellar evolutionary models in which the Eddington limit is reached and exceeded, and explore the rich diversity of physical phenomena which take place in their envelopes, and investigate their observational consequences. We use the grids of detailed stellar models by Brott et al. (2011) and Koehler et al. (2015), to investigate the envelope properties of core hydrogen burning massive stars. We find that at the stellar surface, the Eddington limit is almost never reached, even for stars up to 500 Msun. When an appropriate Eddington limit is defined locally in the stellar envelope, most stars more massive than 40 Msun actually exceed this limit, in particular in the partial ionization zones of iron, helium or hydrogen. While most models adjust their structu...

  4. Development of a pulsar-based timescale

    NASA Astrophysics Data System (ADS)

    Hobbs, G.

    2014-12-01

    In this paper we summarise how pulsar observations have been used to create a highly stable timescale. We review recent work from the Parkes Pulsar Timing Array team to create a timescale that has a stability comparable to existing atomic timescales. We discuss how this timescale will improve by combining data from more telescopes. We conclude by considering the long-term possibilities for pulsar-based timescales.

  5. Kaluza Ansatz applied to Eddington inspired Born-Infeld gravity

    NASA Astrophysics Data System (ADS)

    Fernandes, Karan; Lahiri, Amitabha

    2015-02-01

    We apply Kaluza's procedure to a metric version of Eddington-inspired Born-Infeld action in gravity in five dimensions. The resulting action contains, in addition to the usual four-dimensional actions for gravity and electromagnetism, nonlinear couplings between the electromagnetic field strength and curvature. Considering the spherically symmetric solution as an example, we find the lowest-order corrections for the Reissner-Nordström metric and the electromagnetic field.

  6. Kaluza Ansatz applied to Eddington inspired Born-Infeld Gravity

    E-print Network

    Karan Fernandes; Amitabha Lahiri

    2014-11-29

    We apply Kaluza's procedure to Eddington-inspired Born-Infeld action in gravity in five dimensions. The resulting action contains, in addition to the usual four-dimensional actions for gravity and electromagnetism, nonlinear couplings between the electromagnetic field strength and curvature. Considering the spherically symmetric solution as an example we find the lowest order corrections for the Reissner-Nordstr\\"om metric and the electromagnetic field.

  7. Centenarian Einstein

    ScienceCinema

    None

    2011-04-25

    Commémoration de A.Einstein avec 4 orateurs pour honnorer sa mémoire: le prof.Weisskopf parlera de l'homme de science engagé, Daniel Amati du climat de la physique aux années 1920, Sergio Fubini de l'heure scientifique d'A.Einstein et le prof.Berob(?)

  8. Einstein's Universe.

    ERIC Educational Resources Information Center

    Carlson, Eric; Wald, Robert

    1979-01-01

    Presents a guide to be used by students and teachers in conjunction with a television program about Einstein. Provides general information about special and general relativity, and the universe. Includes questions for discussion after each section and a bibliography. (MA)

  9. Spectral indices in Eddington-inspired Born-Infeld inflation

    E-print Network

    Cho, Inyong

    2015-01-01

    We investigate the scalar and the tensor spectral indices of the quadratic inflation model in Eddington-inspired Born-Infeld (EiBI) gravity. We find the EiBI corrections to the spectral indices are of second and first order in the slow-roll approximation for the scalar and the tensor perturbations respectively. This is very promising since the quadratic inflation model in general relativity provides a very nice fit for the spectral indices. Together with the suppression of the tensor-to-scalar ratio EiBI inflation is well along with the observational data.

  10. Einstein's Gravity

    NSDL National Science Digital Library

    In this lesson, students will read the 1919 edition of the Cosmic Times (see related resources) and respond by raising questions to be answered with further research. They will make a model of curved space to view the motion of spheres as explained by Albert Einstein's General Theory of Relativity. After presentations of their research to the class they will create an interview with Einstein. This activity is part of the Cosmic Times teachers guide and is intended to be used in conjunction with the 1919 Cosmic Times Poster.

  11. New method for exploring super-Eddington active galactic nuclei by near-infrared observations

    Microsoft Academic Search

    N. Kawakatu; K. Ohsuga

    2011-01-01

    We propose a new method to explore the candidate super-Eddington active galactic nuclei (AGNs). We examine the properties of infrared (IR) emission from the inner edge of the dusty torus in AGNs, which are powered by super- or sub-Eddington accretion flows around black holes, by considering the dependence of the polar angle on the radiation flux of accretion flows. We

  12. DEPENDENCE OF THE OPTICAL/ULTRAVIOLET VARIABILITY ON THE EMISSION-LINE PROPERTIES AND EDDINGTON RATIO IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Ai, Y. L.; Yuan, W.; Wang, J. G. [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, 650011 Kunming, Yunnan (China); Zhou, H. Y.; Wang, T. G.; Dong, X.-B.; Lu, H. L., E-mail: ayl@ynao.ac.c, E-mail: wmy@ynao.ac.c [Center for Astrophysics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2010-06-10

    The dependence of the long-term optical/UV variability on the spectral and fundamental physical parameters for radio-quiet active galactic nuclei (AGNs) is investigated. The multi-epoch-repeated photometric scanning data in the Stripe-82 region of the Sloan Digital Sky Survey (SDSS) are exploited for two comparative AGN samples (mostly quasars) selected therein: a broad-line Seyfert 1 (BLS1) type sample and a narrow-line Seyfert 1 (NLS1) type AGN sample within redshifts 0.3-0.8. Their spectral parameters are derived from the SDSS spectroscopic data. It is found that on rest-frame timescales of several years the NLS1-type AGNs show systematically smaller variability compared to the BLS1-type AGNs. In fact, the variability amplitude is found to correlate, though only moderately, with the eigenvector 1 parameters, i.e., the smaller the H{beta} linewidth, the weaker the [O III] and the stronger the Fe II emission, the smaller the variability amplitude. Moreover, an interesting inverse correlation is found between the variability and the Eddington ratio, which is perhaps more fundamental. The previously known dependence of the variability on luminosity is not significant, and the dependence on black hole mass-as claimed in recent papers and also present in our data-fades out when controlling for the Eddington ratio in the correlation analysis, though these may be partly due to the limited ranges of luminosity and black hole mass of our samples. Our result strongly supports that an accretion disk is likely to play a major role in producing the optical/UV variability.

  13. Radation force on a relativistic plasma and the Eddington limit

    SciTech Connect

    O'Dell, S.L.

    1981-02-01

    The Thomson-scattering radiation force on a hot isotropic exceeds that on a cold one by a factor of (2/3<(..gamma beta..)/sup 2/>+1), where ..gamma.. = (1-..beta../sup 2/)/sup -1/2/ is the electron Lorentz factor. This excess force results from the anisotropic loss of internal energy. Consequently, a relativistic plasma with <..gamma../sup 2/>>>5/2, when exposed to an anisotropic radiation field, acts as a rocket-a ''Compton rocket'', Compton rockets quite likely play a role in the more exotic astronomical objects (quasars, blazars, Seyfert nuclei, compact galactic X-ray sources, etc.), which appear to operate within a few orders of magnitude of the (classical) Thomson-scattering Eddington limit.

  14. Explaining variance in black carbon's aging timescale

    NASA Astrophysics Data System (ADS)

    Fierce, L.; Riemer, N.; Bond, T. C.

    2015-03-01

    The size and composition of particles containing black carbon (BC) are modified soon after emission by condensation of semivolatile substances and coagulation with other particles, known collectively as "aging" processes. Although this change in particle properties is widely recognized, the timescale for transformation is not well constrained. In this work, we simulated aerosol aging with the particle-resolved model PartMC-MOSAIC (Particle Monte Carlo - Model for Simulating Aerosol Interactions and Chemistry) and extracted aging timescales based on changes in particle cloud condensation nuclei (CCN). We simulated nearly 300 scenarios and, through a regression analysis, identified the key parameters driving the value of the aging timescale. We show that BC's aging timescale spans from hours to weeks, depending on the local environmental conditions and the characteristics of the fresh BC-containing particles. Although the simulations presented in this study included many processes and particle interactions, we show that 80% of the variance in the aging timescale is explained by only a few key parameters. The condensation aging timescale decreased with the flux of condensing aerosol and was shortest for the largest fresh particles, while the coagulation aging timescale decreased with the total number concentration of large (D >100 nm), CCN-active particles and was shortest for the smallest fresh particles. Therefore, both condensation and coagulation play important roles in aging, and their relative impact depends on the particle size range.

  15. Einstein's aborted attempt at a dynamic steady-state universe

    E-print Network

    Nussbaumer, Harry

    2014-01-01

    In June 1930 Einstein visited Cambridge where he stayed with Eddington who had just shown that Einstein's supposedly static universe of 1917 was not stable. This forced Einstein to rethink his cosmology. He spent January and February 1931 at Pasadena. There, he discussed cosmology intensely with Tolman, conscious that he had to replace his original model of 1917. However, at the end of February he still had not made up his mind about an alternative. The Albert Einstein Archives of Jerusalem (AEA) hold an undated draft, handwritten by Einstein, which I date to the beginning of January 1931. In this draft Einstein hopes to have found a solution to the cosmological problem: a stationary, dynamic universe in expansion. His model was stationary because particles leaving a given volume were replaced by particles created out of the vacuum, anticipating an idea of Bondi, Gold and Hoyle published in 1948. He saw the cosmological term as energy reservoir. However, he realised that his calculations contained a numerical...

  16. Three dimensional Eddington-inspired Born-Infeld gravity: Solutions

    NASA Astrophysics Data System (ADS)

    Jana, Soumya; Kar, Sayan

    2013-07-01

    Three dimensional Eddington-inspired Born-Infeld gravity is studied with the goal of finding new solutions. Beginning with cosmology, we obtain analytical and numerical solutions for the scale factor a(t), in spatially flat (k=0) and spatially curved (k=±1) Friedmann-Roberston-Walker universes with (i) pressureless dust (P=0) and (ii) perfect fluid (P=(?)/(2)), as matter sources. When the theory parameter ?>0, our cosmological solutions are generically singular (except for the open universe, with a specific condition). On the other hand, for ?<0 we do find nonsingular cosmologies. We then move on towards finding static, circularly symmetric line elements with matter obeying (i) p=0 and (ii) p=(?)/(2). For p=0, the solution found is nonsingular for ?<0 with the matter-stress-energy representing inhomogeneous dust. For p=(?)/(2) we obtain nonsingular solutions, for all ?, and discuss some interesting characteristics of these solutions. Finally, we look at the rather simple p=-? case where the solutions are either de Sitter or anti-de Sitter or flat spacetime.

  17. LOW-IONIZATION OUTFLOWS IN HIGH EDDINGTON RATIO QUASARS

    SciTech Connect

    Marziani, Paola [Also at INAF, Astronomical Observatory of Padova, Padova, Italy. (Italy)] [Also at INAF, Astronomical Observatory of Padova, Padova, Italy. (Italy); Sulentic, Jack W.; Plauchu-Frayn, Ilse; Del Olmo, Ascension, E-mail: paola.marziani@oapd.inaf.it [Instituto de Astrofisica de Andalucia, CSIC, E-18008 Granada (Spain)

    2013-02-20

    The broad Mg II {lambda}2800 doublet has been frequently studied in connection with its potentially important role as a virial estimator of black hole mass in high-redshift quasars. An important task, therefore, is the identification of any line components that are likely related to broadening by non-virial motions. High signal-to-noise median composite spectra (binned in the {sup f}our-dimensional eigenvector 1'' context of Sulentic et al.) were constructed for the brightest 680 Sloan Digital Sky Survey Data Release 7 quasars in the 0.4 {<=} z {<=} 0.75 range where both Mg II {lambda}2800 and H{beta} are recorded in the same spectra. Composite spectra representing 90% of the quasars confirm previous findings that FWHM(Mg II {lambda}2800) is about 20% narrower than FWHM(H{beta}). The situation is clearly different for the most extreme (Population A) sources, which are the highest Eddington radiators in the sample. In the median spectra of these sources, FWHM Mg II {lambda}2800 is equal to or greater than FWHM(H{beta}) and shows a significant blueshift relative to H{beta}. We interpret the Mg II {lambda}2800 blueshift as the signature of a radiation-driven wind or outflow in the highest accreting quasars. In this interpretation, the Mg II {lambda}2800 line width-affected by blueshifted emission-is unsuitable for virial mass estimation in Almost-Equal-To 10% of quasars.

  18. Lorentzian wormholes in Eddington-inspired Born-Infeld gravity

    E-print Network

    Shaikh, Rajibul

    2015-01-01

    We show, following the work of Olmo, Rubiera-Garcia and Sanchis-Alepuz (Eur. Phys. J. C {\\bf 74}, 2804 (2014)), that it is possible to construct a wide class of Lorentzian wormholes in Eddington-inspired Born-Infeld gravity with a stress energy which does not violate the Weak or Null Energy Condition. The wormholes exist for a negative value of $\\kappa$ (a parameter in the theory). In fact, it is shown that there is a critical value of $x$ (a parameter related to $\\kappa$) below which we have wormholes. Above the critical $x$, we have a regular black hole spacetime. We put a restriction on the equation of state parameter $\\alpha$ ($p_{\\theta}=\\alpha \\rho$) to have wormholes. We also put a lower limit on both $|\\kappa|$ and the throat radius, to restrict the tidal acceleration (at the throat) below one Earth gravity. As a special case of our general solution, we retrieve the wormhole supported by an electric field for a charge-to-mass ratio greater than the critical value $\\left(\\frac{Q}{M}\\right)_c\\approx 1.1...

  19. Water renewal timescales in the Scheldt Estuary

    NASA Astrophysics Data System (ADS)

    de Brye, Benjamin; de Brauwere, Anouk; Gourgue, Olivier; Delhez, Eric J. M.; Deleersnijder, Eric

    2012-06-01

    Using the concepts of the Constituent-oriented Age and Residence time Theory (CART), we compute timescales related to the water renewal in the Scheldt Estuary (The Netherlands/Belgium). Three different timescales are used to better understand and characterize the dynamics of the estuary: the age of the renewing water, the residence time and the exposure time. The residence time is the time taken by a water parcel to leave the estuary for the first time while the exposure time is the total time spent by a water parcel in the estuary including re-entries. The age of a renewing water parcel is defined as the time elapsed since it entered the estuary. The renewing water was split into three types: the water originating from the sea, the water originating from the upstream fresh tidal rivers and the water originating from the different canals and docks connected to the estuary. Every timescale is computed at any time and position by means of the finite-element, unstructured-mesh model SLIM. This results in movies of the timescale fields (shown as Supplementary material), allowing a detailed analysis of their spatial and temporal variabilities. The effect of the M2 tide and the discharge regime (winter, summer or average situation) on the timescales is also investigated. Tidally-averaged timescales vary little over the width of the estuary and hence exhibit a virtually one-dimensional behaviour. However, around these average values, the timescales can vary hugely over a tidal cycle, with amplitudes that significantly depend on the space coordinates. The reason thereof has yet to be elucidated. These results underscore the need for two- or three-dimensional models with high temporal resolution for investigating the dynamics of the Scheldt Estuary.

  20. Bending space–time: a commentary on Dyson, Eddington and Davidson (1920) ‘A determination of the deflection of light by the Sun's gravitational field’

    PubMed Central

    Longair, Malcolm

    2015-01-01

    The famous eclipse expedition of 1919 to Sobral, Brazil, and the island of Principe, in the Gulf of Guinea, led by Dyson, Eddington and Davidson was a turning point in the history of relativity, not only because of its importance as a test of Einstein's General Theory of Relativity, but also because of the intense public interest which was aroused by the success of the expedition. The dramatic sequence of events which occurred is reviewed, as well as the long-term impact of its success. The gravitational bending of electromagnetic waves by massive bodies is a subject of the greatest importance for contemporary and future astronomy, astrophysics and cosmology. Examples of the potential impact of this key tool of modern observational astronomy are presented. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750149

  1. Short Timescale Coronal Variability in Capella

    E-print Network

    Vinay L. Kashyap; Jennifer Posson-Brown

    2007-09-19

    We analyze 205 ks of imaging data of the active binary, Capella, obtained with the Chandra High Resolution Camera Imager (HRC-I) to determine whether Capella shows any variability at timescales < 50 ks. We find that a clear signal for variability is present for timescales < 20 ks, and that the light curves show evidence for excess fluctuation over that expected from a purely Poisson process. This overdispersion is consistent with variability at the 2-7% level, and suggests that the coronae on the binary components of Capella are composed of low-density plasma and low-lying loops.

  2. A NUMERICAL METHOD FOR STUDYING SUPER-EDDINGTON MASS TRANSFER IN DOUBLE WHITE DWARF BINARIES

    SciTech Connect

    Marcello, Dominic C.; Tohline, Joel E., E-mail: dmarcello@phys.lsu.edu, E-mail: tohline@phys.lsu.edu [Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, 202 Nicholson Hall, Baton Rouge, LA (United States)

    2012-04-01

    We present a numerical method for the study of double white dwarf (DWD) binary systems at the onset of super-Eddington mass transfer. We incorporate the physics of ideal inviscid hydrodynamical flow, Newtonian self-gravity, and radiation transport on a three-dimensional uniformly rotating cylindrical Eulerian grid. Care has been taken to conserve the key physical quantities such as angular momentum and energy. Our new method conserves total energy to a higher degree of accuracy than other codes that are presently being used to model mass transfer in DWD systems. We present the results of verification tests and simulate the first 20 + orbits of a binary system of mass ratio q 0.7 at the onset of dynamically unstable direct impact mass transfer. The mass transfer rate quickly exceeds the critical Eddington limit by many orders of magnitude, and thus we are unable to model a trans-Eddington phase. It appears that radiation pressure does not significantly affect the accretion flow in the highly super-Eddington regime. An optically thick common envelope forms around the binary within a few orbits. Although this envelope quickly exceeds the spatial domain of the computational grid, the fraction of the common envelope that exceeds zero gravitational binding energy is extremely small, suggesting that radiation-driven mass loss is insignificant in this regime. It remains to be seen whether simulations that capture the trans-Eddington phase of such flows will lead to the same conclusion or show that substantial material gets expelled.

  3. Super-Eddington mechanical power of an accreting black hole in M83.

    PubMed

    Soria, R; Long, K S; Blair, W P; Godfrey, L; Kuntz, K D; Lenc, E; Stockdale, C; Winkler, P F

    2014-03-21

    Mass accretion onto black holes releases energy in the form of radiation and outflows. Although the radiative flux cannot substantially exceed the Eddington limit, at which the outgoing radiation pressure impedes the inflow of matter, it remains unclear whether the kinetic energy flux is bounded by this same limit. Here, we present the detection of a radio-optical structure, powered by outflows from a non-nuclear black hole. Its accretion disk properties indicate that this black hole is less than 100 solar masses. The optical-infrared line emission implies an average kinetic power of 3 × 10(40) erg second(-1), higher than the Eddington luminosity of the black hole. These results demonstrate kinetic power exceeding the Eddington limit over a sustained period, which implies greater ability to influence the evolution of the black hole's environment. PMID:24578533

  4. Super-Eddington Mechanical Power of an Accreting Black Hole in M83

    NASA Technical Reports Server (NTRS)

    Soria, R.; Long, K. S.; Blair, W. P.; Godfrey, L.; Kuntz, K. D.; Lenc, E.; Stockdale, C.; Winkler, P. F.

    2014-01-01

    Mass accretion onto black holes releases energy in the form of radiation and outflows. Although the radiative flux cannot substantially exceed the Eddington limit, at which the outgoing radiation pressure impedes the inflow of matter, it remains unclear whether the kinetic energy flux is bounded by this same limit. Here, we present the detection of a radio-optical structure, powered by outflows from a non-nuclear black hole. Its accretion disk properties indicate that this black hole is less than 100 solar masses. The optical-infrared line emission implies an average kinetic power of 3 × 10(exp 40) erg second(exp -1), higher than the Eddington luminosity of the black hole. These results demonstrate kinetic power exceeding the Eddington limit over a sustained period, which implies greater ability to influence the evolution of the black hole's environment.

  5. A Limit Relation between Black Hole Mass and H$?$ Width: Testing Super-Eddington Accretion in Active Galactic Nuclei

    E-print Network

    Jian-Min Wang

    2003-02-20

    (abbreviated) We show that there is a limit relation between the black hole mass and the width at the half maximum of H$\\beta$ for active galactic nuclei (AGNs) with super-Eddington accretion rates. When a black hole has a super-Eddington accretion rate, the empirical relation of reverberation mapping has two possible ways. First, it reduces to a relation between the black hole mass and the size of the broad line region due to the photon trapping effects inside the accretion disk. For the Kaspi et al.'s empirical reverberation relation, we get the limit relation as $M_{\\rm BH}=(2.9 - 12.6)\\times 10^6M_{\\odot} (\\upsilon_{\\rm FWHM}/10^3{\\rm km s^{-1}})^{6.67}$, called as the Eddington limit. Second, the Eddington limit luminosity will be relaxed if the trapped photons can escape from the magnetized super-Eddington accretion disk via the photon bubble instability, and the size of the broad line region will be enlarged according to the empirical reverberation relation, leading to a relatively narrow width of H$\\beta$. We call this the Begelman limit. Super-Eddington accretions in a sample composed of 164 AGNs have been searched by this limit relation. We find there are a handful of objects locate between the Eddington and Begelman limit lines, they may be candidates of super-Eddington accretors in a hybrid structure of photon trapping and photon bubble instability. The maximum width of H$\\beta$ is in the reange of $(3.0 - 3.8)\\times 10^3$ km s$^{-1}$ for the maximum mass black holes with super-Eddington accretion rates among AGNs. We suggest that this limit relation is more reliable and convenient to test whether a source is super-Eddington and useful to probe the structure of the super-Eddington accretion process.

  6. A LONG, LONG time ago: geologic timescales

    NSDL National Science Digital Library

    Elizabeth Johnson

    Each student randomly picks a card with a geologic event (written description and an image) on it. A timeline has 11 events, not including the formation of the Earth and today. Students attach their event where they think it should go on a 45.5' timeline (in the hallway) made out of paper adding tape and mark the location on the timeline. They return to the classroom and receive a list of age dates for each event. Each group figures out the scale (1 foot = 100 million years) and then moves their events to the correct locations. Students are asked how the position of the events changed, and answer other questions that reinforce the difference between human timescales and geologic timescales. The powerpoint file below contains a template for making geologic event labels for the index cards. Instructors can tailor the geologic event list to fit their course.

  7. Passive optical limiting in long timescales

    NASA Astrophysics Data System (ADS)

    Stinger, Michael Vincent

    From its use in medicine to measure and/or probe various physiologies to commercial applications such as data storage on optical disks, the laser has positively contributed to the lives of people around the globe. Alongside it's unique properties, the control of laser light poses significant challenges. Optical limiting, or the truncation of optical energy at particular thresholds represents one such challenge. Given the plethora of radiation sources available, it is of significant value to identify a means by which optical limiting can be achieved simultaneously for a wide berth of source parameters. That said, this document focuses on the exploration of a particular optical limiting modality applied to long timescales; That is, optical pulses with durations on the order of hundreds of nanoseconds, microseconds and up to continuous-wave. Given that this modality has been previously shown to be broadband and effective in short timescales, evidence of it's efficacy in long timescales would demonstrate the modality as an exceptional option in the design of truly robust optical limiting devices. The results of L34 optical limiting research with incident laser light at a 750nm wavelength and pulse durations in the microsecond and nanosecond regimes as well as continuous-wave light at 532nm are shown and discussed. Results are discussed for both bulk and liquid-infiltrated capillary-array arrangements and for various output light collection configurations. The mechanisms by which limiting action occurs are discussed and their optimization within various configurations is considered. Through measurement in a variety of experimental situations and device configurations, the organic liquid L34 is shown to be an effective optical limiting material in long timescales. When combined with the fiber array architecture, these results provide evidence that L34 is an excellent candidate for use as a spectrally and temporally robust optical limiting system that is easy to construct and maintain.

  8. The Eddington limit and supercritical accretion. II - Time-dependent calculations

    NASA Astrophysics Data System (ADS)

    Burger, H. L.; Katz, J. I.

    1983-02-01

    Spherically symmetric, time-dependent accretion of an ionized hydrogen plasma onto a neutron star is calculated for accretion rates in excess of the Eddington limit. The coupled oxygen hydrodynamic and frequency integrated radiative transfer equations are solved on an Eulerian grid for these supercritical accretion flows. The results indicate that steady flows are limited to rates at or below the critical rate, with emergent luminosities equal to or less than the Eddington luminosity. Initially supercritical accretion rates generate a large pulse of radiation which reduces the accretion rate to the critical value and produces an extended quasi-static envelope.

  9. Timescales of Land Surface Evapotranspiration Response

    NASA Technical Reports Server (NTRS)

    Scott, Russell; Entekhabi, Dara; Koster, Randal; Suarez, Max

    1997-01-01

    Soil and vegetation exert strong control over the evapotranspiration rate, which couples the land surface water and energy balances. A method is presented to quantify the timescale of this surface control using daily general circulation model (GCM) simulation values of evapotranspiration and precipitation. By equating the time history of evaporation efficiency (ratio of actual to potential evapotranspiration) to the convolution of precipitation and a unit kernel (temporal weighting function), response functions are generated that can be used to characterize the timescales of evapotranspiration response for the land surface model (LSM) component of GCMS. The technique is applied to the output of two multiyear simulations of a GCM, one using a Surface-Vegetation-Atmosphere-Transfer (SVAT) scheme and the other a Bucket LSM. The derived response functions show that the Bucket LSM's response is significantly slower than that of the SVAT across the globe. The analysis also shows how the timescales of interception reservoir evaporation, bare soil evaporation, and vegetation transpiration differ within the SVAT LSM.

  10. Quasars Are Not Light-Bulbs: Testing Models of Quasar Lifetimes with the Observed Eddington Ratio Distribution

    E-print Network

    Hopkins, Philip F

    2008-01-01

    We use the observed distribution of Eddington ratios as a function of supermassive black hole (BH) mass to constrain models of AGN lifetimes and lightcurves. Given the observed AGN luminosity function, a model for AGN lifetimes (time above a given luminosity) translates directly to a predicted Eddington ratio distribution. Models for self-regulated BH growth, in which feedback produces a 'blowout' decay phase after some peak luminosity (shutting down accretion) make specific predictions for the lifetimes distinct from those expected if AGN are simply gas starved (without feedback) and very different from simple phenomenological 'light bulb' models. Present observations of the Eddington ratio distribution, spanning 5 decades in Eddington ratio, 3 in BH mass, and redshifts z=0-1, agree with the predictions of self-regulated models, and rule out 'light-bulb', pure exponential, and gas starvation models at high significance. We compare the Eddington ratio distributions at fixed BH mass and fixed luminosity (both ...

  11. Quantum Physics Einstein's Gravity

    E-print Network

    Visser, Matt

    Quantum Physics confronts Einstein's Gravity Matt Visser Physics Department Washington University Saint Louis USA Science Saturdays 13 October 2001 #12; Quantum Physics confronts Einstein's Gravity and with Einstein's theory of gravity (the general relativity) is still the single biggest theoretical problem

  12. Einstein x-ray observations of cataclysmic variables

    SciTech Connect

    Mason, K.O.; Cordova, F.A.

    1982-01-01

    Observations with the imaging x-ray detectors on the Einstein Observatory have led to a large increase in the number of low luminosity x-ray sources known to be associated with cataclysmic variable stars (CVs). The high sensitivity of the Einstein instrumentation has permitted study of their short timescale variability and spectra. The data are adding significantly to our knowledge of the accretion process in cataclysmic variables and forcing some revision in our ideas concerning the origin of the optical variability in these stars.

  13. Testing Milne-Eddington Inversion Codes Against One-Dimensional Model Atmospheres

    NASA Astrophysics Data System (ADS)

    Lastufka, Erica; Jaeggli, S. A.; Kankelborg, C.; Uitenbroek, H.

    2013-07-01

    Properties of solar vector magnetic fields can be determined by the inversion of polarization spectra. It is therefore important to have accurate inversion methods. Milne-Eddington inversions, used almost exclusively in the photosphere, assume a thin, flat atmosphere and are one of the most widely used inversion techniques. To investigate the potential weaknesses of parameterizing a stratified atmosphere using a single set of properties, we examine the consequences of using a Milne-Eddington inversion to invert spectra of complex atmospheres. Han Uitenbroek's Rybicki-Hummer radiative transfer and chemical equilibrium code was used to generate a series of one-dimensional model atmospheres with predetermined magnetic field configurations. Atmospheres at the quiet Sun temperature contained magnetic fields with strengths up 3000 G and inclination and azimuthal angles from 0 to 180 degrees. We examined the Stokes profiles of the Fe 15648.5 line, which with a Landé g-factor of 3.0 is very sensitive to the magnetic field. Using a simple Milne-Eddington inversion code, we examined the ranges in which the code accurately parameterized the magnetic field. To investigate the confidence intervals associated with the inverted parameters, we used the BayesME code developed by Andres Asensio Ramos. We discuss the key assumptions and limitations of a Milne-Eddington inversion.

  14. Tuning up Mind's Pattern to Nature's Own Idea : Eddington's Early Twenties Case

    E-print Network

    Boyer, Edmond

    Tuning up Mind's Pattern to Nature's Own Idea : Eddington's Early Twenties Case for Variational intended to embody the mind's collusion with nature by linking atomicity of matter with atomicity of action, variational derivatives were at first assigned a dual role requiring of them not only to express mind

  15. Levitating atmospheres of Eddington-luminosity neutron stars I. Optically thin Thomson-scattering atmospheres

    E-print Network

    M. Wielgus; W. Klu?niak; A. S?dowski; R. Narayan; M. Abramowicz

    2015-05-22

    In general relativity static gaseous atmospheres may be in hydrostatic balance in the absence of a supporting stellar surface, provided that the luminosity is close to the Eddington value. We construct analytic models of optically thin, spherically symmetric shells supported by the radiation pressure of a luminous central body in the Schwarzschild metric.

  16. Levitating atmospheres of Eddington-luminosity neutron stars I. Optically thin Thomson-scattering atmospheres

    E-print Network

    Wielgus, M; S?dowski, A; Narayan, R; Abramowicz, M

    2015-01-01

    In general relativity static gaseous atmospheres may be in hydrostatic balance in the absence of a supporting stellar surface, provided that the luminosity is close to the Eddington value. We construct analytic models of optically thin, spherically symmetric shells supported by the radiation pressure of a luminous central body in the Schwarzschild metric.

  17. Advances in time-scale algorithms

    NASA Technical Reports Server (NTRS)

    Stein, S. R.

    1993-01-01

    The term clock is usually used to refer to a device that counts a nearly periodic signal. A group of clocks, called an ensemble, is often used for time keeping in mission critical applications that cannot tolerate loss of time due to the failure of a single clock. The time generated by the ensemble of clocks is called a time scale. The question arises how to combine the times of the individual clocks to form the time scale. One might naively be tempted to suggest the expedient of averaging the times of the individual clocks, but a simple thought experiment demonstrates the inadequacy of this approach. Suppose a time scale is composed of two noiseless clocks having equal and opposite frequencies. The mean time scale has zero frequency. However if either clock fails, the time-scale frequency immediately changes to the frequency of the remaining clock. This performance is generally unacceptable and simple mean time scales are not used. First, previous time-scale developments are reviewed and then some new methods that result in enhanced performance are presented. The historical perspective is based upon several time scales: the AT1 and TA time scales of the National Institute of Standards and Technology (NIST), the A.1(MEAN) time scale of the US Naval observatory (USNO), the TAI time scale of the Bureau International des Poids et Measures (BIPM), and the KAS-1 time scale of the Naval Research laboratory (NRL). The new method was incorporated in the KAS-2 time scale recently developed by Timing Solutions Corporation. The goal is to present time-scale concepts in a nonmathematical form with as few equations as possible. Many other papers and texts discuss the details of the optimal estimation techniques that may be used to implement these concepts.

  18. A Century of Einstein

    NSDL National Science Digital Library

    This intriguing MSNBC website addresses how Einstein's theories still affect the world we live in today. Users can view a Macromedia Flash Player-enhanced slide show summarizing Einstein's life and major accomplishments. Visitors can download the five papers from 1905, Einstein's "miracle year." Students can find a helpful interactive module discussing the principles of relativity and its importance. The website discusses Einstein's personality and beliefs and hypothesizes how Einstein might have faired in today's world. Users can learn about the questions dealing with dark matter and dark energy that scientists are still trying to understand today.

  19. Timescale separation in recurrent neural networks.

    PubMed

    Flynn, Thomas

    2015-06-01

    Supervised learning in recurrent neural networks involves two processes: the neuron activity from which gradients are estimated and the process on connection parameters induced by these measurements. A problem such algorithms must address is how to balance the relative rates of these activities so that accurate sensitivity estimates are obtained while still allowing synaptic modification to take place at a rate sufficient for learning. We show how to calculate a sufficient timescale separation between these two processes for a class of contracting neural networks. PMID:25826019

  20. Super-Eddington wind scenario for the progenitors of type Ia supernovae: binary population synthesis calculations

    NASA Astrophysics Data System (ADS)

    Wang, B.; Ma, X.; Liu, D.-D.; Liu, Z.-W.; Wu, C.-Y.; Zhang, J.-J.; Han, Z.

    2015-04-01

    Context. The super-Eddington wind scenario has been proposed as an alternative way for producing type Ia supernovae (SNe Ia). The super-Eddington wind can naturally prevent the carbon-oxygen white dwarfs (CO WDs) with high mass-accretion rates from becoming red-giant-like stars. Furthermore, it works in low-metallicity environments, which may explain SNe Ia observed at high redshifts. Aims: In this article, we systematically investigated the most prominent single-degenerate WD+MS channel based on the super-Eddington wind scenario. Methods: We combined the Eggleton stellar evolution code with a rapid binary population synthesis (BPS) approach to predict SN Ia birthrates for the WD+MS channel by adopting the super-Eddington wind scenario and detailed mass-accumulation efficiencies of H-shell flashes on the WDs. Results: Our BPS calculations found that the estimated SN Ia birthrates for the WD+MS channel are ~0.009-0.315 × 10-3 yr-1 if we adopt the Eddington accretion rate as the critical accretion rate. These rates are much lower than those of the observations (<10% of the observed SN Ia birthrates). This indicates that the WD+MS channel only contributes a small portion of all SNe Ia. The birthrates in this simulation are lower than those of previous studies, the main reason for which is that new mass-accumulation efficiencies of H-shell flashes are adopted. We also found that the critical mass-accretion rate has significant influence on the birthrates of SNe Ia. Meanwhile, the results of our BPS calculations are sensitive to the values of the common-envelope ejection efficiency.

  1. Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Subthermal Timescales.

    PubMed

    Tauris; van Den Heuvel EP; Savonije

    2000-02-20

    We have performed detailed numerical calculations of the nonconservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M middle dot in circle) donor stars and a 1.3 M middle dot in circle accreting neutron star. We calculated the thermal response of the donor star to mass loss in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic reemission model," we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass transfer phase (1timescale if the convective envelope of the donor star is not too deep. These systems thus provide a new formation channel for binary millisecond pulsars with heavy CO white dwarfs and relatively short orbital periods (3-50 days). However, we conclude that to produce a binary pulsar with a O-Ne-Mg white dwarf or Porb approximately 1 day (e.g., PSR B0655+64) the above scenario does not work, and a spiral-in phase is still considered the most plausible scenario for the formation of such a system. PMID:10655173

  2. IONIZATION EQUILIBRIUM TIMESCALES IN COLLISIONAL PLASMAS

    SciTech Connect

    Smith, Randall K. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hughes, John P., E-mail: rsmith@cfa.harvard.ed, E-mail: jph@physics.rutgers.ed [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854-8019 (United States)

    2010-07-20

    Astrophysical shocks or bursts from a photoionizing source can disturb the typical collisional plasma found in galactic interstellar media or the intergalactic medium. The spectrum emitted by this plasma contains diagnostics that have been used to determine the time since the disturbing event, although this determination becomes uncertain as the elements in the plasma return to ionization equilibrium. A general solution for the equilibrium timescale for each element arises from the elegant eigenvector method of solution to the problem of a non-equilibrium plasma described by Masai and Hughes and Helfand. In general, the ionization evolution of an element Z in a constant electron temperature plasma is given by a coupled set of Z + 1 first-order differential equations. However, they can be recast as Z uncoupled first-order differential equations using an eigenvector basis for the system. The solution is then Z separate exponential functions, with the time constants given by the eigenvalues of the rate matrix. The smallest of these eigenvalues gives the scale of the slowest return to equilibrium independent of the initial conditions, while conversely the largest eigenvalue is the scale of the fastest change in the ion population. These results hold for an ionizing plasma, a recombining plasma, or even a plasma with random initial conditions, and will allow users of these diagnostics to determine directly if their best-fit result significantly limits the timescale since a disturbance or is so close to equilibrium as to include an arbitrarily long time.

  3. Substorm Scenarios: Theoretical Versus Observed Timescales

    NASA Astrophysics Data System (ADS)

    Le Contel, O.; Roux, A.; Perraut, S.; Pellat, R.; Robert, P.; Fontaine, D.; Sauvaud, J.-A.; A Pi Cluster Team

    Schematically, we can distinguish two classes of substorms models depending on the location of the onset : (1) near-Earth tail onset (X 7-15 RE) and (2) middle tail onset (X 23 RE). For both classes, we need to understand by which way the reconfigura- tion of the magnetic field propagates from the near-Earth tail to the middle tail for the first class and vice versa for the second class. The fast flows moving toward the Earth, which are observed in the tail between 10 RE and 20 RE, seem to be a good candi- date for transmitting the information for the second class. Conversely, the first class of model is not inconsistent with a fast earthward motion of the plasma whereas the electromagnetic perturbation propagates tailward. We will present a short review of the most important characteristics of the two classes of model notably for emphazing the comparison between the theoretical timescales and the observational timescales. We will try to show how the new CLUSTER data can give stronger constraints to the- orists. Finally, we will try to formulate some observational tests to separate the two class of models.

  4. Time-scale for accretion of matter

    E-print Network

    F. Combes

    1998-11-09

    Mass accretion is the key factor for evolution of galaxies. It can occur through secular evolution, when gas in the outer parts is driven inwards by dynamical instabilities, such as spirals or bars. This secular evolution proceeds very slowly when spontaneous, and can be accelerated when triggered by companions. Accretion can also occur directly through merging of small companions, or more violent interaction and coalescence. We discuss the relative importance of both processes, their time-scale and frequency along a Hubble time. Signatures of both processes can be found in the Milky Way. It is however likely that our Galaxy had already gathered the bulk of its mass about 8-10 Gyr ago, as is expected in hierarchical galaxy formation scenarios.

  5. Relativistic timescale analysis suggests lunar theory revision

    NASA Astrophysics Data System (ADS)

    Deines, Steven D.; Williams, Carol A.

    1995-05-01

    The SI second of the atomic clock was calibrated to match the Ephemeris Time (ET) second in a mutual four year effort between the National Physical Laboratory (NPL) and the United States Naval Observatory (USNO). The ephemeris time is 'clocked' by observing the elapsed time it takes the Moon to cross two positions (usually occultation of stars relative to a position on Earth) and dividing that time span into the predicted seconds according to the lunar equations of motion. The last revision of the equations of motion was the Improved Lunar Ephemeris (ILE), which was based on E. W. Brown's lunar theory. Brown classically derived the lunar equations from a purely Newtonian gravity with no relativistic compensations. However, ET is very theory dependent and is affected by relativity, which was not included in the ILE. To investigate the relativistic effects, a new, noninertial metric for a gravitated, translationally accelerated and rotating reference frame has three sets of contributions, namely (1) Earth's velocity, (2) the static solar gravity field and (3) the centripetal acceleration from Earth's orbit. This last term can be characterized as a pseudogravitational acceleration. This metric predicts a time dilation calculated to be -0.787481 seconds in one year. The effect of this dilation would make the ET timescale run slower than had been originally determined. Interestingly, this value is within 2 percent of the average leap second insertion rate, which is the result of the divergence between International Atomic Time (TAI) and Earth's rotational time called Universal Time (UT or UTI). Because the predictions themselves are significant, regardless of the comparison to TAI and UT, the authors will be rederiving the lunar ephemeris model in the manner of Brown with the relativistic time dilation effects from the new metric to determine a revised, relativistic ephemeris timescale that could be used to determine UT free of leap second adjustments.

  6. Planetary Chaotic Zone Clearing: Destinations and Timescales

    NASA Astrophysics Data System (ADS)

    Morrison, Sarah; Malhotra, Renu

    2015-01-01

    We investigate the orbital evolution of particles in a planet's chaotic zone to determine their final destinations and their timescales of clearing. There are four possible final states of chaotic particles: collision with the planet, collision with the star, escape, or bounded but non-collision orbits. In our investigations, within the framework of the planar circular restricted three body problem for planet-star mass ratio ? in the range 10-9 to 10-1.5, we find no particles hitting the star. The relative frequencies of escape and collision with the planet are not scale-free, as they depend upon the size of the planet. For planet radius Rp >= 0.001 RH where RH is the planet's Hill radius, we find that most chaotic zone particles collide with the planet for ? <~ 10-5 particle scattering to large distances is significant only for higher mass planets. For fixed ratio Rp /RH , the particle clearing timescale, T cl, has a broken power-law dependence on ?. A shallower power law, T cl ~ ?-1/3, prevails at small ? where particles are cleared primarily by collisions with the planet; a steeper power law, T cl ~ ?-3/2, prevails at larger ? where scattering dominates the particle loss. In the limit of vanishing planet radius, we find T cl ? 0.024 ?-3/2. The interior and exterior boundaries of the annular zone in which chaotic particles are cleared are increasingly asymmetric about the planet's orbit for larger planet masses; the inner boundary coincides well with the classical first order resonance overlap zone, ?a cl, int ~= 1.2 ?0.28 ap ; the outer boundary is better described by ?a cl, ext ~= 1.7 ?0.31 ap , where ap is the planet-star separation.

  7. Einstein A to Z

    NASA Astrophysics Data System (ADS)

    Fox, Karen C.; Keck, Aries

    2004-07-01

    Einstein was the twentieth century's most celebrated scientist - a man who developed the theory of relativity, revolutionised physics and became an iconic genius in the popular imagination. Essays range from the reasonably scientific including the theory of relativity, to the odd and engaging, such as Einstein's brain, his favourite jokes and films. Einstein A to Z provides a vibrant overview of the man and his achievements.

  8. Quasars Are Not Light-Bulbs: Testing Models of Quasar Lifetimes with the Observed Eddington Ratio Distribution

    E-print Network

    Philip F. Hopkins; Lars Hernquist

    2009-04-30

    We use the observed distribution of Eddington ratios as a function of supermassive black hole (BH) mass to constrain models of AGN lifetimes and lightcurves. Given the observed AGN luminosity function, a model for AGN lifetimes (time above a given luminosity) translates directly to a predicted Eddington ratio distribution. Models for self-regulated BH growth, in which feedback produces a 'blowout' decay phase after some peak luminosity (shutting down accretion) make specific predictions for the lifetimes distinct from those expected if AGN are simply gas starved (without feedback) and very different from simple phenomenological 'light bulb' models. Present observations of the Eddington ratio distribution, spanning 5 decades in Eddington ratio, 3 in BH mass, and redshifts z=0-1, agree with the predictions of self-regulated models, and rule out 'light-bulb', pure exponential, and gas starvation models at high significance. We compare the Eddington ratio distributions at fixed BH mass and fixed luminosity (both are consistent, but the latter are much less constraining). We present empirical fits to the lifetime distribution and show how the Eddington ratio distributions place tight limits on AGN lifetimes at various luminosities. We use this to constrain the shape of the typical AGN lightcurve, and provide simple analytic fits. Given independent constraints on episodic lifetimes, most local BHs must have gained their mass in no more than a couple of bright episodes, in agreement with merger-driven fueling models.

  9. Einstein's Light Complex

    Microsoft Academic Search

    Dragan Redzic; Janez Strnad

    2004-01-01

    The light complex introduced by A. Einstein in his first relativity paper has the characteristics of a provisional concept and was soon abandoned. Nevertheless, it was crucial for Einstein's derivation of the equivalence of mass and energy. The discussion of various forms of the light complex strictly within Maxwell's electrodynamics leads to interesting insight.

  10. Einstein for Everyone

    ScienceCinema

    Piccioni, Robert

    2014-06-25

    Young Einstein was a rebel who seemed doomed to fail. How did he overcome rejection to become the most famous scientist in history? We will discuss and explain all his theories in plain English and without math, and we will discover how Einstein's achievements impact our lives through DVDs, GPS, iPods, computers and green energy.

  11. Einstein Observatory (HEAO-2)

    NASA Astrophysics Data System (ADS)

    Bond, P.; Murdin, P.

    2002-04-01

    The second in the series of HIGH ENERGY ASTROPHYSICAL OBSERVATORIES was launched by an Atlas-Centaur rocket on 13 November 1978. Soon after its insertion into a 470 km circular orbit inclined at 23.5° to the equator, HEAO-2 was named the Einstein Observatory, in celebration of the centenary of Albert Einstein's birth....

  12. Modelling periodic oscillation of biological systems with multiple timescale networks

    Microsoft Academic Search

    R. Wang; T. Zhou; Z. Jing; L. Chen

    2004-01-01

    In this paper, we aim to develop a new methodology to model and design periodic oscillators of biological networks, in particular gene regulatory networks with multiple genes, proteins and time delays, by using multiple timescale networks (MTN). Fast reactions constitute a positive feedback-loop network (PFN), while slow reactions consist of a cyclic feedback-loop network (CFN), in MTN. Multiple timescales are

  13. Response to Deines and Williams on Astronomical Timescales

    Microsoft Academic Search

    Victor J. Slabinski

    2009-01-01

    In a paper presented at this conference, Deines and Williams (DW) question the conventional determination and interpretation of the differences between astronomical timescales, such as Universal Time (UT) which deals with Earth rotation, Atomic Time (AT), and planetary ephemeride timescales such as Terrestrial Time (TT). This paper offers explanations attempting to remove some sources of confusion on the subject, in

  14. Einstein and Millikan

    NASA Astrophysics Data System (ADS)

    Erwin, Charlotte

    2005-03-01

    Albert Einstein traveled to America by boat during the great depression to consult with scientists at the California Institute of Technology. He was a theoretical physicist, a Nobel Prize winner, and a 20th century folk hero. Few members of the general public understood his theories, but they idolized him all the same. The invitation came from physicist Robert Millikan, who had initiated a visiting-scholars program at Caltech shortly after he became head of the school in 1921. Einstein's visits to the campus in 1931, 1932, and 1933 capped Millikan's campaign to make Caltech one of the physics capitals of the world. Mount Wilson astronomer Edwin Hubble's discovery that redshifts are proportional to their distances from the observer challenged Einstein's cosmological picture of a static universe. The big question at Caltech in 1931 was whether Einstein would give up his cosmological constant and accept the idea of an expanding universe. By day, Einstein discussed his theory and its interpretation at length with Richard Tolman, Hubble, and the other scientists on the campus. By night, Einstein filled his travel diary with his personal impressions. During his third visit, Einstein sidestepped as long as possible the question of whether conditions in Germany might prevent his return there. After the January 30 announcement that Hitler had become chancellor of Germany, the question could no longer be evaded. He postponed his return trip for a few weeks and then went to Belgium for several months instead of to Berlin. In the fall of 1933, Albert Einstein returned to the United States as an emigre and became a charter member of Abraham Flexner's new Institute for Advanced Study in Princeton, New Jersey. Why did Einstein go to Princeton and not Pasadena?

  15. Einstein's gravitational field

    E-print Network

    Peter M. Brown

    2002-12-23

    There exists some confusion, as evidenced in the literature, regarding the nature of the gravitational field in Einstein's General Theory of Relativity. It is argued here the this confusion is a result of a change in interpretation of the gravitational field. Einstein identified the existence of gravity with the inertial motion of accelerating bodies (i.e. bodies in free-fall) whereas contemporary physicists identify the existence of gravity with space-time curvature (i.e. tidal forces). The interpretation of gravity as a curvature in space-time is an interpretation Einstein did not agree with.

  16. Einstein and 1905

    NASA Astrophysics Data System (ADS)

    Rigden, John

    2005-05-01

    From March 17 to September 29, 1905, just over six months, Einstein wrote five papers that shifted the tectonic foundations of physics and changed the face of Nature. Three of these papers, the March paper presenting the particle of light, the May paper on Brownian motion, and the June paper on the Special Theory of Relativity are universally recognized as fundamental; however, the Brownian motion paper cannot be divorced from Einstein's April paper, A New Determination of the Dimensions of Molecules, and the September paper that gave the world its most famous equation, E = mc^2, cannot be separated from the June paper. These five papers reveal characteristics of Einstein's approach to physics.

  17. Building a Bridge to Deep Time: Sedimentary Systems Across Timescales

    NASA Astrophysics Data System (ADS)

    Romans, B.; Castelltort, S.; Covault, J. A.; Walsh, J. P.

    2013-12-01

    It is increasingly important to understand the complex and interdependent processes associated with sediment production, transport, and deposition at timescales relevant to civilization (annual to millennial). However, predicting the response of sedimentary systems to global environmental change across a range of timescales remains a significant challenge. For example, a significant increase in global average temperature at the Paleocene-Eocene boundary (55.8 Ma) is interpreted to have occurred over millennial timescales; however, the specific response of sedimentary systems (e.g., timing and magnitude of sediment flux variability in river systems) to that forcing is debated. Thus, using such environmental perturbations recorded in sedimentary archives as analogs for ongoing/future global change requires improved approaches to bridging across time. Additionally, the ability to bridge timescales is critical for addressing other questions about sedimentary system behavior, including signal propagation and signal versus ';noise' in the record. The geologic record provides information that can be used to develop a comprehensive understanding of process-response behavior at multiple timescales. The geomorphic ';snapshot' of present-day erosional and depositional landscapes can be examined to reconstruct the history of processes that created the observable configurations. Direct measurement and monitoring of active processes are used to constrain conceptual and numerical models and develop sedimentary system theory. But real-time observations of active Earth-surface processes are limited to the very recent, and how such processes integrate over longer timescales to transform into strata remains unknown. At longer timescales (>106 yr), the stratigraphic record is the only vestige of ancient sedimentary systems. Stratigraphic successions contain a complex record of sediment deposition and preservation, as well as the detrital material that originated in long since denuded orogenic belts. Moreover, as the timescale of the duration of the process-response behavior and/or system age increase, additional aspects must be considered (e.g., significant tectonic regime change, rare but significant events, non-periodic global change, etc.). In this presentation we discuss several examples of sedimentary system analysis at different timescales with the goal of highlighting various approaches at one timescale and how they can (or cannot) be applied for questions at different timescales. Examples include: (1) brief review of decadal to centennial sediment budgets; (2) land-to-sea sediment budget reconstructions from southern California at millennial to multi-millennial timescales, and (3) sedimentary system response to climatic and tectonic forcings at ?105 yr timescales.

  18. Event Rate and Einstein Time Evaluation in Pixel Microlensing

    SciTech Connect

    Baltz, Edward A.; Silk, Joseph

    2000-02-20

    In previous work it has been shown that a flux-weighted FWHM timescale of a microlensing event can be used as an unbiased estimator of the optical depth. For the first time, this allows the optical depth, which is effectively the microlensing probability, to be easily estimated from pixel microlensing data. In this paper we derive analytic expressions for the observed rate of pixel lensing events as a function of the FWHM timescale. This contrasts works in the literature that express rates in terms of an ''event duration'' or Einstein time, which require knowledge of the magnification, which is difficult to determine in a pixel event. The FWHM is the most directly measured timescale. We apply these results to possible pixel lensing surveys, using the Hubble Space Telescope (HST) for M87 and the Canada-France-Hawaii Telescope (CFHT) for M31. We predict M87 microlensing rates for the HST Advanced Camera and for the Next-Generation Space Telescope (NGST), and demonstrate that one will be able to probe the stellar initial mass function (IMF). Next, we describe a new method by which a crude measurement of the magnification can be made in the regime of magnifications A{approx}10-100. This in turn gives a crude measurement of the Einstein time. This program requires good photometry and sampling in the low-magnification tails of an event, but is feasible with today's technology. (c) 2000 The American Astronomical Society.

  19. Einstein in Wyoming.

    ERIC Educational Resources Information Center

    Elliot, Ian

    1996-01-01

    Describes "Einstein's Adventurarium," a science center housed in an empty shopping mall in Gillette, Wyoming, created through school, business, and city-county government partnership. Describes how interactive exhibits allow exploration of life sciences, physics, and paleontology. (KDFB)

  20. Origin of the universe: A hint from Eddington-inspired Born-Infeld gravity

    E-print Network

    Hyeong-Chan Kim

    2013-12-03

    We study the `initial state' of an anisotropic universe in Eddington-inspired Born-Infeld gravity filled with a scalar field, whose potential has various forms. With this purpose, the evolution of a spatially-flat, homogeneous anisotropic Kasner universe is studied. We find an exact evolution of universe for each scalar potential by imposing a maximal pressure condition. The solution is shown to describe the initial state of the universe. The state is regular if the scalar potential increases not faster than the quadratic power for large field values. We also show that the anisotropy does not raise any defect in early universe contrary to the case of general relativity.

  1. Direct dark matter event rates with a velocity distribution in the Eddington approach

    SciTech Connect

    Vergados, J. D. [University of Ioannina, Ioannina, GR 45110 (Greece); Owen, D. [Department of Physics, Ben Gurion University (Israel)

    2007-02-15

    Exotic dark matter together with the vacuum energy (associated with the cosmological constant) seem to dominate the Universe. Thus its direct detection is central to particle physics and cosmology. Supersymmetry provides a natural dark matter candidate, the lightest supersymmetric particle (LSP). One essential ingredient in obtaining the direct detection rates is the density and the velocity distribution of the LSP in our vicinity. In the present paper we study simultaneously density profiles and velocity distributions in the context of the Eddington approach. In such an approach, unlike the commonly assumed Maxwell-Boltzmann (M-B) distribution, the upper bound of the velocity arises naturally from the potential.

  2. A link between ghost-free bimetric and Eddington-inspired Born-Infeld theory

    E-print Network

    Angnis Schmidt-May; Mikael von Strauss

    2014-12-11

    We provide an auxiliary field formulation of the full ghost-free bimetric theory which avoids the explicit presence of a square-root matrix in the action. This description always allows for a branch of solutions where the auxiliary fields can be integrated out to give back the ghost-free theory. For certain parameter regions the two formulations are dynamically equivalent, but in the general case another branch of solutions also exists. We show that this second branch, with certain restrictions on the parameters of the theory, is dynamically equivalent to Eddington-inspired Born-Infeld gravity. This establishes a definite connection between two seemingly unrelated theories of modified gravity.

  3. Profile: Albert Einstein

    NSDL National Science Digital Library

    This online article is from the Museum's Seminars on Science, a series of distance-learning courses designed to help educators meet the new national science standards. "Profile: Albert Einstein," part of the Frontiers in Physical Science seminar, briefly covers Einstein's life and work including his Special Theory of Relativity and the paper that gave the world E=mc², his Nobel Prize in Physics, his influence yet exclusion from the Manhattan Project, and his promotion of peace and human rights.

  4. A super-Eddington wind scenario for the progenitors of type Ia supernovae: binary population synthesis calculations

    E-print Network

    Wang, Bo; Liu, Dongdong; Liu, Zhengwei; Wu, Chengyuan; Zhang, Jujia; Han, Zhanwen

    2015-01-01

    The super-Eddington wind scenario has been proposed as an alternative way for producing type Ia supernovae (SNe Ia). The super-Eddington wind can naturally prevent the carbon--oxygen white dwarfs (CO WDs) with high mass-accretion rates from becoming red-giant-like stars. Furthermore, it works in low-metallicity environments, which may explain SNe Ia observed at high redshifts. In this article, we systematically investigated the most prominent single-degenerate WD+MS channel based on the super-Eddington wind scenario. We combined the Eggleton stellar evolution code with a rapid binary population synthesis (BPS) approach to predict SN Ia birthrates for the WD+MS channel by adopting the super-Eddington wind scenario and detailed mass-accumulation efficiencies of H-shell flashes on the WDs. Our BPS calculations found that the estimated SN Ia birthrates for the WD+MS channel are ~0.009-0.315*10^{-3}{yr}^{-1} if we adopt the Eddington accretion rate as the critical accretion rate, which are much lower than that of ...

  5. 2010 Einstein Fellows Chosen

    NASA Astrophysics Data System (ADS)

    2010-02-01

    NASA has announced the selection of the 2010 Einstein Fellows who will conduct research related to NASA's Physics of the Cosmos program, which aims to expand our knowledge of the origin, evolution, and fate of the Universe. The Einstein Fellowship provides support to the awardees for three years, and the Fellows may pursue their research at a host university or research center of their choosing in the United States. The new Fellows will begin their programs in the fall of 2010. The new Einstein Fellows and their host institutions are listed below: * Simona Giacintucci (Smithsonian Astrophysical Observatory, Cambridge, Mass.) * Boaz Katz (Institute for Advanced Studies, Princeton, N.J.) * Matthew Kerr (Stanford University, Palo Alto, Calif.) * Matthew Kistler (California Institute of Technology, Pasadena) * Emily Levesque (University of Colorado, Boulder) * Xin Liu (Harvard, Cambridge, Mass.) * Tony Mroczkowski (University of Pennsylvania, Philadelphia) * Ryan O'Leary (University of California at Berkeley) * Dov Poznanski (Lawrence Berkeley National Laboratory. Berkeley, Calif.) * Nicolas Yunes (Massachusetts Institute of Technology, Cambridge, Mass.) The Einstein Fellowships are administered for NASA by the Chandra X-ray Center in Cambridge, Mass. Along with the Hubble and Sagan Fellowships, the Einstein Fellowships are made possible by the Astrophysics Division within NASA's Science Mission Directorate. More information on the Einstein Fellowships can be found at: http://cxc.harvard.edu/fellows/CfPfellow.2009.html

  6. Einstein studies in Russia

    NASA Astrophysics Data System (ADS)

    Balashov, Yuri; Vizgin, Vladimir

    This volume presents a selection of the best contributions by Russian scholars - historians and philosophers of science - to the Einstein Studies industry, broadly construed. Many of the papers were first published in Russian, in the Einshteinovskiy Sbornik series (Einstein Studies) initiated by I. Tamm in 1966. This book explores the historical and foundational issues in general relativity and relativistic cosmology, Einstein's contributions to quantum theory of radiation, and the rise of Dirac's quantum electrodynamics. It also includes a detailed description of the physics colloquium Einstein established and coordinated in 1912- 1914 in Zürich. The contributors draw extensively on documentation previously unavailable to most scholars. Materials from various Russian archives shed new light on the famous exchange (regarding the first evolutionary cosmological models) between Einstein and Alexander Friedmann in the early 1920's and on the role of Boris Podolsky and Vladimir Fock in the emergence of quantum electrodynamics. The little-known correspondence between Einstein and a famous German pilot Paul Erhardt suggests that during World War I, the former was involved with aero- and hydrodynamics research and ways of improving airplane design. Other articles introduce new approaches to important foundational questions in general relativity and cosmology. Historians, philosophers, and sociologists of science will find much new and unexpected material in this engaging volume presenting the best of recent Russian scholarship in the field. The book is also very accessible to the general reader.

  7. The geomagnetic secularvariation timescale in observations and numerical dynamo models

    E-print Network

    Aubert, Julien

    Lhuillier,1 Alexandre Fournier,1 Gauthier Hulot,1 and Julien Aubert1 Received 3 March 2011; accepted 29. Fournier, G. Hulot, and J. Aubert (2011), The geomagnetic secularvariation timescale in observa- tions

  8. Photon trapping enables super-Eddington growth of black hole seeds in galaxies at high redshift

    NASA Astrophysics Data System (ADS)

    Wyithe, J. Stuart B.; Loeb, Abraham

    2012-10-01

    We identify a physical mechanism that would have resulted in rapid, obscured growth of seed supermassive black holes in galaxies at z?6. Specifically, we find that the density at the centre of typical high-redshift galaxies was at a level where the Bondi accretion rate implies a diffusion speed of photons that was slower than the gravitational infall velocity, resulting in photons being trapped within the accretion flow and advected into the black hole. We show that there is a range of black hole masses (Mbh ˜ 103 - 5 M?) where the accretion flow traps radiation, corresponding to black holes that were massive enough to generate a photon trapping accretion flow, but small enough that their Bondi radii did not exceed the isothermal scale height of self-gravitating gas. Under these conditions we find that the accretion reaches levels far in excess of the Eddington rate. A prediction of this scenario is that X-ray number counts of active galactic nuclei at z?6 would exhibit a cutoff at the low luminosities corresponding to black hole masses below ˜105 M?. The super-Eddington growth of ˜105 M? seed black holes at high redshift may have provided a natural acceleration towards the growth of supermassive black holes at z˜6-7, less than a billion years after the big bang.

