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1

Einstein, Eddington and the 1919 Eclipse  

E-print Network

The modern era of cosmology began with the publication of Einstein's general theory of relativity in 1915. The first experimental test of this theory was Eddington's famous expedition to measure the bending of light at a total solar eclipse in 1919. So famous is this experiment, and so dramatic was the impact on Einstein himself, that history tends not to recognize the controversy that surrounded the results at the time. In this paper I discuss the experiment in its historical and sociological context and show that it provides valuable lessons for modern astronomy and cosmology.

Peter Coles

2001-02-27

2

Weyl-Eddington-Einstein affine gravity in the context of modern cosmology  

Microsoft Academic Search

We propose new models of the “affine” theory of gravity in multidimensional space-times with symmetric connections. We use\\u000a and develop ideas of Weyl, Eddington, and Einstein, in particular, Einstein’s proposed method for obtaining the geometry using\\u000a the Hamilton principle. More specifically, the connection coefficients are determined using a “geometric” Lagrangian that\\u000a is an arbitrary function of the generalized (nonsymmetric) Ricci

A. T. Filippov

2010-01-01

3

Einstein  

NSDL National Science Digital Library

From the American Museum of Natural History comes the online exhibit on the life and legacy of Albert Einstein. Students (who should probably be at least of high school age) can learn about Einstein's revolutionary thinking; his work with light, time, energy, and gravity; his thoughts on peace and war, on being a global citizen, and his legacy according to the museum. Although fairly brief, the site contains some interesting photographs and does a good job of describing the uniqueness of one of history's greatest minds.

4

Classical Novae as Super-Eddington Objects  

E-print Network

Several of the inconsistencies plaguing the field of novae are resolved once we consider novae to be steady state super-Eddington objects. In particular, we show that the super-Eddington shell burning state is a natural consequence of the equations of stellar structure, and that the predicted mass loss in the super-Eddington state agrees with nova observations. We also find that the transition phase of novae can be naturally explained as "stagnating" winds.

Nir J. Shaviv

2002-07-29

5

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

SciTech Connect

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.

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

6

Cosmological Evolution of Massive Black Holes: Effects of Eddington Ratio Distribution and Quasar Lifetime  

Microsoft Academic Search

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

Xinwu Cao

2010-01-01

7

Cosmological evolution of massive black holes: effects of Eddington ratio distribution and quasar lifetime  

E-print Network

A power-law time-dependent lightcurve 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 set a constraint on the minimal Eddington ratio for AGNs on the assumption of a power-law AGN lightcurve. 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 ~0.1 and a suitable power-law index for the Eddington ratio distrib...

Cao, Xinwu

2010-01-01

8

PHOTON FEEDBACK: SCREENING AND THE EDDINGTON LIMIT  

SciTech Connect

Bright star-forming galaxies radiate well below their Eddington limits. The value of the flux-mean opacity that mediates the radiation force onto matter is orders of magnitude smaller than the UV or optical dust opacity. On empirical grounds, it is shown that high-redshift ULIRGs radiate at two orders of magnitude below their Eddington limits, while the local starbursters M82 and Arp 220 radiate at a few percent of their Eddington limits. A model for the radiative transfer of UV and optical light in dust-rich environments is considered. Radiation pressure on dust does not greatly affect the large-scale gas dynamics of star-forming galaxies.

Socrates, Aristotle [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Sironi, Lorenzo, E-mail: socrates@ias.edu, E-mail: lsironi@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)

2013-08-01

9

Chandrasekhar vs. Eddington - An Unanticipated Confrontation.  

ERIC Educational Resources Information Center

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.…

Wali, Kameshwar C.

1982-01-01

10

Eddington's theory of gravity and its progeny.  

PubMed

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

Bañados, Máximo; Ferreira, Pedro G

2010-07-01

11

Should Eddington concentrate on M stars?  

NASA Astrophysics Data System (ADS)

In a recent preprint, Pepper et al. (2002) evaluate the sensitivity of photon-noise limited transit searches for habitable planets. They conclude that these searches have the largest chance of success if they are optimized toward the surveying of M stars. Such an optimisation implies several constraints and trade-offs. The principal one is that M star surveys need to observe at fainter magnitudes than surveys of solar-like stars. The required shift to fainter magnitudes is in principle possible, as M stars require less photometric precision in order to detect transits of their habitable planets. However, relatively higher noise from sky-background and increased crowding at fainter magnitudes requires the employment of optics with adequately small point-spread functions, with consequences on the observable dynamic range. A review of the merit of this strategy is given, first in terms of habitability of M star planets. Though being tidally locked to the central star, these planets are valuable and interesting targets, and can still potentially host life. Second, potential implications for the Eddington mission are discussed, and estimates for the noise sources and stellar crowding are given. A preliminary recommendation is to optimise Eddington for mid-K stars, employing moderately smaller apertures. Such an optimisation should allow Eddington to access both neighbouring specral classes (G and M) as well, and habitable planets with and without tidal locking may be detected.

Deeg, H. J.

2004-01-01

12

Compact stars in Eddington inspired gravity.  

PubMed

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

Pani, Paolo; Cardoso, Vitor; Delsate, Térence

2011-07-15

13

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

E-print Network

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.

Weinstein, Galina

2013-01-01

14

BAL QSOs AND EXTREME UFOs: THE EDDINGTON CONNECTION  

SciTech Connect

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby active galactic nuclei (AGNs), and the slower and less ionized winds of broad absorption line (BAL) QSOs. The primary difference is the mass-loss rate in the wind, which is ultimately determined by the rate at which mass is fed toward the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to {approx}10-50 times this in BAL QSOs. For UFOs this implies black hole accretion rates and wind mass-loss rates which are at most comparable to Eddington, giving fast, highly ionized winds. In contrast, BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass-loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently discovered one in SDSS J1106+1939. We suggest that luminous AGNs may evolve through a sequence from BAL QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors drop during the decay of a bright accretion event. LoBALs correspond to a short-lived stage in which the AGN radiation pressure largely evacuates the ionization cone, but before the large-scale accretion rate has dropped to the Eddington value. We show that sub-Eddington wind rates would produce an M-{sigma} relation lying above that observed. We conclude that significant SMBH mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme UFOs, or obscured from direct observation.

Zubovas, Kastytis; King, Andrew, E-mail: kastytis.zubovas@ftmc.lt [Theoretical Astrophysics Group, University of Leicester, Leicester LE1 7RH (United Kingdom)

2013-05-20

15

BAL QSOs and Extreme UFOs: The Eddington Connection  

NASA Astrophysics Data System (ADS)

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby active galactic nuclei (AGNs), and the slower and less ionized winds of broad absorption line (BAL) QSOs. The primary difference is the mass-loss rate in the wind, which is ultimately determined by the rate at which mass is fed toward the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to ~10-50 times this in BAL QSOs. For UFOs this implies black hole accretion rates and wind mass-loss rates which are at most comparable to Eddington, giving fast, highly ionized winds. In contrast, BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass-loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently discovered one in SDSS J1106+1939. We suggest that luminous AGNs may evolve through a sequence from BAL QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors drop during the decay of a bright accretion event. LoBALs correspond to a short-lived stage in which the AGN radiation pressure largely evacuates the ionization cone, but before the large-scale accretion rate has dropped to the Eddington value. We show that sub-Eddington wind rates would produce an M-? relation lying above that observed. We conclude that significant SMBH mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme UFOs, or obscured from direct observation.

Zubovas, Kastytis; King, Andrew

2013-05-01

16

Quasifision timescale: Zeptosecond versus attosecond  

NASA Astrophysics Data System (ADS)

Recently a controversy has developed regarding the timescales of quasifission and fission processes of highly excited (EX > 50 MeV) transuranium and uranium-like nuclei. The mass-angle distributions of quasifission fragments indicate exponential decay law giving timescale of the order of 10-21 sec for the quasifission process, whereas for the similar reactions, timescale of the order of 10-18 sec were obtained from the crystal blocking technique. In the case of fission of highly excited uranium-like and transuranium nuclei, X-ray-fission fragment coincidence technique gives similar timescales ~10-18 sec, contradicting much shorter timescales obtained from nuclear techniques. We think the quantum decoherence time of the quasifission/fission decay process could be of the order of 10-18 sec and present a quantum mechanical explanation to resolve the puzzle.

Ray, A.; Sikdar, A. K.; De, A.

2015-01-01

17

BAL QSOs and Extreme UFOs: the Eddington connection  

E-print Network

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby AGN, and the slower and less ionized winds of BAL QSOs. The primary difference is the mass loss rate in the wind, which is ultimately determined by the rate at which mass is fed towards the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to $\\sim 10-50$ times this in BAL QSOs. For UFOs this implies black hole accretion rates and wind mass loss rates which are at most comparable to Eddington, giving fast, highly-ionized winds. In contrast BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently-discovered one in SDSS J1106+1939. We suggest tha...

Zubovas, Kastytis

2013-01-01

18

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

E-print Network

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 ...

Kennefick, Daniel

2007-01-01

19

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

E-print Network

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.

Daniel Kennefick

2007-09-05

20

Centenarian Einstein  

ScienceCinema

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(?)

None

2011-04-25

21

FOREWORD: Modern Applications of Timescales Modern Applications of Timescales  

NASA Astrophysics Data System (ADS)

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".

Arias, E. F.; Lewandowski, W.

2011-08-01

22

Development of a pulsar-based timescale  

NASA Astrophysics Data System (ADS)

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.

Hobbs, G.

2014-12-01

23

Einsteins dream  

SciTech Connect

This book discusses the following topics: the search for meaning; Einstein's dream; curved space; Einstein and warped space-time and extreme wraping; early unified field theories; star death; beyond the white dwarf; the early universe; the hadron, Lepton, and Radiation eras; the redshift controversy; other universes; the final fate of the universe; the missing mass; bounce; fate of the open universe; the world of particles and fields; Dirac's equation; Yukawa; gauge theory; quantum chromodynamics; supergravity and superstrings; twistors and heaven; and the new Einstein.

Parker, B.

1986-01-01

24

Celebrating Einstein  

NASA Astrophysics Data System (ADS)

The Gravity Group at Montana State University (MSU) hosted Celebrating Einstein, a free public arts and multimedia event celebrating Einstein and his ideas in Bozeman, Montana April 2-6, 2013. The products of our efforts are now available to any party interested in hosting a similar event. Celebrating Einstein is a truly interdisciplinary effort including art, film, dance, music, physics, history, and education. Events included a black hole immersive art installation, a series of public talks by physicists, and Einstein lessons in the public schools leading up to a live free public multimedia performance including a professional dance company, a live interview with a renowned physicist, and an original score composed for the MSU student symphony to be performed with an original film produced by the Science and Natural History film program at MSU. This project is funded by the Montana Space Grant Consortium, Montana State University, and the National Science Foundation.

Shapiro Key, Joey; Yunes, Nicolas

2013-04-01

25

Electron positron pair winds and the Eddington limit  

NASA Technical Reports Server (NTRS)

The dynamics of pair winds in the environment of the central engine of Active Galactic Nuclei (AGN) are investigated assuming super Eddington accretion onto black holes. If the accretion is assumed to be spherically symmetric with the accreting matter occurring in discrete cool blobs, and pairs are produced by a nonthermal mechanism, these pairs are blown out by radiation pressure if the coupling between the pairs and accreting blobs is not complete. The coupling also determines the escaping luminosity. If the maximal coupling constraint is relaxed, then a qualitative argument shows that the classical Eddington limit may be exceeded. When the pairs are considered to be noninteracting particles, the outflow is optically thin. Frame dependent effects are considered. Equations are derived considering pair production in the rest frame of the wind and also in the rest frame of the accreting cool blobs. The hydrodynamic equations are integrated numerically.

Leighly, K. M.; Tsuruta, S.

1989-01-01

26

Radiation force on a relativistic plasma and the Eddington limit  

NASA Technical Reports Server (NTRS)

Calculations of the radiation force due to Thomson scattering on a relativistic plasma are presented and discussed in relation to certain astronomical objects which operate within a few orders of magnitude of their Eddington luminosity. The radiation force on a hot isotropic plasma is shown to exceed that on a cold plasma by a factor depending on the electron Lorentz factor, which can be substantial in a relativistic plasma. In such a plasma, radiative bulk acceleration is found to occur through the anisotropic loss of internal energy during the Thomson scattering, resulting in an effect termed a Compton rocket. The Compton rocket is shown to be a relevant acceleration mechanism in situations where a relativistic electron plasma lies in the vicinity of a luminous source operating near the classical Eddington limit, including compact galactic X-ray sources and objects associated with active galactic nuclei (quasars, blazars, and Seyfert nuclei).

Odell, S. L.

1981-01-01

27

Accretion Timescales from Kepler AGN  

NASA Astrophysics Data System (ADS)

We constrain AGN accretion disk variability mechanisms using the optical light curves of AGN observed by Kepler. AGN optical fluxes are known to exhibit stochastic variations on timescales of hours, days, months and years. The excellent sampling properties of the original Kepler mission - high S/N ratio (105), short sampling interval (30 minutes), and long sampling duration (~ 3.5 years) - allow for a detailed examination of the differences between the variability processes present in various sub-types of AGN such as Type I and II Seyferts, QSOs, and Blazars. We model the flux data using the Auto-Regressive Moving Average (ARMA) representation from the field of time series analysis. We use the Kalman filter to determine optimal mode parameters and use the Akaike Information Criteria (AIC) to select the optimal model. We find that optical light curves from Kepler AGN cannot be fit by low order statistical models such as the popular AR(1) process or damped random walk. Kepler light curves exhibit complicated power spectra and are better modeled by higher order ARMA processes. We find that Kepler AGN typically exhibit power spectra that change from a bending power law (PSD ~ 1/fa) to a flat power spectrum on timescales in the range of ~ 5 - 100 days consistent with the orbital and thermal timescales of a typical 107 solar mass black hole.

Kasliwal, Vishal P.; Vogeley, Michael S.; Richards, Gordon T.

2015-01-01

28

Kaluza Ansatz applied to Eddington inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

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.

Fernandes, Karan; Lahiri, Amitabha

2015-02-01

29

Is Eddington-Born-Infeld theory really free of cosmological singularities?  

E-print Network

The Eddington-inspired-Born-Infeld (EiBI) theory has been recently resurrected. Such a theory is characterized by being equivalent to Einstein theory in vacuum but differing from it in the presence of matter. One of the virtues of the theory is to avoid the Big Bang singularity for a radiation filled universe. In this paper, we analyze singularity avoidance in this kind of model. More precisely, we analyze the behavior of a homogeneous and isotropic universe filled with phantom energy in addition to the dark and baryonic matter. Unlike the Big Bang singularity that can be avoided in this kind of model through a bounce or a loitering effect on the physical metric, we find that the Big Rip singularity is unavoidable in the EiBI phantom model even though it can be postponed towards a slightly further future cosmic time as compared with the same singularity in other models based on the standard general relativity and with the same matter content described above.

Mariam Bouhmadi-Lopez; Che-Yu Chen; Pisin Chen

2013-02-20

30

Is Eddington-Born-Infeld theory really free of cosmological singularities?  

NASA Astrophysics Data System (ADS)

The Eddington-inspired-Born-Infeld (EiBI) theory has recently been resurrected. Such a theory is characterized by being equivalent to Einstein theory in vacuum but differing from it in the presence of matter. One of the virtues of the theory is that it avoids the Big Bang singularity for a radiation-filled universe. In this paper, we analyze singularity avoidance in this kind of model. More precisely, we analyze the behavior of a homogeneous and isotropic universe filled with phantom energy in addition to the dark and baryonic matter. Unlike the Big Bang singularity that can be avoided in this kind of model through a bounce or a loitering effect on the physical metric, we find that the Big Rip singularity is unavoidable in the EiBI phantom model even though it can be postponed towards a slightly further future cosmic time as compared with the same singularity in other models based on the standard general relativity and with the same matter content as described above.

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

2014-03-01

31

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.

32

Einstein's Mirror  

ERIC Educational Resources Information Center

Reflection of light from a plane mirror in uniform rectilinear motion is a century-old problem, intimately related to the foundations of special relativity. The problem was first investigated by Einstein in his famous 1905 paper by using the Lorentz transformations to switch from the mirror's rest frame to the frame where the mirror moves at a…

Gjurchinovski, Aleksandar; Skeparovski, Aleksandar

2008-01-01

33

Einstein's Mirror  

Microsoft Academic Search

Einstein's Mirror is a companion to the authors' highly successful book, The Quantum Universe. In it Hey and Walters have adopted a similar approach with the clear intention of providing a broadly accessible survey of relativistic physics. The book is well illustrated with photographs and line drawings and covers the development, experimental tests and implications of both the special and

Steve Adams

1997-01-01

34

Einstein Revisited  

ERIC Educational Resources Information Center

A brief description on the work and life of the great physicist scientist Albert Einstein is presented. The photoelectric paper written by him in 1905 led him to the study of fluctuations in the energy density of radiation and from there to the incomplete nature of the equipartition theorem of classical mechanics, which failed to account for…

Fine, Leonard

2005-01-01

35

Einstein's Relativity  

NSDL National Science Digital Library

These web pages, authored by Nick Strobel, contain material explaining Einstein's general and special theories of relativity. Gravity and warped spacetime are included, along with explanations of the impact on observational astronomy. This is part of Astronomy Notes, an educational resource for introductory astronomy classes. This is a great resource for instructors looking to enhance their physics or astronomy curriculum.

Strobel, Nick

36

The controversy between Alexander Friedmann and Albert Einstein about the possibility of a non-static world (German Title: Die Kontroverse zwischen Alexander Friedmann und Albert Einstein um die Möglichkeit einer nichtstatischen Welt)  

Microsoft Academic Search

Einstein's treatment of the cosmological problem as well as his unshakeable adherence to his own static solution of the complete field equations was throughout determined by Ernst Mach's idea of relativity of inertia. Friedmann, however, like Eddington, Weyl and others did not consider Mach's principle to be a part of general relativity, and so he regarded a time dependent developing

Georg Singer

2005-01-01

37

Genomic clocks and evolutionary timescales  

NASA Technical Reports Server (NTRS)

For decades, molecular clocks have helped to illuminate the evolutionary timescale of life, but now genomic data pose a challenge for time estimation methods. It is unclear how to integrate data from many genes, each potentially evolving under a different model of substitution and at a different rate. Current methods can be grouped by the way the data are handled (genes considered separately or combined into a 'supergene') and the way gene-specific rate models are applied (global versus local clock). There are advantages and disadvantages to each of these approaches, and the optimal method has not yet emerged. Fortunately, time estimates inferred using many genes or proteins have greater precision and appear to be robust to different approaches.

Blair Hedges, S.; Kumar, Sudhir

2003-01-01

38

BOOK REVIEW: Einsteins Kosmos. Untersuchungen zur Geschichte der Kosmologie Relativitatstheorie und zu Einsteins Wirken und Nachwirken  

NASA Astrophysics Data System (ADS)

This book collects about 15 papers (most of them by one single author) on Einstein and the history of general relativity (GR) and the foundations of relativistic cosmology. The matter not only deals with Einstein and his times, but also with pre-GR ideas, and with the interplay of Einstein and his colleagues (opposing as well as supporting personalities). As the title indicates, all papers are written in German, but they include comprehensive Abstracts both in German and English. The book is illustrated with quite a number classical - but also some far more original though not less beautiful - photographs and facsimiles of documents. The book is edited very well, though the style of references is not quite homogeneous. There is no Index. K. Hentschel covers Einstein's argumentation for the existence of graviational redshift, and the initial search for empirical support. The error analysis of observational evidence supporting relativistic light deflection is discussed in a paper by P. Brosche. In particular, H. Duerbeck and P. Flin - in their description of the life and work of Silberstein, who was quite sceptic on the significance of the observational verifications a la Eddington - include the transcription of two most revealing letters by Silberstein to Sommerfeld (1919) and to Einstein (1934). In the first letter, Silberstein clearly shows his scientific maturity and integrity by scrutinising the observational evidence supporting light deflection, presented at a joint meeting of the Royal Society and the Royal Astronomical Society. The second letter, which is more a personal letter, includes lots of political references and connotations. Some of Einstein's political views are also revealed by D.B. Herrmann on the basis of his own correspondence with E.G. Straus, a collaborator of Einstein's. In a consequent paper, S. Grundmann gives remarks on Herrmann's contribution and illustrates Einstein's attitude towards Marx, Engels, Lenin and Stalin. M. Schemmel discusses Schwarzschild's cosmological speculations, and wonders why some people do immediately grasp the meaning and consequence of newly proposed doctrines, whereas the bulk of the contemporaneous scientists respond in a rather low profile. T. Jung reviews Einstein's contribution to cosmology, leading to the Friedmann-Einstein and Einstein-de Sitter universes (with a detailed Appendix on the Friedmann-Lemaitre cosmology), and also presents the cosmological work of Selety, and his correspondence with Einstein. In a subsequent paper, H.-J. Schmidt comments on Einstein's criticism on de Sitter's solution of the Einstein field equations. Controversies with Einstein are elaborated by G. Singer (on Friedmann) and by K. Roessler (on Lemaitre). J. Renn and T. Sauer discuss Mandl's role in the publication history of Einstein's papers, notably Einstein's short paper on gravitational lensing. Finally, the book concludes with a contribution by D.B. Herrmann about the relationship between Einstein and Archenhold Observatory (where Einstein gave his first Berlin popular lecture in 1915), the transcription of H.-J. Treder's 1979 public address at the Einstein memorial plaque, and an inventory list of about 50 Einstein memorabilia - monuments, busts, plaques - compiled by W.R. Dick. This book is based on ideas approached in a historical context from the individual perspective of the authors. It is a real treasure trove of information and basic references on the history of GR, and it also covers quite some grounds with mathematical equations.

Sterken, C.; Duerbeck, H. W.; Dick, W. R.

2006-12-01

39

The distance scale and Eddington efficiency of luminous quasars  

E-print Network

The relation between the central mass and quasar luminosity (M_BH \\propto L^{\\alpha}FHWM^2) links a given Eddington ratio with a value of H_0, within a cosmology with fixed (\\Omega_m,\\Omega_{\\Lambda}). We point out that because the relation is calibrated at low z using distance independent reverberation mapping to get the BLR size, the derived M_BH interestingly does not depend on H_0, while L/L_Edd is sensitive to H_0, but rather robust to changes of \\Omega_{\\Lambda} in the standard flat model. This means, e.g., that enough of extragalactic objects radiating at the Eddington limit could be used to study the global Hubble constant in a new way, bypassing the local distance ladder. The method could become practical when systematic errors in derived M_BH are understood and objects with L /leq L_Edd can be independently identified. As an illustration, if we take a sample of tranquil very luminous quasars in the redshift range 0.5 < z < 1.6, and assume that they are radiating with L_bol \\leq L_Edd, then the usual numeric factors used for calculating M_BH and L_bol would lead to the result that the Hubble constant must be larger than 45 km/s/Mpc.

P. Teerikorpi

2005-10-13

40

Transforming Education at Einstein  

E-print Network

of Albert Einstein College of Medicine of Yeshiva University #12;2 EinstEin : WintEr/spring 2012 Meet Our trANsfOrMiNg eDuCAtiON At eiNsteiN Education at Albert Einstein College of Medicine is undergoing the magazine for alumni, faculty, students, friends and supporters of Albert einstein College of Medicine

Yates, Andrew

41

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

SciTech Connect

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.

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

42

Einstein Light  

NSDL National Science Digital Library

This award-winning site provides an accessible introduction to the theories of Galileo, Newton, Maxwell, and Einstein. It uses multimedia modules with animations and video clips to explain mechanics and Galilean relativity, electricity and magnetism, and how the principle of Special Relativity links these concepts together. It also develops some of the consequences of relativity for our ideas of time, space and mechanics (time dilation, length contraction), and the relationship of matter and energy (the famous equation E=mc2). Each module is available as a multimedia (Flash-based) or smaller HTML version and includes links to supporting materials and references.

Written and presented by Joe Wolfe

2006-01-08

43

Evolution of anisotropies in Eddington-Born-Infeld cosmology  

SciTech Connect

Recently a Born-Infeld action for dark energy and dark matter that uses additional affine connections was proposed. At the background level, it was shown that the new proposal can mimic the standard cosmological evolution. In Bianchi cosmologies, contrary to the scalar field approach (e.g., Chaplygin gas), the new approach leads to anisotropic pressure, raising the issues of stability of the isotropic solution under anisotropic perturbations and, being stable, how the anisotropies evolve. In this work, the Eddington-Born-Infeld proposal is extended to a Bianchi type I scenario and residual post-inflationary anisotropies are shown to decay in time. Moreover, it is shown that the shears decay following a damped oscillatory pattern, instead of the standard exponential-like decay. Allowing for some fine-tuning on the initial conditions, standard theoretical bounds on the shears can be avoided.

Rodrigues, Davi C. [Departamento de Fisica, Universidad de Santiago de Chile, Casilla 307, Santiago (Chile) and Departamento de Fisica, P. Universidad Catolica de Chile, Casilla 306, Santiago (Chile)

2008-09-15

44

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

E-print Network

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...

Nussbaumer, Harry

2014-01-01

45

Explaining variance in black carbon's aging timescale  

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

46

Was Einstein A Laplacean?  

E-print Network

distinguished physicists, Niels Bohr and Albert Einstein. It is widely believed that the dynamics of this dialogue were dictated by an overview of "physical reality" held by Einstein. Such interpretations typically presume that Einstein's arguments.... Colodny, ed., Paradigms and Paradoxes, Pittsburgh, 1972, pp. 67-302. 4 Victor F. Lenzen, "Einstein's Theory of Knowledge," in P. A. Schilpp, ed., Albert Einstein: Philosopher-Scientist, Open Court, 1970, pp7 357-82. 5 W. H. Furry, "Note...

Horner, Jack K.

47

Three dimensional Eddington--inspired Born--Infeld gravity: solutions  

E-print Network

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,-1) Friedmann-Roberston-Walker universes with (i) pressureless dust (P=0) and (ii) perfect fluid (P=\\rho/2), as matter sources. When the theory parameter \\kappa>0, our cosmological solutions are generically singular (except for the open universe, with a specific condition). On the other hand, for \\kappa<0 we do find non-singular cosmologies. We then move on towards finding static, circularly symmetric line elements with matter obeying (i) p=0 and (ii) p=\\rho/2. For p=0, the solution found is nonsingular for \\kappa<0 with the matter--stress--energy representing inhomogeneous dust. For p=\\rho/2 we obtain nonsingular solutions, for all \\kappa, and discuss some interesting characteristics of these solutions. Finally, we look at the rather simple p=-\\rho case where the solutions are either de Sitter or anti-de Sitter or flat spacetime.

Soumya Jana; Sayan Kar

2013-05-16

48

Eddington-Malmquist bias in a cosmological context  

NASA Astrophysics Data System (ADS)

Aims: In 1914, Eddington derived a formula for the difference between the mean absolute magnitudes of stars "in space" or gathered "from the sky". In 1920, Malmquist derived a general relation for this difference in Euclidean space. Here we study this statistical bias in cosmology, clarifying and expanding previous work. Methods: We derived the Malmquist relation within a general cosmological framework, including Friedmann's model, analogously to the way Malmquist showed in 1936 that his formula is also valid in the presence of extinction in Euclidean space. We also discuss some conceptual aspects that explain the wide scope of the bias relation. Results: The Malmquist formula for the intrinsic difference ? M ? m - M0 = -?M2{d ln{ a(m)}/{dm}} is also valid for observations made in an expanding Friedmann universe. This holds true for bolometric and finite-band magnitudes when a(m) refers to the distribution of observed (uncorrected for K-effect or z-dependent extinction) apparent magnitudes.

Teerikorpi, P.

2015-04-01

49

A Modeling of the Super-Eddington Luminosity in Nova Outbursts: V1974 Cygni  

E-print Network

We have modeled nova light curves exceeding the Eddington luminosity. It has been suggested that a porous structure develops in nova envelopes during the super Eddington phase and the effective opacity is much reduced for such a porous atmosphere. Based on this reduced opacity model, we have calculated envelope structures and light curves of novae. The optically thick wind model is used to simulate nova winds. We find that the photospheric luminosity and the wind mass-loss rate increase inversely proportional to the reducing factor of opacities, but the wind velocity hardly changes. We also reproduce the optical light curve of V1974 Cygni (Nova Cygni 1992) in the super-Eddington phase, which lasts 13 days from the optical peak 1.7 mag above the Eddington luminosity.

Mariko Kato; Izumi Hachisu

2005-10-02

50

Eddington-class flares and their distance from the central black hole in blazars  

NASA Astrophysics Data System (ADS)

The distance from the central engine at which the bright gamma-ray flares of blazars take place is an open question with implications on our understanding of jet formation and collimation. In some cases, pair opacity arguments suggest that the detection of sub-TeV photons points to the emission taking place beyond the ~ 0.1 pc size broad line region. Here we show that for bright flares having beaming-corrected luminosity comparable to the Eddington luminosity (Eddington-class flares), strong deceleration due to Compton drag is expected if the flare takes place inside the 1-few pc molecular torus region. This is incompatible with the highly superluminal speeds these sources exhibit, requiring that Eddington-class flares take place beyond the molecular torus. We demonstrate this in the case of the MAGIC-detected source PKS 1222+21 (Aleksicet al. 2011), a source that exhibited Eddington-class flares in 2010 (Tanaka11).

Georganopoulos, Markos; Rivas, David

2014-08-01

51

Timescales of seawater intrusion and retreat  

NASA Astrophysics Data System (ADS)

Quantifying the timescales associated with moving freshwater-seawater interfaces is critical for effective management of coastal groundwater resources. In this study, timescales of interface movement in response to both inland and coastal water level variations are investigated. We first assume that seawater intrusion (SWI) and retreat (SWR) are driven by an instantaneous freshwater-level variation at the inland boundary. Numerical modelling results reveal that logarithmic timescales of SWI (lnTi) and SWR (lnTr) can be described respectively by various simple linear equations. For example, SWI timescales are described by lnTi = a + blnh'f-s, where a and b are linear regression coefficients and h'f-s is the boundary head difference after an instantaneous drop of inland freshwater head. For SWR cases with the same initial conditions, but with different increases in freshwater head, lnTr = c + d?XT, where c and d are regression coefficients and ?XT is the distance of toe response that can be estimated by a steady-state, sharp-interface analytical solution. For SWR cases with the same freshwater head increase, but with different initial conditions, in contrast, lnTr = e + fln?XT, where e and f are regression coefficients. The timescale of toe response caused by an instantaneous variation of sea level is almost equivalent to that induced by an instantaneous inland head variation with the same magnitude of water level change, but opposite in direction. Accordingly, the empirical equations of this study are also applicable for sea-level variations in head-controlled systems or for simultaneous variations of both inland and coastal water levels. Despite the idealised conceptual models adopted in this study, the results imply that for a particular coastal aquifer, SWI timescales are controlled by the boundary water levels after variations, whereas SWR timescales are dominated by the distance of toe response.

Lu, Chunhui; Werner, Adrian D.

2013-09-01

52

Millisecond timescale synchrony among hippocampal neurons.  

PubMed

Inhibitory neurons in cortical circuits play critical roles in composing spike timing and oscillatory patterns in neuronal activity. These roles in turn require coherent activation of interneurons at different timescales. To investigate how the local circuitry provides for these activities, we applied resampled cross-correlation analyses to large-scale recordings of neuronal populations in the cornu ammonis 1 (CA1) and CA3 regions of the hippocampus of freely moving rats. Significant counts in the cross-correlation of cell pairs, relative to jittered surrogate spike-trains, allowed us to identify the effective couplings between neurons in CA1 and CA3 hippocampal regions on the timescale of milliseconds. In addition to putative excitatory and inhibitory monosynaptic connections, we uncovered prominent millisecond timescale synchrony between cell pairs, observed as peaks in the central 0 ms bin of cross-correlograms. This millisecond timescale synchrony appeared to be independent of network state, excitatory input, and ? oscillations. Moreover, it was frequently observed between cells of differing putative interneuronal type, arguing against gap junctions as the sole underlying source. Our observations corroborate recent in vitro findings suggesting that inhibition alone is sufficient to synchronize interneurons at such fast timescales. Moreover, we show that this synchronous spiking may cause stronger inhibition and rebound spiking in target neurons, pointing toward a potential function for millisecond synchrony of interneurons in shaping and affecting timing in pyramidal populations within and downstream from the circuit. PMID:25378164

Diba, Kamran; Amarasingham, Asohan; Mizuseki, Kenji; Buzsáki, György

2014-11-01

53

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

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

Longair, Malcolm

2015-01-01

54

Einstein Books for Adults  

NSDL National Science Digital Library

This reference list has more than 15 books and articles on Einstein that are written for adults, including biographies and some of Einstein's own writings. For each title, the author's name, publisher, and publication date are included.

55

Albert Einstein's Methodology  

E-print Network

This paper discusses Einstein's methodology. 1. Einstein characterized his work as a theory of principle and reasoned that beyond kinematics, the 1905 heuristic relativity principle could offer new connections between non-kinematical concepts. 2. Einstein's creativity and inventiveness and process of thinking; invention or discovery. 3. Einstein considered his best friend Michele Besso as a sounding board and his class-mate from the Polytechnic Marcel Grossman, as his active partner. Yet, Einstein wrote to Arnold Sommerfeld that Grossman will never claim to be considered a co-discoverer of the Einstein-Grossmann theory. He only helped in guiding Einstein through the mathematical literature, but contributed nothing of substance to the results of the theory. Hence, Einstein neither considered Besso or Grossmann as co-discoverers of the relativity theory which he invented.

Weinstein, Galina

2012-01-01

56

Posing Einstein's Question: Questioning Einstein's Pose.  

ERIC Educational Resources Information Center

Discusses the events surrounding a famous picture of Albert Einstein in which he poses near a blackboard containing a tensor form of his 10 field equations for pure gravity with a question mark after it. Speculates as to the content of Einstein's lecture and the questions he might have had about the equation. (Contains over 30 references.) (WRM)

Topper, David; Vincent, Dwight E.

2000-01-01

57

Einstein's Philosophy of Science  

E-print Network

interest, not only because of his contributions to science, but also because he spoke in great detail about his own philosophy, is Albert Einstein. This paper will cover only three main aspects of Einstein's philosophy of science: the nature... Einstein, On The Method of Theoretical Physics (New York: Oxford University Press, 1933), "p. 6. Albert Einstein, The Philosophy of Bertrand Russell, The Libary of Living Philosophers, vol. V, ed. Paul A. Schilpp, rpt. in Ideas and Opinions, Albert...

Holmer, Bruce

58

Quantum Physics Einstein's Gravity  

E-print Network

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

Visser, Matt

59

Einstein as Evaluator?  

ERIC Educational Resources Information Center

Like any other person, Albert Einstein was an informal evaluator, engaged in placing value on various aspects of his life, work, and the world. Based on Einstein's own statements, this paper speculates about what Einstein would have been like as a connoisseur evaluator, a conceptual evaluator, or a responsive evaluator. (Author/BW)

Caulley, Darrel N.

