Aspects of electrostatics in a weak gravitational field
Hamsa Padmanabhan; T. Padmanabhan
2009-10-06
Several features of electrostatics of point charged particles in a weak, homogeneous, gravitational field are discussed using the Rindler metric to model the gravitational field. Some previously known results are obtained by simpler and more transparent procedures and are interpreted in an intuitive manner. Specifically: (i) We show that the electrostatic potential of a charge at rest in the Rindler frame is expressible as A_0=(q/l) where l is the affine parameter distance along the null geodesic from the charge to the field point. (ii) We obtain the sum of the electrostatic forces exerted by one charge on another in the Rindler frame and discuss its interpretation. (iii) We show how a purely electrostatic term in the Rindler frame appears as a radiation term in the inertial frame. (In part, this arises because charges at rest in a weak gravitational field possess additional weight due to their electrostatic energy. This weight is proportional to the acceleration and falls inversely with distance -- which are the usual characteristics of a radiation field.) (iv) We also interpret the origin of the radiation reaction term by extending our approach to include a slowly varying acceleration. Many of these results might have possible extensions for the case of electrostatics in an arbitrary static geometry. [Abridged Abstract
Aspects of electrostatics in a weak gravitational field
NASA Astrophysics Data System (ADS)
Padmanabhan, Hamsa; Padmanabhan, T.
2010-05-01
Several features of electrostatics of point charged particles in a weak, homogeneous, gravitational field are discussed using the Rindler metric to model the gravitational field. Some previously known results are obtained by simpler and more transparent procedures and are interpreted in an intuitive manner. Specifically: (a) We discuss possible definitions of the electric field in curved spacetime (and noninertial frames), argue in favour of a specific definition for the electric field and discuss its properties. (b) We show that the electrostatic potential of a charge at rest in the Rindler frame (which is known and is usually expressed as a complicated function of the coordinates) is expressible as A 0 = q/ ? where ? is the affine parameter distance along the null geodesic from the charge to the field point. (c) This relates well with the result that the electric field lines of a charge coincide with the null geodesics; that is, both light and the electric field lines ‘bend’ in the same manner in a weak gravitational field. We provide a simple proof for this result as well as for the fact that the null geodesics (and field lines) are circles in space. (d) We obtain the sum of the electrostatic forces exerted by one charge on another in the Rindler frame and discuss its interpretation. In particular, we compare the results in the Rindler frame and in the inertial frame and discuss their consistency. (e) We show how a purely electrostatic term in the Rindler frame appears as a radiation term in the inertial frame. (In part, this arises because charges at rest in a weak gravitational field possess additional weight due to their electrostatic energy. This weight is proportional to the acceleration and falls inversely with distance—which are the usual characteristics of a radiation field.) (f) We also interpret the origin of the radiation reaction term by extending our approach to include a slowly varying acceleration. Many of these results might have possible extensions for the case of electrostatics in an arbitrary static geometry.
Casimir effect in a weak gravitational field and the spacetime index of refraction
B. Nazari; M. Nouri-Zonoz
2010-10-07
In a recent paper [arXiv:0904.2904] using a conjecture it is shown how one can calculate the effect of a weak stationary gravitational field on vacuum energy in the context of Casimir effect in an external gravitational field treated in 1+3 formulation of spacetime decomposition.. In this article, employing quntum field theory in curved spacetime, we explicitly calculate the effect of a weak static gravitational field on virtual massless scalar particles in a Casimir apparatus. It is shown that, as expected from the proposed conjecture, both the frequency and renormalized energy of the virtual scalar field are affected by the gravitational field through its index of refraction. This could be taken as a strong evidence in favour of the proposed conjecture. Generalizations to weak {\\it stationary} spacetimes and virtual photons are also discussed.
NASA Astrophysics Data System (ADS)
Pires, Sandrine; Starck, Jean-Luc; Leonard, Adrienne; Réfrégier, Alexandre
2012-03-01
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.
Gravitational lensing beyond the weak-field approximation
NASA Astrophysics Data System (ADS)
Perlick, Volker
2014-01-01
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.
Gravitational lensing beyond the weak-field approximation
Perlick, Volker
2014-01-14
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.
Napolitano, George M.; Esposito, Giampiero; Rosa, Luigi
2008-11-15
We consider a Casimir apparatus consisting of two perfectly conducting parallel plates, subject to the weak gravitational field of the Earth. The aim of this paper is the calculation of the energy-momentum tensor of this system for a free, real massless scalar field satisfying Neumann boundary conditions on the plates. The small gravity acceleration (considered here as not varying between the two plates) allows us to perform all calculations to first order in this parameter. Some interesting results are found: a correction, depending on the gravity acceleration, to the well-known Casimir energy and pressure on the plates. Moreover, this scheme predicts a tiny force in the upwards direction acting on the apparatus. These results are supported by two consistency checks: the covariant conservation of the energy-momentum tensor and the vanishing of its regularized trace, when the scalar field is conformally coupled to gravity.
Multiscale analysis of the electromagnetic self-force in a weak gravitational field
Pound, Adam; Poisson, Eric
2008-02-15
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.
Irene P. Denisova; Igor V. Krivchenkov; Polina A. Vshivtseva; Alexander A. Zubrilo
2004-01-01
The eikonal equation is constructed for a weak electromagnetic wave that propagates by the laws of parameterized post-Maxwellian electrodynamics of vacuum in the magnetic dipole and gravitational fields of pulsars and magnetars. An approximate solution has been found for the equation for the rays, along which two mutually perpendicular normal modes of electromagnetic wave are propagating. The ray bending angles
Andrei Lebed
2012-05-14
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.
Lebed, Andrei
2012-01-01
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 ove...
NASA Astrophysics Data System (ADS)
Capozziello, Salvatore; Faraoni, Valerio
Astrophysical applications of ETGs include the possibility of replacing dark matter in galaxy and clusters with modifications of gravity, the weak-field (Newtonian and post-Newtonian) limit, and gravitational waves. Dark matter at galactic and cluster scales is traditionally included in the realm of cosmology and is discussed in Chap. 7. Here we focus on the weak-field limit of metric f(R) gravity, referring the reader to well known sources for other ETGs. We then discuss gravitational waves in ETGs.
The generation of gravitational waves. 1. Weak-field sources: A plug-in-and-grind formalism
NASA Technical Reports Server (NTRS)
Thorne, K. S.; Kovacs, S. J.
1974-01-01
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.
M. Schreck
2015-08-02
The current article shall contribute to understanding the classical analogue of the minimal photon sector in the Lorentz-violating Standard-Model Extension (SME). It is supposed to complement all studies performed on classical point-particle equivalents of SME fermions. The classical analogue of a photon is not a massive particle being described by a usual equation of motion, but a geometric ray underlying the eikonal equation. The first part of the paper will set up the necessary tools to understand this correspondence for interesting cases of the minimal SME photon sector. In conventional optics the eikonal equation follows from an action principle, which is demonstrated to work in most (but not all) Lorentz-violating cases as well. The integrands of the action functional correspond to Finsler structures, which establishes the connection to Finsler geometry. The second part of the article treats Lorentz-violating light rays in a weak gravitational background by implementing the principle of minimal coupling. Thereby it is shown how Lorentz violation in the photon sector can be constrained by measurements of light bending at massive bodies such as the Sun. The phenomenological studies are based on the currently running ESA mission GAIA and the planned NASA/ESA mission LATOR. The final part of the paper discusses certain aspects of explicit Lorentz violation in gravity based on the setting of Finsler geometry.
Weak gravitational lensing with SKA
Peter Schneider
1999-07-12
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.
Weak gravitational lensing with DEIMOS
NASA Astrophysics Data System (ADS)
Melchior, P.; Viola, M.; Schäfer, B. M.; Bartelmann, M.
2011-04-01
We introduce a novel method for weak-lensing measurements, which is based on a mathematically exact deconvolution of the moments of the apparent brightness distribution of galaxies from the telescope's point spread function (PSF). No assumptions on the shape of the galaxy or the PSF are made. The (de)convolution equations are exact for unweighted moments only, while in practice a compact weight function needs to be applied to the noisy images to ensure that the moment measurement yields significant results. We employ a Gaussian weight function, whose centroid and ellipticity are iteratively adjusted to match the corresponding quantities of the source. The change of the moments caused by the application of the weight function can then be corrected by considering higher order weighted moments of the same source. Because of the form of the deconvolution equations, even an incomplete weighting correction leads to an excellent shear estimation if galaxies and PSF are measured with a weight function of identical size. We demonstrate the accuracy and capabilities of this new method in the context of weak gravitational lensing measurements with a set of specialized tests and show its competitive performance on the GREAT08 Challenge data. A complete C++ implementation of the method can be requested from the authors.
Lerner, David E.; Porter, J. R.
1974-01-01
on JR4 (Weierstrass test); and in the notation of Sec. II we have 00 == 1 +.6 (j + 1) "bJ+l < co. j=O So g-! is well defined. Let r~ (g) be the Christoffel symbols of g with respect to (x a). Setting Hdbc == Hhab,c + hac,/) - hoc,a}, we have...
NASA Astrophysics Data System (ADS)
Rowland, David R.
2015-06-01
Galaxy rotation curves are generally analyzed theoretically using Newtonian physics; however, two groups of authors have claimed that for self-gravitating dusts, general relativity (GR) makes significantly different predictions to Newtonian physics, even in the weak field, low velocity limit. One group has even gone so far as to claim that nonlinear general relativistic effects can explain flat galactic rotation curves without the need for cold dark matter. These claims seem to contradict the well-known fact that the weak field, low velocity, low pressure correspondence limit of GR is Newtonian gravity, as evidenced by solar system tests. Both groups of authors claim that their conclusions do not contradict this fact, with Cooperstock and Tieu arguing that the reason is that for the solar system, we have test particles orbiting a central gravitating body, whereas for a galaxy, each star is both an orbiting body and a contributor to the net gravitational field, and this supposedly makes a difference due to nonlinear general relativistic effects. Given the significance of these claims for analyses of the flat galactic rotation curve problem, this article compares the predictions of GR and Newtonian gravity for three cases of self-gravitating dusts for which the exact general relativistic solutions are known. These investigations reveal that GR and Newtonian gravity are in excellent agreement in the appropriate limits, thus supporting the conventional use of Newtonian physics to analyze galactic rotation curves. These analyses also reveal some sources of error in the referred to works.
Instrumental systematics and weak gravitational lensing
NASA Astrophysics Data System (ADS)
Mandelbaum, R.
2015-05-01
We present a pedagogical review of the weak gravitational lensing measurement process and its connection to major scientific questions such as dark matter and dark energy. Then we describe common ways of parametrizing systematic errors and understanding how they affect weak lensing measurements. Finally, we discuss several instrumental systematics and how they fit into this context, and conclude with some future perspective on how progress can be made in understanding the impact of instrumental systematics on weak lensing measurements.
Instrumental systematics and weak gravitational lensing
Mandelbaum, Rachel
2015-01-01
We present a pedagogical review of the weak gravitational lensing measurement process and its connection to major scientific questions such as dark matter and dark energy. Then we describe common ways of parametrizing systematic errors and understanding how they affect weak lensing measurements. Finally, we discuss several instrumental systematics and how they fit into this context, and conclude with some future perspective on how progress can be made in understanding the impact of instrumental systematics on weak lensing measurements.
NASA Astrophysics Data System (ADS)
Doyen, G.; Drakova, D.
2015-08-01
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 characteristics 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 gravonons are localized in the environment of the massive particles which generate them. The solution of the Schrödinger 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 at present cannot be controlled experimentally and therefore let the choice 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 depend on subtleties of the gravonon structure which at present cannot be controlled experimentally and therefore let the telegraph-like jumps 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 CQM 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 Schrödinger's equation without the need of introducing a probabilistic interpretation.
Weak gravitational lensing with DEIMOS
Melchior, Peter; Schäfer, Björn Malte; Bartelmann, Matthias
2010-01-01
We introduce a novel method for weak-lensing measurements, which is based on a mathematically exact deconvolution of the moments of the apparent brightness distribution of galaxies from the telescope's PSF. No assumptions on the shape of the galaxy or the PSF are made. The (de)convolution equations are exact for unweighted moments only, while in practice a compact weight function needs to be applied to the noisy images to ensure that the moment measurement yields significant results. We employ a Gaussian weight function, whose centroid and ellipticity are iteratively adjusted to match the corresponding quantities of the source. The change of the moments caused by the application of the weight function can then be corrected by considering higher-order weighted moments of the same source. Because of the form of the deconvolution equations, even an incomplete weighting correction leads to an excellent shear estimation if galaxies and PSF are measured with a weight function of identical size. We demonstrate the a...
Weak gravitational lensing with the Square Kilometre Array
Brown, M L; Camera, S; Harrison, I; Joachimi, B; Metcalf, R B; Pourtsidou, A; Takahashi, K; Zuntz, J A; Abdalla, F B; Bridle, S; Jarvis, M; Kitching, T D; Miller, L; Patel, P
2015-01-01
We investigate the capabilities of various stages of the SKA to perform world-leading weak gravitational lensing surveys. We outline a way forward to develop the tools needed for pursuing weak lensing in the radio band. We identify the key analysis challenges and the key pathfinder experiments that will allow us to address them in the run up to the SKA. We identify and summarize the unique and potentially very powerful aspects of radio weak lensing surveys, facilitated by the SKA, that can solve major challenges in the field of weak lensing. These include the use of polarization and rotational velocity information to control intrinsic alignments, and the new area of weak lensing using intensity mapping experiments. We show how the SKA lensing surveys will both complement and enhance corresponding efforts in the optical wavebands through cross-correlation techniques and by way of extending the reach of weak lensing to high redshift.
Precision cosmology with weak gravitational lensing
NASA Astrophysics Data System (ADS)
Hearin, Andrew P.
In recent years, cosmological science has developed a highly predictive model for the universe on large scales that is in quantitative agreement with a wide range of astronomical observations. While the number and diversity of successes of this model provide great confidence that our general picture of cosmology is correct, numerous puzzles remain. In this dissertation, I analyze the potential of planned and near future galaxy surveys to provide new understanding of several unanswered questions in cosmology, and address some of the leading challenges to this observational program. In particular, I study an emerging technique called cosmic shear, the weak gravitational lensing produced by large scale structure. I focus on developing strategies to optimally use the cosmic shear signal observed in galaxy imaging surveys to uncover the physics of dark energy and the early universe. In chapter 1 I give an overview of a few unsolved mysteries in cosmology and I motivate weak lensing as a cosmological probe. I discuss the use of weak lensing as a test of general relativity in chapter 2 and assess the threat to such tests presented by our uncertainty in the physics of galaxy formation. Interpreting the cosmic shear signal requires knowledge of the redshift distribution of the lensed galaxies. This redshift distribution will be significantly uncertain since it must be determined photometrically. In chapter 3 I investigate the influence of photometric redshift errors on our ability to constrain dark energy models with weak lensing. The ability to study dark energy with cosmic shear is also limited by the imprecision in our understanding of the physics of gravitational collapse. In chapter 4 I present the stringent calibration requirements on this source of uncertainty. I study the potential of weak lensing to resolve a debate over a long-standing anomaly in CMB measurements in chapter 5. Finally, in chapter 6 I summarize my findings and conclude with a brief discussion of my outlook on the future of weak lensing studies of cosmology.
Gravitational Potential Reconstruction from Peculiar Velocity and Weak Lensing Measurements
Olivier Doré; Lloyd Knox; Alan Peel
2002-07-18
We present an analytic method for rapidly forecasting the accuracy of gravitational potential reconstruction possible from measurement of radial peculiar velocities of every galaxy cluster with M > M_th in solid angle \\theta^2 and over redshift range z_min gravitational potential (on length scales > 60 Mpc) can be reconstructed for every ~8 cluster velocity determinations. Deeper surveys require measurement of more clusters per S/N > 1 mode. Accuracy is limited by the ``undersampling noise'' due to our non-observation of the large fraction of mass that is not in galaxy clusters. Determining the gravitational potential will allow for detailed study of the relationship between galaxies and their surrounding large-scale density fields over a wide range of redshifts, and test the gravitational instability paradigm on very large scales. Observation of weak lensing by large-scale structure provides complementary information since lensing is sensitive to the tangential modes that do not affect the velocity.
On Weak Fields in Finsler Spaces
G. I. Garas'ko
2007-09-17
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.
Weak 'Antigravity' Fields in General Relativity
F. S. Felber
2009-02-10
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.
Weak 'Antigravity' Fields in General Relativity
Felber, F S
2005-01-01
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.
Field equations of electromagnetic and gravitational fields
Zihua Weng
2009-05-16
The paper studies the validity of Maxwell equation in the case for coexistence of electromagnetic field and gravitational field. With the algebra of quaternions, the Newton's law of gravitation is the same as that in classical theory of gravitational field. Meanwhile the Maxwell equation is identical with that in classical theory of electromagnetic field. And the related conclusions can be spread to the case for coexistence of electromagnetic field and gravitational field by the algebra of octonions. The study claims that Maxwell equation keeps unchanged in the case for coexistence of gravitational field and electromagnetic field, except for the direction of displacement current.
Effective refractive index tensor for weak field gravity
Petarpa Boonserm; Celine Cattoen; Tristan Faber; Matt Visser; Silke Weinfurtner
2005-03-18
Gravitational lensing in a weak but otherwise arbitrary gravitational field can be described in terms of a 3 x 3 tensor, the "effective refractive index". If the sources generating the gravitational field all have small internal fluxes, stresses, and pressures, then this tensor is automatically isotropic and the "effective refractive index" is simply a scalar that can be determined in terms of a classic result involving the Newtonian gravitational potential. In contrast if anisotropic stresses are ever important then the gravitational field acts similarly to an anisotropic crystal. We derive simple formulae for the refractive index tensor, and indicate some situations in which this will be important.
Atomic Inference from Weak Gravitational Lensing Data
Marshall, Phil; /KIPAC, Menlo Park
2005-12-14
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.
The general theory of secondary weak gravitational lensing
NASA Astrophysics Data System (ADS)
Clarkson, Chris
2015-09-01
Weak gravitational lensing is normally assumed to have only two principle effects: a magnification of a source and a distortion of the sources shape in the form of a shear. However, further distortions are actually present owing to changes in the gravitational field across the scale of the ray bundle of light propagating to us, resulting in the familiar arcs in lensed images. This is normally called the flexion, and is approximated by Taylor expanding the shear and magnification across the image plane. However, the physical origin of this effect arises from higher-order corrections in the geodesic deviation equation governing the gravitational force between neighbouring geodesics— so involves derivatives of the Riemann tensor. We show that integrating the second-order geodesic deviation equation results in a `Hessian map' for gravitational lensing, which is a higher-order addition to the Jacobi map. We derive the general form of the Hessian map in an arbitrary spacetime paying particular attention to the separate effects of local Ricci versus non-local Weyl curvature. We then specialise to the case of a perturbed FLRW model, and give the general form of the Hessian for the first time. This has a host of new contributions which could in principle be used as tests for modified gravity.
The general theory of secondary weak gravitational lensing
Clarkson, Chris
2015-01-01
Weak gravitational lensing is normally assumed to have only two principle effects: a magnification of a source and a distortion of the sources shape in the form of a shear. However, further distortions are actually present owing to changes in the gravitational field across the scale of the ray bundle of light propagating to us, resulting in the familiar arcs in lensed images. This is normally called the flexion, and is approximated by Taylor expanding the shear and magnification across the image plane. However, the physical origin of this effect arises from higher-order corrections in the geodesic deviation equation governing the gravitational force between neighbouring geodesics - so involves derivatives of the Riemann tensor. We show that integrating the second-order geodesic deviation equation results in a 'Hessian map' for gravitational lensing, which is a higher-order addition to the Jacobi map. We derive the general form of the Hessian map in an arbitrary spacetime paying particular attention to the sep...
The general theory of secondary weak gravitational lensing
Chris Clarkson
2015-03-30
Weak gravitational lensing is normally assumed to have only two principle effects: a magnification of a source and a distortion of the sources shape in the form of a shear. However, further distortions are actually present owing to changes in the gravitational field across the scale of the ray bundle of light propagating to us, resulting in the familiar arcs in lensed images. This is normally called the flexion, and is approximated by Taylor expanding the shear and magnification across the image plane. However, the physical origin of this effect arises from higher-order corrections in the geodesic deviation equation governing the gravitational force between neighbouring geodesics - so involves derivatives of the Riemann tensor. We show that integrating the second-order geodesic deviation equation results in a 'Hessian map' for gravitational lensing, which is a higher-order addition to the Jacobi map. We derive the general form of the Hessian map in an arbitrary spacetime paying particular attention to the separate effects of local Ricci versus non-local Weyl curvature. We then specialise to the case of a perturbed FLRW model, and give the general form of the Hessian for the first time. This has a host of new contributions which could in principle be used as tests for modified gravity.
Simulating weak gravitational lensing for cosmology
Kiessling, Alina Anne
2011-11-23
This thesis will present a new cosmic shear analysis pipeline SUNGLASS (Simulated UNiverses for Gravitational Lensing Analysis and Shear Surveys). SUNGLASS is a pipeline that rapidly generates simulated universes for ...
Spherically Symmetric Gravitational Fields
NASA Astrophysics Data System (ADS)
Vargas Moniz, P.
The purpose of this paper is to investigate the quantum vacua directly implied by the wave function of a gravitational configuration characterized by the presence of an apparent horizon, namely the Vaidya space-time solution. Spherical symmetry is a main feature of this configuration, with a scalar field constituting a source [a Klein-Gordon geon or Berger-Chitre-Moncrief-Nutku (BCMN) type model]. The subsequent analysis requires solving a Wheeler-DeWitt equation near the apparent horizon (following the guidelinesintroduced by A. Tomimatsu,18; M. Pollock, 19 and developed by A. Hosoya and I. Oda20,21) with the scalar field herein expanded in terms of S2 spherical harmonics: midisuperspace quantization. The main results present in this paper are as follows. It is found that the mass function characteristic of the Vaidya metric is positive definite within this quantum approach. Furthermore, the inhomogeneous matter sector determines a descrip-tion in terms of open quantum (sub)systems, namely in the form of an harmonic oscillator whose frequency depends on the mass function. For this open (sub)system, a twofold approach is employed. On the one hand, an exact invariant observable is obtained from the effective Hamiltonian for the inhomogeneous matter modes. It is shown that this invariant admits a set of discrete eigenvalues which depend on the mass function. The corresponding set of eigenstates is constructed from a particular vacuum state. On the other hand, exact solutions are found for the Schrädinger equation associated with the inhomogeneous matter modes. This paper is concluded with a discussion, where two other issues are raised: (i) the possible application to realistic black hole dynamics of the results obtained for a simplified (BCMN) model and (ii) whether such vacuum states could be related with others defined instead within scalar field theories constructed in classical backgrounds.
NASA Astrophysics Data System (ADS)
Chen, Shao-Guang
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
Radio Weak Gravitational Lensing with VLA and MERLIN
Patel, P; Beswick, R J; Muxlow, T W B; Hoyle, B
2009-01-01
We carry out an exploratory weak gravitational lensing analysis on a combined VLA and MERLIN radio data set: a deep (3.3 micro-Jy beam^-1 rms noise) 1.4 GHz image of the Hubble Deep Field North. We measure the shear estimator distribution at this radio sensitivity for the first time, finding a similar distribution to that of optical shear estimators for HST ACS data in this field. We examine the residual systematics in shear estimation for the radio data, and give cosmological constraints from radio-optical shear cross-correlation functions. We emphasize the utility of cross-correlating shear estimators from radio and optical data in order to reduce the impact of systematics. Unexpectedly we find no evidence of correlation between optical and radio intrinsic ellipticities of matched objects; this result improves the properties of optical-radio lensing cross-correlations. We explore the ellipticity distribution of the radio counterparts to optical sources statistically, confirming the lack of correlation; as a...
Detection of (dark) matter concentrations via weak gravitational lensing
Peter Schneider
1996-01-16
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.
Digging into Dark Matter with Weak Gravitational Lensing
NASA Astrophysics Data System (ADS)
Massey, R.
2010-07-01
Ordinary baryonic particles (such as protons and neutrons) account for only one-sixth of the total matter in the Universe. The remainder is a mysterious “dark matter” component, which does not interact via the electromagnetic force and thus neither emits nor reflects light. However, evidence is mounting for its gravitational influence. The past few years have seen particular progress in observations of weak gravitational lensing, the slight deflection of light from distant galaxies due to the curvature of space around foreground mass. Recent surveys from the Hubble Space Telescope have provided direct proof for dark matter, and the first measurements of its properties. We review recent results, then prospects and challenges for future gravitational lensing surveys.
The gravitational field of Phobos
Chao, B.F.; Rubincam, D.P. )
1989-08-01
The external gravitational field produced by a rigid body of uniform density but irregular shape is formulated in terms of spherical harmonics. The formalism is applied to the Martian satellite Phobos. Based on a 3-dimensional shape model of Phobos by Duxbury, the gravitational coefficients up to degree and order 4 for a homogeneous Phobos are computed. In particular, the authors find J{sub 2} = 0.105. The in-plane liberation amplitude of a homogeneous Phobos is predicted to be 0.97{degree}, within the rather large uncertainty of the observed value of 0.78 {plus minus} 0.4{degree}.
Forces in electromagnetic field and gravitational field
Zihua Weng
2011-03-31
The force can be defined from the linear momentum in the gravitational field and electromagnetic field. But this definition can not cover the gradient of energy. In the paper, the force will be defined from the energy and torque in a new way, which involves the gravitational force, electromagnetic force, inertial force, gradient of energy, and some other new force terms etc. One of these new force terms can be used to explain why the solar wind varies velocity along the magnetic force line in the interplanetary space between the sun and the earth.
Gravitational mass in electromagnetic field
Zihua Weng
2009-08-09
A fraction of energy is theoretically predicted to be captured from electromagnetic field to form a gravitating mass, when a low-mass charged particle enters the strong field from a region of no electromagnetism. In this paper the mass variation has been calculated for a charged particle on free-fall in the constraint electromagnetic field. It has been shown that there is an evident effect to the variation in mass when the low-mass charged particle is in the strong field.
Karhunen-Loeve Analysis for Weak Gravitational Lensing
Vanderplas, Jacob T
2013-01-01
In the past decade, weak gravitational lensing has become an important tool in the study of the universe at the largest scale, giving insights into the distribution of dark matter, the expansion of the universe, and the nature of dark energy. This thesis research explores several applications of Karhunen-Loeve (KL) analysis to speed and improve the comparison of weak lensing shear catalogs to theory in order to constrain cosmological parameters in current and future lensing surveys. After providing a brief introduction to cosmology and to KL analysis, this work addresses three related aspects of weak lensing analysis: (1) Three-dimensional tomographic mapping (based on work published in Vanderplas et al. 2011); (2) Shear peak statistics with incomplete/gappy data (based on work published in Vanderplas et al. 2012); and (3) two-point parameter estimation from gappy data using KL modes (previously unpublished)... [this abstract has been abbreviated; please see the thesis for the full abstract].
Classical field approach to quantum weak measurements.
Dressel, Justin; Bliokh, Konstantin Y; Nori, Franco
2014-03-21
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 postselection 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 postselected ensembles, and why they can also be measured using classical field techniques that are not weak for individual excitations of the field. PMID:24702338
Classical effective field theory for weak ultra relativistic scattering
NASA Astrophysics Data System (ADS)
Kol, Barak
2011-07-01
Inspired by the problem of Planckian scattering we describea classical effective field theory for weak ultra relativistic scattering in which field propagation is instantaneous and transverse and the particles' equations of motion localize to the instant of passing. An analogy with the non-relativistic (post-Newtonian) approximation is stressed. The small parameter is identified and power counting rules are established. The theory is applied to reproduce the leading scattering angle for either a scalar interaction field or electro-magnetic or gravitational; to compute some subleading corrections, including the interaction duration; and to allow for non-zero masses. For the gravitational case we present an appropriate decomposition of the gravitational field onto the transverse plane together with its whole non-linear action. On the way we touch upon the relation with the eikonal approximation, some evidence for censorship of quantum gravity, and an algebraic ring structure on 2d Minkowski spacetime.
Weak Gravitational Lensing from Regular Bardeen Black Holes
NASA Astrophysics Data System (ADS)
Ghaffarnejad, Hossein; niad, Hassan
2015-09-01
In this article we study weak gravitational lensing of regular Bardeen black hole which has scalar charge g and mass m. We investigate the angular position and magnification of non-relativistic images in two cases depending on the presence or absence of photon sphere. Defining dimensionless charge parameter q=g/2m we seek to disappear photon sphere in the case of |q|>{24?5}/{125} for which the space time metric encounters strongly with naked singularities. We specify the basic parameters of lensing in terms of scalar charge by using the perturbative method and found that the parity of images is different in two cases: (a) The strongly naked singularities is present in the space time. (b) singularity of space time is weak or is eliminated (the black hole lens).
Invariants in electromagnetic and gravitational adjoint fields
Zihua Weng
2009-06-22
The paper discusses the impact of adjoint fields on the conservation laws in the gravitational field and electromagnetic field, by means of the characteristics of octonions. When the adjoint field can not be neglected, it will cause the predictions to departure slightly from the conservation laws, which include mass continuity equation, charge continuity equation, and conservation of spin. The adjoint field of electromagnetic field has an effect on conservation of mass, and that of gravitational field on conservation of charge. The inferences explain how the adjoint field influences some conservation laws in the gravitational field and electromagnetic field.
On the consequences of the weak field approximation
NASA Astrophysics Data System (ADS)
Laubenstein, John
2013-04-01
General Relativity reduces to Newtonian gravity within the appropriate limit. But, what is that limit? The conventional response is that of the weak field approximation in which the gravitating source is weak and velocities are low. But, this is a far cry from a quantitative statement. In that regard, the weak field may be defined more quantitatively as one in which any error introduced is far beyond the level of precision required. Since the field can always be made incrementally weaker there is no limit as to the degree of precision that can be achieved. In this regard, GR reduces exactly to Newtonian gravity at the limit where velocity goes to zero. It is only out of convenience that we extend this to include those conditions where v << c with the argument that any error is arbitrarily small. However, in practice GR can be shown to reduce to an exact Newtonian expression at v > 0. How can this observation fit with the quantitative definition of the weak field? This paper explores the consequences of the weak field approximation and the fact that GR reduces directly to Newtonian gravity within the weak field as opposed to the more specific condition where v = zero.
Scalar invariants in gravitational and electromagnetic fields
Zihua Weng
2009-06-22
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.
Helmut Kling
2015-05-24
A mass distribution is analyzed in terms of classical gravitational field theory. Newton's law of gravitation is consistently applied on the assumption that the equivalence of energy and mass according to Einstein's theory of relativity is valid for gravitational fields as well. Different from standard approaches the gravitational field, via its associated field energy, is handled as a source of gravitation by itself. Starting from these principles a gravitational self-shielding phenomenon is derived as a common characteristic of all mass/energy distributions. Moreover, it is demonstrated that even in the absence of any stimulating mass the existence of independent static gravitational fields is fully consistent with Newton's law of gravitation as long as the equivalence of energy and mass is respected. From a distance such gravitational fields appear as negative masses.
Thermal effective Lagrangian of static gravitational fields
NASA Astrophysics Data System (ADS)
Brandt, F. T.; Siqueira, J. B.
2012-03-01
We compute the effective Lagrangian of static gravitational fields interacting with thermal fields. Our approach employs the usual imaginary time formalism as well as the equivalence between the static and space-time independent external gravitational fields. This allows to obtain a closed form expression for the thermal effective Lagrangian in d space-time dimensions.
Thermal Effective Lagrangian of Static Gravitational Fields
F T Brandt; J B Siqueira
2012-03-08
We compute the effective Lagrangian of static gravitational fields interacting with thermal fields. Our approach employs the usual imaginary time formalism as well as the equivalence between the static and space-time independent external gravitational fields. This allows to obtain a closed form expression for the thermal effective Lagrangian in $d$ space-time dimensions.
Gravitational failure of sea cliffs in weakly lithified sediment
Hampton, M.A.
2002-01-01
Gravitational failure of sea cliffs eroded into weakly lithified sediment at several sites in California involves episodic stress-release fracturing and cantilevered block falls. The principal variables that influence the gravitational stability are tensional stresses generated during the release of horizontal confining stress and weakening of the sediment with increased saturation levels. Individual failures typically comprise less than a cubic meter of sediment, but large areas of a cliff face can be affected by sustained instability over a period of several days. Typically, only the outer meter or so of sediment is removed during a failure episode. In-place sediment saturation levels vary over time and space, generally being higher during the rainy season but moderate to high year-round. Laboratory direct-shear tests show that sediment cohesion decreases abruptly with increasing saturation level; the decrease is similar for all tested sediment if the cohesion is normalized by the maximum, dry-sediment cohesion. Large failures that extend over most or all of the height of the sea cliff are uncommon, but a few large wedge-shaped failures sometimes occur, as does separation of large blocks at sea cliff-gully intersections.
Quantum Lukewarm Black Holes and Weak Gravitational Lensing
Ghaffarnejad, H
2015-01-01
Aim of the paper is study gravitational lensing of quantum Lukewarm black hole (QLBL) and compare with results of gravitational lensing from classical Lukewarm black hole lens (CLBL). Applying numerical method, we evaluate deflection angle, image positions and magnifications in weak deflection limits. In CLBL case, bending light ray moves from both side of the lens but in QLBL case it moves from one side of the lens. Increasing amount of dimensionless cosmological parameter (quantum matter interaction parameter), rake of bending light ray is decreased in case of QLBL with respect to CLBL. Number and size of radius of Einstein rings rises in case of QLBL with respect to CLBL. Maximum number of rings is 3 in case of QLBL namely one more with respect to case of CLBL which is physically related to effects of quantum matter. There is two images (elementary and secondary) with maximum magnification which their locations are changed in case of QLBL with respect to case of CLBL. Also their locations changed by increa...
Bacterial Growth in Weak Magnetic Field
NASA Astrophysics Data System (ADS)
Masood, Samina
2015-03-01
We study the growth of bacteria in a weak magnetic field. Computational analysis of experimental data shows that the growth rate of bacteria is affected by the magnetic field. The effect of magnetic field depends on the strength and type of magnetic field. It also depends on the type of bacteria. We mainly study gram positive and gram negative bacteria of rod type as well as spherical bacteria. Preliminary results show that the weak magnetic field enhances the growth of rod shape gram negative bacteria. Gram positive bacteria can be even killed in the inhomogeneous magnetic field.
Some theorems in gravitational and electromagnetic fields
Zihua Weng
2009-06-12
The paper discusses the influences of velocity curl and field strength on some theorems in the electromagnetic field and gravitational field. With the characteristics of the algebra of quaternions, the theorem of linear momentum, conservation of linear momentum, and conservation of angular momentum etc. can be deduced from the quaternionic definitions of physical quantities. And the strength of gravitational field and electromagnetic field have an influence on some theorems directly. While the velocity curl has an effect on some theorems also.
LIGHT ON DARK MATTER WITH WEAK GRAVITATIONAL LENSING 1 Light on Dark Matter
Starck, Jean-Luc
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 decades showing that the visible matter represents only about 4-5% of the Universe, the rest being dark
Angular momentum effects in weak gravitational fields
A. Tartaglia
2002-01-02
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.
Action of the gravitational field on the dynamical Casimir effect
L. C. Céleri; F. Pascoal; M. H. Y. Moussa
2008-09-22
In this paper we analyze the action of the gravitational field on the dynamical Casimir effect. We consider a massless scalar field confined in a cuboid cavity placed in a gravitational field described by a static and diagonal metric. With one of the plane mirrors of the cavity allowed to move, we compute the average number of particles created inside the cavity by means of the Bogoliubov coefficients computed through perturbative expansions. We apply our result to the case of an oscillatory motion of the mirror, assuming a weak gravitational field described by the Schwarzschild metric. The regime of parametric amplification is analyzed in detail, demonstrating that our computed result for the mean number of particles created agrees with specific associated cases in the literature. Our results, obtained in the framework of the perturbation theory, are restricted, under resonant conditions, to a short-time limit.
Gravitational Field of Fractal Distribution of Particles
Vasily E. Tarasov
2006-04-24
In this paper we consider the gravitational field of fractal distribution of particles. To describe fractal distribution, we use the fractional integrals. The fractional integrals are considered as approximations of integrals on fractals. Using the fractional generalization of the Gauss's law, we consider the simple examples of the fields of homogeneous fractal distribution. The examples of gravitational moments for fractal distribution are considered.
Karhunen-Loeve Analysis for Weak Gravitational Lensing
NASA Astrophysics Data System (ADS)
Vanderplas, Jacob T.
In the past decade, weak gravitational lensing has become an important tool in the study of the universe at the largest scale, giving insights into the distribution of dark matter, the expansion of the universe, and the nature of dark energy. This thesis research explores several applications of Karhunen-Loève (KL) analysis to speed and improve the comparison of weak lensing shear catalogs to theory in order to constrain cosmological parameters in current and future lensing surveys. This work addresses three related aspects of weak lensing analysis: Three-dimensional Tomographic Mapping: (Based on work published in Vanderplas et al 2011) We explore a new fast approach to three-dimensional mass mapping in weak lensing surveys. The KL approach uses a KL-based filtering of the shear signal to reconstruct mass structures on the line-of-sight, and provides a unified framework to evaluate the efficacy of linear reconstruction techniques. We find that the KL-based filtering leads to near-optimal angular resolution, and computation times which are faster than previous approaches. We also use the KL formalism to show that linear non-parametric reconstruction methods are fundamentally limited in their ability to resolve lens redshifts. Shear Peak Statistics with Incomplete Data: (Based on work published in Vanderplas et al 2012) We explore the use of KL eigenmodes for interpolation across masked regions in observed shear maps. Mass mapping is an inherently non-local calculation, meaning gaps in the data can have a significant effect on the properties of the derived mass map. Our KL mapping procedure leads to improvements in the recovery of detailed statistics of peaks in the mass map, which holds promise of improved cosmological constraints based on such studies. Two-point parameter estimation with KL modes: The power spectrum of the observed shear can yield powerful cosmological constraints. Incomplete survey sky coverage, however, can lead to mixing of power between Fourier modes, and obfuscate the cosmologically sensitive signal. We show that KL can be used to derive an alternate orthonormal basis for the problem which avoids mode-mixing and allows a convenient formalism for cosmological likelihood computations. Cosmological constraints derived using this method are shown to be competitive with those from the more conventional correlation function approach. We also discuss several aspects of the KL approach which will allow improved handling of correlated errors and redshift information in future surveys.