  9. Einstein flow and cosmology

    NASA Astrophysics Data System (ADS)

    Kouneiher, J.

    2015-07-01

    The recent evolution of the observational technics and the development of new tools in cosmology and gravitation have a significant impact on the study of the cosmological models. In particular, the qualitative and numerical methods used in dynamical system and elsewhere, enable the resolution of some difficult problems and allow the analysis of different cosmological models even with a limited number of symmetries. On the other hand, following Einstein point of view the manifold ? and the metric should be built simultaneously when solving Einstein’s equation R?? ?1 2Rg?? = T??. From this point of view, the only kinematic condition imposed is that at each point of space-time, the tangent space is endowed with a metric (which is a Minkowski metric in the physical case of pseudo-Riemannian manifolds and an Euclidean one in the Riemannian analogous problem). Then the field (g??) describes the way these metrics depend on the point in a smooth way and the Einstein equation is the “dynamical” constraint on g??. So, we have to imagine an infinite continuous family of copies of the same Minkowski or Euclidean space and to find a way to sew together these infinitesimal pieces into a manifold, by respecting Einstein’s equation. Thus, Einstein field equations do not fix once and for all the global topology. 34 Given this freedom in the topology of the space-time manifold, a question arises as to how free the choice of these topologies may be and how one may hope to determine them, which in turn is intimately related to the observational consequences of the space-time possessing nontrivial topologies. Therefore, in this paper we will use a different qualitative dynamical methods to determine the actual topology of the space-time.

  10. Short timescale variability of the mesospheric sodium layer

    Microsoft Academic Search

    C. O'Sullivan; R. M. Redfern; N. Ageorges; H.-C. Holstenberg; W. Hackenberg; T. Ott; S. Rabien; R. Davies; A. Eckart

    2000-01-01

    In this article we investigate the short-term characteristics of the sodium layer and their implications for laser guide star systems. We report measurements of sodium density andcentroid-height variations on timescales of 100 ms upwards. Significant centroid-height variations on short timescales may necessitate frequent refocussing of the beam and wavefront sensor system.We present results from observations of the mesospheric sodium layer

  11. On the stability of multiple time-scale systems

    Microsoft Academic Search

    EYAD H. ABED

    1986-01-01

    The stability of time-invariant multiparameter singular perturbation problems is considered and the implications of two time-scale stability results for multiple time-scale systems are clarified. An example shows that the asymptotic stability of a multiparameter singular perturbation problem under the ‘bounded mutual ratios’ assumption for arbitrary bounds on the ratios of the small parameters does not imply asymptotic stability under the

  12. Geometric structure of multiple time-scale nonlinear dynamical systems

    Microsoft Academic Search

    Sanjay Bharadwaj

    1999-01-01

    A new methodology to analyze time-scale structure of smooth finite-dimensional nonlinear dynamical systems is developed. This approach does not assume apriori knowledge of slow and fast variables for special coordinates that simplify the form of the nonlinear dynamics. Conventional approaches to analyze time-scale structure of nonlinear dynamics such as singular perturbation theory proceed from such specialized apriori knowledge which is

  13. Timescale separation of nonlinear singularly perturbed discrete systems

    Microsoft Academic Search

    Kyun-Sang Park; Jong-Tae Lim

    2010-01-01

    In this paper, we investigate the time-scale decomposition of the nonlinear singularly perturbed discrete system into lower-order subsystems; the slow subsystem and fast subsystems. In the singular perturbation method, the time-scale separation is inevitable for the analysis of the system stability and the composite control design. Using Tikhonov's theorem, we obtain the slow subsystem and the fast subsystem separated from

  14. CHEMICAL TIMESCALES IN THE ATMOSPHERES OF HIGHLY ECCENTRIC EXOPLANETS

    SciTech Connect

    Visscher, Channon [Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States)

    2012-09-20

    Close-in exoplanets with highly eccentric orbits are subject to large variations in incoming stellar flux between periapse and apoapse. These variations may lead to large swings in atmospheric temperature, which in turn may cause changes in the chemistry of the atmosphere from higher CO abundances at periapse to higher CH{sub 4} abundances at apoapse. Here, we examine chemical timescales for CO{r_reversible}CH{sub 4} interconversion compared to orbital timescales and vertical mixing timescales for the highly eccentric exoplanets HAT-P-2b and CoRoT-10b. As exoplanet atmospheres cool, the chemical timescales for CO{r_reversible}CH{sub 4} tend to exceed orbital and/or vertical mixing timescales, leading to quenching. The relative roles of orbit-induced thermal quenching and vertical quenching depend upon mixing timescales relative to orbital timescales. For both HAT-P-2b and CoRoT-10b, vertical quenching will determine disequilibrium CO{r_reversible}CH{sub 4} chemistry at faster vertical mixing rates (K{sub zz} > 10{sup 7} cm{sup 2} s{sup -1}), whereas orbit-induced thermal quenching may play a significant role at slower mixing rates (K{sub zz} < 10{sup 7} cm{sup 2} s{sup -1}). The general abundance and chemical timescale results-calculated as a function of pressure, temperature, and metallicity-can be applied for different atmospheric profiles in order to estimate the quench level and disequilibrium abundances of CO and CH{sub 4} on hydrogen-dominated exoplanets. Observations of CO and CH{sub 4} on highly eccentric exoplanets may yield important clues to the chemical and dynamical properties of their atmospheres.

  15. Compact binary coalescence and the science case for Einstein Telescope

    E-print Network

    Chris Van Den Broeck

    2010-03-06

    Einstein Telescope (ET) is a possible third generation ground-based gravitational wave observatory for which a design study is currently being carried out. A brief (and non-exhaustive) overview is given of ET's projected capabilities regarding astrophysics and cosmology through observations of inspiraling and coalescing compact binaries. In particular, ET would give us unprecedented insight into the mass function of neutron stars and black holes, the internal structure of neutron stars, the evolution of coalescence rates over cosmological timescales, and the geometry and dynamics of the Universe as a whole.

  16. Einstein as Myth and Muse

    NASA Astrophysics Data System (ADS)

    Friedman, Alan. J.; Donley, Carol C.

    1989-04-01

    Preface; Introduction; 1. The popularization of the new physical ideas; 2. Newtonian mechanics and literary responses; 3. Einstein's revolution; 4. Einstein becomes a muse; 5. The second revolution; 6. A myth portrayed.

  17. Reprint of Water renewal timescales in the Scheldt Estuary

    NASA Astrophysics Data System (ADS)

    de Brye, Benjamin; de Brauwere, Anouk; Gourgue, Olivier; Delhez, Eric J. M.; Deleersnijder, Eric

    2013-12-01

    Using the concepts of the Constituent-oriented Age and Residence time Theory (CART), we compute timescales related to the water renewal in the Scheldt Estuary (The Netherlands/Belgium). Three different timescales are used to better understand and characterize the dynamics of the estuary: the age of the renewing water, the residence time and the exposure time. The residence time is the time taken by a water parcel to leave the estuary for the first time while the exposure time is the total time spent by a water parcel in the estuary including re-entries. The age of a renewing water parcel is defined as the time elapsed since it entered the estuary. The renewing water was split into three types: the water originating from the sea, the water originating from the upstream fresh tidal rivers and the water originating from the different canals and docks connected to the estuary. Every timescale is computed at any time and position by means of the finite-element, unstructured-mesh model SLIM. This results in movies of the timescale fields (shown as Supplementary material), allowing a detailed analysis of their spatial and temporal variabilities. The effect of the M2 tide and the discharge regime (winter, summer or average situation) on the timescales is also investigated.Tidally-averaged timescales vary little over the width of the estuary and hence exhibit a virtually one-dimensional behaviour. However, around these average values, the timescales can vary hugely over a tidal cycle, with amplitudes that significantly depend on the space coordinates. The reason thereof has yet to be elucidated. These results underscore the need for two- or three-dimensional models with high temporal resolution for investigating the dynamics of the Scheldt Estuary.

  18. Radiation pressure supported stars in Einstein gravity: eternally collapsing objects

    NASA Astrophysics Data System (ADS)

    Mitra, A.

    2006-06-01

    Even when we consider Newtonian stars, that is, stars with surface gravitational redshift z << 1, it is well known that, theoretically, it is possible to have stars supported against self-gravity almost entirely by radiation pressure. However, such Newtonian stars must necessarily be supermassive. We point out that this requirement for excessively large M in the Newtonian case is a consequence of the occurrence of low z << 1. However, if we remove such restrictions, and allow for the possible occurrence of a highly general relativistic regime, z >> 1, we show that it is possible to have radiation pressure supported stars (RPSSs) at an arbitrary value of M. Since RPSSs necessarily radiate at the Eddington limit, in Einstein gravity, they are never in strict hydrodynamical equilibrium. Further, it is believed that sufficiently massive or dense objects undergo continued gravitational collapse to the black hole (BH) stage characterized by z = ?. Thus, late stages of BH formation, by definition, would have z >> 1, and hence would be examples of quasi-stable general relativistic RPSSs. It is shown that the observed duration of such Eddington limited radiation pressure dominated states is t ~ 5 × 108 (1 + z) yr. Thus, t -> ? as BH formation (z -> ?) takes place. Consequently, such radiation pressure dominated extreme general relativistic stars become eternally collapsing objects (ECOs) and the BH state is preceded by such an ECO phase. This result is also supported by our previous finding that trapped surfaces are not formed in gravitational collapse and the value of the integration constant in the vacuum Schwarzschild solution is zero. Hence the supposed observed BHs are actually ECOs.

  19. Multi--dimensional Cosmological Radiative Transfer with a Variable Eddington Tensor Formalism

    E-print Network

    Nickolay Y. Gnedin; Tom Abel

    2001-06-15

    We present a new approach to numerically model continuum radiative transfer based on the Optically Thin Variable Eddington Tensor (OTVET) approximation. Our method insures the exact conservation of the photon number and flux (in the explicit formulation) and automatically switches from the optically thick to the optically thin regime. It scales as N logN with the number of hydrodynamic resolution elements and is independent of the number of sources of ionizing radiation (i.e. works equally fast for an arbitrary source function). We also describe an implementation of the algorithm in a Soften Lagrangian Hydrodynamic code (SLH) and a multi--frequency approach appropriate for hydrogen and helium continuum opacities. We present extensive tests of our method for single and multiple sources in homogeneous and inhomogeneous density distributions, as well as a realistic simulation of cosmological reionization.

  20. HIGH-VELOCITY OUTFLOWS WITHOUT AGN FEEDBACK: EDDINGTON-LIMITED STAR FORMATION IN COMPACT MASSIVE GALAXIES

    SciTech Connect

    Diamond-Stanic, Aleksandar M.; Moustakas, John; Coil, Alison L. [Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, CA 92093 (United States); Tremonti, Christy A.; Sell, Paul H. [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Hickox, Ryan C. [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Robaina, Aday R. [Institut de Ciencies del Cosmos, University of Barcelona, 08028 Barcelona (Spain); Rudnick, Gregory H., E-mail: aleks@ucsd.edu [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 (United States)

    2012-08-20

    We present the discovery of compact, obscured star formation in galaxies at z {approx} 0.6 that exhibit {approx}> 1000 km s{sup -1} outflows. Using optical morphologies from the Hubble Space Telescope and infrared photometry from the Wide-field Infrared Survey Explorer, we estimate star formation rate (SFR) surface densities that approach {Sigma}{sub SFR} Almost-Equal-To 3000 M{sub Sun} yr{sup -1} kpc{sup -2}, comparable to the Eddington limit from radiation pressure on dust grains. We argue that feedback associated with a compact starburst in the form of radiation pressure from massive stars and ram pressure from supernovae and stellar winds is sufficient to produce the high-velocity outflows we observe, without the need to invoke feedback from an active galactic nucleus.

  1. A Global 3D Radiation MHD Simulation of Super-Eddington Accretion Disks

    NASA Astrophysics Data System (ADS)

    Jiang, Yanfei

    2014-10-01

    We study how black holes can accrete above the Eddington limit using a global three dimensional radiation magneto-hydrodynamic simulation without ad-hoc assumptions. The simulation reaches an accretion rate ~ 220L_Edd/c^2 and forms a radiation driven outflow along the rotation axis. The radiative luminosity of this flow is ~ 10L_Edd. This yields a radiative efficiency ~ 4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in slim disk model, which neglect vertical advection. The results have important implications for the growth of supermassive black holes in the early universe, tidal disruption events and ultra-luminous X-ray sources.

  2. The Complex Emission States of a near-Eddington Black Hole: IGR J17091-3624

    NASA Astrophysics Data System (ADS)

    Court, J.

    2015-07-01

    IGR J17091-3624 is an ultra-low mass black hole LMXB believed to be accreting at close to the Eddington Limit. This object displays a large number of complex and varied emission states, in a similar way to the well-studied BHC GRS 1915-105. These states are believed to be caused by instabilities in matter close to the inner edge of the accretion disk. Although a model-independent classification and analysis of the emission states of GRS 1915-105 has already been undertaken, no such study has been performed on IGR J17091-3624. Here I present the findings of the first model-independent classification of the emission states of IGR J17091-3624, using both colour and timing analysis methods. Particular attention is focused on the analysis of the phenomenology seen in this object, and a comparison to the behaviour of GRS 1915+105.

  3. From Newton to Einstein.

    ERIC Educational Resources Information Center

    Ryder, L. H.

    1987-01-01

    Discusses the history of scientific thought in terms of the theories of inertia and absolute space, relativity and gravitation. Describes how Sir Isaac Newton used the work of earlier scholars in his theories and how Albert Einstein used Newton's theories in his. (CW)

  4. 2011 Einstein Fellows Chosen

    NASA Astrophysics Data System (ADS)

    2011-03-01

    ASA has announced the selection of the 2011 Einstein Fellows who will conduct research related to NASA's Physics of the Cosmos program, which aims to expand our knowledge of the origin, evolution, and fate of the Universe. The Einstein Fellowship provides support to the awardees for three years, and the Fellows may pursue their research at a host university or research center of their choosing in the United States. The new Fellows will begin their programs in the fall of 2011. The new Einstein Fellows and their host institutions are listed below: * Akos Bogdan (Smithsonian Astrophysical Observatory, Cambridge, Mass.) * Samuel Gralla (University of Maryland, College Park, Md.) * Philip Hopkins (University of California at Berkeley) * Matthew Kunz (Princeton University, Princeton, N.J.) * Laura Lopez (Massachusetts Institute of Technology, Cambridge, Mass.) * Amy Reines (National Radio Astronomy Observatory, Charlottesville, Virg.) * Rubens Reis (University of Michigan, Ann Arbor) * Ken Shen (Lawrence Berkeley National Laboratory, Berkeley, Calif.) * Jennifer Siegal-Gaskins (California Institute of Technology, Pasadena) * Lorenzo Sironi (Harvard University, Cambridge, Mass.) NASA has two other astrophysics theme-based fellowship programs: the Sagan Fellowship Program, which supports research into exoplanet exploration, and the Hubble Fellowship Program, which supports research into cosmic origins. More information on the Einstein Fellowships can be found at: http://cxc.harvard.edu/fellows/

  5. Einstein's Unified Field Theory

    Microsoft Academic Search

    Behram Kursunoglu

    1952-01-01

    In this paper it is shown that, under certain assumptions about the metric of the space-time, energy momentum tensor of the total field, when Einstein's field equations are satisfied, vanishes identically.A new version of the unified field theory is suggested, and it is indicated briefly that a genuine energy momentum tensor exists which is conserved and has a structure similar

  6. SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant

    NASA Astrophysics Data System (ADS)

    Mauerhan, Jon C.; Van Dyk, Schuyler D.; Graham, Melissa L.; Zheng, WeiKang; Clubb, Kelsey I.; Filippenko, Alexei V.; Valenti, Stefano; Brown, Peter; Smith, Nathan; Howell, D. Andrew; Arcavi, Iair

    2015-02-01

    We present observations of SN Hunt 248, a new supernova (SN) impostor in NGC 5806, which began a multistage outburst in 2014 May. The `2014a' discovery brightening exhibited an absolute magnitude of M ? -12 and the spectral characteristics of a cool, dense outflow, including P Cygni lines of Fe II, H I, and Na I, and line blanketing from metals. The source rapidly climbed and peaked at M ? -15 mag after two additional weeks. During this bright `2014b' phase the spectrum became dominated by Balmer emission and a stronger blue continuum, similar to the SN impostor SN 1997bs. Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a luminous (4 × 105 L?) variable precursor star. Its location on the Hertzsprung-Russell diagram is consistent with a massive (Minit ? 30 M?) cool hypergiant having an extremely dense wind and an Eddington ratio (?) just below unity. At the onset of the 2014a brightening, however, the object was super-Eddington (? = 4-12). The subsequent boost in luminosity during the 2014b phase probably resulted from circumstellar interaction. SN Hunt 248 provides the first case of a cool hypergiant undergoing a giant eruption reminiscent of outbursts from luminous blue variable stars (LBVs). This lends support to the hypothesis that some cool hypergiants, such as ? Cas, could be LBVs masquerading under a pseudo-photosphere created by their extremely dense winds. Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can rival in peak luminosity the giant outbursts of much more massive systems like ? Car.

  7. SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant

    NASA Astrophysics Data System (ADS)

    Mauerhan, Jon; Van Dyk, Schuyler D.; Graham, Melissa Lynn; Zheng, WeiKang; Clubb, Kelsey I.; Filippenko, Alexei V.; Valenti, Stefano; Brown, Peter; Smith, Nathan; Howell, Dale Andrew; Arcavi, Iair

    2015-01-01

    We present observations of SN Hunt 248, a new supernova (SN) impostor in NGC 5806, which began a multi-stage outburst in May 2014. The "2014a" discovery brightening exhibited an absolute magnitude of M ? -12 and the spectral characteristics of a cool dense outflow, with P-Cygni lines of H?, Fe II, and Na I. The source rapidly climbed and peaked at M ? -15 mag after two additional weeks. During this bright "2014b'' phase the spectrum became hotter, dominated by Balmer emission and a stronger blue continuum, similar to the SN impostor SN 1997bs. Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a luminous (4×105 L?) variable precursor star. Its location on the Hertzsprung-Russell diagram is consistent with a massive (Minit ? 30 M?) cool hypergiant having an extremely dense wind and an Eddington ratio (?) just below unity. At the onset of the 2014a brightening, however, the object was super-Eddington (? = 4 - 12). The subsequent boost in luminosity during the 2014b phase probably resulted from circumstellar interaction. SN Hunt 248 provides the first case of a cool hypergiant undergoing a giant eruption reminiscent of outbursts from luminous blue variable stars (LBVs). This lends support to the hypothesis that some cool hypergiants, such as ?Cas, could be LBVs masquerading under a pseudo-photosphere created by their extremely dense winds. Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can rival in peak luminosity the giant outbursts of much more massive systems like ?Car.

  8. THE STAR FORMATION LAWS OF EDDINGTON-LIMITED STAR-FORMING DISKS

    SciTech Connect

    Ballantyne, D. R.; Armour, J. N.; Indergaard, J., E-mail: david.ballantyne@physics.gatech.edu [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States)

    2013-03-10

    Two important avenues into understanding the formation and evolution of galaxies are the Kennicutt-Schmidt (K-S) and Elmegreen-Silk (E-S) laws. These relations connect the surface densities of gas and star formation ({Sigma}{sub gas} and {Sigma}-dot{sub *}, respectively) in a galaxy. To elucidate the K-S and E-S laws for disks where {Sigma}{sub gas} {approx}> 10{sup 4} M{sub Sun} pc{sup -2}, we compute 132 Eddington-limited star-forming disk models with radii spanning tens to hundreds of parsecs. The theoretically expected slopes ( Almost-Equal-To 1 for the K-S law and Almost-Equal-To 0.5 for the E-S relation) are relatively robust to spatial averaging over the disks. However, the star formation laws exhibit a strong dependence on opacity that separates the models by the dust-to-gas ratio that may lead to the appearance of a erroneously large slope. The total infrared luminosity (L{sub TIR}) and multiple carbon monoxide (CO) line intensities were computed for each model. While L{sub TIR} can yield an estimate of the average {Sigma}-dot{sub *} that is correct to within a factor of two, the velocity-integrated CO line intensity is a poor proxy for the average {Sigma}{sub gas} for these warm and dense disks, making the CO conversion factor ({alpha}{sub CO}) all but useless. Thus, observationally derived K-S and E-S laws at these values of {Sigma}{sub gas} that uses any transition of CO will provide a poor measurement of the underlying star formation relation. Studies of the star formation laws of Eddington-limited disks will require a high-J transition of a high density molecular tracer, as well as a sample of galaxies with known metallicity estimates.

  9. A Two-Timescale Discretization Scheme for Collocation

    NASA Technical Reports Server (NTRS)

    Desai, Prasun; Conway, Bruce A.

    2004-01-01

    The development of a two-timescale discretization scheme for collocation is presented. This scheme allows a larger discretization to be utilized for smoothly varying state variables and a second finer discretization to be utilized for state variables having higher frequency dynamics. As such. the discretization scheme can be tailored to the dynamics of the particular state variables. In so doing. the size of the overall Nonlinear Programming (NLP) problem can be reduced significantly. Two two-timescale discretization architecture schemes are described. Comparison of results between the two-timescale method and conventional collocation show very good agreement. Differences of less than 0.5 percent are observed. Consequently. a significant reduction (by two-thirds) in the number of NLP parameters and iterations required for convergence can be achieved without sacrificing solution accuracy.

  10. Two-timescale analysis of accelerated planar motions

    SciTech Connect

    Ahmadi, N. [Department of Physics, University of Tehran, North Kargar Avenue, Tehran 14395-547 (Iran, Islamic Republic of)

    2011-01-15

    Two-timescale analysis has long been known as a particularly useful tool for studying dynamical systems with two different length scales. The parameter space of some accelerated worldlines shows such a situation. In this paper we find different sets of solutions for the equations of motion governing these worldlines by using two-timescale expansions. The general properties of these solutions are examined. This helps to derive simple schemes that reproduce secular effects of interacting forces. Rigorous prescriptions are given for computing the leading order motion which highlight the importance of dissipative terms in the force functions. In the end, we discuss some potential ambiguities in the two-timescale approach and possible deviations these prescriptions may have, from the exact worldlines.

  11. Diffusion Time-Scale of Porous Pressure-Sensitive Paint

    NASA Technical Reports Server (NTRS)

    Liu, Tianshu; Teduka, Norikazu; Kameda, Masaharu; Asai, Keisuke

    2001-01-01

    Pressure-sensitive paint (PSP) is an optical pressure sensor that utilizes the oxygen quenching of luminescence. PSP measurements in unsteady aerodynamic flows require fast time response of the paint. There are two characteristic time-scales that are related to the time response of PSP. One is the luminescent lifetime representing an intrinsic physical limit for the achievable temporal resolution of PSP. Another is the time-scale of oxygen diffusion across the PSP layer. When the time-scale of oxygen diffusion is much larger than the luminescent lifetime, the time response of PSP is controlled by oxygen diffusion. In a thin homogenous polymer layer where diffusion is Fickian, the oxygen concentration 1021 can be described by the diffusion equation in one-dimension.

  12. Action Planning and the Timescale of Evidence Accumulation

    PubMed Central

    Donner, Tobias H.

    2015-01-01

    Perceptual decisions are based on the temporal integration of sensory evidence for different states of the outside world. The timescale of this integration process varies widely across behavioral contexts and individuals, and it is diagnostic for the underlying neural mechanisms. In many situations, the decision-maker knows the required mapping between perceptual evidence and motor response (henceforth termed “sensory-motor contingency”) before decision formation. Here, the integrated evidence can be directly translated into a motor plan and, indeed, neural signatures of the integration process are evident as build-up activity in premotor brain regions. In other situations, however, the sensory-motor contingencies are unknown at the time of decision formation. We used behavioral psychophysics and computational modeling to test if knowledge about sensory-motor contingencies affects the timescale of perceptual evidence integration. We asked human observers to perform the same motion discrimination task, with or without trial-to-trial variations of the mapping between perceptual choice and motor response. When the mapping varied, it was either instructed before or after the stimulus presentation. We quantified the timescale of evidence integration under these different sensory-motor mapping conditions by means of two approaches. First, we analyzed subjects’ discrimination threshold as a function of stimulus duration. Second, we fitted a dynamical decision-making model to subjects’ choice behavior. The results from both approaches indicated that observers (i) integrated motion information for several hundred ms, (ii) used a shorter than optimal integration timescale, and (iii) used the same integration timescale under all sensory-motor mappings. We conclude that the mechanisms limiting the timescale of perceptual decisions are largely independent from long-term learning (under fixed mapping) or rapid acquisition (under variable mapping) of sensory-motor contingencies. This conclusion has implications for neurophysiological and neuroimaging studies of perceptual decision-making. PMID:26068458

  13. Action Planning and the Timescale of Evidence Accumulation.

    PubMed

    Tsetsos, Konstantinos; Pfeffer, Thomas; Jentgens, Pia; Donner, Tobias H

    2015-01-01

    Perceptual decisions are based on the temporal integration of sensory evidence for different states of the outside world. The timescale of this integration process varies widely across behavioral contexts and individuals, and it is diagnostic for the underlying neural mechanisms. In many situations, the decision-maker knows the required mapping between perceptual evidence and motor response (henceforth termed "sensory-motor contingency") before decision formation. Here, the integrated evidence can be directly translated into a motor plan and, indeed, neural signatures of the integration process are evident as build-up activity in premotor brain regions. In other situations, however, the sensory-motor contingencies are unknown at the time of decision formation. We used behavioral psychophysics and computational modeling to test if knowledge about sensory-motor contingencies affects the timescale of perceptual evidence integration. We asked human observers to perform the same motion discrimination task, with or without trial-to-trial variations of the mapping between perceptual choice and motor response. When the mapping varied, it was either instructed before or after the stimulus presentation. We quantified the timescale of evidence integration under these different sensory-motor mapping conditions by means of two approaches. First, we analyzed subjects' discrimination threshold as a function of stimulus duration. Second, we fitted a dynamical decision-making model to subjects' choice behavior. The results from both approaches indicated that observers (i) integrated motion information for several hundred ms, (ii) used a shorter than optimal integration timescale, and (iii) used the same integration timescale under all sensory-motor mappings. We conclude that the mechanisms limiting the timescale of perceptual decisions are largely independent from long-term learning (under fixed mapping) or rapid acquisition (under variable mapping) of sensory-motor contingencies. This conclusion has implications for neurophysiological and neuroimaging studies of perceptual decision-making. PMID:26068458

  14. Relativistic fireballs - Energy conversion and time-scales

    NASA Technical Reports Server (NTRS)

    Rees, M. J.; Meszaros, P.

    1992-01-01

    The expansion energy of a relativistic fireball can be reconverted into radiation when it interacts with an external medium. For expansion with Lorentz factors greater than or approximately equal to 1000 into a typical galactic environment, the corresponding time-scale in the frame of the observer is of the order of seconds. This mechanism would operate in any cosmological scenario of gamma-ray bursts involving initial energies of order a percent of a stellar rest mass, and implies photon energies and time-scales compatible with those observed in gamma-ray bursts.

  15. The time-scale associated with flux expulsion

    NASA Astrophysics Data System (ADS)

    Moffatt, H. K.; Kamkar, H.

    A simple model problem is solved in order to show that the time-scale associated with the process of flux expulsion is tfe = Rm1/3t0 where t0 is a time-scale characterising the flow (for example, the eddy turnover time, or inverse shear rate) and Rm is the magnetic Reynolds number. By decomposing the vector potential into a product of a rapidly varying part (in space) and a slowly varying part, it is shown how numerical work can be extended to much higher values of Rm than has been achieved hitherto.

  16. The anti-Einstein equations

    E-print Network

    Evangelos Chaliasos

    2006-11-12

    As we know, from the Einstein equations the vanishing of the four-divergence of the energy-momentum tensor follows. This is the case because the four-divergence of the Einstein tensor vanishes identically. Inversely, we find that from the vanishing of the four-divergence of the energy-momentum tensor not only the Einstein equations follow. Besides, the so-named anti-Einstein equations follow. These equations must be considered as complementary to the Einstein equations. And while from the Einstein equations the energy density (or the pressure) can be found, from the anti-Einstein equations the pressure (or the energy density) can be also found, without having to use an additional (but arbitrary) equation of state.

  17. Einstein@Home

    NSDL National Science Digital Library

    Bruce Allen developed this World Year of Physics 2005 project for the Laser Interferometer Gravitational Wave Observatory (LIGO) Scientific Collaboration to recruit Internet users to help determine whether gravitational wave exist. "Einstein@Home is a program that uses your computer's idle time to search for spinning neutron stars (also called pulsars) using data from the LIGO and GEO gravitational wave detectors." Users need only a computer with a fast connection to the Internet and the Einstein@Home screensaver. After learning about the program's rules and policies, visitors can create an account and download the necessary components. The website offers a user profile zone where visitors can share information and opinions as well as links to news stories about the project.

  18. Indirect detonation initiation using acoustic timescale thermal power deposition

    NASA Astrophysics Data System (ADS)

    Regele, J. D.; Kassoy, D. R.; Vezolainen, A.; Vasilyev, O. V.

    2013-09-01

    A fluid dynamics video is presented that demonstrates an indirect detonation initiation process. In this process, a transient power deposition adds heat to a spatially resolved volume of fluid in an amount of time that is similar to the acoustic timescale of the fluid volume. A highly resolved two-dimensional simulation shows the events that unfold after the heat is added.

  19. Stochastic Simulation of Enzyme-Catalyzed Reactions with Disparate Timescales

    E-print Network

    Paul, Mark

    Stochastic Simulation of Enzyme-Catalyzed Reactions with Disparate Timescales Debashis Barik-steady-state approximation'' for enzyme-catalyzed reactions provides a useful framework for efficient and accurate stochastic simulations. The method is applied to three examples: a simple enzyme-catalyzed reaction where enzyme

  20. Distinct Neural Mechanisms Mediate Olfactory Memory Formation at Different Timescales

    ERIC Educational Resources Information Center

    McNamara, Ann Marie; Magidson, Phillip D.; Linster, Christiane; Wilson, Donald A.; Cleland, Thomas A.

    2008-01-01

    Habituation is one of the oldest forms of learning, broadly expressed across sensory systems and taxa. Here, we demonstrate that olfactory habituation induced at different timescales (comprising different odor exposure and intertrial interval durations) is mediated by different neural mechanisms. First, the persistence of habituation memory is…

  1. On the pathways and timescales of intercontinental air pollution transport

    Microsoft Academic Search

    Andreas Stohl; Sabine Eckhardt; Caroline Forster; Paul James; Nicole Spichtinger

    2002-01-01

    This paper presents results of a 1-year simulation of the transport of six passive tracers, released over the continents according to an emission inventory for carbon monoxide (CO). Lagrangian concepts are introduced to derive age spectra of the tracer concentrations on a global grid in order to determine the timescales and pathways of pollution export from the continents. Calculating these

  2. Energetic outer zone electron loss timescales during low geomagnetic activity

    Microsoft Academic Search

    Nigel P. Meredith; Richard B. Horne; Sarah A. Glauert; Richard M. Thorne; Danny Summers; Jay M. Albert; Roger R. Anderson

    2006-01-01

    Following enhanced magnetic activity the fluxes of energetic electrons in the Earth's outer radiation belt gradually decay to quiet-time levels. We use CRRES observations to estimate the energetic electron loss timescales and to identify the principal loss mechanisms. Gradual loss of energetic electrons in the region 3.0 ? L ? 5.0 occurs during quiet periods (Kp 7), indicating that the

  3. Timescale decomposition of the reachable set of constrained linear systems

    Microsoft Academic Search

    A. L. Dontchevt

    1992-01-01

    We consider a linear control system with a multiparameter singular perturbation representing multiple time scales and with constraints for the control and the slow state. The Hausdorff limit of the reachable set when the small parameters tend to zero is found. The result provides a basis for a time-scale approximation of the reachable set.

  4. Short Time-Scale Emission Line Variations in Mira B

    NASA Astrophysics Data System (ADS)

    Chamber, H. L., II; Moffett, T. J.; Barnes, T. G., III

    1997-05-01

    Spectra of Mira were taken at McDonald Observatory near Mira A minimum in December 1975 using an image tube spectrograph. Series of spectra on a two to three minute time-scale show significant line strength variations in the emission lines associated with Mira B.

  5. Optimum signal synthesis for time-scale estimation

    Microsoft Academic Search

    Ovarlez Jean

    1998-01-01

    In signal analysis, the joint estimation of the time-scale parameters which can affect a known signal (Doppler effect or scale effect, delay…) may be a problem of interest. An important result has shown that, even if the quality of the time delay estimation is classically given by the inverse spread of the signal spectral density, the quality of the scale

  6. On the timescales characterizing groundwater discharge at springs

    Microsoft Academic Search

    Michael Manga

    1999-01-01

    In some regions, measurements made at springs can be used to study regional hydrogeologic processes, and determine hydraulic and transport properties of aquifers. Here, input–output models, spectral analysis, and time series analysis are used to identify three different timescales characterizing discharge at springs. First, the “hydraulic time scale” depends on the transmissivity of the aquifer and relates long term changes

  7. Stratospheric variability and tropospheric annular mode timescales1

    E-print Network

    Wirosoetisno, Djoko

    Stratospheric variability and tropospheric annular mode timescales1 1234567 89A64BC7DEF72B4 4BEEE%72B43&E5E7D43 7D436BE27B725CE9393BE647 #12;Stratospheric variability and tropospheric annular mode Model, using a novel technique to quantify the influence of stratospheric variability on tropospheric

  8. Bose-Einstein Condensation

    SciTech Connect

    El-Sherbini, Th.M. [Physics Department, Faculty of Science, Cairo University, Giza (Egypt)

    2005-03-17

    This article gives a brief review of Bose-Einstein condensation. It is an exotic quantum phenomenon that was observed in dilute atomic gases for the first time in 1995. It exhibits a new state of matter in which a group of atoms behaves as a single particle. Experiments on this form of matter are relevant to many different areas of physics- from atomic clocks and quantum computing to super fluidity, superconductivity and quantum phase transition.

  9. The Einstein Slew Survey

    Microsoft Academic Search

    Martin Elvis; David Plummer; Jonathan Schachter; G. Fabbiano

    1992-01-01

    A catalog of 819 sources detected in the Einstein IPC Slew Survey of the X-ray sky is presented; 313 of the sources were not previously known as X-ray sources. Typical count rates are 0.1 IPC count\\/s, roughly equivalent to a flux of 3 x 10 exp -12 ergs\\/sq cm s. The sources have positional uncertainties of 1.2 arcmin (90 percent

  10. Einstein et «Zweistein»

    Microsoft Academic Search

    John Stachel

    2005-01-01

    Résumé  Comme le suggère le sobriquet «Zweistein», Wolfgang Pauli fut considéré par la communauté des théoriciens de la physique comme\\u000a son membre le plus éminent après Albert Einstein. Durant plus de trente-cinq ans, les deux hommes entretinrent des relations\\u000a intellectuelles et personnelles. Cet article analyse les relations entre quatre thèmes récurrents de leurs discussions. 1)\\u000a La théorie de la relativité: à

  11. Through Einstein's Eyes

    NSDL National Science Digital Library

    Savage, Craig M.

    Through Einstein's Eyes is the online version of a multimedia project based around how things look at relativistic speeds. It is aimed at high school to early university level physics students. There are two sections. One is fun and spectacular, with a relativistic rollercoaster ride and a tour of the solar system. The other explores the physics of special relativity. CD and DVD versions of the material are available, and are helpful because of the large size of some of the video files.

  12. TIMESCALES ON WHICH STAR FORMATION AFFECTS THE NEUTRAL INTERSTELLAR MEDIUM

    SciTech Connect

    Stilp, Adrienne M.; Dalcanton, Julianne J.; Weisz, Daniel R.; Williams, Benjamin F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Warren, Steven R. [Department of Astronomy, University of Maryland, CSS Building, Room 1024, Stadium Drive, College Park, MD 20742-2421 (United States); Skillman, Evan [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Ott, Juergen [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States)

    2013-08-01

    Turbulent neutral hydrogen (H I) line widths are often thought to be driven primarily by star formation (SF), but the timescale for converting SF energy to H I kinetic energy is unclear. As a complication, studies on the connection between H I line widths and SF in external galaxies often use broadband tracers for the SF rate, which must implicitly assume that SF histories (SFHs) have been constant over the timescale of the tracer. In this paper, we compare measures of H I energy to time-resolved SFHs in a number of nearby dwarf galaxies. We find that H I energy surface density is strongly correlated only with SF that occurred 30-40 Myr ago. This timescale corresponds to the approximate lifetime of the lowest mass supernova progenitors ({approx}8 M{sub Sun }). This analysis suggests that the coupling between SF and the neutral interstellar medium is strongest on this timescale, due either to an intrinsic delay between the release of the peak energy from SF or to the coherent effects of many supernova explosions during this interval. At {Sigma}{sub SFR} > 10{sup -3} M{sub Sun} yr{sup -1} kpc{sup -2}, we find a mean coupling efficiency between SF energy and H I energy of {epsilon} = 0.11 {+-} 0.04 using the 30-40 Myr timescale. However, unphysical efficiencies are required in lower {Sigma}{sub SFR} systems, implying that SF is not the primary driver of H I kinematics at {Sigma}{sub SFR} < 10{sup -3} M{sub Sun} yr{sup -1} kpc{sup -2}.

  13. The global monsoon across timescales: coherent variability of regional monsoons

    NASA Astrophysics Data System (ADS)

    Wang, P. X.; Wang, B.; Cheng, H.; Fasullo, J.; Guo, Z. T.; Kiefer, T.; Liu, Z. Y.

    2014-11-01

    Monsoon has earned increasing attention from the climate community since the last century, yet only recently have regional monsoons been recognized as a global system. It remains a debated issue, however, as to what extent and at which timescales the global monsoon can be viewed as a major mode of climate variability. For this purpose, a PAGES (Past Global Changes) working group (WG) was set up to investigate the concept of the global monsoon and its future research directions. The WG's synthesis is presented here. On the basis of observation and proxy data, the WG found that the regional monsoons can vary coherently, although not perfectly, at various timescales, varying between interannual, interdecadal, centennial, millennial, orbital and tectonic timescales, conforming to the global monsoon concept across timescales. Within the global monsoon system, each subsystem has its own features, depending on its geographic and topographic conditions. Discrimination between global and regional components in the monsoon system is a key to revealing the driving factors in monsoon variations; hence, the global monsoon concept helps to enhance our understanding and to improve future projections of the regional monsoons. This paper starts with a historical review of the global monsoon concept in both modern and paleo-climatology, and an assessment of monsoon proxies used in regional and global scales. The main body of the paper is devoted to a summary of observation data at various timescales, providing evidence of the coherent global monsoon system. The paper concludes with a projection of future monsoon shifts in a warming world. The synthesis will be followed by a companion paper addressing driving mechanisms and outstanding issues in global monsoon studies.

  14. Some Timescales and Time Lags in the Magnetosphere-Ionosphere System

    NASA Astrophysics Data System (ADS)

    Borovsky, J. E.; Denton, M. H.

    2012-12-01

    To understand a complicated system like the solar-wind-driven magnetosphere, an assessment of characteristic timescales and the identification of operational time lags could be of use. Several (but not all) of these timescales are discussed. One dramatic internal timescale of the magnetosphere is the substorm-recurrence period of ~3 hours. Two other important timescales are the Goertz-Shan-Smith timescales for the penetration of electric fields from the solar wind to the dayside and nightside polar ionosphere; these timescales will lead to various time lags between the solar-wind electric field and various geomagnetic indices. An important operational time lag is the several-hour timescale for solar-wind plasma to enter the magnetosphere and be convected from the nightside, around the dipole, to the dayside. One more timescale will be considered: the timescale for the plasmaspheric drainage plume to form and convect to the dayside magnetopause where it can interfere with reconnection at the magnetopause.

  15. OWL representation of the geologic timescale implementing stratigraphic best practice

    NASA Astrophysics Data System (ADS)

    Cox, S. J.

    2011-12-01

    The geologic timescale is a cornerstone of the earth sciences. Versions are available from many sources, with the following being of particular interest: (i) The official International Stratigraphic Chart (ISC) is maintained by the International Commission for Stratigraphy (ICS), following principles developed over the last 40 years. ICS provides the data underlying the chart as part of a specialized software package, and the chart itself as a PDF using the standard colours; (ii) ITC Enschede has developed a representation of the timescale as a thesaurus in SKOS, used in a Web Map Service delivery system; (iii) JPL's SWEET ontology includes a geologic timescale. This takes full advantage of the capabilities of OWL. However, each of these has limitations - The ISC falls down because of incompatibility with web technologies; - While SKOS supports multilingual labelling, SKOS does not adequately support timescale semantics, in particular since it does not include ordering relationships; - The SWEET version (as of version 2) is not fully aligned to the model used by ICS, in particular not recognizing the role of the Global Boundary Stratotype Sections and Point (GSSP). Furthermore, it is distributed as static documents, rather than through a dynamic API using SPARQL. The representation presented in this paper overcomes all of these limitations as follows: - the timescale model is formulated as an OWL ontology - the ontology is directly derived from the UML representation of the ICS best practice proposed by Cox & Richard [2005], and subsequently included as the Geologic Timescale package in GeoSciML (http://www.geosciml.org); this includes links to GSSPs as per the ICS process - key properties in the ontology are also asserted to be subProperties of SKOS properties (topConcept and broader/narrower relations) in order to support SKOS-based queries; SKOS labelling is used to support multi-lingual naming and synonyms - the International Stratigraphic Chart is implemented as a set of instances of classes from the ontology, and published through a SPARQL end-point - the elements of the Stratigraphic chart are linked to the corresponding elements in SWEET (Raskin et al., 2011) and DBpedia to support traceability between different commonly accessed representations. The ontology builds on standard geospatial information models, including the Observations and Measurements model (ISO 19156), and GeoSciML. This allows the ages given in the chart to be linked to the evidence basis found in the associated GeoSciML features.

  16. Super-Eddington Accretion in the Ultraluminous X-Ray Source NGC 1313 X-2: An Ephemeral Feast

    NASA Astrophysics Data System (ADS)

    Weng, Shan-Shan; Zhang, Shuang-Nan; Zhao, Hai-Hui

    2014-01-01

    We investigate the X-ray spectrum, variability, and the surrounding ionized bubble of NGC 1313 X-2 to explore the physics of super-Eddington accretion. Beyond the Eddington luminosity, the accretion disk of NGC 1313 X-2 is truncated at a large radius (~50 times the innermost stable circular orbit), and displays the similar evolution track with both luminous Galactic black-hole and neutron star X-ray binaries (XRBs). In super-critical accretion, the speed of radiatively driven outflows from the inner disk is mildly relativistic. Such ultra-fast outflows would be overionized and might produce weak Fe K absorption lines, which may be detected by the coming X-ray mission Astro-H. If NGC 1313 X-2 is a massive stellar XRB, the high luminosity indicates that an ephemeral feast is held in the source. That is, the source must be accreting at a hyper-Eddington mass rate to give the super-Eddington emission over ~104-105 yr. The expansion of the surrounding bubble nebula with a velocity of ~100 km s-1 might indicate that it has existed over ~106 yr and is inflated by the radiatively driven outflows from the transient with a duty cycle of activity of ~ a few percent. Alternatively, if the surrounding bubble nebula is produced by line-driven winds, less energy is required than the radiatively driven outflow scenario, and the radius of the Strömgren radius agrees with the nebula size. Our results are in favor of the line-driven winds scenario, which can avoid the conflict between the short accretion age and the apparently much longer bubble age inferred from the expansion velocity in the nebula.

  17. Integral equations of the photon fluence rate and flux based on a generalized Delta-Eddington phase function

    PubMed Central

    Cong, Wenxiang; Shen, Haiou; Cong, Alexander X.; Wang, Ge

    2009-01-01

    We present a generalized Delta-Eddington phase function to simplify the radiative transfer equation to integral equations with respect to both photon fluence rate and flux vector. The photon fluence rate and flux can be solved from the system of integral equations. By comparing to the Monte Carlo simulation results, the solutions of the system of integral equations accurately model the photon propagation in biological tissue over a wide range of optical parameters. PMID:18465979

  18. Eddington-inspired Born-Infeld gravity: Astrophysical and cosmological constraints

    NASA Astrophysics Data System (ADS)

    Avelino, P. P.

    2012-05-01

    In this paper we compute stringent astrophysical and cosmological constraints on a recently proposed Eddington-inspired Born-Infeld theory of gravity. We find, using a generalized version of the Zel’dovich approximation, that in this theory a pressureless, cold-dark matter fluid has a nonzero effective sound speed. We compute the corresponding effective Jeans length and show that it is approximately equal to the fundamental length of the theory R*=?1/2G-1/2, where ? is the only additional parameter of theory with respect to general relativity and G is the gravitational constant. This scale determines the minimum size of compact objects which are held together by gravity. We also estimate the critical mass above which pressureless compact objects are unstable against collapse into a black hole, showing that it is approximately equal to the fundamental mass M*=?1/2c2G-3/2, and we show that the maximum density attainable inside stable compact stars is roughly equal to the fundamental density ?*=?-1c2, where c is the speed of light in vacuum. We find that the mere existence of astrophysical objects of size R, which are held together by their own gravity, leads to the constraint ?

  19. Physics at the surface of a star in Eddington-inspired Born-Infeld Gravity

    NASA Astrophysics Data System (ADS)

    Kim, Hyeong-Chan

    2014-03-01

    We study phenomena happening at the surface of a star in Eddington-inspired Born-Infeld (EiBI) gravity. The star is made of particles, which are effectively described by a polytropic fluid. The EiBI theory was known to have a pathology that singularities happen at a star surface. We suggest that the gravitational backreaction on the particles cures the problem. Strong tidal forces near the (surface) singularity modify the effective equation of state of the particles or make the surface be unstable depending on its matter contents. The geodesic deviation equations take after Hooke's law, where its frequency squared is proportional to the scalar curvature at the surface. For a positive curvature, a particle collides with a probing wall more often and increases the pressure. With the increased pressure, the surface is no longer singular. For a negative curvature, the matters around the surface experience repulsions with infinite accelerations. Therefore, the EiBI gravity is saved from the pathology of a surface singularity.

  20. A Niching Genetic Algorithm For Milne-Eddington Spectral Line Inversions

    NASA Astrophysics Data System (ADS)

    Harker, Brian; Balasubramaniam, K.; Sojka, Jan

    2006-10-01

    Stokes profile inversions form a basis for ``measuring'' solar magnetic fields. The High Altitude Observatory (HAO) Milne-Eddington (M-E) spectral line inversions have traditionally been used as initializations to more sophisticated inversion procedures. One such code uses a genetic-algorithm initialization to search the parameter space on a more global scale, in an effort to obtain a good starting guess for a more traditional hill-climbing (e.g. Levenberg-Marquardt) algorithm. A serious drawback to the type of genetic algorithm used is that it has been shown to perform poorly on high-dimensional spaces with multiple optima. A single-component M-E model atmosphere is typically described by about 7 free parameters, indicating a fairly high parameter space dimensionality. Two-component models increase the ability to fit frequently-observed asymmetric spectral lines, at the price of nearly doubling the dimension of the parameter space. Furthermore, spectral lines for large magnetic field strengths and large inclinations are very similar to profiles for weaker field strengths and small inclinations, indicating the potential presence of multiple optima that correspond to very different physical conditions. This poster presents an initial investigation into alleviating these difficulties by incorporating a more sophisticated evolutionary strategy into the SGA, and parallelizing over multiple processors.

  1. Black hole solution and strong gravitational lensing in Eddington-inspired Born-Infeld gravity

    NASA Astrophysics Data System (ADS)

    Wei, Shao-Wen; Yang, Ke; Liu, Yu-Xiao

    2015-06-01

    A new theory of gravity called Eddington-inspired Born-Infeld (EiBI) gravity was recently proposed by Bañados and Ferreira. This theory leads to some exciting new features, such as free of cosmological singularities. In this paper, we first obtain a charged EiBI black hole solution with a nonvanishing cosmological constant when the electromagnetic field is included in. Then based on it, we study the strong gravitational lensing by the asymptotic flat charged EiBI black hole. The strong deflection limit coefficients and observables are shown to closely depend on the additional coupling parameter in the EiBI gravity. It is found that, compared with the corresponding charged black hole in general relativity, the positive coupling parameter will shrink the black hole horizon and photon sphere. Moreover, the coupling parameter will decrease the angular position and relative magnitudes of the relativistic images, while increase the angular separation, which may shine new light on testing such gravity theory in near future by the astronomical instruments.

  2. A Correlation between the Ionization State of the Inner Accretion Disk and the Eddington Ratio of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Ballantyne, David R.; McDuffie, J.; Rusin, J.

    2011-09-01

    X-ray reflection features observed from the innermost regions of accretion disks in Active Galactic Nuclei (AGNs) allow important tests of accretion theory. In recent years it has been possible to use the Fe K? line and reflection continuum to parametrize the ionization state of the irradiated inner accretion disk. Here, we collect 10 measurements of ?, the disk ionization parameter, from 8 AGNs with strong evidence for reflection from the inner accretion disk and good black hole mass estimates. We find strong statistical evidence (98.56% confidence) for a nearly linear correlation between ? and the AGN Eddington ratio. Moreover, such a correlation is predicted by a simple application of ?-disk accretion theory, albeit with a stronger dependence on the Eddington ratio. The theory shows that there will be intrinsic scatter to any correlation as a result of different black hole spins and radii of reflection. There are several possibilities to soften the predicted dependence on the Eddington ratio to allow a closer agreement with the observed correlation, but the current data does not allow for an unique explanation. The correlation can be used to estimate that MCG-6-30-15 should have a highly ionized inner accretion disk, which would imply a black hole spin of 0.8. Additional measurements of ? from a larger sample of AGNs are needed to confirm the existence of this correlation, and will allow investigation of the accretion disk/corona interaction in the inner regions of accretion disks.

  3. A Correlation between the Ionization State of the Inner Accretion Disk and the Eddington Ratio of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Ballantyne, D. R.; McDuffie, J. R.; Rusin, J. S.

    2011-06-01

    X-ray reflection features observed from the innermost regions of accretion disks in active galactic nuclei (AGNs) allow important tests of accretion theory. In recent years, it has been possible to use the Fe K? line and reflection continuum to parameterize the ionization state of the irradiated inner accretion disk. Here, we collect 10 measurements of ?, the disk ionization parameter, from eight AGNs with strong evidence for reflection from the inner accretion disk and good black hole mass estimates. We find strong statistical evidence (98.56% confidence) for a nearly linear correlation between ? and the AGN Eddington ratio. Moreover, such a correlation is predicted by a simple application of ?-disk accretion theory, albeit with a stronger dependence on the Eddington ratio. The theory shows that there will be intrinsic scatter to any correlation as a result of different black hole spins and radii of reflection. There are several possibilities to soften the predicted dependence on the Eddington ratio to allow a closer agreement with the observed correlation, but the current data do not allow for a unique explanation. The correlation can be used to estimate that MCG-6-30-15 should have a highly ionized inner accretion disk, which would imply a black hole spin of ~0.8. Additional measurements of ? from a larger sample of AGNs are needed to confirm the existence of this correlation, and will allow investigation of the accretion disk/corona interaction in the inner regions of accretion disks.

  4. Einstein and His Times

    NSDL National Science Digital Library

    2012-08-03

    In this lesson, students will read about and research the major historical events that occurred throughout the year 1919. They will use different readings and articles to understand and describe what life was like during this time. In addition, the students will present their case as to whether or not Albert Einstein should be voted "Man of the Year" for 1919. This activity is from the Cosmic Times teachers guide and is intended to be used in conjunction with the 1919 Cosmic Times Poster.

  5. Einstein spectra of quasars

    NASA Technical Reports Server (NTRS)

    Wilkes, Belinda J.

    1988-01-01

    The results of the initial stage of the CfA survey of quasar energy distributions are reviewed. Einstein imaging proportional counter spectra of 33 quasars have been studied by fitting a single power law slope and absorption by an equivalent column density of neutral hydrogen. Comparison with the higher energy HEAO-A2 data leads to a two-component model for the X-ray spectrum. The X-ray column density is systematically lower than the 21-cm measured Galactic column density along the same line of sight.

  6. Particle-acceleration timescales in TeV blazar flares

    E-print Network

    Joni Tammi; Peter Duffy

    2008-12-01

    Observations of minute-scale flares in TeV Blazars place constraints on particle acceleration mechanisms in those objects. The implications for a variety of radiation mechanisms have been addressed in the literature; in this paper we compare four different acceleration mechanisms: diffusive shock acceleration, second-order Fermi, shear acceleration and the converter mechanism. When the acceleration timescales and radiative losses are taken into account, we can exclude shear acceleration and the neutron-based converted mechanism as possible acceleration processes in these systems. The first-order Fermi process and the converter mechanism working via SSC photons are still practically instantaneous, however, provided sufficient turbulence is generated on the timescale of seconds. We propose stochastic acceleration as a promising candidate for the energy-dependent time delays in recent gamma-ray flares of Markarian 501.

  7. The Einstein Dossiers: Science and Politics - Einstein's Berlin Period with an Appendix on Einstein's FBI File

    NASA Astrophysics Data System (ADS)

    Grundmann, Siegfried

    In 1919 the Prussian Ministry of Science, Arts and Culture opened a dossier on "Einstein's Theory of Relativity." It was rediscovered by the author in 1961 and is used in conjunction with numerous other subsequently identified 'Einstein' files as the basis of this fascinating book. In particular, the author carefully scrutinizes Einstein's FBI file from 1950-55 against mostly unpublished material from European including Soviet sources and presents hitherto unknown documentation on Einstein's alleged contacts with the German Communist Party and the Comintern.

  8. Response to Deines and Williams on Astronomical Timescales

    NASA Astrophysics Data System (ADS)

    Slabinski, Victor J.

    2009-05-01

    In a paper presented at this conference, Deines and Williams (DW) question the conventional determination and interpretation of the differences between astronomical timescales, such as Universal Time (UT) which deals with Earth rotation, Atomic Time (AT), and planetary ephemeride timescales such as Terrestrial Time (TT). This paper offers explanations attempting to remove some sources of confusion on the subject, in particular: 1) To explain large discrepancies in the determined values for the tidal deceleration of Earth spin rate, we show that the rotational acceleration producing decadal variations in Earth spin are large compared to the tidal deceleration and easily mask the latter signal in rotation data spanning less than 200 years. 2) DW argue that the absence of a leap second between 1999 Jan 1 and 2005 Dec 31 is a statistically improbable event and is an artifact of the UT formula redefinition adopted in 2003. We offer a counterexample. If the Terrestrial Time second had been defined to match the UT second at an epoch other than the effective 1819 epoch that was used, a seven year span without leap seconds can be produced in other decades, decades without a redefinition of the UT formula. This shows that several seven year spans without leap seconds are possible and thereby negates the DW statistical argument. 3) DW also argue that there is a divergence in the TT timescale because relativistic time dilation was not included in Newcomb's analysis of the Sun's apparent motion. We show by a simple analysis that any such dilation was absorbed into the observationally determined elements of Earth's solar orbit. The resulting theory then accurately predicts the Sun's position using TT as told by Earth mounted clocks without any explicit use of time dilation, that is, there is no observational indication of timescale divergence.

  9. Timescale algorithms combining cesium clocks and hydrogen masers

    NASA Technical Reports Server (NTRS)

    Breakiron, Lee A.

    1992-01-01

    The United States Naval Observatory (USNO) atomic timescale, formerly based on an ensemble of cesium clocks, is now produced by an ensemble of cesium clocks and hydrogen masers. In order to optimize stability and reliability, equal clock weighting has been replaced by a procedure reflecting the relative, time-varying noise characteristics of the two different types of clocks. Correlation of frequency drift is required, and residual drift is avoided by the eventual complete deweighting of the masers.

  10. Geol 102 Historical Geology The Geologic Timescale 2012

    E-print Network

    Holtz Jr., Thomas R.

    Geol 102 Historical Geology The Geologic Timescale 2012 EON ERA PERIOD (Special Units) EPOCH Range.332 Oligocene 33.9 - 23.03 Eocene 56.0 - 33.9 Paleocene 66.0 - 56.0 Cretaceous 145.0 - 66.0 Jurassic 201.3 - 145.0 Triassic 252.2 - 201.3 Permian 298.9 - 252.2 Pennsylvanian Sub-period 323.2 - 298.9 Mississippian Sub-period

  11. Geol 102 Historical Geology The Geologic Timescale 2009

    E-print Network

    Holtz Jr., Thomas R.

    Geol 102 Historical Geology The Geologic Timescale 2009 EON ERA PERIOD (Special Units) EPOCH Range.5 - 55.8 Mesozoic Cretaceous 145.5 - 65.5 Jurassic 199.6 - 145.5 Triassic 251.0 - 199.6 Paleozoic Permian 299.0 - 251.0 Carboniferous Pennsylvanian Sub-period 318.1 - 299.0 Mississippian Sub-period 359

  12. Geol 102 Historical Geology The Geologic Timescale 2011

    E-print Network

    Holtz Jr., Thomas R.

    Geol 102 Historical Geology The Geologic Timescale 2011 EON ERA PERIOD (Special Units) EPOCH Range 65.5 - 55.8 Mesozoic Cretaceous 145.5 - 65.5 Jurassic 201.5 - 145.5 Triassic 252.3 - 201.5 Paleozoic Permian 299.0 - 252.3 Carboniferous Pennsylvanian Sub-period 318.1 - 299.0 Mississippian Sub-period 359

  13. EMCCD Technology in High Precision Photometry on Short Timescales

    Microsoft Academic Search

    Niall Smith; Alan Giltinan; Aidan O’Connor; Stephen O’Driscoll; Adrian Collins; Dylan Loughnan; Andreas Papageorgiou

    2008-01-01

    We discuss the advantages and limitations of Electron Multiplying CCD technology in high precision photometry on short timescales,\\u000a with special emphasis on probing the smallest structures in active galactic jets. Factors external to the EMCCD, rather than\\u000a the architecture of the EMCCD itself, most often limit the precision of photometry that can be reached with groundbased observations.\\u000a Although EMCCDs can

  14. Characterization of discontinuities in the Stripa granite. Timescale heater experiment

    Microsoft Academic Search

    Thorpe

    1979-01-01

    The report describes the methodology and results of a detailed study of geologic discontinuities associated with the time-scale heater test at the Stripa mine in Sweden. Mapping of the floor of the experiment tunnel coupled with observation of core samples from beneath the drift indicate that four N-striking shear fractures dip steeply through the 6 x 10 x 25-m rock

  15. Broad absorption line variability on multi-year timescales in a large quasar sample

    NASA Astrophysics Data System (ADS)

    Filiz Ak, Nurten

    Outflows launched near the central supermassive black holes (SMBHs) are a common and important component of active galactic nuclei (AGNs). Outflows in luminous AGNs (i.e., quasars) play a key role in mass accretion onto SMBH as well as in the feedback into host galaxies. The most prominent signature of such outflows appears as broad absorption lines (BALs) that are blueshifted from the emission line with a few thousands km s--1 velocities. In this dissertation, I place further constrains upon the size scale, internal structure, dynamics, and evolution of the outflows investigating profiles, properties, and variation characteristics of BAL troughs. I present observational results on BAL troughs in a large quasar sample utilizing spectroscopic observations from the Sloan Digital Sky Survey spanning on multi-year timescales. The results presented here, for the first time, provide a large and well-defined variability data base capable of discriminating between time-dependent hydrodynamic wind calculations in a statistically powerful manner. In a study of 582 quasars, I present 21 examples of BAL trough disappearance. Approximately 3.3% of BAL quasars show disappearing C IV trough on rest-frame timescales of 1.1--3.9 yr. BAL disappearance appears to occur mainly for shallow and weak or moderate-strength absorption troughs but not the strongest ones. When one BAL trough in a quasar spectrum disappears, the other present troughs usually weaken. Possible causes of such coordinated variations could be disk-wind rotation or variations of shielding gas that lead to variations of ionizing-continuum radiation. I present a detailed study on the variability of 428 C IV and 235 Si IV BAL troughs using a systematically observed sample of 291 BAL quasars. BAL variation distributions indicate that BAL disappearance is an extreme type of general BAL variability, rather than a qualitatively distinct phenomenon. The high observed frequency of BAL variability on multi-year timescales is generally supportive of models where most BAL absorption arises at radii of 10--1000 light days. Average lifetime for a BAL trough along our line-of-sight is a few thousand years which is long compared to the orbital time of the accretion disk at the wind-launching radius. We have examined if BAL variations on several timescales depend upon quasar properties, including quasar luminosity, Eddington luminosity ratio, black hole mass, redshift, and radio loudness. Within the ranges of these properties spanned by our sample, we do not find any strong dependences. The coordinated trough variability of BAL quasars with multiple troughs suggests that changes in "shielding gas" may play a significant role in driving general BAL variability. I present a study investigating the dependence of C IV BAL properties and variation characteristics on accompanying Si IV and Al III absorption. Results of this study show that C IV BAL trough shapes, depths, velocity widths and strengths show a strong dependence on the presence of Si IV and Al III BAL troughs at corresponding velocities. Similarly, the variation characteristics and depth variation profiles of C IV BAL troughs also show a strong connection to BAL troughs in these transitions. Using these ions as a basic tracer of ionization level of the absorbing gas, systematic measurements of variability and profiles for a large sample of C IV , Si IV, and Al III BAL troughs present observational evidences of the relation between ionization level, column density and kinematics of outflows. Utilizing observational investigations on a large BAL quasar sample, we show that ionization level, column density and kinematics of outflows show correlated object-to-object differences. We present a detailed comparison between the observational results of this study and the well studied disk-wind model of quasar outflows, which suggests that the wind is launched from the accretion disk at ˜ 1016--1017 cm and radiatively driven by UV line pressure. Results of this study show that lines-of-sight with different viewing inclinations suc

  16. 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.

