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1

Gravitational lensing in Tangherlini spacetime in the weak gravitational field and the strong gravitational field  

NASA Astrophysics Data System (ADS)

The gravitational lensing effects in the weak gravitational field by exotic lenses have been investigated intensively to find nonluminous exotic objects. Gravitational lensing based on 1/rn fall-off metric, as a one-parameter model that can treat by hand both the Schwarzschild lens (n =1) and the Ellis wormhole (n =2) in the weak field, has been recently studied. Only for n=1 case, however, it has been explicitly shown that effects of relativistic lens images by the strong field on the light curve can be neglected. We discuss whether relativistic images by the strong field can be neglected for n>1 in the Tangherlini spacetime which is one of the simplest models for our purpose. We calculate the divergent part of the deflection angle for arbitrary n and the regular part for n=1, 2 and 4 in the strong field limit, the deflection angle for arbitrary n under the weak gravitational approximation. We also compare the radius of the Einstein ring with the radii of the relativistic Einstein rings for arbitrary n. We conclude that the images in the strong gravitational field have little effect on the total light curve and that the time-symmetric demagnification parts in the light curve will appear even after taking account of the images in the strong gravitational field for n>1.

Tsukamoto, Naoki; Kitamura, Takao; Nakajima, Koki; Asada, Hideki

2014-09-01

2

Strong and weak gravitational field in $R+?^4/R$ gravity  

E-print Network

We introduce a new approach for investigating the weak field limit of vacuum field equations in $f(R)$ gravity and we find the weak field limit of $f(R)=R+\\mu ^4/R$ gravity. Furthermore, we study the strong gravity regime in $R+\\mu^{4}/R$ model of $f(R)$ gravity. We show the existence of strong gravitational field in vacuum for such model. We find out in the limit $\\mu\\rightarrow 0$, the weak field limit and the strong gravitational field can be regarded as a perturbed Schwarzschild metric.

Kh. Saaidi; A. Vajdi; S. W. Rabiei; A. Aghamohammadi; H. Sheikhahmadi

2010-01-25

3

Weakly bound states of neutrons in gravitational fields  

E-print Network

In this paper a quantum-mechanical behaviour of neutrons in gravitational fields is considered. A first estimation is made using the semiclassical approximation, neglecting General Relativity, magnetic and rotation effects, for neutrons in weakly bound states in the weak gravitational field of the Earth. This result was generalized for a case, in which the Randall - Sundrum correction to Newton's gravitational law on the small scales was applied. Application of the results to Neutron Star physics is considered and further possible perspectives are discussed.

Avas V. Khugaev; Renat A. Sultanov; Dennis Guster

2010-12-24

4

Interaction of Dirac and Majorana neutrinos with weak gravitational fields  

SciTech Connect

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

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

2008-12-01

5

Weak Gravitational Lensing  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

6

Weak Gravitational Field in Finsler-Randers Space and Raychaudhuri Equation  

E-print Network

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

P. Stavrinos

2012-02-17

7

Fluctuations in the Gravitational, Strong and Weak Nuclear Fields through an Effective Harmonic Oscillator Model  

E-print Network

We propose an effective harmonic oscillator model in order to treat the fluctuations of the gravitational, strong and weak nuclear fields. With respect to the gravitational field, first we use the model to estimate its fluctuating strength, necessary to decohere the wavefunction of a cubic centimeter of air at the standard temperature and pressure conditions. Second, the fluctuation of a point mass through a distance equal to the Planck length leads to the self-gravitational interaction of a particle, which can be related to its de Broglie frequency. Third, by making the equality of the fluctuating field strength with the gravitational field of a mass M at half of its Schwarzschild radius, we obtain an estimate of the mass of the Universe. We also consider the fluctuations of the strong nuclear field, as a means to estimate the separation in energy between the ground state and the centroid of the excitated states of the nucleon. Finally, taking into account the neutron-proton mass difference, we use the fluctuations of the weak nuclear field in order to evaluate the weak coupling constant.

P. R. Silva

2001-12-10

8

Energy-momentum tensor for a scalar Casimir apparatus in a weak gravitational field: Neumann conditions  

SciTech Connect

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.

Napolitano, George M. [Dipartimento di Scienze Fisiche, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); Esposito, Giampiero [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); Rosa, Luigi [Dipartimento di Scienze Fisiche, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy)

2008-11-15

9

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

SciTech Connect

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

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

2008-02-15

10

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

E-print Network

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

Andrei Lebed

2012-05-14

11

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

E-print Network

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

Lebed, Andrei

2012-01-01

12

Wave propagation in a weak gravitational field and the validity of the thin lens approximation  

E-print Network

Wave effects can be important for the gravitational lensing of gravitational waves. In such a case, wave optics must be used in stead of geometric optics. We consider a plane wave entering a lens object and solve numerically the wave equation for three lens models: the uniform density sphere, the singular isothermal sphere, and the Hernquist model. By comparing our numerical solutions with the analytical solutions under the thin lens approximation, we evaluate the error of this approximation. The results show that the relative error of the thin lens approximation is small if the geometrical thickness of the lens is much smaller than the distance between the lens and the observer.

Teruaki Suyama; Ryuichi Takahashi; Shugo Michikoshi

2005-05-02

13

From Rindler space to the electromagnetic energy-momentum tensor of a Casimir apparatus in a weak gravitational field  

SciTech Connect

This paper studies two perfectly conducting parallel plates in the weak gravitational field on the surface of the Earth. Since the appropriate line element, to first order in the constant gravity acceleration g, is precisely of the Rindler type, we can exploit the formalism for studying Feynman Green functions in Rindler spacetime. Our analysis does not reduce the electromagnetic potential to the transverse part before quantization. It is instead fully covariant and well suited for obtaining all components of the regularized and renormalized energy-momentum tensor to arbitrary order in the gravity acceleration g. The general structure of the calculation is therefore elucidated, and the components of the Maxwell energy-momentum tensor are evaluated up to second order in g, improving a previous analysis by the authors and correcting their old first-order formula for the Casimir energy.

Bimonte, Giuseppe; Rosa, Luigi [Dipartimento di Scienze Fisiche, Universita di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); Esposito, Giampiero [INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy)

2008-07-15

14

Weak gravitational lensing of intrinsically aligned galaxies  

NASA Astrophysics Data System (ADS)

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

Giahi-Saravani, Aram; Schäfer, Björn Malte

2014-01-01

15

Continuous image distortion in weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We examine the shearing and magnification of images distorted by the weak gravitational lensing of a thick gravitational lens using a perturbation theory approach based on the optical scalar and geodesic deviation equations with no reference to lens planes. We compare the image distortion from optical scalars with the typical thin-lens image distortion for realistic, axially symmetric astrophysical lens, finding that the thin-lens approach often overestimates the ellipticity by up to 2 sigma near the lens. Application to non-symmetric lenses is discussed. )

Kling, Thomas

2010-02-01

16

Galaxy Halo Masses from Weak Gravitational Lensing  

E-print Network

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

Mandelbaum, Rachel

2014-01-01

17

Probing Satellite Halos with Weak Gravitational Lensing  

E-print Network

We demonstrate the possibility of detecting tidal stripping of dark matter subhalos within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups, using various models with different distributions of mass between galaxy and group halos to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 10^12--10^15 Msun.

Gillis, Bryan R; Hilbert, Stefan; Hartlap, Jan

2012-01-01

18

Probing satellite haloes with weak gravitational lensing  

NASA Astrophysics Data System (ADS)

We demonstrate the possibility of detecting tidal stripping of dark matter subhaloes within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups using various models with different distributions of mass between galaxy and group haloes to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 1012-1015 M?.

Gillis, Bryan R.; Hudson, Michael J.; Hilbert, Stefan; Hartlap, Jan

2013-02-01

19

Weak 'Antigravity' Fields in General Relativity  

Microsoft Academic Search

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

F. S. Felber

2005-01-01

20

Atomic Inference from Weak Gravitational Lensing Data  

SciTech Connect

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

Marshall, Phil; /KIPAC, Menlo Park

2005-12-14

21

Field equations of electromagnetic and gravitational fields  

E-print Network

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.

Zihua Weng

2007-09-16

22

Studying the LSS through weak gravitational lensing maps  

E-print Network

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

Antonio C. C. Guimarães

2001-12-10

23

Weak 'Antigravity' Fields in General Relativity  

E-print Network

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

F. S. Felber

2005-05-19

24

Weak 'Antigravity' Fields in General Relativity  

E-print Network

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

Felber, F S

2005-01-01

25

The Cluster Mass Function from Weak Gravitational Lensing  

E-print Network

We present the first measurement of the mass function of galaxy clusters based directly on cluster masses derived from observations of weak gravitational lensing. To investigate the degree of sample incompleteness resulting from the X-ray based selection of the target clusters, we use a sample of 50 clusters with weak lensing mass measurements to empirically determine the relation between lensing mass and X-ray luminosity and the scatter about this relation. We use a complete, volume-limited sub-sample of 35 X-ray luminous clusters of galaxies at 0.15~ 10^15/h M_sun) clusters. From this, we constrain sigma_8(Omega_m/0.3)^{0.37} = 0.67^{+0.04}_{-0.05} (68% confidence limits), agreeing well with constraints from the 3-year WMAP CMB measurements and estimates of cluster abundances based on X-ray observations, but somewhat lower than constraints from ``cosmic shear'' weak lensing measurements in random fields.

H. Dahle

2006-08-23

26

Cosmological electromagnetic fields due to gravitational wave perturbations Mattias Marklund*  

E-print Network

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

Dunsby, Peter

27

Einstein's Energy-Free Gravitational Field  

E-print Network

We show that Einstein's gravitational field has zero energy, momentum, and stress. This conclusion follows directly from the gravitational field equations, in conjunction with the differential law of energy-momentum conservation $ T^{\\mu\

Kenneth Dalton

1995-12-04

28

Gravitational mass in electromagnetic field  

E-print Network

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.

Zihua Weng

2008-07-28

29

Forces in electromagnetic field and gravitational field  

E-print Network

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.

Zihua Weng

2008-06-21

30

Scalar invariants in gravitational and electromagnetic fields  

E-print Network

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

Zihua Weng

2008-11-01

31

Invariants in electromagnetic and gravitational adjoint fields  

E-print Network

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.

Zihua Weng

2008-05-21

32

Primordial magnetic seed field amplification by gravitational waves  

SciTech Connect

Using second-order gauge-invariant perturbation theory, a self-consistent framework describing the nonlinear coupling between gravitational waves and a large-scale homogeneous magnetic field is presented. It is shown how this coupling may be used to amplify seed magnetic fields to strengths needed to support the galactic dynamo. In situations where the gravitational wave background is described by an 'almost' Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmology we find that the magnitude of the original magnetic field is amplified by an amount proportional to the magnitude of the gravitational wave induced shear anisotropy and the square of the field's initial comoving scale. We apply this mechanism to the case where the seed field and gravitational wave background are produced during inflation and find that the magnitude of the gravitational boost depends significantly on the manner in which the estimate of the shear anisotropy at the end of inflation is calculated. Assuming a seed field of 10{sup -34} G spanning a comoving scale of about 10 kpc today, the shear anisotropy at the end of inflation must be at least as large as 10{sup -40} in order to obtain a generated magnetic field of the same order of magnitude as the original seed. Moreover, contrasting the weak-field approximation to our gauge-invariant approach, we find that while both methods agree in the limit of high conductivity, their corresponding solutions are otherwise only compatible in the limit of infinitely long-wavelength gravitational waves.

Betschart, Gerold; Zunckel, Caroline [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); Dunsby, Peter K.S. [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); South African Astronomical Observatory, Observatory 7925, Cape Town (South Africa); Marklund, Mattias [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2005-12-15

33

Classical effective field theory for weak ultra relativistic scattering  

NASA Astrophysics Data System (ADS)

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.