Mars gravitational field estimation error
NASA Technical Reports Server (NTRS)
Compton, H. R.; Daniels, E. F.
1972-01-01
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.
Gravity as a Higgs Field. III. Nongravitional Deviations of Gravitational Fields
G. Sardanashvily
1994-11-06
In Parts I and II of the work (gr-qc/9405013, 9407032), we have shown that gravity is {\\it sui generis} a Higgs field corresponding to spontaneous symmetry breaking when the fermion matter admits only the Lorentz subgroup of world symmetries of the geometric arena. From the mathematical viewpoint, the Higgs nature of gravity issues from the fact that different gravitational fields are responsible for nonequivalent representations of cotangent vectors to a world manifold by $\\gamma$-matrices on spinor bundles. It follows that gravitational fields fail to form an affine space modelled on a linear space of deviations of some background field. In other words, even weak gravitational fields do not satisfy the superposition principle and, in particular, can not be quantized by usual methods. At the same time, one can examine superposable deviations $\\sigma$ of a gravitational field $h$ so that $h+\\sigma$ fails to be a gravitational field. These deviations are provided with the adequate mathematical description in the framework of the affine group gauge theory in dislocated manifolds, and their Lagrangian densities differ from the familiar gravitational ones. They make contribution to the standard gravitational effects, e.g., modify Newton's gravitational potential.
String pair production in a time-dependent gravitational field
Tolley, Andrew J.; Wesley, Daniel H. [Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States)
2005-12-15
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.
Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements
NASA Astrophysics Data System (ADS)
Seshadri, S.; Shapiro, C.; Goodsall, T.; Fucik, J.; Hirata, C.; Rhodes, J. D.; Rowe, B. T. P.; Smith, R. M.
2013-09-01
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.
Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit
NASA Astrophysics Data System (ADS)
Gyulchev, G. N.; Yazadjiev, S. S.
2010-11-01
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?/b, where M is the black hole mass, a is the angular momentum, r? = Q2/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.
Neutrino Oscillations in Strong Gravitational Fields
Dardo Píriz; Mou Roy; José Wudka
1996-04-25
Neutrino oscillations in the presence of strong gravitational fields are studied. We look at very high energy neutrinos ($\\sim $1 TeV) emanating from Active Galactic Nuclei (AGN). It is observed that spin flavor resonant transitions of such neutrinos may occur in the vicinity of AGN due to {\\it gravitational} effects and due to the presence of a large magnetic field ($\\sim $1 Tesla). A point to note is that matter effects (normal MSW transitions) become negligible in comparison o gravitational effects in our scenario.
Galilean-invariant scalar fields can strengthen gravitational lensing.
Wyman, Mark
2011-05-20
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
Luigi Delle Rose
2013-08-01
The principal goal of the physics of the fundamental interactions is to provide a consistent description of the nature of the subnuclear forces, which manifest in our universe, together with the gravitational force, in a unified framework. This attempt, which is far from being complete, is characterized by two milestones, the Standard Model of the elementary particles and the Einstein's theory of General Relativity. The coupling of a quantum field theory, such as the Standard Model, to a weak gravitational background provides significant information concerning the coupling of matter to gravity and allows to study in a systematic way the origin of the conformal anomaly. For this reason, the computation of correlation functions in a weak gravitational background is of remarkable interest and the consequences of this analysis are also of phenomenological relevance. For instance, they concern the appearance in the spectrum of the theory of a composite state, the dilaton, which is identified, in perturbation theory, by an infrared coupled anomaly pole. The study of some applications of the methods discussed so far is presented in the second part of this thesis. In particular it is shown that the analysis of the classical metric perturbations in gravity can be related to some specific field theories via a holographic mapping. This requires the computation of correlators of energy-momentum tensors in $d=3$ dimensions and plays a role in the study of the non-gaussianities of the cosmic background radiation in the early universe. Finally, we mention an application in momentum space of the constraints derived from the conformal symmetry in the characterization of some correlation functions. This relies on the solution of a system of second order partial differential equations for a certain class of generalized hypergeometric functions of two variables.
The Equivalence of Time and Gravitational Field
NASA Astrophysics Data System (ADS)
Baruk?i?a, Ilija
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.
Helicity Observation of Weak and Strong Fields
Mei Zhang
2006-06-09
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.
Spin-2 particles in gravitational fields
G. Papini
2007-02-01
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.
Physical optics in a uniform gravitational field
NASA Astrophysics Data System (ADS)
Hacyan, Shahen
2012-01-01
The motion of a (quasi-)plane wave in a uniform gravitational field is studied. It is shown that the energy of an elliptically polarized wave does not propagate along a geodesic, but in a direction that is rotated with respect to the gravitational force. The similarity with the walk-off effect in anisotropic crystals or the optical Magnus effect in inhomogeneous media is pointed out.
On the linear and weak-field limits of scalar-tensor theories of gravity
Marcelo Salgado
2002-02-21
The linear approximation of scalar-tensor theories of gravity is obtained in the physical (Jordan) frame under the 4+0 (covariant) and 3+1 formalisms. Then the weak-field limit is analyzed and the conditions leading to significant deviations of the $1/r^{2}$ Newton's law of gravitation are discussed. Finally, the scalarization effects induced by these theories in extended objects are confronted within the weak-field limit.
Gravitational waves induced by spinor fields
Feng, Kaixi
2015-01-01
In realistic model-building, spinor fields with various masses are present. During inflation, spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of single massive spinor field to the power spectrum of primordial gravitational wave by using retarded Green propagator. We find that the correction is scale-invariant and of order $H^4/M_P^4$ for arbitrary spinor mass $m_{\\psi}$. Additionally, we also observe that when $m_\\psi \\gtrsim H$, the dependence of correction on $m_\\psi/H$ is nontrivial.
Gravitational waves induced by spinor fields
Kaixi Feng; Yun-Song Piao
2015-09-03
In realistic model-building, spinor fields with various masses are present. During inflation, spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of single massive spinor field to the power spectrum of primordial gravitational wave by using retarded Green propagator. We find that the correction is scale-invariant and of order $H^4/M_P^4$ for arbitrary spinor mass $m_{\\psi}$. Additionally, we also observe that when $m_\\psi \\gtrsim H$, the dependence of correction on $m_\\psi/H$ is nontrivial.
Gravitational waves induced by spinor fields
NASA Astrophysics Data System (ADS)
Feng, Kaixi; Piao, Yun-Song
2015-07-01
In realistic model building, spinor fields with various masses are present. During inflation, a spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of a single massive spinor field to the power spectrum of primordial gravitational wave by using a retarded Green propagator. We find that the correction is scale invariant and of order H4/MP4 for arbitrary spinor mass m?. Additionally, we also observe that when m??H , the dependence of correction on m?/H is nontrivial.
Gravitational waves from scalar field accretion
Darío Núnez; Juan Carlos Degollado; Claudia Moreno
2011-09-03
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.
Ren, Jing; Xianyu, Zhong-Zhi; He, Hong-Jian, E-mail: jingren2004@gmail.com, E-mail: xianyuzhongzhi@gmail.com, E-mail: hjhe@tsinghua.edu.cn [Institute of Modern Physics and Center for High Energy Physics, Tsinghua University, Beijing 100084 (China)
2014-06-01
We study gravitational interaction of Higgs boson through the unique dimension-4 operator ?H{sup †}HR, with H the Higgs doublet and R the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling ? on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone equivalence theorem with nonzero ? coupling in both frames, and analyze the unitarity constraints. We study the ?-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 (14 TeV) and the next generation pp colliders (50-100 TeV). 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.
Light clocks in strong gravitational fields
Raffaele Punzi; Frederic P. Schuller; Mattias N. R. Wohlfarth
2009-02-11
We argue that the time measured by a light clock operating with photons rather than classical light requires a refinement of the standard clock postulate in general relativity. In the presence of a gravitational field, already the one-loop quantum corrections to classical Maxwell theory affect light propagation and the construction of observers' frames of reference. Carefully taking into account these kinematic effects, a concise geometric expression for the time shown by a light clock is obtained. This result has far-reaching implications for physics in strong gravitational fields.
Chameleon scalar fields in relativistic gravitational backgrounds
Shinji Tsujikawa; Takashi Tamaki; Reza Tavakol
2009-04-03
We study the field profile of a scalar field $\\phi$ that couples to a matter fluid (dubbed a chameleon field) in the relativistic gravitational background of a spherically symmetric spacetime. Employing a linear expansion in terms of the gravitational potential $\\Phi_c$ at the surface of a compact object with a constant density, we derive the thin-shell field profile both inside and outside the object, as well as the resulting effective coupling with matter, analytically. We also carry out numerical simulations for the class of inverse power-law potentials $V(\\phi)=M^{4+n} \\phi^{-n}$ by employing the information provided by our analytical solutions to set the boundary conditions around the centre of the object and show that thin-shell solutions in fact exist if the gravitational potential $\\Phi_c$ is smaller than 0.3, which marginally covers the case of neutron stars. Thus the chameleon mechanism is present in the relativistic gravitational backgrounds, capable of reducing the effective coupling. Since thin-shell solutions are sensitive to the choice of boundary conditions, our analytic field profile is very helpful to provide appropriate boundary conditions for $\\Phi_c \\lesssim O(0.1)$.
Chameleon scalar fields in relativistic gravitational backgrounds
Tsujikawa, Shinji; Tamaki, Takashi; Tavakol, Reza E-mail: tamaki@gravity.phys.waseda.ac.jp
2009-05-15
We study the field profile of a scalar field {phi} that couples to a matter fluid (dubbed a chameleon field) in the relativistic gravitational background of a spherically symmetric spacetime. Employing a linear expansion in terms of the gravitational potential {Phi}{sub c} at the surface of a compact object with a constant density, we derive the thin-shell field profile both inside and outside the object, as well as the resulting effective coupling with matter, analytically. We also carry out numerical simulations for the class of inverse power-law potentials V({phi}) = M{sup 4+n}{phi}{sup -n} by employing the information provided by our analytical solutions to set the boundary conditions around the centre of the object and show that thin-shell solutions in fact exist if the gravitational potential {Phi}{sub c} is smaller than 0.3, which marginally covers the case of neutron stars. Thus the chameleon mechanism is present in the relativistic gravitational backgrounds, capable of reducing the effective coupling. Since thin-shell solutions are sensitive to the choice of boundary conditions, our analytic field profile is very helpful to provide appropriate boundary conditions for {Phi}{sub c}{approx}
Detection of Weak Lensing in the Fields of Luminous Radiosources
B. Fort; Y. Mellier; M. Dantel-Fort; H. Bonnet; J. -P. Kneib
1995-07-20
We present a first attempt to reveal the possible existence of large foreground mass condensations directly responsible for the gravitational magnification of four distant luminous radiosources and one optical QSO. The technique uses a weak lensing analysis of the distant galaxies in the field of each source. We find a coherent shear map with a large magnification bias on the line of sight to Q1622+0328. The local shear in the field of the bright radiosources is also often correlated with nearby groups or poor clusters of galaxies. For three of them, the groups are identified as gravitational deflectors that magnify the radiosources. This suggests that a substantial amount of invisible mass is condensed in groups and poor clusters It may explain the origin of a large angular correlation between the distribution of distant radiosources and the distribution of low redshift galaxies. We discuss the feasability and consequences of a future systematic survey to investigate the problem of magnification bias in the fields of luminous distant objects and to probe the mass distributions of galaxy groups at intermediate redshifts.
Quantum fields as gravitational sources
Mark J Hadley
2008-08-13
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.
Gravitational Radiation from Preheating with Many Fields
John T. Giblin Jr; Larry R. Price; Xavier Siemens
2010-06-11
Parametric resonances provide a mechanism by which particles can be created just after inflation. Thus far, attention has focused on a single or many inflaton fields coupled to a single scalar field. However, generically we expect the inflaton to couple to many other relativistic degrees of freedom present in the early universe. Using simulations in an expanding Friedmann-Lema\\^itre-Robertson-Walker spacetime, in this paper we show how preheating is affected by the addition of multiple fields coupled to the inflaton. We focus our attention on gravitational wave production--an important potential observational signature of the preheating stage. We find that preheating and its gravitational wave signature is robust to the coupling of the inflaton to more matter fields.
Gravitational radiation from preheating with many fields
Jr, John T. Giblin; Price, Larry R.; Siemens, Xavier E-mail: larry@gravity.phys.uwm.edu
2010-08-01
Parametric resonances provide a mechanism by which particles can be created just after inflation. Thus far, attention has focused on a single or many inflaton fields coupled to a single scalar field. However, generically we expect the inflaton to couple to many other relativistic degrees of freedom present in the early universe. Using simulations in an expanding Friedmann-Lemaître-Robertson-Walker spacetime, in this paper we show how preheating is affected by the addition of multiple fields coupled to the inflaton. We focus our attention on gravitational wave production — an important potential observational signature of the preheating stage. We find that preheating and its gravitational wave signature is robust to the coupling of the inflaton to more matter fields.
Rotation of the cosmic microwave background polarization from weak gravitational lensing.
Dai, Liang
2014-01-31
When a cosmic microwave background (CMB) photon travels from the surface of last scatter through spacetime metric perturbations, the polarization vector may rotate about its direction of propagation. This gravitational rotation is distinct from, and occurs in addition to, the lensing deflection of the photon trajectory. This rotation can be sourced by linear vector or tensor metric perturbations and is fully coherent with the curl deflection field. Therefore, lensing corrections to the CMB polarization power spectra as well as the temperature-polarization cross correlations due to nonscalar perturbations are modified. The rotation does not affect lensing by linear scalar perturbations, but needs to be included when calculations go to higher orders. We present complete results for weak lensing of the full-sky CMB power spectra by general linear metric perturbations, taking into account both deflection of the photon trajectory and rotation of the polarization. For the case of lensing by gravitational waves, we show that the B modes induced by the rotation largely cancel those induced by the curl component of deflection. PMID:24580435
BE condensates of weakly interacting bosons in gravity fields
Yukio Tomozawa
2012-11-21
The Bose-Einstein (BE) condensates of weakly interacting bosons in a strong gravity field, such as AGN (Active Galactic Nuclei), BHs (black holes) and neutron stars, are discussed. Being bound systems in gravity fields, these are stable reservoirs for the Higgs bosons, and vector bosons of Z and W as well as supersymmetric bosons. Upon gravitational disturbances, such as a gravitational collapse, these objects are relieved from the BE condensate bound states and decay or interact with each other freely. Using the repulsive nature of gravity at short distances which was obtained by the present author as quantum corrections to gravity, the particles produced by the decays or interactions of the bosons liberated from BE condensates can be emitted outside the horizon for our observation. It is suggested that the recently observed gamma ray peak at 129.8 +- 2.4 GeV from FERMI Large Area Telescope may be evidence for the existence of the Higgs boson condensates. The BE condensates of supersymmetric bosons are the most likely sources for the gamma rays from DMP (dark matter particle) and anti-DMP collisions. It is shown that the said process from DMPs spread in the galaxy is too small for the incident DMP with the intensity of the cosmic ray energy spectrum.
Lognormal Property of Weak-Lensing Fields
NASA Astrophysics Data System (ADS)
Taruya, Atsushi; Takada, Masahiro; Hamana, Takashi; Kayo, Issha; Futamase, Toshifumi
2002-06-01
The statistical properties of weak-lensing fields are studied quantitatively using ray-tracing simulations. Motivated by an empirical lognormal model that excellently characterizes the probability distribution function of a three-dimensional mass distribution, we critically investigate the validity of the lognormal model in weak-lensing statistics. Assuming that the convergence field ? is approximately described by the lognormal distribution, we present analytic formulae of convergence for the one-point probability distribution function (PDF) and the Minkowski functionals. The validity of the lognormal models is checked in detail by comparing those predictions with ray-tracing simulations in various cold dark matter models. We find that the one-point lognormal PDF can accurately describe the non-Gaussian tails of convergence fields up to ?~10, where ? is the level threshold given by ???/1/2, although the systematic deviation from the lognormal prediction becomes manifest at higher source redshift and larger smoothing scales. The lognormal formulae for Minkowski functionals also fit the simulation results when the source redshift is low, zs=1. Accuracy of the lognormal fit remains good even at small angular scales 2'<~?<~4', where the perturbation formulae by the Edgeworth expansion break down. On the other hand, the lognormal model enables us to predict higher order moments, i.e., skewness S3,? and kurtosis S4,?, and we thus discuss the consistency by comparing the predictions with the simulation results. Since these statistics are very sensitive to the high- and low-convergence tails, the lognormal prediction does not provide a successful quantitative fit. We therefore conclude that the empirical lognormal model of the convergence field is safely applicable as a useful cosmological tool, as long as we are concerned with the non-Gaussianity of ?<~5 for low-zs samples.
Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit
Gyulchev, G. N.; Yazadjiev, S. S.
2010-11-25
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.
GRAVITATIONAL FIELD SHIELDING AND SUPERNOVA EXPLOSIONS
Zhang, T. X.
2010-12-20
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.
Constraining modified gravitational theories by weak lensing with Euclid
Martinelli, Matteo; Calabrese, Erminia; De Bernardis, Francesco; Melchiorri, Alessandro; Pagano, Luca; Scaramella, Roberto
2011-01-15
Future proposed satellite missions such as Euclid can offer the opportunity to test general relativity on cosmic scales through mapping of the galaxy weak-lensing signal. In this paper we forecast the ability of these experiments to constrain modified gravity scenarios such as those predicted by scalar-tensor and f(R) theories. We find that Euclid will improve constraints expected from the Planck satellite on these modified theories of gravity by 2 orders of magnitude. We discuss parameter degeneracies and the possible biases introduced by modifications to gravity.
Graphene transparency in weak magnetic fields
David Valenzuela; Saúl Hernández-Ortiz; Marcelo Loewe; Alfredo Raya
2014-10-20
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.
Effect of quantum statistics on the gravitational weak equivalence principle
Mousavi, S V; Home, D
2015-01-01
We study the effect of quantum statistics on the arrival time distribution of quantum particles computed through the probability current density. It is shown that symmetrization or asymmetrization of the wave function affects the arrival time distribution for even freely propagating particles. In order to investigate the effect of statistics on the weak equivalence principle in quantum mechanics (WEQ), we then compute the mean arrival time for wave packets in free fall. The violation of WEQ through the effect of statistics on the mass-dependence of the mean arrival time is clearly exhibited. We finally evaluate the effect of spin on the violation of WEQ using a different approach by including an explicit spin-dependence in the probability current distribution, and compare it with the approach using particle statistics. Our results show WEQ re-emerges smoothly in the limit of large mass.
Effect of quantum statistics on the gravitational weak equivalence principle
S. V. Mousavi; A. S. Majumdar; D. Home
2015-09-10
We study the effect of quantum statistics on the arrival time distribution of quantum particles computed through the probability current density. It is shown that symmetrization or asymmetrization of the wave function affects the arrival time distribution for even freely propagating particles. In order to investigate the effect of statistics on the weak equivalence principle in quantum mechanics (WEQ), we then compute the mean arrival time for wave packets in free fall. The violation of WEQ through the effect of statistics on the mass-dependence of the mean arrival time is clearly exhibited. We finally evaluate the effect of spin on the violation of WEQ using a different approach by including an explicit spin-dependence in the probability current distribution, and compare it with the approach using particle statistics. Our results show WEQ re-emerges smoothly in the limit of large mass.
Problems in field theoretical approach to gravitation
A. I. Nikishov
2004-10-20
We consider gravitational self interaction in the lowest approximation and assume that graviton interacts with gravitational energy-momentum tensor in the same way as it interacts with particles. We show that, using gravitational vertex with a preferred gravitational energy-momentum tensor, it is possible to obtain a metric necessary for explaining perihelion precession. The preferred gravitational energy-momentum tensor gives positive gravitational energy density of Newtonian center. We show also that, employing "improvement" technique, any gravitational energy-momentum tensor can be made suitable for using in gravitational wave equation for obtaining metric which explains perihelion precession. Yet the "improvement" leads to negative gravitational energy density of the Newtonian center.
Gravitational collapse of charged scalar fields
NASA Astrophysics Data System (ADS)
Torres, Jose M.; Alcubierre, Miguel
2014-09-01
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|
Gravitational collapse of charged scalar fields
Jose M. Torres; Miguel Alcubierre
2014-07-29
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|
Gravitational Descendants in Symplectic Field Theory
Fabert, Oliver
2009-01-01
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 that for the trivial curves in SFT, that is, branched covers of trivial cylinders over closed Reeb orbits, the gravitational descendants have a geometric interpretation in terms of branching conditions, we compute the corresponding sequences of Poisson-commuting functions when the contact manifold is the unit cotangent bundle of a Riemannian manifold, where it turns out that we can no longer expect to have completeness.
Gravitational descendants in symplectic field theory
Oliver Fabert
2010-03-25
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 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 compute the corresponding sequences of Poisson-commuting functions when the contact manifold is the unit cotangent bundle of a Riemannian manifold.
How to Extract Energy Directly from a Gravitational Field
Fran De Aquino
2000-01-01
Gravity is related to gravitational mass of the bodies. According to the weak form of Einstein's General Relativity equivalence principle, the gravitational and inertial masses are equivalent. However recent calculations (gr-qc\\/9910036) have revealed that they are correlated by an adimensional factor, which depends on the incident radiation upon the particle. It was shown that there is a direct correlation between
Covariant description for superfluids in gravitational fields
H. Casini; R. Montemayor
1999-11-01
In this paper we develop a formalism to describe a superfluid in a gravitational background. This formalism is based on a covariant generalization of the field description for a superconductor in terms of a U(1) spontaneous symmetry breaking. We study the stability of the solutions for a vortexless fluid and the force acting on vortices in the fluid, which is a generalization of the well-known flat space-time Magnus force. To clarify the development we include the explicit discussion of two particular cases, one of them of astrophysical interest.
On the statistics of the gravitational field
A. Del Popolo
2001-10-26
In this paper we extend Chandrasekhar and von Neumann's analysis of the statistics of the gravitational field to systems in which particles (e.g. stars, galaxies) are not homogeneously distributed. We derive a distribution function W(F,d F/dt) giving the joint probability that a test particle is subject to a force F and an associated rate of change of F given by d F/dt. We calculate the first moment of d F/dt to study the effects of inhomogenity on dynamical friction.
Neutrino Oscillations in Strong Gravitational Fields
NASA Astrophysics Data System (ADS)
Roy, Mou
1997-11-01
Neutrino oscillations in the presence of strong gravitational fields are studied considering Dirac and Majorana neutrinos. We look at very high energy neutrinos (~1 TeV) emanating from Active Galactic Nuclei (AGN). It is observed that spin flavor resonant transitions of such neutrinos may occur in the vicinity of AGN due to gravitational effects and the presence of a large magnetic field (~1 Tesla) dominating over matter induced oscillations. Such oscillations occur at energies in the PeV range for magnetic moments in the 10-17?B range. Probabilities are calculated and we predict significant increase of Tau neutrino flux to which future neutrino telescopes will be sensitive. The violation of the equivalence principle (VEP) causing neutrino oscillations is of current interest. We have studied also the the possibility of spin flavor oscillation of such ultra high energy neutrinos due to VEP and due to the presence of a large magnetic field in AGN. In particular we look at the resonance spin flavor conversion driven by the AGN potential. Interesting bounds on the transition magnetic moment of neutrinos may therefore be obtained. The search for such high energy neutrinos by the neutrino telescopes (e.g. AMANDA, BAIKAL, km3 etc.) which are under construction necessitates a clear picture of the expected neutrino fluxes from these objects. That is the main motivation behind this study.
Coincident-Frequency Entangled Photons in a Homogenous Gravitational Field - A Thought Experiment
Clovis Jacinto de Matos
2010-11-24
Assuming that the Principle of energy conservation holds for coincident-frequency entangled photons propagating in a homogeneous gravitational field. It is argued that in this physical context, either Quantum entanglement or the weak equivalence principle are broken by the photons.
NASA Astrophysics Data System (ADS)
Yahalom, Asher
2011-11-01
In this study, stability conditions of self-gravitating disc models are obtained. The self-gravitating disc models under study include known models such as the Maclaurin disc and the infinite, self-gravitating, rotating sheet. These models also include a new class of analytically solvable models denoted by 'generalized Maclaurin discs'. These self-gravitating, finite discs are differentially rotating with adiabatic index ? > 2 and have the property that the derivatives of densities go smoothly to zero at the boundary. Stability conditions of the various models are obtained through the 'weak energy principle' introduced by Katz, Inagaki & Yahalom. It is shown that necessary and sufficient conditions of stability are obtained when we have only pair coupling in the gyroscopic terms of the perturbed Lagrangian; otherwise, the 'weak energy principle' gives only sufficient conditions. All perturbations considered are in the same plane as the configurations. For differentially rotating discs, we consider only radial perturbations. The limits of stability are identical with those given by a dynamical analysis when available, and with the results of the strong energy principle analysis when given. Thus, although the 'weak energy' method is mathematically more simple than the 'strong energy' method of Katz et al., since it does not involve solving second-order partial differential equations, it is by no means less effective. Additional results also derived through the 'weak energy principle' include stability conditions for the 2D Rayleigh flows and Toomre's local criterion for the stability of rotating discs. Among the most interesting results is an exact extension of Toomre's criterion to the global stability of generalized Maclaurin discs, whereby a necessary condition for local stability becomes a sufficient condition for global stability.
Symmetries in tetrad theories. [of gravitational fields and general relativity
NASA Technical Reports Server (NTRS)
Chinea, F. J.
1988-01-01
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.
If the spin of gravitational field depends on spacetime dimension
K. Kaviani; F. Atyabi
2015-04-14
In this manuscript a different perspective on gravitational field has been proposed, suggesting different features of gravity depending on spacetime dimension, which can explain preventing the formation of singularity inside blackholes and also suggest interpreting spin-1 fields emerged in theories with dimensional reduction mechanism, as different aspects of gravitational field.
Gravitational radiative corrections from effective field theory
Walter D. Goldberger; Andreas Ross
2010-07-21
In this paper we construct an effective field theory (EFT) that describes long wavelength gravitational radiation from compact systems. To leading order, this EFT consists of the multipole expansion, which we describe in terms of a diffeomorphism invariant point particle Lagrangian. The EFT also systematically captures "post-Minkowskian" corrections to the multipole expansion due to non-linear terms in general relativity. Specifically, we compute long distance corrections from the coupling of the (mass) monopole moment to the quadrupole moment, including up to two mass insertions. Along the way, we encounter both logarithmic short distance (UV) and long wavelength (IR) divergences. We show that the UV divergences can be (1) absorbed into a renormalization of the multipole moments and (2) resummed via the renormalization group. The IR singularities are shown to cancel from properly defined physical observables. As a concrete example of the formalism, we use this EFT to reproduce a number of post-Newtonian corrections to the gravitational wave energy flux from non-relativistic binaries, including long distance effects up to 3PN ($v^6$) order. Our results verify that the factorization of scales proposed in the NRGR framework of Goldberger and Rothstein is consistent up to order 3PN.
Gravitational Descendants in Symplectic Field Theory
NASA Astrophysics Data System (ADS)
Fabert, Oliver
2011-02-01
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 (
Gravitational radiative corrections from effective field theory
Goldberger, Walter D
2009-01-01
In this paper we construct an effective field theory (EFT) that describes long wavelength gravitational radiation from compact systems. To leading order, this EFT consists of the multipole expansion, which we describe in terms of a diffeomorphism invariant point particle Lagrangian. The EFT also systematically captures "post-Minkowskian" corrections to the multipole expansion due to non-linear terms in general relativity. Specifically, we compute long distance corrections from the coupling of the (mass) monopole moment to the quadrupole moment, including up to two mass insertions. Along the way, we encounter both logarithmic short distance (UV) and long wavelength (IR) divergences. We show that the UV divergences can be (1) absorbed into a renormalization of the multipole moments and (2) resummed via the renormalization group. The IR singularities are shown to cancel from properly defined physical observables. As a concrete example of the formalism, we use this EFT to reproduce a number of post-Newtonian corr...
Consequences of Coupled Electromagnetic-Gravitational Fields
NASA Technical Reports Server (NTRS)
Smalley, Larry
2002-01-01
In the late 1980s there was a flurry of activities involving the newly discovered high Tc superconductors in the development of new devices such as more efficient current transmission, transformers, generators, and motors. One such developmental project by Podkletnov in 1992 noted some small, anomalous gravitational behaviors. A following unpublished paper by Podkletnov 1995 provided data with larger effects using a larger (approx. 25 cm) superconducting disk. Unfortunately this disk was extremely fragile and was broken beyond repair. To date, these experiments have not been successfully repeated because of the difficulties of producing stable, durable (and fired) superconducting disks. This problem with firing these disks has been solved by Li. What remains is to install the disk in "motor", at superconducting temperatures in the presence of appropriately tailored magnetic fields.
David Tsiklauri
1999-04-01
Linear stability of an isothermal, pressure-bounded, self-gravitating gas slab which is gravitationally coupled with the background weakly interacting massive particles (WIMPs) is investigated. Analytic dispersion relations describing such a configuration are derived. Two novel, distinct oscillatory modes are found. Astrophysical implications of the results are discussed.
The Gravitational Field of a Plane Slab
NASA Astrophysics Data System (ADS)
Gamboa Saraví, Ricardo E.
We discuss the exact solution to Einstein's equation corresponding to a static and plane symmetric distribution of matter with constant positive density located below z = 0 matched to vacuum solutions. The internal solution depends essentially on two constants: the density ? and a parameter ?. We show that these space-times finish down below at an inner singularity at finite depth d <= ? {(? )/(24? )}. We show that for ? ? 0.3513 ?, the dominant energy condition is satisfied all over the space-time. We match these singular solutions to the vacuum one and compute the external gravitational field in terms of slab's parameters. Depending on the value of ?, these slabs are either attractive, repulsive or neutral. The external solution turns out to be a Rindler's space-time. Repulsive slabs explicitly show how negative, but finite pressure can dominate the attraction of the matter. In this case, the presence of horizons in the vacuum shows that there are null geodesics which never reach the surface of the slab. We also consider a static and plane symmetric nonsingular distribution of matter with constant positive density ? and thickness d(0 < d < ? {(? )/(24? )}) surrounded by two external vacuums. We explicitly write down the pressure and the external gravitational fields in terms of ? and d. The solution turns out to be attractive and remarkably asymmetric: the "upper" solution is Rindler's vacuum, whereas the "lower" one is the singular part of Taub's plane symmetric solution. Inside the slab, the pressure is positive and bounded, presenting a maximum at an asymmetrical position between the boundaries. We show that if $0 < \\sqrt{6\\pi\\rho} d < 1.527 ?ots, the dominant energy condition is satisfied all over the space-time. We also show how the mirror symmetry is restored at the Newtonian limit. We also find thinner repulsive slabs by matching a singular slice of the inner solution to the vacuum. We also discuss solutions in which an attractive slab and a repulsive one, and two neutral ones are joined. We also discuss how to assemble a "gravitational capacitor" by inserting a slice of vacuum between two such slabs.
How to Extract Energy Directly from a Gravitational Field
Fran De Aquino
2000-01-01
Gravity is related to gravitational mass of the bodies. According to the weak\\u000aform of Einstein's General Relativity equivalence principle, the gravitational\\u000aand inertial masses are equivalent. However recent calculations (gr-qc\\/9910036)\\u000ahave revealed that they are correlated by an adimensional factor, which depends\\u000aon the incident radiation upon the particle. It was shown that there is a\\u000adirect correlation between
NASA Astrophysics Data System (ADS)
Ivanov, A. N.; Wellenzohn, M.
2015-09-01
We analyze a nonrelativistic approximation of the Dirac equation for slow fermions, coupled to the chameleon field and torsion in the spacetime with the Schwarzschild metric, taken in the weak gravitational field of the Earth approximation. We follow the analysis of the Dirac equation in the curved spacetime with torsion, proposed by Kostelecky [Phys. Rev. D 69, 105009 (2004)], and apply the Foldy-Wouthuysen transformations. We derive the effective low-energy gravitational potentials for slow fermions, coupled to the gravitational field of the Earth, the chameleon field and to torsion with minimal and nonminimal couplings.
A. N. Ivanov; M. Wellenzohn
2015-09-14
We analyse a non-relativistic approximation of the Dirac equation for slow fermions, coupled to the chameleon field and torsion in the spacetime with the Schwarzschild metric, taken in the weak gravitational field of the Earth approximation. We follow the analysis of the Dirac equation in the curved spacetime with torsion, proposed by Kostelecky (Phys. Rev. D69, 105009 (2004)), and apply the Foldy--Wouthuysen transformations. We derive the effective low-energy gravitational potentials for slow fermions, coupled to the gravitational field of the Earth, the chameleon field and to torsion with minimal and non-minimal couplings.
Ivanov, A N
2015-01-01
We analyse a non-relativistic approximation of the Dirac equation for slow fermions, coupled to the chameleon field and torsion in the spacetime with the Schwarzschild metric, taken in the weak gravitational field of the Earth approximation. We follow the analysis of the Dirac equation in the curved spacetime with torsion, proposed by Kostelecky (Phys. Rev. D69, 105009 (2004)), and apply the Foldy--Wouthuysen transformations. We derive the effective low-energy gravitational potentials for slow fermions, coupled to the gravitational field of the Earth, the chameleon field and to torsion with minimal and non-minimal couplings.
The Energy-Momentum Tensor for the Gravitational Field
S. V. Babak; L. P. Grishchuk
1999-04-01
The field theoretical description of the general relativity (GR) is further developed. The action for the gravitational field and its sources is given explicitely. The equations of motion and the energy-momentum tensor for the gravitational field are derived by applying the variational principle. We have succeeded in constructing the unique gravitational energy-momentum tensor which is 1) symmetric, 2) conserved due to the field equations, and 3) contains not higher than the first order derivatives of the field variables. It is shown that the Landau-Lifshitz pseudotensor is an object most closely related to the derived energy-momentum tensor.
Lensing by Distant Clusters: HST Observations of Weak Shear in the Field of 3C324
Ian Smail; Mark Dickinson
1995-10-08
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.
An accurate and practical method for inference of weak gravitational lensing from galaxy images
Bernstein, Gary M; Krawiec, Christina; March, Marisa C
2015-01-01
We demonstrate recovery of weak gravitational lensing shear at parts-per-thousand accuracy using an implementation of the Bayesian Fourier Domain (BFD) method proposed by Bernstein \\& Armstrong (2014, BA14). The BFD formalism is rigorously correct for Nyquist-sampled, background-limited, uncrowded image of background galaxies. BFD does not assign shapes to galaxies, instead compressing the pixel data D into a vector of moments M, such that we have an analytic expression for the probability P(M|g) of obtaining the observations with gravitational lensing distortion g along the line of sight. We extend the BA14 formalism to include detection and selection of galaxies without inducing biases on the inferred g. We describe a practical algorithm for conducting BFD's integrations over the population of unlensed source galaxies. Our BFD implementation measures ~10 galaxies per second per core on current hardware, a speed that will be largely independent of the number of images taken of each target. Initial tests ...
Field theory on R × S 3 topology. VI: Gravitation
M. Carmeli; S. Malin
1987-01-01
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 theory on R× S 3 topology. VI: Gravitation
M. Carmeli; S. Malin
1987-01-01
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
Barnes, Joshua Edward
of the acceleration rather than the force; this integral is the potential energy per unit mass or gravitational potential, "(x), 47 #12;48 CHAPTER 7. GRAVITATIONAL FIELDS and the potential energy of a test mass m is just.1 Conservative Force Fields In a one-dimensional system it is always possible to define a potential energy
The Effect of Weak Gravitational Lensing on the Angular Distribution of Gamma-Ray Bursts
L. L. R. Williams
1996-06-10
If Gamma-Ray Bursts (GRBs) are cosmologically distributed standard candles and are associated with the luminous galaxies, then the observed angular distribution of all GRBs is altered due to weak gravitational lensing of bursts by density inhomogeneities. The amplitude of the effect is generally small. For example, if the current catalogs extend to $z_{max}\\sim 1$ and we live in a flat $\\Omega=1$ Universe, the angular auto-correlation function of GRBs will be enhanced by $\\sim 8\\%$ due to lensing, on all angular scales. For an extreme case of $z_{max}= 1.5$ and ($\\Omega$, $\\Lambda$)=(0.2, 0.8), an enhancement of $\\sim 33\\%$ is predicted. If the observed distribution of GRBs is used in the future to derive power spectra of mass density fluctuations on large angular scales, the effect of weak lensing should probably be taken into account.
Gravitational consequences of modern field theories
NASA Technical Reports Server (NTRS)
Horowitz, Gary T.
1989-01-01
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.
Biological effects due to weak magnetic field on plants
NASA Astrophysics Data System (ADS)
Belyavskaya, N. A.