  17. Liouville gravity from Einstein gravity

    E-print Network

    D. Grumiller; R. Jackiw

    2007-12-28

    We show that Liouville gravity arises as the limit of pure Einstein gravity in 2+epsilon dimensions as epsilon goes to zero, provided Newton's constant scales with epsilon. Our procedure - spherical reduction, dualization, limit, dualizing back - passes several consistency tests: geometric properties, interactions with matter and the Bekenstein-Hawking entropy are as expected from Einstein gravity.

  18. Unified field theories and Einstein

    E-print Network

    S C Tiwari

    2006-02-16

    Einstein's contribution to relativity is reviewed. It is pointed out that Weyl gave first unified theory of gravitation and electromagnetism and it was different than the five dimensional theory of Kaluza. Einstein began his work on unification in 1925 that continued whole through the rest of his life.

  19. What, Precisely, Is "Thinking"? Einstein's Answer.

    ERIC Educational Resources Information Center

    Holton, Gerald

    1979-01-01

    Gives an analysis of how Einstein viewed "thinking," and the nature of scientific discovery, using extensive quotations from Einstein's own writings, and especially from his essay "Autobiographical Notes."

  20. A Global Three-dimensional Radiation Magneto-hydrodynamic Simulation of Super-Eddington Accretion Disks

    NASA Astrophysics Data System (ADS)

    Jiang, Yan-Fei; Stone, James M.; Davis, Shane W.

    2014-12-01

    We study super-Eddington accretion flows onto black holes using a global three-dimensional radiation magneto-hydrodynamical simulation. We solve the time-dependent radiative transfer equation for the specific intensities to accurately calculate the angular distribution of the emitted radiation. Turbulence generated by the magneto-rotational instability provides self-consistent angular momentum transfer. The simulation reaches inflow equilibrium with an accretion rate ~220 L Edd/c 2 and forms a radiation-driven outflow along the rotation axis. The mechanical energy flux carried by the outflow is ~20% of the radiative energy flux. The total mass flux lost in the outflow is about 29% of the net accretion rate. The radiative luminosity of this flow is ~10 L Edd. This yields a radiative efficiency ~4.5%, which is comparable to the value in a standard thin disk model. In our simulation, vertical advection of radiation caused by magnetic buoyancy transports energy faster than photon diffusion, allowing a significant fraction of the photons to escape from the surface of the disk before being advected into the black hole. We contrast our results with the lower radiative efficiencies inferred in most models, such as the slim disk model, which neglect vertical advection. Our inferred radiative efficiencies also exceed published results from previous global numerical simulations, which did not attribute a significant role to vertical advection. We briefly discuss the implications for the growth of supermassive black holes in the early universe and describe how these results provided a basis for explaining the spectrum and population statistics of ultraluminous X-ray sources.

  1. Radiation hydrodynamics with neutrinos. Variable Eddington factor method for core-collapse supernova simulations

    NASA Astrophysics Data System (ADS)

    Rampp, M.; Janka, H.-T.

    2002-12-01

    Neutrino transport and neutrino interactions in dense matter play a crucial role in stellar core collapse, supernova explosions and neutron star formation. Here we present a detailed description of a new numerical code for treating the time and energy dependent neutrino transport in hydrodynamical simulations of such events. The code is based on a variable Eddington factor method to deal with the integro-differential character of the Boltzmann equation. The moments of the neutrino distribution function and the energy and lepton number exchange with the stellar medium are determined by iteratively solving the zeroth and first order moment equations in combination with a model Boltzmann equation. The latter is discretized on a grid of tangent rays. The integration of the transport equations and the neutrino source terms is performed in a time-implicit way. In the present version of the program, the transport part is coupled to an explicit hydrodynamics code which follows the evolution of the stellar plasma by a finite-volume method with piecewise parabolic interpolation, using a Riemann solver to calculate the hydrodynamic states. The neutrino source terms are implemented in an operator-split step. Neutrino transport and hydrodynamics can be calculated with different spatial grids and different time steps. The structure of the described code is modular and offers a high degree of flexibility for an application to relativistic and multi-dimensional problems at different levels of refinement and accuracy. We critically evaluate results for a number of test cases, including neutrino transport in rapidly moving stellar media and approximate relativistic core collapse, and suggest a path for generalizing the code to be used in multi-dimensional simulations of convection in neutron stars and supernovae. Appendices A and B and all their figures are only available at http://www.edpsciences.org

  2. Searching For the Physical Drivers of Eigenvector 1: Influence of Black Hole Mass and Eddington Ratio

    E-print Network

    Paola Marziani; Radoslav K. Zamanov; Jack W. Sulentic; Massimo Calvani

    2003-07-21

    [Abridged] We compute the virial mass of the central black hole (M) and the luminosity-to-mass (L/M) ratio of ~ 300 low-z quasars and luminous Seyfert 1 nuclei. We analyze: (1) whether radio-quiet and radio-loud objects show systematic differences in terms of M and L/M; (2) the influence of M and L/M on the shape of the H-beta broad component line profile; (3) the significance of the so-called "blue outliers" i.e., sources showing a significant blueshift of the [OIII] 4959, 5007 lines with respect to the narrow component of H-beta which is used as an estimator of the quasar reference frame. We show that M and L/M distributions for RQ and RL sources are likely different for samples matched in luminosity and redshift. Line profile comparisons for median spectra computed over narrow ranges of M and L/M indicate that a Lorentz function provides a better fit for higher L/M sources and a double Gaussian for lower L/M values. A second (redshifted) Gaussian component at low L/M appears as a red asymmetry frequently observed in radio-loud and radio-quiet sources with broader (FWHM > 4000 km/s) H-beta broad component profiles. This component becomes stronger in larger mass and lower L/M sources. No specific influence of radio loudness on the H-beta broad component profile is detected, although equivalent widths of H-beta broad component and especially of [OIII] 4959,5007 are larger for radio-loud sources. We identify five more "blue outlier" sources. Since these sources are, on average, one magnitude brighter than other AGNs with similar mass, they are accreting at an Eddington ratio that is 2-3 times higher. We hint at evolutionary effects that explain some of these results and reinforce the "Eigenvector 1" correlations.

  3. Eddington-limited Accretion and the Black Hole Mass Function at Redshift 6

    NASA Astrophysics Data System (ADS)

    Willott, Chris J.; Albert, Loic; Arzoumanian, Doris; Bergeron, Jacqueline; Crampton, David; Delorme, Philippe; Hutchings, John B.; Omont, Alain; Reylé, Céline; Schade, David

    2010-08-01

    We present discovery observations of a quasar in the Canada-France High-z Quasar Survey (CFHQS) at redshift z = 6.44. We also use near-infrared spectroscopy of nine CFHQS quasars at z ~ 6 to determine black hole masses. These are compared with similar estimates for more luminous Sloan Digital Sky Survey quasars to investigate the relationship between black hole mass and quasar luminosity. We find a strong correlation between Mg II FWHM and UV luminosity and that most quasars at this early epoch are accreting close to the Eddington limit. Thus, these quasars appear to be in an early stage of their life cycle where they are building up their black hole mass exponentially. Combining these results with the quasar luminosity function, we derive the black hole mass function at z = 6. Our black hole mass function is ~104 times lower than at z = 0 and substantially below estimates from previous studies. The main uncertainties which could increase the black hole mass function are a larger population of obscured quasars at high redshift than is observed at low redshift and/or a low quasar duty cycle at z = 6. In comparison, the global stellar mass function is only ~102 times lower at z = 6 than at z = 0. The difference between the black hole and stellar mass function evolution is due to either rapid early star formation which is not limited by radiation pressure as is the case for black hole growth or inefficient black hole seeding. Our work predicts that the black hole mass-stellar mass relation for a volume-limited sample of galaxies declines rapidly at very high redshift. This is in contrast to the observed increase at 4 < z < 6 from the local relation if one just studies the most massive black holes.

  4. An astronomical polarity timescale for the late middle Miocene based on cyclic continental sequences

    E-print Network

    Utrecht, Universiteit

    An astronomical polarity timescale for the late middle Miocene based on cyclic continental an astronomically tuned polarity timescale for the late middle Miocene based on a cyclic shallow lacustrine, cyclostratigraphy, astronomical timescale, orbital forcing, Miocene Citation: Abdul Aziz, H., W. Krijgsman, F. J

  5. Ocean-atmosphere partitioning of anthropogenic carbon dioxide on centennial timescales

    E-print Network

    Follows, Mick

    Ocean-atmosphere partitioning of anthropogenic carbon dioxide on centennial timescales Philip-atmosphere partitioning of anthropogenic carbon dioxide on centennial timescales is presented. The partial pressure carbon dioxide on centennial timescales, Global Biogeochem. Cycles, 21, GB1014, doi:10.1029/2006GB002810

  6. To be published in SIAM Review Profits and pitfalls of timescales in asymptotics

    E-print Network

    Verhulst, Ferdinand

    To be published in SIAM Review Profits and pitfalls of timescales in asymptotics Ferdinand Verhulst Abstract The method of multiple timescales is widely used in engineering and mathematical physics where we can obtain an advantage from the concept of timescales and we present examples where

  7. Distance Learning in Einstein’s Fourth Dimension

    Microsoft Academic Search

    Robin Throne

    2007-01-01

    This article blends the concepts of spacetime from theoretical physics and Einstein’s Relativity Theory to discuss the spatiotemporal nature of distance education. By comparing and contrasting speed-of-light space travel with the speed of computer processing, the leap is made to consider the fourth dimension and its phenomena for the Web traveler. Learning events are compared with events in time to

  8. Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit

    E-print Network

    G. Graefener; W. -R. Hamann

    2008-03-06

    The mass loss from Wolf-Rayet (WR) stars is of fundamental importance for the final fate of massive stars and their chemical yields. Its Z-dependence is discussed in relation to the formation of long-duration Gamma Ray Bursts (GRBs) and the yields from early stellar generations. However, the mechanism of formation of WR-type stellar winds is still under debate. We present the first fully self-consistent atmosphere/wind models for late-type WN stars. We investigate the mechanisms leading to their strong mass loss, and examine the dependence on stellar parameters, in particular on the metallicity Z. We identify WNL stars as very massive stars close to the Eddington limit, potentially still in the phase of central H-burning. Due to their high L/M ratios, these stars develop optically thick, radiatively driven winds. These winds show qualitatively different properties than the thin winds of OB stars. The resultant mass loss depends strongly on Z, but also on the Eddington factor, and the stellar temperature. We combine our results in a parametrized mass loss recipe for WNL stars. According to our present model computations, stars close to the Eddington limit tend to form strong WR-type winds, even at very low Z. Our models thus predict an efficient mass loss mechanism for low metallicity stars. For extremely metal-poor stars, we find that the self-enrichment with primary nitrogen can drive WR-type mass loss. These first WN stars might play an important role in the enrichment of the early ISM with freshly produced nitrogen.

  9. Eddington-inspired Born-Infeld gravity: nuclear physics constraints and the validity of the continuous fluid approximation

    E-print Network

    P. P. Avelino

    2012-07-19

    In this paper we investigate the classical non-relativistic limit of the Eddington-inspired Born-Infeld theory of gravity. We show that strong bounds on the value of the only additional parameter of the theory \\kappa, with respect to general relativity, may be obtained by requiring that gravity plays a subdominant role compared to electromagnetic interactions inside atomic nuclei. We also discuss the validity of the continuous fluid approximation used in this and other astrophysical and cosmological studies. We argue that although the continuous fluid approximation is expected to be valid in the case of sufficiently smooth density distributions, its use should eventually be validated at a quantum level.

  10. Probing the Peculiar Behavior of GRS 1915+105 at Near-Eddington Luminosity

    NASA Astrophysics Data System (ADS)

    Vierdayanti, Kiki; Mineshige, Shin; Ueda, Yoshihiro

    2010-04-01

    To understand the nature of supercritical accretion, we systematically analyzed the RXTE/PCA data of GRS 1915+105 in its quasi-steady states, by choosing data with small variability during 1999-2000. We applied a multicolor disk plus a thermal Comptonization model, and took into consideration accurate interstellar absorption, a reflection component (with an iron-K emission line), and absorption features from the disk wind self-consistently. The total luminosity ranges from ˜0.2LE to slightly above LE. There is a strong correlation between the inner disk temperature and the fraction of the disk component. Most of the Comptonization-dominated (>50% total flux) spectra show Tin ˜ 1 keV with a high electron temperature of >10 keV, which may correspond to the very high state in canonical black hole X-ray binaries (BHBs). In contrast, the disk-dominated spectra have Tin ˜ 2 keV with a low temperature (<10 keV) and optically thick Comptonization, and show two separate branches in the luminosity vs. innermost temperature (L-Tin) diagram. The lower branch clearly follows the L ? T4in-track. Furthermore, by applying the extended disk blackbody (or p-free disk) model, we found that 9 out of 12 datasets with disk luminosity above 0.3LE prefer a flatter temperature gradient than that in the standard disk (p < 0.7). We interpret that, in the lower branch, the disk extends down to the innermost stable circular orbit, and the source is most probably in the slim-disk state. A rapidly spinning black hole can explain both the lack of the L ? T2in-track and a high value of the spectral hardening factor (˜4) that would be required for a non-rotating black hole. The spectra in the upper branch are consistent with the picture of a truncated disk with low-temperature Comptonization. This state was uniquely observed from GRS 1915+105 among BHBs, which may be present at near-Eddington luminosity.

  11. Timescales and bottlenecks in miRNA-dependent gene regulation

    PubMed Central

    Hausser, Jean; Syed, Afzal Pasha; Selevsek, Nathalie; van Nimwegen, Erik; Jaskiewicz, Lukasz; Aebersold, Ruedi; Zavolan, Mihaela

    2013-01-01

    MiRNAs are post-transcriptional regulators that contribute to the establishment and maintenance of gene expression patterns. Although their biogenesis and decay appear to be under complex control, the implications of miRNA expression dynamics for the processes that they regulate are not well understood. We derived a mathematical model of miRNA-mediated gene regulation, inferred its parameters from experimental data sets, and found that the model describes well time-dependent changes in mRNA, protein and ribosome density levels measured upon miRNA transfection and induction. The inferred parameters indicate that the timescale of miRNA-dependent regulation is slower than initially thought. Delays in miRNA loading into Argonaute proteins and the slow decay of proteins relative to mRNAs can explain the typically small changes in protein levels observed upon miRNA transfection. For miRNAs to regulate protein expression on the timescale of a day, as miRNAs involved in cell-cycle regulation do, accelerated miRNA turnover is necessary. PMID:24301800

  12. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerone C.; Kolody, Mark R.

    2011-01-01

    Evaluation of metal-based structures has long relied on atmospheric exposure test sites to determine corrosion resistance in marine environments. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions of the corrosive environment. Their success for correlation to atmospheric exposure is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated laboratory testing, which often focuses on the electrochemical reactions that occur during corrosion conditions, has yet to be universally accepted as a useful tool in predicting the long term service life of a metal despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard and their use is imperative, a method that correlates timescales from atmospheric exposure to accelerated testing would be very valuable. This work uses surface chemistry to interpret the chemical changes occurring on low carbon steel during atmospheric and accelerated corrosion conditions with the objective of finding a correlation between its accelerated and long-term corrosion performance. The current results of correlating data from marine atmospheric exposure conditions at the Kennedy Space Center beachside corrosion test site, alternating seawater spray, and immersion in typical electrochemical laboratory conditions, will be presented. Key words: atmospheric exposure, accelerated corrosion testing, alternating seawater spray, marine, correlation, seawater, carbon steel, long-term corrosion performance prediction, X-ray photoelectron spectroscopy.

  13. Oceanic control of Northeast Pacific hurricane activity at interannual timescales

    NASA Astrophysics Data System (ADS)

    Balaguru, Karthik; Leung, L. Ruby; Yoon, Jin-ho

    2013-12-01

    Sea surface temperature (SST) is not the only oceanic parameter that can play a key role in the interannual variability of Northeast Pacific hurricane activity. Using several observational data sets and the statistical technique of multiple linear regression analysis, we show that, along with SST, the thermocline depth (TD) plays an important role in hurricane activity at interannual timescales in this basin. Based on the parameter that dominates, the ocean basin can be divided into two sub-regions. In the Southern sub-region, which includes the hurricane main development area, interannual variability of the upper-ocean heat content (OHC) is primarily controlled by TD variations. Consequently, the interannual variability in the hurricane power dissipation index (PDI), which is a measure of the intensity of hurricane activity, is driven by that of the TD. On the other hand, in the Northern sub-region, SST exerts the major control over the OHC variability and, in turn, the PDI. Our study suggests that both SST and TD have a significant influence on the Northeast Pacific hurricane activity at interannual timescales and that their respective roles are more clearly delineated when sub-regions along an approximate north-south demarcation are considered rather than the basin as a whole.

  14. Short timescale behavior of colliding heavy nuclei at intermediate energies

    E-print Network

    Hudan, S; Ono, A

    2006-01-01

    An Antisymmetrized Molecular Dynamics model is used to explore the collision of $^{114}$Cd projectiles with $^{92}$Mo target nuclei at E/A=50 MeV over a broad range in impact parameter. The atomic number (Z), velocity, and emission pattern of the reaction products are examined as a function of the impact parameter and the cluster recognition time. The non-central collisions are found to be essentially binary in character resulting in the formation of an excited projectile-like fragment (PLF$^*$) and target-like fragment (TLF$^*$). The decay of these fragments occurs on a short timescale, 100$\\le$t$\\le$300 fm/c. The average excitation energy deduced for the PLF$^*$ and TLF$^*$ `saturates for mid-central collisions, 3.5$\\le$b$\\le$6 fm, with its magnitude depending on the cluster recognition time. For short cluster recognition times (t=150 fm/c), an average excitation energy as high as $\\approx$6 MeV is predicted. Short timescale emission leads to a loss of initial correlations and results in features such as an...

  15. Einstein: The Gourmet of Creativity.

    ERIC Educational Resources Information Center

    Greenberg, Joel

    1979-01-01

    Reports a psychiatrist's analysis of Einstein's personal account of how he developed the theory of relativity. The psychiatrist cites Janusian thinking, actively conceiving two or more opposite concepts simultaneously, as a characteristic of much creative thought in general. (MA)

  16. Einstein's 1919 View

    NASA Astrophysics Data System (ADS)

    Goradia, Shantilal

    2012-10-01

    When Rutherford discovered the nuclear force in 1919, he felt the force he discovered reflected some deviation of Newtonian gravity. Einstein too in his 1919 paper published the failure of the general relativity and Newtonian gravity to explain nuclear force and, in his concluding remarks, he retracted his earlier introduction of the cosmological constant. Consistent with his genius, we modify Newtonian gravity as probabilistic gravity using natural Planck units for a realistic study of nature. The result is capable of expressing both (1) nuclear force [strong coupling], and (2) Newtonian gravity in one equation, implying in general, in layman's words, that gravity is the cumulative effect of all quantum mechanical forces which are impossible to measure at long distances. Non discovery of graviton and quantum gravity silently support our findings. Continuing to climb on the shoulders of the giants enables us to see horizons otherwise unseen, as reflected in our book: ``Quantum Consciousness - The Road to Reality,'' and physics/0210040, where we derive the fine structure constant as a function of the age of the universe in Planck times consistent with Gamow's hint, using natural logarithm consistent with Feynman's hint.

  17. Correlations of the IR Luminosity and Eddington Ratio with a Hard X-ray Selected Sample of AGN

    NASA Technical Reports Server (NTRS)

    Mushotzy, Richard F.; Winter, Lisa M.; McIntosh, Daniel H.; Tueller, Jack

    2008-01-01

    We use the SWIFT Burst Alert Telescope (BAT) sample of hard x-ray selected active galactic nuclei (AGN) with a median redshift of 0.03 and the 2MASS J and K band photometry to examine the correlation of hard x-ray emission to Eddington ratio as well as the relationship of the J and K band nuclear luminosity to the hard x-ray luminosity. The BAT sample is almost unbiased by the effects of obscuration and thus offers the first large unbiased sample for the examination of correlations between different wavelength bands. We find that the near-IR nuclear J and K band luminosity is related to the BAT (14 - 195 keV) luminosity over a factor of 10(exp 3) in luminosity (L(sub IR) approx.equals L(sub BAT)(sup 1.25) and thus is unlikely to be due to dust. We also find that the Eddington ratio is proportional to the x-ray luminosity. This new result should be a strong constraint on models of the formation of the broad band continuum.

  18. BOOK REVIEW: Once Upon Einstein

    NASA Astrophysics Data System (ADS)

    Giannetto, E.

    2007-07-01

    Thibault Damour is a theoretical physicist, and a member of the French Academy of Sciences. This book is the translation, by Eric Novak, of the original French Si Einstein m'etait conté (Le Cherche Midi, 2005). It is neither a book of theoretical physics nor a biography of Einstein. It is not a book of history nor philosophy of science. In Damour's words it was written to encourage the reader to share with Einstein `those times when he understood some part of the hidden order of the universe'. It is a relatively short book, written in a very fluent style, but it deals with all the major problems and achievements of Einstein's works. Starting from special relativity, it continues with general relativity, quantum theories, unified field theory and a brief overview of the actual research related to Einstein's legacy. It is essentially a popular science book with some related exploration in history and philosophy to interpret physical theories. The most important problem discussed by Damour is the nature of time. On this subject, there is a very interesting short paragraph (pp 33--35) dedicated to the reception of the relativity idea by the great writer Marcel Proust and its counterpart within À la Recherche du Temps Perdu. A correct discussion of the implications of a relativistic time should imply the distinction of the different possible interpretations of this concept. Damour seems to conclude that only one interpretation is possible: `time does not exist', flowing of time is an illusion. One has to know that Einstein's ideas on time were related to Spinoza's perspective of a knowledge sub specie aeternitatis. However, other interpretations are possible and are related to the idea of time as an actuality. Damour speaks about the controversy between Einstein and Bergson, but Bergson is considered as a philosopher who did not understand relativity. This philosophical problem of relativistic time is indeed related to a historical problem briefly discussed by Damour (pp 17--21, 48--52 and related endnotes): had Henri Poincaré constructed a special relativistic dynamics before Einstein? There is a long debate on this subject in the literature. Damour's answer is negative and his conclusions seem related to the conservation of a myth of Einstein, that is, the rise of special relativity is considered as a creatio ex nihilo within Einstein's mind and Einstein is considered as the only genius able to conceive the relativity of time. Poincaré's texts are undervalued and misunderstood by Damour's cutting quotations from their context. Damour never quotes La Science et l'Hypothèse (1902): we know it was read by Einstein and here Poincaré first (within chapters already published as separate papers in 1900) stated the relativity of time and of simultaneity. Damour never quotes Poincaré's paper published on 5 June 1905, La dynamique de l'èlectron, which presents the first relativistic dynamics, invariant by Lorentz transformations. Poincaré's (July 1905) introduction of a quadrimensional space-time is considered by Damour only a mathematical artifice (p 51) and Damour never said that Minkowski took this idea from Poincaré! Poincaré's interpretation of relativistic time implies that it is not an illusion but a complex net of different real flows related to different processes. Poincaré and Einstein had different conceptions of Nature at the root of special relativity: respectively an electromagnetic conception (Poincaré) and a semi-mechanist one (Einstein). Thus, the (philosophical) meaning of relativity can be very different from the one presented by Damour. Furthermore, Damour accepts Kantian philosophy as a key to understanding relativity and quantum theories. This perspective seems to me very anachronistic and based on a misunderstanding: an interpretation of 20th century physical theories (relativity and quantum physics) is given within the framework of an 18th century philosophical perspective, created to give a foundation to Newton's theory. Relativity and quantum physics imply a breakdown of Kantian philosophy (see,

  19. Validating Computational Cognitive Process Models across Multiple Timescales

    NASA Astrophysics Data System (ADS)

    Myers, Christopher; Gluck, Kevin; Gunzelmann, Glenn; Krusmark, Michael

    2010-12-01

    Model comparison is vital to evaluating progress in the fields of artificial general intelligence (AGI) and cognitive architecture. As they mature, AGI and cognitive architectures will become increasingly capable of providing a single model that completes a multitude of tasks, some of which the model was not specifically engineered to perform. These models will be expected to operate for extended periods of time and serve functional roles in real-world contexts. Questions arise regarding how to evaluate such models appropriately, including issues pertaining to model comparison and validation. In this paper, we specifically address model validation across multiple levels of abstraction, using an existing computational process model of unmanned aerial vehicle basic maneuvering to illustrate the relationship between validity and timescales of analysis.

  20. Timescale for trans-Planckian collisions in Kerr spacetime

    NASA Astrophysics Data System (ADS)

    Patil, Mandar; Joshi, Pankaj S.; Nakao, Ken-ichi; Kimura, Masashi; Harada, Tomohiro

    2015-05-01

    We make a critical comparison between ultra-high–energy particle collisions around an extremal Kerr black hole and that around an over-spinning Kerr singularity, mainly focusing on the issue of the timescale of collisions. We show that the time required for two massive particles with the proton mass or two massless particles of GeV energies to collide around the Kerr black hole with Planck energy is several orders of magnitude longer than the age of the Universe for astro-physically relevant masses of black holes, whereas time required in the over-spinning case is of the order of ten million years, which is much shorter than the age of the Universe. Thus, from the point of view of observation of Planck scale collisions, the over-spinning Kerr geometry, subject to their occurrence, has distinct advantage over their black-hole counterparts.

  1. Reconstructing disturbances and their biogeochemical consequences over multiple timescales

    USGS Publications Warehouse

    McLauchlan, Kendra K.; Higuera, Philip E.; Gavin, Daniel G.; Perakis, Steven S.; Mack, Michelle C.; Alexander, Heather; Battles, John; Biondi, Franco; Buma, Brian; Colombaroli, Daniele; Enders, Sara K.; Engstrom, Daniel R.; Hu, Feng Sheng; Marlon, Jennifer R.; Marshall, John; McGlone, Matt; Morris, Jesse L.; Nave, Lucas E.; Shuman, Bryan; Smithwick, Erica A.H.; Urrego, Dunia H.; Wardle, David A.; Williams, Christopher J.; Williams, Joseph J.

    2014-01-01

    Ongoing changes in disturbance regimes are predicted to cause acute changes in ecosystem structure and function in the coming decades, but many aspects of these predictions are uncertain. A key challenge is to improve the predictability of postdisturbance biogeochemical trajectories at the ecosystem level. Ecosystem ecologists and paleoecologists have generated complementary data sets about disturbance (type, severity, frequency) and ecosystem response (net primary productivity, nutrient cycling) spanning decadal to millennial timescales. Here, we take the first steps toward a full integration of these data sets by reviewing how disturbances are reconstructed using dendrochronological and sedimentary archives and by summarizing the conceptual frameworks for carbon, nitrogen, and hydrologic responses to disturbances. Key research priorities include further development of paleoecological techniques that reconstruct both disturbances and terrestrial ecosystem dynamics. In addition, mechanistic detail from disturbance experiments, long-term observations, and chronosequences can help increase the understanding of ecosystem resilience.

  2. Timescales for planet formation: Constraints from the Kuiper Belt

    NASA Astrophysics Data System (ADS)

    Malhotra, Renu

    There is now growing recognition of the phenomenon of orbital migration of the giant planets during the late stages of planet formation when the major planets clear away the remaining disk of planetesimal debris. The trans-Neptunian population of small bodies is a present-day remnant of the Solar system's planetesimal disk. Its mass, size and orbital distribution reflect the combined effects of formation processes and post-formation dynamical sculpting by gravitational perturbations over the ~4.5 Byr age of the system. Recent progress in theoretical and numerical studies of this region has helped in some measure to identify the effects of these different processes. I will review the state of theoretical models and observational evidence for the phenomenon of planet migration in the early history of our Solar system, and its implications for our understanding of the timescales of the formation of the outer planets and post-formation dynamical processing of minor bodies.

  3. Dynamical Mass Segregation on a Very Short Timescale

    NASA Astrophysics Data System (ADS)

    Allison, Richard J.; Goodwin, Simon P.; Parker, Richard J.; de Grijs, Richard; Portegies Zwart, Simon F.; Kouwenhoven, M. B. N.

    2009-08-01

    We discuss the observations and theory of star cluster formation to argue that clusters form dynamically cool (subvirial) and with substructure. We then perform an ensemble of simulations of cool, clumpy (fractal) clusters and show that they often dynamically mass segregate on timescales far shorter than expected from simple models. The mass segregation comes about through the production of a short-lived, but very dense core. This shows that in clusters like the Orion Nebula Cluster the stars >= 4 M sun can dynamically mass segregate within the current age of the cluster. Therefore, the observed mass segregation in apparently dynamically young clusters need not be primordial, but could be the result of rapid and violent early dynamical evolution.

  4. Memory on multiple time-scales in an Abelian sandpile

    NASA Astrophysics Data System (ADS)

    Sokolov, Andrey; Melatos, Andrew; Kieu, Tien; Webster, Rachel

    2015-06-01

    We report results of a numerical analysis of the memory effects in two-dimensional Abelian sandpiles. It is found that a sandpile forgets its instantaneous configuration in two distinct stages: a fast stage and a slow stage, whose durations roughly scale as N and N2 respectively, where N is the linear size of the sandpile. We confirm the presence of the longer time-scale by an independent diagnostic based on analysing emission probabilities of a hidden Markov model applied to a time-averaged sequence of avalanche sizes. The application of hidden Markov modelling to the output of sandpiles is novel. It discriminates effectively between a sandpile time series and a shuffled control time series with the same time-averaged event statistics and hence deserves further development as a pattern-recognition tool for Abelian sandpiles.

  5. From lifetime to evolution: timescales of human gut microbiota adaptation

    PubMed Central

    Quercia, Sara; Candela, Marco; Giuliani, Cristina; Turroni, Silvia; Luiselli, Donata; Rampelli, Simone; Brigidi, Patrizia; Franceschi, Claudio; Bacalini, Maria Giulia; Garagnani, Paolo; Pirazzini, Chiara

    2014-01-01

    Human beings harbor gut microbial communities that are essential to preserve human health. Molded by the human genome, the gut microbiota (GM) is an adaptive component of the human superorganisms that allows host adaptation at different timescales, optimizing host physiology from daily life to lifespan scales and human evolutionary history. The GM continuously changes from birth up to the most extreme limits of human life, reconfiguring its metagenomic layout in response to daily variations in diet or specific host physiological and immunological needs at different ages. On the other hand, the microbiota plasticity was strategic to face changes in lifestyle and dietary habits along the course of the recent evolutionary history, that has driven the passage from Paleolithic hunter-gathering societies to Neolithic agricultural farmers to modern Westernized societies. PMID:25408692

  6. Tidal Disruption of Strengthless Rubble Piles--A Timescale Analysis

    NASA Astrophysics Data System (ADS)

    Rettig, T. W.; Hahn, J. M.; Ward, W. R.

    1997-12-01

    The brief and dramatic appearance of Comet Shoemaker--Levy 9 (S--L 9) has punctuated the notion that many small members of the solar system might be strengthless `rubble-piles'. Models of the S--L 9 encounter indicate that only a relatively strengthless rubble-pile is able to catastrophically disrupt into a cloud of debris that later condenses into twenty or so gravitating `clumps' having the S--L 9 `string-of-pearls' morphology (e.g., Asphaug and Benz 1996). These models show that gravitational condensation of the debris into distinct clumps depends sensitively on the progenitor's density as well as its orbit. This phenomenon is re-examined by tracking the orbital motion andthe local mass density of a tidally disrupted projectile (see also Rettig et al. 1996). By employing elementary orbit mechanics, it is shown that when the debris' gravitational contraction timescale becomes shorter than its orbital spreading timescale, the debris breaks up into n L/D distinct clumps, where L is the debris length and D is the progenitor's diameter. Without appealing to a CPU--intensive calculation, we extend the available N--body simulations to unexplored regions of parameter space and reveal how the number of clumps n depends upon the progenitor's density, its periapse distance, and velocity at infinity (the problem is generalized to hyperbolic encounters as well). These findings also provide an additional constraint for the Galilean crater chain problem. We find that the projectile's responsible for the Gomul and Gipul crater chains on Callisto likely had comet--like densities of p<1 gm/cm(3) . However we are unable to distinguish between cometary and asteroidal impactors for the remaining chains which have fewer numbers of craters.

  7. Tidal Disruption of Strengthless Rubble Piles--A Timescale Analysis

    NASA Astrophysics Data System (ADS)

    Rettig, T.; Hahn, J.

    1998-05-01

    The brief and dramatic appearance of Comet Shoemaker--Levy 9 (S--L 9) has punctuated the notion that many small members of the solar system might be strengthless `rubble-piles'. Models of the S--L 9 encounter indicate that only a relatively strengthless rubble-pile is able to catastrophically disrupt into a cloud of debris that later condenses into twenty or so gravitating `clumps' having the S--L 9 `string-of-pearls' morphology (e.g., Asphaug and Benz 1996). These models show that gravitational condensation of the debris into distinct clumps depends sensitively on the progenitor's density as well as its orbit. This phenomenon is re-examined by tracking the orbital motion andthe local mass density of a tidally disrupted projectile (see also Rettig et al. 1996). By employing elementary orbit mechanics, it is shown that when the debris' gravitational contraction timescale becomes shorter than its orbital spreading timescale, the debris breaks up into n L/D distinct clumps, where L is the debris length and D is the progenitor's diameter. Without appealing to a CPU--intensive calculation, we extend the available N--body simulations to unexplored regions of parameter space and reveal how the number of clumps n depends upon the progenitor's density, its periapse distance, and velocity at infinity (the problem is generalized to hyperbolic encounters as well). These findings also provide an additional constraint for the Galilean crater chain problem. We find that the projectile's responsible for the Gomul and Gipul crater chains on Callisto likely had comet--like densities of p<1 gm/cm(3) . However we are unable to distinguish between cometary and asteroidal impactors for the remaining chains which have fewer numbers of craters.

  8. Tidal Disruption of Strengthless Rubble Piles---A Timescale Analysis

    NASA Astrophysics Data System (ADS)

    Hahn, J. M.; Rettig, T. W.; Ward, W. R.

    1997-07-01

    The brief and dramatic appearance of Comet Shoemaker--Levy 9 (S--L 9) has punctuated the notion that many small members of the solar system might be strengthless `rubble-piles'. Models of the S--L 9 encounter indicate that only a relatively strengthless rubble-pile is able to catastrophically disrupt into a cloud of debris that later condenses into twenty or so gravitating `clumps' having the S--L 9 `string-of-pearls' morphology (e.g., Asphaug and Benz 1996). These models show that gravitational condensation of the debris into distinct clumps depends sensitively on the progenitor's density as well as its orbit. This phenomenon is re-examined by tracking the orbital motion and the local mass density of a tidally disrupted projectile (see also Rettig et al. 1996). By employing elementary orbit mechanics, it is shown that when the debris' gravitational contraction timescale becomes shorter than its orbital spreading timescale, the debris breaks up into n ~ L/D distinct clumps, where L is the debris length and D is the progenitor's diameter. Without appealing to a CPU--intensive calculation, we extend the available N--body simulations to unexplored regions of parameter space and reveal how the number of clumps n depends upon the progenitor's density, its periapse distance, and velocity at infinity (the problem is generalized to hyperbolic encounters as well). These findings also provide an additional constraint for the Galilean crater chain problem. We find that the projectile's responsible for the Gomul and Gipul crater chains on Callisto likely had comet--like densities of rho_0 ?1 gm/cm(3) . However we are unable to distinguish between cometary and asteroidal impactors for the remaining chains which have fewer numbers of craters.

  9. Computational methods for time-scale analysis of nonlinear dynamical systems

    Microsoft Academic Search

    Shawn Iravanchy

    2003-01-01

    Knowledge of the time-scale structure of a smooth finite dimensional nonlinear dynamical system provides the opportunity for model decomposition, if there are two or more disparate time-scales. A few benefits of such model decomposition are simplified control design and analysis and reduced computational effort in simulation. Singular perturbation theory provides the tools necessary to analyze and decompose a multiple time-scale

  10. Triangle Anomalies from Einstein Manifolds

    E-print Network

    Sergio Benvenuti; Leopoldo A. Pando Zayas; Yuji Tachikawa

    2006-07-20

    The triangle anomalies in conformal field theory, which can be used to determine the central charge a, correspond to the Chern-Simons couplings of gauge fields in AdS under the gauge/gravity correspondence. We present a simple geometrical formula for the Chern-Simons couplings in the case of type IIB supergravity compactified on a five-dimensional Einstein manifold X. When X is a circle bundle over del Pezzo surfaces or a toric Sasaki-Einstein manifold, we show that the gravity result is in perfect agreement with the corresponding quiver gauge theory. Our analysis reveals an interesting connection with the condensation of giant gravitons or dibaryon operators which effectively induces a rolling among Sasaki-Einstein vacua.

  11. Evidence for Two Distinct Morphological Classes of Gamma-Ray Bursts from their Short Timescale Variability

    E-print Network

    D. Q. Lamb; C. Graziani; I. A. Smith

    1993-06-15

    We have analyzed the 241 bursts for which peak counts $\\C$ exist in the publicly available Burst and Transient Source Experiment (BATSE) catalog. Introducing peak counts in 1024 ms as a measure of burst brightness $\\B$ and the ratio of peak counts in 64 and 1024 ms as a measure of short timescale variability $\\V$, we find a statistically significant correlation between the brightness and the short timescale variability of \\g-ray bursts. The bursts which are smoother on short timescales are both faint and bright, while the bursts which are variable on short timescales are faint only, suggesting the existence of two distinct morphological classes of bursts.

  12. Schwinger's Approach to Einstein's Gravity

    NASA Astrophysics Data System (ADS)

    Milton, Kim

    2012-05-01

    Albert Einstein was one of Julian Schwinger's heroes, and Schwinger was greatly honored when he received the first Einstein Prize (together with Kurt Godel) for his work on quantum electrodynamics. Schwinger contributed greatly to the development of a quantum version of gravitational theory, and his work led directly to the important work of (his students) Arnowitt, Deser, and DeWitt on the subject. Later in the 1960's and 1970's Schwinger developed a new formulation of quantum field theory, which he dubbed Source Theory, in an attempt to get closer contact to phenomena. In this formulation, he revisited gravity, and in books and papers showed how Einstein's theory of General Relativity emerged naturally from one physical assumption: that the carrier of the gravitational force is a massless, helicity-2 particle, the graviton. (There has been a minor dispute whether gravitational theory can be considered as the massless limit of a massive spin-2 theory; Schwinger believed that was the case, while Van Dam and Veltman concluded the opposite.) In the process, he showed how all of the tests of General Relativity could be explained simply, without using the full machinery of the theory and without the extraneous concept of curved space, including such effects as geodetic precession and the Lense-Thirring effect. (These effects have now been verified by the Gravity Probe B experiment.) This did not mean that he did not accept Einstein's equations, and in his book and full article on the subject, he showed how those emerge essentially uniquely from the assumption of the graviton. So to speak of Schwinger versus Einstein is misleading, although it is true that Schwinger saw no necessity to talk of curved spacetime. In this talk I will lay out Schwinger's approach, and the connection to Einstein's theory.

  13. HOST GALAXIES, CLUSTERING, EDDINGTON RATIOS, AND EVOLUTION OF RADIO, X-RAY, AND INFRARED-SELECTED AGNs

    SciTech Connect

    Hickox, Ryan C.; Jones, Christine; Forman, William R.; Murray, Stephen S.; Brodwin, Mark; Narayan, Ramesh; Kenter, Almus; Caldwell, Nelson; Anderson, Michael E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kochanek, Christopher S. [Department of Astronomy and Center for Cosmology and Astroparticle Physics, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210-1173 (United States); Eisenstein, Daniel [Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Jannuzi, Buell T.; Dey, Arjun [National Optical Astronomy Observatory, Tucson, AZ 85726-6732 (United States); Brown, Michael J. I. [School of Physics, Monash University, Clayton 3800, Victoria (Australia); Stern, Daniel; Eisenhardt, Peter R.; Gorjian, Varoujan [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Cool, Richard J. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544-1001 (United States)], E-mail: rhickox@cfa.harvard.edu

    2009-05-01

    We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of AGNs selected in the radio, X-ray, and infrared (IR) wavebands. We study a sample of 585 AGNs at 0.25 < z < 0.8 using redshifts from the AGN and Galaxy Evolution Survey (AGES). We select AGNs with observations in the radio at 1.4 GHz from the Westerbork Synthesis Radio Telescope, X-rays from the Chandra XBooetes Survey, and mid-IR from the Spitzer IRAC Shallow Survey. The radio, X-ray, and IR AGN samples show only modest overlap, indicating that to the flux limits of the survey, they represent largely distinct classes of AGNs. We derive host galaxy colors and luminosities, as well as Eddington ratios, for obscured or optically faint AGNs. We also measure the two-point cross-correlation between AGNs and galaxies on scales of 0.3-10 h {sup -1} Mpc, and derive typical dark matter halo masses. We find that: (1) radio AGNs are mainly found in luminous red sequence galaxies, are strongly clustered (with M {sub halo} {approx} 3 x 10{sup 13} h {sup -1} M {sub sun}), and have very low Eddington ratios {lambda} {approx}< 10{sup -3}; (2) X-ray-selected AGNs are preferentially found in galaxies that lie in the 'green valley' of color-magnitude space and are clustered similar to the typical AGES galaxies (M {sub halo} {approx} 10{sup 13} h {sup -1} M {sub sun}), with 10{sup -3} {approx}< {lambda} {approx}< 1; (3) IR AGNs reside in slightly bluer, slightly less luminous galaxies than X-ray AGNs, are weakly clustered (M {sub halo} {approx}< 10{sup 12} h {sup -1} M {sub sun}), and have {lambda}>10{sup -2}. We interpret these results in terms of a simple model of AGN and galaxy evolution, whereby a 'quasar' phase and the growth of the stellar bulge occurs when a galaxy's dark matter halo reaches a critical mass between {approx}10{sup 12} and 10{sup 13} M {sub sun}. After this event, star formation ceases and AGN accretion shifts from radiatively efficient (optical- and IR-bright) to radiatively inefficient (optically faint, radio-bright) modes.

  14. Timescales of transport from the troposphere into the lowermost stratosphere

    NASA Astrophysics Data System (ADS)

    Boenisch, Harald; Hoor, Peter; Wernli, Heini

    2010-05-01

    The lowermost stratosphere (LMS) as part of the extratropical UTLS can be divided into dynamically and chemically distinct regions. A layer of mixed tropospheric and stratospheric tracer characteristics in the proximity of the extratropical tropopause: the extratropical tropopause transition layer (ExTL). This chemically distinct layer roughly coincides with a layer of strongly enhanced thermal stratification: the tropopause inversion layer (TIL) (Birner, 2006). The LMS above the ExTL, also named the free LMS (Bönisch et al., 2009), is less coupled to the local extratropical troposphere. Simultaneous in-situ measurements of CO2 and SF6 have been used to calculate mean transport time from the troposphere to the measurement location in the free LMS (Bönisch et al., 2009) which is on the order of months. In this study, we will use backward trajectories driven by operational ECMWF analyses wind fields to investigate the TST timescales into the LMS using the LAGRANTO scheme (Wernli and Davies, 1997). We applied a statistical data set of trajectories, which were initialized on isentropes above the 2 PVU surface up to 450K and calculated backward over 270 days (9 month) for our analysis. The results will be compared with the results from mass balance studies based on in-situ observations (Hoor et al., 2005; Bönisch et al., 2009). Furthermore, a focus is on the role of timescales of TIL formation in the LMS. Birner, T.: Fine-scale structure of the extratropical tropopause region, Journal of Geophysical Research-Atmospheres, 111, Doi 10.1029/2005jd006301, 2006. Bönisch, H., Engel, A., Curtius, J., Birner, T., and Hoor, P.: Quantifying transport into the lowermost stratosphere using simultaneous in-situ measurements of sf6 and co2, Atmospheric Chemistry and Physics, 9, 5905-5919, 2009. Hoor, P., Gurk, C., Brunner, D., Hegglin, M. I., Wernli, H., and Fischer, H.: Seasonality and extent of extratropical tst derived from in-situ co measurements during spurt, Atmospheric Chemistry and Physics, 4, 1427-1442, 2004. Hoor, P., Fischer, H., and Lelieveld, J.: Tropical and extratropical tropospheric air in the lowermost stratosphere over europe: A co-based budget, Geophysical Research Letters, 32, Doi 10.1029/2004gl022018, 2005. Wernli, H., and Davies, H. C.: A lagrangian-based analysis of extratropical cyclones .1. The method and some applications, Quarterly Journal of the Royal Meteorological Society, 123, 467-489, 1997.

  15. Spectral decomposition of time-scales in hyporheic exchange

    NASA Astrophysics Data System (ADS)

    Wörman, Anders; Riml, Joakim

    2015-04-01

    Hyporheic exchange of heat and solute mass in streams is manifested both in form of different exchange mechanisms and their associated distributions of residence times as well as the range of time-scales characterizing the forcing boundary conditions. A recently developed analytical technique separates the spectrum of time-scales and relates the forcing boundary fluctuations of heat and solute mass through a physical model of the hydrological transport to the response of heat and solute mass. This spectral decomposition can be done both for local (point-scale) observations in the hyporhiec zone itself as well as for transport processes on the watershed scale that can be considered 'well-behaved' in terms of knowledge of the forcing (input) quantities. This paper presents closed-form solutions in spectral form for the point-, reach- and watershed-scale and discusses their applicability to selected data of heat and solute concentration. We quantify the reliability and highlight the benefits of the spectral approach to different scenarios and, peculiarly, the importance for linking the periods in the spectral decomposition of the solute response to the distribution of transport times that arise due to the multitude of exchange mechanisms existing in a watershed. In a point-scale example the power spectra of in-stream temperature is related to the power spectrum of the temperature at a specific sediment depth by means of exact solutions of a physically based formulation of the vertical heat transport. It is shown that any frequency (?) of in-stream temperature fluctuation scales with the effective thermal diffusivity (?e) and the vertical separation distance between the pairs of temperature (É?) data as ? ? ?e/(2É?2), which implies a decreasing weight to higher frequencies (shorter periods) with depth. Similarly on the watershed-scale one can link the watershed dispersion to the damping of the concentration fluctuations in selected frequency intervals reflecting various environments responsible for the damping. The frequency-dependent parameters indicate that different environments dominate the response at different temporal scales.

  16. Stability and (quasi-)localization of gravitational fluctuations in Eddington-Inspired Born-Infeld brane system

    E-print Network

    Qi-Ming Fu; Li Zhao; Ke Yang; Bao-Min Gu; Yu-Xiao Liu

    2014-10-07

    Stability and localization of the gravitational perturbations for a special brane system in Eddington-inspired Born-Infeld (EiBI) gravity were studied in [Phys. Rev. D 85, 124053 (2012)]. In this paper, we show that the gravitational perturbations for a general brane system are stable, the four-dimensional graviton (massless KK graviton) can be localized on the brane, and the mass spectrum of massive KK gravitons are gapless and continuous. Two models are constructed as examples. In the first model, which is a generalization of [Phys. Rev. D 85, 124053 (2012)], the brane has no inner structure and there is no gravitational resonance (quasi-localized KK gravitons). In the second one, the background scalar field is a double-kink when the parameter in the model approaches its critical value. Correspondingly, the brane has inner structure and some gravitational resonances appear.

  17. HOMOGENEOUS EINSTEIN METRICS Megan M. Kerr

    E-print Network

    Kerr, Megan M.

    HOMOGENEOUS EINSTEIN METRICS Megan M. Kerr A Dissertation in Mathematics Presented to the Faculties;ABSTRACT HOMOGENEOUS EINSTEIN METRICS Megan M. Kerr Wolfgang Ziller (Supervisor) We consider homogeneous Einstein metrics on symmetric spaces and we describe their geometry. For compact irreducible symmetric

  18. HOMOGENEOUS EINSTEIN METRICS Megan M. Kerr

    E-print Network

    Kerr, Megan M.

    HOMOGENEOUS EINSTEIN METRICS Megan M. Kerr A Dissertation in Mathematics Presented to the Faculties; ABSTRACT HOMOGENEOUS EINSTEIN METRICS Megan M. Kerr Wolfgang Ziller (Supervisor) We consider homogeneous Einstein metrics on symmetric spaces and we describe their geometry. For compact irreducible symmetric

  19. Einstein, Mach, and the Fortunes of Gravity

    Microsoft Academic Search

    David Kaiser

    2005-01-01

    Early in his life, Albert Einstein considered himself a devoted student of the physicist and philosopher Ernst Mach. Mach's famous critiques of Newton's absolute space and time -- most notably Mach's explanation of Newton's bucket experiment -- held a strong sway over Einstein as he struggled to formulate general relativity. Einstein was convinced that his emerging theory of gravity should

  20. Albert Einstein, 1905: Ein 3-Gange Menu

    E-print Network

    Dutz, Hartmut

    , Umzug nach M¨unchen Pauline Einstein, geb. Koch Hermann Einstein #12;KINDHEIT in M¨UNCHEN ¨Altestes Atoome san Escht" · 1827 Entdeckung durch Botaniker Robert Brown · Detaillierte Beobachtungen, schließt biologische Ursachen aus. · Aber was soll man hier messen? Einstein! Robert Brown #12;1827 - 1900

  1. Differential force microscope for long time-scale biophysical measurements

    PubMed Central

    Choy, Jason L.; Parekh, Sapun H.; Chaudhuri, Ovijit; Liu, Allen P.; Bustamante, Carlos; Footer, Matthew J.; Theriot, Julie A.; Fletcher, Daniel A.

    2011-01-01

    Force microscopy techniques including optical trapping, magnetic tweezers, and atomic force microscopy (AFM) have facilitated quantification of forces and distances on the molecular scale. However, sensitivity and stability limitations have prevented the application of these techniques to biophysical systems that generate large forces over long times, such as actin filament networks. Growth of actin networks drives cellular shape change and generates nano-Newtons of force over time scales of minutes to hours, and consequently network growth properties have been difficult to study. Here, we present an AFM-based differential force microscope with integrated epifluorescence imaging in which two adjacent cantilevers on the same rigid support are used to provide increased measurement stability. We demonstrate 14 nm displacement control over measurement times of 3 hours and apply the instrument to quantify actin network growth in vitro under controlled loads. By measuring both network length and total network fluorescence simultaneously, we show that the average cross-sectional density of the growing network remains constant under static loads. The differential force microscope presented here provides a sensitive method for quantifying force and displacement with long time-scale stability that is useful for measurements of slow biophysical processes in whole cells or in reconstituted molecular systems in vitro. PMID:17477674

  2. Thermal Timescale Mass Transfer In Binary Population Synthesis

    NASA Astrophysics Data System (ADS)

    Justham, S.; Kolb, U.

    2004-07-01

    Studies of binary evolution have, until recently, neglected thermal timescale mass transfer (TTMT). Recent work has suggested that this previously poorly studied area is crucial in the understanding of systems across the compact binary spectrum. We use the state-of-the-art binary population synthesis code BiSEPS (Willems and Kolb, 2002, MNRAS 337 1004-1016). However, the present treatment of TTMT is incomplete due to the nonlinear behaviour of stars in their departure from gravothermal `equilibrium'. Here we show work that should update the ultrafast stellar evolution algorithms within BiSEPS to make it the first pseudo-analytic code that can follow TTMT properly. We have generated fits to a set of over 300 Case B TTMT sequences with a range of intermediate-mass donors. These fits produce very good first approximations to both HR diagrams and mass-transfer rates (see figures 1 and 2), which we later hope to improve and extend. They are already a significant improvement over the previous fits.

  3. On stress relaxation timescales for dense binary particulate systems

    NASA Astrophysics Data System (ADS)

    Mao, Shaolin

    2015-06-01

    We study contact stress relaxation timescales, especially the temporal correlation involved in dense binary particulate systems, which offers insight into the intriguing relationship between the contact stresses and the contact time of particle interactions under non-equilibrium state. The contact time (also referred to as contact age) of a pair of particles is defined by the duration between current time and the instant when the contact was formed. The interspecies inter-particles contact stresses are derived from Liouville's theorem. We apply particle dynamics methods (e.g. molecular dynamics, discrete element method) to simulate 3D dense binary particulate systems with periodic boundary conditions. External perturbation is exerted on the system to balance the dissipation of energy due to the viscoelastic collisions. The contact stresses, Reynolds stresses, and the probability density function of the contact time of particles are predicted at different volume fraction of particles. The obtained stress-strain rate data are used to examine the constitutive relation of macroscopic materials. The study targets the impact of the short-term and the long-term contact/collision on the contact stress relaxation. The simulation results reveal distinct effects of the short-term and the long-term contact/collision on the contact stresses, which have been treated by only an averaged expression of particle interactions in discrete element methods before.

  4. Quasar Jets on the kpc scale: Fast and Super-Eddington or Slow and Multi-TeV Accelerators?

    NASA Astrophysics Data System (ADS)

    Meyer, Eileen T.; Georganopoulos, Markos; Sparks, William B.

    2014-08-01

    A long-standing debate exists around the nature of the anomalously high X-ray emission from the kpc-scale resolved quasar jet emission, which is related to the question of their speeds on the kpc scale. Are they fast (Lorentz factors ~10-20) and powerful (in many cases super-Eddington) or slow, sub-Eddington, and multi-TeV particle accelerators?. This question has direct bearing on the physics of cluster heating by powerful jets. Also, the slow jet case implies that the beaming-corrected radiated power of the jet on kpc scales may be comparable to, or even exceed that of the blazar (core) emission, with important implications for the GeV background radiation and the heating of intergalactic gas by TeV photons. The widely accepted model for producing the high X-ray emission has been a highly-relativistic kpc-scale jet producing inverse Compton emission by up-scattering the cosmic microwave background (IC/CMB), though the X-rays could also be synchrotron emission from a multi-TeV electron population accelerated in situ, as both models can reproduce the observed radio to X-ray spectra. We present very recent work by our group, showing that IC/CMB model is ruled out in at least two cases. In both 3C 273 PKS 0637-752, the uniquely determined GeV flux predicted by the IC/CMB model overproduces the 99.9% flux limits obtained from recent Fermi gamma-ray observations.

  5. The Meaning of Einstein's Equation

    Microsoft Academic Search

    John C. Bae; Emory F. Bunny

    This is a brief introduction to general relativity, designed for both students and teachers of the subject. While there are many excellent expositions of general relativity, few adequately explain the geometrical meaning of the basic equation of the theory: Einstein's equation. Here we give a simple formulation of this equation in terms of the motion of freely falling test particles.

  6. Retroactivity Attenuation in Bio-molecular Systems Based on Timescale Separation

    E-print Network

    Del Vecchio, Domitilla

    1 Retroactivity Attenuation in Bio-molecular Systems Based on Timescale Separation Shridhar Jayanthi and Domitilla Del Vecchio Abstract--As with several engineering systems, bio-molecular systems a mechanism that exploits the natural timescale separation present in bio-molecular systems to attenuate

  7. Time Dilation and the Length of the Second: Why Timescales Diverge

    Microsoft Academic Search

    Steven D. Deines; Carol A. Williams

    2007-01-01

    We show that the timescale divergence between Universal Time (UT1) and international atomic time (TAI), which is compensated for by the occasional addition of a leap second, is due to the fact that the Système Internationale (SI) second is shorter than the UT second. Celestial mechanicians saw the necessity of introducing a timescale that eliminated the discrepancy between the observed

  8. Evaluation of processes that affect the photochemical timescale of the sodium layer

    Microsoft Academic Search

    Jiyao Xu; A. K. Smith

    2005-01-01

    We apply the method of the eigenvalue and eigenvector analysis (EEA method) to analyze the photochemical timescale of the sodium layer chemical system to perturbations. The results show that the timescales of three important sodium species, Na, Na+ and NaHCO3, vary strongly with altitude and are significantly different during day and night. For these three species, the EEA method gives

  9. Adaptive dynamics on an environmental gradient that changes over a geological time-scale.

    PubMed

    Fortelius, Mikael; Geritz, Stefan; Gyllenberg, Mats; Toivonen, Jaakko

    2015-07-01

    The standard adaptive dynamics framework assumes two timescales, i.e. fast population dynamics and slow evolutionary dynamics. We further assume a third timescale, which is even slower than the evolutionary timescale. We call this the geological timescale and we assume that slow climatic change occurs within this timescale. We study the evolution of our model population over this very slow geological timescale with bifurcation plots of the standard adaptive dynamics framework. The bifurcation parameter being varied describes the abiotic environment that changes over the geological timescale. We construct evolutionary trees over the geological timescale and observe both gradual phenotypic evolution and punctuated branching events. We concur with the established notion that branching of a monomorphic population on an environmental gradient only happens when the gradient is not too shallow and not too steep. However, we show that evolution within the habitat can produce polymorphic populations that inhabit steep gradients. What is necessary is that the environmental gradient at some point in time is such that the initial branching of the monomorphic population can occur. We also find that phenotypes adapted to environments in the middle of the existing environmental range are more likely to branch than phenotypes adapted to extreme environments. PMID:25861870

  10. Non-convergence of the critical cooling timescale for fragmentation of self-gravitating discs

    E-print Network

    Meru, Farzana

    2010-01-01

    We carry out a resolution study on the fragmentation boundary of self-gravitating discs. We perform three-dimensional Smoothed Particle Hydrodynamics simulations of discs to determine whether the critical value of the cooling timescale in units of the orbital timescale, beta_{crit}, converges with increasing resolution. Using particle numbers ranging from 31,250 to 16 million (the highest resolution simulations to date) we do not find convergence. Instead, fragmentation occurs for longer cooling timescales as the resolution is increased. These results suggest that at the very least, the critical value of the cooling timescale is longer than previously thought. However, the absence of convergence also raises the question of whether or not a critical value exists. In light of these results, we caution against using cooling timescale or gravitational stress arguments to deduce whether gravitational instability may or may not have been the formation mechanism for observed planetary systems.

  11. The Lifecycles of Drought: Informing Responses Across Timescales

    NASA Astrophysics Data System (ADS)

    Pulwarty, R. S.; Schubert, S. D.

    2014-12-01

    Drought is a slow-onset hazard that is a normal part of climate. Drought onset and demise are difficult to determine. Impacts are mostly nonstructural, spread over large geographical areas, and can persist long after precipitation deficits end. These factors hinder development of accurate, timely estimates of drought severity and resultant responses. Drivers of drought range from SST anomalies and global scale atmospheric response, through regional forcing and local land-surface feedbacks. Key climatological questions related to drought risk assessment, perception and management include, "Does a drought end by a return to normal precipitation; how much moisture is required and over what period; can the end of a drought be defined by the diminishing impacts e.g. soil moisture, reservoir volumes; will precipitation patterns on which management systems rely, change in the future?" Effective early warning systems inform strategic responses that anticipate crises and crisis evolution across climate timescales. While such "early information" is critical for defining event onset, it is even more critical for identifying the potential for increases in severity. Many social and economic systems have buffers in place to respond to onset (storage, transfers and purchase of grain) but lack response capabilities as drought intensifies, as buffers are depleted. Throughout the drought lifecycle (and between events), monitoring, research and risk assessments are required to: Map decision-making processes and resource capabilities including degradation of water and ecosystems Place multiple climate and land surface indicators within a consistent triggering framework (e.g. climate and vegetation mapping) before critical thresholds are reached Identify policies and practices that impede or enable the flow of information, through policy gaming and other exercises The presentation will outline the capabilities and framework needed to ensure improved scientific inputs to preparedness and adaptation. Lessons will be drawn from recent and ongoing events in California, the Midwest, and globally.

  12. Release timescales of solar energetic particles in the low corona

    NASA Astrophysics Data System (ADS)

    Agueda, N.; Klein, K.-L.; Vilmer, N.; Rodríguez-Gasén, R.; Malandraki, O. E.; Papaioannou, A.; Subirà, M.; Sanahuja, B.; Valtonen, E.; Dröge, W.; Nindos, A.; Heber, B.; Braune, S.; Usoskin, I. G.; Heynderickx, D.; Talew, E.; Vainio, R.

