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1

Index of refraction for scalar, electromagnetic, and gravitational waves in weak gravitational fields  

Microsoft Academic Search

We consider the solutions of the scattering of scalar, electromagnetic, and gravitational waves by the gravitational field of a single particle, for the case of small wave amplitudes and weak gravitational fields. Scatterings are considered for both incident plane waves and incident spherical waves. For plane waves incident on a thin sheet of matter composed of free particles, the superimposed

P. C. Peters

1974-01-01

2

Interaction of Dirac and Majorana neutrinos with weak gravitational fields  

SciTech Connect

In this paper the interaction of high energy neutrinos with weak gravitational fields is briefly explored. The form of the graviton-neutrino vertex is motivated from Lorentz and gauge invariance and the nonrelativistic interpretations of the neutrino-gravitational form factors are obtained. We comment on the renormalization conditions, the preservation of the weak equivalence principle and the definition of the neutrino mass radius. We associate the neutrino-gravitational form factors with specific angular momentum states. Based on Feynman diagrams, spin-statistics, CP invariance and symmetries of the angular momentum states in the graviton-neutrino vertex, we deduce differences between the Majorana and Dirac cases. It is then proved that in spite of the theoretical differences between the two cases, as far as experiments are considered, they would be virtually indistinguishable for any space-time geometry satisfying the weak-field condition. We then calculate the transition gravitational form factors for the neutrino by evaluating the relevant Feynman diagrams at 1-loop and estimate a neutrino transition mass radius. The form factor is seen to depend on the momentum transfer very weakly. It is also seen that the neutrino transition mass radius is smaller than the typical neutrino charge radius by a couple of orders of magnitude.

Menon, A.; Thalapillil, Arun M. [Michigan Center for Theoretical Physics and Department of Physics, University of Michigan, 500 East University Avenue, Michigan 48109-1120 (United States); Enrico Fermi Institute and Department of Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States)

2008-12-01

3

The generation of gravitational waves. I - Weak-field sources  

NASA Technical Reports Server (NTRS)

This paper derives and summarizes a 'plug-in-and-grind' formalism for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, the formalism reduces to standard 'linearized theory'. Independent of the effects of gravity on the motions, the formalism reduces to the standard 'quadrupole-moment formalism' if the motions are slow and internal stresses are weak. In the general case, the formalism expresses the radiation in terms of a retarded Green's function for slightly curved spacetime and breaks the Green's function integral into five easily understood pieces: direct radiation, produced directly by the motions of the source; whump radiation, produced by the 'gravitational stresses' of the source; transition radiation, produced by a time-changing time delay ('Shapiro effect') in the propagation of the nonradiative 1/r field of the source; focusing radiation, produced when one portion of the source focuses, in a time-dependent way, the nonradiative field of another portion of the source; and tail radiation, produced by 'back-scatter' of the nonradiative field in regions of focusing.

Thorne, K. S.; Kovacs, S. J.

1975-01-01

4

Weak gravitational field in Finsler-Randers space and Raychaudhuri equation  

NASA Astrophysics Data System (ADS)

The linearized form of the metric of a Finsler-Randers space is studied in relation to the equations of motion, the deviation of geodesics and the generalized Raychaudhuri equation are given for a weak gravitational field. This equation is also derived in the framework of a tangent bundle. By using Cartan or Berwald-like connections we get some types "gravito-electromagnetic" curvature. In addition we investigate the conditions under which a definite Lagrangian in a Randers space leads to Einstein field equations under the presence of electromagnetic field. Finally, some applications of the weak field in a generalized Finsler spacetime for gravitational waves are given.

Stavrinos, P. C.

2012-12-01

5

Weak Gravitational Field in Finsler-Randers Space and Raychaudhuri Equation  

E-print Network

The linearized form of the metric of a Finsler - Randers space is studied in relation to the equations of motion, the deviation of geodesics and the generalized Raychaudhuri equation are given for a weak gravitational field. This equation is also derived in the framework of a tangent bundle. By using Cartan or Berwald-like connections we get some types "gravito - electromagnetic" curvature. In addition we investigate the conditions under which a definite Lagrangian in a Randers space leads to Einstein field equations under the presence of electromagnetic field. Finally, some applications of the weak field in a generalized Finsler spacetime for gravitational waves are given.

Stavrinos, P

2012-01-01

6

Weak Gravitational Field in Finsler-Randers Space and Raychaudhuri Equation  

E-print Network

The linearized form of the metric of a Finsler - Randers space is studied in relation to the equations of motion, the deviation of geodesics and the generalized Raychaudhuri equation are given for a weak gravitational field. This equation is also derived in the framework of a tangent bundle. By using Cartan or Berwald-like connections we get some types "gravito - electromagnetic" curvature. In addition we investigate the conditions under which a definite Lagrangian in a Randers space leads to Einstein field equations under the presence of electromagnetic field. Finally, some applications of the weak field in a generalized Finsler spacetime for gravitational waves are given.

P. Stavrinos

2012-09-13

7

Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

This chapter reviews the data mining methods recently developed to solve standard data problems in weak gravitational lensing. We detail the different steps of the weak lensing data analysis along with the different techniques dedicated to these applications. An overview of the different techniques currently used will be given along with future prospects. Until about 30 years ago, astronomers thought that the Universe was composed almost entirely of ordinary matter: protons, neutrons, electrons, and atoms. The field of weak lensing has been motivated by the observations made in the last decades showing that visible matter represents only about 4-5% of the Universe (see Figure 14.1). Currently, the majority of the Universe is thought to be dark, that is, does not emit electromagnetic radiation. The Universe is thought to be mostly composed of an invisible, pressure less matter - potentially relic from higher energy theories - called "dark matter" (20-21%) and by an even more mysterious term, described in Einstein equations as a vacuum energy density, called "dark energy" (70%). This "dark" Universe is not well described or even understood; its presence is inferred indirectly from its gravitational effects, both on the motions of astronomical objects and on light propagation. So this point could be the next breakthrough in cosmology. Today's cosmology is based on a cosmological model that contains various parameters that need to be determined precisely, such as the matter density parameter Omega_m or the dark energy density parameter Omega_lambda. Weak gravitational lensing is believed to be the most promising tool to understand the nature of dark matter and to constrain the cosmological parameters used to describe the Universe because it provides a method to directly map the distribution of dark matter (see [1,6,60,63,70]). From this dark matter distribution, the nature of dark matter can be better understood and better constraints can be placed on dark energy, which affects the evolution of structures. Gravitational lensing is the process by which light from distant galaxies is bent by the gravity of intervening mass in the Universe as it travels toward us. This bending causes the images of background galaxies to appear slightly distorted, and can be used to extract important cosmological information. In the beginning of the twentieth century, A. Einstein predicted that massive bodies could be seen as gravitational lenses that bend the path of light rays by creating a local curvature in space time. One of the first confirmations of Einstein's new theory was the observation during the 1919 solar eclipse of the deflection of light from distant stars by the sun. Since then, a wide range of lensing phenomena have been detected. The gravitational deflection of light by mass concentrations along light paths produces magnification, multiplication, and distortion of images. These lensing effects are illustrated by Figure 14.2, which shows one of the strongest lenses observed: Abell 2218, a very massive and distant cluster of galaxies in the constellation Draco. The observed gravitational arcs are actually the magnified and strongly distorted images of galaxies that are about 10 times more distant than the cluster itself. These strong gravitational lensing effects are very impressive but they are very rare. Far more prevalent are weak gravitational lensing effects, which we consider in this chapter, and in which the induced distortion in galaxy images is much weaker. These gravitational lensing effects are now widely used, but the amplitude of the weak lensing signal is so weak that its detection relies on the accuracy of the techniques used to analyze the data. Future weak lensing surveys are already planned in order to cover a large fraction of the sky with high accuracy, such as Euclid [68]. However, improving accuracy also places greater demands on the methods used to extract the available information.

Pires, Sandrine; Starck, Jean-Luc; Leonard, Adrienne; Réfrégier, Alexandre

2012-03-01

8

Gravitational lensing beyond the weak-field approximation  

SciTech Connect

Gravitational lensing is considered in the full spacetime formalism of general relativity, assuming that the light rays are lightlike geodesics in a Lorentzian manifold. The review consists of three parts. The first part is devoted to spherically symmetric and static spacetimes. In particular, an exact lens map for this situation is discussed. The second part is on axisymmetric and stationary spacetimes. It concentrates on the investigation of the photon region, i.e., the region filled by spherical lightlike geodesics, in the Kerr spacetime. The photon region is of crucial relevance for the formation of a shadow. Finally, the third part briefly addresses two topics that apply to spacetimes without symmetry, namely Fermat’s principle and the exact lens map of Frittelli and Newman.

Perlick, Volker, E-mail: perlick@zarm.uni-bremen.de [ZARM, University of Bremen, 28359 Bremen (Germany)

2014-01-14

9

Gravitational lensing beyond the weak-field approximation  

NASA Astrophysics Data System (ADS)

Gravitational lensing is considered in the full spacetime formalism of general relativity, assuming that the light rays are lightlike geodesics in a Lorentzian manifold. The review consists of three parts. The first part is devoted to spherically symmetric and static spacetimes. In particular, an exact lens map for this situation is discussed. The second part is on axisymmetric and stationary spacetimes. It concentrates on the investigation of the photon region, i.e., the region filled by spherical lightlike geodesics, in the Kerr spacetime. The photon region is of crucial relevance for the formation of a shadow. Finally, the third part briefly addresses two topics that apply to spacetimes without symmetry, namely Fermat's principle and the exact lens map of Frittelli and Newman.

Perlick, Volker

2014-01-01

10

Relativistic Phase Shifts for Dirac Particles Interacting with Weak Gravitational Fields in Matter—Wave Interferometers  

Microsoft Academic Search

We present a second-quantized field theory of massive spin one-half particles or antiparticles in the presence of a weak gravitational\\u000a field treated as a spin two external field in a flat Minkowski background. We solve the difficulties which arise from the\\u000a derivative coupling and we are able to introduce an interaction picture. We derive expressions for the scattering amplitude\\u000a and

Christian J. Borde; Jean-Claude Houard; Alain Karasiewicz

2001-01-01

11

Weak-field approximation of effective gravitational theory with local Galilean invariance  

NASA Astrophysics Data System (ADS)

We examine the weak-field approximation of locally Galilean invariant gravitational theories with general covariance in a (4 + 1)-dimensional Galilean framework. The additional degrees of freedom allow us to obtain Poisson, diffusion, and Schrödinger equations for the fluctuation field. An advantage of this approach over the usual (3 + 1)-dimensional General Relativity is that it allows us to choose an ansatz for the fluctuation field that can accommodate the field equations of the Lagrangian approach to MOdified Newtonian Dynamics (MOND) known as AQUAdratic Lagrangian (AQUAL). We investigate a wave solution for the Schrödinger equations.

Cuzinatto, R. R.; Pompeia, P. J.; de Montigny, M.; Khanna, F. C.

2009-09-01

12

Multiscale analysis of the electromagnetic self-force in a weak gravitational field  

SciTech Connect

We examine the motion of a charged particle in a weak gravitational field. In addition to the Newtonian gravity exerted by a large central body, the particle is subjected to an electromagnetic self-force that contains both a conservative piece and a radiation-reaction piece. This toy problem shares many of the features of the strong-field gravitational self-force problem, and it is sufficiently simple that it can be solved exactly with numerical methods, and approximately with analytical methods. We submit the equations of motion to a multiscale analysis, and we examine the roles of the conservative and radiation-reaction pieces of the self-force. We show that the radiation-reaction force drives secular changes in the orbit's semilatus rectum and eccentricity, while the conservative force drives a secular regression of the periapsis and affects the orbital time function; neglect of the conservative term can hence give rise to an important phasing error. We next examine what might be required in the formulation of a reliable secular approximation for the orbital evolution; this would capture all secular changes in the orbit and discard all irrelevant oscillations. We conclude that such an approximation would be very difficult to formulate without prior knowledge of the exact solution.

Pound, Adam; Poisson, Eric [Department of Physics, University of Guelph, Guelph, Ontario, N1G 2W1 (Canada)

2008-02-15

13

Breakdown of the Equivalence between Energy Content and Weight in a Weak Gravitational Field for a Quantum Body  

E-print Network

It is shown that weight operator of a composite quantum body in a weak external gravitational field in the post-Newtonian approximation of the General Relativity does not commute with its energy operator, taken in the absence of the field. Nevertheless, the weak equivalence between the expectations values of weight and energy is shown to survive at a macroscopic level for stationary quantum states for the simplest composite quantum body - a hydrogen atom. Breakdown of the weak equivalence between weight and energy at a microscopic level for stationary quantum states can be experimentally detected by studying unusual electromagnetic radiation, emitted by the atoms, supported and moved in the Earth gravitational field with constant velocity, using spacecraft or satellite. For superpositions of stationary quantum states, a breakdown of the above mentioned equivalence at a macroscopic level leads to time dependent oscillations of the expectation values of weight, where the equivalence restores after averaging over time procedure.

Andrei Lebed

2012-05-14

14

The generation of gravitational waves. 1. Weak-field sources: A plug-in-and-grind formalism  

NASA Technical Reports Server (NTRS)

A plug-in-and-grind formalism is derived for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, then the formalism reduces to standard linearized theory. Whether or not gravity affects the motions, if the motions are slow and internal stresses are weak, then the new formalism reduces to the standard quadrupole-moment formalism. In the general case the new formalism expresses the radiation in terms of a retarded Green's function for slightly curved spacetime, and then breaks the Green's-function integral into five easily understood pieces: direct radiation, produced directly by the motions of the sources; whump radiation, produced by the the gravitational stresses of the source; transition radiation, produced by a time-changing time delay (Shapiro effect) in the propagation of the nonradiative, 1/r field of the source; focussing radiation produced when one portion of the source focusses, in a time-dependent way, the nonradiative field of another portion of the source, and tail radiation, produced by backscatter of the nonradiative field in regions of focussing.

Thorne, K. S.; Kovacs, S. J.

1974-01-01

15

Weak gravitational lensing with SKA  

E-print Network

I shall outline the basic principles and some observational aspects of weak gravitational lensing, and discuss several applications of this powerful tool in observational cosmology. It will be explained why the applications have been restricted to optical observations up to now, and why SKA is going to change this. I conclude with a few general remarks on a comparison between SKA and the NGST, both being facilities which will provide a tremendous step forward in radio and near-IR astronomy, respectively, into completely unknown territory.

Peter Schneider

1999-07-12

16

Rabi oscillations in gravitational fields: Exact solution  

Microsoft Academic Search

The exact solution for a two-level atom interacting with a laser field in a gravitational field is given. The modifications due to a weak gravitational field are discussed and some applications are proposed.

Claus Lämmerzahl; Christian J. Bordé

1995-01-01

17

Poisson equation for weak gravitational lensing  

SciTech Connect

Using the Newman and Penrose [E. T. Newman and R. Penrose, J. Math. Phys. (N.Y.) 3, 566 (1962).] spin-coefficient formalism, we examine the full Bianchi identities of general relativity in the context of gravitational lensing, where the matter and space-time curvature are projected into a lens plane perpendicular to the line of sight. From one component of the Bianchi identity, we provide a rigorous, new derivation of a Poisson equation for the projected matter density where the source term involves second derivatives of the observed weak gravitational lensing shear. We also show that the other components of the Bianchi identity reveal no new results. Numerical integration of the Poisson equation in test cases shows an accurate mass map can be constructed from the combination of a ground-based, wide-field image and a Hubble Space Telescope image of the same system.

Kling, Thomas P.; Campbell, Bryan [Department of Physics, Bridgewater State College, Bridgewater, Massachusetts 02325 (United States)

2008-06-15

18

Weak gravitational lensing of intrinsically aligned galaxies  

NASA Astrophysics Data System (ADS)

Subject of this paper is the weak lensing effect on galaxies that show intrinsically correlated ellipticities. In our model, we investigate the distortion of the ellipticity field if the galaxies experience an apparent shift in their position by weak lensing deflection and compare this effect to the shearing effect induced by tidal fields. Starting with a derivation of intrinsic ellipticity spectra by employing a tidal torquing model generating galactic angular momenta, we model the galaxy ellipticity by assuming that the galactic disc forms perpendicularly to the host halo angular momentum direction and derives intrinsic ellipticity E-mode and B-mode spectra from the angular momentum statistics. The lensing effect on the ellipticity field is modelled by employing the methodology developed in the framework of lensing of the cosmic microwave background polarization. For Euclid, ellipticity correlations are altered by lensing deflection on multipoles ? ? 1000 by ˜5 per cent for the ellipticity E modes and ˜30 per cent for the B modes, while a shallower survey would exhibit larger changes on larger angular scales. In addition to the convolving effect of lensing on the ellipticity spectra, we investigate the E/B-mode conversion and discuss the possibility of measuring correlations between different multipoles, which is evoked by the homogeneity breaking effect of the lensing displacement. Our conclusion is that although shape correlations generated by weak gravitational shear is dominant, the shifting effect due to lensing is shaping the ellipticity spectra on small angular scales and causing a number of interesting phenomena, which might be observable by future surveys.

Giahi-Saravani, Aram; Schäfer, Björn Malte

2014-01-01

19

Copenhagen Quantum Mechanics Emerges from a Deterministic Schroedinger Theory in 11 Dimensional Spacetime Including Weak Field Gravitation  

E-print Network

We construct a world model consisting of a matter field living in 4 dimensional spacetime and a gravitational field living in 11 dimensional spacetime. The seven hidden dimensions are compactified within a radius estimated by reproducing the particle - wave characteristic of diffraction experiments. In the presence of matter fields the gravitational field develops localized modes with elementary excitations called gravonons which are induced by the sources (massive particles). The final world model treated here contains only gravonons and a scalar matter field. The solution of the Schroedinger equation for the world model yields matter fields which are localized in the 4 dimensional subspace. The localization has the following properties: (i) There is a chooser mechanism for the selection of the localization site. (ii) The chooser selects one site on the basis of minor energy differences and differences in the gravonon structure between the sites, which appear statistical. (iii) The changes from one localization site to a neighbouring one take place in a telegraph-signal like manner. (iv) The times at which telegraph like jumps occur dependent on subtleties of the gravonon structure which appear statistical. (v) The fact that the dynamical law acts in the configuration space of fields living in 11 dimensional spacetime lets the events observed in 4 dimensional spacetime appear non-local. In this way the phenomenology of Copenhagen quantum mechanics is obtained without the need of introducing the process of collapse and a probabilistic interpretation of the wave function. Operators defining observables need not be introduced. All experimental findings are explained in a deterministic way as a consequence of the time development of the wave function in configuration space according to Schroedinger's equation.

Gerold Doyen; Deiana Drakova

2014-08-12

20

On Gravitational anomaly and Hawking radiation near weakly isolated horizon  

E-print Network

Based on the idea of the work by Wilczek and his collaborators, we consider the gravitational anomaly near weekly isolated horizon. We find that there exists a universal choice of tortoise coordinate for any weakly isolated horizon. Under this coordinate, the leading behavior of a quite arbitrary scalar field near horizon is a 2-dimensional chiral scalar field. This means we can extend the idea of Wilczek and his collaborators to more general cases and show the relation between gravitational anomaly and Hawking radiation is a universal property of black hole horizon.

Xiaoning Wu; Chao-Guang Huang; Jia-Rui Sun

2008-01-09

21

Weak 'Antigravity' Fields in General Relativity  

Microsoft Academic Search

Within the weak-field approximation of general relativity, new exact\\u000asolutions are derived for the gravitational field of a mass moving with\\u000aarbitrary velocity and acceleration. A mass having a constant velocity greater\\u000athan 3^-1\\/2 times the speed of light gravitationally repels other masses at\\u000arest within a narrow cone. At high Lorentz factors (gamma >> 1), the force of\\u000arepulsion

F. S. Felber

2005-01-01

22

Resonant Interaction Between a Weak Gravitational Wave and a Microwave Beam in the Double Polarized States Through a Static Magnetic Field  

E-print Network

We investigate the resonant interaction to the weak gravitational waves in a coupling electromagnetic system, which consists of a Gaussian beam with the double polarized transverse electric modes, a static magnetic field and the fractal membranes. We find that under the syncroresonance condition a high-frequency GW (HFGW) of h=10^-30,v_g=3GHz may produce the perturbative photon flux (PPF) of 2.15*10/s in a surface of 0.01m^2. The PPF can be pumped out from the background photon fluxes and one might obtain the amplified signal photon flux of 2.15*10^4s^-1 by cascade fractal membranes. It appears to be worthwhile to study this effect for the detection of the high-frequency relic GWs in quintessential inflationary models and the HFGWs expected by possible laboratory schemes.

Fang-Yu Li; Nan Yang

2004-10-14

23

Galaxy Halo Masses from Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

In this review, I discuss the use of galaxy-galaxy weak lensing measurements to study the masses of dark matter halos in which galaxies reside. After summarizing how weak gravitational lensing measurements can be interpreted in terms of halo mass, I review measurements that were used to derive the relationship between optical galaxy mass tracers, such as stellar mass or luminosity, and dark matter halo mass. Measurements of galaxy-galaxy lensing from the past decade have led to increasingly tight constraints on the connection between dark matter halo mass and optical mass tracers, including both the mean relationships between these quantities and the intrinsic scatter between them. I also review some of the factors that can complicate analysis, such as the choice of modeling procedure, and choices made when dividing up samples of lens galaxies.

Mandelbaum, Rachel

2015-04-01

24

On Weak Fields in Finsler Spaces  

E-print Network

It is shown that in the weak field approximation the new geometrical approach can lead to the linear field equations for the several independent fields. For the stronger fields and in the second order approximation the field equations become non-linear, and the fields become dependent. This breaks the superposition principle for every separate field and produces the interaction between different fields.The unification of the gravitational and electromagnetic field theories is performed in frames of the geometrical approach in the pseudo Riemannian space and in the curved Berwald-Moor space.

G. I. Garas'ko

2007-09-17

25

Weak Gravitational Lensing in Fourth Order Gravity  

E-print Network

For a general class of analytic $f(R,R_{\\alpha\\beta}R^{\\alpha\\beta},R_{\\alpha\\beta\\gamma\\delta}R^{\\alpha\\beta\\gamma\\delta})$ we discuss the gravitational lensing in the Newtonian Limit of theory. From the properties of Gauss Bonnet invariant it is successful to consider only two curvature invariants between the Ricci and Riemann tensor. Then we analyze the dynamics of photon embedded in a gravitational field of a generic $f(R,R_{\\alpha\\beta}R^{\\alpha\\beta})$-Gravity. The metric is time independent and spherically symmetric. The metric potentials are Schwarzschild-like, but there are two additional Yukawa terms linked to derivatives of $f$ with respect to two curvature invariants. Considering the case of a point-like lens, and after of a generic matter distribution of lens, we study the deflection angle and the images angular position. Though the additional Yukawa terms in the gravitational potential modifies dynamics with respect to General Relativity, the geodesic trajectory of photon is unaffected by the modification in the action by only $f(R)$. While we find different results (deflection angle smaller than one of General Relativity) only thank to introduction of a generic function of Ricci tensor square. Finally we can affirm the lensing phenomena for all $f(R)$-Gravities are equal to the ones known from General Relativity. We conclude the paper showing and comparing the deflection angle and image positions for $f(R,R_{\\alpha\\beta}R^{\\alpha\\beta})$-Gravity with respect to ones of General Relativity.

A. Stabile; An. Stabile

2011-12-21

26

Redshift and the Rotating Gravitational Field  

E-print Network

Previously it was shown that if a weak gravitational field is modeled as a background of oscillating gravitons described by normal coordinates, then the field naturally exhibits rotational kinetic energy. The conformal metric associated with this oscillatory motion is given by g{\\mu}{\

Walter James Christensen Jr

2010-07-27

27

Weak 'Antigravity' Fields in General Relativity  

E-print Network

Within the weak-field approximation of general relativity, new exact solutions are derived for the gravitational field of a mass moving with arbitrary velocity and acceleration. A mass having a constant velocity greater than 3^-1/2 times the speed of light gravitationally repels other masses at rest within a narrow cone. At high Lorentz factors (gamma >> 1), the force of repulsion in the forward direction is about -8(gamma^5) times the Newtonian force, offering opportunities for laboratory tests of gravity at extreme velocities. One such experiment is outlined for the Large Hadron Collider.

F. S. Felber

2009-02-10

28

Weak 'Antigravity' Fields in General Relativity  

E-print Network

Within the weak-field approximation of general relativity, new exact solutions are derived for the gravitational field of a mass moving with arbitrary velocity and acceleration. Owing to an inertial-pushing effect, a mass having a constant velocity greater than 3^-1/2 times the speed of light gravitationally repels other masses at rest within a narrow cone. At high Lorentz factors (gamma >> 1), the force of repulsion in the forward direction is about -8(gamma^5) times the Newtonian force, offering opportunities for laboratory tests of gravity at extreme velocities.

Felber, F S

2005-01-01

29

Atomic Inference from Weak Gravitational Lensing Data  

SciTech Connect

We present a novel approach to reconstructing the projected mass distribution from the sparse and noisy weak gravitational lensing shear data. The reconstructions are regularized via the knowledge gained from numerical simulations of clusters, with trial mass distributions constructed from n NFW profile ellipsoidal components. The parameters of these ''atoms'' are distributed a priori as in the simulated clusters. Sampling the mass distributions from the atom parameter probability density function allows estimates of the properties of the mass distribution to be generated, with error bars. The appropriate number of atoms is inferred from the data itself via the Bayesian evidence, and is typically found to be small, reecting the quality of the data. Ensemble average mass maps are found to be robust to the details of the noise realization, and succeed in recovering the demonstration input mass distribution (from a realistic simulated cluster) over a wide range of scales. As an application of such a reliable mapping algorithm, we comment on the residuals of the reconstruction and the implications for predicting convergence and shear at specific points on the sky.

Marshall, Phil; /KIPAC, Menlo Park

2005-12-14

30

Studying the LSS through weak gravitational lensing maps  

E-print Network

Weak gravitational lensing is a promising tool for the study of the mass distribution in the Universe. Here we report some partial results that show how lensing maps can be used to differentiate between cosmological models. We pay special attention to the role of noise and smoothing. As an application, we use mock convergence fields constructed from N-body simulations of the large-scale structure for three historically important cosmological models. Various map analyses are used, including Minkowski functionals, and their ability to differentiate the models is calculated and discussed.

Antonio C. C. Guimarães

2001-12-10

31

Weak Gravitational Lensing by Large-Scale Structure  

Microsoft Academic Search

Weak gravitational lensing provides a unique method to map directly the distribution of dark matter in the universe and to measure cosmological parameters. This cosmic-shear technique is based on the measurement of the weak distortions that lensing induces in the shape of background galaxies as photons travel through large-scale structures. This technique is now widely used to measure the mass

Alexandre Refregier

2003-01-01

32

Cosmological electromagnetic fields due to gravitational wave perturbations Mattias Marklund*  

E-print Network

Cosmological electromagnetic fields due to gravitational wave perturbations Mattias Marklund that the coupling between gravitational waves and a weak magnetic test field can generate electromagnetic waves. We show that this coupling leads to an initial pulse of electromagnetic waves whose width and amplitude

Dunsby, Peter

33

Basal electric and magnetic fields of celestial bodies come from positive-negative charge separation caused by gravitation of quasi-Casimir pressure in weak interaction  

NASA Astrophysics Data System (ADS)

According to f =d(mv)/dt=m(dv/dt)+ v(dm/dt), a same gravitational formula had been de-duced from the variance in physical mass of QFT and from the variance in mass of inductive energy-transfer of GR respectively: f QF T = f GR = -G (mM/r2 )((r/r)+(v/c)) when their interaction-constants are all taken the experimental values (H05-0029-08, E15-0039-08). f QF T is the quasi-Casimir pressure. f GR is equivalent to Einstein's equation, then more easy to solve it. The hypothesis of the equivalent principle is not used in f QF T , but required by f GR . The predictions of f QF T and f GR are identical except that f QF T has quantum effects but f GR has not and f GR has Lense-Thirring effect but f QF T has not. The quantum effects of gravitation had been verified by Nesvizhevsky et al with the ultracold neutrons falling in the earth's gravitational field in 2002. Yet Lense-Thirring effect had not been measured by GP-B. It shows that f QF T is essential but f GR is phenomenological. The macro-f QF T is the statistic average pressure collided by net virtual neutrinos ? 0 flux (after self-offset in opposite directions) and in direct proportion to the mass. But micro-f QF T is in direct proportion to the scattering section. The electric mass (in inverse proportion to de Broglie wavelength ?) far less than nucleonic mass and the electric scattering section (in direct proportion to ?2 ) far large than that of nucleon, then the net ? 0 flux pressure exerted to electron far large than that to nucleon and the electric displacement far large than that of nucleon, it causes the gravitational polarization of positive-negative charge center separation. Because the gravity far less than the electromagnetic binding force, in atoms the gravitational polarization only produces a little separation. But the net ? 0 flux can press a part freedom electrons in plasma of ionosphere into the earth's surface, the static electric force of redundant positive ions prevents electrons from further falling and till reach the equilibrium of stable spatial charge distribution, which is just the cause of the geomagnetic field and the geo-electric field (the observational value on the earth surface is about 120 V/m downward equivalent to 500000 Coulomb negative charges in the earth surface). All celestial bodies are gravitation sources and attract the molecules and ions in space to its circumference by the gravitation of own and other celestial bodies, e.g., all planets in the solar system have their own atmospheres. Therefore, the origin mechanism of geo-electric and geomagnetic fields caused by gravitation is very universal, at least it is appli-cable to all the planets in the solar system. For planets, the joint result of the gravitations of the planets and the sun makes the negative charges and dipolar charges distributed in the surfaces of the celestial bodies. The quicker the rotation is, the larger the angular momentum U is, then larger the accompanying current and magnetic moment P, it accord a experiential law found by subsistent observational data of all celestial bodies in solar system: P = -G 1/2 U cos ? / c (1), ? is the angle between the net ? 0 flux direction (mark by CMB) and the rotational axis of celestial body (Chen Shao-Guang, Chinese Science Bulletin, 26,233,1981). Uranian and Neptunian P predicted with Eq.(1) in 1981 are about -3.4•1028 Gs•cm3 and 1.9•1028 Gs•cm3 respectively (use new rotate speed measured by Voyager 2). The P measured by Voyager 2 in 1986 and 1989 are about -1.9 •1028 Gs•cm3 and 1.5•1028 Gs•cm3 respectively (the contribution of quadrupole P is converted into the contribution of dipole P alone). The neutron star pos-sesses much high density and rotational speed because of the conservation of the mass and the angular momentum during the course of the formation, then has strong gravity and largerU. From Eq.(1) there is a larger P and extremely strong surface magnetic field in neutron star. The origin mechanism of basal electric and magnetic fields of celestial bodies will affect directly all fields refer

Chen, Shao-Guang

34

Clustering of Faint Galaxies: $\\\\w $, Induced by Weak Gravitational Lensing  

Microsoft Academic Search

Weak gravitational lensing by large scale structure affects the number counts of faint galaxies through the ``magnification bias'' and thus affects the measurement of the angular two-point correlation function $\\\\w $. At faint magnitudes the clustering amplitude will decrease differently with limiting magnitude than expected from Limber's equation. The amplitude will hit a minimum and then rise with limiting magnitude.

Jens Verner Villumsen; Max Planck; Karl Schwarzschild-Str

1995-01-01

35

The Intrinsic Alignment of Galaxies and Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

Galaxy intrinsic alignments (IA) are correlations between intrinsic galaxy shapes and the surrounding density field. These correlations can bias weak gravitational lensing measurements and are the most significant source of astrophysical uncertainty for the next generation of lensing experiments. Despite its importance, IA is poorly understood. The work presented here aims to improve our understanding through both modeling and measuring IA. First, we examine the most frequently employed IA model, the tidal (linear) alignment model, in which galaxy shapes are closely correlated with the surrounding gravitational tidal field. The tidal alignment model provides an accurate description of IA on large scales (r > 10 Mpc/h), as measured for luminous red galaxies in the Sloan Digital Sky Survey (SDSS). The IA amplitude for these objects, as determined in this analysis, will allow predictions for possible contamination in current and future lensing studies. We explore several ways in which the model could be improved and expanded, including how the relationship between galaxies and their host halos can modulate the strength of IA, as well as relevant effects on smaller scales (r < 10 Mpc/h). Second, we develop a method to separate IA from galaxy-galaxy lensing measurements using photometric redshift information. This technique allows the removal of contamination from the desired lensing signal while also providing a probe of IA in different galaxy populations. We employ this method to constrain fractional IA contamination in the SDSS lensing sample to 1-2%, finding that it is a subdominant source of uncertainty at the current level of statistical precision. These developments in both modeling and measurement techniques can be applied in future lensing analyses to mitigate potential contamination from IA. Such considerations will become more important as statistical precision continues to improve.

Blazek, Jonathan

2014-01-01

36

Topological quantization of gravitational fields  

Microsoft Academic Search

We introduce the method of topological quantization for gravitational fields in a systematic manner. First we show that any vacuum solution of Einstein's equations can be represented in a principal fiber bundle with a connection that takes values in the Lie algebra of the Lorentz group. This result is generalized to include the case of gauge matter fields in multiple

Leonardo Patiño; Hernando Quevedo

2005-01-01

37

Induction and Amplification of Non-Newtonian Gravitational Fields  

E-print Network

One obtains a Maxwell-like structure of gravitation by applying the weak-field approximation to the well accepted theory of general relativity or by extending Newton's laws to time-dependent systems. This splits gravity in two parts, namely a gravitoelectric and gravitomagnetic (or cogravitational) one. Due to the obtained similar structure between gravitation and electromagnetism, one can express one field by the other one using a coupling constant depending on the mass to charge ratio of the field source. Calculations of induced gravitational fields using state-of-the-art fusion plasmas reach only accelerator threshold values for laboratory testing. Possible amplification mechanisms are mentioned in the literature and need to be explored. The possibility of using the principle of equivalence in the weak field approximation to induce non-Newtonian gravitational fields and the influence of electric charge on the free fall of bodies are also investigated, leading to some additional experimental recommendations.

M. Tajmar; C. J. de Matos

2001-07-04

38

Detection of (dark) matter concentrations via weak gravitational lensing  

E-print Network

The distortion of images of faint background galaxies by (weak) gravitational lensing can be used to measure the mass distribution of the deflector. The image distortions can be used to define a weighted mean of the mass inside a circular aperture, as was first suggested by Kaiser. The aperture mass can be used to {\\it detect} dark matter concentrations. Keeping in mind that wide-field cameras will become increasingly available, this method can be used to search for mass concentrations on wide-field images. To do this, the aperture mass measure is generalized to account for different weighting functions. For each such weighting function, a signal-to-noise ratio can be calculated. For an assumed mass profile of the density concentrations, the weighting function can be chosen such as to maximize the resulting signal-to-noise ratio. Numerical simulations which adopt parameters characteristic of 4-m class telescopes are then used to show that dark halos with a velocity dispersion in excess of $\\sim 600$\\ts km/s can be reliably detected as significant peaks in the signal-to-noise map. The effects of seeing and an anisotropic PSF are then investigated and shown to be less important than might be feared. It is thus suggested that the method of aperture mass measures developed here can be used to obtain a mass-selected sample of dark halos, in contrast to flux-selected samples. Shear fields around high-redshift bright QSOs as detected by Fort et al. provide a first successful application of this strategy. The simplicity of the method allows its routine application to wide-field images of sufficient depth and image quality.

Peter Schneider

1996-01-16

39

Scalar, electromagnetic, and gravitational fields interaction: Particlelike solutions  

Microsoft Academic Search

Particlelike static spherically symmetric solutions to massless scalar and electromagnetic field equations combined with gravitational field equations are considered. Two criteria for particlelike solutions are formulated: the strong one (solutions are required to be singularity free) and the weak one (singularities are admitted but the total energy and material field energy should be finite). Exact solutions for the following physical

K. A. Bronnikov; V. N. Melnikov; G. N. Shikin; K. P. Staniukovich

1979-01-01

40

Topological quantization of gravitational fields  

E-print Network

We introduce the method of topological quantization for gravitational fields in a systematic manner. First we show that any vacuum solution of Einstein's equations can be represented in a principal fiber bundle with a connection that takes values in the Lie algebra of the Lorentz group. This result is generalized to include the case of gauge matter fields in multiple principal fiber bundles. We present several examples of gravitational configurations that include a gravitomagnetic monopole in linearized gravity, the C-energy of cylindrically symmetric fields, the Reissner-Nordstr\\"om and the Kerr-Newman black holes. As a result of the application of the topological quantization procedure, in all the analyzed examples we obtain conditions implying that the parameters entering the metric in each case satisfy certain discretization relationships.

Leonardo Patino; Hernando Quevedo

2004-04-26

41

Matter and light wave interferometry in gravitational fields  

Microsoft Academic Search

We consider the problem of finding the quantum mechanical phase associated with the propagation of a particle in a given external gravitational field, and conclude that it ism? ds. In weak fieldsh?? this allows us to calculate the gravitationally induced phase on a freely traveling particle as 1\\/2 ?h??P?dx? whereP? is the ordinary momentum. This formula has the expected Newtonian

Leo Stodolsky

1979-01-01

42

Classical Field Approach to Quantum Weak Measurements  

E-print Network

By generalizing the quantum weak measurement protocol to the case of quantum fields, we show that weak measurements probe an effective classical background field that describes the average field configuration in the spacetime region between pre- and post-selection boundary conditions. The classical field is itself a weak value of the corresponding quantum field operator and satisfies equations of motion that extremize an effective action. Weak measurements perturb this effective action, producing measurable changes to the classical field dynamics. As such, weakly measured effects always correspond to an effective classical field. This general result explains why these effects appear to be robust for pre- and post-selected ensembles, and why they can also be measured using classical field techniques that are not weak for individual excitations of the field.

Justin Dressel; Konstantin Y. Bliokh; Franco Nori

2014-03-21

43

The Einstein-Maxwell-Particle System: II) The Weak Field Approximation in the 3-Orthogonal Gauges and Hamiltonian Post-Minkowskian Gravity: the N-Body Problem and Gravitational Waves with Asymptotic Background  

E-print Network

In this second paper we define a Post-Minkowskian weak field approximation leading to a linearization of the Hamilton equations of ADM tetrad gravity in the York canonical basis in a family of non-harmonic 3-orthogonal Schwinger time gauges. The York time ${}^3K$ (the relativistic inertial gauge variable, not existing in Newtonian gravity, parametrizing the family and connected to the freedom in clock synchronization, i.e. to the definition of the instantaneous 3-spaces) is put equal to an arbitrary numerical function. The matter are point particles, with a Grassmann regularization of self-energies, and the electro-magnetic field in the radiation gauge: a ultraviolet cutoff allows a consistent linearization, which is shown to be the lowest order of a Hamiltonian Post-Minkowskian (HPM) expansion. We solve the constraints and the Hamilton equations for the tidal variables and we find Post-Minkowskian gravitational waves with asymptotic background (and the correct quadrupole emission formula) propagating on dyna...

Alba, David

2010-01-01

44

Scalar invariants in gravitational and electromagnetic fields  

E-print Network

The paper discusses some scalar invariants in the gravitational field and electromagnetic field by means of the characteristics of the quaternions. When we emphasize some definitions of quaternion physical quantities, the speed of light, mass density, energy density, power density, charge density, and spin magnetic moment density etc. will remain the same respectively in the gravitational and electromagnetic fields under the coordinate transformation. The results explain why there are some relationships among different invariants in the gravitational and electromagnetic fields.

Zihua Weng

2009-06-22

45

LIGHT ON DARK MATTER WITH WEAK GRAVITATIONAL LENSING 1 Light on Dark Matter  

E-print Network

LIGHT ON DARK MATTER WITH WEAK GRAVITATIONAL LENSING 1 Light on Dark Matter with Weak Gravitational reviews statistical methods re- cently developed to reconstruct and analyze dark matter mass maps from higher energy theories- called "dark matter" (20-21%) and by an even more mysterious term, described

Starck, Jean-Luc

46

Angular momentum effects in weak gravitational fields  

E-print Network

It is shown that, contrary to what is normally expected, it is possible to have angular momentum effects on the geometry of space time at the laboratory scale, much bigger than the purely Newtonian effects. This is due to the fact that the ratio between the angular momentum of a body and its mass, expressed as a length, is easily greater than the mass itself, again expressed as a length.

A. Tartaglia

2002-01-02

47

Mars gravitational field estimation error  

NASA Technical Reports Server (NTRS)

The error covariance matrices associated with a weighted least-squares differential correction process have been analyzed for accuracy in determining the gravitational coefficients through degree and order five in the Mars gravitational potential junction. The results are presented in terms of standard deviations for the assumed estimated parameters. The covariance matrices were calculated by assuming Doppler tracking data from a Mars orbiter, a priori statistics for the estimated parameters, and model error uncertainties for tracking-station locations, the Mars ephemeris, the astronomical unit, the Mars gravitational constant (G sub M), and the gravitational coefficients of degrees six and seven. Model errors were treated by using the concept of consider parameters.

Compton, H. R.; Daniels, E. F.

1972-01-01

48

String pair production in a time-dependent gravitational field  

SciTech Connect

We study the pair creation of point particles and strings in a time-dependent, weak gravitational field. We find that, for massive string states, there are surprising and significant differences between the string and point-particle results. Central to our approach is the fact that a weakly curved spacetime can be represented by a coherent state of gravitons, and therefore we employ standard techniques in string perturbation theory. String and point-particle pairs are created through tree-level interactions between the background gravitons. In particular, we focus on the production of excited string states and perform explicit calculations of the production of a set of string states of arbitrary excitation level. The differences between the string and point-particle results may contain important lessons for the pair production of strings in the strong gravitational fields of interest in cosmology and black hole physics.

Tolley, Andrew J.; Wesley, Daniel H. [Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States)

2005-12-15

49

Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements  

NASA Astrophysics Data System (ADS)

Weak gravitational lensing observations are a key science driver for the NASA Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of the WFIRST infrared detectors, we have performed a laboratory emulation of weak gravitational lensing measurements. Our experiments used a custom precision projector system to image a target mask composed of a grid of pinholes, emulating stellar point sources, onto a 1.7 ?m cut-off Teledyne HgCdTe/H2RG detector. We used a 0.88 ?m LED illumination source and f/22 pupil stop to produce undersampled point spread functions similar to those expected from WFIRST. We also emulated the WFIRST image reconstruction strategy, using the image combination (IMCOM) algorithm to derive oversampled images from dithered, undersampled input images. We created shear maps for this data and computed shear correlation functions to mimic a real weak lensing analysis. After removing only second-order polynomial fits to the shear maps, we found that the correlation functions could be reduced to O(10-6). This places a conservative upper limit on the detector-induced bias to the correlation function (under our test conditions). This bias is two orders of magnitude lower than the expected weak lensing signal. Restricted to scales relevant to dark energy analyses (sky separations >0.5'), the bias is O(10-7) - comparable to the requirement for future weak lensing missions to avoid biasing cosmological parameter estimates. Our experiment will need to be upgraded and repeated under different configurations to fully characterize the shape measurement performance of WFIRST IR detectors.

Seshadri, S.; Shapiro, C.; Goodsall, T.; Fucik, J.; Hirata, C.; Rhodes, J. D.; Rowe, B. T. P.; Smith, R. M.

2013-09-01

50

Statistical properties of the convergence due to weak gravitational lensing by non-linear structures  

E-print Network

Density fluctuations in the matter distribution lead to distortions of the images of distant galaxies through weak gravitational lensing effects. This provides an efficient probe of the cosmological parameters and of the density field. In this article, we investigate the statistical properties of the convergence due to weak gravitational lensing by non-linear structures (i.e. we consider small angular windows $\\theta \\la 1'$). Previous studies have shown how to relate the second and third order moments of the convergence to those of the density contrast while models based on the Press-Schechter prescription provide an estimate of the tail of $P(\\kappa)$. Here we present a method to obtain an estimate of the full p.d.f. of the convergence $P(\\kappa)$. It is based on a realistic description of the density field which applies to overdense as well as underdense regions. We show that our predictions agree very well with the results of N-body simulations for the convergence. This could allow one to derive the cosmological parameters $(\\Omega_m,\\Omega_{\\Lambda})$ as well as the full p.d.f. $P(\\delta_R)$ of the density contrast itself in the non-linear regime from observations. Hence this gives a very powerfull tool to constrain scenarios of structure formation.

P. Valageas

2000-05-12

51

Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales  

Microsoft Academic Search

Most of the matter in the Universe is not luminous, and can be observed only through its gravitational influence on the appearance of luminous matter. Weak gravitational lensing is a technique that uses the distortions of the images of distant galaxies as a tracer of dark matter: such distortions are induced as the light passes through large-scale distributions of dark

J. Anthony Tyson; David Kirkman; Ian Dell'Antonio; Gary Bernstein; David M. Wittman

2000-01-01

52

The Equivalence of Time and Gravitational Field  

NASA Astrophysics Data System (ADS)

The relationship between energy, time and space is still not solved in an appropriate manner. According to Newton's concept of time and space, both have to be taken as absolute. If we follow Leibniz and his arguments, space and time are relative. Since Einstein's theory of relativity we know at least that energy, time and space are deeply related. Albert Einstein originally predicted that time is nothing absolute but something relative, time changes and can change. Especially, time and gravitational field are related somehow even in detail if we still don't know how. According to the gravitational time dilation, the lower the gravitational potential, the more slowly time passes and vice versa. Somehow, it appears to be that the behaviour of time is directly linked to the behaviour of the gravitational field. The aim of this publication is to work out the interior logic between time and gravitational field and to make the proof that time is equivalent to the gravitational field and vice versa.

Baruk?i?a, Ilija

53

Galilean-invariant scalar fields can strengthen gravitational lensing.  

PubMed

The mystery of dark energy suggests that there is new gravitational physics on long length scales. Yet light degrees of freedom in gravity are strictly limited by Solar System observations. We can resolve this apparent contradiction by adding a Galilean-invariant scalar field to gravity. Called Galileons, these scalars have strong self-interactions near overdensities, like the Solar System, that suppress their dynamical effect. These nonlinearities are weak on cosmological scales, permitting new physics to operate. In this Letter, we point out that a massive-gravity-inspired coupling of Galileons to stress energy can enhance gravitational lensing. Because the enhancement appears at a fixed scaled location for dark matter halos of a wide range of masses, stacked cluster analysis of weak lensing data should be able to detect or constrain this effect. PMID:21668215

Wyman, Mark

2011-05-20

54

Spin-2 particles in gravitational fields  

E-print Network

We give a solution of the wave equation for massless, or massive spin-2 particles propagating in a gravitational background. The solution is covariant, gauge-invariant and exact to first order in the background gravitational field. The background contribution is confined to a phase factor from which geometrical and physical optics can be derived. The phase also describes Mashhoon's spin-rotation coupling and, in general, the spin-gravity interaction.

G. Papini

2007-02-01

55

Scalar, electromagnetic, and gravitational self-forces in weakly curved spacetimes  

E-print Network

We calculate the self-force experienced by a point scalar charge, a point electric charge, and a point mass moving in a weakly curved spacetime characterized by a time-independent Newtonian potential. The self-forces are calculated by first computing the retarded Green's functions for scalar, electromagnetic, and (linearized) gravitational fields in the weakly curved spacetime, and then evaluating an integral over the particle's past world line. In all three cases the self-force contains both a conservative and a nonconservative (radiation-reaction) part. The conservative part of the self-force is directly related to the presence of matter in the spacetime. The radiation-reaction part of the self-force, on the other hand, is insensitive to the presence of matter. Our result for the gravitational self-force is disturbing: a radiation-reaction force should not appear in the equations of motion at this level of approximation, and it should certainly not give rise to radiation antidamping. The last section of this paper attempts to make sense of this result by placing it in the context of the post-Newtonian N-body problem.

Michael J. Pfenning; Eric Poisson

2001-09-12

56

Gravitational waves from scalar field accretion  

E-print Network

Our aim in this work is to outline some physical consequences of the interaction between black holes and scalar field halos in terms of gravitational waves. In doing so, the black hole is taken as a static and spherically symmetric gravitational source, {\\it i. e.} the Schwarzschild black hole, and we work within the test field approximation, considering that the scalar field lives in the curved space-time outside the black hole. We focused on the emission of gravitational waves when the black hole is perturbed by the surrounding scalar field matter. The symmetries of the spacetime and the simplicity of the matter source allow, by means of a spherical harmonic decomposition, to study the problem by means of a one dimensional description. Some properties of such gravitational waves are discussed as a function of the parameters of the infalling scalar field, and allow us to make the conjecture that the gravitational waves carry information on the type of matter that generated them.

Darío Núnez; Juan Carlos Degollado; Claudia Moreno

2011-09-03

57

Higgs Gravitational Interaction, Weak Boson Scattering, and Higgs Inflation in Jordan and Einstein Frames  

E-print Network

We study gravitational interaction of Higgs boson through the unique dimension-4 operator $\\xi H^\\dag H R$, with $H$ the Higgs doublet and $R$ the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling $\\xi$ on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone boson equivalence theorem with nonzero $\\xi$ coupling in both frames, and analyze the unitarity constraints. We study the $\\xi$-induced weak boson scattering cross sections at O(1-30)TeV scales, and propose to probe the Higgs-gravity coupling via weak boson scattering experiments at the LHC(14TeV) and the next generation pp colliders (50-100TeV). We further extend our study to Higgs inflation, and quantitatively derive the perturbative unitarity bounds via coupled channel analysis, under large field background at the inflation scale. We analyze the unitarity constraints on the parameter space in both the conventional Higgs inflation and the improved models in light of the recent BICEP2 data.