2004-01-01
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.
Gravity as a Higgs Field. II.Fermion-Gravitation Complex
G. Sardanashvily
1994-07-22
Gravitation theory meets spontaneous symmetry breaking when the structure group of the principal linear frame bundle $LX$ over a world manifold $X^4$ is reducible to the Lorentz group $SO(3,1)$. The physical underlying reason of this reduction is Dirac fermion matter possessing only exact Lorentz symmetries. The associated Higgs field is a tetrad gravitational field $h$ represented by a section of the quotient $\\Si$ of $LX$ by $SO(3,1)$. The feature of gravity as a Higgs field issues from the fact that, in the presence of different tetrad fields, there are nonequivalent representations of cotangent vectors to $X^4$ by Dirac's matrices. It follows that fermion fields must be regarded only in a pair with a certain tetrad field. These pairs constitute the so-called fermion-gravitation complex and are represented by sections of the composite spinor bundle $S\\to\\Si\\to X^4$ where values of tetrad gravitational fields play the role of coordinate parameters, besides familiar world coordinates. In Part I of the work [gr-qc:9405013], geometry of this composite spinor bundle has been investigated. This Part is devoted to dynamics of the fermion-gravitation complex. It is a constraint system to describe which we use the covariant multimomentum Hamiltonian formalism when canonical momenta correspond to derivatives of fields with respect to all world coordinates, not only time. On the constraint space, the canonical momenta of tetrad gravitational fields are equal to zero, otherwise in the presence of fermion fields.
Hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit
Abril Suárez; Pierre-Henri Chavanis
2015-04-05
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 an arbitrary potential of the form $V(|\\varphi|^2)$. 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. Nonrelativistic hydrodynamic equations based on the Schr\\"odinger-Poisson equations or on the Gross-Pitaevskii-Poisson equations are recovered in the limit $c\\rightarrow +\\infty$.
A possible quantum probability increase of the cylindrical gravitational field
D. Bar
2011-01-07
As known, the cylindrical gravitational field (wave) have been canonically quantized and its wave function, as the quantum one, interpreted in probability terms. We show in this work, using quantum Zeno methods, that this probability may be substantially increased and even approach unity. For that we first show, in detailed manner, that the cylindrical gravitational field may be discussed in the commutation number representation. We also discuss this field in the transverse-traceless (TT) gauge and calculate the related trapped surface.
Computing Gravitational Fields of Finite-Sized Bodies
NASA Technical Reports Server (NTRS)
Quadrelli, Marco
2005-01-01
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.
Cosmological electromagnetic fields due to gravitational wave perturbations Mattias Marklund*
Dunsby, Peter
show that this coupling leads to an initial pulse of electromagnetic waves whose width and amplitude to produce a pulse of gravitationally induced electromagnetic waves. In particular, because of the differentCosmological electromagnetic fields due to gravitational wave perturbations Mattias Marklund
Electrical charges in gravitational fields, and Einstein's equivalence principle
Gerold Gründler
2015-10-06
According to Larmor's formula, accelerated electric charges radiate electromagnetic waves. Hence charges should radiate, if they are in free fall in gravitational fields, and they should not radiate if they are supported at rest in gravitational fields. But according to Einstein's equivalence principle, charges in free fall should not radiate, while charges supported at rest in gravitational fields should radiate. In this article we point out indirect experimental evidence, indicating that the equivalence principle is correct, while Larmor's formula must be interpreted different than commonly accepted.
Interactions of cosmological gravitational waves and magnetic fields
Elisa Fenu; Ruth Durrer
2009-01-05
The energy momentum tensor of a magnetic field always contains a spin-2 component in its anisotropic stress and therefore generates gravitational waves. It has been argued in the literature (Caprini & Durrer \\cite{CD}) that this gravitational wave production can be very strong and that back-reaction cannot be neglected. On the other hand, a gravitational wave background does affect the evolution of magnetic fields. It has also been argued (Tsagas et al. \\cite{Tsagas:2001ak},\\cite{Tsagas:2005ki}) that this can lead to very strong amplification of a primordial magnetic field. In this paper we revisit these claims and study back reaction to second order.
Electrical charges in gravitational fields, and Einstein's equivalence principle
Gerold Gründler
2015-09-14
According to Larmor's formula, accelerated electric charges radiate electromagnetic waves. Hence charges should radiate, if they are in free fall in gravitational fields, and they should not radiate if they are supported at rest in gravitational fields. But according to Einstein's equivalence principle, charges in free fall should not radiate, while charges supported at rest in gravitational fields should radiate. In this article we point out indirect experimental evidence, indicating that the equivalence principle is correct, while Larmor's formula must be interpreted different than commonly accepted.
Electrical charges in gravitational fields, and Einstein's equivalence principle
Gründler, Gerold
2015-01-01
According to Larmor's formula, accelerated electric charges radiate electromagnetic waves. Hence charges should radiate, if they are in free fall in gravitational fields, and they should not radiate if they are supported at rest in gravitational fields. But according to Einstein's equivalence principle, charges in free fall should not radiate, while charges supported at rest in gravitational fields should radiate. In this article we point out indirect experimental evidence, indicating that the equivalence principle is correct, while Larmor's formula must be interpreted different than commonly accepted.
Electrical charges in gravitational fields, and Einstein's equivalence principle
Gerold Gründler
2015-10-12
According to Larmor's formula, accelerated electric charges radiate electromagnetic waves. Hence charges should radiate, if they are in free fall in gravitational fields, and they should not radiate if they are supported at rest in gravitational fields. But according to Einstein's equivalence principle, charges in free fall should not radiate, while charges supported at rest in gravitational fields should radiate. In this article we point out indirect experimental evidence, indicating that the equivalence principle is correct, while the traditional interpretation of Larmor's formula must be amended.
Yu. G. Ignatyev
2011-01-05
On the basis of simple principles we derive and investigate the equations of relativistic plasma magnetohydrodynamics (MHD) in an arbitrary gravitational field. An exact solution describing the motion of magnetoactive plasma against the background of the metric of a plane gravitational wave (PGW) with an arbitrary amplitude is obtained. It is shown that in strong magnetic fields even a sufficiently small amplitude PGW can create a shock MHD wave, propagating at a subluminal velocity. Astrophysical consequences of the anomalous plasma acceleration are considered.
Fast appearances and disappearances of weak intranetwork magnetic fields
NASA Astrophysics Data System (ADS)
Shi, Zhong-Xian; Wang, Jing-Xiu; Liu, Jian-Qiang; Han, Feng; Liu, Gui-Lin
1990-03-01
Results are presented of the analysis of magnetograms obtained, under conditions of best visibility, at the Huairou Station of the Beijing Observatory on September 5, 1988. The magnetograms showed the existence of weak intranetwork magnetic fields (INFs) which were appearing and disappearing, with a maximum flux B between 5 and 10 G. Evidence is presented that the weak appearing and disappearing INFs are real structures; about 70 percent of INFs become undetectable at the level of about 5 G after 3.4 min of observation; about 30 percent of INFs can be seen again. The number of weak INFs decreases exponentially with time, leading to an upper limit of about 3 min for the mean life of a weak INF. It is suggested that a weak INF is a collection of unresolved flux elements, with a flux between 2.0(+16) and 1.0(+18) Mx.
Electromagnetic Waves in a Uniform Gravitational Field and Planck's Postulate
Acedo, L
2015-01-01
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 resulting gravitational time-dilation near these masses gives rise to a frequency change of any periodic process, including electromagnetic oscillations as the wave propagates across the gravitational field. This phenomenon can be tackled with classical electrodynamics assuming a curved spacetime background and Maxwell's equations in a generally covariant form. In the present paper, we show that in a classical field-theoretical context the gravitational redshift can be interpreted as the propagation of electromagnetic waves in a medium with corresponding conductivity $\\sigma=g/(\\mu_0 c^3)$, where $g$ is the gravitational acceleration and $\\mu_0$ is the vacuum magnetic p...
[Biological detector of weak cosmic fields].
Kopvillem, U Kh; Sharipov, R Z; Zapol'ski?, A M; A?zda?cher, N A
1992-01-01
Possibility of use of biological object as a detector of faint cosmophysical fields is discussed. The signals of free induction and electric echo caused by a short-term effect of light with an intensity of approximately 0.2 mWt/sm2 on biological systems were observed. The experiments with Blatella germanica, Muska domestica were performed in vivo and with red and green seaweeds and yeast cells in vitro. The signals were detected by means of the dielectric permeability measurement in a dynamic regime. Main features of the observed responses are described and assumption on mechanisms of their origin are given. An example of registration of the Lunar eclipse on a detector with in active element of Blatella germanica is given. PMID:1420418
Densities of Electron's Continuum in Gravitational and Electromagnetic Fields
I. E. Bulyzhenkov
2012-11-18
Relativistic dynamics of distributed mass and charge densities of the extended classical particle is discussed for arbitrary gravitational and electromagnetic fields. Vector geodesic relations for material space densities are consequences of tensor gravitational equations for continuous sources and their fields. Classical four-flows of elementary material space depend on local four-potentials for charged densities, like in quantum theory. Six electromagnetic intensities can describe satisfactorily only the simplest, potential kind of continuous matter motion.
Gravitational waves from self-ordering scalar fields
Elisa Fenu; Daniel G. Figueroa; Ruth Durrer; Juan Garcia-Bellido
2009-08-20
Gravitational waves were copiously produced in the early Universe whenever the processes taking place were sufficiently violent. The spectra of several of these gravitational wave backgrounds on subhorizon scales have been extensively studied in the literature. In this paper we analyze the shape and amplitude of the gravitational wave spectrum on scales which are superhorizon at the time of production. Such gravitational waves are expected from the self ordering of randomly oriented scalar fields which can be present during a thermal phase transition or during preheating after hybrid inflation. We find that, if the gravitational wave source acts only during a small fraction of the Hubble time, the gravitational wave spectrum at frequencies lower than the expansion rate at the time of production behaves as $\\Omega_{\\rm GW}(f) \\propto f^3$ with an amplitude much too small to be observable by gravitational wave observatories like LIGO, LISA or BBO. On the other hand, if the source is active for a much longer time, until a given mode which is initially superhorizon ($k\\eta_* \\ll 1$), enters the horizon, for $k\\eta \\gtrsim 1$, we find that the gravitational wave energy density is frequency independent, i.e. scale invariant. Moreover, its amplitude for a GUT scale scenario turns out to be within the range and sensitivity of BBO and marginally detectable by LIGO and LISA. This new gravitational wave background can compete with the one generated during inflation, and distinguishing both may require extra information.
Substructure in the Hubble Frontier Fields clusters from weak lensing flexion measurements
NASA Astrophysics Data System (ADS)
Rexroth, Markus
2015-08-01
Flexion is the second order weak gravitational lensing effect which is responsible for the arclike appearance of lensed sources. Its strong signal in the intermediate regime and the orthogonality to the shear field make flexion an ideal complement to today's strong and weak lensing measurements. Furthermore, its high sensitivity to local density peaks makes it a great tool for detecting substructure and increasing the resolution of mass maps. The strength of the Hubble Frontier Fields clusters and the high quality of the data make these objects a prime target for flexion measurements. We present an automated measurement pipeline and substructure constraints from its application to the clusters MACSJ0416.1-2403 and Abell 2744.
Neutron interference in the gravitational field of a ring laser
NASA Astrophysics Data System (ADS)
Fischetti, Robert D.; Mallett, Ronald L.
2015-07-01
The neutron split-beam interferometer has proven to be particularly useful in measuring Newtonian gravitational effects such as those studied by Colella, Overhauser, and Werner (COW). The development of the ring laser has led to numerous applications in many areas of physics including a recent general relativistic prediction of frame dragging in the gravitational field produced by the electromagnetic radiation in a ring laser. This paper introduces a new general technique based on a canonical transformation of the Dirac equation for the gravitational field of a general linearized spacetime. Using this technique it is shown that there is a phase shift in the interference of two neutron beams due to the frame-dragging nature of the gravitational field of a ring laser.
NASA Computational Case Study: Modeling Planetary Magnetic and Gravitational Fields
NASA Technical Reports Server (NTRS)
Simpson, David G.; Vinas, Adolfo F.
2014-01-01
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.
Magnetic Field in the Gravitationally Stratified Coronal Loops
NASA Astrophysics Data System (ADS)
Dwivedi, B. N.; Srivastava, A. K.
2015-03-01
We study the effect of gravitational stratification on the estimation of magnetic fields in the coronal loops. By using the method of MHD seismology of kink waves for the estimation of magnetic field of coronal loops, we derive a new formula for the magnetic field considering the effect of gravitational stratification. The fast-kink wave is a potential diagnostic tool for the estimation of magnetic field in fluxtubes. We consider the eleven kink oscillation cases observed by TRACE between July 1998 and June 2001. We calculate magnetic field in the stratified loops ( B str) and compare them with the previously calculated absolute magnetic field ( B abs). The gravitational stratification efficiently affects the magnetic field estimation in the coronal loops as it affects also the properties of kink waves. We find ?22% increment in the magnetic field for the smallest ( L = 72 Mm) while ? 42% increment in the absolute magnetic field for the longest ( L = 406 Mm) coronal loops. The magnetic fields B str and B abs also increase with the number density, if the loop length does not vary much. The increment in the magnetic field due to gravitational stratification is small at the lower number densities, however, it is large at the higher number densities. We find that damping time of kink waves due to phase-mixing is less in the case of gravitationally stratified loops compared to nonstratified ones. This indicates the more rapid damping of kink waves in the stratified loops. In conclusion, we find that the gravitational stratification efficiently affects the estimation of magnetic field and damping time estimation especially in the longer coronal loops.
Quantum physics in inertial and gravitational fields
G. Papini
2003-04-22
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.
Wittman; Tyson; Kirkman; Dell'Antonio; Bernstein
2000-05-11
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 matter in the foreground. The patterns of the induced distortions reflect the density of mass along the line of sight and its distribution, and the resulting 'cosmic shear' can be used to distinguish between alternative cosmologies. But previous attempts to measure this effect have been inconclusive. Here we report the detection of cosmic shear on angular scales of up to half a degree using 145,000 galaxies and along three separate lines of sight. We find that the dark matter is distributed in a manner consistent with either an open universe, or a flat universe that is dominated by a cosmological constant. Our results are inconsistent with the standard cold-dark-matter model. PMID:10821262
Vacuum entanglement enhancement by a weak gravitational field
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
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.
Energy Density, Pressure, and Particles Produced by a Spherical, Static Gravitational Field
NASA Astrophysics Data System (ADS)
Massacand, Christophe M.
We compute the energy density and pressures due to the quantum production of particles of a scalar field. This scalar field propagates in the external gravitational field of a (3+1)-dimensional, spherically symmetric, static geometry with flat spatial sections. We assume that the gravitational potential is weak, and we work to the first order in the strength of this potential. We consider only the l=0 sector of the scalar field. Our method for computing the energy density is based on the gauge-invariant definition of particles and normal ordering with respect to the energy measurable on a hypersurface with no extrinsic curvature. The initial state of the quantum field is the gauge-invariant vacuum on one of these hypersurfaces. Our computations are finite step by step. For the pressures we use the covariant conservation of T?? and its four-dimensional trace. We apply our results to the gravitational potential of a homogeneous spherical body. At late times, i.e. when all switch-on effects are far away from the body, the result is that a static, gravitational vacuum polarization cloud of energy and pressure is formed inside and outside the body.
Andrew J. Barber; Peter A. Thomas; H. M. P. Couchman; C. J. Fluke
2000-02-23
We present the results of weak gravitational lensing statistics in four different cosmological $N$-body simulations. The data has been generated using an algorithm for the three-dimensional shear, which makes use of a variable softening facility for the $N$-body particle masses, and enables a physical interpretation for the large-scale structure to be made. Working in three-dimensions also allows the correct use of the appropriate angular diameter distances. Our results are presented on the basis of the filled beam approximation in view of the variable particle softening scheme in our algorithm. The importance of the smoothness of matter in the universe for the weak lensing results is discussed in some detail. The low density cosmology with a cosmological constant appears to give the broadest distributions for all the statistics computed for sources at high redshifts. In particular, the range in magnification values for this cosmology has implications for the determination of the cosmological parameters from high-redshift Type Ia Supernov\\ae. The possibility of determining the density parameter from the non-Gaussianity in the probability distribution for the convergence is discussed.
Gravitational radiation generated by cosmological phase transition magnetic fields
Kahniashvili, Tina; Kisslinger, Leonard; Stevens, Trevor
2010-01-15
We study gravitational waves generated by the cosmological magnetic fields induced via bubble collisions during the electroweak (EW) and QCD phase transitions. The magnetic field generation mechanisms considered here are based on the use of the fundamental EW minimal supersymmetric and QCD Lagrangians. The gravitational waves spectrum is computed using a magnetohydrodynamic turbulence model. We find that the gravitational wave spectrum amplitude generated by the EW phase transition peaks at a frequency of approximately 1-2 mHz, and is of the order of 10{sup -20}-10{sup -21}; thus this signal is possibly detectable by the Laser Interferometer Space Antenna (LISA). The gravitational waves generated during the QCD phase transition, however, are outside the LISA sensitivity bands.
Gravitational radiation in d>4 from effective field theory
Cardoso, Vitor [CENTRA, Department de Fisica, Instituto Superior Tecnico, Avenue Rovisco Pais 1, 1049-001 Lisboa (Portugal); Department of Physics and Astronomy, The University of Mississippi, University, Mississippi 38677-1848 (United States); Dias, Oscar J. C. [Departament de Fisica Fonamental, Universitat de Barcelona, Avenue Diagonal 647, E-08028 Barcelona (Spain); Department de Fisica e Centro de Fisica do Porto, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169 - 007 Porto (Portugal); Figueras, Pau [Center for Particle Theory and Department of Mathematical Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE (United Kingdom)
2008-11-15
Some years ago, a new powerful technique, known as the classical effective field theory, was proposed to describe classical phenomena in gravitational systems. Here we show how this approach can be useful to investigate theoretically important issues, such as gravitational radiation in any spacetime dimension. In particular, we derive for the first time the Einstein-Infeld-Hoffman Lagrangian and we compute Einstein's quadrupole formula for any number of flat spacetime dimensions.
The gravitational field of a disk. [for studying Saturn's rings
NASA Technical Reports Server (NTRS)
Krough, F. T.; Ng, E. W.; Snyder, W. V.
1982-01-01
The gravitational potential of a disk is given, as is the gravitational field at a point in space. It is pointed out that formulas for a ring can be obtained as the difference between the results presented here for two different values of the disk radius. Results are obtained in terms of elliptic integrals and it is shown how these functions can be computed efficiently. Formulas necessary for the computation of partial derivatives are also presented.
Why are living things sensitive to weak magnetic fields?
Liboff, Abraham R
2014-09-01
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
Does the charge of a body reduce its gravitational field?
V. Hushwater
2010-06-02
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.
Spin Hall effect induced by a gravitational field
Dartora, C.A., E-mail: cadartora@yahoo.com.b [Electrical Engineering Department, Federal University of Parana (UFPR) (Brazil); Cabrera, G.G. [Instituto de Fisica 'Gleb Wataghin', Universidade Estadual de Campinas (UNICAMP), C.P. 6165, Campinas 13.083-970 SP (Brazil)
2010-06-15
The experiment by Collela et al. (1975) evidenced in a striking manner how the gravitational field appears in quantum mechanics. Within the modern framework of gauge theories, one can ascribe such effect as due to gauge fields originated from fundamental symmetries of spacetime: local transformations of the Lorentz-Poincare group. When this gauge principle is applied to the Dirac equation, we obtain kinematical correlations between the gravitational field and the spin of the particles. The phenomenon is similar to the spin Hall effect found in condensed matter systems, although much smaller in magnitude. Actual measurements may require highly precision interferometric techniques with spin-polarized neutrons.
Unification of Gravitational and Electromagnetic Fields in Riemannian Geometry
Yi-Fang Chang
2009-06-12
The gravitational field and the source-free electromagnetic field can be unified preliminarily by the equations in the Riemannian geometry, both are contractions of im and ik, respectively. So it will be equivalent to the Yang gravitational equations. From this we can obtain the Lorentz equations of motion, the first system and second source-free system of Maxwell field equations. This unification can be included in the gauge theory, and the unified gauge group is GL(2,C), which is just the same as the gauge group of the Riemanian manifold.
Contributions of Spherical Harmonics to Magnetic and Gravitational Fields
NASA Technical Reports Server (NTRS)
Roithmayr, Carlos M.
2004-01-01
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.
Dalkarov, O D
2015-01-01
A study of gravitational properties of matter presents a fundamental interest. The possibility of investigation of quantum gravitational states of matter by the example of helium atom is shown. The capability of the existence of helium quantum states in the gravitational field of a cold neutron star is examined. Observation of such states is done with the help of rotating neutron star's magnetic field. Periodically changing magnetic field induces transitions between gravitational states of helium atom and leads to the appearance of gravitational transitions' spectral lines in gigahertz frequency range.
Using Gravitational Analogies to Introduce Elementary Electrical Field Theory Concepts
ERIC Educational Resources Information Center
Saeli, Susan; MacIsaac, Dan
2007-01-01
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…
Metaphors for the effects of weak, sequentially complex magnetic fields.
Persinger, M A
1997-08-01
Metaphors to explain the effects of weak, complex magnetic fields upon the neuromatrices of organisms are suggested. The ratio of the amplitude of the time-varying components to steady-state components for complex magnetic field for effective biological responses may display Weber values that are similar to those for the electrical activity of the brain, the detection of changes in sound pressure by the ear and for more classical sensory thresholds. The nonlinear, suprathreshold characteristic of weak magnetic field effects would be similar to the effective narrow windows of concentrations of ligands values for receptor subtypes with different affinities. Signals composed of trains of between 100 and 1000 successive, fast (1 to 3 msec.) transients, which would contain the most biological information, would require low amplitudes to which the substrates could respond and with which the neuromatrix could resonate. PMID:9293578
PROTOSTELLAR DISK FORMATION ENABLED BY WEAK, MISALIGNED MAGNETIC FIELDS
Krumholz, Mark R.; Crutcher, Richard M.; Hull, Charles L. H.
2013-04-10
The gas from which stars form is magnetized, and strong magnetic fields can efficiently transport angular momentum. Most theoretical models of this phenomenon find that it should prevent formation of large (>100 AU), rotationally supported disks around most protostars, even when non-ideal magnetohydrodynamic (MHD) effects that allow the field and gas to decouple are taken into account. Using recent observations of magnetic field strengths and orientations in protostellar cores, we show that this conclusion is incorrect. The distribution of magnetic field strengths is very broad, and alignments between fields and angular momentum vectors within protostellar cores are essentially random. By combining the field strength and misalignment data with MHD simulations showing that disk formation is expected for both weak and misaligned fields, we show that these observations imply that we should expect disk fractions of {approx}10%-50% even when protostars are still deeply embedded in their parent cores, and even if the gas is governed by ideal MHD.
On the gravitational scattering of gravitational waves
NASA Astrophysics Data System (ADS)
Sorge, Francesco
2015-02-01
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.
Anisotropic parametrized post-Newtonian gravitational metric field
NASA Technical Reports Server (NTRS)
Nordtvedt, K., Jr.
1976-01-01
The anisotropic generalization of the parameterized post-Newtonian (PPN) gravitational metric field is made for the case of theories with energy and momentum conservation laws. Such an anisotropic metric field will generally result in two-tensor or bimetric theories of gravity in an anisotropic universe. New anisotropic 3 x 3 spatial PPN matrices are introduced into the general metric expansion. Earth gravimeter measurements strongly restrict some anisotropies, while anisotropic inertial and gravitational mass for celestial bodies result from other combinations of the PPN matrices.
Probing Dark Energy via Weak Gravitational Lensing with the Supernova Acceleration Probe (SNAP)
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
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.
Weak magnetic fields in central stars of planetary nebulae?
NASA Astrophysics Data System (ADS)
Steffen, M.; Hubrig, S.; Todt, H.; Schöller, M.; Hamann, W.-R.; Sandin, C.; Schönberner, D.
2014-10-01
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)).
Zhang Pengjie, E-mail: pjzhang@shao.ac.c [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China)
2010-09-10
The galaxy intrinsic alignment is a severe challenge to precision cosmic shear measurement. We propose self-calibrating the induced gravitational shear-galaxy intrinsic ellipticity correlation (the GI correlation) in weak lensing surveys with photometric redshift measurements. (1) We propose a method to extract the intrinsic ellipticity-galaxy density cross-correlation (I-g) from the galaxy ellipticity-density measurement in the same redshift bin. (2) We also find a generic scaling relation to convert the extracted I-g correlation to the necessary GI correlation. We perform a concept study under simplified conditions and demonstrate its capability to significantly reduce GI contamination. We discuss the impact of various complexities on the two key ingredients of the self-calibration technique, namely the method for extracting the I-g correlation and the scaling relation between the I-g and the GI correlation. We expect that none of them will likely be able to completely invalidate the proposed self-calibration technique.
Pengjie Zhang
2010-07-14
The galaxy intrinsic alignment is a severe challenge to precision cosmic shear measurement. We propose to self-calibrate the induced gravitational shear-galaxy intrinsic ellipticity correlation (the GI correlation, \\citealt{Hirata04b}) in weak lensing surveys with photometric redshift measurement. (1) We propose a method to extract the intrinsic ellipticity-galaxy density cross correlation (I-g) from the galaxy ellipticity-density measurement in the same redshift bin. (2) We also find a generic scaling relation to convert the extracted I-g correlation to the demanded GI correlation. We perform concept study under simplified conditions and demonstrate its capability to significantly reduce the GI contamination. We discuss the impact of various complexities on the two key ingredients of the self-calibration technique, namely the method to extract the I-g correlation and the scaling relation between the I-g and the GI correlation. We expect none of them is likely able to completely invalidate the proposed self-calibration technique.
Weak-Field Gravity of Revolving Circular Cosmic Strings
Des J. Mc Manus; Michel A. Vandyck
1992-12-10
A weak-field solution of Einstein's equations is constructed. It is generated by a circular cosmic string revolving in its plane about the centre of the circle. (The revolution is introduced to prevent the string from collapsing.) This solution exhibits a conical singularity, and the corresponding deficit angle is the same as for a straight string of the same linear energy density, irrespective of the angular velocity of the string.
Direct measurements of electric fields in weak OH · · ? hydrogen bonds
Saggu, Miguel; Levinson, Nicholas M.; Boxer, Steven G.
2011-01-01
Hydrogen bonds and aromatic interactions are of widespread importance in chemistry, biology and materials science. Electrostatics play a fundamental role in these interactions, but the magnitude of the electric fields that support them has not been quantified experimentally. Phenol forms a weak hydrogen bond complex with the ?-cloud of benzene and we used this as a model system to study the role of electric fields in weak OH · · ? hydrogen bonds. The effects of complex formation on the vibrational frequency of the phenol OH or OD stretches were measured in a series of benzene-based aromatic solvents. Large shifts are observed and these can be converted into electric fields via the measured vibrational Stark effect. A comparison of the measured fields with quantum chemical calculations demonstrates that calculations performed in the gas-phase are surprisingly effective at capturing the electrostatics observed in solution. The results provide quantitative measurements of the magnitude of electric fields and electrostatic binding energies in these interactions and suggest that electrostatics dominate them. The combination of vibrational Stark effect (VSE) measurements of electric fields and high-level quantum chemistry calculations is a general strategy for quantifying and characterizing the origins of intermolecular interactions. PMID:21936553
Weak and strong field approximations and circular orbits of Kehagias-Sfetsos space-time
M. Dwornik; Zs. Horváth; L. Á. Gergely
2013-12-16
The Kehagias-Sfetsos asymptotically flat black hole and naked singularity solutions of Ho\\v{r}ava-Lifshitz gravity are investigated both in the weak-field and strong-field regimes. In the weak-field limit the gravitational field generated by the Kehagias-Sfetsos spherically symmetric solution is weaker then in the case of the Schwarzschild black hole of general relativity. In the strong-field regime naked singularities with $\\omega_{0} \\ll 1 $ display an unusual distance dependence: gravity becomes weaker when approaching the singularity. The stability of circular orbits is also analyzed. While in the black hole case the square of the angular momentum should be larger than a certain finite, non-zero minimal value, in the naked singularity case there are stable circular orbits for any non-zero value of the angular momentum. In this regime we prove the existence of an infimum of the allowed radii of circular orbits (corresponding to vanishing angular momentum).
Scalar field as a time variable during gravitational evolution
Nakonieczna, Anna
2015-01-01
Using a scalar field as an intrinsic 'clock' while investigating the dynamics of gravitational systems has been successfully pursued in various researches on the border between classical and quantum gravity. The objective of our research was to check explicitly whether the scalar field can serve as a time variable during dynamical evolution of the matter-geometry system, especially in regions of high curvature, which are essential from the perspective of quantum gravity. For this purpose, we analyzed a gravitational collapse of a self-interacting scalar field within the framework of general relativity. The obtained results indicated that the hypersurfaces of constant scalar field are spacelike in dynamical regions nearby the singularities formed during the investigated process. The scalar field values change monotonically in the areas, in which the constancy hypersurfaces are spacelike.
Electromagnetic Waves in a Uniform Gravitational Field and Planck's Postulate
L. Acedo; M. M. Tung
2015-05-27
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 resulting gravitational time-dilation near these masses gives rise to a frequency change of any periodic process, including electromagnetic oscillations as the wave propagates across the gravitational field. This phenomenon can be tackled with classical electrodynamics assuming a curved spacetime background and Maxwell's equations in a generally covariant form. In the present paper, we show that in a classical field-theoretical context the gravitational redshift can be interpreted as the propagation of electromagnetic waves in a medium with corresponding conductivity $\\sigma=g/(\\mu_0 c^3)$, where $g$ is the gravitational acceleration and $\\mu_0$ is the vacuum magnetic permeability. Moreover, the energy density of the wave remains proportional to its frequency in agreement with Planck's postulate.
Nbody Simulations and Weak Gravitational Lensing using new HPC-Grid resources: the PI2S2 project
NASA Astrophysics Data System (ADS)
Becciani, U.; Antonuccio-Delogu, V.; Costa, A.; Comparato, M.
2008-08-01
We present the main project of the new grid infrastructure and the researches, that have been already started in Sicily and will be completed by next year. The PI2S2 project of the COMETA consortium is funded by the Italian Ministry of University and Research and will be completed in 2009. Funds are from the European Union Structural Funds for Objective 1 regions. The project, together with a similar project called Trinacria GRID Virtual Laboratory (Trigrid VL), aims to create in Sicily a computational grid for e-science and e-commerce applications with the main goal of increasing the technological innovation of local enterprises and their competition on the global market. PI2S2 project aims to build and develop an e-Infrastructure in Sicily, based on the grid paradigm, mainly for research activity using the grid environment and High Performance Computer systems. As an example we present the first results of a new grid version of FLY a tree Nbody code developed by INAF Astrophysical Observatory of Catania, already published in the CPC program Library, that will be used in the Weak Gravitational Lensing field.
Torsionally-gravitating charged matter fields and quanta
NASA Astrophysics Data System (ADS)
Fabbri, Luca
2015-10-01
In the present article we shall consider the torsional completion of a gravitational background that is filled with electrodynamically interacting material fields, taken to be of fermionic type, eventually deriving properties like the impossibility of singularities and the possibility of confinement, both necessary for a correct quantum description.
Gravitational and electromagnetic fields of a charged tachyon
K. S. Virbhadra
1995-09-21
An axially symmetric exact solution of the Einstein-Maxwell equations is obtained and is interpreted to give the gravitational and electromagnetic fields of a charged tachyon. Switching off the charge parameter yields the solution for the uncharged tachyon which was earlier obtained by Vaidya. The null surfaces for the charged tachyon are discussed.
Torsionally-gravitating charged matter fields and quanta
Luca Fabbri
2015-03-17
In the present article we shall consider the torsional completion of a gravitational background that is filled with electrodynamically interacting material fields, taken to be of fermionic type, eventually deriving properties like the impossibility of singularities and the possibility of confinement, both necessary for a correct quantum description.
A complete set of observables for cylindrically symmetric gravitational fields
C. G. Torre
1991-01-01
The author constructs a complete set of observables on the infinite-dimensional phase space of cylindrically symmetric gravitational fields. These observables have vanishing Poisson brackets with all constraint functions of the theory and are complete in the sense that any 'gauge invariant' function can, on the constraint surface, be expressed as a function of the observables. The key to the isolation
M. A. Troxel; Mustapha Ishak
2014-12-07
The wealth of incoming and future cosmological observations will allow us to map out the structure and evolution of the observable universe to an unprecedented level of precision. Among these observations is the weak gravitational lensing of galaxies, e.g., cosmic shear that measures the minute distortions of background galaxy images by intervening cosmic structure. Weak lensing and cosmic shear promise to be a powerful probe of astrophysics and cosmology, constraining models of dark energy, measuring the evolution of structure in the universe, and testing theories of gravity on cosmic scales. However, the intrinsic alignment of galaxies -- their shape and orientation before being lensed -- may pose a great challenge to the use of weak gravitational lensing as an accurate cosmological probe, and has been identified as one of the primary physical systematic biases in cosmic shear studies. Correlations between this intrinsic alignment and the lensing signal can persist even for large physical separations, and isolating the effect of intrinsic alignment from weak lensing is not trivial. A great deal of work in the last two decades has been devoted to understanding and characterizing this intrinsic alignment, which is also a direct and complementary probe of structure formation and evolution in its own right. In this review, we report in a systematic way the state of our understanding of the intrinsic alignment of galaxies, with a particular emphasis on its large-scale impact on weak lensing measurements and methods for its isolation or mitigation. (Abridged)
Gravitational cubic interactions for a massive mixed symmetry gauge field
NASA Astrophysics Data System (ADS)
Zinoviev, Yu M.
2012-01-01
In a recent paper (Boulanger et al 2011 J. Phys. A: Math. Theor. 44 415403), cubic gravitational interactions for a massless mixed symmetry field in an AdS space have been constructed. In the current paper, we extend these results to the case of massive field. We work in a Fradkin-Vasiliev approach and use a frame-like gauge-invariant description for the massive field which works in the AdS spaces with arbitrary values of the cosmological constant including a flat Minkowski space. In this, the massless limit in the AdS space coincides with the results of Boulanger et al (2011) while we show that it is impossible to switch on a gravitational interaction for the massless field in the dS space.
Tail terms in gravitational radiation reaction via effective field theory
S. Foffa; R. Sturani
2012-12-24
Gravitational radiation reaction affects the dynamics of gravitationally bound binary systems. Here we focus on the leading "tail" term which modifies binary dynamics at fourth post-Newtonian order, as first computed by Blanchet and Damour. We re-produce this result using effective field theory techniques in the framework of the Lagrangian formalism suitably extended to include dissipation effects. We recover the known logarithmic tail term, consistently with the recent interpretation of the logarithmic tail term in the mass parameter as a renormalization group effect of the Bondi mass of the system.
Hirata, Christopher M.; Cutler, Curt
2010-06-15
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.
Strong field limit analysis of gravitational retro-lensing
Ernesto F. Eiroa; Diego F. Torres
2003-12-12
We present a complete treatment in the strong field limit of gravitational retro-lensing by a static spherically symmetric compact object having a photon sphere. The results are compared with those corresponding to ordinary lensing in similar strong field situations. As examples of application of the formalism, a supermassive black hole at the galactic center and a stellar mass black hole in the galactic halo are studied as retro-lenses, in both cases using the Schwarzschild and Reissner-Nordstrom geometries.
Strong field limit analysis of gravitational retro-lensing
Eiroa, E F; Eiroa, Ernesto F.; Torres, Diego F.
2004-01-01
We present a complete treatment in the strong field limit of gravitational retro-lensing by a static spherically symmetric compact object having a photon sphere. The results are compared with those corresponding to ordinary lensing in similar strong field situations. As examples of application of the formalism, a supermassive black hole at the galactic center and a stellar mass black hole in the galactic halo are studied as retro-lenses, in both cases using the Schwarzschild and Reissner-Nordstrom geometries.
On naked singularities and the collapse of self-gravitating Higgs fields
Mihalis Dafermos
2004-11-02
We consider the problem of collapse of a self-gravitating Higgs field, with potential bounded below by a (possibly negative) constant. The behaviour at infinity may be either asymptotically flat or asymptotically AdS. This problem has received much attention as a source for possible violations of weak cosmic censorship in string theory. In this paper, we prove under spherical symmetry that ``first singularities'' arising in the non-trapped region must necessarily emanate from the centre. In particular, this excludes the formation of a certain type of naked singularity which was recently conjectured to occur.
Effects of Electromagnetic Field on Gravitational Collapse
M. Sharif; G. Abbas
2009-05-16
In this paper, the effect of electromagnetic field has been investigated on the spherically symmetric collapse with the perfect fluid in the presence of positive cosmological constant. Junction conditions between the static exterior and non-static interior spherically symmetric spacetimes are discussed. We study the apparent horizons and their physical significance. It is found that electromagnetic field reduces the bound of cosmological constant by reducing the pressure and hence collapsing process is faster as compared to the perfect fluid case. This work gives the generalization of the perfect fluid case to the charged perfect fluid. Results for the perfect fluid case are recovered.
Physical decomposition of the gauge and gravitational fields
Chen Xiangsong; Zhu Benchao
2011-04-15
Physical decomposition of the non-Abelian gauge field has recently helped to achieve a meaningful gluon spin. Here we extend this approach to gravity and attempt a meaningful gravitational energy. The metric is unambiguously separated into a pure geometric term which contributes a 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 pseudotensors of the gravitational stress-energy are easily rescued to produce a definite physical result. Our decomposition applies to any symmetric tensor, and has an interesting relation to the transverse-traceless decomposition discussed by Arnowitt, Deser and Misner, and by York.