    2014-10-01

    Aims: We present a systematic study of the timing and duration of the release processes of near-relativistic (NR; >50 keV) electrons in the low corona. Methods: We analyze seven well-observed events using in situ measurements by both the ACE and Wind spacecraft and context electromagnetic observations in soft X-rays, radio, hard X-rays and white light. We make use of velocity dispersion analysis to estimate the release time of the first arriving electrons and compare with the results obtained by using a simulation-based approach, taking interplanetary transport effects into account to unfold the NR electron release time history from in situ measurements. Results: The NR electrons observed in interplanetary space appear to be released during either short (<30 min) or long (>2 h) periods. The observation of NR electron events showing beamed pitch-angle distributions (PADs) during several hours is the clearest observational signature of sustained release in the corona. On the other hand, the in situ observation of PADs isotropizing in less than a couple of hours is a clear signature of a prompt release of electrons in the low corona. Short release episodes appear to originate in solar flares, in coincidence with the timing of the observed type III radio bursts. Magnetic connectivity plays an important role. Only type III radio bursts reaching the local plasma line measured at 1 AU are found to be related with an associated release episode in the low corona. Other type III bursts may also have a release of NR electrons associated with them, but these electrons do not reach L1. Long release episodes appear associated with signatures of long acceleration processes in the low corona (long decay of the soft X-ray emission, type IV radio bursts, and time-extended microwave emission). Type II radio bursts are reported for most of the events and do not provide a clear discrimination between short and long release timescales.

  13. Time-scale modelling of the invasive species Robinia pseudoacacia

    NASA Astrophysics Data System (ADS)

    Tomaž, Podobnikar; Andraž, Ä.?Arni; Imelda, Somodi

    2010-05-01

    Our contribution is part of the TransEcoNet project (Transnational Ecological Networks in Central Europe) that aims to investigate transboundary ecological networks across Central Europe. An objective of this project is to contribute towards awareness rising on the value and role of ecological networks. This poster presents the activities that are carried out in Pomurje region, Slovenia as our case study area. Pomurje region borders with Austria in the north, to Hungary in the east, and to Croatia in the south. We are investigating the spread of the invasive species Robinia pseudacacia and the underlying causes, and assess landscape scale ecological dynamics (e.g. Mura River floodplains) in ecological networks. The study comprises investigation and mapping of the R. pseudacacia spread with time-series analysis to understand its spatial dynamics. The preliminary studies show that the R. pseudacacia had the most expanded in the region since 1980s. Some of the surfaces were cut and converted back to fields. This reflects the socioeconomic situation in the region. The further study will include statistic, GIS (geographical information systems) and remote sensing techniques. We will apply various character data: satellite imagery, IR-orthophotos, digital elevation models, including LIDAR, contemporary and historical maps, and other spatial/non-spatial data sources. The outputs will include reconstruction of R. pseudacacia-dynamics in the recent decade, modelling the distribution of R. pseudacacia in relation to abiotic environmental factors and land use, and modelling (prediction) the expected distribution of R. pseudacacia in case of climate and land use change. Keywords: invasive species, Robinia pseudacacia, spatial analysis, time-scale analysis, remote sensing, land use change, climate change

  14. Geometric integrators for multiple time-scale simulation

    NASA Astrophysics Data System (ADS)

    Jia, Zhidong; Leimkuhler, Ben

    2006-05-01

    In this paper, we review and extend recent research on averaging integrators for multiple time-scale simulation such as are needed for physical N-body problems including molecular dynamics, materials modelling and celestial mechanics. A number of methods have been proposed for direct numerical integration of multiscale problems with special structure, such as the mollified impulse method (Garcia-Archilla, Sanz-Serna and Skeel 1999 SIAM J. Sci. Comput. 20 930-63) and the reversible averaging method (Leimkuhler and Reich 2001 J. Comput. Phys. 171 95-114). Features of problems of interest, such as thermostatted coarse-grained molecular dynamics, require extension of the standard framework. At the same time, in some applications the computation of averages plays a crucial role, but the available methods have deficiencies in this regard. We demonstrate that a new approach based on the introduction of shadow variables, which mirror physical variables, has promised for broadening the usefulness of multiscale methods and enhancing accuracy of or simplifying computation of averages. The shadow variables must be computed from an auxiliary equation. While a geometric integrator in the extended space is possible, in practice we observe enhanced long-term energy behaviour only through use of a variant of the method which controls drift of the shadow variables using dissipation and sacrifices the formal geometric properties such as time-reversibility and volume preservation in the enlarged phase space, stabilizing the corresponding properties in the physical variables. The method is applied to a gravitational three-body problem as well as a partially thermostatted model problem for a dilute gas of diatomic molecules.

  15. Science at the Time-scale of the Electron

    NASA Astrophysics Data System (ADS)

    Murnane, Margaret

    2010-03-01

    Replace this text with your abstract Ever since the invention of the laser 50 years ago and its application in nonlinear optics, scientists have been striving to extend coherent laser beams into the x-ray region of the spectrum. Very recently however, the prospects for tabletop coherent sources, with attosecond pulse durations, at very short wavelengths even in the hard x-ray region of the spectrum at wavelengths < 1nm, have brightened considerably. These advances are possible by taking nonlinear optics techniques to an extreme, and are the direct result of a new ability to manipulate electrons on the fastest, attosecond, time-scales of our natural world. My talk will discuss new experimental data that demonstrates high harmonic generation of laser-like, fully coherent, 10 attosecond duration, soft x-ray beams at photon energies around 0.5keV. Several applications will also be discussed, including making a movie of how electron orbitals in a molecule change shape as a molecule breaks apart, following how fast a magnetic material can flip orientation, understanding how fast heat flows in a nanocircuit, or building a microscope without lenses. [4pt] [1] T. Popmintchev et al., ``Phase matched upconversion of coherent ultrafast laser light into the soft and hard x-ray regions of the spectrum'', PNAS 106, 10516 (2009). [0pt] [2] C. LaOVorakiat et al., ``Ultrafast Soft X-Ray Magneto-Optics at the M-edge Using a Tabletop High-Harmonic Source'', Physical Review Letters 103, 257402 (2009). [0pt] [3] M. Siemens et al. ``Measurement of quasi-ballistic heat transport across nanoscale interfaces using ultrafast coherent soft x-ray beams'', Nature Materials 9, 26 (2010). [0pt] [4] K. Raines et al., ``Three-dimensional structure determination from a single view,'' Nature 463, 214 (2010). [0pt] [5] W. Li et al., ``Time-resolved Probing of Dynamics in Polyatomic Molecules using High Harmonic Generation'', Science 322, 1207 (2008).

  16. Unifying Einstein and Palatini gravities

    SciTech Connect

    Amendola, Luca; Enqvist, Kari; Koivisto, Tomi [Institut fuer Theoretische Physik, University of Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); Physics Department, University of Helsinki, and Helsinki Institute of Physics, FIN-00014 University of Helsinki (Finland); Institute for Theoretical Physics and Spinoza Institute, Leuvenlaan 4, 3584 CE Utrecht (Netherlands)

    2011-02-15

    We consider a novel class of f(R) gravity theories where the connection is related to the conformally scaled metric g{sub {mu}{nu}=}C(R)g{sub {mu}{nu}} with a scaling that depends on the scalar curvature R only. We call them C theories and show that the Einstein and Palatini gravities can be obtained as special limits. In addition, C theories include completely new physically distinct gravity theories even when f(R)=R. With nonlinear f(R), C theories interpolate and extrapolate the Einstein and Palatini cases and may avoid some of their conceptual and observational problems. We further show that C theories have a scalar-tensor formulation, which in some special cases reduces to simple Brans-Dicke-type gravity. If matter fields couple to the connection, the conservation laws in C theories are modified. The stability of perturbations about flat space is determined by a simple condition on the Lagrangian.

  17. Parameterized Beyond-Einstein Growth

    SciTech Connect

    Linder, Eric; Linder, Eric V.; Cahn, Robert N.

    2007-09-17

    A single parameter, the gravitational growth index gamma, succeeds in characterizing the growth of density perturbations in the linear regime separately from the effects of the cosmic expansion. The parameter is restricted to a very narrow range for models of dark energy obeying the laws of general relativity but can take on distinctly different values in models of beyond-Einstein gravity. Motivated by the parameterized post-Newtonian (PPN) formalism for testing gravity, we analytically derive and extend the gravitational growth index, or Minimal Modified Gravity, approach to parameterizing beyond-Einstein cosmology. The analytic formalism demonstrates how to apply the growth index parameter to early dark energy, time-varying gravity, DGP braneworld gravity, and some scalar-tensor gravity.

  18. Einstein Gravitation Theory: Experimental Tests

    E-print Network

    M. Cattani

    2010-07-01

    In order to test the Einstein gravitation theory (EGT) we compare their predictions with the measured results in the following phenomena: the perihelion advance of planets, deflection of light, radar echo delays around the Sun and an overall planetary motion in Solar System. In our calculation we have used the Schwarzschild metric that is defined in the surrounding vacuum of a spherically symmetric mass distribution, not in rotation. This article was written to graduate and postgraduate students of Physics.

  19. Multisoliton solutions to Einstein's equations

    SciTech Connect

    Ibaez, J.; Verdaguer, E.

    1985-01-15

    We discuss a multisoliton solution to Einstein's equations in vacuum. The solution is interpreted as many gravitational solitons propagating and colliding on a homogeneous cosmological background. Following a previous letter, we characterize the solitons by their localizability and by their peculiar properties under collisions. Furthermore, we define an associated frame-dependent velocity field which illustrates the solitonic character of these gravitational solitons in the classical sense.

  20. Einstein And The Evolving Universe

    E-print Network

    A. N. Mitra

    2005-10-19

    A panoramic view, preceded by a short background of Newtonian mechanics and Maxwellian electrodynamics, is offered on the extent of how Einstein's space-time geometry, believed to be central to an understanding of the structure of the universe, is overshadowed by several hitherto unheard of features like dark matter and dark energy, that seem to be necessary, but by no means sufficient, for a more complete picture.

  1. Timescales of orogeny: Jurassic construction of the Klamath Mountains

    NASA Astrophysics Data System (ADS)

    Hacker, Bradley R.; Donato, Mary M.; Barnes, Calvin G.; McWilliams, M. O.; Ernst, W. G.

    1995-06-01

    An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 94YCJ2454, Timescales of orogeny: Jurassic construction of the Klamath Mountains, B.R. Hacker, M.M. Donato, C.G. Barnes, M.O. McWilliams, and W.G. Ernst). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00. Payment must accompany order. Classical interpretations of orogeny were based on relatively imprecise biostratigraphic and isotopic age determinations that necessitated grouping apparently related features that may in reality have been greatly diachronous. Isotopic age techniques now have the precision required to resolve the timing of orogenic events on a scale much smaller than that of entire mountain belts. Forty-five new 40Ar/39Ar ages from the Klamath Mountains illuminate the deformation, metamorphism, magmatism, and sedimentation involved in the Jurassic construction of that orogen, leading to a new level of understanding regarding how preserved orogenic features relate to ancient plate tectonic processes. The new geochronologic relationships show that many Jurassic units of the Klamath Mountains had 200 Ma or older volcanoplutonic basement. Subsequent formation of a large ˜170 Ma arc was followed by contractional collapse of the arc. Collision with a spreading ridge may have led to large-scale NW-SE extension in the central and northern Klamaths from 167 to ˜155 Ma, coincident with the crystallization of voluminous plutonic and volcanic suites. Marked cooling of a large region of the central Klamath Mountains to below ˜350°C at ˜150 Ma may have occurred as the igneous belt was extinguished by subduction of colder material at deeper structural levels. These data demonstrate that the Klamath Mountains—and perhaps other similar orogens—were constructed during areally and temporally variant episodes of contraction, extension, and magmatism that do not fit classical definitions of orogeny.

  2. Reliable timescale inference of HBV genotype A origin and phylodynamics.

    PubMed

    Zehender, Gianguglielmo; Svicher, Valentina; Gabanelli, Elena; Ebranati, Erika; Veo, Carla; Lo Presti, Alessandra; Cella, Eleonora; Giovanetti, Marta; Bussini, Linda; Salpini, Romina; Alteri, Claudia; Lai, Alessia; Tanzi, Elisabetta; Perno, Carlo Federico; Galli, Massimo; Ciccozzi, Massimo

    2015-06-01

    The worldwide distributed Hepatitis B virus (HBV) genotype A is classified into three subgenotypes, and one quasi-subgenotype. The majority of HBV-A subgenotypes are widespread in Africa and in ethnic groups that have relatively recently emigrated from African countries, whereas HBV-A2 is highly prevalent among subjects at high risk for sexual exposure to HBV in north-western Europe and the USA. The aim of this study was to reconstruct the origin and dispersion of HBV-A subgenotypes on a reliable timescale using short-term calibration based on heterochronous sampling for HBV-A2, and long-term calibration based on historical data for the other subgenotypes. To this aim, we analysed 113 newly characterised HBV-A isolates with 247 reference sequences retrieved from a public database. The phylodynamic reconstruction was performed by a Bayesian framework. The common ancestor of the currently circulating A subgenotypes was placed in west-central Africa a mean 1057 years ago. The genotype diverged into two main clades at the beginning of the 13th century: one including all of the west-central African quasi-subgenotypes and the other corresponding to subgenotype A1, originating in east Africa and further segregating into two main subclades: an "African" and a "cosmopolitan" clade. It is likely that the slave trade was the main source the spread of cosmopolitan HBV-A1, which was exported to Asia in the 17th century as a result of Arab or Portuguese trade, and to Latin America in the 18th centuries through the trans-Atlantic slave trade. The origin of the currently circulating A2 strains dates back to the first decades of the 20th century, and the evolutionary demography analysis suggests an exponential growth of infections, between 1970s and the mid-1990s. In conclusion, the very different epidemiological and evolutionary histories of HBV-A subgenotypes justify the use of different calibration approaches to reconstruct their reciprocal phylodynamics. PMID:25784568

  3. Signal-independent timescale analysis (SITA) and its application for neural coding during reaching and walking

    PubMed Central

    Zacksenhouse, Miriam; Lebedev, Mikhail A.; Nicolelis, Miguel A. L.

    2014-01-01

    What are the relevant timescales of neural encoding in the brain? This question is commonly investigated with respect to well-defined stimuli or actions. However, neurons often encode multiple signals, including hidden or internal, which are not experimentally controlled, and thus excluded from such analysis. Here we consider all rate modulations as the signal, and define the rate-modulations signal-to-noise ratio (RM-SNR) as the ratio between the variance of the rate and the variance of the neuronal noise. As the bin-width increases, RM-SNR increases while the update rate decreases. This tradeoff is captured by the ratio of RM-SNR to bin-width, and its variations with the bin-width reveal the timescales of neural activity. Theoretical analysis and simulations elucidate how the interactions between the recovery properties of the unit and the spectral content of the encoded signals shape this ratio and determine the timescales of neural coding. The resulting signal-independent timescale analysis (SITA) is applied to investigate timescales of neural activity recorded from the motor cortex of monkeys during: (i) reaching experiments with Brain-Machine Interface (BMI), and (ii) locomotion experiments at different speeds. Interestingly, the timescales during BMI experiments did not change significantly with the control mode or training. During locomotion, the analysis identified units whose timescale varied consistently with the experimentally controlled speed of walking, though the specific timescale reflected also the recovery properties of the unit. Thus, the proposed method, SITA, characterizes the timescales of neural encoding and how they are affected by the motor task, while accounting for all rate modulations. PMID:25191263

  4. Einstein, Kaluza, and the Fifth Dimension

    Microsoft Academic Search

    Daniela Wünsch

    2005-01-01

    This article argues that the influence Kaluza’s theory had on Einstein was mainly epistemological. The resulting profound\\u000a change, between 1919 and 1921, in Einstein’s epistemology led him to regard geometrized unified field theories as the most\\u000a promising route toward progress in theoretical physics. Thus his program in unified field theory emerged. His new epistemology\\u000a was based on the concept of

  5. Bridging the timescales between thermochronological and cosmogenic nuclide data

    NASA Astrophysics Data System (ADS)

    Glotzbach, Christoph

    2015-04-01

    Reconstructing the evolution of Earth's landscape is a key to understand its future evolution and to identify the driving forces that shape Earth's surface. Cosmogenic nuclide and thermochronological methods are routinely used to quantify Earth surface processes over 102-104 yr and 106-107 yr, respectively (e.g. Lal 1991; Reiners and Ehlers 2005; von Blanckenburg 2006). A comparison of the rates of surface processes derived from these methods is, however, hampered by the large difference in their timescales. For instance, a constant erosion rate of 0.1 mm/yr yield an apatite (U-Th)/He age of ~24 Ma and a 10Be age of ~6 ka, respectively. Analytical methods that bridge this time gap are on the way, but are not yet fully established (e.g. Herman et al. 2010). A ready to use alternative are river profiles, which record the regional uplift history over 102-107 yr (e.g. Pritchard et al. 2009). Changes in uplift are retained in knickzones that propagate with a distinct velocity upstream, and therefore the time of an uplift event can be estimated. Here I present an integrative inverse modelling approach to simultaneously reconstruct river profiles, model thermochronological and cosmogenic nuclide data and to derive robust information about landscape evolution over thousands to millions of years. An efficient inversion routine is used to solve the forward problem and find the best uplift history and erosional parameters that reproduce the observed data. I test the performance of the algorithm by inverting a synthetic dataset and a dataset from the Sila massif (Italy). Results show that even complicated uplift histories can be reliably retrieved by the combined interpretation of river profiles, thermochronological and cosmogenic nuclide data. References Gallagher, K., Brown, R. & Johnson, C. (1998): Fission track analysis and its applications to geological problems. - Annu. Rev. Earth Planet., 26: 519-572. Herman, F., Rhodes, E.J., Braun, J. & Heiniger, L. (2010): Uniform erosion rates and relief amplitude during glacial cycles in the Southern Alps of New Zealand, as revealed from OSL-thermochronology. - Earth Planet. Sci. Lett., 297: 183-189. Lal, D. (1991): Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and erosion models. - Earth Planet. Sci. Lett. 104: 424-439. Pritchard, D., Roberts, G.G., White, N.J. & Richardson, C.N. (2009): Uplift histories from river profiles. - Geophys. Res. Lett., 36, L24301, doi:10.1029/2009GL040928. Reiners, P.W. & Ehlers, T.A. (2005): Low-temperature Thermochronology: Techniques, Interpretations, and Applications. - Rev. Mineral. Geochem., 58. Von Blanckenburg, F. (2006): The control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment. - Earth Planet. Sci. Lett., 242: 462-479.

  6. Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H? Time Lags and Implications for Super-Eddington Accretion

    NASA Astrophysics Data System (ADS)

    Du, Pu; Hu, Chen; Lu, Kai-Xing; Huang, Ying-Ke; Cheng, Cheng; Qiu, Jie; Li, Yan-Rong; Zhang, Yang-Wei; Fan, Xu-Liang; Bai, Jin-Ming; Bian, Wei-Hao; Yuan, Ye-Fei; Kaspi, Shai; Ho, Luis C.; Netzer, Hagai; Wang, Jian-Min; SEAMBH Collaboration

    2015-06-01

    We have completed two years of photometric and spectroscopic monitoring of a large number of active galactic nuclei (AGNs) with very high accretion rates. In this paper, we report on the result of the second phase of the campaign, during 2013–2014, and the measurements of five new H? time lags out of eight monitored AGNs. All five objects were identified as super-Eddington accreting massive black holes (SEAMBHs). The highest measured accretion rates for the objects in this campaign are \\mathscr{\\dot{M}} {\\mkern 1mu} ? 200, where \\mathscr{\\dot{M}} {\\mkern 1mu} ={{\\dot{M}}\\bullet }/{{L}Edd}{{c}-2}, {{\\dot{M}}\\bullet } is the mass accretion rates, {{L}Edd} is the Eddington luminosity and c is the speed of light. We find that the H? time lags in SEAMBHs are significantly shorter than those measured in sub-Eddington AGNs, and the deviations increase with increasing accretion rates. Thus, the relationship between broad-line region size ({{R}_{H? }}) and optical luminosity at 5100 Å, {{R}_{H? }}-{{L}5100}, requires accretion rate as an additional parameter. We propose that much of the effect may be due to the strong anisotropy of the emitted slim-disk radiation. Scaling {{R}_{H? }} by the gravitational radius of the black hole (BH), we define a new radius–mass parameter (Y) and show that it saturates at a critical accretion rate of \\mathscr{\\dot{M}} {\\mkern 1mu} {{}c}=6? 30, indicating a transition from thin to slim accretion disk and a saturated luminosity of the slim disks. The parameter Y is a very useful probe for understanding the various types of accretion onto massive BHs. We briefly comment on implications to the general population of super-Eddington AGNs in the universe and applications to cosmology.

  7. Relationship between X-ray spectral index and X-ray Eddington ratio for Mrk 335 and Ark 564

    E-print Network

    Sarma, R; Misra, R; Dewangan, G; Pathak, A; Sarma, J K

    2015-01-01

    We present a comprehensive flux resolved spectral analysis of the bright Narrow line Seyfert I AGNs, Mrk~335 and Ark~564 using observations by XMM-Newton satellite. The mean and the flux resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low energy soft excess and the other for the high energy power-law. A broad Iron line and a couple of low energies edges are required to explain the spectra. For Mrk~335, the 0.3 - 10 keV luminosity relative to the Eddington value, L{$_{X}$}/L$_{Edd}$, varied from 0.002 to 0.06. The index variation can be empirically described as $\\Gamma$ = 0.6 log$_{10}$ L{$_{X}$}/L$_{Edd}$ + 3.0 for $0.005 < L{_{X}}/L_{Edd} < 0.04$. At $ L_{{X}}/L_{Edd} \\sim 0.04$ the spectral index changes and then continues to follow $\\Gamma$ = 0.6 log$_{10}$ L$_{{X}}$/L$_{Edd}$ + 2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3 - 10 keV band by only a powe...

  8. XMM-Newton Observations of the Super-Eddington Intermediate-Mass Black Hole: RX J1140.1+0307

    NASA Astrophysics Data System (ADS)

    Jin, C.; Done, C.; Ward, M.

    2015-07-01

    RX J1140.1+0307 is an intriguing IMBH. Last year we obtained data from two new observations of this source with XMM-Newton to study its spectral components and variability. Here we report the latest results from all three XMM-Newton observations of this source. We find the data show a strong soft X-ray component superimposed on a steep 2-10 keV power law, where the power law is more variable than the soft X-ray in high frequency. These properties are similar to a special group of NLS1s such as PG 1244+026 and RE J1034+396, making it natural to assume that the accretion flow in all these sources is at L˜L_{Edd}. We tried various methods to constrain its black hole mass, and conformed M<1.E+6 Msun. With the mass being so small, the variable optical flux requires a mass accretion rate of L/L$_{Edd}˜10 through the outer disk. Such high mass accretion rate would dramatically over-predicts the observed X-ray flux unless there is substantial energy loss through winds and/or advection, as is expected at such highly super-Eddington rates. But this is inconsistent with the X-ray spectral and variability properties, leaving us an unsolved puzzle about the formation mechanism of its X-ray spectra.

  9. NuSTAR J095551+6940.8: a highly magnetized neutron star with super-Eddington mass accretion

    NASA Astrophysics Data System (ADS)

    Dall'Osso, Simone; Perna, Rosalba; Stella, Luigi

    2015-05-01

    The identification of the ultraluminous X-ray source (ULX) X-2 in M82 as an accreting pulsar has shed new light on the nature of a subset of ULXs, while rising new questions on the nature of the super-Eddington accretion. Here, by numerically solving the torque equation of the accreting pulsar within the framework of the magnetically threaded-disc scenario, we show that three classes of solutions, corresponding to different values of the magnetic field, are mathematically allowed. We argue that the highest magnetic field one, corresponding to B ˜ 1013 G, is favoured based on physical considerations and the observed properties of the source. In particular, that is the only solution which can account for the observed variations in dot{P} (over four time intervals) without requiring major changes in dot{M}, which would be at odds with the approximately constant X-ray emission of the source during the same time. For this solution, we find that the source can only accommodate a moderate amount of beaming, 0.5 ? b < 1. Last, we show that the upper limit on the luminosity, LX < 2.5 × 1038 erg s-1 from archival observations, is consistent with a highly magnetized neutron star being in the propeller phase at that time.

  10. Einstein's Apple and Relativity's Gravitational Field

    E-print Network

    Engelbert L. Schucking

    2009-03-31

    The foundations of Einstein's first (1907) principle of equivalence are explored and their consequences are stated in terms of invariance under generalized Lorentz transformations, first explored by Hessenberg.

  11. Determining timescales of natural carbonation of peridotite in the Samail Ophiolite, Sultanate of Oman

    E-print Network

    Mervine, Evelyn Martinique

    2012-01-01

    Determining timescales of the formation and preservation of carbonate alteration products in mantle peridotite is important in order to better understand the role of this potentially important sink in the global carbon ...

  12. VARIABILITY OF GAMMA-RAY EMISSION FROM BLAZARS ON BLACK HOLE TIMESCALES

    SciTech Connect

    Vovk, Ie.; Neronov, A. [ISDC Data Centre for Astrophysics, Ch. d'Ecogia 16, CH-1290, Versoix (Switzerland)

    2013-04-20

    We investigate the variability properties of blazars in the GeV band using data from the Fermi/Large Area Telescope (LAT) telescope. We find that blazars exhibit variability down to the minimum timescale resolvable by Fermi; this variability is a function of the peak photon count rate in the LAT. This implies that the real minimum variability timescales for the majority of blazars are typically shorter than those resolvable by the LAT. We find that for several blazars these minimum variability timescales reach those associated with the blazar central engine, the supermassive black hole. At the same time, none of the blazars exhibits variability on a timescale shorter than the black hole horizon light-crossing time and/or the period of rotation around the last stable circular orbit. Based on this fact, we argue that the timing properties of the {gamma}-ray signal could be determined by the processes in the direct vicinity of the supermassive black hole.

  13. An extraterrestrial 3 He-based timescale for the PaleoceneEocene

    E-print Network

    Zachos, James

    An extraterrestrial 3 He-based timescale for the Paleocene­Eocene thermal maximum (PETM) from. The extraterrestrial 3 He, 3 HeET, concentrations replicate trends observed at ODP Site 690 by Farley and Eltgroth

  14. Retroactivity Attenuation in Bio-Molecular Systems Based on Timescale Separation

    E-print Network

    Jayanthi, Shridhar

    As with several engineering systems, bio-molecular systems display impedance-like effects at interconnections, called retroactivity. In this paper, we propose a mechanism that exploits the natural timescale separation ...

  15. Existence of Solutions for a One Dimensional p-Laplacian on Time-Scales

    E-print Network

    Anderson, Douglas R.

    real numbers), or hZ (a constant graininess), the p-Laplacian arises in non-Newtonian fluids, in some theorem of Calculus, a result that has been generalized and extended to time-scales; to gain a good

  16. Objective, observations-based, automatic estimation of the catchment response timescale

    NASA Astrophysics Data System (ADS)

    Morin, Efrat; Georgakakos, Konstantine P.; Shamir, Uri; Garti, Rami; Enzel, Yehouda

    2002-10-01

    A new characteristic timescale of a catchment is presented, the response timescale (RTS). It is a range of averaging time intervals which, when applied to catchment rainfall, yield smoothed time series that best approximate that of the resultant runoff. In determining the RTS, nothing is assumed about the nature of the rainfall-runoff transformation. In addition, this new measure is shown to be robust against measurement errors. An objective, automatic, observations-based algorithm is described that introduces the concept of peaks density for the estimation of RTS. Estimation is exemplified for single and multiple rainfall-runoff events through application to small catchments in Panama and Israel. In all cases, relatively stable values of response timescale are obtained. It is concluded that at least for the case studies, the response timescale is an intrinsic characteristic of the catchment and it is generally expected to be different from the catchment lag time and time of concentration.

  17. Non-convergence of the critical cooling timescale for fragmentation of self-gravitating discs

    E-print Network

    Meru, Farzana

    2010-01-01

    We carry out a resolution study on the fragmentation boundary of self-gravitating discs. We perform three-dimensional Smoothed Particle Hydrodynamics (SPH) simulations of discs to determine whether the critical value of the cooling timescale in units of the orbital timescale, beta_{crit}, converges with increasing resolution. Using particle numbers ranging from 31,250 to 16 million (the highest resolution simulations to date) we do not find convergence. Instead, fragmentation occurs for longer cooling timescales as the resolution is increased. These results certainly suggest that beta_{crit} is larger than previously thought. However, the absence of convergence also questions whether or not a critical value exists. In light of these results, we caution against using cooling timescale or gravitational stress arguments to deduce whether gravitational instability may or may not have been the formation mechanism for observed planetary systems.

  18. SYSTEMATIC UNCERTAINTIES IN THE SPECTROSCOPIC MEASUREMENTS OF NEUTRON-STAR MASSES AND RADII FROM THERMONUCLEAR X-RAY BURSTS. II. EDDINGTON LIMIT

    SciTech Connect

    Guever, Tolga; Oezel, Feryal; Psaltis, Dimitrios [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2012-03-01

    Time-resolved X-ray spectroscopy of thermonuclear bursts observed from low-mass X-ray binaries offer a unique tool to measure neutron-star masses and radii. In this paper, we continue our systematic analysis of all the X-ray bursts observed with Rossi X-ray Timing Explorer from X-ray binaries. We determine the events that show clear evidence for photospheric radius expansion and measure the Eddington limits for these accreting neutron stars using the bolometric fluxes attained at the touchdown moments of each X-ray burst. We employ a Bayesian technique to investigate the degree to which the Eddington limit for each source remains constant between bursts. We find that for sources with a large number of radius expansion bursts, systematic uncertainties are at a 5%-10% level. Moreover, in six sources with only pairs of Eddington-limited bursts, the distribution of fluxes is consistent with a {approx}10% fractional dispersion. This indicates that the spectroscopic measurements of neutron-star masses and radii using thermonuclear X-ray bursts can reach the level of accuracy required to distinguish between different neutron-star equations of state, provided that uncertainties related to the overall flux calibration of X-ray detectors are of comparable magnitude.

  19. Multi time-scale structure assignment for linear multivariable systems-Singular perturbation approach

    Microsoft Academic Search

    A. Saberi; P. Sannuti

    1986-01-01

    In this paper we examine the problem of high-gain output feedback for linear time-invariant multivariable systems. More specifically, we do the following: ¿ We study the possible set of multiple time-scale structures that can be assigned via high-gain output feedback control laws (We refer to this set as a set of 'achievable multiple time-scale structures'). ¿ We propose a design

  20. Multiple time-scales in nonlinear flight mechanics: diagnosis and modeling

    Microsoft Academic Search

    K. D. Mease

    2005-01-01

    There are often disparate time-scales in the dynamics of flight, creating the potential for reduced-order modeling to simplify simulation, analysis and design. There have been notable successes in developing reduced-order models; however, in the case of nonlinear dynamics, which one must typically deal with in guidance problems, there has not been a systematic, reliable means of diagnosing disparate time-scales and

  1. Critical Collapse of Einstein Cluster

    E-print Network

    Ashutosh Mahajan; Tomohiro Harada; Pankaj S. Joshi; Ken-ichi Nakao

    2007-10-23

    We observe critical phenomena in spherically symmetric gravitational collapse of Einstein Cluster. We show analytically that the collapse evolution ends either in formation of a black hole or in dispersal depending on the values of initial parameters which characterize initial density and angular momentum of the collapsing cloud. Near the threshold of black hole formation, we obtain scaling relation for the mass of the black hole and find the critical exponent value to be 3/2. We numerically confirm that there exist wide ranges of initial parameter values around the critical configuration for which the model remains shell-crossing free.

  2. The Meaning of Einstein's Equation

    E-print Network

    John C. Baez; Emory F. Bunn

    2015-06-12

    This is a brief introduction to general relativity, designed for both students and teachers of the subject. While there are many excellent expositions of general relativity, few adequately explain the geometrical meaning of the basic equation of the theory: Einstein's equation. Here we give a simple formulation of this equation in terms of the motion of freely falling test particles. We also sketch some of its consequences, and explain how the formulation given here is equivalent to the usual one in terms of tensors. Finally, we include an annotated bibliography of books, articles and websites suitable for the student of relativity.

  3. Cosmography with the Einstein Telescope

    E-print Network

    B. S. Sathyaprakash; Bernard Schutz; Chris Van Den Broeck

    2009-06-23

    Einstein Telescope (ET) is a 3rd generation gravitational-wave (GW) detector that is currently undergoing a design study. ET can detect millions of compact binary mergers up to redshifts 2-8. A small fraction of mergers might be observed in coincidence as gamma-ray bursts, helping to measure both the luminosity distance and red-shift to the source. By fitting these measured values to a cosmological model, it should be possible to accurately infer the dark energy equation-of-state, dark matter and dark energy density parameters. ET could, therefore, herald a new era in cosmology.

  4. CONSTRAINTS ON BLACK HOLE GROWTH, QUASAR LIFETIMES, AND EDDINGTON RATIO DISTRIBUTIONS FROM THE SDSS BROAD-LINE QUASAR BLACK HOLE MASS FUNCTION

    SciTech Connect

    Kelly, Brandon C.; Hernquist, Lars; Siemiginowska, Aneta [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Vestergaard, Marianne; Fan Xiaohui [Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Hopkins, Philip, E-mail: bckelly@cfa.harvard.ed [Department of Astronomy, University of California, Berkeley, CA (United States)

    2010-08-20

    We present an estimate of the black hole mass function of broad-line quasars (BLQSOs) that self-consistently corrects for incompleteness and the statistical uncertainty in the mass estimates, based on a sample of 9886 quasars at 1 < z < 4.5 drawn from the Sloan Digital Sky Survey (SDSS). We find evidence for 'cosmic downsizing' of black holes in BLQSOs, where the peak in their number density shifts to higher redshift with increasing black hole mass. The cosmic mass density for black holes seen as BLQSOs peaks at z {approx} 2. We estimate the completeness of the SDSS as a function of the black hole mass and Eddington ratio, and find that at z > 1 it is highly incomplete at M {sub BH} {approx}< 10{sup 9} M {sub sun} and L/L{sub Edd} {approx}< 0.5. We estimate a lower limit on the lifetime of a single BLQSO phase to be t {sub BL} > 150 {+-} 15 Myr for black holes at z = 1 with a mass of M {sub BH} = 10{sup 9} M{sub sun}, and we constrain the maximum mass of a black hole in a BLQSO to be {approx}3 x 10{sup 10} M{sub sun}. Our estimated distribution of BLQSO Eddington ratios peaks at L/L {sub Edd} {approx} 0.05 and has a dispersion of {approx}0.4 dex, implying that most BLQSOs are not radiating at or near the Eddington limit; however, the location of the peak is subject to considerable uncertainty. The steep increase in number density of BLQSOs toward lower Eddington ratios is expected if the BLQSO accretion rate monotonically decays with time. Furthermore, our estimated lifetime and Eddington ratio distributions imply that the majority of the most massive black holes spend a significant amount of time growing in an earlier obscured phase, a conclusion which is independent of the unknown obscured fraction. These results are consistent with models for self-regulated black hole growth, at least for massive systems at z > 1, where the BLQSO phase occurs at the end of a fueling event when black hole feedback unbinds the accreting gas, halting the accretion flow.

  5. Einstein Manifolds as Yang-Mills Instantons

    NASA Astrophysics Data System (ADS)

    Oh, John J.; Yang, Hyun Seok

    2013-07-01

    It is well known that Einstein gravity can be formulated as a gauge theory of Lorentz group where spin connections play a role of gauge fields and Riemann curvature tensors correspond to their field strengths. One can then pose an interesting question: What is the Einstein equation from the gauge theory point of view? Or equivalently, what is the gauge theory object corresponding to Einstein manifolds? We show that the Einstein equations in four dimensions are precisely self-duality equations in Yang-Mills gauge theory and so Einstein manifolds correspond to Yang-Mills instantons in SO(4) = SU(2)L × SU(2)R gauge theory. Specifically, we prove that any Einstein manifold with or without a cosmological constant always arises as the sum of SU(2)L instantons and SU(2)R anti-instantons. This result explains why an Einstein manifold must be stable because two kinds of instantons belong to different gauge groups, instantons in SU(2)L and anti-instantons in SU(2)R, and so they cannot decay into a vacuum. We further illuminate the stability of Einstein manifolds by showing that they carry nontrivial topological invariants.

  6. Why is an Einstein Ring Blue?

    Microsoft Academic Search

    Jonathan Blackledge

    2011-01-01

    Albert Einstein predicted the existence of `Einstein rings' as a consequence of his general theory of relativity. The phenomenon is a direct result of the idea that if a mass warps space-time then light (and other electromagnetic waves) will be `lensed' by the strong gravitational field produced by a large cosmological body such as a galaxy. Since 1998, when the

  7. Hypermass generalization of Einstein's gravitation theory

    Microsoft Academic Search

    James D. Edmonds; J. D. Jr

    1973-01-01

    The curvilinear invariant quaternion formalism is examined for curved space time. Einstein's gravitation equation is shown to have a sample and natural form in this notation. The hypermass generalization of particle mass, which was generated in our studies of the Dirac equation, is incorporated in gravitation by generalizing Einstein's equation. Covariance requires that the gravitational constant be generalized to an

  8. Einstein's Revolutionary Light-Quantum Hypothesis

    Microsoft Academic Search

    Roger H. Stuewer

    2005-01-01

    The paper in which Albert Einstein proposed his light-quantum hypothesis was the only one of his great papers of 1905 that he himself termed ``revolutionary.'' Contrary to widespread belief, Einstein did not propose his light-quantum hypothesis ``to explain the photoelectric effect.'' Instead, he based his argument for light quanta on the statistical interpretation of the second law of thermodynamics, with

  9. Astrophysical Observations: Lensing and Eclipsing Einstein's Theories

    E-print Network

    Charles L. Bennett

    2005-03-15

    Albert Einstein postulated the equivalence of energy and mass, developed the theory of special relativity, explained the photoelectric effect, and described Brownian motion in five papers, all published in 1905, 100 years ago. With these papers, Einstein provided the framework for understanding modern astrophysical phenomena. Conversely, astrophysical observations provide one of the most effective means for testing Einstein's theories. Here, I review astrophysical advances precipitated by Einstein's insights, including gravitational redshifts, gravitational lensing, gravitational waves, the Lense-Thirring effect, and modern cosmology. A complete understanding of cosmology, from the earliest moments to the ultimate fate of the universe, will require developments in physics beyond Einstein, to a unified theory of gravity and quantum physics.

  10. Albert Einstein's Magic Mountain: An Aarau Education*

    NASA Astrophysics Data System (ADS)

    Hunziker, Herbert

    2015-03-01

    For economic reasons, the electrotechnical factory J. Einstein & Cie. (co-owned by Albert Einstein's father Hermann) had to be closed in the summer of 1894. While Albert's parents emigrated to Italy to build a new existence, he remained in Munich to complete his studies at the Gymnasium. Left behind, however, he had a difficult time with what he considered the rigid educational practices at the Munich Luitpold-Gymnasium and quit without a diploma. The present article discusses Einstein's richly winding path to the Aargau Cantonal School (Switzerland), especially its history and educational philosophy during the time of his stay in Aarau. There, Einstein met some outstanding teachers, who could serve him as models of scholars and human beings. In spite of Einstein's distinct independence of mind, these personalities may well have had a significant influence on the alignment of his inner compass.

  11. Astrophysical observations: lensing and eclipsing Einstein's theories.

    PubMed

    Bennett, Charles L

    2005-02-11

    Albert Einstein postulated the equivalence of energy and mass, developed the theory of special relativity, explained the photoelectric effect, and described Brownian motion in five papers, all published in 1905, 100 years ago. With these papers, Einstein provided the framework for understanding modern astrophysical phenomena. Conversely, astrophysical observations provide one of the most effective means for testing Einstein's theories. Here, I review astrophysical advances precipitated by Einstein's insights, including gravitational redshifts, gravitational lensing, gravitational waves, the Lense-Thirring effect, and modern cosmology. A complete understanding of cosmology, from the earliest moments to the ultimate fate of the universe, will require developments in physics beyond Einstein, to a unified theory of gravity and quantum physics. PMID:15705841

  12. The neural processing of hierarchical structure in music and speech at different timescales

    PubMed Central

    Farbood, Morwaread M.; Heeger, David J.; Marcus, Gary; Hasson, Uri; Lerner, Yulia

    2015-01-01

    Music, like speech, is a complex auditory signal that contains structures at multiple timescales, and as such is a potentially powerful entry point into the question of how the brain integrates complex streams of information. Using an experimental design modeled after previous studies that used scrambled versions of a spoken story (Lerner et al., 2011) and a silent movie (Hasson et al., 2008), we investigate whether listeners perceive hierarchical structure in music beyond short (~6 s) time windows and whether there is cortical overlap between music and language processing at multiple timescales. Experienced pianists were presented with an extended musical excerpt scrambled at multiple timescales—by measure, phrase, and section—while measuring brain activity with functional magnetic resonance imaging (fMRI). The reliability of evoked activity, as quantified by inter-subject correlation of the fMRI responses, was measured. We found that response reliability depended systematically on musical structure coherence, revealing a topographically organized hierarchy of processing timescales. Early auditory areas (at the bottom of the hierarchy) responded reliably in all conditions. For brain areas at the top of the hierarchy, the original (unscrambled) excerpt evoked more reliable responses than any of the scrambled excerpts, indicating that these brain areas process long-timescale musical structures, on the order of minutes. The topography of processing timescales was analogous with that reported previously for speech, but the timescale gradients for music and speech overlapped with one another only partially, suggesting that temporally analogous structures—words/measures, sentences/musical phrases, paragraph/sections—are processed separately.

  13. Dynamic hyporheic exchange at intermediate timescales: testing the relative importance of evapotranspiration and flood pulses

    USGS Publications Warehouse

    Larsen, Laurel G.; Harvey, Judson W.; Maglio, Morgan M.

    2014-01-01

    Hyporheic fluxes influence ecological processes across a continuum of timescales. However, few studies have been able to characterize hyporheic fluxes and residence time distributions (RTDs) over timescales of days to years, during which evapotranspiration (ET) and seasonal flood pulses create unsteady forcing. Here we present a data-driven, particle-tracking piston model that characterizes hyporheic fluxes and RTDs based on measured vertical head differences. We used the model to test the relative influence of ET and seasonal flood pulses in the Everglades (FL, USA), in a manner applicable to other low-energy floodplains or broad, shallow streams. We found that over the multiyear timescale, flood pulses that drive relatively deep (?1 m) flow paths had the dominant influence on hyporheic fluxes and residence times but that ET effects were discernible at shorter timescales (weeks to months) as a break in RTDs. Cumulative RTDs on either side of the break were generally well represented by lognormal functions, except for when ET was strong and none of the standard distributions applied to the shorter timescale. At the monthly timescale, ET increased hyporheic fluxes by 1–2 orders of magnitude; it also decreased 6 year mean residence times by 53–87%. Long, slow flow paths driven by flood pulses increased 6 year hyporheic fluxes by another 1–2 orders of magnitude, to a level comparable to that induced over the short term by shear flow in streams. Results suggest that models of intermediate-timescale processes should include at least two-storage zones with different RTDs, and that supporting field data collection occur over 3–4 years.

  14. Time Dilation and the Length of the Second: Why Timescales Diverge

    NASA Astrophysics Data System (ADS)

    Deines, Steven D.; Williams, Carol A.

    2007-07-01

    We show that the timescale divergence between Universal Time (UT1) and international atomic time (TAI), which is compensated for by the occasional addition of a leap second, is due to the fact that the Système Internationale (SI) second is shorter than the UT second. Celestial mechanicians saw the necessity of introducing a timescale that eliminated the discrepancy between the observed and calculated longitudes of the Moon, Sun, and planets. This timescale, called ephemeris time (ET), was measured and used to calibrate the length of the SI second. It has been shown that ET and TAI are equivalent for all practical purposes. We show that the length of the ET second (and consequently the length of the SI second) was shorter than the length of the UT second at the beginning of the tropical year 1900.0, even though it was intended that the ET second would equal this length. We further show that this difference in the lengths of the UT and SI seconds is due to time dilation. The ET (or equivalently the SI) second is a measure of the scale of coordinate time, while the UT second is a measure of proper time for an observer moving with the Earth. Our calculation of the time dilation effect matches both the difference between the SI and UT seconds and also the leap-second insertion rate to within 0.2% since atomic time began in 1958 up to 2000, when UT was redefined. The deceleration of Earth's rotation contributes less than 1% of this timescale divergence according to the measurements from paleontological records of tidal friction. One possible method to convert from the TAI timescale is to use a multiplicative scalar to obtain a UT timescale. This method would necessitate the insertion of a leap second into the UT timescale only once in approximately 14 decades to account for tidal friction.

  15. Eddington-Born-Infeld cosmology: a cosmographic approach, a tale of doomsdays and the fate of bound structures

    NASA Astrophysics Data System (ADS)

    Bouhmadi-López, Mariam; Chen, Che-Yu; Chen, Pisin

    2015-02-01

    The Eddington-inspired-Born-Infeld scenario (EiBI) can prevent the big bang singularity for a matter content whose equation of state is constant and positive. In a recent paper [Bouhmadi-Lopez et al. (Eur. Phys. J. C 74:2802, 2014)] we showed that, on the contrary, it is impossible to smooth a big rip in the EiBI setup. In fact the situations are still different for other singularities. In this paper we show that a big freeze singularity in GR can in some cases be smoothed to a sudden or a type IV singularity under the EiBI scenario. Similarly, a sudden or a type IV singularity in GR can be replaced in some regions of the parameter space by a type IV singularity or a loitering behaviour, respectively, in the EiBI framework. Furthermore, we find that the auxiliary metric related to the physical connection usually has a smoother behaviour than that based on the physical metric. In addition, we show that bound structures close to a big rip or a little rip will be destroyed before the advent of the singularity and will remain bound close to a sudden, big freeze or type IV singularity. We then constrain the model following a cosmographic approach, which is well known to be model independent, for a given Friedmann-Lemaître-Robertson-Walker geometry. It turns out that among the various past or present singularities, the cosmographic analysis can pick up the physical region that determines the occurrence of a type IV singularity or a loitering effect in the past. Moreover, to determine which of the future singularities or doomsdays is more probable, observational constraints on the higher-order cosmographic parameters are required.

  16. Einstein Ring in Distant Universe

    NASA Astrophysics Data System (ADS)

    2005-06-01

    Using ESO's Very Large Telescope, Rémi Cabanac and his European colleagues have discovered an amazing cosmic mirage, known to scientists as an Einstein Ring. This cosmic mirage, dubbed FOR J0332-3557, is seen towards the southern constellation Fornax (the Furnace), and is remarkable on at least two counts. First, it is a bright, almost complete Einstein ring. Second, it is the farthest ever found. ESO PR Photo 20a/05 ESO PR Photo 20a/05 Deep Image of a Region in Fornax (FORS/VLT) [Preview - JPEG: 400 x 434 pix - 60k] [Normal - JPEG: 800 x 867 pix - 276k] [Full Res - JPEG: 1859 x 2015 pix - 3.8M] ESO PR Photo 20b/05 ESO PR Photo 20b/05 Zoom-in on the Newly Found Einstein Ring (FORS/VLT) [Preview - JPEG: 400 x 575 pix - 168k] [Normal - JPEG: 630 x 906 pix - 880k] Caption: ESO PR Photo 20a/05 is a composite image taken in two bands (B and R) with VLT/FORS1 of a small portion of the sky (field-of-view 7x7' or 1/15th of the area of the full moon). The faintest object seen in the image has a magnitude 26, that is, it is 100 million times fainter than what can be observed with the unaided eye. The bright elliptical galaxy on the lower-left quadrant is a dwarf galaxy part of a large nearby cluster in the Fornax constellation. As for all deep images of the sky, this field shows a variety of objects, the brightest ponctual sources being stars from our Galaxy. By far the field is dominated by thousands of faint background galaxies the colours of which are related to the age of their dominant stellar population, their dust content and their distance. The newly found Einstein ring is visible in the top right part of the image. ESO PR Photo 20b/05 zooms-in on the position of the newly found cosmic mirage. ESO PR Photo 20c/05 ESO PR Photo 20c/05 Einstein Ring in Distant Universe (FORS/VLT) [Preview - JPEG: 400 x 584 pix - 104k] [Normal - JPEG: 800 x 1168 pix - 292k] [Full Res - JPEG: 1502 x 2192 pix - 684k] Caption of ESO PR Photo 20c/05: The left image is magnified and centred on the newly discovered Einstein ring. The image quality ("seeing") of the R-band image is exceptional (0.5") and the image reveals the lensing system in stunning details. The central dot is the lens, a quiescent massive galaxy that distort the light emitted by background sources. The large arc surrounding the central lens is a part of the Einstein-ring created by a background source finely aligned with the lens. The reddish colour indicates that the redshift of the system is very large. FORS2 spectroscopy of the lensing system yield a redshift close to 1 for the lens (we see the lens as it was when the universe was half its present size), and a record-breaking redshift z=3.8 for a background source of such brightness, hence we see the object (a star forming galaxy) as it was when the universe was only 12% of its present age. The lensing model indicates that the light of the source is magnified at least 13 times. The right panel shows the reconstructed image based on the model of the lens and the source, showing the ring to extend over 3/4 of a circle. "There are only a very few optical rings or arcs known, and even less so in which the lens and the source are at large distance, i.e. more than about 7,000 million light-years away (or half the present age of the Universe)", says Rémi Cabanac, former ESO Fellow and now working at the Canada-France-Hawaii Telescope. "Moreover, very few are nearly complete", he adds. But in the case of this newly found cosmic ring, the images show it to extend to almost 3/4 of a circle. The lensing galaxy is located at a distance of about 8,000 million light-years from us, while the source galaxy whose light is distorted, is much farther away, at 12,000 million light-years. Thus, we see this galaxy as it was when the universe was only 12% of its present age. The lens magnifies the source almost 13 times. The observations reveal the galaxy acting as a lens to be a rather quiet galaxy, 40,000 light-years wide, with an old stellar population. The far away lensed galaxy, however, is extremely active,

  17. A particle-resolved modeling approach for estimating black carbon aging time-scales

    NASA Astrophysics Data System (ADS)

    Riemer, N. S.; West, M.; Zaveri, R. A.; Easter, R. C.; Fierce, L. M.; Bond, T. C.

    2012-12-01

    The composition of carbonaceous aerosol particles changes continuously after emission during their transport in the atmosphere. Coagulation and condensation are contributing processes, collectively known as aging. This changes the particles' physico-chemical properties, in particular their hygroscopicity, from initially hydrophobic to more hydrophilic, and hence their ability to act as cloud condensation nuclei. In many global models the aging process is modeled as a first-order system with the single parameter of aging rate or its inverse, the aging time-scale. Sensitivity studies have shown that the black carbon burden in global models depends strongly on the assumed aging time-scale, hence constraining this value is important for predicting the black carbon climate impacts. Here we will present a method for explicitly calculating aging time-scales of black carbon aerosol using the particle-resolved model PartMC-MOSAIC. We used the activation of the particles at a given supersaturation as a criterion for aging, and consider condensation of semivolatile species and coagulation as aging mechanisms. We then developed a library of approximately 300 scenarios to explore the sensitivity of this aging time-scale to a range of environmental parameters and pollution characteristics. From this ensemble of simulations the following results emerge: The aging time-scale is heavily dependent on the chosen supersaturation threshold. Decreasing this threshold from 0.6% to 0.1% increases the aging time-scale by a factor of 20 (median). The nitrate-dominated simulations, which have the highest rates of gas-to-particle conversion, lead to the lowest aging time-scales, with day-time averages on the order of 1 hour for the 0.6% supersaturation threshold. This value depends in turn on temperature and relative humidity as they govern nitrate formation. Daytime aging time-scales are about a factor of 5 smaller than the corresponding nighttime aging time-scales when the 0.6% supersaturation threshold is used. This day-night difference decreases for smaller supersaturation thresholds. We are also able to quantify the extent to which aging is due to condensation versus coagulation processes. Both of them play important roles in aging, and their relative impact depends on the particle size range.

  18. A multi-timescale analysis of phase transitions in precessing black-hole binaries

    E-print Network

    Gerosa, Davide; Sperhake, Ulrich; Berti, Emanuele; O'Shaughnessy, Richard

    2015-01-01

    The dynamics of precessing binary black holes (BBHs) in the post-Newtonian regime has a strong timescale hierarchy: the orbital timescale is very short compared to the spin-precession timescale which, in turn, is much shorter than the radiation-reaction timescale on which the orbit is shrinking due to gravitational-wave emission. We exploit this timescale hierarchy to develop a multi-scale analysis of BBH dynamics elaborating on the analysis of Kesden et al. (2015). We solve the spin-precession equations analytically on the precession time and then implement a quasi-adiabatic approach to evolve these solutions on the longer radiation-reaction time. This procedure leads to an innovative "precession-averaged" post-Newtonian approach to studying precessing BBHs. We use our new solutions to classify BBH spin precession into three distinct morphologies, then investigate phase transitions between these morphologies as BBHs inspiral. These precession-averaged post-Newtonian inspirals can be efficiently calculated fr...

  19. Timescales of Quartz Crystallization and the Longevity of the Bishop Giant Magma Body

    PubMed Central

    Gualda, Guilherme A. R.; Pamukcu, Ayla S.; Ghiorso, Mark S.; Anderson, Alfred T.; Sutton, Stephen R.; Rivers, Mark L.

    2012-01-01

    Supereruptions violently transfer huge amounts (100 s–1000 s km3) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ?760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500–3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies. PMID:22666359

  20. Colocalization of fast and slow timescale dynamics in the allosteric signaling protein CheY

    PubMed Central

    McDonald, Leanna R.; Whitley, Matthew J.; Boyer, Joshua A.; Lee, Andrew L.

    2013-01-01

    It is now widely recognized that dynamics are important to consider for understanding allosteric protein function. However, dynamics occur over a wide range of timescales, and how these different motions relate to one another is not well understood. Here, we report an NMR relaxation study of dynamics over multiple timescales at both backbone and side-chain sites upon an allosteric response to phosphorylation. The response regulator, Escherichia coli CheY, allosterically responds to phosphorylation with a change in dynamics on both the ?s-ms timescale and ps-ns timescale. We observe an apparent decrease and redistribution of ?s-ms dynamics upon phosphorylation (and accompanying Mg2+ saturation) of CheY. Additionally, methyl groups with the largest changes in ps-ns dynamics localize to the regions of conformational change measured by ?s-ms dynamics. The limited spread of changes in ps-ns dynamics suggests a distinct relationship between motions on the ?s-ms and ps-ns timescales in CheY. The allosteric mechanism utilized by CheY highlights the diversity of roles dynamics play in protein function. PMID:23648838

  1. Time-scales of close-in exoplanet radio emission variability

    NASA Astrophysics Data System (ADS)

    See, V.; Jardine, M.; Fares, R.; Donati, J.-F.; Moutou, C.

    2015-07-01

    We investigate the variability of exoplanetary radio emission using stellar magnetic maps and 3D field extrapolation techniques. We use a sample of hot Jupiter hosting stars, focusing on the HD 179949, HD 189733 and ? Boo systems. Our results indicate two time-scales over which radio emission variability may occur at magnetized hot Jupiters. The first is the synodic period of the star-planet system. The origin of variability on this time-scale is the relative motion between the planet and the interplanetary plasma that is corotating with the host star. The second time-scale is the length of the magnetic cycle. Variability on this time-scale is caused by evolution of the stellar field. At these systems, the magnitude of planetary radio emission is anticorrelated with the angular separation between the subplanetary point and the nearest magnetic pole. For the special case of ? Boo b, whose orbital period is tidally locked to the rotation period of its host star, variability only occurs on the time-scale of the magnetic cycle. The lack of radio variability on the synodic period at ? Boo b is not predicted by previous radio emission models, which do not account for the co-rotation of the interplanetary plasma at small distances from the star.

  2. Timescales of Quartz Crystallization and the Longevity of the Bishop Giant Magma Body

    SciTech Connect

    Gualda, Guilherme A.R.; Pamukcu, Ayla S.; Ghiorso, Mark S.; Anderson, Jr. , Alfred T.; Sutton, Stephen R.; Rivers, Mark L. (OFM Res.); (Vanderbilt); (UC)

    2013-04-08

    Supereruptions violently transfer huge amounts (100 s-1000 s km{sup 3}) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted {approx}760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500-3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies.

  3. Timescales of quartz crystallization and the longevity of the Bishop giant magma body.

    PubMed

    Gualda, Guilherme A R; Pamukcu, Ayla S; Ghiorso, Mark S; Anderson, Alfred T; Sutton, Stephen R; Rivers, Mark L

    2012-01-01

    Supereruptions violently transfer huge amounts (100 s-1000 s km(3)) of magma to the surface in a matter of days and testify to the existence of giant pools of magma at depth. The longevity of these giant magma bodies is of significant scientific and societal interest. Radiometric data on whole rocks, glasses, feldspar and zircon crystals have been used to suggest that the Bishop Tuff giant magma body, which erupted ~760,000 years ago and created the Long Valley caldera (California), was long-lived (>100,000 years) and evolved rather slowly. In this work, we present four lines of evidence to constrain the timescales of crystallization of the Bishop magma body: (1) quartz residence times based on diffusional relaxation of Ti profiles, (2) quartz residence times based on the kinetics of faceting of melt inclusions, (3) quartz and feldspar crystallization times derived using quartz+feldspar crystal size distributions, and (4) timescales of cooling and crystallization based on thermodynamic and heat flow modeling. All of our estimates suggest quartz crystallization on timescales of <10,000 years, more typically within 500-3,000 years before eruption. We conclude that large-volume, crystal-poor magma bodies are ephemeral features that, once established, evolve on millennial timescales. We also suggest that zircon crystals, rather than recording the timescales of crystallization of a large pool of crystal-poor magma, record the extended periods of time necessary for maturation of the crust and establishment of these giant magma bodies. PMID:22666359

  4. Einstein Gravity from Conformal Gravity

    E-print Network

    Juan Maldacena

    2011-06-09

    We show that that four dimensional conformal gravity plus a simple Neumann boundary condition can be used to get the semiclassical (or tree level) wavefunction of the universe of four dimensional asymptotically de-Sitter or Euclidean anti-de Sitter spacetimes. This simple Neumann boundary condition selects the Einstein solution out of the more numerous solutions of conformal gravity. It thus removes the ghosts of conformal gravity from this computation. In the case of a five dimensional pure gravity theory with a positive cosmological constant we show that the late time superhorizon tree level probability measure, $|\\Psi [ g ]|^2$, for its four dimensional spatial slices is given by the action of Euclidean four dimensional conformal gravity.

  5. Cosmography with the Einstein Telescope

    NASA Astrophysics Data System (ADS)

    Sathyaprakash, B. S.; Schutz, B. F.; Van Den Broeck, C.

    2010-11-01

    The Einstein Telescope, a third-generation gravitational-wave detector under a design study, could detect millions of binary neutron star inspirals each year. A small fraction of these events might be observed as gamma-ray bursts, helping to measure both the luminosity distance DL to and redshift {\\bm z} of the source. By fitting these measured values of DL and {\\bm z} to a cosmological model, it would be possible to infer the dark energy equation of state to within 1.5% without the need to correct for errors in DL caused by weak lensing. This compares favourably with 0.3-10% accuracy that can be achieved with the Laser Interferometer Space Antenna (where weak lensing will need to be dealt with) as well as with dedicated dark energy missions that have been proposed, where 3.5-11% uncertainty is expected.

  6. Microphysical Timescales in Clouds and their Application in Cloud-Resolving Modeling

    NASA Technical Reports Server (NTRS)

    Zeng, Xi-Ping; Tao, Wei-Kuo; Simpson, Joanne

    2004-01-01

    Computational phenomena (i.e., spurious supersaturation and negative mixing ratio of cloud water) usually exist in cloud-resolving models when the time step for explicit integration is larger than a microphysical timescale in clouds. In this paper, the microphysical timescales in clouds are studied, showing that the timescale of water vapor condensation (or cloud water evaporation) is smaller than 10 s - the order of a typical time step for cloud-resolving models. To avoid spurious computational phenomena in cloud-resolving modeling, it is suggested that moist entropy be used as a prognostic thermodynamic variable, and temperature be diagnosed from that and other prognostic variables. A simple numerical model with moist entropy as a prognostic variable, for example, is presented to show that spurious computational phenomena are removed when moist entropy is used as a prognostic variable.