Jing Ren; Zhong-Zhi Xianyu; Hong-Jian He

2014-05-16

58

Lognormal Property of Weak Lensing Fields  

E-print Network

The statistical property of the weak lensing fields is studied quantitatively using the ray-tracing simulations. Motivated by the empirical lognormal model that characterizes the probability distribution function(PDF) of the three-dimensional mass distribution excellently, we critically investigate the validity of lognormal model in the weak lensing statistics. Assuming that the convergence field, $\\kappa$, is approximately described by the lognormal distribution, we present analytic formulae of convergence for the one-point PDF and the Minkowski functionals. Comparing those predictions with ray-tracing simulations in various cold dark matter models, we find that the one-point lognormal PDF can describe the non-Gaussian tails of convergence fields accurately up to $\

A. Taruya; M. Takada; T. Hamana; I. Kayo; T. Futamase

2002-02-05

59

Helicity Observation of Weak and Strong Fields  

E-print Network

We report in this letter our analysis of a large sample of photospheric vector magnetic field measurements. Our sample consists of 17200 vector magnetograms obtained from January 1997 to August 2004 by Huairou Solar Observing Station of the Chinese National Astronomical Observatory. Two physical quantities, $\\alpha$ and current helicity, are calculated and their signs and amplitudes are studied in a search for solar cycle variations. Different from other studies of the same type, we calculate these quantities for weak ($100G1000G$) fields separately. For weak fields, we find that the signs of both $\\alpha$ and current helicity are consistent with the established hemispheric rule during most years of the solar cycle and their magnitudes show a rough tendency of decreasing with the development of solar cycle. Analysis of strong fields gives an interesting result: Both $\\alpha$ and current helicity present a sign opposite to that of weak fields. Implications of these observations on dynamo theory and helicity production are also briefly discussed.

Mei Zhang

2006-06-09

60

A weak combined magnetic field changes root gravitropism  

NASA Astrophysics Data System (ADS)

Immobile higher plants are oriented in the gravitational field due to gravitropim that is a physiological growth reaction and consists of three phases: reception of a gravitational signal by statocytes, its transduction to the elongation zone, and finally the organ bending. According to the starch-statolith hypothesis, amyloplasts in the specialized graviperceptive cells - statocytes sediment in the direction of a gravitational vector in the distal part of a cell. The polar arrangement of organelles is maintained by means of the cytoskeleton. On the Kholodny-Went's, theory the root bending is provided by the polar movement of auxin from a root cap to the elongation zone. It is also known that gravistimulation initiates a rapid Ca2+ redistribution in a root apex. Calcium ions modify an activity of many cytoskeletal proteins and clustering of calcium channels may be directed by actin microfilaments. Although the available data show the Ca2+ and cytoskeleton participation in graviperception and signal transduction, the clear evidence with regard to the participation of cytoskeletal elements and calcium ions in these processes is therefore substantial but still circumstantial and requires new experimental data. Roots are characterized with positive gravitropism, i. e. they grow in the direction of a gravitational vector. It was first shown by us that roots change the direction of a gravitropic reaction under gravistimulation in the weak combined magnetic field with a frequency of 32 Hz. 2-3-day old cress seedlings were gravistimulated in moist chambers, which are placed in ?-metal shields. Inside ? -metal shields, combined magnetic fields have been created. Experiments were performed in darkness at temperature 20±10C. Measurements of the magnitude of magnetic fields were carried out with a flux-gate magnetometer. Cress roots reveal negative gravitropism, i. e. they grow in the opposite direction to a gravitational vector, during 2 h of gravistimulation and then roots begin to grow more or less parallel to the Earth's surface, i.e. they reveal plagiotropism. Since such combined magnetic field is adjusted to the cyclotron frequency of Ca2+ ions, these observations demonstrate the participation of calcium ions in root gravitropism. Cyclotron frequency of Ca2+ ions is the formal frequency of ion rotation in the static magnetic field. Simultaneous applying the altering magnetic field with the same frequency can provoke auto-oscillation in the system and consequently change the rate and/or the direction of Ca2+ ion flow in a root under gravistimulation. The data of light, electron, and confocal laser microscopy and kinetics of a gravitropic reaction, which have been obtained on such the new original model, are discussed in the light of current concepts of root gravitropism.

Kordyum, E. L.; Bogatina, N. I.; Kalinina, Ja. M.; Sheykina, N. V.

61

Gravitational repulsion in the Schwarzschild field  

SciTech Connect

To the distant observer, who uses measuring instruments not affected by gravity, gravitational repulsion can occur anywhere in the Schwarzschild field. It depends on the relationship between the transverse and radial Schwarzschild velocities. On the other hand, local observers, whose measuring instruments are affected by gravity, can not detect a positive value for the acceleration of gravity.

McGruder, C.H. III

1982-06-15

62

Quantum fields as gravitational sources  

E-print Network

The practice of setting quantum fields as sources for classical general relativity is examined. Several conceptual problems are identified which invalidate apparently innocuous equations. Alternative ways to links classical general relativity with quantum theory using Bohm's theory are proposed.

Mark J Hadley

2008-08-13

63

Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit  

SciTech Connect

We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r{sub {alpha}}/b, where M is the black hole mass, a is the angular momentum, r{sub {alpha}}= Q{sup 2}/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

Gyulchev, G. N. [Department of Physics, Biophysics and Roentgenology, Faculty of Medicine, St. Kliment Ohridski, University of Sofia, 1 Kozyak str., 1407 Sofia (Bulgaria); Yazadjiev, S. S. [Department of Theoretical Physics, Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia (Bulgaria)

2010-11-25

64

GRAVITATIONAL FIELD SHIELDING AND SUPERNOVA EXPLOSIONS  

SciTech Connect

A new mechanism for supernova explosions called gravitational field shielding is proposed, in accord with a five-dimensional fully covariant Kaluza-Klein theory with a scalar field that unifies the four-dimensional Einsteinian general relativity and Maxwellian electromagnetic theory. It is shown that a dense compact collapsing core of a star will suddenly turn off or completely shield its gravitational field when the core collapses to a critical density, which is inversely proportional to the square of mass of the core. As the core suddenly turns off its gravity, the extremely large pressure immediately stops the core collapse and pushes the mantle material of supernova moving outward. The work done by the pressure in the expansion can be the order of energy released in a supernova explosion. The gravity will resume and stop the core from a further expansion when the core density becomes less than the critical density. Therefore, the gravitational field shielding leads a supernova to impulsively explode and form a compact object such as a neutron star as a remnant. It works such that a compressed spring will shoot the oscillator out when the compressed force is suddenly removed.

Zhang, T. X. [Physics Department, Alabama A and M University, Normal, AL 35762 (United States)

2010-12-20

65

The gravitational field of a global monopole  

E-print Network

We present an exact solution to the non-linear equation which describes a global monopole in the flat space. We re-examine the metric and the geodesics outside the global monopole. We will see that a global monopole produces a repulsive gravitational field outside the core in addition to a solid angular deficit. The lensing property of the global monopole and the global monopole-antimonopole annihilation mechanism are studied.

Xin Shi; Xin-zhou Li

2009-03-18

66

Testing dark energy paradigms with weak gravitational lensing R. Ali Vanderveld,1  

E-print Network

Testing dark energy paradigms with weak gravitational lensing R. Ali Vanderveld,1 Michael J all quintessence models, with or without early dark energy. We further explore how uncertainties a given dark energy paradigm, such as the standard CDM model of cold dark matter and a cosmological

Hu, Wayne

67

Purely radiating and nonradiating scalar, electromagnetic and weak gravitational sources  

Microsoft Academic Search

It has been known for some time that localized sources to the scalar wave equation and Maxwell's equations exist which do not radiate. Such sources, referred to as non-radiating (NR) sources, generate vanishing fields outside their spatial support which prevents them from interacting with nearby objects by means of their fields. Work on NR sources dates back to Sommerfeld, Herglotz,

Edwin A. Marengo; Richard W. Ziolkowski

2000-01-01

68

On the universality of linear Lagrangians for gravitational field  

SciTech Connect

For a large class of purely metric, metric--affine, and purely affine theories of gravitation with nonlinear Lagrangians, it is proved that the theory is equivalent to the standard Einstein theory of gravitation interacting with additional matter fields.

Jakubiec, A.; Kijowski, J.

1989-05-01

69

Gravitational collapse of charged scalar fields  

NASA Astrophysics Data System (ADS)

In order to study the gravitational collapse of charged matter we analyze the simple model of an self-gravitating massless scalar field coupled to the electromagnetic field in spherical symmetry. The evolution equations for the Maxwell-Klein-Gordon sector are derived in the 3+1 formalism, and coupled to gravity by means of the stress-energy tensor of these fields. To solve consistently the full system we employ a generalized Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of General Relativity that is adapted to spherical symmetry. We consider two sets of initial data that represent a time symmetric spherical thick shell of charged scalar field, and differ by the fact that one set has zero global electrical charge while the other has non-zero global charge. For compact enough initial shells we find that the configuration doesn't disperse and approaches a final state corresponding to a sub-extremal Reissner-N\\"ordstrom black hole with $|Q|field $q$ we find that the final black hole tends to become more and more neutral. Our results support the cosmic censorship conjecture for the case of charged matter.

Torres, Jose M.; Alcubierre, Miguel

2014-09-01

70

Gravitational collapse of charged scalar fields  

E-print Network

In order to study the gravitational collapse of charged matter we analyze the simple model of an self-gravitating massless scalar field coupled to the electromagnetic field in spherical symmetry. The evolution equations for the Maxwell-Klein-Gordon sector are derived in the 3+1 formalism, and coupled to gravity by means of the stress-energy tensor of these fields. To solve consistently the full system we employ a generalized Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of General Relativity that is adapted to spherical symmetry. We consider two sets of initial data that represent a time symmetric spherical thick shell of charged scalar field, and differ by the fact that one set has zero global electrical charge while the other has non-zero global charge. For compact enough initial shells we find that the configuration doesn't disperse and approaches a final state corresponding to a sub-extremal Reissner-N\\"ordstrom black hole with $|Q|scalar field $q$ we find that the final black hole tends to become more and more neutral. Our results support the cosmic censorship conjecture for the case of charged matter.

Jose M. Torres; Miguel Alcubierre

2014-07-29

71

Mapping the dark matter with weak gravitational lensing  

Microsoft Academic Search

We consider the problem of reconstructing the projected mass distribution in clusters from coherent distortions of background galaxies. The ellipticity of a background galaxy provides an estimate of the trace-free components of the tidal field. We present a technique for inverting this problem. The resulting surface density contains a strong, but incoherent, random component arising from the random intrinsic galaxy

Nick Kaiser; Gordon Squires

1993-01-01

72

Fast Reconnection of Weak Magnetic Fields  

NASA Technical Reports Server (NTRS)

Fast magnetic reconnection refers to annihilation or topological rearrangement of magnetic fields on a timescale that is independent (or nearly independent) of the plasma resistivity. The resistivity of astrophysical plasmas is so low that reconnection is of little practical interest unless it is fast. Yet, the theory of fast magnetic reconnection is on uncertain ground, as models must avoid the tendency of magnetic fields to pile up at the reconnection layer, slowing down the flow. In this paper it is shown that these problems can be avoided to some extent if the flow is three dimensional. On the other hand, it is shown that in the limited but important case of incompressible stagnation point flows, every flow will amplify most magnetic fields. Although examples of fast magnetic reconnection abound, a weak, disordered magnetic field embedded in stagnation point flow will in general be amplified, and should eventually modify the flow. These results support recent arguments against the operation of turbulent resistivity in highly conducting fluids.

Zweibel, Ellen G.

1998-01-01

73

Graphene transparency in weak magnetic fields  

E-print Network

We carry out an explicit calculation of the vacuum polarization tensor for an effective low-energy model of monolayer graphene in the presence of a weak magnetic field of intensity $B$ perpendicularly aligned to the membrane. By expanding the quasiparticle propagator in the Schwinger proper time representation up to order $(eB)^2$, where $e$ is the unit charge, we find an explicitly transverse tensor, consistent with gauge invariance. Furthermore, assuming that graphene is radiated with monochromatic light of frequency $\\omega$ along the external field direction, from the modified Maxwell's equations we derive the intensity of transmitted light and the angle of polarization rotation in terms of the longitudinal ($\\sigma_{xx}$) and transverse ($\\sigma_{xy}$) conductivities. Corrections to these quantities, both calculated and measured, are of order $(eB)^2/\\omega^4$. Our findings generalize and complement previously known results reported in literature regarding the light absorption problem in graphene from the experimental and theoretical points of view, with and without external magnetic fields.

David Valenzuela; Saúl Hernández-Ortiz; Marcelo Loewe; Alfredo Raya

2014-10-20

74

Weak lensing galaxy cluster field reconstruction  

NASA Astrophysics Data System (ADS)

In this paper, we compare three methods to reconstruct galaxy cluster density fields with weak lensing data. The first method called FLens integrates an inpainting concept to invert the shear field with possible gaps, and a multi-scale entropy denoising procedure to remove the noise contained in the final reconstruction, that arises mostly from the random intrinsic shape of the galaxies. The second and third methods are based on a model of the density field made of a multi-scale grid of radial basis functions. In one case, the model parameters are computed with a linear inversion involving a singular value decomposition (SVD). In the other case, the model parameters are estimated using a Bayesian Monte Carlo Markov Chain optimization implemented in the lensing software LENSTOOL. Methods are compared on simulated data with varying galaxy density fields. We pay particular attention to the errors estimated with resampling. We find the multi-scale grid model optimized with Monte Carlo Markov Chain to provide the best results, but at high computational cost, especially when considering resampling. The SVD method is much faster but yields noisy maps, although this can be mitigated with resampling. The FLens method is a good compromise with fast computation, high signal-to-noise ratio reconstruction, but lower resolution maps. All three methods are applied to the MACS J0717+3745 galaxy cluster field, and reveal the filamentary structure discovered in Jauzac et al. We conclude that sensitive priors can help to get high signal-to-noise ratio, and unbiased reconstructions.

Jullo, E.; Pires, S.; Jauzac, M.; Kneib, J.-P.

2014-02-01

75

Theory of microemulsions in a gravitational field  

NASA Technical Reports Server (NTRS)

A theory of microemulsions developed previously is extended to include the effect of a gravitational field. It predicts variation with position of drop size, drop volume fraction, and area per molecule in the surfactant films within a microemulsion phase. Variation in volume fraction is greatest and occurs in such a way that oil content increases with increasing elevation, as has been found experimentally. Large composition variations are predicted within a middle phase microemulsion near optimal conditions because inversion from the water-continuous to the oil-continuous arrangement occurs with increasing elevation. Generally speaking, gravity reduces solubilization within microemulsions and promotes separation of excess phases.

Jeng, J. F.; Miller, Clarence A.

1989-01-01

76

Symmetries in tetrad theories. [of gravitational fields and general relativity  

NASA Technical Reports Server (NTRS)

The isometry conditions for gravitational fields are given directly at the tetrad level, rather than in terms of the metric. As an illustration, an analysis of the curvature collineations and Killing fields for a twisting type-N vacuum gravitational field is made.

Chinea, F. J.

1988-01-01

77

Atomic Interferometry in Gravitational Fields: Influence of Gravitation on the Beam Splitter  

Microsoft Academic Search

The laser induced splitting of atomic beams inthe presence of a gravitational field is analyzed. Inthe frame of a quasiclassical approximation, the motionof the atomic beam through a laser region with rectangular profile is calculated. Beside theusual beam splitting due to the atomlaser interaction,an additional splitting occurs due to the anomalouseffective interaction with the gravitational field. In a first order

Claus Lämmerzahl; Christian J. Borde

1999-01-01

78

Weakly chiral networks and two-dimensional delocalized states in a weak magnetic field  

Microsoft Academic Search

We study numerically the localization properties of two-dimensional electrons in a weak perpendicular magnetic field. For this purpose we construct weakly chiral network models on the square and triangular lattices. The prime idea is to separate in space the regions with phase action of magnetic field, where it affects interference in course of multiple disorder scattering, and the regions with

V. V. Mkhitaryan; V. Kagalovsky; M. E. Raikh

2010-01-01

79

Gravitational Descendants in Symplectic Field Theory  

NASA Astrophysics Data System (ADS)

It was pointed out by Y. Eliashberg in his ICM 2006 plenary talk that the rich algebraic formalism of symplectic field theory leads to a natural appearance of quantum and classical integrable systems, at least in the case when the contact manifold is the prequantization space of a symplectic manifold. In this paper we generalize the definition of gravitational descendants in SFT from circle bundles in the Morse-Bott case to general contact manifolds. After we have shown using the ideas in Okounkov and Pandharipande (Ann Math 163(2):517-560, 2006) that for the basic examples of holomorphic curves in SFT, that is, branched covers of cylinders over closed Reeb orbits, the gravitational descendants have a geometric interpretation in terms of branching conditions, we follow the ideas in Cieliebak and Latschev ( http://arixiv.org/abs/0706.3284v2 [math.s6], 2007) to compute the corresponding sequence of Poisson-commuting functions when the contact manifold is the unit cotangent bundle of a Riemannian manifold.

Fabert, Oliver

2011-02-01

80

Local freedom in the gravitational field  

E-print Network

In a cosmological context, the electric and magnetic parts of the Weyl tensor, E_{ab} and H_{ab}, represent the locally free curvature - i.e. they are not pointwise determined by the matter fields. By performing a complete covariant decomposition of the derivatives of E_{ab} and H_{ab}, we show that the parts of the derivative of the curvature which are locally free (i.e. not pointwise determined by the matter via the Bianchi identities) are exactly the symmetrised trace-free spatial derivatives of E_{ab} and H_{ab} together with their spatial curls. These parts of the derivatives are shown to be crucial for the existence of gravitational waves.

Roy Maartens; George Ellis; Stephen Siklos

1997-03-07

81

Vacuum polarization in gravitational and electromagnetic fields around a superconducting string  

SciTech Connect

We have calculated the polarization current induced in the physical vacuum around a superconducting cosmic string taking into account the gravitational field of the string. The current can be calculated as an expansion in powers of the inverse of the electron mass. In the region far from the string, where it is justified to keep only the lowest term of this expansion, the polarization current turns out to screen the original current in the string, but the effect is very weak. A direct calculation of terms due to the presence of the gravitational field shows that they are dominated, for realistic string parameters, by the purely electromagnetic contribution.

Mankiewicz, L. (Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, 00-716 Warsaw, ul. Bartycka 18, Poland (PL)); Misiak, M. (Institute for Theoretical Physics, University of Warsaw, 00-681 Warsaw, ul. Hoza 69, Poland)

1989-09-15

82

Effects of asphericity and substructure on the determination of cluster mass with weak gravitational lensing  

E-print Network

Weak gravitational lensing can be used to directly measure the mass along a line-of-sight without any dependence on the dynamical state of the mass, and thus can be used to measure the masses of clusters even if they are not relaxed. One common technique used to measure cluster masses is fitting azimuthally-averaged gravitational shear profiles with a spherical mass model. In this paper we quantify how asphericity and projected substructure in clusters can affect the virial mass and concentration measured with this technique by simulating weak lensing observations on 30 independent lines-of-sights through each of four high-resolution N-body cluster simulations. We find that the variations in the measured virial mass and concentration are of a size similar to the error expected in ideal weak lensing observations and are correlated, but that the virial mass and concentration of the mean shear profile agree well with that measured in three dimensional models of the clusters. The dominant effect causing the variations is the proximity of the line-of-sight to the major axis of the 3-D cluster mass distribution, with projected substructure only causing minor perturbations in the measured concentration. Finally we find that the best-fit "universal" CDM models used to fit the shear profiles over-predict the surface density of the clusters due to the cluster mass density falling off faster than the r^{-3} model assumption.

D. Clowe; G. De Lucia; L. King

2004-02-12

83

Weak equivalence principle for self-gravitating bodies: A sieve for purely metric theories of gravity  

E-print Network

We propose the almost-geodesic motion of self-gravitating test bodies as a possible selection rule among metric theories of gravity. Starting from a heuristic statement, the "gravitational weak equivalence principle", we build a formal, operative test able to probe the validity of the principle for any metric theory of gravity, in an arbitrary number of spacetime dimensions. We show that, if the theory admits a well-posed variational formulation, this test singles out only the purely metric theories of gravity. This conclusion reproduces known results in the cases of general relativity (also with a cosmological constant term), and scalar-tensor theories, but extends also to debated or unknown scenarios, such as f(R) and Lanczos-Lovelock theories. We thus provide new tools going beyond the standard methods, where the latter turn out to be inconclusive or inapplicable.

Eolo Di Casola; Stefano Liberati; Sebastiano Sonego

2014-04-11

84

GaBoDS: The Garching-Bonn Deep Survey -- II. Confirmation of EIS cluster candidates by weak gravitational lensing  

E-print Network

We report the first confirmation of colour-selected galaxy cluster candidates by means of weak gravitational lensing. Significant lensing signals were identified in the course of the shear-selection programme of dark matter haloes in the Garching-Bonn Deep Survey, which currently covers 20 square degrees of deep, high-quality imaging data on the southern sky. The detection was made in a field that was previously covered by the ESO Imaging Survey (EIS) in 1997. A highly significant shear-selected mass-concentration perfectly coincides with the richest EIS cluster candidate at z~0.2, thus confirming its cluster nature. Several other shear patterns in the field can also be identified with cluster candidates, one of which could possibly be part of a filament at z~0.45.

Mischa Schirmer; Thomas Erben; Peter Schneider; Christian Wolf; Klaus Meisenheimer

2004-01-12

85

Weak gravitational lensing as a method to constrain unstable dark matter  

SciTech Connect

The nature of the dark matter remains a mystery. The possibility of an unstable dark matter particle decaying to invisible daughter particles has been explored many times in the past few decades. Meanwhile, weak gravitational lensing shear has gained a lot of attention as a probe of dark energy, though it was previously considered a dark matter probe. Weak lensing is a useful tool for constraining the stability of the dark matter. In the coming decade a number of large galaxy imaging surveys will be undertaken and will measure the statistics of cosmological weak lensing with unprecedented precision. Weak lensing statistics are sensitive to unstable dark matter in at least two ways. Dark matter decays alter the matter power spectrum and change the angular diameter distance-redshift relation. We show how measurements of weak lensing shear correlations may provide the most restrictive, model-independent constraints on the lifetime of unstable dark matter. Our results rely on assumptions regarding nonlinear evolution of density fluctuations in scenarios of unstable dark matter and one of our aims is to stimulate interest in theoretical work on nonlinear structure growth in unstable dark matter models.

Wang Meiyu; Zentner, Andrew R. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

2010-12-15

86

Field theory on R× S 3 topology. VI: Gravitation  

Microsoft Academic Search

We extend to curved space-time the field theory on R×S3 topology in which field equations were obtained for scalar particles, spin one-half particles, the electromagnetic field of magnetic moments, an SU2 gauge theory, and a Schrödinger-type equation, as compared to ordinary field equations that are formulated on a Minkowskian metric. The theory obtained is an angular-momentum representation of gravitation. Gravitational

M. Carmeli; S. Malin

1987-01-01

87

Field theory on R × S 3 topology. VI: Gravitation  

Microsoft Academic Search

We extend to curved space-time the field theory on R×S3 topology in which field equations were obtained for scalar particles, spin one-half particles, the electromagnetic field of magnetic moments, an SU2 gauge theory, and a Schrödinger-type equation, as compared to ordinary field equations that are formulated on a Minkowskian metric. The theory obtained is an angular-momentum representation of gravitation. Gravitational

M. Carmeli; S. Malin

1987-01-01

88

Gravitational consequences of modern field theories  

NASA Technical Reports Server (NTRS)

Some gravitational consequences of certain extensions of Einstein's general theory of relativity are discussed. These theories are not alternative theories of gravity in the usual sense. It is assumed that general relativity is the appropriate description of all gravitational phenomena which were observed to date.

Horowitz, Gary T.

1989-01-01

89

Fermat principle in arbitrary gravitational fields  

Microsoft Academic Search

The Fermat principle is reviewed and used to derive the zigzag path constructed for massive and massless particles in order to determine if these paths are a suitable approximation to the first order of the gravitational lens effect. It is found that such paths are suitable for thin comoving gravitational lenses to the first order in the lens effect, and

Israel Kovner

1990-01-01

90

The Continuum Limit of a Fermion System Involving Neutrinos: Weak and Gravitational Interactions  

E-print Network

We analyze the causal action principle for a system of relativistic fermions composed of massive Dirac particles and neutrinos. In the continuum limit, we obtain an effective interaction described by a left-handed, massive SU(2) gauge field and a gravitational field. The off-diagonal gauge potentials involve a unitary mixing matrix, which is similar to the Maki-Nakagawa-Sakata matrix in the standard model.

Felix Finster

2014-09-08

91

Gravitational Lensing and the Hubble Deep Field  

E-print Network

We calculate the expected number of multiply-imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with m_I < 27 that were detected in all four HDF passbands. A comparison of these expectations with the observed number of strongly lensed galaxies constrains the current value of Omega_m-Omega_Lambda, where Omega_m is the mean mass density of the universe and Omega_Lambda is the normalized cosmological constant. Based on current estimates of the HDF luminosity function and associated uncertainties in individual parameters, our 95% confidence lower limit on Omega_m-Omega_Lambda ranges between -0.44, if there are no strongly lensed galaxies in the HDF, and -0.73, if there are two strongly lensed galaxies in the HDF. If the only lensed galaxy in the HDF is the one presently viable candidate, then, in a flat universe (Omega_m+Omega_Lambda=1), Omega_Lambda < 0.79 (95% C.L.). These limits are compatible with estimates based on high-redshift supernovae and with previous limits based on gravitational lensing.

Asantha R. Cooray; Jean M. Quashnock; M. Coleman Miller

1998-11-07

92

Computing Gravitational Fields of Finite-Sized Bodies  

NASA Technical Reports Server (NTRS)

A computer program utilizes the classical theory of gravitation, implemented by means of the finite-element method, to calculate the near gravitational fields of bodies of arbitrary size, shape, and mass distribution. The program was developed for application to a spacecraft and to floating proof masses and associated equipment carried by the spacecraft for detecting gravitational waves. The program can calculate steady or time-dependent gravitational forces, moments, and gradients thereof. Bodies external to a proof mass can be moving around the proof mass and/or deformed under thermoelastic loads. An arbitrarily shaped proof mass is represented by a collection of parallelepiped elements. The gravitational force and moment acting on each parallelepiped element of a proof mass, including those attributable to the self-gravitational field of the proof mass, are computed exactly from the closed-form equation for the gravitational potential of a parallelepiped. The gravitational field of an arbitrary distribution of mass external to a proof mass can be calculated either by summing the fields of suitably many point masses or by higher-order Gauss-Legendre integration over all elements surrounding the proof mass that are part of a finite-element mesh. This computer program is compatible with more general finite-element codes, such as NASTRAN, because it is configured to read a generic input data file, containing the detailed description of the finiteelement mesh.

Quadrelli, Marco

2005-01-01

93

Static spheres — Sources of scalar, electromagnetic, and gravitational fields  

Microsoft Academic Search

Static sources of scalar, electromagnetic, and gravitational fields are considered within the theory of general relativity and within the class of scalar-tensor gravitation theories. From the conditions of regularity and nonnegativeness of matter density a number of limitations on the possible model parameters are obtained. An example of a regular model in general relativity is presented.

K. A. Bronnikov; A. V. Khodunov

1977-01-01

94

Lensing by Distant Clusters: HST Observations of Weak Shear in the Field of 3C324  

E-print Network

We present the detection of weak gravitational lensing in the field of the radio galaxy 3C324 (z=1.206) using deep HST imaging. ~From an analysis of the shapes of faint R=24.5-27.5 galaxies in the field we measure a weak, coherent distortion centered close to the radio source. This shear field most likely arises from gravitational lensing of distant field galaxies by a foreground mass concentration. In the light of previous observations of this region, which indicate the presence of a rich cluster around the radio source, we suggest that the most likely candidate for the lens is the cluster associated with the radio galaxy at z=1.2. If so, this is the most distant cluster to have been detected by weak shear observations. Such a statement has two important consequences. Firstly, it shows that massive, collapsed structures exist in the high redshift Universe, and secondly that a significant fraction of the R=24.5-27.5 field galaxy population lies beyond z=1.2.

Ian Smail; Mark Dickinson

1995-10-08

95

Gravitational Field Inside and Near a Caustic Ring  

E-print Network

We present an analytic calculation of the gravitational field inside and near a caustic ring of dark matter. The calculation may facilitate N-body simulation studies on the effects that dark matter caustics have on galaxy formation.

Heywood Tam

2012-05-07

96

Weak Gravitational Lensing as a Probe of Physical Properties of Substructures in Dark Matter Halos  

NASA Astrophysics Data System (ADS)

We propose a novel method to select satellite galaxies in outer regions of galaxy groups or clusters using weak gravitational lensing. The method is based on the theoretical expectation that the tangential shear pattern around satellite galaxies would appear with negative values at an offset distance from the center of the main halo. We can thus locate the satellite galaxies statistically with an offset distance of several lensing smoothing scales by using the standard reconstruction of surface mass density maps from weak lensing observation. We test the idea using high-resolution cosmological simulations. We show that subhalos separated from the center of the host halo are successfully located even without assuming the position of the center. For a number of such subhalos, the characteristic mass and offset length can be also estimated on a statistical basis. We perform a Fisher analysis to show how well upcoming weak lensing surveys can constrain the mass density profile of satellite galaxies. In the case of the Large Synoptic Survey Telescope with a sky coverage of 20,000 deg2, the mass of the member galaxies in the outer region of galaxy clusters can be constrained with an accuracy of ~0.1 dex for galaxy clusters with mass 1014 h –1 M ? at z = 0.15. Finally we explore the detectability of tidal stripping features for subhalos having a wide range of masses of 1011-1013 h –1 M ?.

Shirasaki, Masato

2015-02-01

97

Weak lensing studies with GOODS/ACS fields  

NASA Astrophysics Data System (ADS)

The main goal of this thesis is to improve current understanding of structure formation in the universe at z ~ 1--2 through weak lensing studies with the Hubble Space Telescope ( HST ) Advanced Camera for Surveys (ACS) data, obtained as part of the Great Observatories Origin Deep Survey (GOODS) project. In this thesis, we present a uniform approach to describes light propagation in both isotropic universe and weakly perturbed universe to discuss the effects of gravitational lensing, apply it to two prime applications of gravitational lensing to cosmology; lensing by dark matter halos and lensing by the large- scale structure, investigate the expected weak lensing effects from the applications and discuss how the effects can be measured through galaxy shape. We describe how galaxy shapes are measured from the GOODS data. We present preliminary measurements of galaxy-galaxy lensing and detection of cosmic shear. We detect a clear galaxy-galaxy lensing signal for lens galaxies at z ~ 0.5 at projected separations ranging from 10" to 200". The detected shear is compatible with ground-based measurements obtained for low-redshift galaxies. We also detect a clear cosmic shear signal using source galaxies at z ~ 1.0. The detected shear is generally consistent with other observations that measured s 8 ~= 0.7.

Park, Yousin

2006-06-01

98

Fermat principle in arbitrary gravitational fields  

SciTech Connect

The Fermat principle is reviewed and used to derive the zigzag path constructed for massive and massless particles in order to determine if these paths are a suitable approximation to the first order of the gravitational lens effect. It is found that such paths are suitable for thin comoving gravitational lenses to the first order in the lens effect, and also if there is a nonstationary perturbation. As an example, the Fermat principle is applied to a perturbation by gravitational waves, and the transverse velocity of the caustic motion is derived. This velocity creates difficulty for the proposal by McBreen and Metcalfe (1988) that gamma-ray bursts come from small, hot BL Lac cores crossed by microcaustics. 23 refs.

Kovner, I. (Weizmann Institute of Science, Rehovot (Israel))

1990-03-01

99

Biological effects due to weak magnetic field on plants  

NASA Astrophysics Data System (ADS)

Throughout the evolution process, Earth's magnetic field (MF, about 50 ?T) was a natural component of the environment for living organisms. Biological objects, flying on planned long-term interplanetary missions, would experience much weaker magnetic fields, since galactic MF is known to be 0.1-1 nT. However, the role of weak magnetic fields and their influence on functioning of biological organisms are still insufficiently understood, and is actively studied. Numerous experiments with seedlings of different plant species placed in weak magnetic field have shown that the growth of their primary roots is inhibited during early germination stages in comparison with control. The proliferative activity and cell reproduction in meristem of plant roots are reduced in weak magnetic field. Cell reproductive cycle slows down due to the expansion of G 1 phase in many plant species (and of G 2 phase in flax and lentil roots), while other phases of cell cycle remain relatively stabile. In plant cells exposed to weak magnetic field, the functional activity of genome at early pre-replicate period is shown to decrease. Weak magnetic field causes intensification of protein synthesis and disintegration in plant roots. At ultrastructural level, changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells were observed in pea roots exposed to weak magnetic field. Mitochondria were found to be very sensitive to weak magnetic field: their size and relative volume in cells increase, matrix becomes electron-transparent, and cristae reduce. Cytochemical studies indicate that cells of plant roots exposed to weak magnetic field show Ca 2+ over-saturation in all organelles and in cytoplasm unlike the control ones. The data presented suggest that prolonged exposures of plants to weak magnetic field may cause different biological effects at the cellular, tissue and organ levels. They may be functionally related to systems that regulate plant metabolism including the intracellular Ca 2+ homeostasis. However, our understanding of very complex fundamental mechanisms and sites of interactions between weak magnetic fields and biological systems is still incomplete and still deserve strong research efforts.

Belyavskaya, N. A.

2004-01-01

100

H2+ in a weak magnetic field  

NASA Astrophysics Data System (ADS)

The electronic energy of H2+ in magnetic fields of up to B=0.2{{B}0} (or 4.7× {{10}4} T) is investigated. Numerical values of the magnetic susceptibility for both the diamagnetic and paramagnetic contributions are reported for arbitrary orientations of the molecule in the magnetic field. It is shown that both diamagnetic and paramagnetic susceptibilities grow with inclination, while paramagnetic susceptibility is systematically much smaller than the diamagnetic one. Accurate two-dimensional Born–Oppenheimer surfaces are obtained with special trial functions. Using these surfaces, vibrational and rotational states are computed and analyzed for the isotopologues H2+ and D2+.

Medel Cobaxin, Héctor; Alijah, Alexander; López Vieyra, Juan Carlos; Turbiner, Alexander V.

2015-02-01

101

Einstein's 1912-1913 struggles with Gravitation Theory: Importance of Static Gravitational Fields Theory  

E-print Network

In December 1911, Max Abraham published a paper on gravitation at the basis of which was Albert Einstein's 1911 June conclusion about a relationship between the velocity of light and the gravitational potential. In February 1912, Einstein published his work on static gravitational fields, which was based on his 1911 June theory. In March 1912, Einstein corrected his paper, but Abraham claimed that Einstein borrowed his equations; however, it was actually Abraham who needed Einstein's ideas and not the other way round. Einstein thought that Abraham converted to his theory of static fields while Abraham presumed exactly the opposite. Einstein then moved to Zurich and switched to new mathematical tools. He examined various candidates for generally covariant field equations, and already considered the field equations of his general theory of relativity about three years before he published them in November 1915. However, he discarded these equations only to return to them more than three years later. Einstein's 1...

Weinstein, Galina

2012-01-01

102

Probing Dark Energy via Weak Gravitational Lensing with the SuperNova Acceleration Probe (SNAP)  

E-print Network

SNAP is a candidate for the Joint Dark Energy Mission (JDEM) that seeks to place constraints on the dark energy using two distinct methods. The first, Type Ia SN, is discussed in a companion white paper. The second method is weak gravitational lensing, which relies on the coherent distortions in the shapes of background galaxies by foreground mass structures. The excellent spatial resolution and photometric accuracy afforded by a 2-meter space-based observatory are crucial for achieving the high surface density of resolved galaxies, the tight control of systematic errors in the telescope's Point Spread Function (PSF), and the exquisite redshift accuracy and depth required by this project. These are achieved by the elimination of atmospheric distortion and much of the thermal and gravity loads on the telescope. The SN and WL methods for probing dark energy are highly complementary and the error contours from the two methods are largely orthogonal.

SNAP Collaboration

2005-07-19

103

Quantum physics in inertial and gravitational fields  

E-print Network

Covariant generalizations of well-known wave equations predict the existence of inertial-gravitational effects for a variety of quantum systems that range from Bose-Einstein condensates to particles in accelerators. Additional effects arise in models that incorporate Born reciprocity principle and the notion of a maximal acceleration. Some specific examples are discussed in detail.

G. Papini

2003-04-22

104

Unification of Gravitation, Gauge Field and Dark Energy  

E-print Network

This paper is composed of two correlated topics: 1. unification of gravitation with gauge fields; 2. the coupling between the daor field and other fields and the origin of dark energy. After introducing the concept of ``daor field" and discussing the daor geometry, we indicate that the complex daor field has two kinds of symmetry transformations. Hence the gravitation and SU(1,3) gauge field are unified under the framework of the complex connection. We propose a first-order nonlinear coupling equation of the daor field, which includes the coupling between the daor field and SU(1,3) gauge field and the coupling between the daor field and the curvature, and from which Einstein's gravitational equation can be deduced. The cosmological observations imply that dark energy cannot be zero, and which will dominate the doom of our Universe. The real part of the daor field self-coupling equation can be regarded as Einstein's equation endowed with the cosmological constant. It shows that dark energy originates from the self-coupling of the space-time curvature, and the energy-momentum tensor is proportional to the square of coupling constant \\lambda. The dark energy density given by our scenario is in agreement with astronomical observations. Furthermore, the Newtonian gravitational constant G and the coupling constant \\epsilon of gauge field satisfy G= \\lambda^{2}\\epsilon^{2}.

Xin-Bing Huang

2005-08-26

105

NASA Computational Case Study: Modeling Planetary Magnetic and Gravitational Fields  

NASA Technical Reports Server (NTRS)

In this case study, we model a planet's magnetic and gravitational fields using spherical harmonic functions. As an exercise, we analyze data on the Earth's magnetic field collected by NASA's MAGSAT spacecraft, and use it to derive a simple magnetic field model based on these spherical harmonic functions.

Simpson, David G.; Vinas, Adolfo F.

2014-01-01

106

Weyl fluid dark matter model tested on the galactic scale by weak gravitational lensing  

NASA Astrophysics Data System (ADS)

The higher-dimensional Weyl curvature induces on the brane a new source of gravity. This Weyl fluid of geometrical origin (reducing in the spherically symmetric, static configuration to a dark radiation and dark pressure) modifies spacetime geometry around galaxies and has been shown to explain the flatness of galactic rotation curves. Independent observations for discerning between the Weyl fluid and other dark matter models are necessary. Gravitational lensing could provide such a test. Therefore we study null geodesics and weak gravitational lensing in the dark radiation dominated region of galaxies in a class of spherically symmetric braneworld metrics. We find that the lensing profile in the braneworld scenario is distinguishable from dark matter lensing, despite both the braneworld scenario and dark matter models fitting the rotation curve data. In particular, in the asymptotic regions, light deflection is 18% enhanced as compared to dark matter halo predictions. For a linear equation of state of the Weyl fluid, we further find a critical radius below which braneworld effects reduce, while above it they amplify light deflection. This is in contrast to any dark matter model, the addition of which always increases the deflection angle.

Wong, K. C.; Harko, T.; Cheng, K. S.; Gergely, L. Á.

2012-08-01

107

Vacuum entanglement enhancement by a weak gravitational field  

SciTech Connect

Separate regions in space are generally entangled, even in the vacuum state. It is known that this entanglement can be swapped to separated Unruh-DeWitt detectors, i.e., that the vacuum can serve as a source of entanglement. Here, we demonstrate that, in the presence of curvature, the amount of entanglement that Unruh-DeWitt detectors can extract from the vacuum can be increased.

Cliche, M. [Department of Physics, Cornell University, Ithaca, New York, 14853 (United States); Kempf, A. [Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada)

2011-02-15

108

The quadratic Zeeman effect for weak fields on hydrogen  

Microsoft Academic Search

Using classical mechanics the author analyses the effect of a magnetic field on a hydrogen atom. The field is assumed weak enough for both classical and quantal degenerate perturbation theory to be valid. An approximate Hamiltonian describing the mean motion is found and is shown to have several unusual features. In particular it has a double minimum with phase space

D. Richards

1983-01-01

109

Quantum gravitational optics in the field of a gravitomagnetic monopole  

E-print Network

Vacuum polarization in QED in a background gravitational field induces interactions which {\\it effectively} modify the classical picture of light rays as the null geodesics of spacetime. After a short introduction on the main aspects of the quantum gravitational optics, as a nontrivial example, we study this effect in the background of NUT space characterizing the spacetime of a spherical mass endowed with a gravitomagnetic monopole charge, the so called NUT factor.

N. Ahmadi; S. Khoeini-Moghaddam; M. Nouri-Zonoz

2006-12-26

110

The Theory of Superconducting Quantum Networks in Weak Magnetic Fields  

Microsoft Academic Search

High-T_{rm c} superconductors exhibit reproducible magnetoconductance and microwave absorption in weak magnetic fields. We have modeled the high-T_{rm c} ceramics as a network of superconducting wires weakly coupled at nodes. A linear network model is developed in which the wires and nodes are represented by S matrices. A total network S matrix is constructed from the wire and node S

Mark John Jeffery

1991-01-01

111

Does the charge of a body reduce its gravitational field?  

E-print Network

One can get the impression from the Reissner-Nordstrom solution of Einstein's equations that the charge of a body reduces its gravitational field. This looks surprising since the energy of the electrostatic field surrounding a charged body, must contribute positively, as an additional, "electromagnetic mass", to the gravitational field produced by the body. We resolve this puzzle by showing that the mass M in the Reissner-Nordstrom solution is not the "bare mass" of the body, but its "renormalized mass". I. e. M, in addition to the bare mass, includes the total electromagnetic mass of the body. But at finite distances from the body only a part of the electromagnetic mass contributes to the gravitational field. That is why the gravity of a charged body is determined by the quantity smaller than M.

V. Hushwater

2010-06-02

112

Topological quantization of gravitational fields as generalized harmonic maps  

E-print Network

We apply the topological quantization method to some gravitational fields which can be represented as generalized harmonic maps. This representation extends the well-known concept of harmonic maps and allows us to describe some solutions to the Einstein field equations as generalized strings, where the base space for the generalized harmonic map is a two-dimensional manifold. The results obtained here point to an incompatibility of the classical description of the gravitational field and its symmetries with a discretization of the parameters that enter in its description.

Francisco Nettel

2015-02-03

113

Topological quantization of gravitational fields as generalized harmonic maps  

E-print Network

We apply the topological quantization method to some gravitational fields which can be represented as generalized harmonic maps. This representation extends the well-known concept of harmonic maps and allows us to describe some solutions to the Einstein field equations as generalized strings, where the base space for the generalized harmonic map is a two-dimensional manifold. The results obtained here point to an incompatibility of the classical description of the gravitational field and its symmetries with a discretization of the parameters that enter in its description.

Nettel, Francisco

2015-01-01

114

Contributions of Spherical Harmonics to Magnetic and Gravitational Fields  

NASA Technical Reports Server (NTRS)

Gravitational forces are of cardinal importance in the dynamics of spacecraft; magnetic attractions sometime play a significant role also, as was the case with the Long Duration Exposure Facility, and as is now true for the first segment of Space Station Freedom. Both satellites depend on gravitational moment and a device known as a magnetic damper to stabilize their orientation. Magnetic fields are mathematically similar to gravitational fields in one important respect: each can be regarded as a gradient of a potential function that, in turn, can be described as an infinite series of spherical harmonics. Consequently, the two fields can be computed, in part, with quantities that need only be evaluated once, resulting in a savings of time when both fields are needed. The objective of this material is to present magnetic field and gravitational force expressions, and point out the terms that belong to both this is accomplished in Section 1 and 2. Section 3 contains the deductive reasoning with which one obtains the expressions of interest. Finally, examples in Section 4 show these equations can be used to reproduce others that arise in connection with special cases such as the magnetic field produced by a tilted dipole, and gravitational force exerted by an oblate spheroid. The mathematics are discussed in the context of terrestrial fields; however, by substituting appropriate constants, the results can be made applicable to fields belonging to other celestial bodies. The expressions presented here share the characteristics of algorithms set forth for computing gravitational force. In particular, computation is performed speedily by means of recursion formulae, and the expressions do not suffer from the shortcoming of a singularity when evaluated at points that lie on the polar axis.

Roithmayr, Carlos M.

2004-01-01

115

Using Gravitational Analogies to Introduce Elementary Electrical Field Theory Concepts  

ERIC Educational Resources Information Center

Since electrical field concepts are usually unfamiliar, abstract, and difficult to visualize, conceptual analogies from familiar gravitational phenomena are valuable for teaching. Such analogies emphasize the underlying continuity of field concepts in physics and support the spiral development of student understanding. We find the following four…

Saeli, Susan; MacIsaac, Dan

2007-01-01

116

Gravitational Lens Systems to probe Extragalactic Magnetic Fields  

E-print Network

The Faraday rotation measurements of multiply-imaged gravitational lens systems can be effectively used to probe the existence of large-scale ordered magnetic fields in lensing galaxies and galaxy clusters. The available sample of lens systems appears to suggest the presence of a coherent large-scale magnetic field in giant elliptical galaxies somewhat similar to the spiral galaxies.

Narasimha, D

2008-01-01

117

Decoherence and coherence in gravitational, electric and strong nuclear fields  

E-print Network

Inspired in the work of Erich Joos which appreciated the role played by matter in making the decoherence of the gravitational field, we developed an alternative way of treating the former problem. Besides this, we used the alternative approach to examine the decoherence of the electric field performed by the conduction electrons in metals. As a counterpoint, we studied the coherence of the electric color field inside nucleons, which renders the strong field a totally quantum character.

P. R. Silva

2010-10-25

118

On the gravitational scattering of gravitational waves  

NASA Astrophysics Data System (ADS)

We discuss the scattering of weak gravitational waves from a slowly rotating gravitational source, having mass M and angular momentum J. We start considering the dynamics of a massless spin-2 field {{? }? ? } propagating in the weak gravitational field of the source, writing down the Fierz-Pauli in the presence of a slightly curved background. We adopt a semiclassical framework, where the gravitational background is described as a classical external field; meanwhile, the spin-2 field is treated quantum mechanically. In the weak-coupling limit, in which the typical wavelength of {{? }? ? } satisfies {{? }? }\\gg {{R}s} (where Rs is the Schwarzschild radius of the source), we obtain the cross-section for the scattering process in the Born approximation. We also discuss helicity asymmetry, showing its relationship with the spin-2 field coupling to the derivatives of the background metric. We finally consider the transition to the case of gravitational wave scattering, showing that—under reasonable assumptions—gravitational waves are expected to follow the same behavior. Our results partly agree with those presented through the years by various authors. The present analysis suggests that the scattering of weak gravitational waves in the field of a macroscopic gravitational source still represents an interesting open issue for further careful investigation.

Sorge, Francesco

2015-02-01

119

The Coupling of a Linearized Gravitational Wave to Electromagnetic Fields and Relevant Noise Issues  

E-print Network

According to electrodynamical equations in curved spacetime we consider the coupling of a linearized weak gravitational wave (GW) to a Gaussian beam passing through a static magnetic field. It is found that unlike the properties of the "left-circular" and "right-circular" waves of the tangential perturbative photon fluxes in the cylindrical polar coordinates, the resultant effect of the tangential and radial perturbations can produce the unique nonvanishing photon flux propagating along the direction of the electric field of the Gaussian beam. This result might provide a larger detecting space for the high-frequency GWs in GHz band. Moreover, we also discuss the relevant noise issues.

Fang-Yu Li; Zhang-Han Wu; Yi Zhang

2003-11-21

120

Is the Quantum Hall Effect influenced by the gravitational field?  

E-print Network

Most of the experiments on the quantum Hall effect (QHE) were made at approximately the same height above sea level. A future international comparison will determine whether the gravitational field $\\mathbf{g}(x)$ influences the QHE. In the realm of (1 + 2)-dimensional phenomenological macroscopic electrodynamics, the Ohm-Hall law is metric independent (`topological'). This suggests that it does not couple to $\\mathbf{g}(x)$. We corroborate this result by a microscopic calculation of the Hall conductance in the presence of a post-Newtonian gravitational field.

Friedrich W. Hehl; Yuri N. Obukhov; Bernd Rosenow

2003-10-13

121

Probing Dark Energy via Weak Gravitational Lensing with the Supernova Acceleration Probe (SNAP)  

SciTech Connect

SNAP is a candidate for the Joint Dark Energy Mission (JDEM) that seeks to place constraints on the dark energy using two distinct methods. The first, Type Ia SN, is discussed in a separate white paper. The second method is weak gravitational lensing, which relies on the coherent distortions in the shapes of background galaxies by foreground mass structures. The excellent spatial resolution and photometric accuracy afforded by a 2-meter space-based observatory are crucial for achieving the high surface density of resolved galaxies, the tight control of systematic errors in the telescope's Point Spread Function (PSF), and the exquisite redshift accuracy and depth required by this project. These are achieved by the elimination of atmospheric distortion and much of the thermal and gravity loads on the telescope. The SN and WL methods for probing dark energy are highly complementary and the error contours from the two methods are largely orthogonal. The nominal SNAP weak lensing survey covers 1000 square degrees per year of operation in six optical and three near infrared filters (NIR) spanning the range 350 nm to 1.7 {micro}m. This survey will reach a depth of 26.6 AB magnitude in each of the nine filters and allow for approximately 100 resolved galaxies per square arcminute, {approx} 3 times that available from the best ground-based surveys. Photometric redshifts will be measured with statistical accuracy that enables scientific applications for even the faint, high redshift end of the sample. Ongoing work aims to meet the requirements on systematics in galaxy shape measurement, photometric redshift biases, and theoretical predictions.