Kol, Barak

2011-07-01

34

Some helicities in electromagnetic and gravitational fields  

E-print Network

The paper investigates the influences of the helicity on the gravitational mass density, the field source, the charge continuity equation, and the mass continuity equation etc in the electromagnetic field and gravitational field. By means of the algebra of octonions, the magnetic helicity, the current helicity, the cross helicity, the kinetic helicity, the field energy, the enstrophy, and some new helicity terms can be derived from the octonion definitions of the linear mentum and the force in some field descriptions with different operators. The study claims that the gravitational mass density, the field source, the charge continuity equation, and the mass continuity equation will be impacted by the helicity, the field strength, and the vorticity of the rotational objects and of the spinning charged objects in the gravitational field and the electromagnetic field with their adjoint fields.

Zi-Hua Weng

2011-01-15

35

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

E-print Network

LIGHT ON DARK MATTER WITH WEAK GRAVITATIONAL LENSING 1 Light on Dark Matter with Weak Gravitational reviews statistical methods re- cently developed to reconstruct and analyze dark matter mass maps from decades showing that the visible matter represents only about 4-5% of the Universe, the rest being dark

Starck, Jean-Luc

36

Some theorems in gravitational and electromagnetic fields  

E-print Network

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.

Zihua Weng

2008-03-30

37

Weak Gravitational lensing from regular Bardeen black holes  

E-print Network

In this article we consider regular charged Bardeen black hole as a gravitational lens. Weak deflection limit is studied for deflection angle by regarding perturbation approach presented by Keeton et al. From which we obtain the positions and magnifications of the non-relativistic images. In this article we assume that the quotient between the charge $|q|$ and twice the mass $2m$ of the Bardeen black hole is $|g|/2m>2\\sqrt{3}/9$ in which apparent horizon and photon sphere disappear. Results of this work predicts for a fixed $|g|/2m$ (impact parameter), the deflection angle decreases with respect to impact parameter ($|g|/2m$). Fixing position of the source and increasing ($|g|/2m$), positions of the non-relativistic images are closer and primary images locations transmit to corresponding secondary image positions. Magnification of the images reduces to an infinite value for Einstein rings for different values of the charge parameter ($|g|/2m$) and its absolute value increases in terms of positions of the sour...

Ghaffarnejad, Hossein

2014-01-01

38

Angular momentum effects in weak gravitational fields  

E-print Network

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

A. Tartaglia

2002-01-02

39

Gravitational field of relativistic gyratons  

E-print Network

The metric ansatz is used to describe the gravitational field of a beam-pulse of spinning radiation (gyraton) in an arbitrary number of spacetime dimensions D. First we demonstrate that this metric belongs to the class of metrics for which all scalar invariants constructed from the curvature and its covariant derivatives vanish. Next, it is shown that the vacuum Einstein equations reduce to two linear problems in (D-2)-dimensional Euclidean space. The first is to find the static magnetic potential created by a point-like source. The second requires finding the electric potential created by a point-like source surrounded by given distribution of the electric charge. To obtain a generic gyraton-type solution of the vacuum Einstein equations it is sufficient to allow the coefficients in the corresponding harmonic decompositions of solutions of the linear problems to depend arbitrarily on retarded time and substitute the obtained expressions in the metric ansatz. We discuss properties of the solutions for relativistic gyratons and consider special examples.

Valeri P. Frolov; Werner Israel; Andrei Zelnikov

2005-06-01

40

Electromagnetic Effects in Superconductors in Gravitational Field  

E-print Network

The general relativistic modifications to the resistive state in superconductors of second type in the presence of a stationary gravitational field are studied. Some superconducting devices that can measure the gravitational field by its red-shift effect on the frequency of radiation are suggested. It has been shown that by varying the orientation of a superconductor with respect to the earth gravitational field, a corresponding varying contribution to AC Josephson frequency would be added by gravity. A magnetic flux (being proportional to angular velocity of rotation $\\Omega$) through a rotating hollow superconducting cylinder with the radial gradient of temperature $\

B. J. Ahmedov; V. G. Kagramanova

2006-08-03

41

Combining Strong and Weak Gravitational Lensing in Abell 1689  

E-print Network

We present a reconstruction of the mass distribution of galaxy cluster Abell 1689 at z = 0.18 using detected strong lensing features from deep HST/ACS observations and extensive ground based spectroscopy. Earlier analyses have reported up to 32 multiply imaged systems in this cluster, of which only 3 were spectroscopically confirmed. In this work, we present a parametric strong lensing mass reconstruction using 24 multiply imaged systems with newly determined spectroscopic redshifts, which is a major step forward in building a robust mass model. In turn, the new spectroscopic data allows a more secure identification of multiply imaged systems. The resultant mass model enables us to reliably predict the redshifts of additional multiply imaged systems for which no spectra are currently available, and to use the location of these systems to further constrain the mass model. In particular, we have detected 5 strong galaxy-galaxy lensing systems just outside the Einstein ring region, further constraining the mass profile. Our strong lensing mass model is consistent with that inferred from our large scale weak lensing analysis derived using CFH12k wide field images. Thanks to a new method for reliably selecting a well defined background lensed galaxy population, we resolve the discrepancy found between the strong and weak lensing mass models reported in earlier work. [ABRIDGED

M. Limousin; J. Richard; E. Jullo; J. -P. Kneib; B. Fort; G. Soucail; A. Elíasdóttir; P. Natarajan; R. S. Ellis; I. Smail; O. Czoske; G. P. Smith; P. Hudelot; S. Bardeau; H. Ebeling; E. Egami; K. K. Knudsen

2006-12-06

42

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

E-print Network

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

P. Valageas

1999-11-17

43

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

Microsoft Academic Search

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

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

2000-01-01

44

The Equivalence of Time and Gravitational Field  

NASA Astrophysics Data System (ADS)

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

Baruk?i?a, Ilija

45

Gravitational field uncertainty modeling for aerospace vehicles  

NASA Astrophysics Data System (ADS)

Statistical gravitational modeling concepts and assumptions are reviewed, and four self-consistent gravitational uncertainty models are examined with reference to their performance in predicting inertial system and ballistic missile errors caused by the earth gravity disturbance field. The models discussed are the third-order Markov model, a model proposed by Tscherning and Rapp (1974), the attenuated white noise model, and the STAG model. In particular, consideration is given to the relative effects of the different gravitational models on impact accuracy for a ballistic missile trajectory. Finally, current activities in gravity modeling are briefly discussed.

Heller, W. G.

1982-08-01

46

Neutrino oscillations in the gravitational field  

SciTech Connect

We calculate the gravitational correction to the phase difference between neutrino mass eigenstates for the spherically symmetric gravitational field described by the Schwarzschild metric. This correction was calculated in a number of works, but the results of these works differ from each other. Our result does not coincide with the results ever published. In this work, we make calculations in the simplest way and verify our result by several tests.

Godunov, S. I., E-mail: sgodunov@itep.ru; Pastukhov, G. S., E-mail: grigoriypas@gmail.com [Moscow Institute of Physics and Technology (Russian Federation)

2011-02-15

47

Physical optics in a uniform gravitational field  

NASA Astrophysics Data System (ADS)

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.

Hacyan, Shahen

2012-01-01

48

Spin-2 particles in gravitational fields  

E-print Network

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

G. Papini

2007-02-01

49

Galilean-invariant scalar fields can strengthen gravitational lensing.  

PubMed

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

Wyman, Mark

2011-05-20

50

Gravitationally Induced Electric Fields in Conductors  

Microsoft Academic Search

An estimate for the gravitationally induced electric field is presented that is based on a statistical model for the electrons in a metal in which their long-range electrostatic interaction with a differentially compressed lattice of positive ions is taken into account. The field is in the upward direction and is estimated to be of the order of magnitude E~Mge, where

A. J. Dessler; F. C. Michel; H. E. Rorschach; G. T. Trammell

1968-01-01

51

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

E-print Network

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

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

2014-04-17

52

Gravitational repulsion in the Schwarzschild field  

SciTech Connect

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

McGruder, C.H. III

1982-06-15

53

Neutrino optics and oscillations in gravitational fields  

E-print Network

We study the propagation of neutrinos in gravitational fields using wave functions that are exact to first order in the metric deviation. For illustrative purposes, the geometrical background is represented by the Lense-Thirring metric. We derive explicit expressions for neutrino deflection, helicity transitions, flavor oscillations and oscillation Hamiltonian.

G. Lambiase; G. Papini; R. Punzi; G. Scarpetta

2005-03-07

54

Gravitational radiation from preheating with many fields  

SciTech Connect

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.

Jr, John T. Giblin [Department of Physics, Kenyon College, 201 North College Road, Gambier, OH 43022 (United States); Price, Larry R.; Siemens, Xavier, E-mail: giblinj@kenyon.edu, E-mail: larry@gravity.phys.uwm.edu, E-mail: siemens@gravity.phys.uwm.edu [Center for Gravitation and Cosmology, Department of Physics, University of Wisconsin — Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States)

2010-08-01

55

Quantum fields as gravitational sources  

E-print Network

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

Mark J Hadley

2008-08-13

56

Analytic Expression of the Genus in Weakly Non-Gaussian Field Induced by Gravity  

E-print Network

The gravitational evolution of the genus of the density field in large-scale structure is analytically studied in a weakly nonlinear regime using second-order perturbation theory. Weakly nonlinear evolution produces asymmetry in the symmetric genus curve for Gaussian initial density field. The effect of smoothing the density field in perturbation theory on the genus curve is also evaluated and gives the dependence of the asymmetry of the genus curve on spectra of initial fluctuations.

T. Matsubara

1994-05-16

57

Constraining modified gravitational theories by weak lensing with Euclid  

SciTech Connect

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.

Martinelli, Matteo; Calabrese, Erminia; De Bernardis, Francesco; Melchiorri, Alessandro; Pagano, Luca [Physics Department and INFN, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Scaramella, Roberto [INAF, Osservatorio Astronomico di Roma, via Frascati 33, 0040 Monte Porzio Catone (Italy)

2011-01-15

58

A compilation of weak gravitational lensing studies of clusters of galaxies  

E-print Network

We present a list of clusters that have had their dark matter content measured using weak gravitational lensing. The list consists of 139 clusters, with weak lensing measurements reported in 64 different publications. Details are provided about the selection criteria and some basic properties of the sample, such as the redshift distribution. An electronic, sortable version of this list with links to public database information on the clusters and publications is provided at http://folk.uio.no/hdahle/WLclusters.html

H. Dahle

2007-01-21

59

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

E-print Network

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

Hu, Wayne

60

A weak combined magnetic field changes root gravitropism  

NASA Astrophysics Data System (ADS)

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

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

61

Mapping the dark matter with weak gravitational lensing  

Microsoft Academic Search

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

Nick Kaiser; Gordon Squires

1993-01-01

62

Gravitational collapse of charged scalar fields  

NASA Astrophysics Data System (ADS)

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

Torres, Jose M.; Alcubierre, Miguel

2014-09-01

63

3D Weak Gravitational Lensing of the CMB and Galaxies  

E-print Network

In this paper we present a power spectrum formalism that combines the full three-dimensional information from the galaxy ellipticity field, with information from the cosmic microwave background (CMB). We include in this approach galaxy cosmic shear and galaxy intrinsic alignments, CMB deflection, CMB temperature and CMB polarisation data; including the inter-datum power spectra between all quantities. We apply this to forecasting cosmological parameter errors for CMB and imaging surveys and show that the additional covariance between the CMB and ellipticity measurements can improve galaxy intrinsic alignment measurements by a factor of two, and dark energy equation of state measurements by thirty percent. We present predictions for Euclid-like, KiDS, ACTPoL, and CoRE-like experiments and show that the combination of cosmic shear and the CMB, from Euclid-like and CoRE-like experiments, can measure the sum of neutrino masses with an error of 0.02 eV, and the dark energy equation of state with an error on w0 of ...