Tachyon motion in a black hole gravitational field
V. M. Lipunov
2013-01-23
The motion of superluminal particles in the gravitational field of a non-rotating black hole is analyzed. The relativistic Hamilton-Jacobi equation is solved for particles with imaginary rest mass. It is shown that there are no stable circular orbits and generally no finite motions for tachyons in the Schwarzschild metric and that all unstable circular tachyon orbits lie in a region extending from the gravitational radius to 1.5 times that radius. The particles with speeds exceeding the speed of light are noticed to be able to escape from the space limited by the gravitational radius. The results also indicate that low-energy tachyons near a black hole may acquire higher energies and that this in turn may lead to observable effects.
Quark deconfinement and gluon condensate in a weak magnetic field
Ayala, Alejandro; Hernandez, L A; Loewe, M; Rojas, Juan Cristobal; Villavicencio, Cristian
2015-01-01
We study QCD finite energy sum rules (FESR) for the axial-vector current correlator in the presence of a magnetic field, in the weak field limit and at zero temperature. We find that the perturbative QCD as well as the hadronic contribution to the sum rules get explicit magnetic field-dependent corrections and that these in turn induce a magnetic field dependence on the deconfinement phenomenological parameter s_0 and on the gluon condensate. The leading corrections turn out to be quadratic in the field strength. We find from the dimension d=2 first FESR that the magnetic field dependence of s_0 is proportional to the absolute value of the light-quark condensate. Hence, it increases with increasing field strength. This implies that the parameters describing chiral symmetry restoration and deconfinement behave similarly as functions of the magnetic filed. Thus, at zero temperature the magnetic field is a catalysing agent of both chiral symmetry breaking and confinement. From the dimension d=4 second FESR we ob...
Gravitational collapse of homogeneous scalar fields
Roberto Giambó
2005-05-27
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.
Gravitational Field of a Charged Particle with a Field Mass in Three-Dimensional Electrodynamics
NASA Astrophysics Data System (ADS)
Pevzner, M. Sh.
2015-08-01
In three-dimensional electrodynamics in the Newtonian approximation the gravitational field of a charged particle with a field mass of classical origin has been investigated; the potential and the intensity of the gravitational field have been calculated, both taking the contribution of polarization of the fermion vacuum to the classical potential of the electric field into account and without taking it into account. It has been shown that taking the polarization of the vacuum into account, both with massive fermions in the vacuum loops and with massless fermions in the vacuum loops, does not alter the asymptotic behavior or the intensity of the gravitational field at large distances, which is evidence of the presence of gravitational confinement. The influence of the simplifications made here on the final results is discussed, as are also prospects for their improvement.
Jet deflection by very weak guide fields during magnetic reconnection.
Goldman, M V; Lapenta, G; Newman, D L; Markidis, S; Che, H
2011-09-23
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(+) 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. PMID:22026861
BPS Dyon in a Weak Electromagnetic Field: Equations of Motion and Radiation Fields
Dongsu Bak; Choonkyu Lee
1994-02-09
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.
Was the Earth's Magnetic Field Weak in the Late Devonian?
NASA Astrophysics Data System (ADS)
Anwar, T.; Biggin, A. J.; Kravchinsky, V. A.; Pavlov, V.
2014-12-01
Very few data exist to describe geomagnetic field behaviour in the Late Devonian (LD). Samples, which have recently been Ar-Ar dated to 364-377 Myr ago, of LD-aged volcanics and instrusives from the Viluy large igneous province in Siberia are investigated. These units have already demonstrated reliable, palaeomagnetic directions consistent with the retention of a primary remanence. Microwave Thellier-type palaeointensity experiments (mostly IZZI protocol with partial thermoremanent magnetization checks) were performed on 55 samples from 16 sites, of which, 12 samples from 4 sites provide satisfactory paleointensity data. Arai plots are strongly concave-up in shape but multiple lines of evidence support that this is caused by a strong component of magnetisation overprinting a weak primary magnetisation rather than by lab-induced alteration or multidomain behaviour. The samples display corresponding distinct directional components, positive pTRM checks and little or no zig-zagging of the Arai plot. Furthermore, the results of non-heating pseudo-Thellier experiments support the existence of a strong component overprinting a much weaker one. The site-mean paleointensities, ranging from 5.3-11.1 ?T and which correspond to a virtual axial dipole moments (VADMs) of (1.0-2.1) ×1022 Am2, indicate that the LD was a time of extremely weak magnetic field intensity. It provides the evidence that the superchron state, between ~310 and 265 Myr ago, is preceded by very weak field in the LD (~60 Myr before the superchron). If low dipole moment can be considered an indicator of high reversal frequency (as appears to be the case in the mid-Jurassic) then our results support that rapid transitions between reversal hyperactivity and superchron states are a recurring feature in the palaeomagnetic record, potentially linked to simultaneous episodes of true polar wander.
Differentiation of optical isomers through enhanced weak-field interactions
NASA Technical Reports Server (NTRS)
Aronowitz, S.
1980-01-01
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.
Diffusion of relativistic gas mixtures in gravitational fields
Gilberto M. Kremer
2013-03-26
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.
Gravitational waves from stochastic relativistic sources: primordial turbulence and magnetic fields
Durrer, Ruth
in gravitational wave energy on super-horizon scales. Turbulence instead acts as a source for gravitational waves. The potential detection of a gravitational wave background of primordial origin provides an ob- servationalGravitational waves from stochastic relativistic sources: primordial turbulence and magnetic fields
Optimal weak lensing tomography for CFHTLenS
Grocutt, Emma Liana
2012-11-28
Weak gravitational lensing is a powerful astronomical tool for constraining cosmological parameters that is entering its prime. Lensing occurs because gravitational fields deflect light rays and measuring this deflection ...
The Energy-Momentum Tensor for the Gravitational Field
S V Babak; L P Grishchuk
1999-10-30
The search for the gravitational energy-momentum tensor is often qualified as an attempt of looking for ``the right answer to the wrong question''. This position does not seem convincing to us. We think that we have found the right answer to the properly formulated question. We have further developed the field theoretical formulation of the general relativity which treats gravity as a non-linear tensor field in flat space-time. The Minkowski metric is a reflection of experimental facts, not a possible choice of the artificial ``prior geometry''. In this approach, we have arrived at the gravitational energy-momentum tensor which is: 1) derivable from the Lagrangian in a regular prescribed way, 2) tensor under arbitrary coordinate transformations, 3) symmetric in its components, 4) conserved due to the equations of motion derived from the same Lagrangian, 5) free of the second (highest) derivatives of the field variables, and 6) is unique up to trivial modifications not containing the field variables. There is nothing else, in addition to these 6 conditions, that one could demand from an energy-momentum object, acceptable both on physical and mathematical grounds. The derived gravitational energy-momentum tensor should be useful in practical applications.
New symbolic tools for differential geometry, gravitation, and field theory
NASA Astrophysics Data System (ADS)
Anderson, I. M.; Torre, C. G.
2012-01-01
DifferentialGeometry is a Maple software package which symbolically performs fundamental operations of calculus on manifolds, differential geometry, tensor calculus, spinor calculus, Lie algebras, Lie groups, transformation groups, jet spaces, and the variational calculus. These capabilities, combined with dramatic recent improvements in symbolic approaches to solving algebraic and differential equations, have allowed for development of powerful new tools for solving research problems in gravitation and field theory. The purpose of this paper is to describe some of these new tools and present some advanced applications involving: Killing vector fields and isometry groups, Killing tensors, algebraic classification of solutions of the Einstein equations, and symmetry reduction of field equations.
Riemannian and Teleparallel Descriptions of the Scalar Field Gravitational Interaction
V. C. de Andrade; J. G. Pereira
1997-08-25
A comparative study between the metric and the teleparallel descriptions of gravitation is made for the case of a scalar field. In contrast to the current belief that only spin matter could detect the teleparallel geometry, scalar matter being able to feel the metric geometry only, we show that a scalar field is able not only to feel anyone of these geometries, but also to produce torsion. Furthermore, both descriptions are found to be completely equivalent, which means that in fact, besides coupling to curvature, a scalar field couples also to torsion.
Effective field theory of weakly coupled inflationary models
Rhiannon Gwyn; Gonzalo A. Palma; Mairi Sakellariadou; Spyros Sypsas
2013-04-04
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 \\omega ~ p^2. In addition, provided that modes crossed the horizon within this energy range, the prediction of inflationary observables - including non-Gaussian signatures - are significantly affected by the new scales characterizing it.
Effective field theory of weakly coupled inflationary models
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
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.
Comparison of two field theoretical forms of gravitational wave equations
A. I. Nikishov
2004-08-08
In the lowest nonlinear approximation I compare two gravitational wave equations,- those of Weinberg and Papapetrou. The first one is simply a form of Einstein equation and the second is claimed to be yet another field theoretical form in which the energy-momentum tensor is obtained by Belinfante or Rosenfeld method. I show that for interacting gravitational field these methods lead to different energy-momentum tensors. Both these tensors need to be complemented "by hand" with some interaction energy-momentum tensors in order that the conservation laws of the total energy-momentum tensor give equation of motion for particles in agreement with general relativity. In approximation considered by Thirring, the Papapetrou wave equation must coincide with that of Thirring. But they differ because Thirring inserted the necessary interaction term. I show that Thirring wave equation is equivalent to Weinberg's one. Hence the Papapetrou equation is not yet another form of Einstein equation.
The effects of weak magnetic fields on radical pairs.
Barnes, Frank S; Greenebaum, Ben
2015-01-01
It is proposed that radical concentrations can be modified by combinations of weak, steady and alternating magnetic fields that modify the population distribution of the nuclear and electronic spin state, the energy levels and the alignment of the magnetic moments of the components of the radical pairs. In low external magnetic fields, the electronic and nuclear angular momentum vectors are coupled by internal forces that outweigh the external fields' interactions and are characterized in the Hamiltonian by the total quantum number F. Radical pairs form with their unpaired electrons in singlet (S) or triplet (T) states with respect to each other. At frequencies corresponding to the energy separation between the various states in the external magnetic fields, transitions can occur that change the populations of both electron and nuclear states. In addition, the coupling between the nuclei, nuclei and electrons, and Zeeman shifts in the electron and nuclear energy levels can lead to transitions with resonances spanning frequencies from a few Hertz into the megahertz region. For nuclear energy levels with narrow absorption line widths, this can lead to amplitude and frequency windows. Changes in the pair recombination rates can change radical concentrations and modify biological processes. The overall conclusion is that the application of magnetic fields at frequencies ranging from a few Hertz to microwaves at the absorption frequencies observed in electron and nuclear resonance spectroscopy for radicals can lead to changes in free radical concentrations and have the potential to lead to biologically significant changes. PMID:25399679
Generalized Fubini instantons of a self-gravitating scalar field
NASA Astrophysics Data System (ADS)
Lee, Bum-Hoon; Lee, Wonwoo; Ro, Daeho; Yeom, Dong-han
2014-09-01
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.
Probing the Brans-Dicke Gravitational Field by Cerenkov Radiation
G. Lambiase
2001-10-25
The possibility that a charged particle propagating in a gravitational field described by Brans-Dicke theory of gravity could emit Cerenkov radiation is explored. This process is kinematically allowed depending on parameters occurring in the theory. The Cerenkov effect disappears as the BD parameter omega tends to inftinity, i.e. in the limit in which the Einstein theory is recovered, giving a signature to probe the validity of the Brans-Dicke theory.
The Electric Field of a Weakly Electric Fish
NASA Astrophysics Data System (ADS)
Rasnow, Brian K.
Freshwater fish of the genus Apteronotus (family Gymnotidae) generate a weak, high frequency electric field (<100 mV/cm, 0.5-10 kHz) which permeates their local environment. These nocturnal fish are acutely sensitive to perturbations in their electric field caused by other electric fish, and nearby objects whose impedance is different from the surrounding water. This thesis presents high temporal and spatial resolution maps of the electric potential and field on and near Apteronotus. The fish's electric field is a complicated and highly stable function of space and time. Its characteristics, such as spectral composition, timing, and rate of attenuation, are examined in terms of physical constraints, and their possible functional roles in electroreception. Temporal jitter of the periodic field is less than 1 musec. However, electrocyte activity is not globally synchronous along the fish's electric organ. The propagation of electrocyte activation down the fish's body produces a rotation of the electric field vector in the caudal part of the fish. This may assist the fish in identifying nonsymmetrical objects, and could also confuse electrosensory predators that try to locate Apteronotus by following its fieldlines. The propagation also results in a complex spatiotemporal pattern of the EOD potential near the fish. Visualizing the potential on the same and different fish over timescales of several months suggests that it is stable and could serve as a unique signature for individual fish. Measurements of the electric field were used to calculate the effects of simple objects on the fish's electric field. The shape of the perturbation or "electric image" on the fish's skin is relatively independent of a simple object's size, conductivity, and rostrocaudal location, and therefore could unambiguously determine object distance. The range of electrolocation may depend on both the size of objects and their rostrocaudal location. Only objects with very large dielectric constants cause appreciable phase shifts, and these are strongly dependent on the water conductivity.
D. -S. Lee; P. N. McGraw; Y. J. Ng; I. A. Shovkovy
1998-10-19
The effective potential for the composite fields responsible for chiral symmetry breaking in weakly coupled QED in a magnetic field is derived. The global minimum of the effective potential is found to acquire a non-vanishing expectation value of the composite fields that leads to generating the dynamical fermion mass by an external magnetic field. The results are compared with those for the Nambu-Jona-Lasinio model.
Weak scattering of scalar and electromagnetic random fields
NASA Astrophysics Data System (ADS)
Tong, Zhisong
This dissertation encompasses several studies relating to the theory of weak potential scattering of scalar and electromagnetic random, wide-sense statistically stationary fields from various types of deterministic or random linear media. The proposed theory is largely based on the first Born approximation for potential scattering and on the angular spectrum representation of fields. The main focus of the scalar counterpart of the theory is made on calculation of the second-order statistics of scattered light fields in cases when the scattering medium consists of several types of discrete particles with deterministic or random potentials. It is shown that the knowledge of the correlation properties for the particles of the same and different types, described with the newly introduced pair-scattering matrix, is crucial for determining the spectral and coherence states of the scattered radiation. The approach based on the pair-scattering matrix is then used for solving an inverse problem of determining the location of an "alien" particle within the scattering collection of "normal" particles, from several measurements of the spectral density of scattered light. Weak scalar scattering of light from a particulate medium in the presence of optical turbulence existing between the scattering centers is then approached using the combination of the Born's theory for treating the light interaction with discrete particles and the Rytov's theory for light propagation in extended turbulent medium. It is demonstrated how the statistics of scattered radiation depend on scattering potentials of particles and the power spectra of the refractive index fluctuations of turbulence. This theory is of utmost importance for applications involving atmospheric and oceanic light transmission. The second part of the dissertation includes the theoretical procedure developed for predicting the second-order statistics of the electromagnetic random fields, such as polarization and linear momentum, scattered from static media. The spatial distribution of these properties of scattered fields is shown to be substantially dependent on the correlation and polarization properties of incident fields and on the statistics of the refractive index distribution within the scatterers. Further, an example is considered which illustrates the usefulness of the electromagnetic scattering theory of random fields in the case when the scattering medium is a thin bio-tissue layer with the prescribed power spectrum of the refractive index fluctuations. The polarization state of the scattered light is shown to be influenced by correlation and polarization states of the illumination as well as by the particle size distribution of the tissue slice.
The angular momentum of the gravitational field and the Poincare group
J. W. Maluf; S. C. Ulhoa; F. F. Faria; J. F. da Rocha-Neto
2006-09-06
We redefine the gravitational angular momentum in the framework of the teleparallel equivalent of general relativity. In similarity to the gravitational energy-momentum, the new definition for the gravitational angular momentum is coordinate independent. By considering the Poisson brackets in the phase space of the theory, we find that the gravitational energy-momentum and angular momentum correspond to a representation of the Poincar\\'e group. This result allows us to define Casimir type invariants for the gravitational field.
New Techniques for Analysing Axisymmetric Gravitational Systems. 1. Vacuum Fields
Chris Doran; Anthony Lasenby
2002-11-21
A new framework for analysing the gravitational fields in a stationary, axisymmetric configuration is introduced. The method is used to construct a complete set of field equations for the vacuum region outside a rotating source. These equations are under-determined. Restricting the Weyl tensor to type D produces a set of equations which can be solved, and a range of new techniques are introduced to simplify the problem. Imposing the further condition that the solution is asymptotically flat yields the Kerr solution uniquely. The implications of this result for the no-hair theorem are discussed. The techniques developed here have many other applications, which are described in the conclusions.
The Gravitational Field of a Radiating Electromagnetic Dipole
Tim Adamo; Ezra T Newman
2008-07-22
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.
Hubble Frontier Fields : ``A New Era for Gravitational Lensing''
NASA Astrophysics Data System (ADS)
Jauzac, Mathilde; Eckert, Dominique; Jullo, Eric; Richard, Johan; Ebeling, Harald; Kneib, Jean-Paul; Limousin, Marceau; Atek, Hakim; Natarajan, Priyamvada; Rexroth, Markus
2015-08-01
The Hubble Frontier Fields (HFF) initiative constitutes the largest commitment ever of HST time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters.I will present the new gravitational lensing pictures of the first HFF complex clusters. We have demonstrated that we are now able to `weight’ these clusters' cores down to the percent level precision (recently published works), serving our quest for the high-redshift Universe.However, while the depth of these dataset makes these clusters amazing Cosmic Telescopes, it also enables us to get an unprecedented understanding of the cluster physics.Therefore, presenting the case of MACSJ0416 and Abell 2744, I will demonstrate the importance of such high-quality data to analyse the merging/dynamical history of the cluster itself while comparing dark matter, light and gas distributions.
Apparatus and method for producing an artificial gravitational field
NASA Technical Reports Server (NTRS)
Mccanna, Jason (inventor)
1993-01-01
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.
Quantum limit on time measurement in a gravitational field
NASA Astrophysics Data System (ADS)
Sinha, Supurna; Samuel, Joseph
2015-01-01
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.
The Negative Energy of Gravitation as Stabilizational Factor in Field Theory and Cosmology
Zakir, Z
1998-01-01
The left hand side of Einstein's equations G=-T is defined as the tensor of energy-momentum of gravitational field. Here the energy of gravitation is negative, the full energy of the system matter+gravitation is equal to zero and appeared a new process - the annihilation of matter and gravitation. As result, the cosmological constant is vanished, singularities not exist and black holes annihilated during the collaps. It is shown, that in field theories not need in mass renormalization because of automatical compensation of infinities by their own gravitational energy. The main surprise is the renormalizability of quantum gravity with negative energy of gravitational background.
Non-relativistic Limit of Dirac Equations in Gravitational Field and Quantum Effects of Gravity
NASA Astrophysics Data System (ADS)
Wu, Ning
2006-03-01
Based on unified theory of electromagnetic interactions and gravitational interactions, the non-relativistic limit of the equation of motion of a charged Dirac particle in gravitational field is studied. From the Schrödinger equation obtained from this non-relativistic limit, we can see that the classical Newtonian gravitational potential appears as a part of the potential in the Schrödinger equation, which can explain the gravitational phase effects found in COW experiments. And because of this Newtonian gravitational potential, a quantum particle in the earth's gravitational field may form a gravitationally bound quantized state, which has already been detected in experiments. Three different kinds of phase effects related to gravitational interactions are studied in this paper, and these phase effects should be observable in some astrophysical processes. Besides, there exists direct coupling between gravitomagnetic field and quantum spin, and radiation caused by this coupling can be used to directly determine the gravitomagnetic field on the surface of a star.
Non-Relativistic Limit of Dirac Equations in Gravitational Field and Quantum Effects of Gravity
Ning Wu
2005-04-23
Based on unified theory of electromagnetic interactions and gravitational interactions, the non-relativistic limit of the equation of motion of a charged Dirac particle in gravitational field is studied. From the Schrodinger equation obtained from this non-relativistic limit, we could see that the classical Newtonian gravitational potential appears as a part of the potential in the Schrodinger equation, which can explain the gravitational phase effects found in COW experiments. And because of this Newtonian gravitational potential, a quantum particle in earth's gravitational field may form a gravitationally bound quantized state, which had already been detected in experiments. Three different kinds of phase effects related to gravitational interactions are discussed in this paper, and these phase effects should be observable in some astrophysical processes. Besides, there exists direct coupling between gravitomagnetic field and quantum spin, radiation caused by this coupling can be used to directly determine the gravitomagnetic field on the surface of a star.
Saturn's fast spin determined from its gravitational field and oblateness
NASA Astrophysics Data System (ADS)
Helled, Ravit; Galanti, Eli; Kaspi, Yohai
2015-04-01
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.
Field theory and weak Euler-Lagrange equation for classical particle-field systems
Qin, Hong; Davidson, Ronald C
2015-01-01
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 underly...
Field theory and weak Euler-Lagrange equation for classical particle-field systems
Hong Qin; J. W. Burby; Ronald C. Davidson
2015-04-17
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.
Field theory and weak Euler-Lagrange equation for classical particle-field systems
NASA Astrophysics Data System (ADS)
Qin, Hong; Burby, Joshua W.; Davidson, Ronald C.
2014-10-01
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.
M. Bradac; M. Lombardi; P. Schneider
2004-07-01
Weak gravitational lensing is considered to be one of the most powerful tools to study the mass and the mass distribution of galaxy clusters. However, weak lensing mass reconstructions are plagued by the so-called mass-sheet degeneracy--the surface mass density \\kappa of the cluster can be determined only up to a degeneracy transformation \\kappa \\to \\kappa' = \\lambda \\kappa + (1 -\\lambda), where \\lambda is an arbitrary constant. This transformation fundamentally limits the accuracy of cluster mass determinations if no further assumptions are made. We discuss here a possibility to break the mass-sheet degeneracy in weak lensing mass maps using distortion and redshift information of background galaxies. Compared to other techniques proposed in the past, it does not rely on any assumptions on cluster potential and does not make use of weakly constrained information (such as the source number counts, used in the magnification effect).Our simulations show that we are effectively able to break the mass-sheet degeneracy for supercritical lenses and that for undercritical lenses the mass-sheet degeneracy is very difficult to be broken, even under idealised conditions.
Bradac, M; Schneider, P
2004-01-01
Weak gravitational lensing is considered to be one of the most powerful tools to study the mass and the mass distribution of galaxy clusters. However, weak lensing mass reconstructions are plagued by the so-called mass-sheet degeneracy--the surface mass density \\kappa of the cluster can be determined only up to a degeneracy transformation \\kappa \\to \\kappa' = \\lambda \\kappa + (1 -\\lambda), where \\lambda is an arbitrary constant. This transformation fundamentally limits the accuracy of cluster mass determinations if no further assumptions are made. We discuss here a possibility to break the mass-sheet degeneracy in weak lensing mass maps using distortion and redshift information of background galaxies. Compared to other techniques proposed in the past, it does not rely on any assumptions on cluster potential and does not make use of weakly constrained information (such as the source number counts, used in the magnification effect).Our simulations show that we are effectively able to break the mass-sheet degene...
QED plasma in a background of static gravitational fields
NASA Astrophysics Data System (ADS)
Brandt, F. T.; Frenkel, J.; Siqueira, J. B.
2014-02-01
We derive, in d-dimensional space-time, the effective Lagrangian of static gravitational fields interacting with a QED plasma at high temperature. Using the equivalence between the static hard thermal loops and those with zero external energy-momentum, we compute the effective Lagrangian up to two-loop order. We also obtain a nonperturbative contribution which arises from the sum of all infrared divergent ring diagrams. From the gauge and Weyl symmetries of the theory, we deduce to all orders that this effective Lagrangian is equivalent to the pressure of a QED plasma in Minkowski space-time, with the global temperature replaced by the Tolman local temperature.
On the role of pressure in generating the gravitational field
A. I. Nikishov
2009-12-28
The Einstein equations for static gravitational field depend on energy density and pressure. So one may expect that solutions should depend on two parameters: mass and its analogue originated from pressure. Yet the Schwarzschild solution have only mass parameter. So does its linear approximation. On the other hand the solutions of linearized Einstein equations, obtained using graviton propagator, contain mass and its pressure analogue. This suggests that a phenomenological approach to gravity, using propagators and many graviton vertices, should lead to a theory different from general relativity.
Remarks on the energy of the gravitational field
NASA Astrophysics Data System (ADS)
Ferraris, Marco; Francaviglia, Mauro
The problem of coherently defining Noether's currents in general relativity is examined. The study is based on the existence of a whole family of first-order Lagrangians for general relativity and the results of Ferraris and Francaviglia (1985) concerning energy and conserved quantities in higher-order field theories. A family of global covariant superpotentials is generated, including the purely gravitational part from the Hilbert Lagrangian and a superpotential describing the energy relative to the background. The use of these superpotentials in the asymptotically flat case is demonstrated with an example of calculations for a charged black hole represented by the Kerr-Newmann solution.
NASA Astrophysics Data System (ADS)
Rivera, Susana
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.
NASA Technical Reports Server (NTRS)
Eby, P. B.
1978-01-01
The construction of a clock based on the beta decay process is proposed to test for any violations by the weak interaction of the strong equivalence principle bu determining whether the weak interaction coupling constant beta is spatially constant or whether it is a function of gravitational potential (U). The clock can be constructed by simply counting the beta disintegrations of some suitable source. The total number of counts are to be taken a measure of elapsed time. The accuracy of the clock is limited by the statistical fluctuations in the number of counts, N, which is equal to the square root of N. Increasing N gives a corresponding increase in accuracy. A source based on the electron capture process can be used so as to avoid low energy electron discrimination problems. Solid state and gaseous detectors are being considered. While the accuracy of this type of beta decay clock is much less than clocks based on the electromagnetic interaction, there is a corresponding lack of knowledge of the behavior of beta as a function of gravitational potential. No predictions from nonmetric theories as to variations in beta are available as yet, but they may occur at the U/sg C level.
Gravitational fields and the cosmological constant in multidimensional Newtonian universes
Wilkins, D.
1986-08-01
The distance dependence of gravity is found in Newtonian universes with any number n-italic of space dimensions. Two independent derivations given are based either on (i) requiring that a (hyper) spherical mass gravitate as if all its mass were concentrated at its center, or (ii) using the field equations of general relativity with the cosmological constant ..lambda... Both approaches lead to identical results. The gravity field at distance r-italic from a point mass has two parts, one going as r-italic/sup 1-//sup n-italic/, the other as r-italic, i.e., Hooke's law. The Hookian field obeys a novel form of Gauss's (flux) law, and is closely related to ..lambda... The simple mechanical interpretation which emerges gives insight into the meaning of ..lambda.. and helps counteract certain prevalent misconceptions.
Effects of the Interaction of a Rotating Ideal Liquid with a Vortical Gravitational Field
NASA Astrophysics Data System (ADS)
Krechet, V. G.; Oshurko, V. B.; Rodichev, S. V.
2015-07-01
Stationary configurations of self-gravitating, rotating liquids with barotropic equation of state are considered within the framework of GTR. It is shown that such a rotating self-gravitating continuous medium can induce the formation of a vortical gravitational field, which can lead to the appearance of a geometry of spacetime with nontrivial topology, for example wormholes.
Hamber, Herbert W.
Nonlocal effective gravitational field equations and the running of Newton's constant G H. W, which are intended to incorporate the gravitational, vacuum-polarization induced, running of Newton to parametrize the gravitational running in the infrared region. If one is willing to accept such a scenario
Deep HST imaging of distant weak radio and field galaxies
NASA Technical Reports Server (NTRS)
Windhorst, R. A.; Gordon, J. M.; Pascarelle, S. M.; Schmidtke, P. C.; Keel, W. C.; Burkey, J. M.; Dunlop, J. S.
1994-01-01
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.
Cosmological equivalence principle and the weak-field limit
Wiltshire, David L. [Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8140 (New Zealand) and International Center for Relativistic Astrophysics Network (ICRANet), P.le della Repubblica 10, Pescara 65121 (Italy)
2008-10-15
The strong equivalence principle is extended in application to averaged dynamical fields in cosmology to include the role of the average density in the determination of inertial frames. The resulting cosmological equivalence principle is applied to the problem of synchronization of clocks in the observed universe. Once density perturbations grow to give density contrasts of order 1 on scales of tens of megaparsecs, the integrated deceleration of the local background regions of voids relative to galaxies must be accounted for in the relative synchronization of clocks of ideal observers who measure an isotropic cosmic microwave background. The relative deceleration of the background can be expected to represent a scale in which weak-field Newtonian dynamics should be modified to account for dynamical gradients in the Ricci scalar curvature of space. This acceleration scale is estimated using the best-fit nonlinear bubble model of the universe with backreaction. At redshifts z < or approx. 0.25 the scale is found to coincide with the empirical acceleration scale of modified Newtonian dynamics. At larger redshifts the scale varies in a manner which is likely to be important for understanding dynamics of galaxy clusters, and structure formation. Although the relative deceleration, typically of order 10{sup -10} ms{sup -2}, is small, when integrated over the lifetime of the universe it amounts to an accumulated relative difference of 38% in the rate of average clocks in galaxies as compared to volume-average clocks in the emptiness of voids. A number of foundational aspects of the cosmological equivalence principle are also discussed, including its relation to Mach's principle, the Weyl curvature hypothesis, and the initial conditions of the universe.
Gravitational Waves and Scalar Perturbations from Spectator Fields
Matteo Biagetti; Emanuela Dimastrogiovanni; Matteo Fasiello; Marco Peloso
2014-11-12
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.
Variations in Gravitational Field, Tidal Force, Electromagnetic Waves and Earthquakes
NASA Astrophysics Data System (ADS)
Strasser, Valentino
2010-12-01
This paper is the report on an experiment carried out between the month of December 2009 and the month of April 2010 between the Venetian Lagoon and the Northern Apennines in Italy, to check on a potential relationship between earthquakes and variations in the local gravitational field, the effect on the tide exercised by the interaction between the moon and the Sun, the appearance of anomalous light effects in the atmosphere ("Earth lights"), and the emission of radio waves caused by stresses in the Earth's crust. The cases studied show that there is indeed some concomitance between the periodic rising and falling of the sea level and the terrestrial tide effect, due to the gravitational attraction of the moon and sun on the Earth. In fact, changes in the local force of gravity coincided with the cycle of high and low tides and, in certain cases, with a variation in the electromagnetic field that preceded the occurrence of a seismic event by just a few hours. The o! bservations in the article are limited to the magnitude range discussed in the paper.
Iron snow zones as a mechanism for generating Mercury's weak observed magnetic field
Hauck II, Steven A.
(established from studies of the Earth's field), therefore, Mercury's dynamo must be unique in the solar systemIron snow zones as a mechanism for generating Mercury's weak observed magnetic field R. Vilim,1 S; published 12 November 2010. [1] The anomalously weak observed magnetic field of Mercury is difficult
Ning Wu; Dahua Zhang
2005-01-01
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
Biological effects due to weak magnetic fields on plants
NASA Astrophysics Data System (ADS)
Belyavskaya, N.
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.
Classical Gravitational Interactions and Gravitational Lorentz Force
Ning Wu
2005-04-23
In quantum gauge theory of gravity, the gravitational field is represented by gravitational gauge field. The field strength of gravitational gauge field has both gravitational electric component and gravitational magnetic component. In classical level, gauge theory of gravity gives out classical Newtonian gravitational interactions in a relativistic form. Besides, it gives out gravitational Lorentz force which is the gravitational force on a moving object in gravitational magnetic field. The direction of gravitational Lorentz force does not along that of classical gravitational Newtonian force. Effects of gravitational Lorentz force should be detectable, and these effects can be used to discriminate gravitational magnetic field from ordinary electromagnetic magnetic field.
Standard Electroweak Interactions in Gravitational Theory with Chameleon Field and Torsion
A. N. Ivanov; M. Wellenzohn
2015-04-22
We propose a version of a gravitational theory with the torsion field, induced by the chameleon field. Following Hojman et al. Phys. Rev. D17, 3141 (1976) the results, obtained in Phys. Rev. D90, 045040 (2014), are generalised by extending the Einstein gravity to the Einstein-Cartan gravity with the torsion field as a gradient of the chameleon field through a modification of local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant beta_(gamma) is equal to the chameleon-matter coupling constant beta, i.e. beta_(gamma) = beta, the experimental constraints on beta, obtained in terrestrial laboratories by T. Jenke et al. (Phys. Rev. Lett. 112, 115105 (2014)) and by H. Lemmel et al. (Phys. Lett. B743, 310 (2015)), can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage et al. (Phys. Rev. D79, 044028 (2009)), A.-Ch. Davis et al. (Phys. Rev. D80, 064016 (2009), and in references therein, where chameleons induce photons because of direct chameleon-photon transitions in the magnetic fields.
Standard electroweak interactions in gravitational theory with chameleon field and torsion
NASA Astrophysics Data System (ADS)
Ivanov, A. N.; Wellenzohn, M.
2015-04-01
We propose a version of a gravitational theory with a torsion field, induced by the chameleon field. Following Hojman et al. [Phys. Rev. D 17, 3141 (1976)], the results obtained in Phys. Rev. D 90, 045040 (2014) are generalized by extending Einstein gravity to Einstein-Cartan gravity with a torsion field as a gradient of the chameleon field through a modification of the local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant ?? is equal to the chameleon-matter coupling constant ? , i.e., ??=? , the experimental constraints on ? —obtained in terrestrial laboratories by T. Jenke et al. [Phys. Rev. Lett. 112, 115105 (2014)] and by H. Lemmel et al. [Phys. Lett. B 743, 310 (2015)]—can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage et al. [Phys. Rev. D 79, 044028 (2009)], A.-C. Davis et al. [Phys. Rev. D 80, 064016 (2009)], and in references therein, where chameleons induce photons because of direct chameleon-photon transitions in the magnetic fields.
Shape and gravitational field of the ellipsoidal satellites
NASA Astrophysics Data System (ADS)
Gao, BuXi; Huang, Yong
2014-10-01
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.
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
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.
Rocha, Jorge V.; Cardoso, Vitor
2011-05-15
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.
Weak gravitational lensing due to large-scale structure of the universe
NASA Technical Reports Server (NTRS)
Jaroszynski, Michal; Park, Changbom; Paczynski, Bohdan; Gott, J. Richard, III
1990-01-01
The effect of the large-scale structure of the universe on the propagation of light rays is studied. The development of the large-scale density fluctuations in the omega = 1 universe is calculated within the cold dark matter scenario using a smooth particle approximation. The propagation of about 10 to the 6th random light rays between the redshift z = 5 and the observer was followed. It is found that the effect of shear is negligible, and the amplification of single images is dominated by the matter in the beam. The spread of amplifications is very small. Therefore, the filled-beam approximation is very good for studies of strong lensing by galaxies or clusters of galaxies. In the simulation, the column density was averaged over a comoving area of approximately (1/h Mpc)-squared. No case of a strong gravitational lensing was found, i.e., no 'over-focused' image that would suggest that a few images might be present. Therefore, the large-scale structure of the universe as it is presently known does not produce multiple images with gravitational lensing on a scale larger than clusters of galaxies.
Roald Sosnovskiy
2009-01-16
The cause of an infringement in GR of a gravitational field energy conservation law is investigated . The equation of a gravitational field not contradicting to the energy conservation law is suggested. This equation satisfy to the Einstein,s requirement of equivalence of all energy kinds as sources of a gravitational field. This equation is solved in paper for cosmic objects. It is showed, that results for some objects - for black holes and gravitating strings-essentialy differ from such for Einstein,s equation, have the symple meaning and do not contradictions.
Comment on 'Primordial magnetic seed field amplification by gravitational waves'
Tsagas, Christos G.
2007-04-15
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.
On holographic thermalization and gravitational collapse of tachyonic scalar fields
Bin Wu
2013-03-24
In this paper we study the thermalization of a spatially homogeneous system in a strongly coupled CFT. The non-equilibrium initial state is created by switching on a relevant perturbation in the CFT vacuum during Delta t >= t >= -Delta t. Via AdS/CFT, the thermalization process corresponds to the gravitational collapse of a tachyonic scalar field (m^2 = -3) in the Poincare patch of AdS_5. In the limit Delta t = 1/T, we also obtain double-collapse solutions but with a non-equilibrium intermediate state at t = 0. In all the cases our results show that the system thermalizes in a typical time t_T ~ O(1)/T. Besides, a conserved energy-moment current in the bulk is found, which helps understand the qualitative difference of the collapse process in the Poincare patch from that in global AdS[9, 10].
On the Energy Source of the Gravitational Field
NASA Astrophysics Data System (ADS)
Mayer, Alexander
2011-11-01
According to the principles of special relativity, the systemic energy budget of a quantum harmonic oscillator exceeds canonical ``total energy" (E) by the difference between the 1?-norm and 2?-norm (E) of the complex number (mc^2 + ipc). This surplus energy manifests as a spatially unbounded continuous waveform centered on the source particle, having a phase velocity equal to the speed of light. In the immediate vicinity of a source particle and at corresponding high radial amplitude variation, the interaction between this waveform and spacetime induces various quantum effects. A kilogram of mass contains ˜ 0^27 subatomic harmonic oscillators (e.g., quarks); decoherent superposition of their momentum-driven (/?x) radiated waveforms provides an isotropic monotonically-decreasing space energy density. Spacetime response to the presence of this distributed energy manifests as the gravitational field in accord with the basic interpretation of general relativity: ``energy curves spacetime.'' Hypotheses put forward in this discussion are empirically testable with tabletop experiments.