Albert, J.; Aldering, G.; Allam, S.; Althouse, W.; Amanullah, R.; Annis, J.; Astier, P.; Aumeunier, M.; Bailey, S.; Baltay, C.; Barrelet, E.; Basa, S.; Bebek, C.; Bergstom, L.; Bernstein, G.; Bester, M.; Besuner, B.; Bigelow, B.; Blandford, R.; Bohlin, R.; Bonissent, A.; /Caltech /LBL, Berkeley /Fermilab /SLAC /Stockholm U. /Paris, IN2P3

2005-08-08

122

Field theory on R× S 3 topology. VI: Gravitation  

NASA Astrophysics Data System (ADS)

We extend to curved space-time the field theory on R×S3 topology in which field equations were obtained for scalar particles, spin one-half particles, the electromagnetic field of magnetic moments, an SU2 gauge theory, and a Schrödinger-type equation, as compared to ordinary field equations that are formulated on a Minkowskian metric. The theory obtained is an angular-momentum representation of gravitation. Gravitational field equations are presented and compared to the Einstein field equations, and the mathematical and physical similarity and differences between them are pointed out. The problem of motion is discussed, and the equations of motion of a rigid body are developed and given explicitly. One result which is worth emphazing is that while general relativity theory yields Newton's law of motion in the lowest approximation, our theory gives Euler's equations of motion for a rigid body in its lowest approximation.

Carmeli, M.; Malin, S.

1987-04-01

123

Why are living things sensitive to weak magnetic fields?  

PubMed

There is evidence for robust interactions of weak ELF magnetic fields with biological systems. Quite apart from the difficulties attending a proper physical basis for such interactions, an equally daunting question asks why these should even occur, given the apparent lack of comparable signals in the long-term electromagnetic environment. We suggest that the biological basis is likely to be found in the weak (?50?nT) daily swing in the geomagnetic field that results from the solar tidal force on free electrons in the upper atmosphere, a remarkably constant effect exactly in phase with the solar diurnal change. Because this magnetic change is locked into the solar-derived everyday diurnal response in living things, one can argue that it acts as a surrogate for the solar variation, and therefore plays a role in chronobiological processes. This implies that weak magnetic field interactions may have a chronodisruptive basis, homologous to the more familiar effects on the biological clock arising from sleep deprivation, phase-shift employment and light at night. It is conceivable that the widespread sensitivity of biological systems to weak ELF magnetic fields is vestigially derived from this diurnal geomagnetic effect. PMID:23915203

Liboff, Abraham R

2014-09-01

124

Penetration of a weak magnetic field into superconducting indium  

SciTech Connect

The penetration depth of a low frequency, weak magnetic field into superconducting indium has been studied as a function of temperature between 2 K and T/sub c/. The data are analyzed in terms of the BCS theory. Values of lambdaL-italic(0) and lambda(0) have been determined as 299 and 553 A, respectively, with an accuracy of 10%.

Raychaudhuri, A.K.; Egloff, C.; Rinderer, L.

1985-06-01

125

Self-consistent Mean Field theory in weakly ionized media  

E-print Network

We present a self-consistent mean field theory of the dynamo in 3D and turbulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreaction does not alter the beta effect while it suppresses the alpha effect when the strength of a mean magnetic field exceeds a critical value. These results suggest that a mean field dynamo operates much more efficiently in weakly ionized gas compared to the fully ionized gas. Furthermore, we show that in 2D, the turbulent diffusion is suppressed by back reaction when a mean magnetic field reaches the same critical strength, with the upper bound on turbulent diffusion given by its kinematic value. Astrophysical implications are discussed.

Nicolas Leprovost; Eun-Jin Kim

2007-10-10

126

Pair production in a strong magnetic field: the effect of a strong background gravitational field  

Microsoft Academic Search

We present the calculation of the probability production of an\\u000aelectron-positron pair in the presence of a strong magnetic field with\\u000atime-varying strength. The calculation takes into account the presence of a\\u000astrong, constant and uniform gravitational field in the same direction of the\\u000amagnetic field. The results show that the presence of the gravitational field\\u000ain general enhances the

Antonino Di Piazza; Giorgio Calucci

2004-01-01

127

Weak and strong magnetic fields in the solar photosphere  

SciTech Connect

We discuss very high-resolution (1/2'') magnetograms of quiet Sun and plage, which were obtained by using a tunable birefringent filter in Fe I lambda6302. A search for a turbulent bipolar field, using co-added and spatially filtered frames, is unsuccessful. Statistical analysis sets an upper limit of 50 gauss on the rms vertical component of such a field and probably rules out the possibility of field strengths exceeding 100 gauss in the inner network field observed at Kitt Peak. The area, total flux, and energy content of the strong (kilogauss) network fields are measured and compared with the upper limits for these properties of a hypothetical, widespread weak field. In quiet photosphere, a weak background field may contain interesting amounts of flux and energy, but the strong fields are dominant at higher levels and in plage. The total magnetic energy in quiet photosphere is roughly equal to the kinetic energy of granular and oscillatory velocities at the same level. By flux conservation, field strengths in the transition region are greater than 25 gauss in quiet network and 100 gauss in plage.

Tarbell, T.D.; Title, A.M.; Schoolman, S.A.

1979-04-01

128

The Phase Space Quantum Description of Linearized Gravitational Field  

NASA Astrophysics Data System (ADS)

The Weyl-Wigner-Groenewold-Moyal quantization formalism is applied to the linearized gravitational field. Under this method the ground state Wigner functional and the propagator for the graviton are obtained. These results are compared with those found previously by other quantization techniques.

García-Compeán, Hugo; Turrubiates, Francisco J.

2015-01-01

129

Gravitational collapse of massless scalar field and cosmic censorship  

SciTech Connect

We present a numerical study of the gravitational collapse of a massless scalar field. We calculate the future evolution of new initial data, suggested by Christodoulou, and we show that in spite of the original expectations these data lead only to singularities engulfed by an event horizon.

Goldwirth, D.S.; Piran, T.

1987-12-15

130

Gravitation Field Calculations on a Dynamic Lattice by Distributed Computing  

Microsoft Academic Search

A new method of calculating numerically time evolution of a gravitational field in General Relatity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting

Petri Mähönen; Veikko Punkka

1991-01-01

131

Gravitational field calculations on a dynamic lattice by distributed computing  

Microsoft Academic Search

A new method of calculating numerically time evolution of a gravitational field in general relativity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting

P. Mähönen; V. Punkka

1991-01-01

132

Self-interacting gas in a gravitational wave field  

E-print Network

We investigate a relativistic self-interacting gas in the field of an external {\\it pp} gravitational wave. Based on symmetry considerations we ask for those forces which are able to compensate the imprint of the gravitational wave on the macroscopic 4-acceleration of the gaseous fluid. We establish an exactly solvable toy model according to which the stationary states which characterize such a situation have negative entropy production and are accompanied by instabilities of the microscopic particle motion. These features are similar to those which one encounters in phenomena of self-organization in many-particle systems.

Alexander B. Balakin; Winfried Zimdahl

2003-01-23

133

The MOG weak field approximation and observational test of galaxy rotation curves  

NASA Astrophysics Data System (ADS)

As an alternative to dark matter models, Modified Gravity (MOG) theory is a covariant modification of Einstein gravity. The theory introduces two additional scalar fields and one vector field. The aim is to explain the dynamics of astronomical systems based only on their baryonic matter. The effect of the vector field in the theory resembles a Lorentz force where each particle has a charge proportional to its inertial mass. The weak field approximation of MOG is derived by perturbing the metric and the fields around Minkowski space-time. We obtain an effective gravitational potential which yields the Newtonian attractive force plus a repulsive Yukawa force. This potential, in addition to the Newtonian gravitational constant, GN, has two additional constant parameters ? and ?. We use The H I Nearby Galaxy Survey catalogue of galaxies and fix the two parameters ? and ? of the theory to be ? = 8.89 ± 0.34 and ? = 0.042 ± 0.004 kpc-1. We then apply the effective potential with the fixed universal parameters to the Ursa Major catalogue of galaxies and obtain good fits to galaxy rotation curve data with an average value of ?2 = 1.07. In the fitting process, only the stellar mass-to-light ratio (M/L) of the galaxies is a free parameter. As predictions of MOG, our derived M/L is shown to be correlated with the colour of galaxies. We also fit the Tully-Fisher relation for galaxies. As an alternative to dark matter, introducing an effective weak field potential for MOG opens a new window to the astrophysical applications of the theory.

Moffat, J. W.; Rahvar, S.

2013-12-01

134

Gravitational instantons, extra dimensions and form fields  

E-print Network

A broad class of higher dimensional instanton solutions are found for a theory which contains gravity, a scalar field and antisymmetric tensor fields of arbitrary rank. The metric used, a warp product of an arbitrary number of any compact Einstein manifolds, includes many of great interest in particle physics and cosmology. For example 4D FRW universes with additional dimensions compactified on a Calabi-Yau three fold, a torus, a compact hyperbolic manifold or a sphere are all included. It is shown that the solution of this form which dominates the Hartle Hawking path integral is always a higher dimensional generalisation of a Hawking Turok instanton when the potential of the scalar field is such that these instantons can exist. On continuation to Lorentzian signature such instantons give rise to a spacetime in which all of the spatial dimensions are of equal size and where the spatial topology is that of a sphere. The extra dimensions are thus not hidden. In the case where the potential for the scalar field is generated solely by a dilatonic coupling to the form fields we find no integrable instantons at all. In particular we find no integrable solutions of the type under consideration for the supergravity theories which are the low energy effective field theories of superstrings.

J. A. Gray; E. J. Copeland

2001-02-15

135

Reducing the weak lensing noise for the gravitational wave Hubble diagram using the non-Gaussianity of the magnification distribution  

SciTech Connect

Gravitational wave sources are a promising cosmological standard candle because their intrinsic luminosities are determined by fundamental physics (and are insensitive to dust extinction). They are, however, affected by weak lensing magnification due to the gravitational lensing from structures along the line of sight. This lensing is a source of uncertainty in the distance determination, even in the limit of perfect standard candle measurements. It is commonly believed that the uncertainty in the distance to an ensemble of gravitational wave sources is limited by the standard deviation of the lensing magnification distribution divided by the square root of the number of sources. Here we show that by exploiting the non-Gaussian nature of the lensing magnification distribution, we can improve this distance determination, typically by a factor of 2-3; we provide a fitting formula for the effective distance accuracy as a function of redshift for sources where the lensing noise dominates.

Hirata, Christopher M. [Caltech M/C 350-17, Pasadena, California 91125 (United States); Holz, Daniel E. [Theoretical Division, MS-B227, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Cutler, Curt [Jet Propulsion Laboratory, M/S 169-327, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)

2010-06-15

136

SL(2C) invariance of the gravitational field  

Microsoft Academic Search

The gravitational field equations of general relativity theory are cast into a Yang-Mills-type theory by use of the group SL(2,C). The spin coefficients take the rôle of the Yang-Mills-like potentials, whereas the Riemann tensor takes the rôle of the fields. Comparison of this formalism with that of Utiyama and Kibble who related invariance under the Lorentz and the Poincaré groups

Moshe Carmeli; Wright-Patterson AFB

1972-01-01

137

Physical decomposition of the gauge and gravitational fields  

E-print Network

Physical decomposition of the non-Abelian gauge field has recently solved the two-decade-lasting problem of a meaningful gluon spin. Here we extend this approach to gravity and attack the century-lasting problem of a meaningful gravitational energy. The metric is unambiguously separated into a pure geometric term which contributes null curvature tensor, and a physical term which represents the true gravitational effect and always vanishes in a flat space-time. By this decomposition the conventional pseudo-tensors of the gravitational stress-energy are easily rescued to produce definite physical result. Our decomposition applies to any symmetric tensor, and has interesting relation to the transverse-traceless (TT) decomposition discussed by Arnowitt, Deser and Misner, and by York.

Xiang-Song Chen; Ben-Chao Zhu

2011-01-19

138

Turbulent Diffusion of Magnetic Fields in Weakly Ionized Gas  

E-print Network

The diffusion of uni-directional magnetic fields by two dimensional turbulent flows in a weakly ionized gas is studied. The fields here are orthogonal to the plane of fluid motion. This simple model arises in the context of the decay of the mean magnetic flux to mass ratio in the interstellar medium. When ions are strongly coupled to neutrals, the transport of a large--scale magnetic field is driven by both turbulent mixing and nonlinear, ambipolar drift. Using a standard homogeneous and Gaussian statistical model for turbulence, we show rigorously that a large-scale magnetic field can decay on at most turbulent mixing time scales when the field and neutral flow are strongly coupled. There is no enhancement of the decay rate by ambipolar diffusion. These results extend the Zeldovich theorem to encompass the regime of two dimensional flows and orthogonal magnetic fields, recently considered by Zweibel (2002). The limitation of the strong coupling approximation and its implications are discussed.

Eun-jin Kim; P. H. Diamond

2002-09-25

139

Improving three-dimensional mass mapping with weak gravitational lensing using galaxy clustering  

NASA Astrophysics Data System (ADS)

Context. The weak gravitational lensing distortion of distant galaxy images (defined as sources) probes the projected large-scale matter distribution in the Universe. The availability of redshift information in galaxy surveys also allows us to recover the radial matter distribution to a certain degree. Aims: To improve quality in the mass mapping, we combine the lensing information with the spatial clustering of a population of galaxies (defined as tracers) that trace the matter density with a known galaxy bias. Methods: We construct a minimum-variance estimator for the 3D matter density that incorporates the angular distribution of galaxy tracers, which are coarsely binned in redshift. Merely the second-order bias of the tracers has to be known, which can in principle be self-consistently constrained in the data by lensing techniques. This synergy introduces a new noise component because of the stochasticity in the matter-tracer density relation. We give a description of the stochasticity noise in the Gaussian regime, and we investigate the estimator characteristics analytically. We apply the estimator to a mock survey based on the Millennium Simulation. Results: The estimator linearly mixes the individual lensing mass and tracer number density maps into a combined smoothed mass map. The weighting in the mix depends on the signal-to-noise ratio (S/N) of the individual maps and the correlation, R, between the matter and galaxy density. The weight of the tracers can be reduced by hand. For moderate mixing, the S/N in the mass map improves by a factor ~2-3 for R ? 0.4. Importantly, the systematic offset between a true and apparent mass peak distance (defined as z-shift bias) in a lensing-only map is eliminated, even for weak correlations of R ~ 0.4. Conclusions: If the second-order bias of tracer galaxies can be determined, the synergy technique potentially provides an option to improve redshift accuracy and completeness of the lensing 3D mass map. Herein, the aim is to visualise the spatial distribution of cluster-sized mass peaks. Our noise description of the estimator is accurate in the linear, Gaussian regime. However, its performance on sub-degree scales depends on the details in the galaxy bias mechanism and, hence, on the choice of the tracer population. Nonetheless, we expect that the mapping technique yields qualitatively reasonable results even for arcmin smoothing scales, as observed when this technique is applied to the mock survey with two different tracer populations.

Simon, Patrick

2013-12-01

140

Gravitational collapse of homogeneous scalar fields  

E-print Network

Conditions under which gravity coupled to self interacting scalar field determines singularity formation are found and discussed. It is shown that, under a suitable matching with an external space, the boundary, if collapses completely, may give rise to a naked singularity. Issues related to the strength of the singularity are discussed.

Roberto Giambó

2005-05-27

141

Weak magnetic fields in central stars of planetary nebulae?  

NASA Astrophysics Data System (ADS)

Context. It is not yet clear whether magnetic fields play an essential role in shaping planetary nebulae (PNe), or whether stellar rotation alone and/or a close binary companion, stellar or substellar, can account for the variety of the observed nebular morphologies. Aims: In a quest for empirical evidence verifying or disproving the role of magnetic fields in shaping planetary nebulae, we follow up on previous attempts to measure the magnetic field in a representative sample of PN central stars. Methods: We obtained low-resolution polarimetric spectra with FORS 2 installed on the Antu telescope of the VLT for a sample of 12 bright central stars of PNe with different morphologies, including two round nebulae, seven elliptical nebulae, and three bipolar nebulae. Two targets are Wolf-Rayet type central stars. Results: For the majority of the observed central stars, we do not find any significant evidence for the existence of surface magnetic fields. However, our measurements may indicate the presence of weak mean longitudinal magnetic fields of the order of 100 Gauss in the central star of the young elliptical planetary nebula IC 418 as well as in the Wolf-Rayet type central star of the bipolar nebula Hen 2-113 and the weak emission line central star of the elliptical nebula Hen 2-131. A clear detection of a 250 G mean longitudinal field is achieved for the A-type companion of the central star of NGC 1514. Some of the central stars show a moderate night-to-night spectrum variability, which may be the signature of a variable stellar wind and/or rotational modulation due to magnetic features. Conclusions: Since our analysis indicates only weak fields, if any, in a few targets of our sample, we conclude that strong magnetic fields of the order of kG are not widespread among PNe central stars. Nevertheless, simple estimates based on a theoretical model of magnetized wind bubbles suggest that even weak magnetic fields below the current detection limit of the order of 100 G may well be sufficient to contribute to the shaping of the surrounding nebulae throughout their evolution. Our current sample is too small to draw conclusions about a correlation between nebular morphology and the presence of stellar magnetic fields. Based on observations obtained at the European Southern Observatory, Paranal, Chile (ESO program No. 088.D-0425(A)).

Steffen, M.; Hubrig, S.; Todt, H.; Schöller, M.; Hamann, W.-R.; Sandin, C.; Schönberner, D.

2014-10-01

142

The non-linear interaction of the planetary gravitational field on earthquakes  

NASA Astrophysics Data System (ADS)

Researches, which refer to triggering of earthquakes, do not take into account the interactions of the gravitation of the planets. Despite the very weak effects of the interaction, an influence of the gravitation cannot always be neglected, specifically in critical conditions in the earth's crust before an earthquake. Tensions in the earth's crust are mostly the cause of earthquakes. If these tensions are in a critical condition, then also the fluctuations of the planetary gravitational field can cause these vibrations. Compared with other interactive forces, the weak fluctuations of the gravitation can only have an effect, if they are considered and observed as a "stimulation-field" over a long period of time. Indeed the system of the planets is very stable. The orbits of the big planets are very stable during millions of years. In addition to this, there is another important circumstance: the orbits of the planets lie almost on the same level. They represent natural oscillators on a big scale. Such a rhythm or such duration of vibration is determined by the time period from conjunction to conjunction of two planets. These are relatively stable frequencies. A non-linear correlation function forms a good way of describing these processes. Hij = a_1 cos(?ij) + a_2 cos(2?ij) + a_3 cos(3?ij) + ... (? is the angle between planets i and j) It can be shown that this correlation function can also be interpreted as a non-linear interaction of the planetary fluctuations of the gravitational field with material structures. The vibrations of the planetary gravitational field lead to higher vibrations, to higher harmonics, in material structures. The problems of the correlation function are the coefficients a_k and the meaning of Hij. In my researches I restricted myself to the polar qualities which are associated with the concepts of "stability" and "instability". The change from stable to unstable conditions and vice versa, can be observed in the evolution of many complex systems. Statistical researches will be presented and show this non-linear influence.

Nitsche, M. E.

2003-04-01

143

Influence of weak electric fields on the flame structure  

Microsoft Academic Search

A two-dimensional numerical model of a laminar premixed methane-air flame affected by weak direct-current electric field has been built based on the ANSYS CFX hydrodynamic solver. The chemical transformations in the model are described by the GRI-Mech scheme and are solved within the CHEMKIN package. Both packages exchange data during the runtime via ANSYS CFX programming interface. The steady-state simulations

Andrei Starikowskii; Michael Skoblin; Thomas Hammer

2008-01-01

144

The Weak-Field Limit of the Magnetorotational Instability  

NASA Astrophysics Data System (ADS)

We investigate the behavior of the magnetorotational instability in the limit of extremely weak magnetic field, i.e., as the ratio of ion cyclotron frequency to orbital frequency (X) becomes small. Considered only in terms of cold two-fluid theory, instability persists to arbitrarily small values of X, and the maximum growth rate is of the order of the orbital frequency except for the range me/mi<|X|<1, where it can be rather smaller. In this range, field aligned with rotation (X>0) produces slower growth than antialigned field (X<0). The maximum growth rate is generally achieved at smaller and smaller wavelengths as |X| diminishes. When |X|field. Because the most rapidly growing modes have extremely short wavelengths when |X| is small, they are often subject to viscous or resistive damping, which can result in suppressing all but the longest wavelengths, for which growth is much slower. We find that this sort of damping is likely to severely curtail the frequently invoked mechanism for cosmological magnetic field growth in which a magnetic field seeded by the Biermann battery is then amplified by the magnetorotational instability. On the other hand, the small-|X| case may introduce interesting effects in weakly ionized disks in which dust grains carry most of the electric charge.

Krolik, Julian H.; Zweibel, Ellen G.

2006-06-01

145

On gravitational waves  

NASA Astrophysics Data System (ADS)

Gravitational wave is produced whenever massive bodies accelerate under gravitational or nongravitational driving forces. The equations of Einstein's general theory of relativity have solutions in the weak field approximations which are very similar to those of electrodynamics. Analogies may be made between gravitational radiation and the electromagnetic radiation from accelerated charges although care has to be taken to recognize the limitations of such analogies. Because of the weakness of the Einstein's qravitational constant, the rate of energy radiated is normally very small. It is very desirable to be able to generate dynamic Newtonian gravitational field with sufficient intensity to be detected in the small laboratory. Experimental techniques used in generation and detection of dynamic Newtonian gravitational fields are reviewed and their application to Morse code communication in very near zone, as one approach to the gravitational wave technology.

Chiba, J.

1984-11-01

146

Diffusion of relativistic gas mixtures in gravitational fields  

E-print Network

A mixture of relativistic gases of non-disparate rest masses in a Schwarzschild metric is studied on the basis of a relativistic Boltzmann equation in the presence of gravitational fields. A BGK-type model equation of the collision operator of the Boltzmann equation is used in order to compute the non-equilibrium distribution functions by the Chapman-Enskog method. The main focus of this work is to obtain Fick's law without the thermal-diffusion cross-effect. Fick's law has four contributions, two of them are the usual terms proportional to the gradients of concentration and pressure. The other two are of the same nature as those which appears in Fourier's law in the presence of gravitational fields and are related with an acceleration and gravitational potential gradient, but unlike Fourier's law these two last terms are of non-relativistic order. Furthermore, it is shown that the coefficients of diffusion depend on the gravitational potential and they become larger than those in the absence of it.

Gilberto M. Kremer

2013-03-26

147

Numerical Tests of Fast Reconnection in Weakly Stochastic Magnetic Fields  

NASA Astrophysics Data System (ADS)

We study the effects of turbulence on magnetic reconnection using three-dimensional direct numerical simulations. This is the first attempt to test a model of fast magnetic reconnection in the presence of weak turbulence proposed by Lazarian & Vishniac. This model predicts that weak turbulence, which is generically present in most astrophysical systems, enhances the rate of reconnection by reducing the transverse scale for reconnection events and by allowing many independent flux reconnection events to occur simultaneously. As a result, the reconnection speed becomes independent of Ohmic resistivity and is determined by the magnetic field wandering induced by turbulence. We test the dependence of the reconnection speed on turbulent power, the energy injection scale, and resistivity. We apply the open and experiment with the outflow boundary conditions in our numerical model and discuss the advantages and drawbacks of various setups. To test our results, we also perform simulations of turbulence with the same outflow boundaries but without a large-scale field reversal, thus without large-scale reconnection. To quantify the reconnection speed we use both an intuitive definition, i.e., the speed of the reconnected flux inflow, and a more sophisticated definition based on a formally derived analytical expression. Our results confirm the predictions of the Lazarian and Vishniac model. In particular, we find that the reconnection speed is proportional to the square root of the injected power, as predicted by the model. The dependence on the injection scale for some of our models is a bit weaker than expected, i.e., l 3/4 inj, compared to the predicted linear dependence on the injection scale, which may require some refinement of the model or may be due to effects such as the finite size of the excitation region, which are not a part of the model. The reconnection speed was found to depend on the expected rate of magnetic field wandering and not on the magnitude of the guide field. In our models, we see no dependence on the guide field when its strength is comparable to the reconnected component. More importantly, while in the absence of turbulence we successfully reproduce the Sweet-Parker scaling of reconnection, in the presence of turbulence we do not observe any dependence on Ohmic resistivity, confirming that the reconnection of the weakly stochastic field is fast. We also do not observe a dependence on anomalous resistivity, which suggests that the presence of anomalous effects, e.g., Hall MHD effects, may be irrelevant for astrophysical systems with weakly stochastic magnetic fields.

Kowal, Grzegorz; Lazarian, A.; Vishniac, E. T.; Otmianowska-Mazur, K.

2009-07-01

148

Magnetophoresis of diamagnetic microparticles in a weak magnetic field.  

PubMed

Magnetic manipulation is a promising technique for lab-on-a-chip platforms. The magnetic approach can avoid problems associated with heat, surface charge, ionic concentration and pH level. The present paper investigates the migration of diamagnetic particles in a ferrofluid core stream that is sandwiched between two diamagnetic streams in a uniform magnetic field. The three-layer flow is expanded in a circular chamber for characterisation based on imaging of magnetic nanoparticles and fluorescent microparticles. A custom-made electromagnet generates a uniform magnetic field across the chamber. In a relatively weak uniform magnetic field, the diamagnetic particles in the ferrofluid move and spread across the chamber. Due to the magnetization gradient formed by the ferrofluid, diamagnetic particles undergo negative magnetophoresis and move towards the diamagnetic streams. The effects of magnetic field strength and the concentration of diamagnetic particles are studied in detail. PMID:25325774

Zhu, Gui-Ping; Hejiazan, Majid; Huang, Xiaoyang; Nguyen, Nam-Trung

2014-12-21

149

Gravitational Field Measurements for Understanding Planetary Internal Structures  

NASA Astrophysics Data System (ADS)

A powerful tool of investigating the interior structures of planets and their satellites in our solar system is the precision measurement of their gravitational fields. Spacecraft missions to the planets are equipped with quality radio systems for communications and navigation. Along with precision instrumentation at ground stations, the end-to-end radio links provide for very precise tracking of the Doppler effect resulting from the gravity signals. Detailed and proven mathematical formulations are used to construct gravitational fields of various sizes (degree and order) and resolution depending on the length of the mission and coverage of the target body. This has been applied at practically every planet and large satellite in the solar system. Recently, extensive work has been done on the asteroid Vesta and the Moon. This paper will summarize the techniques and methodologies and results from recent missions, such as GRAIL and Dawn, and the implications for interior structure.

Asmar, Sami; Konopliv, Alex

150

Generation of magnetic fields and gravitational waves at neutrino decoupling.  

PubMed

We show that an inhomogeneous cosmological lepton number may have produced turbulence in the primordial plasma when neutrinos entered the (almost) free-streaming regime. This effect may be responsible for the origin of cosmic magnetic fields and give rise to a detectable background of gravitational waves. An existence of inhomogeneous lepton asymmetry could be naturally generated by active-sterile neutrino oscillations or by some versions of the Affleck-Dine baryogenesis scenario. PMID:11800930

Dolgov, Alexander D; Grasso, Dario

2002-01-01

151

Normal Coordinates Describing Coupled Oscillations in the Gravitational Field  

E-print Network

The motion of a local source inducing small oscillations in the gravitational field is investigated and shown to exhibit pure rotational kinetic energy. Should the net affect of these slow, revolving oscillations cause large-scale rotations in spacetime it would certainly result in anomalous celestial accelerations. When this angular rotational frequency of spacetime is applied to the anomalous acceleration of the Pioneer 10/11 spacecrafts, the correlation is promising.

Walter J. Christensen Jr

2007-07-10

152

Generalized Fubini instantons of a self-gravitating scalar field  

NASA Astrophysics Data System (ADS)

We investigate the various types of Fubini instantons in the presence of gravity. The Fubini instanton describes the decay of a vacuum state as a consequence of tunneling from the top of a potential to an arbitrary state instead of a rolling down on the tachyonic potential. In this work, we concentrate on the tunneling solutions as representing the generalized Fubini instantons of a self-gravitating scalar field with the tachyonic potential having both quartic and quadratic terms.

Lee, Bum-Hoon; Lee, Wonwoo; Ro, Daeho; Yeom, Dong-han

2014-09-01

153

Gravitational field of a stationary circular cosmic string loop  

E-print Network

Gravitational field of a stationary circular cosmic string loop has been studied in the context of full nonlinear Einstein's theory of gravity. It has been assumed that the radial and tangential stresses of the loop are equal to the energy density of the string loop. An exact solution for the system has been presented which has a singularity at a finite distance from the axis,but is regular for any other distances from the axis of the loop.

A; A. Sen; N. Banerjee

1998-06-22

154

Controllability of spacecraft systems in a central gravitational field  

Microsoft Academic Search

The configuration space for rigid spacecraft systems in a central gravitational field can be modeled by SO(3)× IR3, where the special orthogonal group SO(3) represents the attitude dynamics and IR3 is for the orbital motion. The attitude dynamics of the spacecraft system is affected by the orbital elements through the well-known gravity-gradient torque. On the other hand, the effects of

Kuang-Yow Lian; Li-Sheng Wang; Li-Chen Fu

1994-01-01

155

Gravitation Field Calculations on a Dynamic Lattice by Distributed Computing  

NASA Astrophysics Data System (ADS)

A new method of calculating numerically time evolution of a gravitational field in General Relatity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting of two or more black holes or the structure of worm holes.

Mähönen, Petri; Punkka, Veikko

156

Gravitational field calculations on a dynamic lattice by distributed computing.  

NASA Astrophysics Data System (ADS)

A new method of calculating numerically time evolution of a gravitational field in general relativity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting of two or more black holes or the structure of worm holes.

Mähönen, P.; Punkka, V.

157

Quantum Statistical Field Theory in Gravitation and Cosmology  

Microsoft Academic Search

We describe how the concepts of quantum open systems and the methods of\\u000aclosed-time-path (CTP) effective action and influence functional (IF) can be\\u000ausefully applied to the analysis of statistical mechanical problems involving\\u000aquantum fields in gravitation and cosmology. In the first lecture we discuss in\\u000ageneral terms the relevance of open system concepts in the description of a\\u000avariety

B. L. Hu

1994-01-01

158

Electromagnetic waves in the gravitational field of massive dark halos  

E-print Network

The propagation of plane electromagnetic waves in the gravitational field inside a rotating cloud of dark matter is analyzed. Formulas for the deflection and absorption of light, and the rotation of the polarization plane are obtained in closed form in terms of the mass density and the angular velocity of the cloud. It is shown that the formulas can be considerably simplified for axisymmetric configurations. As an example, the formalism is applied to a rotating massive cloud described by a Plummer potential.

Shahen Hacyan

2014-01-31

159

Weak Gravitational Lensing by a Sample of X-Ray Luminous Clusters of Galaxies -- II. Comparison with Virial Masses  

E-print Network

Dynamic velocity dispersion and mass estimates are given for a sample of five X-ray luminous rich clusters of galaxies at intermediate redshifts (z~0.3) drawn from a sample of 39 clusters for which we have obtained gravitational lens mass estimates. The velocity dispersions are determined from between 9 and 20 redshifts measured with the LDSS spectrograph of the William Herschel Telescope, and virial radii are determined from imaging using the UH8K mosaic CCD camera on the University of Hawaii 2.24m telescope. Including clusters with velocity dispersions taken from the literature, we have velocity dispersion estimates for 12 clusters in our gravitational lensing sample. For this sample we compare the dynamical velocity dispersion estimates with our estimates of the velocity dispersions made from gravitational lensing by fitting a singular isothermal sphere profile to the observed tangential weak lensing distortion as a function of radius. In all but two clusters, we find a good agreement between the velocity dispersion estimates based on spectroscopy and on weak lensing.

Ragnvald J. Irgens; Per B. Lilje; Haakon Dahle; S. J. Maddox

2002-08-01

160

Gravitational lens  

NASA Astrophysics Data System (ADS)

After some historical remarks, we consider observational data on the gravitational lensing, different types of lensing: strong, weak, and microlensing, discovery of planets around distant stars by microlensing. We consider lensing with large deviation angles, when light passes close to the gravitational radius of the lens, and formation of weak relativistic rings. In the last part we consider an influence of plasma on the gravitational lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and due to a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. Both effects are taken into account. Dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, which strongest action is for longest radiowaves. We have shown that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.

Bisnovatyi-Kogan, G. S.; Tsupko, O. Yu.

161

Constraints on the shapes of galaxy dark matter haloes from weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We study the shapes of galaxy dark matter haloes by measuring the anisotropy of the weak gravitational lensing signal around galaxies in the second Red-sequence Cluster Survey (RCS2). We determine the average shear anisotropy within the virial radius for three lens samples: the "all" sample, which contains all galaxies with 19 < mr' < 21.5, and the "red" and "blue" samples, whose lensing signals are dominated by massive low-redshift early-type and late-type galaxies, respectively. To study the environmental dependence of the lensing signal, we separate each lens sample into an isolated and clustered part and analyse them separately. We address the impact of several complications on the halo ellipticity measurement, including PSF residual systematics in the shape catalogues, multiple deflections, and the clustering of lenses. We estimate that the impact of these is small for our lens selections. Furthermore, we measure the azimuthal dependence of the distribution of physically associated galaxies around the lens samples. We find that these satellites preferentially reside near the major axis of the lenses, and constrain the angle between the major axis of the lens and the average location of the satellites to ??? = 43.7° ± 0.3° for the "all" lenses, ??? = 41.7° ± 0.5° for the "red" lenses and ??? = 42.0° ± 1.4° for the "blue" lenses. We do not detect a significant shear anisotropy for the average "red" and "blue" lenses, although for the most elliptical "red" and "blue" galaxies it is marginally positive and negative, respectively. For the "all" sample, we find that the anisotropy of the galaxy-mass cross-correlation function ?f - f45? = 0.23 ± 0.12, providing weak support for the view that the average galaxy is embedded in, and preferentially aligned with, a triaxial dark matter halo. Assuming an elliptical Navarro-Frenk-White profile, we find that the ratio of the dark matter halo ellipticity and the galaxy ellipticity fh = eh/eg = 1.50-1.01+1.03, which for a mean lens ellipticity of 0.25 corresponds to a projected halo ellipticity of eh = 0.38-0.25+0.26 if the halo and the lens are perfectly aligned. For isolated galaxies of the "all" sample, the average shear anisotropy increases to ?f-f45? = 0.51-0.25+0.26 and fh = 4.73-2.05+2.17, whilst for clustered galaxies the signal is consistent with zero. These constraints provide lower limits on the average dark matter halo ellipticity, as scatter in the relative position angle between the galaxies and the dark matter haloes is expected to reduce the shear anisotropy by a factor ~2.

van Uitert, E.; Hoekstra, H.; Schrabback, T.; Gilbank, D. G.; Gladders, M. D.; Yee, H. K. C.

2012-09-01

162

Defect Mass in Gravitational Field and Red Shift of Atomic and Nuclear Radiation Spectra  

E-print Network

It is shown, that radiation spectrum of atoms (or nuclei) in the gravitational field has a red shift since the effective mass of radiating electrons (or nucleons) changes in this field. This red shift is equal to the red shift of radiation spectrum in the gravitational field measured in existence experiments. The same shift must arise when the photon (or $ \\gamma $ quantum) is passing through the gravitational field if it participates in gravitational interactions (photon has no rest mass). The absence of the double effect in the experiments, probably, means that photons (or $ \\gamma $ quanta) are passing through the gravitational field without interactions.

Kh. M. Beshtoev

2000-04-19

163

Jet Deflection by Very Weak Guide Fields during Magnetic Reconnection  

SciTech Connect

Previous 2D simulations of reconnection using a standard model of initially antiparallel magnetic fields have detected electron jets outflowing from the x point into the ion outflow exhausts. Associated with these jets are extended ''outer electron diffusion regions.'' New PIC simulations with an ion to electron mass ratio as large as 1836 (an H{sup +} plasma) now show that the jets are strongly deflected and the outer electron diffusion region is broken up by a very weak out-of-plane magnetic guide field, even though the diffusion rate itself is unchanged. Jet outflow and deflection are interpreted in terms of electron dynamics and are compared to recent measurements of jets in the presence of a small guide field in Earth's magnetosheath.

Goldman, M. V.; Newman, D. L.; Che, H. [Department of Physics and CIPS, University of Colorado, Boulder, Colorado 80309 (United States); Lapenta, G.; Markidis, S. [Centrum voor Plasma-Astrofysica, Katholieke Universiteit, Leuven (Belgium)

2011-09-23

164

The impact of thermodynamics on gravitational collapse: filament formation and magnetic field amplification  

E-print Network

Stars form by the gravitational collapse of interstellar gas. The thermodynamic response of the gas can be characterized by an effective equation of state. It determines how gas heats up or cools as it gets compressed, and hence plays a key role in regulating the process of stellar birth on virtually all scales, ranging from individual star clusters up to the galaxy as a whole. We present a systematic study of the impact of thermodynamics on gravitational collapse in the context of high-redshift star formation, but argue that our findings are also relevant for present-day star formation in molecular clouds. We consider a polytropic equation of state, P = k rho^Gamma, with both sub-isothermal exponents Gamma 1. We find significant differences between these two cases. For Gamma > 1, pressure gradients slow down the contraction and lead to the formation of a virialized, turbulent core. Weak magnetic fields are strongly tangled and efficiently amplified via the small-scale turbulent dynamo on timescales corresponding to the eddy-turnover time at the viscous scale. For Gamma < 1, on the other hand, pressure support is not sufficient for the formation of such a core. Gravitational contraction proceeds much more rapidly and the flow develops very strong shocks, creating a network of intersecting sheets and extended filaments. The resulting magnetic field lines are very coherent and exhibit a considerable degree of order. Nevertheless, even under these conditions we still find exponential growth of the magnetic energy density in the kinematic regime.

Thomas Peters; Dominik R. G. Schleicher; Ralf S. Klessen; Robi Banerjee; Christoph Federrath; Rowan J. Smith; Sharanya Sur

2012-09-26

165

Differentiation of optical isomers through enhanced weak-field interactions  

NASA Technical Reports Server (NTRS)

The influence of weak field interaction terms due to the cooperative effects which arise from a macroscopic assemblage of interacting sites is studied. Differential adsorption of optical isomers onto an achiral surface is predicted to occur if the surface was continuous and sufficiently large. However, the quantity of discontinuous crystal surfaces did not enhance the percentage of differentiation and thus the procedure of using large quantities of small particles was not a viable technique for obtaining a detectable differentiation of optical isomers on an achiral surface.

Aronowitz, S.

1980-01-01

166

BPS Dyon in a Weak Electromagnetic Field: Equations of Motion and Radiation Fields  

E-print Network

Dynamics of a BPS dyon in a weak, constant, electromagnetic field is studied through a perturbative analysis of appropriate non-linear field equations. The full Lorentz force law for a BPS dyon is established. Also derived are the radiation fields accompanying the motion.

Dongsu Bak; Choonkyu Lee

1994-02-09

167

The Gravitational Field of a Radiating Electromagnetic Dipole  

E-print Network

We begin with the time-dependent electric and magnetic dipole solution of Maxwell's equations in Minkowski space. This Maxwell field is then used to determine the behavior of the gravitational field (the Weyl tensor) as a second-order perturbation off of the Minkowski background. From the Weyl tensor we go on and find the spin-coefficients and the full metric in this approximation. The physical meaning of many of the relations is discussed. In particular we can identify the conservation law of angular momentum that contains an angular momentum flux term.

Tim Adamo; Ezra T Newman

2008-07-22

168

Vacuum Effects in Gravitational Fields: Theory and Detectability  

E-print Network

In this thesis, we investigate quantum vacuum effects in the presence of gravitational fields. After discussing the general theory of vacuum effects in strong fields we apply it to the relevant issue of the interaction of the quantum vacuum with black hole geometries. In particular we consider the long-standing problem of the interpretation of gravitational entropy. After these investigations, we discuss the possible experimental tests of particle creation from the quantum vacuum. This leads us to study acoustic geometries and their way of ``simulating'' gravitational structures, such as horizons and black holes. We study the stability of these structures and the problems related to setting up experimental detection of ``phonon Hawking flux'' from acoustic horizons. This line of research then leads us to propose a new model for explaining the emission of light in the phenomenon of Sonoluminescence, based on the dynamical Casimir effect. This is possibly amenable to experimental investigation. Finally we consider high energy phenomena in the early universe. In particular we discuss inflation and possible alternative frameworks for solving the cosmological puzzles.

S. Liberati

2000-09-14

169

Apparatus and method for producing an artificial gravitational field  

NASA Technical Reports Server (NTRS)

An apparatus and method is disclosed for producing an artificial gravitational field in a spacecraft by rotating the same around a spin axis. The centrifugal force thereby created acts as an artificial gravitational force. The apparatus includes an engine which produces a drive force offset from the spin axis to drive the spacecraft towards a destination. The engine is also used as a counterbalance for a crew cabin for rotation of the spacecraft. Mass of the spacecraft, which may include either the engine or crew cabin, is shifted such that the centrifugal force acting on that mass is no longer directed through the center of mass of the craft. This off-center centrifugal force creates a moment that counterbalances the moment produced by the off-center drive force to eliminate unwanted rotation which would otherwise be precipitated by the offset drive force.

Mccanna, Jason (inventor)

1993-01-01

170

Quantum limit on time measurement in a gravitational field  

NASA Astrophysics Data System (ADS)

Good clocks are of importance both to fundamental physics and for applications in astronomy, metrology and global positioning systems. In a recent technological breakthrough, researchers at NIST have been able to achieve a stability of one part in 1018 using an ytterbium clock. This naturally raises the question of whether there are fundamental limits to time keeping. In this article we point out that gravity and quantum mechanics set a fundamental limit on the fractional frequency uncertainty of clocks. This limit comes from a combination of the uncertainty relation, the gravitational redshift and the relativistic time dilation effect. For example, a single ion aluminium clock in a terrestrial gravitational field cannot achieve a fractional frequency uncertainty better than one part in 1022. This fundamental limit explores the interaction between gravity and quantum mechanics on a laboratory scale.

Sinha, Supurna; Samuel, Joseph

2015-01-01

171

Effective field theory of weakly coupled inflationary models  

SciTech Connect

The application of Effective Field Theory (EFT) methods to inflation has taken a central role in our current understanding of the very early universe. The EFT perspective has been particularly useful in analyzing the self-interactions determining the evolution of co-moving curvature perturbations (Goldstone boson modes) and their influence on low-energy observables. However, the standard EFT formalism, to lowest order in spacetime differential operators, does not provide the most general parametrization of a theory that remains weakly coupled throughout the entire low-energy regime. Here we study the EFT formulation by including spacetime differential operators implying a scale dependence of the Goldstone boson self-interactions and its dispersion relation. These operators are shown to arise naturally from the low-energy interaction of the Goldstone boson with heavy fields that have been integrated out. We find that the EFT then stays weakly coupled all the way up to the cutoff scale at which ultraviolet degrees of freedom become operative. This opens up a regime of new physics where the dispersion relation is dominated by a quadratic dependence on the momentum ? ? p{sup 2}. In addition, provided that modes crossed the Hubble scale within this energy range, the predictions of inflationary observables — including non-Gaussian signatures — are significantly affected by the new scales characterizing it.

Gwyn, Rhiannon [Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut, Am Mühlenberg 1, D-14476 Potsdam (Germany); Palma, Gonzalo A. [Physics Department, FCFM, Universidad de Chile, Blanco Encalada 2008, Santiago (Chile); Sakellariadou, Mairi; Sypsas, Spyros, E-mail: rhiannon.gwyn@aei.mpg.de, E-mail: gpalmaquilod@ing.uchile.cl, E-mail: mairi.sakellariadou@kcl.ac.uk, E-mail: spyridon.sypsas@kcl.ac.uk [Department of Physics, King's College London, Strand, London WC2R 2LS (United Kingdom)

2013-04-01

172

Interaction between weak low frequency magnetic fields and cell membranes.  

PubMed

The question of whether very weak low frequency magnetic fields can affect biological systems, has attracted attention by many research groups for quite some time. Still, today, the theoretical possibility of such an interaction is often questioned and the site of interaction in the cell is unknown. In the present study, the influence of extremely low frequency (ELF) magnetic fields on the transport of Ca(2+) was studied in a biological system consisting of highly purified plasma membrane vesicles. We tested two quantum mechanical theoretical models that assume that biologically active ions can be bound to a channel protein and influence the opening state of the channel. Vesicles were exposed for 30 min at 32 degrees C and the calcium efflux was studied using radioactive (45)Ca as a tracer. Static magnetic fields ranging from 27 to 37 micro T and time varying magnetic fields with frequencies between 7 and 72 Hz and amplitudes between 13 and 114 micro T (peak) were used. We show that suitable combinations of static and time varying magnetic fields directly interact with the Ca(2+) channel protein in the cell membrane, and we could quantitatively confirm the model proposed by Blanchard. PMID:12929158

Bauréus Koch, C L M; Sommarin, M; Persson, B R R; Salford, L G; Eberhardt, J L

2003-09-01

173

The MOG Weak Field approximation II. Observational test of Chandra X-ray Clusters  

E-print Network

We apply the weak field approximation limit of the covariant Scalar-Tensor-Vector Gravity (STVG) theory, so-called MOdified gravity (MOG), to the dynamics of clusters of galaxies by using only baryonic matter. The MOG effective gravitational potential in the weak field approximation is composed of an attractive Newtonian term and a repulsive Yukawa term with two parameters $\\alpha$ and $\\mu$. The numerical values of these parameters have been obtained by fitting the predicted rotation curves of galaxies to observational data, yielding the best fit result: $\\alpha = 8.89 \\pm 0.34$ and $\\mu= 0.042\\pm 0.004$ kpc$^{-1}$~\\cite{rah13}. We extend the observational test of this theory to clusters of galaxies, using data for the ionized gas and the temperature profile of nearby clusters obtained by the Chandra X-ray telescope. Using the MOG virial theorem for clusters, we compare the mass profiles of clusters from observation and theory for eleven clusters. The theoretical mass profiles for the inner parts of clusters exceed the observational data. However, the observational data for the inner parts of clusters (i.e., $rkpc, the observed and predicted mass profiles converge. Our results indicate that MOG as a theory of modified gravity is compatible with the observational data from the the solar system to Mega parsec scales without invoking dark matter.

J. W. Moffat; S. Rahvar

2014-06-07

174

The MOG weak field approximation - II. Observational test of Chandra X-ray clusters  

NASA Astrophysics Data System (ADS)

We apply the weak field approximation limit of the covariant scalar-tensor-vector gravity theory, so-called MOdified gravity (MOG), to the dynamics of clusters of galaxies by using only baryonic matter. The MOG effective gravitational potential in the weak field approximation is composed of an attractive Newtonian term and a repulsive Yukawa term with two parameters ? and ?. The numerical values of these parameters have been obtained by fitting the predicted rotation curves of galaxies to observational data, yielding the best-fitting result: ? = 8.89 ± 0.34 and ? = 0.042 ± 0.004 kpc-1. We extend the observational test of this theory to clusters of galaxies, using data for the ionized gas and the temperature profile of nearby clusters obtained by the Chandra X-ray telescope. Using the MOG virial theorem for clusters, we compare the mass profiles of clusters from observation and theory for 11 clusters. The theoretical mass profiles for the inner parts of clusters exceed the observational data. However, the observational data for the inner parts of clusters (i.e. r < 0.1r500) is scattered, but at distances larger than ˜300 kpc, the observed and predicted mass profiles converge. Our results indicate that MOG as a theory of modified gravity is compatible with the observational data from the Solar system to megaparsec scales without invoking dark matter.

Moffat, J. W.; Rahvar, S.

2014-07-01

175

Saturn's fast spin determined from its gravitational field and oblateness  

NASA Astrophysics Data System (ADS)

The alignment of Saturn's magnetic pole with its rotation axis precludes the use of magnetic field measurements to determine its rotation period. The period was previously determined from radio measurements by the Voyager spacecraft to be 10 h 39 min 22.4 s (ref. 2). When the Cassini spacecraft measured a period of 10 h 47 min 6 s, which was additionally found to change between sequential measurements, it became clear that the radio period could not be used to determine the bulk planetary rotation period. Estimates based upon Saturn's measured wind fields have increased the uncertainty even more, giving numbers smaller than the Voyager rotation period, and at present Saturn's rotation period is thought to be between 10 h 32 min and 10 h 47 min, which is unsatisfactory for such a fundamental property. Here we report a period of 10 h 32 min 45 s +/- 46 s, based upon an optimization approach using Saturn's measured gravitational field and limits on the observed shape and possible internal density profiles. Moreover, even when solely using the constraints from its gravitational field, the rotation period can be inferred with a precision of several minutes. To validate our method, we applied the same procedure to Jupiter and correctly recovered its well-known rotation period.

Helled, Ravit; Galanti, Eli; Kaspi, Yohai

2015-04-01

176

Saturn's fast spin determined from its gravitational field and oblateness.  

PubMed

The alignment of Saturn's magnetic pole with its rotation axis precludes the use of magnetic field measurements to determine its rotation period. The period was previously determined from radio measurements by the Voyager spacecraft to be 10 h 39 min 22.4 s (ref. 2). When the Cassini spacecraft measured a period of 10 h 47 min 6 s, which was additionally found to change between sequential measurements, it became clear that the radio period could not be used to determine the bulk planetary rotation period. Estimates based upon Saturn's measured wind fields have increased the uncertainty even more, giving numbers smaller than the Voyager rotation period, and at present Saturn's rotation period is thought to be between 10 h 32 min and 10 h 47 min, which is unsatisfactory for such a fundamental property. Here we report a period of 10 h 32 min 45 s ± 46 s, based upon an optimization approach using Saturn's measured gravitational field and limits on the observed shape and possible internal density profiles. Moreover, even when solely using the constraints from its gravitational field, the rotation period can be inferred with a precision of several minutes. To validate our method, we applied the same procedure to Jupiter and correctly recovered its well-known rotation period. PMID:25807487

Helled, Ravit; Galanti, Eli; Kaspi, Yohai

2015-04-01

177

Circular, elliptic and oval billiards in a gravitational field  

NASA Astrophysics Data System (ADS)

We consider classical dynamical properties of a particle in a constant gravitational force and making specular reflections with circular, elliptic or oval boundaries. The model and collision map are described and a detailed study of the energy regimes is made. The linear stability of fixed points is studied, yielding exact analytical expressions for parameter values at which a period-doubling bifurcation occurs. The dynamics is apparently ergodic at certain energies in all three models, in contrast to the regularity of the circular and elliptic billiard dynamics in the field-free case. This finding is confirmed using a sensitive test involving Lyapunov weighted dynamics. In the last part of the paper a time dependence is introduced in the billiard boundary, where it is shown that for the circular billiard the average velocity saturates for zero gravitational force but in the presence of gravitational it increases with a very slow growth rate, which may be explained using Arnold diffusion. For the oval billiard, where chaos is present in the static case, the particle has an unlimited velocity growth with an exponent of approximately 1/6.

da Costa, Diogo Ricardo; Dettmann, Carl P.; Leonel, Edson D.