Kitching, T D; Das, S

2014-01-01

64

Theory of microemulsions in a gravitational field  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

65

Significant effects of weak gravitational lensing on determinations of the cosmology from Type Ia supernovae  

Microsoft Academic Search

Significant adjustments to the values of the cosmological parameters estimated from high-redshift Type Ia supernovae data are reported, almost an order of magnitude greater than previously found. They arise from the effects of weak gravitational lensing on observations of high-redshift sources. The lensing statistics used have been obtained from computations of the three-dimensional shear in a range of cosmological N-body

Andrew J. Barber

2000-01-01

66

Stability in the weak variational principle of barotropic flows and implications for self-gravitating discs  

NASA Astrophysics Data System (ADS)

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.

Yahalom, Asher

2011-11-01

67

Gravitational Descendants in Symplectic Field Theory  

NASA Astrophysics Data System (ADS)

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

Fabert, Oliver

2011-02-01

68

Gravitational radiative corrections from effective field theory  

SciTech Connect

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 nonlinear 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 nonrelativistic binaries, including long distance effects up to 3 post-Newtonian (v{sup 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.

Goldberger, Walter D.; Ross, Andreas [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2010-06-15

69

Graphene transparency in weak magnetic fields  

E-print Network

We carry out an explicit calculation of the vacuum polarization tensor for an effective low-energy model of monolayer graphene in the presence of a weak magnetic field of intensity $B$ perpendicularly aligned to the membrane. By expanding the quasiparticle propagator in the Schwinger proper time representation up to order $(eB)^2$, where $e$ is the unit charge, we find an explicitly transverse tensor, consistent with gauge invariance. Furthermore, assuming that graphene is radiated with monochromatic light of frequency $\\omega$ along the external field direction, from the modified Maxwell's equations we derive the intensity of transmitted light and the angle of polarization rotation in terms of the longitudinal ($\\sigma_{xx}$) and transverse ($\\sigma_{xy}$) conductivities. Corrections to these quantities, both calculated and measured, are of order $(eB)^2/\\omega^4$. Our findings generalize and complement previously known results reported in literature regarding the light absorption problem in graphene from th...

Valenzuela, David; Loewe, Marcelo; Raya, Alfredo

2014-01-01

70

Consequences of Coupled Electromagnetic-Gravitational Fields  

NASA Technical Reports Server (NTRS)

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.

Smalley, Larry

2002-01-01

71

Gravitational Field of Shells and Disks in General Relativity  

Microsoft Academic Search

The problem of obtaining the gravitational field of static, axially symmetric, thin shells is elucidated. In particular, a clear distinction between global and local frames is made. An algorithm is given for obtaining the fields of disks. There are two significant gravitational potentials lambda and phi. The potential lambda is straightforwardly determined from the radial stresses by solving a two-dimensional

Lesley Morgan; Thomas Morgan

1970-01-01

72

Graphene transparency in weak magnetic fields  

E-print Network

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

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

2014-10-20

73

Weak gravitational lensing as a method to constrain unstable dark matter  

SciTech Connect

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

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

2010-12-15

74

Gravitational consequences of modern field theories  

NASA Technical Reports Server (NTRS)

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

Horowitz, Gary T.

1989-01-01

75

Casimir effect due to a slowly rotating source in the weak-field approximation  

NASA Astrophysics Data System (ADS)

We calculate the renormalized vacuum energy density for a massless scalar field confined between two nearby parallel plates formed by ideal uncharged conductors, placed very close to the surface of a rotating spherical gravitational source with mass M, radius R and angular momentum J, at the equatorial region. We consider that the source rotates slowly and that the gravitational field is weak. Corrections to the Casimir energy density induced by the gravitational field generated by this source are calculated up to M/R2 order. The results obtained show us that there is an important modification in the Casimir energy only in this order of approximation, which depends on the surface gravity as well as on the rotation of the source. Thermal corrections to the Casimir energy found are also calculated in all these orders.

Bezerra, V. B.; Mota, H. F.; Muniz, C. R.

2014-02-01

76

Casimir effect due to a slowly rotating source in the weak field approximation  

E-print Network

We calculate the renormalized vacuum energy density for a massless scalar field confined between two nearby parallel plates formed by ideal uncharged conductors, placed very close to the surface of a rotating spherical gravitational source with mass $M$, radius $R$ and momentum angular $J$, at the equatorial region. We consider that the source rotates slowly and that the gravitational field is weak. Corrections to the Casimir energy density induced by the gravitational field generated by this source are calculated up to $M/R^2$ order. The obtained results show us that there is an important modification in the Casimir energy only in this order of approximation, which depends on the surface gravity as well as on the rotation of the source. Thermal corrections to the Casimir energy found also are calculated in all these orders.

Bezerra, V B; Muniz, C R

2014-01-01

77

Casimir effect due to a slowly rotating source in the weak field approximation  

E-print Network

We calculate the renormalized vacuum energy density for a massless scalar field confined between two nearby parallel plates formed by ideal uncharged conductors, placed very close to the surface of a rotating spherical gravitational source with mass $M$, radius $R$ and momentum angular $J$, at the equatorial region. We consider that the source rotates slowly and that the gravitational field is weak. Corrections to the Casimir energy density induced by the gravitational field generated by this source are calculated up to $M/R^2$ order. The obtained results show us that there is an important modification in the Casimir energy only in this order of approximation, which depends on the surface gravity as well as on the rotation of the source. Thermal corrections to the Casimir energy found also are calculated in all these orders.

V. B. Bezerra; H. F. Mota; C. R. Muniz

2014-01-09

78

Microcanonical functional integral for the gravitational field  

NASA Astrophysics Data System (ADS)

The gravitational field in a spatially finite region is described as a microcanonical system. The density of states ? is expressed formally as a functional integral over Lorentzian metrics and is a functional of the geometrical boundary data that are fixed in the corresponding action. These boundary data are the thermodynamical extensive variables, including the energy and angular momentum of the system. When the boundary data are chosen such that the system is described semiclassically by any real stationary axisymmetric black hole, then in this same approximation ln? is shown to equal 1/4 the area of the black-hole event horizon. The canonical and grand canonical partition functions are obtained by integral transforms of ? that lead to ``imaginary-time'' functional integrals. A general form of the first law of thermodynamics for stationary black holes is derived. For the simpler case of nonrelativistic mechanics, the density of states is expressed as a real-time functional integral and then used to deduce Feynman's imaginary-time functional integral for the canonical partition function.

Brown, J. David; York, James W., Jr.

1993-02-01

79

Interaction of gravitational waves with magnetic and electric fields  

SciTech Connect

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.

Barrabes, C.; Hogan, P. A.

2010-03-15

80

Weighing 40 X-ray Luminous Clusters of Galaxies with Weak Gravitational Lensing  

E-print Network

Deep two-color imaging of 40 clusters of galaxies with the NOT and the University of Hawaii 2.24-m telescope is used to measure the weak gravitational shear acting on faint background galaxies. From this, maps of the projected cluster mass distribution are constructed, and the cluster masses are measured within circular apertures of up to ~3 Mpc/h. The results are used to derive the cluster mass function at z~0.2. The average mass-to-light ratio of the clusters indicate a low-density Universe with Omega_0 around 0.25. Additional mass concentrations are found along the lines of sight to the clusters, some of which are most likely associated with clusters at z > 0.5. In addition, the data are used to measure weak gravitational lensing due to large-scale structures along the line of sight. The future prospects for this kind of research with the NOT are briefly discussed.

H. Dahle

2000-09-25

81

Lorentz violation in a uniform Newtonian gravitational field  

NASA Astrophysics Data System (ADS)

Lorentz invariance is one of the fundamental principles of physics, and, as such, it must be experimentally tested. The purpose of this work is to obtain, within the Standard-Model Extension, the dynamics of a Lorentz-violating spinor in a uniform Newtonian gravitational field. This is achieved by treating the spinor as a test particle and introducing the gravitational field through a uniformly accelerated observer. The nonrelativistic Hamiltonian is obtained, and some experimental consequences are discussed. One unexpected outcome of this work is that the gravitational field helps disentangle bounds on coefficients for Lorentz violation.

Bonder, Yuri

2013-11-01

82

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

Microsoft Academic Search

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

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

2010-01-01

83

Gravitational waves from self-ordering scalar fields  

SciTech Connect

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 ?{sub GW}(f) ? f{sup 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?{sub *} << 1), enters the horizon, for k? ?> 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.

Fenu, Elisa; Durrer, Ruth [Institute de Physique Théorique, Université de Genève, 24 quai E. Ansermet, 1211 Genève 4 (Switzerland); Figueroa, Daniel G.; García-Bellido, Juan, E-mail: elisa.fenu@unige.ch, E-mail: daniel.figueroa@uam.es, E-mail: ruth.durrer@unige.ch, E-mail: juan.garciabellido@uam.es [Instituto de Física Teórica CSIC-UAM and Departamento de Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

2009-10-01

84

Weak gravitational lensing as a probe of physical properties of substructures in dark matter halos  

E-print Network

We propose a novel method to select satellite galaxies in outer regions of galaxy groups or clusters using weak gravitational lensing. The method is based on the theoretical expectation that the tangential shear pattern around satellite galaxies would appear with negative values at the offset distance from the center of the main halo. We can thus locate the satellite galaxies statistically with a offset distance of several lensing smoothing scales by using the standard reconstruction of surface mass density maps from weak lensing observation. We test the idea using high resolution cosmological simulations. We show that subhalos separated from the center of the host halo are successfully located even without assuming the position of the center. For a number of such subhalos, the characteristic mass and the off-set length can be also estimated on a statistical basis. We perform a Fisher analysis to show how well upcoming weak lensing surveys can constrain the mass density profile of satellite galaxies. In the c...

Shirasaki, Masato

2014-01-01

85

Densities of Electron's Continuum in Gravitational and Electromagnetic Fields  

E-print Network

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.

I. E. Bulyzhenkov

2012-11-18

86

Gravitational field maps and navigational errors [unmanned underwater vehicles  

Microsoft Academic Search

Gravitational field maps are used to correct navigational errors that tend to accumulate in some navigational systems presently in use on unmanned underwater vehicles (UUVs). Two essential elements of such a system are an algorithm to calculate field maps from sparsely and irregularly sampled measured field data and an algorithm to match locally measured field values to an a priori

Garner C. Bishop

2002-01-01

87

Topological Vortex Formation in BEC under Gravitational Field  

E-print Network

Topological phase imprinting is a unique technique for vortex formation in a Bose-Einstein condensate (BEC) of alkali metal gas, in that it does not involve rotation: BEC is trapped in a quadrupole field with a uniform bias field which is reversed adiabatically leading to vortex formation at the center of the magnetic trap. The scenario has been experimentally verified by MIT group employing $^{23}$Na atoms. Recently similar experiments have been conducted at Kyoto University, in which BEC of $^{87}$Rb atoms has been used. In the latter experiments they found that the fine-tuning of the field reverse time $T_{\\rm rev}$ is required to achieve stable vortex formation. Otherwise, they often observed vortex fragmentations or a condensate without a vortex. It is shown in this paper that this behavior is attributed to the heavy mass of the Rb atom. The confining potential, which depends on the eigenvalue $m_B$ of the hyperfine spin $\\bv{F}$ along the magnetic field, is now shifted by the gravitational field perpendicular to the vortex line. Then the positions of two weak-field-seeking states with $m_B=1$ and 2 deviate from each other. This effect is more prominent for BEC with a heavy atomic mass, for which the deviation is greater and, moreover, the Thomas-Fermi radius is smaller. We found, by solving the Gross-Pitaevskii equation numerically, that two condensates interact in a very complicated way leading to fragmentation of vortices, unless $T_{\\rm rev}$ is properly tuned.