Standard Electroweak Interactions in Gravitational Theory with Chameleon Field and Torsion
Ivanov, A N
2015-01-01
We propose a version of a gravitational theory with the torsion field, induced by the chameleon field. Following Hojman et al. Phys. Rev. D17, 3141 (1976) the results, obtained in Phys. Rev. D90, 045040 (2014), are generalised by extending the Einstein gravity to the Einstein-Cartan gravity with the torsion field as a gradient of the chameleon field through a modification of local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant beta_(gamma) is equal to the chameleon-matter coupling constant beta, i.e. beta_(gamma) = beta, the experimental constraints on beta, obtained in terrestrial laboratories by T. Jenke et al. (Phys. Rev. Lett. 112, 115105 (2014)) and by H. Lemmel et al. (Phys. Lett. B743, 310 (2015)), can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage e...
Weakly periodic Gibbs measures of the Ising model with an external field on the Cayley tree
NASA Astrophysics Data System (ADS)
Rahmatullaev, M. M.
2015-06-01
We study weakly periodic Gibbs measures of the Ising model with an external field on the Cayley tree. We prove that under some conditions on the model parameters, there exist at least two weakly periodic Gibbs measures for the antiferromagnetic Ising model with an external field.
Enrique Martinez-Gonzalez; Jose L. Sanz; Laura Cayon
1997-02-26
We have studied the effect of gravitational lensing on the Cosmic Microwave Background (CMB) anisotropy in flat and open universes. We develop a formalism to calculate the changes on the radiation power spectrum induced by lensing in the Newtonian and synchronous-comoving gauges. The previously considered negligible contribution to the CMB radiation power spectrum of the anisotropic term of the lensing correlation is shown to be appreciable. However, considering the nonlinear evolution of the matter power spectrum produces only slight differences on the results based on linear evolution. The general conclusion for flat as well as open universes is that lensing slightly smoothes the radiation power spectrum. For a given range of multipoles the effect of lensing increases with Omega but for the same acoustic peak it decreases with $\\Omega$. The maximum contribution of lensing to the radiation power spectrum for $l\\leq 2000$ is $\\sim$ 5% for $\\Omega$ values in the range 0.1-1.
Nonlinear gravitational self-force: Field outside a small body
NASA Astrophysics Data System (ADS)
Pound, Adam
2012-10-01
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.
Gravitational collapse with tachyon field and barotropic fluid
Yaser Tavakoli; João Marto; Amir Hadi Ziaie; Paulo Vargas Moniz
2013-01-21
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.
Free-fall in a uniform gravitational field in non-commutative quantum mechanics
K. H. C. Castello-Branco; A. G. Martins
2011-05-23
We study the free-fall of a quantum particle in the context of noncommutative quantum mechanics (NCQM). Assuming noncommutativity of the canonical type between the coordinates of a two-dimensional configuration space, we consider a neutral particle trapped in a gravitational well and exactly solve the energy eigenvalue problem. By resorting to experimental data from the GRANIT experiment, in which the first energy levels of freely falling quantum ultracold neutrons were determined, we impose an upper-bound on the noncommutativity parameter. We also investigate the time of flight of a quantum particle moving in a uniform gravitational field in NCQM. This is related to the weak equivalence principle. As we consider stationary, energy eigenstates, i.e., delocalized states, the time of flight must be measured by a quantum clock, suitably coupled to the particle. By considering the clock as a small perturbation, we solve the (stationary) scattering problem associated and show that the time of flight is equal to the classical result, when the measurement is made far from the turning point. This result is interpreted as an extension of the equivalence principle to the realm of NCQM.
Free-fall in a uniform gravitational field in noncommutative quantum mechanics
Castello-Branco, K. H. C. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Av. Trabalhador Sao-Carlense, 400, Sao Carlos, Sao Paulo 13560-970 (Brazil); Martins, A. G. [Departamento de Ciencias Naturais, Universidade do Estado do Para, Av. Djalma Dutra, s/n, Belem, Para 66113-200 (Brazil)
2010-10-15
We study the free-fall of a quantum particle in the context of noncommutative quantum mechanics (NCQM). Assuming noncommutativity of the canonical type between the coordinates of a two-dimensional configuration space, we consider a neutral particle trapped in a gravitational well and exactly solve the energy eigenvalue problem. By resorting to experimental data from the GRANIT experiment, in which the first energy levels of freely falling quantum ultracold neutrons were determined, we impose an upper-bound on the noncommutativity parameter. We also investigate the time of flight of a quantum particle moving in a uniform gravitational field in NCQM. This is related to the weak equivalence principle. As we consider stationary, energy eigenstates, i.e., delocalized states, the time of flight must be measured by a quantum clock, suitably coupled to the particle. By considering the clock as a small perturbation, we solve the (stationary) scattering problem associated and show that the time of flight is equal to the classical result, when the measurement is made far from the turning point. This result is interpreted as an extension of the equivalence principle to the realm of NCQM.
On the gravitational field (A suggestion about a possible experimental research)
B. Ferretti
2003-07-08
After a preliminary discussion of the relevance of the field nature of gravitation interaction, both for the fundamental interaction of particles and the topology of space time, a method is proposed to produce and detect a dynamical gravitational field, allowing the determination of the order of magnitude of its propagation velocity.
Baryon masses in the three-state Potts field theory in a weak magnetic field
NASA Astrophysics Data System (ADS)
Rutkevich, S. B.
2015-01-01
The 3-state Potts field theory describes the scaling limit of the 3-state Potts model on the two-dimensional lattice near its continuous phase transition point. In the presence of thermal and magnetic field perturbations, the 3-state Potts field theory in the ordered phase exhibits confinement of kinks, which allows both mesons and baryons. We calculate the masses of light baryons in this model in the weak confinement regime in leading order of the small magnetic field. In leading order of perturbation theory, the light baryons can be viewed as bound states of three quantum particles—the kinks, which move on a line and interact via a linear potential. We determine the masses of the lightest baryons by numerical solution of the associated non-relativistic one-dimensional quantum three-body problem.
Mass and concentration estimates from weak and strong gravitational lensing: a systematic study
NASA Astrophysics Data System (ADS)
Giocoli, Carlo; Meneghetti, Massimo; Metcalf, R. Benton; Ettori, Stefano; Moscardini, Lauro
2014-05-01
We study how well halo properties of galaxy clusters, such as mass and concentration, are recovered using lensing data. In order to generate a large sample of systems at different redshifts, we use the code MOKA. We measure halo mass and concentration using weak lensing data alone (WL), fitting to a Navarro, Frenk & White (NFW) profile the reduced tangential shear profile, or by combining weak and strong lensing data, by adding information about the size of the Einstein radius (WL+SL). For different redshifts, we measure the mass and the concentration biases and find that these are mainly caused by the random orientation of the halo ellipsoid with respect to the line of sight. Since our simulations account for the presence of a bright central galaxy, we perform mass and concentration measurements using a generalized NFW profile which allows for a free inner slope. This reduces both the mass and the concentration biases. We discuss how the mass function and the concentration-mass relation change when using WL and WL+SL estimates. We investigate how selection effects impact the measured concentration-mass relation showing that strong lens clusters may have a concentration 20-30 per cent higher than the average, at fixed mass, considering also the particular case of strong lensing selected samples of relaxed clusters. Finally, we notice that selecting a sample of relaxed galaxy clusters, as is done in some cluster surveys, explains the concentration-mass relation biases.
Leonardo Modesto
2004-01-04
In this paper we work in perturbative Quantum Gravity coupled to Scalar Matter at tree level and we introduce a new effective model in analogy with the Fermi theory of weak interaction and in relation with a previous work where we have studied only the gravity and its self-interaction. This is an extension of the I.T.B model (Intermediate-Tensor-Boson) for gravity also to gravitational interacting scalar matter. We show that in a particular gauge the infinite series of interactions containing "n" gravitons and two scalars could be rewritten in terms of only two Lagrangians containing a massive field, the graviton and, obviously, the scalar field. Using the S-matrix we obtain that the low energy limit of the amplitude reproduce the local Lagrangian for the scalar matter coupled to gravity.
Prabir Rudra; Ritabrata Biswas; Ujjal Debnath
2012-04-03
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.
The HST Frontier Fields: Gravitational Lensing Models Release
NASA Astrophysics Data System (ADS)
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
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.
Conflict between the Gravitational Field Energy and the Experiments
Rafael A. Vera
2001-02-07
From the equivalence principle and true gravitational (G) time dilation experiments it is concluded that ``matter is not invariable after a change of relative position with respect to other bodies''. As a general principle (GP), such variations cannot be locally detected because the basic parameters of all of the 'well-defined parts' of the instruments change, lineally, in the same proportion with respect to their original values''. Only observers that don't change of position can detect them. Thus, to relate quantities measured by observers in different G potentials they must be previously transformed after Lorenz and G transformations derived from experiments. They are account for all of the ``G tests''. However ``they are not consistent with the presumed energy exchange between the field and the bodies''. The lack of energy of the G field is justified from the GP, according to which particles models made up of photons in stationary state obey same inertial and G laws as particle. Such model has been previously tested with relativistic quantum-mechanics and all of the G tests. PACS: 04.80.cc, 04.20.Cv, 04.80.-y, 98.80.Cq
Classic field theories of gravitation embedded in ten dimensions
Frank B. Estabrook
2006-06-09
Two classic field theories of metric gravitation are given as constant-coefficient Exterior Differential Systems (EDS) on the flat orthonormal frame bundle over ten dimensional space. They are derivable by variation of Cartan 4-forms, and shown to be well-posed by calculation of their Cartan characteristic integers. Their solutions are embedded Riemannian 4-spaces. The first theory is generated by torsion 2-forms and Ricci-flat 3-forms and is a constant-coefficient EDS for vacuum tetrad gravity; its Cartan character table is the same as found for an EDS recently given in terms of tetrad frame and connection variables [1] [2]. The second constant-coefficient EDS is generated solely by 2-forms, and has a Cartan form of quadratic Yang-Mills type. Its solutions lie in torsion free 6-spaces and are fibered over 3-spaces. We conjecture that these solutions may be classically related to 10-dimensional quantum field theoretic constructions of cosmological vacua [3].
Influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction
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
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.
Effective Field Theory Methods in Gravitational Physics and Tests of Gravity
NASA Astrophysics Data System (ADS)
Cannella, Umberto
2011-03-01
In this PhD thesis I make use of the "Effective Field Theory of Gravity for Extended Objects" by Goldberger and Rothstein in order to investigate theories of gravity and to take a different point of view on the physical information that can be extracted from experiments. In the first work I present, I study a scalar-tensor theory of gravity and I address the renormalization of the energy-momentum tensor for point-like and string-like sources. The second and third study I report are set in the context of testing gravity. So far experiments have probed dynamical regimes only up to order (v/c)^5 in the post-Newtonian expansion, which corresponds to the very first term of the radiative sector in General Relativity. In contrast, by means of gravitational-wave astronomy, one aims at testing General Relativity up to (v/c)^(12)! It is then relevant to envisage testing frameworks which are appropriate to this strong-field/radiative regime. In the last two chapters of this thesis a new such framework is presented. Using the effective field theory approach, General Relativity non-linearities are described by Feynman diagrams in which classical gravitons interact with matter sources and among themselves. Tagging the self-interaction vertices of gravitons with parameters it is possible, for example, to translate the measure of the period decay of Hulse-Taylor pulsar in a constraint on the three-graviton vertex at the 0.1% level; for comparison, LEP constraints on the triple-gauge-boson couplings of weak interactions are accurate at 3%. With future observations of gravitational waves, higher order graviton vertices can in principle be constrained through a Fisher matrix analysis.
Electromagnetic signatures of far-field gravitational radiation in the 1 + 3 approach
NASA Astrophysics Data System (ADS)
Chua, Alvin J. K.; Cañizares, Priscilla; Gair, Jonathan R.
2015-01-01
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.
Polarization and trapping of weakly bound atoms in penning trap fields.
Kuzmin, S G; O'Neil, T M
2004-06-18
The ATHENA and ATRAP groups at CERN recently reported the production of weakly bound antihydrogen atoms in a non-neutral positron-antiproton plasma. This Letter derives an equation of motion for weakly bound atoms in the electric and magnetic fields of the plasma and trap. The atoms are polarized by the electric field and can be trapped radially in the edge region of the plasma where the electric field is maximum. PMID:15245082
NASA Technical Reports Server (NTRS)
Peng, Huei; Torr, Douglas G.
1990-01-01
This paper investigates the effect of gravitational waves on a superconductor. It is found that the key properties of a superconductor, namely zero resistance and perfect diamagnetism, give rise to an important new effect, the presence of an induced electric field E in the interior of the superconductor. The E field reacts with the ions and superelectrons. It is argued that the induced E field might provide a significantly more sensitive means of detecting gravitational waves. It appears likely that existing resonant-mass superconducting antennas with L about 3m, Q about 10 to the 8th could be readily modified to detect E fields induced by GWs of dimensionless amplitude h about 10 to the -24th.
On The Interaction of Gravitational Waves with Magnetic and Electric Fields
C. Barrabes; P. A. Hogan
2010-03-02
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.
Do the constants of nature couple to strong gravitational fields?
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
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.
Constraints on Gravitational Scaling Dimensions from Non-Local Effective Field Equations
Herbert W. Hamber; Ruth M. Williams
2006-07-28
Quantum corrections to the classical field equations, induced by a scale dependent gravitational constant, are analyzed in the case of the static isotropic metric. The requirement of general covariance for the resulting non-local effective field equations puts severe restrictions on the nature of the solutions that can be obtained. In general the existence of vacuum solutions to the effective field equations restricts the value of the gravitational scaling exponent $\
Evolution of Disturbances in Isothermal Self-gravitating Fields
NASA Astrophysics Data System (ADS)
Nomura, Hideko; Kamaya, Hideyuki; Mineshige, Shin
1998-12-01
We study the evolution of waves generated by compact sources of turbulence in self-gravitating fields under isothermal conditions. We apply the theory of aerodynamically generated sound waves, originally developed by Lighthill, and solve the linearized wave equation by Green's method. We adopt a uniform and stationary background as the initial condition. We consider two cases for the time development of an added disturbance. In the first, the disturbance is imposed on a compact region in a pulselike form, and the density grows exponentially around the source, producing a density concentration that has a Gaussian density profile centered at the source with increasing amplitude and width. This is understood in terms of the development of Jeans-unstable modes generated by the disturbance. In contrast, if the source of disturbance is oscillating with a frequency of ?0, we first observe oscillations and then an exponential growth of the density concentration. This can be interpreted as follows: Oscillating and growing modes correspond to different Fourier components. At first the amplitude of the former modes is largest, thus producing oscillatory wave patterns in density distribution. After the sound crossing time over the Jeans length, however, the latter dominate over the former in amplitude because of the development of Jeans instability. In conclusion, any compact disturbance in self-gravitating media can generate Jeans-unstable waves, regardless of whether the disturbance is instantaneous or oscillating. The implications of our results are discussed in the context of star formation in molecular clouds. The outflow lobes associated with young stellar objects act as sources of turbulence. Hence, the density of ambient matter around the lobes may at first be forced to oscillate, but it will grow exponentially on timescales of several million years. As a consequence, the outflow lobes associated with protostars of an old generation may trigger the formation of a new dense core and/or protostars of a new generation. Sequential star formation is thus possible not only in the OB associations but also in the formation regions of low-mass stars.
A study of Overhauser pumping in weak magnetic fields
Gondran, Gregory Rhea
1986-01-01
of the signal. 23 DIGITAL SYNTHESIZER ATTENUATOR BRIDGE PREAMP LOCK IN TO SAMPLE COIL Big. FUNCTION GENERATOR X XY RECORDER DC POWER SUPPLY SOLENOID FIELD SWEEP HELMHOLTZ COIL Fig. 5. The dc and proton field system. 24 Tlie Proton Field System... magnetic resonance (NMR) signal in hydrogen through Overhauser pumping has been measured as a function of pumping power and pumping agent molarity. Benzene is used as the source of hydrogen nuclei and galvinoxyl is the free radical which provides...
Gravitational Field of the Early Universe: I.Non-linear Scalar Field as the Source
S. V. Chervon
1997-06-10
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.
Local Determination of the Light Deflection in the Sperically Symmetric Static Gravitational Field
S. Tertychniy
1993-11-02
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.)
Do Gravitational Fields Have Mass? Or on the Nature of Dark Matter
Ernst Karl Kunst
1999-01-01
As has been shown before (a brief comment will be given in the text), relativistic mass and relativistic time dilation of moving bodies are equivalent as well as time and mass in the rest frame. This implies that the time dilation due to the gravitational field is combined with inertial and gravitational mass as well and permits the computation of
On the problem of uniqueness of energy-momentum tensor of gravitational field
A. I. Nikishov
2003-10-14
For an island-like distribution of matter the gravitational energy-momentum tensor is defined according to Weinberg as a source of metric. If this source is formed by self-interactions of gravitons, so that nonphysical degrees of freedom are excluded, then this source is a reasonable candidate for the energy-momentum tensor of gravitational field. The disastrous influence of the nonphysical degrees of freedom is demonstrated by comparing the gravitational energy-momentum tensors in the harmonic, isotropic and standard frames for the Schwarzschild solution. The harmonic frame is clearly preferable for defining the gravitational energy-momentum tensor.
Wang, Wenting; Mandelbaum, Rachel; Henriques, Bruno; Anderson, Michael E; Han, Jiaxin
2015-01-01
We use weak gravitational lensing to measure mean mass profiles around Locally Brightest Galaxies (LBGs). These are selected from the SDSS/DR7 spectroscopic and photometric catalogues to be brighter than any neighbour projected within 1.0 Mpc and differing in redshift by $ 83\\%$) are expected to be the central galaxies of their dark matter halos. Previous stacking analyses have used this LBG sample to measure mean Sunyaev-Zeldovich flux and mean X-ray luminosity as a function of LBG stellar mass. In both cases, a simulation of the formation of the galaxy population was used to estimate effective halo mass for LBGs of given stellar mass, allowing the derivation of scaling relations between the gas properties of halos and their mass. By comparing results from a variety of simulations to our lensing data, we show that this procedure has significant model dependence reflecting: (i) the failure of any given simulation to reproduce observed galaxy abundances exactly; (ii) a dependence on the cosmology underlying th...
Investigation of Electromagnetic Field Penetration in ICP and Weakly-Magnetized ICP Discharges
Chen, Francis F.
#12;Investigation of Electromagnetic Field Penetration in ICP and Weakly-Magnetized ICP Discharges, California, USA The relationship between the penetration of RF fields and power deposition in ICP discharges the plasma properties of low pressure ICP discharges. To this end, investigation of RF field penetration
Critical turbulent energy reductions in plasmas using weak magnetic fields
NASA Astrophysics Data System (ADS)
Raynor, Chavis T.; Mezonlin, Ephrem D.; Johnson, Joseph A.
2009-02-01
With an arc-driven shock tube, laser induced fluorescence, and a multipoint density diagnostic technique, we study the turbulence behind an ionizing shock wave in the presence of a magnetic field. The magnetic field is directed either parallel to or antiparallel to the direction of the shock wave's propagation, and is configured in such a way as to couple with turbulent velocity fluctuations in the plane perpendicular to the direction of flow. We find that the magnetic field can be used to reduce the turbulent energy in a plasma system. Further, when the evolution to turbulence is treated as a second-order phase transformation, the critical turbulent energy decreases with increasing magnetic field.
The fluctuating gravitational field in inhomogeneous and clustered self-gravitating systems.
NASA Astrophysics Data System (ADS)
Del Popolo, A.
1996-07-01
In this paper I extend the results of Ahmad & Cohen (1973), regarding the study of the probability distribution of the stochastic force in homogeneous gravitational systems, to inhomogeneous gravitational ones. To this aim, I study the stochastic force distribution using N-body realizations of Plummer's spherically symmetric models. I find that the stochastic force distribution obtained for the evolved system is in good agreement with Kandrup's (1980) theory of stochastic force in inhomogeneous systems. Correlation effects that arise during the evolution of the system of particles are well described by Antonuccio-Delogu & Atrio-Barandela's (1992) theory.
Weak Lensing PSF Correction of Wide-field CCD Mosaic Images (SULI Paper)
Cevallos, Marissa; /Caltech /SLAC
2006-01-04
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.
Jet deflection by very weak guide fields during magnetic reconnection
Goldman, Martin; Newman, David; Markidis, Stefan; Che, Haihong
2010-01-01
Simulations of antiparallel reconnection have shown collimated electron jets outflowing from the x-point, and associated highly elongated "outer electron diffusion regions." New PIC simulations with ion/electron mass ratios as large as 1836 show that jets are deflected towards the magnetic separatrix by out-of-plane guide fields, Bg, as small as 0.05 times the asymptotic reconnecting field, B0. The outer electron diffusion region is distorted and broken up, but the diffusion rate is unchanged. These results are interpreted in terms of electron dynamics and are compared to recent measurements of reconnection jets in the magnetosheath.
Cosmology and Gravitation: Summary talk at the XXIV Brazilian Meeting on Particles and Fields
M. D. Maia
2004-04-06
This is a brief summary with comments on selected contributions to the Cosmology and Gravitation section at the $24^{th}$ Brazilian Meeting on Particle and Fields (ENFPC XXIV), held at Caxambu, from September 30 to October 4, 2003.
Stability of Naked Singularity arising in gravitational collapse of Type I matter fields
Sanjay B. Sarwe; R. V. Saraykar
2004-10-06
Considering gravitational collapse of Type I matter fields, we prove that, given an arbitrary $C^{2}$- mass function $\\textit{M}(r,v)$ and a $C^{1}$- function $h(r,v)$ (through the corresponding $C^{1}$- metric function $\
Jet Deflection by Very Weak Guide Fields during Magnetic Reconnection
M. V. Goldman; G. Lapenta; D. L. Newman; S. Markidis; H. Che
2011-01-01
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+ plasma) now show that the jets
The measurements of weak stellar magnetic fields at the BTA
NASA Astrophysics Data System (ADS)
Chountonov, G. A.
2007-10-01
The methods of stellar magnetic field measurements at BTA using Zeeman effect are described. The limiting factors are analysed. The solutions to increase accuracy are proposed. It is necessary about 3 hours at MSS for 5^m with slicers to run up to 1 G using 50 spectral lines.
Field Methods for Characterizing Weak Rock for Engineering
of corestones and matrix, strength, influence of discontinuities, and reactivity to water. Finally, field-testing methods that estimate strength, permeability, durability, and re- action to water are identified. These include point load index, Norwegian Geotechnical Institute Rock Mass Classification, jar slake, and hammer
Alexander L. Dmitriev
2009-03-25
On the basis of the field concept of gravitation and gravitational analogue of the Faradays induction law the difference of inertial mass of a body at its accelerated movement in horizontal and vertical directions relative to the Earth is shown. For an illustration of such a distinction the results of comparison of a motion of balance mechanical watch at horizontal and vertical orientations of balance axis are given. The expediency of statement of precision mechanical experiments with measurement of anisotropy of the inertial mass is noted, allowing to estimate the validity of the field approach in the description of gravitation.
Acceleration of low energy charged particles by gravitational waves
G. Voyatzis; L. Vlahos; S. Ichtiaroglou; D. Papadopoulos
2005-12-07
The acceleration of charged particles in the presence of a magnetic field and gravitational waves is under consideration. It is shown that the weak gravitational waves can cause the acceleration of low energy particles under appropriate conditions. Such conditions may be satisfied close to the source of the gravitational waves if the magnetized plasma is in a turbulent state.
Multiple Dp-branes in weak background fields
Washington Taylor IV; Mark Van Raamsdonkb
2000-01-01
We find the terms in the non-abelian world-volume action of a system of many Dp-branes which describe the leading coupling to all type II supergravity background fields. These results are found by T-dualizing earlier results for D0-branes, which in turn were determined from calculations of the M(atrix) theory description of the supercurrent of 11D supergravity. Our results are compatible with
Novel method for detecting weak magnetic fields at low frequencies
NASA Astrophysics Data System (ADS)
González-Martínez, S.; Castillo-Torres, J.; Mendoza-Santos, J. C.; Zamorano-Ulloa, R.
2005-06-01
A low-level-intensity magnetic field detection system has been designed and developed based on the amplification-selection process of signals. This configuration is also very sensitive to magnetic field changes produced by harmonic-like electrical currents transported in finite-length wires. Experimental and theoretical results of magnetic fields detection as low as 10-9T at 120Hz are also presented with an accuracy of around 13%. The assembled equipment is designed to measure an electromotive force induced in a free-magnetic-core coil in order to recover signals which are previously selected, despite the fact that their intensities are much lower than the environment electromagnetic radiation. The prototype has a signal-to-noise ratio of 60dB. This system also presents the advantage for using it as a portable unit of measurement. The concept and prototype may be applied, for example, as a nondestructive method to analyze any corrosion formation in metallic oil pipelines which are subjected to cathodic protection.
NASA Technical Reports Server (NTRS)
Voorhies, Coerte V.
2004-01-01
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.
On the gravitational potential and field anomalies due to thin mass layers
NASA Technical Reports Server (NTRS)
Ockendon, J. R.; Turcotte, D. L.
1977-01-01
The gravitational potential and field anomalies for thin mass layers are derived using the technique of matched asymptotic expansions. An inner solution is obtained using an expansion in powers of the thickness and it is shown that the outer solution is given by a surface distribution of mass sources and dipoles. Coefficients are evaluated by matching the inner expansion of the outer solution with the outer expansion of the inner solution. The leading term in the inner expansion for the normal gravitational field gives the Bouguer formula. The leading term in the expansion for the gravitational potential gives an expression for the perturbation to the geoid. The predictions given by this term are compared with measurements by satellite altimetry. The second-order terms in the expansion for the gravitational field are required to predict the gravity anomaly at a continental margin. The results are compared with observations.
The Deviation of the Vacuum Refractive Index Induced by a Static Gravitational Field
Xing-Hao Ye; Qiang Lin
2007-04-10
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.
Dielectronic recombination and autoionization yields in weak static electric fields
Nunkaew, J.; Gallagher, T. F.
2010-02-15
Dielectronic recombination (DR) of ions and electrons occurs via intermediate doubly excited Rydberg states converging to an excited state of the ion, and the total energy-integrated rate is the sum of the rates through the n,l Rydberg states. To make stringent comparisons between calculated and observed rates, it is useful to resolve the contributions to DR of different n and l states. It is possible to separate experimentally the n states due to their different energies, but it is not possible to separate the nearly degenerate high-l states. We propose that it should be possible to measure the contribution to DR of energetically unresolved high-l states by measuring the recombination rate as a function of electric field. As the field is raised, progressively lower l states are converted to Stark states. Autoionization rates increase as l is decreased, and when the field is raised to the point that an l state with an autoionization rate in excess of the radiative decay rate is added to the manifold of Stark states, the DR rate will exhibit an observable increase. To test this proposal we have made measurements of autoionization yields of the autoionizing Ba 6p{sub 1/2}nk and 6p{sub 3/2}nk Stark states. The autoionization yield is complementary to DR, and the measurements indicate that the proposed approach should work well. Although it is not surprising that this approach works for excited ion states that are isotropic, such as the Ba{sup +} 6p{sub 1/2} state, it is less obvious that it should work for an anisotropic ion state, such as the Ba{sup +} 6p{sub 3/2} state. In the latter case there are four quantum defects for each l state instead of one, and the Stark effect of the Ba 6p{sub 3/2}nk Stark states is far more complex than that of the Ba 6p{sub 1/2}nk Stark states. Calculations of the Stark effect reveal that, while there are four times as many 6p{sub 3/2}nk levels as 6p{sub 1/2}nk levels, many of the interactions of the 6p{sub 3/2}nk levels are negligible, and in practice the problem is no more complicated than the 6p{sub 1/2}nk Stark problem.
Impurity-Assisted Tunneling Magnetoresistance under a Weak Magnetic Field
NASA Astrophysics Data System (ADS)
Txoperena, Oihana; Song, Yang; Qing, Lan; Gobbi, Marco; Hueso, Luis E.; Dery, Hanan; Casanova, Fèlix
2014-10-01
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.
Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields
Halgamuge, Malka N.
Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields Chathurika D,malka.nisha}@unimelb.edu.au Abstract--Adverse biological outcomes due to thermal effects of exposure to high power magnetic fields the past few decades a controversy has arisen over possible adverse biological effects due to exposure
Closed-form weak-field expansion of two-loop Euler-Heisenberg Lagrangians
G. V. Dunne; A. Huet; D. Rivera; C. Schubert
2006-09-10
We obtain closed-form expressions, in terms of the Faulhaber numbers, for the weak-field expansion coefficients of the two-loop Euler-Heisenberg effective Lagrangians in a magnetic or electric field. This follows from the observation that the magnetic worldline Green's function has a natural expansion in terms of the Faulhaber numbers.
Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields
Halgamuge, Malka N.
Engineering, Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville, VIC whether these effects arise from induced electric fields or currents, sensitivity of the part of the body based on the physical analysis of energy content in these weak fields and thermal electrical noise
Electromagnetic Waves in a Uniform Gravitational Field and Planck's Postulate
ERIC Educational Resources Information Center
Acedo, Luis; Tung, Michael M.
2012-01-01
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…
Polarization and Trapping of Weakly Bound Atoms in Penning Trap Fields S. G. Kuzmin and T. M. O'Neil
California at San Diego, University of
Polarization and Trapping of Weakly Bound Atoms in Penning Trap Fields S. G. Kuzmin and T. M. O of weakly bound antihydrogen atoms in a non-neutral positron-antiproton plasma. This Letter derives an equation of motion for weakly bound atoms in the electric and magnetic fields of the plasma and trap
NASA Technical Reports Server (NTRS)
Lerche, I.; Low, B. C.
1980-01-01
Exact analytic solutions are presented for equilibrium states of a self-gravitating one-dimensional cloud of gas, embedded in an external gravitational field due to a plane of 'stars' being heated at a rate proportional to the local gas density, and cooling by thermal conduction. It is found that the general topology of the solutions is such that the gas density has a minimum on the plane of 'stars', rising to an infinite but integrable peak away from the plane so that the total mass of gas in the cloud is finite. The results may be of interest in investigations of interstellar molecular clouds and of filamentary structures in supernova remnants as well as in the modeling of gas distributions around 'cocoon' protostars.
Embryological changes induced by weak, extremely low frequency electromagnetic fields.
Delgado, J M; Leal, J; Monteagudo, J L; Gracia, M G
1982-01-01
Fertilized chicken eggs were incubated for 48 hours while exposed to extremely low frequency magnetic fields (ELMF) of 10 Hz, 100 Hz and 1000 Hz with intensities of 0.12, 1.2 and 12 micro T. Gross morphological and histological analysis of the exposed embryos revealed the following effects: (1) ELMF of 100 Hz/1.2 micro T had the most consistent and powerful inhibitory effect on embryogenesis. Development of embryos was reduced to the formation of the three primitive layers. Brain vesicles, auditory pit, neural tube, foregut, heart, vessels, and somites were not developed. Glycosaminoglycans were almost absent. (2) The above results demonstrate a window effect because embryos exposed to 100 Hz/1.2 micro T were less developed than embryos exposed at lower and higher intensities and frequencies. (3) Developing organs reacted with different sensitivity to ELMF of specific frequencies and intensities. Somites were not disturbed by exposure to 10 Hz with any of the intensities used. Formation of blood vessels was completely blocked by ELMF of 1000 Hz/12 micro T while traces of other organs were present. (4) The drastic embryological disturbances described were obtained with much lower intensities (1 micro T = 0.01 Gauss) than those used in studies by other investigators. (5) Embryological alterations induced by ELMF may depend on disturbances in the presence and structure of glycosaminoglycans which are essential elements in cellular activities, including cell migration. (6) The use of ELMF of low intensity may be a powerful method to investigate embryogenetic mechanisms and may also be a useful technique for investigation of other biological systems. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 PMID:7107514
Gravitational waves from the evolution of magnetic field after electroweak epoch
Oleksandr Tomalak; Yuri Shtanov
2014-09-17
It was recently demonstrated that the evolution of helical magnetic field in the primordial plasma at temperatures $T\\gtrsim10$ MeV is affected by the phenomenon of chiral quantum anomaly in the electroweak model, leading to a possibility of self-sustained existence of magnetic field and chiral asymmetry in the electronic distribution. This may serve as a mechanism for generating primordial magnetic field in the early universe. Violent magnetic-field generation may lead to production of gravitational waves which, regardless of the fate of magnetic field itself, survive until today. We estimate the threshold value of the initial chiral asymmetry above which the generated gravitational waves would affect the big-bang nucleosynthesis and would show up in the current and future experiments on gravitational-wave detection.
Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space?
Baryshev, Y
2006-01-01
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...
Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space
NASA Astrophysics Data System (ADS)
Baryshev, Yurij
2006-03-01
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.
Inversion symmetry of gravitational coupling in cubic string field theory
NASA Astrophysics Data System (ADS)
Hata, Hiroyuki; Kojita, Toshiko
2013-12-01
It was found that the canonical energy of multi-brane solutions in CSFT constructed by the KBc algebra has a symmetry under the exchange of K = 0 and K = ? (inversion symmetry). On the other hand, the gauge invariant observable (GIO), which is regarded as the energy defined by the gravitational coupling of open string, cannot count the energy from K = ? and therefore is not equal to the canonical energy. To resolve this discrepancy, we examine the recent argument of Baba and Ishibashi which directly relates the two energies. We find that the gravitational coupling which is equivalent to the canonical energy consists of the GIO and another new term, and the whole has the inversion symmetry.
Gravitational Hertz experiment with electromagnetic radiation in a strong magnetic field
N. I. Kolosnitsyn; V. N. Rudenko
2015-04-24
Brief review of principal ideas in respect of the high frequency gravitational radiation generated and detected in the laboratory condition is presented. Interaction of electro-magnetic and gravitational waves into a strong magnetic field is considered as a more promising variant of the laboratory GW-Hertz experiment. The formulae of the direct and inverse Gertsenshtein-Zeldovich effect are derived. Numerical estimates are given and a discussion of a possibility of observation of these effects in a lab is carried out.
Gravitational Hertz experiment with electromagnetic radiation in a strong magnetic field
NASA Astrophysics Data System (ADS)
Kolosnitsyn, N. I.; Rudenko, V. N.
2015-06-01
A brief review of the principal ideas in respect of high frequency gravitational radiation generated and detected in laboratory conditions is presented. Interaction of electromagnetic and gravitational waves in a strong magnetic field is considered as a more promising variant of the laboratory GW-Hertz experiment. The formulae of the direct and inverse Gertsenshtein–Zeldovich effect are derived. Numerical estimates are given and a discussion of the possibility of observation of these effects in a laboratory is carried out.
{lambda}N{yields}NN weak interaction in effective-field theory
Parreno, Assumpta [Departament ECM, Facultat de Fisica, Universitat de Barcelona, E-08028, Barcelona (Spain); Bennhold, Cornelius [Center of Nuclear Studies, Department of Physics, George Washington University, Washington, DC 20052 (United States); Holstein, Barry R. [Department of Physics-LGRT, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Thomas Jefferson National Accelerator Facility, Theory Group, Newport News, Virginia 23606 (United States)
2004-11-01
The nonleptonic weak |{delta}S|=1 {lambda}N interaction, responsible for the dominant nonmesonic decay of all but the lightest hypernuclei, is studied in the framework of an effective-field theory. The long-range physics is described through tree-level exchange of the SU(3) Goldstone bosons, while the short-range potential is parametrized in terms of the lowest-order contact terms. We obtain reasonable fits to available weak hypernuclear decay rates and quote the values for the parity-violating asymmetry as predicted by the present effective-field theory.
Weak Solutions to Fokker-Planck Equations and Mean Field Games
NASA Astrophysics Data System (ADS)
Porretta, Alessio
2015-04-01
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.
Strong field gravitational lensing in the deformed Ho?ava-Lifshitz black hole
NASA Astrophysics Data System (ADS)
Chen, Songbai; Jing, Jiliang
2009-07-01
Adopting the strong field limit approach, we studied the properties of strong field gravitational lensing in the deformed Ho?ava-Lifshitz black hole and obtained the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy described by this metric, we estimated the numerical values of the coefficients and observables for gravitational lensing in the strong field limit. Comparing with the Reissner-Nordström black hole, we find that with the increase of parameter ?, the angular position ?? decreases more slowly and rm more quickly, but angular separation s increases more rapidly. This may offer a way to distinguish a deformed Ho?ava-Lifshitz black hole from a Reissner-Nordström black hole by the astronomical instruments in the future.
NASA Astrophysics Data System (ADS)
Suárez, Abril; Chavanis, Pierre-Henri
2015-07-01
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 ? |? |4 potential. We study the evolution of the spatially 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. Nonrelativistic hydrodynamic equations based on the Schrödinger-Poisson equations or on the Gross-Pitaevskii-Poisson equations are recovered in the limit c ?+?. 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 perturbations 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 is substantially faster than in the cold dark matter model. When the wavelength of the perturbations approaches the cosmological horizon (Hubble length), a relativistic treatment is mandatory. In that case, we find that relativistic effects attenuate or even prevent the growth of perturbations. This paper exposes the general formalism and provides illustrations in simple cases. Other applications of our formalism will be considered in companion papers.
Can Surface Flux Transport Account for the Weak Polar Field in Cycle 23?