1982-01-01

60

Relativistic radiative transfer in relativistic plane-parallel flows: Behavior of the Eddington factor  

NASA Astrophysics Data System (ADS)

Relativistic radiative transfer in a relativistic plane-parallel flow which is accelerated from its base, like an accretion disk wind, is numerically examined under a fully special-relativistic treatment. We first derive relativistic formal solutions. We then iteratively solve the relativistic transfer equation for several cases such as radiative equilibrium or local thermodynamic equilibrium, and obtain specific intensities in the inertial and comoving frames, as well as moment quantities and the Eddington factor. Moment quantities are rather different in each case, but the behavior of the Eddington factor for the plane-parallel case is quite similar in all cases. The Eddington factor generally depends on the flow velocity v as well as the optical depth ?. In the case of relativistic plane-parallel flows, in an optically thin regime of ? ? 1, it is slightly larger than 1/3 at very slow speed, it becomes smaller than 1/3 at mildly relativistic speed, and it again increases up to unity in the highly relativistic case. At highly relativistic speed, on the other hand, it becomes larger than 1/3 even in an optically thick regime. We find the Eddington approximation is fairly good, except for ? ? 1 or v/c ? 0.9, although the moment formalism under the Eddington approximation has some defects at v/c=1/?{3}.

Fukue, Jun

2014-07-01

61

The ultraluminous state refined: spectral and temporal characteristics of super-Eddington accretion  

NASA Astrophysics Data System (ADS)

Recent evidence - in particular the hard X-ray spectra obtained by NuSTAR - reveals that ultraluminous X-ray source (ULX) behaviour is inconsistent with known sub-Eddington accretion modes, as would be expected for an intermediate-mass black hole. Instead, it appears that the majority of ULXs are powered by super-Eddington accretion onto stellar-mass black holes. The key question for ULXs then becomes: how does this super-Eddington accretion work? Here we present new results from ULX spectral and timing studies that delve deeper into their underlying physical mechanisms. We firstly show that the spectral and temporal characteristics of ULXs appear intrinsically interwoven, with high levels of variability apparent when the spectra are dominated by a soft component. It has been suggested that this component represents the emission from an optically-thick wind driven radiatively from the ULX; we examine evidence that may corroborate this model. Finally, we present a revised picture of super-Eddington processes in which we also consider how both mass accretion rate variability propagating through a super-Eddington disc, and scattering within the wind, might affect the X-ray characteristics as a function of accretion rate and of viewing angle. We show that its predictions are qualitatively similar to the observed behaviour of ULXs.

Roberts, T.; Middleton, M.; Sutton, A.; Heil, L.; Walton, D.

2014-07-01

62

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.

63

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

PubMed

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

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

2014-03-21

64

Lyapunov timescales and black hole binaries  

E-print Network

Black holes binaries support unstable orbits at very close separations. In the simplest case of geodesics around a Schwarzschild black hole the orbits, though unstable, are regular. Under perturbation the unstable orbits can become the locus of chaos. All unstable orbits, whether regular or chaotic, can be quantified by their Lyapunov exponents. The exponents are observationally relevant since the phase of gravitational waves can decohere in a Lyapunov time. If the timescale for dissipation due to gravitational waves is shorter than the Lyapunov time, chaos will be damped and essentially unobservable. We find the timescales can be comparable. We emphasize that the Lyapunov exponents must only be used cautiously for several reasons: they are relative and depend on the coordinate system used, they vary from orbit to orbit, and finally they can be deceptively diluted by transient behaviour for orbits which pass in and out of unstable regions.

Neil J. Cornish; Janna Levin

2003-04-15

65

A LONG, LONG time ago: geologic timescales  

NSDL National Science Digital Library

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.

Elizabeth Johnson

66

Timescales of Disk Evolution and Planet Formation  

E-print Network

It has been suggested that circumstellar disks evolve from dense, actively accreting structures to low-mass, replenished remnants. During this transition, grains may assemble into planetesimals, or the disk may be cleared by newborn planets. Recently identified nearby groups of young stars provide valuable laboratories for probing disk evolution. I discuss the properties of dust disks in the TW Hydrae Association and the MBM 12 cloud, and compare the results to other studies of disk evolution and planet formation timescales.

Ray Jayawardhana

2000-11-15

67

Timescale Spectra in High Energy Astrophysics  

E-print Network

A technique of timescale analysis performed directly in the time domain has been developed recently. We have applied the technique to studying rapid variabilities of hard X-rays from neutron star and black hole binaries, gamma-ray bursts and terrestrial gamma-ray flashes. The results indicate that the time domain method of spectral analysis is a powerful tool in revealing the underlying physics in high-energy processes in objects.

T. P. Li

2002-12-02

68

Picosecond timescale Raman processes and spectroscopy  

E-print Network

Pure & App!. Chem., Vol. 57, No. 2, pp. 195—200, 1985. Printed in Great Britain. © 1985 IUPAC Picosecond timescale Raman processes and spectroscopy C. K. Johnson, G. A. Dalickas, S. A. Payne and R. M. Hochstrasser Department of Chemistry, University... the Raman spectra obtained from focused with those from unfocused picosecond laser beans (2. This technique allows the detection of transient Raman spectra but does not provide much information about their time dependence. Quite recently a pump—probe Raman...

Johnson, Carey K.; Dalickas, G. A.; Payne, S. A.; Hochstrasser, R. M.

1985-01-01

69

AIDS Arises and Einstein Responds  

E-print Network

and Friends of Albert Einstein College of Medicine of Yeshiva University #12;2 EinstEin : summEr/fall 2011 The magazine for alumni, faculty, students, friends and supporters of albert einstein College of medicine.yu.edu Website: www.einstein.yu.edu Copyright © 2011 albert einstein College of medicine of Yeshiva university

Yates, Andrew

70

Neuromythology of Einstein's brain.  

PubMed

The idea that the brain of the great physicist Albert Einstein is different from "average" brains in both cellular structure and external shape is widespread. This belief is based on several studies examining Einstein's brain both histologically and morphologically. This paper reviews these studies and finds them wanting. Their results do not, in fact, provide support for the claim that the structure of Einstein's brain reflects his intellectual abilities. PMID:24836969

Hines, Terence

2014-07-01

71

Einstein in Time  

NSDL National Science Digital Library

This fun Web site is part of OLogy, where kids can collect virtual trading cards and create projects with them. Here, they are introduced to Einstein's scientific and humanitarian pursuits with two engaging, kid-friendly sections: Einstein in Time, a fascinating look at the major events in his life presented in a timeline and Everyday Einstein: Humanitarian, a quick overview of how he used his fame to draw attention to the things he believed in.

72

The use of the Milne-Eddington absorption coefficient for radiative heat transfer in combustion systems  

Microsoft Academic Search

The applicability of the Milne-Eddington absorption coefficient approximation is discussed in relation to the calculation of radiative transport involving the two distinct types of species produced in combustion systems - gases and soot particles. The approximation is found to apply well to hydrocarbon soot particles and as a result analytical closed-form solutions are derived for the radiative heat transfer inside

J. D. Felske; C. L. Tien

1977-01-01

73

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

E-print Network

black holes releases energy in the form of radiation and outflows. Although the radiative flux cannotSuper-Eddington Mechanical Power of an Accreting Black Hole in M83 R. Soria,1 * K. S. Long,2 W. P the detection of a radio-optical structure, powered by outflows from a non-nuclear black hole. Its accretion

Napp, Nils

74

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

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

75

Einstein, Bose and Bose-Einstein Statistics  

NASA Astrophysics Data System (ADS)

In June 1924, a relatively unknown Satyendra Nath Bose from Dacca, India, wrote a letter to Einstein beginning with ``Respected Sir, I have ventured to send you the accompanying article for your perusal. I am anxious to know what you think of it. You will see that I have ventured to deduce the coefficient 8??^2/c^3 in Planck's law independent of the classical electrodynamics, only assuming that the ultimate elementary regions in Phase-space have the content h^3. I do not know sufficient German to translate the paper. If you think the paper worth publication, I shall be grateful if you arrange for its publication in Zeitschrift für Physik.'' Einstein did translate the article himself and got it published. He wrote to Ehrenfest: ``The Indian Bose has given a beautiful derivation of Planck's law, including the constant [i.e.8??^2/c^3].'' Einstein extended the ideas of Bose that implied, among other things, a new statistics for the light-quanta to the molecules of an ideal gas and wrote to Ehrenfest, `from a certain temperature on, the molecules ``condense'' without attractive forces, that is, they accumulate at zero velocity. The theory is pretty, but is there also some truth to it?' Abraham Pais has called Bose's paper ``the fourth and the last revolutionary papers of the old quantum theory.'' My paper will present the works of Bose and Einstein in their historical perspective and the eventual birth of the new quantum Bose-Einstein statistics.

Wali, Kameshwar C.

2005-05-01

76

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

NASA Astrophysics Data System (ADS)

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.

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

2015-04-01

77

Einstein for Everyone  

SciTech Connect

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.

Piccioni, Robert

2010-10-05

78

Einstein for Everyone  

ScienceCinema

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.

Piccioni, Robert

2014-06-25

79

When Art Meets Einstein  

ERIC Educational Resources Information Center

This article deals with a pale blue sculpture entitled "A New World View", as an homage to the most famous scientist in modern history, Albert Einstein. It has 32 bas-relief squares composed of glass and steel that represent one aspect of the life and legacy of Albert Einstein. Images of children's faces peer out from behind the glass squares,…

Science Scope, 2006

2006-01-01

80

Einstein and Boltzmann  

NASA Astrophysics Data System (ADS)

In 1916 Einstein published a remarkable paper entitled ``On the Quantum Theory of Radiation''ootnotetextA. Einstein ``On the Quantum theory of Radiation,'' Phys. Zeitschrift 18 (1917) 121. First printed in Mitteilungender Physikalischen Gesellschaft Zurich. No 18, 1916. Translated into English in Van der Waerden ``Sources of Quantum Mechanics'' (North Holland 1967) pp. 63-77. in which he obtained Planck's formula for black-body radiation by introducing a new statistical hypothesis for the emmision and absorption of electromagneic radiation based on discrete bundles of energy and momentum which are now called photons. Einstein radiation theory replaced Maxwell's classical theory by a stochastic process which, when properly interpreted, also gives well known statistics of massless particles with even spin.^2 This quantum distribution, however, was not discovered by Einstein but was communicated to him by Bose in 1924. Like Boltzmann's classical counterpart, Einstein's statistical theory leads to an irreversible approach to thermal equilibrium, but because this violates time reversal, Einstein theory can not be regarded as a fundamental theory of physical process.ootnotetextM. Nauenberg ``The evolution of radiation towards thermal equilibrium: A soluble model which illustrates the foundations of statistical mechanics,'' American Journal of Physics 72 (2004) 313 Apparently Einstein and his contemporaries were unaware of this problem, and even today this problem is ignored in contemporary discussions of Einstein's treatment of the black-body spectrum.

Nauenberg, Michael

2005-03-01

81

Einstein Educator's Guide Insert  

NSDL National Science Digital Library

This printable two-page handout includes a timeline of Einstein's life that showcases the causes he supported, along with his scientific discoveries and a copy of the letter Einstein sent to the editor of a Japanese magazine in 1952, in which he explains why he signed the letter to President Roosevelt that advocated atomic energy research.

82

Two-timescale analysis of extreme mass ratio inspirals in Kerr spacetime: Orbital motion  

SciTech Connect

Inspirals of stellar-mass compact objects into massive black holes are an important source for future gravitational wave detectors such as Advanced LIGO and LISA. The detection and analysis of these signals rely on accurate theoretical models of the binary dynamics. We cast the equations describing binary inspiral in the extreme mass ratio limit in terms of action-angle variables, and derive properties of general solutions using a two-timescale expansion. This provides a rigorous derivation of the prescription for computing the leading order orbital motion. As shown by Mino, this leading order or adiabatic motion requires only knowledge of the orbit-averaged, dissipative piece of the self-force. The two-timescale method also gives a framework for calculating the post-adiabatic corrections. For circular and for equatorial orbits, the leading order corrections are suppressed by one power of the mass ratio, and give rise to phase errors of order unity over a complete inspiral through the relativistic regime. These post-1-adiabatic corrections are generated by the fluctuating, dissipative piece of the first order self-force, by the conservative piece of the first order self-force, and by the orbit-averaged, dissipative piece of the second order self-force. We also sketch a two-timescale expansion of the Einstein equation, and deduce an analytic formula for the leading order, adiabatic gravitational waveforms generated by an inspiral.

Hinderer, Tanja [Center for Radiophysics and Space Research, Cornell University, Ithaca, New York 14853 (United States); Flanagan, Eanna E. [Center for Radiophysics and Space Research, Cornell University, Ithaca, New York 14853 (United States); Laboratory for Elementary Particle Physics, Cornell University, Ithaca, New York 14853 (United States)

2008-09-15

83

Gamma-ray burster recurrence timescales  

NASA Technical Reports Server (NTRS)

Three optical transients have been found which are associated with gamma-ray bursters (GRBs). The deduced recurrence timescale for these optical transients (tau sub opt) will depend on the minimum brightness for which a flash would be detected. A detailed analysis using all available data of tau sub opt as a function of E(gamma)/E(opt) is given. For flashes similar to those found in the Harvard archives, the best estimate of tau sub opt is 0.74 years, with a 99% confidence interval from 0.23 years to 4.7 years. It is currently unclear whether the optical transients from GRBs also give rise to gamma-ray events. One way to test this association is to measure the recurrence timescale of gamma-ray events tau sub gamma. A total of 210 gamma-ray error boxes were examined and it was found that the number of observed overlaps is not significantly different from the number expected from chance coincidence. This observation can be used to place limits on tau sub gamma for an assumed luminosity function. It was found that tau sub gamma is approx. 10 yr if bursts are monoenergetic. However, if GRBs have a power law luminosity function with a wide dynamic range, then the limit is tau sub gamma 0.5 yr. Hence, the gamma-ray data do not require tau sub gamma and tau sub opt to be different.

Schaefer, B. E.; Cline, T. L.

1984-01-01

84

Einstein, Bose and Bose-Einstein Statistics  

Microsoft Academic Search

In June 1924, a relatively unknown Satyendra Nath Bose from Dacca, India, wrote a letter to Einstein beginning with ``Respected Sir, I have ventured to send you the accompanying article for your perusal. I am anxious to know what you think of it. You will see that I have ventured to deduce the coefficient 8piupsilo^2\\/c^3 in Planck's law independent of

Kameshwar C. Wali

2005-01-01

85

Hindcasting of decadal?timescale estuarine bathymetric change with a tidal?timescale model  

USGS Publications Warehouse

Hindcasting decadal-timescale bathymetric change in estuaries is prone to error due to limited data for initial conditions, boundary forcing, and calibration; computational limitations further hinder efforts. We developed and calibrated a tidal-timescale model to bathymetric change in Suisun Bay, California, over the 1867–1887 period. A general, multiple-timescale calibration ensured robustness over all timescales; two input reduction methods, the morphological hydrograph and the morphological acceleration factor, were applied at the decadal timescale. The model was calibrated to net bathymetric change in the entire basin; average error for bathymetric change over individual depth ranges was 37%. On a model cell-by-cell basis, performance for spatial amplitude correlation was poor over the majority of the domain, though spatial phase correlation was better, with 61% of the domain correctly indicated as erosional or depositional. Poor agreement was likely caused by the specification of initial bed composition, which was unknown during the 1867–1887 period. Cross-sectional bathymetric change between channels and flats, driven primarily by wind wave resuspension, was modeled with higher skill than longitudinal change, which is driven in part by gravitational circulation. The accelerated response of depth may have prevented gravitational circulation from being represented properly. As performance criteria became more stringent in a spatial sense, the error of the model increased. While these methods are useful for estimating basin-scale sedimentation changes, they may not be suitable for predicting specific locations of erosion or deposition. They do, however, provide a foundation for realistic estuarine geomorphic modeling applications.

Ganju, Neil K.; Schoellhamer, David H.; Jaffe, Bruce E.

2009-01-01

86

Einstein and Millikan  

NASA Astrophysics Data System (ADS)

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?

Erwin, Charlotte

2005-03-01

87

Einstein and 1905  

NASA Astrophysics Data System (ADS)

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.

Rigden, John

2005-05-01

88

PHYSICS AND REALITY. ALBERT EINSTEIN.  

E-print Network

PHYSICS AND REALITY. BY ALBERT EINSTEIN. (Translation by Jean Piccard.) § I. GENERALCONSIDERATION " of their connection. But even the concept of the Copyright, 1936, by Albert Einstein. 349 www.kostic.niu.eduHosted by Prof. M. Kostic at: Physics and Reality by Albert Einstein #12;35 ° ALBERT EINSTEIN. [J. F. I. " real

Kostic, Milivoje M.

89

The stolen brain of Einstein  

Microsoft Academic Search

Pathologist Thomas Stoltz Harvey performed an autopsy on Einstein after his death in 1955. During the autopsy Harvey removed Einstein's brain, took pictures of it and then cut it into several pieces. A lot of scientific attention has been devoted to Einstein' brain, and it still comes up once in a while. We've all heard something or other about Einstein's

Kavan Modi

2008-01-01

90

Personal Recollections of Albert Einstein  

Microsoft Academic Search

My grandparents were good friends of Albert Einstein in Berlin. Later my parents also were on friendly terms with him. I had the opportunity to meet Einstein four times after my parents and I came to the United States in 1940. My parents and I, on occasion, had correspondence with Einstein and took a few photos of him. Albert Einstein

Steven Moszkowski

2005-01-01

91

Relativistic timescale analysis suggests lunar theory revision  

NASA Technical Reports Server (NTRS)

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.

Deines, Steven D.; Williams, Carol A.

1995-01-01

92

The Theory of Steady State Super-Eddington Winds and its Application to Novae  

E-print Network

We present a model for steady state winds of systems with super-Eddington luminosities. These radiatively driven winds are expected to be optically thick and clumpy as they arise from an instability driven porous atmosphere. The model is then applied to derive the mass loss observed in bright classical novae. The main results are: 1) A general relation between the mass loss rate and the total luminosity in super-Eddington systems. 2) A quantitative agreement between the observed luminosity evolution which is used to predict both the mass loss and temperature evolution, and their observations. 3) An agreement between the predicted average integrated mass loss of novae as a function of WD mass and its observations. 4) A natural explanation for the `transition phase' of novae. 5) Agreement with eta Carinae which was used to double check the theory. The prediction for the mass shed in the star's great eruption agrees with observations to within the measurement error.

Nir J. Shaviv

2001-04-10

93

Mysticism and Marxism: A.S. Eddington, Chapman Cohen, and Political Engagement Through Science Popularization  

Microsoft Academic Search

This paper argues that that political context of British science popularization in the inter-war period was intimately tied\\u000a to contemporary debates about religion and science. A leading science popularizer, the Quaker astronomer A.S. Eddington, and\\u000a one of his opponents, the materialist Chapman Cohen, are examined in detail to show the intertwined nature of science, philosophy,\\u000a religion, and politics.

Matthew Stanley

2008-01-01

94

Tensor-to-scalar ratio in Eddington-inspired Born-Infeld inflation  

NASA Astrophysics Data System (ADS)

We investigate the scalar perturbation of the inflation model driven by a massive scalar field in Eddington-inspired Born-Infeld gravity. We focus on the perturbation at the attractor stage in which the first and the second slow-roll conditions are satisfied. The scalar perturbation exhibits the corrections to the chaotic inflation model in general relativity. We find that the tensor-to-scalar ratio becomes smaller than that of the usual chaotic inflation.

Cho, Inyong; Singh, Naveen K.

2014-11-01

95

Inflationary Tensor Perturbation in Eddington-inspired Born-Infeld gravity  

E-print Network

We investigate the tensor perturbation in the inflation model driven by a massive-scalar field in Eddington-inspired Born-Infeld gravity. For short wave-length modes, the perturbation feature is very similar to that of the usual chaotic inflation. For long wave-length modes, the perturbation exhibits a peculiar rise in the power spectrum which may leave a signature in the cosmic microwave background radiation.

Inyong Cho; Hyeong-Chan Kim

2014-04-24

96

Einstein in Wyoming.  

ERIC Educational Resources Information Center

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)

Elliot, Ian

1996-01-01

97

Albert Einstein Cancer Center  

Cancer.gov

The clinical research activities of AECC are conducted primarily at the Montefiore Medical Center which houses the Montefiore-Einstein Center for Cancer Care and encompasses participation from all the clinical oncologic academic disciplines.

98

Evidence for Enhanced Persistent Emission During Sub-Eddington Thermonuclear Bursts  

NASA Astrophysics Data System (ADS)

In a recent paper we found evidence for an increase in the accretion rate during photospheric radius expansion bursts, quantified by a variable normalization factor fa on the preburst persistent emission. Here we follow this result up on a much larger sample of 1759 type I X-ray bursts from 56 sources. We show that the variable persistent flux method provides improvements in the quality of spectral fits for type I bursts, whether or not they reach the Eddington luminosity. The new approach has an estimated Bayes factor of 64 improvement over the standard method, and we recommend that the procedure be adopted as standard for analyzing type I bursts. We show evidence that the remaining discrepancies to a formally consistent spectral model are due to the burst component deviating significantly from a blackbody, rather than variations in the spectral shape of the persistent emission component. In bursts that do not show radius expansion, the persistent emission enhancement does not exceed 37% of the Eddington flux. We use this observation to constrain the Eddington flux of sources for which {{F}Edd} has not been directly measured.

Worpel, Hauke; Galloway, Duncan K.; Price, Daniel J.

2015-03-01

99

Mid-Infrared Selected Quasars I: Virial Black Hole Mass and Eddington Ratios  

NASA Astrophysics Data System (ADS)

We provide a catalog of 391 mid-infrared-selected (MIR, 24?m) broad-emission-line (BEL, type 1) quasars in the 20 square deg SWIRE Lockman Hole field. This quasar sample is selected in the MIR from Spitzer MIPS with S24 >0.4mJy, and jointly with an optical magnitude limit of r (AB)= 22.5. The catalog is based on MMT spectroscopy to select BEL quasars, and extends the SDSS coverage to fainter magnitudes and a more complete quasar population. The MIR-selected quasar sample peaks at z ?1.4, and shows a significant and constant (20%) fraction of objects with extended SDSS photometry, previously missed by the SDSS optical point source dominant color selection. This sample also recovers a significant population of z < 3 quasars at i > 19.1, previously dropped by SDSS for efficiency consideration. We also investigate the continuum luminosity and line profile of these MIR quasars, estimate their virial black hole masses, and provide the Eddington ratios. The SMBH mass shows evidence of downsizing, though the Eddington ratios remain constant at 1 < z < 4. Compared to point sources in the same redshift range, extended sources at z < 1 show systematically lower Eddington ratios. The catalog and spectra will be publicly available online.

Dai, Yu Sophia; Elvis, Martin; Bergeron, Jacqueline; Fazio, Giovanni G.; Huang, Jiasheng; Wilkes, Belinda J.; Willmar, Christopher

2014-06-01

100

Mid-infrared-selected Quasars. I. Virial Black Hole Mass and Eddington Ratios  

NASA Astrophysics Data System (ADS)

We provide a catalog of 391 mid-infrared-selected (MIR; 24 ?m) broad-emission-line (BEL; type 1) quasars in the 22 deg2 SWIRE Lockman Hole field. This quasar sample is selected in the MIR from Spitzer MIPS with S 24 > 400 ?Jy, jointly with an optical magnitude limit of r (AB) < 22.5 for broad line identification. The catalog is based on MMT and Sloan Digital Sky Survey (SDSS) spectroscopy to select BEL quasars, extending the SDSS coverage to fainter magnitudes and lower redshifts, and recovers a more complete quasar population. The MIR-selected quasar sample peaks at z ~ 1.4 and recovers a significant and constant (20%) fraction of extended objects with SDSS photometry across magnitudes, which were not included in the SDSS quasar survey dominated by point sources. This sample also recovers a significant population of z < 3 quasars at i > 19.1. We then investigate the continuum luminosity and line profiles of these MIR quasars, and estimate their virial black hole masses and the Eddington ratios. The supermassive black hole mass shows evidence of downsizing, although the Eddington ratios remain constant at 1 < z < 4. Compared to point sources in the same redshift range, extended sources at z < 1 show systematically lower Eddington ratios. The catalog and spectra are publicly available online. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.

Dai, Y. Sophia; Elvis, Martin; Bergeron, Jacqueline; Fazio, Giovanni G.; Huang, Jia-Sheng; Wilkes, Belinda J.; Willmer, Christopher N. A.; Omont, Alain; Papovich, Casey

2014-08-01

101

Einstein's Big Idea  

NSDL National Science Digital Library

This free digital library resource is tied to standards and includes downloadable video and audio segments, Flash interactives, and more.In this segment, NOVA explores the stories behind E = mc2 and relates how Einstein came to his startling conclusion that mass and energy are two forms of the same thing. A brief biography is given along with Einsteins achievements, and his discoveries about energy, mass, special relativity, and atoms.

2005-11-11

102

Albert Einstein's Hypothetism  

NASA Astrophysics Data System (ADS)

This paper would like to show that Albert Einstein preceded Karl Popper in formulating the fundamental ideas of the so-called hypothetism. The ideas closest to Popper''s later view were presented by Einstein in a very interesting, yet little known article entitled ''Induction and Deduction in Physics'' published in a Berlin daily Berliner Tageblatt on Christmas Day of 1919. The text and ideas of this article will be presented (with German original appended) and comments will be made on them.

Kostro, Ludwik

103

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.

104

2010 Einstein Fellows Chosen  

NASA Astrophysics Data System (ADS)

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

2010-02-01

105

Timescale Measures for Irregularly Sampled, Aperiodic Light Curves  

NASA Astrophysics Data System (ADS)

We present preliminary results of a project to determine the most robust methods for identifying the characteristic timescale(s) of an aperiodic signal given noise and uneven sampling. While periodograms have been a staple of the analysis of periodic signals for decades, the analogous situation for aperiodic signals involves a mixture of competing heuristic techniques. We present both theoretical and empirical characterizations of the accuracy, precision, and robustness of a variety of techniques, and outline recommendations for the most practical timescale measures.

Findeisen, Krzysztof; Hillenbrand, L.

2013-06-01

106

Event Rate and Einstein Time Evaluation in Pixel Microlensing  

SciTech Connect

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.

Baltz, Edward A.; Silk, Joseph

2000-02-20

107

Einstein and Bose  

NASA Astrophysics Data System (ADS)

In June 1924, a relatively unknown Satyendra Nath Bose from Dacca, India, wrote a letter to Einstein beginning with ``Respected Sir, I have ventured to send you the accompanying article for your perusal. I am anxious to know what you think of it. You will see that I have ventured to deduce the coefficient 8??^2/c^3 in Planck's law independent of the classical electrodynamics, only assuming that the ultimate elementary regions in Phase-space have the content h^3. I do not know sufficient German to translate the paper. If you think the paper worth publication, I shall be grateful if you arrange for its publication in Zeitschrift für Physik.'' Einstein did translate the article himself and got it published. He wrote to Ehrenfest: ``The Indian Bose has given a beautiful derivation of Planck's law, including the constant [i.e.8??^2/c^3].'' Einstein extended the ideas of Bose that implied, among other things, a new statistics for the light-quanta to the molecules of an ideal gas and wrote to Ehrenfest, `from a certain temperature on, the molecules ``condense'' without attractive forces, that is, they accumulate at zero velocity. The theory is pretty, but is there also some truth to it?' Abraham Pais has called Bose's paper ``the fourth and the last revolutionary papers of the old quantum theory.'' My paper will present the works of Bose and Einstein in their historical perspective and the eventual birth of the new quantum Bose-Einstein statistics.

Wali, Kameshwar C.

2005-04-01

108

Multiple Timescales of Memory in Lateral Habenula and Dopamine Neurons  

E-print Network

Neuron Article Multiple Timescales of Memory in Lateral Habenula and Dopamine Neurons Ethan S of their reward memory and the factors that control its timescale. Here we recorded from dopamine neurons, as well memory expressed when a future reward outcome was revealed. The short- and long-time- scale memories were

Nakahara, Hiroyuki

109

Writing and Being Written: Issues of Identity across Timescales  

ERIC Educational Resources Information Center

This article argues for the differentiation according to timescales of aspects of writer identity. It presents a framework for investigating the discoursal construction of writer identity that develops the categories proposed by Ivanic in two ways. First, it distinguishes aspects of writer identity according to the timescales over which they…

Burgess, Amy; Ivanic, Roz

2010-01-01

110

BOOK REVIEW: Einstein's Jury: The Race to Test Relativity  

NASA Astrophysics Data System (ADS)

'I know very well that my theory rests on a shaky foundation. What attracts me to it is that it leads to consequences that seem to be accessible to experiment, and it provides a starting point for the theoretical understanding of gravitation', wrote Einstein in 1911. Einstein's Jury by Jeffrey Crelinsten—well documented, well written, and fascinating to read—describes how, from 1909 on, Einstein's two theories of relativity became known to astronomers, and how the predictions made between 1907 and 1915 were received as challenges to observers. The author gives a non-technical account of the efforts made until 1930 to test these predictions; he focuses on two of the three classical tests, namely gravitational redshift and bending of light; the 'jury' consists mainly of American observers—Adams, Campbell, Curtis, Hale, Perrin, St John, Trumpler and others—working with newly built large telescopes, and the Britons Eddington and Evershed. The major steps which, after a long struggle, convinced the majority of astronomers that Einstein was right, are narrated chronologically in rather great detail, especially the work at Lick Observatory, before and after the famous British observation of 1919, on solar eclipses, and the work at Mount Wilson and the Indian Kodaikanal Observatories to extract the gravitational redshift from the complicated spectrum of the sun. The account of the eclipse work which was carried out between 1918 and 1923 by Lick astronomers corrects the impression suggested by many historical accounts that the British expedition alone settled the light-bending question. Apart from these main topics, the anomalous perihelion advance of Mercury and the ether problem are covered. By concentrating on astronomy rather than on physics this book complements the rich but repetitive literature on Einstein and relativity which appeared in connection with the commemoration of Einstein's annus mirabilis, 2005. The well told stories include curiosities such as the Vulcan hypothesis, Evershed's Earth effect, and D C Miller's ether drift experiments. In particular, the sections on the history of the Californian observatories, their leading personalities, the differing attitudes of American and European scientists, and the influence of World War 1 on science, add interesting and informative aspects to the narrative. Those sections which report logistic and instrumental details of, for example, eclipse expeditions, were (to me) somewhat tiring. A weakness seems to be that the scientific importance of relativity problems is not stated clearly. On p43, the reader learns that Curtis quoted de Sitter's theoretical result of 7.15'' per century for Mercury's anomalous perihelion shift, but it is not mentioned that this value was due only to the special-relativistic variation of mass with velocity and already known to be much smaller than the observed value given on p88 and explained by general relativity, which includes, in particular, space curvature. In connection with light bending, the 'factor 2' is mentioned in several places without the explanation that this doubling is due to space curvature, the principal new effect whose observation created such a stir in 1919. Moreover, technical terms, for example absolute space, inertial frame, state of rest and (anomalous) dispersion, are used without explanation. Besides, readers interested as much in science as in its history would probably have appreciated a brief account of the present state of knowledge concerning the issues treated in this book and related ones. There are a few deplorable errors, for example the spectrum of the Andromeda nebula is shifted not towards the red, but towards the blue (p12); Eddington's limb deflection is given (p144) as 0.61'', while the correct value is 1.61''; misprints like that on p147 (coefficient of dr²), mistaking the astronomer Soldner (not Solden) for a physicist (p164). On p34 one reads 'Minkowski did not really grasp the physical implications of Einstein's work'—a strange judgment which contradicts the historical record. Thus reader

Ehlers, Jürgen

2007-10-01

111

Formation Timescales of the Martian Valley Networks  

NASA Astrophysics Data System (ADS)

The presence of valley networks across much of the ancient surface of Mars [e.g. 1] together with the locations and morphologies of the Martian deltas [e.g. 2] and ancient paleolakes [e.g. 3, 4], provides strong evidence that the Martian surface environment was once capable of sustaining long-lived flowing water. Many of the larger Martian valley networks exhibit characteristics consistent with their formation primarily from surface runoff of precipitated water [5-7]. Their formation likely followed similar processes as those that formed terrestrial river valleys, including the gradual erosion and transport of sediment downstream by bed load, suspended load, and wash load processes. When quantifying flow rates on Mars, some researchers have modified the Manning equation for depth- and width-averaged flow velocity in an attempt to better-fit Martian conditions [e.g. 3, 8-10]. These attempts, however, often result in flow velocities on Mars that are overestimated by up to a factor of two [10]. An alternative to the Manning equation that is often overlooked in the planetary science community is the Darcy-Weisbach (D-W) equation [11], which, unlike the Manning equation, maintains a dependence on the acceleration due to gravity. Although the D-W equation relies on a dimensionless friction function that has been fitted to terrestrial data, it is not a constant like the Manning coefficient. Rather, the D-W friction factor is a function of bed slope, flow depth, and median grain size [e.g. 8, 10, 12-14], and therefore it is better suited to model flow velocity on Mars. In this work, we investigate the formation timescales of the Martian valley networks through the use of four different sediment transport models [14], the D-W equation for average flow velocity, and a variety of parameters to encompass a range of possible formation conditions. This is done specific to each of eight large valley networks, all of which have crater densities that place their formation in the Late Noachian and Early Hesperian [15, 16], approximately 3.6 to 3.8 billion years ago. The preferred model scenario includes bankfull flows of 4-5 m depths corresponding to precipitation rates of 5 to 36 mm/day, depending on the valley network, and occurring intermittently 5% of the time. Results of the preferred model include formation timescales of 104 years (3°S, 5°E) to 108 years (east branch of Naktong Valles and 6°S, 45°E). References: [1] Hynek et al. (2010) JGR, doi:10.1029/2009JE003548; [2] Di Achille and Hynek (2010) Nature Geoscience, 3, 459-463; [3] Irwin et al. (2005) JGR, 110, E12S15; [4] Fassett and Head (2008) Icarus, 198, 37-56; [5] Craddock and Howard (2002) JGR, 107, 5111; [6] Howard et al. (2005) JGR, 110, E12S14; [7] Barnhart et al. (2009) JGR, 114, E01003; [8] Komar (1979) Icarus, 37, 156-181; [9] Goldspiel and Squyres (1991) Icarus, 89, 392-410; [10] Wilson et al. (2004) JGR, 109, E09003; [11] Leopold et al. (1964) Fluvial Processes in Geomorphology, 522pp; [12] Bathurst (1993) in Channel Network Hydrology, eds. Beven and Kirkby, p69-98; [13] Komar (1980) Icarus, 42, 317-329; [14] Kleinhans (2005) JGR, 110, E12003; [15] Fassett and Head (2008) Icarus, 195, 61-89; [16] Hoke and Hynek (2009) JGR, 114, E08002.