Yuki Kawaguchi; Mikio Nakahara; Tetsuo Ohmi

2004-05-17

88

Quantum physics in inertial and gravitational fields  

E-print Network

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

G. Papini

2003-04-22

89

Unification of Gravitation, Gauge Field and Dark Energy  

E-print Network

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

Xin-Bing Huang

2004-10-27

90

Soliton solutions in relativistic field theories and gravitation  

E-print Network

We report on some recent results on a class of relativistic lagrangian field theories supporting non-topological soliton solutions and their applications in the contexts of Gravitation and Cosmology. We analyze one and many-components scalar fields and gauge fields.

Joaquin Diaz-Alonso; Diego Rubiera-Garcia

2007-12-11

91

NASA Computational Case Study: Modeling Planetary Magnetic and Gravitational Fields  

NASA Technical Reports Server (NTRS)

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

Simpson, David G.; Vinas, Adolfo F.

2014-01-01

92

Significant Effects of Weak Gravitational Lensing on Determinations of the Cosmology from Type Ia Supernovae  

E-print Network

Significant adjustments to the values of the cosmological parameters estimated from high-redshift Type Ia Supernov\\ae data are reported, almost an order of magnitude greater than previously found. They arise from the effects of weak gravitational lensing on observations of high-redshift sources. The lensing statistics used have been obtained from computations of the three-dimensional shear in a range of cosmological N-body simulations, from which it is estimated that cosmologies with an underlying deceleration parameter q_0 = -0.51 +0.03/-0.24 may be interpreted as having q_0 = -0.55 (appropriate to the currently popular cosmology with density parameter $\\Omega_M = 0.3$ and vacuum energy density parameter $\\Omega_{\\Lambda} = 0.7$). In addition, the standard deviation expected from weak lensing for the peak magnitudes of Type Ia Supernov\\ae at redshifts of 1 is expected to be approximately 0.078 magnitudes, and 0.185 magnitudes at redshift 2. This latter value is greater than the accepted intrinsic dispersion ...

Barber, A J

2000-01-01

93

Quantum gravitational optics in the field of a gravitomagnetic monopole  

E-print Network

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

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

2006-07-29

94

REVIEWS OF TOPICAL PROBLEMS: Motion of particles and photons in the gravitational field of a rotating body (In memory of Vladimir Afanas'evich Ruban)  

NASA Astrophysics Data System (ADS)

A study is made of the trajectories of free motion of test particles and photons in the Kerr metric, which describes the gravitational field of a rotating massive body. The trajectories are classified on the basis of the integrals of the motion, which have a clear physical meaning. The cases of a strong gravitational field in the neighborhood of a rotating black hole as well as the weak-field approximation describing the motion of particles in the gravitational field of a rotating star or galaxy are considered. The review includes bound states (orbits) in the field of a rotating mass, scattering and gravitational capture of particles and photons by a rotating black hole, trajectories of falling into a black hole, and the bending of light rays and the gravitational time delay of signals in the gravitational field of a rotating body.

Dymnikova, I. G.

1986-03-01

95

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

E-print Network

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

Ian Smail; Mark Dickinson

1995-10-08

96

Unification of Gravitational and Electromagnetic Fields in Riemannian Geometry  

E-print Network

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.

Yi-Fang Chang

2009-01-01

97

Lorentz covariant theory of light propagation in gravitational fields of arbitrary-moving bodies  

NASA Astrophysics Data System (ADS)

The Lorentz covariant theory of the propagation of light in the (weak) gravitational fields of N-body systems consisting of arbitrarily moving pointlike bodies with constant masses ma (a=1,2,...,N) is constructed. The theory is based on the Liénard-Wiechert representation of the metric tensor which describes a retarded type solution of the gravitational field equations. A new approach for integrating the equations of motion of light particles (photons) depending on the retarded time argument is invented. Its application in the first post-Minkowskian approximation, which is linear with respect to the universal gravitational constant G makes it evident that the equations of light propagation admit to be integrated straightforwardly by quadratures. Explicit expressions for the trajectory of a light ray and its tangent vector are obtained in algebraically closed form in terms of functionals of retarded time. General expressions for the relativistic time delay, the angle of light deflection, and the gravitational shift of electromagnetic frequency are derived in the form of instantaneous functions of retarded time. They generalize previously known results for the case of static or uniformly moving bodies. The most important applications of the theory to relativistic astrophysics and astrometry are given. They include a discussion of the velocity-dependent terms in the gravitational lens equation, the Shapiro time delay in binary pulsars, gravitational Doppler shift, and a precise theoretical formulation of the general relativistic algorithms of data processing of radio and optical astrometric measurements made in the nonstationary gravitational field of the solar system. Finally, proposals for future theoretical work being important for astrophysical applications are formulated.

Kopeikin, Sergei M.; Schäfer, Gerhard

1999-12-01

98

Lorentz Covariant Theory of Light Propagation in Gravitational Fields of Arbitrary-Moving Bodies  

E-print Network

The Lorentz covariant theory of propagation of light in the (weak) gravitational fields of N-body systems consisting of arbitrarily moving point-like bodies with constant masses is constructed. The theory is based on the Lienard-Wiechert presentation of the metric tensor. A new approach for integrating the equations of motion of light particles depending on the retarded time argument is applied. In an approximation which is linear with respect to the universal gravitational constant, G, the equations of light propagation are integrated by quadratures and, moreover, an expression for the tangent vector to the perturbed trajectory of light ray is found in terms of instanteneous functions of the retarded time. General expressions for the relativistic time delay, the angle of light deflection, and gravitational red shift are derived. They generalize previously known results for the case of static or uniformly moving bodies. The most important applications of the theory are given. They include a discussion of the velocity dependent terms in the gravitational lens equation, the Shapiro time delay in binary pulsars, and a precise theoretical formulation of the general relativistic algorithm of data processing of radio and optical astrometric measurements in the non-stationary gravitational field of the solar system. Finally, proposals for future theoretical work being important for astrophysical applications are formulated.

Sergei M. Kopeikin; Gerhard Schafer

1999-02-11

99

Orbital dynamics of the gravitational field of stringy black holes  

NASA Astrophysics Data System (ADS)

In this paper, we study the orbital dynamics of the gravitational field of stringy black holes by analyzing the effective potential and the phase plane diagram. By solving the equation of Lagrangian, the general relativistic equations of motion in the gravitational field of stringy black holes are given. It is easy to find that the motion of test particles depends on the energy and angular momentum of the test particles. Using the phase plane analysis method and combining the conditions of the stability, we discuss different types of the test particles' orbits in the gravitational field of stringy black holes. We get the innermost stable circular orbit which occurs at rmin = 5.47422 and when the angular momentum b ? 4.3887 the test particles will fall into the black hole.

Zhang, Yu; Geng, Jin-Ling; Li, En-Kun

2014-09-01

100

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

SciTech Connect

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

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

2005-08-08

101

Measuring the Galaxy-Galaxy-Mass Three-point Correlation Function with Weak Gravitational Lensing  

E-print Network

We discuss the galaxy-galaxy-mass three-point correlation function and show how to measure it with weak gravitational lensing. The method entails choosing a large of pairs of foreground lens galaxies and constructing a mean shear map with respect to their axis, by averaging the ellipticities of background source galaxies. An average mass map can be reconstructed from this shear map and this will represent the average mass distribution around pairs of galaxies. We show how this mass map is related to the projected galaxy-galaxy-mass three-point correlation function. Using a large N-body dark matter simulation populated with galaxies using the Halo Occupation Distribution (HOD) bias prescription, we compute these correlation functions, mass maps, and shear maps. The resultant mass maps are distinctly bimodal, tracing the galaxy centers and remaining anisotropic up to scales much larger than the galaxy separation. At larger scales, the shear is approximately tangential about the center of the pair but with small azimuthal variation in amplitude. We estimate the signal-to-noise ratio of the reconstructed mass maps for a survey of similar depth to the Sloan Digital Sky Survey (SDSS) and conclude that the galaxy-galaxy-mass three-point function should be measurable with the current SDSS weak lensing data. Measurements of this three-point function, along with galaxy-galaxy lensing and galaxy auto-correlation functions, will provide new constraints on galaxy bias models. The anisotropic shear profile around close pairs of galaxies is a prediction of cold dark matter models and may be difficult to reconcile with alternative theories of gravity without dark matter.

David E. Johnston

2005-03-13

102

SELF-CONSISTENT MEAN FIELD THEORY IN WEAKLY IONIZED GAS  

E-print Network

of the dynamo in 3D and tur- bulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreac to the fully ionized gas. Furthermore, we show that in 2D, the turbulent diffusion is suppressed by backSELF-CONSISTENT MEAN FIELD THEORY IN WEAKLY IONIZED GAS Nicolas Leprovost Groupe Instabilit´e et

Paris-Sud XI, Université de

103

Anisotropic parametrized post-Newtonian gravitational metric field  

NASA Technical Reports Server (NTRS)

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.

Nordtvedt, K., Jr.

1976-01-01

104

Weakly bound electrons in external magnetic field  

E-print Network

The effect of the uniform magnetic field on the electron in the spherically symmetric square-well potential is studied. A transcendental equation that determines the electron energy spectrum is derived. The approximate value of the lowest (bound) energy state is found. The approximate wave function and probability current density of this state are constructed.

I. V. Mamsurov; F. Kh. Chibirova

2007-03-07

105

Spin Hall effect of photons in a static gravitational field  

SciTech Connect

Starting from a Hamiltonian description of the photon within the set of Bargmann-Wigner equations we derive new semiclassical equations of motion for the photon propagating in a static gravitational field. These equations which are obtained in the representation diagonalizing the Hamiltonian at the order ({Dirac_h}/2{pi}), present the first order corrections to the geometrical optics. The photon Hamiltonian shows a new kind of helicity-torsion coupling. However, even for a torsionless space-time, photons do not follow the usual null geodesic as a consequence of an anomalous velocity term. This term is responsible for the gravitational birefringence phenomenon: photons with distinct helicity follow different geodesics in a static gravitational field.

Gosselin, Pierre [Universite Grenoble I, Institut Fourier, UMR 5582 CNRS-UJF, UFR de Mathematiques, BP74, 38402 Saint Martin d'Heres, Cedex (France); Berard, Alain; Mohrbach, Herve [Universite Paul Verlaine, Institut de Physique, ICPMB1-FR CNRS 2843, Laboratoire de Physique Moleculaire et des Collisions, 1, boulevard Arago, 57078 Metz (France)

2007-04-15

106

Field Methods for Characterizing Weak Rock for Engineering  

E-print Network

a range of properties intermediate to soil and rock.'' This observation could lead one to group weak, or high moisture content. Methods of field description were chosen based on a review of existing methods

107

Causality, the Coulomb field, and Newton's law of gravitation  

Microsoft Academic Search

Causality in classical field theories must be inserted by hand by choosing the retarded solution. It is shown how apparent contradictions in the Coulomb gauge can be resolved and that a causal Coulomb field exists despite the appearance to the contrary. Similarly, it is shown how Newtonian gravitation leads from action-at-a-distance to a causal field when a first-order correction for

F. Rohrlich

2002-01-01

108

Biological effects due to weak magnetic field on plants  

NASA Astrophysics Data System (ADS)

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

Belyavskaya, N. A.