NASA Astrophysics Data System (ADS)
Jiang, Jie; Cameron, Robert H.; Schmitt, Dieter; Schüssler, Manfred
2013-06-01
To reproduce the weak magnetic field on the polar caps of the Sun observed during the declining phase of cycle 23 poses a challenge to surface flux transport models since this cycle has not been particularly weak. We use a well-calibrated model to evaluate the parameter changes required to obtain simulated polar fields and open flux that are consistent with the observations. We find that the low polar field of cycle 23 could be reproduced by an increase of the meridional flow by 55% in the last cycle. Alternatively, a decrease of the mean tilt angle of sunspot groups by 28% would also lead to a similarly low polar field, but cause a delay of the polar field reversals by 1.5 years in comparison to the observations.
Pudlak, M. [Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 043 53 Kosice (Slovakia); Pincak, R.; Osipov, V. A. [Joint Institute for Nuclear Research, BLTP, 141980 Dubna, Moscow region (Russian Federation)
2007-06-15
The effect of a weak uniform magnetic field on the electronic structure of slightly deformed fullerene molecules is studied within the continuum field-theory model. It is shown that fine structure of the electronic energy spectrum is very sensitive to the orientation of the magnetic field. In particular, we found that the magnetic field pointed in the x direction does not influence the first electronic level whereas it causes a splitting of the second energy level. This behavior differs markedly from the case of the magnetic field pointed in the z direction, where z is chosen to be the symmetry axis of the fullerene.
Complex structures in galaxy cluster fields: implications for gravitational lensing mass models
NASA Astrophysics Data System (ADS)
King, Lindsay; Corless, Virginia
2007-01-01
The distribution of mass on galaxy cluster scales is an important test of structure formation scenarios, providing constraints on the nature of dark matter itself. Several techniques have been used to probe the mass distributions of clusters, sometimes yielding results which are discrepant, or at odds with clusters formed in simulations - for example giving Navarro-Frenk-White (NFW) concentration parameters much higher than expected in the standard cold dark matter (CDM) model. In addition, the velocity fields of some well-studied galaxy clusters reveal the presence of several structures close to the line of sight, often not dynamically bound to the cluster itself. We investigate what impact such neighbouring but unbound massive structures would have on the determination of cluster profiles using weak gravitational lensing. Depending on its concentration and mass ratio to the primary halo, one secondary halo close to the line-of-sight can cause the estimated NFW concentration parameter to be significantly higher than that of the primary halo, and also cause the estimated mass to be biased high. Although it is difficult to envisage how this mechanism alone could yield concentrations as high as reported for some clusters, multiple haloes close to the line-of-sight, such as in the case of Abell 1689, can substantially increase the concentration parameter estimate. Together with the fact that clusters are triaxial, and that including baryonic physics also leads to an increase in the concentration of a dark matter halo, the tension between observations and the standard CDM model is eased. Additionally, we note that if the alignment with the secondary structure is imprecise, then the estimated concentration parameter can also be even lower than that of the primary halo, reinforcing the importance of identifying structures in cluster fields.
High order well-balanced WENO scheme for the gas dynamics equations under gravitational fields
Xing, Yulong
High order well-balanced WENO scheme for the gas dynamics equations under gravitational fields field, admit the hydro- static balance where the flux produced by the pressure is exactly canceled high order well-balanced finite difference WENO schemes to this system, which can preserve
Lichnerowicz-type theorems for self-gravitating systems with nonlinear electromagnetic fields
NASA Astrophysics Data System (ADS)
Cao, Li-Ming; Peng, Yuxuan; Xu, Jianfei
2014-07-01
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.
Plasma waves driven by gravitational waves in an expanding universe
D. B. Papadopoulos
2002-05-22
In a Friedmann-Robertson-Walker (FRW) cosmological model with zero spatial curvature, we consider the interaction of the gravitational waves with the plasma in the presence of a weak magnetic field. Using the relativistic hydromagnetic equations it is verified that large amplitude magnetosonic waves are excited, assuming that both, the gravitational field and the weak magnetic field do not break the homogeneity and isotropy of the considered FRW spacetime.
Escape of gravitational radiation from the field of massive bodies
NASA Technical Reports Server (NTRS)
Price, Richard H.; Pullin, Jorge; Kundu, Prasun K.
1993-01-01
We consider a compact source of gravitational waves of frequency omega in or near a massive spherically symmetric distribution of matter or a black hole. Recent calculations have led to apparently contradictory results for the influence of the massive body on the propagation of the waves. We show here that the results are in fact consistent and in agreement with the 'standard' viewpoint in which the high-frequency compact source produces the radiation as if in a flat background, and the background curvature affects the propagation of these waves.
Magnetite in human tissues: A mechanism for the biological effects of weak ELF magnetic fields
Kirschvink, J.L.; Kobayashi-Kirschvink, A.; Diaz-Ricci, J.C.; Kirschvink, S.J. (California Institute of Technology, Pasadena (United States))
1992-01-01
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.
Alexander B. Balakin; Jose' P. S. Lemos
2001-01-30
Evolution of electric and magnetic fields in dielectric media, driven by the influence of a strong gravitational wave, is considered for four exactly integrable models. It is shown that the gravitational wave field gives rise to new effects and to singular behaviour in the electromagnetic field.
Wu Ning; Zhang Da-Hua
2007-01-01
A systematic method is developed to study the classical motion of a mass point in gravitational gauge field. First, by using Mathematica, a spherical symmetric solution of the field equation of gravitational gauge field is obtained, which is just the traditional Schwarzschild solution. Combining the principle of gauge covariance and Newton's second law of motion, the equation of motion of
A Test to Verify the Speed Change of Light in the Gravitational Field of the Earth
Mei Xiaochun
2006-12-03
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
Gravitational waves from stochastic relativistic sources: primordial turbulence and magnetic fields
Chiara Caprini; Ruth Durrer
2006-09-15
The power spectrum of a homogeneous and isotropic stochastic variable, characterized by a finite correlation length, does in general not vanish on scales larger than the correlation scale. If the variable is a divergence free vector field, we demonstrate that its power spectrum is blue on large scales. Accounting for this fact, we compute the gravitational waves induced by an incompressible turbulent fluid and by a causal magnetic field present in the early universe. The gravitational wave power spectra show common features: they are both blue on large scales, and peak at the correlation scale. However, the magnetic field can be treated as a coherent source and it is active for a long time. This results in a very effective conversion of magnetic energy in gravitational wave energy at horizon crossing. Turbulence instead acts as a source for gravitational waves over a time interval much shorter than a Hubble time, and the conversion into gravitational wave energy is much less effective. We also derive a strong constraint on the amplitude of a primordial magnetic field when the correlation length is much smaller than the horizon.
Exact deflection of a Neutral-Tachyon in the Kerr's Gravitational field
G. V. Kraniotis
2011-10-06
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.
Integration of Einstein's Equations in the Weak Field Domain Using the "Einstein" Gauge
E. Hitzer; H. Dehnen
1998-07-18
We propose a new alternative gauge for the Einstein equations instead of the de Donder gauge, which allows in the limit of weak fields a straightforward integration of these equations. The Newtonian potential plays a new interesting role in this framework. The calculations are demonstrated explicitely for 2 simple astrophysical models.
Quantum Field Theoretic Derivation of the Einstein Weak Equivalence Principle Using Emqg Theory
Tom Ostoma; Mike Trushyk
1999-01-01
We provide a quantum field theoretic derivation of Einstein's Weak Equivalence Principle of general relativity using a new quantum gravity theory proposed by the authors called Electro-Magnetic Quantum Gravity or EMQG (ref. 1). EMQG is based on a new theory of inertia (ref. 5) proposed by R. Haisch, A. Rueda, and H. Puthoff (which we modified and called Quantum Inertia).
Reduction of degenerate four-wave mixing spectra to relative populations I. Weak-field limit
molecular sample to be decomposed into a sum of three multipole moments in the weak-field (no saturation). Under the assumption that the rates of collisional relaxation of the population, the orientation (collisional relaxation),4-6 and the laser power employed (saturation).7-9 In general, the population as well
Behavioral responses to weak electric fields and a lanthanide metal in two shark species
Kajiura, Stephen
Behavioral responses to weak electric fields and a lanthanide metal in two shark species Laura K Keywords: Bycatch Deterrent Elasmobranch Electroreception The unintentional catch of sharks on hooks to repel sharks from baited hooks by applying various lanthanide metals and alloys to stimulate
Short guide to direct gravitational field modelling with Hotine's equations
NASA Astrophysics Data System (ADS)
Sebera, Josef; Wagner, Carl A.; Bezd?k, Aleš; Kloko?ník, Jaroslav
2013-03-01
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.
Effects of a Weak Planetary Field on a Model Venus Ionosphere
NASA Astrophysics Data System (ADS)
Luhmann, Janet G.; Ma, Yingjuan; Villarreal, Michaela
2014-05-01
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.
Detecting weak magnetic fields in the central stars of planetary nebulae
NASA Astrophysics Data System (ADS)
Steffen, M.; Hubrig, S.; Todt, H.; Schöller, M.; Sandin, C.; Hamann, W.-R.; Schönberner, D.
2014-11-01
We have carried out low-resolution spectropolarimetric observations with FORS 2, installed on the VLT, ESO, of a representative sample of 12 bright central stars of Planetary Nebulae (PNe) with different morphology. Two of the sample are hydrogen-deficient (Wolf-Rayet type) stars. Our measurements rule out the existence of strong global magnetic fields of the order of kG in any of the PN central stars of our sample. Even so, our data may indicate the presence of weak mean longitudinal magnetic fields of a few hundred Gauss in the central stars of two elliptical nebulae, IC 418 and NGC 2392, and a very weak magnetic field of about 100 G in the Wolf-Rayet type central star Hen 2-113. However, the significance of these marginal detections depends on the method adopted for estimating the uncertainties in the magnetic-field measurements.
Lifetime and decay of unstable particles in strong gravitational fields
Douglas Fregolente; Alberto Saa
2008-04-21
We consider here the decay of unstable particles in geodesic circular motion around compact objects. For the neutron, in particular, strong and weak decay are calculated by means of a semiclassical approach. Noticeable effects are expected to occur as one approaches the photonic circular orbit of realistic black-holes. We argue that, in such a limit,the quasi-thermal spectrum inherent to extremely relativistic observers in circular motion plays a role similar to the Unruh radiation for uniformly accelerated observers.
The bioeffects of extremely weak power-frequency alternating magnetic fields
N. A. Belova; O. N. Ermakova; A. M. Ermakov; Z. Ye. Rojdestvenskaya; V. V. Lednev
2007-01-01
We report the results of a study of the influence of extremely-weak alternating magnetic fields (EW AMF) directed co-linearly\\u000a to the static Earth’s magnetic field on the rate of regeneration in planarians and also on the rate of gravitropic response\\u000a in the stem segments of flax. In particular we obtained the data on the dependence of the value of bioeffects
Leeuwen-Segarceanu, Elena M. van; Dorresteijn, Lucille D.A.; Pillen, Sigrid; Biesma, Douwe H.; Vogels, Oscar J.M.; Alfen, Nens van
2012-02-01
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.
NASA Astrophysics Data System (ADS)
Abanov, Alexander G.; Gromov, Andrey
2014-07-01
We compute electromagnetic, gravitational, and mixed linear response functions of two-dimensional free fermions in an external quantizing magnetic field at an integer filling factor. The results are presented in the form of the effective action and as an expansion of currents and stresses in wave vectors and frequencies of the probing electromagnetic and metric fields. In addition to the well-studied U (1) Chern-Simons and Wen-Zee terms we find a gravitational Chern-Simons term that controls the correction to the Hall viscosity due to the background curvature. We relate the coefficient in front of the term with the chiral central charge.
The global gravitational anomaly of the self-dual field theory
Samuel Monnier
2013-05-10
We derive a formula for the global gravitational anomaly of the self-dual field theory on an arbitrary compact oriented Riemannian manifold. Along the way, we uncover interesting links between the theory of determinant line bundles of Dirac operators, Siegel theta functions and a functor constructed by Hopkins and Singer. We apply our result to type IIB supergravity and show that in the naive approximation where the Ramond-Ramond fields are treated as differential cohomology classes, the global gravitational anomaly vanishes on all 10-dimensional spin manifolds. We sketch a few other important physical applications.
Claudio Nassif
2014-10-14
This seminal work aims to develop a fundamental approach in order to get a consistent coupling constant between electromagnetic and gravitational fields by using an electron that couples with a gravitational potential by means of its electromagnetic fields. We get a tiny value for such coupling, giving a possible explanation for the hierarchical problem. This coupling constant depends on the speed of light and also an invariant minimum speed which represents the lowest limit of speed for any particle with lower energy, thus leading to a doubly (symmetrical) special relativity with two invariant speeds given for higher and lower energies.
Cosmological Applications of Gravitational Lensing
Peter Schneider
1995-12-08
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.
Bi-Local Field in Gravitational Shock Wave Background
Naohiro Kanda; Shigefumi Naka
2014-10-28
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.
Strong Gravitational Lens Candidates in the GOODS ACS Fields
C. D. Fassnacht; L. A. Moustakas; S. Casertano; H. C. Ferguson; R. A. Lucas; Y. Park
2003-09-02
We present results from a systematic search for strong gravitational lenses in the GOODS ACS data. The search technique involves creating a sample of likely lensing galaxies, which we define as massive early-type galaxies in a redshift range 0.3 < z <1.3. The target galaxies are selected by color and magnitude, giving a sample of 1092 galaxies. For each galaxy in the sample, we subtract a smooth description of the galaxy light from the z_{850}-band data. The residuals are examined, along with true-color images created from the B_{435}V_{606}i_{775} data, for morphologies indicative of strong lensing. We present our six most promising lens candidates, as well as our full list of candidates.
Extreme Ultraviolet Sources Generation by Using the Two-Color Multi-Cycle Weak Inhomogeneous Field
NASA Astrophysics Data System (ADS)
Feng, Li-Qiang; Li, Wen-Liang
2015-01-01
An efficient method for attosecond extreme ultraviolet source generation under the two-color multi-cycle weak pulse has been theoretically presented by using the concept of the plasmonic field enhancement in the vicinity of metallic nanostructures. The results show that by properly choosing the inhomogeneity of the two-color multi-cycle (20 fs) weak pulse (1013 W/cm2), not only the harmonic cutoff has been extended, resulting in a broadband XUV continuum, but also the single short quantum path has been selected to contribute to the harmonic. As a result, two isolated XUV pulses with durations of 68as and 66as can be obtained.
Gravitational Waves from the First Order Phase Transition of the Higgs Field at High Energy Scales
Jinno, Ryusuke; Takimoto, Masahiro
2015-01-01
In a wide class of new physics models, there exist scalar fields which obtain vacuum expectation values of high energy scales. We study the possibility that the standard model Higgs field has experienced first-order phase transition at the high energy scale due to the couplings with these scalar fields.We estimate the amount of gravitational waves produced by the phase transition, and discuss observational consequences.
The prevalence of weak magnetic fields in Herbig Ae stars: the case of PDS 2
NASA Astrophysics Data System (ADS)
Hubrig, S.; Carroll, T. A.; Schöller, M.; Ilyin, I.
2015-04-01
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 (
Dust acoustic shock wave in electronegative dusty plasma: Roles of weak magnetic field
Ghosh, Samiran; Ehsan, Z.; Murtaza, G.
2008-02-15
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.
Iron snow zones as a mechanism for generating Mercury’s weak observed magnetic field
NASA Astrophysics Data System (ADS)
Vilim, R.; Stanley, S.; Hauck, S. A.
2010-11-01
The anomalously weak observed magnetic field of Mercury is difficult to explain by appealing to crustal remanent magnetism or Earth-like dynamo mechanisms. Although the field is likely caused by a hydromagnetic dynamo, the field strength is far weaker than the characteristic strength expected from an active, strong field dynamo. Recent experimental work has shown that sources of compositional convection exist in mixtures of sulfur and iron at temperatures and pressures relevant to Mercury’s core. The number and location of these iron “snow” zones is dependent on the sulfur content of the liquid portion of the core. We use a numerical dynamo model to show that the core states which include a snow zone midway through the core produce the observed field strength and expected field partitioning of the Mercurian magnetic field.
Quasistationary solutions of self-gravitating scalar fields around collapsing stars
Nicolas Sanchis-Gual; Juan Carlos Degollado; Pedro J. Montero; José A. Font; Vassilios Mewes
2015-07-30
Recent work has shown that scalar fields around black holes can form long-lived, quasistationary configurations surviving for cosmological timescales. With this requirement, scalar fields cannot be discarded as viable candidates for dark matter halo models in galaxies around central supermassive black holes (SMBH). One hypothesis for the formation of most SMBHs at high redshift is the gravitational collapse of supermassive stars (SMS) with masses of $\\sim10^5 \\rm {M_{\\odot}}$. Therefore, a constraint for the existence of quasi-bound states of scalar fields is their survival to such dynamic events. To answer this question we present in this paper the results of a series of numerical relativity simulations of gravitationally collapsing, spherically symmetric stars surrounded by self-gravitating scalar fields. We use an ideal fluid equation of state with adiabatic index $\\Gamma=4/3$ which is adequate to simulate radiation-dominated isentropic SMSs. Our results confirm the existence of oscillating, long-lived, self-gravitating scalar field configurations around non-rotating black holes after the collapse of the stars.
Physics of Gravitational Interaction: Geometry of Space or Quantum Field in Space?
Yurij Baryshev
2005-09-27
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.
Effects of Electromagnetic Field on The Collapse and Expansion of Anisotropic Gravitating Source
G. Abbas
2014-05-27
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.
A spherically symmetric gravitational collapse-field with radiation
P C Vaidya; L K Patel
1996-01-01
An interior spherically symmetric solution of Einstein’s field equations corresponding to perfect fluid plus a flowing radiation-field\\u000a is presented. The physical 3-spacet=constant of our solution is spheroidal. Vaidya’s pure radiation field is taken as the exterior solution. The inward motion\\u000a of the collapsing boundary surface follows from the equations of fit. An approximation procedure is used to get a generalization
Relativistic weak lensing from a fully non-linear cosmological density field
NASA Astrophysics Data System (ADS)
Thomas, D. B.; Bruni, M.; Wands, D.
2015-09-01
In this paper we examine cosmological weak lensing on non-linear scales and show that there are Newtonian and relativistic contributions and that the latter can also be extracted from standard Newtonian simulations. We use the post-Friedmann formalism, a post-Newtonian type framework for cosmology, to derive the full weak-lensing deflection angle valid on non-linear scales for any metric theory of gravity. We show that the only contributing term that is quadratic in the first order deflection is the expected Born correction and lens-lens coupling term. We use this deflection angle to analyse the vector and tensor contributions to the E- and B- mode cosmic shear power spectra. In our approach, once the gravitational theory has been specified, the metric components are related to the matter content in a well-defined manner. Specifying General Relativity, we write down a complete set of equations for a GR+?CDM universe for computing all of the possible lensing terms from Newtonian N-body simulations. We illustrate this with the vector potential and show that, in a GR+?CDM universe, its contribution to the E-mode is negligible with respect to that of the conventional Newtonian scalar potential, even on non-linear scales. Thus, under the standard assumption that Newtonian N-body simulations give a good approximation of the matter dynamics, we show that the standard ray tracing approach gives a good description for a ?CDM cosmology.
Gravitational field of an infinitely long supermassive cosmic string
M. M. Som; Marcelo de Oliveira Souza
1994-11-18
We obtain an exact solution of the coupled Einstein-scalar-gauge field equations for a local infinitely long supermassive cosmic string. The solution correponds to that of Hiscock-Gott . The string appears to be due to the freezing of the scalar field at the null value giving rise to a constant linear energy density.
Gravitational wave production: A strong constraint on primordial magnetic fields
Chiara Caprini; Ruth Durrer
2001-10-01
We compute the gravity waves induced by anisotropic stresses of stochastic primordial magnetic fields. The nucleosynthesis bound on gravity waves is then used to derive a limit on the magnetic field amplitude as function of the spectral index. The obtained limits are extraordinarily strong: If the primordial magnetic field is produced by a causal process, leading to a spectral index $n\\ge 2$ on super horizon scales, galactic magnetic fields produced at the electroweak phase transition or earlier have to be weaker than $B_\\la \\le 10^{-27}$Gauss! If they are induced during an inflationary phase (reheating temperature $T\\sim 10^{15}$GeV) with a spectral index $n\\sim 0$, the magnetic field has to be weaker than $B_\\la \\le 10^{-39}$Gauss! Only very red magnetic field spectra, $n\\sim -3$ are not strongly constrained. We also find that a considerable amount of the magnetic field energy is converted into gravity waves. The gravity wave limit derived in this work rules out most of the proposed processes for primordial seeds for the large scale coherent magnetic fields observed in galaxies and clusters.
Higgs and gravitational scalar fields together induce Weyl gauge
NASA Astrophysics Data System (ADS)
Scholz, Erhard
2015-02-01
A common biquadratic potential for the Higgs field and an additional scalar field , non minimally coupled to gravity, is considered in a locally scale symmetric approach to standard model fields in curved spacetime. A common ground state of the two scalar fields exists and couples both fields to gravity, more precisely to Weyl geometric scalar curvature . In Einstein gauge (, often called "Einstein frame"), also is scaled to a constant. This condition makes perfect sense, even in the general case, in the Weyl geometric approach. There it has been called Weyl gauge, because it was first considered by Weyl in the different context of his original scale geometric theory of gravity of 1918. Now it may get new meaning as a combined effect of electroweak theory and gravity, and their common influence on atomic frequencies.
NASA Astrophysics Data System (ADS)
Lucchesi, D. M.; Anselmo, L.; Bassan, M.; Pardini, C.; Peron, R.; Pucacco, G.; Visco, M.
2015-08-01
In this work, the Laser Ranged Satellites Experiment (LARASE) is presented. This is a research program that aims to perform new refined tests and measurements of gravitation in the field of the Earth in the weak field and slow motion (WFSM) limit of general relativity (GR). For this objective we use the free available data relative to geodetic passive satellite lasers tracked from a network of ground stations by means of the satellite laser ranging (SLR) technique. After a brief introduction to GR and its WFSM limit, which aims to contextualize the physical background of the tests and measurements that LARASE will carry out, we focus on the current limits of validation of GR and on current constraints on the alternative theories of gravity that have been obtained with the precise SLR measurements of the two LAGEOS satellites performed so far. Afterward, we present the scientific goals of LARASE in terms of upcoming measurements and tests of relativistic physics. Finally, we introduce our activities and we give a number of new results regarding the improvements to the modelling of both gravitational and non-gravitational perturbations to the orbit of the satellites. These activities are a needed prerequisite to improve the forthcoming new measurements of gravitation. An innovation with respect to the past is the specialization of the models to the LARES satellite, especially for what concerns the modelling of its spin evolution, the neutral drag perturbation and the impact of Earth's solid tides on the satellite orbit.
Dmitriy Palatnik
2002-10-24
In this note one suggests a possibility of direct observation of the $\\theta$-parameter, introduced in the Born--Infeld theory of electroweak and gravitational fields, developed in quant-ph/0202024. Namely, one may treat $\\theta$ as a universal constant, responsible for correction to the Coulomb and Newton laws, allowing direct interaction between electrical charges and masses.
Variations of the gravitational field as a motive power for rhythmics of biochemical processes
NASA Astrophysics Data System (ADS)
Troshichev, O. A.; Gorshkov, E. S.; Shapovalov, S. N.; Sokolovskii, V. V.; Ivanov, V. V.; Vorobeitchikov, V. M.
2004-01-01
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.
Exact solution for the gravitational field of a string with a nonzero cosmological constant
NASA Astrophysics Data System (ADS)
Novello, M.; Motta da Silva, M. C.
1993-11-01
We generalize arguments presented by Gott and Hiscock regarding the external gravitational field of a string, in order to allow for larger values of the string's linear density. In this way we are able to envision the string as being related to fundamental states of bosons of arbitrary mass.
Contact angle hysteresis generated by the residual gravitational field of the Space Shuttle
Ward, Charles A.
Contact angle hysteresis generated by the residual gravitational field of the Space Shuttle C. A. This difference in contact angles can be measured, and from the measured values, the theory can be used mm diam glass cylinder that had a height of 86 mm was observed to have a contact angle at the upper
R. Chan; M. F. A. da Silva; Jaime F. Villas da Rocha
2005-05-10
The 2+1-dimensional geodesic circularly symmetric solutions of Einstein-massless-scalar field equations with negative cosmological constant are found and their local and global properties are studied. It is found that one of them represents gravitational collapse where black holes are always formed.
Where Else Is Null the Gravitational Field between Two Massive Spheres?
ERIC Educational Resources Information Center
Lima, F. M. S.
2009-01-01
To find the point between two massive spherical bodies at which their gravitational fields cancel is an apparently simple problem usually found in introductory physics textbooks. However, by noting that such a point does not exist when the distance between the spheres is small and one of the masses is much smaller than the other--e.g., between the…
The prevalence of weak magnetic fields in Herbig Ae stars: The case of PDS2
Hubrig, S; Schöller, M; Ilyin, I
2015-01-01
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,...
Thermoelectric Magnetohydrodynamic Flow During Crystal Growth with a Moderate or Weak Magnetic Field
NASA Technical Reports Server (NTRS)
Khine, Y. Y.; Walker, John S.; Szofran, Frank R.; Rose, M. Franklin (Technical Monitor)
2000-01-01
This paper treats a steady, axisymmetric melt motion in a cylindrical ampoule with a uniform, axial magnetic field and with an electric current due to a radial temperature variation along the crystal-melt interface, where the values of the absolute thermoelectric power for the crystal and melt are different. The radial component of the thermoelectric current in the melt produces an azimuthal body force, and the axial variation of the centrifugal force due to the azimuthal motion drives a meridional circulation with radial and axial velocities. For moderate magnetic field strengths, the azimuthal velocity and magnetic field produce a radial induced electric field which partially cancels the Seebeck electromotive force in the melt, so that the thermoelectric current and the melt motion are coupled. For weak magnetic fields, the thermoelectric current is decoupled from the melt motion, which is an ordinary hydrodynamic flow driven by a known azimuthal body force. The results show how the flow varies with the strength of the magnetic field and with the magnitude of the temperature variation along the crystal-melt interface. They also define the parameter ranges for which the simpler weak-field decoupled analysis gives accurate predictions.
Jonckheere, Thibaut
Weak-field Hall effect and static polarizability of Bloch electrons Pavel Steda1 and Thibaut November 2008; published 18 March 2009 A theory of the weak-field Hall effect of Bloch electrons based originated in demagnetization currents. The Hall resistance as a function of the electron concentration
MagnetoSperm: A microrobot that navigates using weak magnetic fields
NASA Astrophysics Data System (ADS)
Khalil, Islam S. M.; Dijkslag, Herman C.; Abelmann, Leon; Misra, Sarthak
2014-06-01
In this work, a propulsion system similar in motion to a sperm-cell is investigated. This system consists of a structure resembling a sperm-cell with a magnetic head and a flexible tail of 42 ?m and 280 ?m in length, respectively. The thickness, length, and width of this structure are 5.2 ?m, 322 ?m, and 42 ?m, respectively. The magnetic head includes a 200 nm-thick cobalt-nickel layer. The cobalt-nickel layer provides a dipole moment and allows the flexible structure to align along oscillating weak (less than 5 mT) magnetic field lines, and hence generates a propulsion thrust force that overcomes the drag force. The frequency response of this system shows that the propulsion mechanism allows for swimming at an average speed of 158 ± 32 ?m/s at alternating weak magnetic field of 45 Hz. In addition, we experimentally demonstrate controlled steering of the flexible structure towards reference positions.
On the equilibrium shape of a heavily charged drop suspended in a weak electrostatic field
NASA Astrophysics Data System (ADS)
Shiryaeva, S. O.; Petrushov, N. A.; Grigor'ev, A. I.
2015-08-01
The object of investigation is the shape of a heavily charged drop placed in a weak electrostatic field. Calculations were carried out in the fourth order of smallness in the eccentricity, through which the steady-state deformation of the drop is measured. It is shown that the equilibrium shape of such a drop can be approximated by a prolate spheroid. This shape is due to the self-charge of the drop rather than to the external field, which is very weak and merely specifies a preferred direction. In an electrostatic suspension, where such a situation may take place, the deformation-related measurement inaccuracy of the critical charge can be totally eliminated if fine droplets are used.
Vibrational spectra of free and intracellular DNA in the weak electromagnetic field
NASA Astrophysics Data System (ADS)
Dovbeshko, Galina I.
1998-09-01
Vibrational bands of DNA molecules from birds' erythrocytes, as well as Dunaliella viridis alga cells and Escherichia coli bacteria clinical strains in the weak microwave field were investigated with IR spectroscopy. Drastic changes were detected in the intensities and fine structure of C equals O and PL2 bands for polarized spectra of irradiated samples of DNA molecules as compared with the reference samples in the 1700-1000 cm-1 region. No essential changes were detected in the IR spectra in the region of PO2 bands of DNA for the Escherichia coli, irradiated by the weak electromagnetic field, but essential redistribution of intensities and change in halfwidths of the PO2 symmetrical bonds were detected for Dunaliella viridis alga cells.
Effects of the Electromagnetic Field on Five-dimensional Gravitational Collapse
M. Sharif; G. Abbas
2010-01-29
This paper investigates the five-dimensional(5D) spherically symmetric gravitational collapse with positive cosmological constant in the presence of an electromagnetic field. The junction conditions between the 5D non-static interior and the static exterior spacetimes are derived using the Israel criteria modified by Santos. We use the energy conditions to discuss solution to the field equations of the interior spacetime with a charged perfect fluid for the marginally bound and the non-marginally bound cases. We found that the range of apparent horizon was larger than that for 4D gravitational collapse with an electromagnetic field. This analysis gives the irreducible and the reducible extensions of 4D perfect fluid collapse with an electromagnetic field and 5D perfect fluid collapse, respectively. Moreover, for the later case, the results can be recovered under some restrictions.
Stability of relative equilibria in arbitrary axisymmetric gravitational and magnetic fields
NASA Astrophysics Data System (ADS)
Howard, James E.
1999-05-01
Relative equilibria occur in a wide variety of physical applications, including celestial mechanics, particle accelerators, plasma physics, and atomic physics. We derive sufficient conditions for Lyapunov stability of circular orbits in arbitrary axisymmetric gravitational (electrostatic) and magnetic fields, including the effects of local mass (charge) and current density. Particularly simple stability conditions are derived for source-free regions, where the gravitational field is harmonic (?2U = 0) or the magnetic field irrotational (? × B = 0). In either case the resulting stability conditions can be expressed geometrically (coordinate-free) in terms of dimensionless stability indices. Stability bounds are calculated for several examples, including the problem of two fixed centers, the J2 planetary model, galactic disks, and a toroidal quadrupole magnetic field.
B. V. Vasiliev
2003-07-09
The equilibrium of a hot dense plasma in a gravitational field is considered. From the standard equilibrium equations, the energy minimum at density about $10^{25}$ particles per $cm^3$ and temperature about $10^7 K$ was found. This effect plays an important role for astrophysics. It enables to explain the mechanism of the star magnetic field generation and to make a prediction for the spectrum of a star mass with a wholly satisfactory agreement for the observation data.
Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam 2.3 Square Degree Field
Miyazaki, Satoshi; Hamana, Takashi; Tanaka, Masayuki; Miller, Lance; Utsumi, Yousuke; Komiyama, Yutaka; Furusawa, Hisanori; Sakurai, Junya; Kawanomoto, Satoshi; Nakata, Fumiaki; Uraguchi, Fumihiro; Koike, Michitaro; Tomono, Daigo; Lupton, Robert; Gunn, James; Karoji, Hiroshi; Aihara, Hiroaki; Murayama, Hitoshi; Takada, Masahiro
2015-01-01
We present properties of moderately massive clusters of galaxies detected by the newly developed Hyper Suprime-Cam on the Subaru telescope using weak gravitational lensing. Eight peaks exceeding a S/N ratio of 4.5 are identified on the convergence S/N map of a 2.3 square degree field observed during the early commissioning phase of the camera. Multi-color photometric data is used to generate optically selected clusters using the CAMIRA algorithm. The optical cluster positions were correlated with the peak positions from the convergence map. All eight significant peaks have optical counterparts. The velocity dispersion of clusters are evaluated by adopting the Singular Isothemal Sphere (SIS) fit to the tangential shear profiles, yielding virial mass estimates, M500c, of the clusters which range from 2.7x10^13 to 4.4x10^14 solar mass. The number of peaks is considerably larger than the average number expected from LambdaCDM cosmology but this is not extremely unlikely if one takes the large sample variance in t...
Neutrino spin oscillations in gravitational fields in non-commutative Spaces
S. A. Alavi; S. Nodeh
2014-12-19
We study neutrino spin oscillations in gravitational fields in non-commutative spaces. For the Schwarzschild metric the maximum frequency decreases with increasing the noncommutativity parameter. In the case of Reissner-Nordstrom (RN) metric, the maximum frequency of oscillation is a monotonically increasing function of the noncommutativity parameter .In both cases, the frequency of spin oscillations decreases as the distance from the gravitational source grows. We present a phenomenological application of our results. It is also shown that the noncommutativity parameter is bounded as 0.1 l_p.
The gravitational time delay in the field of a slowly moving body with arbitrary multipoles
Michael H. Soffel; Wen-Biao Han
2014-12-25
We calculate the time delay of light in the gravitational field of a slowly moving body with arbitrary multipoles (mass and spin multipole moments) by the Time-Transfer-Function (TTF) formalism. The parameters we use, first introduced by Kopeikin for a gravitational source at rest, make the integration of the TTF very elegant and simple. Results completely coincide with expressions from the literature. The results for a moving body (with constant velocity) with complete multipole-structure are new, according to our knowledge.
The Quasi-Linear Evolution of the Density Field in Models of Gravitational Instability
F. Bernardeau; T. P. Singh; B. Banerjee; S. M. Chitre
1993-11-22
Two quasi-linear approximations, the frozen flow approximation (FFA) and the frozen potential approximation (FPA), have been proposed recently for studying the evolution of a collisionless self-gravitating fluid. In the FFA it is assumed that the velocity field remains unchanged from its value obtained from the linear theory whereas in FPA the same approximation is made for the gravitational potential. In this paper we compare these and the older Zel'dovich approximation by calculating the evolution of the density in perturbation theory. In particular we compute the skewness, including the smoothing effects, and the kurtosis for the FFA, FPA and Zel'dovich approximation and compare their relative accuracy.
S. -Y. Wang
2006-06-20
In a recent article, Ayala et al. [Phys. Rev. D 73, 105009 (2006)] have studied the dynamical generation of masses for fundamental fermions in strongly coupled QED in the presence of weak magnetic fields. We argue that the results and conclusions of the article are not reliable as they are subject to gauge dependent artifacts resulting from an inconsistent truncation of the Schwinger-Dyson equations.
Detection of a weak magnetic field via cavity enhanced Faraday rotation
Keyu Xia; Nan Zhao; Jason Twamley
2015-07-01
We study the sensitive detection of a weak static magnetic field via Faraday rotation induced by an ensemble of spins in a bimodal degenerate microwave cavity. We determine the limit of the resolution for the sensitivity of the magnetometry achieved using either single-photon or multiphoton inputs. For the case of a microwave cavity containing an ensemble of Nitrogen-vacancy defects in diamond, we obtain a magnetometry sensitivity exceeding $0.5~\\text{\
Weak asymptotics of the Spectral Shift Function in strong constant magnetic field
Vincent Bruneau; Mouez Dimassi
odinger operator, Spectral Shift Function, operator valued pseudo-differential operators. MSC (2000) 81Q10 35J10 35P05 47A55 47B25 47F05 47N50 47A56 We consider the three-dimensional Schrodinger operator with constant magnetic field of strength b > 0, and with smooth electric potential. The weak asymptotics of the Spectral Shift Function with respect to b % +1 is studied. First, we fix the distance
[Effects of weak magnetic fields on different phases of planarian regeneration].
Tiras, Kh P; Petrova, O N; Miakisheva, S N; Popova, S S; Aslanidi, K B
2015-01-01
We analyzed the effects of weak combined magnetic fields, tuned to the cyclotron resonance condition for calcium ions, obtained in different phases of planarian regeneration. We showed that the result of regeneration in 72 hours after decapitation depends on the length of exposure, and the time between decapitation and initiation of a half-hour exposure. The experimental dependence can be explained by a multiplicity of enzymatic targets activated in different phases of the regeneration process. PMID:25868354
Linearization stability of Einstein equations coupled with self-gravitating scalar fields
Saraykar, R.V.; Joshi, N.E.
1981-02-01
In this paper, we extend the work of Fischer-Marsden and Moncrief on the linearization stability of vacuum spacetimes to the case of vacuum Einstein equations coupled with self-gravitating scalar fields. We prove that the coupled system is linearization stable under some suitable conditions. We also prove the relation between linearization stability and the condition that spacetime admits Killing fields analogous to the work of Moncrief.
Giambó, R; Magli, G
2008-01-01
The gravitational collapse of a wide class of self-interacting homogeneous scalar fields models is analyzed. The class is characterized by certain general conditions on the scalar field potential, which, in particular, include both asymptotically polynomial and exponential behaviors. Within this class, we show that the generic evolution is always divergent in a finite time, and then make use of this result to construct radiating star models of the Vaidya type. It turns out that blackholes are generically formed in such models.
R. Giambó; F. Giannoni; G. Magli
2008-02-07
The gravitational collapse of a wide class of self-interacting homogeneous scalar fields models is analyzed. The class is characterized by certain general conditions on the scalar field potential, which, in particular, include both asymptotically polynomial and exponential behaviors. Within this class, we show that the generic evolution is always divergent in a finite time, and then make use of this result to construct radiating star models of the Vaidya type. It turns out that blackholes are generically formed in such models.
Evolution of the gravitational fields and figures of Jupiter and Saturn
Bobrov, A.M.; Vasil'ev, P.P.; Trubitsyn, V.P.