Hoke, M. T.; Hynek, B. M.

2010-12-01

112

NOVA: Einstein's Big Idea  

NSDL National Science Digital Library

It is hard to overestimate the importance of Albert Einstein's equation, "Energy equals mass times the speed of light squared." A recent special from NOVA explores many different facets of the lasting and pervasive effects of this revolutionary statement. The website was developed to provide a host of complementary resources to the actual television program, and as such, anyone with even a trace of interest in the history of science or physics will want to take a close look. The interactive features are excellent; they include 10 top physicist's explanation of the famous equation and a timeline of Einstein's life. The essays offered here are also top-notch, and they include a piece titled "Einstein the Nobody" by David Bodanis and "Relativity and the Cosmos" by Alan Lightman.

2005-01-01

113

Eye on Einstein  

NSDL National Science Digital Library

This OLogy activity challenges students to find nine inventions that Einstein's ideas helped to create. The activity begins with an illustration of Al's Junk Shop. Mixed in with his junk are a Global Positioning System, CD player, computer, calculator, scanner, laser pointer, TV, and representations of both laser surgery and nuclear energy. After making a mental list of their nine choices, students can click to a second page to check their answers. Each invention has a rollover note about how Einstein's ideas helped pave the way for its creation. Alternately, the first page could be printed and used as a handout for an offline activity.

114

Albert Einstein Online  

NSDL National Science Digital Library

Created by Steven Morgan Friedman of his site Westegg.com, this site offers a collection of papers and resources on Albert Einstein, his published papers, studies, and personal information. The page is nothing more than just links to external websites, but it is still quite useful for this reason. Structured in this fashion: overviews, moments, writings, quotes, pictures, miscellaneous, announcements and an about page, this site offers a nice overview of all things Einstein. This is a great resource for any student or instructor looking for a list of credible resources about this famous scientist.

Friedman, Steven Morgan

115

Conversations With Albert Einstein. II  

ERIC Educational Resources Information Center

Discusses Einstein's views on the role of Michelson-Morley, Fizeau, and Miller experiments in the development of relativity and his attitude toward the theories of new quantum mechanics. Indicates that Einstein's opposition to quantum mechanics is beyond dispute. (CC)

Shankland, R. S.

1973-01-01

116

Building a Bridge to Deep Time: Sedimentary Systems Across Timescales  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

117

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

E-print Network

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.

Angnis Schmidt-May; Mikael von Strauss

2014-12-11

118

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

E-print Network

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.

Hyeong-Chan Kim

2013-12-03

119

Geonic black holes and remnants in Eddington-inspired Born-Infeld gravity  

E-print Network

We show that electrically charged solutions within the Eddington-inspired Born-Infeld theory of gravity replace the central singularity by a wormhole supported by the electric field. As a result, the total energy associated with the electric field is finite and similar to that found in the Born-Infeld electromagnetic theory. When a certain charge-to-mass ratio is satisfied, in the lowest part of the mass and charge spectrum the event horizon disappears yielding stable remnants. We argue that quantum effects in the matter sector can lower the mass of these remnants from the Planck scale down to the TeV scale.

Gonzalo J. Olmo; D. Rubiera-Garcia; Helios Sanchis-Alepuz

2014-04-28

120

Geonic black holes and remnants in Eddington-inspired Born-Infeld gravity  

E-print Network

We show that electrically charged solutions within the Eddington-inspired Born-Infeld theory of gravity replace the central singularity by a wormhole supported by the electric field. As a result, the total energy associated with the electric field is finite and similar to that found in the Born-Infeld electromagnetic theory. When a certain charge-to-mass ratio is satisfied, in the lowest part of the mass and charge spectrum the event horizon disappears yielding stable remnants. We argue that quantum effects in the matter sector can lower the mass of these remnants from the Planck scale down to the TeV scale.

Olmo, Gonzalo J; Sanchis-Alepuz, Helios

2014-01-01

121

Geonic black holes and remnants in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

We show that electrically charged solutions within the Eddington-inspired Born-Infeld theory of gravity replace the central singularity by a wormhole supported by the electric field. As a result, the total energy associated with the electric field is finite and similar to that found in the Born-Infeld electromagnetic theory. When a certain charge-to-mass ratio is satisfied, in the lowest part of the mass and charge spectrum the event horizon disappears, yielding stable remnants. We argue that quantum effects in the matter sector can lower the mass of these remnants from the Planck scale down to the TeV scale.

Olmo, Gonzalo J.; Rubiera-Garcia, D.; Sanchis-Alepuz, Helios

2014-03-01

122

A modified Eddington-Barbier relation in highly coherent resonance-line wings  

NASA Technical Reports Server (NTRS)

It is shown that resonance-line wings are just as useful in inferring plane-parallel stellar chromospheric S sub L distributions as complete redistribution (CRD) profiles. Although coherent scattering effects at a given frequency tend to average depth-dependent parameters over a larger volume than in CRD, this effect can be offset by simply looking closer to line center, where the same depth-dependent information exists as in CRD, albeit somewhat more compressed in frequency space. For resonance lines with high excitation energies such as Ly-alpha, steep Planck function gradients can invalidate the modified Eddington-Barbier approach given, but this problem also exists in CRD.

Gayley, K. G.

1992-01-01

123

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

E-print Network

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 ...

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

2015-01-01

124

2011 Einstein Fellows Chosen  

NASA Astrophysics Data System (ADS)

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/

2011-03-01

125

The Einstein Toolkit  

NASA Astrophysics Data System (ADS)

The Einstein Toolkit Consortium is developing and supporting open software for relativistic astrophysics. Its aim is to provide the core computational tools that can enable new science, broaden our community, facilitate interdisciplinary research and take advantage of petascale computers and advanced cyberinfrastructure. The Einstein Toolkit currently consists of an open set of over 100 modules for the Cactus framework, primarily for computational relativity along with associated tools for simulation management and visualization. The toolkit includes solvers for vacuum spacetimes as well as relativistic magneto-hydrodynamics, along with modules for initial data, analysis and computational infrastructure. These modules have been developed and improved over many years by many different researchers. The Einstein Toolkit is supported by a distributed model, combining core support of software, tools, and documentation in its own repositories and through partnerships with other developers who contribute open software and coordinate together on development. As of January 2012 it has 68 registered members from 30 research groups world-wide. This talk will present the current capabilities of the Einstein Toolkit and will point to information how to leverage it for future research.

Löffler, Frank

2012-03-01

126

Einstein in My Hometown  

NASA Astrophysics Data System (ADS)

During the 22 years Albert Einstein lived and worked in the United States, he frequently took long summer vacations. Generally he chose quiet, out-of-the-way vacation spots, and because of his love of sailing, places close to bodies of water. Among other locations, he vacationed at Saranac Lake in upstate New York, the Rhode Island coast, and, during the summers of 1937-39, at Nassau Point on the North Fork of Long Island. Nassau Point is a part of the small town of Cutchogue and is located on Peconic Bay, about 90 miles from New York City. It was an ideal spot for Einstein both because it was off the beaten path and because of the outstanding sailing conditions on Peconic Bay. Einstein rented a cabin just a stone's throw from the bay. I myself have a special interest in Cutchogue because it's the place where I was born and where I spent the first few years of my life. Unfortunately, I came along five or six years too late to have actually seen Einstein there, but he did have encounters with some of my older friends and relatives.

Mamola, Karl

2005-12-01

127

Einstein and baseball  

NASA Astrophysics Data System (ADS)

Although Albert Einstein disliked games, he used the game of dice to illustrate his criticisms of quantum theory. If, however, he had considered basebal, he would have confronted a game whose unpredictable plays rise in wavelike rhythms analogous to quantum physics.

Pesic, Peter

1999-04-01

128

Einstein Books for Kids  

NSDL National Science Digital Library

This OLogy reference list has 10 kid-friendly books on physics. A short description is given for each title, along with author name and publisher. The list includes engaging biographies covering Einstein's life and contributions, collections of easy-to-complete science experiments, and illustrated looks at energy, time and space, light, and matter.

129

Einstein, Ethics and Science  

Microsoft Academic Search

In celebration of Einstein's remarkable achievements in 1905, this essay examines some of his views on the role of “intellectuals” in developing and advocating socio-economic and political positions and policies, the historical roots of his ethical views and certain aspects of his philosophy of science. As an outstanding academic and public citizen, his life and ideas continue to provide good

Alex C. Michalos

2005-01-01

130

Einstein Archives Online  

NSDL National Science Digital Library

Officially released on the Web last week, this impressive digital archive features the writings, scholarship, and thoughts of Albert Einstein, one of the 20th century's greatest scientists. The site allows visitors to view and browse 3,000 high-quality digitized images of Einstein's writings, ranging from his travel diaries (many of which are in German) to his published and unpublished scholarly manuscripts. The online archive draws on the manuscripts held by the Albert Einstein Archives at the Hebrew University of Jerusalem, and was produced by the Jewish National & University Library's Digitization Project. Additionally, visitors have access to the archive database, which contains 43,000 records of Einstein related documents, such as his notebooks and third-party items. More casual visitors will want to visit the online gallery, which contains a selection of some of the key documents available here, such as his famous article that mentions the equation E=mc2. Overall, this is a thoroughly engaging and informative trove of digitized material on one of the world's most respected scientists.

131

When Art Meets Einstein  

NSDL National Science Digital Library

A New World View, a composition of pale blue glass and steel, is an homage to the most famous scientist in modern history -- Albert Einstein. View this masterpiece for yourself by visiting the World Year of Physics (WYP) team's website that includes a number of extension activities to help middle school students explore their understanding and appreciation of science through art.

American Physical Society

2006-02-01

132

From Newton to Einstein.  

ERIC Educational Resources Information Center

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)

Ryder, L. H.

1987-01-01

133

Examining the Enigmatic Einstein  

ERIC Educational Resources Information Center

Albert Einstein is the icon of scientific genius. His is one the most recognizable faces in the history of mankind. This paper takes a cursory look at the man who is commonly perceived to be the epitome of eccentricity. We manage to sum up his salient traits which are associated with his name. The traits are based on anecdotal evidence. This…

Khoon, Koh Aik

2007-01-01

134

Einstein Year 2005  

NSDL National Science Digital Library

Einstein Year marks the centenary of the three papers that Albert Einstein published in 1905, which of course, included the paper on photoelectric effect that led to his Nobel Prize in Physics. The primary aim of Einstein Year is "to enthuse young people, and those who influence them, about physics, whilst building a sustainable increase in public awareness of physics and its role in society." On the site, visitors can learn about the various ongoing activities being coordinated around the world, read a biography about Einstein, and check out the "Experiment" section, where users can explore physics through a number of simple and thoughtful experiments. A real highlight of the site is the "If you could teach the world just one thing about science" feature, which was conducted by the online magazine, _spiked_. The magazine asked dozens of scientists what "one thing" they would pick to teach the world about science, and their responses (including a few video clips) are posted on the site.

135

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

NASA Astrophysics Data System (ADS)

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.

Wyithe, J. Stuart B.; Loeb, Abraham

2012-10-01

136

Wind Power Forecasting Error Distributions over Multiple Timescales: Preprint  

SciTech Connect

In this paper, we examine the shape of the persistence model error distribution for ten different wind plants in the ERCOT system over multiple timescales. Comparisons are made between the experimental distribution shape and that of the normal distribution.

Hodge, B. M.; Milligan, M.

2011-03-01

137

Characteristic Ultraviolet/Optical Timescales in Active Galactic Nuclei  

NASA Technical Reports Server (NTRS)

The UV/optical light curves of active galactic nuclei (AGNs) may be roughly characterized by a periodic fractional flux variations of approx. 10% on timescales of 1 month. The physical mechanism(s) responsible remain ill defined. We present a structure function analysis, i.e., measure the power distribution over a range of timescales tau, of 13 AGNs to constrain the origin of UV/optical emission. On timescales tau approx. 5- 60 days, the mean UV and optical power density spectra (PDS) are equivalent. This may suggest that the underlying energy generating mechanism is identical. The combined W/optical PDS is P(f) proportional to f(sup -alpha)- with alpha = 2.13(sup +0.22, sub -0.06). For sources with measured X-ray PDS indices, we find they are indistinguishable from their UV/optical counterparts. This supports scenarios whereby X-rays are generated via Compton upscattering of UV photons, to later radiatively drive optical variations. At the same time, we present evidence for characteristic variability timescales tau(sub char) of approx. 5-100 days in 10 sources. These variability timescales combined with reverberation based masses M suggest a M - tau(sub char) relationship; higher mass systems have larger characteristic timescales. The UV tau(sub char) may possibly reflect dynamical or accretion disk thermal timescales. We find suggestive evidence for a dichotomy, at tau approx. 30 days and M approx. l0(exp 7) solar mass, between short- and long-time scale optical variations. These optical variations may be attributable to dynamical and accretion disk thermal or starburst activity timescales, respectively.

Collier, Stefan; Peterson, Bradley M.

2001-01-01

138

Einstein's Real "biggest Blunder"  

NASA Astrophysics Data System (ADS)

Albert Einstein's real "biggest blunder" was not the 1917 introduction into his gravitational field equations of a cosmological constant term ?, rather was his failure in 1916 to distinguish between the entirely different concepts of active gravitational mass and passive gravitational mass. Had he made the distinction, and followed David Hilbert's lead in deriving field equations from a variational principle, he might have discovered a true (not a cut and paste) Einstein-Rosen bridge and a cosmological model that would have allowed him to predict, long before such phenomena were imagined by others, inflation, a big bounce (not a big bang), an accelerating expansion of the universe, dark matter, and the existence of cosmic voids, walls, filaments and nodes.

Ellis, Homer G.

2012-10-01

139

Through Einstein's Eyes  

NSDL National Science Digital Library

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.

Savage, Craig M.

140

Albert Einstein: Rebellious Wunderkind  

E-print Network

Childhood and Schooldays: Albert Einstein, and the family members seemed to have exaggerated the story of Albert who developed slowly, learned to talk late, and whose parents thought he was abnormal. These and other stories were adopted by biographers as if they really happened in the form that Albert and his sister told them. Hence biographers were inspired by them to create a mythical public image of Albert Einstein. Albert had tendency toward temper tantrums, the young impudent rebel Einstein had an impulsive and upright nature. He rebelled against authority and refused to learn by rote. He could not easily bring himself to study what did not interest him at school, especially humanistic subjects. And so his sister told the story that his Greek professor, to whom he once submitted an especially poor paper, went so far in his anger to declare that nothing would ever become of him. Albert learned subjects in advance when it came to sciences; and during the vacation of a few months from school, Albert indepen...

Weinstein, Galina

2012-01-01

141

The controversy between Alexander Friedmann and Albert Einstein about the possibility of a non-static world (German Title: Die Kontroverse zwischen Alexander Friedmann und Albert Einstein um die Möglichkeit einer nichtstatischen Welt)  

NASA Astrophysics Data System (ADS)

Einstein's treatment of the cosmological problem as well as his unshakeable adherence to his own static solution of the complete field equations was throughout determined by Ernst Mach's idea of relativity of inertia. Friedmann, however, like Eddington, Weyl and others did not consider Mach's principle to be a part of general relativity, and so he regarded a time dependent developing spatial geometry as being consistent with world matter at relative rest. In his final statement to the controversy, Einstein acknowledged just formal correctness of Friedmann's results. Actually his criticism was not due ``to a miscalculation'', as he was ready to admit, but was owed to a fundamental fixed idea which continued to exist and which was the cause of his disavowal of physical significance of dynamical solutions.

Singer, Georg

142

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

SciTech Connect

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.

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

143

Dark matter density profile and galactic metric in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

We consider the density profile of pressureless dark matter in Eddington-inspired Born-Infeld (EiBI) gravity. The gravitational field equations are investigated for a spherically symmetric dark matter galactic halo, by adopting a phenomenological tangential velocity profile for test particles moving in stable circular orbits around the galactic center. The density profile and the mass distribution, as well as the general form of the metric tensor is obtained by numerically integrating the gravitational field equations, and in an approximate analytical form by using the Newtonian limit of the theory. In the weak field limit, the dark matter density distribution is described by the Lane-Emden equation with polytropic index n = 1, and is nonsingular at the galactic center. The parameter ? of the theory is determined so that the theory could provide a realistic description of the dark matter halos. The gravitational properties of the dark matter halos are also briefly discussed in the Newtonian approximation.

Harko, Tiberiu; Lobo, Francisco S. N.; Mak, M. K.; Sushkov, Sergey V.

2014-03-01

144

Observational discrimination of Eddington-inspired Born-Infeld gravity from general relativity  

E-print Network

Direct observations of neutron stars could tell us an imprint of modified gravity. However, it is generally difficult to resolve the degeneracy due to the uncertainties in equation of state (EOS) of neutron star matter and in gravitational theories. In this paper, we are successful to find the observational possibility to distinguish Eddington-inspired Born-Infeld gravity (EiBI) from general relativity. We show that the radii of neutron stars with $0.5M_{sun}$ are strongly correlated with the neutron skin thickness of ${}^{208}$Pb independently of EOS, while this correlation depends on the coupling constant in EiBI. As a result, via the direct observations of radius of neutron star with $0.5M_{sun}$ and the measurements of neutron skin thickness of ${}^{208}$Pb by the terrestrial experiments, one could not only discriminate EiBI from general relativity but also estimate the coupling constant in EiBI.

Hajime Sotani

2014-04-22

145

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

NASA Astrophysics Data System (ADS)

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 the 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 does not increase faster than the quadratic power for large-field values. We also show that the anisotropy does not raise any defect in the early universe, contrary to the case of general relativity.

Kim, Hyeong-Chan

2014-09-01

146

Radial oscillations and stability of compact stars in Eddington-inspired Born-Infeld gravity  

E-print Network

We study the hydrostatic equilibrium structure of compact stars in the Eddington-inspired Born-Infeld gravity recently proposed by Banados and Ferreira [Phys. Rev. Lett. 105, 011101 (2010)]. We also develop a framework to study the radial perturbations and stability of compact stars in this theory. We find that the standard results of stellar stability still hold in this theory. The frequency square of the fundamental oscillation mode vanishes for the maximum-mass stellar configuration. The dependence of the oscillation mode frequencies on the coupling parameter \\kappa of the theory is also investigated. We find that the fundamental mode is insensitive to the value of \\kappa, while higher order modes depend more strongly on \\kappa.

Y. -H. Sham; L. -M. Lin; P. T. Leung

2012-09-21

147

Compact stars in Eddington-inspired Born-Infeld gravity: Anomalies associated with phase transitions  

E-print Network

We study how generic phase transitions taking place in compact stars constructed in the framework of the Eddington-inspired Born-Infeld (EiBI) gravity can lead to anomalous behavior of these stars. For the case with first-order phase transitions, compact stars in EiBI gravity with a positive coupling parameter $\\kappa $ exhibit a finite region with constant pressure, which is absent in general relativity. However, for the case with a negative $\\kappa $, an equilibrium stellar configuration cannot be constructed. Hence, EiBI gravity seems to impose stricter constraints on the microphysics of stellar matter. Besides, in the presence of spatial discontinuities in the sound speed $c_s$ due to phase transitions, the Ricci scalar is spatially discontinuous and contains $\\delta$-function singularities proportional to the jump in $c_s^2$ acquired in the associated phase transition.

Y. -H. Sham; P. T. Leung; L. -M. Lin

2013-04-09

148

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

SciTech Connect

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.

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

149

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

NASA Astrophysics Data System (ADS)

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.

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

150

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

NASA Astrophysics Data System (ADS)

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.

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

151

Einstein Toolkit for Relativistic Astrophysics  

NASA Astrophysics Data System (ADS)

The Einstein Toolkit is a collection of software components and tools for simulating and analyzing general relativistic astrophysical systems. Such systems include gravitational wave space-times, collisions of compact objects such as black holes or neutron stars, accretion onto compact objects, core collapse supernovae and Gamma-Ray Bursts. The Einstein Toolkit builds on numerous software efforts in the numerical relativity community including CactusEinstein, Whisky, and Carpet. The Einstein Toolkit currently uses the Cactus Framework as the underlying computational infrastructure that provides large-scale parallelization, general computational components, and a model for collaborative, portable code development.

Collaborative Effort

2011-02-01

152

Einstein from "B" to "Z"  

NASA Astrophysics Data System (ADS)

Einstein from 'B' to 'Z' is a unique collection of 37 published and unpublished papers on Albert Einstein that have been written by John Stachel, a physicist and historian of science. Stachel has written about Einstein - the man, his philosophy, and his work - for more than 40 years. The articles included in this volume will present a coherent picture of the new view of Einstein which is emerging from recent detailed documentation and studies of activities and work during Einstein's formative years about which so many old and new myths abound. Stachel's special introduction to the collection will explicitly tie together the themes implicit in the papers. This work will be of particular interest to historians of 20th century science, students and practitioners of physics, and the apparently large section of the general reading public that continues to be fascinated with Einstein. It will serve as an excellent reference text. The essays are grouped thematically into the following areas: 1. The human side. 2. Editing the Einstein papers. 3. Surveys of Einstein's work. 4. Special relativity. 5. General relativity. 6. Quantum theory. 7. Einstein and others. 8. Book reviews.

Stachel, John

153

THE CAMPAIGN TO TRANSFORM EINSTEIN 2 THE CAMPAIGN TO TRANSFORM EINSTEIN  

E-print Network

THE CAMPAIGN TO TRANSFORM EINSTEIN #12;2 THE CAMPAIGN TO TRANSFORM EINSTEIN #12;ALBERT EINSTEIN COLLEGE OF MEDICINE 1 F or more than five decades, Albert Einstein College of Medicine has responded: Albert Einstein grants his name to the Albert Einstein College of Medicine 1970s: Establishment

Yates, Andrew

154

Einstein's principle of Equivalence S What was Einstein's principle of  

E-print Network

Einstein's principle of Equivalence S What was Einstein's principle of Equivalence?* JOHN NORTON 1 experimentD smll hmers suh s #12;T John Norton n elevtorD is elerted in order to trnsforms wy grvittionl s the ox eomes ritrrily smllF por exmpleD the tidl ulges rising in freely flling liquid droplet do

155

Einstein and His Times  

NSDL National Science Digital Library

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.

2012-08-03

156

A Two-Timescale Discretization Scheme for Collocation  

NASA Technical Reports Server (NTRS)

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.

Desai, Prasun; Conway, Bruce A.

2004-01-01

157

BINARY ASTEROID ENCOUNTERS WITH TERRESTRIAL PLANETS: TIMESCALES AND EFFECTS  

SciTech Connect

Many asteroids that make close encounters with terrestrial planets are in a binary configuration. Here, we calculate the relevant encounter timescales and investigate the effects of encounters on a binary's mutual orbit. We use a combination of analytical and numerical approaches with a wide range of initial conditions. Our test cases include generic binaries with close, moderate, and wide separations, as well as seven well-characterized near-Earth binaries. We find that close approaches (<10 Earth radii) occur for almost all binaries on 1-10 million year timescales. At such distances, our results suggest substantial modifications to a binary's semimajor axis, eccentricity, and inclination, which we quantify. Encounters within 30 Earth radii typically occur on sub-million year timescales and significantly affect the wider binaries. Important processes in the lives of near-Earth binaries, such as tidal and radiative evolution, can be altered or stopped by planetary encounters.

Fang, Julia; Margot, Jean-Luc [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)

2012-01-15

158

Diffusion Time-Scale of Porous Pressure-Sensitive Paint  

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

159

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

NASA Astrophysics Data System (ADS)

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.

Grundmann, Siegfried

160

Einstein's cosmological considerations  

E-print Network

The objective of this paper is not simply to present an historical overview of Einstein's cosmological considerations, but to discuss the central role they played in shaping the paradigm of relativistic cosmology. This, we'll show, was a result of both his actions and, perhaps more importantly, his inactions. Accordingly, discussion won't simply be restricted to Einstein's considerations, as we'll analyse relevant contributions to the relativistic expansion paradigm during the approximately twenty years following Slipher's first redshift measurements in 1912. Our aim is to shed some light on why we think some of the things we do, with the idea that a better understanding of the reasoning that fundamentally influenced the common idea of our expanding universe might help to resolve some of the significant problems that modern cosmology now faces; and we eventually use this knowledge to probe the foundations of the standard model. Much of the information we present, including many of the historical details, we e...

Janzen, Daryl

2014-01-01

161

Einstein Inflationary Probe (EIP)  

NASA Technical Reports Server (NTRS)

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.

Hinshaw, Gary

2004-01-01

162

Einstein, Entropy and Anomalies  

NASA Astrophysics Data System (ADS)

This paper strengthens and defends the pluralistic implications of Einstein's successful, quantitative predictions of Brownian motion for a philosophical dispute about the nature of scientific advance that began between two prominent philosophers of science in the second half of the twentieth century (Thomas Kuhn and Paul Feyerabend). Kuhn promoted a monistic phase-model of scientific advance, according to which a paradigm driven `normal science' gives rise to its own anomalies, which then lead to a crisis and eventually a scientific revolution. Feyerabend stressed the importance of pluralism for scientific progress. He rejected Kuhn's model arguing that it fails to recognize the role that alternative theories can play in identifying exactly which phenomena are anomalous in the first place. On Feyerabend's account, Einstein's predictions allow for a crucial experiment between two incommensurable theories, and are an example of an anomaly that could refute the reigning paradigm only after the development of a competitor. Using Kuhn's specification of a disciplinary matrix to illustrate the incommensurability between the two paradigms, we examine the different research strategies available in this peculiar case. On the basis of our reconstruction, we conclude by rebutting some critics of Feyerabend's argument.

Sirtes, Daniel; Oberheim, Eric

2006-11-01

163

Albert Einstein 1879-1955.  

ERIC Educational Resources Information Center

Celebrates the centennial of Einstein's birth with an eight-page pictorial biography and two special articles: (1) Einstein the catalyst; and (2) Unitary field theories. His special and general theories of relativity and his contributions to quantum physics and other topics are also presented. (HM)

Physics Today, 1979

1979-01-01

164

Liouville gravity from Einstein gravity  

E-print Network

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.

D. Grumiller; R. Jackiw

2007-12-28

165

Comprehensive Scenarios of Millennial Timescale Carbon Cycle and Climate  

E-print Network

Comprehensive Scenarios of Millennial Timescale Carbon Cycle and Climate Change in a new Earth Model Efficient Numerical Terrestrial Scheme (ENTS) Millennial carbon cycle and climate change 6PacificGlobal #12;Carbon cycle and future emissions 1990s CO2 = 352ppmv (below observations) Ocean C sink = 3.2 Gt

Williamson, Mark

166

Distinct Neural Mechanisms Mediate Olfactory Memory Formation at Different Timescales  

ERIC Educational Resources Information Center

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…

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

2008-01-01

167

BATSS discovery of short timescale flaring from AGN?  

Microsoft Academic Search

BATSS discovery of short timescale flaring from AGN? For the past 2.5 years, we have been carrying out a slew survey with the BAT detector on the Swift satellite. The BAT Slew Survey (BATSS) uses BAT event mode data from about half of the 60 slews done each day with the Swift satellite to construct wide-field images (typically 80 x

Jonathan Grindlay

2010-01-01

168

On the pathways and timescales of intercontinental air pollution transport  

Microsoft Academic Search

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

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

2002-01-01

169

Dynamical masses, time-scales, and evolution of star clusters  

E-print Network

This review discusses (i) dynamical methods for determining the masses of Galactic and extragalactic star clusters, (ii) dynamical processes and their time-scales for the evolution of clusters, including evaporation, mass segregation, core collapse, tidal shocks, dynamical friction and merging. These processes lead to significant evolution of globular cluster systems after their formation.

Ortwin Gerhard

2000-07-18

170

The time-scale of escape from star clusters  

Microsoft Academic Search

In this paper a cluster is modelled as a smooth potential (due to the cluster stars) plus the steady tidal field of the Galaxy. In this model there is a minimum energy below which stars cannot escape. Above this energy, however, the time-scale on which a star escapes varies with the orbital parameters of the star (mainly its energy) in

T. Fukushige; D. C. Heggie

2000-01-01

171

Stochastic Simulation of Enzyme-Catalyzed Reactions with Disparate Timescales  

E-print Network

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

Paul, Mark

172

Why Mountains? Tales & Timescales of their Birth & Death  

E-print Network

Why Mountains? Tales & Timescales of their Birth & Death Saturday, September 12, 2009: 2146 Snee:40-10:00 Chris Andronicos (Cornell) The Birth, Life, and Death of North America's Largest Batholith: The Coast as the Hills: A Thermochronological View of the Birth and Death of Mountains 2:40-3:00 Frank Pazzaglia (Lehigh

Pritchard, Matthew

173

LOCALLY RECURRENT NETWORKS WITH MULTIPLE TIME-SCALES  

E-print Network

the standard tap delay line solutions can require thousands of taps. Unfortunately, the gamma structure has the time- constant along the delay line, a single delay line is able to represent signals that include delay line because of its ability to automatically choose an appropriate time-scale [l][2] [3

Harris, John G.

174

TIMESCALES ON WHICH STAR FORMATION AFFECTS THE NEUTRAL INTERSTELLAR MEDIUM  

SciTech Connect

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}.

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

175

Bianchi Type I Cosmological Models in Eddington-inspired Born-Infeld Gravity  

NASA Astrophysics Data System (ADS)

We consider the dynamics of a barotropic cosmological fluid in an anisotropic, Bianchi type I space-time in Eddington-inspired Born-Infeld (EiBI) gravity. By assuming an isotropic pressure distribution, we obtain the general solution of the field equations in an exact parametric form. The behavior of the geometric and thermodynamic parameters of the Bianchi type I Universe is studied, by using both analytical and numerical methods, for some classes of high density matter, described by the stiff causal, radiation, and pressureless fluid equations of state. In all cases the study of the models with different equations of state can be reduced to the integration of a highly nonlinear second order ordinary differential equation for the energy density. The time evolution of the anisotropic Bianchi type I Universe strongly depends on the initial values of the energy density and of the Hubble function. An important observational parameter, the mean anisotropy parameter is also studied in detail, and we show that for the dust filled Universe the cosmological evolution always ends into an isotropic phase, while for high density matter filled universes the isotropization of Bianchi type I universes is essentially determined by the initial conditions of the energy density.

Harko, Tiberiu; Lobo, Francisco; Mak, Man

2014-10-01

176

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

E-print Network

A new theory of gravity called Eddington-inspired Born-Infeld (EiBI) gravity was recently proposed by Ba\\~{n}ados 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 $\\kappa$ in the EiBI gravity. It is found that, compared with the corresponding charged black hole in general relativity, the positive coupling parameter $\\kappa$ 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.

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

2014-08-29

177

Properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity  

E-print Network

We systematically examine the properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity with not only the positive but also the negative coupling constant in the theory. As a result, we numerically find that the black hole solution exists even with the negative coupling constant, where the electric charge of black hole can be larger than the black hole mass. We also clarify the parameter space where the black hole solution exists. On the other hand, to examine the particle motion around such black hole, we derive the geodesic equation. The behavior of the effective potential for the radial particle motion is almost the same as that in general relativity, but the radius of the innermost stable circular orbit and the angular momentum giving the innermost stable circular orbit can be changed, depending on the coupling constant. In particular, we find that the radius of innermost stable circular orbit with the specific value of the coupling constant can be smaller than that for th...

Sotani, Hajime

2014-01-01

178

Properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity  

E-print Network

We systematically examine the properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity with not only the positive but also the negative coupling constant in the theory. As a result, we numerically find that the black hole solution exists even with the negative coupling constant, where the electric charge of black hole can be larger than the black hole mass. We also clarify the parameter space where the black hole solution exists. On the other hand, to examine the particle motion around such black hole, we derive the geodesic equation. The behavior of the effective potential for the radial particle motion is almost the same as that in general relativity, but the radius of the innermost stable circular orbit and the angular momentum giving the innermost stable circular orbit can be changed, depending on the coupling constant. In particular, we find that the radius of innermost stable circular orbit with the specific value of the coupling constant can be smaller than that for the extreme case in general relativity. Such a particle can release the gravitational binding energy more than the prediction in general relativity, which could be important from the observational point of view.

Hajime Sotani; Umpei Miyamoto

2014-12-13

179

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

E-print Network

A new theory of gravity called Eddington-inspired Born-Infeld (EiBI) gravity was recently proposed by Ba\\~{n}ados 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 $\\kappa$ in the EiBI gravity. It is found that, compared with the corresponding charged black hole in general relativity, the positive coupling parameter $\\kappa$ 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 ...

Wei, Shao-Wen; Liu, Yu-Xiao

2014-01-01

180

Structure of neutron, quark, and exotic stars in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

We consider the structure and physical properties of specific classes of neutron, quark, and “exotic” stars in Eddington-inspired Born-Infeld (EiBI) gravity. The latter reduces to standard general relativity in vacuum, but presents a different behavior of the gravitational field in the presence of matter. The equilibrium equations for a spherically symmetric configuration (mass continuity and Tolman-Oppenheimer-Volkoff) are derived, and their solutions are obtained numerically for different equations of state of neutron and quark matter. More specifically, stellar models, described by the stiff fluid, radiationlike, polytropic and the bag model quark equations of state are explicitly constructed in both general relativity and EiBI gravity, thus allowing a comparison between the predictions of these two gravitational models. As a general result it turns out that for all the considered equations of state, EiBI gravity stars are more massive than their general relativistic counterparts. Furthermore, an exact solution of the spherically symmetric field equations in EiBI gravity, describing an exotic star, with decreasing pressure but increasing energy density, is also obtained. As a possible astrophysical application of the obtained results we suggest that stellar mass black holes, with masses in the range of 3.8M? and 6M?, respectively, could be in fact EiBI neutron or quark stars.

Harko, Tiberiu; Lobo, Francisco S. N.; Mak, M. K.; Sushkov, Sergey V.

2013-08-01

181

Properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity  

NASA Astrophysics Data System (ADS)

We systematically examine the properties of an electrically charged black hole in Eddington-inspired Born-Infeld gravity with not only the positive but also the negative coupling constant in the theory. As a result, we numerically find that the black hole solution exists even with the negative coupling constant, where the electric charge of black hole can be larger than the black hole mass. We also clarify the parameter space where the black hole solution exists. On the other hand, to examine the particle motion around such black hole, we derive the geodesic equation. The behavior of the effective potential for the radial particle motion is almost the same as that in general relativity, but the radius of the innermost stable circular orbit and the angular momentum giving the innermost stable circular orbit can be changed, depending on the coupling constant. In particular, we find that the radius of innermost stable circular orbit with the specific value of the coupling constant can be smaller than that for the extreme case in general relativity. Such a particle can release the gravitational binding energy more than the prediction in general relativity, which could be important from the observational point of view.