2004-01-01

109

Effects and molecular mechanisms of the biological action of weak and extremely weak magnetic fields  

Microsoft Academic Search

A number of effects of weak combined (static and alternating) magnetic fields with an alternating component of tens and hundreds\\u000a nT at a collinear static field of 42 ?T, which is equivalent to the geomagnetic field, have been found: activation of fission\\u000a and regeneration of planarians Dugesia tigrina, inhibition of the growth of the Ehrlich ascites carcinoma in mice, stimulation

V. V. Novikov; V. O. Ponomarev; G. V. Novikov; V. V. Kuvichkin; E. V. Yablokova; E. E. Fesenko

2010-01-01

110

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

SciTech Connect

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

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

2010-06-15

111

? (?) Cantorian space-time, polarization gravitational field and van der Waals-type forces  

Microsoft Academic Search

Some abilities of the SRT theory in studying the polarization gravitational field are analyzed. Thus, one builds a set of Maxwell-type equations for the polarization gravitational field and one studies the behaviour of a gravitomagnetic charge in such fields on a fractalic space-time. One finds that the interaction between the gravitomagnetic charge and the polarization gravitational field reduces to the

M. Agop; P. D. Ioannou; P. Nica; C. Gh. Buzea; M. Jarcau

2003-01-01

112

The Gravitational Behaviour of an Effective Topological Field Theory  

E-print Network

Effective topological field theories describe the topological properties of Dirac fermions in the low-energy regime. In this work, we consider fermions coupled to a $SO(5)$ Cartan connection on suitable four-dimensional compact manifolds. We show that the corresponding effective topological field theory, suitably constrained on the basis of topological motivations, gives rise to a gravitational action with a cosmological constant and Barbero-Immirzi parameter which is compatible, at classical level, with the vacuum general relativity.

Giandomenico Palumbo

2014-01-08

113

Effects of Electromagnetic Field on Gravitational Collapse  

E-print Network

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.

M. Sharif; G. Abbas

2009-05-16

114

No cosmological domain wall problem for weakly coupled fields  

NASA Astrophysics Data System (ADS)

After inflation occurs, a weakly coupled scalar field will in general not be in thermal equilibrium but have a distribution of values determined by the inflationary Hubble parameter. If such a field subsequently undergoes discrete symmetry breaking, then the different degenerate vacua may not be equally populated so the domain walls which form will be ``biased'' and the wall network will subsequently collapse. Thus the cosmological domain wall problem may be solved for sufficiently weakly coupled fields in a post inflationary universe. We quantify the criteria for determining whether this does happen, using a Higgs-like potential, with a spontaneously broken Z2 symmetry.

Casini, Horacio; Sarkar, Subir

2002-01-01

115

Gravitational wave in Lorentz violating gravity  

E-print Network

By making use of the weak gravitational field approximation, we obtain a linearized solution of the gravitational vacuum field equation in an anisotropic spacetime. The plane-wave solution and dispersion relation of gravitational wave is presented explicitly. There is possibility that the speed of gravitational wave is larger than the speed of light and the casuality still holds. We show that the energy-momentum of gravitational wave in the ansiotropic spacetime is still well defined and conserved.

Xin Li; Zhe Chang

2011-11-06

116

Gravitation  

NSDL National Science Digital Library

Known world-wide as "MTW". A classic, graduate level textbook on general relativity. Includes both "math-first" and "physics-first" elements. This text covers material for a graduate level course on gravitation physics and general relativity. Topics include flat spacetime, tools of modern geometry, Einstein's geometric framework for physics, applications such as pulsars and neutron stars, cosmology, gravitational collapse, and gravitational waves. It also includes information on experimental tests of General Relativity, superspace, and quantum geometrodynamics.

Misner, Charles; Thorne, Kip S.; Wheeler, John A.

2004-06-14

117

Two-time physics with gravitational and gauge field backgrounds  

SciTech Connect

It is shown that all possible gravitational, gauge and other interactions experienced by particles in ordinary d dimensions (one time) can be described in the language of two-time physics in a spacetime with d+2 dimensions. This is obtained by generalizing the world line formulation of two-time physics by including background fields. A given two-time model, with a fixed set of background fields, can be gauged fixed from d+2 dimensions to (d-1)+1 dimensions to produce diverse one-time dynamical models, all of which are dually related to each other under the underlying gauge symmetry of the unified two-time theory. To satisfy the gauge symmetry of the two-time theory the background fields must obey certain coupled differential equations that are generally covariant and gauge invariant in the target (d+2)-dimensional spacetime. The gravitational background obeys a closed homothety condition while the gauge field obeys a differential equation that generalizes a similar equation derived by Dirac in 1936. Explicit solutions to these coupled equations show that the usual gravitational, gauge, and other interactions in d dimensions may be viewed as embedded in the higher (d+2)-dimensional space, thus displaying higher spacetime symmetries that otherwise remain hidden.

Bars, Itzhak

2000-10-15

118

General models of Einstein gravity with a non-Newtonian weak-field limit  

E-print Network

We investigate Einstein theories of gravity, coupled to a scalar field \\vphi and point-like matter, which are characterized by a scalar field-dependent matter coupling function e^{H(\\vphi)}. We show that under mild constraints on the form of the potential for the scalar field, there are a broad class of Einstein-like gravity models -characterized by the asymptotic behavior of H- which allow for a non-Newtonian weak-field limit with the gravitational potential behaving for large distances as ln r. The Newtonian term GM/r appears only as sub-leading. We point out that this behavior is also shared by gravity models described by f(R) Lagrangians. The relevance of our results for the building of infrared modified theories of gravity and for modified Newtonian dynamics is also discussed.

M. Cadoni; M. Casula

2009-01-08

119

?N?NN weak interaction in effective-field theory  

NASA Astrophysics Data System (ADS)

The nonleptonic weak ? ?S ? =1 ?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.

Parreño, Assumpta; Bennhold, Cornelius; Holstein, Barry R.

2004-11-01

120

Oscillations and Waves in Strong Gravitational and Electromagnetic Fields.  

NASA Astrophysics Data System (ADS)

This book emerged from a course given at Moscow State University and provides an introduction to current research in general relativity, relativistic gas dynamics, and cosmology, touching as well on the different methods used in wave theory. Each chapter begins with an elementary introduction and then proceeds to a more sophisticated discussion including a presentation of the current state of the art. Topics covered include: original results of and approaches to the mathematical theory of strong gravitational and electromagnetic fields in general relativity which reduce the problem to a single linear integral equation; the theory of black holes; wave propagation in the vicinity of black holes; the effect of strong external electromagnetic fields on gravitational and electromagnetic waves of short length; the theory of integrable nonlinear two-dimensional systems in theoretical physics; methods of relativistic and magneto gas dynamics in cosmology including shock and acoustic waves; hydrodynamical effects due to the rotation of a pulsar in a closed binary system.

Sibgatullin, Nail R.; Queen, N. M.

121

New symbolic tools for differential geometry, gravitation, and field theory  

NASA Astrophysics Data System (ADS)

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.

Anderson, I. M.; Torre, C. G.

2012-01-01

122

New Symbolic Tools for Differential Geometry, Gravitation, and Field Theory  

E-print Network

DifferentialGeometry is a Maple software package which symbolically performs fundamental operations of calculus on manifolds, differential geometry, tensor 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 and other tensorial invariants, algebraic classification of curvature, and symmetry reduction of field equations.

I. M. Anderson; C. G. Torre

2011-03-08

123

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

NASA Astrophysics Data System (ADS)

Dynamic velocity dispersion and mass estimates are given for a sample of five X-ray-luminous rich clusters of galaxies at intermediate redshifts (z~0.3) drawn from a sample of 39 clusters for which we have obtained gravitational lens mass estimates. The velocity dispersions are determined from between nine and 20 redshifts measured with the low-dispersion survey spectrograph (LDSS) of the William Herschel Telescope, and virial radii are determined from imaging using the UH8K mosaic CCD camera on the University of Hawaii 2.24 m telescope. Including clusters with velocity dispersions taken from the literature, we have velocity dispersion estimates for 12 clusters in our gravitational lensing sample. For this sample we compare the dynamic velocity dispersion estimates with our estimates of the velocity dispersions made from gravitational lensing by fitting a singular isothermal sphere profile to the observed tangential weak lensing distortion as a function of radius. In all but two clusters, we find a good agreement between the velocity dispersion estimates based on spectroscopy and those based on weak lensing. Based on observations made with the William Herschel Telescope, operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

Irgens, Ragnvald J.; Lilje, Per B.; Dahle, Håkon; Maddox, S. J.

2002-11-01

124

Gravitational field of a stationary circular cosmic string loop  

E-print Network

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

A; A. Sen; N. Banerjee

1997-09-26

125

Electromagnetic waves in the gravitational field of massive dark halos  

E-print Network

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

Shahen Hacyan

2014-01-31

126

The Equation of Atom Motion in an External Gravitational Field  

E-print Network

It is shown that the motion of a multielectron atom in an external gravitational field in a good approximation is described by system of the Mathisson-Papapetrou equations, if we put as a classical angular momentum of the atom the expectation value of the operator of the full angular momentum of the system, which includes spins of the nucleus and electrons, and orbital momentums of the electrons in the atom.

G. V. Basalyga; A. K. Gorbatsievich

1999-01-30

127

Clock Synchronisation in Inertial Frames and Gravitational Fields  

E-print Network

The special relativistic test theory of Mansouri and Sexl is sketched. Theories based on different clock synchronisations are found to be equivalent to special relativity, as regards experimental results. The conventionality of clock synchronisation is shown not to hold, by means of an example, in a simple accelerated system and through the principle of equivalence in gravitational fields, especially when the metric is not static. Experimental implications on very precise clock synchronisation on earth are discussed.

François Goy

1996-07-20

128

Analytic perturbative theories in highly inhomogeneous gravitational fields  

NASA Astrophysics Data System (ADS)

Orbital motion about irregular bodies is highly nonlinear due to inhomogeneities in the gravitational field. Classical theories of motion close to spheroidal bodies cannot be applied as for inhomogeneous bodies the Keplerian forces do not provide a good approximation of the system dynamics. In this paper a closed form, analytical method for developing the motion of a spacecraft around small bodies is presented, for the so called fast rotating case, which generalize previous results to second order, arbitrary degree, gravitational fields. Through the application of two different Lie transformations, suitable changes of coordinates are found, which reduce the initial nonintegrable Hamiltonian of the system into an integrable one plus a negligible, perturbative remainder of higher degree. In addition, an explicit analytical formulation for the relegated, first and second order, arbitrary degree Hamiltonian for relatively high altitude motion in any inhomogeneous gravitational field is derived in closed-form. Applications of this algorithm include a method for determining initial conditions for frozen orbits around any irregular body by simply prescribing the desired inclination and eccentricity of the orbit. This method essentially reduces the problem of computing frozen orbits to a problem of solving a 2-D algebraic equation. Results are shown for the Asteroid 433-Eros.

Ceccaroni, Marta; Biggs, James

2013-05-01

129

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

E-print Network

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

Kh. M. Beshtoev

2000-04-19

130

Experimental Data Demonstrating Augmentation of Ambient Gravitational and Geomagnetic Fields  

NASA Astrophysics Data System (ADS)

Despite significant documentation and rigorously controlled conditions, most research involving extraordinary human-generated phenomena (e.g. remote viewing, teleportation, etc.) has focused either upon the observation of the macro-phenomena itself, or cumulative statistical deviation from chance. This paper, however, examines the influences upon and augmentation of ambient gravitational and geomagnetic fields, a previously unobserved and unrecognized concomitant physics phenomenon during activities requiring singular and total concentration. Utilizing simple field measurement instrumentation, original experimental data is presented, discussed, and compared with controlled baselines. Whereas some previous research has examined the influence of ambient fields upon human subjects, published literature is sparse concerning the influence of human subjects specifically upon ambient fields. As well, research that rigorously pursued the study of the effects of indirect human interference on engineering instrumentation did not consider ambient fields for experimental control, perhaps limiting potential theoretical modeling and integration. The presented empirical data demonstrates that gravitational and geomagnetic field augmentation occurring during such all-consuming activity is neither incidental nor subtle and may well be a worthy consideration for modeling frontier scientific theories and expanding current physics paradigms. Insomuch as natural, human-generated phenomena currently stand as the most accessible and repeatable examples of anomalous environmental interactivity, this data and suggested research protocols presented offer exploratory perspectives for observing the underlying scientific principals and physics concepts of ambient field interface as well as potential applications in developing more effective theoretical models for frontier space science.