  7. Response of vegetation to drought time-scales across global land biomes

    PubMed Central

    Vicente-Serrano, Sergio M.; Gouveia, Célia; Camarero, Jesús Julio; Beguería, Santiago; Trigo, Ricardo; López-Moreno, Juan I.; Azorín-Molina, César; Pasho, Edmond; Lorenzo-Lacruz, Jorge; Revuelto, Jesús; Morán-Tejeda, Enrique; Sanchez-Lorenzo, Arturo

    2013-01-01

    We evaluated the response of the Earth land biomes to drought by correlating a drought index with three global indicators of vegetation activity and growth: vegetation indices from satellite imagery, tree-ring growth series, and Aboveground Net Primary Production (ANPP) records. Arid and humid biomes are both affected by drought, and we suggest that the persistence of the water deficit (i.e., the drought time-scale) could be playing a key role in determining the sensitivity of land biomes to drought. We found that arid biomes respond to drought at short time-scales; that is, there is a rapid vegetation reaction as soon as water deficits below normal conditions occur. This may be due to the fact that plant species of arid regions have mechanisms allowing them to rapidly adapt to changing water availability. Humid biomes also respond to drought at short time-scales, but in this case the physiological mechanisms likely differ from those operating in arid biomes, as plants usually have a poor adaptability to water shortage. On the contrary, semiarid and subhumid biomes respond to drought at long time-scales, probably because plants are able to withstand water deficits, but they lack the rapid response of arid biomes to drought. These results are consistent among three vegetation parameters analyzed and across different land biomes, showing that the response of vegetation to drought depends on characteristic drought time-scales for each biome. Understanding the dominant time-scales at which drought most influences vegetation might help assessing the resistance and resilience of vegetation and improving our knowledge of vegetation vulnerability to climate change. PMID:23248309

  8. Moist Static Energy Budget Analysis on Various Time-scales during TOGA COARE

    NASA Astrophysics Data System (ADS)

    Inoue, K.; Back, L. E.

    2014-12-01

    Temperature variability is small in the tropics, so anomalous moist static energy (MSE) is primarily due to anomalous moisture variability which is tightly connected with precipitation variability. Thus careful analysis of MSE budgets improves our understanding of the dynamics of tropical convection. Previous studies suggested that a recharge-discharge cycle of column-integrated MSE can be observed in the MJO life-cycle and life-cycles of equatorial Kelvin waves. Does this imply that the thermodynamics in the MJO is regulated by a similar process to that of higher frequency variability? To answer this question, we explore the recharge and discharge mechanisms of column-integrated MSE for various time-scales of variability using the TOGA COARE data set. We find that the MSE budgets behave in significantly different ways on the different time-scales. The relative contribution of each MSE budget term to the recharge-discharge mechanism gradually changes as the time-scale gets longer, making the MSE budget behavior on the MJO time-scale distinct from that on the shorter time-scales. For each frequency, we estimate the gross moist stability (GMS), which represents efficiency of MSE export via convection and associated large-scale circulations. The GMS has been used in many MJO studies. One of the popular usages is a linearization of vertical MSE advection in simplified MJO models with an assumption that the GMS is constant. In our analysis, we find that as the time-scale gets longer, the GMS, which is generally a highly variable quantity in a convective life-cycle, becomes a more constant quantity. We show that this more-constant GMS is primarily due to different patterns of the evolution of the vertical velocity profile.

  9. Star Witness News: Albert Einstein, A Genius... Relatively Speaking

    NSDL National Science Digital Library

    This story highlights Albert Einstein’s miracle year when he wrote five scientific papers. Connections are made between Einstein’s work and that of the Hubble Space Telescope. The article is from the Amazing Space science newspaper, The Star Witness, which can be used as a science content reading.

  10. Some new stability properties of dynamic neural networks with different time-scales.

    PubMed

    Yu, Wen; Sandoval, Alejandro Cruz

    2006-06-01

    Dynamic neural networks with different time-scales include the aspects of fast and slow phenomenons. Some applications require that the equilibrium points of these networks to be stable. The main contribution of the paper is that Lyapunov function and singularly perturbed technique are combined to access several new stable properties of different time-scales neural networks. Exponential stability and asymptotic stability are obtained by sector and bound conditions. Compared to other papers, these conditions are simpler. Numerical examples are given to demonstrate the effectiveness of the theoretical results. PMID:17044240

  11. RAS Awards and Prizes: RAS Awards 2009; Gold Medal: Prof. David Williams; Gold Medal: Prof. Eric Priest; Price Medal: Prof. Malcolm Sambridge; Eddington Medal: Prof. James Pringle

    NASA Astrophysics Data System (ADS)

    2009-02-01

    Each year the RAS recognizes outstanding achievement in astronomy and geophysics by the award of medals and prizes. Candidates are nominated by Fellows and the awards made by a committee of Fellows, ensuring that these scientists have earned the respect and admiration of their peers in the research community. The Gold Medal for Astronomy is awarded to Prof. David Williams of University College London. The Gold Medal for Geophysics is awarded to Prof. Eric Priest of the University of St Andrews. The Price Medal is awarded to Prof. Malcolm Sambridge of the Australian National University. The Eddington Medal is given to Prof. James Pringle of the University of Cambridge.

  12. The modification of Einstein`s gravitational field equation following from the energy conservation law

    E-print Network

    Roald Sosnovskiy

    2009-01-16

    The cause of an infringement in GR of a gravitational field energy conservation law is investigated . The equation of a gravitational field not contradicting to the energy conservation law is suggested. This equation satisfy to the Einstein,s requirement of equivalence of all energy kinds as sources of a gravitational field. This equation is solved in paper for cosmic objects. It is showed, that results for some objects - for black holes and gravitating strings-essentialy differ from such for Einstein,s equation, have the symple meaning and do not contradictions.

  13. Quantum reflection of Bose-Einstein Condensates

    E-print Network

    Pasquini, Thomas A., Jr

    2007-01-01

    Recent developments in atom optics have brought Bose-Einstein condensates within 1 pm of solid surfaces where the atom-surface interactions can no longer be ignored. At long- range, the atom-surface interaction is described ...

  14. The creativity of Einstein and astronomy

    NASA Technical Reports Server (NTRS)

    Zeldovich, Y. B.

    1980-01-01

    A discussion of Einstein's scientific achievements for the 100th anniversary of his birth is presented. His works dealing with thermodynamics are described, along with his quantum theory of radiation. Most of the article discusses his general theory of relativity.

  15. Einstein/Roosevelt Letters: A Unit.

    ERIC Educational Resources Information Center

    Bodle, Walter S.

    1985-01-01

    The letters in this unit of study intended for secondary students are facsimile reproductions of the correspondence between Albert Einstein and President Roosevelt on the possibility of constructing an atomic bomb. Classroom activities are also suggested. (RM)

  16. Einstein Light: Galilean Relativity and Newtonian Mechanics

    NSDL National Science Digital Library

    Hatsidimitris, George

    This page of the Einstein Light site presents the concept of an inertial reference frame, along with explanations of Newton's three laws. The site includes a video depicting the principle and is produced at the University of New South Wales.

  17. Einstein--Open Mind, Open Heart.

    ERIC Educational Resources Information Center

    M'Bow, Amadou-Mahtar

    1979-01-01

    This is a part of a presentation made in 1978 at the symposium on the Influence of Modern Scientific Ideas on Society organized by UNESCO in West Germany. An analysis of Einstein's intellectual courage and behavior is discussed. (HM)

  18. Causality in scalar-Einstein waves

    E-print Network

    Mark D. Roberts

    2015-03-13

    A wavelike scalar-Einstein solution is found and indicating vectors constructed from the Bel-Robinson tensor are used to study which objects co-move with the wave and whether gravitational energy transfer is null.

  19. Overview of Special Relativity Einstein's Two Postulates

    E-print Network

    Hart, Gus

    Overview of Special Relativity Einstein's Two Postulates Relativistic mechanics modify Newton vectors: antisymmetric tensor (4-d) 3 #12;Galilean versus Special Relativity Galilean Relativity Special transformations Relativistic equations for mechanics Principle of relativity: the laws of physics apply in all

  20. Coherent decay of Bose-Einstein condensates

    E-print Network

    Cragg, George E. (George Edwin), 1972-

    2006-01-01

    As the coldest form of matter known to exist, atomic Bose-Einstein condensates are unique forms of matter where the constituent atoms lose their individual identities, becoming absorbed into the cloud as a whole. Effectively, ...

  1. Einstein and General Relativity: Historical Perspectives.

    ERIC Educational Resources Information Center

    Chandrasekhar, S.

    1979-01-01

    This paper presented in the 1978 Oppenheimer Memorial Lecture at Los Alamos Scientific Laboratories on August 17, 1978, discusses Einstein's contributions to physics, in particular, his discovery of the general theory of relativity. (HM)

  2. Einstein's Biggest Blunder: A Cosmic Mystery Story

    ScienceCinema

    Lawrence Krauss

    2010-09-01

    The standard model of cosmology built up over 20 years is no longer accepted as accurate. New data suggest that most of the energy density of the universe may be contained in empty space. Remarkably, this is exactly what would be expected if Einstein's cosmological constant really exists. If it does, its origin is the biggest mystery in physics and presents huge challenges for the fundamental theories of elementary particles and fields. Krauss explains Einstein's concept and describes its possible implications.

  3. Teleparallel Killing Vectors of the Einstein Universe

    E-print Network

    M. Sharif; M. Jamil Amir

    2007-08-27

    In this short paper we establish the definition of the Lie derivative of a second rank tensor in the context of teleparallel theory of gravity and also extend it for a general tensor of rank $p+q$. This definition is then used to find Killing vectors of the Einstein universe. It turns out that Killing vectors of the Einstein universe in the teleparallel theory are the same as in General Relativity.

  4. Critical exponents in quantum Einstein gravity

    E-print Network

    S. Nagy; B. Fazekas; L. Juhasz; K. Sailer

    2013-07-02

    The quantum Einstein gravity is treated by the functional renormalization group method using the Einstein-Hilbert action. The ultraviolet non-Gaussian fixed point is determined and its corresponding exponent of the correlation length is calculated for a wide range of regulators. It is shown that the exponent provides a minimal sensitivity to the parameters of the regulator which correspond to the Litim's regulator.

  5. Einstein's Apple: His First Principle of Equivalence

    E-print Network

    Engelbert L. Schucking; Eugene J. Surowitz

    2012-08-09

    After a historical discussion of Einstein's 1907 principle of equivalence, a homogeneous gravitational field in Minkowski spacetime is constructed. It is pointed out that the reference frames in gravitational theory can be understood as spaces with a flat connection and torsion defined through teleparallelism. This kind of torsion was introduced by Einstein in 1928. The concept of torsion is discussed through simple examples and some historical observations.

  6. Timescales of IP3-Evoked Ca2D Spikes Emerge from Ca2D

    E-print Network

    Parker, Ian

    Timescales of IP3-Evoked Ca2D Spikes Emerge from Ca2D Puffs Only at the Cellular Level Kevin behavior generates cellular behavior. Ca2þ signaling by inositol trisphosphate receptors (IP3R) offers interactions between IP3R. Ca2þ released by a cluster of IP3R (giving a local Ca2þ puff) diffuses and ignites

  7. Millennial timescale carbon cycle and climate change in an efficient Earth system model.

    E-print Network

    Edwards, Neil

    Millennial timescale carbon cycle and climate change in an efficient Earth system model. T. M team November 18, 2005 Abstract A new Earth system model, GENIE-1, is presented which comprises a 3-D and for traceability to earlier work. The model versions have climate sensitivity of 2.8-3.3 C and predict atmospheric

  8. Extending Molecular Dynamics Timescales with Milestoning: Example of Complex Kinetics in A

    E-print Network

    Elber, Ron

    1 Extending Molecular Dynamics Timescales with Milestoning: Example of Complex Kinetics straightforward Molecular Dynamics by a factor of about 9, and non- exponential. A general scaling argument-equilibrium motions along one (or a few) degrees of freedom. #12;3 I. Introduction Molecular Dynamics (MD) simulations

  9. Multiple TimeScales in Classical and QuantumClassical Molecular Dynamics

    E-print Network

    Reich, Sebastian

    Multiple Time­Scales in Classical and Quantum­Classical Molecular Dynamics Sebastian Reich \\Lambda October 1, 1998 Abstract The existence of multiple time scales in molecular dynamics poses interesting. The discussion focuses on classical molecular dynamics (CMD) with fast bond stretching and bending modes and the

  10. Understanding the change in the coastal and oceanic winds off Peru at seasonal to interdecadal timescales.

    E-print Network

    Understanding the change in the coastal and oceanic winds off Peru at seasonal to interdecadal,2) , Carlos Ruiz(1) and Carlos Quispe(1) (1)Instituto del Mar del Peru. Esquina Gamarra y Valle S/N.Callao-Peru to the equatorial dynamics, the upwelling off Peru is influenced by climate variability at a variety of timescales

  11. Nonequilibrium, multiple-timescale simulations of ligand-receptor interactions in structured protein systems

    Microsoft Academic Search

    Ying Zhang; Michael H. Peters; Yaohang Li

    2003-01-01

    Predicting the long-time, nonequi- librium dynamics of receptor-ligand interactions for structured proteins in a host fluid is a formi- dable task, but of great importance to predicting and analyzing cell-signaling processes and small molecule drug efficacies. Such processes take place on timescales on the order of milliseconds to sec- onds, so \\

  12. Metal Accretion onto White Dwarfs. I. The Approximate Approach Based on Estimates of Diffusion Timescales

    NASA Astrophysics Data System (ADS)

    Fontaine, G.; Brassard, P.; Dufour, P.; Tremblay, P.-E.

    2015-06-01

    The accretion-diffusion picture is the model par excellence for describing the presence of planetary debris polluting the atmospheres of relatively cool white dwarfs. Some important insights into the process may be derived using an approximate approach which combines static stellar models with estimates of diffusion timescales at the base of the outer convection zone or, in its absence, at the photosphere. Until recently, and to our knowledge, values of diffusion timescales in white dwarfs have all been obtained on the basis of the same physics as that developed initially by Paquette et al., including their diffusion coefficients and thermal diffusion coefficients. In view of the recent exciting discoveries of a plethora of metals (including some never seen before) polluting the atmospheres of an increasing number of cool white dwarfs, we felt that a new look at the estimates of settling timescales would be worthwhile. We thus provide improved estimates of diffusion timescales for all 27 elements from Li to Cu in the periodic table in a wide range of the surface gravity-effective temperature domain and for both DA and non-DA stars.

  13. Transient evolution regimes in a multiscale dynamo model: Timescales of the reversal mechanism

    E-print Network

    Narteau, Clément

    , the electric and magnetic fields affect the fluid's motions through electro- dynamic forces. The fullyTransient evolution regimes in a multiscale dynamo model: Timescales of the reversal mechanism C understand the origin and nature of reversals of the Earth's magnetic field, we examine the reversal

  14. Application of Markov State Models to simulate long timescale dynamics of biological macromolecules.

    PubMed

    Da, Lin-Tai; Sheong, Fu Kit; Silva, Daniel-Adriano; Huang, Xuhui

    2014-01-01

    Conformational changes of proteins are an*Author contributed equally with all other contributors. essential part of many biological processes such as: protein folding, ligand binding, signal transduction, allostery, and enzymatic catalysis. Molecular dynamics (MD) simulations can describe the dynamics of molecules at atomic detail, therefore providing a much higher temporal and spatial resolution than most experimental techniques. Although MD simulations have been widely applied to study protein dynamics, the timescales accessible by conventional MD methods are usually limited to timescales that are orders of magnitude shorter than the conformational changes relevant for most biological functions. During the past decades great effort has been devoted to the development of theoretical methods that may enhance the conformational sampling. In recent years, it has been shown that the statistical mechanics framework provided by discrete-state and -time Markov State Models (MSMs) can predict long timescale dynamics from a pool of short MD simulations. In this chapter we provide the readers an account of the basic theory and selected applications of MSMs. We will first introduce the general concepts behind MSMs, and then describe the existing procedures for the construction of MSMs. This will be followed by the discussions of the challenges of constructing and validating MSMs, Finally, we will employ two biologically-relevant systems, the RNA polymerase and the LAO-protein, to illustrate the application of Markov State Models to elucidate the molecular mechanisms of complex conformational changes at biologically relevant timescales. PMID:24446356

  15. Empirical Study of the Impact of Sampling Timescales and Strategies on Measurement of Available Bandwidth

    E-print Network

    Kaur, Jasleen

    tools have been designed for measuring end-to-end available bandwidth (AB) of a path by injecting probe used. In this paper, we address this issue by studying the impact of the measurement time-scale, tool path. Several tools--henceforth, referred to as AB estimation tools (ABETs)--that measure the end

  16. Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano

    E-print Network

    Boyer, Edmond

    1 Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano T Ferollerie, 45071 Orleans, France Caldera-forming volcanic eruptions are low-frequency, high-impact events of geophysical signals obtained during recent episodes of caldera unrest are difficult to interpret, and not all

  17. Daily foraging cycles create overlapping time-scales in functional responses

    E-print Network

    Giron, David - Institut de Recherche sur la Biologie de l'Insecte, Université François Rabelais

    or constrained by short foraging windows, cannot achieve the behavioural or physiological stationarity assumed1966 Daily foraging cycles create overlapping time-scales in functional responses Jérôme Casas of how predator attack rates vary with prey density are fundamental components of consumer

  18. Shadowing Time-Scale Admission and Power Control for Small Cell Networks

    E-print Network

    Boyer, Edmond

    Shadowing Time-Scale Admission and Power Control for Small Cell Networks Siew Eng Nai, Tony Q. S, Singapore 138632 SUPELEC, 3 rue Joliot-Curie, 91192 Gif-sur-Yvette, France Abstract--Small cell networks problem in two-tier small cell networks. We aim to maximize the number of small cell users that can

  19. Erosion Rates Over Millennial and Decadal Timescales at Caspar Creek and Redwood

    E-print Network

    Standiford, Richard B.

    Erosion Rates Over Millennial and Decadal Timescales at Caspar Creek and Redwood Creek, Northern California1 Ken L. Ferrier,2 James W. Kirchner,3 and Robert C. Finkel4 Erosion rate measurements ecosystems. Traditionally, erosion rates have been determined by measuring stream sediment fluxes over

  20. Solar radiation-induced changes in ionospheric height and the Schumann resonance waveguide on different timescales

    Microsoft Academic Search

    E. R. Williams; G. Sátori

    2007-01-01

    This study draws together the available observations in the Schumann resonance frequency range to examine the general issue of sensitivity of ionospheric height variations to changes in ionizing radiation from the Sun on different timescales. Ionospheric height can be formally defined, and two characteristic heights are recognized in the Schumann resonance frequency range. In general, order of magnitude changes in

  1. Tropospheric ozone variability in the tropics from ENSO to MJO and shorter timescales

    NASA Astrophysics Data System (ADS)

    Ziemke, J. R.; Douglass, A. R.; Oman, L. D.; Strahan, S. E.; Duncan, B. N.

    2015-03-01

    Aura OMI and MLS measurements are combined to produce daily maps of tropospheric ozone beginning October 2004. We show that El Ni no Southern Oscillation (ENSO) related inter-annual change in tropospheric ozone in the tropics is small compared to combined intra-seasonal/Madden-Julian Oscillation (MJO) and shorter timescale variability by a factor ~ 3-10 (largest in the Atlantic). Outgoing Longwave Radiation (OLR) indicates further that deep convection is the primary driver of the observed tropospheric ozone variability from ENSO down to weekly timescales. We compare tropospheric ozone and OLR satellite observations with two simulations: (1) the Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) that uses observed sea surface temperatures and is otherwise free-running, and (2) the NASA Global Modeling Initiative (GMI) chemical transport model (CTM) that is driven by Modern-Era Retrospective Analysis for Research and Applications (MERRA) analyses. It is shown that the CTM-simulated ozone accurately matches measurements for timescales from ENSO to intra-seasonal/MJO and even 1-2 week periods; however (though not unexpected) the CCM simulation reproduces ENSO variability but not shorter timescales. These analyses suggest that using a model to delineate temporal/spatial properties of tropospheric ozone and convection in the tropics will require that the model reproduce the non-ENSO variability that dominates.

  2. Timescales of mixing and mobilisation in the Bishop Tuff magma body: perspectives from diffusion chronometry

    NASA Astrophysics Data System (ADS)

    Chamberlain, Katy J.; Morgan, Daniel J.; Wilson, Colin J. N.

    2014-07-01

    We present two-feldspar thermometry and diffusion chronometry from sanidine, orthopyroxene and quartz from multiple samples of the Bishop Tuff, California, to constrain the temperature stratification within the pre-eruptive magma body and the timescales of magma mixing prior to its evacuation. Two-feldspar thermometry yields estimates that agree well with previous Fe-Ti oxide thermometry and gives a ~80 °C temperature difference between the earlier- and later-erupted regions of the magma chamber. Using the thermometry results, we model diffusion of Ti in quartz, and Ba and Sr in sanidine as well as Fe-Mg interdiffusion in orthopyroxene to yield timescales for the formation of overgrowth rims on these crystal phases. Diffusion profiles of Ti in quartz and Fe-Mg in orthopyroxene both yield timescales of <150 years for the formation of overgrowth rims. In contrast, both Ba and Sr diffusion in sanidine yield nominal timescales 1-2 orders of magnitude longer than these two methods. The main cause for this discrepancy is inferred to be an incorrect assumption for the initial profile shape for Ba and Sr diffusion modelling (i.e. growth zoning exists). Utilising the divergent diffusion behaviour of Ba and Sr, we place constraints on the initial width of the interface and can refine our initial conditions considerably, bringing Ba and Sr data into alignment, and yielding timescales closer to 500 years, the majority of which are then within uncertainty of timescales modelled from Ti diffusion in quartz. Care must be thus taken when using Ba in sanidine geospeedometry in evolved magmatic systems where no other phases or elements are available for comparative diffusion profiling. Our diffusion modelling reveals piecemeal rejuvenation of the lower parts of the Bishop Tuff magma chamber at least 500 years prior to eruption. Timescales from our mineral profiling imply either that diffusion coefficients currently used are uncertain by 1-2 orders of magnitude, or that the minerals concerned did not experience a common history, despite being extracted from the same single pumice clasts. Introduction of the magma initiating crystallisation of the contrasting rims on sanidine, quartz, orthopyroxene and zircon was prolonged, and may be a marker of other processes that initiated the Bishop Tuff eruption rather than the trigger itself.

  3. The Deep Lens Survey Transient Search. I. Short Timescale and Astrometric Variability

    NASA Astrophysics Data System (ADS)

    Becker, A. C.; Wittman, D. M.; Boeshaar, P. C.; Clocchiatti, A.; Dell'Antonio, I. P.; Frail, D. A.; Halpern, J.; Margoniner, V. E.; Norman, D.; Tyson, J. A.; Schommer, R. A.

    2004-08-01

    We report on the methodology and first results from the Deep Lens Survey (DLS) transient search. We utilize image subtraction on survey data to yield all sources of optical variability down to 24th magnitude. Images are analyzed immediately after acquisition, at the telescope, and in near-real time, to allow for follow-up in the case of time-critical events. All classes of transients are posted to the World Wide Web upon detection. Our observing strategy allows sensitivity to variability over several decades in timescale. The DLS is the first survey to classify and report all types of photometric and astrometric variability detected, including solar system objects, variable stars, supernovae, and short timescale phenomena. Three unusual optical transient (OT) events were detected, flaring on 1000 s timescales. All three events were seen in the B passband, suggesting blue color indices for the phenomena. One event (OT 20020115) is determined to be from a flaring Galactic dwarf star of spectral type dM4. From the remaining two events, we find an overall rate of ?=1.4 events deg-2 day-1 on 1000 s timescales, with a 95% confidence limit of ?<4.3. One of these events (OT 20010326) originated from a compact precursor in the field of galaxy cluster A1836, and its nature is uncertain. For the second (OT 20030305) we find strong evidence for an extended extragalactic host. A dearth of such events in the R passband yields an upper 95% confidence limit on short-timescale astronomical variability in the range 19.5

  4. A comparison of solar energetic particle event timescales with properties of associated coronal mass ejections

    SciTech Connect

    Kahler, S. W., E-mail: AFRL.RVB.PA@kirtland.af.mil [Air Force Research Laboratory, Space Vehicles Directorate, 3550 Aberdeen Avenue, Kirtland AFB, NM 87117 (United States)

    2013-06-01

    The dependence of solar energetic proton (SEP) event peak intensities Ip on properties of associated coronal mass ejections (CMEs) has been extensively examined, but the dependence of SEP event timescales is not well known. We define three timescales of 20 MeV SEP events and ask how they are related to speeds v {sub CME} or widths W of their associated CMEs observed by LASCO/SOHO. The timescales of the EPACT/Wind 20 MeV events are TO, the onset time from CME launch to SEP onset; TR, the rise time from onset to half the peak intensity (0.5Ip); and TD, the duration of the SEP intensity above 0.5Ip. This is a statistical study based on 217 SEP-CME events observed during 1996-2008. The large number of SEP events allows us to examine the SEP-CME relationship in five solar-source longitude ranges. In general, we statistically find that TO declines slightly with v {sub CME}, and TR and TD increase with both v {sub CME} and W. TO is inversely correlated with log Ip, as expected from a particle background effect. We discuss the implications of this result and find that a background-independent parameter TO+TR also increases with v {sub CME} and W. The correlations generally fall below the 98% significance level, but there is a significant correlation between v {sub CME} and W which renders interpretation of the timescale results uncertain. We suggest that faster (and wider) CMEs drive shocks and accelerate SEPs over longer times to produce the longer TR and TD SEP timescales.

  5. Timescales of magmatic processes at Ruapehu volcano from diffusion chronometry and their comparison to monitoring data

    NASA Astrophysics Data System (ADS)

    Kilgour, G. N.; Saunders, K. E.; Blundy, J. D.; Cashman, K. V.; Scott, B. J.; Miller, C. A.

    2014-11-01

    Recent eruptions from Mt. Ruapehu have been difficult to predict, despite the presence of a multi-parametric monitoring network. As a result, it is necessary to assess precursory signals prior to an eruption and align those to magmatic processes at depth. Fortuitously, scoria from all historical Ruapehu eruptions contains pyroxene crystals that are strongly reversely zoned in the form of a thin (2 to 3 ?m), outermost rim. These crystals therefore preserved changes in the magmatic system soon before their eruption. We used experimentally determined diffusion coefficients to assess the timescales of magma-magma interaction, and compared those to the monitoring record. Four of the five eruptions analysed (1969, 1971, 1977, 1995) gave diffusion timescales ~ 3 to 5 months before their eruption, with an increased number of crystals recording timescales within 1 month of eruption. Pyroxene crystals from the 1996 eruption record events that occurred prior to and during the 1995 eruption suggesting that the bulk of the 1996 crystals was derived from the 1995 magma. These diffusion timescales do not compare well to a change in any monitoring signal before historical eruptions. However, an examination of recent seismicity (2005-2013) since a significant upgrade (both in number of stations and type of seismometers) showed that two phreatic eruptions in 2006 and 2007 were preceded by a seismic swarm from ~ 5 to 15 km depth, ~ 3 to 5 months before each eruption - consistent with the diffusion timescales. Based on this correlation, deep seismic swarms likely indicate a period of pressurisation in the magmatic system, which may lead to gas-rich, phreatic eruptions.

  6. Einstein's Revolutionary Light-Quantum Hypothesis

    NASA Astrophysics Data System (ADS)

    Stuewer, Roger H.

    2005-05-01

    The paper in which Albert Einstein proposed his light-quantum hypothesis was the only one of his great papers of 1905 that he himself termed ``revolutionary.'' Contrary to widespread belief, Einstein did not propose his light-quantum hypothesis ``to explain the photoelectric effect.'' Instead, he based his argument for light quanta on the statistical interpretation of the second law of thermodynamics, with the photoelectric effect being only one of three phenomena that he offered as possible experimental support for it. I will discuss Einstein's light-quantum hypothesis of 1905 and his introduction of the wave-particle duality in 1909 and then turn to the reception of his work on light quanta by his contemporaries. We will examine the reasons that prominent physicists advanced to reject Einstein's light-quantum hypothesis in succeeding years. Those physicists included Robert A. Millikan, even though he provided convincing experimental proof of the validity of Einstein's equation of the photoelectric effect in 1915. The turning point came after Arthur Holly Compton discovered the Compton effect in late 1922, but even then Compton's discovery was contested both on experimental and on theoretical grounds. Niels Bohr, in particular, had never accepted the reality of light quanta and now, in 1924, proposed a theory, the Bohr-Kramers-Slater theory, which assumed that energy and momentum were conserved only statistically in microscopic interactions. Only after that theory was disproved experimentally in 1925 was Einstein's revolutionary light-quantum hypothesis generally accepted by physicists---a full two decades after Einstein had proposed it.

  7. Einstein's equivalence principle in cosmology

    NASA Astrophysics Data System (ADS)

    Kopeikin, Sergei

    We study physical consequences of the Einstein equivalence principle (EEP) for a Hubble observer in FLRW universe. We introduce the local inertial coordinates with the help of a special conformal transformation. The local inertial metric is Minkowski-flat and materialized by a congruence of time-like geodesics of static observers. The static observers are equipped with the ideal clocks measuring the proper time that is synchronized with the clocks of the Hubble observer. The local inertial metric is used for physical measurements of spacetime intervals with the ideal clocks and rulers. The special conformal transformation preserves null geodesics but does not keep invariant time-like geodesics. Moreover, it makes the rate of the local time coordinate dependent on velocity of the particle which makes impossible to rich the uniform parameterization of the world lines of static observers and light geodesics with a single parameter - they differ by the conformal factor of FLRW metric. It tells us that the metric on the light cone is not Minkowski-flat but depends on the scale factor of FLRW universe and it can be interpreted as a weak violation of EEP for photons. The importance of this violation for gravitational physics is that some of local experiments conducted with freely-propagating electromagnetic waves may be sensitive to the Hubble expansion. We show that the Hubble constant H can be measured within the solar system by means of high-precision spacecraft Doppler tracking as a blue shift of frequency of radio waves circulating in the Earth-spacecraft radio link. We also analyze the behavior of the standing wave in a microwave resonator and show that the standing wave is insensitive to the Hubble expansion.

  8. Einstein@Home all-sky search for periodic gravitational waves in LIGO S5 data

    E-print Network

    J. Aasi; J. Abadie; B. P. Abbott; R. Abbott; T. D. Abbott; M. Abernathy; T. Accadia; F. Acernese; C. Adams; T. Adams; P. Addesso; R. Adhikari; C. Affeldt; M. Agathos; K. Agatsuma; P. Ajith; B. Allen; A. Allocca; E. Amador Ceron; D. Amariutei; S. B. Anderson; W. G. Anderson; K. Arai; M. C. Araya; S. Ast; S. M. Aston; P. Astone; D. Atkinson; P. Aufmuth; C. Aulbert; B. E. Aylott; S. Babak; P. Baker; G. Ballardin; S. Ballmer; Y. Bao; J. C. B. Barayoga; D. Barker; F. Barone; B. Barr; L. Barsotti; M. Barsuglia; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; A. Basti; J. Batch; J. Bauchrowitz; Th. S. Bauer; M. Bebronne; D. Beck; B. Behnke; M. Bejger; M. G. Beker; A. S. Bell; C. Bell; I. Belopolski; M. Benacquista; J. M. Berliner; A. Bertolini; J. Betzwieser; N. Beveridge; P. T. Beyersdorf; T. Bhadbade; I. A. Bilenko; G. Billingsley; J. Birch; R. Biswas; M. Bitossi; M. A. Bizouard; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; B. Bland; M. Blom; O. Bock; T. P. Bodiya; C. Bogan; C. Bond; R. Bondarescu; F. Bondu; L. Bonelli; R. Bonnand; R. Bork; M. Born; V. Boschi; S. Bose; L. Bosi; B. Bouhou; S. Braccini; C. Bradaschia; P. R. Brady; V. B. Braginsky; M. Branchesi; J. E. Brau; J. Breyer; T. Briant; D. O. Bridges; A. Brillet; M. Brinkmann; V. Brisson; M. Britzger; A. F. Brooks; D. A. Brown; T. Bulik; H. J. Bulten; A. Buonanno; J. Burguet--Castell; D. Buskulic; C. Buy; R. L. Byer; L. Cadonati; G. Cagnoli; G. Cagnoli; E. Calloni; J. B. Camp; P. Campsie; K. Cannon; B. Canuel; J. Cao; C. D. Capano; F. Carbognani; L. Carbone; S. Caride; S. Caudill; M. Cavaglià; F. Cavalier; R. Cavalieri; G. Cella; C. Cepeda; E. Cesarini; T. Chalermsongsak; P. Charlton; E. Chassande-Mottin; W. Chen; X. Chen; Y. Chen; A. Chincarini; A. Chiummo; H. S. Cho; J. Chow; N. Christensen; S. S. Y. Chua; C. T. Y. Chung; S. Chung; G. Ciani; F. Clara; D. E. Clark; J. A. Clark; J. H. Clayton; F. Cleva; E. Coccia; P. -F. Cohadon; C. N. Colacino; A. Colla; M. Colombini; A. Conte; R. Conte; D. Cook; T. R. Corbitt; M. Cordier; N. Cornish; A. Corsi; C. A. Costa; M. Coughlin; J. -P. Coulon; P. Couvares; D. M. Coward; M. Cowart; D. C. Coyne; J. D. E. Creighton; T. D. Creighton; A. M. Cruise; A. Cumming; L. Cunningham; E. Cuoco; R. M. Cutler; K. Dahl; M. Damjanic; S. L. Danilishin; S. D'Antonio; K. Danzmann; V. Dattilo; B. Daudert; H. Daveloza; M. Davier; E. J. Daw; R. Day; T. Dayanga; R. De Rosa; D. DeBra; G. Debreczeni; J. Degallaix; W. Del Pozzo; T. Dent; V. Dergachev; R. DeRosa; S. Dhurandhar; L. Di Fiore; A. Di Lieto; I. Di Palma; M. Di Paolo Emilio; A. Di Virgilio; M. Díaz; A. Dietz; A. Dietz; F. Donovan; K. L. Dooley; S. Doravari; S. Dorsher; M. Drago; R. W. P. Drever; J. C. Driggers; Z. Du; J. -C. Dumas; S. Dwyer; T. Eberle; M. Edgar; M. Edwards; A. Effler; P. Ehrens; G. Endröczi; R. Engel; T. Etzel; K. Evans; M. Evans; T. Evans; M. Factourovich; V. Fafone; S. Fairhurst; B. F. Farr; M. Favata; D. Fazi; H. Fehrmann; D. Feldbaum; I. Ferrante; F. Ferrini; F. Fidecaro; L. S. Finn; I. Fiori; R. P. Fisher; R. Flaminio; S. Foley; E. Forsi; N. Fotopoulos; J. -D. Fournier; J. Franc; S. Franco; S. Frasca; F. Frasconi; M. Frede; M. A. Frei; Z. Frei; A. Freise; R. Frey; T. T. Fricke; D. Friedrich; P. Fritschel; V. V. Frolov; M. -K. Fujimoto; P. J. Fulda; M. Fyffe; J. Gair; M. Galimberti; L. Gammaitoni; J. Garcia; F. Garufi; M. E. Gáspár; G. Gelencser; G. Gemme; E. Genin; A. Gennai; L. Á. Gergely; S. Ghosh; J. A. Giaime; S. Giampanis; K. D. Giardina; A. Giazotto; S. Gil-Casanova; C. Gill; J. Gleason; E. Goetz; G. González; M. L. Gorodetsky; S. Goßler; R. Gouaty; C. Graef; P. B. Graff; M. Granata; A. Grant; C. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; C. Griffo; H. Grote; K. Grover; S. Grunewald; G. M. Guidi; C. Guido; R. Gupta; E. K. Gustafson; R. Gustafson; J. M. Hallam; D. Hammer; G. Hammond; J. Hanks; C. Hanna; J. Hanson; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; M. T. Hartman; K. Haughian; K. Hayama; J. -F. Hayau; J. Heefner; A. Heidmann; H. Heitmann; P. Hello; M. A. Hendry; I. S. Heng; A. W. Heptonstall; V. Herrera; M. Heurs; M. Hewitson; S. Hild; D. Hoak; K. A. Hodge; K. Holt; M. Holtrop; T. Hong; S. Hooper; J. Hough; E. J. Howell; B. Hughey; S. Husa; S. H. Huttner; T. Huynh-Dinh; D. R. Ingram; R. Inta; T. Isogai; A. Ivanov; K. Izumi; M. Jacobson; E. James; Y. J. Jang; P. Jaranowski; E. Jesse; W. W. Johnson; D. I. Jones; R. Jones; R. J. G. Jonker; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; G. Kang; J. B. Kanner; M. Kasprzack; R. Kasturi; E. Katsavounidis; W. Katzman; H. Kaufer; K. Kaufman; K. Kawabe; S. Kawamura; F. Kawazoe; D. Keitel; D. Kelley; W. Kells; D. G. Keppel; Z. Keresztes; A. Khalaidovski; F. Y. Khalili; E. A. Khazanov; B. K. Kim; C. Kim; H. Kim; K. Kim; N. Kim; Y. M. Kim; P. J. King; D. L. Kinzel; J. S. Kissel; S. Klimenko; J. Kline; K. Kokeyama; V. Kondrashov; S. Koranda; W. Z. Korth; I. Kowalska

    2012-08-04

    This paper presents results of an all-sky searches for periodic gravitational waves in the frequency range [50, 1190] Hz and with frequency derivative ranges of [-2 x 10^-9, 1.1 x 10^-10] Hz/s for the fifth LIGO science run (S5). The novelty of the search lies in the use of a non-coherent technique based on the Hough-transform to combine the information from coherent searches on timescales of about one day. Because these searches are very computationally intensive, they have been deployed on the Einstein@Home distributed computing project infrastructure. The search presented here is about a factor 3 more sensitive than the previous Einstein@Home search in early S5 LIGO data. The post-processing has left us with eight surviving candidates. We show that deeper follow-up studies rule each of them out. Hence, since no statistically significant gravitational wave signals have been detected, we report upper limits on the intrinsic gravitational wave amplitude h0. For example, in the 0.5 Hz-wide band at 152.5 Hz, we can exclude the presence of signals with h0 greater than 7.6 x 10^-25 with a 90% confidence level.

  9. On (ab)normality: Einstein's fusiform gyrus.

    PubMed

    Weiner, Kevin S

    2015-03-01

    Recently, Hines (2014) wrote an evocative paper challenging findings from both histological and morphological studies of Einstein's brain. In this discussion paper, I extend Hines' theoretical point and further discuss how best to determine 'abnormal' morphology. To do so, I assess the sulcal patterning of Einstein's fusiform gyrus (FG) for the first time. The sulcal patterning of the FG was unconsidered in prior studies because the morphological features of the mid-fusiform sulcus have only been clarified recently. On the one hand, the sulcal patterning of Einstein's FG is abnormal relative to averages of 'normal' brains generated from two independent datasets (N = 39 and N = 15, respectively). On the other hand, within the 108 hemispheres used to make these average brains, it is not impossible to find FG sulcal patterns that resemble those of Einstein. Thus, concluding whether a morphological pattern is normal or abnormal heavily depends on the chosen analysis method (e.g. group average vs. individual). Such findings question the functional meaning of morphological 'abnormalities' when determined by comparing an individual to an average brain or average frequency characteristics. These observations are not only important for analyzing a rare brain such as that of Einstein, but also for comparing macroanatomical features between typical and atypical populations. PMID:25562419

  10. Macroscopic superpositions of Bose-Einstein condensates

    E-print Network

    Janne Ruostekoski; M. J. Collett; Robert Graham; Dan F. Walls

    1997-08-13

    We consider two dilute gas Bose-Einstein condensates with opposite velocities from which a monochromatic light field detuned far from the resonance of the optical transition is coherently scattered. In the thermodynamic limit, when the relative fluctuations of the atom number difference between the two condensates vanish, the relative phase between the Bose-Einstein condensates may be established in a superposition state by detections of spontaneously scattered photons, even though the condensates have initially well-defined atom numbers. For a finite system, stochastic simulations show that the measurements of the scattered photons lead to a randomly drifting relative phase and drive the condensates into entangled superpositions of number states. This is because according to Bose-Einstein statistics the scattering to an already occupied state is enhanced.

  11. Bose-Einstein condensation in microgravity.

    PubMed

    van Zoest, T; Gaaloul, N; Singh, Y; Ahlers, H; Herr, W; Seidel, S T; Ertmer, W; Rasel, E; Eckart, M; Kajari, E; Arnold, S; Nandi, G; Schleich, W P; Walser, R; Vogel, A; Sengstock, K; Bongs, K; Lewoczko-Adamczyk, W; Schiemangk, M; Schuldt, T; Peters, A; Könemann, T; Müntinga, H; Lämmerzahl, C; Dittus, H; Steinmetz, T; Hänsch, T W; Reichel, J

    2010-06-18

    Albert Einstein's insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter. PMID:20558713

  12. Multiple Timescale Dispatch and Scheduling for Stochastic Reliability in Smart Grids with Wind Generation Integration

    E-print Network

    He, Miao; Zhang, Junshan

    2010-01-01

    Integrating volatile renewable energy resources into the bulk power grid is challenging, due to the reliability requirement that at each instant the load and generation in the system remain balanced. In this study, we tackle this challenge for smart grid with integrated wind generation, by leveraging multi-timescale dispatch and scheduling. Specifically, we consider smart grids with two classes of energy users - traditional energy users and opportunistic energy users (e.g., smart meters or smart appliances), and investigate pricing and dispatch at two timescales, via day-ahead scheduling and realtime scheduling. In day-ahead scheduling, with the statistical information on wind generation and energy demands, we characterize the optimal procurement of the energy supply and the day-ahead retail price for the traditional energy users; in realtime scheduling, with the realization of wind generation and the load of traditional energy users, we optimize real-time prices to manage the opportunistic energy users so as...

  13. Elucidation of the timescales and origins of quantum electronic coherence in LHCII

    NASA Astrophysics Data System (ADS)

    Schlau-Cohen, Gabriela S.; Ishizaki, Akihito; Calhoun, Tessa R.; Ginsberg, Naomi S.; Ballottari, Matteo; Bassi, Roberto; Fleming, Graham R.

    2012-05-01

    Photosynthetic organisms harvest sunlight with near unity quantum efficiency. The complexity of the electronic structure and energy transfer pathways within networks of photosynthetic pigment-protein complexes often obscures the mechanisms behind the efficient light-absorption-to-charge conversion process. Recent experiments, particularly using two-dimensional spectroscopy, have detected long-lived quantum coherence, which theory suggests may contribute to the effectiveness of photosynthetic energy transfer. Here, we present a new, direct method to access coherence signals: a coherence-specific polarization sequence, which isolates the excitonic coherence features from the population signals that usually dominate two-dimensional spectra. With this polarization sequence, we elucidate coherent dynamics and determine the overall measurable lifetime of excitonic coherence in the major light-harvesting complex of photosystem II. Coherence decays on two distinct timescales of 47 fs and ~800 fs. We present theoretical calculations to show that these two timescales are from weakly and moderately strongly coupled pigments, respectively.

  14. Timescales of Coherent Dynamics in the Light Harvesting Complex 2 (LH2) of Rhodobacter sphaeroides

    PubMed Central

    Fidler, Andrew F.; Singh, Ved P.; Long, Phillip D.; Dahlberg, Peter D.; Engel, Gregory S.

    2013-01-01

    The initial dynamics of energy transfer in the light harvesting complex 2 from Rhodobacter sphaeroides were investigated with polarization controlled two-dimensional spectroscopy. This method allows only the coherent electronic motions to be observed revealing the timescale of dephasing among the excited states. We observe persistent coherence among all states and assign ensemble dephasing rates for the various coherences. A simple model is utilized to connect the spectroscopic transitions to the molecular structure, allowing us to distinguish coherences between the two rings of chromophores and coherences within the rings. We also compare dephasing rates between excited states to dephasing rates between the ground and excited states, revealing that the coherences between excited states dephase on a slower timescale than coherences between the ground and excited states. PMID:23878622

  15. Time-scale separation: Michaelis and Menten's old idea, still bearing fruit

    PubMed Central

    Gunawardena, Jeremy

    2013-01-01

    Michaelis and Menten introduced to biochemistry the idea of time-scale separation, in which part of a system is assumed to be operating sufficiently fast compared to the rest that it may be assumed to have reached a steady state. This allows, in principle, the fast components to be eliminated, resulting in a simplified description of the system's behaviour. Similar ideas have been widely used in different areas of biology, including enzyme kinetics, protein allostery, receptor pharmacology, gene regulation and post-translational modification. However, the methods used have been independent and ad hoc. Here, we review the use of time-scale separation as a means to simplify the description of molecular complexity and discuss recent work which sets out a single framework which unifies these separate calculations. The framework offers new capabilities for mathematical analysis and helps to do justice to Michaelis and Menten's insights about individual enzymes in the context of multi-enzyme biological systems. PMID:24103070

  16. Slow Cortical Dynamics and the Accumulation of Information over Long Timescales

    PubMed Central

    Honey, Christopher J.; Thesen, Thomas; Donner, Tobias H.; Silbert, Lauren J.; Carlson, Chad E.; Devinsky, Orrin; Doyle, Werner K.; Rubin, Nava; Heeger, David J.; Hasson, Uri

    2012-01-01

    SUMMARY Making sense of the world requires us to process information over multiple timescales. We sought to identify brain regions that accumulate information over short and long timescales and to characterize the distinguishing features of their dynamics. We recorded electrocorticographic (ECoG) signals from individuals watching intact and scrambled movies. Within sensory regions, fluctuations of high-frequency (64–200 Hz) power reliably tracked instantaneous low-level properties of the intact and scrambled movies. Within higher order regions, the power fluctuations were more reliable for the intact movie than the scrambled movie, indicating that these regions accumulate information over relatively long time periods (several seconds or longer). Slow (<0.1 Hz) fluctuations of high-frequency power with time courses locked to the movies were observed throughout the cortex. Slow fluctuations were relatively larger in regions that accumulated information over longer time periods, suggesting a connection between slow neuronal population dynamics and temporally extended information processing. PMID:23083743

  17. Estimating Black Carbon Aging Time-Scales with a Particle-Resolved Aerosol Model

    SciTech Connect

    Riemer, Nicole; West, Matt; Zaveri, Rahul A.; Easter, Richard C.

    2010-01-13

    Understanding the aging process of aerosol particles is important for assessing their chemical reactivity, cloud condensation nuclei activity, radiative properties and health impacts. In this study we investigate the aging of black carbon containing particles in an idealized urban plume using a new approach, the particleresolved aerosol model PartMC-MOSAIC. We present a method to estimate aging time-scales using an aging criterion based on cloud condensation nuclei activation. The results show a separation into a daytime regime where condensation dominates and a nighttime regime where coagulation dominates. For the chosen urban plume scenario, depending on the supersaturation threshold, the values for the aging timescales vary between 0.06 hours and 10 hours during the day, and between 6 hours and 20 hours during the night.

  18. Time-Scale and Noise Optimality in Self-Organized Critical Adaptive Networks

    E-print Network

    Kuehn, Christian

    2011-01-01

    Recent studies have shown that adaptive networks driven by simple local rules can organize into "critical" global steady states, thereby providing another framework for self-organized criticality (SOC). Here we study SOC in an adaptive network considered first by Bornholdt and Rohlf [PRL, 84(26), p.6114-6117, 2000]. We focus on the important convergence to criticality and discover time-scale and noise optimal behaviour as well as a noise-induced phase transition. Due to the complexity of adaptive networks dynamics we suggest to investigate each effect separately by developing simple models. These models reveal three generically possible low-dimensional dynamical behaviors: time-scale resonance (TR), a simplified version of stochastic resonance - which call steady state stochastic resonance (SSR) - as well as noise-induced phase transitions. Thereby, our study not only opens up new directions for optimality in SOC but also applies to a much wider class of dynamical systems.

  19. Timescales and mechanisms of fluid infiltration in a marble: an ion microprobe study

    Microsoft Academic Search

    Colin M. Graham; John W. Valley; John M. Eiler; Hideki Wada

    1998-01-01

    Using a recently developed ion microprobe technique, a detailed oxygen isotope map of calcite grains in a coarse-grained\\u000a marble has been constructed, supported by trace element (Mn, Sr, Fe) analysis and cathodoluminescence (CL) imaging, in order\\u000a to constrain scales of oxygen isotope equilibrium, timescales and mechanisms of metamorphic fluid infiltration, and fluid\\u000a sources and pathways. Results are compared with a

  20. Oceanic and atmospheric response to climate change over varying geologic timescales 

    E-print Network

    Woodard, Stella C.

    2012-07-16

    of the requirements for the degree of DOCTOR OF PHILOSOPHY May 2011 Major Subject: Oceanography Oceanic and Atmospheric Response to Climate Change Over Varying Geologic Timescales Copyright 2011 Stella C. Woodard... for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Deborah J. Thomas Committee Members, Ethan Grossman Mitchell Lyle Franco Marcantonio Niall Slowey Head of Department, Piers Chapman May 2011 Major Subject: Oceanography...

  1. Factors Affecting the Fragmentation of Peptide Ions: Metal Cationization and Fragmentation Timescale 

    E-print Network

    Kmiec, Kevin

    2012-10-19

    of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2012 Major Subject: Chemistry Factors Affecting the Fragmentation of Peptide Ions: Metal Cationization and Fragmentation Timescale Copyright 2011... group as he showed me the ropes of one of the more difficult experiments in the Russell Group, photodissociation tandem time-of-flight mass spectrometry. Jody inspired me to become more interested in mass spectrometry instrument development...

  2. Timescale modification of speech based on short-time Fourier analysis

    Microsoft Academic Search

    M. Portnoff

    1981-01-01

    This paper develops the theoretical basis for time-scale modification of speech based on short-time Fourier analysis. The goal is the development of a high-quality system for changing the apparent rate of articulation of recorded speech, while at the same time preserving such qualities as naturalness, intelligibility, and speaker-dependent features. The results of the theoretical study were used as the framework

  3. Optimal detection using bilinear time-frequency and time-scale representations

    Microsoft Academic Search

    A. M. Sayeed; D. L. Jones

    1995-01-01

    Bilinear time-frequency representations (TFRs) and time-scale representations (TSRs) are potentially very useful for detecting a nonstationary signal in the presence of nonstationary noise or interference. As quadratic signal representations, they are promising for situations in which the optimal detector is a quadratic function of the observations. All existing time-frequency formulations of quadratic detection either implement classical optimal detectors equivalently in

  4. Naturally rare versus newly rare: demographic inferences on two timescales inform conservation of Galápagos giant tortoises

    PubMed Central

    Garrick, Ryan C; Kajdacsi, Brittney; Russello, Michael A; Benavides, Edgar; Hyseni, Chaz; Gibbs, James P; Tapia, Washington; Caccone, Adalgisa

    2015-01-01

    Long-term population history can influence the genetic effects of recent bottlenecks. Therefore, for threatened or endangered species, an understanding of the past is relevant when formulating conservation strategies. Levels of variation at neutral markers have been useful for estimating local effective population sizes (Ne) and inferring whether population sizes increased or decreased over time. Furthermore, analyses of genotypic, allelic frequency, and phylogenetic information can potentially be used to separate historical from recent demographic changes. For 15 populations of Galápagos giant tortoises (Chelonoidis sp.), we used 12 microsatellite loci and DNA sequences from the mitochondrial control region and a nuclear intron, to reconstruct demographic history on shallow (past ?100 generations, ?2500 years) and deep (pre-Holocene, >10 thousand years ago) timescales. At the deep timescale, three populations showed strong signals of growth, but with different magnitudes and timing, indicating different underlying causes. Furthermore, estimated historical Ne of populations across the archipelago showed no correlation with island age or size, underscoring the complexity of predicting demographic history a priori. At the shallow timescale, all populations carried some signature of a genetic bottleneck, and for 12 populations, point estimates of contemporary Ne were very small (i.e., < 50). On the basis of the comparison of these genetic estimates with published census size data, Ne generally represented ?0.16 of the census size. However, the variance in this ratio across populations was considerable. Overall, our data suggest that idiosyncratic and geographically localized forces shaped the demographic history of tortoise populations. Furthermore, from a conservation perspective, the separation of demographic events occurring on shallow versus deep timescales permits the identification of naturally rare versus newly rare populations; this distinction should facilitate prioritization of management action. PMID:25691990

  5. X-ray Capabilities on the Picosecond Timescale at the Advanced Photon Source

    Microsoft Academic Search

    B. Adams; M. Borland; L. X. Chen; P. Chupas; N. Dashdorj; G. Doumy; E. Dufresne; S. Durbin; H. Dürr; P. Evans; T. Graber; R. Henning; E. P. Kanter; D. Keavney; C. Kurtz; Y. Li; A. M. March; K. Moffat; A. Nassiri; S. H. Southworth; V. Srajer; D. M. Tiede; D. Walko; J. Wang; H. Wen; L. Young; X. Zhang; A. Zholents

    2012-01-01

    The Advanced Photon Source (APS) operates with a timing structure advantageous for ultrafast dynamics experiments and, as a result, X-ray time-resolved studies on the 100-picosecond timescale have flourished. The standard operating mode, 24-bunch mode, runs 65% of the time and a hybrid singlet mode runs 15% of the time, yielding a total of 80% of beamtime easily accessible for studies

  6. Magnetic vortex dynamics on a picosecond timescale in a hexagonal permalloy pattern

    SciTech Connect

    Shim, J.-H.; Kim, D.-H.; Mesler, B.; Moon, J.-H.; Lee, K.-J.; Anderson, E. H.; Fischer, P.

    2009-12-02

    We have observed a motion of magnetic vortex core in a hexagonal Permalloy pattern by means of Soft X-ray microscopy. Pump-probe stroboscopic observation on a picosecond timescale has been carried out after exciting a ground state vortex structure by an external field pulse of 1 ns duration. Vortex core is excited off from the center position of the hexagonal pattern but the analysis of the core trajectory reveals that the motion is nongyrotropic.

  7. Retroactivity Attenuation in BioMolecular Systems Based on Timescale Separation

    Microsoft Academic Search

    Shridhar Jayanthi; Domitilla Del Vecchio

    2011-01-01

    As with several engineering systems, bio-molecular systems display impedance-like effects at interconnections, called retroactivity. In this paper, we propose a mechanism that exploits the natural timescale separation present in bio-molecular systems to attenuate retroactivity. Retroactivity enters the dynamics of a bio-molecular system as a state dependent disturbance multiplied by gains that can be very large. By virtue of the system

  8. A Non-Gaussian Stock Price Model: Options, Credit and a Multi-Timescale Memory

    NASA Astrophysics Data System (ADS)

    Borland, L.

    We review a recently proposed model of stock prices, based on astatistical feedback model that results in a non-Gaussian distribution of price changes. Applications to option pricing and the pricing of debt is discussed. A generalization to account for feedback effects over multiple timescales is also presented. This model reproduces most of the stylized facts (ie statistical anomalies) observed in real financial markets.

  9. Decadal-Timescale Estuarine Geomorphic Change Under Future Scenarios of Climate and Sediment Supply

    Microsoft Academic Search

    Neil K. Ganju; David H. Schoellhamer

    2010-01-01

    Future estuarine geomorphic change, in response to climate change, sea-level rise, and watershed sediment supply, may govern\\u000a ecological function, navigation, and water quality. We estimated geomorphic changes in Suisun Bay, CA, under four scenarios\\u000a using a tidal-timescale hydrodynamic\\/sediment transport model. Computational expense and data needs were reduced using the\\u000a morphological hydrograph concept and the morphological acceleration factor. The four scenarios

  10. Hierarchical structure and multi time-scale in large scale dynamical systems

    Microsoft Academic Search

    Koichi Tojo; Koji Tsumura

    2008-01-01

    In this paper, we deal with approximation methods of large-scale systems which describe the macroscopic behavior of the whole system and simultaneously the partially microscopic one of the objective subsystems. We propose a hierarchical representation of such large-scale systems by employing the connection graph structure of the elements and multiple time-scale dynamics. The approximation accuracy is rigorously induced and numerical

  11. New time-scale criteria for model simplification of bio-reaction systems

    Microsoft Academic Search

    Junwon Choi; Kyung-won Yang; Tai-yong Lee; Sang Yup Lee

    2008-01-01

    BACKGROUND: Quasi-steady state approximation (QSSA) based on time-scale analysis is known to be an effective method for simplifying metabolic reaction system, but the conventional analysis becomes time-consuming and tedious when the system is large. Although there are automatic methods, they are based on eigenvalue calculations of the Jacobian matrix and on linear transformations, which have a high computation cost. A

  12. A versatile microfluidic chip for millisecond time-scale kinetic studies by electrospray mass spectrometry

    Microsoft Academic Search

    Tamanna Rob; Derek J. Wilson

    2009-01-01

    An electrospray coupled microfluidic reactor for the measurement of millisecond time-scale, solution phase kinetics is introduced.\\u000a The device incorporates a simple two-channel design that is etched into polymethyl methacrylate (PMMA) by laser ablation.\\u000a The outlet of the device is laser cut to a sharp tip, facilitating low dead volume ‘on chip’ electrospray. Fabrication is\\u000a fast, straightforward and highly reproducible, supporting

  13. Long-timescale motions in glycerol-monopalmitate lipid bilayers investigated using molecular dynamics simulation.

    PubMed

    Laner, Monika; Horta, Bruno A C; Hünenberger, Philippe H

    2015-02-01

    The occurrence of long-timescale motions in glycerol-1-monopalmitate (GMP) lipid bilayers is investigated based on previously reported 600 ns molecular dynamics simulations of a 2×8×8 GMP bilayer patch in the temperature range 302-338 K, performed at three different hydration levels, or in the presence of the cosolutes methanol or trehalose at three different concentrations. The types of long-timescale motions considered are: (i) the possible phase transitions; (ii) the precession of the relative collective tilt-angle of the two leaflets in the gel phase; (iii) the trans-gauche isomerization of the dihedral angles within the lipid aliphatic tails; and (iv) the flipping of single lipids across the two leaflets. The results provide a picture of GMP bilayers involving a rich spectrum of events occurring on a wide range of timescales, from the 100-ps range isomerization of single dihedral angles, via the 100-ns range of tilt precession motions, to the multi-?s range of phase transitions and lipid-flipping events. PMID:25437095

  14. Relationship between sea level and climate forcing by CO2 on geological timescales

    PubMed Central

    Foster, Gavin L.; Rohling, Eelco J.

    2013-01-01

    On 103- to 106-year timescales, global sea level is determined largely by the volume of ice stored on land, which in turn largely reflects the thermal state of the Earth system. Here we use observations from five well-studied time slices covering the last 40 My to identify a well-defined and clearly sigmoidal relationship between atmospheric CO2 and sea level on geological (near-equilibrium) timescales. This strongly supports the dominant role of CO2 in determining Earth’s climate on these timescales and suggests that other variables that influence long-term global climate (e.g., topography, ocean circulation) play a secondary role. The relationship between CO2 and sea level we describe portrays the “likely” (68% probability) long-term sea-level response after Earth system adjustment over many centuries. Because it appears largely independent of other boundary condition changes, it also may provide useful long-range predictions of future sea level. For instance, with CO2 stabilized at 400–450 ppm (as required for the frequently quoted “acceptable warming” of 2 °C), or even at AD 2011 levels of 392 ppm, we infer a likely (68% confidence) long-term sea-level rise of more than 9 m above the present. Therefore, our results imply that to avoid significantly elevated sea level in the long term, atmospheric CO2 should be reduced to levels similar to those of preindustrial times. PMID:23292932

  15. Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing - Part 2

    NASA Technical Reports Server (NTRS)

    Montgomery, Eliza L.; Calle, Luz Marina; Curran, Jerome C.; Kolody, Mark R.

    2012-01-01

    Evaluation of metals to predict service life of metal-based structures in corrosive environments has long relied on atmospheric exposure test sites. Traditional accelerated corrosion testing relies on mimicking the exposure conditions, often incorporating salt spray and ultraviolet (UV) radiation, and exposing the metal to continuous or cyclic conditions similar to those of the corrosive environment. Their reliability to correlate to atmospheric exposure test results is often a concern when determining the timescale to which the accelerated tests can be related. Accelerated corrosion testing has yet to be universally accepted as a useful tool in predicting the long-term service life of a metal, despite its ability to rapidly induce corrosion. Although visual and mass loss methods of evaluating corrosion are the standard, and their use is crucial, a method that correlates timescales from accelerated testing to atmospheric exposure would be very valuable. This paper presents work that began with the characterization of the atmospheric environment at the Kennedy Space Center (KSC) Beachside Corrosion Test Site. The chemical changes that occur on low carbon steel, during atmospheric and accelerated corrosion conditions, were investigated using surface chemistry analytical methods. The corrosion rates and behaviors of panels subjected to long-term and accelerated corrosion conditions, involving neutral salt fog and alternating seawater spray, were compared to identify possible timescale correlations between accelerated and long-term corrosion performance. The results, as well as preliminary findings on the correlation investigation, are presented.