1983-03-01
The gravitational fields and figures of Jupiter and Saturn at different times in their evolutionary contraction are found through a numerical solution of the system of integrodifferential figure equations. The time variation of their angular velocity and radial density distribution is taken into account. Time dependences are obtained for the flattening of the planetary figures and the field harmonics of numbers 2, 4, and 6.
Gravitational collapse of scalar fields via spectral methods
Oliveira, H. P. de; Rodrigues, E. L.; Skea, J. E. F.
2010-11-15
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.
Gravitational collapse of scalar fields via spectral methods
NASA Astrophysics Data System (ADS)
de Oliveira, H. P.; Rodrigues, E. L.; Skea, J. E. F.
2010-11-01
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.
NASA Astrophysics Data System (ADS)
Lahav, Ofer; Terlevich, Elena; Terlevich, Roberto J.
1996-07-01
Preface; Part I. Galactic Structure: 1. Dynamics of triaxial systems P. T. de Zeeuw; 2. The mass of the galactic halo D. N. C. Lin; 3. Negative specific heat in clusters of atoms R. M. Lynden-Bell; 4. Dynamical evolution of globular clusters J. P. Ostriker; 5. Disc stability J. C. B. Papaloizou; 6. Protostellar discs J. E. Pringle; 7. Dynamics of warped galaxies S. D. Tremaine; Part II. Quasars, Galaxy Formation and Evolution: 8. Jets and cooling flows J. J. Binney; 9. Galactic nuclei M. J. Rees; 10. Optical quasar surveys M. Schmidt; 11. Violent relaxation in hierarchical clustering S. D. M. White; Part III. Cosmology: 12. Observational tests of general relativity R. D. Blandford; 13. A reconsideration of the peculiar velocity field within the local supercluster D. Burnstein; 14. Cosmology with the APM G. P. Efstathiou; 15. Geometric algebra, spacetime physics and gravitation S. F. Gull; 16. Weak gravitational lensing N. Kaiser; 17. Energy in general relativity J. Katz; 18. Gravitational dynamics in an expanding universe T. Padmanabhan; 19. Dynamics of the relative motions of the galaxies in and near the local group P. J. E. Peebles; 20. Inertia D. Lynden-Bell; Epilogue V. C. Rubin; Appendices Donald Lynden-Bell and D. J. D. Earn.
Surface electrostatic field below weak precipitation and stratiform regions of mid-latitude storms
NASA Astrophysics Data System (ADS)
Soula, S.; Georgis, J. F.
2013-10-01
The electrostatic field is measured below thunderstorms at two sites in south-western France thanks to a field mill. It is recorded with a 1-s time resolution, simultaneously to the precipitation current measured with a specific sensor. The variations of both parameters are analyzed for two cases out of three storms considered in the study. Cloud-to-Ground (CG) lightning data from Météorage network and scans from a C-band radar included in the French network ARAMIS are used to characterize the storms. The magnitude of the electrostatic field can reach large values below the weak precipitation regions compared to the convective regions: between 5 and 6 kV m- 1, and between 2 and 3 kV m- 1, respectively. The field polarity is commonly negative (downward field) but it can reverse as the rainfall carries positive charge to the ground. So, the mirror effect is generally observed between the electrostatic field and the precipitation current. The electrostatic field magnitude can indicate the presence of large amounts of charge within the weak precipitation region above, although the lightning ground strokes remain relatively far. The fast field variations produced by CG flashes are analyzed. A strong dissymmetry for both CG polarities is observed: the + CG flashes can produce larger field discontinuities (~ 10 kV m- 1) even when their striking points are at about a distance of 40 km from the sensor, while the - CG flashes produce discontinuities lower than 4 kV m- 1 even when the striking points are within 4 km around the sensor. This indicates that either the charge removed by a + CG flash can be horizontally displaced with respect to the ground stroke location, or it can be much larger compared to that removed by a negative CG flash. Our observations suggest the surface electrostatic field measured below these regions may provide valuable information for estimating local lightning risk.
Dark-field hyperlens: Super-resolution imaging of weakly scattering objects
Repän, Taavi; Zhukovsky, Sergei V
2015-01-01
We propose and numerically demonstrate a technique for subwavelength imaging based on a metal-dielectric multilayer hyperlens designed in such a way that only the large-wavevector waves are transmitted while all propagating waves from the image area are blocked by the hyperlens. As a result, the image plane only contains scattered light from subwavelength features of the objects and is free from background illumination. Similar in spirit to conventional dark-field microscopy, the proposed dark-field hyperlens is promising for optical imaging of weakly scattering subwavelength objects, such as optical nanoscopy of label-free biological objects.
Weak-Field Spherically Symmetric Solutions in $f(T)$ gravity
Ruggiero, Matteo Luca
2015-01-01
We study weak-field solutions having spherical symmetry in $f(T)$ gravity; to this end, we solve the field equations for a non diagonal tetrad, starting from Lagrangian in the form $f(T)=T+\\alpha T^{n}$, where $\\alpha$ is a small constant, parameterizing the departure of the theory from GR. We show that the classical spherically symmetric solutions of GR, i.e. the Schwarzschild and Schwarzschild-de Sitter solutions, are perturbed by terms in the form $\\propto r^{2-2n}$ and discuss the impact of these perturbations in observational tests.
Weak-Field Spherically Symmetric Solutions in $f(T)$ gravity
Matteo Luca Ruggiero; Ninfa Radicella
2015-04-21
We study weak-field solutions having spherical symmetry in $f(T)$ gravity; to this end, we solve the field equations for a non diagonal tetrad, starting from Lagrangian in the form $f(T)=T+\\alpha T^{n}$, where $\\alpha$ is a small constant, parameterizing the departure of the theory from GR. We show that the classical spherically symmetric solutions of GR, i.e. the Schwarzschild and Schwarzschild-de Sitter solutions, are perturbed by terms in the form $\\propto r^{2-2n}$ and discuss the impact of these perturbations in observational tests.
Small-$x$ QCD evolution of $2 n$ Wilson line correlator: the weak field limit
Alejandro Ayala; Erike R. Cazaroto; Luis Alberto Hernández; Jamal Jalilian-Marian; Maria Elena Tejeda-Yeomans
2015-04-03
We write down explicit expressions for the $x$-evolution (equivalent to energy or rapidity evolution) of $2 n$ ($n = 1, 2, ...$) Wilson lines using the JIMWLK equation and the Color Glass Condensate formalism. We investigate the equation in the weak gluon field limit (linear regime) by expanding the Wilson lines in powers of the gluon field and show that it reduces to the BJKP equation describing the evolution of a state of $2 n$ Reggeized gluons with energy. We also make available for download a {\\it Mathematica} program which provides this expression for any value of $n$.
Electrostatic self-force in a static weak gravitational field with cylindrical symmetry
B. Boisseau; C. Charmousis; B. Linet
1996-03-04
We determine the electrostatic self-force at rest in an arbitrary static metric with cylindrical symmetry in the linear approximation in the Newtonian constant. In linearised Einstein theory, we express it in terms of the components of the energy-momentum tensor.
Quark deconfinement and gluon condensate in a weak magnetic field from QCD sum rules
NASA Astrophysics Data System (ADS)
Ayala, Alejandro; Dominguez, C. A.; Hernandez, L. A.; Loewe, M.; Rojas, Juan Cristobal; Villavicencio, Cristian
2015-07-01
We study QCD finite energy sum rules (FESR) for the axial-vector current correlator in the presence of a magnetic field, in the weak field limit and at zero temperature. We find that the perturbative QCD and the hadronic contribution to the sum rules get explicit magnetic-field-dependent corrections and that these in turn induce a magnetic field dependence on the deconfinement phenomenological parameter s0 and on the gluon condensate. The leading corrections turn out to be quadratic in the field strength. We find from the dimension d =2 first FESR that the magnetic field dependence of s0 is proportional to the absolute value of the light-quark condensate. Hence, it increases with increasing field strength. This implies that the parameters describing chiral symmetry restoration and deconfinement behave similarly as functions of the magnetic filed. Thus, at zero temperature the magnetic field is a catalyzing agent of both chiral symmetry breaking and confinement. From the dimension d =4 second FESR we obtain the behavior of the gluon condensate in the presence of the external magnetic field. This condensate also increases with increasing field strength.
Weak cosmic censorship, dyonic Kerr-Newman black holes and Dirac fields
Toth, Gabor Zsolt
2015-01-01
It was investigated recently, with the aim of testing the weak cosmic censorship conjecture, whether an extremal Kerr black hole can be converted into a naked singularity by interaction with a massless classical Dirac test field, and it was found that this is possible. We generalize this result to electrically and magnetically charged rotating extremal black holes (i.e. extremal dyonic Kerr-Newman black holes) and massive Dirac test fields, allowing magnetically or electrically uncharged or nonrotating black holes and the massless Dirac field as special cases. We show that the possibility of the conversion is a direct consequence of the fact that the Einstein-Hilbert energy-momentum tensor of the classical Dirac field does not satisfy the null energy condition, and is therefore not in contradiction with the weak cosmic censorship conjecture. We give a derivation of the absence of superradiance of the Dirac field without making use of the complete separability of the Dirac equation in dyonic Kerr-Newman backgr...
[Mechanism of action of combined extremely weak magnetic field on aqueous solution of amino acid].
Zhadin, M N; Bakharev, B V; Bobkova, N V
2014-01-01
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
Gravitating tensor monopole in a Lorentz-violating field theory
Xin-zhou Li; Ping Xi; Qun Zhang
2012-04-06
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.
Resonant amplification of magnetic seed fields by gravitational waves in the early universe
Tsagas, Christos G.
2005-12-15
Inflation is known to produce both gravitational waves and seed magnetic fields on scales well beyond the size of the horizon. The general relativistic study of the interaction between these two sources after 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 gravitomagnetic 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.
Charge Separation within Superconductors in the Presence of Tidal Gravitational Fields
Minter, Stephen J.; Wegter-McNelly, Kirk; Chiao, Raymond Y.
2009-09-09
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.
Horizon thermodynamics and gravitational field equations in Horava-Lifshitz gravity
Cai Ronggen; Ohta, Nobuyoshi
2010-04-15
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.
Locality of Gravitational Systems from Entanglement of Conformal Field Theories.
Lin, Jennifer; Marcolli, Matilde; Ooguri, Hirosi; Stoica, Bogdan
2015-06-01
The Ryu-Takayanagi formula relates the entanglement entropy in a conformal field theory to the area of a minimal surface in its holographic dual. We show that this relation can be inverted for any state in the conformal field theory to compute the bulk stress-energy tensor near the boundary of the bulk spacetime, reconstructing the local data in the bulk from the entanglement on the boundary. We also show that positivity, monotonicity, and convexity of the relative entropy for small spherical domains between the reduced density matrices of any state and of the ground state of the conformal field theory are guaranteed by positivity conditions on the bulk matter energy density. As positivity and monotonicity of the relative entropy are general properties of quantum systems, this can be interpreted as a derivation of bulk energy conditions in any holographic system for which the Ryu-Takayanagi prescription applies. We discuss an information theoretical interpretation of the convexity in terms of the Fisher metric. PMID:26196612
Gravitation: Field theory par excellence Newton, Einstein, and beyond
Yilmaz, H.
1984-09-01
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.
Locality of Gravitational Systems from Entanglement of Conformal Field Theories
NASA Astrophysics Data System (ADS)
Lin, Jennifer; Marcolli, Matilde; Ooguri, Hirosi; Stoica, Bogdan
2015-06-01
The Ryu-Takayanagi formula relates the entanglement entropy in a conformal field theory to the area of a minimal surface in its holographic dual. We show that this relation can be inverted for any state in the conformal field theory to compute the bulk stress-energy tensor near the boundary of the bulk spacetime, reconstructing the local data in the bulk from the entanglement on the boundary. We also show that positivity, monotonicity, and convexity of the relative entropy for small spherical domains between the reduced density matrices of any state and of the ground state of the conformal field theory are guaranteed by positivity conditions on the bulk matter energy density. As positivity and monotonicity of the relative entropy are general properties of quantum systems, this can be interpreted as a derivation of bulk energy conditions in any holographic system for which the Ryu-Takayanagi prescription applies. We discuss an information theoretical interpretation of the convexity in terms of the Fisher metric.
Gravitational radiation from collapsing magnetized dust
Sotani, Hajime; Yoshida, Shijun; Kokkotas, Kostas D.
2007-04-15
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.
Gravitational radiation from collapsing magnetized dust
Hajime Sotani; Shijun Yoshida; Kostas D. Kokkotas
2007-02-15
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.
Humphreys, Eugene
Cenozoic slab windows beneath the western United States ABSTRACT The weak lithosphere and high-slab subduction cooled and hydrated the base of western U.S. lithosphere and slab removal brought asthenosphere in contact with this conditioned lithosphere, causing a phase of intense magmatism that propagated in two
A new high-integrated weak field sensor for automotive applications
NASA Astrophysics Data System (ADS)
Thiessen, T.; Prochaska, M.
2009-05-01
Especially in the field of automotive applications smart sensor systems for magnetic field sensing face increasing requirements concerning low cost, low power consumption and high magnetic performance. Over the past years AMR sensors play a decisive role in this application area because of their robustness and stability. In the following a high-integrated smart sensor system for magnetic field sensing is presented. A novel approach for the detection of weak magnetic fields is shown, which is based on an AC-excitation of AMR elements. In contrast to common used sensors this concept is based on a nonlinear AMR element without Barber pole construction. By means of this methodology sensitivity as well as temperature and life time stability is significantly improved, while the production costs compared to common-used sensors are reduced. Within this novel approach new signal conditioning algorithms and analog circuit topologies are presented, which are able to meet low offset and low noise requirements.
Rectification and signal averaging of weak electric fields by biological cells.
Astumian, R D; Weaver, J C; Adair, R K
1995-01-01
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
A Quantum Weak Energy Inequality for Spin-One Fields in Curved Spacetime
Christopher J. Fewster; Michael J. Pfenning
2003-03-26
Quantum weak energy inequalities (QWEI) provide state-independent lower bounds on averages of the renormalised energy density of a quantum field. We derive QWEIs for the electromagnetic and massive spin-one fields in globally hyperbolic spacetimes whose Cauchy surfaces are compact and have trivial first homology group. These inequalities provide lower bounds on weighted averages of the renormalized energy density as ``measured'' along an arbitrary timelike trajectory, and are valid for arbitrary Hadamard states of the spin-one fields. The QWEI bound takes a particularly simple form for averaging along static trajectories in ultrastatic spacetimes; as specific examples we consider Minkowski space [in which case the topological restrictions may be dispensed with] and the static Einstein universe. A significant part of the paper is devoted to the definition and properties of Hadamard states of spin-one fields in curved spacetimes, particularly with regard to their microlocal behaviour.
A Quantum Weak Energy Inequality for Spin-One Fields in Curved Spacetime
Fewster, C J; Fewster, Christopher J.; Pfenning, Michael J.
2003-01-01
Quantum weak energy inequalities (QWEI) provide state-independent lower bounds on averages of the renormalised energy density of a quantum field. We derive QWEIs for the electromagnetic and massive spin-one fields in globally hyperbolic spacetimes whose Cauchy surfaces are compact and have trivial first homology group. These inequalities provide lower bounds on weighted averages of the renormalized energy density as ``measured'' along an arbitrary timelike trajectory, and are valid for arbitrary Hadamard states of the spin-one fields. The QWEI bound takes a particularly simple form for averaging along static trajectories in ultrastatic spacetimes; as specific examples we consider Minkowski space [in which case the topological restrictions may be dispensed with] and the static Einstein universe. A significant part of the paper is devoted to the definition and properties of Hadamard states of spin-one fields in curved spacetimes, particularly with regard to their microlocal behaviour.
Detecting the presence of weak magnetic fields using nitrogen-vacancy centers
NASA Astrophysics Data System (ADS)
Chaudhry, Adam Zaman
2015-06-01
We show how nitrogen-vacancy centers can be used to detect the presence of weak magnetic fields, that is, to find out whether a magnetic field, about which we may not have complete information, is actually present or not. The solution to this problem comes from quantum state discrimination theory. The effect of decoherence is taken into account to optimize the time over which the nitrogen-vacancy center is allowed to interact with the magnetic field before making a measurement. We also find the optimum measurement that should be performed. We then show how multiple measurements reduce the error in detecting the magnetic field. Finally, a major limitation of the measurement process, namely, limited photon detection efficiency, is taken into account. Our proposals should be implementable with current experimental technology.
Dark sector impact on gravitational collapse of an electrically charged scalar field
Anna Nakonieczna; Marek Rogatko; ?ukasz Nakonieczny
2015-08-11
Dark matter and dark energy are dominating components of the Universe. Their presence affects the course and results of processes, which are driven by the gravitational interaction. The objective of the paper was to examine the influence of the dark sector on the gravitational collapse of an electrically charged scalar field. A phantom scalar field was used as a model of dark energy in the system. Dark matter was modeled by a complex scalar field with a quartic potential, charged under an U(1)-gauge field. The dark components were coupled to the electrically charged scalar field via the exponential coupling and the gauge field-Maxwell field kinetic mixing, respectively. Complete non-linear simulations of the investigated process were performed. They were conducted from regular initial data to the end state, which was the matter dispersal or a singularity formation in a spacetime. During the collapse in the presence of dark energy dynamical wormholes and naked singularities were formed in emerging spacetimes. The wormhole throats were stabilized by the violation of the null energy condition, which occurred due to a significant increase of a value of the phantom scalar field function in its vicinity. The square of mass parameter of the dark matter scalar field potential controlled the formation of a Cauchy horizon or wormhole throats in the spacetime. The joint impact of dark energy and dark matter on the examined process indicated that the former decides what type of an object forms, while the latter controls the amount of time needed for the object to form. Additionally, the dark sector suppresses the natural tendency of an electrically charged scalar field to form a dynamical Reissner-Nordstr\\"{o}m spacetime during the gravitational collapse.
Is ‘dark matter’ made entirely of the gravitational field?
NASA Astrophysics Data System (ADS)
Kleinert, Hagen
2012-11-01
We argue that part of ‘dark matter’ is not made of matter, but of the singular world lines and world surfaces in the solutions of Einstein's vacuum field equation G?? = 0. Their Einstein-Hilbert action governs, in a slightly modified form, also their quantum fluctuations in a partition function formed from a sum over all line and surface configurations. For world surfaces, the Einstein-Hilbert action coincides with that of closed bosonic ‘strings’ in four spacetime dimensions, which appear here in a new physical context.
Approximate gravitational field of a rotating deformed mass
Jose Luis Hernandez Pastora
2006-01-26
A new approximate solution of vacuum and stationary Einstein field equations is obtained. This solution is constructed by means of a power series expansion of the Ernst potential in terms of two independent and dimensionless parameters representing the quadrupole and the angular momentum respectively. The main feature of the solution is a suitable description of small deviations from spherical symmetry through perturbations of the static configuration and the massive multipole structure by using those parameters. This quality of the solution might eventually provide relevant differences with respect to the description provided by the Kerr solution.
Travelling wave deceleration of heavy polar molecules in weak-field seeking states
NASA Astrophysics Data System (ADS)
Hendricks, Richard; Bulleid, Nicholas; Skoff, Sarah; Segal, Daniel; Sauer, Ben; Tarbutt, Michael; Hinds, Edward; Meek, Samuel; Osterwalder, Andreas; Parsons, Maxwell; Santambrogio, Gabriele; Meijer, Gerard
2012-06-01
Electrostatic forces can be used to decelerate neutral molecules via the Stark interaction. Most Stark decelerators to date use switched dc electric fields to manipulate light molecules in weak field seeking states. More massive molecules have smaller rotational constants and greater kinetic energies at a given velocity, and would require very long decelerators to bring them to rest. We have combined a new cryogenic source of YbF molecules, based on a pulsed solenoid valve cooled to 4K, with a 48cm long travelling wave Stark decelerator that is suitable for decelerating heavy molecules in weak-field seeking states. This decelerator uses continuously modulated sinusoidal electric fields to produce a series of moving 3-dimensional traps that can be continuously slowed to decelerate the molecules within them. We have decelerated YbF molecules from 300m/s to 276m/s. This implies that a 3 metre long decelerator could produce trapped YbF molecules at rest. In a different configuration, our source produces broader pulses of YbF molecules with speeds of 200m/s or less that could be brought to rest with a decelerator that is just 1 metre in length.
Gravitational Field of A Radiating Star in Higher Dimensions
B. C. Paul; P. K. Chattopadhyay
2007-08-06
We obtain fields of a relativistic radiating star of non-static mass in the framework of higher dimensional spacetime. Assuming energy-momentum tensor in Higher dimensions analogous to that considered by Vaidya in 4 dimensions we obtain solution of a radiating spherically symmetric star. The solution obtained here is new in higher dimensions which however reduces to that obtained by Vaidya in 4 dimensions. It is also different in form from that obtained by Iyer and Vishveshwara. The interesting observation is that the radius of a radiating star in higher dimensions oscillates. The radial size of radiating star oscillates with a period which depends on the modes of vibration and dimensions of the space-time.
Thick branes from self-gravitating scalar fields
Novikov, Oleg O.; Andrianov, Vladimir A.; Andrianov, Alexander A.
2014-07-23
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.
Blake, Chris; Heymans, Catherine; Choi, Ami; Erben, Thomas; Harnois-Deraps, Joachim; Hildebrandt, Hendrik; Joachimi, Benjamin; Nakajima, Reiko; van Waerbeke, Ludovic; Viola, Massimo
2015-01-01
The unknown nature of dark energy motivates continued cosmological tests of large-scale gravitational physics. We present a new consistency check based on the relative amplitude of non-relativistic galaxy peculiar motions, measured via redshift-space distortion, and the relativistic deflection of light by those same galaxies traced by galaxy-galaxy lensing. We take advantage of the latest generation of deep, overlapping imaging and spectroscopic datasets, combining the Red Cluster Sequence Lensing Survey (RCSLenS), the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the WiggleZ Dark Energy Survey and the Baryon Oscillation Spectroscopic Survey (BOSS). We quantify the results using the "gravitational slip" statistic E_G, which we estimate as 0.48 +/- 0.10 at z=0.32 and 0.30 +/- 0.07 at z=0.57, the latter constituting the highest redshift at which this quantity has been determined. These measurements are consistent with the predictions of General Relativity, for a perturbed Friedmann-Robertson-Walker ...
D. B. Papadopoulos
2003-12-23
The equations which determine the response of a spinning charged particle moving in a uniform magnetic field to an incident gravitational wave are derived in the linearized approximation to general relativity. We verify that 1) the components of the 4-momentum, 4-velocity and the components of the spinning tensor, both electric and magnetic moments, exhibit resonances and 2) the co-existence of the uniform magnetic field and the GW are responsible for the resonances appearing in our equations. In the absence of the GW, the magnetic field and the components of the spin tensor decouple and the magnetic resonances disappear.
Exact solutions of a two-dimensional Kemmer oscillator in the gravitational field of cosmic string
NASA Astrophysics Data System (ADS)
Messai, Nadjette; Boumali, Abdelmalek
2015-07-01
The two-dimensional Kemmer oscillator under the influence of the gravitational field produced by a topology such as the cosmic string spacetime and in the presence of a uniform magnetic field as well as without magnetic field are investigated. The eigensolutions of our problem have been found by using the generalized parametric Nikiforov-Uvarov (NU) method, and the influence of the cosmic string spacetime on the energy spectrum has been analyzed. We show that the dependence of the energy levels of the quantum system with the angular deficit ?, which characterizes the global structure of the metric in the cosmic string spacetime, breaks the degeneracy of these levels.
Equation of Motion of a Spinning Test Particle in Gravitational Field
Ning Wu
2006-08-08
Based on the coupling between the spin of a particle and gravitoelectromagnetic field, the equation of motion of a spinning test particle in gravitational field is deduced. From this equation of motion, it is found that the motion of a spinning particle deviates from the geodesic trajectory, and this deviation originates from the coupling between the spin of the particle and gravitoelectromagnetic field, which is also the origin of Lense-Thirring effects. In post-Newtonian approximations, this equation gives out the same results as those of Papapetrou equation. Effect of the deviation of geodesic trajectory is detectable.
M. Sharif; M. Azam
2013-05-31
In this paper, we discuss the effects of electromagnetic field on the dynamical instability of a spherically symmetric expansionfree gravitational collapse. Darmois junction conditions are formulated by matching interior spherically symmetric spacetime to exterior Reissner-Nordstr$\\ddot{o}$m spacetime. We investigate the role of different terms in the dynamical equation at Newtonian and post Newtonian regimes by using perturbation scheme. It is concluded that instability range depends upon pressure anisotropy, radial profile of energy density and electromagnetic field, but not on the adiabatic index $\\Gamma$. In particular, the electromagnetic field reduces the unstable region.
General Relativistic Theory of the VLBI Time Delay in the Gravitational Field of Moving Bodies
NASA Technical Reports Server (NTRS)
Kopeikin, Sergei
2003-01-01
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.
Observing black holes with gravitational waves Eric Gourgoulhon
Gourgoulhon, Eric
(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
Interaction of gravitational waves with matter from Special Relativity
NASA Astrophysics Data System (ADS)
Christillin, Paolo
2015-07-01
The predictions of the effective vector formulation of gravitation (GEV), valid for the weak field situation of radiation, are compared to those of General Relativity (GR) for the interaction of gravitational waves with matter. It is shown that their effect is much smaller than what predicted by GR.
NASA Astrophysics Data System (ADS)
Kirschvink, Joseph L.
1992-08-01
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.
Snow Load Effect on the Earth's Rotation and Gravitational Field, 1979–1985
B. Fong Chao; William P. O'Connor; Alfred T. C. Chang; Dorothy K. Hall; James L. Foster
1987-01-01
A global, monthly snow depth data set has been generated from the Nimbus 7 satellite observations using passive microwave remote-sensing techniques. In this paper we analyze 7 years of data, 1979-1985, to compute the snow load effects on the earth's rotation and low-degree zonal gravitational field. A uniform sea level decrease has been assumed in order to conserve water mass.
A comparative review of certain gauge theories of the gravitational field
NASA Astrophysics Data System (ADS)
Basombrio, F. G.
1980-02-01
A general formal analysis is made in order to obtain a better understanding and greater synthesis of the mathematical structure of the gravitational field gauge theories. Under this approach, some misstatements appearing in current theories are detected. A theory based on the direct product groups T(4) x GL(4) and T(4) O(1, 3) is suggested (in contrast to those using the Poincare group, semidirect product). Such a theory corrects the above-mentioned deficiencies.
Do Gravitational Fields Have Mass? Or on the Nature of Dark Matter
Ernst Karl Kunst
1999-01-01
As has been shown before (a brief comment will be given in the text),\\u000arelativistic mass and relativistic time dilation of moving bodies are\\u000aequivalent as well as time and mass in the rest frame. This implies that the\\u000atime dilation due to the gravitational field is combined with inertial and\\u000agravitational mass as well and permits the computation of
Weak localization effects on the upper critical field of bulk superconductors
NASA Astrophysics Data System (ADS)
Wong, K. M.; Poon, S. J.; Lambrecht, A.; Naugle, D. G.
1987-04-01
Weak localization effects on bulk superconductivity are investigated by measuring the upper critical field (Hc2) and the heat capacity (C) on the same sample of a given alloy composition. Systems studied include rapidly solidified glassy Zr70Ni30, Zr75Rh25, and body-centered cubic Hf90Mo10. The homogeneity of samples are examined. Without including quantum corrections, very good fits to the Hc2 curves predicted by the classical theory of dirty superconductors are obtained by varying the Pauli paramagnetic limiting and spin-orbit scattering parameters. However, the initial gradients obtained from fitting the Hc2 data are ~(10-30)% higher than those determined by the ?N*?(0) products [ ? is the electrical resistivity and N*?(0) is the density of states obtained from heat-capacity measurements]. These relative enhancements of the upper critical fields are attributed to field-induced delocalization effects. The results are analyzed in the framework of the Fukuyama, Ebisawa, and Maekawa theory of weak localization.
Effect of a weak electric field on the cubic blue phases of cholesteric liquid crystals
NASA Astrophysics Data System (ADS)
Lubin, Dror; Hornreich, R. M.
1987-07-01
The effect of a weak electric field E on the cubic blue phases (BP's) of cholesteric liquid crystals is considered. A Landau model, modified to include the uniaxiality induced by the field, is used. It is shown for space groups O8 and O2, which are believed to characterize BP I and BP II, respectively, that a free crystal will orient itself such that the field is parallel to a fourfold axis (a <001> direction), in agreement with experiment. For O5, the stable orientation would be with the field parallel to a threefold axis (a <111> direction). In addition, in the presence of the field, there is (for all three cases) an induced birefringence. There are also shifts in the wavelengths of the Bragg reflections, and the cubic unit cell is distorted by a field in a <001> (<111>) direction into one having tetragonal (trigonal) symmetry. The ratio of the cell dimensions parallel and perpendicular to the field, the induced birefringence, and the wavelength shifts are, to lowest order, quadratic in E as expected from symmetry considerations. These results provide additional evidence for the generally accepted assignment of O8 (O2) for BP I (BP II), and for ruling out an O5 structure for the observed BP.
Jenrow, K.A.; Smith, C.H.; Liboff, A.R.
1996-12-31
The authors recently reported that cephalic regeneration in the planarian Dugesia tigrina was significantly delayed in populations exposed continuously to combined parallel DC and AC magnetic fields. This effect was consistent with hypotheses suggesting an underlying resonance phenomenon. The authors report here, in a parallel series of investigations on the same model system, that the incidence of regeneration anomalies presenting as tumor-like protuberances also increases significantly (P < .001) in association with exposure to weak 60 Hz magnetic fields, with peak intensities ranging between 1.0 and 80.0 {micro}T. These anomalies often culminate in the complete disaggregation of the organism. Similar to regeneration rate effects, the incidence of regeneration anomalies is specifically dependent upon the planaria possessing a fixed orientation with respect to the applied magnetic field vectors. However, unlike the regeneration rate effects, the AC magnetic field alone, in the absence of any measurable DC field, is capable of producing these anomalies. Moreover, the incidence of regeneration anomalies follows a clear dose-response relationship as a function of AC magnetic field intensity, with the threshold for induced electric field intensity estimated at 5 {micro} V/m. The addition of either 51.1 or 78.4 {micro}T DC magnetic fields, applied in parallel combination with the AC field, enhances the appearance of anomalies relative to the 60 Hz AC field alone, but only at certain AC field intensities. Thus, whereas the previous study of regeneration rate effects appeared to involve exclusively resonance interactions, the regeneration anomalies reported here appear to result primarily from Faraday induction coupling.
Weak lensing calibrated M-T scaling relation of galaxy groups in the cosmos field
Kettula, K.; Finoguenov, A. [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, FI-00014 Helsinki (Finland); Massey, R. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Rhodes, J. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Hoekstra, H. [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333-CA Leiden (Netherlands); Taylor, J. E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Spinelli, P. F. [Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG), Rua do Matão, 1226 Cidade Universitária 05508-090, São Paulo, SP (Brazil); Tanaka, M. [National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Ilbert, O. [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, F-13013 Marseille (France); Capak, P. [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard Pasadena, CA 91125 (United States); McCracken, H. J. [Institut d'Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, F-75014 Paris (France); Koekemoer, A., E-mail: kimmo.kettula@iki.fi [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2013-11-20
The scaling between X-ray observables and mass for galaxy clusters and groups is instrumental for cluster-based cosmology and an important probe for the thermodynamics of the intracluster gas. We calibrate a scaling relation between the weak lensing mass and X-ray spectroscopic temperature for 10 galaxy groups in the COSMOS field, combined with 55 higher-mass clusters from the literature. The COSMOS data includes Hubble Space Telescope imaging and redshift measurements of 46 source galaxies per arcminute{sup 2}, enabling us to perform unique weak lensing measurements of low-mass systems. Our sample extends the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study, resulting in a power-law slope of 1.48{sub ?0.09}{sup +0.13}. The slope is consistent with the self-similar model, predictions from simulations, and observations of clusters. However, X-ray observations relying on mass measurements derived under the assumption of hydrostatic equilibrium have indicated that masses at group scales are lower than expected. Both simulations and observations suggest that hydrostatic mass measurements can be biased low. Our external weak lensing masses provide the first observational support for hydrostatic mass bias at group level, showing an increasing bias with decreasing temperature and reaching a level of 30%-50% at 1 keV.
Dark sector impact on gravitational collapse of an electrically charged scalar field
Nakonieczna, Anna; Nakonieczny, ?ukasz
2015-01-01
Dark matter and dark energy are dominating components of the Universe. Their presence affects the course and results of processes, which are driven by the gravitational interaction. The objective of the paper was to examine the influence of the dark sector on the gravitational collapse of an electrically charged scalar field. A phantom scalar field was used as a model of dark energy in the system. Dark matter was modeled by a complex scalar field with a quartic potential, charged under an U(1)-gauge field. The dark components were coupled to the electrically charged scalar field via the exponential coupling and the gauge field-Maxwell field kinetic mixing, respectively. Complete non-linear simulations of the investigated process were performed. They were conducted from regular initial data to the end state, which was the matter dispersal or a singularity formation in a spacetime. During the collapse in the presence of dark energy dynamical wormholes and naked singularities were formed in emerging spacetimes. ...
Laser-pulse-shape control of photofragmentation in the weak-field limit
NASA Astrophysics Data System (ADS)
Tiwari, Ashwani K.; Dey, Diptesh; Henriksen, Niels E.
2014-02-01
We demonstrate theoretically that laser-induced coherent quantum interference control of asymptotic states of dissociating molecules is possible even in the (one-photon) weak-field limit starting from a single vibrational eigenstate. Thus, phase dependence in the interaction with a fixed energy phase-modulated pulse can persist for some time after the pulse is over. This is illustrated for the nonadiabatic process: I +Br*?IBr?I +Br, where the relative yield of excited Br* can be changed by pure phase modulation. It is shown that the phase is able to influence wave-packet spreading in the continuum as well as the average internuclear distance in each channel.
Reversing the weak measurement of an arbitrary field with finite photon number
Sun, Qingqing; Al-Amri, M.; Zubairy, M. Suhail.
2009-01-01
the King Abdul Aziz City for Science and Technology ?KACST?. ?1? J. von Neumann, Mathematical Foundations of Quantum Me- chanics ?Princeton University Press, Princeton, 1955?. ?2? A. N. Korotkov, Phys. Rev. B 60, 5737 ?1999?. ?3? H. Mabuchi and P... the weak measurement of an arbitrary field with finite photon number Qingqing Sun,1,* M. Al-Amri,2 and M. Suhail Zubairy1 1Department of Physics and Institute of Quantum Studies, Texas A&M University, College Station, Texas 77843, USA 2The National...
Random fields and the weakly first-order phase transition in superconductors
Busiello, G.; De Cesare, L.; Uzunov, D.I.
1986-10-01
We study the influence of random fields with short-range and long-range correlations on the weakly first-order phase transition in superconductors. Renormalization-group (RG) analysis near the upper critical dimensionality d/sub u/ = 6 (short-range correlations) reveals a new critical behavior which holds if the number of the order-parameter components is n>10. In the long-range case, the RG transformation is self-consistent only if the parameter theta of the long-range correlations is assumed of order epsilon, epsilon = 6-d.
M. V. Gorbatenko; V. P. Neznamov
2010-07-27
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.
Gravitational quantum states of Antihydrogen
Voronin, A. Yu. [P. N. Lebedev Physical Institute, 53 Leninsky Prospect, 117924 Moscow (Russian Federation); Froelich, P. [Department of Quantum Chemistry, Uppsala University, Box 518, SE-75120 Uppsala (Sweden); Nesvizhevsky, V. V. [Institut Laue-Langevin (ILL), 6 rue Jules Horowitz, F-38042 Grenoble (France)
2011-03-15
We present a theoretical study of the motion of the antihydrogen atom (H) in the gravitational field of Earth above a material surface. We predict that the H atom, falling in the gravitational field of Earth above a material surface, would settle into long-lived quantum states. We point out a method of measuring the difference in the energy of H in such states. The method allows for spectroscopy of gravitational levels based on atom-interferometric principles. We analyze the general feasibility of performing experiments of this kind. We point out that such experiments provide a method of measuring the gravitational force (Mg) acting on H and that they might be of interest in the context of testing the weak equivalence principle for antimatter.
Gravitational Lensing Analyzed by Graded Refractive Index of Vacuum
Xing-Hao Ye; Qiang Lin
2008-02-13
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.
Gravitational field of a Schwarzschild black hole and a rotating mass ring
NASA Astrophysics Data System (ADS)
Sano, Yasumichi; Tagoshi, Hideyuki
2014-08-01
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.
Domenico Giulini; André Großardt
2012-06-19
In this paper we show that the Schr\\"odinger-Newton equation for spherically symmetric gravitational fields can be derived in a WKB-like expansion in 1/c from the Einstein-Klein-Gordon and Einstein-Dirac system.
M. Mohammadi; M. H. Naderi; M. Soltanolkotabi
2007-11-24
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.
Fitzpatrick, Richard
Error-field induced electromagnetic torques in a large aspect-ratio, low- , weakly shaped tokamak://scitation.aip.org/termsconditions. Downloaded to IP: 128.83.61.231 On: Wed, 04 Feb 2015 21:59:18 #12;Error-field induced electromagnetic torques which occurs naturally in all tokamak plasmas affords them some level of protection against error-field
Electrodiffusiophoresis of a large-zeta-potential particle in weak fields.