2015-05-01

178

Pollux: a stable weak dipolar magnetic field but no planet?  

NASA Astrophysics Data System (ADS)

Pollux is considered as an archetype of a giant star hosting a planet: its radial velocity (RV) presents sinusoidal variations with a period of about 590 d, which have been stable for more than 25 years. Using ESPaDOnS and Narval we have detected a weak (sub-gauss) magnetic field at the surface of Pollux and followed up its variations with Narval during 4.25 years, i.e. more than for two periods of the RV variations. The longitudinal magnetic field is found to vary with a sinusoidal behaviour with a period close to that of the RV variations and with a small shift in phase. We then performed a Zeeman Doppler imaging (ZDI) investigation from the Stokes V and Stokes I least-squares deconvolution (LSD) profiles. A rotational period is determined, which is consistent with the period of variations of the RV. The magnetic topology is found to be mainly poloidal and this component almost purely dipolar. The mean strength of the surface magnetic field is about 0.7 G. As an alternative to the scenario in which Pollux hosts a close-in exoplanet, we suggest that the magnetic dipole of Pollux can be associated with two temperature and macroturbulent velocity spots which could be sufficient to produce the RV variations. We finally investigate the scenarii of the origin of the magnetic field which could explain the observed properties of Pollux.

Aurière, Michel; Konstantinova-Antova, Renada; Espagnet, Olivier; Petit, Pascal; Roudier, Thierry; Charbonnel, Corinne; Donati, Jean-François; Wade, Gregg A.

2014-08-01

179

The Gravitational Fields of the Galilean Satellites -- Revisited  

NASA Astrophysics Data System (ADS)

One of the major scientific results from the Galileo mission to the Jovian system was the determination of the gravitational fields of the Galilean satellites. Schubert et al. summarize those results in chapter 13 of Jupiter: The planet, satellites and magnetosphere (Bagenal, Dowling, and McKinnon, eds., Cambridge U. Press, 2004). As a part of our recent update of the ephemerides of the Galilean satellites, we redetermined the satellite gravitational fields from the Galileo data. Our reprocessing of the data included, for the first time, calibrations for the effects of Io's plasma torus. We also removed some close encounter data at Europa and Callisto which was corrupted by the encountered satellite ionosphere. In fitting the data we employed a data whitening algorithm, developed for Cassini gravity science data processing, which takes into account the effect of the solar plasma on the Doppler data. Our new results confirm the previous ones for Io and Europa; the Io torus has a negligible effect on the fit to the Io encounter data. However, for Ganymede we found that the data whitening removes the data signature which was previous attributed to mass anomalies (Palguta et al. 2006, Icarus 180), and for Callisto we found that removing the ionosphere corruption significantly reduced the J2. Our overall conclusion is that a quadrupole field in hydrostatic equilibrium is sufficient to fit the data for all four satellites.

Jacobson, Robert A.

2013-10-01

180

Pair production in a strong time-depending magnetic field: The effect of a strong gravitational field  

Microsoft Academic Search

We present the calculation of the probability production of an electron–positron pair in the presence of a strong magnetic field with time-varying strength. The calculation takes into account the presence of a strong, constant and uniform gravitational field in the same direction of the magnetic field. The results show that the presence of the gravitational field in general enhances very

Antonino Di Piazza; Giorgio Calucci

2006-01-01

181

Primordial magnetic fields and gravitational baryogenesis in nonlinear electrodynamics  

SciTech Connect

The amplification of the primordial magnetic fields and the gravitational baryogenesis, a mechanism that allows one to generate the baryon asymmetry in the Universe by means of the coupling between the Ricci scalar curvature and the baryon current, are reviewed in the framework of the nonlinear electrodynamics. To study the amplification of the primordial magnetic field strength, we write down the gauge invariant wave equations and then solve them (in the long wavelength approximation) for three different eras of the Universe: de Sitter, the reheating, and the radiation-dominated era. Constraints on parameters entering the nonlinear electrodynamics are obtained by using the amplitude of the observed galactic magnetic fields and the baryon asymmetry, which are characterized by the dimensionless parameters r{approx}10{sup -37} and {eta}{sub B} < or approx. 9x10{sup -11}, respectively.

Mosquera Cuesta, Herman J. [Instituto de Cosmologia, Relatividade e Astrofisica (ICRA-BR), Centro Brasileiro de Pesquisas Fisicas (CBPF), Rua Dr. Xavier Sigaud 150, 22290-180, RJ (Brazil); ICRANet International Coordinating Centre, P.le della Repubblica 10, 65100, Pescara (Italy); Lambiase, Gaetano [Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno, 84081 Baronissi (Italy); INFN, Sezione di Napoli (Italy)

2009-07-15

182

Strings: A possible alternative explanation for the Unification of Gravitation Field and Electromagnetic Field  

NASA Astrophysics Data System (ADS)

Throughout the last century, since the last decades of the XIX century, until present day, there had been many attempts to achieve the unification of the Forces of Nature. First unification was done by James Clerk Maxwell, with his Electromagnetic Theory. Then Max Plank developed his Quantum Theory. In 1905, Albert Einstein gave birth to the Special Relativity Theory, and in 1916 he came out with his General Relativity Theory. He noticed that there was an evident parallelism between the Gravitational Force, and the Electromagnetic Force. So, he tried to unify these forces of Nature. But Quantum Theory interposed on his way. On the 1940’s it had been developed the Quantum Electrodynamics (QED), and with it, the unified field theory had an arise interest. On the 60’s and 70’s there was developed the Quantum Chromodynamics (QCD). Along with these theories came the discovery of the strong interaction force and weak interaction force. And though there had been many attempts to unify all these forces of the nature, it could only be achieved the Unification of strong interaction, weak interaction and Electromagnetic Force. On the late 80”s and throughout the last two decades, theories such as “super-string theory”, “or the “M-theory”, among others, groups of Scientists, had been doing grand efforts and finally they came out with the unification of the forces of nature, being the only limitation the use of more than 11 dimensions. Using an ingenious mathematical tool known as the super symmetries, based on the Kaluza - Klein work, they achieve this goal. The strings of these theories are in the rank of 10-33 m. Which make them undetectable. There are many other string theories. The GEUFT theory is based on the existence of concentrated energy lines, which vibrates, expands and contracts, submitting and absorbing energy, matter and antimatter, and which yields a determined geometry, that gives as a result the formation of stars, galaxies, nebulae, clusters on the Macrocosmic level, and that allows the formation of fundamental particles on the Microcosmic level. The strings are described by a function named Symbiosis (?), which depends on four energetic contributions: (1) Radiation Energy (2) Plasma Energy (3) Conducted Flux Energy and (4) Mass Energy. There is an intimate relation between them, and depending on the value they have at a certain moment and at a certain time, the string dynamics and its geometry are settled. That means that symbiosis describes the strings state in any point of the geometer - energy field. ? = F [Er(?), Ep(?), Ef(?), Em(?)] (1) This work is an attempt to achieve the unification of the forces of nature, based on the existence of a four dimension Universe.

Rivera, Susana

183

Gravitational waves and scalar perturbations from spectator fields  

NASA Astrophysics Data System (ADS)

The most conventional mechanism for gravitational waves (gw) production during inflation is the amplification of vacuum metric fluctuations. In this case the gw production can be uniquely related to the inflationary expansion rate H. For example, a gw detection close to the present experimental limit (tensor-to-scalar ratio r ~ 0.1) would indicate an inflationary expansion rate close to 1014 GeV. This conclusion, however, would be invalid if the observed gw originated from a different source. We construct and study one of the possible covariant formulations of the mechanism suggested in [1], where a spectator field ? with a sound speed cs ll 1 acts as a source for gw during inflation. In our formulation ? is described by a so-called P(X) Lagrangian and a non-minimal coupling to gravity. This field interacts only gravitationally with the inflaton, which has a standard action. We compute the amount of scalar and tensor density fluctuations produced by ? and find that, in our realization, r is not enhanced with respect to the standard result but it is strongly sensitive to cs, thus breaking the direct r leftrightarrow H connection.

Biagetti, Matteo; Dimastrogiovanni, Emanuela; Fasiello, Matteo; Peloso, Marco

2015-04-01

184

Gravitational Waves and Scalar Perturbations from Spectator Fields  

E-print Network

The most conventional mechanism for gravitational waves (gw) production during inflation is the amplification of vacuum metric fluctuations. In this case the gw production can be uniquely related to the inflationary expansion rate $H$. For example, a gw detection close to the present experimental limit (tensor-to-scalar ratio $r \\sim 0.1$) would indicate an inflationary expansion rate close to $10^{14} \\, {\\rm GeV}$. This conclusion, however, would be invalid if the observed gw originated from a different source. We construct and study one of the possible covariant formulations of the mechanism suggested in [43], where a spectator field $\\sigma$ with a sound speed $c_{s} \\ll 1$ acts as a source for gw during inflation. In our formulation $\\sigma$ is described by a so-called $P(X)$ Lagrangian and a non-minimal coupling to gravity. This field interacts only gravitationally with the inflaton, which has a standard action. We compute the amount of scalar and tensor density fluctuations produced by $\\sigma$ and find that, in our realization, $r$ is not enhanced with respect to the standard result but it is strongly sensitive to $c_s$, thus breaking the direct $r \\leftrightarrow H$ connection.

Matteo Biagetti; Emanuela Dimastrogiovanni; Matteo Fasiello; Marco Peloso

2014-11-12

185

Laboratory simulation of Euclid-like sky images to study the impact of CCD radiation damage on weak gravitational lensing  

NASA Astrophysics Data System (ADS)

Euclid is the ESA mission to map the geometry of the dark universe. It uses weak gravitational lensing, which requires the accurate measurement of galaxy shapes over a large area in the sky. Radiation damage in the 36 Charge-Coupled Devices (CCDs) composing the Euclid visible imager focal plane has already been identified as a major contributor to the weak-lensing error budget; radiation-induced charge transfer inefficiency (CTI) distorts the galaxy images and introduces a bias in the galaxy shape measurement. We designed a laboratory experiment to project Euclid-like sky images onto an irradiated Euclid CCD. In this way - and for the first time - we are able to directly assess the effect of CTI on the Euclid weak-lensing measurement free of modelling uncertainties. We present here the experiment concept, setup, and first results. The results of such an experiment provide test data critical to refine models, design and test the Euclid data processing CTI mitigation scheme, and further optimize the Euclid CCD operation.

Prod'homme, T.; Verhoeve, P.; Oosterbroek, T.; Boudin, N.; Short, A.; Kohley, R.

2014-07-01

186

Slowly and Rapidly Propagating "Liquid Flames" in Gravitational Fields  

NASA Technical Reports Server (NTRS)

We consider the combustion, in a gravitational field, of a heterogeneous powder mixture compressed into a solid sample, in which the high temperature ahead of the reaction zone destroys the solid, due, e.g. to melting of some of components of the mixture. Thus, a suspension is formed, consisting of a liquid bath containing solid or liquid particles. Processes such as heat and mass transfer as well as chemical reactions in the suspension determine the structure of the combustion wave and its propagation velocity. Under the influence of gravitational forces there is the possibility of relative motion of the liquid and solid. Previous theoretical analyses considered the rate of beat transfer between the solid and liquid phases to be sufficiently large that their two distinct temperatures rapidly equilibrated to a single temperature. In addition to this case, we also consider the case when the rate of heat transfer is not so large and the model involves the separate temperatures of the solid and liquid phases. We find that multiplicity of traveling wave structures is possible. In particular, in addition to a low velocity structure, which is essentially the same as that obtained from the one temperature description, we find a high velocity structure, which does not exist in the one temperature description, but rather depends on the fact that the solid and fluid temperatures differ from each other. Both structures can exist for the same parameter values in a given range. We describe the dependence of the combustion characteristics of the two structures on gravitational forces and other factors. In particular, we compare the characteristics in gravity and microgravity environments.

Shkadinsky, K. G.; Shkadinskaya, G. V.; Matkowsky, B. J.; Gokoglu, S. (Technical Monitor)

2000-01-01

187

Classical Solution of Field Equation of Gravitational Gauge Field and Classical Tests of Gauge Theory of Gravity  

Microsoft Academic Search

A systematic method is developed to study classical motion of a mass point in gravitational gauge field. First, the formulation of gauge theory of gravity in arbitrary curvilinear coordinates is given. Then in spherical coordinates system, a spherical symmetric solution of the field equation of gravitational gauge field is obtained, which is just the Schwarzschild solution. In gauge theory of

Ning Wu; Dahua Zhang

2005-01-01

188

Field theory and weak Euler-Lagrange equation for classical particle-field systems.  

PubMed

It is commonly believed as a fundamental principle that energy-momentum conservation of a physical system is the result of space-time symmetry. However, for classical particle-field systems, e.g., charged particles interacting through self-consistent electromagnetic or electrostatic fields, such a connection has only been cautiously suggested. It has not been formally established. The difficulty is due to the fact that the dynamics of particles and the electromagnetic fields reside on different manifolds. We show how to overcome this difficulty and establish the connection by generalizing the Euler-Lagrange equation, the central component of a field theory, to a so-called weak form. The weak Euler-Lagrange equation induces a new type of flux, called the weak Euler-Lagrange current, which enters conservation laws. Using field theory together with the weak Euler-Lagrange equation developed here, energy-momentum conservation laws that are difficult to find otherwise can be systematically derived from the underlying space-time symmetry. PMID:25375609

Qin, Hong; Burby, Joshua W; Davidson, Ronald C

2014-10-01

189

Shape and gravitational field of the ellipsoidal satellites  

NASA Astrophysics Data System (ADS)

The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite formation, strong tidal friction allowed the satellites move in a synchronous orbit and evolve into a triaxial ellipsoidal shape. Because the tidal potential from the associated primary and the centrifugal potential from the satellite spin are nearly fixed at the surface, the early satellites are the viscoelastic celestial body, and their surfaces are nearly in the hydrostatic equilibrium state. The deformation is fixed in the surface of the satellite. By using the related parameters of primary and satellite, the tidal height and the theoretical lengths of three primary radii of the ellipsoidal satellite are calculated. Secondly, the current ellipsoidal satellites nearly maintain their ellipsoidal shape from solidification, which happened a few billion years ago. According to the satellite shape, we estimated the orbital period and spinning angular velocity, and then determined the evolution of the orbit. Lastly, assuming an ellipsoidal satellite originated in the hydrostatic equilibrium state, the surface shape could be determined by tidal, rotation, and additional potentials. However, the shape of the satellite's geoid differs from its surface shape. The relationship between these shapes is discussed and a formula for the gravitational harmonic coefficients is presented.

Gao, BuXi; Huang, Yong

2014-10-01

190

The dark matter haloes of moderate luminosity X-ray AGN as determined from weak gravitational lensing and host stellar masses  

NASA Astrophysics Data System (ADS)

Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter haloes in which they reside is key to constraining how black hole fuelling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modelling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to the fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies, irrespective of nuclear activity. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z < 1 from the COSMOS field, we report the first measurements of weak gravitational lensing from an X-ray-selected sample. Comparing this signal to predictions from the global SHMR, we find that, contrary to previous results, most X-ray AGN do not live in medium size groups - nearly half reside in relatively low mass haloes with M200b ˜ 1012.5 M?. The AGN occupation function is well described by the same form derived for all galaxies but with a lower normalization - the fraction of haloes with AGN in our sample is a few per cent. The number of AGN satellite galaxies scales as a power law with host halo mass with a power-law index ? = 1. By highlighting the relatively `normal' way in which moderate luminosity X-ray AGN hosts occupy haloes, our results suggest that the environmental signature of distinct fuelling modes for luminous quasars compared to moderate luminosity X-ray AGN is less obvious than previously claimed.

Leauthaud, Alexie; J. Benson, Andrew; Civano, Francesca; L. Coil, Alison; Bundy, Kevin; Massey, Richard; Schramm, Malte; Schulze, Andreas; Capak, Peter; Elvis, Martin; Kulier, Andrea; Rhodes, Jason

2015-01-01

191

Gravitational perturbation of the BTZ black hole induced by test particles and weak cosmic censorship in AdS spacetime  

SciTech Connect

We analyze the gravitational perturbations induced by particles falling into a three dimensional, asymptotically AdS black hole geometry. More specifically, we solve the linearized perturbation equations obtained from the geodesic motion of a ringlike distribution of test particles in the BTZ background. This setup ensures that the U(1) symmetry of the background is preserved. The nonasymptotic flatness of the background raises difficulties in attributing the significance of energy and angular momentum to the conserved quantities of the test particles. This issue is well known but, to the best of our knowledge, has never been addressed in the literature. We confirm that the naive expressions for energy and angular momentum are the correct definitions. Finally, we put an asymptotically AdS version of the weak cosmic censorship to a test: by attempting to overspin the BTZ black hole with test particles it is found that the black hole cannot be spun-up past its extremal limit.

Rocha, Jorge V. [CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049 Lisboa (Portugal); Cardoso, Vitor [CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049 Lisboa (Portugal); Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677 (United States)

2011-05-15

192

THE IMPACT OF THERMODYNAMICS ON GRAVITATIONAL COLLAPSE: FILAMENT FORMATION AND MAGNETIC FIELD AMPLIFICATION  

SciTech Connect

Stars form by the gravitational collapse of interstellar gas. The thermodynamic response of the gas can be characterized by an effective equation of state. It determines how gas heats up or cools as it gets compressed, and hence plays a key role in regulating the process of stellar birth on virtually all scales, ranging from individual star clusters up to the galaxy as a whole. We present a systematic study of the impact of thermodynamics on gravitational collapse in the context of high-redshift star formation, but argue that our findings are also relevant for present-day star formation in molecular clouds. We consider a polytropic equation of state, P = k{rho}{sup {Gamma}}, with both sub-isothermal exponents {Gamma} < 1 and super-isothermal exponents {Gamma} > 1. We find significant differences between these two cases. For {Gamma} > 1, pressure gradients slow down the contraction and lead to the formation of a virialized, turbulent core. Weak magnetic fields are strongly tangled and efficiently amplified via the small-scale turbulent dynamo on timescales corresponding to the eddy-turnover time at the viscous scale. For {Gamma} < 1, on the other hand, pressure support is not sufficient for the formation of such a core. Gravitational contraction proceeds much more rapidly and the flow develops very strong shocks, creating a network of intersecting sheets and extended filaments. The resulting magnetic field lines are very coherent and exhibit a considerable degree of order. Nevertheless, even under these conditions we still find exponential growth of the magnetic energy density in the kinematic regime.

Peters, Thomas; Klessen, Ralf S.; Federrath, Christoph; Smith, Rowan J. [Zentrum fuer Astronomie, Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Schleicher, Dominik R. G. [Institut fuer Astrophysik, Georg-August-Universitaet, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Banerjee, Robi [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Sur, Sharanya, E-mail: tpeters@physik.uzh.ch [Raman Research Institute, C. V. Raman Avenue, Sadashivnagar, Bangalore 560080 (India)

2012-12-01

193

Thermal transpiration of a slightly rarefied gas through a horizontal straight pipe in the presence of weak gravitation  

NASA Astrophysics Data System (ADS)

Thermal transpiration of a slightly rarefied gas through a horizontal straight pipe in the presence of weak gravitation is studied on the basis of kinetic theory. We consider the situation in which the Knudsen number (the mean free path divided by the characteristic length of the cross section) is small and the dimensionless gravity (the characteristic length divided by the ascent height of the molecules against gravity) is of the order of the square of the Knudsen number. The behavior of the gas is studied analytically on the basis of the fluid-dynamic-type equation and the slip-type boundary condition derived from the Boltzmann equation for small Knudsen numbers. Extending the analysis of the two-dimensional channel problem, the solution for a pipe with an arbitrary cross section is obtained in a semianalytical form. When the temperature gradient is imposed along the pipe, the pressure gradient is produced not only in the vertical direction but also in the horizontal direction due to the effect of gravity. Although this pressure gradient is of the order of the square of the Knudsen number, it induces a flow of the order of the Knudsen number. As a result, the apparently higher order effect of gravity produces a relatively finite effect on thermal transpiration. This phenomenon, first observed in plane thermal transpiration, is clarified for a pipe with a general cross section. The explicit solution is obtained for the pipe with the cross section of an annulus between eccentric circular cylinders. Based on the solution, the effect of weak gravitation on the mass flow rate of the gas, as well as on the flow velocity, is clarified over a wide range of the radii ratio and the eccentricity of the cylinders.

Doi, Toshiyuki

2013-10-01

194

Deep HST imaging of distant weak radio and field galaxies  

NASA Technical Reports Server (NTRS)

We present deep Hubble Space Telescope (HST) Wide-Field Camera (WFC) V- and I-band images of three distant weak radio galaxies with z = 0.311-2.390 and seven field galaxies with z = 0.131-0.58. The images were deconvolved with both the Lucy and multiresolution CLEAN methods, which yield a restoring Full Width at Half Maximum (FWHM) of less than or equal to 0.2 sec, (nearly) preserve photons and signal-to-noise ratio at low spatial frequencies, and produce consistent light profiles down to our 2 sigma surface brightness sensitivity limit of V approximately 27.2 and I approximately 25.9 mag/sq arcsec. Multi-component image modeling was used to provide deconvolution-independent estimates of structural parameters for symmetric galaxies. We present 12-band (m(sub 2750) UBVRIgriJHK) photometry for a subset of the galaxies and bootstrap the unknown FOC/48 zero point at 2750 A in three independent ways (yielding m(sub 2750) = 21.34 +/- 0.09 mag for 1.0 e(-)/s). Two radio galaxies with z = 0.311 and 0.528, as well as one field galaxy with z = 0.58, have the colors and spectra of early-type galaxies, and a(exp 1/4)-like light profiles in the HST images. The two at z greater than 0.5 have little or no color gradients in V - I and are likely giant ellipticals, while the z = 0.311 radio galaxy has a dim exponential disk and is likely an S0. Six of the seven field galaxies have light profiles that indicate (small) inner bulges following a(exp 1/4) laws and outer exponential disks, both with little or no color gradients. These are (early-type) spiral galaxies with z = 0.131-0.528. About half have faint companions or bars. One shows lumpy structure, possibly a merger. The compact narrow-line galaxy 53W002 at z = 2.390 has less than or = 30% +/- 10% of its HST V and I flux in the central kiloparsec (due to its weak Active Galactic Nucleus (AGN)). Most of its light (V approximately equal to 23.3) occurs in a symmetric envelope with a regular a(exp 1/4)-like profile of effective radius a approximately equal to 1.1 sec (approximately equal to 12 kpc for H(sub 0) = 50, q(sub 0) = 0.1. Its (HST) V - I color varies at most from approximately 0.3 mag at a approximately equal to 0.2 sec to approximately 1.2 mag at a approximately greater than 0.4 sec, and possibly to approximately greater than 2.2 mag at a approximately greater than 1.2 sec. Together with its I - K color (approximately equal to 2.5 mag for a approximately greater than 1.0 sec-2.0 sec), this is consistent with an aging stellar population approximately 0.3-0.5 Gyr old in the galaxy center (a approx. less than 2 kpc radius), and possibly approximately 0.5-1.0 Gyr old at a approximately greater than 10 kpc radius. While its outer part may thus have started to collapse at z = 2.5-4, its inner part still is aligned with its redshifted Ly(alpha) cloud and its radio axis, possibly caused by star formation associated with the radio jet, or by reflection from its AGN cone.

Windhorst, R. A.; Gordon, J. M.; Pascarelle, S. M.; Schmidtke, P. C.; Keel, W. C.; Burkey, J. M.; Dunlop, J. S.

1994-01-01

195

Scalar, electromagnetic, and gravitational self-forces in weakly curved spacetimes  

Microsoft Academic Search

We calculate the self-force experienced by a point scalar charge q, a point electric charge e, and a point mass m moving in a weakly curved spacetime characterized by a time-independent Newtonian potential Phi. We assume that the matter distribution responsible for this potential is bounded, so that Phi~-M\\/r at large distances r from the matter, whose total mass is

Michael J. Pfenning; Eric Poisson

2002-01-01

196

CHARGED TORI IN SPHERICAL GRAVITATIONAL AND DIPOLAR MAGNETIC FIELDS  

SciTech Connect

A Newtonian model of non-conductive, charged, perfect fluid tori orbiting in combined spherical gravitational and dipolar magnetic fields is presented and stationary, axisymmetric toroidal structures are analyzed. Matter in such tori exhibits a purely circulatory motion and the resulting convection carries charges into permanent rotation around the symmetry axis. As a main result, we demonstrate the possible existence of off-equatorial charged tori and equatorial tori with cusps that also enable outflows of matter from the torus in the Newtonian regime. These phenomena qualitatively represent a new consequence of the interplay between gravity and electromagnetism. From an astrophysical point of view, our investigation can provide insight into processes that determine the vertical structure of dusty tori surrounding accretion disks.

Slany, P.; Kovar, J.; Stuchlik, Z. [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava Bezrucovo nam. 13, CZ-746 01 Opava (Czech Republic)] [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava Bezrucovo nam. 13, CZ-746 01 Opava (Czech Republic); Karas, V., E-mail: petr.slany@fpf.slu.cz [Astronomical Institute, Academy of Sciences, Bocni II, Prague CZ-141 31 (Czech Republic)

2013-03-01

197

On the Gravitational Field of the Electric Charge  

E-print Network

The idea has been spoken that any of Dirac and Pauli form factors of leptonic current includes both normal and anomalous components. From this point of view, the dependence of independent parts of charge and magnetic moment is established with the use of cross sections of elastic scattering of unpolarized and longitudinal polarized electrons and their neutrinos by spinless nuclei. Some considerations of a connection between the mass of a particle and its electromagnetic nature are listed which can explain also the appearance of gravitational field of a Coulomb interaction. All they state that a massive four-component neutrino similarly to the electron must have the normal as well as the anomalous electric charge.

Rasulkhozha S. Sharafiddinov

2010-12-08

198

On the Gravitational Field of the Electric Charge  

E-print Network

The idea has been speaked out that any of Dirac and Pauli form factors of leptonic current includes in self both normal and anomalous components. From this point of view, with the use of cross sections of elastic scattering of unpolarized and longitudinal polarized electrons and their neutrinos by spinless nuclei the dependence of independent parts of charge and magnetic moment is established. Some considerations of a connection between the mass of a particle and its electromagnetic nature are listed which can explain also the appearance of gravitational field of a Coulomb interaction. All they state that a massive four - component neutrino similarly to the electron must have the normal as well as the anomalous electric charge.

Sharafiddinov, R S

2000-01-01

199

Comment on 'Primordial magnetic seed field amplification by gravitational waves'  

SciTech Connect

We consider the amplification of cosmological magnetic fields by gravitational waves as it was recently presented by Betschart et al. That study confined to infinitely conductive environments, arguing that on spatially flat Friedmann backgrounds the gravito-magnetic interaction proceeds always as if the Universe were a perfect conductor. We explain why this claim is not correct and then reexamine the Maxwell-Weyl coupling at the limit of ideal magnetohydrodynamics. We find that the scales of the main results of Betschart et al. were not properly assessed and that the incorrect scale assessment has compromised both the physical and the numerical results of the paper. This comment aims to clarify these issues on the one hand, while on the other it takes a closer look at the gauge invariance and the nonlinearity of the formalism proposed by Betschart et al.

Tsagas, Christos G. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)

2007-04-15

200

Charged Tori in Spherical Gravitational and Dipolar Magnetic Fields  

NASA Astrophysics Data System (ADS)

A Newtonian model of non-conductive, charged, perfect fluid tori orbiting in combined spherical gravitational and dipolar magnetic fields is presented and stationary, axisymmetric toroidal structures are analyzed. Matter in such tori exhibits a purely circulatory motion and the resulting convection carries charges into permanent rotation around the symmetry axis. As a main result, we demonstrate the possible existence of off-equatorial charged tori and equatorial tori with cusps that also enable outflows of matter from the torus in the Newtonian regime. These phenomena qualitatively represent a new consequence of the interplay between gravity and electromagnetism. From an astrophysical point of view, our investigation can provide insight into processes that determine the vertical structure of dusty tori surrounding accretion disks.

Slaný, P.; Ková?, J.; Stuchlík, Z.; Karas, V.

2013-03-01

201

Neutron Interference in the Gravitational Field of a Ring Laser  

NASA Astrophysics Data System (ADS)

A number of analyses of neutron interference effects due to various metric perturbations have been found in the literature [1,2]. However, the approach of each author depends on a specific metric. I will present a new general technique giving the Foldy-Wouthuysen transformed Hamiltonian for a Dirac particle in the most general linearized space-time metric. I will then apply this new technique to calculate the phase shift on a neutron beam interferometer due to the gravitational field of a ring laser [3].[4pt] [1] D. M Greenberger and A. W. Overhauser, Rev. Mod. Phys. 51, 43--78 (1979).[0pt] [2] F. W. Hehl and W. T. Ni, Phys. Rev. D, vol 42, no. 6, pp. 2045-2048, 1990.[0pt] [3] R. L. Mallett, Phys. Lett. A 269, 214 (2000).

Fischetti, Robert

2013-04-01

202

Nonlinear gravitational self-force: Field outside a small body  

NASA Astrophysics Data System (ADS)

A small extended body moving through an external spacetime g?? creates a metric perturbation h??, which forces the body away from geodesic motion in g??. The foundations of this effect, called the gravitational self-force, are now well established, but concrete results have mostly been limited to linear order. Accurately modeling the dynamics of compact binaries requires proceeding to nonlinear orders. To that end, I show how to obtain the metric perturbation outside the body at all orders in a class of generalized wave gauges. In a small buffer region surrounding the body, the form of the perturbation can be found analytically as an expansion for small distances r from a representative worldline. Given only a specification of the body’s multipole moments, the field obtained in the buffer region suffices to find the metric everywhere outside the body via a numerical puncture scheme. Following this procedure at first and second order, I calculate the field in the buffer region around an arbitrarily structured compact body at sufficiently high order in r to numerically implement a second-order puncture scheme, including effects of the body’s spin. I also define nth-order (local) generalizations of the Detweiler-Whiting singular and regular fields and show that in a certain sense, the body can be viewed as a skeleton of multipole moments.

Pound, Adam

2012-10-01

203

Gravitational collapse with tachyon field and barotropic fluid  

E-print Network

A particular class of space-time, with a tachyon field, \\phi, and a barotropic fluid constituting the matter content, is considered herein as a model for gravitational collapse. For simplicity, the tachyon potential is assumed to be of inverse square form i.e., V(\\phi) \\sim \\phi^{-2}. Our purpose, by making use of the specific kinematical features of the tachyon, which are rather different from a standard scalar field, is to establish the several types of asymptotic behavior that our matter content induces. Employing a dynamical system analysis, complemented by a thorough numerical study, we find classical solutions corresponding to a naked singularity or a black hole formation. In particular, there is a subset where the fluid and tachyon participate in an interesting tracking behaviour, depending sensitively on the initial conditions for the energy densities of the tachyon field and barotropic fluid. Two other classes of solutions are present, corresponding respectively, to either a tachyon or a barotropic fluid regime. Which of these emerges as dominant, will depend on the choice of the barotropic parameter, \\gamma. Furthermore, these collapsing scenarios both have as final state the formation of a black hole.

Yaser Tavakoli; João Marto; Amir Hadi Ziaie; Paulo Vargas Moniz

2013-01-21

204

Saturn's fast spin determined from its gravitational field and oblateness  

E-print Network

The alignment of Saturn's magnetic pole with its rotation axis precludes the use of magnetic field measurements to determine its rotation period. The period was previously determined from radio measurements by the Voyager spacecraft to be 10h 39m 22.4s. When the Cassini spacecraft measured a period of 10h 47m 6s, which was additionally found to change between sequential measurements, it became clear that the radio period could not be used to determine the bulk planetary rotation period. Estimates based upon Saturn's measured wind fields have increased the uncertainty even more, giving numbers smaller than the Voyager rotation period, and at present Saturn's rotation period is thought to be between 10h 32m and 10h 47m, which is unsatisfactory for such a fundamental property. Here we report a period of 10h 32m 45s +- 46s, based upon an optimization approach using Saturn's measured gravitational field and limits on the observed shape and possible internal density profiles. Moreover, even when solely using the co...

Helled, Ravit; Kaspi, Yohai

2015-01-01

205

Biological effects due to weak magnetic fields on plants  

NASA Astrophysics Data System (ADS)

In the evolution process, living organisms have experienced the action of the Earth's magnetic field (MF) that is a natural component of our environment. It is known that a galactic MF induction does not exceed 0.1 nT, since investigations of weak magnetic field (WMF) effects on biological systems have attracted attention of biologists due to planning long-term space flights to other planets where the magnetizing force is near 10-5 Oe. However, the role of WMF and its influence on organisms' functioning are still insufficiently investigated. A large number of experiments with seedlings of different plant species placed in WMF has found that the growth of their primary roots is inhibited during the early terms of germination in comparison with control. The proliferation activity and cell reproduction are reduced in meristem of plant roots under WMF application. The prolongation of total cell reproductive cycle is registered due to the expansion of G phase in1 different plant species as well as of G phase in flax and lentil roots along with2 relative stability of time parameters of other phases of cell cycle. In plant cells exposed to WMF, the decrease in functional activity of genome at early prereplicate period is shown. WMF causes the intensification in the processes of proteins' synthesis and break-up in plant roots. Qualitative and quantitative changes in protein spectrum in growing and differentiated cells of plant roots exposed to WMF are revealed. At ultrastructural level, there are observed such ultrastructural peculiarities as changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells of pea roots exposed to WMF. Mitochondria are the most sensitive organelle to WMF application: their size and relative volume in cells increase, matrix is electron-transparent, and cristae reduce. Cytochemical studies indicate that cells of plant roots exposed to WMF show the Ca2 + oversaturation both in all organelles and in a hyaloplasm of the cells unlike the control ones. The data presented suggest that prolonged plant exposures to WMF may cause different biological effects at the cellular, tissue and organ level. They may be functionally related to systems that regulate plant metabolism including the intracellular Ca 2 + homeostasis. The understanding of the fundamental mechanisms and sites of interactions between WMF and biological systems are complex and still deserve strong efforts, particular addressed to basic principles of coupling between field energy and biomolecules.

Belyavskaya, N.

206

[Two-phase Interfaces in Weak External Fields  

NASA Technical Reports Server (NTRS)

Our aim has been that of understanding from first principles the behavior of two-phase interfaces in the absence of gravitational constraints. This is fundamental to our ability to deal with the fluid structures that abound in the real biological, chemical, and physical world. A substantial effort was mounted to determine how familiar hydrodynamic concepts have to be modified and interpreted to make them appropriate to the multi-level structure alluded to above. This was primarily in the context of the microscopic symmetric pressure tensor, which was, for the first time, expressed in the invaluable density functional format, and the used to follow the predictions of popular microscopic models of the energetics of interfacial systems. In the course of these investigations, the previous murky relation between pressure tensor and thermodynamics was completely clarified. The process of extending thermodynamic information to interfacial dynamics was initiated along two paths. One was from the viewpoint of an inertialess lattice gas, resulting in the surprising conclusion that at this level, all transport is governed by precisely the thermodynamic free energy, albeit with a non-trivial effective particle mobility. The other aimed at understanding the fashion in which slow macroscopic motions, accounted for by a time-varying microscopic energy, generate effective hydrodynamic parameters. By examining a solvable model system, it was found that all current procedures for doing so are deficient, and suitable alleviation suggested. The major effect of this project was to set the stage for the analysis of the substantial dynamical regimes in which extensive equilibrium information provides the dominant background. This produces a smooth junction to the models of Araki and Munakata, Giacomin and Lebowitz, and Oxtoby. It is also crucial to our understanding of the complex interfacial equilibrium configurations required for intermediate stages of two-phase separation, for which the "phase-field" techniques we have been developing are uniquely effective. And it puts us within striking range of the physical experiments that can provide incisive tests of the theoretical framework.

Percus, J. K.

1996-01-01

207

Field theory of gravitation and new notions of space and time  

SciTech Connect

A field theory of gravitation is constructed on the basis of two principles: 1. The existence of conservation laws for the matter and the gravitational field, which is achieved by choosing a pseudo-Euclidean geometry as a natural geometry for the gravitational field. 2. A geometrization principle (identity principle), which asserts that the equations of motion for matter under the influence of the gravitational field in the pseudo-Euclidean space-time can be represented identically as the equations of motion of matter in some effective Riemannian space-time with metric tensor that depends on the gravitational field and on the metric tensor of the pseudo-Euclidean space-time.

Denisov, V.I.; Logunov, A.A.; Mestvirishvili, M.A.

1981-01-01

208

Hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit: I. General formalism and perturbations analysis  

E-print Network

Using a generalization of the Madelung transformation, we derive the hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit. We consider a complex self-interacting scalar field with a $\\lambda|\\varphi|^4$ potential. We study the evolution of the homogeneous background in the fluid representation and derive the linearized equations describing the evolution of small perturbations in a static and in an expanding universe. We compare the results with simplified models in which the gravitational potential is introduced by hand in the Klein-Gordon equation, and assumed to satisfy a (generalized) Poisson equation. We study the evolution of the perturbations in the matter era using the nonrelativistic limit of our formalism. Perturbations whose wavelength is below the Jeans length oscillate in time while pertubations whose wavelength is above the Jeans length grow linearly with the scale factor as in the cold dark matter model. The growth of perturbations in the scalar field model ...

Suárez, Abril

2015-01-01

209

Static spherically symmetric solution for scalar and electromagnetic fields in the relativistic theory of gravitation  

Microsoft Academic Search

A general static spherically symmetric solution for free scalar and electromagnetic fields in the relativistic theory of gravitation is obtained. In the special cases of absence of the scalar, electromagnetic, or both fields, it reduces to the corresponding known solutions.

P. K. Silaev

1992-01-01

210

Presence of Dark Energy and Dark Matter : Does Cosmic Acceleration signifies a Weak Gravitational collapse?  

E-print Network

In this work the collapsing process of a spherically symmetric star, made of dust cloud, in the background of dark energy is studied for two different gravity theories separately, i.e., DGP Brane gravity and Loop Quantum gravity. Two types of dark energy fluids, namely, Modified Chaplygin gas and Generalised Cosmic Chaplygin gas are considered for each model. Graphs are drawn to characterize the nature and the probable outcome of gravitational collapse. A comparative study is done between the collapsing process in the two different gravity theories. It is found that in case of dark matter, there is a great possibility of collapse and consequent formation of Black hole. In case of dark energy possibility of collapse is far lesser compared to the other cases, due to the large negative pressure of dark energy component. There is an increase in mass of the cloud in case of dark matter collapse due to matter accumulation. The mass decreases considerably in case of dark energy due to dark energy accretion on the cloud. In case of collapse with a combination of dark energy and dark matter, it is found that in the absence of interaction there is a far better possibility of formation of black hole in DGP brane model compared to Loop quantum cosmology model.

Prabir Rudra; Ritabrata Biswas; Ujjal Debnath

2012-04-03

211

The HST Frontier Fields: Gravitational Lensing Models Release  

NASA Astrophysics Data System (ADS)

The Hubble Frontier Fields (HFF) is a Director's Discretionary Time (DDT) program to deeply observe up to six massive strong-lensing galaxy clusters and six "blank" fields in parallel. These complementary observations will yield magnified and direct images of some of the most distant galaxies yet observed. The strongly lensed images will be our deepest views of our universe to date. Interpretation of some (but not all) observed properties of the strongly lensed galaxies requires gravitational lens modeling. In order to maximize the value of this public dataset to the extragalactic community, STScI commissioned five teams funded by NASA to derive the best possible lens models from existing data. After coordinating to share observational constraints, including measured redshifts of strongly lensed galaxies, the teams independently derived lens models using robust, established methodologies. STScI released these models to the community in October before HFF observations of the first cluster, Abell 2744. Here we describe these models as well as a web tool which allows users to extract magnification estimates with uncertainties from all models for any galaxy strongly lensed by a HFF cluster. Inputs are the galaxy's coordinates (RA and Dec), redshift, and (optionally) observed radius. We also discuss ongoing work to study lens model uncertainties by modeling simulated clusters.

Coe, Dan A.; Lotz, J.; Natarajan, P.; Richard, J.; Zitrin, A.; Kneib, J.; Ebeling, H.; Sharon, K.; Johnson, T.; Limousin, M.; Bradac, M.; Hoag, A.; Cain, B.; Merten, J.; Williams, L. L.; Sebesta, K.; Meneghetti, M.; Koekemoer, A. M.; Barker, E. A.

2014-01-01

212

Influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction  

SciTech Connect

The interaction between gravitational and electromagnetic waves in the presence of a static magnetic field is studied. The field strength of the static field is allowed to surpass the Schwinger critical field, such that the QED effects of vacuum polarization and magnetization are significant. Equations governing the interaction are derived and analyzed. It turns out that the energy conversion from gravitational to electromagnetic waves can be significantly altered due to the QED effects. The consequences of our results are discussed.

Forsberg, M.; Brodin, G. [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Papadopoulos, D. [Department of Physics, Section of Astrophysics, Astronomy and Mechanics, 54124 Thessaloniki (Greece)

2010-07-15

213

The influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction  

E-print Network

The interaction between gravitational and electromagnetic waves in the presence of a static magnetic field is studied. The field strength of the static field is allowed to surpass the Schwinger critical field, such that the quantum electrodynamical (QED) effects of vacuum polarization and magnetization are significant. Equations governing the interaction are derived and analyzed. It turns out that the energy conversion from gravitational to electromagnetic waves can be significantly altered due to the QED effects. The consequences of our results are discussed.

Mats Forsberg; Demetrios Papadopoulos; Gert Brodin

2010-05-28

214

Probing Strong-field General Relativity with Gravitational Waves  

NASA Astrophysics Data System (ADS)

We are on the verge of a new era in astrophysics as a world-wide effort to observe the universe with gravitational waves takes hold---ground based laser interferometers (Hz to kHz), pulsar timing (micro to nano Hz), measurements of polarization of the cosmic microwave background (sub-nano Hz), and the planned NASA/ESA mission LISA (.1 mHz to .1 Hz). This project will study the theoretical nature of gravitational waves (GWs) emitted by two sources in the LISA band, namely supermassive-black-hole (SMBH) binary mergers, and extreme-mass-ratio-inspirals (EMRI's)---the merger of a stellar mass black hole, neutron star, or white dwarf with a SMBH. The primary goal will be to ascertain how well LISA, by observing these sources, could answer the following related questions about the fundamental nature of strong-field gravity: Does Einstein's theory of general relativity (GR) describe the geometry of black holes in the universe? What constraints can GW observations of SMBH mergers and EMRIs place on alternative theories of gravity? If there are deviations from GR, are there statistics that could give indications of a deviation if sources are detected using a search strategy based solely on GR waveforms? The primary reasons for focusing on LISA sources to answer these questions are (a) binary SMBH mergers could be detected by LISA with exquisitely high signal-to- noise, allowing enough parameters of the system to be accurately extracted to perform consistency checks of the underlying theory, (b) EMRIs will spend numerous orbits close to the central black hole, and thus will be quite sensitive to even small near-horizon deviations from GR. One approach to develop the requisite knowledge and tools to answer these questions is to study a concrete, theoretically viable alternative to GR. We will focus on the dynamical variant of Chern-Simons modified gravity (CSMG), which is interesting for several reasons, chief among which are (1) that CSMG generically arises in both string theory and loop quantum gravity, and (2) that although CSMG is consistent with all present day tests of GR, it still allows for significant, near-horizon deformations in the geometry of rotating (Kerr) black holes. Here is a brief list of the steps and research methodology we will employ:?(i) Obtain the equivalent of the full Kerr solution in CSMG using numerical methods. (ii) Explore the structure of GWs emitted by EMRIs about the CS rotating black hole solution. Given simulated LISA noise curves, we can then address the questions posed above within the context of CSMG. (iii) Simulate the latter stages of comparable mass SMBH binary mergers in CSMG by numerically solving the full CSMG field equations to learn about highly dynamical, non- linear GR deformations. We can then repeat the analysis of (ii). (iv) Study whether CSMG GWs fit in the recently proposed parameterized post- Einsteinian (ppE) framework, to study generic deviations from GR in a statistical fashion. One can then repeat the analysis of (ii) but within the ppE scheme. We believe this proposed work is of significance and import to both the objectives of this solicitation, and the interests of NASA---knowing the nature of strong-field gravity will be one of the keys to unraveling the origin of the universe, and will tell us how black holes behave and interact with their environs, the details of which are important in understanding the formation and evolution of structure in the universe. Furthermore, these questions are best suited to be answered by LISA, a planned joint NASA-ESA mission. The ultimate success of LISA is very much dependent on (amongst other things) how well the community understands the complete nature of gravitational wave sources.

Pretorius, Frans

215

Electromagnetic signatures of far-field gravitational radiation in the 1 + 3 approach  

NASA Astrophysics Data System (ADS)

Gravitational waves (GWs) from astrophysical sources can interact with background electromagnetic fields, giving rise to distinctive and potentially detectable electromagnetic signatures. In this paper, we study such interactions for far-field gravitational radiation using the 1 + 3 approach to relativity. Linearized equations for the electromagnetic field on perturbed Minkowski space are derived and solved analytically. The inverse Gertsenshte?n conversion of GWs in a static electromagnetic field is rederived, and the resultant electromagnetic radiation is shown to be significant for highly magnetized pulsars in compact binary systems. We also obtain a variety of nonlinear interference effects for interacting gravitational and electromagnetic waves, although wave-wave resonances previously described in the literature are absent when the electric-magnetic self-interaction is taken into account. The fluctuation and amplification of electromagnetic energy flux as the GW strength increases towards the gravitational-electromagnetic frequency ratio is a possible signature of gravitational radiation from extended astrophysical sources.

Chua, Alvin J. K.; Cañizares, Priscilla; Gair, Jonathan R.

2015-01-01

216

Was Newton right? A search for non-Newtonian behavior of weak-field gravity  

NASA Astrophysics Data System (ADS)

Empirical tests of Einstein's metric theory of gravitation, even in the non-relativistic, weak-field limit, could play an important role in judging theory-driven extensions of the current Standard Model of fundamental interactions. Guided by Galileo's work and his own experiments, Newton formulated a theory of gravity in which the force of attraction between two bodies is independent of composition and proportional to the inertia of each, thereby transparently satisfying Galileo's empirically informed conjecture regarding the Universality of Free Fall. Similarly, Einstein honored the manifest success of Newton's theory by assuring that the linearized equations of GTR matched the Newtonian formalism under "classical" conditions. Each of these steps, however, was explicitly an approximation raised to the status of principle. Perhaps, at some level, Newtonian gravity does not accurately describe the physical interaction between uncharged, unmagnetized, macroscopic bits of ordinary matter. What if Newton were wrong? Detecting any significant deviation from Newtonian behavior, no matter how small, could provide new insights and possibly reveal new physics. In the context of physics as an empirical science, for us this yet unanswered question constitutes sufficient motivation to attempt precision measurements of the kind described here. In this paper we report the current status of a project to search for violation of the Newtonian inverse square law of gravity.

Boynton, Paul; Moore, Michael; Newman, Riley; Berg, Eric; Bonicalzi, Ricco; McKenney, Keven

2014-06-01

217

Gravitational field of vacuum domain walls and strings  

Microsoft Academic Search

The gravitational properties of vacuum domain walls and strings are studied in the linear approximation of general relativity. These properties are shown to be very different from those of regular massive planes and rods. It is argued that the domain walls are gravitationally unstable and collapse at a certain time approx.t\\/sub c\\/ after their creation. If the vacuum walls ever

Alexander Vilenkin

1981-01-01

218

Field theory and weak Euler-Lagrange equation for classical particle-field systems  

SciTech Connect

It is commonly believed that energy-momentum conservation is the result of space-time symmetry. However, for classical particle-field systems, e.g., Klimontovich-Maxwell and Klimontovich- Poisson systems, such a connection hasn't been formally established. The difficulty is due to the fact that particles and the electromagnetic fields reside on different manifolds. To establish the connection, the standard Euler-Lagrange equation needs to be generalized to a weak form. Using this technique, energy-momentum conservation laws that are difficult to find otherwise can be systematically derived.

Qin, Hong [PPPL; Burby, Joshua W [PPPL; Davidson, Ronald C [PPPL

2014-10-01

219

On The Interaction of Gravitational Waves with Magnetic and Electric Fields  

E-print Network

The existence of large--scale magnetic fields in the universe has led to the observation that if gravitational waves propagating in a cosmological environment encounter even a small magnetic field then electromagnetic radiation is produced. To study this phenomenon in more detail we take it out of the cosmological context and at the same time simplify the gravitational radiation to impulsive waves. Specifically, to illustrate our findings, we describe the following three physical situations: (1) a cylindrical impulsive gravitational wave propagating into a universe with a magnetic field, (2) an axially symmetric impulsive gravitational wave propagating into a universe with an electric field and (3) a `spherical' impulsive gravitational wave propagating into a universe with a small magnetic field. In cases (1) and (3) electromagnetic radiation is produced behind the gravitational wave. In case (2) no electromagnetic radiation appears after the wave unless a current is established behind the wave breaking the Maxwell vacuum. In all three cases the presence of the magnetic or electric fields results in a modification of the amplitude of the incoming gravitational wave which is explicitly calculated using the Einstein--Maxwell vacuum field equations.

C. Barrabes; P. A. Hogan

2010-03-02

220

Do the constants of nature couple to strong gravitational fields?  