  16. Multi-band optical-NIR variability of blazars on diverse timescales

    E-print Network

    Agarwal, Aditi; Bachev, R; Strigachev, A; Semkov, E; Wiita, Paul J; Bottcher, M; Boeva, S; Gaur, H; Gu, M F; Peneva, S; Ibryamov, S; Pandey, U S

    2015-01-01

    To search for optical variability on a wide range of timescales, we have carried out photometric monitoring of two flat spectrum radio quasars, 3C 454.3 and 3C 279, plus one BL Lac, S5 0716+714, all of which have been exhibiting remarkably high activity and pronounced variability at all wavelengths. CCD magnitudes in B, V, R and I pass-bands were determined for $\\sim$ 7000 new optical observations from 114 nights made during 2011 - 2014, with an average length of $\\sim$ 4 h each, at seven optical telescopes: four in Bulgaria, one in Greece, and two in India. We measured multiband optical flux and colour variations on diverse timescales. Discrete correlation functions were computed among B, V, R, and I observations, to search for any time delays. We found weak correlations in some cases with no significant time lags. The structure function method was used to estimate any characteristic time-scales of variability. We also investigated the spectral energy distribution of the three blazars using B, V, R, I, J and...

  17. Variability of El Niño/Southern Oscillation activity at millennial timescales during the Holocene epoch.

    PubMed

    Moy, Christopher M; Seltzer, Geoffrey O; Rodbell, Donald T; Anderson, David M

    2002-11-14

    The variability of El Niño/Southern Oscillation (ENSO) during the Holocene epoch, in particular on millennial timescales, is poorly understood. Palaeoclimate studies have documented ENSO variability for selected intervals in the Holocene, but most records are either too short or insufficiently resolved to investigate variability on millennial scales. Here we present a record of sedimentation in Laguna Pallcacocha, southern Ecuador, which is strongly influenced by ENSO variability, and covers the past 12,000 years continuously. We find that changes on a timescale of 2-8 years, which we attribute to warm ENSO events, become more frequent over the Holocene until about 1,200 years ago, and then decline towards the present. Periods of relatively high and low ENSO activity, alternating at a timescale of about 2,000 years, are superimposed on this long-term trend. We attribute the long-term trend to orbitally induced changes in insolation, and suggest internal ENSO dynamics as a possible cause of the millennial variability. However, the millennial oscillation will need to be confirmed in other ENSO proxy records. PMID:12432388

  18. Exchanged ridge demodulation of time-scale manifold for enhanced fault diagnosis of rotating machinery

    NASA Astrophysics Data System (ADS)

    Wang, Jun; He, Qingbo

    2014-05-01

    The vibration or acoustic signal from rotating machinery with localized fault usually behaves as the form of amplitude modulation (AM) and/or frequency modulation (FM). The demodulation techniques are conventional ways to reveal the fault characteristics from the analyzed signals. One of these techniques is the time-scale manifold (TSM) ridge demodulation method with the merits of good time-frequency localization and in-band noise suppression properties. However, due to the essential attribute of wavelet ridge, the survived in-band noise on the achieved TSM will still disturb the envelope extraction of fault-induced impulses. This paper presents an improved TSM ridge demodulation method, called exchanged ridge demodulation of TSM, by combining the benefits of the first two TSMs: the noise suppression of the first TSM and the noise separation of the second TSM. Specifically, the ridge on the second TSM can capture the fault-induced impulses precisely while avoiding the in-band noise smartly. By putting this ridge on the first TSM, the corresponding instantaneous amplitude (IA) waveform can represent the real envelope of pure faulty impulses. Moreover, an adaptive selection method for Morlet wavelet parameters is also proposed based on the smoothness index (SI) in the time-scale domain for an optimal time-scale representation of analyzed signal. The effectiveness of the proposed method is verified by means of a simulation study and applications to diagnosis of bearing defects and gear fault.

  19. Simulating oligomerization at experimental concentrations and long timescales: A Markov state model approach

    NASA Astrophysics Data System (ADS)

    Kelley, Nicholas W.; Vishal, V.; Krafft, Grant A.; Pande, Vijay S.

    2008-12-01

    Here, we present a novel computational approach for describing the formation of oligomeric assemblies at experimental concentrations and timescales. We propose an extension to the Markovian state model approach, where one includes low concentration oligomeric states analytically. This allows simulation on long timescales (seconds timescale) and at arbitrarily low concentrations (e.g., the micromolar concentrations found in experiments), while still using an all-atom model for protein and solvent. As a proof of concept, we apply this methodology to the oligomerization of an A? peptide fragment (A?21-43). A? oligomers are now widely recognized as the primary neurotoxic structures leading to Alzheimer's disease. Our computational methods predict that A? trimers form at micromolar concentrations in 10ms, while tetramers form 1000 times more slowly. Moreover, the simulation results predict specific intermonomer contacts present in the oligomer ensemble as well as putative structures for small molecular weight oligomers. Based on our simulations and statistical models, we propose a novel mutation to stabilize the trimeric form of A? in an experimentally verifiable manner.

  20. Tree imbalance causes a bias in phylogenetic estimation of evolutionary timescales using heterochronous sequences.

    PubMed

    Duchêne, David; Duchêne, Sebastian; Ho, Simon Y W

    2015-07-01

    Phylogenetic estimation of evolutionary timescales has become routine in biology, forming the basis of a wide range of evolutionary and ecological studies. However, there are various sources of bias that can affect these estimates. We investigated whether tree imbalance, a property that is commonly observed in phylogenetic trees, can lead to reduced accuracy or precision of phylogenetic timescale estimates. We analysed simulated data sets with calibrations at internal nodes and at the tips, taking into consideration different calibration schemes and levels of tree imbalance. We also investigated the effect of tree imbalance on two empirical data sets: mitogenomes from primates and serial samples of the African swine fever virus. In analyses calibrated using dated, heterochronous tips, we found that tree imbalance had a detrimental impact on precision and produced a bias in which the overall timescale was underestimated. A pronounced effect was observed in analyses with shallow calibrations. The greatest decreases in accuracy usually occurred in the age estimates for medium and deep nodes of the tree. In contrast, analyses calibrated at internal nodes did not display a reduction in estimation accuracy or precision due to tree imbalance. Our results suggest that molecular-clock analyses can be improved by increasing taxon sampling, with the specific aims of including deeper calibrations, breaking up long branches and reducing tree imbalance. PMID:25431227

  1. The Response of Giant Stars to Dynamical-timescale Mass Loss

    NASA Astrophysics Data System (ADS)

    Passy, Jean-Claude; Herwig, Falk; Paxton, Bill

    2012-11-01

    We study the response of giant stars to mass loss. One-dimensional simulations of red and asymptotic giant branch stars with mass loss rates from 10-3 up to a few M ?yr-1 show in no case any significant radius increase. The largest radius increase of 0.2% was found in the case with the lowest mass loss rate. For dynamical-timescale mass loss rates that may be encountered during a common envelope phase, the evolution is not adiabatic. The superadiabatic outer layer of the giant's envelope has a local thermal timescale comparable to the dynamical timescale. Therefore, this layer has enough time to readjust thermally. Moreover, the giant star is driven out of hydrostatic equilibrium and evolves dynamically. In these cases no increase of the stellar radius with respect to its initial value is found. If the mass loss rate is high enough, the superadiabaticity of the outer layer is lost progressively and a radiative zone forms due to a combination of thermal and dynamical readjustment. Conditions for unstable mass transfer based on adiabatic mass loss models that predict a significant radius increase may need to be re-evaluated.

  2. The Einstein on-line service

    E-print Network

    Harris, D E; Andernach, H; Harris, D E; Grant, C S

    1994-01-01

    The Einstein On-Line Service (EOLS) is a simple menu-driven system which provides an intuitive method of querying over one hundred database catalogs. In addition, the EOLS contains over 30 CDROMs of images from the Einstein X-ray Observatory which are available for downloading. The EOLS provides all of our databases to the NASA Astrophysics Data System (ADS) and our documents which describe each table are written in the ADS format. In conjunction with the IAU working group on Radioastronomical Databases, the EOLS serves as an experimental platform for on-line access to radio source catalogs. The number of entries in these catalogs exceeds half a million.

  3. Collisions of Einstein-Conformal Scalar Waves

    E-print Network

    C. Klim?{\\'?}k; P. Koln{\\'?}k

    1992-12-18

    A large class of solutions of the Einstein-conformal scalar equations in D=2+1 and D=3+1 is identified. They describe the collisions of asymptotic conformal scalar waves and are generated from Einstein-minimally coupled scalar spacetimes via a (generalized) Bekenstein transformation. Particular emphasis is given to the study of the global properties and the singularity structure of the obtained solutions. It is shown, that in the case of the absence of pure gravitational radiation in the initial data, the formation of the final singularity is not only generic, but is even inevitable.

  4. Einstein gravity on the codimension 2 brane?

    PubMed

    Bostock, Paul; Gregory, Ruth; Navarro, Ignacio; Santiago, Jose

    2004-06-01

    We look at general brane worlds in six-dimensional Einstein-Gauss-Bonnet gravity. We find the general matching conditions for the brane world, which remarkably give precisely the four-dimensional Einstein equations for the brane, even when the extra dimensions are noncompact and have infinite volume. Relaxing regularity of the curvature in the vicinity of the brane, or having a thick brane, gives rise to an additional term containing information on the brane's embedding in the bulk. We comment on the relevance of these results to a possible solution of the cosmological constant problem. PMID:15245210

  5. An axiomatic approach to Einstein's boxes

    E-print Network

    Thomas V Marcella

    2006-06-17

    The fallacies inherent in the Einstein's Boxes thought experiment are made evident by taking an axiomatic approach to quantum mechanics while ignoring notions not supported by the postulates or by experimental observation. We emphasize that the postulates contain everything needed to completely describe a quantum experiment. We discuss the non-classical nature of both the state vector and the experiment that it represents. Einstein's Boxes is then described by the formalism alone. We see that it is no different from any other experiment in which a two-state observable is measured.

  6. Bose-Einstein condensation: Twenty years after

    E-print Network

    Bagnato, V S; Kevrekidis, P G; Malomed, B A; Mihalache, D

    2015-01-01

    The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.

  7. Buffer-Gas Cooled Bose-Einstein Condensate

    E-print Network

    Ketterle, Wolfgang

    We report the creation of a Bose-Einstein condensate using buffer-gas cooling, the first realization of Bose-Einstein condensation using a broadly general method which relies neither on laser cooling nor unique atom-surface ...

  8. ??Rubidium Bose-Einstein condensates in optical lattices

    E-print Network

    Campbell, Gretchen K. (Gretchen Kathleen)

    2007-01-01

    Bose-Einstein condensates in optical lattices have proven to be a powerful tool for studying a wide variety of physics. In this thesis a series of experiments using optical lattices to manipulate 87Rb Bose-Einstein condensates ...

  9. On the Nature of the Prototype Luminous Blue Variable AG Carinae. II. Witnessing a Massive Star Evolving Close to the Eddington and Bistability Limits

    NASA Astrophysics Data System (ADS)

    Groh, J. H.; Hillier, D. J.; Damineli, A.

    2011-07-01

    We show that the significantly different effective temperatures (T eff) achieved by the luminous blue variable AG Carinae during the consecutive visual minima of 1985-1990 (T eff ~= 22,800 K) and 2000-2001 (T eff ~= 17,000 K) place the star on different sides of the bistability limit, which occurs in line-driven stellar winds around T eff ~ 21,000 K. Decisive evidence is provided by huge changes in the optical depth of the Lyman continuum in the inner wind as T eff changes during the S Dor cycle. These changes cause different Fe ionization structures in the inner wind. The bistability mechanism is also related to the different wind parameters during visual minima: the wind terminal velocity was 2-3 times higher and the mass-loss rate roughly two times smaller in 1985-1990 than in 2000-2003. We obtain a projected rotational velocity of 220 ± 50 km s-1 during 1985-1990 which, combined with the high luminosity (L sstarf = 1.5 × 106 L sun), puts AG Car extremely close to the Eddington limit modified by rotation (?? limit): for an inclination angle of 90°, ?? >~ 1.0 for M sun <~ 60. Based on evolutionary models and mass budget, we obtain an initial mass of ~100 M sun and a current mass of ~60-70 M sun for AG Car. Therefore, AG Car is close to, if not at, the ?? limit during visual minimum. Assuming M = 70 M sun, we find that ?? decreases from 0.93 to 0.72 as AG Car expands toward visual maximum, suggesting that the star is not above the Eddington limit during maximum phases.

  10. Timescales of Porphyry Cu Formation: Bajo de la Alumbrera, NW Argentina

    NASA Astrophysics Data System (ADS)

    Buret, Y.; Von Quadt, A.; Heinrich, C. A.; Peytcheva, I.

    2014-12-01

    Using high-precision U-Pb dating we are potentially able to determine timescales of porphyry emplacement and ore formation. Previous studies have suggested timescales of porphyry Cu formation ranging from <100 yr, based on modelling diffusive equilibrium between fluids and altered rocks [1], to as much as 1 Ma using U-Pb LA-ICP-MS and SHRIMP dating techniques on zircons [2], [3]. In contrast recent numerical simulations suggest Cu precipitation occurs in the range of 50-100 ka [4]. Therefore in order to better constrain timescales of porphyry Cu formation, we apply high precision U-Pb zircon geochronology, using the youngest zircon date to estimate the emplacement age of each porphyry [5].This study focuses on the ~7 Ma Bajo de la Alumbrera Cu-Au deposit, NW Argentina. The deposit consists of a composite stock of dacitic porphyries. The relative timing of each porphyry intrusion is established based on clear cross-cutting relationships between different porphyry intrusions, which include the pre-mineralisation P2 porphyry, pre-syn-minerlisation EP3 porphyry, and the post-mineralisation LP3 and P4 porphyries.Single zircon crystals from individual porphyry intrusions (P2, EP3, LP3, P4) in the Alumbrera deposit have been dated using CA-ID-TIMS, employing the ET2535 tracer solution for maximum precision and accuracy. All porphyries display protracted zircon crystal growth over 100-200 ka timescales. Using the youngest zircons from each of the porphyry intrusions, Cu mineralisation occurred on 10 ka timescales, similar to those proposed by recent numerical predictions [4]. Trace element and Hf isotopic analyses may reveal geochemical distinctions within the porphyry intrusions and record temporal changes in the magmatic evolution. References: [1] Cathles and Shannon (2007) EPSL 262:92-108; [2] Ballard et al. (2001) Geology 29:383-386; [3] Harris et al. (2008) Min Dep 43: 295-314; [4] Weis et al. (2012) Science 338: 1613-1616; [5] von Quadt et al. (2011) Geology 39: 731-734.

  11. Zu den Einstein-Schrödingerschen Feldgleichungen mit Materie

    NASA Astrophysics Data System (ADS)

    Treder, Hans-Jürgen

    Die physikalische Bedeutung des Materietensors in der unitären Feldtheorie von Einstein und Schrödinger wird diskutiert.Translated AbstractOn the Einstein-Schrödinger Field Equations with MatterA discussion of the physical meaning of sources of the Einstein-Schrödinger unified field theory.

  12. NEW EXAMPLES OF HOMOGENEOUS EINSTEIN METRICS MEGAN M. KERR

    E-print Network

    Kerr, Megan M.

    NEW EXAMPLES OF HOMOGENEOUS EINSTEIN METRICS MEGAN M. KERR 1. Introduction A Riemannian metric is said to be Einstein if the Ricci curvature is a constant multiple of the metric. Given a manifold M , one can ask whether M carries an Einstein metric, and if so, how many. This fundamental question

  13. Special Relativity in a Nutshell Basic Postulates: Einstein 1905

    E-print Network

    Peters, Achim

    COSMOLOGY Special Relativity in a Nutshell Basic Postulates: Einstein 1905 All observers moving Lect. 4 R 138 #12;COSMOLOGY Special Relativity in a Nutshell Basic Postulates: Einstein 1905 All;COSMOLOGY Special Relativity in a Nutshell Basic Postulates: Einstein 1905 All observers moving uniformly

  14. The Einstein All-Sky Slew Survey

    NASA Technical Reports Server (NTRS)

    Elvis, Martin S.

    1992-01-01

    The First Einstein IPC Slew Survey produced a list of 819 x-ray sources, with f(sub x) approximately 10(exp -12) - 10(exp -10) erg/sq cm s and positional accuracy of approximately 1.2 feet (90 percent radius). The aim of this program was to identify these x-ray sources.

  15. Entanglement equilibrium and the Einstein equation

    E-print Network

    Jacobson, Ted

    2015-01-01

    We show that the semiclassical Einstein equation holds if and only if the entanglement entropy in small causal diamonds is stationary at constant volume, when varied from a maximally symmetric vacuum state of geometry and quantum fields. The argument hinges on a conjecture about the variation of the conformal boost energy of quantum fields in small diamonds.

  16. Entanglement equilibrium and the Einstein equation

    E-print Network

    Ted Jacobson

    2015-05-18

    We show that the semiclassical Einstein equation holds if and only if the entanglement entropy in small causal diamonds is stationary at constant volume, when varied from a maximally symmetric vacuum state of geometry and quantum fields. The argument hinges on a conjecture about the variation of the conformal boost energy of quantum fields in small diamonds.

  17. Sasaki-Einstein Manifolds and Volume Minimisation

    E-print Network

    Dario Martelli; James Sparks; Shing-Tung Yau

    2008-04-23

    We study a variational problem whose critical point determines the Reeb vector field for a Sasaki-Einstein manifold. This extends our previous work on Sasakian geometry by lifting the condition that the manifolds are toric. We show that the Einstein-Hilbert action, restricted to a space of Sasakian metrics on a link L in a Calabi-Yau cone X, is the volume functional, which in fact is a function on the space of Reeb vector fields. We relate this function both to the Duistermaat-Heckman formula and also to a limit of a certain equivariant index on X that counts holomorphic functions. Both formulae may be evaluated by localisation. This leads to a general formula for the volume function in terms of topological fixed point data. As a result we prove that the volume of a Sasaki-Einstein manifold, relative to that of the round sphere, is always an algebraic number. In complex dimension n=3 these results provide, via AdS/CFT, the geometric counterpart of a-maximisation in four dimensional superconformal field theories. We also show that our variational problem dynamically sets to zero the Futaki invariant of the transverse space, the latter being an obstruction to the existence of a Kahler-Einstein metric.

  18. Chromohydrodynamics in Einstein-Cartan theory

    SciTech Connect

    Amorim, R.

    1986-05-15

    The complete dynamical system for a classical fluid endowed with non-Abelian charge density is obtained by using variational techniques. Spin density appears in a natural way, as a consequence of a usual gauge construction. Einstein-Cartan, Yang-Mills, and generalized Wong equations are explicitly shown.

  19. Multiple-soliton solutions of Einstein's equations

    SciTech Connect

    Economou, A.; Tsoubelis, D.

    1989-07-01

    Using the Belinsky--Zakharov generating technique and a flat metric as aseed, two- and four-soliton solutions of the Einstein vacuum equations for thecases of stationary axisymmetric, cylindrically symmetric, or plane symmetricgravitational fields are considered. Three- and five-parameter classes of exactsolutions are obtained, some of which are new.

  20. Momentum conservation and Einstein's 1905 Gedankenexperiment

    Microsoft Academic Search

    Dragan V. Redzic

    2005-01-01

    Einstein's original Gedankenexperiment leading to the relation between inertial mass and rest energy is analysed in a new perspective, applying the principle of conservation of momentum. The analysis implies both the relativistic momentum and mass-energy relation in a simple way.

  1. Einstein-Yang-Mills theory: Asymptotic symmetries

    NASA Astrophysics Data System (ADS)

    Barnich, Glenn; Lambert, Pierre-Henry

    2013-11-01

    Asymptotic symmetries of the Einstein-Yang-Mills system with or without cosmological constant are explicitly worked out in a unified manner. In agreement with a recent conjecture, one finds a Virasoro-Kac-Moody type algebra not only in three dimensions but also in the four-dimensional asymptotically flat case.

  2. Infrared fixed point in quantum Einstein gravity

    E-print Network

    S. Nagy; J. Krizsan; K. Sailer

    2012-06-28

    We performed the renormalization group analysis of the quantum Einstein gravity in the deep infrared regime for different types of extensions of the model. It is shown that an attractive infrared point exists in the broken symmetric phase of the model. It is also shown that due to the Gaussian fixed point the IR critical exponent $\

  3. The Economist on 100 years of Einstein

    Microsoft Academic Search

    Thomas Colignatus

    2005-01-01

    An important aspect for economics and its methodology is the relation between its definitions and the reality that those definitions (should) reflect. Creative minds coin definitions that maximize explanatory power. An example that highlights this phenomenon can be found in physics and notably by the article in The Economist January 1 2005 on 100 years of Einstein. Physics with its

  4. A REAPPRAISAL OF THE EINSTEIN MODEL

    Microsoft Academic Search

    Rati Ram Sharma

    A wave exists only in its propagating medium but Einstein erred to discard the medium for 'light-wave' and introduce 4-D spacetime continuum. It denied him the chance to address wave- quantum Unity of light and to predict the existence of 'basic substance' to compose all forms of E & m so compellingly demanded by E=mc2, otherwise E & m could

  5. Einstein-aether gravity: a status report

    Microsoft Academic Search

    Ted Jacobson

    2008-01-01

    This paper reviews the theory, phenomenology, and observational constraints on the coupling parameters of Einstein-aether gravity, i.e. General Relativity coupled to a dynamical unit timelike vector field. A discussion of open questions concerning both phenomenology and fundamental issues is included.

  6. Einstein and a century of time

    Microsoft Academic Search

    D. J. Raine

    2005-01-01

    In a world overabundant in information, a subject is defined by its iconography. Physics is the falling apple, the planetary atom, the laser, the mushroom cloud and the image of the later Einstein - images that represent, respectively, gravity, atomic theory, quantum theory, mass-energy and the scientist who had a hand in all four. It is therefore appropriate that World

  7. Einstein's Revolutionary Light--Quantum Hypothesis

    Microsoft Academic Search

    R. H. Stuewer

    2006-01-01

    Albert Einstein's light-quantum paper was the only one of his great papers of 1905 that he himself called ``very revolutionary''. I sketch his arguments for light quanta, his analysis of the photoelectric effect, and his introduction of the wave-particle duality into physics in 1909. I show that Robert Andrews Millikan, in common with almost all physicists at the time, rejected

  8. The Excellence of Einstein's Theory of Gravitation.

    ERIC Educational Resources Information Center

    Dirac, P. A. M.

    1979-01-01

    This article is adapted from a presentation made in 1978 at the symposium on the Impact of Modern Scientific Ideas on Society organized by UNESCO in Ulm, West Germany. It discusses Einstein's theory of gravitation and how it started a new line of activity for physicists. (HM)

  9. Passing the Einstein-Rosen bridge

    E-print Network

    M. O. Katanaev

    2013-10-28

    We relax the requirement of geodesic completeness of a space-time. Instead, we require test particles trajectories to be smooth only in the physical sector. Test particles trajectories for Einstein--Rosen bridge are proved to be smooth in the physical sector, and particles can freely penetrate the bridge in both directions.

  10. General proof of entropy principle in Einstein-Maxwell theory

    E-print Network

    Fang, Xiongjun

    2015-01-01

    We consider a static self-gravitating charged perfect fluid system in the Einstein-Maxwell theory. Assume Maxwell's equation and the Einstein constraint equation are satisfied, and the temperature of the fluid obeys Tolman's law. Then we prove that the total entropy of the fluid achieves an extremum implies other components of Einstein's equation for any variations of metric and electrical potential with fixed boundary values. Conversely, if Einstein's equation and Maxwell's equations hold, the total entropy achieves an extremum. Our work suggests that the maximum entropy principle is consistent with Einstein's equation when electric field is taken into account.

  11. Discovery of a ~5 Day Characteristic Timescale in the Kepler Power Spectrum of Zw 229-15

    NASA Astrophysics Data System (ADS)

    Edelson, R.; Vaughan, S.; Malkan, M.; Kelly, B. C.; Smith, K. L.; Boyd, P. T.; Mushotzky, R.

    2014-11-01

    We present time series analyses of the full Kepler data set of Zw 229-15. This Kepler light curve—with a baseline greater than 3 yr, composed of virtually continuous, evenly sampled 30 minute measurements—is unprecedented in its quality and precision. We utilize two methods of power spectral analysis to investigate the optical variability and search for evidence of a bend frequency associated with a characteristic optical variability timescale. Each method yields similar results. The first interpolates across data gaps to use the standard Fourier periodogram. The second, using the CARMA-based time-domain modeling technique of Kelly et al., does not need evenly sampled data. Both methods find excess power at high frequencies that may be due to Kepler instrumental effects. More importantly, both also show strong bends (?? ~ 2) at timescales of ~5 days, a feature similar to those seen in the X-ray power spectral densities of active galactic nuclei (AGNs) but never before in the optical. This observed ~5 day timescale may be associated with one of several physical processes potentially responsible for the variability. A plausible association could be made with light-crossing dynamical or thermal timescales depending on the assumed value of the accretion disk size and on unobserved disk parameters such as ? and H/R. This timescale is not consistent with the viscous timescale, which would be years in a ~107 M ? AGN such as Zw 229-15. However, there must be a second bend on long (gsim 1 yr) timescales and that feature could be associated with the viscous timescale.

  12. Trends and Correlation Estimation in Climate Sciences: Effects of Timescale Errors

    NASA Astrophysics Data System (ADS)

    Mudelsee, M.; Bermejo, M. A.; Bickert, T.; Chirila, D.; Fohlmeister, J.; Köhler, P.; Lohmann, G.; Olafsdottir, K.; Scholz, D.

    2012-12-01

    Trend describes time-dependence in the first moment of a stochastic process, and correlation measures the linear relation between two random variables. Accurately estimating the trend and correlation, including uncertainties, from climate time series data in the uni- and bivariate domain, respectively, allows first-order insights into the geophysical process that generated the data. Timescale errors, ubiquitious in paleoclimatology, where archives are sampled for proxy measurements and dated, poses a problem to the estimation. Statistical science and the various applied research fields, including geophysics, have almost completely ignored this problem due to its theoretical almost-intractability. However, computational adaptations or replacements of traditional error formulas have become technically feasible. This contribution gives a short overview of such an adaptation package, bootstrap resampling combined with parametric timescale simulation. We study linear regression, parametric change-point models and nonparametric smoothing for trend estimation. We introduce pairwise-moving block bootstrap resampling for correlation estimation. Both methods share robustness against autocorrelation and non-Gaussian distributional shape. We shortly touch computing-intensive calibration of bootstrap confidence intervals and consider options to parallelize the related computer code. Following examples serve not only to illustrate the methods but tell own climate stories: (1) the search for climate drivers of the Agulhas Current on recent timescales, (2) the comparison of three stalagmite-based proxy series of regional, western German climate over the later part of the Holocene, and (3) trends and transitions in benthic oxygen isotope time series from the Cenozoic. Financial support by Deutsche Forschungsgemeinschaft (FOR 668, FOR 1070, MU 1595/4-1) and the European Commission (MC ITN 238512, MC ITN 289447) is acknowledged.

  13. Relationship of fast- and slow-timescale neuronal dynamics in human MEG and SEEG.

    PubMed

    Zhigalov, Alexander; Arnulfo, Gabriele; Nobili, Lino; Palva, Satu; Palva, J Matias

    2015-04-01

    A growing body of evidence suggests that the neuronal dynamics are poised at criticality. Neuronal avalanches and long-range temporal correlations (LRTCs) are hallmarks of such critical dynamics in neuronal activity and occur at fast (subsecond) and slow (seconds to hours) timescales, respectively. The critical dynamics at different timescales can be characterized by their power-law scaling exponents. However, insight into the avalanche dynamics and LRTCs in the human brain has been largely obtained with sensor-level MEG and EEG recordings, which yield only limited anatomical insight and results confounded by signal mixing. We investigated here the relationship between the human neuronal dynamics at fast and slow timescales using both source-reconstructed MEG and intracranial stereotactical electroencephalography (SEEG). Both MEG and SEEG revealed avalanche dynamics that were characterized parameter-dependently by power-law or truncated-power-law size distributions. Both methods also revealed robust LRTCs throughout the neocortex with distinct scaling exponents in different functional brain systems and frequency bands. The exponents of power-law regimen neuronal avalanches and LRTCs were strongly correlated across subjects. Qualitatively similar power-law correlations were also observed in surrogate data without spatial correlations but with scaling exponents distinct from those of original data. Furthermore, we found that LRTCs in the autonomous nervous system, as indexed by heart-rate variability, were correlated in a complex manner with cortical neuronal avalanches and LRTCs in MEG but not SEEG. These scalp and intracranial data hence show that power-law scaling behavior is a pervasive but neuroanatomically inhomogeneous property of neuronal dynamics in central and autonomous nervous systems. PMID:25834062

  14. Eruption and emplacement timescales of ignimbrite super-eruptions from thermo-kinetics of glass shards

    NASA Astrophysics Data System (ADS)

    Lavallée, Yan; Wadsworth, Fabian; Vasseur, Jérémie; Russell, James; Andrews, Graham; Hess, Kai-Uwe; von Aulock, Felix; Kendrick, Jackie; Tuffen, Hugh; Biggin, Andy; Dingwell, Donald

    2015-02-01

    Super-eruptions generating hundreds of cubic kilometres of pyroclastic density currents are commonly recorded by thick, welded and lava-like ignimbrites. Despite the huge environmental impact inferred for this type of eruption, little is yet known about the timescales of deposition and post-depositional flow. Without these timescales, the critical question of the duration of any environmental impact, and the ensuing gravity of its effects for the Earth system, eludes us. The eruption and welding of ignimbrites requires three transects of the glass transition. Magma needs to: 1) fragment during ascent, 2) liquefy and relax during deposition, agglutination and welding (sintering), and 3) quench by cooling into the glassy state. Here we show that welding is a rapid, syn-depositional process and that the welded ignimbrite sheet may flow for up to a few hours before passing through the glass transition a final time. Geospeedometry reveals that the basal vitrophyre of the Grey’s Landing ignimbrite underwent the glass transition at a rate of ~0.1 °C.min^-1 at 870 °C; that is, 30-180 °C below pre-eruptive geothermometric estimates. Application of a 1-D cooling model constrains the timescale of deposition, agglutination, and welding of the basal vitrophyre to less than 1 hour, and possibly even tens of minutes. Thermo-mechanical iteration of the sintering process indicates an optimal temperature solution for the emplacement of the vitrophyres at 966 °C. The vitrophyres reveal a Newtonian rheology up to 46 MPa, which suggests that the ash particles annealed entirely during welding and that viscous energy dissipation is unlikely from loading conditions alone, unless shear stresses imposed by the overlying ash flow were excessively high and sustained over long distances. The findings underline the value of the term 'lava-like' flow to describe the end rheology of Snake River-type ignimbrites, fully consistent with the typical lithofacies observed.

  15. Coupling between annual and ENSO timescales in the malaria-climate association in Colombia.

    PubMed Central

    Poveda, G; Rojas, W; Quiñones, M L; Vélez, I D; Mantilla, R I; Ruiz, D; Zuluaga, J S; Rua, G L

    2001-01-01

    We present evidence that the El Niño phenomenon intensifies the annual cycle of malaria cases for Plasmodium vivax and Plasmodium falciparum in endemic areas of Colombia as a consequence of concomitant anomalies in the normal annual cycle of temperature and precipitation. We used simultaneous analyses of both variables at both timescales, as well as correlation and power spectral analyses of detailed spatial (municipal) and temporal (monthly) records. During "normal years," endemic malaria in rural Colombia exhibits a clear-cut "normal" annual cycle, which is tightly associated with prevalent climatic conditions, mainly mean temperature, precipitation, dew point, and river discharges. During historical El Niño events (interannual time scale), the timing of malaria outbreaks does not change from the annual cycle, but the number of cases intensifies. Such anomalies are associated with a consistent pattern of hydrological and climatic anomalies: increase in mean temperature, decrease in precipitation, increase in dew point, and decrease in river discharges, all of which favor malaria transmission. Such coupling explains why the effect appears stronger and more persistent during the second half of El Niño's year (0), and during the first half of the year (+1). We illustrate this finding with data for diverse localities in Buenaventura (on the Pacific coast) and Caucasia (along the Cauca river floodplain), but conclusions have been found valid for multiple localities throughout endemic regions of Colombia. The identified coupling between annual and interannual timescales in the climate-malaria system shed new light toward understanding the exact linkages between environmental, entomological, and epidemiological factors conductive to malaria outbreaks, and also imposes the coupling of those timescales in public health intervention programs. PMID:11401760

  16. Assessment of Large-scale Terrestrial Water Storage Dynamics at Multiple Timescales from Multiple Sources

    NASA Astrophysics Data System (ADS)

    Yeh, P. J.

    2009-12-01

    Among global water cycle components, Terrestrial Water Storage (TWS) is one of the most difficult to estimate. Despite its importance in affecting global circulation of atmosphere and ocean and shaping weather and climate of the Earth, there are no extensive in-situ networks existent for monitoring large-scale TWS variations. At present, three methods are most commonly used to estimate large-scale TWS variations. First, the atmospheric column-integrated water vapor convergence provides a global distribution of precipitation minus evapotranspiration. The combined land-atmosphere water balance computation can be used to estimate the temporal change of spatially averaged TWS over large areas. Second, satellite observations of Earth’s time-variable gravity field from the Gravity Recovery and Climate Experiment (GRACE) mission provides a unique opportunity of monitoring TWS variations from space. Short-term (monthly, seasonal, and interannual) temporal variations in gravity on land are largely due to corresponding changes in vertically integrated TWS. Third, land surface hydrologic modeling is perhaps the only available tool to estimate TWS variations at any temporal and spatial scales, provided that the land surface models used are well constrained by realistic meteorological forcing and satellite- and ground-based observational data. Previous estimates on TWS found in literature focused only on the long-term climatology or monthly to seasonal timescales. In this study, large-scale TWS variations are estimated over selected world largest river basins by using combining atmospheric-land water balance computation at daily, monthly, seasonal and interannual timescales from 1984-2006. The estimates are then compared with direct observations (only in Illinois), land surface model simulations, and GRACE TWS data. The ultimate goal is to provide a quantitative assessment on the dynamics controlling the propagation of hydroclimatic anomalies across the atmospheric and terrestrial branches of regional hydrology from daily to interannual timescales.

  17. An 8 h characteristic time-scale in submillimetre light curves of Sagittarius A*

    NASA Astrophysics Data System (ADS)

    Dexter, Jason; Kelly, Brandon; Bower, Geoffrey C.; Marrone, Daniel P.; Stone, Jordan; Plambeck, Richard

    2014-08-01

    We compile and analyse long-term (?10 yr) submillimetre (submm - 1.3, 0.87, 0.43 mm) wavelength light curves of the Galactic Centre black hole, Sagittarius A*. The 0.87 and 0.43 mm data are taken from the literature, while the majority of the 1.3 mm light curve is from previously unpublished SMA and CARMA data. We show that on minute to a few hour time-scales, the variability is consistent with a red noise process with a 230 GHz power-spectrum slope of ? =2.3^{+0.8}_{-0.6} at 95 per cent confidence. The light curve is decorrelated (white noise) on long (month to year) times. We measure a transition time between red and white noise of ? = 8_{-4}^{+3} h at 230 GHz at 95 per cent confidence, with consistent results at 345 and 690 GHz. This corresponds to ?10 orbital times or ?1 inflow (viscous) time at R = 3Rs, a typical radius producing the 230 GHz emission as measured by very long baseline interferometry and found in theoretical accretion flow and jet models. This time-scale is shorter (longer) than those measured by some analyses of radio (near-infrared) light curves. It is roughly consistent with the analogous time-scale inferred in studies of quasar optical light curves after accounting for the difference in emission radius. We find evidence that the submm variability persists at least down to the innermost stable circular orbit, if not the event horizon. These results can be compared quantitatively with similar analyses at different wavebands to test for connections between the variability mechanisms, and with light curves from theoretical models of accreting black holes.

  18. Timescales of bubble coalescence, outgassing, and foam collapse in decompressed rhyolitic melts

    NASA Astrophysics Data System (ADS)

    Martel, Caroline; Iacono-Marziano, Giada

    2015-02-01

    The timescale of degassing and outgassing in hydrous rhyolitic melts is investigated in a wide range of conditions by means of decompression experiments. The evolution of vesicularity, bubble diameter, and number density is characterized as a function of time either of decompression or spent at final pressure, in order to determine the effect of final pressure, temperature, syn- versus post-decompression degassing, melt composition, and microlites, on the timescale of bubble growth, coalescence, and outgassing. The result suggests that different bubble evolution and degassing-outgassing timescale corresponding to explosive and effusive eruption regimes can be cast in bulk viscosity (melt + bubbles; ?bulk) versus decompression time (rather than path) space. The ?bulk-time relationship defines three domains of (i) bubble nucleation and growth, restricted to short durations and high ?bulk (< ? 0.03 h for ?bulk ?105-6 Pas), (ii) equilibrium degassing with coalescence increasing from negligible (permeability >10-13m2) to extensive (permeability ?10 - 11- 12m2), and (iii) outgassing, restricted to long durations and low ?bulk (> ? 10 h for ?bulk <106 Pas; permeability >10-10m2) that eventually leads to foam collapse. These findings are applied to the case studies of Mt Pelée and Mt Pinatubo to infer the transition from pumice to dense pyroclasts in volcanic eruptions and the possibility of evolving from an explosive Plinian eruption to an effusive dome-growth event by giving the vesicular magma enough time to outgas and collapse (i.e. hundreds to tens of hours for ?bulk ?105 to 104 Pas, respectively). We also show the drastic effect of microlites on re-arranging preexistent bubbles and potentially triggering a late nucleation event.

  19. Lagged processes and critical timescales in boreal forest response to climate

    NASA Astrophysics Data System (ADS)

    Wofsy, S. C.; Dunn, A. L.; Amiro, B. D.; Barr, A.; Rocha, A. V.; Goulden, M. L.

    2006-12-01

    Long-term eddy covariance datasets have recorded the response of boreal ecosystems to climate on timescales up to decadal (Dunn et al. 2006, Barr et al. 2006). Carbon balances in these forests are very dynamic, responding to climatic anomalies on timescales of months to years. A boreal black spruce forest in central Manitoba, Canada, was a source of carbon to the atmosphere in the mid-1990s (55 g C m^{- 2} y-1, 1995-1997), but switched to a sink in recent years (-25 g C m-2 y-1, 2003-2005). The short-term carbon exchange at this site was strongly controlled by temperature, but on long timescales the water balance was more important (Dunn et al. 2006). In a boreal aspen forest in central Saskatchewan, Canada, temperature was the main driver of phenology and canopy duration, but drought status, and especially the persistence of drought over multiple years, was a critical control on ecosystem respiration and resultant carbon balance (Barr et al. 2006). Lagged processes are especially important in the boreal forest: Dunn et al. (2006) found that carbon balances, and especially ecosystem respiration, were strongly controlled by the integrated water balance over preceding years, suggesting that the effects of climatic anomalies are expressed slowly in these forests. Rocha et al. (2006) found similar evidence in tree-ring cores from the NOBS site, which showed a strong correlation with lagged water balances, suggesting that wood growth in these forests is a process integrating over prior years. In a tree-ring analysis across aspen stands in western Canada, Hogg et al. (2005) found that current and lagged (up to four years) moisture status were critical factors regulating ecosystem carbon balance. These results from long-term boreal datasets suggest that the vulnerability of these forests to climate change will be strongly dependent on the future balance between precipitation and temperature. Persistent perturbations to the local climate will likely shift overall biome carbon balance.

  20. Microphysical Timescales in Clouds and their Application in Cloud-Resolving Modeling

    NASA Technical Reports Server (NTRS)

    Zeng, Xiping; Tao, Wei-Kuo; Simpson, Joanne

    2007-01-01

    Independent prognostic variables in cloud-resolving modeling are chosen on the basis of the analysis of microphysical timescales in clouds versus a time step for numerical integration. Two of them are the moist entropy and the total mixing ratio of airborne water with no contributions from precipitating particles. As a result, temperature can be diagnosed easily from those prognostic variables, and cloud microphysics be separated (or modularized) from moist thermodynamics. Numerical comparison experiments show that those prognostic variables can work well while a large time step (e.g., 10 s) is used for numerical integration.

  1. Iterative time series prediction and analysis by embedding and multiple time-scale decomposition networks

    NASA Astrophysics Data System (ADS)

    Hazarika, Neep; Lowe, David

    1997-04-01

    In this work we describe a method of estimating and characterizing appropriate data and model complexity in the context of long term iterated time series forecasting using embeddings and multiple time-scale decomposition techniques. An embedding of a signal is obtained which decouples multiple time scale effects such as seasonality and trend. The complexity and stability of networks are estimated and the performance of long term iteration is examined. The performance of the technique is tested using the real world time series problems of electricity load forecasting, and financial futures contracts.

  2. Was Einstein Really a Pacifist? Einstein's Independent, Forward-Thinking, Flexible, and Self-Defined Pacifism

    NASA Astrophysics Data System (ADS)

    Holmes, Virginia Iris

    2005-03-01

    Perhaps motivated by an admiration for Einstein and a desire to identify with him, combined with a majority world-view in opposition to pacifism, skeptics may often question whether Einstein was really a pacifist. They might point to the fact that his dramatic contributions to the field of physics at the beginning of the twentieth century made nuclear weapons possible, as well as his 1939 letter to President Franklin D. Roosevelt urging him to develop such weapons before the Nazis would, as examples of at least an inconsistent stance on pacifism across time on Einstein's part. However, as this paper will show, Einstein's pacifism began early in his life, was a deep-seated conviction that he expressed repeatedly across the years, and was an independent pacifism that flowed from his own responses to events around him and contained some original and impressively forward-thinking elements. Moreover, in calling himself a pacifist, as Einstein did, he defined pacifism in his own terms, not according to the standards of others, and this self-defined pacifism included the flexibility to designate the Nazis as a special case that had to be opposed through the use of military violence, in his view. As early as during his childhood, Einstein already disliked competitive games, because of the necessity of winners and losers, and disliked military discipline. In his late thirties, living in Germany during the First World War with a prestigious academic position in Berlin, yet retaining his identity as a Swiss citizen, Einstein joined a small group of four intellectuals who signed the pacifist ``Appeal to the Europeans'' in response to the militarist ``Manifesto to the Civilized World'' signed by 93 German intellectuals. In private, throughout that War, Einstein repeatedly expressed his disgust and sense of alienation at the ``war-enthusiasm'' sentiment of the majority. In the aftermath of the War, Einstein was involved in a German private commission to investigate German war crimes and the publication that it produced, and throughout the Weimar period of 1918 to 1933 Einstein continued to take public and private stances as a pacifist. As did many pacifists, Einstein also linked his advocacy for peace with a concern for social justice, which included opposition to antisemitism and advocacy for Zionism, and in 1929, after violent clashes between Jews and Arabs in Palestine, in which hundreds died on both sides, Einstein made some impressively forward-thinking statements about Jewish-Arab conciliation, and even published in an Arab newspaper his own proposal to set up a joint Jewish-Arab council for purposes of conflict resolution. But Einstein's pacifism was not forever obliterated by the Nazi era and the Holocaust, despite his well-known encouragement to Roosevelt to develop the bomb. In the United States, where he lived from 1933 on, in the first ten years after World War II, also the last decade of his life, Einstein inspired American pacifists with his strong stances against war and nuclear weapons.

  3. Lorentzian Einstein metrics with prescribed conformal infinity

    E-print Network

    Alberto Enciso; Niky Kamran

    2014-12-14

    We prove that there are asymptotically anti-de Sitter Einstein metrics with prescribed conformal infinity. More precisely we show that, given any suitably small perturbation $\\hat g$ of the conformal metric of the $(n+1)$-dimensional anti-de Sitter space at timelike infinity, which is given by the canonical Lorentzian metric on the $n$-dimensional cylinder, there is a Lorentzian Einstein metric on $(-T,T)\\times \\mathbb{B}^n$ whose conformal geometry is given by $\\hat g$. This is a Lorentzian counterpart of the Graham-Lee theorem in Riemannian geometry and is motivated by the holographic prescription problem in the context of the AdS/CFT correspondence in string theory.

  4. Nonlinear cosmological power spectrum in Einstein's gravity

    SciTech Connect

    Noh, Hyerim; Hwang, Jai-chan [Korea Astronomy and Space Science Institute, Daejon (Korea, Republic of); Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Taegu (Korea, Republic of)

    2008-06-15

    Is Newton's gravity sufficient to handle the weakly nonlinear evolution stages of the large-scale cosmic structures? Here we resolve the issue by analytically deriving the density and velocity power spectra to the second order in the context of Einstein's gravity. The recently found pure general relativistic corrections appearing in the third-order perturbation contribute to power spectra to the second order. In this work the complete density and velocity power spectra to the second order are derived. The power transfers among different scales in the density power spectrum are estimated in the context of Einstein's gravity. The relativistic corrections in the density power spectrum are estimated to be smaller than the Newtonian one to the second order, but these could be larger than higher-order nonlinear Newtonian terms.

  5. Quantifying Einstein-Podolsky-Rosen steering.

    PubMed

    Skrzypczyk, Paul; Navascués, Miguel; Cavalcanti, Daniel

    2014-05-01

    Einstein-Podolsky-Rosen steering is a form of bipartite quantum correlation that is intermediate between entanglement and Bell nonlocality. It allows for entanglement certification when the measurements performed by one of the parties are not characterized (or are untrusted) and has applications in quantum key distribution. Despite its foundational and applied importance, Einstein-Podolsky-Rosen steering lacks a quantitative assessment. Here we propose a way of quantifying this phenomenon and use it to study the steerability of several quantum states. In particular, we show that every pure entangled state is maximally steerable and the projector onto the antisymmetric subspace is maximally steerable for all dimensions; we provide a new example of one-way steering and give strong support that states with positive-partial transposition are not steerable. PMID:24856679

  6. Taming the Nonlinearity of the Einstein Equation

    NASA Astrophysics Data System (ADS)

    Harte, Abraham I.

    2014-12-01

    Many of the technical complications associated with the general theory of relativity ultimately stem from the nonlinearity of Einstein's equation. It is shown here that an appropriate choice of dynamical variables may be used to eliminate all such nonlinearities beyond a particular order: Both Landau-Lifshitz and tetrad formulations of Einstein's equation are obtained that involve only finite products of the unknowns and their derivatives. Considerable additional simplifications arise in physically interesting cases where metrics become approximately Kerr or, e.g., plane waves, suggesting that the variables described here can be used to efficiently reformulate perturbation theory in a variety of contexts. In all cases, these variables are shown to have simple geometrical interpretations that directly relate the local causal structure associated with the metric of interest to the causal structure associated with a prescribed background. A new method to search for exact solutions is outlined as well.

  7. The Semiclassical Einstein Equation on Cosmological Spacetimes

    E-print Network

    Siemssen, Daniel

    2015-01-01

    The subject of this thesis is the coupling of quantum fields to a classical gravitational background in a semiclassical fashion. It contains a thorough introduction into quantum field theory on curved spacetime with a focus on the stress-energy tensor and the semiclassical Einstein equation. Basic notions of differential geometry, topology, functional and microlocal analysis, causality and general relativity will be summarised, and the algebraic approach to QFT on curved spacetime will be reviewed. Apart from these foundations, the original research of the author and his collaborators will be presented: Together with Fewster, the author studied the up and down structure of permutations using their decomposition into so-called atomic permutations. The relevance of these results to this thesis is their application in the calculation of the moments of quadratic quantum fields. In a work with Pinamonti, the author showed the local and global existence of solutions to the semiclassical Einstein equation in flat co...

  8. Axions: Bose Einstein Condensate or Classical Field?

    E-print Network

    Sacha Davidson

    2014-12-20

    The axion is a motivated dark matter candidate, so it would be interesting to find features in Large Scale Structures specific to axion dark matter. Such features were proposed for a Bose Einstein condensate of axions, leading to confusion in the literature (to which I contributed) about whether axions condense due to their gravitational interactions. This note argues that the Bose Einstein condensation of axions is a red herring: the axion dark matter produced by the misalignment mechanism is already a classical field, which has the distinctive features attributed to the axion condensate (BE condensates are described as classical fields). This note also estimates that the rate at which axion particles condense to the field, or the field evaporates to particles, is negligeable.

  9. Taming the nonlinearity of the Einstein equation.

    PubMed

    Harte, Abraham I

    2014-12-31

    Many of the technical complications associated with the general theory of relativity ultimately stem from the nonlinearity of Einstein's equation. It is shown here that an appropriate choice of dynamical variables may be used to eliminate all such nonlinearities beyond a particular order: Both Landau-Lifshitz and tetrad formulations of Einstein's equation are obtained that involve only finite products of the unknowns and their derivatives. Considerable additional simplifications arise in physically interesting cases where metrics become approximately Kerr or, e.g., plane waves, suggesting that the variables described here can be used to efficiently reformulate perturbation theory in a variety of contexts. In all cases, these variables are shown to have simple geometrical interpretations that directly relate the local causal structure associated with the metric of interest to the causal structure associated with a prescribed background. A new method to search for exact solutions is outlined as well. PMID:25615299

  10. Impacts of Variability and Uncertainty in Solar Photovoltaic Generation at Multiple Timescales

    SciTech Connect

    Ela, E.; Diakov, V.; Ibanez, E.; Heaney, M.

    2013-05-01

    The characteristics of variability and uncertainty of PV solar power have been studied extensively. These characteristics can create challenges for system operators who must ensure a balance between generation and demand while obeying power system constraints at the lowest possible cost. A number of studies have looked at the impact of wind power plants, and some recent studies have also included solar PV. The simulations that are used in these studies, however, are typically fixed to one time resolution. This makes it difficult to analyze the variability across several timescales. In this study, we use a simulation tool that has the ability to evaluate both the economic and reliability impacts of PV variability and uncertainty at multiple timescales. This information should help system operators better prepare for increases of PV on their systems and develop improved mitigation strategies to better integrate PV with enhanced reliability. Another goal of this study is to understand how different mitigation strategies and methods can improve the integration of solar power more reliably and efficiently.

  11. Constraints on Black Hole Masses with Timescales of Variations in Blazars

    NASA Astrophysics Data System (ADS)

    Liu, H. T.; Bai, J. M.

    2015-06-01

    In this paper, we investigated the issue of black hole masses and minimum timescales of jet emission for blazars. We proposed a sophisticated model that sets an upper limit to the central black hole masses {{M}\\bullet } with the minimum timescales {? }tmin ob of variations observed in blazars. The value of {? }tmin ob presents an upper limit to the size of the blob in the jet. The blob is assumed to be generated in the jet-production region in the vicinity of the black hole, and then the expanding blob travels outward along the jet. We applied the model to 32 blazars, 29 of which were detected in gamma-rays by satellites, and these {? }tmin ob are on the order of hours, with large variability amplitudes. In general, the {{M}\\bullet } estimated with this method are not inconsistent with those masses reported in the literature. This model is natural for connecting {{M}\\bullet } with {? }tmin ob for blazars, and seems to be applicable in constraining {{M}\\bullet } in the central engines of blazars.

  12. Statistical Characterization of Solar Photovoltaic Power Variability at Small Timescales: Preprint

    SciTech Connect

    Shedd, S.; Hodge, B.-M.; Florita, A.; Orwig, K.

    2012-08-01

    Integrating large amounts of variable and uncertain solar photovoltaic power into the electricity grid is a growing concern for power system operators in a number of different regions. Power system operators typically accommodate variability, whether from load, wind, or solar, by carrying reserves that can quickly change their output to match the changes in the solar resource. At timescales in the seconds-to-minutes range, this is known as regulation reserve. Previous studies have shown that increasing the geographic diversity of solar resources can reduce the short term-variability of the power output. As the price of solar has decreased, the emergence of very large PV plants (greater than 10 MW) has become more common. These plants present an interesting case because they are large enough to exhibit some spatial smoothing by themselves. This work examines the variability of solar PV output among different arrays in a large ({approx}50 MW) PV plant in the western United States, including the correlation in power output changes between different arrays, as well as the aggregated plant output, at timescales ranging from one second to five minutes.

  13. Bridging physiological and evolutionary time-scales in a gene regulatory network.

    PubMed

    Marchand, Gwenaëlle; Huynh-Thu, Vân Anh; Kane, Nolan C; Arribat, Sandrine; Varès, Didier; Rengel, David; Balzergue, Sandrine; Rieseberg, Loren H; Vincourt, Patrick; Geurts, Pierre; Vignes, Matthieu; Langlade, Nicolas B

    2014-07-01

    Gene regulatory networks (GRNs) govern phenotypic adaptations and reflect the trade-offs between physiological responses and evolutionary adaptation that act at different time-scales. To identify patterns of molecular function and genetic diversity in GRNs, we studied the drought response of the common sunflower, Helianthus annuus, and how the underlying GRN is related to its evolution. We examined the responses of 32,423 expressed sequences to drought and to abscisic acid (ABA) and selected 145 co-expressed transcripts. We characterized their regulatory relationships in nine kinetic studies based on different hormones. From this, we inferred a GRN by meta-analyses of a Gaussian graphical model and a random forest algorithm and studied the genetic differentiation among populations (FST ) at nodes. We identified two main hubs in the network that transport nitrate in guard cells. This suggests that nitrate transport is a critical aspect of the sunflower physiological response to drought. We observed that differentiation of the network genes in elite sunflower cultivars is correlated with their position and connectivity. This systems biology approach combined molecular data at different time-scales and identified important physiological processes. At the evolutionary level, we propose that network topology could influence responses to human selection and possibly adaptation to dry environments. PMID:24786523

  14. Transport Timescales in the Lowermost Stratosphere: Observations and Results from ECHAM5/MESSy

    NASA Astrophysics Data System (ADS)

    Hoor, P.; Fischer, H.; Joeckel, P.; Lelieveld, J.; Brenninkmeijer, C.; Gurk, C.; Hegglin, M. I.; Brunner, D.; Krebsbach, M.; Schiller, C.; Bruehl, C.; Steil, B.

    2006-12-01

    We present a comparison of high resolution in-situ measurements in the lowermost stratosphere over Europe and model results obtained with the new chemistry circulation model ECHAM5/MESSy. Model calculations were performed using T42 spectral resolution and 90 vertical levels from the surface up to 80 km providing a vertical resolution of about 600 m in the extratropical lowermost stratosphere. The model was nudged in the troposphere up to 200 hPa using operational ECMWF data. We compare in particular CO, CO2, N2O and O3 data with in-situ observations from SPURT between 2001 and 2003 with corresponding model data interpolated in time and space. Trace gas profiles and correlations of in-situ observations and modelled data show a remarkable agreement. To deduce transport time scales we compare probability density functions of trace gases in different layers relative to the dynamical tropopause and on N2O-isopleths. To extend the data to a global scale and investigate transport time scales we will use NMVOC data from CARIBIC and compare them with model derived data. The CO2 seasonal cycle and its propagation in the stratosphere provides further information on transport timescales from the tropopause to the lowermost stratosphere. The good agreement between the model and the SPURT observations allows to investigate transport timescales in the UTLS region on global scales.

  15. Investigating the value of fire indices for decision making on seasonal timescales

    NASA Astrophysics Data System (ADS)

    Golding, Nicola; Bedia Jiménez, Joaquín

    2015-04-01

    As part of the FP7 EUPORIAS project we are considering the use of fire indices to provide climate information to relevant decision makers on seasonal timescales. This work is composed of several elements. Firstly we seek to better understand the information needs on this timescale from land and fire management communities, focusing on the Mediterranean region, but also learning from experience in other countries. From this we define a clear decision-making need. We then investigate the skill of two fire indices, the MacArthur Forest Fire Danger Index and the Fire Weather Index, in representing fire danger, and the skill of seasonal forecasts at forecasting the relevant climate variables at relevant lead times. We use this to evaluate the value of such index forecasts in the decision-making situation identified. This work is part of a wider effort in the EUPORIAS project which is considering the use of climate impact indices in the place of either direct seasonal forecasts or more complex impacts models.

  16. BROAD ABSORPTION LINE DISAPPEARANCE ON MULTI-YEAR TIMESCALES IN A LARGE QUASAR SAMPLE

    SciTech Connect

    Filiz Ak, N.; Brandt, W. N.; Schneider, D. P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Hall, P. B. [Department of Physics and Astronomy, York University, 4700 Keele St., Toronto, Ontario M3J 1P3 (Canada); Anderson, S. F.; Gibson, R. R. [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Lundgren, B. F. [Department of Physics, Yale University, New Haven, CT 06511 (United States); Myers, A. D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Petitjean, P. [Institut d'Astrophysique de Paris, Universite Paris 6, F-75014, Paris (France); Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 92420 (United States); Shen Yue [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States); York, D. G. [Department of Astronomy and Astrophysics, and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Bizyaev, D.; Brinkmann, J.; Malanushenko, E.; Oravetz, D. J.; Pan, K.; Simmons, A. E. [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); Weaver, B. A., E-mail: nfilizak@astro.psu.edu [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States)

    2012-10-01

    We present 21 examples of C IV broad absorption line (BAL) trough disappearance in 19 quasars selected from systematic multi-epoch observations of 582 bright BAL quasars (1.9 < z < 4.5) by the Sloan Digital Sky Survey-I/II (SDSS-I/II) and SDSS-III. The observations span 1.1-3.9 yr rest-frame timescales, longer than have been sampled in many previous BAL variability studies. On these timescales, Almost-Equal-To 2.3% of C IV BAL troughs disappear and Almost-Equal-To 3.3% of BAL quasars show a disappearing trough. These observed frequencies suggest that many C IV BAL absorbers spend on average at most a century along our line of sight to their quasar. Ten of the 19 BAL quasars showing C IV BAL disappearance have apparently transformed from BAL to non-BAL quasars; these are the first reported examples of such transformations. The BAL troughs that disappear tend to be those with small-to-moderate equivalent widths, relatively shallow depths, and high outflow velocities. Other non-disappearing C IV BALs in those nine objects having multiple troughs tend to weaken when one of them disappears, indicating a connection between the disappearing and non-disappearing troughs, even for velocity separations as large as 10,000-15,000 km s{sup -1}. We discuss possible origins of this connection including disk-wind rotation and changes in shielding gas.

  17. Mechanism of transient force augmentation varying with two distinct timescales for interacting vortex rings

    NASA Astrophysics Data System (ADS)

    Fu, Zhidong; Qin, Suyang; Liu, Hong

    2014-01-01

    The dynamics of dual vortex ring flows is studied experimentally and numerically in a model system that consists of a piston-cylinder apparatus. The flows are generated by double identical strokes which have the velocity profile characterized by the sinusoidal function of half the period. By calculating the total wake impulse in two strokes in the experiments, it is found that the average propulsive force increases by 50% in the second stroke for the sufficiently small stroke length, compared with the first stroke. In the numerical simulations, two types of transient force augmentation are revealed, there being the transient force augmentation for the small stroke lengths and the absolute transient force augmentation for the large stroke lengths. The relative transient force augmentation increases to 78% for L/D = 1, while the absolute transient force augmentation for L/D = 4 is twice as much as that for L/D = 1. Further investigation demonstrates that the force augmentation is attributed to the interaction between vortex rings, which induces transport of vortex impulse and more evident fluid entrainment. The critical situation of vortex ring separation is defined and indicated, with vortex spacing falling in a narrow gap when the stroke lengths vary. A new model is proposed concerning the limiting process of impulse, further suggesting that apart from vortex formation timescale, vortex spacing should be interpreted as an independent timescale to reflect the dynamics of vortex interaction.

  18. PROTOTYPING NON-EQUILIBRIUM VISCOUS-TIMESCALE ACCRETION THEORY USING LMC X-3

    SciTech Connect

    Cambier, Hal J.; Smith, David M. [Physics Department, University of California, Santa Cruz, CA 95064 (United States)] [Physics Department, University of California, Santa Cruz, CA 95064 (United States)

    2013-04-10

    Explaining variability observed in the accretion flows of black hole X-ray binary systems remains challenging, especially concerning timescales less than, or comparable to, the viscous timescale but much larger than the inner orbital period despite decades of research identifying numerous relevant physical mechanisms. We take a simplified but broad approach to study several mechanisms likely relevant to patterns of variability observed in the persistently high-soft Roche-lobe overflow system LMC X-3. Based on simple estimates and upper bounds, we find that physics beyond varying disk/corona bifurcation at the disk edge, Compton-heated winds, modulation of total supply rate via irradiation of the companion, and the likely extent of the partial hydrogen ionization instability is needed to explain the degree, and especially the pattern, of variability in LMC X-3 largely due to viscous dampening. We then show how evaporation-condensation may resolve or compound the problem given the uncertainties associated with this complex mechanism and our current implementation. We briefly mention our plans to resolve the question, refine and extend our model, and alternatives we have not yet explored.

  19. First results from the BARREL 2013 campaign; Observations of precipitation on drift echo timescales

    NASA Astrophysics Data System (ADS)

    Halford, A.; Millan, R. M.; Fennell, J. F.; Claudepierre, S. G.

    2013-12-01

    Throughout the BARREL 2013 campaign and during previous balloon missions, electron precipitation has been observed to occur on many different time scales, from millisecond microbursts to minute-long ULF time scales to tens of minutes. These longer period oscillations have not been previously examined in detail because satellite data were unavailable to identify the nature of the longer period oscillations. In this study we will present BARREL observations of precipitation along with observations of drift echoes in electron data from the MagEIS instrument on the Van Allen Probes. One example occurred on January 26, 2013 where precipitation showed an approximate 20 -minute modulation and drift echoes were observed at similar timescales in the approximately 230-350 keV electrons by MagEIS. The precipitation also shows temporal structure at faster timescales including approximately 90-second ULF modulation and millisecond microbursts. This suggest that the drift echoes may determine when there are particles available to be precipitated by some other mechanism such as scattering by VLF waves.