Tricoli, Vincenzo; Orsini, Gabriele
2015-10-21
The electrodiffusiophoresis of a large-zeta-potential (?) particle in weak fields is investigated. In this large-? regime, Debye-layer kinetics determines O(1) perturbations to the electric- and concentration fields in the surrounding electroneutral solution. Taking these effects into account, the expressions of the slip-flow coefficient and the effective surface boundary-conditions for the electric- and concentration fields are derived. For binary and symmetric electrolyte where only one ion species carries the current in the electroneutral domain, the far-field salt gradient as related to the electric field is determined. The electrodiffusiophoretic mobility is obtained for three particle geometries: sphere, cylinder and spheroid arbitrarily oriented with respect to the externally applied field. Strong departure from Smoluchowskian behavior is found. If co-ion is the current carrier, the mobility is independent of ?, regardless of the body shape. Also, the hydrodynamic flow-field is irrotational. If counter-ion is the current carrier, the problem formulated in terms of a properly-defined scalar field (?), which embodies both the electric potential (?) and the salt concentration, becomes formally identical to the one addressed in our previous work, concerning the small-? regime, with negligible salt gradients. Then, all the results obtained in that study are extended and applied even to the large-? regime considered here, provided the new expressions now derived for the surface boundary conditions and the slip-flow coefficient are employed and ? is used in place of ?. The present results are discussed also in comparison with the classical studies of Dukhin et al and O'Brien et al concerning electrophoresis of highly charged particles with no salt gradient at infinity, and with recent studies of electrodiffusiophoresis, which, however, neglected the fields perturbations caused by Debye-layer kinetics. It is found that the effects addressed and incorporated in the present study determine remarkably different mobility-versus-? behaviour as compared to those previous theories. PMID:26414651
NASA Astrophysics Data System (ADS)
del Moral, A.; Azanza, María J.
2015-03-01
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.
Enhancing weak magnetic fabrics using field-impressed anisotropy: application to the Chinese loess
NASA Astrophysics Data System (ADS)
Liu, Qingsong; Yu, Yongjae; Deng, Chenglong; Pan, Yongxin; Zhu, Rixiang
2005-08-01
The anisotropy of the low-field magnetic susceptibility (AMS), alternating-field-treated AMS (AF-AMS), and anisotropy of anhysteretic remanent magnetization (AARM) have been systematically examined for a sandwich sequence of loess/palaeosols crossing the upper loess unit L2 (Marine Oxygen Isotope Stage 6, MIS6) to the last interglacial maximum (palaeosol unit S1S3, MIS5e) from the Yuanbao section, northwestern China. Results show that a weak, but detectable, magnetic lineation is controlled by coarse-grained aeolian Fe3O4 (magnetite). Because the long axes of the coarse-grained magnetites are statistically parallel to the palaeowind directions, the declination of the maximum susceptibility principal axis of AMS can be used as an indicator of palaeowind direction. In contrast, fine-grained pedogenic magnetic particles are responsible for the magnetic foliation. We found that AF-AMS can indicate the domain state of the magnetic particles, which is consistent with Potter & Stephenson's earlier model. We also found that AF demagnetization can significantly alter the AMS. In conclusion, the angular dependence of AF-AMS can enhance the weak AMS fabrics.
Weak-field multiphoton femtosecond coherent control in the single-cycle regime.
Chuntonov, Lev; Fleischer, Avner; Amitay, Zohar
2011-03-28
Weak-field coherent phase control of atomic non-resonant multiphoton excitation induced by shaped femtosecond pulses is studied theoretically in the single-cycle regime. The carrier-envelope phase (CEP) of the pulse, which in the multi-cycle regime does not play any control role, is shown here to be a new effective control parameter that its effect is highly sensitive to the spectral position of the ultrabroad spectrum. Rationally chosen position of the ultrabroadband spectrum coherently induces several groups of multiphoton transitions from the ground state to the excited state of the system: transitions involving only absorbed photons as well as Raman transitions involving both absorbed and emitted photons. The intra-group interference is controlled by the relative spectral phase of the different frequency components of the pulse, while the inter-group interference is controlled jointly by the CEP and the relative spectral phase. Specifically, non-resonant two- and three-photon excitation is studied in a simple model system within the perturbative frequency-domain framework. The developed intuition is then applied to weak-field multiphoton excitation of atomic cesium (Cs), where the simplified model is verified by non-perturbative numerical solution of the time-dependent Schrödinger equation. We expect this work to serve as a basis for a new line of femtosecond coherent control experiments. PMID:21451714
Conformal Gauge Relativity - On the Geometrical Unification of Gravitation and Gauge Fields
Juan Andres Musante
2010-08-13
A Lagrangian depending on geometric variables (metric, affine connection, gauge group generators) is given which maintains compatibility with General Relativity. It generates the dynamics for Electromagnetism and other Gauge Fields along with Gravitation, at the time it gives a geometric foundation for the stress-energy tensor of continuous matter. The geometric-invariance principle under this integration is exposed and the resulting field equations are obtained. The theory is developed over the tangent space of a four-dimensional real manifold and the generators become those from the Homogenous Lorentz group.
Dark-field hyperlens: Super-resolution imaging of weakly scattering objects.
Repän, Taavi; Lavrinenko, Andrei V; Zhukovsky, Sergei V
2015-09-21
We propose a device for subwavelength optical imaging based on a metal-dielectric multilayer hyperlens designed in such a way that only large-wavevector (evanescent) waves are transmitted while all propagating (small-wavevector) waves from the object area are blocked by the hyper-lens. We numerically demonstrate that as the result of such filtering, the image plane only contains scattered light from subwavelength features of the objects and is completely free from background illumination. Similar in spirit to conventional dark-field microscopy, the proposed dark-field hyperlens is shown to enhance the subwavelength image contrast by more than two orders of magnitude. These findings are essential for optical imaging of weakly scattering subwavelength objects, such as real-time dynamic nanoscopy of label-free biological objects. PMID:26406731
Spectral response of magnetically trapped Bose gases to weak microwave fields
NASA Astrophysics Data System (ADS)
Federsel, P.; Rogulj, C.; Menold, T.; Fortágh, J.; Günther, A.
2015-09-01
Microwave fields can be used to drive local spin transitions in quantum gases and for outcoupling of cold atomic beams from magnetic traps. In this paper, we derive an analytic theory for the outcoupling rate as a response to weak microwave fields of varying frequency and power. The theory holds for thermal clouds and Bose-Einstein condensates. It allows for calculating transition rates in arbitrary magnetic trap geometries and includes the effect of gravity. We verify our theory by measuring the flux of outcoupled atoms at the single-particle level. The derived spectral response is important for magnetic noise spectroscopy with quantum gases, and for probing quantum gas dynamics with single atom detectors in real time.
Nonlinear ion acoustic wave in a pair-ion plasma in a uniform weak magnetic field
NASA Astrophysics Data System (ADS)
Maity, Biplab; Ghosh, Samiran; Bharuthram, R.
2015-04-01
The dynamics of the nonlinear ion acoustic waves are investigated in the presence of an external weak magnetic field in pair-ion plasma in which the mass (temperature) of the positive ions are smaller (larger) than that of the negative ions. The linear dispersion relation of the ion acoustic wave is found to be modified by the externally applied magnetic field. The standard perturbative approach leads to a modified form of Korteweg–de Vries equation. The analytical as well as numerical solutions reveal that the localized (solitary wave) solutions decay slowly algebraically due to the Lorentz force by radiating energy to the tails of the dispersive ion acoustic waves. The results are discussed in the context of the lower region of D-layer ionospheric plasma.
Control of Optical Transitions with Magnetic Fields in Weakly Bound Molecules
NASA Astrophysics Data System (ADS)
McGuyer, B. H.; McDonald, M.; Iwata, G. Z.; Skomorowski, W.; Moszynski, R.; Zelevinsky, T.
2015-07-01
In weakly bound diatomic molecules, energy levels are closely spaced and thus more susceptible to mixing by magnetic fields than in the constituent atoms. We use this effect to control the strengths of forbidden optical transitions in 88Sr2 over 5 orders of magnitude with modest fields by taking advantage of the intercombination-line threshold. The physics behind this remarkable tunability is accurately explained with both a simple model and quantum chemistry calculations, and suggests new possibilities for molecular clocks. We show how mixed quantization in an optical lattice can simplify molecular spectroscopy. Furthermore, our observation of formerly inaccessible f -parity excited states offers an avenue for improving theoretical models of divalent-atom dimers.
Theory of tunneling ionization of molecules: Weak-field asymptotics including dipole effects
Tolstikhin, Oleg I.; Morishita, Toru; Madsen, Lars Bojer
2011-11-15
The formulation of the parabolic adiabatic expansion approach to the problem of ionization of atomic systems in a static electric field, originally developed for the axially symmetric case [Phys. Rev. A 82, 023416 (2010)], is generalized to arbitrary potentials. This approach is used to rederive the asymptotic theory of tunneling ionization in the weak-field limit. In the atomic case, the resulting formulas for the ionization rate coincide with previously known results. In addition, the present theory accounts for the possible existence of a permanent dipole moment of the unperturbed system and, hence, applies to polar molecules. Accounting for dipole effects constitutes an important difference of the present theory from the so-called molecular Ammosov-Delone-Krainov theory. The theory is illustrated by comparing exact and asymptotic results for a set of model polar molecules and a realistic molecular ion HeH{sup 2+} in the 2p{sigma} state.
Bashinsky, Sergei
2015-01-01
We study a finite basic structure that possibly underlies the observed elementary quantum fields with gauge and gravitational interactions. Realistic wave functions of locally interacting quantum fields emerge naturally as fitting functions for the generic distribution of many quantifiable properties of arbitrary static objects. We prove that in any quantum theory with the superposition principle, evolution of a current state of fields unavoidably continues along alternate routes with every conceivable Hamiltonian for the fields. This applies to the emergent quantum fields too. Yet the Hamiltonian is unambiguous for isolated emergent systems with sufficient local symmetry. The other emergent systems, without specific physical laws, cannot be inhabitable. The acceptable systems are eternally inflating universes with reheated regions. We see how eternal inflation perpetually creates new short-scale physical degrees of freedom and why they are initially in the ground state. In the emergent quantum worlds probabi...
V. Majernik
2004-08-19
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.
An Investigation into Quantifying Micron-G Changes in a Gravitational Field of 1G
NASA Technical Reports Server (NTRS)
Gauthier, Richard R.; Gilbert, John A.
1997-01-01
This project called for the development of an accelerometer designed to be used in conjunction with gravity shielding experiments. The device had to measure local gravitational changes on the order of a few micro-G's (micron-G) with a spatial resolution greater than one measurement per ten square centimeters. Measurements had to be made at a minimum rate of two per second. Tasks included the design, development and demonstration of a prototype. The deliverable consisted of three copies of this final report. The study resulted in the development of a Transversely Suspended Accelerometer (TSA) which met all of the technical specifications. Different generations of the device were demonstrated to NASA/MSFC personnel as they were developed. The final prototype is available for further demonstration and future use. The study draws attention to the fact that the magnetic fields required to produce gravitational shielding may result in apparent decreases in the weights of suspended objects on the order of those attributed to the effect itself. This observation reinforces the need to quantify the influences of the magnetic field on any measurement device used to study gravitational shielding. This task was accomplished for the TSA.
Three dimensional Loop Quantum Gravity: towards a self-gravitating Quantum Field Theory
Karim Noui
2006-12-22
In a companion paper, we have emphasized the role of the Drinfeld double DSU(2) in the context of three dimensional Riemannian Loop Quantum Gravity coupled to massive spinless point particles. We make use of this result to propose a model for a self-gravitating quantum field theory (massive spinless non-causal scalar field) in three dimensional Riemannian space. We start by constructing the Fock space of the free self-gravitating field: the vacuum is the unique DSU(2) invariant state, one-particle states correspond to DSU(2) unitary irreducible simple representations and any multi-particles states is obtained as the symmetrized tensor product between simple representations. The associated quantum field is defined by the usual requirement of covariance under DSU(2). Then, we introduce a DSU(2)-invariant self-interacting potential (the obtained model is a Group Field Theory) and compute explicitely the lowest order terms (in the self-interaction coupling constant $\\lambda$) of the propagator and of the three-points function. Finally, we compute the lowest order quantum gravity corrections (in the Newton constant G) to the propagator and to the three-points function.
The deflection of light induced by the Sun's gravitational field and measured with geodetic VLBI
Titov, O
2015-01-01
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.
The deflection of light induced by the Sun's gravitational field and measured with geodetic VLBI
O. Titov; A. Girdiuk
2015-02-25
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.
NASA Astrophysics Data System (ADS)
Mogavero, Federico; Schekochihin, Alexander A.
2014-06-01
In weakly collisional plasmas such as the intracluster medium (ICM), the viscous stress and the rate of change of the magnetic energy are proportional to the local pressure anisotropy, so subject to constraints imposed by the pressure-anisotropy-driven microinstabilities (mirror and firehose) and controlled by the local instantaneous plasma ?. The dynamics of such plasmas can be dramatically different from a conventional magnetohydrodynamic fluid. The plasma is expected to stay locally marginal with respect to the instabilities, but how it does this remains an open question. Two models of magnetic field evolution are investigated. In the first, marginality is achieved via suppression of the rate of change of the field. In the second, the instabilities give rise to anomalous collisionality, reducing pressure anisotropy to marginal - at the same time decreasing viscosity and so increasing the turbulent rate of strain. Implications of these two models are studied in a simplified zero-dimensional setting. In the first model, the field grows explosively but on a time-scale that scales with the initial ?, while in the second, dynamical field strength can be reached in one large-scale turbulence turnover time regardless of the initial seed. Both models produce very intermittent fields. Both also suffer from fairly strong constraints on their applicability: for typical cluster-core conditions, scale separation between the fluid motions (with account of suppressed viscous stress) and the miscoscale fluctuations break down at ? ˜ 104-105. At larger ? (weaker fields), a fully collisionless plasma dynamo theory is needed to justify field growth from a tiny primordial seed. However, the models discussed here are appropriate for studying the structure of the currently observed field as well as large-scale dynamics and thermodynamics of the magnetized ICM or similarly dilute astrophysical plasmas.
Agathos, M.
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 ...
Cosmology with weak lensing surveys.
Munshi, Dipak; Valageas, Patrick
2005-12-15
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
Dynamical and Gravitational Instability of Oscillating-Field Dark Energy and Dark Matter
Matthew C. Johnson; Marc Kamionkowski
2008-05-12
Coherent oscillations of a scalar field can mimic the behavior of a perfect fluid with an equation-of-state parameter determined by the properties of the potential, possibly driving accelerated expansion in the early Universe (inflation) and/or in the Universe today (dark energy) or behaving as dark matter. We consider the growth of inhomogeneities in such a field, mapping the problem to that of two coupled anharmonic oscillators. We provide a simple physical argument that oscillating fields with a negative equation-of-state parameter possess a large-scale dynamical instability to growth of inhomogeneities. This instability renders these models unsuitable for explaining cosmic acceleration. We then consider the gravitational instability of oscillating fields in potentials that are close to, but not precisely, harmonic. We use these results to show that if axions make up the dark matter, then the small-scale cutoff in the matter power spectrum is around $10^{-15} M_\\oplus$.
Gravitational self-force in non-vacuum spacetimes: an effective field theory derivation
Peter Zimmerman
2015-07-13
In this paper we investigate the motion of small compact objects in non-vacuum spacetimes using methods from effective field theory in curved spacetime. Although a vacuum formulation is sufficient in many astrophysical contexts, there are applications such as the role of the self-force in enforcing cosmic-censorship in the context of the overcharging problem, which necessitate an extension into the non-vacuum regime. The defining feature of the self-force problem in non-vacuum spacetimes is the coupling between gravitational and non-gravitational field perturbations. The formulation of the self-force problem for non-vacuum spacetimes was recently provided in simultaneous papers by Zimmerman and Poisson [1] and Linz, Friedmann, Wiseman [2]. Here we distinguish ourselves by working with the effective action rather than the field equations. The formalism utilizes the multi-index notation developed by Zimmerman and Poisson [1] to accommodate the coupling between the different fields. Using dimensional regularization, we arrive at a finite expression for the local self-force expressed in terms of multi-index quantities evaluated in the background spacetime. We then apply the formalism to compute the coupled gravitational self-force in two explicit cases. First, we calculate the self-force on a massive particle possessing scalar charge and moving in an scalarvac spacetime. We then derive an expression for the self-force on an electrically charged, massive particle moving in an electrovac spacetime. In both cases, the force is expressed as a sum of local terms involving tensors defined in the background spacetime and evaluated at the current position of the particle, as well as tail integrals that depend on the past history of the particle.
Effect of weak static magnetic fields on the development of cultured skeletal muscle cells.
Surma, Sergei V; Belostotskaya, Galina B; Shchegolev, Boris F; Stefanov, Vasily E
2014-12-01
We studied the effect produced on the development and functional activity of skeletal muscle cells from newborn Wistar rats in primary culture by weak static magnetic fields (WSMF; 60-400 µT) with a high capacity of penetrating the biological media. To reduce the impact of external magnetic fields, cells were cultured at 37?°C in a multilayered shielding chamber with the attenuation coefficient equal to 160. WSMF inside the chamber was created by a circular permanent magnet. We found that the application of WSMF with the magnetic field strength only a few times that of the geomagnetic field can accelerate the development of skeletal muscle cells, resulting in the formation of multinuclear hypertrophied myotubes. WSMF was shown to induce 1.5- to 3.5-fold rise in the concentration of intracellular calcium [Ca(2+)]i due to the release of Ca(2+) from the sarcoplasmic reticulum (SR) through ryanodine receptors (RyR), which increases in the maturation of myotubes. We also found that fully differentiated myotubes at late stages of development were less sensitive to WSMF, manifesting a gradual decrease in the frequency of contractions. However, myotubes at the stage when electromechanical coupling was forming dramatically reduced the frequency of contractions during the first minutes of their exposure to WSMF. PMID:25266690
Excitation of parasitic waves in forward-wave amplifiers with weak guiding fields
NASA Astrophysics Data System (ADS)
Nusinovich, G. S.; Romero-Talamás, C. A.; Han, Y.
2012-12-01
To produce high-power coherent electromagnetic radiation at frequencies from microwaves up to terahertz, the radiation sources should have interaction circuits of large cross sections, i.e., the sources should operate in high-order modes. In such devices, the excitation of higher-order parasitic modes near cutoff where the group velocity is small and, hence, start currents are low can be a serious problem. The problem is especially severe in the sources of coherent, phase-controlled radiation, i.e., the amplifiers or phase-locked oscillators. This problem was studied earlier [Nusinovich, Sinitsyn, and Antonsen, Phys. Rev. EPLEEE81063-651X10.1103/PhysRevE.82.046404 82, 046404 (2010)] for the case of electron focusing by strong guiding magnetic fields. For many applications it is desirable to minimize these focusing fields. Therefore in this paper we analyze the problem of excitation of parasitic modes near cutoff in forward-wave amplifiers with weak focusing fields. First, we study the large-signal operation of such a device with a signal wave only. Then, we analyze the self-excitation conditions of parasitic waves near cutoff in the presence of the signal wave. It is shown that the main effect is the suppression of the parasitic wave in large-signal regimes. At the same time, there is a region of device parameters where the presence of signal waves can enhance excitation of parasitic modes. The role of focusing fields in such effects is studied.
Unified quantum jump superoperator for optical fields from the weak- to the strong-coupling limit
Haeyrynen, Teppo; Oksanen, Jani; Tulkki, Jukka [Department of Biomedical Engineering and Computational Science, Aalto University School of Science and Technology, Post Office Box 12200, FI-00076 AALTO (Finland)
2010-06-15
We derive a generalized quantum jump superoperator that can be used in the quantum trajectory description of single photon detectors, light-emitting diodes (LEDs), and lasers. Our model describes an optical single-mode cavity field coupled to a reservoir through a two-state quantum system and includes three physical parameters: the coupling of the field to the two-state system, the coupling of the two-state system to the reservoir, and the cavity loss rate. In this setup, the two-state system can act as a photodetector or as an energy-adding mechanism. In the first case, we assume that the reservoir acts as a damping mechanism for an ideal cavity and derive reduced field operators describing the photon detection events. Our model coincides with the commonly known quantum trajectory based photon counting models at the weak- and strong-coupling limits and is, furthermore, also applicable between their validity regimes. In the second case, we assume that the reservoir injects energy into a lossy cavity through the two-state system. Again we derive the reduced field operators describing photon creation events into the lossy cavity. We show that this setup can act as an LED or as a laser depending on the strength of the injection. We also investigate how the setup operates at the close proximity of the lasing threshold.
Synchronization dynamics induced on pairs of neurons under applied weak alternating magnetic fields.
Azanza, María J; del Moral, A; Calvo, A C; Pérez-Bruzón, R N; Junquera, C
2013-12-01
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
Orbital diamagnetism of weakly doped bilayer graphene in a magnetic field
NASA Astrophysics Data System (ADS)
Lv, Min; Wan, Shaolong
2011-06-01
We investigate the orbital diamagnetism of weakly doped bilayer graphene (BLG) in a spatially smoothly varying magnetic field and obtain the general analytic expression for the orbital susceptibility of BLG, with finite wavenumber and Fermi energy, at zero temperature. We find that the magnetic field screening factor of BLG is dependent on the wavenumber, which results in a more complicated screening behavior compared with that of monolayer graphene (MLG). We also study the induced magnetization and electric current in BLG, under a nonuniform magnetic field, and find that they are qualitatively different from those for MLG and the two-dimensional electron gas (2DEG). However, as for MLG, a magnetic object placed above BLG is repelled by a diamagnetic force from the BLG, which is approximately equivalent to the force produced by its mirror image on the other side of the BLG with a reduced amplitude dependent on the typical length of the systems. BLG shows crossover behaviors in the responses to the external magnetic field, intermediate between those of MLG and 2DEG.
NASA Astrophysics Data System (ADS)
Gross, R. S.; Chao, B. F.
2005-05-01
Besides generating seismic waves, which eventually dissipate, an earthquake also generates a static displacement field everywhere within the Earth. This global displacement field rearranges the Earth's mass, causing the Earth's rotation and gravitational field to change. The size of these changes depends upon the size, focal mechanism, and location of the earthquake. The Sumatran earthquake of December 26, 2004 is the largest earthquake to have occurred since the 1964 Alaskan earthquake. The coseismic effect of the Sumatran earthquake upon the Earth's length-of-day, polar motion, and low-degree harmonic coefficients of the gravitational field are computed. It is found that this earthquake should have caused the length-of-day to decrease by 2.68 ?sec, the position of the mean rotation pole to shift 0.821 mas towards 145°E longitude, the Earth's oblateness J2 to decrease by 0.90×10-11, and the Earth's pear-shapedness J3 to decrease by 0.19×10-11. This predicted change in the length-of-day is probably not detectable by current measurement systems, the change in oblateness is perhaps just detectable, and the change in the mean position of the rotation pole is perhaps detectable if other effects, such as those of the atmosphere, oceans, and continental water storage, can be adequately removed from the observations.
Quantum Vacuum Effects in the Gravitational Field of a Global Monopole
NASA Astrophysics Data System (ADS)
Saharian, A. A.
2004-04-01
A study is made of the vacuum expectation values for the energy-momentum tensor of a massive scalar field that satisfy a Robin mixed boundary condition on a spherical surface with a background gravitational field from a D+1-dimensional global monopole. Expressions are derived for the Wightman function, vacuum expectation of the square of the field, vacuum energy density, and the radial and azimuthal pressures inside the spherical surface. The regularization procedure involves using the generalized Abel-Plana formula for series in terms of the zeroes of cylindrical functions. This formula makes it possible to separate the part owing to the gravitational field of a global monopole without boundaries from the vacuum expectation and to represent the parts induced by the boundary in the form of exponentially converging integrals which are especially convenient for numerical calculations. The asymptotic behavior of the vacuum averages is studied at the center of the sphere and near its surface. It is shown that for small values of the parameter describing the solid-angle deficit in the geometry of a global monopole, the vacuum stresses induced by the boundary are highly anisotropic.
arXiv:1207.2442v1[gr-qc]10Jul2012 Torsion-balance tests of the weak equivalence
Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group
identity of inertial mass mi (the mass appearing in Newton's second law) and gravitational mass mg (the of these results for the gravitational properties of antimatter and dark matter, and speculate about the prospects The weak equivalence principle (WEP) states that in a uniform gravitational field all objects, regardless
Relativistic generalization of the inertial and gravitational masses equivalence principle
Nikolai V. Mitskievich
2006-01-01
The Newtonian approximation for the gravitational field equation should not necessarily involve admission of non-relativistic properties of the source terms in Einstein's equations: it is sufficient to merely consider the weak-field condition for gravitational field. When a source has electromagnetic nature, one simply {\\\\em cannot} ignore its intrinsically relativistic properties, since there cannot be invented any non-relativistic approximation which would
Relativistic Generalization of the Inertial and Gravitational Masses Equivalence Principle
Nikolai V. Mitskievich
2008-01-01
The Newtonian approximation in the gravitational field description not necessarily involves admission of non-relativistic properties of the source terms in Einstein's equations: it is sufficient to merely consider the weak-field condition for gravitational field. When, e.g., a source has electromagnetic nature, one simply cannot ignore its intrinsically relativistic properties, since there cannot be invented any non-relativistic approximation which would adequately
Ultra-weak magnetic fields in Am stars: ? UMa and ? Leo
NASA Astrophysics Data System (ADS)
Blazère, A.; Petit, P.; Lignières, F.; Aurière, M.; Ballot, J.; Böhm, T.; Folsom, C.; Ariste, A. López; Wade, G. A.
2015-10-01
An extremely weak circularly-polarized signature was recently detected in the spectral lines of the Am star Sirius A. With a prominent positive lobe, the shape of the phase-averaged Stokes V line profile is atypical of stellar Zeeman signatures, casting doubts on its magnetic origin. We report here on ultra-deep spectropolarimetric observations of two more bright Am stars: ? Uma and ? Leo. Stokes V line signatures are detected in both objects, with a shape and amplitude similar to the one observed on Sirius A. We demonstrate that the amplitude of the Stokes V line profiles depend on various line parameters (Landé factor, wavelength, depth) as expected from a Zeeman signature, confirming that extremely weak magnetic fields are likely present in a large fraction of Am stars. We suggest that the strong asymmetry of the polarized signatures, systematically observed so far in Am stars and never reported in strongly magnetic Ap stars, bears unique information about the structure and dynamics of the thin surface convective shell of Am stars.
NASA Astrophysics Data System (ADS)
Grunskaya, Lubov; Isakevich, Valiriy; Efimov, Vladislav; Zakirov, Alexander
Experimental investigations of electromagnetic fields in the atmosphere boundary layer are done at the distance spaced stations, situated on VSU test ground, at Main Geophysical Observa-tory(St. Petersburg), on Kamchatka pen., on Lake Baikal. The distance spaced reception of electrical and magnetic fields will allow to analyze more widely the nature of the investigated interactions. Monitoring of electromagnetic fields in the ELF range is being realized. The work is connected with search of interconnection of the electromagnetic field of the atmosphere boundary layer with the gravitational Compact Binaries wave fields. For analyzing Compact Binaries were taken with ELF of GW-radiation: J 0700+6418, J 1012+5307, J 1537+1155, J 1959+2048, J 2130+1210, J 1915+1606, J 1910+0004, J 1910+0004, J 1748-2446A.For analyz-ing the spectrum of the magnetic fields there was used the information of VSU station and the monitoring information of Japanese geomagnetic stations Kakioka and Mambetsu. The aim of such investigations is connected with displaying tide processes (the Moon tides) and gravita-tional wave influence of Compact Binaries in the electromagnetic fields.On the first stage of the investigations a correlative spectral analysis of the experimental data was being carried out. There was factually extracted the influence of the atmosphere lower layer electromagnetic field of the thermogravitational solar tides and a number of gravitational: M1, M2, N2. It was ob-tained that astrophysical sources GV-6, GV-3,GV-4, GV-8, GV-9 have the most probability of non-casual of events. The subsequent investigations are connected with search of main features accompanying such influences. They are signal modulations by diurnal and year's rotation of the Earth. Such modulations are peculiar to sources of non-terrestrial origin. We are planning an extraction of the radiation frequency change of the source because of energy loss for the radiation of GW. Such investigations turned out to be possible after developing the method of scanning experimental signal of electromagnetic field into non-correlated components. There is shown efficiency of using latent vectors of covariance matrixes to expose complex periodical component of time series, including the ease when such components don't have energetic dom-inate in time series.The work was carried out with supporting of grants RFBR 09-05-08176, Program DSPHS 2.1.1/5660.
A. N. Ivanov; R. Höllwieser; T. Jenke; M. Wellenzohen; H. Abele
2012-07-02
We calculate the chameleon field potential for ultracold neutrons, bouncing on top of one or between two neutron mirrors in the gravitational field of the Earth. For the resulting non--linear equations of motion we give approximate analytical solutions and compare them with exact numerical ones for which we propose the analytical fit. The obtained solutions may be used for the quantitative analysis of contributions of a chameleon field to the transition frequencies of quantum states of ultra-cold neutrons bound in the gravitational field of the Earth.
Temperature and magnetic field dependence of a Kondo system in the weak coupling regime
NASA Astrophysics Data System (ADS)
Zhang, Yong-Hui; Kahle, Steffen; Herden, Tobias; Stroh, Christophe; Mayor, Marcel; Schlickum, Uta; Ternes, Markus; Wahl, Peter; Kern, Klaus
2013-07-01
The Kondo effect arises due to the interaction between a localized spin and the electrons of a surrounding host. Studies of individual magnetic impurities by scanning tunneling spectroscopy have renewed interest in Kondo physics; however, a quantitative comparison with theoretical predictions remained challenging. Here we show that the zero-bias anomaly detected on an organic radical weakly coupled to a Au (111) surface can be described with astonishing agreement by perturbation theory as originally developed by Kondo 60 years ago. Our results demonstrate that Kondo physics can only be fully conceived by studying both temperature and magnetic field dependence of the resonance. The identification of a spin 1/2 Kondo system is of relevance not only as a benchmark for predictions for Kondo physics but also for correlated electron materials in general.
Frozen-In Magnetic Field Lines and Alfvén Wave Generation in Weakly Ionized Plasma
NASA Astrophysics Data System (ADS)
Tsap, Y. T.; Stepanov, A. V.; Kopylova, Y. G.
2015-07-01
On the basis of the three-fluid approximation, we consider the generation of linear Alfvén waves with periods in the collisional partially ionized plasma of the solar photosphere. The results obtained in previous work (Tsap, Stepanov, and Kopylova in Solar Phys. 270, 205, 2011) are generalized for the case of the arbitrary ratio between the initial velocities of ions and neutral atoms. We find that the ponderomotive force plays an important role during Alfvén wave excitation and propagation. Furthermore, the energy flux of Alfvén waves does not depend on the degree of the plasma ionization if the magnetic field lines are frozen into the charged particles. These modes can be effectively generated in the weakly ionized plasma of the solar photosphere.
Frozen-In Magnetic Field Lines and Alfvén Wave Generation in Weakly Ionized Plasma
NASA Astrophysics Data System (ADS)
Tsap, Y. T.; Stepanov, A. V.; Kopylova, Y. G.
2015-07-01
On the basis of the three-fluid approximation, we consider the generation of linear Alfvén waves with periods ? 10^{-3} s in the collisional partially ionized plasma of the solar photosphere. The results obtained in previous work (Tsap, Stepanov, and Kopylova in Solar Phys. 270, 205, 2011) are generalized for the case of the arbitrary ratio between the initial velocities of ions and neutral atoms. We find that the ponderomotive force plays an important role during Alfvén wave excitation and propagation. Furthermore, the energy flux of Alfvén waves does not depend on the degree of the plasma ionization if the magnetic field lines are frozen into the charged particles. These modes can be effectively generated in the weakly ionized plasma of the solar photosphere.
Scattering of Straight Cosmic Strings by Black Holes: Weak Field Approximation
Jean-Pierre De Villiers; Valeri Frolov
1998-04-30
The scattering of a straight, infinitely long string moving with velocity $v$ by a black hole is considered. We analyze the weak-field case, where the impact parameter ($b_{imp}$) is large, and obtain exact solutions to the equations of motion. As a result of scattering, the string is displaced in the direction perpendicular to the velocity by an amount $\\Delta b\\sim -2\\pi GMv\\gamma/c^3 -\\pi (GM)^2/ (4c^3 v b_{imp})$, where $\\gamma=(1-(v/c)^2)^{-1/2}$. The second term dominates at low velocities $v/c<(GM/b_{imp})^{1/2}$ . The late-time solution is represented by a kink and anti-kink, propagating in opposite directions at the speed of light, and leaving behind them the string in a new ``phase''. The solutions are applied to the problem of string capture, and are compared to numerical results.
Weakly perturbed Schwarzschild lens in the strong deflection limit
Bozza, V. [Dipartimento di Fisica E.R. Caianiello, Universita di Salerno, via Allende, I-84081 Baronissi (Saudi Arabia) (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy); Sereno, M. [Institut fuer Theoretische Physik der, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland)
2006-05-15
We investigate the strong deflection limit of gravitational lensing by a Schwarzschild black hole embedded in an external gravitational field. The study of this model, analogous to the Chang and Refsdal lens in the weak deflection limit, is important to evaluate the gravitational perturbations on the relativistic images that appear in proximity of supermassive black holes hosted in galactic centers. By a simple dimensional argument, we prove that the tidal effect on the light ray propagation mainly occurs in the weak field region far away from the black hole and that the external perturbation can be treated as a weak field quadrupole term. We provide a description of relativistic critical curves and caustics and discuss the inversion of the lens mapping. Relativistic caustics are shifted and acquire a finite diamond shape. Sources inside the caustics produce four sequences of relativistic images. On the other hand, retro-lensing caustics are only shifted while remaining pointlike to the lowest order.
Bhardwaj, S [University of Chicago; Mkhitaryan, V V [Ames Laboratory; Gruzberg, I A [Ohio State University
2014-06-01
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.
The magnetic field and spectral variability of the He-weak star HR 2949
Shultz, M; Folsom, C P; Wade, G A; Townsend, R H D; Sikora, J; Grunhut, J; Stahl, O
2015-01-01
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...
Mass and weak-field limit of boson stars in Brans-Dicke gravity
NASA Astrophysics Data System (ADS)
Whinnett, A. W.
1999-08-01
We study boson stars in Brans-Dicke (BD) 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 icons/Journals/Common/omega" ALT="omega" ALIGN="TOP"/> = -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 icons/Journals/Common/omega" ALT="omega" ALIGN="TOP"/> = -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 icons/Journals/Common/omega" ALT="omega" ALIGN="TOP"/>. The analysis supports the conjecture that the tensor mass uniquely describes the total energy of an asymptotically flat solution in BD gravity.
Weak Field-Induced Evolution of Spiral Wave in Small-World Networks of Hodgkin—Huxley Neurons
NASA Astrophysics Data System (ADS)
Wang, Ya-Min; Liu, Yong; Wang, Jing; Liu, Yu-Rong
2012-08-01
An external weak electric field is introduced into the small-world networks of Hodgkin-Huxley neurons to study the control and breakup of a spiral wave. The effect of an external electric field on the neurons in the small-world network is described by an additive perturbation on the membrane potentials of neurons at the cellular level, in which an additive term VE is imposed on the physiological membrane potential. A statistical factor of synchronization is used to measure the collective behaviour of spiral waves by changing the electric field; it is confirmed that a smaller factor of synchronization is associated with the survival of a spiral wave. In the case of no channel noise, the spiral wave could be removed under a certain intensity of constant electric field; it keeps robustly to the weak electric field when the electric field changes periodically. In the case of weak channel noise, a breakup of the spiral wave is observed when the intensity of the electric field exceeds certain thresholds, which could be measured from the curve for synchronization factors. No drift of the spiral wave is observed under the weak electric field.
A new line element derived from the variable rest mass in gravitational field
N. Ben-Amots
2008-08-19
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.
Effect of the Earth's time-retarded transverse gravitational field on the motion of the Moon
J. C. Hafele
2012-02-27
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.
Global surface-water-induced seasonal variations in the earth's rotation and gravitational field
NASA Technical Reports Server (NTRS)
Chao, B. F.; O'Connor, William P.
1988-01-01
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.
Effects of Electromagnetic Field on Energy Density Inhomogeneity in Self-Gravitating Fluids
M. Sharif; Neelum Bashir
2012-09-25
This paper is devoted to study the effects of electromagnetic field on the energy density inhomogeneity in the relativistic self-gravitating fluids for spherically symmetric spacetime. Two important equations of the Weyl tensor are formulated which help to analyze the energy density inhomogeneity in this scenario. We investigate two types of fluids, i.e., non-dissipative and dissipative. The non-dissipative fluid further includes dust, locally isotropic, and locally anisotropic charged fluids. We explore the effects of different factors on energy density inhomogeneity in all these cases, in particular, the effect of charge.
Pulsar Kicks Induced by Spin Flavor Oscillations of Neutrinos in Gravitational Fields
G. Lambiase
2005-07-15
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_\
The statistics of the gravitational field arising from an inhomogenous system of particles
A. Del Popolo; M. Gambera; x
1998-10-27
In this paper we extend Chandrasekhar and von Neumann's analysis of the statistics of the gravitational field to systems in which particles (e.g. stars, galaxies) are not homogeneously distributed. We derive a distribution function W({F},dF/dt) giving the joint probability that a test particle is subject to a force F and an associated rate of change of F given by dF/dt. We calculate the first moment of dF/dt to study the effects of inhomogenity on dynamical friction.
Stabilization of Neutral Thin Shells By Gravitational Effects From Electric Fields
Eduardo I. Guendelman; Idan Shilon
2009-02-06
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.