Graham, Danielle

2006-01-01

131

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

NASA Astrophysics Data System (ADS)

We study numerically the localization properties of two-dimensional electrons in a weak perpendicular magnetic field. For this purpose we construct weakly chiral network models on the square and triangular lattices. The prime idea is to separate in space the regions with phase action of magnetic field, where it affects interference in course of multiple disorder scattering, and the regions with orbital action of magnetic field, where it bends electron trajectories. In our models, the disorder mixes counterpropagating channels on the links, while scattering matrices at the nodes describe exclusively the bending of electron trajectories. By artificially introducing a strong spread in the scattering strengths on the links (but keeping the average strength constant), we eliminate the interference and reduce the electron propagation over a network to a classical percolation problem. In this limit we establish the form of the disorder-magnetic field phase diagram. This diagram contains the regions with and without edge states, i.e., the regions with zero and quantized Hall conductivities. Taking into account that, for a given disorder, the scattering strength scales as inverse electron energy, we find agreement of our phase diagram with levitation scenario: energy separating the Anderson and quantum-Hall insulating phases floats up to infinity upon decreasing magnetic field. From numerical study, based on the analysis of quantum transmission of the network with random phases on the links, we conclude that the positions of the weak-field quantum-Hall transitions on the phase diagram are very close to our classical-percolation results. We checked that, in accord with the Pruisken theory, presence or absence of time-reversal symmetry on the links has no effect on the line of delocalization transitions. We also find that floating up of delocalized states in energy is accompanied by doubling of the critical exponent of the localization radius. We establish the origin of this doubling within classical-percolation analysis.

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

2010-04-01

132

Self-consistent Mean Field theory in weakly ionized media  

E-print Network

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

Nicolas Leprovost; Eun-Jin Kim

2007-10-10

133

Self-Consistent Mean Field Theory in Weakly Ionized Gas  

Microsoft Academic Search

We present a self-consistent mean field theory of the dynamo in 3D and turbulent diffusion in 2D in weakly ionized gas. We find that in 3D, the backreaction does not alter the beta effect while it suppresses the alpha effect when the strength of a mean magnetic field exceeds the critical value Bc ˜&surd;nu_in taun \\/R_m. Here, nu_in, tau_n, and

Nicolas Leprovost; Eun-Jin Kim

2003-01-01

134

Vacuum Effects in Gravitational Fields: Theory and Detectability  

E-print Network

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

S. Liberati

2000-09-14

135

Quantum Limit on Stability of Clocks in a Gravitational Field  

E-print Network

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 1 part in $10^{18}$ using an Ytterbium clock. This naturally raises the question of whether there are fundamental limits to the stability of clocks. In this paper we point out that gravity and quantum mechanics set a fundamental limit on the stability 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 hydrogen maser clock in a terrestrial gravitational field cannot achieve a stability better than one part in $10^{22}$. This observation has implications for laboratory experiments involving both gravity and quantum theory.

Supurna Sinha; Joseph Samuel

2014-01-04

136

The Gravitational Field of a Radiating Electromagnetic Dipole  

E-print Network

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

Tim Adamo; Ezra T Newman

2008-07-22

137

Hawking radiation of a vector field and gravitational anomalies  

NASA Astrophysics Data System (ADS)

Recently, the relation between Hawking radiation and gravitational anomalies has been used to estimate the flux of Hawking radiation for a large class of black objects. In this paper, we extend the formalism, originally proposed by Robinson and Wilczek, to the Hawking radiation of vector particles (photons). It is explicitly shown, with the Hamiltonian formalism, that the theory of an electromagnetic field on d-dimensional spherical black holes reduces to one of an infinite number of massive complex scalar fields on 2-dimensional spacetime, for which the usual anomaly-cancellation method is available. It is found that the total energy emitted from the horizon for the electromagnetic field is just (d-2) times that for a scalar field. The results support the picture that Hawking radiation can be regarded as an anomaly eliminator on horizons. Possible extensions and applications of the analysis are discussed.

Murata, Keiju; Miyamoto, Umpei

2007-10-01

138

Weak magnetic fields in central stars of planetary nebulae?  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

139

Weak-Field Gravity of Revolving Circular Cosmic Strings  

E-print Network

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.

Des J. Mc Manus; Michel A. Vandyck

1992-12-10

140

Weak-Field Gravity of Circular Cosmic Strings  

E-print Network

A weak-field solution of Einstein's equations is constructed. It is generated by a circular cosmic string externally supported against collapse. The solution exhibits a conical singularity, and the corresponding deficit angle is the same as for a straight string of the same linear energy density. This confirms the deficit-angle assumption made in the Frolov-Israel-Unruh derivation of the metric describing a string loop at a moment of time symmetry.

Shane J. Hughes; Des J. Mc Manus; Michel A. Vandyck

1992-11-09

141

QED plasma in a background of static gravitational fields  

E-print Network

We obtain 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 non-perturbative 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.

F. T. Brandt; J. Frenkel; J. B. Siqueira

2013-11-11

142

Saturn's gravitational field, internal rotation, and interior structure.  

PubMed

Saturn's internal rotation period is unknown, though it must be less than 10 hours, 39 minutes, and 22 seconds, as derived from magnetic field plus kilometric radiation data. By using the Cassini spacecraft's gravitational data, along with Pioneer and Voyager radio occultation and wind data, we obtain a rotation period of 10 hours, 32 minutes, and 35 +/- 13 seconds. This more rapid spin implies slower equatorial wind speeds on Saturn than previously assumed, and the winds at higher latitudes flow both east and west, as on Jupiter. Our related Saturn interior model has a molecular-to-metallic hydrogen transition about halfway to the planet's center. PMID:17823351

Anderson, John D; Schubert, Gerald

2007-09-01

143

A weak combined magnetic field changes root gravitropism  

NASA Astrophysics Data System (ADS)

Although gravitropism has been studied for many decades, many questions on plant gravitropism, including the participation of Ca 2+ ions in graviperception and signal transduction, remain open and require new experiments. We have studied gravistimulation and root gravitropism in the presence of the weak, alternating magnetic field that consisted of a sinusoidal frequency of 32 Hz inside a ?-metal shield. We discovered that this field changes normally positively gravitropic cress root to exhibit negative gravitropism. Because the combined magnetic field was adjusted to the cyclotron frequency of Ca 2+ ions, the obtained data suggest that calcium ion participate in root gravitropism. Simultaneous application of the oscillating magnetic field of the same frequency ion induce oscillation of Ca 2+ ions and can change the rate and/or the direction of Ca 2+ ion flux in roots. Control and magnetic field-exposed roots were examined for change in the distribution of amyloplasts and cellular organelles by light, electron, and confocal laser microscopy.

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

144

Gravitational fields and the cosmological constant in multidimensional Newtonian universes  

SciTech Connect

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.

Wilkins, D.

1986-08-01

145

Effective gravitational couplings for cosmological perturbations in the most general scalar-tensor theories with second-order field equations  

NASA Astrophysics Data System (ADS)

In the Horndeski's most general scalar-tensor theories the equations of scalar density perturbations are derived in the presence of non-relativistic matter minimally coupled to gravity. Under a quasi-static approximation on sub-horizon scales we obtain the effective gravitational coupling G associated with the growth rate of matter perturbations as well as the effective gravitational potential ? relevant to the deviation of light rays. We then apply our formulas to a number of modified gravitational models of dark energy - such as those based on f(R) theories, Brans-Dicke theories, kinetic gravity braidings, covariant Galileons, and field derivative couplings with the Einstein tensor. Our results are useful to test the large-distance modification of gravity from the future high-precision observations of large-scale structure, weak lensing, and cosmic microwave background.

de Felice, Antonio; Kobayashi, Tsutomu; Tsujikawa, Shinji

2011-12-01

146

Ultrafast heating and magnetic switching with weak external magnetic field  

NASA Astrophysics Data System (ADS)

The TbFeCo magneto-optical media with the coercivity of bigger than 1.0 kOe are used for the investigation of ultrafast heating and magnetic switching with the weak external magnetic field. It has been found that the laser-induced active region becomes larger with an external magnetic field because the boundary of the active region is magnetized with the assistance of the external field during the ultrafast heating. According to this physical phenomenon, the so called "mark expansion method" has been proposed for visual observation of ultrafast switching marks. Using this method, the ultrafast magnetic switching in TbFeCo media has been studied using 40 fs laser pulse with linear polarization. The result shows that the ultrafast magnetic switching can be implemented by the laser pulse with assistance of the weak external field of about 0.7 kOe. Further studies show that the area percentage of the magnetic mark expansion relative to its thermal mark decreases with the increasing of the laser pulse energy. There exists the threshold pulse energy that the active region is fully magnetized. The theoretical analysis of electron, spin, and lattice temperatures has been conducted to the active region of the media where the maximum spin temperature is close to the Curie temperature of the media. The result indicates that the media become active at 4.137 ps and the ultrafast heating plays a key role for the ultrafast magnetic switching. The weak external magnetic field provides sufficient driving force to control the magnetization direction in the media.

Li, J. M.; Xu, B. X.; Zhang, J.; Ye, K. D.

2013-01-01

147

Magnetophoresis of diamagnetic microparticles in a weak magnetic field.  

PubMed

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

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

2014-12-21

148

Responses of soil microbial communities to weak electric fields.  

PubMed

Electrokinetically stimulated bioremediation of soils (electro-bioremediation) requires that the application of weak electric fields has no negative effect on the contaminant degrading microbial communities. This study evaluated the hypothesis that weak direct electric current (DC) fields per se do not negatively influence the physiology and composition of soil microbial communities given that secondary electrokinetic phenomena such as soil pH changes and temperatures are minimized. Mildly buffered, water-saturated laboratory mesocosms with agricultural soil were subjected for 34 days to a constant electric field (X=1.4 V cm(-1); J approximately 1.0 mA cm(-2)) and the spatiotemporal changes of soil microbial communities assessed by fingerprints of phospholipids fatty acids (PLFA) and terminal restriction fragment length polymorphisms (T-RFLP) of bacterial 16S rRNA genes. DC-induced electrolysis of the pore water led to pH changes (<1.5 pH units) in the immediate vicinity of the electrodes and concomitant distinct soil microbial community changes. By contrast, DC-treated bulk soil distant to the electrodes showed no pH changes and developed similar PLFA- and T-RFLP-fingerprints as control soil in the absence of DC. Our data suggest that the presence of an electric field, if suitably applied, will not influence the composition and physiology of soil microbial communities and hence not affect their potential to biodegrade contaminants. PMID:20663541

Wick, Lukas Y; Buchholz, Friederike; Fetzer, Ingo; Kleinsteuber, Sabine; Härtig, Claus; Shi, Lei; Miltner, Anja; Harms, Hauke; Pucci, Graciela N

2010-09-15

149

Einstein's first gravitational field equation 101 years latter  

E-print Network

We review and strengthen the arguments given by Einstein to derive his first gravitational field equation for static fields and show that, although it was ultimately rejected, it follows from General Relativity (GR) for negligible pressure. Using this equation and considerations folowing directly from the equivalence principle (EP), we show how Schwarzschild metric and other vacum metrics can be obtained immediately. With this results and some basic principles, we obtain the metric in the general spherically symmetric case and the corresponding hydrostatic equilibrium equation. For this metrics we obtain the motion equations in a simple and exact manner that clearly shows the three sources of difference (implied by various aspects of the EP) with respect to the Newtonian case and use them to study the classical tests of GR. We comment on the origin of the problems of Einstein first theory of gravity and discuss how, by removing it the theory could be made consistent and extended to include rotations, we also ...