Sotani, Hajime; Miyamoto, Umpei

2014-12-01

182

Magnetized relativistic stellar models in Eddington-inspired Born-Infeld gravity  

E-print Network

We consider the structure of the magnetic fields inside the neutron stars in Eddington-inspired Born-Infeld (EiBI) gravity. In order to construct the magnetic fields, we derive the relativistic Grad-Shafranov equation in EiBI, and numerically determine the magnetic distribution in such a way that the interior magnetic fields should be connected to the exterior distribution. Then, we find that the magnetic distribution inside the neutron stars in EiBI is qualitatively similar to that in general relativity, where the deviation of magnetic distribution in EiBI from that in general relativity is almost comparable to uncertainty due to the equation of state (EOS) for the neutron star matter. However, we also find that the magnetic fields in the crust region are almost independent of the coupling constant in EiBI, which suggests a possibility to obtain the information about the crust EOS independently of the gravitational theory via the observations of the phenomena associated with the crust region. In any case, si...

Sotani, Hajime

2015-01-01

183

Bianchi type I cosmological models in Eddington-inspired Born-Infeld gravity  

E-print Network

We consider the dynamics of a barotropic cosmological fluid in an anisotropic, Bianchi type I space-time in Eddington-inspired Born-Infeld (EiBI) gravity. By assuming an isotropic pressure distribution, we obtain the general solution of the field equations in an exact parametric form. The behavior of the geometric and thermodynamic parameters of the Bianchi type I Universe is studied, by using both analytical and numerical methods, for some classes of high density matter, described by the stiff causal, radiation, and pressureless fluid equations of state. In all cases the study of the models with different equations of state can be reduced to the integration of a highly nonlinear second order ordinary differential equation for the energy density. The time evolution of the anisotropic Bianchi type I Universe strongly depends on the initial values of the energy density and of the Hubble function. An important observational parameter, the mean anisotropy parameter is also studied in detail, and we show that for the dust filled Universe the cosmological evolution always ends into an isotropic phase, while for high density matter filled universes the isotropization of Bianchi type I universes is essentially determined by the initial conditions of the energy density.

Tiberiu Harko; Francisco S. N. Lobo; M. K. Mak

2014-10-28

184

Comparison of inversion codes for polarized line formation in MHD simulations. I. Milne-Eddington codes  

E-print Network

Milne-Eddington (M-E) inversion codes for the radiative transfer equation are the most widely used tools to infer the magnetic field from observations of the polarization signals in photospheric and chromospheric spectral lines. Unfortunately, a comprehensive comparison between the different M-E codes available to the solar physics community is still missing, and so is a physical interpretation of their inferences. In this contribution we offer a comparison between three of those codes (VFISV, ASP/HAO, and HeLIx$^+$). These codes are used to invert synthetic Stokes profiles that were previously obtained from realistic non-grey three-dimensional magnetohydrodynamical (3D MHD) simulations. The results of the inversion are compared with each other and with those from the MHD simulations. In the first case, the M-E codes retrieve values for the magnetic field strength, inclination and line-of-sight velocity that agree with each other within $\\sigma_B \\leq 35$ (Gauss), $\\sigma_\\gamma \\leq 1.2\\deg$, and $\\sigma_{\\r...

Borrero, J M; Lagg, A; Rezaei, R; Rempel, M

2014-01-01

185

Applicability of Milne-Eddington inversions to high spatial resolution observations of the quiet Sun  

NASA Astrophysics Data System (ADS)

Context. The physical conditions of the solar photosphere change on very small spatial scales both horizontally and vertically. Such a complexity may pose a serious obstacle to the accurate determination of solar magnetic fields. Aims: We examine the applicability of Milne-Eddington (ME) inversions to high spatial resolution observations of the quiet Sun. Our aim is to understand the connection between the ME inferences and the actual stratifications of the atmospheric parameters. Methods: We use magnetoconvection simulations of the solar surface to synthesize asymmetric Stokes profiles such as those observed in the quiet Sun. We then invert the profiles with the ME approximation. We perform an empirical analysis of the heights of formation of ME measurements and analyze the uncertainties brought about by the ME approximation. We also investigate the quality of the fits and their relationship with the model stratifications. Results: The atmospheric parameters derived from ME inversions of high-spatial resolution profiles are reasonably accurate and can be used for statistical analyses of solar magnetic fields, even if the fit is not always good. We also show that the ME inferences cannot be assigned to a specific atmospheric layer: different parameters sample different ranges of optical depths, and even the same parameter may trace different layers depending on the physical conditions of the atmosphere. Despite this variability, ME inversions tend to probe deeper layers in granules than in intergranular lanes. Figure 10 and appendix are only available in electronic form at http://www.aanda.org

Orozco Suárez, D.; Bellot Rubio, L. R.; Vögler, A.; Del Toro Iniesta, J. C.

2010-07-01

186

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

187

The bolometric luminosity of type 2 AGN from extinction-corrected [OIII]. No evidence of Eddington-limited sources  

NASA Astrophysics Data System (ADS)

Context: There have been recent claims that a significant fraction of type 2 AGN accrete close to or even above the Eddington limit. In type 2 AGN, the bolometric luminosity (L_b) is generally inferred from the [OIII] emission line luminosity (L_OIII). The key issue in estimating the bolometric luminosity in these AGN, is therefore to know the bolometric correction to be applied to L_OIII. A complication arises from the observed L_OIII being affected by extinction, most likely from dust within the narrow line region. The extinction-corrected [OIII] luminosity (L^c_OIII) is a better estimator of the nuclear luminosity than L_OIII. However, only the bolometric correction to be applied to the uncorrected L_OIII has been evaluated so far. Aims: This paper is devoted to estimating the bolometric correction C_OIII=L_b/L^c_OIII for deriving the Eddington ratios for the type 2 AGN in a sample of SDSS objects. Methods: We collected 61 sources from the literature with reliable estimates of both L^c_OIII and X-ray luminosities (L_X). To estimate C_OIII, we combined the observed correlation between L^c_OIII and LX with the X-ray bolometric correction. Results: In contrast to previous studies, we found a linear correlation between L^c_OIII and L_X. We estimated C_OIII using an earlier luminosity-dependent X-ray bolometric correction, and we found a mean value of C_OIII in the luminosity ranges log L_OIII = 38-40, 40-42, and 42-44 of 87, 142, and 454, respectively. We used it to calculate the Eddington ratio distribution of type 2 SDSS AGN at 0.3Eddington limit, contrary to previous claims.

Lamastra, A.; Bianchi, S.; Matt, G.; Perola, G. C.; Barcons, X.; Carrera, F. J.

2009-09-01

188

Science Frustrated: The ‘Einstein Institute’ In Madrid  

Microsoft Academic Search

In April 1933, Albert Einstein was offered an ‘Extraordinary’ Chair of Physics at the University of Madrid. Einstein first accepted, then sought to withdraw without causing damage to the anti-Fascist Republican government. However, this proved an opportunity for the Spanish press to harness Einstein’s notoriety to their own programmes. This article discusses the genesis and resolution of this episode, which

Thomas F. Glick; José M. Sánchez Ron

2006-01-01

189

The Collected Papers of Albert Einstein  

E-print Network

The Collected Papers of Albert Einstein The Collected Papers of Albert Einstein is one of the most from among more than 40,000 documents contained in the personal collection of Albert Einstein now housed at the Albert Ein- stein Archives at Hebrew University,and 15,000 Ein- stein and Einstein

Landweber, Laura

190

The Einstein Fellowship 2014 Awarded by the Einstein Forum and the Daimler and Benz Foundation  

E-print Network

, FROM THE APPLICANT'S PREVIOUS WORK. Albert Einstein-Stipendium 2014 Vergeben vom Einstein Forum und derThe Einstein Fellowship 2014 Awarded by the Einstein Forum and the Daimler and Benz Foundation The Einstein Forum and the Daimler and Benz Foundation are offering a fellowship for outstanding young thinkers

Heermann, Dieter W.

191

OWL representation of the geologic timescale implementing stratigraphic best practice  

NASA Astrophysics Data System (ADS)

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.

Cox, S. J.

2011-12-01

192

Einstein's Thoughts on the Ether  

NSDL National Science Digital Library

Do light waves travel through the ether like waves on a lake travel through water? In this video segment adapted from NOVA, a young Albert Einstein grapples with this question while examining the speed of light.

WGBH Educational Foundation

2004-02-20

193

Timescales Trips to PG Quasars: The Mkn 478 Case  

NASA Astrophysics Data System (ADS)

The X-ray bright PG quasar PG 1440+356 (Mkn 478) was observed four times across 13 months with the XMM-Newton observatory. Flux variations with a dynamical range of a factor about 6 were observed in both the soft (E < 1 keV) and the hard (E > 3 keV) X-ray band. However, large spectral variations are observed in the latter band only. We suggest that the X-ray emission in this object is due to Comptonization of kT ? 60 eV disk photons by a 20--50 keV plasma with a complex density structure. Analysis of the harmonic content of Mkn 478 light curves unveils a characteristic timescale ˜1 day, common to both energy bands. A longer (˜months) timescale is detected in the soft X-ray band only.

Guainazzi, M.; Loiseau, N.; Matt, G.; Orr, A.

194

Characteristic microvessel relaxation timescales associated with ultrasound-activated microbubbles  

PubMed Central

Ultrasound-activated microbubbles were used as actuators to deform microvessels for quantifying microvessel relaxation timescales at megahertz frequencies. Venules containing ultrasound contrast microbubbles were insonified by short 1?MHz ultrasound pulses. Vessel wall forced-deformations were on the same microsecond timescale as microbubble oscillations. The subsequent relaxation of the vessel was recorded by high-speed photomicrography. The tissue was modeled as a simple Voigt solid. Relaxation time constants were measured to be on the order of ?10??s. The correlation coefficients between the model and 38 data sets were never lower than 0.85, suggesting this model is sufficient for modeling tissue relaxation at these frequencies. The results place a bound on potential numerical values for viscosity and elasticity of venules. PMID:23152641

Chen, Hong; Brayman, Andrew A.; Matula, Thomas J.

2012-01-01

195

Satellite animations reveal ocean surface dynamics for shortest timescales ever  

NASA Astrophysics Data System (ADS)

Scientists can now monitor the displacement and evolution of ocean surface thermal patterns on a shorter timescale than ever before possible, thanks to a new satellite detection method. Animations of daily composites of sea surface temperature (SST) from GOES [Menzel and Purdom, 1994” are allowing even a first-time observer to instantly recognize the relevant patterns at timescales from several hours to several months.Meteorologists have used GOES effectively to monitor cloud motions and to track storms, and now oceanographers can benefit too. Each individual daily composite is still partly cloud covered, but rapid display provides the appearance of continuity. So by viewing the composites rapidly the human eye can separate the fast moving residual clouds from the slower moving SST patterns associated with ocean currents, eddies, and upwelling.

Legeckis, Richard; Zhu, Paul Chang Tong; Chen, Shuangian

196

Video Gallery: Reflection on Einstein  

NSDL National Science Digital Library

This online video gallery is from the Museum's Seminars on Science, a series of distance-learning courses designed to help educators meet the new national science standards. Reflections on Einstein, part of the Frontiers in Physical Science seminar, is available in broadband and modem formats and with a printable PDF transcript. The video shows excerpts of a panel of seven scientists reflecting on Einstein's influence.

197

The NASA Beyond Einstein Program  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna (LISA) mission is part of NASA s Beyond Einstein program. This program seeks to answer the questions What Powered the Big Bang?, What happens at the edge of a Black Hole?, and What is Dark Energy?. LISA IS the first mission to be launched in this new program. This paper will give an overview of the Beyond Einstein program, its current status and where LISA fits in.

White, Nicholas E.

2004-01-01

198

Geol 102 Historical Geology The Geologic Timescale 2011  

E-print Network

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

Holtz Jr., Thomas R.

199

Geol 102 Historical Geology The Geologic Timescale 2012  

E-print Network

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

Holtz Jr., Thomas R.

200

Response to Deines and Williams on Astronomical Timescales  

NASA Astrophysics Data System (ADS)

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.

Slabinski, Victor J.

2009-05-01

201

Timescale algorithms combining cesium clocks and hydrogen masers  

NASA Technical Reports Server (NTRS)

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.

Breakiron, Lee A.

1992-01-01

202

The effects of clock errors on timescale stability  

NASA Technical Reports Server (NTRS)

The weighting scheme for the cesium clocks and hydrogen masers constituting the USNO timing ensemble is reexamined from an empirical standpoint of maximizing both frequency accuracy and timescale uniformity. The utility of a sliding-weight relation between the masers and the cesiums is reaffirmed, but improvement is found if one incorporates inverse Allan variances for sampling times of 12 and 6 hours for the cesiums and masers, respectively, with some dependence on clock model.

Breakiron, Lee A.

1995-01-01

203

Shape invariant time-scale and pitch modification of speech  

Microsoft Academic Search

The simplified linear model of speech production predicts that when the rate of articulation is changed, the resulting waveform takes on the appearance of the original, except for a change in the time scale. A time-scale modification system that preserves this shape-invariance property during voicing is developed. This is done using a version of the sinusoidal analysis-synthesis system that models

Thomas F. Quatieri; Robert J. McAulay

1992-01-01

204

Timescales of fluvial activity and intermittency in Milna Crater, Mars  

NASA Astrophysics Data System (ADS)

Milna Crater, Mars (23.4S, 12.3W) exhibits signs of fluvial modification early in Mars history, including a large multi-lobed fan deposit cut by several sinuous valleys. We describe the past hydrologic conditions in Milna and the surrounding area, including a potential lake with a volume of 50 km3. We also introduce new methods (i) to calculate the timescale of sediment deposition by considering fluvial sediment input into the entire crater while accounting for non-fluvial input, and (ii) to place improved constraints on the channel dimensions through which sediment was delivered to Milna by comparing to the dimensions of inner channels found in valleys in the region surrounding Milna. By calculating the flux of fluid and sediment into the crater, we find that the crater cavity was flooded for at least months and that the time of active fluvial sediment transport without hiatus is on the order of decades to centuries, with a preferred timescale of centuries. We also calculate the total amount of water required to transport the volume of sediment we measure in Milna and conclude that impacts alone are likely insufficient to deliver enough water to Milna to allow the sedimentary fill we see. Combining the timescales of fluvial activity in the adjacent Paraná Valles with estimates for global Noachian erosion rates, we calculate an intermittency factor for fluvial activity of ?0.01-0.1% during 105-106 yr near the Noachian-Hesperian boundary in the Paraná Valles region. These values are comparable to arid climates on Earth where the majority of fluvial sedimentary transport takes place during floods with multi-year to decadal recurrence intervals. Our calculations of intermittency help to quantitatively reconcile the divergent estimates of the short and long timescales of fluvial activity on Mars reported in the literature.

Buhler, Peter B.; Fassett, Caleb I.; Head, James W.; Lamb, Michael P.

2014-10-01

205

The NASA Beyond Einstein Program  

NASA Technical Reports Server (NTRS)

Einstein's legacy is incomplete, his theory of General relativity raises -- but cannot answer --three profound questions: What powered the big bang? What happens to space, time, and matter at the edge of a black hole? and What is the mysterious dark energy pulling the Universe apart? The Beyond Einstein program within NASA's Office of Space Science aims to answer these questions, employing a series of missions linked by powerful new technologies and complementary approaches towards shared science goals. The Beyond Einstein program has three linked elements which advance science and technology towards two visions; to detect directly gravitational wave signals from the earliest possible moments of the BIg Bang, and to image the event horizon of a black hole. The central element is a pair of Einstein Great Observatories, Constellation-X and LISA. Constellation-X is a powerful new X-ray observatory dedicated to X-Ray Spectroscopy. LISA is the first spaced based gravitational wave detector. These powerful facilities will blaze new paths to the questions about black holes, the Big Bang and dark energy. The second element is a series of competitively selected Einstein Probes, each focused on one of the science questions and includes a mission dedicated resolving the Dark Energy mystery. The third element is a program of technology development, theoretical studies and education. The Beyond Einstein program is a new element in the proposed NASA budget for 2004. This talk will give an overview of the program and the missions contained within it.

White, Nicholas E.

2006-01-01

206

Timescales of emulsion formation caused by anisotropic particles.  

PubMed

Particle stabilized emulsions have received much interest in the recent past, but our understanding of the dynamics of emulsion formation is still limited. For simple spherical particles, the time dependent growth of fluid domains is dominated by the formation of droplets, particle adsorption and coalescence of droplets (Ostwald ripening), which eventually can be almost fully blocked due to the presence of the particles. Ellipsoidal particles are known to be more efficient stabilizers of fluid interfaces than spherical particles and their anisotropic shape and the related additional rotational degrees of freedom have an impact on the dynamics of emulsion formation. In this paper, we investigate this point by means of simple model systems consisting of a single ellipsoidal particle or a particle ensemble at a flat interface as well as a particle ensemble at a spherical interface. By applying combined multicomponent lattice Boltzmann and molecular dynamics simulations we demonstrate that the anisotropic shape of ellipsoidal particles causes two additional timescales to be of relevance in the dynamics of emulsion formation: a relatively short timescale can be attributed to the adsorption of single particles and the involved rotation of particles towards the interface. As soon as the interface is jammed, however, capillary interactions between the particles cause a local reordering on very long timescales leading to a continuous change in the interface configuration and increase of the interfacial area. This effect can be utilized to counteract the thermodynamic instability of particle stabilized emulsions and thus offers the possibility to produce emulsions with exceptional stability. PMID:24888563

Günther, Florian; Frijters, Stefan; Harting, Jens

2014-07-21

207

Simulated Performance of Timescale Metrics for Aperiodic Light Curves  

NASA Astrophysics Data System (ADS)

Aperiodic variability is a characteristic feature of young stars, massive stars, and active galactic nuclei. With the recent proliferation of time-domain surveys, it is increasingly essential to develop methods to quantify and analyze aperiodic variability. We develop three timescale metrics that have been little used in astronomy—?m-?t plots, peak-finding, and Gaussian process regression—and present simulations comparing their effectiveness across a range of aperiodic light curve shapes, characteristic timescales, observing cadences, and signal to noise ratios. We find that Gaussian process regression is easily confused by noise and by irregular sampling, even when the model being fit reflects the process underlying the light curve, but that ?m-?t plots and peak-finding can coarsely characterize timescales across a broad region of parameter space. We make public the software we used for our simulations, both in the spirit of open research and to allow others to carry out analogous simulations for their own observing programs.

Findeisen, Krzysztof; Cody, Ann Marie; Hillenbrand, Lynne

2015-01-01

208

Timescales of emulsion formation caused by anisotropic particles  

E-print Network

Particle stabilized emulsions have received an enormous interest in the recent past, but our understanding of the dynamics of emulsion formation is still limited. For simple spherical particles, the time dependent growth of fluid domains is dominated by the formation of droplets, particle adsorption and coalescence of droplets (Ostwald ripening), which eventually can be almost fully blocked due to the presence of the particles. Ellipsoidal particles are known to be more efficient stabilizers of fluid interfaces than spherical particles and their anisotropic shape and the related additional rotational degrees of freedom have an impact on the dynamics of emulsion formation. In this paper, we investigate this point by means of simple model systems consisting of a single ellipsoidal particle or a particle ensemble at a flat interface as well as a particle ensemble at a spherical interface. By applying combined multicomponent lattice Boltzmann and molecular dynamics simulations we demonstrate that the anisotropic shape of ellipsoidal particles causes two additional timescales to be of relevance in the dynamics of emulsion formation: a relatively short timescale can be attributed to the adsorption of single particles and the involved rotation of particles towards the interface. As soon as the interface is jammed, however, capillary interactions between the particles cause a local reordering on very long timescales leading to a continuous change in the interface configuration and increase of interfacial area. This effect can be utilized to counteract the thermodynamic instability of particle stabilized emulsions and thus offers the possibility to produce emulsions with exceptional stability.

Florian Günther; Stefan Frijters; Jens Harting

2014-04-01

209

Einstein's 1919 View  

NASA Astrophysics Data System (ADS)

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.

Goradia, Shantilal

2012-10-01

210

Comparison of inversion codes for polarized line formation in MHD simulations. I. Milne-Eddington codes  

NASA Astrophysics Data System (ADS)

Milne-Eddington (M-E) inversion codes for the radiative transfer equation are the most widely used tools to infer the magnetic field from observations of the polarization signals in photospheric and chromospheric spectral lines. Unfortunately, a comprehensive comparison between the different M-E codes available to the solar physics community is still missing, and so is a physical interpretation of their inferences. In this contribution we offer a comparison between three of those codes (VFISV, ASP/HAO, and HeLIx+). These codes are used to invert synthetic Stokes profiles that were previously obtained from realistic non-grey three-dimensional magnetohydrodynamical (3D MHD) simulations. The results of the inversion are compared with each other and with those from the MHD simulations. In the first case, the M-E codes retrieve values for the magnetic field strength, inclination and line-of-sight velocity that agree with each other within ?B ? 35 (Gauss), ?? ? 1.2°, and ?v ? 10 m s-1, respectively. Additionally, M-E inversion codes agree with the numerical simulations, when compared at a fixed optical depth, within ?B ? 130 (Gauss), ?? ? 5°, and ?v ? 320 m s-1. Finally, we show that employing generalized response functions to determine the height at which M-E codes measure physical parameters is more meaningful than comparing at a fixed geometrical height or optical depth. In this case the differences between M-E inferences and the 3D MHD simulations decrease to ?B ? 90 (Gauss), ?? ? 3°, and ?v ? 90 m s-1.

Borrero, J. M.; Lites, B. W.; Lagg, A.; Rezaei, R.; Rempel, M.

2014-12-01

211

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

212

BOOK REVIEW: Once Upon Einstein  

NASA Astrophysics Data System (ADS)

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,

Giannetto, E.

2007-07-01

213

Einstein boundary conditions for the 3+1 Einstein equations  

E-print Network

In the 3+1 framework of the Einstein equations for the case of vanishing shift vector and arbitrary lapse, we calculate explicitly the four boundary equations arising from the vanishing of the projection of the Einstein tensor along the normal to the boundary surface of the initial-boundary value problem. Such conditions take the form of evolution equations along (as opposed to across) the boundary for certain components of the extrinsic curvature and for certain space-derivatives of the intrinsic metric. We argue that, in general, such boundary conditions do not follow necessarily from the evolution equations and the initial data, but need to be imposed on the boundary values of the fundamental variables. Using the Einstein-Christoffel formulation, which is strongly hyperbolic, we show how three of the boundary equations should be used to prescribe the values of some incoming characteristic fields. Additionally, we show that the fourth one imposes conditions on some outgoing fields.

Simonetta Frittelli; Roberto Gomez

2003-08-06

214

Detecting Einstein geodesics: Einstein metrics in projective and conformal geometry  

E-print Network

Here we treat the problem: given a torsion-free connection do its geodesics, as unparametrised curves, coincide with the geodesics of an Einstein metric? We find projective invariants such that the vanishing of these is necessary for the existence of such a metric, and in generic settings the vanishing of these is also sufficient. We also obtain results for the problem of metrisability (without the Einstein condition): We show that the odd Chern type invariants of an affine connection are projective invariants that obstruct the existence of a projectively related Levi-Civita connection. In addition we discuss a concrete link between projective and conformal geometry and the application of this to the projective-Einstein problem.

A. Rod Gover; Heather Macbeth

2012-12-27

215

Einstein's Radiation Formula and Modifications to the Einstein Equation  

NASA Astrophysics Data System (ADS)

Einstein's radiation formula is supported by the Taylor-Hulse experiment, but its derivation is not self-consistent. Furthermore, as discovered by Einstein, his radiation formula is not compatible with his field equation. As suggested by Einstein's own remark, modifications to the source tensor are necessary. Based on the Taylor-Hulse experiment, in this paper a theory is developed within the theoretical framework of general relativity within which the radiation formula remains the same for binary stars. Concurrently, it is determined that, because of radiation, the source tensor is not zero in a vacuum. Antigravity coupling, suggested by Pauli as a possibility, is a necessary feature. In addition, it is shown that the current theory of linearized gravity is not valid for radiation.

Lo, C. Y.

1995-12-01

216

Ocean-atmosphere partitioning of anthropogenic carbon dioxide on centennial timescales  

E-print Network

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

Follows, Mick

217

The Short-Timescale Behavior of Glacial Ice  

NASA Astrophysics Data System (ADS)

Glaciers are often assumed to deform only at slow (i.e., glacial) rates. However, with the advent of high rate geodetic observations of ice motion, many of the intricacies of glacial deformation on hourly and daily timescales have been observed and quantified. This thesis explores two such short timescale processes: the tidal perturbation of ice stream motion and the catastrophic drainage of supraglacial meltwater lakes. Our investigation into the transmission length-scale of a tidal load represents the first study to explore the daily tidal influence on ice stream motion using three-dimensional models. Our results demonstrate both that the implicit assumptions made in the standard two-dimensional flow-line models are inherently incorrect for many ice streams, and that the anomalously large spatial extent of the tidal influence seen on the motion of some glaciers cannot be explained, as previously thought, through the elastic or viscoelastic transmission of tidal loads through the bulk of the ice stream. We then discuss how the phase delay between a tidal forcing and the ice stream's displacement response can be used to constrain in situ viscoelastic properties of glacial ice. Lastly, for the problem of supraglacial lake drainage, we present a methodology for implementing linear viscoelasticity into an existing model for lake drainage. Our work finds that viscoelasticity is a second-order effect when trying to model the deformation of ice in response to a meltwater lake draining to a glacier's bed. The research in this thesis demonstrates that the first-order understanding of the short-timescale behavior of naturally occurring ice is incomplete, and works towards improving our fundamental understanding of ice behavior over the range of hours to days.

Thompson, Jeffrey Muir

218

Dynamics and Time-scales in Breakup and Fusion  

NASA Astrophysics Data System (ADS)

Nuclear reaction dynamics at energies near the fusion barrier is known to be dominated by quantum effects, such as tunneling, and quantum superpositions that gives rise to channel couplings. The understanding of near-barrier reaction dynamics continues to evolve as improved experimental techniques reveal new facets of interaction dynamics. Recent coincidence measurements using weakly bound stable nuclei have not only provided a complete picture of the physical mechanisms triggering breakup, but have also shown how information on reaction dynamics occurring on time-scales of ~zepto-seconds can be obtained experimentally. These new experimental findings demand major developments in quantum models of low energy nuclear reactions.

Dasgupta, M.; Luong, D. H.; Hinde, D. J.; Evers, M.; Lin, C. J.; du Rietz, R.

2013-03-01

219

Mass Segregation in Star Clusters: Analytic Estimation of the Timescale  

E-print Network

Mass segregation in a star cluster is studied in an analytical manner. We consider a two-component cluster, which consists of two types of stars with different masses. Plummer's model is used for the initial condition. We trace the overall behaviors of the probability distribution functions of the two components and obtain the timescale of mass segregation as a simple function of the cluster parameters. The result is used to discuss the origin of a black hole with mass of > 1000 M(sun) found in the starburst galaxy M82.

H. Mouri; Y. Taniguchi

2002-08-02

220

Triangle Anomalies from Einstein Manifolds  

E-print Network

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.

Sergio Benvenuti; Leopoldo A. Pando Zayas; Yuji Tachikawa

2006-07-20

221

Schwinger's Approach to Einstein's Gravity  

NASA Astrophysics Data System (ADS)

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.

Milton, Kim

2012-05-01

222

Einstein metrics in projective geometry  

E-print Network

It is well known that pseudo-Riemannian metrics in the projective class of a given torsion free affine connection can be obtained from (and are equivalent to) the solutions of a certain overdetermined projectively invariant differential equation. This equation is a special case of a so-called first BGG equation. The general theory of such equations singles out a subclass of so-called normal solutions. We prove that non-degerate normal solutions are equivalent to pseudo-Riemannian Einstein metrics in the projective class and observe that this connects to natural projective extensions of the Einstein condition.

A. Cap; A. R. Gover; H. R. Macbeth

2014-06-18

223

Galileo and Einstein Home Page  

NSDL National Science Digital Library

These lecture notes from Michael Fowler, Physics professor at University of Virginia, explore "two revolutions in our perception of the universe," the impacts of Galileo and then Einstein on our understanding of physics. The 27 lectures included here may be a useful supplement and teaching aid for educators. The lectures begin with the early Greeks and follow the progress of scientific thought through the work of Galileo, Isaac Newton, and Einstein. The lectures themselves are clear and offer interesting historic details and a conversational approach to explaining concepts. Though the lectures were written a few years ago, the content is timeless, and many of the lectures have been recently updated.

224

Einstein Session of the Pontifical Academy.  

ERIC Educational Resources Information Center

The texts of four speeches, given at the 1979 Einstein Session of the Pontifical Academy held in Rome, are presented. Each address relates to some aspect of the life and times of Albert Einstein. (SA)

Science, 1980

1980-01-01

225

Einstein: Physicist, Philosopher, Humanitarian Youngstown State March 25, 2009 Albert Einstein: Physicist,  

E-print Network

Einstein: Physicist, Philosopher, Humanitarian ­ Youngstown State ­ March 25, 2009 Albert Einstein and Philosophy of Science University of Notre Dame Youngstown State University March 25, 2009 Einstein as a college student, ca. 1900 #12;Einstein: Physicist, Philosopher, Humanitarian ­ Youngstown State ­ March 25

Howard, Don

226

Oceanic control of Northeast Pacific hurricane activity at interannual timescales  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

227

Timescale Correlation between Marine Atmospheric Exposure and Accelerated Corrosion Testing  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

228

A Hierarchy of Time-Scales and the Brain  

PubMed Central

In this paper, we suggest that cortical anatomy recapitulates the temporal hierarchy that is inherent in the dynamics of environmental states. Many aspects of brain function can be understood in terms of a hierarchy of temporal scales at which representations of the environment evolve. The lowest level of this hierarchy corresponds to fast fluctuations associated with sensory processing, whereas the highest levels encode slow contextual changes in the environment, under which faster representations unfold. First, we describe a mathematical model that exploits the temporal structure of fast sensory input to track the slower trajectories of their underlying causes. This model of sensory encoding or perceptual inference establishes a proof of concept that slowly changing neuronal states can encode the paths or trajectories of faster sensory states. We then review empirical evidence that suggests that a temporal hierarchy is recapitulated in the macroscopic organization of the cortex. This anatomic-temporal hierarchy provides a comprehensive framework for understanding cortical function: the specific time-scale that engages a cortical area can be inferred by its location along a rostro-caudal gradient, which reflects the anatomical distance from primary sensory areas. This is most evident in the prefrontal cortex, where complex functions can be explained as operations on representations of the environment that change slowly. The framework provides predictions about, and principled constraints on, cortical structure–function relationships, which can be tested by manipulating the time-scales of sensory input. PMID:19008936

Kiebel, Stefan J.; Daunizeau, Jean; Friston, Karl J.

2008-01-01

229

Progress Towards Atomistic Simulations that Reach Anthropological Timescale and Beyond  

NASA Astrophysics Data System (ADS)

Atomistic and first-principles modeling, which describe the world as assembly of atoms and electrons, provide the most fundamental answer to problems of materials. However, they also suffer the most severe timescale limitations. For instance, in molecular dynamics (MD) simulations, in order to resolve atomic vibrations, the integration time step is limited to hundredth of a picosecond, and therefore the simulation duration is limited to sub-microsecond due to computational cost. Although a nanosecond simulation is often enough (surprisingly) for many physical and chemical properties, it is usually insufficient for predicting microstructural evolution and thermo-mechanical properties of materials. In this invited talk I will discuss recent attempts at overcoming the timescale challenges of atomic-resolution simulations: (a) strain-boost hyperdynamics [Phys. Rev. B 82 (2010) 184114] for simulating primarily displacive events and associated issues of activation entropy and the Meyer-Neldel compensation rule, (b) diffusive molecular dynamics (DMD) [Phys. Rev. B 84 (2011) 054103] for microstructural evolution driven by repetitive diffusion events and coupled displacive-diffusive processes, and (c) a Markovian network statistical mechanical treatment of the energy-landscape basin connectivity and a formula for the viscosity of supercooled liquid and glass [PLoS ONE 6 (2011) e17909]. Challenges and future directions are discussed.

Li, Ju

2012-02-01

230

winter 2008 I EinstEin EINSTEINwinter 2008  

E-print Network

:Apublicationforfaculty,students,alumni,friendsandsupporters oftheAlbertEinsteinCollegeofMedicineofYeshivaUniversity. Visitusonlineatwww.aecom.yu.edu. ©2008Volume28winter 2008 I EinstEin EINSTEINwinter 2008 THE EINSTEIN EDGE TODAY'S SCIENCE... TOMORROW'S MEDICINE #12; EinstEin I winter 2008 winter 2008 I EinstEin EINSTEINCONTENTSwinter 2008 EINSTEIN

Yates, Andrew

231

Einstein for Schools and the General Public  

ERIC Educational Resources Information Center

In April 2005 the World Year of Physics (Einstein Year in the UK and Ireland) was celebrated with an Einstein week in Stockholm House of Science. Seven experiments illustrated Einstein's remarkable work in 1905 on Brownian motion, the photoelectric effect and special relativity. Thirteen school classes with 260 pupils, 30 teachers and 25 members…

Johansson, K. E.; Kozma, C; Nilsson, Ch

2006-01-01

232

The General Introduction of Einstein meets Magritte  

E-print Network

long and exhausting and the press were doing all they could to get Albert Einstein and Ren´e MagritteThe General Introduction of Einstein meets Magritte Diederik Aerts, Center Leo Apostel, Brussels Free University, Brussels, Belgium. The series of books `Einstein meets Magritte' presented here

Aerts, Diederik

233

100 years since Einstein's less known revolution  

E-print Network

) to their microscopic components and interactions with the environment. Albert Einstein made crucial contributions of semi-conductors and the computer revolution that followed. It is amazing that Albert Einstein when he1 100 years since Einstein's less known revolution: From the pollen dance to atoms and back

Andelman, David

234

Albert Einstein: Relativity, War, Daniel J. Kevles  

E-print Network

Albert Einstein: Relativity, War, and Fame Daniel J. Kevles In 1922, Princeton University Press published Albert Einstein's The Meaning of Relativity, a popularization of his theory that has remained as succes- sive editions of his writings appear. Albert Einstein burst upon the world of physics in 1905

Landweber, Laura

235

Einstein Room Reservations Rules and Regulations  

E-print Network

in accordance to Albert Einstein College of Medicine's Alcohol Policy. Before your request is confirmed you mustEinstein Room Reservations Rules and Regulations Before Reservation: Requests are not confirmed Activities, Joan Junger, (718) 430-2105 or student.activities@einstein.yu.edu. A meeting or conversation

Yates, Andrew

236

Albert Einstein, 1905: Ein 3-Gange Menu  

E-print Network

, 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, schlie�t biologische Ursachen aus. · Aber was soll man hier messen? Einstein! Robert Brown #12;1827 - 1900

Dutz, Hartmut

237

Approaching Bose-Einstein Condensation  

ERIC Educational Resources Information Center

Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…

Ferrari, Loris

2011-01-01

238

Schroedinger's cat in Einstein's box  

E-print Network

Using the Einstein's boxes thought experiment, as well as EPR and Heisenberg's ones, the local-realistic hidden-variable interpretation of quantum mechanics is explained. The key hidden variable is the consciousness forecasting the future. It is supposed that atoms and particles are complex products of evolution.