E-print Network

Recently, white dwarf stars have found a new use in the fundamental physics community. Many prospective theories of the fundamental interactions of Nature allow traditional constants, like the fine structure constant $\\alpha$, to vary in some way. A study by Berengut et al. (2013) used the Fe/Ni V line measurements made by Preval et al. (2013) from the hot DA white dwarf G191-B2B, in an attempt to detect any variation in $\\alpha$. It was found that the Fe V lines indicated an increasing alpha, whereas the Ni V lines indicated a decreasing alpha. Possible explanations for this could be misidentification of the lines, inaccurate atomic data, or wavelength dependent distortion in the spectrum. We examine the first two cases by using a high S/N reference spectrum from the hot sdO BD+28$^{\\circ}$4211 to calibrate the Fe/Ni V atomic data. With this new data, we re-evaluate the work of Berengut et al. (2013) to derive a new constraint on the variation of alpha in a gravitational field.

S. P. Preval; M. A. Barstow; J. B. Holberg; J. D. Barrow; J. C. Berengut; J. K. Webb; D. Dougan; J. Hu

2014-10-13

221

Do the constants of nature couple to strong gravitational fields?  

E-print Network

Recently, white dwarf stars have found a new use in the fundamental physics community. Many prospective theories of the fundamental interactions of Nature allow traditional constants, like the fine structure constant $\\alpha$, to vary in some way. A study by Berengut et al. (2013) used the Fe/Ni V line measurements made by Preval et al. (2013) from the hot DA white dwarf G191-B2B, in an attempt to detect any variation in $\\alpha$. It was found that the Fe V lines indicated an increasing alpha, whereas the Ni V lines indicated a decreasing alpha. Possible explanations for this could be misidentification of the lines, inaccurate atomic data, or wavelength dependent distortion in the spectrum. We examine the first two cases by using a high S/N reference spectrum from the hot sdO BD+28$^{\\circ}$4211 to calibrate the Fe/Ni V atomic data. With this new data, we re-evaluate the work of Berengut et al. (2013) to derive a new constraint on the variation of alpha in a gravitational field.

Preval, S P; Holberg, J B; Barrow, J D; Berengut, J C; Webb, J K; Dougan, D; Hu, J

2014-01-01

222

MEASURING THE GEOMETRY OF THE UNIVERSE FROM WEAK GRAVITATIONAL LENSING BEHIND GALAXY GROUPS IN THE HST COSMOS SURVEY  

SciTech Connect

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component {Omega}{sub X} at greater than 99% confidence for an equation-of-state parameter -2.5 {<=} w {<=} -0.1. For the case w = -1, we find a value for the cosmological constant density parameter {Omega}{sub {Lambda}} = 0.85{sup +0.044}{sub -}0{sub .19} (68% CL) and detect cosmic acceleration (q{sub 0} < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys.

Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Massey, Richard J. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Rhodes, Jason; Ellis, Richard; Scoville, Nick [California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kitching, Thomas D. [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Ilbert, Olivier; Kneib, Jean-Paul [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Jullo, Eric [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Koekemoer, Anton M., E-mail: taylor@uwaterloo.ca [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2012-04-20

223

Chiral Imprint of a Cosmic Gauge Field on Primordial Gravitational Waves  

E-print Network

A cosmological gauge field with isotropic stress-energy introduces parity violation into the behavior of gravitational waves. We show that a primordial spectrum of inflationary gravitational waves develops a preferred handedness, left- or right-circularly polarized, depending on the abundance and coupling of the gauge field during the radiation era. A modest abundance of the gauge field would induce parity-violating correlations of the cosmic microwave background temperature and polarization patterns that could be detected by current and future experiments.

Jannis Bielefeld; Robert R. Caldwell

2014-12-18

224

Local Determination of the Light Deflection in the Sperically Symmetric Static Gravitational Field  

E-print Network

The new method of invariant definition of the measurable angle of light deflection in the static central symmetric gravitational field is suggested. The predicted pure gravitational contribution to the deflection angle slightly differs from its classical estimate and one may hope that this discrepancy could be experimentally detected in the near future. (uuencoded,compressed PostScript, 23 p. inc. 2 fig.)

S. Tertychniy

1993-11-02

225

Bifurcation and fine structure phenomena in critical collapse of a self-gravitating $?$-field  

E-print Network

Building on previous work on the critical behavior in gravitational collapse of the self-gravitating SU(2) $\\sigma$-field and using high precision numerical methods we uncover a fine structure hidden in a narrow window of parameter space. We argue that this numerical finding has a natural explanation within a dynamical system framework of critical collapse.

Peter C. Aichelburg; Piotr Bizon; Zbislaw Tabor

2005-12-22

226

CFHTLenS: the relation between galaxy dark matter haloes and baryons from weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We present a study of the relation between dark matter halo mass and the baryonic content of their host galaxies, quantified through galaxy luminosity and stellar mass. Our investigation uses 154 deg2 of Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) lensing and photometric data, obtained from the CFHT Legacy Survey. To interpret the weak lensing signal around our galaxies, we employ a galaxy-galaxy lensing halo model which allows us to constrain the halo mass and the satellite fraction. Our analysis is limited to lenses at redshifts between 0.2 and 0.4, split into a red and a blue sample. We express the relationship between dark matter halo mass and baryonic observable as a power law with pivot points of 10^{11} h_{70}^{-2} L_{{?}} and 2× 10^{11} h_{70}^{-2} M_{{?}} for luminosity and stellar mass, respectively. For the luminosity-halo mass relation, we find a slope of 1.32 ± 0.06 and a normalization of 1.19^{+0.06}_{-0.07}× 10^{13} h_{70}^{-1} M_{{?}} for red galaxies, while for blue galaxies the best-fitting slope is 1.09^{+0.20}_{-0.13} and the normalization is 0.18^{+0.04}_{-0.05}× 10^{13} h_{70}^{-1} M_{{?}}. Similarly, we find a best-fitting slope of 1.36^{+0.06}_{-0.07} and a normalization of 1.43^{+0.11}_{-0.08}× 10^{13} h_{70}^{-1} M_{{?}} for the stellar mass-halo mass relation of red galaxies, while for blue galaxies the corresponding values are 0.98^{+0.08}_{-0.07} and 0.84^{+0.20}_{-0.16}× 10^{13} h_{70}^{-1} M_{{? }}. All numbers convey the 68 per cent confidence limit. For red lenses, the fraction which are satellites inside a larger halo tends to decrease with luminosity and stellar mass, with the sample being nearly all satellites for a stellar mass of 2× 109 h_{70}^{-2} M_{{?}}. The satellite fractions are generally close to zero for blue lenses, irrespective of luminosity or stellar mass. This, together with the shallower relation between halo mass and baryonic tracer, is a direct confirmation from galaxy-galaxy lensing that blue galaxies reside in less clustered environments than red galaxies. We also find that the halo model, while matching the lensing signal around red lenses well, is prone to overpredicting the large-scale signal for faint and less massive blue lenses. This could be a further indication that these galaxies tend to be more isolated than assumed.

Velander, Malin; van Uitert, Edo; Hoekstra, Henk; Coupon, Jean; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bonnett, Christopher; Fu, Liping; Giodini, Stefania; Hudson, Michael J.; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta

2014-01-01

227

Fractional phase transition in medium size metal clusters and some remarks on magic numbers in gravitationally and weakly interacting clusters  

E-print Network

Based on the Riemann- and Caputo definition of the fractional derivative we use the fractional extensions of the standard rotation group SO(3) to construct a higher dimensional representation of a fractional rotation group with mixed derivative types. An analytic extended symmetric rotor model is derived, which correctly predicts the sequence of magic numbers in metal clusters. It is demonstrated, that experimental data may be described assuming a sudden change in the fractional derivative parameter $\\alpha$ which is interpreted as a second order phase transition in the region of cluster size with $200 \\leq N \\leq 300$. Furthermore it is demonstrated, that the four different realizations of higher dimensional fractional rotation groups may successfully be connected to the four fundamental interaction types realized in nature and may be therefore used for a prediction of magic numbers and binding energies of clusters with gravitational force and weak force respectively bound constituents. The results presented lead to the conclusion, that mixed fractional derivative operators might play a key role for a successful unified theoretical description of all four fundamental forces realized in nature.

Richard Herrmann

2009-07-11

228

Gravitational perturbation of the BTZ black hole induced by test particles and weak cosmic censorship in AdS spacetime  

E-print Network

We analyze the gravitational perturbations induced by particles falling into a three dimensional, asymptotically AdS black hole geometry. More specifically, we solve the linearized perturbation equations obtained from the geodesic motion of a ring-like distribution of test particles in the BTZ background. This setup ensures that the U(1) symmetry of the background is preserved. The non-asymptotic flatness of the background raises difficulties in attributing the significance of energy and angular momentum to the conserved quantities of the test particles. This issue is well known but, to the best of our knowledge, has never been addressed in the literature. We confirm that the naive expressions for energy and angular momentum are the correct definitions. Finally, we put an asymptotically AdS version of the weak cosmic censorship to a test: by attempting to overspin the BTZ black hole with test particles it is found that the black hole cannot be spun-up past its extremal limit.

Jorge V. Rocha; Vitor Cardoso

2011-05-20

229

Gravitational Field of the Early Universe: I.Non-linear Scalar Field as the Source  

E-print Network

In this review article we consider three most important sources of the gravitational field of the Early Universe: self-interacting scalar field, chiral field and gauge field. The correspondence between all of them are pointed out. More attention is payed to nonlinear scalar field source of gravity. The progress in finding the exact solutions in inflationary universe is reviewed. The basic idea of `fine turning of the potential' method is discussed and computational background is presented in details. A set of new exact solutions for standard inflationary model and conformally-flat space-times are obtained. Special attention payed to relations between `fine turning of the potential' and Barrow's approaches. As the example of a synthesis of both methods new exact solution is obtained.

S. V. Chervon

1997-06-10

230

The SuperCLASS Weak Lensing Deep Field Survey  

NASA Astrophysics Data System (ADS)

SuperCLASS is a survey of 1.75 square degrees of the Northern sky using the e-MERLIN telescope array at a frequency of 1.4GHz, aiming to reach an image noise RMS level of 4 micro-Jy/beam. The primary goal is to use the expected source density of ~1 per square arcminute (giving a total of ~10,000), ~150 milli-arcsecond resolution and presence in the survey region of 5 massive Abell clusters to measure a significant weak lensing effect in the radio band for only the second time, proving the potential of radio weak lensing as a powerful tool for mapping dark matter and constraining cosmological models. In doing this we will also learn a significant amount about the source population (star forming galaxies and radio AGN) themselves and their polarisation properties. SuperCLASS will not only require development of a pipeline for making the highly accurate determination of shapes of a large number of sources for performing standard weak lensing measurements, but will also form a test bed for new methods, such as the use of polarisation information to mitigate the biasing effect of intrinsic alignments between galaxies, which will be a key systematic for future weak lensing surveys. Whilst the challenges of the necessary shape measurement in image plane optical data are relatively well-explored, there is little experience in meeting those involved in the use of data from radio interferometers. The knowledge gained about efficient and accurate techniques for large scale radio astronomy from SuperCLASS will be invaluable in the build up to the next generation of experiments.

Harrison, Ian; Superclass Collaboration

2014-04-01

231

Gravitational Waves from Abelian Gauge Fields and Cosmic Strings at Preheating  

E-print Network

Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic microwave background. The detection of these waves will open a new window into the early Universe, and therefore it is important to characterize in detail all possible sources of primordial gravitational waves. In this paper we develop theoretical and numerical methods to study the production of gravitational waves from out-of-equilibrium gauge fields at preheating. We then consider models of preheating after hybrid inflation, where the symmetry breaking field is charged under a local U(1) symmetry. We analyze in detail the dynamics of the system in both momentum and configuration space, and show that gauge fields leave specific imprints in the resulting gravitational wave spectra, mainly through the appearence of new peaks at characteristic frequencies that are related to the mass scales in the problem. We also show how these new features in the spectra correlate with string-like spatial configurations in both the Higgs and gauge fields that arise due to the appearance of topological winding numbers of the Higgs around Nielsen-Olesen strings. We study in detail the time evolution of the spectrum of gauge fields and gravitational waves as these strings evolve and decay before entering a turbulent regime where the gravitational wave energy density saturates.

Jean-Francois Dufaux; Daniel G. Figueroa; Juan Garcia-Bellido

2010-09-23

232

Gravitational waves from Abelian gauge fields and cosmic strings at preheating  

SciTech Connect

Primordial gravitational waves provide a very important stochastic background that could be detected soon with interferometric gravitational wave antennas or indirectly via the induced patterns in the polarization anisotropies of the cosmic microwave background. The detection of these waves will open a new window into the early Universe, and therefore it is important to characterize in detail all possible sources of primordial gravitational waves. In this paper we develop theoretical and numerical methods to study the production of gravitational waves from out-of-equilibrium gauge fields at preheating. We then consider models of preheating after hybrid inflation, where the symmetry breaking field is charged under a local U(1) symmetry. We analyze in detail the dynamics of the system in both momentum and configuration space. We show that gauge fields leave specific imprints in the resulting gravitational wave spectra, mainly through the appearance of new peaks at characteristic frequencies that are related to the mass scales in the problem. We also show how these new features in the spectra correlate with stringlike spatial configurations in both the Higgs and gauge fields that arise due to the appearance of topological winding numbers of the Higgs around Nielsen-Olesen strings. We study in detail the time evolution of the spectrum of gauge fields and gravitational waves as these strings evolve and decay before entering a turbulent regime where the gravitational wave energy density saturates.

Dufaux, Jean-Francois [APC, UMR 7164 (CNRS-Universite Paris 7), 10 rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13 (France); Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Figueroa, Daniel G. [Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Department of Physics, CERN-Theory Division, CH-1211 Geneva 23 (Switzerland); Garcia-Bellido, Juan [Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Departement de Physique Theorique, Universite de Geneve, CH-1211 Geneve 4 (Switzerland)

2010-10-15

233

Effects of a weak transverse magnetic field on negative ion transport in negative ion sources  

Microsoft Academic Search

The effects of a weak transverse magnetic field on negative ion (H-) extraction in a negative ion source have been studied by two-dimensional electrostatic particle simulation. A particle-in-cell model is used which simulates motion of charged particles in their self-consistent electric field. The extraction of H- ions is significantly improved by the weak transverse magnetic field in simulation as well

T. Sakurabayashi; A. Hatayama; M. Bacal

2004-01-01

234

Gravitational Waves from the $r$-mode instability of neutron stars: effect of magnetic field  

E-print Network

Studies have shown that emission of gravitational wave drives an instability in the $r$-modes of young rapidly rotating neutron stars carrying away most of the angular momentum through gravitational wave emission in the first year or so after their formation. Magnetic field plays a crucial role in the evolution of these $r$-modes and hence the evolution of the neutron star itself. An attempt is made here to investigate the role of magnetic field in the evolution of $r$-mode instability and detectibility of gravitational waves emitted by a newly born, hot and rapidly and differentially rotating neutron star. It is found that magnetic field tend to suppress the $r$-mode amplitude. The {\\it signal-to-noise ratio} analysis shows that gravitational waves emitted from the $r$-mode instability from neutron stars with magnetic fields upto the order of $10^{14}$ gauss may be detectable by the Advanced LIGO at 20 Mpc.

Bhim Prasad Sarmah; H. L. Duorah

2010-11-16

235

Gravitational Fields with Sources, Regular Black Holes, Quasiblack Holes, and Analogue Black Holes  

NASA Astrophysics Data System (ADS)

We discuss recent developments in gravitational fields with sources, regular black holes, quasiblack holes, and analogue black holes, related to the talks presented at the corresponding Parallel Session AT3 of the 13th Marcel Grossmann Meeting.

Lemos, José P. S.; Pani, Paolo

2015-01-01

236

On Axionic Field Ranges, Loopholes and the Weak Gravity Conjecture  

E-print Network

In this short note we clarify some aspects of the impact that the Weak Gravity Conjecture has on models of (generalized) natural inflation. We address in particular certain technical and conceptual concerns recently raised regarding the stringent constraints and conclusions found in our previous work (arXiv:1503.04783). We also point out the difficulties faced by attempts to evade these constraints. These new considerations improve the understanding of the quantum gravity constraints we found and further support the conclusion that it remains challenging for axions to drive natural inflation.

Brown, Jon; Shiu, Gary; Soler, Pablo

2015-01-01

237

Kink-like Configurations of Interacting Scalar, Electromagnetic, and Gravitational Fields  

E-print Network

We have obtained exact kink-like static plane-symmetric solutions to the self-consistent system of electromagnetic, scalar, and gravitational field equations. It was shown that under certain choice of the interaction Lagrangian the solutions are regular and have localized energy. The linearized instability of corresponding solutions was established both for the case of flat space-time and that of interaction with the proper gravitational field.

D. S. Kulyabov; Yu. P. Rybakov; G. N. Shikin; L. P. Yuschenko

1999-02-08

238

Molecular gyroscopes and biological effects of weak ELF magnetic fields  

E-print Network

Extremely-low-frequency magnetic fields are known to affect biological systems. In many cases, biological effects display `windows' in biologically effective parameters of the magnetic fields: most dramatic is the fact that relatively intense magnetic fields sometimes do not cause appreciable effect, while smaller fields of the order of 10--100 $\\mu$T do. Linear resonant physical processes do not explain frequency windows in this case. Amplitude window phenomena suggest a nonlinear physical mechanism. Such a nonlinear mechanism has been proposed recently to explain those `windows'. It considers quantum-interference effects on protein-bound substrate ions. Magnetic fields cause an interference of ion quantum states and change the probability of ion-protein dissociation. This ion-interference mechanism predicts specific magnetic-field frequency and amplitude windows within which biological effects occur. It agrees with a lot of experiments. However, according to the mechanism, the lifetime $\\Gamma^{-1}$ of ion ...

Savin, A V

2002-01-01

239

Measuring the Geometry of the Universe from Weak Gravitational Lensing behind Galaxy Groups in the HST COSMOS Survey  

NASA Astrophysics Data System (ADS)

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component ? X at greater than 99% confidence for an equation-of-state parameter -2.5 <= w <= -0.1. For the case w = -1, we find a value for the cosmological constant density parameter ?? = 0.85+0.044 -0.19 (68% CL) and detect cosmic acceleration (q 0 < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA Inc. under the NASA contract NAS 5-26555; the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the European Southern Observatory under the Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

Taylor, James E.; Massey, Richard J.; Leauthaud, Alexie; George, Matthew R.; Rhodes, Jason; Kitching, Thomas D.; Capak, Peter; Ellis, Richard; Finoguenov, Alexis; Ilbert, Olivier; Jullo, Eric; Kneib, Jean-Paul; Koekemoer, Anton M.; Scoville, Nick; Tanaka, Masayuki

2012-04-01

240

The Deviation of the Vacuum Refractive Index Induced by a Static Gravitational Field  

E-print Network

We analyzed the influence of static gravitational field on the vacuum and proposed the concept of inhomogeneous vacuum. According to the observational result of the light deflection in solar gravitational field as well as the corresponding Fermat's principle in the general relativity, we derived an analytical expression of the refractive index of vacuum in a static gravitational field. We found that the deviation of the vacuum refractive index is composed of two parts: one is caused by the time dilation effect, the other is caused by the length contraction effect. As an application, we simulated the effect of the gravitational lensing through computer programming and found that the missing central imaging could be interpreted in a reasonable way.

Xing-Hao Ye; Qiang Lin

2007-04-10

241

ON THE GRAVITATIONAL FIELD OF THE ELECTRIC CHARGE  

E-print Network

The idea has been speaked out that any of Dirac and Pauli form factors of leptonic current includes in self both normal and anomalous components. From this point of view, with the use of cross sections of elastic scattering of unpolarized and longitudinal polarized electrons and their neutrinos by spinless nuclei the dependence of independent parts of charge and magnetic moment is established. Some considerations of a connection between the mass of a particle and its electromagnetic nature are listed which can explain also the appearance of gravitational field of a Coulomb interaction. All they state that a massive four- component neutrino similarly to the electron must have the normal as well as the anomalous electric charge. 1 Owing to the Dirac nature of mass, the neutrino can interact with all gauge bosons which plays an important part in establishing the physical picture of massive fermions. Here the processes on the nuclear targets are particularly interesting, because they give the possibility to investigate of compound structure of an incoming particle [1, 2] as well as of the unified system of hadrons [3] themselves. The interaction of light leptons (l = e, ?e) with the virtual photon strongly depends on the two scalar functions F1l(q 2) and F2l(q 2) are the Dirac and Pauli form factors of vector current. Of them F1l(0) defines the electric charge: F1l(0) = el. It appears that F2l(0) gives only the anomalous magnetic moment [4], and a particle full magnetic moment will have [5] the estimate [6] of µ full l = (F1l(0)/2ml) + F2l(0). We assuume that each of existing types of magnetic moments must arise as a consequence of the availability of a kind of charge. From this point of view, the functions Fil(q2) may be written as Fil(q 2) = fil(0) + Ail ( ? q 2) +..., (1) where fil(0) are the normal charge and moment: f1l(0) = e norm l, f2l(0) = µ norm l. The terms Ail ( ? q 2) characterize the anomalous behaviour of form factors and in the low energy limit ( ? q 2 = 0) have the size A1l(0) = e anom l, A2l(0) = µ anom l. Such a sight to the interaction nature can also explain the fact that F1l(0) and F2l(0) give the full static values of a Dirac particle electric charge and magnetic moment: F1l(0) = e full l = e norm

Rasulkhozha S. Sharafiddinov

2003-01-01

242

A study of Overhauser pumping in weak magnetic fields  

E-print Network

with the ESR pumping coil outside the NMR coil. ACKNOWLEDGEMENTS I greatly appreciate the many hours of help and guidance given to me by Dr. Nelion Duller throughout the course of this project. The curve fitting anlysis and graphs were done by Al Gondran... Field System, The Proton Field System. The Overhauser Pumping System. VI. EXPERIMENTAL RESULTS Preliminary Measurements and Experimental Details Sample Preparation Enhancement Data VII. SUMMARY LITERATURE CITED 10 15 . . . 22 22 . 32...

Gondran, Gregory Rhea

1986-01-01

243

Electromagnetic Waves in a Uniform Gravitational Field and Planck's Postulate  

ERIC Educational Resources Information Center

The gravitational redshift forms the central part of the majority of the classical tests for the general theory of relativity. It could be successfully checked even in laboratory experiments on the earth's surface. The standard derivation of this effect is based on the distortion of the local structure of spacetime induced by large masses. The…

Acedo, Luis; Tung, Michael M.

2012-01-01

244

Weak Lensing PSF Correction of Wide-field CCD Mosaic Images (SULI Paper)  

SciTech Connect

Gravitational lensing provides some of the most compelling evidence for the existence of dark matter. Dark matter on galaxy cluster scales can be mapped due to its weak gravitational lensing effect: a cluster mass distribution can be inferred from the net distortion of many thousands of faint background galaxies that it induces. Because atmospheric aberration and defects in the detector distort the apparent shape of celestial objects, it is of great importance to characterize accurately the point spread function (PSF) across an image. In this research, the PSF is studied in images from the Canada-France-Hawaii Telescope (CFHT), whose camera is divided into 12 CCD chips. Traditional weak lensing methodology involves averaging the PSF across the entire image: in this work we investigate the effects of measuring the PSF in each chip independently. This chip-by-chip analysis was found to reduce the strength of the correlation between star and galaxy shapes, and predicted more strongly the presence of known galaxy clusters in mass maps. These results suggest correcting the CFHT PSF on an individual chip basis significantly improves the accuracy of detecting weak lensing.

Cevallos, Marissa; /Caltech /SLAC

2006-01-04

245

Iron K? Line Profiles and Shadow Shapes as Evidences of Gravitational Lensing in a Strong Gravitational Field Near BHs  

NASA Astrophysics Data System (ADS)

Based on ray-shooting method we simulate Fe K? line profiles discovered in microquasars and Seyfert galaxies. Using narrow disk model for the emission line we describe transformations of characteristic two-peak profiles into one-peak profiles. In 2007 radio telescope Radioastron will be launched at a high elliptical orbit and it will be used as a space dish for VLBI observations with space-ground base. This interferometer will have extraordinary angular resolution (10-6 as). We discuss a procedure to measure masses, charges and spins analyzing these forms of mirages (shadows). Actually, that is a manifestation of gravitational lens effect in the strong gravitational field near black hole horizon.

Zakharov, Alexander F.; de Paolis, Francesco; Nucita, Achille A.; Ingrosso, Gabriele

2008-09-01

246

Generalized crossing states in the interacting case: The uniform gravitational field  

SciTech Connect

We reconsider Baute et al.'s free crossing states [Phys. Rev. A 61, 022118 (2000)] and show that if we require a generalization in the interacting case that goes in complete parallel with the free-particle case, then this generalized crossing state cannot be arbitrary but is determined by the null space of the particle's quantum time-of-arrival operator. Nonetheless, the free crossing states appear as the leading term in the asymptotic expansion of our generalized crossing state in the limit of large momentum. We then examine the quantum time-of-arrival problem of a spinless particle in a uniform gravitational field. Mass-dependent time-of-arrival probability distributions emerge, signifying quantum departures from the weak equivalence principle. However, in the classical limit of large mass and vanishing uncertainty in position, the mass dependence of the quantum time-of-arrival distribution becomes exponentially small and the mean quantum time of arrival reduces to the classical time of arrival.

Villanueva, Anthony D.; Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman Quezon City, 1101 Philippines (Philippines)

2010-11-15

247

Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space  

NASA Astrophysics Data System (ADS)

Thirring-Feynman's tensor field approach to gravitation opens new understanding on the physics of gravitational interaction and stimulates novel experiments on the nature of gravity. According to Field Gravity, the universal gravity force is caused by exchange of gravitons - the quanta of gravity field. Energy of this field is well-defined and excludes the singularity. All classical relativistic effects are the same as in General Relativity. The intrinsic scalar (spin 0) part of gravity field corresponds to ``antigravity'' and only together with the pure tensor (spin 2) part gives the usual Newtonian force. Laboratory and astrophysical experiments which may test the predictions of FG, will be performed in near future. In particular, observations at gravity observatories with bar and interferometric detectors, like Explorer, Nautilus, LIGO and VIRGO, will check the predicted scalar gravitational waves from supernova explosions. New types of cosmological models in Minkowski space are possible too.

Baryshev, Yurij

2006-03-01

248

Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space?  

E-print Network

Gravity theory is the basis of modern cosmological models. Thirring-Feynman's tensor field approach to gravitation is an alternative to General Relativity (GR). Though Field Gravity (FG) approach is still developing subject, it opens new understanding of gravitational interaction, stimulates novel experiments on the nature of gravity and gives possibility to construct new cosmological models in Minkowski space. According to FG, the universal gravity force is caused by exchange of gravitons - the quanta of gravity field. Energy of this field is well-defined and excludes the singularity. All classical relativistic effects are the same as in GR, though there are new effects, such as free fall of rotating bodies, scalar gravitational radiation, surface of relativistic compact bodies, which may be tested experimentally. The intrinsic scalar (spin 0) part of gravity field corresponds to "antigravity" and only together with the pure tensor (spin 2) part gives the usual Newtonian force. Laboratory and astrophysical e...

Baryshev, Y

2006-01-01

249

Universitat Regensburg Weak solutions to a multi-phase field  

E-print Network

divided by the temperature and phase field variables describing the presence of the possible phases in terms of thermodynamic potentials corresponding to (inverse) temperature and chemical poten- tials)i,j of real-valued functions of ,u and . The second set (2) of the equations is of a gradient flow structure

Regensburg, Universität - Naturwissenschaftliche Fakultät I

250

ON THE EFFECT OF A WEAK INTERPLANETARY MAGNETIC FIELD ON THE INTERACTION BETWEEN THE SOLAR WIND AND THE GEOMAGNETIC FIELD  

Microsoft Academic Search

the presence of a weak interplanetary magnetic field may lead to the ; formation of a collision-free shock wave upstream from the boundary of the ; geomagnetic field and to a transition region characterized by an irregular ; magnetic field in the intervening space. Previous calculations of the ; coordinates of the shock wave are improved upon by application of

John R. Spreiter; Wm. Prichard Jones

1963-01-01

251

Mathematical matrix theory of the field in n-dimensional metric space: rigorous derivation of the equations of the field with application in electromagnetic-gravitational fields  

E-print Network

During the last century the tensor theory of the gravitational field was developed. We propose and develop the novel, pure mathematical, matrix theory of the field in n-dimensional metric space. The definition of the mathematical field matrix and the equations of motion of the mathematical point are given. The interpretation of the nature of the mathematical field and the mathematical points can be different and depends on our knowledge of the nature. It is shown that the equations of motion are different for symmetric and antisymmetric field matrices. In the matrix field theory the equations of the field are rigorously derived. This theory reveals that in the 4-dimensional metric space the field matrix is the electromagnetic-gravitational field matrix, where the antisymmetric part is the matrix of electromagnetic field and the symmetric part is the gravitational field matrix. The partial cases of this matrix are electric-gravitational, magnetic-gravitational and gravitational field matrices. It is shown that the elements of all obtained matrices are the Christoffel symbols of the first and the second order or their derivatives.

Alexander D. Dymnikov

2012-11-19

252

Do fermions and bosons produce the same gravitational field?  

SciTech Connect

We examine some cosmological consequences of gravity coupling with different strength to fermions and bosons. We show that this leads to a different perturbation of the standard picture of primordial nucleosynthesis than the addition of extra neutrino types or overall scaling of the value of G. Observed abundances of deuterium and {sup 4}He place bounds on the ratio of the bosonic gravitational constant (G{sub B}) to the fermionic gravitational constant (G{sub F}) of 0.45

Barrow, John D.; Scherrer, Robert J. [DAMTP, Centre for Mathematical Sciences, Cambridge University, Cambridge CB3 0WA (United Kingdom); Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States)

2004-11-15

253

Narrow Scale Flow and a Weak Field by the Top of Earth's Core: Evidence from Orsted, Magsat and Secular Variation  

NASA Technical Reports Server (NTRS)

As Earth's main magnetic field weakens, our magnetic shield against the onslaught of the solar wind thins. And the field strength needed to fend off battering by solar coronal mass ejections is decreasing, just when the delicate complexity of modem, vulnerable, electro-technological systems is increasing at an unprecedented rate. Recently, a working group of distinguished scientist from across the nation has asked NASA's Solid Earth and Natural Hazards program a key question: What are the dynamics of Earth s magnetic field and its interactions with the Earth system? Paleomagnetic studies of crustal rocks magnetized in the geologic past reveal that polarity reversals have occurred many times during Earth s history. Networked super-computer simulations of core field and flow, including effects of gravitational, pressure, rotational Coriolis, magnetic and viscous forces, suggest how this might happen in detail. And space-based measurements of the real, time-varying magnetic field help constrain estimates of the speed and direction of fluid iron flowing near the top of the core and enable tests of some hypotheses about such flow. Now scientists at NASA s Goddard Space Flight Center have developed and applied methods to test the hypotheses of narrow scale flow and of a dynamically weak magnetic field near the top of Earth s core. Using two completely different methods, C. V. Voorhies has shown these hypotheses lead to specific theoretical forms for the "spectrum" of Earth s main magnetic field and the spectrum of its rate of change. Much as solar physicists use a prism to separate sunlight into its spectrum, from long wavelength red to short wavelength blue light, geophysicists use a digital prism, spherical harmonic analysis, to separate the measured geomagnetic field into its spectrum, from long to short wavelength fields. They do this for the rate of change of the field as well.

Voorhies, Coerte V.

2004-01-01

254

Can the energy density of gravitational field be interpreted as dark energy?  

E-print Network

After a brief review of the Maxwell-like approach to gravity we consider the issue of the negative energy of gravitational field which is a consequence of the field approach to the phenomenon of gravitation. Due to the existence of the negative field energy {\\it within} a mass body its total energy content is smaller than the positive energy assigned to its mass energy. We study the total energy content of a spherically symmetrical mass body having constant matter density, and show that its total energy content depends on its radius. We show that under certain circumstances, the total energy content of a mass body achieves negative values so that the force at its surface becomes repulsive. We apply this idea to the evolution of universe filled by matter and the negative energy density of its gravitational field. Since the negative energy density causes the negative pressure it might be considered as an agent which causes the acceleration of the universe.

V. Majernik

2008-07-31

255

Impurity-Assisted Tunneling Magnetoresistance under a Weak Magnetic Field  

NASA Astrophysics Data System (ADS)

Injection of spins into semiconductors is essential for the integration of the spin functionality into conventional electronics. Insulating layers are often inserted between ferromagnetic metals and semiconductors for obtaining an efficient spin injection, and it is therefore crucial to distinguish between signatures of electrical spin injection and impurity-driven effects in the tunnel barrier. Here we demonstrate an impurity-assisted tunneling magnetoresistance effect in nonmagnetic-insulator-nonmagnetic and ferromagnetic-insulator-nonmagnetic tunnel barriers. In both cases, the effect reflects on-off switching of the tunneling current through impurity channels by the external magnetic field. The reported effect is universal for any impurity-assisted tunneling process and provides an alternative interpretation to a widely used technique that employs the same ferromagnetic electrode to inject and detect spin accumulation.

Txoperena, Oihana; Song, Yang; Qing, Lan; Gobbi, Marco; Hueso, Luis E.; Dery, Hanan; Casanova, Fèlix

2014-10-01

256

Reproducible magnetic features of high-T/sub c/ superconductors in weak fields  

SciTech Connect

The microwave absorption spectrum of the high-T/sub c/ granular superconductor YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/ measured in a weak magnetic field with small modulation exhibits reproducible oscillations as a function of external field. We have modeled the high-T/sub c/ ceramics as a network of superconducting wires weakly coupled at randomly placed nodes. Quantum network simulations of the behavior of this system in a magnetic field reveal strong similarities between the computed magnetoconductance, magnetization, and susceptibility and the experimentally observed microwave absorption spectrum.

Jeffery, M.; Green, C.; Tyagi, S.; Gilmore, R.

1989-05-01

257

A static spherically symmetric solution for interacting scalar, electromagnetic, and gravitational fields  

Microsoft Academic Search

A unified theory of interacting scalar, electromagnetic, and gravitational fields constructed in previous papers by the author is used in considering a static spherically symmetrical case. An effective one-dimensional Lagrangian is derived together with the corresponding Hamilton-Jacobi equation. The solution to this equation is used in deriving a solution to Einstein's equations for the initial system of interacting fields. Some

V. D. Gladush

1980-01-01

258

Attempt at demonstrating the effect of a weak magnetic field on Taraxacum officinale  

Microsoft Academic Search

The exposure ofTaraxacum officinale L. at flowering time to a weak magnetic field resulted in (1) retarded opening and the closing of the inflorescence, (2)\\u000a wilting and death after prolonged exposure. Controls were unchanged. Plants exposed to the effect of magnetic fields were\\u000a degenerated in subsequent year.

Josef Novák; Ladislav Válek

1965-01-01

259

Transient effect of weak electromagnetic fields on calcium ion concentration in Arabidopsis thaliana  

Microsoft Academic Search

BACKGROUND: Weak magnetic and electromagnetic fields can influence physiological processes in animals, plants and microorganisms, but the underlying way of perception is poorly understood. The ion cyclotron resonance is one of the discussed mechanisms, predicting biological effects for definite frequencies and intensities of electromagnetic fields possibly by affecting the physiological availability of small ions. Above all an influence on Calcium,

Alexander Pazur; Valentina Rassadina

2009-01-01

260

Lichnerowicz-type theorems for self-gravitating systems with nonlinear electromagnetic fields  

NASA Astrophysics Data System (ADS)

We consider a self-gravitating system containing a globally timelike Killing vector and a nonlinear Born-Infeld electromagnetic field and scalar fields. We prove that under certain boundary conditions (asymptotically flat/anti-de Sitter) there cannot be any nontrivial field configurations in the spacetime. To explore nontrivial solutions, one should break any of the conditions we imposed. The case with another type of nonlinear electromagnetic field is also analyzed, and similar conclusions have been obtained under certain conditions.

Cao, Li-Ming; Peng, Yuxuan; Xu, Jianfei

2014-07-01

261

Lichnerowicz-Type Theorems for Self-gravitating Systems with Nonlinear Electromagnetic Fields  

E-print Network

We consider a self-gravitating system containing a globally timelike Killing vector and a nonlinear Born-Infeld electromagnetic field and scalar fields. We prove that under certain boundary conditions (asymptotically flat/AdS) there can't be any nontrivial field configurations in the spacetime. To explore nontrivial solutions one should break any of the conditions we imposed. The case with another type of nonlinear electromagnetic field is also analyzed, and similar conclusions have been obtained under certain conditions.

Li-Ming Cao; Yuxuan Peng; Jianfei Xu

2014-07-11

262

Modified Gravitational Theory and Galaxy Rotation Curves  

E-print Network

The nonsymmetric gravitational theory predicts an acceleration law that modifies the Newtonian law of attraction between particles. For weak fields a fit to the flat rotation curves of galaxies is obtained in terms of the mass (mass-to-light ratio M/L) of galaxies. The fits assume that the galaxies are not dominated by exotic dark matter. The equations of motion for test particles reduce for weak gravitational fields to the GR equations of motion and the predictions for the solar system and the binary pulsar PSR 1913+16 agree with the observations. The gravitational lensing of clusters of galaxies can be explained without exotic dark matter.

J. W. Moffat

2004-08-26

263

A Test to Verify the Speed Change of Light in the Gravitational Field of the Earth  

E-print Network

Based on the Schwarzschild solution of the Einstein equation of gravitational field, it is proved that the speed of light speed would change and isotropy of light speed would be violated in gravitational field with spherical symmetry. On the surface of the earth, the speed of light vertical to the surface is 0.2m/s less than that parallel to the surface. It is suggested to use the method of the Michelson Morley interference to verify the change of light speed and the violation of isotropy in the gravitational field of the earth. In the proposed experiment, one arm of interferometer is vertical to the earth surface while another is parallel to the surface. When two arms are turned over 90 degree, the shift of about 0.07 interference stripe would be caused which can be observed directly. So this experiment can be considered as a new verification for general relativity in the gravitational field with spherical symmetry. If the experiment shows that gravitation would change the speed of light and violate the isotropy of light speed, the result would cause great effects on foundational physics, astrophysics and cosmolo

Mei Xiaochun

2006-12-03

264

Non-equilibrium dynamics of a thermal plasma in a gravitational field  

E-print Network

We introduce functional methods to study the non-equilibrium dynamics of a quantum massless scalar field at finite temperature in a gravitational field. We calculate the Close Time Path (CTP) effective action and, using its formal equivalence with the influence functional, derive the noise and dissipation kernels of the quantum open system in terms of quantities in thermodynamical equilibrium. Using this fact, we formally prove the existence of a Fluctuation-Dissipation Relation (FDR) at all temperatures between the quantum fluctuations of the plasma in thermal equilibrium and the energy dissipated by the external gravitational field. What is new is the identification of a stochastic source (noise) term arising from the quantum and thermal fluctuations in the plasma field, and the derivation of a Langevin-type equation which describes the non-equilibrium dynamics of the gravitational field influenced by the plasma. The back reaction of the plasma on the gravitational field is embodied in the FDR. From the CTP effective action the contribution of the quantum scalar field to the thermal graviton polarization tensor can also be derived and it is shown to agree with other techniques, most notably, Linear Response Theory (LRT). We show the connection between the LRT, which is applicable for near-equilibrium conditions and the functional methods used in this work which are useful for fully non-equilibrium conditions.

Antonio Campos; B. L. Hu

1998-12-10

265

Short guide to direct gravitational field modelling with Hotine's equations  

NASA Astrophysics Data System (ADS)

This paper presents a unified approach to the least squares spherical harmonic analysis of the acceleration vector and Eötvös tensor (gravitational gradients) in an arbitrary orientation. The Jacobian matrices are based on Hotine's equations that hold in the Earth-fixed Cartesian frame and do not need any derivatives of the associated Legendre functions. The implementation was confirmed through closed-loop tests in which the simulated input is inverted in the least square sense using the rotated Hotine's equations. The precision achieved is at the level of rounding error with RMS about 10^{-12}{-}10^{-14} m in terms of the height anomaly. The second validation of the linear model is done with help from the standard ellipsoidal correction for the gravity disturbance that can be computed with an analytic expression as well as with the rotated equations. Although the analytic expression for this correction is only of a limited accuracy at the submillimeter level, it was used for an independent validation. Finally, the equivalent of the ellipsoidal correction, called the effect of the normal, has been numerically obtained also for other gravitational functionals and some of their combinations. Most of the numerical investigations are provided up to spherical harmonic degree 70, with degree 80 for the computation time comparison using real GRACE data. The relevant Matlab source codes for the design matrices are provided.

Sebera, Josef; Wagner, Carl A.; Bezd?k, Aleš; Kloko?ník, Jaroslav

2013-03-01

266

Exact deflection of a Neutral-Tachyon in the Kerr's Gravitational field  

E-print Network

We solve in closed analytic form space-like geodesic equations in the Kerr gravitational field. Such geodesic equations describe the motion of neutral tachyons (faster than light particles) in the Kerr spacetime. More specifically we derive the closed form solution for the deflection angle of a neutral tachyon on an equatorial orbit in Kerr spacetime. The solution is expressed elegantly in terms of Lauricella's hypergeometric function F_{D}.We applied our results to three cases: first, for the calculation of the deflection angle of a neutral tachyon on an equatorial trajectory in the gravitational field of a Kerr black hole. Subsequently, we applied our exact solutions to compute the deflection angle of equatorial spacelike geodesics in the gravitational fields of Sun and Earth assuming the Kerr spacetime geometry.

G. V. Kraniotis

2011-10-06

267

Gravitation and electromagnetism in theory of a unified four-vector field  

E-print Network

A four-vector field in flat space-time, satisfying a gauge-invariant set of second-order differential equations, is considered as a unified field. The model variational principle corresponds to the general covariance idea and gives rise to nonlinear Born-Infeld electrodynamics. Thus the four-vector field is considered as an electromagnetic potential. It is suggested that space-localized (particle) solutions of the nonlinear field model correspond to material particles. Electromagnetic and gravitational interactions between field particles appear naturally when a many-particle solution is investigated with the help of a perturbation method. The electromagnetic interaction appears in the first order in the small field of distant particles. In the second order, there is an effective Riemannian space induced by the field of distant particles. This Riemannian space can be connected with gravitation.

Alexander A. Chernitskii

2006-09-28

268

Cosmological Applications of Gravitational Lensing  

E-print Network

The last decade has seen an enormous increase of activity in the field of gravitational lensing, mainly driven by improvements of observational capabilities. I will review the basics of gravitational lens theory, just enough to understand the rest of this contribution, and will then concentrate on several of the main applications in cosmology. Cluster lensing, and weak lensing, will constitute the main part of this review.

Peter Schneider

1995-12-08

269

Gravitational Effects of Quantum Fields in the Interior of a Cylindrical Black Hole  

E-print Network

The gravitational back-reaction is calculated for the conformally invariant scalar field within a black cosmic string interior with cosmological constant. Using the perturbed metric, the gravitational effects of the quantum field are calculated. It is found that the perturbations initially strengthen the singularity. This effect is similar to the case of spherical symmetry (without cosmological constant). This indicates that the behaviour of quantum effects may be universal and not dependent on the geometry of the spacetime nor the presence of a non-zero cosmological constant.

A. DeBenedictis

1998-11-18

270

Bi-Local Field in Gravitational Shock Wave Background  

E-print Network

The particles with almost light velocity are able to be sources of the shock-wave gravity (SWG). Then, for ultra-high-energy particles, there exist two-body scatterings such that one particle is scattered from the gravitational background produced by another particle. Since the spacetime of SWG is closely related to a pp-wave solution of AdS-type background, this type of interaction is also interesting in AdS dual gauge theories. From those viewpoints, the scattering of point particles or strings by the SWG were studied. In this paper, we study the case of the bi-local models, which are simple relativistic bound systems having a close relation with specific modes of open strings. In particular, we analyze the bound-state effect on the scattering amplitudes, which describe the interaction between this model and SWG.

Naohiro Kanda; Shigefumi Naka

2014-10-28

271

Bi-local field in gravitational shockwave background  

NASA Astrophysics Data System (ADS)

Particles with almost light velocity are able to be sources of shockwave gravity (SWG). Then, for ultra-high-energy particles, there exist two-body scatterings such that one particle is scattered from the gravitational background produced by another particle. Since the spacetime of SWG is closely related to a pp-wave solution of the AdS-type background, this type of interaction is also interesting in AdS dual gauge theories. From those viewpoints, the scattering of point particles or strings by SWG were studied. In this paper, we study the case of the bi-local models, which are simple relativistic bound systems having a close relation with specific modes of open strings. In particular, we analyze the bound-state effect on the scattering amplitudes, which describe the interaction between this model and SWG.

Kanda, N.; Naka, S.

2015-03-01

272

Weak Solutions to Fokker-Planck Equations and Mean Field Games  

NASA Astrophysics Data System (ADS)

We deal with systems of PDEs, arising in mean field games theory, where viscous Hamilton-Jacobi and Fokker-Planck equations are coupled in a forward-backward structure. We consider the case of local coupling, when the running cost depends on the pointwise value of the distribution density of the agents, in which case the smoothness of solutions is mostly unknown. We develop a complete weak theory, proving that those systems are well-posed in the class of weak solutions for monotone couplings under general growth conditions, and for superlinear convex Hamiltonians. As a key tool, we prove new results for Fokker-Planck equations under minimal assumptions on the drift, through a characterization of weak and renormalized solutions. The results obtained give new perspectives even for the case of uncoupled equations as far as the uniqueness of weak solutions is concerned.

Porretta, Alessio

2015-04-01

273

Effects of Electromagnetic Field on The Collapse and Expansion of Anisotropic Gravitating Source  

E-print Network

This paper is devoted to study the effects of electromagnetic on the collapse and expansion of anisotropic gravitating source. For this purpose, we have evaluated the generating solutions of Einstein-Maxwell field equations with spherically symmetric anisotropic gravitating source. We found that a single function generates the various anisotropic solutions. In this case every generating function involves an arbitrary function of time which can be chosen to fit several astrophysical time profiles. Two physical phenomenon occur, one is gravitational collapse and other is the cosmological expanding solution. In both cases electromagnetic field effects the anisotropy of the model. For collapse the anisotropy is increased while for expansion it deceases from maximum value to finite positive value. In case of collaps there exits two horizons like in case of Reissner-Nordstr$\\ddot{o}$m metric.

G. Abbas

2014-05-27

274

Analytical solution from vector potentials for the gravitational field of a general polyhedron  

NASA Astrophysics Data System (ADS)

Closed form solutions in terms of elementary functions are given for the Newtonian gravitational field and potential of a general constant density polyhedron, using a gravitational vector potential formulation. The solution constants are given in terms of scalar and vector products involving the position vectors of the field point and the polyhedron's vertices, giving one analytical expression for each edge of the polyhedron. It is shown that in this vector potential formulation, the gravitational problem is related to the point-in-polygon problem of computational geometry. The solution is derived using a new vector theorem giving the integral over a flat surface of a scalar potential as a line integral of a vector potential around its boundary. The method is also valid in the interior of the polyhedron and can be extended to polyhedra with linear spatial variation of the density. Numerical results are compared with results in the literature and detailed results are given for the five regular Platonic polyhedra.

Conway, John T.

2015-01-01

275

Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space?  

E-print Network

Gravity theory is the basis of modern cosmological models. Thirring-Feynman's tensor field approach to gravitation is an alternative to General Relativity (GR). Though Field Gravity (FG) approach is still developing subject, it opens new understanding of gravitational interaction, stimulates novel experiments on the nature of gravity and gives possibility to construct new cosmological models in Minkowski space. According to FG, the universal gravity force is caused by exchange of gravitons - the quanta of gravity field. Energy of this field is well-defined and excludes the singularity. All classical relativistic effects are the same as in GR, though there are new effects, such as free fall of rotating bodies, scalar gravitational radiation, surface of relativistic compact bodies, which may be tested experimentally. The intrinsic scalar (spin 0) part of gravity field corresponds to "antigravity" and only together with the pure tensor (spin 2) part gives the usual Newtonian force. Laboratory and astrophysical experiments for testing new predictions of FG, will be performed in near future. In particular observations with bar and interferometric detectors, like Explorer, Nautilus, LIGO and VIRGO, will check the predicted scalar gravitational waves from supernova explosions.

Yurij Baryshev

2005-09-27

276

GMM-1: A 50 degree and order gravitational field model for Mars  

NASA Technical Reports Server (NTRS)

Knowledge of the gravitational field, in combination with surface topography, provides one of the principal means of inferring the internal structure of a planetary body. The highest resolution gravitational field for Mars published thus far was derived from Doppler tracking data from the Mariner 9 and Viking 1 and 2 spacecraft and is complete to degree and order 18 corresponding to a half wavelength resolution of approximately 600 km. This field, which is characterized by a spatial resolution that is slightly better than that of the highest resolution (16x16) topographic model, has been utilized extensively in analyses of the state of stress and isostatic compensation of the Martian lithosphere. However, the resolution and quality of current gravity and topographic fields are such that the origin and evolution of even the major physiographic features on Mars, such as the hemispheric dichotomy and Tharsis rise, are not well understood. We have re-analyzed the Viking and Mariner data sets and have derived a new gravitational field, which we designated GMM-1 (Goddard Mars Model-1). This model is complete to spherical harmonic degree and order 50 with a corresponding (half wavelength) spatial resolution of 200-300 km where the data permit. In contrast to previous models, GMM-1 was solved to as high degree and order as necessary to nearly exhaust the attenuated gravitational signal contained in the tracking data.

Smith, D. E.; Lerch, F. J.; Nerem, R. S.; Zuber, M. T.; Patel, G. B.; Fricke, S. K.; Lemoine, F. G.