Betancort-Rijo, Juan

2014-01-01

150

Slowly and Rapidly Propagating "Liquid Flames" in Gravitational Fields  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

151

Evidence for Weak Crustal Magnetic Fields Over the Hellas Basin  

NASA Astrophysics Data System (ADS)

The Electron Reflectometer (ER) onboard Mars Global Surveyor (MGS) detected a plasma boundary between the ionosphere and the solar wind as the latter is diverted around and past the planet [Mitchell et al., GRL 27, 1871, 2000; Mitchell et al. JGR 106, 23419, 2001]. Above this boundary the 10-1000 eV electron population is dominated by solar wind electrons, while below the boundary it is dominated by ionospheric photoelectrons. This "photoelectron boundary", or PEB, is sensitive to pressure variations and moves vertically in response to changes in the ionospheric pressure from below and the solar wind pressure from above. The PEB is also sensitive to crustal magnetic fields, which locally increase the total ionospheric pressure and positively bias the PEB altitude. A map of the PEB altitude closely resembles maps of the crustal magnetic field intensity measured at 400 km by the MGS Magnetometer. As expected, the best correlation is between the PEB altitude and the horizontal magnetic field component, which provides vertical pressure support. We have analyzed more than 4.8 million electron spectra obtained in the mapping orbit, covering over 1.5 Martian years. We have empirically modeled and removed systematic variations in the PEB altitude associated with the solar wind interaction, thus isolating perturbations caused by crustal magnetic fields. We find a PEB altitude bias over the Hellas basin that is consistent with a horizontal magnetic field with an intensity of several nanotesla at 400 km altitude. This is compatible with upper limits to the horizontal crustal field strength set by MGS Magnetometer measurements. Weak crustal magnetic fields within the Hellas basin suggest that a weak Martian dynamo was still present when that basin cooled. No detectable PEB or magnetic signature is observed over the younger Argyre basin.

Mitchell, D. L.; Lee, C.; Lin, R. P.; Reme, H.; Cloutier, P. A.; Acuna, M. H.

2002-12-01

152

Weak gravitational lensing due to large-scale structure of the universe  

NASA Technical Reports Server (NTRS)

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.

Jaroszynski, Michal; Park, Changbom; Paczynski, Bohdan; Gott, J. Richard, III

1990-01-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

154

H. Bhringer LMU Lecture: Observational Cosmology II ( 8) SS 2010 1 Weak Gravitational Lensing & Cosmic Shear  

E-print Network

Lensing Basics I Light deflection of a point mass : Deflection by a mass distribution (linear: Observational Cosmology II (§ 8) SS 2010 6 Weak Lensing Basics V Deflection: Deformation: ~ 2 i j to through an operation in Fourier space: minus x ellipticity structure created by a ,,point mass

Boehringer, Hans

155

Shape and gravitational field of the ellipsoidal satellites  

NASA Astrophysics Data System (ADS)

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

Gao, BuXi; Huang, Yong

2014-10-01

156

Constants of motion in stationary axisymmetric gravitational fields  

NASA Astrophysics Data System (ADS)

The motion of test particles in stationary axisymmetric gravitational fields is generally non-integrable unless a non-trivial constant of motion, in addition to energy and angular momentum along the symmetry axis, exists. The Carter constant in Kerr-de Sitter space-time is the only example known to date. Proposed astrophysical tests of the black hole no-hair theorem have often involved integrable gravitational fields more general than the Kerr family, but the existence of such fields has been a matter of debate. To elucidate this problem, we treat its Newtonian analogue by systematically searching for non-trivial constants of motion polynomial in the momenta and obtain two theorems. First, solving a set of quadratic integrability conditions, we establish the existence and uniqueness of the family of stationary axisymmetric potentials admitting a quadratic constant. As in Kerr-de Sitter space-time, the mass moments of this class satisfy a `no-hair' recursion relation M2l +2 = a2M2l, and the constant is Noether related to a second-order Killing-Stäckel tensor. Second, solving a new set of quartic integrability conditions, we establish non-existence of quartic constants. Remarkably, a subset of these conditions is satisfied when the mass moments obey a generalized `no-hair' recursion relation M2l +4 = (a2 + b2)M2l +2 - a2b2M2l. The full set of quartic integrability conditions, however, cannot be satisfied non-trivially by any stationary axisymmetric vacuum potential.

Markakis, C.

2014-07-01

157

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

NASA Astrophysics Data System (ADS)

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

Rivera, Susana

158

Weak electric field interactions in the central nervous system.  

PubMed

Exposure to extremely low frequency electric and magnetic fields will induce electric fields and currents within the body, but these are almost always much lower than those that can stimulate peripheral nerve tissue. Guidance on exposure to such fields has been published by NRPB and ICNIRP, which is based on the avoidance of acute effects in the central nervous system. Weak electric field effects, below action potential thresholds, have been demonstrated in vitro in brain slice preparations; thresholds can be estimated to be above about 1 mV mm(-1) (around 100 mA m(-2), taking a brain tissue conductivity of around 0.1 S m(-1)), depending on stimulus conditions. Some studies suggest possible effects at lower induced field strengths. The intact nervous system might be expected to be more sensitive to induced electric fields and currents than in vitro preparations, due to a higher level of spontaneous activity and a greater number of interacting neurons. There is good evidence that electrically excitable cells in the retina can be affected in vivo by induced currents as low as 10 mA m(-2). It has been suggested that induced current densities above 10 mA m(-2) may have effects on other central nervous system functions but few studies have been carried out. Further research in experimental animals using both in vitro and in vivo approaches is needed to clarify this issue. PMID:12199550

Saunders, Richard D; Jefferys, John G R

2002-09-01

159

On the Energy Source of the Gravitational Field  

NASA Astrophysics Data System (ADS)

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.

Mayer, Alexander

2011-11-01

160

CHARGED TORI IN SPHERICAL GRAVITATIONAL AND DIPOLAR MAGNETIC FIELDS  

SciTech Connect

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

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

2013-03-01

161

Effective field theory of weakly coupled inflationary models  

SciTech Connect

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

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

2013-04-01

162

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

E-print Network

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

Dongsu Bak; Choonkyu Lee

1994-02-09

163

Means of confusion: how pixel noise affects shear estimates for weak gravitational lensing  

NASA Astrophysics Data System (ADS)

Weak-lensing shear estimates show a troublesome dependence on the apparent brightness of the galaxies used to measure the ellipticity: in several studies, the amplitude of the inferred shear falls sharply with decreasing source significance. This dependence limits the overall ability of upcoming large weak-lensing surveys to constrain cosmological parameters. We seek to provide a concise overview of the impact of pixel noise on weak-lensing measurements, covering the entire path from noisy images to shear estimates. We show that there are at least three distinct layers, where pixel noise not only obscures but also biases the outcome of the measurements: (1) the propagation of pixel noise to the non-linear observable ellipticity; (2) the response of the shape-measurement methods to limited amount of information extractable from noisy images and (3) the reaction of shear estimation statistics to the presence of noise and outliers in the measured ellipticities. We identify and discuss several fundamental problems and show that each of them is able to introduce biases in the range of a few tens to a few per cent for galaxies with typical significance levels. Furthermore, all of these biases do not only depend on the brightness of galaxies but also depend on their ellipticity, with more elliptical galaxies often being harder to measure correctly. We also discuss existing possibilities to mitigate and novel ideas to avoid the biases induced by pixel noise. We present a new shear estimator that shows a more robust performance for noisy ellipticity samples. Finally, we release the open-source PYTHON code to predict and efficiently sample from the noisy ellipticity distribution and the shear estimators used in this work at https://github.com/pmelchior/epsnoise.

Melchior, P.; Viola, M.

2012-08-01

164

Nonlinear gravitational self-force: Field outside a small body  

NASA Astrophysics Data System (ADS)

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

Pound, Adam

2012-10-01

165

Proton-Proton Weak Capture in Chiral Effective Field Theory  

NASA Astrophysics Data System (ADS)

The astrophysical S factor for proton-proton weak capture is calculated in chiral effective field theory over the center-of-mass relative-energy range 0-100 keV. The chiral two-nucleon potential derived up to next-to-next-to-next-to leading order is augmented by the full electromagnetic interaction including, beyond Coulomb, two-photon and vacuum-polarization corrections. The low-energy constants entering the weak current operators are fixed so as to reproduce the A=3 binding energies and magnetic moments and the Gamow-Teller matrix element in tritium ? decay. Contributions from S and P partial waves in the incoming two-proton channel are retained. The S factor at zero energy is found to be S(0)=(4.030±0.006)×10-23MeVfm2, with a P-wave contribution of 0.020×10-23MeVfm2. The theoretical uncertainty is due to the fitting procedure of the low-energy constants and to the cutoff dependence.

Marcucci, L. E.; Schiavilla, R.; Viviani, M.

2013-05-01

166

Singularity analysis of potential fields to enhance weak anomalies  

NASA Astrophysics Data System (ADS)

Geoanomalies generally are nonlinear, non-stationary and weak, especially in the land cover areas, however, the traditional methods of geoanomaly identification are usually based on linear theory. In past two decades, many power-law function models have been developed based on fractal concept in mineral exploration and mineral resource assessment, such that the density-area (C-A) model and spectrum-area model (S-A) suggested by Qiuming Cheng have played important roles in extracting geophysical and geochemical anomalies. Several power-law relationships are evident in geophysical potential fields, such as field value-distance, power spectrum-wave number as well as density-area models. The singularity index based on density-area model involves the first derivative transformation of the measure. Hence, we introduce the singularity analysis to develop a novel high-pass filter for extracting gravity and magnetic anomalies with the advantage of scale invariance. Furthermore, we suggest that the statistics of singularity indices can provide a new edge detection scheme for the gravity or magnetic source bodies. Meanwhile, theoretical magnetic anomalies are established to verify these assertions. In the case study from Nanling mineral district in south China and Qikou Depression in east China, compared with traditional geophysical filtering methods including multiscale wavelet analysis and total horizontal gradient methods, the singularity method enhances and extracts the weak anomalies caused by buried magmatic rocks more effectively, and provides more distinct boundary information of rocks. Moreover, the singularity mapping results have good correspondence relationship with both the outcropping rocks and known mineral deposits to support future mineral resource exploration. The singularity method based on fractal analysis has potential to be a new useful theory and technique for processing gravity and magnetic anomaly data.

Chen, G.; Cheng, Q.; Liu, T.

2013-12-01

167

Free-fall in a uniform gravitational field in non-commutative quantum mechanics  

E-print Network

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.

K. H. C. Castello-Branco; A. G. Martins

2008-03-06

168

Mapping Weak Crustal Magnetic Fields on Mars with Electron Reflectometry  

NASA Technical Reports Server (NTRS)

One of the great surprises of the Mars Global Surveyor (MGS) mission was the discovery of intensely magnetized crust. These magnetic sources are at least ten times stronger than their terrestrial counterparts, probably requiring large volumes of coherently magnetized material, very strong remanence, or both. Perhaps the most intriguing aspect of these fields is their large scale coherence and organization into east-west stripes thousands of kilometers long. The anomalies were almost certainly created by thermoremanent magnetization (TRM) in the presence of a strong Martian dynamo. With few exceptions, the crustal fields are associated with the oldest terrain on Mars. Much of the northern lowlands appears to be non-magnetic, except for the relatively weak north polar anomalies and a few sources adja-cent to the dichotomy boundary, which appear to be associated with strongly magnetized crust south of the boundary. There is clear evidence for impact demagnetization of the Hellas, Argyre, and Isidis basins. Thus, Mars' crustal magnetic fields are among the oldest preserved geologic features on the planet.

Mitchell, D. L.; Lillis, R.; Lin, R. P.; Connerney, J. E. P.; Acuna, M. H.

2004-01-01

169

Classic field theories of gravitation embedded in ten dimensions  

E-print Network

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].

Frank B. Estabrook

2006-06-09

170

The HST Frontier Fields: Gravitational Lensing Models Release  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

171

The electric field induced by a gravitational wave in a superconductor - A principle for a new gravitational wave antenna  

NASA Technical Reports Server (NTRS)

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.

Peng, Huei; Torr, Douglas G.