Raoul Nakhmanson

2005-08-19

239

Is radio jet power linearly proportional to the product of central black hole mass and Eddington ratio in AGN?  

NASA Astrophysics Data System (ADS)

A model for the relation between radio jet power and the product of central black hole (BH) mass and Eddington ratio of AGN is proposed, and the model is examined with data from the literature. We find that radio jet power positively correlates but not linearly with the product of BH mass ( m in solar mass) and Eddington ratio ( ?), and the power law indices ( ?) are significantly less than unity for relatively low accretion ( ?<0.1) AGN, P j ?( ?m) ? , in the radio galaxies and the Seyfert galaxies. This leads to a negative correlation between radio loudness and ?m for the low luminosity AGN, i.e. R?( ?m) ? with ?=(7/6) ?-1<0, which may be attributed to a contribution of BH spin to total jet power assuming that the spin induced jet is gradually suppressed as the accretion rate increases. Whereas, for the high- z quasars which often show the slope ??1, a positive correlation between the radio loudness and disc luminosity is predicted. We discuss that the jet powers of the high- z FRII quasars are likely dominated by the accretion disc rather than by the BH spin.

Liu, Xiang; Han, Zhenhua

2014-12-01

240

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

NASA Technical Reports Server (NTRS)

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.

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

2008-01-01

241

Validating Computational Cognitive Process Models across Multiple Timescales  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

242

Timescale for trans-Plankian collisions in Kerr spacetime  

E-print Network

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 order 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, have distinct advantage over their black hole counterparts.

Patil, Mandar; Nakao, Ken-ichi; Kimura, Masashi; Harada, Tomohiro

2015-01-01

243

Reconstructing disturbances and their biogeochemical consequences over multiple timescales  

USGS Publications Warehouse

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.

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

244

From lifetime to evolution: timescales of human gut microbiota adaptation  

PubMed Central

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

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

245

Serotonergic neurons signal reward and punishment on multiple timescales.  

PubMed

Serotonin's function in the brain is unclear. One challenge in testing the numerous hypotheses about serotonin's function has been observing the activity of identified serotonergic neurons in animals engaged in behavioral tasks. We recorded the activity of dorsal raphe neurons while mice experienced a task in which rewards and punishments varied across blocks of trials. We 'tagged' serotonergic neurons with the light-sensitive protein channelrhodopsin-2 and identified them based on their responses to light. We found three main features of serotonergic neuron activity: (1) a large fraction of serotonergic neurons modulated their tonic firing rates over the course of minutes during reward vs punishment blocks; (2) most were phasically excited by punishments; and (3) a subset was phasically excited by reward-predicting cues. By contrast, dopaminergic neurons did not show firing rate changes across blocks of trials. These results suggest that serotonergic neurons signal information about reward and punishment on multiple timescales. PMID:25714923

Cohen, Jeremiah Y; Amoroso, Mackenzie W; Uchida, Naoshige

2015-01-01

246

Modelling the dynamical friction timescale of sinking satellite  

E-print Network

When a satellite galaxy falls into a massive dark matter halo, it suffers the dynamical friction force which drag it into the halo center and finally it merger with the central galaxy. The time interval between entry and merger is called as the dynamical friction timescale (T_df). Many studies have been dedicated to derive T_df using analytical models or N-body simulations. These studies have obtained qualitative agreements on how T_df depends on the orbit parameters, and mass ratio between satellite and host halo. However, there are still disagreements on the accurate form of T_df . In this paper, we present a semi-analytical model to predict T_df and we focus on interpreting the discrepancies among different studies. We find that the treatment of mass loss from satellite by tidal stripping dominates the behavior of T_df . We also identify other model parameters which affect the predicted T_df.

Gan, Jianling; Hou, Jinliang; Chang, Ruixiang

2010-01-01

247

Runaway Merging of Black Holes: Analytical Constraint on the Timescale  

E-print Network

Following the discovery of a black hole (BH) with a mass of 10^3-10^6 M(sun) in a starburst galaxy M82, we study formation of such a BH via successive merging of stellar-mass BHs within a star cluster. The merging has a runaway characteristic. This is because massive BHs sink into the cluster core and have a high number density, and because the merging probability is higher for more massive BHs. We use the Smoluchowski equation to study analytically the evolution of the BH mass distribution. Under favorable conditions, which are expected for some star clusters in starburst galaxies, the timescale of the runaway merging is at most of order 10^7 yr. This is short enough to account for the presence of a BH heavier than 10^3 M(sun) in an ongoing starburst region.

H. Mouri; Y. Taniguchi

2002-01-08

248

Timescales of Multineuronal Activity Patterns Reflect Temporal Structure of Visual Stimuli  

Microsoft Academic Search

The investigation of distributed coding across multiple neurons in the cortex remains to this date a challenge. Our current understanding of collective encoding of information and the relevant timescales is still limited. Most results are restricted to disparate timescales, focused on either very fast, e.g., spike-synchrony, or slow timescales, e.g., firing rate. Here, we investigated systematically multineuronal activity patterns evolving

Ovidiu F. Jurjut; Danko Nikolic; Wolf Singer; Shan Yu; Martha N. Havenith; Raul C. Muresan; Olaf Sporns

2011-01-01

249

Polymer Bose--Einstein Condensates  

E-print Network

In this work we analyze a non--interacting one dimensional polymer Bose--Einstein condensate in an harmonic trap within the semiclassical approximation. We use an effective Hamiltonian coming from the polymer quantization that arises in loop quantum gravity. We calculate the number of particles in order to obtain the critical temperature. The Bose--Einstein functions are replaced by series, whose high order terms are related to powers of the polymer length. It is shown that the condensation temperature presents a shift respect to the standard case, for small values of the polymer scale. In typical experimental conditions, it is possible to establish a bound for $\\lambda^{2}$ up to $ \\lesssim 10 ^{-16}$m$^2$. To improve this bound we should decrease the frequency of the trap and also decrease the number of particles.

E. Castellanos; G. Chacon-Acosta

2013-01-22

250

Parameterized Beyond-Einstein Growth  

SciTech Connect

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.

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

2007-09-17

251

Albert Einstein - a Pious Atheist  

E-print Network

We consider Einstein's attitude with regard to religion both from sociological and epistemological points of view. An attempt to put it into a wider socio-historical perspective has been made, with the emphasis on his ethnic and religious background. The great scientist was neither anatheist nor a believer in the orthodox sense and the closest labels one might apply would be pantheism/cosmism (ontological view) and agnosticism (epistemological view). His ideas on the divine could be considered as a continuation of a line that can be traced back to Philo of Alexandria, who himself followed the Greek Stoics and Neoplatonists and especially Baruch Spinoza. Einstein's scientific (or rational) and religious (or intuitive) thinking was deeply rooted in the Hellenic culture.

V. Djokovic; P. Grujic

2007-06-29

252

Albert Einstein and Scientific Theology  

E-print Network

In recent centuries the world has become increasingly dominated by empirical evidence and theoretic science in developing worldviews. Advances in science have dictated Roman Catholic doctrine such as the acceptance of Darwinian evolution and Big Bang cosmology. Albert Einstein created an indelible impact on the relationship between science and religion. The question is whether or not his work was deleterious for church doctrine or whether it was compatible with, or even advanced, church dogma. It's my contention that Einstein revived the relationship between science and theology and did not create a bifurcation between the two. Despite his personal religious beliefs, his work has helped to reinforce the harmonious conjunction of science with religion, which cannot be ignored by succeeding scientists and theologians.

Andrews, Max L E

2012-01-01

253

Entropic corrections to Einstein equations  

SciTech Connect

Considering the general quantum corrections to the area law of black hole entropy and adopting the viewpoint that gravity interprets as an entropic force, we derive the modified forms of Modified Newtonian dynamics (MOND) theory of gravitation and Einstein field equations. As two special cases we study the logarithmic and power-law corrections to entropy and find the explicit form of the obtained modified equations.

Hendi, S. H. [Physics Department, College of Sciences, Yasouj University, Yasouj 75914 (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Sheykhi, A. [Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Department of Physics, Shahid Bahonar University, P.O. Box 76175-132, Kerman (Iran, Islamic Republic of)

2011-04-15

254

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

E-print Network

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.

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

1993-06-15

255

Stability and (quasi)localization of gravitational fluctuations in an Eddington-inspired Born-Infeld brane system  

NASA Astrophysics Data System (ADS)

The stability and localization of the gravitational perturbations for a special brane system in Eddington-inspired Born-Infeld gravity were studied in Liu et al. [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 spectra of massive KK gravitons are gapless and continuous. Two models are constructed as examples. In the first model, which is a generalization of Liu et al. [Phys. Rev. D 85, 124053 (2012)], the brane has no inner structure and there is no gravitational resonance (quasilocalized 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.

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

2014-11-01

256

Eddington ratio distribution of X-ray selected broad-line AGNs at 1.0  

NASA Astrophysics Data System (ADS)

We investigate the Eddington ratio distribution of X-ray selected broad-line AGNs in the redshift range 1.0

Suh, Hyewon

2014-11-01

257

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

E-print Network

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 data in the 3 - 10 keV band by only a powe...

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

2015-01-01

258

Observations of Eddington-limited type-I X-ray bursts from 4U 1812-12  

E-print Network

During more than 3 years (August 1996-October 1999) monitoring of a 40x40 degree sky region around the Galactic Centre by the Wide Field Cameras on board BeppoSAX, a total of 8 type-I bursts have been detected from a sky position consistent with that of 4U 1812-12, a likely neutron-star low-mass X-ray binary. We present the results of a detailed study of the bursts of 4U 1812-12, about 15 years after the last reported observations of X-ray bursts from this source (Murakami et al. 1983). Clear evidence for photospheric radius expansion due to Eddington-limited burst luminosity is present in most of the observed events, allowing an accurate estimate of the source distance (~4 kpc) and its burst parameters.

M. Cocchi; A. Bazzano; L. Natalucci; P. Ubertini; J. Heise; E. Kuulkers; J. M. Muller; J. J. M. in 't Zand

2000-03-10

259

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

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

260

LETTER TO THE EDITOR: Generating ring currents, solitons and svortices by stirring a Bose-Einstein condensate in a toroidal trap  

Microsoft Academic Search

We propose a simple stirring experiment to generate quantized ring currents and solitary excitations in Bose-Einstein condensates in a toroidal trap geometry. Simulations of the three-dimensional Gross-Pitaevskii equation show that pure ring current states can be generated efficiently by adiabatic manipulation of the condensate, which can be realized on experimental timescales. This is illustrated by simulated generation of a ring

Joachim Brand; William P. Reinhardt

2001-01-01

261

Serotonergic neurons signal reward and punishment on multiple timescales  

PubMed Central

Serotonin's function in the brain is unclear. One challenge in testing the numerous hypotheses about serotonin's function has been observing the activity of identified serotonergic neurons in animals engaged in behavioral tasks. We recorded the activity of dorsal raphe neurons while mice experienced a task in which rewards and punishments varied across blocks of trials. We ‘tagged’ serotonergic neurons with the light-sensitive protein channelrhodopsin-2 and identified them based on their responses to light. We found three main features of serotonergic neuron activity: (1) a large fraction of serotonergic neurons modulated their tonic firing rates over the course of minutes during reward vs punishment blocks; (2) most were phasically excited by punishments; and (3) a subset was phasically excited by reward-predicting cues. By contrast, dopaminergic neurons did not show firing rate changes across blocks of trials. These results suggest that serotonergic neurons signal information about reward and punishment on multiple timescales. DOI: http://dx.doi.org/10.7554/eLife.06346.001 PMID:25714923

Cohen, Jeremiah Y; Amoroso, Mackenzie W; Uchida, Naoshige

2015-01-01

262

Modeling the Short Timescale Inner Disk Changes of HD169142  

NASA Astrophysics Data System (ADS)

Recent observations of circumstellar disks of gas and dust found around young stars present the unique opportunity for the study of planetary formation regions in their infancy. Observations dating from the early 1990s until the early 2000s on the Herbig Ae star HD169142 show changes in the 1-5 micron fluxes of up to 30%. We present two models for the disk around HD169142 - representing the two distinct flux states observed in the spectral energy distributions, that prior to the year 2000, and that post-2000. The short 10 years) timescale of the changes demands that whatever changes are made to the models occur within the inner few AU of the disk. In accordance with this and popular consensus on the origin of high near-IR flux in these disks, our models fit the change in near infrared flux by changing the puffed up inner rim by a decrease in its height and length. However, this change alone affects the shadowing of the outer disk and thus affects the far infrared flux levels. Observations from both eras lack any such change in far infrared flux. This might be due to either a tilted inner disk (so changes in shadowing of the outer disk are minimized) or because of the long thermal time scale of the outer disk. This work was supported by NASA ADAP grant NNX09AC73G, Hubble Space Telescope grant HST-GO-13032, and the IR&D program at The Aerospace Corporation.

Wagner, Kevin; Sitko, M. L.; Whitney, B.; Swearingen, J. R.; Champney, E. H.; Johnson, A. N.; Warren, C. C.; Russell, R. W.; Grady, C. A.; Fukagawa, M.; Hashimoto, J.

2014-01-01

263

Molecular-clock methods for estimating evolutionary rates and timescales.  

PubMed

The molecular clock presents a means of estimating evolutionary rates and timescales using genetic data. These estimates can lead to important insights into evolutionary processes and mechanisms, as well as providing a framework for further biological analyses. To deal with rate variation among genes and among lineages, a diverse range of molecular-clock methods have been developed. These methods have been implemented in various software packages and differ in their statistical properties, ability to handle different models of rate variation, capacity to incorporate various forms of calibrating information and tractability for analysing large data sets. Choosing a suitable molecular-clock model can be a challenging exercise, but a number of model-selection techniques are available. In this review, we describe the different forms of evolutionary rate heterogeneity and explain how they can be accommodated in molecular-clock analyses. We provide an outline of the various clock methods and models that are available, including the strict clock, local clocks, discrete clocks and relaxed clocks. Techniques for calibration and clock-model selection are also described, along with methods for handling multilocus data sets. We conclude our review with some comments about the future of molecular clocks. PMID:25290107

Ho, Simon Y W; Duchêne, Sebastián

2014-12-01

264

Complex Processes from Dynamical Architectures with Time-Scale Hierarchy  

PubMed Central

The idea that complex motor, perceptual, and cognitive behaviors are composed of smaller units, which are somehow brought into a meaningful relation, permeates the biological and life sciences. However, no principled framework defining the constituent elementary processes has been developed to this date. Consequently, functional configurations (or architectures) relating elementary processes and external influences are mostly piecemeal formulations suitable to particular instances only. Here, we develop a general dynamical framework for distinct functional architectures characterized by the time-scale separation of their constituents and evaluate their efficiency. Thereto, we build on the (phase) flow of a system, which prescribes the temporal evolution of its state variables. The phase flow topology allows for the unambiguous classification of qualitatively distinct processes, which we consider to represent the functional units or modes within the dynamical architecture. Using the example of a composite movement we illustrate how different architectures can be characterized by their degree of time scale separation between the internal elements of the architecture (i.e. the functional modes) and external interventions. We reveal a tradeoff of the interactions between internal and external influences, which offers a theoretical justification for the efficient composition of complex processes out of non-trivial elementary processes or functional modes. PMID:21347363

Perdikis, Dionysios; Huys, Raoul; Jirsa, Viktor

2011-01-01

265

Beyond the Einstein Addition Law and its Gyroscopic Thomas Precession  

E-print Network

: THE MISSING LINK 1 1 A Brief History of the Thomas Precession 1 2 The Einstein Velocity Addition 3 3 Thomas 2 The Einstein Half 76 3 The Einstein Metric 77 4 Metric Geometry of Einstein Gyrovector Spaces 80 5 The Einstein Geodesics 84 6 Gyrovector Spaces 86 7 Solving a Simple System of Two Equations in a Gyrovector

Ungar, Abraham A.

266

Type II Einstein spacetimes in higher dimensions  

NASA Astrophysics Data System (ADS)

This paper shows that many of the results derived by Pravda et al (2007 Class. Quantum Grav. 24 4407-28) for higher-dimensional type D Einstein spacetimes can be generalized to all Einstein spacetimes admitting a multiple Weyl-aligned null direction (WAND), the main new result being the extension to include the type II case. Examples of type D Einstein spacetimes admitting non-geodesic multiple WANDs are given in all dimensions greater than 4.

Durkee, Mark

2009-10-01

267

MhringerWeg Albert-Einstein-Allee  

E-print Network

N MähringerWeg Oberer Eselsberg Oberer Eselsberg Albert-Einstein-Allee Helmholtzstr. James-Franck-Ring Staudingerstr. Hans- Krebs- Weg Robert-Koch-Str. Albert- Einstein- Allee W ilhelm -Runge-Str. Berliner Ring Albert- Einstein- Allee Lise- Meitner -Str. Lise-Meitner-Str. 2/1 148 11 8 8 11 5 8/1 8 10 14 12 22 20 18

Pfeifer, Holger

268

Einstein's Apple and Relativity's Gravitational Field  

E-print Network

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.

Engelbert L. Schucking

2009-03-31

269

Einstein as a Missionary of Science  

NASA Astrophysics Data System (ADS)

The paper reviews Einstein's engagement as a mediator and popularizer of science. It discusses the formative role of popular scientific literature for the young Einstein, showing that not only his broad scientific outlook but also his internationalist political views were shaped by these readings. Then, on the basis of recent detailed studies, Einstein's travels and their impact on the dissemination of relativity theory are examined. These activities as well as Einstein's own popular writings are interpreted in the context of his understanding of science as part of human culture.

Renn, Jürgen

2013-10-01

270

U SERIES DISEQUILIBRIA: INSIGHTS INTO MANTLE MELTING AND THE TIMESCALES OF MAGMA  

E-print Network

U SERIES DISEQUILIBRIA: INSIGHTS INTO MANTLE MELTING AND THE TIMESCALES OF MAGMA DIFFERENTIATION] Several U series nuclides have half-lives (230 Th, 76 kyr; 231 Pa, 33 kyr; and 226 Ra, 1.6 kyr) comparable to timescales of magmatic processes. We review the basic principles of extracting time information from U series

Jellinek, Mark

271

On the absence of intrahelical DNA dynamics on the ?s to ms timescale.  

PubMed

DNA helices display a rich tapestry of motion on both short (<100?ns) and long (>1?ms) timescales. However, with the exception of mismatched or damaged DNA, experimental measures indicate that motions in the 1??s to 1?ms range are effectively absent, which is often attributed to difficulties in measuring motions in this time range. We hypothesized that these motions have not been measured because there is effectively no motion on this timescale, as this provides a means to distinguish faithful Watson-Crick base-paired DNA from damaged DNA. The absence of motion on this timescale would present a 'static' DNA sequence-specific structure that matches the encounter timescales of proteins, thereby facilitating recognition. Here we report long-timescale (~10-44??s) molecular dynamics simulations of a B-DNA duplex structure that addresses this hypothesis using both an 'Anton' machine and large ensembles of AMBER GPU simulations. PMID:25351257

Galindo-Murillo, Rodrigo; Roe, Daniel R; Cheatham, Thomas E

2014-01-01

272

Release timescales of solar energetic particles in the low corona  

NASA Astrophysics Data System (ADS)

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.

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

273

Critical Collapse of Einstein Cluster  

E-print Network

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.

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

2007-10-23

274

A Cosmic Vision Beyond Einstein  

E-print Network

The acceleration of the cosmic expansion is a fundamental challenge to standard models of particle physics and cosmology. The new physics of dark energy may lie in the nature of gravity, the quantum vacuum, or extra dimensions. I give a brief overview of the puzzles and possibilities of dark energy, and discuss the confrontation of a wide variety of "beyond Einstein" models with the latest data, showing what we currently know and what we must seek to learn. Next generation experiments using a variety of cosmological probes will deeply explore dark energy, dark matter, and gravitation.

Eric V. Linder

2008-10-09

275

Albert Einstein:. Opportunity and Perception  

NASA Astrophysics Data System (ADS)

The year 1905 has been called Albert Einstein's "Annus Mirabilis." It was during that year that he caused revolutionary changes in man's primordial concepts about the physical world: space, time, energy, light and matter. How could a 26-year-old clerk, previously unknown, cause such profound conceptual changes, and thereby open the door to the era of modern scientific technological world? No one, of course, can answer that question. But one can, perhaps, analyze some factors that were essential to his stepping into such a historic role...

Yang, Chen Ning

2013-05-01

276

ALBERT EINSTEIN COLLEGE OF MEDICINE STRATEGIC RESEARCH PLAN UPDATE 2010  

E-print Network

1 ALBERT EINSTEIN COLLEGE OF MEDICINE STRATEGIC RESEARCH PLAN UPDATE 2010 Table community of the Albert Einstein College of Medicine have undertaken a dynamic strategic planning process/Multi-Modal Image Analysis.................10 Clinical Research Enterprise/Einstein-Montefiore Interface

Bukauskas, Feliksas

277

Bose-Einstein condensate strings  

NASA Astrophysics Data System (ADS)

We consider the possible existence of gravitationally bound general relativistic strings consisting of Bose-Einstein condensate (BEC) matter which is described, in the Newtonian limit, by the zero temperature time-dependent nonlinear Schrödinger equation (the Gross-Pitaevskii equation), with repulsive interparticle interactions. In the Madelung representation of the wave function, the quantum dynamics of the condensate can be formulated in terms of the classical continuity equation and the hydrodynamic Euler equations. In the case of a condensate with quartic nonlinearity, the condensates can be described as a gas with two pressure terms, the interaction pressure, which is proportional to the square of the matter density, and the quantum pressure, which is without any classical analogue, though, when the number of particles in the system is high enough, the latter may be neglected. Assuming cylindrical symmetry, we analyze the physical properties of the BEC strings in both the interaction pressure and quantum pressure dominated limits, by numerically integrating the gravitational field equations. In this way we obtain a large class of stable stringlike astrophysical objects, whose basic parameters (mass density and radius) depend sensitively on the mass and scattering length of the condensate particle, as well as on the quantum pressure of the Bose-Einstein gas.

Harko, Tiberiu; Lake, Matthew J.

2015-02-01

278

Einstein Product Metrics in Diverse Dimensions  

E-print Network

We use direct products of Einstein Metrics to construct new solutions to Einstein's Equations with cosmological constant. We illustrate the technique with three families of solutions having the geometries Kerr/de Sitter X de Sitter, Kerr/anti-de Sitter X anti-de Sitter and Kerr X Kerr.

K. R. Koehler

2006-01-27

279

Einstein's Revolutionary Light-Quantum Hypothesis  

Microsoft Academic Search

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

Roger H. Stuewer

2005-01-01

280

Exact Vacuum Solutions to the Einstein Equation  

E-print Network

In this paper, we present a framework for getting a series of exact vacuum solutions to the Einstein equation. This procedure of resolution is based on a canonical form of the metric. According to this procedure, the Einstein equation can be reduced to some 2-dimensional Laplace-like equations or rotation and divergence equations, which are much convenient for the resolution.

Ying-Qiu Gu

2007-06-17

281

People Interview: Continuing Einstein's great work  

NASA Astrophysics Data System (ADS)

INTERVIEW Continuing Einstein's great work Dr Michio Kaku is a theoretical physicist, bestselling author and popularizer of science. He is the co-founder of string field theory (a branch of string theory) and continues Einstein's search to unite the four fundamental forces of nature into one unified theory. David Smith speaks to him about inspiration and education.

2009-09-01

282

Books on Einstein--Collectors' Delight  

ERIC Educational Resources Information Center

A survey of thirteen books on Einstein is presented. Its gives an idea on how much is written about the man and how frequent are the publications. The year 2005 saw the most publications. It is the centenary for the Miraculous Year. Interestingly some books can just sustain their readers' interest with just words. Einstein comes alive with the…

Khoon, Koh Aik; Jalal, Azman; Abd-Shukor, R.; Yatim, Baharudin; Talib, Ibrahim Abu; Daud, Abdul Razak; Samat, Supian

2009-01-01

283

Born-Infeld-Einstein theory with matter  

Microsoft Academic Search

The field equations associated with the Born-Infeld-Einstein action including matter are derived using a Palatini variational principle. Scalar, electromagnetic, and Dirac fields are considered. It is shown that an action can be chosen for the scalar field that produces field equations identical to the usual Einstein field equations minimally coupled to a scalar field. In the electromagnetic and Dirac cases

Dan N. Vollick; Dan N

2005-01-01

284

Einstein Manifolds as Yang-Mills Instantons  

NASA Astrophysics Data System (ADS)

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.

Oh, John J.; Yang, Hyun Seok

2013-07-01

285

The density and temperature dependence of the cooling timescale for fragmentation of self-gravitating disks  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to explore the influences of cooling timescale on fragmentation of self-gravitating protoplanetary disks. We assume the cooling timescale, expressed in terms of the dynamical timescale ? tcool, has a power-law dependence on temperature and density, ? tcool ? ?-aT-b, where a and b are constants. We use this cooling timescale in a simple prescription for the cooling rate, du/dt = -u/tcool, where u is the internal energy. We perform our simulations using the smoothed particle hydrodynamics method. The simulations demonstrate that the disk is very sensitive to the cooling timescale, which depends on density and temperature. Under such a cooling timescale, the disk becomes gravitationally unstable and clumps form in the disk. This property even occurs for cooling timescales which are much longer than the critical cooling timescale, ? tcool ? 7. We show that by adding the dependence of a cooling timescale on temperature and density, the number of clumps increases and the clumps can also form at smaller radii. The simulations imply that the sensitivity of a cooling timescale to density is more than to temperature, because even for a small dependence of the cooling timescale on density, clumps can still form in the disk. However, when the cooling timescale has a large dependence on temperature, clumps form in the disk. We also consider the effects of artificial viscosity parameters on fragmentation conditions. This consideration is performed in two cases, where ? tcool is a constant and ? tcool is a function of density and temperature. The simulations consider both cases, and results show the artificial viscosity parameters have rather similar effects. For example, using too small of values for linear and quadratic terms in artificial viscosity can suppress the gravitational instability and consequently the efficiency of the clump formation process decreases. This property is consistent with recent simulations of self-gravitating disks. We perform simulations with and without the Balsara form of artificial viscosity. We find that in the cooling and self-gravitating disks without the Balsara switch, the clumps can form more easily than those with the Balsara switch. Moreover, in both cases where the Balsara switch is present or absent, the simulations show that the cooling timescale strongly depends on density and temperature.

Faghei, Kazem

2014-06-01

286

The Albert Einstein College of Medicine of Yeshiva University  

E-print Network

The Albert Einstein College of Medicine of Yeshiva University EMERGENCY PROCEDURES MANUAL Prepared Resources Security Revised ­ May, 2013 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY

Emmons, Scott

287

The Albert Einstein College of Medicine of Yeshiva University  

E-print Network

The Albert Einstein College of Medicine of Yeshiva University EMERGENCY PROCEDURES MANUAL Prepared Supporting Services Revised ­ January, 2012 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY

Yates, Andrew

288

Albert Einstein's Magic Mountain: An Aarau Education*  

NASA Astrophysics Data System (ADS)

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.

Hunziker, Herbert

2015-03-01

289

Astrophysical Observations: Lensing and Eclipsing Einstein's Theories  

E-print Network

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.

Charles L. Bennett

2005-03-15

290

Astrophysical observations: lensing and eclipsing Einstein's theories.  

PubMed

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

Bennett, Charles L

2005-02-11

291

ASYMPTOTIC SELF-SIMILAR SOLUTIONS WITH A CHARACTERISTIC TIMESCALE  

SciTech Connect

For a wide variety of initial and boundary conditions, adiabatic one-dimensional flows of an ideal gas approach self-similar behavior when the characteristic length scale over which the flow takes place, R, diverges or tends to zero. It is commonly assumed that self-similarity is approached since in the R {yields} {infinity}(0) limit the flow becomes independent of any characteristic length or timescales. In this case, the flow fields f(r, t) must be of the form f(r,t)=t{sup {alpha}}{sub f}F(r/R) with R {proportional_to} ({+-}t){sup {alpha}}. We show that requiring the asymptotic flow to be independent only of characteristic length scales implies a more general form of self-similar solutions, f(r,t)=R{sup {delta}}{sub f}F(r/R) with R-dot {proportional_to}R{sup {delta}}, which includes the exponential ({delta} = 1) solutions, R {proportional_to} e {sup t/{tau}}. We demonstrate that the latter, less restrictive, requirement is the physically relevant one by showing that the asymptotic behavior of accelerating blast waves, driven by the release of energy at the center of a cold gas sphere of initial density {rho} {proportional_to} r {sup -{omega}}, changes its character at large {omega}: the flow is described by 0 {<=} {delta} < 1, R {proportional_to} t {sup 1/(1-{delta})}, solutions for {omega} < {omega}{sub c}, by {delta}>1 solutions with R {proportional_to} (-t){sup 1/({delta}-1)} diverging at finite time (t = 0) for {omega}>{omega}{sub c}, and by exponential solutions for {omega} = {omega}{sub c} ({omega}{sub c} depends on the adiabatic index of the gas, {omega}{sub c} {approx} 8 for 4/3 < {gamma} < 5/3). The properties of the new solutions obtained here for {omega} {>=} {omega}{sub c} are analyzed, and self-similar solutions describing the t>0 behavior for {omega}>{omega}{sub c} are also derived.

Waxman, Eli [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Shvarts, Dov [Department of Physics, Nuclear Research Center Negev, P.O. Box 9001, Beer-Sheva 84015 (Israel)

2010-10-01

292

Characteristic Timescales of Shoreface Response to Sea-Level Rise  

NASA Astrophysics Data System (ADS)

On open ocean, wave-dominated, sandy coasts, the response of the shore to sea-level rise is dominated not by inundation, but rather by the dynamic response of sediment transport processes to perturbations of the sea level. In a regime of sea level change, the predominant response of the wave-dominated shoreface depends upon the time-dependent response of the shoreface itself to changes in sea level as well as the potential changes to the shoreline. On a barrier coast, persistent, long-term changes to the shoreline are caused by storm overwash, which transports marine sediment landward, moving the shoreline boundary. Raised sea levels increase the impact and frequency of this overwash as relative barrier elevation is reduced. Overall, sediment transport processes on the shoreface remain poorly understood, complicating predictions of equilibrium shoreface shapes and even net sediment transport directions. However, presuming an equilibrium geometry, energetics-based, time-averaged relationships for cross-shore sediment transport provide a framework to understand the characteristic rates and types of shoreface response to perturbations to either the sea level or the shoreline boundary. In the case of a sea-level rise, we find that the dominant perturbation for a barrier system is not the sea-level rise itself, but rather the movement of the shoreline by overwash. The characteristic response time of the shoreface itself increases significantly at depth, suggesting that the lower shoreface response to a sea level change can be significantly delayed. We estimate the importance of extreme events on shoreface evolution by analyzing decade-long data series of wave characteristics along different open ocean coasts with barriers (Florida Gulf Coast, North Carolina, Marthas Vineyard). Analogous to the effect of floods in fluvial systems, although storm events can move significant sediment, the infrequency of the larger events limits their effect on the shoreface-the morphologically significant event for shoreface evolution has a return interval of less than two years. However, numerical simulations of tens of thousands of synthetic storm strikes at the same locations suggest that the return interval of storm events expected to cause significant overwash is longer, on the order of at least 50 years. To study the interactions between the characteristic timescales of shoreface evolution and barrier overwash, we apply a numerical model of barrier profile evolution that couples shoreface evolution with barrier overwash. This integrated model provides a tool to understand the response of barrier systems to changes in sea level over the late Holocene to the modern. The model also investigates the potential behavior of barrier systems as they (and their human occupants) respond to predicted increased rates of sea-level rise over the coming centuries.

Ashton, A. D.; Ortiz, A.; Lane, P.; Donnelly, J. P.

2011-12-01

293

Timescales in creep and yielding of attractive gels.  

PubMed

The stress-induced yielding scenario of colloidal gels is investigated under rough boundary conditions by means of rheometry coupled with local velocity measurements. Under an applied shear stress ?, the fluidization of gels made of attractive carbon black particles dispersed in a mineral oil is shown to involve a previously unreported shear rate response ? dot above(t) characterized by two well-defined and separated timescales ?c and ?f. First ? dot above decreases as a weak power law strongly reminiscent of the primary creep observed in numerous crystalline and amorphous solids, coined the "Andrade creep". We show that the bulk deformation remains homogeneous at the micron scale, which demonstrates that whether plastic events take place or whether any shear transformation zone exists, such phenomena occur at a smaller scale. As a key result of this paper, the duration ?c of this creep regime decreases as a power law of the viscous stress, defined as the difference between the applied stress and the yield stress ?c, i.e. ?c ? (? - ?c)(-?), with ? = 2-3 depending on the gel concentration. The end of this first regime is marked by a jump of the shear rate by several orders of magnitude, while the gel slowly slides as a solid block experiencing strong wall slip at both walls, despite rough boundary conditions. Finally, a second sudden increase of the shear rate is concomitant with the full fluidization of the material which ends up being homogeneously sheared. The corresponding fluidization time ?f robustly follows an exponential decay with the applied shear stress, i.e. ?f = ?0?exp(-?/?0), as already reported for smooth boundary conditions. Varying the gel concentration C in a systematic fashion shows that the parameter ?0 and the yield stress ?c exhibit similar power-law dependences with C. Finally, we highlight a few features that are common to attractive colloidal gels and to solid materials by discussing our results in the framework of theoretical approaches of solid rupture (kinetic, fiber bundle, and transient network models). PMID:24651869

Grenard, Vincent; Divoux, Thibaut; Taberlet, Nicolas; Manneville, Sébastien

2014-03-14

294

Timescales of orogeny: Jurassic construction of the Klamath Mountains  

NASA Astrophysics Data System (ADS)

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.

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

1995-06-01

295

Timescales of Multineuronal Activity Patterns Reflect Temporal Structure of Visual Stimuli  

PubMed Central

The investigation of distributed coding across multiple neurons in the cortex remains to this date a challenge. Our current understanding of collective encoding of information and the relevant timescales is still limited. Most results are restricted to disparate timescales, focused on either very fast, e.g., spike-synchrony, or slow timescales, e.g., firing rate. Here, we investigated systematically multineuronal activity patterns evolving on different timescales, spanning the whole range from spike-synchrony to mean firing rate. Using multi-electrode recordings from cat visual cortex, we show that cortical responses can be described as trajectories in a high-dimensional pattern space. Patterns evolve on a continuum of coexisting timescales that strongly relate to the temporal properties of stimuli. Timescales consistent with the time constants of neuronal membranes and fast synaptic transmission (5–20 ms) play a particularly salient role in encoding a large amount of stimulus-related information. Thus, to faithfully encode the properties of visual stimuli the brain engages multiple neurons into activity patterns evolving on multiple timescales. PMID:21346812

Jurju?, Ovidiu F.; Nikoli?, Danko; Singer, Wolf; Yu, Shan; Havenith, Martha N.; Mure?an, Raul C.