  20. On the convergence of the critical cooling timescale for the fragmentation of self-gravitating discs

    E-print Network

    Meru, Farzana

    2012-01-01

    We carry out simulations of gravitationally unstable discs using a Smoothed Particle Hydrodynamics (SPH) code and a grid-based hydrodynamics code, FARGO, to understand the previous non-convergent results reported by Meru & Bate (2011a). We obtain evidence that convergence with increasing resolution occurs with both SPH and FARGO and in both cases we find that the critical cooling timescale is larger than previously thought. We show that SPH has a first-order convergence rate while FARGO converges with a second-order rate. We show that the convergence of the critical cooling timescale for fragmentation depends largely on the numerical viscosity employed in both SPH and FARGO. With SPH, particle velocity dispersion may also play a role. We show that reducing the dissipation from the numerical viscosity leads to larger values of the critical cooling time at a given resolution. For SPH, we find that the effect of the dissipation due to the numerical viscosity is somewhat larger than had previously been apprec...

  1. Simulation of stellar instabilities with vastly different timescales using domain decomposition

    E-print Network

    M. Grott; S. Chernigovski; W. Glatzel

    2003-09-25

    Strange mode instabilities in the envelopes of massive stars lead to shock waves, which can oscillate on a much shorter timescale than that associated with the primary instability. The phenomenon is studied by direct numerical simulation using a, with respect to time, implicit Lagrangian scheme, which allows for the variation by several orders of magnitude of the dependent variables. The timestep for the simulation of the system is reduced appreciably by the shock oscillations and prevents its long term study. A procedure based on domain decomposition is proposed to surmount the difficulty of vastly different timescales in various regions of the stellar envelope and thus to enable the desired long term simulations. Criteria for domain decomposition are derived and the proper treatment of the resulting inner boundaries is discussed. Tests of the approach are presented and its viability is demonstrated by application to a model for the star P Cygni. In this investigation primarily the feasibility of domain decomposition for the problem considered is studied. We intend to use the results as the basis of an extension to two dimensional simulations.

  2. Einstein Gravitation Theory: Experimental Tests I

    E-print Network

    M. Cattani

    2010-05-24

    Using the Einstein gravitation theory (EGT) we calculate the Schwarzschild metric that is defined in the surrounding vacuum of a spherically symmetric mass distribution, not in rotation. The field equations of the EGT with this metric were applied to analyze the time dilation and the Doppler Effect of the light in order to test the validity of the EGT. This article was written to graduate and postgraduate students of Physics.

  3. Analogue gravity from Bose-Einstein condensates

    Microsoft Academic Search

    Carlos Barceló; S. Liberati; Matt Visser

    2001-01-01

    We analyse prospects for the use of Bose-Einstein condensates as condensed-matter systems suitable for generating a generic `effective metric', and for mimicking kinematic aspects of general relativity. We extend the analysis due to Garay et al (2000 Phys. Rev. Lett. 85 4643, 2001 Phys. Rev. A 63 023611). Taking a long-term view, we ask what the ultimate limits of such

  4. Fast transport of Bose-Einstein condensates

    E-print Network

    E. Torrontegui; Xi Chen; M. Modugno; S. Schmidt; A. Ruschhaupt; J. G. Muga

    2011-03-13

    We propose an inverse method to accelerate without final excitation the adiabatic transport of a Bose Einstein condensate. The method, applicable to arbitrary potential traps, is based on a partial extension of the Lewis-Riesenfeld invariants, and provides transport protocols that satisfy exactly the no-excitation conditions without constraints or approximations. This inverse method is complemented by optimizing the trap trajectory with respect to different physical criteria and by studying the effect of noise.

  5. Hysteresis effects in Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Sacchetti, Andrea

    2010-07-01

    Here, we consider damped two-component Bose-Einstein condensates with many-body interactions. We show that, when the external trapping potential has a double-well shape and when the nonlinear coupling factors are modulated in time, hysteresis effects may appear under some circumstances. Such hysteresis phenomena are a result of the joint contribution of the appearance of saddle node bifurcations and the damping effect.

  6. Einstein and Besso: Not a Partnership of Equals

    NASA Astrophysics Data System (ADS)

    Janssen, Michel

    2005-04-01

    In the 1905 special relativity paper Einstein famously acknowledged the help of his friend and colleague Michele Besso. Besso had been an ideal sounding board for Einstein's ideas. During the years that Einstein developed general relativity, Besso was a good deal more than a sounding board. He collaborated with Einstein on calculations of the perihelion motion of Mercury in 1913. His contributions were substantial and would have warranted co-authorship of Einstein's famous paper on Mercury's perihelion of November 1915, in which Besso is not mentioned at all. Besso also alerted Einstein to problems with the early version of general relativity that Einstein had worked out together with Marcel Grossmann. Einstein essentially ignored Besso's warnings. In addition, Besso went out of his way during this period to act as a mediator between a not always appreciative Einstein, living in Berlin with his cousin Elsa who would become his second wife, and his estranged first wife Mileva, living in Zurich with the couple's two young sons. This period is much better documented than the period leading up to the 1905 paper and consequently much more revealing about the nature of the relationship between Einstein and Besso.

  7. ON THE NATURE OF THE PROTOTYPE LUMINOUS BLUE VARIABLE AG CARINAE. II. WITNESSING A MASSIVE STAR EVOLVING CLOSE TO THE EDDINGTON AND BISTABILITY LIMITS

    SciTech Connect

    Groh, J. H. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Hillier, D. J. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260 (United States); Damineli, A., E-mail: jgroh@mpifr.de [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, 05508-900, Sao Paulo, SP (Brazil)

    2011-07-20

    We show that the significantly different effective temperatures (T{sub eff}) achieved by the luminous blue variable AG Carinae during the consecutive visual minima of 1985-1990 (T{sub eff} {approx_equal} 22,800 K) and 2000-2001 (T{sub eff} {approx_equal} 17,000 K) place the star on different sides of the bistability limit, which occurs in line-driven stellar winds around T{sub eff} {approx} 21,000 K. Decisive evidence is provided by huge changes in the optical depth of the Lyman continuum in the inner wind as T{sub eff} changes during the S Dor cycle. These changes cause different Fe ionization structures in the inner wind. The bistability mechanism is also related to the different wind parameters during visual minima: the wind terminal velocity was 2-3 times higher and the mass-loss rate roughly two times smaller in 1985-1990 than in 2000-2003. We obtain a projected rotational velocity of 220 {+-} 50 km s{sup -1} during 1985-1990 which, combined with the high luminosity (L{sub *} = 1.5 x 10{sup 6} L{sub sun}), puts AG Car extremely close to the Eddington limit modified by rotation ({Omega}{Gamma} limit): for an inclination angle of 90{sup 0}, {Gamma}{sub {Omega}} {approx}> 1.0 for M{sub sun} {approx}< 60. Based on evolutionary models and mass budget, we obtain an initial mass of {approx}100 M{sub sun} and a current mass of {approx}60-70 M{sub sun} for AG Car. Therefore, AG Car is close to, if not at, the {Omega}{Gamma} limit during visual minimum. Assuming M = 70 M{sub sun}, we find that {Gamma}{sub {Omega}} decreases from 0.93 to 0.72 as AG Car expands toward visual maximum, suggesting that the star is not above the Eddington limit during maximum phases.

  8. On static Poincaré-Einstein metrics

    NASA Astrophysics Data System (ADS)

    Galloway, Gregory J.; Woolgar, Eric

    2015-06-01

    The classification of solutions of the static vacuum Einstein equations, on a given closed manifold or an asymptotically flat one, is a long-standing and much-studied problem. Solutions are characterized by a complete Riemannian n-manifold ( M, g) and a positive function N, called the lapse. We study this problem on Asymptotically Poincaré-Einstein n-manifolds, n ? 3, when the conformal boundary-at-infinity is either a round sphere, a flat torus or smooth quotient thereof, or a compact hyperbolic manifold. Such manifolds have well-defined Wang mass, and are time-symmetric slices of static, vacuum, asymptotically anti-de Sitter spacetimes. By integrating a mildly generalized form of an identity used by Lindblom, Shen, Wang, and others, we give a mass formula for such manifolds. There are no solutions with positive mass. In consequence, we observe that either the lapse is trivial and ( M, g) is Poincaré-Einstein or the Wang mass is negative, as in the case of time symmetric slices of the AdS soliton. As an application, we use the mass formula to compute the renormalized volume of the warped product ( X, ?) ? ( M 3 , g) × N 2 ( S 1 , dt 2).

  9. My Half-Hour with Einstein

    NASA Astrophysics Data System (ADS)

    Romer, Robert H.

    2005-04-01

    Midway during my first year as a Princeton graduate student (1952-53), I was given a letter of introduction to Einstein. Over a year later I finally worked up my courage to use it and -- as a result -- enjoyed a one-on-one conversation with him in the study of his home on Mercer Street. I will describe how my chance to meet Einstein arose and what I can remember of our memorable (to me if not to him) conversation. Among other things, we discussed the bomb, the new state of Israel, fossil horse brains, and evolution. (``Has there really been enough time for all those changes?'') We talked about the Einstein-Rosen-Podolsky problem - though not by that name, and I believe that it was the ``Bohm version'' that he asked me about. (``Do you really believe that if someone here measured the spin of an atom, it could affect the simultaneous measurement of the spin of another atom way over there?'') My major recollection is of my wish that I had been better prepared. As Ehrenfest once wrote: ``Nothing is shabbier than the feeling: now God has granted me the opportunity to meet this man, and I sat before him open-mouthed; how much I might have asked him -- but nothing at all occurred to me.''

  10. On General Solutions of Einstein Equations

    E-print Network

    Sergiu I. Vacaru

    2011-06-23

    We show how the Einstein equations with cosmological constant (and/or various types of matter field sources) can be integrated in a very general form following the anholonomic deformation method for constructing exact solutions in four and five dimensional gravity (S. Vacaru, IJGMMP 4 (2007) 1285). In this letter, we prove that such a geometric method can be used for constructing general non-Killing solutions. The key idea is to introduce an auxiliary linear connection which is also metric compatible and completely defined by the metric structure but contains some torsion terms induced nonholonomically by generic off-diagonal coefficients of metric. There are some classes of nonholonomic frames with respect to which the Einstein equations (for such an auxiliary connection) split into an integrable system of partial differential equations. We have to impose additional constraints on generating and integration functions in order to transform the auxiliary connection into the Levi-Civita one. This way, we extract general exact solutions (parametrized by generic off-diagonal metrics and depending on all coordinates) in Einstein gravity and five dimensional extensions.

  11. Thermodynamic structure of the Einstein tensor

    SciTech Connect

    Kothawala, Dawood [Department of Mathematics and Statistics, University of New Brunswick, Fredericton, NB, E3B 5A3 (Canada)

    2011-01-15

    We analyze the generic structure of Einstein tensor projected onto a 2D spacelike surface S defined by a unit timelike and spacelike vectors u and n, respectively, which describe an accelerated observer (see text). Assuming that flow along u defines an approximate Killing vector {xi}, we then show that near the corresponding Rindler horizon, the flux j{sup a}=G{sub b}{sup a{xi}b} along the ingoing null geodesics k, i.e., j{center_dot}k, has a natural thermodynamic interpretation. Moreover, change in the cross-sectional area of the k congruence yields the required change in area of S under virtual displacements normal to it. The main aim of this paper is to clearly demonstrate how, and why, the content of Einstein equations under such horizon deformations, originally pointed out by Padmanabhan, is essentially different from the result of Jacobson, who employed the so-called Clausius relation in an attempt to derive Einstein equations from such a Clausius relation. More specifically, we show how a very specific geometric term (reminiscent of Hawking's quasilocal expression for energy of spheres) corresponding to change in gravitational energy arises inevitably in the first law: dE{sub G}/d{lambda}{proportional_to}Hd{sup 2}x{radical}({sigma}){sup (2)}R (see text)--the contribution of this purely geometric term would be missed in attempts to obtain area (and hence entropy) change by integrating the Raychaudhuri equation.

  12. Einstein's Revolutionary Light--Quantum Hypothesis

    NASA Astrophysics Data System (ADS)

    Stuewer, R. H.

    2006-03-01

    Albert Einstein's light-quantum paper was the only one of his great papers of 1905 that he himself called ``very revolutionary''. I sketch his arguments for light quanta, his analysis of the photoelectric effect, and his introduction of the wave-particle duality into physics in 1909. I show that Robert Andrews Millikan, in common with almost all physicists at the time, rejected Einstein's light-quantum hypothesis as an interpretation of his photoelectric-effect experiments of 1915. I then trace the complex experimental and theoretical route that Arthur Holly Compton followed between 1916 and 1922 that led to his discovery of the Compton effect, a discovery that Peter Debye also made virtually simultaneously and independently. Compton's discovery, however, was challenged on experimental grounds by William Duane and on theoretical grounds by Niels Bohr in the Bohr--Kramers--Slater theory of 1924, and only after that theory was disproved experimentally the following year by Walther Bothe and Hans Geiger in Berlin and by Compton and Alfred W. Simon in Chicago was Einstein's light-quantum hypothesis generally accepted by physicists.

  13. Einstein Radii from Binary Lensing Events

    E-print Network

    Cheongho Han; Andrew Gould

    1996-06-26

    We show that the Einstein ring radius and transverse speed of a lens projected on the source plane, $\\hat{r}_{\\rm e}$ and $\\hat{v}$, can be determined from the light curve of a binary-source event, followed by the spectroscopic determination of the orbital elements of the source stars. The determination makes use of the same principle that allows one to measure the Einstein ring radii from finite-source effects. For the case when the orbital period of the source stars is much longer than the Einstein time scale, $P\\gg t_{\\rm e}$, there exists a single two-fold degeneracy in determining $\\hat{r}_{\\rm e}$. However, when $P \\lesssim t_{\\rm e}$ the degeneracy can often be broken by making use of the binary-source system's orbital motion. %Once $\\hat{r}_{\\rm e}$, and thus $\\hat{v}$ are determined, one can %distinguish self-lensing events in the Large Magellanic Cloud %from Galactic halo events. For an identifiable 8\\% of all lensing events seen toward the Large Magellanic Cloud (LMC), one can unambiguously determine whether the lenses are Galactic, or whether they lie in the LMC itself. The required observations can be made after the event is over and could be carried out for the $\\sim 8$ events seen by Alcock et al.\\ and Aubourg et al.. In addition, we propose to include eclipsing binaries as sources for gravitational lensing experiments.

  14. Einstein's Materialism and Modern Tests of Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Vigier, J. P.

    After a presentation of Einstein's and Bohr's antagonistic point of view on the interpretation of Quantum Mechanics an illustration of their conflicting positions in the particular case of Young's double slit experiment is presented. It is then shown that in their most recent form (i. e. time dependent neutron interferometry) these experiments suggest (if one accepts absolute energymomentum conservation in all individual microprocesses) that Einstein was right in the Bohr-Einstein controversy.Translated AbstractEinsteins Materialismus und heutige Tests der QuantenmechanikNach einer Darstellung von Einsteins und Bohrs antagonistischen Standpunkten in der Interpretation der Quantenmechanik werden ihre widersprüchlichen Positionen im speziellen Fall des Youngschen Doppelspaltexperiments dargestellt. Es wird dann gezeigt, daß diese Experimente in ihrer neuesten Form (d. h. zeitabhängige Neutroneninterferometrie) Einstein in der Bohr-Einsteinkontroverse recht gaben (wenn man absolute Energie-Impulserhaltung bei allen individuellen Mikroprozessen annimmt).

  15. Newton's law on an Einstein "Gauss-Bonnet" brane

    E-print Network

    Deruelle, N; Deruelle, Nathalie; Sasaki, Misao

    2003-01-01

    It is known that Newton's law of gravity holds asymptotically on a flat "brane" embedded in an anti-de Sitter "bulk" ; this was shown not only when gravity in the bulk is described by Einstein's theory but also in Einstein "Lanczos Lovelock Gauss-Bonnet"'s theory. We give here the expressions for the corrections to Newton's potential in both theories, in analytic form and valid for all distances. We find that in Einstein's theory the transition from the 1/r behaviour at small r to the 1/r^2 one at large r is quite slow. In the Einstein Gauss-Bonnet case on the other hand, we find that the correction to Newton's potential can be small for all r. Hence, Einstein Gauss-Bonnet equations in the bulk (rather than simply Einstein's) induce on the brane a better approximation to Newton's law.

  16. Einstein-Podolsky-Rosen Correlations via Dissociation of a Molecular Bose-Einstein Condensate

    SciTech Connect

    Kheruntsyan, K.V.; Drummond, P.D. [ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Qld 4072 (Australia); Olsen, M.K. [ARC Centre of Excellence for Quantum-Atom Optics, School of Physical Sciences, University of Queensland, Brisbane, Qld 4072 (Australia); Instituto de Fisica da Universidade Federal Fluminense, Boa Viagem 24210-340, Niteroi - Rio de Janeiro (Brazil)

    2005-10-07

    Recent experimental measurements of atomic intensity correlations through atom shot noise suggest that atomic quadrature phase correlations may soon be measured with a similar precision. We propose a test of local realism with mesoscopic numbers of massive particles based on such measurements. Using dissociation of a Bose-Einstein condensate of diatomic molecules into bosonic atoms, we demonstrate that strongly entangled atomic beams may be produced which possess Einstein-Podolsky-Rosen (EPR) correlations in field quadratures in direct analogy to the position and momentum correlations originally considered by EPR.

  17. Short timescale photometric and polarimetric behavior of two BL Lacertae type objects

    NASA Astrophysics Data System (ADS)

    Covino, S.; Baglio, M. C.; Foschini, L.; Sandrinelli, A.; Tavecchio, F.; Treves, A.; Zhang, H.; Barres de Almeida, U.; Bonnoli, G.; Böttcher, M.; Cecconi, M.; D'Ammando, F.; di Fabrizio, L.; Giarrusso, M.; Leone, F.; Lindfors, E.; Lorenzi, V.; Molinari, E.; Paiano, S.; Prandini, E.; Raiteri, C. M.; Stamerra, A.; Tagliaferri, G.

    2015-06-01

    Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, i.e. synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Aims: Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can provide almost indistinguishable predictions for the total flux, but usually are characterized by different polarization properties. We explore the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Methods: Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6 m Telescopio Nazionale Galileo. Several hours of almost continuous observations were obtained for both sources. Results: Our intense monitoring allowed us to draw different scenarios for BL Lacertae and PKS 1424+240, with the former characterized by intense variability and the latter practically constant in total flux. Essentially the same behavior is observed for the polarized flux and the position angle. The variability time-scales turned out to be as short as a few minutes, although involving only a few percent variation of the flux. The polarization variability time-scale is generally consistent with the total flux variability. Total and polarized flux appear to be essentially uncorrelated. However, even during our relatively short monitoring, different regimes can be singled out. Conclusions: No simple scenario is able to satisfactorily model the very rich phenomenology exhibited in our data. Detailed numerical simulations show that the emitting region should be characterized by some symmetry, and the inclusion of turbulence for the magnetic field may constitute the missing ingredient for a more complete interpretation of the data. Partly based on data obtained at the INAF/Telescopio Nazionale Galileo at the Canary Island of La Palma under program Id: A29TAC_21 (PI: S. Covino).

  18. Time-scale bias in evidence for anthropogenic acceleration of soil erosion and floodplain accretion

    NASA Astrophysics Data System (ADS)

    Willenbring, J. K.; Hoffmann, T.; Sadler, P.; Kaplan, J. O.; Chiverrell, R. C.; Erkens, G.; von Blanckenburg, F.

    2014-12-01

    The claim that humans modify the landscape more dramatically than any previous geological agent has impacts for river restoration, conservation and models of both nutrient- and carbon-cycling. This view of extreme sediment mobilization driven by human activities is largely based on data, which unfortunately are measured over discrepant timescales that can introduce bias. Comparing denudation rates discerned from cosmogenic nuclides as 'baseline' or 'natural' rates with continent-scale sediment export rates over modern timescales reveals that most cosmogenic nuclide-based erosion rates are faster than human-impacted rates of sediment yield [1]. One explanation for relatively low recent continental sediment yields is that the eroded sediment may be accumulating and stored for an uncertain duration in swelling floodplains and deltas. We present a global compilation of Holocene floodplain accumulation rates. Rates measured over the last ~100 years are faster than those averaged over ~1000 years, which in turn are faster than those for the last ~10000 years. Floodplain sediment accumulation measurements, however, are taken at discreet cores or bank exposures, and this introduces both temporal and spatial bias. Vertical accumulation rates are calculated by dividing thickness of sediment by the time-span of accumulation for discrete packages of sediment. Thus, time integrates from the present to a past datum provided by 14C measurements for buried organics (or other chronological tools). We argue that the pattern of rate increase in sedimentation over time is related to infilling behavior of all floodplains and not specifically tied to the supply of (anthropogenic) sediment. The apparent acceleration in sedimentation rates appears globally synchronous over 8000-year timescales, despite diachronous human and land use histories. Moreover, some rate acceleration pre-dates significant human land use. When the effect/bias of averaging time is accounted for, recent accumulation rates are similar to past, pre-anthropogenic rates; thus the apparent synchrony of accelerating floodplain accumulation is consistent with a model that could include but does not require anthropogenic erosion. [1] Covault et al. 2013. J. Geol. 121: 35-56

  19. Einsteins Spuren in den Archiven der Wissenschaft: Physikgeschichte

    NASA Astrophysics Data System (ADS)

    Marx, Werner

    2005-07-01

    Die Erwähnungen und Zitierungen von Einsteins Arbeiten dokumentieren lediglich den quantifizierbaren Anteil von Einsteins Beitrag zur Physik. Gleichwohl belegen sie die außergewöhnliche Resonanz und Langzeitwirkung seiner Arbeiten. Die Häufigkeit der Zitierungen entspricht nicht der allgemeinen Einschätzung ihrer Bedeutung. Insbesondere die Pionierarbeiten werden inzwischen als bekannt vorausgesetzt und nicht mehr explizit zitiert. Interessanterweise ist seine nach 1945 meist zitierte Arbeit nicht eine der Pionierarbeiten zur Quantenphysik oder Relativitätstheorie, sondern jene aus dem Jahr 1935 zum berühmten Einstein-Podolsky-Rosen-Paradoxon.

  20. Wer entdeckte die Allgemeine Relativitätstheorie? Prioritätsstreit zwischen Hilbert und Einstein

    NASA Astrophysics Data System (ADS)

    Sommer, Klaus P.

    2005-09-01

    Im November 1915 arbeiteten Albert Einstein und David Hilbert an den Feldgleichungen der Gravitationstheorie. Im Jahre 1997 behaupteten die Wissenschaftshistoriker Corry, Renn und Stachel in einer viel beachteten Arbeit, Hilbert habe die entscheidenden Formeln von Einstein gestohlen. Grundlage ihrer Argumentation war eine wieder gefundene Korrekturfahne von Hilberts entscheidender Arbeit. Die Physikhistorikerin Daniela Wuensch bringt jedoch detaillierte Argumente dafür vor, dass die entscheidende Quelle, nämlich die Korrekturfahne, in neuerer Zeit manipuliert worden ist, um Einsteins Priorität unangetastet zu lassen. Einstein bleibt aber der Entdecker der Allgemeinen Relativitätstheorie.

  1. Why the South matters for global climate variability on millennial to orbital timescales

    NASA Astrophysics Data System (ADS)

    Barker, S.; Knorr, G.

    2011-12-01

    The link between records of millennial-scale (103 yr) climate variability in ice cores from the northern and southern polar regions is well established: to a first approximation, the southern climate signal is an integrated form of the northern signal. The underlying physical mechanisms are less well defined but probably involve changes in ocean circulation and related atmospheric phenomena and the thermal inertia of the Southern Ocean (or an equivalent heat reservoir). A key question remains: is the southern signal merely a tape recording of northern climate variability or does it play a more active role in global climate evolution? Here we will describe some of the possible ways by which the South can be seen as more than just a passive bystander in global climate change, both on millennial and orbital timescales.

  2. A NEW TIMESCALE FOR PERIOD CHANGE IN THE PULSATING DA WHITE DWARF WD 0111+0018

    SciTech Connect

    Hermes, J. J.; Montgomery, M. H.; Winget, D. E. [Department of Astronomy, University of Texas at Austin, Austin, TX - 78712 (United States)] [Department of Astronomy, University of Texas at Austin, Austin, TX - 78712 (United States); Mullally, Fergal [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States)] [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Bischoff-Kim, A., E-mail: jjhermes@astro.as.utexas.edu [Chemistry, Physics and Astronomy Department, Georgia College and State University, Milledgeville, GA 31061 (United States)

    2013-03-20

    We report the most rapid rate of period change measured to date for a pulsating DA (hydrogen atmosphere) white dwarf (WD), observed in the 292.9 s mode of WD 0111+0018. The observed period change, faster than 10{sup -12} s s{sup -1}, exceeds by more than two orders of magnitude the expected rate from cooling alone for this class of slow and simply evolving pulsating WDs. This result indicates the presence of an additional timescale for period evolution in these pulsating objects. We also measure the rates of period change of nonlinear combination frequencies and show that they share the evolutionary characteristics of their parent modes, confirming that these combination frequencies are not independent modes but rather artifacts of some nonlinear distortion in the outer layers of the star.

  3. Adaptive delay concealment for Internet voice applications with packet-based time-scale modification

    NASA Astrophysics Data System (ADS)

    Liu, Fang; Kim, JongWon; Kuo, C.-C. Jay

    2001-03-01

    For Internet audio applications, much effort has been involved in packet-level error control and delay jitter concealment. In this paper, a packet-based time-scale modification scheme for speech signal is applied to provide adaptive delay concealment at the receiver of an Internet voice session. The adaptive playout algorithm strives to minimize receiver packet droppings for late-arrival packets and premature packets while keeping the end-to-end delay constrained. By stretching the voice segment up/down and incorporating the silence interval, the proposed algorithm could adapt quickly to accommodate fluctuating delays including delay spikes. The evaluation verifies the performance of the proposed adaptive playout, which improves the received speech intelligence under a tightly bounded average playout delay.

  4. ACEMD: Accelerating bio-molecular dynamics in the microsecond time-scale

    E-print Network

    Harvey, M J; De Fabritiis, G

    2009-01-01

    The high arithmetic performance and intrinsic parallelism of recent graphical processing units (GPUs) can offer a technological edge for molecular dynamics simulations. ACEMD is a production-class bio-molecular dynamics (MD) simulation program designed specifically for GPUs which is able to achieve supercomputing scale performance of 40 nanoseconds/day for all-atom protein systems with over 23,000 atoms. We illustrate the characteristics of the code, its validation and performance. We also run a microsecond-long trajectory for an all-atom molecular system in explicit TIP3P water on a single workstation computer equipped with just 3 GPUs. This performance on cost effective hardware allows ACEMD to reach microsecond timescales routinely with important implications in terms of scientific applications.

  5. Short Timescale Photometric and Polarimetric Behavior of two BL Lacertae Type Objects

    E-print Network

    Covino, S; Foschini, L; Sandrinelli, A; Tavecchio, F; Treves, A; Zhang, H; de Almeida, U Barres; Bonnoli, G; Boettcher, M; Cecconi, M; D'Ammando, F; di Fabrizio, L; Giarrusso, M; Leone, F; Lindfors, E; Lorenzi, V; Molinari, E; Paiano, S; Prandini, E; Raiteri, C M; Stamerra, A; Tagliaferri, G

    2015-01-01

    Blazars are astrophysical sources whose emission is dominated by non-thermal processes, typically interpreted as synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can often provide almost indistinguishable predictions for the total flux, but usually are characterized by markedly different polarization properties. We explore, with a pilot study, the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6m Telescopio Nazionale ...

  6. The Deuterium Fractionation Timescale in Dense Cloud Cores: A Parameter Space Exploration

    NASA Astrophysics Data System (ADS)

    Kong, Shuo; Caselli, Paola; Tan, Jonathan C.; Wakelam, Valentine; Sipilä, Olli

    2015-05-01

    The deuterium fraction, [N2D+]/[N2H+], may provide information about the ages of dense, cold gas structures, which are important for comparing dynamical models of cloud core formation and evolution. Here we introduce a complete chemical network with species containing up to three atoms, with the exception of the oxygen chemistry, where reactions involving H3O+ and its deuterated forms have been added, significantly improving the consistency with comprehensive chemical networks. Deuterium chemistry and spin states of H2 and H3+ isotopologues are included in this primarily gas-phase chemical model. We investigate the dependence of deuterium chemistry on these model parameters: density ({{n}H}), temperature, cosmic ray ionization rate, and gas-phase depletion factor of heavy elements ({{f}D}). We also explore the effects of time-dependent freeze-out of gas-phase species and the dynamical evolution of density at various rates relative to free-fall collapse. For a broad range of model parameters, the timescales to reach large values of Dfrac{{N2}{{H}+}}? 0.1, observed in some low- and high-mass starless cores, are relatively long compared to the local free-fall timescale. These conclusions are unaffected by introducing time-dependent freeze-out and considering models with evolving density, unless the initial {{f}D} ? 10. For fiducial model parameters, achieving Dfrac{{N2}{{H}+}}? 0.1 requires collapse to be proceeding at rates at least several times slower than that of free-fall collapse, perhaps indicating a dynamically important role for magnetic fields in supporting starless cores and thus the regulation of star formation.

  7. Quantum Control of Electrons in Atoms, Molecules and Materials - from Femtosecond to Attosecond to Zeptosecond Timescales

    NASA Astrophysics Data System (ADS)

    Murnane, Margaret

    2014-03-01

    This talk will discuss strong field quantum control in atomic, molecular and materials systems with applications across a broad range of chemical, physical and materials sciences. Using mid-infrared femtosecond lasers to drive the high harmonic (HHG) frequency upconversion process, strong time-gated phase matching results in bright coherent keV soft X-ray beams on a tabletop for the first time. The new photon energy range accessed of 0.2-1.6 keV (corresponding to wavelengths of 1 - 6 nm) is of particular interest for applications in chemical and materials spectroscopy and imaging. X-rays can penetrate thick (opaque) samples and achieve high spatial resolution (2-50nm) imaging, with the added advantage of elemental and chemical specificity by employing characteristic elemental X-ray absorption edges and chemically-induced fine structure at these edges. Moreover, when atoms are ionized by mid-infrared light, the electron liberated during the HHG process can be driven back to the parent ion multiple times, resulting in quantum interferences and zeptosecond x-ray waveforms. We also recently demonstrated that we can precisely control molecular dynamics on both nuclear (i.e. femtosecond) and electronic (i.e. attosecond) timescales. Using vacuum ultraviolet light pulses that are tunable in wavelength and time structure, it is possible to switch population between electronic excited states on attosecond timescales, and use this ability to select specific pathways for ionization or dissociation of a molecule. Ultrafast lasers can also be used to switch the dissociation pathways of molecules as they explode after irradiation by ionizing light. Finally, we used ultrafast x-rays to capture coherent processes in materials, such how fast a material can change its electronic or magnetic state,... or how fast spin currents can control and enhance magnetization in materials.

  8. Activity-Dependent Transmission and Integration Control the Timescales of Auditory Processing at an Inhibitory Synapse.

    PubMed

    Ammer, Julian J; Siveke, Ida; Felmy, Felix

    2015-06-15

    To capture the context of sensory information, neural networks must process input signals across multiple timescales. In the auditory system, a prominent change in temporal processing takes place at an inhibitory GABAergic synapse in the dorsal nucleus of the lateral lemniscus (DNLL). At this synapse, inhibition outlasts the stimulus by tens of milliseconds, such that it suppresses responses to lagging sounds, and is therefore implicated in echo suppression. Here, we untangle the cellular basis of this inhibition. We demonstrate with in vivo whole-cell patch-clamp recordings in Mongolian gerbils that the duration of inhibition increases with sound intensity. Activity-dependent spillover and asynchronous release translate the high presynaptic firing rates found in vivo into a prolonged synaptic output in acute slice recordings. A key mechanism controlling the inhibitory time course is the passive integration of the hyperpolarizing inhibitory conductance. This prolongation depends on the synaptic conductance amplitude. Computational modeling shows that this prolongation is a general mechanism and relies on a non-linear effect caused by synaptic conductance saturation when approaching the GABA reversal potential. The resulting hyperpolarization generates an efficient activity-dependent suppression of action potentials without affecting the threshold or gain of the input-output function. Taken together, the GABAergic inhibition in the DNLL is adjusted to the physiologically relevant duration by passive integration of inhibition with activity-dependent synaptic kinetics. This change in processing timescale combined with the reciprocal connectivity between the DNLLs implements a mechanism to suppress the distracting localization cues of echoes and helps to localize the initial sound source reliably. PMID:26004766

  9. Motional timescale predictions by molecular dynamics simulations: Case study using proline and hydroxyproline sidechain dynamics

    PubMed Central

    Aliev, Abil E; Kulke, Martin; Khaneja, Harmeet S; Chudasama, Vijay; Sheppard, Tom D; Lanigan, Rachel M

    2014-01-01

    We propose a new approach for force field optimizations which aims at reproducing dynamics characteristics using biomolecular MD simulations, in addition to improved prediction of motionally averaged structural properties available from experiment. As the source of experimental data for dynamics fittings, we use 13C NMR spin-lattice relaxation times T1 of backbone and sidechain carbons, which allow to determine correlation times of both overall molecular and intramolecular motions. For structural fittings, we use motionally averaged experimental values of NMR J couplings. The proline residue and its derivative 4-hydroxyproline with relatively simple cyclic structure and sidechain dynamics were chosen for the assessment of the new approach in this work. Initially, grid search and simplexed MD simulations identified large number of parameter sets which fit equally well experimental J couplings. Using the Arrhenius-type relationship between the force constant and the correlation time, the available MD data for a series of parameter sets were analyzed to predict the value of the force constant that best reproduces experimental timescale of the sidechain dynamics. Verification of the new force-field (termed as AMBER99SB-ILDNP) against NMR J couplings and correlation times showed consistent and significant improvements compared to the original force field in reproducing both structural and dynamics properties. The results suggest that matching experimental timescales of motions together with motionally averaged characteristics is the valid approach for force field parameter optimization. Such a comprehensive approach is not restricted to cyclic residues and can be extended to other amino acid residues, as well as to the backbone. Proteins 2014; 82:195–215. © 2013 Wiley Periodicals, Inc. PMID:23818175

  10. Assessment of rhythmic entrainment at multiple timescales in dyslexia: evidence for disruption to syllable timing.

    PubMed

    Leong, Victoria; Goswami, Usha

    2014-02-01

    Developmental dyslexia is associated with rhythmic difficulties, including impaired perception of beat patterns in music and prosodic stress patterns in speech. Spoken prosodic rhythm is cued by slow (<10 Hz) fluctuations in speech signal amplitude. Impaired neural oscillatory tracking of these slow amplitude modulation (AM) patterns is one plausible source of impaired rhythm tracking in dyslexia. Here, we characterise the temporal profile of the dyslexic rhythm deficit by examining rhythmic entrainment at multiple speech timescales. Adult dyslexic participants completed two experiments aimed at testing the perception and production of speech rhythm. In the perception task, participants tapped along to the beat of 4 metrically-regular nursery rhyme sentences. In the production task, participants produced the same 4 sentences in time to a metronome beat. Rhythmic entrainment was assessed using both traditional rhythmic indices and a novel AM-based measure, which utilised 3 dominant AM timescales in the speech signal each associated with a different phonological grain-sized unit (0.9-2.5 Hz, prosodic stress; 2.5-12 Hz, syllables; 12-40 Hz, phonemes). The AM-based measure revealed atypical rhythmic entrainment by dyslexic participants to syllable patterns in speech, in perception and production. In the perception task, both groups showed equally strong phase-locking to Syllable AM patterns, but dyslexic responses were entrained to a significantly earlier oscillatory phase angle than controls. In the production task, dyslexic utterances showed shorter syllable intervals, and differences in Syllable:Phoneme AM cross-frequency synchronisation. Our data support the view that rhythmic entrainment at slow (?5 Hz, Syllable) rates is atypical in dyslexia, suggesting that neural mechanisms for syllable perception and production may also be atypical. These syllable timing deficits could contribute to the atypical development of phonological representations for spoken words, the central cognitive characteristic of developmental dyslexia across languages. PMID:23916752

  11. An astrophysical peek into Einstein's static universe

    E-print Network

    Abhas Mitra

    2008-08-19

    We derive here the metric for Einstein's static universe (ESU) directly from Einstein equation, i.e., by considering both $G_{ik}$ and $T_{ik}$. We find that in order that the fluid pressure and acceleration are {\\em uniform} and finite despite the presence of a coordinate singularity, the effective density $\\rho_e = \\rho + \\Lambda/8 \\pi =0$, where $\\Lambda$ is the cosmological constant. Under weak energy condition, this would imply $\\rho = \\Lambda =0$ for ESU. This means that if one would need to invoke a source of ``repulsive gravity'' in some model, (i) the model must be non-static, (ii) the repulsive gravity must be due to a ``quintessence'' or a ``dark energy'' fluid with negative pressure and appear on the right hand side (RHS) of the Einstein equation through $T_{ij}$ rather than through a fundamental constant residing on the LHS of the same equation, and (iii) energy density of both normal matter and the ``dark energy fluid'' should be time dependent. In fact, the repulsive gravity would be due to a time independent $\\Lambda$, it would be extremely difficult to understand why the associated energy density should be approximately $10^{120}$ times lower than the value predicted by quantum gravity. On the other hand, for a dark energy fluid whose energy density is time dependent, it would be much easier to understand such an extremely low present energy density: the original initial value of the energy density of the fluid could be equal to the quantum gravity value while the present low value is due to decay with time.

  12. On static Poincaré-Einstein metrics

    E-print Network

    Gregory J Galloway; Eric Woolgar

    2015-04-10

    The classification of solutions of the static vacuum Einstein equations, on a given closed manifold or an asymptotically flat one, is a long-standing and much-studied problem. Solutions are characterized by a complete Riemannian $n$-manifold $(M,g)$ and a positive function $N$, called the lapse. We study this problem on Asymptotically Poincar\\'e-Einstein $n$-manifolds, $n\\ge 3$, when the conformal boundary-at-infinity is either a round sphere, a flat torus or smooth quotient thereof, or a compact hyperbolic manifold. Such manifolds have well-defined Wang mass, and are time-symmetric slices of static, vacuum, asymptotically anti-de Sitter spacetimes. By integrating a mildly generalized form of an identity used by Lindblom, Shen, Wang, and others, we give a mass formula for such manifolds. In consequence, we observe that either the lapse is trivial and $(M,g)$ is Poincar\\'e-Einstein or the Wang mass is negative, as in the case of time symmetric slices of the AdS soliton. As an application, we use the mass formula to compute the renormalized volume of the warped product $(X,\\gamma) = (M^3,g) \\times_{N^2} (S^1,dt^2)$. We also give a mass formula for the case of a metric that is static in the region exterior to a horizon on which the lapse function is zero. Then the manifold $(X,\\gamma)$ is said to have a "bolt" where the $S^1$ factor shrinks to zero length. The renormalized volume of $(X,\\gamma)$ is expected on physical grounds to have the form of the free energy per unit temperature for a black hole in equilibrium with a radiation bath at fixed temperature. When $M$ is 3-dimensional and admits a horizon, we apply this mass formula to compute the renormalized volume of $(X,\\gamma)$ and show that it indeed has the expected thermodynamically motivated form.

  13. Generalised Einstein Relation for Hot Brownian Motion

    E-print Network

    D. Chakraborty; M. V. Gnann; D. Rings; J. Glaser; F. Otto; F. Cichos; K. Kroy

    2011-10-18

    The Brownian motion of a hot nanoparticle is described by an effective Markov theory based on fluctuating hydrodynamics. Its predictions are scrutinized over a wide temperature range using large-scale molecular dynamics simulations of a hot nanoparticle in a Lennard-Jones fluid. The particle positions and momenta are found to be Boltzmann distributed according to distinct effective temperatures $T_\\mathrm{HBM}$ and $T_\\mathrm{k}$ . For $T_\\mathrm{HBM}$ we derive a formally exact theoretical prediction and establish a generalised Einstein relation that links it to directly measurable quantities.

  14. Einstein-Regge equations in spinfoams

    E-print Network

    Claudio Perini

    2011-10-26

    We consider spinfoam quantum gravity on a spacetime decomposition with many 4-simplices, in the double scaling limit in which the Immirzi parameter $\\gamma$ is sent to zero (flipped limit) and the physical area in Planck units ($\\gamma$ times the spin quantum number $j$) is kept constant. We show that the quantum amplitude takes the form of a Regge-like path integral and enforces Einstein equations in the semiclassical regime. In addition to quantum corrections which vanish when the Planck constant goes to zero, we find new corrections due to the discreteness of geometric spectra which is controlled by the Immirzi parameter.

  15. Ill-posedness in the Einstein equations

    E-print Network

    Simonetta Frittelli; Roberto Gomez

    2000-06-22

    It is shown that the formulation of the Einstein equations widely in use in numerical relativity, namely, the standard ADM form, as well as some of its variations (including the most recent conformally-decomposed version), suffers from a certain but standard type of ill-posedness. Specifically, the norm of the solution is not bounded by the norm of the initial data irrespective of the data. A long-running numerical experiment is performed as well, showing that the type of ill-posedness observed may not be serious in specific practical applications, as is known from many numerical simulations.

  16. Uniqueness and nonuniqueness in the Einstein constraints.

    PubMed

    Pfeiffer, Harald P; York, James W

    2005-08-26

    The conformal thin-sandwich (CTS) equations are a set of four of the Einstein equations, which generalize the Laplace-Poisson equation of Newton's theory. We examine numerically solutions of the CTS equations describing perturbed Minkowski space, and find only one solution. However, we find two distinct solutions, one even containing a black hole, when the lapse is determined by a fifth elliptic equation through specification of the mean curvature. While the relationship of the two systems and their solutions is a fundamental property of general relativity, this fairly simple example of an elliptic system with nonunique solutions is also of broader interest. PMID:16197202

  17. Entangled light from Bose-Einstein condensates

    E-print Network

    H. T. Ng; S. Bose

    2008-09-30

    We propose a method to generate entangled light with a Bose-Einstein condensate trapped in a cavity, a system realized in recent experiments. The atoms of the condensate are trapped in a periodic potential generated by a cavity mode. The condensate is continuously pumped by a laser and spontaneously emits a pair of photons of different frequencies in two distinct cavity modes. In this way, the condensate mediates entanglement between two cavity modes which leak out and can be separated and exhibit continuous variable entanglement. The scheme exploits the experimentally demonstrated strong, steady and collective coupling of condensate atoms to a cavity field.

  18. Das ideale Quantenlabor: Bose-Einstein-Kondensation

    NASA Astrophysics Data System (ADS)

    Sengstock, Klaus; Bongs, Kai; Reichel, Jakob

    2003-07-01

    Bose-Einstein-Kondensate (BEC) sind extrem kalte Gase aus bosonischen Atomen, die sich alle im energetischen Grundzustand versammeln. Ein BEC ist ein perfektes Quantenlabor. Es bietet eine makroskopische Materiewelle aus vielen Tausend Teilchen an, die dem Experiment offen zugänglich ist. Das unterscheidet es von anderen makroskopischen Quantenzuständen wie der Suprafluidität oder der Supraleitung, denn diese verbergen sich in Flüssigkeiten oder Festkörpern. Das BEC ist also ein ideales Modellsystem, um diese und andere Phänomene der Quantenmechanik zu studieren. Neue Perspektiven eröffnet die schnelle Erzeugung und leichte Manipulation eines Kondensats auf einem Mikrochip. Dazu gehören auch vielfältige Anwendungen bis hin zum Quantencomputer.

  19. Varying discharge controls on timescales of autogenic storage and release processes in fluvio-deltaic environments: Tank experiments

    NASA Astrophysics Data System (ADS)

    Powell, Erica J.; Kim, Wonsuck; Muto, Tetsuji

    2012-06-01

    Changes in external forcing have traditionally been the main areas of interest in understanding sedimentary records, while in most stratigraphic interpretation, autogenic behavior has been thought of as a "noise" generator. This study aims to investigate autogenic processes in a fluvio-deltaic system under a range of discharge conditions and to show that autogenic processes generate distinct signatures rather than random noise. A matrix of nine different experiments is presented here to systematically evaluate the effects of sediment and water discharge variations on the timescale of fluvial autogenic processes. Temporary sediment storage regularly occurs by backfilling of sediment in the fluvio-deltaic channels, followed by a period of strong channelization that releases the stored sediment. These storage and release processes cycle along with changes in the fluvial slope and planform pattern of the flow. Here we propose that the autogenic behavior of deltaic progradation has a distinct timescale that is controlled by sediment and water discharges. An increase in sediment discharge primarily reduces the autogenic timescale as higher sediment supply fills the channels faster. In contrast, the high sediment discharge causes a morphologic feedback by increasing the magnitude of fluvial slope change between the storage and release events and increasing the size of the temporary sediment storage (termed "the fluvial envelope"). This works against the sediment discharge control as the autogenic timescale is increased. Increasing the water discharge increases the autogenic timescale by improving the fluvial organization toward a strongly channelized system. Changes in autogenic timescale due to variations in the sediment and water discharges are nonlinear for different sediment to water discharge ratios. As the ratio decreases, the fluvial system is better organized and the timescale is more linearly related to the change in sediment discharge. As the ratio increases, deltas develop poorly organized fluvial systems and the associated timescales converge even with different sediment discharges. The results presented here provide enhanced interpretation of sedimentary records by better decoupling of autogenic signatures from allogenic products developed across a wide range of discharge conditions.

  20. Precipitation characteristics of CAM5 physics at mesoscale resolution during MC3E and the impact of convective timescale choice

    SciTech Connect

    Gustafson, William I.; Ma, Po-Lun; Singh, Balwinder

    2014-12-01

    The physics suite of the Community Atmosphere Model version 5 (CAM5) has recently been implemented in the Weather Research and Forecasting (WRF) model to explore the behavior of the parameterization suite at high resolution and in the more controlled setting of a limited area model. The initial paper documenting this capability characterized the behavior for northern high latitude conditions. This present paper characterizes the precipitation characteristics for continental, mid-latitude, springtime conditions during the Midlatitude Continental Convective Clouds Experiment (MC3E) over the central United States. This period exhibited a range of convective conditions from those driven strongly by large-scale synoptic regimes to more locally driven convection. The study focuses on the precipitation behavior at 32 km grid spacing to better anticipate how the physics will behave in the global model when used at similar grid spacing in the coming years. Importantly, one change to the Zhang-McFarlane deep convective parameterization when implemented in WRF was to make the convective timescale parameter an explicit function of grid spacing. This study examines the sensitivity of the precipitation to the default value of the convective timescale in WRF, which is 600 seconds for 32 km grid spacing, to the value of 3600 seconds used for 2 degree grid spacing in CAM5. For comparison, an infinite convective timescale is also used. The results show that the 600 second timescale gives the most accurate precipitation over the central United States in terms of rain amount. However, this setting has the worst precipitation diurnal cycle, with the convection too tightly linked to the daytime surface heating. Longer timescales greatly improve the diurnal cycle but result in less precipitation and produce a low bias. An analysis of rain rates shows the accurate precipitation amount with the shorter timescale is assembled from an over abundance of drizzle combined with too little heavy rain events. With longer timescales one can improve the distribution, particularly for the extreme rain rates. Ultimately, without changing other aspects of the physics, one must choose between accurate diurnal timing and rain amount when choosing an appropriate convective timescale.

  1. From Navier-Stokes To Einstein

    E-print Network

    Irene Bredberg; Cynthia Keeler; Vyacheslav Lysov; Andrew Strominger

    2011-01-14

    We show by explicit construction that for every solution of the incompressible Navier-Stokes equation in $p+1$ dimensions, there is a uniquely associated "dual" solution of the vacuum Einstein equations in $p+2$ dimensions. The dual geometry has an intrinsically flat timelike boundary segment $\\Sigma_c$ whose extrinsic curvature is given by the stress tensor of the Navier-Stokes fluid. We consider a "near-horizon" limit in which $\\Sigma_c$ becomes highly accelerated. The near-horizon expansion in gravity is shown to be mathematically equivalent to the hydrodynamic expansion in fluid dynamics, and the Einstein equation reduces to the incompressible Navier-Stokes equation. For $p=2$, we show that the full dual geometry is algebraically special Petrov type II. The construction is a mathematically precise realization of suggestions of a holographic duality relating fluids and horizons which began with the membrane paradigm in the 70's and resurfaced recently in studies of the AdS/CFT correspondence.

  2. Data Analysis Challenges for the Einstein Telescope

    E-print Network

    Leone Bosi; Edward K. Porter

    2009-10-02

    The Einstein Telescope is a proposed third generation gravitational wave detector that will operate in the region of 1 Hz to a few kHz. As well as the inspiral of compact binaries composed of neutron stars or black holes, the lower frequency cut-off of the detector will open the window to a number of new sources. These will include the end stage of inspirals, plus merger and ringdown of intermediate mass black holes, where the masses of the component bodies are on the order of a few hundred solar masses. There is also the possibility of observing intermediate mass ratio inspirals, where a stellar mass compact object inspirals into a black hole which is a few hundred to a few thousand times more massive. In this article, we investigate some of the data analysis challenges for the Einstein Telescope such as the effects of increased source number, the need for more accurate waveform models and the some of the computational issues that a data analysis strategy might face.

  3. From Time to Timescape — Einstein's Unfinished Revolution

    NASA Astrophysics Data System (ADS)

    Wiltshire, David L.

    I argue that Einstein overlooked an important aspect of the relativity of time in never quite realizing his quest to embody Mach's principle in his theory of gravity. As a step towards that goal, I broaden the strong equivalence principle to a new principle of physics, the cosmological equivalence principle, to account for the role of the evolving average regional density of the universe in the synchronisation of clocks and the relative calibration of inertial frames. In a universe dominated by voids of the size observed in large-scale structure surveys, the density contrasts of expanding regions are strong enough that a relative deceleration of the background between voids and the environment of galaxies, typically of order 10-10 ms-2, must be accounted for. As a result one finds a universe whose present age varies by billions of years according to the position of the observer: a timescape. This model universe is observationally viable: it passes three critical independent tests, and makes additional predictions. Dark energy is revealed as a mis-identification of gravitational energy gradients and the resulting variance in clock rates. Understanding the biggest mystery in cosmology therefore involves a paradigm shift, but in an unexpected direction: the conceptual understanding of time and energy in Einstein's own theory is incomplete.

  4. GENERALIZED KILLING SPINORS ON EINSTEIN MANIFOLDS ANDREI MOROIANU, UWE SEMMELMANN

    E-print Network

    Semmelmann, Uwe

    GENERALIZED KILLING SPINORS ON EINSTEIN MANIFOLDS ANDREI MOROIANU, UWE SEMMELMANN Abstract. We study generalized Killing spinors on compact Einstein manifolds with pos- itive scalar curvature Mathematics Subject Classification: Primary: 53C25, 53C27, 53C40, 83C05 Keywords: generalized Killing spinors

  5. GENERALIZED KILLING SPINORS ON EINSTEIN MANIFOLDS ANDREI MOROIANU, UWE SEMMELMANN

    E-print Network

    Semmelmann, Uwe

    GENERALIZED KILLING SPINORS ON EINSTEIN MANIFOLDS ANDREI MOROIANU, UWE SEMMELMANN Abstract. We study generalized Killing spinors on compact Einstein manifolds with posi- tive scalar curvature Mathematics Subject Classification: Primary: 53C25, 53C27, 53C40, 83C05 Keywords: generalized Killing spinors

  6. A comparative analysis of perspectives of Mileva Maric Einstein

    Microsoft Academic Search

    Carol C. Barnett

    1998-01-01

    This dissertation examines the controversy surrounding Mileva Maric Einstein and the allegations subsequent to the publication of love letters during the time that Mileva Maric and Albert Einstein were students and during the early years of their marriage. It also examines the role of women in science from a historical perspective. Chapter One surveys the history of women in science

  7. Quaternionic contact Einstein structures and the quaternionic contact Yamabe problem

    E-print Network

    Vassilev, Dimiter N.

    Quaternionic contact Einstein structures and the quaternionic contact Yamabe problem Stefan Ivanov@math.unm.edu #12;#12;Contents Chapter 1. Introduction 1 Chapter 2. Quaternionic contact structures and the Biquard.2. The Curvature Tensor 18 Chapter 4. QC-Einstein quaternionic contact structures 23 4.1. The Bianchi identities 24

  8. Modifying the Einstein Equations off the Constraint Hypersuface

    E-print Network

    J. David Brown; Lisa L. Lowe

    2006-06-02

    A new technique is presented for modifying the Einstein evolution equations off the constraint hypersurface. With this approach the evolution equations for the constraints can be specified freely. The equations of motion for the gravitational field variables are modified by the addition of terms that are linear and nonlocal in the constraints. These terms are obtained from solutions of the linearized Einstein constraints.

  9. The Lorentz Theory of Electrons and Einstein's Theory of Relativity

    ERIC Educational Resources Information Center

    Goldberg, Stanley

    1969-01-01

    Traces the development of Lorentz's theory of electrons as applied to the problem of the electrodynamics of moving bodies. Presents evidence that the principle of relativity did not play an important role in Lorentz's theory, and that though Lorentz eventually acknowledged Einstein's work, he was unwilling to completely embrace the Einstein

  10. [Photoeffects, Einstein's light quanta and the history of their acceptance].

    PubMed

    Wiederkehr, Karl Heinrich

    2006-01-01

    It is generally supposed, that the discovery of the efficacy-quantum by Planck was the impetus to Einstein's hypothesis of lightquanta. With its help Einstein could explain the external light-electrical effect. But even years before Einstein had worked at the photoeffect and already made experiments on it. For that reason the article gives a short survey about the history of the lightelectric effects. Lenard's basical work about the release of the photoelectrons is dealt with in detail, without which Einstein would scarcely have found his lightquanta. Furthermore it is shown how difficult it was for the physicists to give up--at least partially--the traditional view of the undulation-nature of light, and how they searched to explain the great energies of the photoelectrons. On the other side it is set forth how Einstein's formula of lightquanta was gradually confirmed. The tragical development of Einstein's personal relations with Johannes Stark and Philipp Lenard are briefly described. Stark was one of the few who supported Einstein's ideas at the beginning. Only with the Compton-effect, which could only be quantitatively interpreted by means of lightquanta and the special theory of relativity 1923, the way was free for the general acceptance of the lightquanta. Einstein did not agree to the obtained dualism of undulation and corpuscle; he had a different solution in mind about the fusion of the two forms of appearance of light. PMID:17338401

  11. On the Diffusion Coefficient: The Einstein Relation and Beyond

    Microsoft Academic Search

    Goran Peskir

    2003-01-01

    We present a detailed derivation of the closed-form expression for the diffusion coefficient that was initially obtained by Einstein.[4] The present derivation does not make use of a fictitious force as did the original Einstein derivation, but instead concentrates directly on establishing a dynamic equilibrium between the forces of pressure and friction acting on a Brownian particle. This approach makes

  12. Sources and Transport of Particulate Matter on an Hourly Time-Scale

    NASA Astrophysics Data System (ADS)

    Ancelet, T.; Davy, P.; Trompetter, B.; Markwitz, A.; Weatherburn, D.

    2012-12-01

    Particulate matter (PM) concentrations in New Zealand urban environments have been shown to have distinct diurnal cycles, independent of community size or population (Trompetter et al., 2010). Peak PM concentrations occur during the winter, when residential wood combustion for domestic heating is common. Little is known about PM sources and their contributions on an hourly timescale (Ancelet et al. 2012), creating a significant gap in current knowledge. As such, we have completed intensive ambient air monitoring campaigns in three locations across New Zealand during the winter (2010 and 2011) with the goal of identifying, using positive matrix factorization, the sources that contribute to measured PM10 concentrations on an hourly timescale. Size-segregated (PM10-2.5 and PM2.5) samples were collected on an hourly basis using Streaker samplers (Annegarn et al., 1988) at four sites within the airsheds of Masterton, Nelson and Alexandra, New Zealand. Three sites were located at ground level; upwind, central and downwind of the general nocturnal (katabatic) drainage flow. The fourth site was located centrally, but at a height of 26 m. Since Streaker filters cannot be used to obtain a gravimetric mass, continuous E-BAMs (MetOne Inc.) PM10 monitors were co-located at each sampling site as was meteorological equipment (Vaisala WXT520 sonic anemometers for wind speed, wind direction, temperature, relative humidity, barometric pressure). The hourly PM10-2.5 and PM2.5 samples were analyzed using ion beam analysis techniques (PIXE, PIGE and RBS) and black carbon was quantified using light reflection. PM10 concentrations at each site varied, but showed distinct diurnal patterns. Black carbon was highly correlated with PM10 concentrations, indicating that combustion sources were dominant at each site. The use of positive matrix factorization (PMF) revealed that biomass burning was the dominant source of PM10 at each site, with varying contributions from sources such as motor vehicles and marine aerosol. The contributions from each source were determined on an hourly timescale to produce a model of PM10 pollution sources and their contributions. The current study has shown that the collection and analysis of PM samples with hourly resolution provides detailed information for understanding urban PM sources and their contributions. The high-resolution sampling not only provides extremely useful temporal information, but also allows a large number of samples to be collected in a short timeframe, making PMF analysis more robust. Hourly contributions from pollution sources can provide regulatory authorities with information that is more relevant to the reduction of PM pollution compared to 24-hour integrated samples. This work was funded by the Ministry of Science and Innovation under contract C05X0903. The authors thank the Greater Wellington Regional Council, the Otago Regional Council and Nelson City Council for their support. The authors also thank Ed Hutchison, Bruce Crothers and Stuart Grange for the support during the monitoring.

  13. Einstein's First Steps Toward General Relativity: Gedanken Experiments and Axiomatics

    NASA Astrophysics Data System (ADS)

    Miller, A. I.

    1999-03-01

    Albert Einstein's 1907 Jahrbuch paper is an extraordinary document because it contains his first steps toward generalizing the 1905 relativity theory to include gravitation. Ignoring the apparent experimental disconfirmation of the 1905 relativity theory and his unsuccessful attempts to generalize the mass-energy equivalence, Einstein boldly raises the mass-energy equivalence to an axiom, invokes equality between gravitational and inertial masses, and then postulates the equivalence between a uniform gravitational field and an oppositely directed constant acceleration, the equivalence principle. How did this come about? What is at issue is scientific creativity. This necessitates broadening historical analysis to include aspects of cognitive science such as the role of visual imagery in Einstein's thinking, and the relation between conscious and unconscious modes of thought in problem solving. This method reveals the catalysts that sparked a Gedanken experiment that occurred to Einstein while working on the Jahrbuch paper. A mental model is presented to further explore Einstein's profound scientific discovery.

  14. A Note On Einstein, Bergmann, and the Fifth Dimension

    E-print Network

    Witten, Edward

    2014-01-01

    This note is devoted to a detail concerning the work of Albert Einstein and Peter Bergmann on unified theories of electromagnetism and gravitation in five dimensions. In their paper of 1938, Einstein and Bergmann were among the first to introduce the modern viewpoint in which a four-dimensional theory that coincides with Einstein-Maxwell theory at long distances is derived from a five-dimensional theory with complete symmetry among all five dimensions. But then they drew back, modifying the theory in a way that spoiled the five-dimensional symmetry and looks contrived to modern readers. Why? According to correspondence of Peter Bergmann with the author, the reason was that the more symmetric version of the theory predicts the existence of a new long range field (a massless scalar field). In 1938, Einstein and Bergmann did not wish to make this prediction. (Based on a lecture at the Einstein Centennial Celebration at the Library of Alexandria, June, 2005.