1993-01-01

277

Traveling-wave tubes and backward-wave oscillators with weak external magnetic fields  

NASA Astrophysics Data System (ADS)

Recent development of plasma-assisted slow-wave oscillators [Goebel et al. IEEE Trans. Plasma Sci. 22, 547 (1994)], microwave sources that operate without guiding magnetic fields, has stimulated interest in the theoretical analysis of such tubes. In principle, in the absence of guiding magnetic fields, due to the space charge forces and the radial electric field of the wave, the electrons may propagate radially outward which increases electron coupling to the slow wave whose field is localized near the slow-wave structure (SWS). This increases the wave growth rate and efficiency, and hence allows one to shorten the interaction region. So the radial electron motion can be beneficial for operation if it does not lead to interception of electrons by the SWS. To avoid this interception a weak external magnetic field can be applied. The theory developed describes the effect of weak magnetic fields on the operation of traveling-wave tubes and backward-wave oscillators with electrons moving not only axially but also transversely. This theory allows one to estimate the magnetic field required for protecting the SWS from electron bombardment at different power levels. Theoretical predictions of the efficiency enhancement due to the weak magnetic field are confirmed in experiments.

Abu-Elfadl, T. M.; Nusinovich, G. S.; Shkvarunets, A. G.; Carmel, Y.; Antonsen, T. M.; Goebel, D.

2001-06-01

278

Magnetite in human tissues: A mechanism for the biological effects of weak ELF magnetic fields  

SciTech Connect

Due to the apparent lack of a biophysical mechanism, the question of whether weak, low-frequency magnetic fields are able to influence living organisms has long been one of the most controversial subjects in any field of science. However, two developments during the past decade have changed this perception dramatically, the first being the discovery that many organisms, including humans, biochemically precipitate the ferrimagnetic mineral magnetite (Fe3O4). In the magnetotactic bacteria, the geomagnetic response is based on either biogenic magnetite or greigite (Fe3S4), and reasonably good evidence exists that this is also the case in higher animals such as the honey bee. Second, the development of simple behavioral conditioning experiments for training honey bees to discriminate magnetic fields demonstrates conclusively that at least one terrestrial animal is capable of detecting earth-strength magnetic fields through a sensory process. In turn, the existence of this ability implies the presence of specialized receptors which interact at the cellular level with weak magnetic fields in a fashion exceeding thermal noise. A simple calculation shows that magnetosomes moving in response to earth-strength ELF fields are capable of opening trans-membrane ion channels, in a fashion similar to those predicted by ionic resonance models. Hence, the presence of trace levels of biogenic magnetite in virtually all human tissues examined suggests that similar biophysical processes may explain a variety of weak field ELF bioeffects. 61 refs.

Kirschvink, J.L.; Kobayashi-Kirschvink, A.; Diaz-Ricci, J.C.; Kirschvink, S.J. (California Institute of Technology, Pasadena (United States))

1992-01-01

279

Hermitian Dirac Hamiltonian in time dependent gravitational field  

E-print Network

It is shown by a straightforward argument that the Hamiltonian generating the time evolution of the Dirac wave function in relativistic quantum mechanics is not hermitian with respect to the covariantly defined inner product whenever the background metric is time dependent. An alternative, hermitian, Hamiltonian is found and is shown to be directly related to the canonical field Hamiltonian used in quantum field theory.

M. Leclerc

2006-05-05

280

Quantum fields on manifolds: PCT and gravitationally induced thermal states  

Microsoft Academic Search

We formulate an axiomatic scheme, designed to provide a framework for a general, rigorous theory of relativistic quantum fields on a class of manifolds, that includes Kruskal's extension of Schwarzchild space-time, as well as Minkowski space-time. The scheme is an adaptation of Wightman's to this class of manifolds. We infer from it that, given an arbitrary field (in general, interacting)

G SEWELL

1982-01-01

281

The Initial Value Problem and the Dynamics of Gravitational Fields1)  

E-print Network

The Initial Value Problem and the Dynamics of Gravitational Fields1) J. E. Marsden (Berkeley order: (a) Fischer and Marsden (19720.] show how to write the evolution equations as a first problem. (e) Hughes, Kato and Marsden [1977] prove a conjecture of Hawking and Ellis, showing

Marsden, Jerrold

282

Illustrating Some Principles of Separation Science through Gravitational Field-Flow Fractionation  

ERIC Educational Resources Information Center

Particle separation is an important but often neglected topic in undergraduate curricula. This article discusses how the method of gravitational field-flow fractionation (GrFFF) can be used to illustrate many principles of separation science and some fundamental concepts of physical chemistry. GrFFF separates particles during their elution through…

Beckett, Ronald; Sharma, Reshmi; Andric, Goja; Chantiwas, Rattikan; Jakmunee, Jaroon; Grudpan, Kate

2007-01-01

283

Anomalies of an external and internal gravitational field of upper Earth layers in square law approximation  

Microsoft Academic Search

The explicit form for the quadratic contribution to the gravitational field from the dipole distributed anomalous masses is found. The anomalous masses are represented in the form of layers of variable height, arranged relative to the reference ellipsoid. The solution is reduced to the mathematical problem of finding an expression for the coefficients of expansion in terms of spherical harmonics

L. P. Nasonova; N. A. Chujkova

2007-01-01

284

The rate of deflection of light in an accelerated frame and a gravitational field  

Microsoft Academic Search

We present calculations of the rate of deflection of light per unit central angle phi in a set of stationary frames along the light path in the gravitational field of the sun and in an equivalent (except for curvature) set of accelerated frames in flat spacetime in a study designed to further understanding of the equivalence principle in general relativity.

William Moreau; Craig Purdie; Joshua Wood

1999-01-01

285

On gravitational coupling for massive higher spin fields in d = 3 space  

NASA Astrophysics Data System (ADS)

In this paper we study the gravitational interaction for massive higher integer spin fields in three dimensional AdS space. Within of gauge invariant description we have constructed cubic vertex s — s — 2 and discuss the possible going beyond the first-order approximation.

Snegirev, T. V.

2014-12-01

286

Variations of the gravitational field as a motive power for rhythmics of biochemical processes  

NASA Astrophysics Data System (ADS)

Variations of the gravitational field affected by the Sun and the Moon while the Earth's moving along the orbit seem to be a powerful source of many rhythmical processes typical of biochemical processes. Studies carried out in AARI revealed the obvious relationships between the dynamics of some biochemical reactions and ?D- function describing the regular variations of the gravitational field under combined influence of the Sun and the Moon. The following of them are examined as examples: the rate of the unithiol oxidation in vitro, concentration of the thiol compounds in human urine, some hematological indicators (rate of the erythrocytes sedimentation, hemoglobin content). Compatibility of run of the biochemical indicators and ?D-function is indicative of essential influence of the regular variations of the gravitational field on rhythmics of the biochemical processes. As this takes place, the solar activity acts like to the instability factor. Balance of the solar activity effects and the varying gravitational field effect alter in time depending on location in the solar activity cycle.

Troshichev, O. A.; Gorshkov, E. S.; Shapovalov, S. N.; Sokolovskii, V. V.; Ivanov, V. V.; Vorobeitchikov, V. M.

2004-01-01

287

The Electronic Structure of Transition Metal Cluster Complexes with Weak and Strong-field Ligands  

Microsoft Academic Search

A systematic account and a survey of the results of quantum-chemical and spectroscopic studies of the electronic structure of transition metal cluster complexes are presented. In terms of the theory of canonical molecular orbitals and the theory of weak- and strong-field ligands, the concept of the structure and stability of the clusters taking into account the influence of the ligands

Galina P. Kostikova; Dimitrii V. Korol'kov

1985-01-01

288

Form factor of a quantum graph in a weak magnetic field  

NASA Astrophysics Data System (ADS)

Using the periodic orbit theory, we evaluate the form factor of a quantum graph to which a very weak magnetic field is applied. The first correction to the diagonal approximation describing the transition between the universality classes is shown to be in agreement with Pandey and Mehta's formula of parametric random matrix theory.

Nagao, Taro; Saito, Keiji

2003-05-01

289

Stellar explosion in the weak field approximation of the Brans–Dicke theory  

Microsoft Academic Search

We treat a very crude model of an exploding star, in the weak field approximation of the Brans–Dicke theory, in a scenario that resembles some characteristic data of a type Ia supernova. The most noticeable feature, in the electromagnetic component, is the relationship between the absolute magnitude at maximum brightness of the star and the decline rate in one magnitude

Victor H. Hamity; Daniel E. Barraco

2005-01-01

290

Stellar explosion in the weak field approximation of the Brans Dicke theory  

Microsoft Academic Search

We treat a very crude model of an exploding star, in the weak field approximation of the Brans Dicke theory, in a scenario that resembles some characteristic data of a type Ia supernova. The most noticeable feature, in the electromagnetic component, is the relationship between the absolute magnitude at maximum brightness of the star and the decline rate in one

Victor H. Hamity; Daniel E. Barraco

2005-01-01

291

The quadratic Zeeman effect for highly excited hydrogen atoms in weak magnetic fields  

Microsoft Academic Search

The hydrogen Rydberg states in the presence of weak magnetic fields are analytically investigated by using quantum mechanical first-order perturbation theory. The unperturbed hydrogenic wavefunctions, which diagonalise the quadatic Zeeman interaction within the subspace of states with fixed principal quantum number n, are obtained by separation of variables on the Fock hypersphere in momentum space. By considering n as a

T. P. Grozdanov; E. A. Solovev

1984-01-01

292

The Phase Matrix for Scattering in a Weak Magnetic Field. The Hanle Effect  

Microsoft Academic Search

A new formulation for the phase matrix for the scattering of radiation in a weak magnetic field is presented. The phase matrix is represented as a product of individual matrices that depend on the angle of incidence and the scattering angle. It is shown that the Hanle effect is absent in observations of scattered light in the solar atmosphere when

D. N. Rachkovskii

2005-01-01

293

Weak electromagnetic field admitting integrability in Kerr-NUT-(A)dS spacetimes  

E-print Network

We investigate properties of higher-dimensional generally rotating black-hole spacetimes, so called Kerr-NUT-(A)dS spacetimes, as well as a family of related spaces which share the same explicit and hidden symmetries. In these spaces, we study a particle motion in the presence of a weak electromagnetic field and compare it with its operator analogies. First, we find general commutativity conditions for classical observables and for their operator counterparts, then we investigate a fulfillment of these conditions in the Kerr-NUT-(A)dS and related spaces. We find the most general form of the weak electromagnetic field compatible with the complete integrability of the particle motion and the comutativity of the field operators. For such a field we solve the charged Hamilton-Jacobi and Klein-Gordon equations by separation of variables.

Kolar, Ivan

2015-01-01

294

Effects of a Weak Planetary Field on a Model Venus Ionosphere  

NASA Astrophysics Data System (ADS)

There are a number of attributes of the near-Venus space environment and upper atmosphere that remain mysterious, including occasional large polar magnetic field stuctures seen on VEX and nightside ionospheric holes seen on PVO. We have been exploring the consequences of a weak global dipole magnetic field of Venus using results of BATS-R-US MHD simulations. An advantage of these models is that they include the effects on a realistic ionosphere. We compare some of the weak magnetosphere's ionospheric properties with the typical unmagnetized ionsphere case. The results show the differences can be quite subtle for dipole fields less than ~10 nT at the equator, as might be expected. Nevertheless the dipole fields do produce distinctive details, especially in the upper regions.

Luhmann, Janet G.; Ma, Yingjuan; Villarreal, Michaela

2014-05-01

295

Zeeman resonances for radical-pair reactions in weak static magnetic fields  

NASA Astrophysics Data System (ADS)

Recent reaction-yield-detected magnetic resonance experiments in weak static magnetic fields and the observation of resonance effects in animal orientation experiments provide the motivation for renewed studies of magnetic field effects on radical-pair reactions. Here, we investigate theoretically resonance patterns for weak static magnetic fields. We focus on the question: for which radical pairs can one expect Zeeman resonances to occur if the static field is weaker than typical hyperfine interactions? Using analytical approaches, we rationalize the occurrence of Zeeman resonances for simple radical pairs. Numerical solutions are presented for a wide range of radical pairs with up to seven hyperfine interactions employing the rotating-frame transformation. The results suggest that resonances occur close to either the Larmor frequency or half the Larmor frequency for a wide variety of radical pairs for spin Hamiltonians with a high degree of symmetry. For larger numbers of hyperfine interactions, Zeeman resonances decrease in size.

Wang, Kefei; Ritz, Thorsten

2006-05-01

296

Super-ferrimagnetism of magnetite nanoparticles in a weak magnetic field  

Microsoft Academic Search

Film composites based on the magnetite Fe3O4 nanoparticles in the polyvinyl alcohol matrix were studied by means of the Mössbauer spectroscopy in a weak magnetic field, mainly at room temperature. The Mössbauer spectra in the absence of a magnetic field show a superposition of minor (poor-resolved) magnetic hyperfine structure and major collapsed spectrum typical for superparamagnetic particles. Such a pattern

M A Polikarpov; V M Cherepanov; M A Chuev; S Yu Shishkov; S S Yakimov

2010-01-01

297

Gravitational Anomaly and Transport  

E-print Network

Quantum anomalies give rise to new transport phenomena. In particular a magnetic field can induce an anomalous current via the chiral magnetic effect and a vortex in the relativistic fluid can also induce a current via the chiral vortical effect. The related transport coefficients can be calculated via Kubo formulas. We evaluate the Kubo formula for the anomalous vortical conductivity at weak coupling and show that it receives contributions proportional to the gravitational anomaly coefficient. The gravitational anomaly gives rise to an anomalous vortical effect even for an uncharged fluid.

Landsteiner, Karl; Pena-Benitez, Francisco

2011-01-01

298

Gravitational Anomaly and Transport  

E-print Network

Quantum anomalies give rise to new transport phenomena. In particular a magnetic field can induce an anomalous current via the chiral magnetic effect and a vortex in the relativistic fluid can also induce a current via the chiral vortical effect. The related transport coefficients can be calculated via Kubo formulas. We evaluate the Kubo formula for the anomalous vortical conductivity at weak coupling and show that it receives contributions proportional to the gravitational anomaly coefficient. The gravitational anomaly gives rise to an anomalous vortical effect even for an uncharged fluid.

Karl Landsteiner; Eugenio Megias; Francisco Pena-Benitez

2011-07-06

299

Gravitational influences on magnetic field structure in accretion disks  

E-print Network

Black holes and compact objects are often surrounded by structures known as accretion disks which consist of ionized plasma. Due to the immense forces present in the disk, interesting and complex magnetic field structures ...

Schneck, Kristiana E. (Kristiana Elizabeth)

2010-01-01

300

Progressive Muscle Atrophy and Weakness After Treatment by Mantle Field Radiotherapy in Hodgkin Lymphoma Survivors  

SciTech Connect

Purpose: To describe the damage to the muscles and propose a pathophysiologic mechanism for muscle atrophy and weakness after mantle field radiotherapy in Hodgkin lymphoma (HL) survivors. Methods and Materials: We examined 12 patients treated by mantle field radiotherapy between 1969 and 1998. Besides evaluation of their symptoms, the following tests were performed: dynamometry; ultrasound of the sternocleidomastoid, biceps, and antebrachial flexor muscles; and needle electromyography of the neck, deltoid, and ultrasonographically affected arm muscles. Results: Ten patients (83%) experienced neck complaints, mostly pain and muscle weakness. On clinical examination, neck flexors were more often affected than neck extensors. On ultrasound, the sternocleidomastoid was severely atrophic in 8 patients, but abnormal echo intensity was seen in only 3 patients. Electromyography of the neck muscles showed mostly myogenic changes, whereas the deltoid, biceps, and antebrachial flexor muscles seemed to have mostly neurogenic damage. Conclusions: Many patients previously treated by mantle field radiotherapy develop severe atrophy and weakness of the neck muscles. Neck muscles within the radiation field show mostly myogenic damage, and muscles outside the mantle field show mostly neurogenic damage. The discrepancy between echo intensity and atrophy suggests that muscle damage is most likely caused by an extrinsic factor such as progressive microvascular fibrosis. This is also presumed to cause damage to nerves within the radiated field, resulting in neurogenic damage of the deltoid and arm muscles.

Leeuwen-Segarceanu, Elena M. van, E-mail: e.segarceanu@antoniusziekenhuis.nl [Department of Internal Medicine, St. Antonius Hospital, Nieuwegein (Netherlands); Dorresteijn, Lucille D.A. [Department of Neurology, Medisch Spectrum Twente, Enschede (Netherlands); Pillen, Sigrid [Department of Neurology and Clinical Neurophysiology, Donders Center for Neuroscience, Radboud University Nijmegen Medical Center, Nijmegen (Netherlands); Biesma, Douwe H. [Department of Internal Medicine, University Medical Center Utrecht (Netherlands); Vogels, Oscar J.M. [Department of Neurology and Clinical Neurophysiology, St. Antonius Hospital, Nieuwegein (Netherlands); Alfen, Nens van [Department of Neurology and Clinical Neurophysiology, Donders Center for Neuroscience, Radboud University Nijmegen Medical Center, Nijmegen (Netherlands)

2012-02-01

301

Ramsey's method of separated oscillating fields and its application to gravitationally induced quantum phase shifts  

SciTech Connect

We propose to apply Ramsey's method of separated oscillating fields to the spectroscopy of the quantum states in the gravity potential above a horizontal mirror. This method allows a precise measurement of quantum mechanical phaseshifts of a Schroedinger wave packet bouncing off a hard surface in the gravitational field of the Earth. Measurements with ultracold neutrons will offer a sensitivity to Newton's law or hypothetical short-ranged interactions, which is about 21 orders of magnitude below the energy scale of electromagnetism.

Abele, H.; Jenke, T.; Leeb, H.; Schmiedmayer, J. [Technische Universitaet Wien, Atominstitut, Stadionallee 2, 1020 Wien (Austria)

2010-03-15

302

Inflationary gravitational waves in the effective field theory of modified gravity  

E-print Network

In the approach of the effective field theory of modified gravity, we derive the second-order action and the equation of motion for tensor perturbations on the flat isotropic cosmological background. This analysis accommodates a wide range of gravitational theories including Horndeski theories, its generalization, and the theories with spatial derivatives higher than second order (e.g., Horava-Lifshitz gravity). We obtain the inflationary power spectrum of gravitational waves by taking into account corrections induced by higher-order spatial derivatives and slow-roll corrections to the de Sitter background. We also show that the leading-order tensor spectrum in concrete modified gravitational theories can be mapped on to that in General Relativity under a disformal transformation. Our general formula will be useful to constrain inflationary models from the future precise measurement of the B-mode polarization in the cosmic microwave background.

Antonio De Felice; Shinji Tsujikawa

2014-11-03

303

Gravitational collapse of scalar fields via spectral methods  

SciTech Connect

In this paper we present a new numerical code based on the Galerkin method to integrate the field equations for the spherical collapse of massive and massless scalar fields. By using a spectral decomposition in terms of the radial coordinate, the field equations were reduced to a finite set of ordinary differential equations in the space of modes associated with the Galerkin expansion of the scalar field, together with algebraic sets of equations connecting modes associated with the metric functions. The set of ordinary differential equations with respect to the null coordinate is then integrated using an eighth-order Runge-Kutta method. The numerical tests have confirmed the high accuracy and fast convergence of the code. As an application we have evaluated the whole spectrum of black hole masses which ranges from infinitesimal to large values obtained after varying the amplitude of the initial scalar field distribution. We have found strong numerical evidence that this spectrum is described by a nonextensive distribution law.

Oliveira, H. P. de; Rodrigues, E. L.; Skea, J. E. F. [Universidade do Estado do Rio de Janeiro, Instituto de Fisica-Departamento de Fisica Teorica, CEP 20550-013 Rio de Janeiro, RJ (Brazil)

2010-11-15

304

The prevalence of weak magnetic fields in Herbig Ae stars: the case of PDS 2  

NASA Astrophysics Data System (ADS)

Models of magnetically driven accretion and outflows reproduce many observational properties of T Tauri stars, but the picture is much less clear for the Herbig Ae/Be stars, due to the poor knowledge of their magnetic field strength and topology. The Herbig Ae star PDS 2 was previously included in two magnetic studies based on low-resolution spectropolarimetric observations. Only in one of these studies the presence of a weak mean longitudinal magnetic field was reported. In the present study, for the first time, high-resolution high accuracy radial velocity planet searcher (HARPS) spectropolarimetric observations of PDS 2 are used to investigate the presence of a magnetic field. A firm detection of a weak longitudinal magnetic field is achieved using the multiline singular value decomposition method for Stokes profile reconstruction ( = 33 ± 5 G). To gain better knowledge of typical magnetic field strengths in late Herbig Be and Herbig Ae stars, we compiled previous magnetic field measurements, revealing that only very few stars have fields stronger than 200 G, and half of the sample possesses fields of about 100 G and less. These results challenge our current understanding of the magnetospheric accretion in intermediate-mass pre-main-sequence stars as they indicate that the magnetic fields in Herbig Ae/Be stars are by far weaker than those measured in T Tauri stars.

Hubrig, S.; Carroll, T. A.; Schöller, M.; Ilyin, I.

2015-04-01

305

Nonminimally coupled gravitational and electromagnetic fields: pp-wave solutions  

SciTech Connect

We give the Lagrangian formulation of a generic nonminimally extended Einstein-Maxwell theory with an action that is linear in the curvature and quadratic in the electromagnetic field. We derive the coupled field equations by a first-order variational principle using the method of Lagrange multipliers. We look for solutions describing plane-fronted Einstein-Maxwell waves with parallel rays. We give a family of exact pp-wave solutions associated with a partially massless spin-2 photon and a partially massive spin-2 graviton.

Dereli, Tekin; Sert, Oezcan [Department of Physics, Koc University, 34450 Sariyer, Istanbul (Turkey); Department of Physics Engineering, Istanbul Technical University, 34469 Maslak, Istanbul (Turkey)

2011-03-15

306

Charge rotating black string in gravitating nonlinear electromagnetic fields  

E-print Network

We construct a new class of charged rotating black string solutions coupled to a nonlinear electromagnetic field in the background of anti-de Sitter spaces. We consider two types of nonlinear electromagnetic field namely, logarithmic and exponential forms. We investigate the geometric effects of nonlinearity parameter and find that for large $r$, these solutions recover the rotating back string solutions of Einstein-Maxwell theory. We calculate the conserved and thermodynamic quantities of the rotating black string. We also analyze thermodynamics of the spacetime and verify the validity of the first law of thermodynamics for the obtained solutions.

Seyed Hossein Hendi; Ahmad Sheykhi

2014-05-24

307

Dust acoustic shock wave in electronegative dusty plasma: Roles of weak magnetic field  

SciTech Connect

The effects of nonsteady dust charge variations and weak magnetic field on small but finite amplitude nonlinear dust acoustic wave in electronegative dusty plasma are investigated. The dynamics of the nonlinear wave are governed by a Korteweg-de Vries Burger equation that possesses dispersive shock wave. The weak magnetic field is responsible for the dispersive term, whereas nonsteady dust charge variation is responsible for dissipative term, i.e., the Burger term. The coefficient of dissipative term depends only on the obliqueness of the magnetic field. It is found that for parallel propagation the dynamics of the nonlinear wave are governed by the Burger equation that possesses monotonic shock wave. The relevances of the findings to cometary dusty plasma, e.g., Comet Halley are briefly discussed.

Ghosh, Samiran [Government College of Engineering and Textile Technology, 4, Cantonment Road, Berhampore, Murshidabad 742101, West Bengal (India); Ehsan, Z.; Murtaza, G. [Salam Chair and Department of Physics, G. C. University Lahore, 54000 Lahore (Pakistan)

2008-02-15

308

[Modulating effect of weak combined magnetic fields on duration of mealworm beetle Tenebrio molitor metamorphosis stage].  

PubMed

It is shown that an exposure of pupae of the mealworm beetle Tenebrio molitor to the combined static (42 ?T) and very weak alternating (250 nT) magnetic fields exerts different influence, depending on the frequency of the alternating magnetic field, on duration of metamorphosis processes in these insects. For instance, an exposure of pupae to weak combined magnetic fields, adjusted to the frequency of ion cyclotron resonance for glutaminic acid (4,4 Hz), stimulates metamorphosis process--a transitional stage from pupae to imago lasts shorter. An inhibiting effect was observed when adjusted to the frequency of ion cyclotron resonance for Ca2 (32,2 Hz). At some frequencies this effect is not seen. For instance, an exposure at a frequency of ion cyclotron resonance for K+ (16,5 Hz) exerts no noticeable effect on the duration of the pupal metamorphosis stage. PMID:25715625

Novikov, V V; She?man, I M; Iablokova, E V; Fesenko, E E

2014-01-01

309

Ultra-weak magnetic fields in Am stars: ? UMa and ? Leo  

NASA Astrophysics Data System (ADS)

An extremely weak circularly-polarized signature was recently discovered in spectral lines of the chemically peculiar Am star Sirius A (Petit et al. 2011). This signal was interpreted as a Zeeman signature related to a sub-gauss longitudinal magnetic field, constituting the first detection of a surface magnetic field in an Am star. We present here ultra-deep spectropolarimetric observations of two other bright Am stars, ? UMa and ? Leo, observed with the NARVAL spectropolarimeter. The line profiles of the two stars display circularly-polarized signatures similar in shape to the observations gathered for Sirius A. These new detections suggest that very weak magnetic fields may be present in the photospheres of a significant fraction of intermediate-mass stars, although the strongly asymmetric Zeeman signatures measured so far in Am stars (featuring a prominent positive lobe and no detected negative lobe) are not expected in the standard theory of the Zeeman effect.

Blazère, A.; Petit, P.; Lignières, F.; Aurière, M.; Böhm, T.; Wade, G.

2014-12-01

310

Plane Symmetric Solutions of Gravitational Field Equations in Five Dimensions  

E-print Network

We present the effective field equations obtained from a generalized gravity action with Euler-Poincare term and a cosmological constant in a $D$ dimensional bulk space-time. A class of plane-symmetric solutions that describe a 3-brane world embedded in a D=5 dimensional bulk space-time are given.

A. N. Aliev; H. Cebeci; T. Dereli

2006-11-13

311

A New Study about the Two Formulations of Conservation Laws for Matter Plus Gravitational Field and Their Experimental Test  

E-print Network

The debate on conservation laws in general relativity eighty years ago is reviewed and restudied. The physical meaning of the identities in the conservation laws for matter plus gravitational field is reexamined and new interpretations for gravitational wave are given. The conclusions of these studies are distinct from the prevalent views, it can be demonstrated that gravitational wave does not transmit energy (and momentum) but only transmits informations. An experimental test is offered to decide which conservation laws are correct.

Fang-Pei Chen

2000-03-02

312

Gravitational radiation from collapsing magnetized dust  

E-print Network

In this article we study the influence of magnetic fields on the axial gravitational waves emitted during the collapse of a homogeneous dust sphere. We found that while the energy emitted depends weakly on the initial matter perturbations it has strong dependence on the strength and the distribution of the magnetic field perturbations. The gravitational wave output of such a collapse can be up to an order of magnitude larger or smaller calling for detailed numerical 3D studies of collapsing magnetized configurations.

Hajime Sotani; Shijun Yoshida; Kostas D. Kokkotas

2007-02-15

313

Gravitational radiation from collapsing magnetized dust  

SciTech Connect

In this article we study the influence of magnetic fields on the axial gravitational waves emitted during the collapse of a homogeneous dust sphere. We found that while the energy emitted depends weakly on the initial matter perturbations it has strong dependence on the strength and the distribution of the magnetic field perturbations. The gravitational wave output of such a collapse can be up to an order of magnitude larger or smaller calling for detailed numerical 3D studies of collapsing magnetized configurations.

Sotani, Hajime [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Yoshida, Shijun [Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kokkotas, Kostas D. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece); Theoretical Astrophysics, University of Tuebingen, Auf der Morgenstelle 10, 72076, Tuebingen (Germany)

2007-04-15

314

Solving the Hamilton-Jacobi equation for gravitationally interacting electromagnetic and scalar fields  

E-print Network

The spatial gradient expansion of the generating functional was recently developed by Parry, Salopek, and Stewart to solve the Hamiltonian constraint in Einstein-Hamilton-Jacobi theory for gravitationally interacting dust and scalar fields. This expansion is used here to derive an order-by-order solution of the Hamiltonian constraint for gravitationally interacting electromagnetic and scalar fields. A conformal transformation and functional integral are used to derive the generating functional up to the terms fourth order in spatial gradients. The perturbations of a flat Friedmann-Robertson-Walker cosmology with a scalar field, up to second order in spatial gradients, are given. The application of this formalism is demonstrated in the specific example of an exponential potential.

B. K. Darian

1997-09-27

315

Resonant amplification of magnetic seed fields by gravitational waves in the early universe  

E-print Network

Inflation is known to produce both gravitational waves and seed magnetic fields on scales well beyond the size of the horizon. The general relativistic interaction between these two sources at the end of inflation showed a significant amplification of the initial magnetic seed, which brought the latter within the currently accepted dynamo limits. In the present article we revisit this gravito-magnetic interaction and argue that the observed strong growth of the field is the result of resonance. More specifically, we show that the maximum magnetic boost always occurs when the wavelength of the inducing gravitational radiation and the scale of the original seed field coincide. We also look closer at the physics of the proposed Maxwell-Weyl coupling, consider the implications of finite electrical conductivity for the efficiency of the amplification mechanism and clarify further the mathematics of the analysis.

Christos G. Tsagas

2005-11-30

316

Horizon thermodynamics and gravitational field equations in Horava-Lifshitz gravity  

SciTech Connect

We explore the relationship between the first law of thermodynamics and gravitational field equation at a static, spherically symmetric black hole horizon in Horava-Lifshitz theory with/without detailed balance. It turns out that as in the cases of Einstein gravity and Lovelock gravity, the gravitational field equation can be cast to a form of the first law of thermodynamics at the black hole horizon. This way we obtain the expressions for entropy and mass in terms of black hole horizon, consistent with those from other approaches. We also define a generalized Misner-Sharp energy for static, spherically symmetric spacetimes in Horava-Lifshitz theory. The generalized Misner-Sharp energy is conserved in the case without matter field, and its variation gives the first law of black hole thermodynamics at the black hole horizon.

Cai Ronggen [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China); Department of Physics, Kinki University, Higashi-Osaka, Osaka 577-8502 (Japan); Ohta, Nobuyoshi [Department of Physics, Kinki University, Higashi-Osaka, Osaka 577-8502 (Japan)

2010-04-15

317

Charge Separation within Superconductors in the Presence of Tidal Gravitational Fields  

SciTech Connect

Tidal gravitational fields affect the Cooper-pair electrons and lattice ions of a type I superconductor differently. The quantum nonlocalizability of the Cooper pairs, which will remain coherent in the presence of interacting fields corresponding to frequencies less than that of the Bardeen-Cooper-Schrieffer (BCS) gap frequency, causes the superconducting electrons to undergo non-classical, non-geodesic motion, in contrast to the classical, geodesic motion of the lattice ions. The ensuing relative motion between the electrons and the ionic lattice causes a charge separation that leads to a measurable voltage potential when a macroscopic, quantum-coherent superconducting system undergoes free fall in the Earth's inhomogeneous gravitational field. Theoretical and experimental implications will be discussed.

Minter, Stephen J. [University of California, Merced, Department of Natural Sciences, 5200 N. Lake Rd., Merced, CA 95343 (United States); Wegter-McNelly, Kirk [Boston University, School of Theology, 745 Commonwealth Ave., Boston, MA 02215 (United States); Chiao, Raymond Y. [University of California, Merced, Departments of Natural Sciences and Engineering, 5200N Lake Rd, Merced, CA 95343 (United States)

2009-09-09

318

Possible quantum gravity effects on the gravitational deflection of light  

E-print Network

We investigate possible quantum gravity (QG) effects on the gravitational deflection of light. Two forms of deformation of the Schwarzschild spacetime are proposed. The first ansatz is a given Finslerian line element, it could be regarded as a weak QG effect on the Schwarzschild spacetime. Starting from this ansatz, we deduce the deflection angle of the light ray which passes a weak gravitational source. The second ansatz could be regarded as a strong QG effect on the Schwarzschild spacetime. The deflection angle of the light ray which passes a weak gravitational source is deduced in this Riemannian spacetime. This QG effect may distinguish the mixed light rays in the absence of gravitational source by a "spectroscope" (the gravitational source). The solutions of gravitational field equation in this Riemannian spacetime indicate that the QG effect could be regarded as the vacuum energy and the energy density of vacuum is related to the spacetime deformation parameter.

Xin Li; Zhe Chang

2010-07-02

319

Gravitational renormalization of quantum field theory: a "conservative" approach  

E-print Network

We propose general guidelines in order to incorporate the geometrical description of gravity in quantum field theory and address the problem of UV divergences non-perturbatively. In our aproach, each virtual particle in a Feynman graph should be described by a modified propagator and move in the space-time generated by the other particles in the same graph according to Einstein's (semiclassical) equations.

Roberto Casadio

2009-02-17

320

Gravitating tensor monopole in a Lorentz-violating field theory  

E-print Network

We present a solution of the coupled Einstein and rank-two antisymmetric tensor field equations where Lorentz symmetry is spontaneously broken, and we discuss its observational signatures. Especially, the deflection angles have important qualitative differences between tensor and scalar monopoles. If a monopole were to be detected, it would be discriminated whether or not to correspond to a tensor one. This phenomenon might open up new direction in the search of Lorentz violation with future astrophysical observations.

Xin-zhou Li; Ping Xi; Qun Zhang

2012-04-06

321

Gravitation: Field theory par excellence Newton, Einstein, and beyond  

SciTech Connect

Newtonian gravity satifies the two principles of equivalence m/sub i/ = m/sub p/ (the passive principle) and m/sub a/ = m/sub p/ (the active principle). A relativistic gauge field concept in D = s+1 dimensional curved-space will, in general, violate these two principles as in m/sub p/ = ..cap alpha..m/sub i/, m/sub a/ = lambdam/sub p/ where ..cap alpha.. = D: 3 and lambda measures the presence of the field stress-energy t/sup ..nu..//sub ..mu../ in the field equations. It is shown that ..cap alpha.. = 1, lambda = 0 corresponds to general relativity and ..cap alpha.. = 1, lambda = 1 to the theory of the author. It is noted that the correspondence limit of general relativity is not Newton's theory but a theory suggested by Robert Hooke a few years before Newton published his in Principia. The gauge is independent of the two principles but had to do with local special relativistic correspondence and compatibility with quantum mechanics. It is shown that unless ..cap alpha.. = 1, lambda = 1 the generalized theory cannot predict correctly many observables effects, including the 532'' per century Newtonian part in Mercury's perihelion advance.

Yilmaz, H.

1984-09-01

322

Gravitational Field Equations and Theory of Dark Matter and Dark Energy  

E-print Network

The main objective of this article is to derive a new set of gravitational field equations and to establish a new unified theory for dark energy and dark matter. The new gravitational field equations with scalar potential $\\varphi$ are derived using the Einstein-Hilbert functional, and the scalar potential $\\varphi$ is a natural outcome of the divergence-free constraint of the variational elements. Gravitation is now described by the Riemannian metric $g_{ij}$, the scalar potential $\\varphi$ and their interactions, unified by the new gravitational field equations. Associated with the scalar potential $\\varphi$ is the scalar potential energy density $\\frac{c^4}{8\\pi G} \\Phi=\\frac{c^4}{8\\pi G} g^{ij}D_iD_j \\varphi$, which represents a new type of energy caused by the non-uniform distribution of matter in the universe. The negative part of this potential energy density produces attraction, and the positive part produces repelling force. This potential energy density is conserved with mean zero: $\\int_M \\Phi dM=0$. The sum of this new potential energy density $\\frac{c^4}{8\\pi G} \\Phi$ and the coupling energy between the energy-momentum tensor $T_{ij}$ and the scalar potential field $\\varphi$ gives rise to a new unified theory for dark matter and dark energy: The negative part of this sum represents the dark matter, which produces attraction, and the positive part represents the dark energy, which drives the acceleration of expanding galaxies. In addition, the scalar curvature of space-time obeys $R=\\frac{8\\pi G}{c^4} T + \\Phi$. Furthermore, the new field equations resolve a few difficulties encountered by the classical Einstein field equations.

Tian Ma; Shouhong Wang

2012-07-11

323

Cartographic generalization of urban street networks based on gravitational field theory  

NASA Astrophysics Data System (ADS)

The automatic generalization of urban street networks is a constant and important aspect of geographical information science. Previous studies show that the dual graph for street-street relationships more accurately reflects the overall morphological properties and importance of streets than do other methods. In this study, we construct a dual graph to represent street-street relationship and propose an approach to generalize street networks based on gravitational field theory. We retain the global structural properties and topological connectivity of an original street network and borrow from gravitational field theory to define the gravitational force between nodes. The concept of multi-order neighbors is introduced and the gravitational force is taken as the measure of the importance contribution between nodes. The importance of a node is defined as the result of the interaction between a given node and its multi-order neighbors. Degree distribution is used to evaluate the level of maintaining the global structure and topological characteristics of a street network and to illustrate the efficiency of the suggested method. Experimental results indicate that the proposed approach can be used in generalizing street networks and retaining their density characteristics, connectivity and global structure.

Liu, Gang; Li, Yongshu; Li, Zheng; Guo, Jiawei

2014-05-01

324

Self-gravitating systems in Extended Gravity  

E-print Network

Starting from the weak field limit, we discuss astrophysical applications of Extended Theories of Gravity where higher order curvature invariants and scalar fields are considered by generalizing the Hilbert-Einstein action linear in the Ricci curvature scalar $R$. Results are compared to General Relativity in the hypothesis that Dark Matter contributions to the dynamics can be neglected thanks to modified gravity. In particular, we consider stellar hydrostatic equilibrium, galactic rotation curves, and gravitational lensing. Finally, we discuss the weak field limit in the Jordan and Einstein frames pointing out how effective quantities, as gravitational potentials, transform from one frame to the other and the interpretation of results can completely change accordingly.

A. Stabile; S. Capozziello

2014-11-12

325

Charged rotating black string in gravitating nonlinear electromagnetic fields  

NASA Astrophysics Data System (ADS)

We obtain a new solution of rotating black string coupled to a nonlinear electromagnetic field in the background of anti-de Sitter spaces. We consider two types of nonlinear electromagnetic Lagrangians, namely, logarithmic and exponential forms. We investigate the geometric effects of nonlinearity parameter and find that for large r, these solutions recover the rotating black string solutions of Einstein-Maxwell theory. We calculate the conserved and thermodynamic quantities of the rotating black string. We also analyze thermodynamics of the spacetime and verify the validity of the first law of thermodynamics for the obtained solutions.

Hendi, S. H.; Sheykhi, A.

2013-08-01

326

The prevalence of weak magnetic fields in Herbig Ae stars: The case of PDS2  

E-print Network

Models of magnetically driven accretion and outflows reproduce many observational properties of T Tauri stars, but the picture is much less clear for the Herbig Ae/Be stars, due to the poor knowledge of their magnetic field strength and topology. The Herbig Ae star PDS2 was previously included in two magnetic studies based on low-resolution spectropolarimetric observations. Only in one of these studies the presence of a weak mean longitudinal magnetic field was reported. In the present study, for the first time, high-resolution HARPS spectropolarimetric observations of PDS2 are used to investigate the presence of a magnetic field. A firm detection of a weak longitudinal magnetic field is achieved using the multi-line singular value decomposition method for Stokes profile reconstruction (=33+-5G). To gain better knowledge of typical magnetic field strengths in late Herbig Be and Herbig Ae stars, we compiled previous magnetic field measurements, revealing that only very few stars have fields stronger than 200G,...

Hubrig, S; Schöller, M; Ilyin, I

2015-01-01

327

Thick branes from self-gravitating scalar fields  

SciTech Connect

The formation of a domain wall ('thick brane') induced by scalar matter dynamics and triggered by a thin brane defect is considered in noncompact five-dimensional space-time with warped AdS type geometry. The scalar matter is composed of two fields with softly broken O(2) symmetry and minimal coupling to gravity. The nonperturbative effects in the invariant mass spectrum of light localized scalar states are investigated for different values of the tension of the thin brane defect. Especially interesting is the case of the thin brane with negative tension when the singular barriers form a potential well with two infinitely tall walls and the discrete spectrum of localized states arises completely isolated from the bulk.

Novikov, Oleg O.; Andrianov, Vladimir A. [V.A. Fock Department of Theoretical Physics, Saint-Petersburg State University, ul. Ulianovskaya, 198504 St. Petersburg (Russian Federation); Andrianov, Alexander A. [V.A. Fock Department of Theoretical Physics, Saint-Petersburg State University, ul. Ulianovskaya, 198504 St. Petersburg, Russia and Institut de Ciències del Cosmos, Universitat de Barcelona, Martí Franquès, 1, E08028 Barcelona (Spain)

2014-07-23

328

Thick branes from self-gravitating scalar fields  

NASA Astrophysics Data System (ADS)

The formation of a domain wall ("thick brane") induced by scalar matter dynamics and triggered by a thin brane defect is considered in noncompact five-dimensional space-time with warped AdS type geometry. The scalar matter is composed of two fields with softly broken O(2) symmetry and minimal coupling to gravity. The nonperturbative effects in the invariant mass spectrum of light localized scalar states are investigated for different values of the tension of the thin brane defect. Especially interesting is the case of the thin brane with negative tension when the singular barriers form a potential well with two infinitely tall walls and the discrete spectrum of localized states arises completely isolated from the bulk.

Novikov, Oleg O.; Andrianov, Alexander A.; Andrianov, Vladimir A.

2014-07-01

329

A Weak Lensing Survey in the Fields of z~1 Luminous Radio Sources  

E-print Network

In this paper we present weak lensing observations of the fields around 8 z~1 luminous radio sources. These data are searched for the lensing signatures of clusters that are either physically associated with the radio objects, or are foreground systems projected along the line of sight. The radio sources were all imaged with WFPC-2/HST providing high quality shape information on large numbers of faint galaxies around them. Statistical analysis of the coherent shear field visible in the shapes of the faint galaxies indicates that we have detected a weak lensing signal close to one of the targets, 3C336 at z=0.927, with a high level of confidence. A second, independent WFPC-2 observation of this target reinforces this detection. Our results support the earlier suggestion of weak lensing in this field by Fort et al (1996) using ground-based data. We also combined the shear distributions in the remaining 7 field to improve our sensitivity to weak shear signals from any structure typically associated with these sources. We find no detectable signal and estimate an upper limit on the maximum shear allowed by our observations. Using an N(z) estimated from lensing analyses we convert our observed lensing signal and limits into estimates of the masses of the various structures. We suggest that further lensing observations of distant radio sources and their host environments may allow the cluster L_X-mass relationship to be mapped at high-z. This is crucial for interpreting the results of the next generation of deep X-ray surveys, and thus constraining the redshift evolution of the cluster mass function out to z=1.

Richard G. Bower; Ian Smail

1996-12-16

330

Spectral form factor for chaotic dynamics in a weak magnetic field  

NASA Astrophysics Data System (ADS)

Using semiclassical periodic orbit theory for a chaotic system in a weak magnetic field, we obtain the form factor predicted by Pandey and Mehta's two matrix model up to the third order. The third order contribution has a peculiar term which exists only in the intermediate crossover domain between the GOE (Gaussian orthogonal ensemble) and the GUE (Gaussian unitary ensemble) universality classes. The exact expression is obtained by taking account of the contribution from encounter regions where orbit loops are connected.

Saito, Keiji; Nagao, Taro

2006-04-01

331

On the weak field approximation of Brans-Dicke theory of gravity  

E-print Network

It is shown that in the weak field approximation solutions of Brans-Dicke equations are simply related to the solutions of General Relativity equations for the same matter distribution. A simple method is developed which permits to obtain Brans-Dicke solutions from Einstein solutions when both theories are considered in their linearized forms. To illustrate the method some examples found in the literature are discussed.

A. Barros; C. Romero

1997-12-18

332

The phase matrix for scattering in a weak magnetic field. The Hanle effect  

Microsoft Academic Search

A new formulation for the phase matrix for the scattering of radiation in a weak magnetic field is presented. The phase matrix\\u000a is represented as a product of individual matrices that depend on the angle of incidence and the scattering angle. It is shown\\u000a that the Hanle effect is absent in observations of scattered light in the solar atmosphere when

2005-01-01

333

Theory of Traveling-wave Tubes with Weak External Magnetic Field  

NASA Astrophysics Data System (ADS)

Recent development of PASOTRONs [1], microwave sources which operate without guiding magnetic fields, stimulated an interest to the theoretical analysis of such tubes. In principle, in the absence of guiding magnetic fields the electrons may propagate radially outward which increases electrons coupling to the slow wave whose field is localized near circuit wall. This increases the wave growth rate and efficiency and allows one to shorten the interaction region. So the radial electron motion can be beneficial for operation if it doesn't lead to interception of electrons with the slow-wave structure (SWS). To avoid this interception a weak external magnetic field can be applied. The theory developed describes the effect of weak magnetic fields on operation of traveling-wave tubes with electrons moving not only axially but also transversely. This theory allows one to estimate the magnetic field required for protecting SWS walls from electron bombardment at different power levels. [1] D. G. Goebel, J. M. Butler, R. W. Schumacher, J. Santoru, and R. L. Eisenhart. IEEE Plasma Science, vol. 22, p. 547, October 1994.

Abuelfadl, Tamer; Nusinovich, Gregory; Carmel, Yuval

2000-10-01

334

On the Effect of Weak Magnetic Field on Solutions of Glutamic Acid: the Function of Water  

NASA Astrophysics Data System (ADS)

Even though a wide literature is available on the effects of weak Extremely Low Frequency ElectroMagnetic Fields (ELF-EMF) on the biochemical reactions, nevertheless the physical nature of these effects is largely unknown. The main challenge is the mismatch between the infinitesimal amount of the energy carried by the perturbation and the entity of the response of the system. More than 10 years ago, it was claimed that a weak current can be induced in a aqueous solution of Glutamic acid exposed to a weak magnetic field having a certain frequency. We have checked the influence of ELF-EMF on Glutamic acid using the FTIR-ATR spectroscopy in order to observe structural changes induced by the exposure. Samples have been exposed for 10, 20 or 30 minutes to a magnetic field generated by Helmoltz coils and then placed into the spectrometer. After the exposure solutions having different pH values always shown a shift toward the de-protonated species. The effect lasts for minutes after the exposure before the native configuration is restored.

De Ninno, A.; Congiu Castellano, A.

2011-12-01

335

General Relativistic Theory of the VLBI Time Delay in the Gravitational Field of Moving Bodies  

NASA Technical Reports Server (NTRS)

The general relativistic theory of the gravitational VLBI experiment conducted on September 8, 2002 by Fomalont and Kopeikin is explained. Equations of radio waves (light) propagating from the quasar to the observer are integrated in the time-dependent gravitational field of the solar system by making use of either retarded or advanced solutions of the Einstein field equations. This mathematical technique separates explicitly the effects associated with the propagation of gravity from those associated with light in the integral expression for the relativistic VLBI time delay of light. We prove that the relativistic correction to the Shapiro time delay, discovered by Kopeikin (ApJ, 556, L1, 2001), changes sign if one retains direction of the light propagation but replaces the retarded for the advanced solution of the Einstein equations. Hence, this correction is associated with the propagation of gravity. The VLBI observation measured its speed, and that the retarded solution is the correct one.

Kopeikin, Sergei

2003-01-01

336

Observing black holes with gravitational waves Eric Gourgoulhon  

E-print Network

(as weak field limit of string theory) From the astrophysical point of view: · Rate of binary blackObserving black holes with gravitational waves Eric Gourgoulhon Laboratoire de l'Univers et de ses. Gravitational radiation from black holes 2. Black hole quasi-normal modes 3. Binary black hole coalescence 4

Gourgoulhon, Eric

337

Some effects of nonlinear vacuum electrodynamics in strong magnetic and gravitational fields of the pulsar  

E-print Network

We consider the propagation of X-ray and gamma ray emissions in strong magnetic and gravitational fields of the pulsar in nonlinear vacuum electrodynamics. We show that the radiation will spread from the pulsar to the detecting device in the form of two normal modes polarized in mutually orthogonal planes, and having different velocities. We have calculated the delay between the two modes, as they propagate from the pulsar to the detecting device.

Medeu Abishev; Yerlan Aimuratov; Yermek Aldabergenov; Nurzada Beissen; Meruert Takibayeva

2014-12-11

338

Gravitational resonance spectroscopy with an oscillating magnetic field gradient in the GRANIT flow through arrangement  

E-print Network

Gravitational resonance spectroscopy consists in measuring the energy spectrum of bouncing ultracold neutrons above a mirror by inducing resonant transitions between different discrete quantum levels. We discuss how to induce the resonances with a flow through arrangement in the GRANIT spectrometer, excited by an oscillating magnetic field gradient. The spectroscopy could be realized in two distinct modes (so called DC and AC) using the same device to produce the magnetic excitation. We present calculations demonstrating the feasibility of the newly proposed AC mode.

G. Pignol; S. Baessler; V. V. Nesvizhevsky; K. Protasov; D. Rebreyend; A. Yu. Voronin

2014-08-05

339

Dark matter annihilation in the gravitational field of a black hole  

E-print Network

In this paper we consider dark matter particle annihilation in the gravitational field of black holes. We obtain exact distribution function of the infalling dark matter particles, and compute the resulting flux and spectra of gamma rays coming from the objects. It is shown that the dark matter density significantly increases near a black hole. Particle collision energy becomes very high affecting relative cross-sections of various annihilation channels. We also discuss possible experimental consequences of these effects.