2011-01-01

296

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

PubMed Central

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

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

2014-01-01

297

Einstein Ring in Distant Universe  

NASA Astrophysics Data System (ADS)

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,

2005-06-01

298

Time-Scales for Non-Inductive Current Buildup in Low-Aspect-Ratio Toroidal Geometry  

SciTech Connect

The fundamental differences between inductive and non-inductive current buildup are clarified and the associated time-scales and other implications are discussed. A simulation is presented whereby the plasma current in a low-aspect-ratio torus is increased primarily by the self-generated bootstrap current with only 10% coming from external current drive. The maximum obtainable plasma current by this process is shown to scale with the toroidal field strength. The basic physics setting the time-scales can be obtained from a 1D analysis. Comparisons are made between the timescales found here and those reported in the experimental literature.

S.C. Jardin

1999-11-01

299

The relationship between the Eddington limit, the observed upper luminosity limit for massive stars, and the luminous blue variables  

NASA Technical Reports Server (NTRS)

The observed upper luminosity limits in the Galaxy and the LMC are compared with the Eddington limit as estimated for plane-parallel LTE model atmospheres which include the full effects of metal line opacities in the ultraviolet. It is shown that the Humphreys-Davidson (HD) limit corresponds to the locus of extremely low effective gravities. This result suggests that stars approaching the HD limit will suffer high mass-loss rates because of the reduction of the effective gravity due to radiation pressure. These high mass-loss rates ultimtely lead to the core mass fraction reaching its critical value and the reversal of the stellar evolution tracks. It is shown that radiation pressure, as an agent for producing enhanced mass loss near the HD limit, can in a natural way explain the kink in the HD limit near T(eff) roughly 10,000 K and the upper luminosity limit for yellow and red supergiants. The high mass-loss rates of the luminous blue variables, their location in the HR diagram, and their evolutionary stage are also discussed.

Lamers, Henny J. G. L. M.; Fitzpatrick, Edward L.

1988-01-01

300

The identification of an optical counterpart to the super-Eddington X-ray source, NGC 5204 X-1  

E-print Network

We report the identification of a possible optical counterpart to the super-Eddington X-ray source NGC 5204 X-1. New Chandra data shows that the X-ray source is point-like, with a luminosity of 5.2 x 10^39 erg/s (0.5 - 8 keV). It displays medium- and long-term X-ray variability in observations spanning a period of 20 years. The accurate Chandra position allows us to identify a blue optical continuum source (m_v = 19.7) at the position of NGC 5204 X-1, using newly-obtained optical data from the INTEGRAL instrument on the William Herschel Telescope. The X-ray and optical source properties are consistent with the scenario in which we are observing the beamed X-ray emission of a high-mass X-ray binary in NGC 5204, composed of an O star with either a black hole or neutron star companion.

T. P. Roberts; M. R. Goad; M. J. Ward; R. S. Warwick; P. T. O'Brien; P. Lira; A. D. P. Hands

2001-05-17

301

Einstein Gravity from Conformal Gravity  

E-print Network

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.

Juan Maldacena

2011-06-09

302

Einstein's Theory Fights off Challengers  

NASA Astrophysics Data System (ADS)

Two new and independent studies have put Einstein's General Theory of Relativity to the test like never before. These results, made using NASA's Chandra X-ray Observatory, show Einstein's theory is still the best game in town. Each team of scientists took advantage of extensive Chandra observations of galaxy clusters, the largest objects in the Universe bound together by gravity. One result undercuts a rival gravity model to General Relativity, while the other shows that Einstein's theory works over a vast range of times and distances across the cosmos. The first finding significantly weakens a competitor to General Relativity known as "f(R) gravity". "If General Relativity were the heavyweight boxing champion, this other theory was hoping to be the upstart contender," said Fabian Schmidt of the California Institute of Technology in Pasadena, who led the study. "Our work shows that the chances of its upsetting the champ are very slim." In recent years, physicists have turned their attention to competing theories to General Relativity as a possible explanation for the accelerated expansion of the universe. Currently, the most popular explanation for the acceleration is the so-called cosmological constant, which can be understood as energy that exists in empty space. This energy is referred to as dark energy to emphasize that it cannot be directly detected. In the f(R) theory, the cosmic acceleration comes not from an exotic form of energy but from a modification of the gravitational force. The modified force also affects the rate at which small enhancements of matter can grow over the eons to become massive clusters of galaxies, opening up the possibility of a sensitive test of the theory. Schmidt and colleagues used mass estimates of 49 galaxy clusters in the local universe from Chandra observations, and compared them with theoretical model predictions and studies of supernovas, the cosmic microwave background, and the large-scale distribution of galaxies. They found no evidence that gravity is different from General Relativity on scales larger than 130 million light years. This limit corresponds to a hundred-fold improvement on the bounds of the modified gravitational force's range that can be set without using the cluster data. "This is the strongest ever constraint set on an alternative to General Relativity on such large distance scales," said Schmidt. "Our results show that we can probe gravity stringently on cosmological scales by using observations of galaxy clusters." The reason for this dramatic improvement in constraints can be traced to the greatly enhanced gravitational forces acting in clusters as opposed to the universal background expansion of the universe. The cluster-growth technique also promises to be a good probe of other modified gravity scenarios, such as models motivated by higher-dimensional theories and string theory. A second, independent study also bolsters General Relativity by directly testing it across cosmological distances and times. Up until now, General Relativity had been verified only using experiments from laboratory to Solar System scales, leaving the door open to the possibility that General Relativity breaks down on much larger scales. To probe this question, a group at Stanford University compared Chandra observations of how rapidly galaxy clusters have grown over time to the predictions of General Relativity. The result is nearly complete agreement between observation and theory. "Einstein's theory succeeds again, this time in calculating how many massive clusters have formed under gravity's pull over the last five billion years," said David Rapetti of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University and SLAC National Accelerator Laboratory, who led the new study. "Excitingly and reassuringly, our results are the most robust consistency test of General Relativity yet carried out on cosmological scales." Rapetti and his colleagues based their results on a sample of 238 c

2010-04-01

303

Revisiting Einstein's brain in Brain Awareness Week.  

PubMed

Albert Einstein's brain has long been an object of fascination to both neuroscience specialists and the general public. However, without records of advanced neuro-imaging of his brain, conclusions regarding Einstein's extraordinary cognitive capabilities can only be drawn based on the unique external features of his brain and through comparison of the external features with those of other human brain samples. The recent discovery of 14 previously unpublished photographs of Einstein's brain taken at unconventional angles by Dr. Thomas Stoltz Harvey, the pathologist, ignited a renewed frenzy about clues to explain Einstein's genius. Dr. Dean Falk and her colleagues, in their landmark paper published in Brain (2013; 136:1304-1327), described in such details about the unusual features of Einstein's brain, which shed new light on Einstein's intelligence. In this article, we ask what are the unique structures of his brain? What can we learn from this new information? Can we really explain his extraordinary cognitive capabilities based on these unique brain structures? We conclude that studying the brain of a remarkable person like Albert Einstein indeed provides us a better example to comprehensively appreciate the relationship between brain structures and advanced cognitive functions. However, caution must be exercised so as not to over-interpret his intelligence solely based on the understanding of the surface structures of his brain. PMID:25382446

Chen, Hao; Chen, Su; Zeng, Lidan; Zhou, Lin; Hou, Shengtao

2014-01-01

304

Systematic Uncertainties in the Spectroscopic Measurements of Neutron-star Masses and Radii from Thermonuclear X-Ray Bursts. II. Eddington Limit  

NASA Astrophysics Data System (ADS)

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 ~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.

Güver, Tolga; Özel, Feryal; Psaltis, Dimitrios

2012-03-01

305

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

E-print Network

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$\\beta$ 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 $\\dot{\\mathscr{M}}\\gtrsim 200$, where $\\dot{\\mathscr{M}}= \\dot{M}_{\\bullet}/L_{\\rm Edd}c^{-2}$, $\\dot{M}_{\\bullet}$ is the mass accretion rates, $L_{\\rm Edd}$ is the Eddington luminosity and $c$ is the speed of light. We find that the H$\\beta$ 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 ($R_{_{\\rm H\\beta}}$) and optical luminosity at 5100\\AA, $R_{_{\\rm H\\beta}}-L...

Du, Pu; 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

2015-01-01

306

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

SciTech Connect

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.

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

2012-03-01

307

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

SciTech Connect

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.

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

2013-04-20

308

ATHENA SWAN 3 YEAR ACTION PLAN THE ROSLIN INSTITUTE Objective Action Timescale Responsibility Success Measure  

E-print Network

ATHENA SWAN 3 YEAR ACTION PLAN ­ THE ROSLIN INSTITUTE Objective Action Timescale Responsibility by relevant committees. #12;ATHENA SWAN 3 YEAR ACTION PLAN ­ THE ROSLIN INSTITUTE 1.5 Increase the number

Hall, Christopher

309

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

E-print Network

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 ...

Mervine, Evelyn Martinique

2012-01-01

310

Boundary conditions for hyperbolic formulations of the Einstein equations  

E-print Network

In regards to the initial-boundary value problem of the Einstein equations, we argue that the projection of the Einstein equations along the normal to the boundary yields necessary and appropriate boundary conditions for a wide class of equivalent formulations. We explicitly show that this is so for the Einstein-Christoffel formulation of the Einstein equations in the case of spherical symmetry.

Simonetta Frittelli; Roberto Gomez

2003-04-09

311

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.

312

Einstein M.D. Program 20132014 applicant guide  

E-print Network

Einstein M.D. Program 2013­2014 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert, I wanted to share with you some of my observations about what makes Albert Einstein College Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop

Yates, Andrew

313

A dynamic multi-timescale method for combustion modeling with detailed and reduced chemical kinetic mechanisms  

Microsoft Academic Search

A new on-grid dynamic multi-timescale (MTS) method is presented to increase significantly the computation efficiency involving multi-physical and chemical processes using detailed and reduced kinetic mechanisms. The methodology of the MTS method using the instantaneous timescales of different species is introduced. The definition of the characteristic time for species is examined and compared with that of the computational singular perturbation

Xiaolong Gou; Wenting Sun; Zheng Chen; Yiguang Ju

2010-01-01

314

COMPARISON OF KEPLER PHOTOMETRIC VARIABILITY WITH THE SUN ON DIFFERENT TIMESCALES  

SciTech Connect

We utilize Kepler data to study the precision differential photometric variability of solar-type and cooler stars at different timescales, ranging from half an hour to three months. We define a diagnostic that characterizes the median differential intensity change between data bins of a given timescale. We apply the same diagnostics to Solar and Heliospheric Observatory data that has been rendered comparable to Kepler. The Sun exhibits similar photometric variability on all timescales as comparable solar-type stars in the Kepler field. The previously defined photometric ''range'' serves as our activity proxy (driven by starspot coverage). We revisit the fraction of comparable stars in the Kepler field that are more active than the Sun. The exact active fraction depends on what is meant by ''more active than the Sun'' and on the magnitude limit of the sample of stars considered. This active fraction is between a quarter and a third (depending on the timescale). We argue that a reliable result requires timescales of half a day or longer and stars brighter than M{sub Kep} of 14, otherwise non-stellar noise distorts it. We also analyze main sequence stars grouped by temperature from 6500 to 3500 K. As one moves to cooler stars, the active fraction of stars becomes steadily larger (greater than 90% for early M dwarfs). The Sun is a good photometric model at all timescales for those cooler stars that have long-term variability within the span of solar variability.

Basri, Gibor [Astronomy Department, University of California, Hearst Field Annex, Berkeley, CA 94720 (United States); Walkowicz, Lucianne M. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, 4 Ivy Lane, Princeton NJ 08534 (United States); Reiners, Ansgar [Georg-August-University Goettingen, Institute for Astrophysics, Friedrich-Hund-Platz 1, DE D-37077, Goettingen (Germany)

2013-05-20

315

Six-Degree-of-Freedom Trajectory Optimization Utilizing a Two-Timescale Collocation Architecture  

NASA Technical Reports Server (NTRS)

Six-degree-of-freedom (6DOF) trajectory optimization of a reentry vehicle is solved using a two-timescale collocation methodology. This class of 6DOF trajectory problems are characterized by two distinct timescales in their governing equations, where a subset of the states have high-frequency dynamics (the rotational equations of motion) while the remaining states (the translational equations of motion) vary comparatively slowly. With conventional collocation methods, the 6DOF problem size becomes extraordinarily large and difficult to solve. Utilizing the two-timescale collocation architecture, the problem size is reduced significantly. The converged solution shows a realistic landing profile and captures the appropriate high-frequency rotational dynamics. A large reduction in the overall problem size (by 55%) is attained with the two-timescale architecture as compared to the conventional single-timescale collocation method. Consequently, optimum 6DOF trajectory problems can now be solved efficiently using collocation, which was not previously possible for a system with two distinct timescales in the governing states.

Desai, Prasun N.; Conway, Bruce A.

2005-01-01

316

Spatial and seasonal variability of the air-sea equilibration timescale of carbon dioxide  

NASA Astrophysics Data System (ADS)

The exchange of carbon dioxide between the ocean and the atmosphere tends to bring waters within the mixed layer toward equilibrium by reducing the partial pressure gradient across the air-water interface. However, the equilibration process is not instantaneous; in general, there is a lag between forcing and response. The timescale of air-sea equilibration depends on several factors involving the depth of the mixed layer, wind speed, and carbonate chemistry. We use a suite of observational data sets to generate climatological and seasonal composite maps of the air-sea equilibration timescale. The relaxation timescale exhibits considerable spatial and seasonal variations that are largely set by changes in mixed layer depth and wind speed. The net effect is dominated by the mixed layer depth; the gas exchange velocity and carbonate chemistry parameters only provide partial compensation. Broadly speaking, the adjustment timescale tends to increase with latitude. We compare the observationally derived air-sea gas exchange timescale with a model-derived surface residence time and a data-derived horizontal transport timescale, which allows us to define two nondimensional metrics of equilibration efficiency. These parameters highlight the tropics, subtropics, and northern North Atlantic as regions of inefficient air-sea equilibration where carbon anomalies are relatively likely to persist. The efficiency parameters presented here can serve as simple tools for understanding the large-scale persistence of air-sea disequilibrium of CO2 in both observations and models.

Jones, Daniel C.; Ito, Takamitsu; Takano, Yohei; Hsu, Wei-Ching

2014-11-01

317

Albert Einstein and Archenhold Observatory 1905 - 2005 (German Title: Albert Einstein und die Archenhold-Sternwarte 1905 -- 2005)  

Microsoft Academic Search

After Einstein came to Berlin, he gave his first popular lecture in the Archenhold Observatory, in 1915, on the special and the general theories of relativity. From then on, friendly relations grew between Archenhold and Einstein, which led to a permanent connection between the Observatory and Einstein's achievement. This contribution presents the background of the connection between Archenhold and Einstein,

Dieter B. Herrmann

2005-01-01

318

Quantum reflection of Bose-Einstein Condensates  

E-print Network

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 ...

Pasquini, Thomas A., Jr

2007-01-01

319

Causality in scalar-Einstein waves  

E-print Network

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.

Mark D. Roberts

2015-03-13

320

Einstein/Roosevelt Letters: A Unit.  

ERIC Educational Resources Information Center

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)

Bodle, Walter S.

1985-01-01

321

How History Helped Einstein in Special Relativity  

NASA Astrophysics Data System (ADS)

I will discuss how the German intellectual movement known as ``critical history'' motivated several physicists in the late 1900s to radically analyze the fundamental principles of mechanics, leading eventually to Einstein's special theory of relativity. Eugen Karl Dühring, Johann Bernhard Stallo, Ludwig Lange, and Ernst Mach wrote critical histories of mechanics, some of which emphasized notions of relativity and observation, in opposition to old metaphysical concepts that seemed to infect the foundations of physics. This strand of critical history included the ``genetic method'' of analyzing how concepts develop over time, in our minds, by way of ordinary experiences, which by 1904 was young Albert Einstein's favorite approach for examining fundamental notions. Thus I will discuss how history contributed in Einstein's path to relativity, as well as comment more generally on Einstein's views on history.

Martinez, Alberto

2013-04-01

322

The happiest thought of Einstein's life.  

NASA Astrophysics Data System (ADS)

It is a commonly told story that Einstein formulated his famous principle of equivalence when thinking about what happens in a freely falling elevator, and that it was an original idea of his genius distinguished by the rare capability to see deep problems in the most ordinary things. In the reading of Einstein's and Ernst Mach's works the author has discovered that it was not a physicist in an elevator which led to the principle of equivalence but rather somebody falling from a roof; moreover, the idea behind the principle was not invented by Einstein himself but rather read by him from the book by Mach entitled The Science of Mechanics. The influence this book had on young Einstein is very well known.

Heller, M.

323

Bose-Einstein Condensation in Microgravity  

NASA Astrophysics Data System (ADS)

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.

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.

2010-06-01

324

The creativity of Einstein and astronomy  

NASA Technical Reports Server (NTRS)

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.

Zeldovich, Y. B.

1980-01-01

325

Einstein and General Relativity: Historical Perspectives.  

ERIC Educational Resources Information Center

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)

Chandrasekhar, S.

1979-01-01

326

Einstein's Apple: His First Principle of Equivalence  

E-print Network

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.

Engelbert L. Schucking; Eugene J. Surowitz

2012-08-09

327

Einstein's Biggest Blunder: A Cosmic Mystery Story  

ScienceCinema

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.

Lawrence Krauss

2010-09-01

328

Human dynamics: Darwin and Einstein correspondence patterns  

Microsoft Academic Search

In an era when letters were the main means of exchanging scientific ideas and results, Charles Darwin (1809-82) and Albert Einstein (1879-1955) were notably prolific correspondents. But did their patterns of communication differ from those associated with the instant-access e-mail of modern times? Here we show that, although the means have changed, the communication dynamics have not: Darwin's and Einstein's

João Gama Oliveira; Albert-László Barabási

2005-01-01

329

Computational methods for time-scale analysis of nonlinear dynamical systems  

NASA Astrophysics Data System (ADS)

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 nonlinear system, provided that it is in standard form. This dissertation contributes to the development of a systematic approach for determining the time-scales and the associated geometric structure in the state-space for a differential equation model in general form. The development began with the Ph.D. research of Bharadwaj[32] and was extended further in the paper by Mease, Bharadwaj, and Iravanchy[31]. The approach proceeds from investigating the behavior of the linear variational dynamics associated with a nonlinear system. By analyzing the propagation of a hyper-sphere of initial conditions which evolves into an hyper-ellipsoid in the tangent space, the time-scale information may be quantified. The time-scale information is characterized by the Lyapunov exponents and vectors, and they are related to the principal axes of the hyper-ellipsoid. The Lyapunov spectrum characterizes the average exponential rates of expansion or decay of nearby trajectories and their associated directions. It is known that the classical eigenspace analysis does not provide the correct information, i.e., eigenvalues and eigenvectors of the linearized dynamics. In this thesis the theory is extended to include dynamical systems that operate in non-Euclidean space, since a state transformation may effectively change the metric. The presentation of the entire theory provides the background for presenting the primary new contributions in this dissertation: the development and application of numerical methods for time-scale analysis. A systematic procedure is developed to diagnose, analyze, and extract the time-scale information for the system under study. The procedure includes the detection of the time-scales and their uniformity, the computation of the time-scale information, and the identification of a slow manifold. The algorithms are analyzed to better understand the error behavior, convergence rates, their geometric representation in state space, and the effect of state transformations. (Abstract shortened by UMI.)

Iravanchy, Shawn

330

Timescales of Freshwater-seawater Interface Movement in Response to Hydrological Variations  

NASA Astrophysics Data System (ADS)

Timescales of a moving freshwater-seawater interface in response to hydrological variations are critical for effective management of coastal groundwater resources, as they provide water resource managers and decision-makers with useful information that helps implement a time-dependent strategy. In this study, we performed comprehensive numerical simulations to quantify the timescales of seawater intrusion (Ti) and retreat (Tr). The movement of freshwater-seawater interface is assumed to occur due to instantaneous inland freshwater-level variations. It is found that the logarithmic timescales of seawater intrusion and retreat can be described respectively by simple linear equations. Specifically, seawater intrusion timescale can be estimated by lnTi = a + blnh'f-s, where a and b are regression coefficients and h'f-s is the boundary water level difference after instantaneous drop. For seawater retreat with constant inland water level before freshwater-level rise but different heads of freshwater-level rise, the toe response timescale can be approximated by lnTr = c + d?XT, where c and d are regression coefficients and ?XT is the toe response distance that can be calculated analytically by a sharp-interface analytical solution, while for seawater retreat with constant head of freshwater-level rise but different inland water levels before freshwater-level rise, in contrast, the toe response timescale can be predicted by lnTr = e + fln?XT, where e and f are regression coefficients. For all cases investigated, empirical equations with strong linear correlations are obtained, as reflected by the values of statistical parameters. Moreover, it is suggested that the timescale of interface movement caused by an instantaneous variation of sea level at coastal boundary is almost equivalent to that induced by an instantaneous variation of freshwater level at inland boundary with the same fluctuation amplitude but opposite direction. Accordingly, the developed empirical equations are also applicable for head-controlled systems that sea level experiences an instantaneous variation or sea level and inland freshwater level undergo an instantaneous variation simultaneously. This study has revealed quantitatively that for a particular coastal aquifer system, the boundary water levels after fluctuations control the timescale of seawater intrusion, while the timescale of seawater retreat is dominated by the toe response distance. More importantly, the empirical equations derived imply that for a particular coastal system, the timescales of seawater intrusion and retreat can be estimated respectively based on the simulation results of two cases.

Lu, C.; Werner, A. D.; Simmons, C.

2012-12-01

331

Beyond Einstein: scientific goals and missions  

NASA Astrophysics Data System (ADS)

A century ago, Albert Einstein began creating his theory of relativity, the ideas we use to understand space, time, and gravity, and he took some of the first steps towards the theory of quantum mechanics, the ideas we use to understand matter and energy. Time magazine named Einstein the “Person of the Century” because his ideas transformed civilization. But his work is not finished: spacetime is not yet reconciled with the quantum. Einstein’s general theory of relativity opened possibilities for the formation and structure of the Universe that seemed unbelievable even to Einstein himself but which have all been subsequently confirmed: that the whole Universe began in a hot, dense Big Bang from which all of space expanded; that dense matter could tie spacetime into tangled knots called black holes; and that “empty” space might contain energy with repulsive gravity. Despite these discoveries, we still do not understand conditions at the beginning of the Universe, how space and time behave at the edge of a black hole, or why distant galaxies are accelerating away from us. These phenomena represent the most extreme interactions of matter and energy with space and time. They are the places to look for clues to the next fundamental revolution in understanding - Beyond Einstein.

White, Nicholas E.

332

Einstein, Mach, and the Fortunes of Gravity  

NASA Astrophysics Data System (ADS)

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 be consistent with Mach's principle, which states that local inertial effects arise due to gravitational interactions with distant matter. Once completed, Einstein's general relativity enjoyed two decades of worldwide attention, only to fall out of physicists' interest during the 1930s and 1940s, when topics like nuclear physics claimed center stage. Gravity began to return to the limelight during the 1950s and especially the 1960s, and once again Mach proved to be a major spur: Princeton physicists Carl Brans and Robert Dicke introduced a rival theory of gravity in 1961 which they argued satisfied Mach's principle better than Einstein's general relativity did. The Brans-Dicke theory, and the new generation of experiments designed to test its predictions against those of general relativity, played a major role in bringing Einstein's beloved topic back to the center of physics.

Kaiser, David

2005-04-01

333

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

NASA Astrophysics Data System (ADS)

We present a comprehensive flux-resolved spectral analysis of the bright narrow-line Seyfert 1 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-energy edges are required to explain the spectra. For Mrk 335, the 0.3-10 keV luminosity relative to the Eddington value, LX/LEdd, varied from 0.002 to 0.06. The index variation can be empirically described as ? = 0.6 log10 LX/LEdd + 3.0 for 0.005 < LX/LEdd < 0.04. At LX/LEdd ˜ 0.04 the spectral index changes and then continues to follow ? = 0.6 log10 LX/LEdd + 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 power law and an iron line. For Ark 564, the index variation can be empirically described as ? = 0.2 log10 LX/LEdd + 2.7 with a significantly large scatter as compared to Mrk 335. Our results indicate that for Mrk 335, there may be accretion disc geometry changes which lead to different parallel tracks. These changes could be related to structural changes in the corona or enhanced reflection at high flux levels. There does not seem to be any homogeneous or universal relationship for the X-ray index and luminosity for different AGNs or even for the same AGN.

Sarma, R.; Tripathi, S.; Misra, R.; Dewangan, G.; Pathak, A.; Sarma, J. K.

2015-04-01

334

The radio luminosity, black hole mass and Eddington ratio for quasars from the Sloan Digital Sky Survey  

E-print Network

We investigate the $\\mbh- \\sigma_*$ relation for radio-loud quasars with redshift $zradio luminosity, including 306 radio-loud quasars, 3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity (181 radio-quiet quasars with measured radio luminosity). The virial supermassive black hole mass (\\mbh) is calculated from the broad \\hb line, the host stellar velocity dispersion ($\\sigma_*$) is traced by the core \\oiii gaseous velocity dispersion, and the radio luminosity and the radio loudness are derived from the FIRST catalog. Our results are follows: (1) For radio-quiet quasars, we confirm that there is no obvious deviation from the $\\mbh- \\sigma_*$ relation defined in inactive galaxies when \\mbh uncertainties and luminosity bias are concerned. (2) We find that radio-loud quasars deviate much from the $\\mbh- \\sigma_*$ relation respect to that for radio-quiet quasars. This deviation is only partly due to the possible cosmology evolution of the $\\mbh- \\sigma_*$ relation and the luminosity bias. (3) The radio luminosity is proportional to $\\mbh^{1.28^{+0.23}_{-0.16}}(\\lb/\\ledd)^{1.29^{+0.31}_{-0.24}}$ for radio-quiet quasars and $\\mbh^{3.10^{+0.60}_{-0.70}}(\\lb/\\ledd)^{4.18^{+1.40}_{-1.10}}$ for radio-loud quasars. The weaker correlation of the radio luminosity dependence upon the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities, such as the black hole spin.

Wei-Hao. Bian; Yan-Mei. Chen; Chen. Hu; Kai. Huang; Yan. Xu

2008-03-24

335

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

NASA Astrophysics Data System (ADS)

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.

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

2015-02-01

336

Einstein’s quantum theory of the monatomic ideal gas: non-statistical arguments for a new statistics  

Microsoft Academic Search

In this article, we analyze the third of three papers, in which Einstein presented his quantum theory of the ideal gas of\\u000a 1924–1925. Although it failed to attract the attention of Einstein’s contemporaries and although also today very few commentators\\u000a refer to it, we argue for its significance in the context of Einstein’s quantum researches. It contains an attempt to

Enric Pérez; Tilman Sauer

2010-01-01

337

Projective Compactifications and Einstein metrics  

E-print Network

For complete affine manifolds we introduce a definition of compactification based on the projective differential geometry (i.e.\\ geodesic path data) of the given connection. The definition of projective compactness involves a real parameter $\\alpha$ called the order of projective compactness. For volume preserving connections, this order is captured by a notion of volume asymptotics that we define. These ideas apply to complete pseudo-Riemannian spaces, via the Levi-Civita connection, and thus provide a notion of compactification alternative to conformal compactification. For each order $\\alpha$, we provide an asymptotic form of a metric which is sufficient for projective compactness of the given order, thus also providing many local examples. Distinguished classes of projectively compactified geometries of orders one and two are associated with Ricci-flat connections and non--Ricci--flat Einstein metrics, respectively. Conversely, these geometric conditions are shown to force the indicated order of projective compactness. These special compactifications are shown to correspond to normal solutions of classes of natural linear PDE (so-called first BGG equations), or equivalently holonomy reductions of projective Cartan/tractor connections. This enables the application of tools already available to reveal considerable information about the geometry of the boundary at infinity. Finally, we show that metrics admitting such special compactifications always have an asymptotic form as mentioned above.

Andreas Cap; A. Rod Gover

2014-06-18

338

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

USGS Publications Warehouse

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.

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

2014-01-01

339

A dynamic multi-timescale method for combustion modeling with detailed and reduced chemical kinetic mechanisms  

SciTech Connect

A new on-grid dynamic multi-timescale (MTS) method is presented to increase significantly the computation efficiency involving multi-physical and chemical processes using detailed and reduced kinetic mechanisms. The methodology of the MTS method using the instantaneous timescales of different species is introduced. The definition of the characteristic time for species is examined and compared with that of the computational singular perturbation (CSP) and frozen reaction rate methods by using a simple reaction system. A hybrid multi-timescale (HMTS) algorithm is constructed by integrating the MTS method with an implicit Euler scheme, respectively, for species with and without the requirement of accurate time histories at sub-base timescales. The efficiency and the robustness of the MTS and HMTS methods are demonstrated by comparing with the Euler and VODE solvers for homogenous ignition and unsteady flame propagation of hydrogen, methane, and n-decane-air mixtures. The results show that both MTS and HMTS reproduce well the species and temperature histories and are able to decrease computation time by about one-order with the same kinetic mechanism. Compared to MTS, HMTS has slightly better computation efficiency but scarifies the stability at large base time steps. The results also show that with the increase of mechanism size and the decrease of time step, the computation efficiency of multi-timescale method increases compared to the VODE solver. In addition, it is shown that the integration of the multi-timescale method with the path flux analysis based mechanism reduction approach can further increase the computation efficiency. Unsteady simulations of outwardly propagating spherical n-decane-air premixed flames demonstrate that the multi-timescale method is rigorous for direct numerical simulations with both detailed and reduced chemistry and can dramatically improve the computation efficiency. (author)

Gou, Xiaolong [Department of Mechanical and Aerospace Engineering, Princeton University, NJ 08544 (United States); College of Power Engineering, Chongqing University, Chongqing 400030 (China); Sun, Wenting; Ju, Yiguang [Department of Mechanical and Aerospace Engineering, Princeton University, NJ 08544 (United States); Chen, Zheng [Department of Mechanical and Aerospace Engineering, Princeton University, NJ 08544 (United States); School of Engineering, Peking University, Beijing 100871 (China)

2010-06-15

340

A dynamic multi-timescale method for combustion modeling with detailed and reduced chemical kinetic mechanisms  

SciTech Connect

A new on-grid dynamic multi-timescale (MTS) method is presented to increase significantly the computation efficiency involving multi-physical and chemical processes using detailed and reduced kinetic mechanisms. The methodology of the MTS method using the instantaneous timescales of different species is introduced. The definition of the characteristic time for species is examined and compared with that of the computational singular perturbation (CSP) and frozen reaction rate methods by using a simple reaction system. A hybrid multi-timescale (HMTS) algorithm is constructed by integrating the MTS method with an implicit Euler scheme, respectively, for species with and without the requirement of accurate time histories at sub-base timescales. The efficiency and the robustness of the MTS and HMTS methods are demonstrated by comparing with the Euler and VODE solvers for homogenous ignition and unsteady flame propagation of hydrogen, methane, and n-decane–air mixtures. The results show that both MTS and HMTS reproduce well the species and temperature histories and are able to decrease computation time by about one-order with the same kinetic mechanism. Compared to MTS, HMTS has slightly better computation efficiency but scarifies the stability at large base time steps. The results also show that with the increase of mechanism size and the decrease of time step, the computation efficiency of multi-timescale method increases compared to the VODE solver. In addition, it is shown that the integration of the multi-timescale method with the path flux analysis based mechanism reduction approach can further increase the computation efficiency. Unsteady simulations of outwardly propagating spherical n-decane–air premixed flames demonstrate that the multi-timescale method is rigorous for direct numerical simulations with both detailed and reduced chemistry and can dramatically improve the computation efficiency.

Gou, Xiaolong; Sun, Wenting; Chen, Zheng; Ju, Yiguang

2010-01-01

341

Focus on quantum Einstein gravity Focus on quantum Einstein gravity  

NASA Astrophysics Data System (ADS)

The gravitational asymptotic safety program summarizes the attempts to construct a consistent and predictive quantum theory of gravity within Wilson's generalized framework of renormalization. Its key ingredient is a non-Gaussian fixed point of the renormalization group flow which controls the behavior of the theory at trans-Planckian energies and renders gravity safe from unphysical divergences. Provided that the fixed point comes with a finite number of ultraviolet-attractive (relevant) directions, this construction gives rise to a consistent quantum field theory which is as predictive as an ordinary, perturbatively renormalizable one. This opens up the exciting possibility of establishing quantum Einstein gravity as a fundamental theory of gravity, without introducing supersymmetry or extra dimensions, and solely based on quantization techniques that are known to work well for the other fundamental forces of nature. While the idea of gravity being asymptotically safe was proposed by Steven Weinberg more than 30 years ago [1], the technical tools for investigating this scenario only emerged during the last decade. Here a key role is played by the exact functional renormalization group equation for gravity, which allows the construction of non-perturbative approximate solutions for the RG-flow of the gravitational couplings. Most remarkably, all solutions constructed to date exhibit a suitable non-Gaussian fixed point, lending strong support to the asymptotic safety conjecture. Moreover, the functional renormalization group also provides indications that the central idea of a non-Gaussian fixed point providing a safe ultraviolet completion also carries over to more realistic scenarios where gravity is coupled to a suitable matter sector like the standard model. These theoretical successes also triggered a wealth of studies focusing on the consequences of asymptotic safety in a wide range of phenomenological applications covering the physics of black holes, early time cosmology and the big bang, as well as TeV-scale gravity models testable at the Large Hadron Collider. On different grounds, Monte-Carlo studies of the gravitational partition function based on the discrete causal dynamical triangulations approach provide an a priori independent avenue towards unveiling the non-perturbative features of gravity. As a highlight, detailed simulations established that the phase diagram underlying causal dynamical triangulations contains a phase where the triangulations naturally give rise to four-dimensional, macroscopic universes. Moreover, there are indications for a second-order phase transition that naturally forms the discrete analog of the non-Gaussian fixed point seen in the continuum computations. Thus there is a good chance that the discrete and continuum computations will converge to the same fundamental physics. This focus issue collects a series of papers that outline the current frontiers of the gravitational asymptotic safety program. We hope that readers get an impression of the depth and variety of this research area as well as our excitement about the new and ongoing developments. References [1] Weinberg S 1979 General Relativity, an Einstein Centenary Survey ed S W Hawking and W Israel (Cambridge: Cambridge University Press)

Ambjorn, Jan; Reuter, Martin; Saueressig, Frank

2012-09-01

342

Liver transplantation at Hospital Israelita Albert Einstein Transplante de fígado no Hospital Israelita Albert Einstein  

Microsoft Academic Search

Objective: To present patients and results of liver transplantation performed by the Liver Unit team at the Hospital Israelita Albert Einstein. Methods: The medical records of all patients transplanted by the team at the Liver Unit of the Hospital Israelita Albert Einstein, from January 2002 to June 2005, were analyzed. Results: During this period, 328 transplants were performed and 64.3%

Sergio Mies

343

Einstein und der Eötvös-Versuch: Ein Brief Albert Einsteins an Willy Wien  

Microsoft Academic Search

Das Aequivalenzprinzip wurde von Einstein erst 1907 in Worte gefasst. Er wendete sich 1912 brieflich an W. Wien mit der Bitte, den Unterschied der Schwingungsdauer eines Uranpendels und eines Bleipendels sowie die Proportionalität der trägen und schweren Massen eines Blei- und eines Urangewichts auszumessen, und zwar mit einer Drehwage. Der Brief macht es klar, dass Einstein bei der Aufstellung des

József Illy

1989-01-01

344

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

SciTech Connect

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.