  15. Timescales of ductility in an extensional shear zone recorded as diffusion profiles in deformed quartz

    NASA Astrophysics Data System (ADS)

    Nachlas, William; Teyssier, Christian; Whitney, Donna

    2015-04-01

    We document rutile needles that were in the process of exsolving from quartz during ductile shearing, and we apply the Arrhenius parameters for Ti diffusion in quartz to extract the timescales over which diffusion transpired. By constraining temperature conditions of deformation using multiple independent thermometers in the same rocks (Ti-in-quartz, Zr-in-rutile, quartz fabrics and microstructures), we estimate the longevity of a ductile shear zone that accommodated extensional collapse in the North American Cordillera. Eocene exhumation of the Pioneer core complex, Idaho, USA, was accommodated by the brittle-ductile Wildhorse detachment system that localized in a zone of sheared metasediments and juxtaposes lower crustal migmatite gneisses with upper crustal Paleozoic sedimentary units. Deformation in the Wildhorse detachment was partly accommodated within a continuous sequence (~200 m) of quartzite mylonites, wherein quartz grains are densely rutilated with microscopic rutile needles that are pervasively oriented into the lineation direction. We apply high-resolution spectroscopic CL analysis to map the Ti concentration field in quartz surrounding rutile needles, revealing depletion halos that indicate exsolution as Ti unmixes from quartz. Linear transects through depletion halos show that concentration profiles exhibit a characteristic diffusion geometry. We apply an error-function diffusion model to fit the measured profiles to extract the temperature or time recorded in the profile. Assuming modest temperature estimates from our combined thermometry analysis, results of diffusion modeling suggest that the quartzite shear zone was deforming over an integrated 0.8 - 3.1 Myr. If samples are permitted to have deformed in discrete intervals, our results suggest deformation of individual samples for timescales as short as 100 kyr. By comparing samples from different levels of the shear zone, we find that deformation was sustained in higher levels of the shear zone for longer duration than in samples deeper into the footwall, which we interpret to reflect progressive downward propagation of a widening ductile zone. Considering the complex nonlinear feedbacks between the temperature- and time-dependence of both lattice diffusion and work hardening of microstructures, our approach introduces a unique opportunity to link timing with kinematics to reconstruct the thermomechanical evolution of a deforming shear zone. As a parallel test of this method, we have applied it to rock deformation experiments where it reproduces the approximate number of hours over which the experiment was conducted, further exemplifying the validity of this approach for constraining earth events.

  16. Young stellar object variability (YSOVAR): Long timescale variations in the mid-infrared

    SciTech Connect

    Rebull, L. M.; Cody, A. M.; Stauffer, J. R.; Morales-Calderón, M.; Carey, S. J. [Spitzer Science Center (SSC), Infrared Processing and Analysis Center (IPAC), 1200 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Covey, K. R. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Günther, H. M.; Poppenhaeger, K.; Wolk, S. J.; Hora, J. L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hillenbrand, L. A. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Plavchan, P. [NASA Exoplanet Science Institute (NExScI), Infrared Processing and Analysis Center (IPAC), 1200 East California Boulevard, California Institute of Technology, Pasadena, CA 91125 (United States); Gutermuth, R. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Song, I. [Physics and Astronomy Department, University of Georgia, Athens, GA 30602-2451 (United States); Barrado, D. [Departamento de Astrofísica, Centro de Astrobiología (INTA-CSIC), ESAC campus, P.O. Box 78, E-28691 Villanueva de la Cañada (Spain); Bayo, A. [Max Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); James, D. [Cerro Tololo InterAmerican Observatory (CTIO), Casilla 603, La Serena (Chile); Vrba, F. J. [US Naval Observatory, Flagstaff Station 10391 West Naval Observatory Road, Flagstaff, AZ 86005 (United States); Alves de Oliveira, C. [European Space Agency (ESA/ESAC), P.O. Box 78, E-28691 Villanueva de la Caãda, Madrid (Spain); Bouvier, J., E-mail: rebull@ipac.caltech.edu [Univ. Grenoble Alpes, IPAG, F-38000 Grenoble (France); and others

    2014-11-01

    The YSOVAR (Young Stellar Object VARiability) Spitzer Space Telescope observing program obtained the first extensive mid-infrared (3.6 and 4.5 ?m) time series photometry of the Orion Nebula Cluster plus smaller footprints in 11 other star-forming cores (AFGL 490, NGC 1333, Mon R2, GGD 12-15, NGC 2264, L1688, Serpens Main, Serpens South, IRAS 20050+2720, IC 1396A, and Ceph C). There are ?29,000 unique objects with light curves in either or both IRAC channels in the YSOVAR data set. We present the data collection and reduction for the Spitzer and ancillary data, and define the 'standard sample' on which we calculate statistics, consisting of fast cadence data, with epochs roughly twice per day for ?40 days. We also define a 'standard sample of members' consisting of all the IR-selected members and X-ray-selected members. We characterize the standard sample in terms of other properties, such as spectral energy distribution shape. We use three mechanisms to identify variables in the fast cadence data—the Stetson index, a ?{sup 2} fit to a flat light curve, and significant periodicity. We also identified variables on the longest timescales possible of six to seven years by comparing measurements taken early in the Spitzer mission with the mean from our YSOVAR campaign. The fraction of members in each cluster that are variable on these longest timescales is a function of the ratio of Class I/total members in each cluster, such that clusters with a higher fraction of Class I objects also have a higher fraction of long-term variables. For objects with a YSOVAR-determined period and a [3.6]-[8] color, we find that a star with a longer period is more likely than those with shorter periods to have an IR excess. We do not find any evidence for variability that causes [3.6]-[4.5] excesses to appear or vanish within our data set; out of members and field objects combined, at most 0.02% may have transient IR excesses.

  17. Determination of Arctic sea ice variability modes on interannual timescales via nonhierarchical clustering

    NASA Astrophysics Data System (ADS)

    Fu?kar, Neven-Stjepan; Guemas, Virginie; Massonnet, François; Doblas-Reyes, Francisco

    2015-04-01

    Over the modern observational era, the northern hemisphere sea ice concentration, age and thickness have experienced a sharp long-term decline superimposed with strong internal variability. Hence, there is a crucial need to identify robust patterns of Arctic sea ice variability on interannual timescales and disentangle them from the long-term trend in noisy datasets. The principal component analysis (PCA) is a versatile and broadly used method for the study of climate variability. However, the PCA has several limiting aspects because it assumes that all modes of variability have symmetry between positive and negative phases, and suppresses nonlinearities by using a linear covariance matrix. Clustering methods offer an alternative set of dimension reduction tools that are more robust and capable of taking into account possible nonlinear characteristics of a climate field. Cluster analysis aggregates data into groups or clusters based on their distance, to simultaneously minimize the distance between data points in a given cluster and maximize the distance between the centers of the clusters. We extract modes of Arctic interannual sea-ice variability with nonhierarchical K-means cluster analysis and investigate the mechanisms leading to these modes. Our focus is on the sea ice thickness (SIT) as the base variable for clustering because SIT holds most of the climate memory for variability and predictability on interannual timescales. We primarily use global reconstructions of sea ice fields with a state-of-the-art ocean-sea-ice model, but we also verify the robustness of determined clusters in other Arctic sea ice datasets. Applied cluster analysis over the 1958-2013 period shows that the optimal number of detrended SIT clusters is K=3. Determined SIT cluster patterns and their time series of occurrence are rather similar between different seasons and months. Two opposite thermodynamic modes are characterized with prevailing negative or positive SIT anomalies over the Arctic basin. The intermediate mode, with negative anomalies centered on the East Siberian shelf and positive anomalies along the North American side of the basin, has predominately dynamic characteristics. The associated sea ice concentration (SIC) clusters vary more between different seasons and months, but the SIC patterns are physically framed by the SIT cluster patterns.

  18. Experimental evidence for millisecond activation timescales using the Fast IN Chamber (FINCH) measurements

    NASA Astrophysics Data System (ADS)

    Bundke, U.; Jaenicke, R.; Klein, H.; Nillius, B.; Reimann, B.; Wetter, T.; Bingemer, H.

    2009-04-01

    Ice formation in clouds is a subject of great practical and fundamental importance since the occurrence of ice particle initializes dramatic changes in the microphysical structure of the cloud, which finally ends in the formation of precipitation. The initially step of ice formation is largely unknown. Homogenous nucleation of ice occurs only below -40 °C. If an ice nucleus (IN) is present, heterogeneous nucleation may occur at higher temperature. Here deposition freezing, condensation and immersion freezing as well as contact freezing are known. Also growth rates of ice particles are known as function of crystal surface properties, temperature and super saturation. Timescales for homogenous freezing activation in the order of 0.01 seconds and nucleation rates have been measured by Anderson et al. (1980) and Hagen et al., (1981) using their expansion cloud chamber. This contribution of deposition mode freezing measurements by the ice nucleus counter FINCH presents evidence that the activation timescale of this freezing mode is in the order of 1E-3 seconds. FINCH is an Ice Nucleus counter which activates IN in a supersaturated environment at freezing temperatures. The activation conditions are actively controlled by mixing three gas flows (aerosol, particle-free cold-dry and warm-humid flows).See Bundke et al. 2008 for details. In a special operation mode of FINCH we are able to produce a controlled peak super saturation in the order of 1 ms duration. For several test aerosols the results observed in this particular mode are comparable to normal mode operations, where the maximum super saturation remains for more than a second, thus leading to the conclusion that the time for activation is in the order of 1ms or less. References: R.J. Anderson et al, "A Study of Homogeneous Condensation Freezing Nucleation of Small Water Droplets in an Expansion Cloud Chamber, Journal of the Atmospheric Sciences, Vol. 37, 2508-2520, 1980 U.Bundke et al., "The fast Ice Nucleus chamber FINCH", Atmospheric Research, Volume 90, Issues 2-4, 180-186, DOI:10.1016/j.atmosres.2008.02.008, 2008 D.E. Hagen et al., "Homogenous Condensation Freezing Nucleation Rate Measurements for Small Water Droplets in an Expansion Cloud Chamber", Journal of the Atmospheric Sciences, Vol 38, 1236-1243, 1981 Acknowledgments: This work was supported by the German Research Foundation: SFB 641 "Tropospheric Ice Phase" TP A1, SPP1294 BU1432/3-1, JA344/12-1, by the Helmholtz Association: VI-233 "Aerosol Cloud Interactions" and by and by the EU FP6 Infastructure Project EUSAAR.

  19. Earth History databases and visualization - the TimeScale Creator system

    NASA Astrophysics Data System (ADS)

    Ogg, James; Lugowski, Adam; Gradstein, Felix

    2010-05-01

    The "TimeScale Creator" team (www.tscreator.org) and the Subcommission on Stratigraphic Information (stratigraphy.science.purdue.edu) of the International Commission on Stratigraphy (www.stratigraphy.org) has worked with numerous geoscientists and geological surveys to prepare reference datasets for global and regional stratigraphy. All events are currently calibrated to Geologic Time Scale 2004 (Gradstein et al., 2004, Cambridge Univ. Press) and Concise Geologic Time Scale (Ogg et al., 2008, Cambridge Univ. Press); but the array of intercalibrations enable dynamic adjustment to future numerical age scales and interpolation methods. The main "global" database contains over 25,000 events/zones from paleontology, geomagnetics, sea-level and sequence stratigraphy, igneous provinces, bolide impacts, plus several stable isotope curves and image sets. Several regional datasets are provided in conjunction with geological surveys, with numerical ages interpolated using a similar flexible inter-calibration procedure. For example, a joint program with Geoscience Australia has compiled an extensive Australian regional biostratigraphy and a full array of basin lithologic columns with each formation linked to public lexicons of all Proterozoic through Phanerozoic basins - nearly 500 columns of over 9,000 data lines plus hot-curser links to oil-gas reference wells. Other datapacks include New Zealand biostratigraphy and basin transects (ca. 200 columns), Russian biostratigraphy, British Isles regional stratigraphy, Gulf of Mexico biostratigraphy and lithostratigraphy, high-resolution Neogene stable isotope curves and ice-core data, human cultural episodes, and Circum-Arctic stratigraphy sets. The growing library of datasets is designed for viewing and chart-making in the free "TimeScale Creator" JAVA package. This visualization system produces a screen display of the user-selected time-span and the selected columns of geologic time scale information. The user can change the vertical-scale, column widths, fonts, colors, titles, ordering, range chart options and many other features. Mouse-activated pop-ups provide additional information on columns and events; including links to external Internet sites. The graphics can be saved as SVG (scalable vector graphics) or PDF files for direct import into Adobe Illustrator or other common drafting software. Users can load additional regional datapacks, and create and upload their own datasets. The "Pro" version has additional dataset-creation tools, output options and the ability to edit and re-save merged datasets. The databases and visualization package are envisioned as a convenient reference tool, chart-production assistant, and a window into the geologic history of our planet.

  20. Conditions and timescales for welding block-and-ash flow deposits

    NASA Astrophysics Data System (ADS)

    Heap, M. J.; Kolzenburg, S.; Russell, J. K.; Campbell, M. E.; Welles, J.; Farquharson, J. I.; Ryan, A.

    2014-12-01

    Welding of pyroclastic deposits to reform a coherent rock mass is a common phenomenon, especially for pumiceous pyroclastic density current deposits (i.e., ignimbrites). However, and despite the pervasive abundance of block-and-ash flow (BAF) deposits in the geological and modern record, instances of strongly welded BAF deposits are few. Here, we present a series of high-temperature (800-900 °C) compaction experiments designed to map the conditions (deposit thickness/stress and temperature/viscosity) and timescales that permit or inhibit the welding of BAF deposits. Our experiments were performed on unconsolidated aggregates (containing an ash and lapilli component) derived from crushed and sieved lava blocks (containing 25% crystals) taken from the well-documented welded BAF deposit at Mount Meager volcano (British Columbia, Canada). The experiments demonstrate that welding efficiency increases with increasing time and temperature. Progressive welding is expressed by increasing axial strain, porosity loss, and bulk density. The rate of change of each of these physical properties reduces as welding progresses. Microstructural analysis of the experimental products shows that the loss of interclast porosity during welding results from the progressive sintering and amalgamation of vitric fragments, and that the pore shape changes from sub-equant pores to stretched lenses sandwiched between vitric and crystal fragments. The coincidence between the microstructure and rock physical properties of the natural and experimental samples highlight that we have successfully reproduced welded BAF in the laboratory. Furthermore, our permeability measurements highlight a hysteresis in the return journey of the "there-and-back-again" volcanic permeability cycle (expressed by an increase in permeability due to vesiculation and fragmentation followed by a decrease due to welding). This hysteresis cannot be described by a single porosity-permeability power law relationship and reflects the change in pore shape and connectivity during welding. Finally, we show that a simple model for welding can accurately forecast the welding timescales of the BAF deposit at Mount Meager (as reconstructed from the collapse of the Lillooet River valley dam) using our experimental data. We use this validation as a platform to provide a universal window for the welding of BAF deposits, also applicable for comparable welded deposits (e.g., welded autobreccias in block-lavas and lava domes), for a broad range of deposit thickness (or stress) and effective viscosity.

  1. Mixing the mantle marble-cake: timescale constraints from Os isotopes

    NASA Astrophysics Data System (ADS)

    Parman, S.; Pearson, G.; Nowell, G.; van Hunen, J.

    2007-12-01

    In their seminal paper, Allegre and Turcotte (1986) presented a model in which the upper mantle is a mixture of depleted, harzburgitic mantle and subducted basalt that has been mechanically mixed together, the mantle marble-cake. Since their publication, most studies of mantle heterogeneity have focused on the enriched components, which are equated with subducted basalt and/or sediments, and successfully explain OIB Sr-Nd-Pb isotopic systematics. In this talk, we will focus on a different part of the marble-cake, depleted (harzburgitic) heterogeneities. Though abundant in abyssal peridotites and ophiolites, these have been difficult to study geochemically because they have very low concentrations of typical trace elements and radiogenic isotopes, and are overprinted by any mixing with enriched mantle or melts. However, Os is compatible during mantle melting, is enriched in depleted mantle and thus is robust with respect to mixing with enriched components or metasomatism. Somewhat surprisingly, Os isotope studies of the convecting mantle show clear evidence for depleted heterogeities up to 2 billion years old, but the relative paucity of data (less than 100 analyses), makes it difficult to extract meaningful mixing information. Rapid analysis of osmiridium grains by laser-ablation inductively coupled multi-collector plasma mass spectrometry now allows large Os datasets to be acquired (100s of datapoints), which are suitable for statistical analyses (Meibom, 2002). Here we present new and published laser-ablation analyses of osmiridiums from a global collection. The data generally show an exponential decrease in heterogeneities with age, such that over 90% of heterogeneities are destroyed within 2 billion years, though rare heterogeneities as old as 2.7 Ga survive. The exponential decrease in survivorship is generally consistent with the mechanical mixing model of Allegre & Turcotte (1986). Subsequent 2-dimensional mixing models suggest that high-viscosity blobs can persist for much longer time-scales than 2 Ga (Manga, 1996). Thus the relatively fast mixing suggested by the Os data may imply that 1) the depleted heterogeneities have similar viscosities to their surrounding mantle, 2) 2D models overestimate mixing timescales or 3) other processes, such as melt infiltration, may destroy depleted heterogeneities.

  2. THE COLORADO PLATEAU CORING PROJECT: THE TIMESCALE AND TEMPO OF BIOTIC CHANGE OF THE EARLY MESOZOIC

    NASA Astrophysics Data System (ADS)

    Olsen, P. E.; Kent, D. V.; Mundil, R.; Irmis, R.; Geissman, J. W.; Martz, J.; Parker, W.

    2009-12-01

    The proposed Colorado Plateau Coring Project (CPCP) is an interdisciplinary, multi-institutional coring project designed to recover continuous core through mostly continental strata spanning ~100 million years of the Triassic and Jurassic. Its principal purpose is to tie the incredibly rich faunas, floras, and environmental record of this interval to a rigorously developed timescale and thus to biotic, environmental, and tectonic events at a global-scale. The overall strategy involves 3 long cores (~1000 m) and 2 shorter cores (300-500 m) intended to recover the full expression of the critical early Mesozoic transitions in clear superposition. The cores would span from the base of the Moenkopi to the top of the Morrison formations with sufficient overlap to splice the sections together without gaps and assess lateral facies variations, thickness changes, and stratigraphic completeness. The initial phase of the CPCP, currently under review, is a ~500 m core at Petrified Forest National Park (PFNP) that will recover virtually the entire pre-Owl Rock Mb. of the Late Triassic age Chinle and underlying Early-Middle Triassic age Moenkopi formations. Despite excellent outcrop and a long and distinguished history of study, striking ambiguities exist in local correlation, the temporal duration and resolution of biotic events, global correlations, and the paleolatitudinal position of the region that prevent tests of major competing climatic, biotic, and tectonic hypotheses of global significance. For example, correlations of existing paleomagnetic polarity data for the Chinle of PFNP (1) with the Newark basin astronomically tuned geomagnetic polarity timescale are consistent with new U-Pb dates from reworked volcanics in the Chinle, and result in three sets of implied hypotheses. First, most or all of the Chinle Fm. is Norian and younger in age (< ~ 220 Ma). Second, the supposed Carnian-Norian boundary in the Chinle is actually a late middle Norian extinction that may coincide with the 215.5 Ma Manicouagan impact (2). Third, tetrapod faunas of tropical Pangea (i.e., Colorado Plateau) were radically different than those from contemporary higher latitudes despite the apparent geographic contiguity. These hypotheses cannot be directly tested, however, because the outcrop data are fraught with numerous intrinsic ambiguities. Unambiguous testing of these ideas requires continuous coring, which promises to fundamentally change the certainty and specificity of addressing questions relating the rich surface record from the Chinle and Moenkopi to Earth system processes. 1, Steiner, M., Lucas, S.G., J.G.R. B, 105(11):25791; 2, Ramezani, J. et al., 2005, Geochim. Cosmochim. Acta 69(10):321 Suppl.

  3. Summer drought in Fennoscandia for the last 750 years - possible forcings on short and long timescales

    NASA Astrophysics Data System (ADS)

    Linderholm, H. W.; Seftigen, K.; Cook, E. R.; Björklund, J.; Ou, T.; Chen, D.

    2013-12-01

    Increased droughts associated with a warming world will significantly affect societies in many different ways. They will likely become more severe and frequent in dry and warm regions, but can also have serious impacts on ecosystems and societies in temperate regions. In Fennoscandia, summer droughts are associated with negative impacts on agriculture, limitations in water use, increased frequency of forest fires and health problems. Thus, planning in a number of societally important sectors would benefit greatly if such high-impact climate events could be predicted seasons to years ahead. Although individual weather events cannot be predicted more than a few days ahead, the potential predictability lies in the components of the climate system exhibiting slow variations, which can have persistent and predictable influences on climate variability. Fennoscandian droughts are related to high-pressure anomalies similar to the summer NAO (SNAO). A likely influencing factor on the SNAO is the phase of the Atlantic Multidecadal Oscillation (AMO), but possibly also sea-ice variability in the arctic and remote influences from the tropics. Thus, several potential forcings needs to be investigated to better understand the mechanisms behind regional summer droughts. However, there is a possibility that parts of the found associations are due to anthropogenic impacts (e.g. increased CO2 and aerosols). Thus, to evaluate to relative influence of the forcing candidates, we need to extend the observational records back in time using proxy data. Numerous tree-ring width and maximum latewood density chronologies from temperature sensitive trees in Fennoscandia have been widely used to reconstruct past temperatures. However, comparatively few efforts have been made to provide tree-ring based hydroclimatological reconstructions for these regions. Here we utilize the first tree-ring derived spatial reconstruction of summer drought for the Fennoscandian region to investigate the long-term forcing on regional drought for the last 750 years. A point-by-point multiple nested regression approach was used to reconstruct June through August average Standardized Precipitation Evaporation Index (SPEI) with a spatial resolution of 0.5°x 0.5°. We present the drought evolution for Fennoscandia, but also look at regional drought patterns through time. Comparisons with independent proxy data (Northeast North Atlantic SST, AMO, NAO and Arctic Sea-Ice extent) show that on interannual timescales, there is an agreement between the NAO and Fennoscandian SPEI, while on decadal and longer timescales there is an influence of North Atlantic SST variability and Arctic Sea Ice extent variability.

  4. A new index to quantify hysteresis at the runoff event timescale

    NASA Astrophysics Data System (ADS)

    Zuecco, Giulia; Penna, Daniele; van Meerveld, Ilja; Borga, Marco

    2015-04-01

    Hysteresis is a non-linear loop-like behavior that is common in natural systems. Hysteresis is common in the relation between streamflow and a number of other hydrologic variables, e.g., groundwater levels, soil moisture, extent of the saturated area, and sediment and solute concentrations. Analysis of these hysteretic patterns at the event time scale can lead to a better understanding of the processes underlying the catchment hydrological response. Hysteretic patterns can also be used for model calibration and testing. Several indexes have been developed to analyze hysteresis and quantify the direction and the extent of the loops, particularly to determine hysteresis in the relation between sediment concentrations and runoff. However, they typically suffer from a degree of subjectivity, do not take into account complex hysteretic patterns and are therefore not always applicable to describe other hysteretic relations as well. Therefore, we present a new versatile index for the quantification of a wide range hysteretic loops between hydrological variables at the runoff event timescale and test the sensitivity of the index to the temporal resolution of the measurement data and measurement errors. The conceptual development of the new hysteresis index is based on i) a normalization to compare hysteretic loops at different space- and timescales, and ii) the computation of the slopes of segments connecting the initial state to observations of the independent variable. The index provides information on the direction, the extent and the shape of the hysteretic loops. The index was tested with hydrological data from three experimental catchments in Northern Italy. Hysteretic relations between streamflow (the independent variable) and four different dependent variables (soil moisture, groundwater level, isotopic composition of stream water and electrical conductivity of stream water) were correctly identified and quantified by the index. The objective quantification of hysteresis by the index allowed for the robust classification of hysteresis in datasets and thus to determine differences in hydrological responses for different events. The index also captured the switch in the direction of the hysteretic relation between soil moisture and streamflow with changes in event size and antecedent wetness conditions well. Finally, the sensitivity analyses showed that the index was little affected by the temporal resolution of the measurements and random errors in the input data. Keywords: hysteresis index; hysteretic loops; streamflow; soil moisture; seasonal dynamics; sensitivity analysis

  5. Influence of equatorial diatom processes on Si deposition and atmospheric CO2 cycles at glacial//interglacial timescales

    E-print Network

    Maine, University of

    Influence of equatorial diatom processes on Si deposition and atmospheric CO2 cycles at glacial diatom processes on Si deposition and atmospheric CO2 cycles at glacial/interglacial timescales, Paleoceanography, 19, PA3011, doi:10.1029/2003PA000929. 1. Introduction [2] CO2 increased before the melting

  6. A Timescale for Evolution, Population Expansion, and Spatial Spread of an Emerging Clone of Methicillin-Resistant Staphylococcus aureus

    Microsoft Academic Search

    Ulrich Nübel; Janina Dordel; Kevin Kurt; Birgit Strommenger; Henrik Westh; Sanjay K. Shukla; Helena Žemli?ková; Raphaël Leblois; Thierry Wirth; Thibaut Jombart; François Balloux; Wolfgang Witte

    2010-01-01

    Due to the lack of fossil evidence, the timescales of bacterial evolution are largely unknown. The speed with which genetic change accumulates in populations of pathogenic bacteria, however, is a key parameter that is crucial for understanding the emergence of traits such as increased virulence or antibiotic resistance, together with the forces driving pathogen spread. Methicillin-resistant Staphylococcus aureus (MRSA) is

  7. A review of Holocene solar-linked climatic variation on centennial to millennial timescales: Physical processes, interpretative frameworks and

    E-print Network

    Usoskin, Ilya G.

    A review of Holocene solar-linked climatic variation on centennial to millennial timescales: Physical processes, interpretative frameworks and a new multiple cross-wavelet transform algorithm Willie Observatory and Department of Physics, University of Oulu, 90014, Finland f Institute of Marine Geology

  8. A joint time-scale representation methodology for the detection of acoustic gravity wave induced by solar eclipses

    E-print Network

    Boyer, Edmond

    A joint time-scale representation methodology for the detection of acoustic gravity wave induced acoustic-gravity waves propagating through Ionosphere. It is based on data consisting of the time. Acoustic- gravity waves (AGW) are the sources of most of the short- time Ionospheric variability and play

  9. Evaluation of electrical conductivity and equations of state of non-ideal plasma through microsecond timescale underwater electrical wire explosion

    Microsoft Academic Search

    D. Sheftman; Ya. E. Krasik

    2011-01-01

    Experimental and simulation results of underwater electrical Cu, Al, and W wire explosions in the microsecond timescale are presented. It was shown that the electrical conductivity results for Cu and Al agree well with modified Lee-More and quantum molecular dynamic models for temperatures above 10 kK. The equation of state (EOS) values based on SESAME tables for Cu and Al

  10. Long-range transport of black carbon to the Pacific Ocean and its dependence on aging timescale

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Liu, J.; Tao, S.; Ban-Weiss, G. A.

    2015-06-01

    Improving the ability of global models to predict concentrations of black carbon (BC) over the Pacific Ocean is essential to evaluate the impact of BC on marine climate. In this study, we tag BC tracers from 13 source regions around the globe in a global chemical transport model MOZART-4. Numerous sensitivity simulations are carried out varying the aging timescale of BC emitted from each source region. The aging timescale for each source region is optimized by minimizing errors in vertical profiles of BC mass mixing ratios between simulations and HIAPER Pole-to-Pole Observations (HIPPO). For most HIPPO deployments, in the Northern Hemisphere, optimized aging timescales are less than half a day for BC emitted from tropical and mid-latitude source regions, and about 1 week for BC emitted from high latitude regions in all seasons except summer. We find that East Asian emissions contribute most to the BC loading over the North Pacific, while South American, African and Australian emissions dominate BC loadings over the South Pacific. Dominant source regions contributing to BC loadings in other parts of the globe are also assessed. The lifetime of BC originating from East Asia (i.e., the world's largest BC emitter) is found to be only 2.2 days, much shorter than the global average lifetime of 4.9 days, making East Asia's contribution to global burden only 36 % of BC from the second largest emitter, Africa. Thus, evaluating only relative emission rates without accounting for differences in aging timescales and deposition rates is not predictive of the contribution of a given source region to climate impacts. Our simulations indicate that lifetime of BC increases nearly linearly with aging timescale for all source regions. When aging rate is fast, the lifetime of BC is largely determined by factors that control local deposition rates (e.g. precipitation). The sensitivity of lifetime to aging timescale depends strongly on the initial hygroscopicity of freshly emitted BC. Our findings suggest that the aging timescale of BC varies significantly by region and season, and can strongly influence the contribution of source regions to BC burdens around the globe. Improving parameterizations of the aging process for BC is important for enhancing the predictive skill of air quality and climate models. Future observations that investigate the evolution of hygroscopicity of BC as it ages from different source regions to the remote atmosphere are urgently needed.

  11. Einstein's cosmology review of 1933: a new perspective on the Einstein-de Sitter model of the cosmos

    NASA Astrophysics Data System (ADS)

    O'Raifeartaigh, Cormac; O'Keeffe, Michael; Nahm, Werner; Mitton, Simon

    2015-06-01

    We present a first English translation and analysis of a little-known review of relativistic cosmology written by Albert Einstein in late 1932. The article, which was published in 1933 in a book of Einstein papers translated into French, contains a substantial review of static and dynamic relativistic models of the cosmos, culminating in a discussion of the Einstein-de Sitter model. The article offers a valuable contemporaneous insight into Einstein's cosmology in the early 1930s and confirms that his interest lay in the development of the simplest model of the cosmos that could account for observation. The article also confirms that Einstein did not believe that simplified relativistic models could give an accurate description of the early universe.

  12. The variability time-scales and brightness temperatures of radio flares from stars to supermassive black holes

    NASA Astrophysics Data System (ADS)

    Pietka, M.; Fender, R. P.; Keane, E. F.

    2015-02-01

    In this paper we compile the analysis of ˜200 synchrotron flare events from ˜90 distinct objects/events for which the distance is well established, and hence the peak luminosity can be accurately estimated. For each event we measure this peak and compare it to the rise and decay time-scales, as fit by exponential functions, which allows us in turn to estimate a minimum brightness temperature for all the events. The astrophysical objects from which the flares originate vary from flare stars to supermassive black holes in active galactic nuclei, and include both repeating phenomena and single cataclysmic events (such as supernovae and gamma-ray burst afterglows). The measured time-scales vary from minutes to longer than years, and the peak radio luminosities range over 22 orders of magnitude. Despite very different underlying phenomena, including relativistic and non-relativistic regimes, and highly collimated versus isotropic phenomena, we find a broad correlation between peak radio luminosity and rise/decay time-scales, approximately of the form L ? ?5. This rather unexpectedly demonstrates that the estimated minimum brightness temperature, when based upon variability time-scales, and with no attempt to correct for relativistic boosting, is a strongly rising function of source luminosity. It furthermore demonstrates that variability time-scales could be used as an early diagnostic of source class in future radio transient surveys. As an illustration of radio transients parameter space, we compare the synchrotron events with coherent bursts at higher brightness temperatures to illustrate which regions of radio transient parameter space have been explored.

  13. Long timescale fMRI neuronal adaptation effects in human amblyopic cortex.

    PubMed

    Li, Xingfeng; Coyle, Damien; Maguire, Liam; McGinnity, Thomas M; Hess, Robert F

    2011-01-01

    An investigation of long timescale (5 minutes) fMRI neuronal adaptation effects, based on retinotopic mapping and spatial frequency stimuli, is presented in this paper. A hierarchical linear model was developed to quantify the adaptation effects in the visual cortex. The analysis of data involved studying the retinotopic mapping and spatial frequency adaptation effects in the amblyopic cortex. Our results suggest that, firstly, there are many cortical regions, including V1, where neuronal adaptation effects are reduced in the cortex in response to amblyopic eye stimulation. Secondly, our results show the regional contribution is different, and it seems to start from V1 and spread to the extracortex regions. Thirdly, our results show that there is greater adaptation to broadband retinotopic mapping as opposed to narrowband spatial frequency stimulation of the amblyopic eye, and we find significant correlation between fMRI response and the magnitude of the adaptation effect, suggesting that the reduced adaptation may be a consequence of the reduced response to different stimuli reported for amblyopic eyes. PMID:22065999

  14. Tracking niche variation over millennial timescales in sympatric killer whale lineages

    PubMed Central

    Foote, Andrew D.; Newton, Jason; Ávila-Arcos, María C.; Kampmann, Marie-Louise; Samaniego, Jose A.; Post, Klaas; Rosing-Asvid, Aqqalu; Sinding, Mikkel-Holger S.; Gilbert, M. Thomas P.

    2013-01-01

    Niche variation owing to individual differences in ecology has been hypothesized to be an early stage of sympatric speciation. Yet to date, no study has tracked niche width over more than a few generations. In this study, we show the presence of isotopic niche variation over millennial timescales and investigate the evolutionary outcomes. Isotopic ratios were measured from tissue samples of sympatric killer whale Orcinus orca lineages from the North Sea, spanning over 10 000 years. Isotopic ratios spanned a range similar to the difference in isotopic values of two known prey items, herring Clupea harengus and harbour seal Phoca vitulina. Two proxies of the stage of speciation, lineage sorting of mitogenomes and genotypic clustering, were both weak to intermediate indicating that speciation has made little progress. Thus, our study confirms that even with the necessary ecological conditions, i.e. among-individual variation in ecology, it is difficult for sympatric speciation to progress in the face of gene flow. In contrast to some theoretical models, our empirical results suggest that sympatric speciation driven by among-individual differences in ecological niche is a slow process and may not reach completion. We argue that sympatric speciation is constrained in this system owing to the plastic nature of the behavioural traits under selection when hunting either mammals or fish. PMID:23945688

  15. Comparisons of characteristic timescales and approximate models for Brownian magnetic nanoparticle rotations

    NASA Astrophysics Data System (ADS)

    Reeves, Daniel B.; Weaver, John B.

    2015-06-01

    Magnetic nanoparticles are promising tools for a host of therapeutic and diagnostic medical applications. The dynamics of rotating magnetic nanoparticles in applied magnetic fields depend strongly on the type and strength of the field applied. There are two possible rotation mechanisms and the decision for the dominant mechanism is often made by comparing the equilibrium relaxation times. This is a problem when particles are driven with high-amplitude fields because they are not necessarily at equilibrium at all. Instead, it is more appropriate to consider the "characteristic timescales" that arise in various applied fields. Approximate forms for the characteristic time of Brownian particle rotations do exist and we show agreement between several analytical and phenomenological-fit models to simulated data from a stochastic Langevin equation approach. We also compare several approximate models with solutions of the Fokker-Planck equation to determine their range of validity for general fields and relaxation times. The effective field model is an excellent approximation, while the linear response solution is only useful for very low fields and frequencies for realistic Brownian particle rotations.

  16. A linear framework for time-scale separation in nonlinear biochemical systems.

    PubMed

    Gunawardena, Jeremy

    2012-01-01

    Cellular physiology is implemented by formidably complex biochemical systems with highly nonlinear dynamics, presenting a challenge for both experiment and theory. Time-scale separation has been one of the few theoretical methods for distilling general principles from such complexity. It has provided essential insights in areas such as enzyme kinetics, allosteric enzymes, G-protein coupled receptors, ion channels, gene regulation and post-translational modification. In each case, internal molecular complexity has been eliminated, leading to rational algebraic expressions among the remaining components. This has yielded familiar formulas such as those of Michaelis-Menten in enzyme kinetics, Monod-Wyman-Changeux in allostery and Ackers-Johnson-Shea in gene regulation. Here we show that these calculations are all instances of a single graph-theoretic framework. Despite the biochemical nonlinearity to which it is applied, this framework is entirely linear, yet requires no approximation. We show that elimination of internal complexity is feasible when the relevant graph is strongly connected. The framework provides a new methodology with the potential to subdue combinatorial explosion at the molecular level. PMID:22606254

  17. Rhythmic Auditory Cortex Activity at Multiple Timescales Shapes Stimulus–Response Gain and Background Firing

    PubMed Central

    Wilson, Caroline; Safaai, Houman; Sakata, Shuzo; Panzeri, Stefano

    2015-01-01

    The phase of low-frequency network activity in the auditory cortex captures changes in neural excitability, entrains to the temporal structure of natural sounds, and correlates with the perceptual performance in acoustic tasks. Although these observations suggest a causal link between network rhythms and perception, it remains unknown how precisely they affect the processes by which neural populations encode sounds. We addressed this question by analyzing neural responses in the auditory cortex of anesthetized rats using stimulus–response models. These models included a parametric dependence on the phase of local field potential rhythms in both stimulus-unrelated background activity and the stimulus–response transfer function. We found that phase-dependent models better reproduced the observed responses than static models, during both stimulation with a series of natural sounds and epochs of silence. This was attributable to two factors: (1) phase-dependent variations in background firing (most prominent for delta; 1–4 Hz); and (2) modulations of response gain that rhythmically amplify and attenuate the responses at specific phases of the rhythm (prominent for frequencies between 2 and 12 Hz). These results provide a quantitative characterization of how slow auditory cortical rhythms shape sound encoding and suggest a differential contribution of network activity at different timescales. In addition, they highlight a putative mechanism that may implement the selective amplification of appropriately timed sound tokens relative to the phase of rhythmic auditory cortex activity. PMID:25995464

  18. Taking the longer view: Timescales, fairness and a forgotten story of irrigation in Australia

    NASA Astrophysics Data System (ADS)

    Gross, Catherine; Dumaresq, David

    2014-11-01

    This paper explores timescales, changing worldviews and the impact of water reform on irrigation communities in Australia whose water sharing arrangements have roots in an earlier era. Through the story of Australian irrigation it describes some subtle shifts and changes in worldviews that have influenced land and water governance reform over time. It shows how reforms can result in tangible adverse effects on communities if they overturn critical features of earlier resource sharing arrangements without consideration of unintended consequences. Where changing worldviews, reforms and the ability of communities to adapt are out of synchronisation then friction ensues, as was seen in the Murray-Darling Basin when proposed reforms have resulted in widespread disputes between reformers and irrigation communities. Failure to understand how perspectives over time have changed leads to a failure to deliver fairness in water governance reforms. If policymakers lose understanding of the rationale for earlier arrangements in land and water governance and introduce reforms that do not take these into account then adaptation to the reform and social acceptance is impeded. Seen in this way, time can be considered a competing element in fair land and water governance. Maintaining an understanding of how and why change takes place over time, and the rationale for key elements of governance developed in an earlier era, is critical for those wishing to overcome the challenges of implementation, deliver fairness, and gain community acceptance of reform.

  19. A multiple time-scale computational model of a tumor and its micro environment.

    PubMed

    DuBois, Christopher; Farnham, Jesse; Aaron, Eric; Radunskaya, Ami

    2013-02-01

    Experimental evidence suggests that a tumor's environment may be critical to designing successful therapeutic protocols: Modeling interactions between a tumor and its environment could improve our understanding of tumor growth and inform approaches to treatment. This paper describes an efficient, flexible, hybrid cellular automaton-based implementation of numerical solutions to multiple time-scale reaction-diffusion equations, applied to a model of tumor proliferation. The growth and maintenance of cells in our simulation depend on the rate of cellular energy (ATP) metabolized from nearby nutrients such as glucose and oxygen. Nutrient consumption rates are functions of local pH as well as local concentrations of oxygen and other fuels. The diffusion of these nutrients is modeled using a novel variation of random-walk techniques. Furthermore, we detail the effects of three boundary update rules on simulations, describing their effects on computational efficiency and biological realism. Qualitative and quantitative results from simulations provide insight on how tumor growth is affected by various environmental changes such as micro-vessel density or lower pH, both of high interest in current cancer research. PMID:23311365

  20. Time-scales of crustal anatexis in the Himalaya revealed by petrochronology

    NASA Astrophysics Data System (ADS)

    Lederer, G. W.; Cottle, J. M.

    2014-12-01

    Accessory phases, such as monazite, xenotime, and zircon, record a wealth of information regarding the timing, duration, and sources of crustal melting. Combined U-Th/Pb and REE analysis of these petrochronometers by Laser Ablation Split Stream (LASS-) ICPMS reveals complex spatiotemporal relationships on a range of scales, from distinct chemical domains within a single crystal, to cross-cutting dikes within heterogeneous plutons composed of multiple melt batches. The anatectic core of the Himalaya exposes mid-crustal rocks well suited for investigations of the time-scales involved in melt processes, such as generation, segregation, amalgamation, mobilization, and emplacement. Three examples from different settings within the Himalayan orogen, including 1) the Leo Pargil leucogranite injection complex exposed in a gneiss dome in the hinterland, 2) the Manaslu pluton at the interface between the anatectic core and overlying metasediments, and 3) Everest region and Mahabharat granites from the anatectic core to the outermost crystalline thrust sheet of the foreland, illustrate the value of inherited monazite, xenotime, and zircon for deciphering crystallization in the source rock and/or earlier melt batches in addition to determining the age of granite emplacement.

  1. Early Solar System hydrothermal activity in chondritic asteroids on 1–10-year timescales

    PubMed Central

    Dyl, Kathryn A.; Bischoff, Addi; Ziegler, Karen; Young, Edward D.; Wimmer, Karl; Bland, Phil A.

    2012-01-01

    Chondritic meteorites are considered the most primitive remnants of planetesimals from the early Solar System. As undifferentiated objects, they also display widespread evidence of water–rock interaction on the parent body. Understanding this history has implications for the formation of planetary bodies, the delivery of water to the inner Solar System, and the formation of prebiotic molecules. The timescales of water–rock reactions in these early objects, however, are largely unknown. Here, we report evidence for short-lived water–rock reactions in the highly metamorphosed ordinary chondrite breccia Villalbeto de la Peña (L6). An exotic clast (d = 2cm) has coexisting variations in feldspar composition and oxygen isotope ratios that can only result from hydrothermal conditions. The profiles were modeled at T = 800 °C and P(H2O) = 1 bar using modified grain-boundary diffusion parameters for oxygen self-diffusion and reaction rates of NaSiCa-1Al-1 exchange in a fumarole. The geochemical data are consistent with hydrothermal activity on the parent body lasting only 1–10 y. This result has wide-ranging implications for the geological history of chondritic asteroids. PMID:23093668

  2. Early Solar System hydrothermal activity in chondritic asteroids on 1-10-year timescales.

    PubMed

    Dyl, Kathryn A; Bischoff, Addi; Ziegler, Karen; Young, Edward D; Wimmer, Karl; Bland, Phil A

    2012-11-01

    Chondritic meteorites are considered the most primitive remnants of planetesimals from the early Solar System. As undifferentiated objects, they also display widespread evidence of water-rock interaction on the parent body. Understanding this history has implications for the formation of planetary bodies, the delivery of water to the inner Solar System, and the formation of prebiotic molecules. The timescales of water-rock reactions in these early objects, however, are largely unknown. Here, we report evidence for short-lived water-rock reactions in the highly metamorphosed ordinary chondrite breccia Villalbeto de la Peña (L6). An exotic clast (d = 2cm) has coexisting variations in feldspar composition and oxygen isotope ratios that can only result from hydrothermal conditions. The profiles were modeled at T = 800 °C and P(H(2)O) = 1 bar using modified grain-boundary diffusion parameters for oxygen self-diffusion and reaction rates of NaSiCa(-1)Al(-1) exchange in a fumarole. The geochemical data are consistent with hydrothermal activity on the parent body lasting only 1-10 y. This result has wide-ranging implications for the geological history of chondritic asteroids. PMID:23093668

  3. Probing of Interactions between the Hot Plasmas and Galaxies in Clusters over a Cosmological Timescale

    NASA Astrophysics Data System (ADS)

    Gu, L.; Makishima, K.

    2014-07-01

    After reionization the Universe can no longer be considered as neutral fluids, but must be treated as ionized media which are ubiquitously threaded by magnetic fields. It remains still unexplored how the magneto-plasma nature of matter affects the formation and evolution of galaxies and galaxy clusters, and how the galaxies and cluster plasmas interact each other. We consider a unique scenario, "galaxies moving through the cluster will interact strongly with the ICM, transfer their free energies to the ICM, and will gradually fall to the cluster center". To verify this scenario, the key is to compare the spatial extents of galaxy and ICM at different redshifts. In Gu et al. 2013, ApJ 767 157, we studied the expected galaxy infall using a sample of 34 massive clusters with redshift range of 0.1 to 0.9. We have detected, for the first time, a significant evolution spanning 6 Gyr; while the galaxy component was as spatially extended as the ICM at z˜0.9, towards the lower redshifts, it has indeed become more centrally-concentrated relative to ICM/DM. Recently we confirm this discovery by a new complete sample of 316 clusters. This reveals the presence of strong ICM drag on galaxies over cosmological timescale.

  4. 137Cs in puddle sediments as timescale tracer in urban environment.

    PubMed

    Seleznev, Andrian A; Yarmoshenko, Ilia V; Sergeev, Alexander P

    2015-04-01

    The (137)Cs-based chronological approach is suggested to identify the age of urban landscapes and the chronology of pollution of soil in residential areas. Three main pivot points constitute the basis of the chronological approach: beginning of the Atomic Era in 1945, the maximum input in 1963 and the Chernobyl accident in 1986. Application of (137)Cs as a timescale tracer was tested on the example of Ekaterinburg, a city in the Middle Urals region of Russia. The sampling of recent urban sediments of micro water bodies (puddles) was carried out in 210 locations in 2007-2010. The concentrations of Pb, Zn, Cu, Ni, Co, Mn and Fe, and activity concentrations of (137)Cs were measured. It was found that the (137)Cs concentrations in the puddle sediments correlated with the age of surrounding buildings determined by the year of construction. The correlations between the concentrations of metals and (137)Cs in the puddle sediments identified the major pollutants of the urban area, assessing their background concentrations and obtaining the average annual inputs. PMID:25615884

  5. Stellar rotation in the Hyades and Praesepe: gyrochronology and braking time-scale

    NASA Astrophysics Data System (ADS)

    Delorme, P.; Collier Cameron, A.; Hebb, L.; Rostron, J.; Lister, T. A.; Norton, A. J.; Pollacco, D.; West, R. G.

    2011-05-01

    We present the results of photometric surveys for stellar rotation in the Hyades and in Praesepe, using data obtained as part of the SuperWASP exoplanetary transit-search programme. We determined accurate rotation periods for more than 120 sources whose cluster membership was confirmed by common proper motion and colour-magnitude fits to the clusters' isochrones. This allowed us to determine the effect of magnetic braking on a wide range of spectral types for expected ages of ˜600 Myr for the Hyades and Praesepe. Both clusters show a tight and nearly linear relation between J-Ks colour and rotation period in the F, G and K spectral range. This confirms that loss of angular momentum was significant enough that stars with strongly different initial rotation rates have converged to the same rotation period for a given mass, by the ages of Hyades and Praesepe. In the case of the Hyades, our colour-period sequence extends well into the M dwarf regime and shows a steep increase in the scatter of the colour-period relation, with identification of numerous rapid rotators from ˜0.5 M? down to the lowest masses probed by our survey (˜0.25 M?). This provides crucial constraints on the rotational braking time-scales and further clears the way to use gyrochronology as an accurate age measurement tool for main-sequence stars.

  6. Stellar Rotation in the Hyades and Praesepe: Gyrochronology and Braking Timescale

    NASA Astrophysics Data System (ADS)

    Delorme, P.; Cameron, A. C.; Hebb, L.; Rostron, J.; Lister, T. A.; Norton, A. J.; Pollacco, D.; West, R. G.

    2011-12-01

    We present the results of photometric surveys for stellar rotation in the Hyades and in Praesepe, using data obtained as part of the SuperWASP exoplanetary transit-search programme. We determined accurate rotation periods for more than 120 sources whose cluster membership was confirmed by common proper motion and colour-magnitude fits to the clusters' isochrones. This allowed us to determine the effect of magnetic braking on a wide range of spectral types for expected ages of ˜600 Myr for the Hyades and Praesepe. Both clusters show a tight and nearly linear relation between J-Ks colour and rotation period in the F, G and K spectral range. This confirms that loss of angular momentum was significant enough that stars with strongly different initial rotation rates have converged to the same rotation period for a given mass, by the age of Hyades and Praesepe. In the case of the Hyades our colour-period sequence extends well into the M dwarf regime and shows a steep increase in the scatter of the colour-period relation, with identification of numerous rapid rotators from ˜0.5M? down to the lowest masses probed by our survey (˜0.25M?). This provides crucial constraints on the rotational braking timescales and further clears the way to use gyrochronology as an accurate age measurement tool for main-sequence stars.

  7. Slingshot Dynamics for Self Replicating Probes and the Effect on Exploration Timescales

    E-print Network

    Nicholson, Arwen

    2013-01-01

    Interstellar probes can carry out slingshot manoeuvres around the stars they visit, gaining a boost in velocity by extracting energy from the star's motion around the Galactic Centre. These maneouvres carry little to no extra energy cost, and in previous work it has been shown that a single Voyager-like probe exploring the galaxy does so 100 times faster when carrying out these slingshots than when navigating purely by powered flight (Forgan et al. 2012). We expand on these results by repeating the experiment with self-replicating probes. The probes explore a box of stars representative of the local Solar neighbourhood, to investigate how self-replication affects exploration timescales when compared with a single non-replicating probe. We explore three different scenarios of probe behaviour: i) standard powered flight to the nearest unvisited star (no slingshot techniques used), ii) flight to the nearest unvisited star using slingshot techniques, and iii) flight to the next unvisited star that will give the m...

  8. Exploring the Interaction of Light and Matter on an Ultrafast Timescale Using Plasma Spectroscopy

    NASA Astrophysics Data System (ADS)

    Penczak, John S.

    The development of intense, sub-picosecond lasers has created a new realm of study concerning the interaction of light and matter. The basic characteristics of this interaction include the rapid ionization of matter, resulting in plasma formation, and the deposition of energy into a material on a timescale shorter than the thermal relaxation of the system. In this thesis, a collection of experimental studies attempt to explain some of the complex phenomena that occur during this interaction under the extreme conditions of a ~50 fs laser pulse, with an intensity ranging from 1014-1016 W/cm2, by spectroscopically analyzing the light given off by the plasma. Further attention is given to the interaction of the light with the laser-generated plasma itself, which dictates the development of many of the different processes. Some of the key aspects investigated are the spectral and polarization characteristics of the plasma light emission, second harmonic generation in plasmas, and the effect of plasma creation on dual-pulse laser ablation.

  9. The modeled relationship between sea level and atmospheric CO2 on geological timescales

    NASA Astrophysics Data System (ADS)

    Gasson, E.; Lunt, D. J.; Deconto, R. M.; Pollard, D.; Siddall, M.

    2013-12-01

    Foster and Rohling [2013, PNAS, 110(4)] recently compiled proxy atmospheric CO2 and sea level data from the past 40 million years in order to investigate the relationship between these two variables on geological timescales. The authors concluded that for atmospheric CO2 concentrations in the range of 400-450 ppm, long-term sea level rise may be of the order of 9 m above present. Here we present GCM-ice sheet model simulations of 2 of the intervals included in their analysis. We present a perturbed parameter ensemble of simulations of the East Antarctic ice sheet across the Eocene / Oligocene transition. In addition we present simulations of the North American and Eurasian ice sheets during the last glacial cycle. Our simulations show a good agreement with the atmospheric CO2 and sea level synthesis of Foster and Rohling. However, the majority of the data included in the synthesis are for a reduction in atmospheric CO2, consistent with the broad trend of declining atmospheric CO2 across the Cenozoic. Idealized simulations for an increase in atmospheric CO2 display a hysteresis effect, which may limit the usefulness of making direct long-term projections of future sea level rise from the paleo-record.

  10. Global-scale modes of surface temperature variability on interannual to century timescales

    NASA Technical Reports Server (NTRS)

    Mann, Michael E.; Park, Jeffrey

    1994-01-01

    Using 100 years of global temperature anomaly data, we have performed a singluar value decomposition of temperature variations in narrow frequency bands to isolate coherent spatio-temporal modes of global climate variability. Statistical significance is determined from confidence limits obtained by Monte Carlo simulations. Secular variance is dominated by a globally coherent trend; with nearly all grid points warming in phase at varying amplitude. A smaller, but significant, share of the secular variance corresponds to a pattern dominated by warming and subsequent cooling in the high latitude North Atlantic with a roughly centennial timescale. Spatial patterns associated with significant peaks in variance within a broad period range from 2.8 to 5.7 years exhibit characteristic El Nino-Southern Oscillation (ENSO) patterns. A recent transition to a regime of higher ENSO frequency is suggested by our analysis. An interdecadal mode in the 15-to-18 years period and a mode centered at 7-to-8 years period both exhibit predominantly a North Atlantic Oscillation (NAO) temperature pattern. A potentially significant decadal mode centered on 11-to-12 years period also exhibits an NAO temperature pattern and may be modulated by the century-scale North Atlantic variability.

  11. Ancient DNA from marine mammals: studying long-lived species over ecological and evolutionary timescales.

    PubMed

    Foote, Andrew D; Hofreiter, Michael; Morin, Phillip A

    2012-01-20

    Marine mammals have long generation times and broad, difficult to sample distributions, which makes inferring evolutionary and demographic changes using field studies of extant populations challenging. However, molecular analyses from sub-fossil or historical materials of marine mammals such as bone, tooth, baleen, skin, fur, whiskers and scrimshaw using ancient DNA (aDNA) approaches provide an opportunity for investigating such changes over evolutionary and ecological timescales. Here, we review the application of aDNA techniques to the study of marine mammals. Most of the studies have focused on detecting changes in genetic diversity following periods of exploitation and environmental change. To date, these studies have shown that even small sample sizes can provide useful information on historical genetic diversity. Ancient DNA has also been used in investigations of changes in distribution and range of marine mammal species; we review these studies and discuss the limitations of such 'presence only' studies. Combining aDNA data with stable isotopes can provide further insights into changes in ecology and we review past studies and suggest future potential applications. We also discuss studies reconstructing inter- and intra-specific phylogenies from aDNA sequences and discuss how aDNA sequences could be used to estimate mutation rates. Finally, we highlight some of the problems of aDNA studies on marine mammals, such as obtaining sufficient sample sizes and calibrating for the marine reservoir effect when radiocarbon-dating such wide-ranging species. PMID:21652193

  12. Solomon Sea circulation and water mass modifications: response at ENSO time-scales

    NASA Astrophysics Data System (ADS)

    Verron, J. A.; Melet, A. V.; Gourdeau, L.; Djath, N.

    2012-12-01

    The South Pacific low latitude western boundary currents (LLWBCs) carry waters of subtropical origin through the Solomon Sea before joining the equatorial Pacific. Changes in their properties or transport are assumed to impact ENSO dynamics. At ENSO time-scales, the LLWBCs transport tends to counterbalance the interior geostrophic one. However, the Solomon Sea is a strong constraint to the propagation of the LLWBCs. In this study, the response of the Solomon Sea circulation to ENSO is investigated based on a numerical simulation. The transport anomalies entering the Solomon Sea from the south are confined to the top 250 m of the water column, and represent 9 Sv (which is half of the mean transport).The induced circulation anomalies are not symmetric between the two ENSO states because of (1) a bathymetric control at Vitiaz Strait, that plays a stronger role during El Niño, and (2) an additional inflow at Solomon Strait during La Niña events. In terms of temperature and salinity, modifications are particularly notable for the thermocline water during El Niño conditions, with cooler and fresher waters compared to a climatological mean. The surface water at Vitiaz Strait and the upper thermocline water at Solomon Strait, feeding respectively the equatorial Pacific warm pool and the Equatorial Undercurrent, particularly affect the heat and salt fluxes. These fluxes can change by up to a factor of 2 between El Niño and La Niña conditions.

  13. Bose-Einstein condensation of metastable helium.

    PubMed

    Pereira Dos Santos, F; Léonard, J; Wang, J; Barrelet, C J; Perales, F; Rasel, E; Unnikrishnan, C S; Leduc, M; Cohen-Tannoudji, C

    2001-04-16

    We have observed a Bose-Einstein condensate in a dilute gas of 4He in the (3)2S(1) metastable state. We find a critical temperature of (4.7+/-0.5) microK and a typical number of atoms at the threshold of 8 x 10(6). The maximum number of atoms in our condensate is about 5 x 10(5). An approximate value for the scattering length a = (16+/-8) nm is measured. The mean elastic collision rate at threshold is then estimated to be about 2 x 10(4) s(-1), indicating that we are deeply in the hydrodynamic regime. The typical decay time of the condensate is 2 s, which places an upper bound on the rate constants for two-body and three-body inelastic collisions. PMID:11327998

  14. Tunable Polarons in Bose-Einstein Condensates

    E-print Network

    E. Compagno; G. De Chiara; D. G. Angelakis; G. M. Palma

    2014-10-31

    A toolbox for the quantum simulation of attractive and repulsive polarons in ultracold atoms is presented. Motivated by impressing experimental advances in the area of ultracold atomic mixtures, we theoretically study the problem of ultracold atomic impurities immersed in a Bose-Einstein condensate (BEC). The impurity-BEC interaction gives rise to the formation of polarons whose interaction can be effectively tuned using an external laser in a quasi-resonant Raman scheme. Our scheme allows one to change the effective interactions between polarons from positive to negative. This is achieved by simply changing the intensity and the frequency of the two lasers. Such arrangement opens new avenues for the study of strongly correlated condensed matter models in ultracold gases.

  15. Neutron stars in Einstein-aether theory

    E-print Network

    Christopher Eling; Ted Jacobson; M. Coleman Miller

    2009-12-06

    As current and future experiments probe strong gravitational regimes around neutron stars and black holes, it is desirable to have theoretically sound alternatives to general relativity against which to test observations. Here we study the consequences of one such generalization, Einstein-aether theory, for the properties of non-rotating neutron stars. This theory has a parameter range that satisfies all current weak-field tests. We find that within this range it leads to lower maximum neutron star masses, as well as larger surface redshifts at a particular mass, for a given nuclear equation of state. For non-rotating black holes and neutron stars, the innermost stable circular orbit is only slightly modified in this theory.

  16. Noncommutative Einstein-Maxwell pp-waves

    E-print Network

    S. Marculescu; F. Ruiz Ruiz

    2006-10-23

    The field equations coupling a Seiberg-Witten electromagnetic field to noncommutative gravity, as described by a formal power series in the noncommutativity parameters $\\theta^{\\alpha\\beta}$, is investigated. A large family of solutions, up to order one in $\\theta^{\\alpha\\beta}$, describing Einstein-Maxwell null pp-waves is obtained. The order-one contributions can be viewed as providing noncommutative corrections to pp-waves. In our solutions, noncommutativity enters the spacetime metric through a conformal factor and is responsible for dilating/contracting the separation between points in the same null surface. The noncommutative corrections to the electromagnetic waves, while preserving the wave null character, include constant polarization, higher harmonic generation and inhomogeneous susceptibility. As compared to pure noncommutative gravity, the novelty is that nonzero corrections to the metric already occur at order one in $\\theta^{\\alpha\\beta}$.

  17. Quantum formulation of the Einstein Equivalence Principle

    E-print Network

    Zych, Magdalena

    2015-01-01

    Validity of just a few physical conditions comprising the Einstein Equivalence Principle (EEP) suffices to ensure that gravity can be understood as space-time geometry. EEP is therefore subject to an ongoing experimental verification, with present day tests reaching the regime where quantum mechanics becomes relevant. Here we show that the classical formulation of the EEP does not apply in such a regime. The EEP requires equivalence between the total rest mass-energy of a system, the mass-energy that constitutes its inertia, and the mass-energy that constitutes its weight. In quantum mechanics internal energy is given by a Hamiltonian operator describing dynamics of internal degrees of freedom. We therefore introduce a quantum formulation of the EEP -- equivalence between the rest, inertial and gravitational internal energy operators. We show that the validity of the classical EEP does not imply the validity of its quantum formulation, which thus requires an independent experimental verification. We reanalyse...

  18. Energy in the Einstein-Aether Theory

    E-print Network

    Christopher Eling

    2009-12-06

    We investigate the energy of a theory with a unit vector field (the "aether") coupled to gravity. Both the Weinberg and Einstein type energy-momentum pseudotensors are employed. In the linearized theory we find expressions for the energy density of the 5 wave modes. The requirement that the modes have positive energy is then used to constrain the theory. In the fully non-linear theory we compute the total energy of an asymptotically flat spacetime. The resulting energy expression is modified by the presence of the aether due to the non-zero value of the unit vector at infinity and its 1/r falloff. The question of non-linear energy positivity is also discussed, but not resolved.

  19. Will gravitational waves confirm Einstein's General Relativity?

    E-print Network

    Christian Corda

    2009-07-21

    Even if Einstein's General Relativity achieved a great success and overcame lots of experimental tests, it also showed some shortcomings and flaws which today advise theorists to ask if it is the definitive theory of gravity. In this proceeding paper it is shown that, if advanced projects on the detection of Gravitational Waves (GWs) will improve their sensitivity, allowing to perform a GWs astronomy, accurate angular and frequency dependent response functions of interferometers for GWs arising from various Theories of Gravity, i.e. General Relativity and Extended Theories of Gravity, will be the ultimate test for General Relativity. This proceeding paper is also a short review of the Essay which won Honorable Mention at the 2009 Gravity Research Foundation Awards.

  20. A molecular timescale for galliform birds accounting for uncertainty in time estimates and heterogeneity of rates of DNA substitutions across lineages and sites

    Microsoft Academic Search

    Sergio L. Pereira; Allan J. Baker

    2006-01-01

    A recent molecular timescale for major lineages of the Galliformes indicated that Megapodiidae and possibly Cracidae, originated in the Cretaceous, while the remaining families originated in the Tertiary. This timescale was based on clock-like evolution in genetic and taxonomic partitions of mitochondrial ND2 and cyt b DNA sequences, and assumed that ordinal diversification of Galloanserae around 90 million years ago