A. N. Baushev

2009-10-08

340

Improved performance of gravitational field-flow fractionation for screening wine-making yeast varieties  

Microsoft Academic Search

Performance of gravitational field-flow fractionation (GFFF) is improved here with respect to the ability to fractionate and distinguish different varieties of wine-making yeast from Saccharomyces cerevisiae. A new GFFF channel with non-polar walls has been employed to enhance fractionation selectivity and reproducibility. Since GFFF retention depends from first principles on particle size, Coulter counter measurements were performed in order to

R Sanz; B Torsello; P Reschiglian; L Puignou; M. T Galceran

2002-01-01

341

Five-dimensional theory of interacting scalar, electromagnetic, and gravitational fields  

Microsoft Academic Search

An (n+1) factorization of an (n+1)-dimensional Riemann manifold is performed. For a space permitting a Killing vector, the (n+l)-dimensional Hubert variational principle reduces to the variational principle for the corresponding quantities in an n-dimensional space. Hence, setting n=4 and n=3, versions of a unified theory of gravitational, electromagnetic, and scalar fields and the steady-space theory of general relativity theory, respectively,

V. D. Gladush

1979-01-01

342

Kink-like Configurations of Interacting Scalar, Electromagnetic, and Gravitational Fields  

Microsoft Academic Search

We have obtained exact kink-like static plane-symmetric solutions to the\\u000aself-consistent system of electromagnetic, scalar, and gravitational field\\u000aequations. It was shown that under certain choice of the interaction Lagrangian\\u000athe solutions are regular and have localized energy. The linearized instability\\u000aof corresponding solutions was established both for the case of flat space-time\\u000aand that of interaction with the proper

D. S. Kulyabov; Yu. P. Rybakov; G. N. Shikin; L. P. Yuschenko

1999-01-01

343

Kink-like Configurations of Interacting Scalar, Electromagnetic, and Gravitational Fields  

Microsoft Academic Search

We have obtained exact kink-like static plane-symmetric solutions to the self-consistent system of electromagnetic, scalar, and gravitational field equations. It was shown that under certain choice of the interaction Lagrangian the solutions are regular and have localized energy. The linearized instability of corresponding solutions was established both for the case of flat space-time and that of interaction with the proper

D. S. Kulyabov; Yu. P. Rybakov; G. N. Shikin; L. P. Yuschenko

1999-01-01

344

A quantum weak energy inequality for the Dirac field in two-dimensional flat spacetime  

E-print Network

Fewster and Mistry have given an explicit, non-optimal quantum weak energy inequality that constrains the smeared energy density of Dirac fields in Minkowski spacetime. Here, their argument is adapted to the case of flat, two-dimensional spacetime. The non-optimal bound thereby obtained has the same order of magnitude, in the limit of zero mass, as the optimal bound of Vollick. In contrast with Vollick's bound, the bound presented here holds for all (non-negative) values of the field mass.

S. P. Dawson

2005-12-14

345

Solution of the problem of uniqueness and hermiticity of hamiltonians for Dirac particles in gravitational fields  

E-print Network

The authors prove that the dynamics of spin 1/2 particles in stationary gravitational fields can be described using an approach, which builds upon the formalism of pseudo-Hermitian Hamiltonians. The proof consists in the analysis of three expressions for Hamiltonians, which are derived from the Dirac equation and describe the dynamics of spin 1/2 particles in the gravitational field of the Kerr solution. The Hamiltonians correspond to different choices of tetrad vectors and differ from each other. The differences between the Hamiltonians confirm the conclusion known from many studies that the Hamiltonians derived from the Dirac equation are non-unique. Application of standard pseudo-Hermitian quantum mechanics rules to each of these Hamiltonians produces the same Hermitian Hamiltonian. The eigenvalue spectrum of the resulting Hamiltonian is the same as that of the Hamiltonians derived from the Dirac equation with any chosen system of tetrad vectors. For description of the dynamics of spin 1/2 particles in stationary gravitational fields can be used not only the formalism of pseudo-Hermitian Hamiltonians, but also an alternative approach, which employs the Parker scalar product. The authors show that the alternative approach is equivalent to the formalism of pseudo-Hermitian Hamiltonians.

M. V. Gorbatenko; V. P. Neznamov

2010-07-27

346

[Mechanism of action of combined extremely weak magnetic field on aqueous solution of amino acid].  

PubMed

The fundamental physical mechanisms of resonance action of an extremely weak (40 nT) alternating magnetic field at the cyclotron frequency combined with a weak (40 ?T) static magnetic field, on living systems are analyzed in the present work. The experimental effects of such sort of magnetic fields were described in different papers: the very narrow resonant peaks in electrical conductivity of the aqueous solutions in the in vitro experiments and the biomedical in vivo effects on living animals of magnetic fields with frequencies tuned to some amino acids. The existing experimental in vitro data had a good repeatability in different laboratories and countries. Unfortunately, for free ions such sort of effects are absolutely impossible because the dimensions of an ion rotation radius should be measured by meters at room temperature and at very low static magnetic fields used in all the above experiments. Even for bound ions these effects should be also absolutely impossible from the positions of classic physics because of rather high viscosity of biological liquid media (blood plasma, cerebrospinal liquid, cytoplasm). Only modern quantum electrodynamics of condensed media opens the new ways for solving these problems. The proposed article is devoted to analysis of quantum mechanisms of these effects. PMID:25707253

Zhadin, M N; Bakharev, B V; Bobkova, N V

2014-01-01

347

Transient effect of weak electromagnetic fields on calcium ion concentration in Arabidopsis thaliana  

PubMed Central

Background Weak magnetic and electromagnetic fields can influence physiological processes in animals, plants and microorganisms, but the underlying way of perception is poorly understood. The ion cyclotron resonance is one of the discussed mechanisms, predicting biological effects for definite frequencies and intensities of electromagnetic fields possibly by affecting the physiological availability of small ions. Above all an influence on Calcium, which is crucial for many life processes, is in the focus of interest. We show that in Arabidopsis thaliana, changes in Ca2+-concentrations can be induced by combinations of magnetic and electromagnetic fields that match Ca2+-ion cyclotron resonance conditions. Results An aequorin expressing Arabidopsis thaliana mutant (Col0-1 Aeq Cy+) was subjected to a magnetic field around 65 microtesla (0.65 Gauss) and an electromagnetic field with the corresponding Ca2+ cyclotron frequency of 50 Hz. The resulting changes in free Ca2+ were monitored by aequorin bioluminescence, using a high sensitive photomultiplier unit. The experiments were referenced by the additional use of wild type plants. Transient increases of cytosolic Ca2+ were observed both after switching the electromagnetic field on and off, with the latter effect decreasing with increasing duration of the electromagnetic impact. Compared with this the uninfluenced long-term loss of bioluminescence activity without any exogenic impact was negligible. The magnetic field effect rapidly decreased if ion cyclotron resonance conditions were mismatched by varying the magnetic fieldstrength, also a dependence on the amplitude of the electromagnetic component was seen. Conclusion Considering the various functions of Ca2+ as a second messenger in plants, this mechanism may be relevant for perception of these combined fields. The applicability of recently hypothesized mechanisms for the ion cyclotron resonance effect in biological systems is discussed considering it's operating at magnetic field strengths weak enough, to occur occasionally in our all day environment. PMID:19405943

Pazur, Alexander; Rassadina, Valentina

2009-01-01

348

Gravitational Lensing Analyzed by Graded Refractive Index of Vacuum  

E-print Network

We found strong similarities between the gravitational lensing and the conventional optical lensing. The similarities imply a graded refractive index description of the light deflection in gravitational field. We got a general approach to this refractive index in a static spherically symmetric gravitational field and obtained its exterior and interior solutions exactly through the general relativity. In weak field case, the two solutions come to a simple unified exponential function of the gravitational potential. With these results, the gravitational lensing can be analyzed in a convenient optical way. Especially, the long puzzling problem of the central image missing can be solved easily. We also pointed out that the graded refraction property of the gravitational spacetime is related to the vacuum influenced by the gravitational matter.

Xing-Hao Ye; Qiang Lin

2008-02-13

349

Rectification and signal averaging of weak electric fields by biological cells.  

PubMed Central

Oscillating electric fields can be rectified by proteins in cell membranes to give rise to a dc transport of a substance across the membrane or a net conversion of a substrate to a product. This provides a basis for signal averaging and may be important for understanding the effects of weak extremely low frequency (ELF) electric fields on cellular systems. We consider the limits imposed by thermal and "excess" biological noise on the magnitude and exposure duration of such electric field-induced membrane activity. Under certain circumstances, the excess noise leads to an increase in the signal-to-noise ratio in a manner similar to processes labeled "stochastic resonance." Numerical results indicate that it is difficult to reconcile biological effects with low field strengths. PMID:7731976

Astumian, R D; Weaver, J C; Adair, R K

1995-01-01

350

Gravitational field of a Schwarzschild black hole and a rotating mass ring  

NASA Astrophysics Data System (ADS)

The linear perturbation of the Kerr black hole has been discussed by using the Newman-Penrose formalism, and the perturbed Weyl scalars, ?0 and ?4 can be obtained from the Teukolsky equation. In order to obtain the other Weyl scalars and the perturbed metric, a formalism was proposed by Chrzanowski and by Cohen and Kegeles to construct these quantities in a radiation gauge via the Hertz potential. As a simple example of the construction of the perturbed gravitational field with this formalism, we consider the gravitational field produced by a rotating circular ring around a Schwarzschild black hole. In the method by Chrzanowski, Cohen, and Kegeles, the metric is constructed in a radiation gauge via the Hertz potential, which is obtained from the solution of the Teukolsky equation. Since the solutions ?0 and ?4 of the Teukolsky equations are spin-2 quantities, the Hertz potential is determined up to its monopole and dipole modes. Without these lower modes, the constructed metric and Newman-Penrose Weyl scalars have unphysical jumps on the spherical surface at the radius of the ring. We find that the jumps of the imaginary parts of the Weyl scalars are cancelled when we add the angular momentum perturbation to the Hertz potential. Finally, by adding the mass perturbation and choosing the parameters which are related to the gauge freedom, we obtain the perturbed gravitational field which is smooth except on the equatorial plane outside the ring. We discuss the implication of these results to the problem of the computation of the gravitational self-force to the point particles in a radiation gauge.

Sano, Yasumichi; Tagoshi, Hideyuki

2014-08-01

351

REVIEWS OF TOPICAL PROBLEMS: Effects of weak magnetic fields on biological systems: physical aspects  

NASA Astrophysics Data System (ADS)

The effect of weak magnetic fields on biosystems is the subject matter of the science of magnetobiology. There are objective factors, due to theory lagging far behind experiment, that are hindering the development of this science. Academic interest in the subject is restrained by the fact that experimental data lack a clear physical explanation. Besides, there is a strong imbalance in how physics and biology are involved in magnetobiology, the former being still in infancy in this respect. It is this imbalance which is currently the driving force for the development of the theory of magnetobiology. This brief analytical review focuses on the physical aspects of magnetobiological research. The task of magnetobiology is to explore the biological effects of weak magnetic fields and to understand mechanisms behind these effects. Magnetobiology is part of a more general issue of the biological impact of weak and hyperweak physico-chemical factors. It is believed that such factors operate even below the trigger threshold for protective biological mechanisms and are therefore capable of accumulating at the subcellular level. The so-called 'kT-problem' is discussed in detail, and the interference mechanisms of the molecular gyroscope and of molecular states in an idealized protein cavity are suggested as candidate solutions.

Bingi, Vladimir N.; Savin, Aleksandr V.

2003-03-01

352

Exact two-soliton solutions to the Einstein gravitational field equations  

NASA Astrophysics Data System (ADS)

Following previous work on the existence of 1-soliton solution to the Einstein gravitational field equations in the presence of a spherically-symmetric static background field, six sets of analytical 2-soliton solutions to the Einstein field equations were found under a certain ansatz in the absence of the stated background field. Numerical analysis shows that, if the two solitons of the transverse nature are injected at space variable z approaches +/- infinity, the longitudinal field component g33 will acquire nonzero values for a bounded spatial region at later time. The nature of the solitons becomes rather complex when they interact. The amplitude g(micro-nu) of each soliton may change its magnitude resulting from the interaction. It was found that the evolution of one field component might be interpreted as the gravitational instanton in the solutions. The total energy of the interacting solitons remains constant, as expected, at all time. These solutions correspond to the situation where the Riemann tensor is in general nonzero and are truly nontrivial solutions.

To, F. T.; Fung, P. C. W.; Au, C.

1991-10-01

353

Weak interactions from 1950-1960: a quantitative bibliometric study of the formation of a field  

SciTech Connect

A quantitative technique is illustrated which uses publication statistics from a bibliography of citations in the area of weak interactions to provide a view of trends and patterns in the development of the field during the period from 1950 to 1960. An overview is given of what the physicists working in weak interactions during this period were doing as indicated by an analysis of the subjects of their papers. The dominant problems and concerns are discussed. Focus is then turned to the events surrounding the emergence of the tau/theta particle puzzle, the discovery of parity nonconservation, and the resolution offered by the V-A theory. Displaying the data from the citation index in unusual ways highlights dominant issues of the period, especially the close relationship between theory and experiment in the latter half of the decade. 64 refs., 14 figs. (LEW)

White, D.H.; Sullivan, D.

1986-01-01

354

K0 meson physics in the gravitation field: a constraint on the equivalence principle  

Microsoft Academic Search

K0-K0bar oscillations are extremely sensitive to the K0 and K0bar energy at\\u000arest. Even assuming m_K0=m_K0bar, the energy is not granted to be the same if\\u000agravitational effects on K0 and K0bar slightly differ. We consider various\\u000agravitation fields present and, in particular, galactic fields, which provide a\\u000anegligible acceleration, but relatively large gravitational potential energy. A\\u000aconstraint from a

Savely G. Karshenboim; D. I. Mendeleev

2008-01-01

355

The vacuum energy excitations due to gravitational field as a possible candidate of dark matter in galaxies  

E-print Network

In this Letter we point out to the possibility that the cloud of the vacuum energy excitations in gravitation fields surrounding galaxies forms a component of dark matter. These clouds of the vacuum energy excitations interact gravitationally with the baryonic matter of galaxies changing their dynamical and kinematical properties. In four model galaxies we show that the dynamic changes due to the vacuum energy excitations of these galaxies are comparable with data. This shows that vacuum energy excitations created in the gravitation field of galaxies may be considered as one of the candidates of dark matter.

V. Majernik

2004-08-19

356

Effects of a classical homogeneous gravitational field on the cavity-field entropy and generation of the Schrodinger-cat states in the Jaynes-Cummings model  

E-print Network

In this paper, we examine the effects of the gravitational field on the dynamical evolution of the cavity-field entropy and the creation of the Schrodinger-cat state in the Jaynes-Cummings model. We consider a moving two-level atom interacting with a single mode quantized cavity-field in the presence of a classical homogeneous gravitational field. Based on an su(2) algebra, as the dynamical symmetry group of the model, we derive the reduced density operator of the cavity-field which includes the effects of the atomic motion and the gravitational field. Also, we obtain the exact solution and the approximate solution for the system-state vector, and examine the atomic dynamics. By considering the temporal evolution of the cavity-field entropy as well as the dynamics of the Q-function of the cavity-field we study the effects of the gravitational field on the generation of the Schrodinger-cat states of the cavity-field by using the Q-function, field entropy and approximate solution for the system-state vector. The results show that the gravitational field destroys the generation of the Schrodinger-cat state of the cavity-field.

M. Mohammadi; M. H. Naderi; M. Soltanolkotabi

2007-11-24

357

Limits on high-frequency gravitational wave background from its interplay with large scale magnetic fields  

SciTech Connect

In this work, we analyze the implications of graviton-to-photon conversion in the presence of large scale magnetic fields. We consider the magnetic fields associated with galaxy clusters, filaments in the large scale structure, as well as primordial magnetic fields. We analyze the interaction of these magnetic fields with an exogenous high-frequency gravitational wave (HFGW) background which may exist in the Universe. We show that, in the presence of the magnetic fields, a sufficiently strong HFGW background would lead to an observable signature in the frequency spectrum of the cosmic microwave background. The sensitivity of current day cosmic microwave background experiments allows one to place significant constraints on the strength of the HFGW background, {omega}{sub GW} < or approx. 1. These limits are about 25 orders of magnitude stronger than currently existing direct constraints in this frequency region.

Pshirkov, M. S.; Baskaran, D. [Pushchino Radio Astronomy Observatory, Astro Space Center, Lebedev Physical Institute, Pushchino (Russian Federation); School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom and Wales Institute of Mathematical and Computational Sciences, Swansea SA2 8PP (United Kingdom)

2009-08-15

358

Volume 28A, number 9 PHYSICS LETTERS 10 February 1969 DETECTION OF VERY WEAK MAGNETIC FIELDS (10 -9 GAUSS)  

E-print Network

Volume 28A, number 9 PHYSICS LETTERS 10 February 1969 DETECTION OF VERY WEAK MAGNETIC FIELDS (10 -9 GAUSS) BY 87Rb ZERO-FIELD LEVEL CROSSING RESONANCES J. DUPONT-ROC, S. HAROCHE and C. COHEN the measurement of 10-9 gauss fields. Zero field level crossing resonances in excited states of atoms are well

Cohen-Tannoudj, Claude

359

The deflection of light induced by the Sun's gravitational field and measured with geodetic VLBI  

E-print Network

The Sun's gravitational field deflects the apparent positions of close objects in accordance with the formulae of general relativity. Optical astrometry is used to test the prediction, but only with the stars close to the Sun and only during total Solar eclipses. Geodetic Very Long Baseline Interferometry (VLBI) is capable of measuring the deflection of the light from distant radio sources anytime and across the whole sky. We show that the effect of light deflection is equivalent to the gravitational delay calculated during the reduction of VLBI data. All reference radio sources display an annual circular motion with the magnitude proportional to their ecliptic latitude. In particular, radio sources near the ecliptic pole draw an annual circle with magnitude of 4 mas. This effect could be easily measured with the current precision of the geodetic VLBI data.

Titov, O

2015-01-01

360

The deflection of light induced by the Sun's gravitational field and measured with geodetic VLBI  

E-print Network

The Sun's gravitational field deflects the apparent positions of close objects in accordance with the formulae of general relativity. Optical astrometry is used to test the prediction, but only with the stars close to the Sun and only during total Solar eclipses. Geodetic Very Long Baseline Interferometry (VLBI) is capable of measuring the deflection of the light from distant radio sources anytime and across the whole sky. We show that the effect of light deflection is equivalent to the gravitational delay calculated during the reduction of VLBI data. All reference radio sources display an annual circular motion with the magnitude proportional to their ecliptic latitude. In particular, radio sources near the ecliptic pole draw an annual circle with magnitude of 4 mas. This effect could be easily measured with the current precision of the geodetic VLBI data.

O. Titov; A. Girdiuk

2015-02-25

361

TIGER: A data analysis pipeline for testing the strong-field dynamics of general relativity with gravitational wave signals from coalescing compact binaries  

E-print Network

The direct detection of gravitational waves with upcoming second-generation gravitational wave observatories such as Advanced LIGO and Advanced Virgo will allow us to probe the genuinely strong-field dynamics of general ...

Agathos, M.

362

Force field parametrization by weak coupling. Re-engineering SPC water  

NASA Astrophysics Data System (ADS)

A recently developed scheme for the automatic adjustment of force field parameters to experimentally observed properties is applied to the simple-point-charge (SPC) water model. The refinement procedure is based on a first-order coupling of a force-field parameter (say, an atomic charge) to the deviation of a calculated bulk liquid property (e.g. the heat of vaporization) from its ideal value. I.e. the method is very similar in spirit to the weak-coupling scheme used to implement constant-temperature or constant-pressure molecular dynamics. With the method we have refined the charges and the Lennard-Jones diameter of the SPC water model at several state points of high temperature and high pressure. We also have studied how these force-field parameters have to be reoptimized as the cutoff distance is varied.

Berweger, Christian D.; van Gunsteren, Wilfred F.; Müller-Plathe, Florian

1995-01-01

363

Mass and Weak Field Limit of Boson Stars in Brans Dicke Gravity  

E-print Network

We study boson stars in Brans Dicke gravity and use them to illustrate some of the properties of three different mass definitions: the Schwarzschild mass, the Keplerian mass and the Tensor mass. We analyse the weak field limit of the solutions and show that only the Tensor mass leads to a physically reasonable definition of the binding energy. We examine numerically strong field $\\omega=-1$ solutions and show how, in this extreme case, the three mass values and the conserved particle number behave as a function of the central boson field amplitude. The numerical studies imply that for $\\omega=-1$, solutions with extremal Tensor mass also have extremal particle number. This is a property that a physically reasonable definition of the mass of a boson star must have, and we prove analytically that this is true for all values of $\\omega$. The analysis supports the conjecture that the Tensor mass uniquely describes the total energy of an asymptotically flat solution in BD gravity.

A. W. Whinnett

1999-06-14

364

Alternatives to Schwarzschild in the weak field limit of General Relativity  

E-print Network

The metric outside an isolated object made up of ordinary matter is bound to be the classical Schwarzschild vacuum solution of General Relativity. Nevertheless, some solutions are known (e.g. Morris-Thorne wormholes) that do not match Schwarzschild asymptotically. In this work, we explore the conditions on the source matter for constructing static spherically symmetric metrics exhibiting an arbitrary power-law as Newtonian limit. We also derive the expressions for the gravitational deflection angle, Shapiro time delay, redshift and force on probe masses for such space-times, which can be used in astrophysical searches of non-Schwarzschild objects made up of exotic matter. Interestingly, we prove that even a minimally coupled scalar field with a power-law potential can support non-Schwarzschild metrics with arbitrary asymptotic behaviour.

V. Bozza

2015-02-18

365

Alternatives to Schwarzschild in the weak field limit of General Relativity  

E-print Network

The metric outside an isolated object made up of ordinary matter is bound to be the classical Schwarzschild vacuum solution of General Relativity. Nevertheless, some solutions are known (e.g. Morris-Thorne wormholes) that do not match Schwarzschild asymptotically. In this work, we explore the conditions on the source matter for constructing static spherically symmetric metrics exhibiting an arbitrary power-law as Newtonian limit. We also derive the expressions for the gravitational deflection angle, Shapiro time delay, redshift and force on probe masses for such space-times, which can be used in astrophysical searches of non-Schwarzschild objects made up of exotic matter. Interestingly, we prove that even a minimally coupled scalar field with a power-law potential can support non-Schwarzschild metrics with arbitrary asymptotic behaviour.

Bozza, V

2015-01-01

366

Comment on ``Constraints on biological effects of weak extremely-low-frequency electromagnetic fields''  

NASA Astrophysics Data System (ADS)

In a recent paper, Adair [Phys. Rev. A 43, 1039 (1991)] concludes that weak extremely-low-frequency (ELF) electromagnetic fields cannot affect biology on the cell level. However, Adair's assertion that few cells of higher organisms contain magnetite (Fe3O4) and his blanket denial of reproducible ELF effects on animals are both wrong. Large numbers of single-domain magnetite particles are present in a variety of animal tissues, including up to a hundred million per gram in human brain tissues, organized in clusters of tens to hundreds of thousand per gram. This is far more than a ``few cells.'' Similarly, a series of reproducible behavioral experiments on honeybees, Apis mellifera, have shown that they are capable of responding to weak ELF magnetic fields that are well within the bounds of Adair's criteria. A biologically plausible model of the interaction of single-domain magnetosomes with a mechanically activated transmembrane ion channel shows that ELF fields on the order of 0.1 to 1 mT are capable of perturbing the open-closed state by an energy of kT. As up to several hundred thousand such structures could fit within a eukaryotic cell, and the noise should go as the square root of the number of independent channels, much smaller ELF sensitivities at the cellular level are possible. Hence, the credibility of weak ELF magnetic effects on living systems must stand or fall mainly on the merits and reproducibility of the biological or epidemiological experiments that suggest them, rather than on dogma about physical implausibility.

Kirschvink, Joseph L.

1992-08-01

367

Control of Optical Transitions with Magnetic Fields in Weakly Bound Molecules  

E-print Network

Forbidden optical transitions in weakly bound $^{88}$Sr$_2$ molecules become strongly enabled with moderate applied magnetic fields. We report the control of transition strengths by five orders of magnitude and measurements of highly nonlinear Zeeman shifts, which we explain with an accurate {\\it ab initio} model. Mixed quantization in an optical lattice enables the experimental procedure. Our observation of formerly inaccessible $f$-parity excited states offers a new avenue for improving theoretical models for divalent atom dimers. Furthermore, magnetically enabled transitions may lead to an extremely precise subradiant molecular lattice clock.

McGuyer, B H; Iwata, G Z; Skomorowski, W; Moszynski, R; Zelevinsky, T

2015-01-01

368

Incommensurate Filling of Ultracold Spin-1 Atoms in Optical Superlattice with a Weak Magnetic Field  

NASA Astrophysics Data System (ADS)

The ground states of ultracold spin-1 atoms trapped in an optical superlattice in a weak magnetic field with incommensurate filling of three atoms in one double-well are obtained. It is shown that the ground-state diagrams of the reduced double-well model are remarkably different for the antiferromagnetic and ferromagnetic atoms. These novel spin-states can be controlled easily and exactly by modulating the tunneling parameter and the quadratic Zeeman energy, which may be a tool for the study of spin-entanglement.

Zheng, Gong-Ping; Qin, Shuai-Feng; Jian, Wen-Tian; Wang, Shou-Yang

2013-08-01

369

Shear Viscosity in Weakly Coupled N-Component Scalar Field Theories  

E-print Network

The rich phenomena of the shear viscosity (eta) to entropy density (s) ratio, eta/s, in weakly coupled N-component scalar field theories are studied. eta/s can have a "double dip" behavior due to resonances and the phase transition. If an explicit goldstone mass term is added, then eta/s can either decrease monotonically in temperature or, as seen in many other systems, reach a minimum at the phase transition. We also show how to go beyond the original variational approach to make the Boltzmann equation computation of eta systematic.

Jiunn-Wei Chen; Mei Huang; Chang-Tse Hsieh; Han-Hsin Lin

2010-11-18

370

Continuous weak measurement of a trapped electron using a percolation field effect transistor  

NASA Astrophysics Data System (ADS)

We investigate the use of a percolation-field-effect-transistor for the continuous weak measurement of a spatially Rabi oscillating trapped electron through the change in percolation pathway of the transistor channel. In contrast to conventional devices, this detection mechanism in principle does not require a change in the stored energy of the gate capacitance to modify the drain current, so reducing the measurement back-action. The signal-to-noise ratio and measurement bandwidth are seen to be improved compared to conventional devices, allowing further aspects of the dynamic behaviour to be observed.

Fleming, S.; Milne, W. I.; Hasko, D. G.

2013-08-01

371

Quantum interference near a photonic band edge beyond the weak-field approximation  

SciTech Connect

We investigate spontaneous emission and quantum interference effects involving a three-level atom in the vicinity of a photonic band edge beyond the weak-driving-field approximation. We consider two different three-level atoms, each subject to a probe field from the ground state and each embedded within a different photonic crystal (PhC). The first atom has the two excited states separated by a dipole transition in the optical frequency range, with this frequency being close to the surrounding PhC's band edge. The probe field couples the ground state and the highest excited state, and is well outside the PhC band gap. If a coupling field is applied between the two upper levels, electromagnetically induced transparency (EIT) may occur, depending on the position of the band edge. The second atom has the two upper levels each dipole-coupled to the ground state and close enough that the emissions from each can coherently interfere. This atom is embedded within a PhC whose band edge lies near the lower of the two excited states, and a probe field is applied that lies just beyond this band edge. This atom exhibits a quantum interference phenomenon related to EIT called field-induced transparency, again depending on the position of the band edge relative to the lower excited state.

Alsing, P. M.; Cardimona, D. A.; Huang, D. H. [Air Force Research Laboratory, Space Vehicles Directorate, 3550 Aberdeen Ave, SE, Kirtland AFB, Albuquerque, New Mexico 87117-5776 (United States)

2007-10-15

372

Cosmology with weak lensing surveys.  

PubMed

Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening mass. Since the lensing effects arise from deflections of the light rays due to fluctuations of the gravitational potential, they can be directly related to the underlying density field of the large-scale structures. Weak gravitational surveys are complementary to both galaxy surveys and cosmic microwave background observations as they probe unbiased nonlinear matter power spectra at medium redshift. Ongoing CMBR experiments such as WMAP and a future Planck satellite mission will measure the standard cosmological parameters with unprecedented accuracy. The focus of attention will then shift to understanding the nature of dark matter and vacuum energy: several recent studies suggest that lensing is the best method for constraining the dark energy equation of state. During the next 5 year period, ongoing and future weak lensing surveys such as the Joint Dark Energy Mission (JDEM; e.g. SNAP) or the Large-aperture Synoptic Survey Telescope will play a major role in advancing our understanding of the universe in this direction. In this review article, we describe various aspects of probing the matter power spectrum and the bi-spectrum and other related statistics with weak lensing surveys. This can be used to probe the background dynamics of the universe as well as the nature of dark matter and dark energy. PMID:16286284

Munshi, Dipak; Valageas, Patrick

2005-12-15

373

REVIEWS OF TOPICAL PROBLEMS Gravitational radiation of systems and the role of their force field  

NASA Astrophysics Data System (ADS)

Gravitational radiation (GR) from compact relativistic systems with a known energy-momentum tensor (EMT) and GR from two masses elliptically orbiting their common center of inertia are considered. In the ultrarelativistic limit, the GR spectrum of a charge rotating in a uniform magnetic field, a Coulomb field, a magnetic moment field, and a combination of the last two fields differs by a factor 4?Gm2?2/e2 (? being of the order of the charge Lorentz factor) from its electromagnetic radiation (EMR) spectrum. This factor is independent of the radiation frequency but does depend on the wave vector direction and the way the field behaves outside of the orbit. For a plane wave external field, the proportionality between the gravitational and electromagnetic radiation spectra is exact, whatever the velocity of the charge. Qualitative estimates of ? are given for a charge moving ultrarelativistically in an arbitrary field, showing that it is of the order of the ratio of the nonlocal and local source contributions to the GR. The localization of external forces near the orbit violates the proportionality of the spectra and reduces GR by about the Lorentz factor squared. The GR spectrum of a rotating relativistic string with masses at the ends is given, and it is shown that the contributions by the masses and string are of the same order of magnitude. In the nonrelativistic limit, the harmonics of GR spectra behave universally for all the rotating systems considered. A trajectory method is developed for calculating the GR spectrum. In this method, the spatial (and hence polarization) components of the conserved EMT are calculated in the long wavelength approximation from the time component of the EMTs of the constituent masses of the system. Using this method, the GR spectrum of two masses moving in elliptic orbits about their common center of inertia is calculated, as are the relativistic corrections to it.

Nikishov, Anatolii I.; Ritus, Vladimir I.

2011-02-01

374

A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field  

NASA Astrophysics Data System (ADS)

A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate ('frequency'), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca2+ Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD-CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD-CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B0 ?0.2-15 mT) AC-MF of frequency fM=50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation.

del Moral, A.; Azanza, María J.

2015-03-01

375

Pulsar Kicks Induced by Spin Flavor Oscillations of Neutrinos in Gravitational Fields  

E-print Network

The origin of pulsar kicks is reviewed in the framework of the spin-flip conversion of neutrinos propagating in the gravitational field of a magnetized protoneutron star. We find that for a mass in rotation with angular velocity ${\\bbox \\omega}$, the spin connections entering in the Dirac equation give rise to the coupling term ${\\bbox \\omega}\\cdot {\\bf p}$, being ${\\bf p}$ the neutrino momentum. Such a coupling can be responsible of pulsar kicks owing to the neutrino emission asymmetry generated by the relative orientation of ${\\bf p}$ with respect to ${\\bbox \\omega}$. For our estimations, the large non standard neutrino magnetic momentum, $\\mu_\

G. Lambiase

2005-07-15

376

A new line element derived from the variable rest mass in gravitational field  

E-print Network

This paper presents a new line element based on the assumption of the variable rest mass in gravitational field, and explores some its implications. This line element is not a vacuum solution of Einstein's equations, yet it is sufficiently close to Schwarzschild's line element to be compatible with all of the experimental and observational measurements made so far to confirm the three Einstein's predictions. The theory allows radiation and fast particles to escape from all massive bodies, even from those that in Einstein's general relativity framework will be black holes. The striking feature of this line element is the non-existence of black holes.

N. Ben-Amots

2008-08-19

377

Effect of the Earth's time-retarded transverse gravitational field on the motion of the Moon  

E-print Network

Classical Newtonian gravitational theory does not satisfy the causality principle because it is based on instantaneous action-at-a-distance. A causal version of Newtonian theory for a large rotating sphere is derived herein by time-retarding the distance between interior circulating point-mass sources and an exterior field-point. The resulting causal theory explains exactly the flyby anomaly reported by NASA scientists in 2008. It also explains exactly an anomalous decrease in the Moon's orbital speed. No other known theory can make both of these claims.

J. C. Hafele

2012-02-27

378

Stabilization of Neutral Thin Shells By Gravitational Effects From Electric Fields  

E-print Network

We study the properties of a system consisting of an uncharged spherically symmetric two dimensional extended object which encloses a stationary point charge placed in the shell's center. We show that there can be a static and stable configuration for the neutral shell, using only the gravitational field of the charged source as a stabilizing mechanism. In particular, two types of shells are studied: a dust shell and a string gas shell. The dynamical possibilities are also analyzed, including the possibility of child universe creation.

Eduardo I. Guendelman; Idan Shilon

2009-02-06

379

Global surface-water-induced seasonal variations in the earth's rotation and gravitational field  

NASA Technical Reports Server (NTRS)

The effects of seasonal changes in continental surface-water storage on the low-degree gravitational-field coefficients (J), the annual wobble excitation (Psi), and the seasonal length-of-day (LOD) variations are investigated by means of numerical simulations based on compiled meteorological data (Willmott et al., 1985) and satellite snow-load estimates (Chao et al., 1987). The formulation of the model equations and the overall characteristics of the data sets are discussed in detail, and the computation results are presented in tables and graphs. The effect on Psi is found to be relatively small due to longitudinal cancellation, but those on LOD and J are considered significant.

Chao, B. F.; O'Connor, William P.

1988-01-01

380

Black Hole Emission as The Gravitational Fowler-Nordheim Cold Emission or Field Emission  

E-print Network

We have solved the Schr$\\ddot{\\rm{o}}$dinger equation for a particle created as particle anti-particle pair in a region of uniform background gravitational field near the event horizon of a black hole. In accordance with the principle of equivalence, this is equivalent to the solution of Schr$\\ddot{\\rm{o}}$dinger equation of a particle in an uniformly accelerated frame of reference in absence of gravity. It has been observed that in the case of one-dimensional case, the Schr$\\ddot{\\rm{o}}$dinger equation can be reduced to a differential form which is exactly identical with that obeyed by an electron emitted from metal surface under the action of an intense and uniform electrostatic field. Historically, this problem was first solved by Fowler and Nordheim using a triangular type surface potential. Since it may occur even at extremely low temperature, the field emission of electrons is also known as the cold emission process.

Sanchari De; Somenath Chakrabarty

2014-12-22

381

Some Aspects of Quantum Mechanics of Particle Motion in Static Centrally Symmetric Gravitational Fields  

E-print Network

The domain of wave functions and effective potentials of the Dirac and Klein-Gordon equations for quantum-mechanical particles in static centrally symmetric gravitational fields are analyzed by taking into account the Hilbert causality condition. For all the explored metrics, assuming existence of event horizons, the conditions of a "fall" of a particle to the appropriate event horizons are implemented. The exclusion is one of the solutions for the Reissner-Nordstroem extreme field with the single event horizon. In this case, while fulfilling the condition found by V.I.Dokuchaev, Yu.N.Yeroshenko, the normalization integral is convergent and the wave functions become zero on the event horizon. This corresponds to the Hilbert causality condition. In our paper, due to the analysis of the effective potential for the Reissner-Nordstroem extreme field with real radial wave functions of the Dirac equation, the impossibility is demonstrated for the bound stationary state existence of quantum-mechanical particles, wit...

Gorbatenko, M V; Popov, E Yu

2015-01-01

382

The effects of weak extremely low frequency magnetic fields on calcium/calmodulin interactions.  

PubMed Central

Mechanisms by which weak electromagnetic fields may affect biological systems are of current interest because of their potential health effects. Lednev has proposed an ion parametric resonance hypothesis (Lednev, 1991, Bioelectromagnetics, 12:71-75), which predicts that when the ac, frequency of a combined dc-ac magnetic field equals the cyclotron frequency of calcium, the affinity of calcium for calcium-binding proteins such as calmodulin will be markedly affected. The present study evaluated Lednev's theory using two independent systems, each sensitive to changes in the affinity of calcium for calmodulin. One of the systems used was the calcium/calmodulin-dependent activation of myosin light chain kinase, a system similar to that previously used by Lednev. The other system monitored optical changes in the binding of a fluorescent peptide to the calcium/calmodulin complex. Each system was exposed to a 20.9 microT static field superimposed on a 20.9 microT sinusoidal field over a narrow frequency range centered at 16 Hz, the cyclotron frequency of the unhydrated calcium ion. In contrast to Lednev's predictions, no significant effect of combined dc-ac magnetic fields on calcium/calmodulin interactions was indicated in either experimental system. PMID:8744329

Hendee, S P; Faour, F A; Christensen, D A; Patrick, B; Durney, C H; Blumenthal, D K

1996-01-01

383

The weak magnetic field of the O9.7 supergiant ?OrionisA  

NASA Astrophysics Data System (ADS)

We report here the detection of a weak magnetic field of 50-100G on the O9.7 supergiant ?OrionisA (?OriA), using spectropolarimetric observations obtained with NARVAL at the 2-m Télescope Bernard Lyot atop Pic du Midi (France). ?OriA is the third O star known to host a magnetic field (along with ?1OriC and HD191612), and the first detection on a `normal' rapidly rotating O star. The magnetic field of ?OriA is the weakest magnetic field ever detected on a massive star. The measured field is lower than the thermal equipartition limit (about 100G). By fitting non-local thermodynamic equilibrium (NLTE) model atmospheres to our spectra, we determined that ?OriA is a 40Msolar star with a radius of 25Rsolar and an age of about 5-6Myr, showing no surface nitrogen enhancement and losing mass at a rate of about 2 × 10-6Msolaryr-1. The magnetic topology of ?OriA is apparently more complex than a dipole and involves two main magnetic polarities located on both sides of the same hemisphere; our data also suggest that ?OriA rotates in about 7.0d and is about 40° away from pole-on to an Earth-based observer. Despite its weakness, the detected magnetic field significantly affects the wind structure; the corresponding Alfvén radius is however very close to the surface, thus generating a different rotational modulation in wind lines than that reported on the two other known magnetic O stars. The rapid rotation of ?OriA with respect to ?1OriC appears as a surprise, both stars having similar unsigned magnetic fluxes (once rescaled to the same radius); it may suggest that the subequipartition field detected on ?OriA is not a fossil remnant (as opposed to that of ?1 OriC and HD191612), but the result of an exotic dynamo action produced through magnetohydrodynamics (MHD) instabilities. Based on observations obtained at the Télescope Bernard Lyot (TBL), operated by the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France. E-mail: jean-claude.bouret@oamp.fr

Bouret, J.-C.; Donati, J.-F.; Martins, F.; Escolano, C.; Marcolino, W.; Lanz, T.; Howarth, I. D.

2008-09-01

384

Gravitational anomaly and transport phenomena.  

PubMed

Quantum anomalies give rise to new transport phenomena. In particular, a magnetic field can induce an anomalous current via the chiral magnetic effect and a vortex in the relativistic fluid can also induce a current via the chiral vortical effect. The related transport coefficients can be calculated via Kubo formulas. We evaluate the Kubo formula for the anomalous vortical conductivity at weak coupling and show that it receives contributions proportional to the gravitational anomaly coefficient. The gravitational anomaly gives rise to an anomalous vortical effect even for an uncharged fluid. PMID:21797593

Landsteiner, Karl; Megías, Eugenio; Pena-Benitez, Francisco

2011-07-01

385

Synchronization dynamics induced on pairs of neurons under applied weak alternating magnetic fields.  

PubMed

Pairs of Helix aspersa neurons show an alternating magnetic field dependent frequency synchronization (AMFS) when exposed to a weak (amplitude B0 between 0.2 and 150 Gauss (G)) alternating magnetic field (AMF) of extremely low frequency (ELF, fM = 50 Hz). We have compared the AMFS patterns of discharge with: i) the synaptic activity promoted by glutamate and acetylcholine; ii) the activity induced by caffeine; iii) the bioelectric activity induced on neurons interconnected by electric synapses. AMFS activity reveals several specific features: i) a tight coincidence in time of the pattern and frequency, f, of discharge; ii) it is induced in the time interval of field application; iii) it is dependent on the intensity of the sinusoidal applied magnetic field; iv) elicited biphasic responses (excitation followed by inhibition) run in parallel for the pair of neurons; and v) some neuron pairs either spontaneously or AMF synchronized can be desynchronized under applied higher AMF. Our electron microscopy studies reveal gap-like junctions confirming our immunocytochemistry results about expression of connexin 26 (Cx26) in 4.7% of Helix neurons. AMF and carbenoxolone did not induce any significant effect on spontaneous synchronization through electric synapses. PMID:24012769

Azanza, María J; del Moral, A; Calvo, A C; Pérez-Bruzón, R N; Junquera, C

2013-12-01

386

Gravitational field of a hedgehog and the evolution of vacuum bubbles  

SciTech Connect

The gravitational field produced by a spherically symmetric hedgehog'' configuration in scalar field theories with global SO(3) symmetry (or higher) is studied in the limit in which these models become nonlinear {sigma} models. The same gravitational effect can be generated by a set of cosmic strings intersecting at a point, in the limit that one considers a continuous distribution of such intersecting strings in a spherically symmetric configuration (to be referred to as the string hedgehog''). When the energy densities associated with the hedgehog are small, we obtain a static geometry, but for higher values, the resulting geometry is that of an anisotropic cosmology. The evolution of bubbles joining two phases, one of which contains a hedgehog (as defined above) is investigated. The role of such configurations in processes that lead to classical false-vacuum destabilization and in the evolution of inflationary bubbles is discussed. The generalization of our results to the gauged case, i.e., to magnetic-monopole hedgehogs, is discussed.

Guendelman, E.I. (Department of Nuclear Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)); Rabinowitz, A. (Department of Physics, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel))

1991-11-15

387

Gravitational field of a hedgehog and the evolution of vacuum bubbles  

NASA Astrophysics Data System (ADS)

The gravitational field produced by a spherically symmetric ``hedgehog'' configuration in scalar field theories with global SO(3) symmetry (or higher) is studied in the limit in which these models become nonlinear ? models. The same gravitational effect can be generated by a set of cosmic strings intersecting at a point, in the limit that one considers a continuous distribution of such intersecting strings in a spherically symmetric configuration (to be referred to as the ``string hedgehog''). When the energy densities associated with the hedgehog are small, we obtain a static geometry, but for higher values, the resulting geometry is that of an anisotropic cosmology. The evolution of bubbles joining two phases, one of which contains a hedgehog (as defined above) is investigated. The role of such configurations in processes that lead to classical false-vacuum destabilization and in the evolution of inflationary bubbles is discussed. The generalization of our results to the gauged case, i.e., to magnetic-monopole hedgehogs, is discussed.

Guendelman, E. I.; Rabinowitz, A.

1991-11-01

388

Gas-Phase Influence on Quasisteady "Liquid Flames" in Gravitational Fields  

NASA Technical Reports Server (NTRS)

We consider the SHS (self-propagating high-temperature synthesis) process for synthesizing materials. In this process a powder mixture of reactants is cold pressed into a sample, which is ignited at one end. A high temperature combustion wave then propagates through the sample converting reactants to the desired product material. In this process, melting of some or all the components is often observed. Therefore, we study combustion waves propagating through a high caloricity inorganic powder mixture whose combustion temperature exceeds the melting temperatures of many components. The solid matrix is thus destroyed by the propagating combustion wave due to melting ahead of the reaction zone, and a liquid bath is formed which contains gaseous bubbles. The waves propagate in the presence of a gravitational field. Due to the effect of gravity, there is relative motion between the rising bubbles and the descending bath, which affects the composition of the medium, its thermophysical properties, the 'liquid flame' structure, and the propagation velocity. To enhance our understanding of phenomena associated with the interaction of the relative motion with the propagating combustion wave we formulate and analyze a relatively simple mathematical model of liquid flames in a gravitational field. We describe the wave structure and combustion characteristics including the combustion velocity. We compare our results to existing experimental observations and suggest new experiments to be performed. We consider the effects of gravity and, in particular, examine both microgravity and large gravity conditions.

Shkadinsky, K. G.; Shkadinskaya, G. V.; Matkowsky, B. J.; Gokoglu, S. (Technical Monitor)

2000-01-01

389

Diffusion phenomenon at the interface of Cu-brass under a strong gravitational field  

NASA Astrophysics Data System (ADS)

To investigate diffusion phenomenon at the interface between Cu and brass under a strong gravitational field generated by ultracentrifuge apparatus, we performed gravity experiments on samples prepared by electroplating with interfaces normal and parallel to the direction of gravity. For the parallel-mode sample, for which sedimentation cannot occur thorough the interface, the concentration change was significant within the lower gravity region; many pores were observed in this region. Many vacancies arising from crystal strain due to the strong gravitational field moved into the lower gravity region, and enhanced the atoms mobilities. For the two normal-mode samples, which have interface normal to the direction of gravity, the composition gradient of the brass-on-Cu sample was steeper than that for Cu-on-brass. This showed that the atoms of denser Cu diffuse in the direction of gravity, whereas Zn atoms diffuse in the opposite direction by sedimentation. The interdiffusion coefficients became higher in the Cu-on-brass sample, and became lower in the brass-on-Cu sample. This rise may be related to the behavior of the vacancies.

Ogata, Yudai; Iguchi, Yusuke; Tokuda, Makoto; Januszko, Kamila; Khandaker, Jahirul Islam; Ono, Masao; Mashimo, Tsutomu

2015-03-01

390

Explaining atomic clock behavior in a gravitational field with only 1905 Relativity  

E-print Network

Supported only in the two 1905 Einstein's papers on Relativity and a very rigid respect for the historical context, an analysis is done of the derivation of the universal mass-energy relationship. It is found, contrary to the today accepted Physics knowledge, that a body's Rest Mass measures its Potential Energy in the 1905 context. After emphasizing the difference between 1905 Relativity (1905R) and Special Relativity (SR), the developing of a 1905R relativistic gravity is started for a small mass m material point moving in the central gravitational field of a great mass M one. A formula for the rest mass m_0 as a function of its distance r from M is obtained. Finally, those results are applied to an atomic clock in a gravitational field, reaching a factor to obtain the clock time rate change very close to the GR one. The factors from 1905R and GR are compared, emphasizing the absent of a singularity in 1905R. In the conclusions, a new road for the development of a 1905R relativistic mechanics is declared, related with the discovery that Rest Mass measures Potential Energy, done by 1905 Einstein even if not realizing it.

Rafael A. Valls Hidalgo-Gato; Natalio Svarch Scharager

2010-09-27

391

A Modified Method for Deriving Self-Conjugate Dirac Hamiltonians in Arbitrary Gravitational Fields and Its Application to Centrally and Axially Symmetric Gravitational Fields  

E-print Network

We have proposed previously a method for constructing self-conjugate Hamiltonians H_eta in the eta-representation with a flat scalar product to describe the dynamics of Dirac particles in arbitrary gravitational fields. In this paper, we prove that, for block-diagonal metrics, the Hamiltonians H_eta can be obtained, in particular, using "reduced" parts of Dirac Hamiltonians, i.e. expressions for Dirac Hamiltonians derived using tetrad vectors in the Schwinger gauge without or with a few summands with bispinor connectivities. Based on these results, we propose a modified method for constructing Hamiltonians in the eta-representation with a significantly smaller amount of required calculations. Using this method, here we for the first time find self-conjugate Hamiltonians for a number of metrics, including the Kerr metric in the Boyer-Lindquist coordinates, the Eddington-Finkelstein, Finkelstein-Lemaitre, Kruskal, Clifford torus metrics and for non-stationary metrics of open and spatially flat Friedmann models.

M. V. Gorbatenko; V. P. Neznamov

2014-08-22

392

A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: The Redshift Catalog  

E-print Network

We present the spectroscopic redshift catalog from a wide-field survey of the fields of 28 galaxy-mass strong gravitational lenses. We discuss the acquisition and reduction of the survey data, collected over 40 nights of 6.5m MMT and Magellan time, employing four different multi-object spectrographs. We determine that no biases are introduced by combining datasets obtained with different instrument/spectrograph combinations. Special care is taken to determine redshift uncertainties using repeat observations. The redshift catalog consists of 9768 new and unique galaxy redshifts. 82.4% of the catalog redshifts are between z=0.1 and z=0.7, and the catalog median redshift is z=0.36. The data from this survey will be used to study the lens environments and line-of-sight structures to gain a better understanding of the effects of large scale structure on lens statistics and lens-derived parameters.

Momcheva, Ivelina; Cool, Richard J; Keeton, Charles R; Zabludoff, Ann I

2015-01-01

393

Conversion of relic gravitational waves into photons in cosmological magnetic fields  

SciTech Connect

Conversion of gravitational waves into electromagnetic radiation is discussed. The probability of transformations of gravitons into photons in presence of cosmological background magnetic field is calculated at the recombination epoch and during subsequent cosmological stages. The produced electromagnetic radiation is concentrated in the X-ray part of the spectrum. It is shown that if the early Universe was dominated by primordial black holes (PBHs) prior to Big Bang Nucleosynthesis (BBN), the relic gravitons emitted by PBHs would transform to an almost isotropic background of electromagnetic radiation due to conversion of gravitons into photons in cosmological magnetic fields. Such extragalactic radiation could be noticeable or even dominant component of Cosmic X-ray Background.

Dolgov, Alexander D.; Ejlli, Damian, E-mail: dolgov@fe.infn.it, E-mail: ejlli@fe.infn.it [Dipartimento di Fisica e Scienze della Terra, Polo Scientifico e Tecnologico-Edificio C, Università degli Studi di Ferrara, Via Saragat 1, 44122 Ferrara (Italy)

2012-12-01

394

Late-time tails of a self-gravitating massless scalar field, revisited  

E-print Network

We discuss the nonlinear origin of the power-law tail in the long-time evolution of a spherically symmetric self-gravitating massless scalar field in even-dimensional spacetimes. Using third-order perturbation method, we derive explicit expressions for the tail (the decay rate and the amplitude) for solutions starting from small initial data and we verify this prediction via numerical integration of the Einstein-scalar field equations in four and six dimensions. Our results show that the coincidence of decay rates of linear and nonlinear tails in four dimensions (which has misguided some tail hunters in the past) is in a sense accidental and does not hold in higher dimensions.