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

345

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

PubMed Central

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

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

2012-01-01

346

Einstein's Revolutionary Light-Quantum Hypothesis  

NASA Astrophysics Data System (ADS)

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.

Stuewer, Roger H.

2005-05-01

347

Einstein's equivalence principle in cosmology  

NASA Astrophysics Data System (ADS)

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.

Kopeikin, Sergei

348

Timescales of geomagnetic secular acceleration in satellite field models and geodynamo models  

NASA Astrophysics Data System (ADS)

Magnetic satellite data from the last decade allow to model geomagnetic secular acceleration, the second time derivative of the field, in a highly precise manner. Robust estimates of the secular acceleration (SA) are obtained by using order six B-Splines as representation of the field variability, which in turn allows us to estimate the characteristic SA timescale, ?SA. We confirm a recent finding that ?SA is of order 10 years and fairly independent of the spherical harmonic degree n. This contrasts with the characteristic timescale of geomagnetic secular variation ?SV, which is a decreasing function of n and is ?100 yr for n? 5. Conceivably the SA timescale might be related to short-term processes in the core, distinct from convective overturn whose timescale is reflected by ?SV. Previously it had been shown that dynamo simulations reproduce the shape of the secular variation (SV) spectrum and, provided their magnetic Reynolds number Rm has an Earth-like value of order 1000, also the absolute values of ?SV. The question arises if dynamo simulations can capture the observed timescales of geomagnetic SA. We determined ?SA(n) for a set of dynamo models, covering a range of values of the relevant control parameters. The selection of models was based on the morphological similarity of their magnetic fields to the geomagnetic field and not on criteria related to the time dependence of the field, or on any aspect of the spectra associated with their field variation. We find that ?SA depends only weakly on n up to degree 10, but for larger n it asymptotically approaches the 1/n-dependence that is also found for ?SV(n). The acceleration timescale at low n varies with magnetic Reynolds number more strongly than ?SV and may also depend on magnetic field strength. For an Earth-like Rm? 1000, ?SA is of order 10 yr for n? 2-10, as found in the field models from satellite data. A simple scaling analysis based on the frozen flux assumption for magnetic variations suggests two contributions to the SA, an advective part that scales with velocity U and has a length scale dependence corresponding to n-1, and a part that depends on the acceleration of the flow ? without explicit dependence on the length scale. Their combination can explain the spectral shape of ?SA(n) in numerical models, with the latter term dominating at n < 10. The characteristic timescale of acceleration of the near surface flow ? correlates with ?SA in the different numerical models and is of the same order as ?SA. This suggests that the observed 10 yr timescale of geomagnetic SA reflects the characteristic time of core flow acceleration. To explain the geomagnetic SV and SA timescales, we find that the rms velocity near the core surface must be 18 km yr-1 and the rms flow acceleration approximately 2 km yr-2, although a statistical analysis of the induction equation suggests that most of the latter may occur at flow scales corresponding to harmonic degrees n > 12. The ability of dynamo models to match simultaneously SV and SA timescales suggests that dynamic processes in the core at the decadal timescale are not fundamentally different from those at the centennial timescale.

Christensen, U. R.; Wardinski, I.; Lesur, V.

2012-07-01

349

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

350

A Search for Short Timescale Microvariability in Active Galactic Nuclei in the Ultraviolet  

NASA Technical Reports Server (NTRS)

We observed four AGNs (the type-1 Seyfert systems 3C249.1, NGC 6814 and Mrk 205, and the BL Lac object 3C371) using the High Speed Photometer on the Hubble Space Telescope to search for short timescale microvariability in the W. Continuous observations of 3 0 0 0 s duration were obtained for each system on several consecutive HST orbits using a 1 s sample time in a 1400 - 3000 2 bandpass. variability > 0.3 % (0 . 003 mag) was detected in any AGN on timescales shorter than 1500 s. The distribution of photon arrival times observed from each source was consistent with Poisson statistics. Because of HST optical problems, the limit on photometric variability at longer timescales is less precise. These results restrict models of supermassive black holes as the central engine of an AGN and the diskoseismology oscillations of any accretion disk around such a black hole.

Dolan, Joseph F.; Clark, L. Lee

2003-01-01

351

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

PubMed

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

Weiner, Kevin S

2015-03-01

352

A MODEL FOR THE CORRELATION OF HARD X-RAY INDEX WITH EDDINGTON RATIO IN BLACK HOLE X-RAY BINARIES  

SciTech Connect

Observations show that there is a positive correlation between the Eddington ratio {lambda} and hard X-ray index {Gamma} for {lambda} {approx}> 0.01, and there is an anti-correlation between {lambda} and {Gamma} for {lambda} {approx}< 0.01 in black hole X-ray binaries (with {lambda} = L {sub bol}/L {sub Edd}). In this work, we theoretically investigate the correlation between {Gamma} and {lambda} within the framework of a disk-corona model. We improve the model by taking into account all cooling processes, including synchrotron and self-Compton radiations in the corona, Comptonization of the soft photons from the underlying accretion disk, and the bremsstrahlung radiations. Presuming that the coronal flow above the disk can reach up to the 0.1 Eddington rate at the outer region, we calculate the structure of the two-phase accretion flows and the emergent spectra for accretion rates from 0.003 to 0.1. We find that at accretion rates larger than bsim0.01 Eddington rate, a fraction of coronal gas condenses into the disk and an inner disk can be sustained by condensation. In this case, the X-ray emission is dominated by the scattering of the soft photon from the underlying disk in the corona. The emission from the inner disk and corona can produce the positive correlation between {lambda} and {Gamma}. While at accretion rates lower than bsim0.01 Eddington accretion rate, the inner disk vanishes completely by evaporation, and the accretion is dominated by advection-dominated accretion flows (ADAFs), in which the X-ray emission is produced by the Comptonization of the synchrotron and bremsstrahlung photons of ADAF itself. The emission from ADAFs can produce the anti-correlation between {lambda} and {Gamma}. We show that our model can roughly explain the observed evolution of {Gamma}{sub 3-25keV} with L {sub 0.5-25keV}/L {sub Edd} for the black hole X-ray transient H1743-322 in the decay of 2003 from the thermal-dominated state to low/hard state.

Qiao, Erlin; Liu, B. F., E-mail: qiaoel@nao.cas.cn [National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2013-02-10

353

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

PubMed

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

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

354

Spatial and seasonal variability of the air-sea equilibration timescale of carbon dioxide  

NASA Astrophysics Data System (ADS)

The exchange of carbon dioxide between the ocean and the atmosphere tends to bring near-surface waters toward equilibrium by reducing the partial pressure gradient across the air-water interface. However, the equilibration process is not instantaneous; in general there is a lag between forcing and response. The timescale of air-sea equilibration depends on several factors involving the depth of the mixed layer, temperature, salinity, wind speed, and carbonate chemistry. In this work, we use a suite of observational datasets to generate climatological and seasonal composite maps of the air-sea equilibration timescale. The relaxation timescale exhibits considerable spatial and seasonal variations, which are largely set by changes in mixed layer depth and wind speed. The net effect is dominated by the mixed layer depth; the gas exchange velocity and carbonate chemistry parameters only provide partial compensation. Broadly speaking, the adjustment timescale tends to increase with latitude. We compare the observationally-derived air-sea gas exchange timescale with a model-derived surface residence time and a data-derived horizontal transport timescale, which allows us to define two non-dimensional metrics of gas exchange efficiency. These parameters highlight the Southern Ocean, equatorial Pacific, and North Atlantic as regions of inefficient air-sea equilibration where carbon anomalies are likely to form and persist. The efficiency parameters presented here can serve as simple tools for understanding regional air-sea disequilibrium in both observations and models. This work is distributed under the Creative Commons Attribution 3.0 Unported License together with an author copyright. This license does not conflict with the regulations of the Crown Copyright.

Jones, Daniel; Ito, Takamitsu; Takano, Yohei; Hsu, Wei-Ching

2014-05-01

355

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

E-print Network

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.

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

356

Bose-Einstein condensation in microgravity.  

PubMed

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

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

357

The Einstein-Boltzmann system and positivity  

E-print Network

The Einstein-Boltzmann system is studied, with particular attention to the non-negativity of the solution of the Boltzmann equation. A new parametrization of post-collisional momenta in general relativity is introduced and then used to simplify the conditions on the collision cross-section given by Bancel and Choquet-Bruhat. The non-negativity of solutions of the Boltzmann equation on a given curved spacetime has been studied by Bichteler and by Tadmon. By examining to what extent the results of these authors apply in the framework of Bancel and Choquet-Bruhat, the non-negativity problem for the Einstein-Boltzmann system is resolved for a certain class of scattering kernels. It is emphasized that it is a challenge to extend the existing theory of the Cauchy problem for the Einstein-Boltzmann system so as to include scattering kernels which are physically well-motivated.

Ho Lee; Alan D. Rendall

2012-03-12

358

Einstein, Ethics and the Atomic Bomb  

NASA Astrophysics Data System (ADS)

Einstein voiced his ethical views against war as well as fascism via venues and alliances with a variety of organizations still debated today. In 1939, he signed a letter to President Roosevelt (drafted by younger colleagues Szilard, Wigner and others) warning the U.S.government about the danger of Nazi Germany gaining control of uranium in the Belgian-controlled Congo in order to develop atomic weapons, based on the discovery of fission by Otto Hahn and Lise Meitner. In 1945, he became a member of the Princeton-based ``Emergency Committee for Atomic Scientists'' organized by Bethe, Condon, Bacher, Urey, Szilard and Weisskopf. Rare Einstein slides will illustrate Dr.Rife's presentation on Albert Einstein's philosophic and ethical convictions about peace, and public stance against war (1914-1950).

Rife, Patricia

2005-03-01

359

PBR theorem and Einstein's quantum hole argument  

E-print Network

This note discusses the latest hot topic: Quantum states: ontic or epistemic? and the PBR theorem. Upon reading Einstein's views on quantum incompleteness in publications or in his correspondence after 1935 (the EPR paradox), one gets a very intense feeling of deja-vu. Einstein presents a quantum hole argument, which somewhat reminds of the hole argument in his 1914 "Entwurf" general theory of relativity. In their paper, PBR write the following: "an important step towards the derivation of our result is the idea that the quantum state is physical if distinct quantum states correspond to non-overlapping distributions for [the set of possible physical states that a system can be in]", and they then refer to Einstein's argument and views.

Weinstein, Galina

2013-01-01

360

Einstein billiards and spatially homogeneous cosmological models  

NASA Astrophysics Data System (ADS)

In this paper, we analyse the Einstein and Einstein Maxwell billiards for all spatially homogeneous cosmological models corresponding to three- and four-dimensional real unimodular Lie algebras and provide a list of those models which are chaotic in the Belinskii, Khalatnikov and Lifschitz (BKL) limit. Through the billiard picture, we confirm that, in D = 5 spacetime dimensions, chaos is present if off-diagonal metric elements are kept: the finite volume billiards can be identified with the fundamental Weyl chambers of hyperbolic Kac Moody algebras. The most generic cases bring in the same algebras as in the inhomogeneous case, but other algebras appear through special initial conditions.

de Buyl, Sophie; Pinardi, Gaïa; Schomblond, Christiane

2003-12-01

361

Collisions of Einstein-Conformal Scalar Waves  

E-print Network

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.

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

1992-12-18

362

Beyond Einstein: Exploring the Extreme Universe  

NASA Technical Reports Server (NTRS)

This paper will give an overview of the NASA Universe Division Beyond Einstein program. The Beyond Einstein program consists of a series of exploratory missions to investigate some of the most important and pressing problems in modern-day astrophysics - including searches for Dark Energy and studies of the earliest times in the universe, during the inflationary period after the Big Bang. A variety of new technologies are being developed both in the science instrumentation these missions will carry and in the spacecraft that will carry those instruments.

Barbier, Louis M.

2005-01-01

363

Comment on "Scalar Einstein-Aether theory"  

E-print Network

A recent paper studies a modification of Einstein-aether theory in which the aether vector is restricted, at the level of the action, to be the gradient of a scalar. In this comment we note that this scalar version of Einstein-aether theory is equivalent to the projectable version of the IR limit of Ho\\v{r}ava gravity when the potential for the scalar is constant. This provides a generally covariant formulation for projectable Ho\\v{r}ava gravity.

Ted Jacobson; Antony J. Speranza

2014-06-12

364

Human dynamics: Darwin and Einstein correspondence patterns  

NASA Astrophysics Data System (ADS)

In an era when letters were the main means of exchanging scientific ideas and results, Charles Darwin (1809-82) and Albert Einstein (1879-1955) were notably prolific correspondents. But did their patterns of communication differ from those associated with the instant-access e-mail of modern times? Here we show that, although the means have changed, the communication dynamics have not: Darwin's and Einstein's patterns of correspondence and today's electronic exchanges follow the same scaling laws. However, the response times of their surface-mail communication is described by a different scaling exponent from e-mail communication, providing evidence for a new class of phenomena in human dynamics.

Oliveira, João Gama; Barabási, Albert-László

2005-10-01

365

??Rubidium Bose-Einstein condensates in optical lattices  

E-print Network

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 ...

Campbell, Gretchen K. (Gretchen Kathleen)

2007-01-01

366

Coherence, Abstraction, and Personal Involvement: Albert Einstein, Physicist and Humanist.  

ERIC Educational Resources Information Center

Reviews Einstein's main contributions to physics, and analyzes the importance of a coherent body of theory. Einstein's involvement in nonscientific issues such as nuclear disarmament is also included. (HM)

Ne'eman, Yuval

1979-01-01

367

Einstein M.D. Program 20132014 applicant guide  

E-print Network

Einstein M.D. Program 2013­2014 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert and our accomplishments. tHe inSide StoRY #12;WelcoMe At Albert Einstein College of Medicine, compassion Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop

Emmons, Scott

368

Einstein M.D. Program 20112012 applicant guide  

E-print Network

Einstein M.D. Program 2011­2012 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert. tHe Big pictuRe tHe inSide StORY #12;MeSSage FROM tHe dean WelcOMe At Albert Einstein College of Medicine Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop

Jenny, Andreas

369

Anti-control of chaos of single time-scale brushless DC motor.  

PubMed

Anti-control of chaos of single time-scale brushless DC motors is studied in this paper. In order to analyse a variety of periodic and chaotic phenomena, we employ several numerical techniques such as phase portraits, bifurcation diagrams and Lyapunov exponents. Anti-control of chaos can be achieved by adding an external constant term or an external periodic term. PMID:16893797

Ge, Zheng-Ming; Chang, Ching-Ming; Chen, Yen-Sheng

2006-09-15

370

Mineral-specific chemical weathering rates over millennial timescales: Measurements at Rio Icacos, Puerto Rico  

E-print Network

Mineral-specific chemical weathering rates over millennial timescales: Measurements at Rio Icacos 2010 Accepted 26 July 2010 Editor: J.D. Blum Keywords: Chemical weathering Mineral weathering Cosmogenic nuclides Rio Icacos Puerto Rico Mineral weathering plays a prominent role in many biogeochemical

Kirchner, James W.

371

Disease dynamics over very different time-scales: foot-and-mouth disease and  

E-print Network

Disease dynamics over very different time-scales: foot-and-mouth disease and scrapie on the network of livestock movements in the UK and the dynamics of two diseases: foot-and-mouth disease (FMD), which has conditions, a static network analysis can be an appropriate tool for gaining insights into disease dynamics

Kiss, Istvan Zoltan

372

A sensitivity study of fast outlet glaciers to short timescale cyclical perturbations  

NASA Astrophysics Data System (ADS)

The dynamic response of outlet glaciers on short (annual to decadal) timescales is affected by various external forcings, such as basal or oceanic conditions. Understanding the sensitivity of the dynamic response to such forcings can help assess more accurate ice volume projections. In this work, we investigate the spatiotemporal sensitivity of outlet glaciers to fast cyclical forcings using a one-dimensional depth and width-averaged heuristic model. Our results indicate that even on such short timescales, nonlinearities in ice dynamics may lead to an asymmetric response, despite the forcing functions being symmetric around each reference value. Results also show that such short-timescale effects become more pronounced as glaciers become closer to flotation. While being qualitatively similar for both downsloping and upsloping bed geometries, the results indicate higher sensitivity for upsloping ("West Antarctica-like") beds. The range in asymmetric response for different configurations motivate parameterizing or including short-timescale effects in models while investigating the dynamic behavior of outlet glaciers.

Aykutlug, E.; Dupont, T. K.

2015-01-01

373

Introductory Invited Paper Gate dielectric breakdown in the time-scale of ESD events  

E-print Network

Introductory Invited Paper Gate dielectric breakdown in the time-scale of ESD events Bonnie E. Weir- scale. ESD protection systems can thus be designed to prevent dielectric breakdown. Important concepts in gate dielec- tric breakdown such as the anode­hole injection model and area and statistical effects

Alam, Muhammad A.

374

Multiresolution sinusoidal model with dynamic segmentation for timescale modification of polyphonic audio signals  

Microsoft Academic Search

In this paper, we propose an efficient sinusoidal model of polyphonic audio signals especially good for the application of timescale modification. One of the critical problem of sinusoidal modeling is that the signal is smeared during the synthesis frame, which is a very undesirable effect for transient parts. We solve this problem by introducing multiresolution analysis-synthesis and dynamic segmentation methods.

Ho Keun Jang; Ju Sung Park

2005-01-01

375

A TIME-SCALE PROBLEM FOR THE FORMATION OF SOOT PRECURSORS IN PREMIXED FLAMES  

E-print Network

A TIME-SCALE PROBLEM FOR THE FORMATION OF SOOT PRECURSORS IN PREMIXED FLAMES Angela Violi1 for Theoretical Chemistry, Department of Chemistry University of Utah Salt Lake City, UT 84112 Introduction of the evolution of soot precursors in an ethylene premixed laminar flame.1,3 In this paper the KMC/MD code is used

Utah, University of

376

Optimal structured feedback policies for ABR flow control using two-timescale SPSA  

Microsoft Academic Search

Optimal structured feedback control policies for rate-based flow control of available bit rate service in asynchronous transfer mode networks are obtained in the presence of information and propagation delays, using a numerically efficient two-timescale simultaneous perturbation stochastic approximation algorithm. Models comprising both a single bottleneck node and a network with multiple bottleneck nodes are considered. A convergence analysis of the

Shalabh Bhatnagar; Michael C. Fu; Steven I. Marcus; Pedram J. Fard

2001-01-01

377

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

E-print Network

subscriber line, cable modem, or an available radio frequency channel. With the use of small cells, users canShadowing 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

Boyer, Edmond

378

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

NASA Astrophysics Data System (ADS)

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.

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

2015-03-01

379

Timescale and Intensity Dependency in Multiplicative Cascades for Temporal Rainfall Disaggregation  

E-print Network

. The elemental MRC model parameter is the cascade weight, which determines how rainfall at one scale "dependent" models were constructed to disaggregate a long time series of daily rainfall to hourly intervals the rainfall was disaggregated, varying model parameters with timescale resulted in minor improvement. 2 #12

Selker, John

380

The role of the North Atlantic Drift in the millennial timescale glacial climate fluctuations  

E-print Network

The role of the North Atlantic Drift in the millennial timescale glacial climate fluctuations Tine, are strongly imprinted in the North Atlantic marine records suggesting that they were linked to North Atlantic and ice rafted debris during the last glacial period in eight cores from the North Atlantic and the Nordic

Ingólfsson, Ólafur

381

Revised calibration of the geomagnetic polarity timescale for the Late Cretaceous and Cenozoic  

Microsoft Academic Search

Recently reported radioisotopic dates and magnetic anomaly spacings have made it evident that modification is required for the age calibrations for the geomagnetic polarity timescale of Cande and Kent (1992) at the Cretaceous\\/Paleogene boundary and in the Pliocene. An adjusted geomagnetic reversal chronology for the Late Cretaceous and Cenozoic is presented that is consistent with astrochronology in the Pleistocene and

S. C. Cande; D. V. Kent

1995-01-01

382

Conceptual Development of Einstein's Mass-Energy Relationship  

ERIC Educational Resources Information Center

Einstein's special theory of relativity was published in 1905. It stands as one of the greatest intellectual achievements in the history of human thought. Einstein described the equivalence of mass and energy as "the most important upshot of the special theory of relativity" (Einstein, 1919). In this paper, we will discuss the evolution of the…

Wong, Chee Leong; Yap, Kueh Chin

2005-01-01

383

PHYSICS BEFORE AND AFTER EINSTEIN This page intentionally left blank  

E-print Network

since he died. There is no question that Albert Einstein with his work on relativity and quantum theoryPHYSICS BEFORE AND AFTER EINSTEIN #12;This page intentionally left blank #12;Physics Before and After Einstein Edited by Marco Mamone Capria University of Perugia, Department of Mathematics

Mamone Capria, Marco

384

Special Relativity in a Nutshell Basic Postulates: Einstein 1905  

E-print Network

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

Peters, Achim

385

August 5, 2009 How Hume and Mach Helped Einstein  

E-print Network

, Albert Einstein: A Biographical Portrait. New York: Albert and Charles Boni, 1930. p.55 #12;2 endeavor1 August 5, 2009 Addendum How Hume and Mach Helped Einstein Find Special Relativity John D. Norton that it overlooked some material that further illuminated Einstein's attitude to David Hume.1 A revealing remark

386

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY on SEXUAL of residents in the programs sponsored by the Albert Einstein College of Medicine, have established employment that no employee is subjected to such conduct. Originated 9/05 Approved 10/05 1 N.B. The Albert Einstein College

Yates, Andrew

387

The Albert Einstein College of Medicine of Yeshiva University  

E-print Network

The Albert Einstein College of Medicine of Yeshiva University EMERGENCY PROCEDURES MANUAL Prepared Resources Security Revised ­ October, 2014 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY............................................................................................................................. 44 #12;ALBERT EINSTEIN COLLEGE of MEDICINE of YESHIVA UNIVERSITY EMERGENCY PROCEDURES MANUAL CIVIL

Jenny, Andreas

388

Albert Einstein College of Medicine Center for Experimental Therapeutics  

E-print Network

Albert Einstein College of Medicine Center for Experimental Therapeutics A Bold New Initiative that afflict humanity. For more than five decades, the Albert Einstein College of Medicine has been one Bringing Hope and Help to Patients #12;Disease Target ID Assay Development HTS* Einstein Center

Kenny, Paraic

389

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY sponsored by the Albert Einstein College of Medicine must not be required to engage in "Moonlighting." 7 May 2002 N.B. The Albert Einstein College of Medicine serves as the ACGME-accredited Institutional

Yates, Andrew

390

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY), as the employers of residents in the programs sponsored by the Albert Einstein College of Medicine have established of LOA should be filed with the Office of GME. Revised May 2002 N.B. The Albert Einstein College

Yates, Andrew

391

Einstein M.D. Program 20142015 APPLICANT GUIDE  

E-print Network

Einstein M.D. Program 2014­2015 APPLICANT GUIDE O F Y E S H I V A U N I V E R S I T Y Albert research and our accomplishments. THE INSIDE STORY #12;WELCOME At Albert Einstein College of Medicine experiences available at Montefiore, the University Hospital and academic medical center for Albert Einstein

Emmons, Scott

392

EINSTEINSpring 2007 spring 2007 I EinstEin  

E-print Network

: A publication for faculty, students, alumni, friends and supporters of the Albert einstein College of Medicine that cover the full spectrum of research currently performed by faculty of the Albert einstein College;spring 2007 I EinstEin eInSTeInCONTENTs 3 A meSSAge from the deAn 4 Children with AidS: the remarkable

Yates, Andrew

393

Albert Einstein College of Medicine Global Health Center  

E-print Network

Albert Einstein College of Medicine Global Health Center Complete and send to Denise Giocondo at that the funds being sent to the account indicated above belong to Albert Einstein College of Medicine: denise.giocondo@einstein.yu.edu Request to wire funds internationally: Name

Yates, Andrew

394

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY RESIDENT program sponsored by the Albert Einstein College of Medicine must assess resident performance and use to support the care of patients. 1 N.B. The Albert Einstein College of Medicine serves as the ACGME

Yates, Andrew

395

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY for residents transferring to an other program. (Revised May 2002) 1 N.B. The Albert Einstein College on Graduate Medical Education of the Albert Einstein College of Medicine has established written policies

Yates, Andrew

396

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY), as the employers of residents in the programs sponsored by the Albert Einstein College of Medicine, have each Process Policies of the employing institution. Revised Sept. 2004 1 N.B. The Albert Einstein College

Yates, Andrew

397

ALBERT EINSTEIN COLLEGE OF MEDICINE OF YESHIVA UNIVERSITY  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE OF YESHIVA UNIVERSITY JACK AND PEARL RESNICK CAMPUS · 1300: Mr/Ms , social security # , who is presently associated with the Albert Einstein College of Medicine radiation exposure records be released to the Albert Einstein College of Medicine's Radiation Safety Office

Emmons, Scott

398

Albert Einstein College of Medicine of Yeshiva University  

E-print Network

4 1 Strategic Research Plan Albert Einstein College of Medicine of Yeshiva University Jack and Pearl Resnick Campus 1300 Morris Park Avenue Bronx, New York 10461 Albert Einstein College of Medicine.A. Cissell Consulting Design: GRAPHIC ARTS CENTER Creative Director: Peter Dama Albert Einstein College

Emmons, Scott

399

Albert Einstein In the spring of 1921, five  

E-print Network

Albert Einstein In the spring of 1921, five years after the appear- ance of his comprehensive paper Study, Albert Einstein toured the United States to help raise funds for the establishment of a Hebrew; the remaining three, more technical in nature, formed the rest of the book. In subsequent editions, Einstein

Landweber, Laura

400

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION  

E-print Network

ALBERT EINSTEIN COLLEGE OF MEDICINE COMMITTEE ON GRADUATE MEDICAL EDUCATION POLICY POLICY approved in lieu of an additional COGME policy. Revised: Sept. 2004 N.B. The Albert Einstein College on Graduate Medical Education of the Albert Einstein College of Medicine has established written policies

Yates, Andrew

401

Einstein 2013-2014 Edition Student to Student  

E-print Network

. This guide does not represent the policies of the Albert Einstein College of Medicine or its affiliated, sexual orientation, or citi- zenship status. Upon hearing of this, Albert Einstein wrote a letter, March 14, 1953, Albert Einstein agreed to lend his name to the medi- cal school, the only institution

Yates, Andrew

402

Hawking Radiation of Black Hole in Einstein-Proca Theory  

NASA Astrophysics Data System (ADS)

The Hawking radiation of black hole in Einstein-Proca theory is discussed in this paper. The Einstein-Proca black hole is more general than Reissner-Nordström black hole, because Proca field is massive vector field. We calculate several quantum perturbations in this spacetime, and obtain the Hawking radiation at the horizon in Einstein-Proca theory.

Yang, Shuzheng; Lin, Kai; Li, Jin

2014-05-01

403

Atmospheric Vapor Isotope Variability on Timescales from an Hour to a Year  

NASA Astrophysics Data System (ADS)

Atmospheric vapor isotope ratios (H218O/H216O and HD16O/H216O) were observed at high frequency for two years in Hanover, NH. Isotopic data were obtained every 100 seconds using a Los Gatos Research ringdown vapor analyzer, and concurrent meteorological data were obtained every 10 min using a collocated Davis Vantage PRO2 weather station. It was determined that variations of ?18O and ?D are dominated by three timescales: (1) A diel timescale, (2) a broadband “weather” timescale with periods from hours to days, and (3) an annual timescale. Variations on the three timescales can be separated by appropriate statistical computations. Each timescale of variability can be examined by evaluating the relationships among pairs of variables, especially those between the isotope ratios, ?18O and ?D, and the dew point temperature TD. The diel cycle in ?18O-TD coordinates appears as a counter-clockwise loop. At different times of day, the progress around the loop is dominated by different processes. In the morning, there is increasing TD during evaporation of fog as solar radiation warms the air. Later in the day, isotopic ratios drop while evapotranspiration rates are at their maximum, and as the boundary layer deepens and entrains isotopically depleted air from above. TD drops as radiative cooling and condensation modify the boundary layer in the late evening and night. Finally, after the upper part of the boundary layer detrains into the air above, the cycle is completed as water vapor re-equilibrates with surface water and ?18O rises in the hours preceding sunrise. Details of the cycle vary gradually as the seasons change. Vapor isotopes also vary on weather timescales; they can change in under an hour during passage of a fast-moving cold front, but may be steady for several days during the passage of a large cyclonic system blocked by a high. The changes are dominated by the displacement of one air mass by another, especially during frontal passage. Vapor isotopes potentially offer insights, not available from conventional meteorological data, into the origin, modification, and structure of air masses in weather systems. The annual cycle of vapor isotopes also loops in a pattern analogous to the diel cycle, but is affected as well by the change of influential air masses from high-latitude continental in the winter, to mid-latitude with more marine influence in the summer. passages, most dramatically during cold front passage.

Posmentier, E. S.; Faiia, A.; Everhart, K.; Feng, X.

2010-12-01

404

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

405

Integrating timescales with time-transfer functions: a practical approach for an INTIMATE database  

NASA Astrophysics Data System (ADS)

The purpose of the INTIMATE project is to integrate palaeo-climate information from terrestrial, ice and marine records so that the timing of environmental response to climate forcing can be compared in both space and time. One of the key difficulties in doing this is the range of different methods of dating that can be used across different disciplines. For this reason, one of the main outputs of INTIMATE has been to use an event-stratigraphic approach which enables researchers to co-register synchronous events (such as the deposition of tephra from major volcanic eruptions) in different archives (Blockley et al., 2012). However, this only partly solves the problem, because it gives information only at particular short intervals where such information is present. Between these points the ability to compare different records is necessarily less precise chronologically. What is needed therefore is a way to quantify the uncertainties in the correlations between different records, even if they are dated by different methods, and make maximum use of the information available that links different records. This paper outlines the design of a database that is intended to provide integration of timescales and associated environmental proxy information. The database allows for the fact that all timescales have their own limitations, which should be quantified in terms of the uncertainties quoted. It also makes use of the fact that each timescale has strengths in terms of describing the data directly associated with it. For this reason the approach taken allows users to look at data on any timescale that can in some way be related to the data of interest, rather than specifying a specific timescale or timescales which should always be used. The information going into the database is primarily: proxy information (principally from sediments and ice cores) against depth, age depth models against reference chronologies (typically IntCal or ice core), and time-transfer functions that relate different timescales to each other, through the use of event stratigraphies or global phenomena such as cosmogenic isotope production rate variations.

Bronk Ramsey, Christopher; Albert, Paul; Blockley, Simon; Hardiman, Mark; Lane, Christine; Macleod, Alison; Matthews, Ian P.; Muscheler, Raimund; Palmer, Adrian; Staff, Richard A.

2014-12-01

406

Integrated Isotopic Dating and Geospeedometry: Timescales of Rhyolite Rejuvenation and Crystallization at Yellowstone  

NASA Astrophysics Data System (ADS)

Two techniques have been primarily used to quantify the timescales associated with the evolution and residence of voluminous rhyolitic magmas: 1) isotopic dating, especially using U-Th-Pb dating of accessory minerals, and 2) "geospeedometry" using the diffusional relaxation of intra-crystal zoning of trace element or isotope composition. These methods can resolve different aspects magma evolution over short and long timescales, yet few studies have combined both. To evaluate the timescales associated with crystallization, storage, and rejuvenation of rhyolitic magma at Yellowstone caldera, we have applied ion microprobe 238U-230Th dating of zircon and geospeedometry using zoned sanidine and pyroxene phenocrysts from the ~260 ka Scaup Lake flow (SLF). The SLF is one of the youngest and most-evolved lavas of the Upper Basin Member, rhyolites which mainly erupted 100 kyr after the 0.6 Ma caldera-forming Lava Creek Tuff, and well before the effusion of the voluminous Central Plateau Member lavas between 170 and 70 ka. SLF zircons yield a 230Th-corrected U-Pb age of 312±45 ka (2?, n=19, MSWD=2.7), suggesting magma generation on the order of 104-105 years before eruption. Most SLF sanidines have significant intra-crystal zoning with multiple resorption surfaces and rims with relatively high Ba and Sr concentrations. Clinopyroxene cores contain exsolution lamellae and are overgrown by inclusion-free rims. Quartz phenocrysts have rims with higher Ti concentrations than their cores. These petrographic observations suggest recycling of subsolidus residue from earlier intrusions and renewed crystallization in new and hotter melt. Diffusion profiles for trace elements across resorption boundaries near sanidine cores yield timescales on the order of 103-104 years, assuming temperatures of 850° C. Profiles across near-rim boundaries suggest insignificant diffusion and that rims formed immediately prior to eruption. Timescales from Fe-Mg diffusion between clinopyroxene cores and rims are similar to those from sanidine. Application of both isotopic dating and geospeedometry to SLF minerals yields timescales over several orders of magnitude, which reflect different aspects of magma evolution. The ages of SLF zircons are likely to reflect a mixture of recycled crystal residue and renewed crystallization. Contrasting timescales from geospeedometry are dependent on petrographic context and reflect different evolutionary "milestones" in the chronology of the SLF magma.

Vazquez, J. A.; Boyce, J. W.; Kyriazis, S. F.; Reid, M. R.

2008-12-01

407

Book Review: A. P. French (ed.): "Einstein: A Centenary Volume" and Gerald Tauber (ed.): "Albert Einstein's Theory of General Relativity"  

E-print Network

A. P. French (ed.): Einstein: A Centenary Volume. Pp. v > 332. Cambridge, Massachusetts: Harvard University Press, 1979. Cloth, $20.00. GeraJd Tauber (ed.): Albert Einstein's Theory of Cenerai Relativity. Pp. 6 + 351. New York: Crown Publishers..., 1979. Cloth, $14.95. Joe D. Van Zandt Theie is much irony in the publication of memorial volumes in honor of Albert Einstein. Einstein repeatedly showed astonishment at the celebrity status his work had brought and often made gently rebuking...