Piotr Bizo?; Tadeusz Chmaj; Andrzej Rostworowski

2009-08-11

395

Equilibrium of a system of superconducting rings in a uniform gravitational field  

NASA Astrophysics Data System (ADS)

To construct a plasma trap with levitating magnetic coils in the thin ring approximation, we derive the expression for the potential energy of a system of several superconducting rings (one of which is fixed) capturing the preset flows in the uniform gravitational field as a function of the coordinates of the free ring (or rings). Calculations performed in the Mathcad system show that the potential energy of such a system has a local minimum for certain values of parameters. Stable levitation of a superconducting ring in the position corresponding to calculations is realized in the field of another superconducting ring, and this leads to the conclusion that a magnetic Galatea trap can be prepared on the basis of a levitating quadrupole.

Bishaev, A. M.; Bush, A. A.; Gavrikov, M. B.; Gordeev, I. S.; Denisyuk, A. I.; Kamentsev, K. E.; Kozintseva, M. V.; Savel'ev, V. V.; Sigov, A. S.

2013-05-01

396

Numerical study on the stability of weakly collisional plasma in E ×B fields  

NASA Astrophysics Data System (ADS)

Plasma stability in weakly collisional plasmas in the presence of E ×B fields is studied with numerical simulations. Different types of ion-neutral collisions are considered in a fully magnetized regime. We study the influence of ion-neutral collisions and the role of collision types on the stability of plasma. It is found that the stability of plasma depends on the type of ion-neutral collisions, with the plasma being unstable for charge exchange collisions, and stable for the elastic scattering. The analysis focuses on the temporal evolution of the velocity phase space, RMS values of the potential fluctuations, and coherent structures in potential densities. For the unstable case, we observe growth and propagation of electrostatic waves. Simulations are performed with a three-dimensional electrostatic particle in cell code.

Horký, M.; Miloch, W. J.

2015-02-01

397

The magnetic field and spectral variability of the He-weak star HR 2949  

E-print Network

We analyze a high resolution spectropolarimetric dataset collected for the He-weak B3p IV star HR 2949. The Zeeman effect is visible in the circularly polarized component of numerous spectral lines. The longitudinal magnetic field varies between approximately $-650$ and $+150$ G. The polar strength of the surface magnetic dipole is calculated to be 2.4$^{+0.3}_{-0.2}$ kG. The star has strong overabundances of Fe-peak elements, along with extremely strong overabundances of rare-earth elements; however, He, Al, and S are underabundant. This implies that HR 2949 is a chemically peculiar star. Variability is seen in all photospheric lines, likely due to abundance patches as seen in many Ap/Bp stars. Longitudinal magnetic field variations measured from different spectral lines yield different results, likely a consequence of uneven sampling of the photospheric magnetic field by the abundance patches. Analysis of photometric and spectroscopic data for both HR 2949 and its companion star, HR 2948, suggests a revisio...

Shultz, M; Folsom, C P; Wade, G A; Townsend, R H D; Sikora, J; Grunhut, J; Stahl, O

2015-01-01

398

Supersymmetry approach to delocalization transitions in a network model of the weak-field quantum Hall effect and related models  

SciTech Connect

We consider a recently proposed network model of the integer quantum Hall (IQH) effect in a weak magnetic field. Using a supersymmetry approach, we reformulate the network model in terms of a superspin ladder. A subsequent analysis of the superspin ladder and the corresponding supersymmetric nonlinear sigma model allows us to establish the phase diagram of the network model, and the form of the critical line of the weak-field IQH transition. Our results confirm the universality of the IQH transition, which is described by the same sigma model in strong and weak magnetic fields. We apply the suspersymmetry method to several related network models that were introduced in the literature to describe the quantum Hall effect in graphene, the spin-degenerate Landau levels, and localization of electrons in a random magnetic field.

Bhardwaj, S [University of Chicago; Mkhitaryan, V V [Ames Laboratory; Gruzberg, I A [Ohio State University

2014-06-01

399

Gravitational Anomaly and Hydrodynamics  

E-print Network

We study the anomalous induced current of a vortex in a relativistic fluid via the chiral vortical effect, which is analogous to the anomalous current induced by a magnetic field via the chiral magnetic effect. We perform this analysis at weak and strong coupling. We discuss inequivalent implementations to the chemical potential for an anomalous symmetry. At strong coupling we use a holographic model with a pure gauge and mixed gauge-gravitational Chern-Simons term in the action. We discuss the holographic renormalization and show that the Chern-Simons terms do not induce new divergences. Strong and weak coupling results agree precisely. We also point out that the holographic calculation can be done without a singular gauge field configuration on the horizon of the black hole.

Landsteiner, Karl; Melgar, Luis; Pena-Benitez, Francisco

2011-01-01

400

Gravitational Anomaly and Hydrodynamics  

E-print Network

We study the anomalous induced current of a vortex in a relativistic fluid via the chiral vortical effect, which is analogous to the anomalous current induced by a magnetic field via the chiral magnetic effect. We perform this analysis at weak and strong coupling. We discuss inequivalent implementations to the chemical potential for an anomalous symmetry. At strong coupling we use a holographic model with a pure gauge and mixed gauge-gravitational Chern-Simons term in the action. We discuss the holographic renormalization and show that the Chern-Simons terms do not induce new divergences. Strong and weak coupling results agree precisely. We also point out that the holographic calculation can be done without a singular gauge field configuration on the horizon of the black hole.

Karl Landsteiner; Eugenio Megias; Luis Melgar; Francisco Pena-Benitez

2011-11-18

401

A search for weak or complex magnetic fields in the B3V star ? Herculis  

NASA Astrophysics Data System (ADS)

We obtained 128 high signal-to-noise ratio Stokes V spectra of the B3V star ? Her on five consecutive nights in 2012 with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, with the aim of searching for the presence of weak and/or complex magnetic fields. Least-squares deconvolution (LSD) mean profiles were computed from individual spectra, averaged over individual nights and over the entire run. No Zeeman signatures are detected in any of the profiles. The longitudinal magnetic field in the grand average profile was measured to be -0.24 ± 0.32 G, as compared to -0.22 ± 0.32 G in the null profile. Our observations therefore provide no evidence for the presence of Zeeman signatures analogous to those observed in the A0V star Vega by Lignières et al. We interpret these observations in three ways. First, we compare the LSD profiles with synthetic Stokes V profiles corresponding to organized (dipolar) magnetic fields, for which we find an upper limit of about 8 G on the polar strength of any surface dipole present. Secondly, we compare the grand average profile with calculations corresponding to the random magnetic spot topologies of Kochukhov & Sudnik, inferring that spots, if present, of 2° radius with strengths of 2-4 G and a filling factor of 50 per cent should have been detected in our data. Finally, we compare the observations with synthetic V profiles corresponding to the surface magnetic maps of Vega (Petit et al.) computed for the spectral characteristics of ? Her. We conclude that while it is unlikely we would have detected a magnetic field identical to Vega's, we would have likely detected one with a peak strength of about 30 G, i.e. approximately four times as strong as that of Vega.

Wade, G. A.; Folsom, C. P.; Petit, P.; Petit, V.; Lignières, F.; Aurière, M.; Böhm, T.

2014-11-01

402

Second-order weak lensing from modified gravity  

E-print Network

We explore the sensitivity of weak gravitational lensing to second-order corrections to the spacetime metric within a cosmological adaptation of the parameterized post-Newtonian framework. Whereas one might expect nonlinearities of the gravitational field to introduce non-Gaussianity into the statistics of the lensing convergence field, we show that such corrections are actually always small within a broad class of scalar-tensor theories of gravity. We show this by first computing the weak lensing convergence within our parameterized framework to second order in the gravitational potential, and then computing the relevant post-Newtonian parameters for scalar-tensor gravity theories. In doing so we show that this potential systematic factor is generically negligible, thus clearing the way for weak lensing to provide a direct tracer of mass on cosmological scales for a wide class of gravity theories despite uncertainties in the precise nature of the departures from general relativity.

R. Ali Vanderveld; Robert R. Caldwell; Jason Rhodes

2011-11-07

403

Weak nonlinear analysis of magneto-convection under magnetic field modulation  

NASA Astrophysics Data System (ADS)

An analytic study of heat transport in an electrically conducting fluid layer is performed under a non-uniform time-dependent magnetic field. The applied vertical magnetic field consists of two parts: a constant part and a time-dependent periodic part, which varies sinusoidally with time. A weakly nonlinear theory has been considered to investigate heat transfer in the fluid layer. The heat transfer coefficient is obtained by deriving the non-autonomous Ginzburg-Landau equation for an amplitude of convection. This amplitude of convection is derived by using NDSolve Mathematica 8, and the results are verified using Runge-Kutta-Fehlberg method. The Nusselt number is obtained in terms of various system parameters and the effect of each parameter on heat transport is reported in detail. The effect of magnetic Prandtl number Pm, amplitude of modulation ? is to enhance the heat transfer. The Chandrasekhar number Q, modulation frequency ? is to stabilize the system. Further, it is found that magnetic modulation can be used effectively in either enhancing the heat transfer or diminishing it.

Bhadauria, B. S.; Kiran, Palle

2014-09-01

404

Characterization of fast photoelectron packets in weak and strong laser fields in ultrafast electron microscopy.  

PubMed

The development of ultrafast electron microscopy (UEM) and variants thereof (e.g., photon-induced near-field electron microscopy, PINEM) has made it possible to image atomic-scale dynamics on the femtosecond timescale. Accessing the femtosecond regime with UEM currently relies on the generation of photoelectrons with an ultrafast laser pulse and operation in a stroboscopic pump-probe fashion. With this approach, temporal resolution is limited mainly by the durations of the pump laser pulse and probe electron packet. The ability to accurately determine the duration of the electron packets, and thus the instrument response function, is critically important for interpretation of dynamics occurring near the temporal resolution limit, in addition to quantifying the effects of the imaging mode. Here, we describe a technique for in situ characterization of ultrashort electron packets that makes use of coupling with photons in the evanescent near-field of the specimen. We show that within the weakly-interacting (i.e., low laser fluence) regime, the zero-loss peak temporal cross-section is precisely the convolution of electron packet and photon pulse profiles. Beyond this regime, we outline the effects of non-linear processes and show that temporal cross-sections of high-order peaks explicitly reveal the electron packet profile, while use of the zero-loss peak becomes increasingly unreliable. PMID:25151361

Plemmons, Dayne A; Tae Park, Sang; Zewail, Ahmed H; Flannigan, David J

2014-11-01

405

Enhanced paramagnetic Cu²? ions removal by coupling a weak magnetic field with zero valent iron.  

PubMed

A weak magnetic field (WMF) was proposed to enhance paramagnetic Cu(2+) ions removal by zero valent iron (ZVI). The rate constants of Cu(2+) removal by ZVI with WMF at pH 3.0-6.0 were -10.8 to -383.7 fold greater than those without WMF. XRD and XPS analyses revealed that applying a WMF enhanced both the Cu(2+) adsorption to the ZVI surface and the transformation of Cu(2+) to Cu(0) by ZVI. The enhanced Cu(2+) sequestration by ZVI with WMF was accompanied with expedited ZVI corrosion and solution ORP drop. The uneven distribution of paramagnetic Cu(2+) along an iron wire in an inhomogeneous MF verified that the magnetic field gradient force would accelerate the paramagnetic Cu(2+) transportation toward the ZVI surface due to the WMF-induced sharp decay of magnetic flux intensity from ZVI surface to bulk Cu(2+) solution. The paramagnetic Fe(2+) ions generated by ZVI corrosion would also accumulate at the position with the highest magnetic flux intensity on the ZVI surface, causing uneven distribution of Fe(2+), and facilitate the local galvanic corrosion of ZVI, and thus, Cu(2+) reduction by ZVI. The electrochemical analysis verified that the accelerated ZVI corrosion in the presence of WMF partly arose from the Lorentz force-enhanced mass transfer. PMID:25464332

Jiang, Xiao; Qiao, Junlian; Lo, Irene M C; Wang, Lei; Guan, Xiaohong; Lu, Zhanpeng; Zhou, Gongming; Xu, Chunhua

2015-02-11

406

Electrodynamics of superconductors. Response to a weak, low-frequency magnetic field  

SciTech Connect

The phenomenon of the penetration of a low-frequency weak magnetic field into a superconductor has stimulated extensive theoretical and experimental studies. These have led to important clarifications regarding the nature of the superconducting phase by, for example, making concrete the idea of the long-range order in terms of the coherence length, which in turn has provided an understanding of the details of the penetration phenomenon under various conditions realized for different relative values of the penetration depth and the coherence length. This work is a review of the theoretical and experimental studies of the penetration phenomenon. The theory of the penetration phenomenon is discussed phenomenologically and microscopically. Different experimental techniques employed to study the phenomenon are discussed. Many of the experimental studies are concerned with the temperature dependence of the penetration depth. These results are reviewed for different elemental superconductors. Practical difficulties in a quantitative analysis of such data are pointed out. A new strategy adopted recently by Egloff et al. for analyzing the penetration depth data of pure lead is discussed. Effects of impurities, anisotropy of the Fermi surface, and the magnetic field on the penetration phenomenon are also discussed.

Raychaudhuri, A.K.; Egloff, C.; Rinderer, L.

1983-12-01

407

Deprotonation of glutamic acid induced by weak magnetic field: an FTIR-ATR study.  

PubMed

It has been claimed that weak extremely low frequency electromagnetic fields (ELF-EMFs) can affect biochemical reactions and a wide-ranging body of literature is available on this topic. Nevertheless, the physical nature of these effects remains largely unknown. We investigated the influence of ELF-EMF on glutamic acid solutions using Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectra. Samples were exposed for 10, 20, or 30?min to a weak EMF generated by Helmoltz coils, and then placed in a spectrometer. After exposure, those solutions that had a pH lower than the isoelectric point tended to show a shift toward the deprotonation of the carboxylic group, while solutions having a pH greater than the isoelectric point showed the deprotonation of the residual amine group. Moreover, at low pH values, we also detected a shift of the ?(antisym) band of the amine. The effects lasted a few minutes after exposure before the native configuration was restored. The spectral modifications were observed after each independent exposure to EMFs, and the same effects were seen by varying the frequencies in the range of 0-7?kHz. Therefore, the hypothesis of the existence of a resonant frequency that has been proposed elsewhere cannot be supported by the results of this study. The most surprising characteristic of this effect is the long-lasting nature of the perturbation, which is hard to be explained in terms of short-living excitations in biological matter. PMID:21125576

De Ninno, A; Congiu Castellano, A

2011-04-01

408

Symmetry breaking in (gravitating) scalar field models describing interacting boson stars and Q-balls  

SciTech Connect

We investigate the properties of interacting Q-balls and boson stars that sit on top of each other in great detail. The model that describes these solutions is essentially a (gravitating) two-scalar field model where both scalar fields are complex. We construct interacting Q-balls or boson stars with arbitrarily small charges but finite mass. We observe that in the interacting case--where the interaction can be either due to the potential or due to gravity--two types of solutions exist for equal frequencies: one for which the two-scalar fields are equal, but also one for which the two-scalar fields differ. This constitutes a symmetry breaking in the model. While for Q-balls asymmetric solutions have always corresponding symmetric solutions and are thus likely unstable to decay to symmetric solutions with lower energy, there exists a parameter regime for interacting boson stars, where only asymmetric solutions exist. We present the domain of existence for two interacting nonrotating solutions as well as for solutions describing the interaction between rotating and nonrotating Q-balls and boson stars, respectively.

Brihaye, Yves; Caebergs, Thierry [Faculte des Sciences, Universite de Mons-Hainaut, 7000 Mons (Belgium); Hartmann, Betti; Minkov, Momchil [School of Engineering and Science, Jacobs University Bremen, 28759 Bremen (Germany)

2009-09-15

409

Symmetry breaking in (gravitating) scalar field models describing interacting boson stars and Q-balls  

E-print Network

We investigate the properties of interacting Q-balls and boson stars that sit on top of each other in great detail. The model that describes these solutions is essentially a (gravitating) two-scalar field model where both scalar fields are complex. We construct interacting Q-balls or boson stars with arbitrarily small charges but finite mass. We observe that in the interacting case - where the interaction can be either due to the potential or due to gravity - two types of solutions exist for equal frequencies: one for which the two scalar fields are equal, but also one for which the two scalar fields differ. This constitutes a symmetry breaking in the model. While for Q-balls asymmetric solutions have always corresponding symmetric solutions and are thus likely unstable to decay to symmetric solutions with lower energy, there exists a parameter regime for interacting boson stars, where only asymmetric solutions exist. We present the domain of existence for two interacting non-rotating solutions as well as for solutions describing the interaction between rotating and non-rotating Q-balls and boson stars, respectively.

Yves Brihaye; Thierry Caebergs; Betti Hartmann; Momchil Minkov

2009-05-27

410

A 660 D&O Gravitational Field of the Moon from the GRAIL Primary Mission  

NASA Astrophysics Data System (ADS)

The Gravity Recovery and Interior Laboratory (GRAIL) mission has completed its primary three-month tour that resulted in a gravitational field of 660 degree-and-order or equivalent surface resolution of 8 km. The primary measurement for the gravity field is the inter-spacecraft K-Band Range Rate (KBRR) measurement derived from dual spacecraft one-way range. Direct Doppler tracking at X-band from the Deep Space Network for Ebb and Flow supplemented The KBRR. Advanced system calibrations and measurement timing have resulted in unprecedented data quality of better than 0.1 microns/sec. The gravity field solution shows an error spectrum with several orders of magnitude improvement for all wavelengths when compared to previous missions. Nearly uniform correlations with topography exist through higher harmonic degrees and are a good measure of field integrity. The results of the mission satisfy the scientific objectives of determining the structure of the lunar interior from crust to core and advancing the understanding of the thermal evolution of the Moon. They also directly address the mission's investigations that include mapping the structure of the crust and lithosphere, understanding the Moon's asymmetric thermal evolution, determining the subsurface structure of impact basins and the origin of mascons, ascertaining the temporal evolution of the crustal brecciation and magmatism, constrain deep interior structure from tides, and place limits on the size of a possible solid inner core.

Yuan, Dah-Ning; Konopliv, Alex; Asmar, Sami; Park, Ryan; Williams, James; Watkins, Michael; Fahnestock, Eugene; Kruizinga, Gerhard; Paik, Meegyeong; Strekalov, Dmitry; Harvey, Nate; Zuber, Maria; Smith, David

2013-04-01

411

An improved model of the Earth's gravitational field: GEM-T1  

NASA Technical Reports Server (NTRS)

Goddard Earth Model T1 (GEM-T1), which was developed from an analysis of direct satellite tracking observations, is the first in a new series of such models. GEM-T1 is complete to degree and order 36. It was developed using consistent reference parameters and extensive earth and ocean tidal models. It was simultaneously solved for gravitational and tidal terms, earth orientation parameters, and the orbital parameters of 580 individual satellite arcs. The solution used only satellite tracking data acquired on 17 different satellites and is predominantly based upon the precise laser data taken by third generation systems. In all, 800,000 observations were used. A major improvement in field accuracy was obtained. For marine geodetic applications, long wavelength geoidal modeling is twice as good as in earlier satellite-only GEM models. Orbit determination accuracy has also been substantially advanced over a wide range of satellites that have been tested.

Marsh, J. G.; Lerch, F. J.; Christodoulidis, D. C.; Putney, B. H.; Felsentreger, T. L.; Sanchez, B. V.; Smith, D. E.; Klosko, S. M.; Martin, T. V.; Pavlis, E. C.

1987-01-01

412

General equations for the motions of ice crystals and water drops in gravitational and electric fields  

NASA Technical Reports Server (NTRS)

General equations for the Reynolds number of a variety of types of ice crystals and water drops are given in terms of the Davies, Bond, and Knudsen numbers. The equations are in terms of the basic physical parameters of the system and are valid for calculating velocities in gravitational and electric fields over a very wide range of sizes and atmospheric conditions. The equations are asymptotically matched at the bottom and top of the size spectrum, useful when checking large computer codes. A numerical system for specifying the dimensional properties of ice crystals is introduced. Within the limits imposed by such variables as particle density, which have large deviations, the accuracy of velocities appears to be within 10 percent over the entire range of sizes of interest.

Nisbet, John S.

1988-01-01

413

On the local standard of rest. [comoving with young objects in gravitational field of spiral galaxies  

NASA Technical Reports Server (NTRS)

Under the influence of a spiral gravitational field, there should be differences among the mean motions of different types of objects with different dispersion velocities in a spiral galaxy. The old stars with high dispersion velocity should have essentially no mean motion normal to the galactic rotation. On the other hand, young objects and interstellar gas may be moving relative to the old stars at a velocity of a few kilometer per second in both the radial (galacto-centric), and circular directions, depending on the spiral model adopted. Such a velocity is usually referred as the systematic motion or the streaming motion. The conventionally adopted local standard of rest is indeed co-moving with the young objects of the solar vicinity. Therefore, it has a net systematic motion with respect to the circular motion of an equilibrium galactic model, defined by the old stars. Previously announced in STAR as N83-24443

Yuan, C.

1983-01-01

414

Stationary bound states of spin-half particles in the Reissner-Nordstroem gravitational field  

E-print Network

We prove the possibility of existence of stationary bound states of spin-half particles in the Reissner-Nordstroem gravitational field using a self-conjugate Hamiltonian with a flat scalar product of wave functions. Bound states of Dirac particles with a real discrete energy spectrum can exist both for particles above the external "event horizon", and for particles under the internal "event horizon", or the Cauchy horizon. The Hilbert condition g_{00}>0 leads to a boundary condition such that components of the vector of current density of Dirac particles are zero near the "event horizons". Based on the results of this study, we can assume that there exists a new type of charged collapsars, for which the Hawking radiation is not present. The results of this study can lead to a revision of some concepts of the standard cosmological model related to the evolution of the universe and interaction of charged collapsars with surrounding matter.

M. V. Gorbatenko; V. P. Neznamov

2013-07-19

415

Magneto-optic and electro-optic effects in electromagnetic and gravitational fields  

E-print Network

The magneto-optic effects and electro-optic effects are the essential optic effects, although their theoretical explanations are not unified in the classical electromagnetic theory. Describing with the algebra of octonions, the electromagnetic theory can derive the magneto-optic effects and electro-optic effects from the same one force definition in the paper. As well as the magneto-optic effect is deduced from the known force term, the electro-optic effect is from the new force term in the octonion space. This description method is different to that in the quantum theory as well as the index ellipsoid approach for the electro-optic effect. One more significant inference is that the gravitational field has an impact on the rotation of linearly polarized light, and then results in the similar birefringence for the transmitted light in the cosmic matter.

Zi-Hua Weng

2010-11-26

416

Capture of cosmic objects by central gravitational field of a galaxy cluster  

E-print Network

The effect of capture of a cosmic object by the central gravitational field of a galaxy cluster is described in the expanding Universe. The cosmic evolution can be the origin of the capture explaining formation of galaxies and their clusters from the homogenous distribution of matter in the Universe. The Newton-like equation of the capture is derived for arbitrary equations of state in terms of the red shift parameter, and the influence of the Hubble velocities on the rotational curves is studied. The obtained rotational curves show us that the deficit of the visible matter for superclusters $M\\sim 10^{15}M_{\\odot}$ can be increased in the version of cosmology where observational quantities are identified with the conformal ones.

Piotr Flin; Victor Pervushin; Andrey Zorin

2004-06-08

417

Evolution of geodesic congruences in a gravitationally collapsing scalar field background  

NASA Astrophysics Data System (ADS)

The evolution of timelike geodesic congruences in a spherically symmetric, nonstatic, inhomogeneous spacetime representing gravitational collapse of a massless scalar field is studied. We delineate how initial values of the expansion, rotation, and shear of a congruence, as well as the spacetime curvature, influence the global behavior and focusing properties of a family of trajectories. Under specific conditions, the expansion scalar is shown to exhibit a finite jump (from negative to positive value) before focusing eventually occurs. This nonmonotonic behavior of the expansion, observed in our numerical work, is successfully explained through an analysis of the equation for the expansion. Finally, we bring out the role of the metric parameters (related to nonstaticity and spatial inhomogeneity) in shaping the overall behavior of geodesic congruences.

Shaikh, Rajibul; Kar, Sayan; DasGupta, Anirvan

2014-12-01

418

Nature of singularity formed by the gravitational collapse in Husain space-time with electromagnetic field and scalar field  

E-print Network

In this work, we have investigated the outcome of gravitational collapse in Husain space-time in the presence of electro-magnetic and a scalar field with potential. In order to study the nature of the singularity, global behavior of radial null geodesics have been taken into account. The nature of singularities formed has been thoroughly studied for all possible variations of the parameters. These choices of parameters has been presented in tabular form in various dimensions. It is seen that irrespective of whatever values of the parameters chosen, the collapse always results in a naked singularity in all dimensions. There is less possibility of formation of a black hole. Hence this work is a significant counterexample of the cosmic censorship hypothesis.

Ujjal Debnath; Prabir Rudra; Ritabrata Biswas

2012-03-09

419

Different elution modes and field programming in gravitational field-flow fractionation. III. Field programming by flow-rate gradient generated by a programmable pump.  

PubMed

Gravitational field-flow fractionation (GFFF) utilizes the Earth's gravitational field as an external force that causes the settlement of particles towards the channel accumulation wall. Hydrodynamic lift forces oppose this action by elevating particles away from the channel accumulation wall. These two counteracting forces enable modulation of the resulting force field acting on particles in GFFF. In this work, force-field programming based on modulating the magnitude of hydrodynamic lift forces was implemented via changes of flow-rate, which was accomplished by a programmable pump. Several flow-rate gradients (step gradients, linear gradients, parabolic, and combined gradients) were tested and evaluated as tools for optimization of the separation of a silica gel particle mixture. The influence of increasing amount of sample injected on the peak resolution under flow-rate gradient conditions was also investigated. This is the first time that flow-rate gradients have been implemented for programming of the resulting force field acting on particles in GFFF. PMID:11407583

Plocková, J; Chmelík, J

2001-05-25

420

Probing gravitational dark matter  

NASA Astrophysics Data System (ADS)

So far all evidences of dark matter (DM) come from astrophysical and cosmological observations, due to the gravitational interactions of DM. It is possible that the true DM particle in the universe joins gravitational interactions only, but nothing else. Such a Gravitational DM (GDM) may act as a weakly interacting massive particle (WIMP), which is conceptually simple and attractive. In this work, we explore this direction by constructing the simplest scalar GDM particle ?s. It is a Bbb Z2 odd singlet under the standard model (SM) gauge group, and naturally joins the unique dimension-4 interaction with Ricci curvature, ?s?s2Script R, where ?s is the dimensionless nonminimal coupling. We demonstrate that this gravitational interaction ?s?s2Script R, together with Higgs-curvature nonminimal coupling term ?hH†HScript R, induces effective couplings between ?s2 and SM fields, and can account for the observed DM thermal relic abundance. We analyze the annihilation cross sections of GDM particles and derive the viable parameter space for realizing the DM thermal relic density. We further study the direct/indirect detections and the collider signatures of such a scalar GDM. These turn out to be highly predictive and testable.

Ren, Jing; He, Hong-Jian

2015-03-01

421

Gravitational and higher-derivative interactions of a massive spin 5/2 field in (A)dS space  

SciTech Connect

Using an on shell gauge invariant formulation of relativistic dynamics I study the interaction vertices for a massive spin 5/2 Dirac field propagating in (anti-)de Sitter [(A)dS] space of dimension greater than or equal to four. The gravitational interaction vertex for the massive spin 5/2 field and all cubic vertices for the massive spin 5/2 field and massless spin 2 field with two and three derivatives are obtained. In dimension greater than four, I demonstrate that the gravitational vertex of the massive spin 5/2 field involves, in addition to the standard minimal gravitational vertex, contributions with two and three derivatives. I find that for the massive spin 5/2 and massless spin 2 fields one can build two higher-derivative vertices with two and three derivatives. Limits of massless and partial massless spin 5/2 fields in (A)dS space and limits of massive and massless spin 5/2 fields in flat space are discussed.

Metsaev, R. R. [Department of Theoretical Physics, P.N. Lebedev Physical Institute, Leninsky Prospect 53, Moscow 119991 (Russian Federation)

2008-01-15

422

Gravitational and higher-derivative interactions of massive spin 5/2 field in (A)dS space  

E-print Network

Using on-shell gauge invariant formulation of relativistic dynamics we study interaction vertices for a massive spin 5/2 Dirac field propagating in (A)dS space of dimension greater than or equal to four. Gravitational interaction vertex for the massive spin 5/2 field and all cubic vertices for the massive spin 5/2 field and massless spin 2 field with two and three derivatives are obtained. In dimension greater that four, we demonstrate that the gravitational vertex of the massive spin 5/2 field involves, in addition to the standard minimal gravitational vertex, contributions with two and three derivatives. We find that for the massive spin 5/2 and massless spin 2 fields one can build two higher-derivative vertices with two and three derivatives. Limits of massless and partial massless spin 5/2 fields in (A)dS space and limits of massive and massless spin 5/2 fields in flat space are discussed.

R. R. Metsaev

2007-09-10

423

The R.I. Pimenov unified gravitation and electromagnetism field theory as semi-Riemannian geometry  

E-print Network

More then forty years ago R.I. Pimenov introduced a new geometry -- semi-Riemannian one -- as a set of geometrical objects consistent with a fibering $ pr: M_n \\to M_m.$ He suggested the heuristic principle according to which the physically different quantities (meter, second, coulomb etc.) are geometrically modelled as space coordinates that are not superposed by automorphisms. As there is only one type of coordinates in Riemannian geometry and only three types of coordinates in pseudo-Riemannian one, a multiple fibered semi-Riemannian geometry is the most appropriate one for the treatment of more then three different physical quantities as unified geometrical field theory. Semi-Euclidean geometry $^{3}R_5^4$ with 1-dimensional fiber $x^5$ and 4-dimensional Minkowski space-time as a base is naturally interpreted as classical electrodynamics. Semi-Riemannian geometry $^{3}V_5^4$ with the general relativity pseudo-Riemannian space-time $^{3}V^4,$ and 1-dimensional fiber $x^5,$ responsible for the electromagnetism, provides the unified field theory of gravitation and electromagnetism. Unlike Kaluza-Klein theories, where the 5-th coordinate appears in nondegenerate Riemannian or pseudo-Riemannian geometry, the theory based on semi-Riemannian geometry is free from defects of the former. In particular, scalar field does not arise. PACS: 04.50.Cd, 02.40.-k, 11.10.Kk

N. A. Gromov

2008-10-02

424

The R.I. Pimenov unified gravitation and electromagnetism field theory as semi-Riemannian geometry  

SciTech Connect

More than forty years ago R.I. Pimenov introduced a new geometry-semi-Riemannian one-as a set of geometrical objects consistent with a fibering pr: M{sub n} {yields} M{sub m}. He suggested the heuristic principle according to which the physically different quantities (meter, second, Coulomb, etc.) are geometrically modelled as space coordinates that are not superposed by automorphisms. As there is only one type of coordinates in Riemannian geometry and only three types of coordinates in pseudo-Riemannian one, a multiple-fibered semi-Riemannian geometry is the most appropriate one for the treatment of more than three different physical quantities as unified geometrical field theory. Semi-Euclidean geometry {sup 3}R{sub 5}{sup 4} with 1-dimensional fiber x{sup 5} and 4-dimensional Minkowski space-time as a base is naturally interpreted as classical electrodynamics. Semi-Riemannian geometry {sup 3}V{sub 5}{sup 4} with the general relativity pseudo-Riemannian space-time {sup 3}V{sub 4}, and 1-dimensional fiber x{sup 5}, responsible for the electromagnetism, provides the unified field theory of gravitation and electromagnetism. Unlike Kaluza-Klein theories, where the fifth coordinate appears in nondegenerate Riemannian or pseudo-Riemannian geometry, the theory based on semi-Riemannian geometry is free from defects of the former. In particular, scalar field does not arise.

Gromov, N. A., E-mail: gromov@dm.komisc.r [Komi Science Center UrD RAS, Department of Mathematics (Russian Federation)

2009-05-15

425

Electromagnetic and gravitational self-force on a relativistic particle from quantum fields in curved space  

E-print Network

We provide a quantum field theoretical derivation of the Abraham-Lorentz-Dirac (ALD) equation, describing the motion of an electric point charge sourcing an electromagnetic field, which back-reacts on the charge as a self-force, and the Mino-Sasaki-Tanaka-Quinn-Wald (MSTQW) equation describing the motion of a point mass with self-force interacting with the linearized metric perturbations caused by the mass off an otherwise vacuous curved background spacetime. We regularize the formally divergent self-force by smearing the direct part of the retarded Green's function and using a quasilocal expansion. We also derive the ALD-Langevin and the MSTQW-Langevin equations with a classical stochastic force accounting for the effect of the quantum fluctuations in the field, which causes small fluctuations on the particle trajectory. These equations will be useful for studying the stochastic motion of charges and small masses under the influence of both quantum and classical noise sources, derived either self-consistently or put in by hand phenomenologically. We also show that history-dependent noise-induced drift motions could arise from such stochastic sources on the trajectory that could be a hidden feature of gravitational wave forms hitherto unknown.

Chad R. Galley; B. L. Hu; Shih-Yuin Lin

2006-03-24

426

Non-thermal mechanism of weak microwave fields influence on neurons  

NASA Astrophysics Data System (ADS)

A non-thermal mechanism of weak microwave field impact on a nerve fiber is proposed. It is shown that in the range of about 30-300 GHz, there are strongly pronounced resonances associated with the excitation of ultrasonic vibrations in the membrane as a result of interaction with electromagnetic radiation. The viscous dissipation limits the resonances and results in their broadening. These forced vibrations create acoustic pressure, which may lead to the redistribution of the protein transmembrane channels, and thus changing the threshold of the action potential excitation in the axons of the neural network. The influence of the electromagnetic microwave radiation on various specific areas of myelin nerve fibers was analyzed: the nodes of Ranvier, and the initial segment—the area between the neuron hillock and the first part of the axon covered with the myelin layer. It was shown that the initial segment is the most sensitive area of the myelined neurons from which the action potential normally starts.

Shneider, M. N.; Pekker, M.

2013-09-01

427

Observing optical coherence across Fock layers with weak-field homodyne detectors.  

PubMed

Quantum properties of optical modes are typically assessed by observing their photon statistics or the distribution of their quadratures. Both particle- and wave-like behaviours deliver important information and each may be used as a resource in quantum-enhanced technologies. Weak-field homodyne (WFH) detection provides a scheme that combines the wave- and particle-like descriptions. Here we show that it is possible to observe a wave-like property such as the optical coherence across Fock basis states in the detection statistics derived from discrete photon counting. We experimentally demonstrate these correlations using two WHF detectors on each mode of two classes of two-mode entangled states. Furthermore, we theoretically describe the response of WHF detection on a two-mode squeezed state in the context of generalized Bell inequalities. Our work demonstrates the potential of this technique as a tool for hybrid continuous/discrete-variable protocols on a phenomenon that explicitly combines both approaches. PMID:25427457

Donati, Gaia; Bartley, Tim J; Jin, Xian-Min; Vidrighin, Mihai-Dorian; Datta, Animesh; Barbieri, Marco; Walmsley, Ian A

2014-01-01

428

Application of the many-electron weak-field asymptotic theory of tunneling ionization to atoms  

NASA Astrophysics Data System (ADS)

The many-electron weak-field asymptotic theory (ME-WFAT) of tunneling ionization [Tolstikhin et al., Phys. Rev. A 89, 013421 (2014), 10.1103/PhysRevA.89.013421] is applied to atoms. The procedure to extract the asymptotic coefficient of a Dyson orbital needed to implement the ME-WFAT from many-electron wave functions given by a linear combination of Slater determinants composed of one-electron orbitals, as is typically the case in practical atomic structure calculations, is discussed. It is shown that in the one-configuration approximation such wave functions enable one to consistently implement the theory and calculate the ionization rate. The effect of relaxation of the ionic orbitals and the dependence of the rate on the total orbital momentum and spin states of the atom and ion are considered. However, wave functions constructed by mixing several electronic configurations, maybe more accurate in some sense, do not have the correct asymptotic behavior required for implementing the ME-WFAT. The theory is illustrated by calculations for atoms of the first three periods with the use of one-electron orbitals obtained by the Hartree-Fock method.

Tolstikhina, Inga Yu.; Morishita, Toru; Tolstikhin, Oleg I.

2014-11-01

429

Analytical device model for graphene bilayer field-effect transistors using weak nonlocality approximation  

NASA Astrophysics Data System (ADS)

We develop an analytical device model for graphene bilayer field-effect transistors (GBL-FETs) with the back and top gates. The model is based on the Boltzmann equation for the electron transport and the Poisson equation in the weak nonlocality approximation for the potential in the GBL-FET channel. The potential distributions in the GBL-FET channel are found analytically. The source-drain current in GBL-FETs and their transconductance are expressed in terms of the geometrical parameters and applied voltages by analytical formulas in the most important limiting cases. These formulas explicitly account for the short-gate effect and the effect of drain-induced barrier lowering. The parameters characterizing the strength of these effects are derived. It is shown that the GBL-FET transconductance exhibits a pronounced maximum as a function of the top-gate voltage swing. The interplay of the short-gate effect and the electron collisions results in a nonmonotonic dependence of the transconductance on the top-gate length.

Ryzhii, V.; Ryzhii, M.; Satou, A.; Otsuji, T.; Mitin, V.

2011-03-01

430

A class of metric theories of gravitation on Minkowski spacetime  

NASA Astrophysics Data System (ADS)

A class of metric theories of gravitation on Minkowski spacetime is considered, which is—provided that certain assumptions (staying close to the original ideas of Einstein) are made—the almost most general one that can be considered. In addition to the Minkowskian metric G a dynamical metric H (called the Einstein metric) is defined by means of a second-rank tensor field S (referred to as gravitational potential). The theory is defined by a Lagrangian ?, from which the field equations as well as, e.g., the energy-momentum tensor field for the gravitational field follow. The case of weak fields is considered explicitly. The static, spherically and time-inversal symmetric field is calculated, and as a first step to investigate the theory's viability the parameters are fitted to the experimental data of the perihelion advance and the deflection of light at the Sun. Finally the question of gauge freedoms in the gravitational potential is briefly discussed.

Nairz, A.

1996-03-01

431

Chemical reactions induced by oscillating external fields in weak thermal environments  

NASA Astrophysics Data System (ADS)

Chemical reaction rates must increasingly be determined in systems that evolve under the control of external stimuli. In these systems, when a reactant population is induced to cross an energy barrier through forcing from a temporally varying external field, the transition state that the reaction must pass through during the transformation from reactant to product is no longer a fixed geometric structure, but is instead time-dependent. For a periodically forced model reaction, we develop a recrossing-free dividing surface that is attached to a transition state trajectory [T. Bartsch, R. Hernandez, and T. Uzer, Phys. Rev. Lett. 95, 058301 (2005)]. We have previously shown that for single-mode sinusoidal driving, the stability of the time-varying transition state directly determines the reaction rate [G. T. Craven, T. Bartsch, and R. Hernandez, J. Chem. Phys. 141, 041106 (2014)]. Here, we extend our previous work to the case of multi-mode driving waveforms. Excellent agreement is observed between the rates predicted by stability analysis and rates obtained through numerical calculation of the reactive flux. We also show that the optimal dividing surface and the resulting reaction rate for a reactive system driven by weak thermal noise can be approximated well using the transition state geometry of the underlying deterministic system. This agreement persists as long as the thermal driving strength is less than the order of that of the periodic driving. The power of this result is its simplicity. The surprising accuracy of the time-dependent noise-free geometry for obtaining transition state theory rates in chemical reactions driven by periodic fields reveals the dynamics without requiring the cost of brute-force calculations.

Craven, Galen T.; Bartsch, Thomas; Hernandez, Rigoberto

2015-02-01

432

Effects of thermal-solutal convection on temperature and solutal fields under various gravitational orientations  

NASA Technical Reports Server (NTRS)

Semiconductor crystals such as Hg(1-x)CD(x)Te grown by unidirectional solidification Bridgmann method have shown compositional segregations in both the axial and radial directions. Due to the wide separation between the liquidus and the solidus of its pseudobinary phase diagram, there is a diffusion layer of higher HgTe content built up in the melt near the melt-solid interface which gives a solute concentration gradient in the axial direction. The value of effective diffusion coefficient calculated from fitting of the data to 1D model varies with Hg(1-x)Cd(x)Te growth conditions. This indicates that the growth condition of the Hg(1-x)Cd(x)Te is not purely diffusion controlled. Because of the higher thermal conductivity in the melt than that in the crystal in the growth system, there is a thermal leakage through the fused silica crucible wall near the melt-solid interface. This gives a thermal gradient in the radial direction. Hart, and Thorpe, Hutt and Soulsby have shown that under such conditon a fluid will become convectively unstable as a result of different diffusitivities of temperature and solute. It is quite important to understand the effects of this thermosolute convection on the compositonal segregation in both axial and radial directions in the unidirectionally solidified crystals under various gravitational directions. To reach this goal, we start with a simplified problem to study the effects of thermal-solutal convection on the temperature and solutal fields under various gravitional orientations. We begin by reviewing model governing equations.

Wang, Jai-Ching

1993-01-01

433

Neuroprotective effect of weak static magnetic fields in primary neuronal cultures.  

PubMed

Low intensity static magnetic fields (SMFs) interact with various biological tissues including the CNS, thereby affecting key biological processes such as gene expression, cell proliferation and differentiation, as well as apoptosis. Previous studies describing the effect of SMFs on apoptotic cell death in several non-neuronal cell lines, emphasize the importance of such a potential modulation in the case of neurodegenerative disorders, where apoptosis constitutes a major route via which neurons degenerate and die. In this study, we examine the effect of SMFs on neuronal survival in primary cortical and hippocampal neurons that constitute a suitable experimental system for modeling the neurodegenerative state in vitro. We show that weak SMF exposure interferes with the apoptotic programing in rat primary cortical and hippocampal neurons, thereby providing protection against etoposide-induced apoptosis in a dose- and time-dependent manner. Primary cortical neurons exposed to SMF (50G) for 7days exhibited a 57.1±6.3% decrease in the percentage of cells undergoing apoptosis induced by etoposide (12?M), accompanied by a marked decrease in the expression of the pro-apoptotic markers: cleaved poly ADP ribose polymerase-1, cleaved caspase-3, active caspase-9 and the phospho-histone H2A variant (Ser139) by 41.0±5.0%, 81.2±5.0%, 72.9±6.4%, 42.75±2.9%, respectively, and by a 57.2±1.0% decrease in the extent of mitochondrial membrane potential collapse. Using the L-type voltage-gated Ca(2+) channel inhibitor nifedipine, which is selective to Ca(2+) influx through Cav1.2, we found that the anti-apoptotic effect of SMFs was mediated by Ca(2+) influx through these channels. Our findings demonstrating altered Ca(2+)-influx in response to thapsigargin stimulation in SMF-exposed cortical neurons, along with enhanced inhibition of KCl-induced Ca(2+)-influx through Cav1.2 channels and enhanced expression of Cav1.2 and Cav1.3 channels, allude to the involvement of voltage- and store-operated Ca(2+) channels in various aspects of the protective effect exerted by SMFs. These findings show the potential susceptibility of the CNS to weak SMF exposure and have implications for the design of novel strategies for the treatment and/or prevention of neurodegenerative diseases. PMID:25171788

Ben Yakir-Blumkin, M; Loboda, Y; Schächter, L; Finberg, J P M

2014-10-10

434

Four-Field Equations: a New Model for Weakly Compressible MHD Turbulence in the Solar Wind and the Interstellar Medium  

E-print Network

Four-Field Equations: a New Model for Weakly Compressible MHD Turbulence in the Solar Wind Flight Center Turbulent plasmas in the solar wind and the interstellar medium of- ten contain a large to be in agreement. The scaling of density uctuations with Mach number are compared with solar wind data from Helios

Ng, Chung-Sang

435

Cavities of Weak Magnetic Field Strength in the Wake of FTEs: Results from Global Magnetospheric MHD Simulations  

NASA Technical Reports Server (NTRS)

We use the global magnetohydrodynamic (MHD) code BATS-R-US to model multipoint observations of Flux Transfer Event (FTE) signatures. Simulations with high spatial and temporal resolution predict that cavities of weak magnetic field strength protruding into the magnetosphere trail FTEs. These predictions are consistent with recently reported multi-point Cluster observations of traveling magnetopause erosion regions (TMERs).

Kuznetsova, M. M.; Sibeck, D. G.; Hesse, M.; Wang, Y.; Rastaetter, L.; Toth, G.; Ridley, A.

2009-01-01

436

Estimation of changes in the variability of human heart rate under the impact of weak acoustic fields  

NASA Astrophysics Data System (ADS)

The results of experimental studies on the cardiovascular system response to the impact of weak low-frequency acoustic fields using ERG characteristics are presented. The slowing of the heart rate under the impact of frequencies 10Hz and 100Hz is shown.

Solovyov, A. V.; Talipov, D. V.; Borodin, A. S.; Tuzhilkin, D. A.; Baklykova, E. S.; Pobachenko, S. V.

2014-11-01

437

Quantum Mechanics and Electromagnetics of Weak Magnetic Field Sensing, Storage and Retrieval in Biosystems and Engineered Systems  

Microsoft Academic Search

We study phenomena and effects which can be utilized to sense weak magnetic fields by engineered systems. Possible mechanisms and phenomena utilized by living systems are outlined and discussed. Assuming the macroscopic device physics, it is found that only fluidic engineered devices can typify a magnetoreception premise believed be utilized by some living systems. It is found that the mechanical

Sergey Edward Lyshevski

2008-01-01

438

Galaxy Dynamics Predictions in the Nonsymmetric Gravitational Theory  

E-print Network

In the weak field approximation, the nonsymmetric gravitational theory has, in addition to the Newtonian gravitational potential, a Yukawa potential produced by the exchange of a spin $1^+$ boson between fermions. If the range $r_0$ is of order $30$ kpc, then the potential due to the interaction of known neutrinos in the halos of galaxies can explain the flat rotation curves of galaxies. The results are based on a physical linear approximation to the NGT field equations and they are consistent with equivalence principle observations, other solar system gravitational experiments and the binary pulsar data.

J. W. Moffat

1994-12-28

439

Black holes and fundamental fields: hair, kicks and a gravitational "Magnus" effect  

E-print Network

Scalar fields pervade theoretical physics and are a fundamental ingredient to solve the dark matter problem, to realize the Peccei-Quinn mechanism in QCD or the string-axiverse scenario. They are also a useful proxy for more complex matter interactions, such as accretion disks or matter in extreme conditions. Here, we study the collision between scalar "clouds" and rotating black holes. For the first time we are able to compare analytic estimates and strong field, nonlinear numerical calculations for this problem. As the black hole pierces through the cloud it accretes according to the Bondi-Hoyle prediction, but is deflected through a purely kinematic gravitational "anti-Magnus" effect, which we predict to be present also during the interaction of black holes with accretion disks. After the interaction is over, we find large recoil velocities in the transverse direction. The end-state of the process belongs to the vacuum Kerr family if the scalar is massless, but can be a hairy black hole when the fundamental scalar is massive.

Hirotada Okawa; Vitor Cardoso

2014-05-19

440

Black holes and fundamental fields: Hair, kicks, and a gravitational Magnus effect  

NASA Astrophysics Data System (ADS)

Scalar fields pervade theoretical physics and are a fundamental ingredient to solve the dark matter problem, to realize the Peccei-Quinn mechanism in QCD or the string-axiverse scenario. They are also a useful proxy for more complex matter interactions, such as accretion disks or matter in extreme conditions. Here, we study the collision between scalar "clouds" and rotating black holes. For the first time we are able to compare analytic estimates and strong field, nonlinear numerical calculations for this problem. As the black hole pierces through the cloud it accretes according to the Bondi-Hoyle prediction, but is deflected through a purely kinematic gravitational "anti-Magnus" effect, which we predict to be present also during the interaction of black holes with accretion disks. After the interaction is over, we find large recoil velocities in the transverse direction. The end-state of the process belongs to the vacuum Kerr family if the scalar is massless, but can be a hairy black hole when the scalar is massive.

Okawa, Hirotada; Cardoso, Vitor

2014-11-01

441

Gravitational collapse of a homogeneous scalar field in deformed phase space  

NASA Astrophysics Data System (ADS)

We study the gravitational collapse of a homogeneous scalar field, minimally coupled to gravity, in the presence of a particular type of dynamical deformation between the canonical momenta of the scale factor and of the scalar field. In the absence of such a deformation, a class of solutions can be found in the literature [R. Goswami and P. S. Joshi], whereby a curvature singularity occurs at the collapse end state, which can be either hidden behind a horizon or be visible to external observers. However, when the phase space is deformed, as implemented herein this paper, we find that the singularity may be either removed or instead, attained faster. More precisely, for negative values of the deformation parameter, we identify the emergence of a negative pressure term, which slows down the collapse so that the singularity is replaced with a bounce. In this respect, the formation of a dynamical horizon can be avoided depending on the suitable choice of the boundary surface of the star. Whereas for positive values, the pressure that originates from the deformation effects assists the collapse toward the singularity formation. In this case, since the collapse speed is unbounded, the condition on the horizon formation is always satisfied and furthermore the dynamical horizon develops earlier than when the phase-space deformations are absent. These results are obtained by means of a thoroughly numerical discussion.

Rasouli, S. M. M.; Ziaie, A. H.; Marto, J.; Moniz, P. V.

2014-02-01

442

Activating persulfate by Fe? coupling with weak magnetic field: performance and mechanism.  

PubMed

Weak magnetic field (WMF) and Fe(0) were proposed to activate PS synergistically (WMF-Fe(0)/PS