Van Zandt, Joe D.

408

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

NASA Astrophysics Data System (ADS)

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

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

409

A Comparison of Solar Energetic Particle Event Timescales with Properties of Associated Coronal Mass Ejections  

NASA Astrophysics Data System (ADS)

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 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 CME, and TR and TD increase with both v 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 CME and W. The correlations generally fall below the 98% significance level, but there is a significant correlation between v 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.

Kahler, S. W.

2013-06-01

410

An operationalistic reformulation of Einstein's equivalence principle  

E-print Network

The Einstein's equivalence principle is formulated in terms of the accuracy of measurements and its dependence of the size of the area of measurement. It is shown that different refinements of the statement 'the spacetime is locally flat' lead to different conculsions about the spacetime geometry.

Vladik Kreinovich; R. R. Zapatrin

1997-05-30

411

Soliton resonance in bose-einstein condensate  

NASA Technical Reports Server (NTRS)

A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

Zak, Michail; Kulikov, I.

2002-01-01

412

Skyrme-Einstein closed cosmic chiral strings  

SciTech Connect

Within the theory of general relativity, the configuration of a closed string (vortex) characterized by a topological charge of the degree type is described for the Skyrme-Einstein SU (2) chiral model. In the approximation of a large vortex-closure radius (a), a solution to equations of motion is obtained, along with estimates for the vortex energy and radius.

Rybakov, Yu. P., E-mail: soliton4@mail.ru; Ivanova, I. S. [Peoples' Friendship University (Russian Federation)

2007-07-15

413

Conformally related null Einstein-Maxwell fields  

NASA Astrophysics Data System (ADS)

We present a class of pairs of non-trivially conformally related solutions of Einstein-Maxwell equations that are not pp-waves. To our knowledge, this is the first such case and thus an extension of theorems by Brinkmann, Daftardar-Gejji and Van den Bergh concerning conformal transformations of solutions with null electromagnetic fields.

Hruška, J.; Žofka, M.

2013-01-01

414

The Einstein All-Sky Slew Survey  

NASA Technical Reports Server (NTRS)

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.

Elvis, Martin S.

1992-01-01

415

Rotating elastic bodies in Einstein gravity  

E-print Network

We prove that, given a stress-free, axially symmetric elastic body, there exists, for sufficiently small values of the gravitational constant and of the angular frequency, a unique stationary axisymmetric solution to the Einstein equations coupled to the equations of relativistic elasticity with the body performing rigid rotations around the symmetry axis at the given angular frequency.

Lars Andersson; Robert Beig; Bernd Schmidt

2008-11-06

416

EINSTEIN DRIVE ON. NFW IFRSFY l  

E-print Network

#12;#12;#12;EINSTEIN DRIVE ON. NFW IFRSFY l 24-8399 (Idx) #12;Institute /or ADVANCED STUDY REPORT FOR THE ACADEMIC YEAR 2 000-2001 PRINCETON NEW JERSEY #12;#12;Institute /or ADVANCED STUDY REPORT FOR THE ACADEMIC, or sex. We feel strongly that the spirit characteristic of America at its noblest, above all the pursuit

417

Multidimensional Einstein-Yang-Mills cosmological models  

E-print Network

We study the process of the evolution of the space of extra dimensions in the framework of Einstein-Yang-Mills cosmological models. It is shown that, for certain classes of models, the static compact space of extra dimensions is the attractor for a wide range of initial conditions. Also the effect of isotropization of extra dimensions in the course of evolution is demonstrated.

Yu. Kubyshin; E. Moreno; J. I. Pérez Cadenas

1994-11-28

418

Einstein's Revolutionary Light--Quantum Hypothesis  

Microsoft Academic Search

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

R. H. Stuewer

2006-01-01

419

Vacuumless cosmic strings in Einstein Cartan theory  

E-print Network

The gravitational fields of vacuumless global and gauge strings have been investigated in the context of Einstein Cartan theory under the weak field assumption of the field equations. It has been shown that global string and gauge string can have only repulsive gravitational effect on a test particle.

F. Rahaman; B. C. Bhui; A Ghosh; R. Mondal

2006-10-20

420

A Science of Sig-Einstein, Inertia,  

E-print Network

12 A Science of Sig- nals: Einstein, Inertia, and the Postal System Jimena Canales What do) with communications me- dia, and, in particular, with their speed. Could love be sent through the mail?, wondered in general. In the process, he learned that neither love nor time could travel at speeds faster than

Canales, Jimena

421

Albert Einstein and the Quantum Riddle  

ERIC Educational Resources Information Center

Derives a systematic structure contributing to the solution of the quantum riddle in Einstein's sense by deducing quantum mechanics from the postulates of symmetry, correspondence, and covariance. Indicates that the systematic presentation is in agreement with quantum mechanics established by Schroedinger, Born, and Heisenberg. (CC)

Lande, Alfred

1974-01-01

422

Einstein and a century of time  

Microsoft Academic Search

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

D. J. Raine

2005-01-01

423

How Einstein Got the Nobel Prize.  

ERIC Educational Resources Information Center

Discusses why the Nobel Committee for Physics waited so long before giving Einstein the Nobel Prize and why they did not award it for relativity, but for the photoelectric effect instead. Focuses on the judgments of leading scientists who made nominations as well as committee members' decisions. (Author/JN)

Pais, Abraham

1982-01-01

424

DESIGN ANALYSIS OF THE EINSTEIN REFRIGERATION CYCLE  

Microsoft Academic Search

After developing the theory of relativity, Albert Einstein spent several years working with Leo Szilard on absorption refrigeration cycles. In 1930, they obtained a U.S. patent for a unique single pressure absorption cycle. The single pressure eliminates the need for a solution pump. Their cycle has only recently been rediscovered. The cycle u tilizes butane as its refrigerant, ammonia as

Sam V. Shelton; Andrew Delano; Laura A. Schaefer

1998-01-01

425

Selfdual Einstein metrics with torus symmetry  

Microsoft Academic Search

It is well known that any 4-dimensional hyperkahler metric with two commuting Killing fields may be obtained explicitly, via the Gibbons-Hawking Ansatz, from a harmonic function invariant under a Killing field on R^3. In this paper, we find all selfdual Einstein metrics of nonzero scalar curvature with two commuting Killing fields. They are given explicitly in terms of a local

David M. J. Calderbank; Henrik Pedersen

2001-01-01

426

Einstein-Yang-Mills theory: Asymptotic symmetries  

NASA Astrophysics Data System (ADS)

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.

Barnich, Glenn; Lambert, Pierre-Henry

2013-11-01

427

Einstein and gravitational redshift (German Title: Einstein und die Gravitations-Rotverschiebung)  

NASA Astrophysics Data System (ADS)

This paper studies Einstein's arguments for the existence of gravitational redshift (GRV) since 1907, his early search for empirical indications and self-confident insistence on this effect around 1919/20 despite a lack of unambiguous proof. In the third part I briefly discuss the role of GRV as a crucial test of the principle of equivalence as a reason for Einstein's strong interest and confidence in its existence.

Hentschel, Klaus

428

Einstein's Foil & the Emergence of Structure  

NASA Astrophysics Data System (ADS)

Before introducing his cosmological constant, Einstein considered a difficulty with Newtonian theory: a steady-state, infinite Newtonian stellar system cannot exist at all. He continues: "It seems hardly possible to surmount these difficulties on the basis of Newtonian theory. We may ask ourselves the question whether they can be removed by a modification of the Newtonian theory. First of all we will indicate a method which does not in itself claim to be taken seriously; it merely serves as a foil for what is to follow. In place of Poisson's equation we write ?? -? ? = 4 ? ? ? where ? denotes a universal constant. If ? be the uniform density of a distribution of mass, then ?=-4? ??/? is a solution." Einstein discarded this foil because it is not compatible with his famed equation for general relativity. In 2004 I proposed a graviton of imaginary mass and a photon of real mass, both equal to 10 -25 eV. Classically this graviton satisfies Einstein's first equation with an empirical value of 2 ?/?-?=Ro/20 = 400 pc. I now suggest an equivalent absolute value -?= (1/2)EH4 2 ? G. where EH is the Hartree energy 2 × 13.6 eV and c=(h/2?) = 1. I will show why this choice and Einstein's second equation gives an emergence of structure at a lookback Z=5.65 dex, a time between nucleosynthesis and recombination when the universe was a plasma of photons, protons, electrons, and helium nuclei. The particular strong structure that I approximate is shown in Hartnett and Hirano (2008). The talk is 3 slides. There will be time for questions. References- "Analogies between electricity and gravity", Metrologia 41(2004)S115-S124. books: Laughlin (2005), Feynman(1995), Weinberg (1977), Lorentz, Einstein, Minkowski, and Weyl (English) (1923).

Bartlett, David F.

2011-01-01

429

Einstein, Schwinger, And The Sinusoidal Potential  

NASA Astrophysics Data System (ADS)

Before introducing his cosmological constant, Einstein considered a difficulty with Newtonian theory: a steady-state, infinite Newtonian stellar system cannot exist at all. He wrote : "We may ask ourselves the question whether [this difficulty] can be removed by a modification of the Newtonian theory. First of all we will indicate a method which does not in itself claim to be taken seriously; it merely serves as a foil for what is to follow. In place of Poisson's equation we write ?? - ? ? = 4 ? G?, where G denotes a universal constant. If ? be the uniform density of a distribution of mass, then ?=-4? G?/? is a solution.” Einstein considered ? to be a positive number. Einstein discarded this foil because it is incompatible with his famed equation for general relativity. In 2004 Bartlett proposed a graviton of imaginary mass and a photon of real mass both equal to 10-25eV. Thus fg = -(GM/r)[cos(k0r)] and fe = (Q/r)[exp(-k0r)]. Classically, this graviton satisfies Einstein's first equation with k02 = -?. Empirically, the value of k0 is 2 ?/?0 with wavelength ?0= Ro / 20 = 400 pc. An equivalent absolute value for k02 is (1/2)EH4 2 ? G, where EH is the Hartree energy, 2 × 13.6 eV, with c=(h/2?) = 1. With this choice and Einstein's second equation we show an emergence of structure at a lookback Z=5.65 dex, a time between nucleosynthesis and recombination when the universe was a plasma of photons, protons, electrons, and helium nuclei. The particular strong structure that we approximate is shown in Hartnett and Hirano (2008).

Cumalat, John Perry; Bartlett, D. F.

2011-04-01

430

Einstein and a century of time  

NASA Astrophysics Data System (ADS)

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 Year of Physics is called Einstein Year in the UK. Of course one can argue that progress in science depends on the contributions of many people; that there are other geniuses in physics, even some colourful personalities. Nevertheless there are fundamental reasons why Einstein's early achievements stand out even in their company. When at last the thought came to him that 'time itself was suspect', Einstein had found a new insight into the nature of the physical universe. It is this: that the universal properties of material objects tell us about the nature of space and time, and it is through these properties, not philosophical logic or common sense, that we discover the structure of spacetime. The later Einstein turned this successful formula on its head and sought to use the properties of spacetime to define those of material objects, thereby seeking to abolish matter entirely in favour of geometry. Before I introduce this special feature of European Journal of Physics I will say a few words about what is not here. Like all great geniuses Einstein can be seen as the climax of what went before him and the initiation of what was to follow. Looking back we can see the influence of Mach's positivism, according to which the role of science is to relate observations to other observations; hence only observations can tell us what is 'real'. But Einstein also grew up with the family electromechanical businesses, which testifies to the reality of the Maxwellian electromagnetic fields: thus only theory can tell us what is real! As is well known, Einstein himself refused to accept the full consequences of this pivotal insight into the role of theory when it came to quantum mechanics. Much has been written about this and we do not add to it in this collection. Quantum theory is a consistent description of nature whatever Einstein may think of 'god' for making it so. Many of us would side with Einstein in hoping it will yet turn out not to be a complete description. This will not happen, as Einstein hoped throughout his later work, from a return to classical field theory. But quantum behaviour is a universal property of matter and may therefore be expected, according to Einstein's way of thought, to have a geometrical origin. The advent of non-commutative quantum geometries may turn out to be a step in this direction. My own introduction to Einstein's physics was through what has come to be known as Mach's principle. My research supervisor, Dennis Sciama, in what he always claimed was probably Einstein's last significant scientific conversation, talked with him on this subject, during which Einstein explained that he had abandoned the idea of Mach's principle. This principle had been a guiding thought in the development of general relativity, but superfluous to its final exposition. It can be interpreted variously as the determination of the local compass of inertia by the distant stars, the non-rotation of the Universe or, more restrictedly, as requiring a critical density universe (to generate the right amount of inertia). This last formulation amounts to G??2 approx 1, where ? is the density of the Universe at time ?. This appears to be a classical expression, which would probably be sufficient to relegate Mach's principle to mere historical interest along with the classical unified field theories. It is also usually considered to be accounted for by inflation, which drives the Universe to ?=1. However, we can also think of the expression as saying that the Universe has a Planck mass in a Planck volume at the Planck time: G=(hc / G)1/2(c3 / Gh)3/2(Gh / c5)=1. This suggests that Mach's principle may yet have a surprising role in expressing the fact that the U

Raine, D. J.

2005-09-01

431

Einstein-Rosen “bridge” needs lightlike brane source  

NASA Astrophysics Data System (ADS)

The Einstein-Rosen “bridge” wormhole solution proposed in the classic paper (Einstein and Rosen (1935) [1]) does not satisfy the vacuum Einstein equations at the wormhole throat. We show that the fully consistent formulation of the original Einstein-Rosen “bridge” requires solving Einstein equations of bulk D = 4 gravity coupled to a lightlike brane with a well-defined world-volume action. The non-vanishing contribution of Einstein-Rosen “bridge” solution to the right-hand side of Einstein equations at the throat matches precisely the surface stress-energy tensor of the lightlike brane which automatically occupies the throat (“horizon straddling”) — a feature triggered by the world-volume lightlike brane dynamics.

Guendelman, Eduardo; Kaganovich, Alexander; Nissimov, Emil; Pacheva, Svetlana

2009-11-01

432

Biographies of Albert Einstein -- Mastermind of Theoretical Physics  

E-print Network

Over the years many have written biographies of Einstein. They all based their biographies on primary sources, archival material: memories and letters of people who were in contact with Einstein, Einstein's own recollections; interviews that Einstein had given over the years, and letters of Einstein to his friends - youth friends like Marcel Grossman and Michele Besso and later friends and colleagues like Heinrich Zangger; and especially his love letters with Mileva Mari\\'c. One can demarcate between two types of biographies, namely, Documentary biographies, and, Non-documentary biographies. Non-documentary biographies were written by people who based themselves on documentary biographies and on other non-documentary biographies. Documentary biographies were written by people who knew Einstein personally, and received information from him and from other people who were in personal contact with him. This type can be further divided into two subgroups: books that were written while Einstein was still alive, and...

Weinstein, Galina

2012-01-01

433

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

NASA Astrophysics Data System (ADS)

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.

Holmes, Virginia Iris

2005-03-01

434

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

PubMed Central

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

Gunawardena, Jeremy

2013-01-01

435

Fission time-scale in experiments and in multiple initiation model  

SciTech Connect

Rate of fission for highly-excited nuclei is affected by the viscose character of the systemmotion in deformation coordinates as was reported for very heavy nuclei with Z{sub C} > 90. The long time-scale of fission can be described in a model of 'fission by diffusion' that includes an assumption of the overdamped diabatic motion. The fission-to-spallation ratio at intermediate proton energy could be influenced by the viscosity, as well. Within a novel approach of the present work, the cross examination of the fission probability, time-scales, and pre-fission neutron multiplicities is resulted in the consistent interpretation of a whole set of the observables. Earlier, different aspects could be reproduced in partial simulations without careful coordination.

Karamian, S. A., E-mail: karamian@nrmail.jinr.ru [Joint Institute for Nuclear Research (Russian Federation)

2011-12-15

436

Rapid Dust Formation in Novae: Speed Class and Grain Formation Timescale  

NASA Astrophysics Data System (ADS)

Observations show that the time of onset of dust formation in classical novae depends strongly on their speed class, with dust typically taking longer to form in slower novae. Using empirical relationships of speed class, luminosity and ejection velocity, it can be shown that dust formation timescale is expected to be essentially independent of speed class. However, following a nova outburst the spectrum of the central hot source evolves, with an increasing proportion of the radiation being emitted blue-wards of the Lyman limit. The rate at which the spectrum evolves depends on the speed class. We have therefore refined the simple model by assuming photons at wavelengths shorter than the Lyman limit are absorbed by neutral hydrogen gas internal to the dust formation sites. We find that the dust formation timescale is then dependent on speed class and the predicted relationship agrees well with the observations.

Williams, S. C.; Bode, M. F.; Darnley, M. J.; Zubko, V.; Evans, A.; Shafter, A. W.

2014-12-01

437

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

PubMed

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 (N e ) 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 N e 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 N e were very small (i.e., < 50). On the basis of the comparison of these genetic estimates with published census size data, N e 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

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

2015-02-01

438

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

SciTech Connect

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.

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

2009-12-02

439

Fast stratocumulus adjustment timescale due to entrainment-liquid flux feedback  

NASA Astrophysics Data System (ADS)

We use a mixed-layer model (MLM) and large eddy simulation (LES) to analyze the response timescales of a stratocumulus-topped boundary layer. From the MLM, we find three separate time scales: a slow adjustment timescale associated with boundary layer deepening (on the order of several days); an intermediate timescale associated with thermodynamic adjustment of the boundary layer (approximately one day); and a fast timescale (6-12 hours) associated with entrainment rate feedbacks. We show that the fast scale is due to entrainment-liquid flux (ELF) adjustment, an internal cloud-regulating feedback between entrainment rate and the cloud liquid water path (LWP). A thicker cloud generates more turbulent kinetic energy and an increased entrainment rate which tends to warm and dry the boundary layer, thereby decreasing the cloud thickness (a negative feedback). Through this mechanism, the cloud base quickly adjusts until the entrainment rate and LWP stabilize as entrainment warming balances boundary-layer radiative cooling. We use two cases based on past model intercomparison studies to investigate the fast time scale. The first (DYCOMS RF01) involves a nocturnal stratocumulus-capped mixed layer with idealized radiative forcing. A perturbation to the free tropospheric relative humidity is shown to induce fast adjustment of cloud thickness in the MLM and also in an LES. A second case with realistic radiation used in past for cloud feedback studies (CGILS S12) is used to show that an instantaneous CO2 increase does not elicit a fast response in cloud thickness. However, an instantaneous temperature increase to the whole atmosphere-ocean column induces a cloud thinning with a few hours in both MLM and LES that largely explains the equilibrium response of the cloud layer to this forcing. This fast ELF adjustment suggests that stratocumulus cloud changes likely have a positive feedback on greenhouse warming.

Jones, C. R.; Bretherton, C. S.; Blossey, P. N.

2013-12-01

440

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

Microsoft Academic Search

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

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

1998-01-01

441

OPTICAL AND INFRARED PHOTOMETRY OF THE BLAZAR PKS 0537-441: LONG AND SHORT TIMESCALE VARIABILITY  

SciTech Connect

We present a large collection of photometric data on the blazar PKS 0537-441 in the VRIJHK bands taken in 2004-2009. At least three flare-like episodes with months duration and >3 mag amplitude are apparent. The spectral energy distribution is consistent with a power law, and no indication of a thermal component is found. We searched for short timescale variability, and an interesting event was identified in the J band, with a duration of {approx}25 minutes.

Impiombato, D.; Treves, A. [Universita dell'Insubria, Dipartimento di Fisica e Matematica, Via Valleggio 11, 22100 Como (Italy); Covino, S.; Foschini, L.; Fugazza, D. [INAF, Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (Saint Lucia) (Italy); Pian, E. [INAF, Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34131 Trieste (Italy); Tosti, G.; Ciprini, S. [Universita di Perugia, Dipartimento di Fisica e Osservatorio Astronomico, Via A. Pascoli, 06123 Perugia (Italy); Nicastro, L. [INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Via Gobetti 101, 40129 Bologna (Italy)

2011-01-15

442

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

PubMed Central

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

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

2015-01-01

443

Evaluating timescales of carbon turnover in temperate forest soils with radiocarbon data  

Microsoft Academic Search

Timescales of soil organic carbon (SOC) turnover in forests were investigated with soil radiocarbon data. The 12C\\/14C ratios were measured by accelerated mass spectroscopy on soil sampled from a deciduous temperate forest in Switzerland during 1969-1995. The resulting Delta14C values (125-1740\\/00) were in line with previously published 14C soil data. We applied FORCLIM-D, a model of nonliving organic matter decomposition

Daniel Perruchoud; Fortunat Joos; Andreas Fischlin; Irka Hajdas; Georges Bonani

1999-01-01

444

Evaluating Timescales of Carbon Turnover in Temperate Forest Soils With Radiocarbon Data  

Microsoft Academic Search

Timescales of soil organic carbon (SOC) turnover in forests were investigated with soil radiocarbon data. The 12CP4C ratios were measured by accelerated mass spectroscopy on soil sampled from a deciduous temperate forest in Switzerland during 1969-1995. The resulting ~14C values (125-174%0) were in line with previously published 14C soil data. We applied FORCLIM-D, a model of nonliving organic matter decomposition

Daniel Perruchoud; Fortunat Joos; Andreas Fischlin; Irka Hajdas; Georges Bonani

1999-01-01

445

Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years  

Microsoft Academic Search

We generated ~200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29-202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we use a benthic delta13C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the

Delia W. Oppo; Scott J. Lehman

1995-01-01

446

Suborbital timescale variability of North Atlantic Deep Water during the past 200,000 years  

Microsoft Academic Search

We generated ?200-kyr-long proxy records of surface and deepwater variability from a subpolar North Atlantic core (V29–202), enabling us to assess the linkage between surface and deepwater changes on suborbital timescales. In particular, we used a benthic ?13C record to evaluate the deep water response to Dansgaard-Oeschger temperature oscillations and to Heinrich events, times of massive iceberg delivery to the

Delia W. Oppo; Scott J. Lehman

1995-01-01

447

Timescales of destructive plate margin magmatism: new insights from Santorini, Aegean volcanic arc  

Microsoft Academic Search

The timescales of element transfer at volcanic arcs provide important insights into magma generation, movement and storage beneath destructive margin volcanoes. Here we present major, trace and Sr-, Nd- and U-series isotope data on <200 ka old samples from Santorini in the Aegean volcanic arc as a case study of a hazardous destructive margin volcano. Samples range from low-K calc-alkaline

Georg Zellmer; Simon Turner; Chris Hawkesworth

2000-01-01

448

North–South Precipitation Patterns in Western North America on Interannual-to-Decadal Timescales  

Microsoft Academic Search

The overall amount of precipitation deposited along the West Coast and western cordillera of North America from 258 to 558N varies from year to year, and superimposed on this domain-average variability are varying north-south contrasts on timescales from at least interannual to interdecadal. In order to better understand the north-south precipitation contrasts, their interannual and decadal variations are studied in

Michael D. Dettinger; Daniel R. Cayan; Henry F. Diaz; David M. Meko

1998-01-01

449

Oceanic Climate Variability at Millennial Time-Scales: Models of Climate Connections  

Microsoft Academic Search

One of the most exciting questions in palaeoclimatology is the study of the complex interactions between the different components\\u000a of the climate system in order to understand how climate changes occur at Milankovitch as well as at millennial and centennial\\u000a time-scales. The primary objective of this paper is to place the PEP III transect palaeo-data within a global climate context

Laurence Vidal; Helge Arz

450

Non-parametric techniques for pitch-scale and time-scale modification of speech  

Microsoft Academic Search

Time-scale and, to a lesser extent, pitch-scale modifications of speech and audio signals are the subject of major theoretical and practical interest. Applications are numerous, including, to name but a few, text-to-speech synthesis (based on acoustical unit concatenation), transformation of voice characteristics, foreign language learning but also audio monitoring or film\\/soundtrack post-synchronization. To fulfill the need for high-quality time and

Eric Moulines; Jean Laroche

1995-01-01

451

The Semiclassical Einstein Equation on Cosmological Spacetimes  

E-print Network

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...

Siemssen, Daniel

2015-01-01

452

Relativistic Bose-Einstein condensation with disorder  

E-print Network

We investigate the thermodynamics of a self-interacting relativistic charged scalar field in the presence of weak disorder. We consider quenched disorder which couples linearly to the mass of the scalar field. After performing noise averages over the free energy of the system, we find that disorder increases the mean-field critical temperature for Bose-Einstein condensation at finite density. The effect of disorder on the temperature dependence of the chemical potential for a fixed charge density is investigated. Significant differences from the mean-field temperature dependence of the chemical potential are observed as the strength of the noise intensity increases. Finally, the temperature dependence of the chemical potential with fixed total charge and entropy is investigated. It is found that there is no Bose-Einstein condensation for a fixed charge to entropy ratio in the presence of weak disorder. The possible relevance of the findings in the present paper in different areas is discussed.

E. Arias; G. Krein; G. Menezes; N. F. Svaiter

2014-10-26

453

Two Versions of Gravity: Newton and Einstein  

NSDL National Science Digital Library

The goal of this lesson is for two groups of students to exchange information (e.g., through poster presentations, Podcasts, debates, or PowerPoint presentations) about how two different theories explain a natural phenomenon: Newton's Law of Gravitation and Einstein's General Theory of Relativity. The lesson will also illustrate how the scientific process allows a new, more complete theory to take the place of an older theory that does not produce accurate results for a new discovery. Students will need to have either studied both Newton's Law of Gravitation and Einstein's Theory of Relativity or be given the time and resources to look up this information. This lesson is part of the Cosmic Times teachers guide and is intended to be used in conjunction with the 1919 Cosmic Times Poster.

2012-08-03

454

How Einstein Discovered E0=mc2  

NASA Astrophysics Data System (ADS)

This paper traces Einstein's discovery of "the equivalence of mass [m] and energy [E0]." He came to that splendid insight in 1905 while employed by the Bern Patent Office, at which time he was not an especially ardent reader of physics journals. How then did the young savant, working outside of academia in semi-isolation, realize that these two seemingly disparate concepts were actually "identical"? Until now little attention has been given to exploring the physics that guided his thinking in this remarkable endeavor. That work culminated (1907) in the equation E0=mc2, where E0 is "rest energy" and m is "invariant mass." Despite claims to the contrary, Einstein did not write this equation, or its ambiguous variant, E =mc2, in 1905. Furthermore, we will propose a compelling reason for his otherwise inexplicable caution. This paper is meant to help clarify the contemporary literature in the service of an informed pedagogy.

Hecht, Eugene

2012-02-01

455

Timescales for Low-Mass Star Formation in Extragalactic Environments: Implications for the Stellar IMF  

E-print Network

We investigate the physical and chemical conditions necessary for low-mass star formation in extragalactic environments by calculating various characteristic timescales associated with star formation for a range of initial conditions. The balance of these timescales indicates whether low-mass star formation is enhanced or inhibited under certain physical conditions. In this study, we consider timescales for free-fall, cooling, freeze-out, desorption, chemistry and ambipolar diffusion and their variations with changes in the gas density, metallicity, cosmic ray ionisation rate and FUV radiation field strength. We find that extragalactic systems with high FUV radiation field strengths and high cosmic ray fluxes considered at a range of metallicities, are likely to have enhanced low-mass star formation unless the magnetic pressure is sufficient to halt collapse. Our results indicate that this is only likely to be the case for high-redshift galaxies approaching solar metallicities. Unless this is true for all high-redshift sources, this study finds little evidence for a high-mass biased IMF at high redshifts.

Manda Banerji; Serena Viti; David A. Williams; Jonathan M. C. Rawlings

2008-10-20

456

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

PubMed

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 Abeta peptide fragment (Abeta(21-43)). Abeta oligomers are now widely recognized as the primary neurotoxic structures leading to Alzheimer's disease. Our computational methods predict that Abeta trimers form at micromolar concentrations in 10 ms, 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 Abeta in an experimentally verifiable manner. PMID:19063575

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

2008-12-01

457

Gravitational Microlensing by Neutron Stars and Radio Pulsars: Event Rates, Timescale Distributions, and Mass Measurements  

NASA Astrophysics Data System (ADS)

We investigate properties of Galactic microlensing events in which a stellar object is lensed by a neutron star. For an all-sky photometric microlensing survey, we determine the number of lensing events caused by ? {{10}5} potentially observable radio pulsars to be ? 0.2 y{{r}-1} for 1010 background stellar sources. We expect a few detectable events per year for the same number of background sources from an astrometric microlensing survey. We show that such a study could lead to precise measurements of radio pulsar masses. For instance, if a pulsar distance could be constrained through radio observations, then its mass would be determined with a precision of ? 10%. We also investigate the timescale distributions for neutron star events, finding that they are much shorter than had been previously thought. For photometric events toward the Galactic center that last ?15 days, around 7% will have a neutron star lens. This fraction drops rapidly for longer timescales. Away from the bulge region we find that neutron stars will contribute ? 40% of the events that last less than ?10 days. These results are in contrast to earlier work which found that the maximum fraction of neutron star events would occur on timescales of hundreds of days.

Dai, S.; Smith, M. C.; Lin, M. X.; Yue, Y. L.; Hobbs, G.; Xu, R. X.

2015-04-01

458

Insights into the mechanisms and timescales of pluton assembly from deformation patterns of mafic enclaves  

NASA Astrophysics Data System (ADS)

We propose a novel method to constrain both timescales and assembly styles of intrusive bodies using the strain recorded by mafic enclaves, a common component of granitic rocks. Petrology, thermal modeling, and magma rheology are combined to investigate the evolution of strain recorded by enclaves during the piecemeal assembly of a pluton growing at various rates of magma input. The different compositions (and hence phase relations) of host magma and enclaves limits homogeneous deformation of these two materials to restricted temperature ranges, which we term "windows of mutual deformability." Outside these windows only the less viscous host granite records any appreciable deformation and enclaves are mainly transported as rigid objects. The temporal and spatial development of the windows of mutual deformability reflects the emplacement rate of magmas into the pluton. Consequently, the radial distribution of strain recorded by enclaves can provide a picture of the thermal and rheological evolution of a magmatic body during its construction. Our approach is applied to deformation patterns of mafic enclaves in the Lago della Vacca Complex (LVC) of the Adamello Massif (Italy), to estimate the timescales of pluton emplacement. Our calculations suggest total emplacement timescales of the order 50 to 150 ky, in excellent agreement with recent high precision radiometric dating of zircons from the LVC.

Caricchi, Luca; Annen, Catherine; Rust, Alison; Blundy, Jon

2012-11-01

459

Dynamics on multiple timescales in the RNA-directed RNA polymerase from the cystovirus ?6  

PubMed Central

The de novo initiating RNA-directed RNA polymerase (RdRP), P2, forms the central machinery in the infection cycle of the bacteriophage ?6 by performing the dual tasks of replication and transcription of the double-stranded RNA genome in the host cell. By measurement and quantitative analysis of multiple-quantum spin-relaxation data for the ?1 positions of Ile residues that are distributed over the 3D-fold of P2, we find that the enzyme is dynamic both on the fast (ps–ns) and slow (µs–ms) timescales. The characteristics of several motional modes including those that coincide with the catalytic timescale (500–800/s) are altered in the presence of substrate analogs and single-stranded RNA templates. These studies reveal the plasticity of this finely tuned molecular machine and represent a first step towards linking structural information available from a host of crystal structures to catalytic mechanisms and timescales obtained from the measurements of kinetics for homologous systems in solution. PMID:20385578

Ren, Zhen; Wang, Hsin; Ghose, Ranajeet

2010-01-01

460

Diversity of timescale promotes the maintenance of extortioners in a spatial prisoner’s dilemma game  

NASA Astrophysics Data System (ADS)

Recently, a class of interesting strategies, named extortion strategies, has attracted considerable attention since such extortion strategies can dominate any opponent in a repeated prisoner's dilemma game. In this paper, we investigate the influence of the strategy-selection timescale on the evolution of extortion and cooperation in networked systems. Through connecting the lifetime of individuals’ strategies with their fitness, we find that extortioners can form long-term stable relationships with cooperative neighbors, whereas the lifetime of a defection strategy is short according to the myopic best response rule. With the separation of interaction and strategy-updating timescales, the extortioners in a square lattice are able to form stable, cross-like structures with cooperators due to the snowdrift-like relation. In scale-free networks the hubs are most likely occupied by extortioners, who furthermore induce their low-degree neighbors to behave as cooperators. Since extortioners in scale-free networks can meet more cooperators than their counterparts in the square lattice, the latter results in higher average fitness of the whole population than the former. The extortioners play the role of a catalyst for the evolution of cooperation, and the diversity of strategy-selection timescale furthermore promotes the maintenance of extortioners with cooperators in networked systems.

Rong, Zhihai; Wu, Zhi-Xi; Hao, Dong; Chen, Michael Z. Q.; Zhou, Tao

2015-03-01

461

Layered decomposition for the model order reduction of timescale separated biochemical reaction networks.  

PubMed

Biochemical reaction networks tend to exhibit behaviour on more than one timescale and they are inevitably modelled by stiff systems of ordinary differential equations. Singular perturbation is a well-established method for approximating stiff systems at a given timescale. Standard applications of singular perturbation partition the state variable into fast and slow modules and assume a quasi-steady state behaviour in the fast module. In biochemical reaction networks, many reactants may take part in both fast and slow reactions; it is not necessarily the case that the reactants themselves are fast or slow. Transformations of the state space are often required in order to create fast and slow modules, which thus no longer model the original species concentrations. This paper introduces a layered decomposition, which is a natural choice when reaction speeds are separated in scale. The new framework ensures that model reduction can be carried out without seeking state space transformations, and that the effect of the fast dynamics on the slow timescale can be described directly in terms of the original species. PMID:24732263

Prescott, Thomas P; Papachristodoulou, Antonis

2014-09-01

462

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

463

Cascade time-scales for energy and helicity in homogeneous isotropic turbulence  

E-print Network

We extend the Kolmogorov phenomenology for the scaling of energy spectra in high-Reynolds number turbulence, to explicitly include the effect of helicity. There exists a time-scale $\\tau_H$ for helicity transfer in homogeneous, isotropic turbulence with helicity. We arrive at this timescale using the phenomenological arguments used by Kraichnan to derive the timescale $\\tau_E$ for energy transfer (J. Fluid Mech. {\\bf 47}, 525--535 (1971)). We show that in general $\\tau_H$ may not be neglected compared to $\\tau_E$, even for rather low relative helicity. We then deduce an inertial range joint cascade of energy and helicity in which the dynamics are dominated by $\\tau_E$ in the low wavenumbers with both energy and helicity spectra scaling as $k^{-5/3}$; and by $\\tau_H$ at larger wavenumbers with spectra scaling as $k^{-4/3}$. We demonstrate how, within this phenomenology, the commonly observed ``bottleneck'' in the energy spectrum might be explained. We derive a wav