1990-01-01

172

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

E-print Network

Gravitational waves 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. Linearised equations for the electromagnetic field on perturbed Minkowski space are derived and solved analytically. The inverse Gertsenshtein conversion of gravitational waves in a static electromagnetic field is rederived, and the resultant electromagnetic radiation is shown to be significant for highly magnetised 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 gravitational wave strength increase...

Chua, Alvin J K; Gair, Jonathan R

2014-01-01

173

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

E-print Network

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

Forsberg, Mats; Brodin, Gert

2010-01-01

174

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

NASA Astrophysics Data System (ADS)

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

Forsberg, M.; Papadopoulos, D.; Brodin, G.

2010-07-01

175

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

NASA Astrophysics Data System (ADS)

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

Papadopoulos, D.

2012-01-01

176

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

E-print Network

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

Mats Forsberg; Demetrios Papadopoulos; Gert Brodin

2010-05-28

177

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

SciTech Connect

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

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

2010-07-15

178

Cylindrically Symmetric Solitons with Nonlinear Self-Gravitating Scalar Fields  

E-print Network

Static, cylindrically symmetric solutions to nonlinear scalar-Einstein equations are considered. Regularity conditions on the symmetry axis and flat or string asymptotic conditions are formulated in order to select soliton-like solutions. Some non-existence theorems are proved, in particular, theorems asserting (i) the absence of black-hole and wormhole-like cylindrically symmetric solutions for any static scalar fields minimally coupled to gravity and (ii) the absence of solutions with a regular axis for scalar fields with the Lagrangian $L=F(I)$, $I=\\phi^\\alpha \\phi_\\alpha$, for any function $F(I)$ possessing a correct weak field limit. Exact solutions for scalar fields with an arbitrary potential function $V(\\phi)$ are obtained by quadratures and are expressed in a parametric form in a few ways, where the parameter may be either the coordinate $x$, or the $\\phi$ field, or one of the metric coefficients. Soliton-like solutions are shown to exist only with $V(\\phi)$ having a variable sign. Some explicit examples of solutions (including a soliton-like one) and their flat-space limit are discussed.}

K. A. Bronnikov; G. N. Shikin

2001-01-22

179

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

SciTech Connect

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

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

2012-04-20

180

Do the constants of nature couple to strong gravitational fields?  

E-print Network

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

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

2014-01-01

181

Gravitational field models for the earth (GEM 1 and 2)  

NASA Technical Reports Server (NTRS)

Two models of the earth's gravitational field have been computed at Goddard Space Flight Center. The first, Goddard Earth Model 1 (GEM 1), has been derived from satellite tracking data. The second, Goddard Earth Model 2 (GEM 2), has been derived from a combination of satellite tracking and surface gravimetric data. The geopotential models are represented in spherical harmonics complete to degree and order 16 for the combined solution and complete to degree and order 12 for the satellite solution. Both solutions include zonal terms to degree 21 and related satellite resonant coefficients to degree 22. The satellite data consisted primarily of optical data processed on 300 weekly orbital arcs for 25 close earth satellites. Surface gravity data were employed in the form of 5 deg x 5 deg mean free-air gravity anomalies providing about 70% world coverage. Station locations were obtained for 46 tracking sites by combining electronic, laser, and additional optical tracking data with the above satellite data. Analysis of the radial positions of these stations and a value of mean gravity on the geoid indicated a mean equatorial radius for the earth of about 6378145 meters. Results of geopotential tests on satellite data not used in the solution show that better agreement was obtained with the GEM 1 and GEM 2 models than with the 1969 Smithsonian Standard Earth 2 model.

Lerch, F. J.; Wagner, C. A.; Smith, D. E.; Andson, M. L.; Brownd, J. E.; Richardson, J. A.

1972-01-01

182

Improved Gravitation Field Algorithm and Its Application in Hierarchical Clustering  

PubMed Central

Background Gravitation field algorithm (GFA) is a new optimization algorithm which is based on an imitation of natural phenomena. GFA can do well both for searching global minimum and multi-minima in computational biology. But GFA needs to be improved for increasing efficiency, and modified for applying to some discrete data problems in system biology. Method An improved GFA called IGFA was proposed in this paper. Two parts were improved in IGFA. The first one is the rule of random division, which is a reasonable strategy and makes running time shorter. The other one is rotation factor, which can improve the accuracy of IGFA. And to apply IGFA to the hierarchical clustering, the initial part and the movement operator were modified. Results Two kinds of experiments were used to test IGFA. And IGFA was applied to hierarchical clustering. The global minimum experiment was used with IGFA, GFA, GA (genetic algorithm) and SA (simulated annealing). Multi-minima experiment was used with IGFA and GFA. The two experiments results were compared with each other and proved the efficiency of IGFA. IGFA is better than GFA both in accuracy and running time. For the hierarchical clustering, IGFA is used to optimize the smallest distance of genes pairs, and the results were compared with GA and SA, singular-linkage clustering, UPGMA. The efficiency of IGFA is proved. PMID:23173043

Zheng, Ming; Sun, Ying; Liu, Gui-xia; Zhou, You; Zhou, Chun-guang

2012-01-01

183

The Gravitational Field of an Electrically Charged Mass Point and the Causality Principle in the RTG  

Microsoft Academic Search

We find the effective Riemannian space–time corresponding to the gravitational field generated by a charged mass point in the framework of the relativistic theory of gravity. The causality principle plays an important role in solving this problem. The analytic form and the domain of definition, i.e., the gravitational radius, of the obtained solution differ from the corresponding results in Einstein's

D. Ionescu

2003-01-01

184

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

E-print Network

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

S. Tertychniy

1993-11-02

185

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

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

186

Deep HST imaging of distant weak radio and field galaxies  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

187

[Two-phase Interfaces in Weak External Fields  

NASA Technical Reports Server (NTRS)

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

Percus, J. K.

1996-01-01

188

Propagation of Light in the Field of Stationary and Radiative Gravitational Multipoles  

E-print Network

Extremely high precision of near-future radio/optical interferometric observatories like SKA, Gaia, SIM and the unparalleled sensitivity of LIGO/LISA gravitational-wave detectors demands more deep theoretical treatment of relativistic effects in the propagation of electromagnetic signals through variable gravitational fields of the solar system, oscillating and precessing neutron stars, coalescing binary systems, exploding supernova, and colliding galaxies. Especially important for future gravitational-wave observatories is the problem of propagation of light rays in the field of multipolar gravitational waves emitted by a localized source of gravitational radiation. Present paper suggests physically-adequate and consistent mathematical solution of this problem in the first post-Minkowskian approximation of General Relativity which accounts for all time-dependent multipole moments of an isolated astronomical system.

Sergei Kopeikin; Pavel Korobkov; Alexander Polnarev

2006-03-15

189

Gravitational waves from Abelian gauge fields and cosmic strings at preheating  

SciTech Connect

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

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

2010-10-15

190

Effect of magnetic field on Jeans instability of self gravitating strongly coupled dusty plasma  

NASA Astrophysics Data System (ADS)

The effect of the magnetic field on the Jeans instability of self-gravitating strongly coupled dusty plasma is investigated. The medium consists of extremely massive, negatively charged strongly correlated dust grains and weakly correlated Boltzmann distributed electrons and ions. The basic equations of the problem are constructed using generalized hydrodynamic model. In deriving dispersion relation the plane wave solutions are used on the linearized perturbation equations. The analysis is done by normal mode analysis theory. The dispersion relation is found to be affected due to the presence of viscoelastic effects and magnetic field. The dispersion relation is further reduced for hydrodynamic and kinetic regime of propagation. The condition of Jeans instability is also obtained for both the regimes of propagation. Numerical results are presented to show the effect of magnetic field and time relaxation parameter which is found to have stabilizing influence on growth rate of Jeans instability in strongly coupled dusty plasma. The condition of Jeans instability are compared in kinetic and hydrodynamic regime.

Chhajlani, R. K.; Sharma, Prerana

2014-09-01

191

Biological effects due to weak magnetic fields on plants  

NASA Astrophysics Data System (ADS)

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

Belyavskaya, N.

192

Student Understanding Of Gravitational Potential Energy And The Motion Of Bodies In A Gravitational Field  

NSDL National Science Digital Library

We have been investigating student understanding of energy concepts in the context of introductory courses for non-science majors as well as those for science and engineering majors. We have found that many students develop incomplete and incorrect understandings of the concept of gravitational potential energy. Moreover, students often have incorrect notions about the motion of bodies under the influence of gravity. These incorrect beliefs may prevent the development of a coherent understanding of energy as a conserved quantity.

Loverude, Michael E.

2010-01-18

193

On Lynden-Bell and Katz's definition of gravitational field energy  

NASA Astrophysics Data System (ADS)

The covariant definition of gravitational field energy given by Lynden-Bell and Katz is expressed in terms of Israel's theory of surface layers in general relativity. In this way an expression, valid for arbitrary radial coordinates, of the gravitational field energy in a static, spherically symmetric space-time, is deduced. This expression is applied to the Schwarschild and Reissner-Nordstrom space-times, and leads here to the same results as those given by Einstein's pseudotensor expression in isotropic coordinates.

Gron, O.

1986-09-01

194

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

Microsoft Academic Search

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

M. Forsberg; G. Brodin; D. Papadopoulos

2010-01-01

195

Gravitational field of a spinning sigma-model cosmic string  

SciTech Connect

We study the effect of internal space rotation on the gravitational properties of infinite straight and stationary cosmic strings. From the approximate solution of Einstein equations for the spinning Q-lump string, we obtain long-range gravitational acceleration resembling that of a rotating massive cylindrical shell. We also compute the angular velocity of the inertial frame dragging and the angle of light deflection by the Q-lump string. Matter accretion onto spinning strings can play a role in galaxy formation when the angular velocity times the string width is comparable to the speed of light.

Simanek, E. [Department of Physics, University of California, Riverside, California 92521 (United States)

2008-08-15

196

Topological vortex formation in a Bose-Einstein condensate under gravitational field  

SciTech Connect

Topological phase imprinting is a unique technique for vortex formation in a Bose-Einstein condensate (BEC) of an alkali-metal gas, in that it does not involve rotation: the BEC is trapped in a quadrupole field with a uniform bias field which is reversed adiabatically leading to vortex formation at the center of the magnetic trap. The scenario has been experimentally verified by Leanhardt et al. employing {sup 23}Na atoms. Recently similar experiments have been conducted by Hirotani et al. in which a BEC of {sup 87}Rb atoms was used. In the latter experiments the authors found that fine-tuning of the field reverse time T{sub rev} is required to achieve stable vortex formation. Otherwise, they often observed vortex fragmentation or a condensate without a vortex. It is shown in this paper that this behavior can be attributed to the heavy mass of the Rb atom. The confining potential, which depends on the eigenvalue m{sub B} of the hyperfine spin F along the magnetic field, is now shifted by the gravitational field perpendicular to the vortex line. Then the positions of two weak-field-seeking states with m{sub B}=1 and 2 deviate from each other. This effect is more prominent for BECs with a heavy atomic mass, for which the deviation is greater and, moreover, the Thomas-Fermi radius is smaller. We found, by solving the Gross-Pitaevskii equation numerically, that two condensates interact in a very complicated way leading to fragmentation of vortices, unless T{sub rev} is properly tuned.

Kawaguchi, Yuki; Ohmi, Tetsuo [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Nakahara, Mikio [Department of Physics, Kinki University, Higashi-Osaka 577-8502 (Japan)

2004-10-01

197

Inversion symmetry of gravitational coupling in cubic string field theory  

NASA Astrophysics Data System (ADS)

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.

Hata, Hiroyuki; Kojita, Toshiko

2013-12-01

198

Approximations by gravitational fields due to restricted unit point masses  

E-print Network

) December 1973 ABSTRACT Approximations by Gravitational Pields Due to Restricted Unit Point Masses. (December 1973) Carolyn Flowers Shull, B. S. , Stephen P. Austin State University Directed by: Dr. Charles K. Chui The objective of this thesis.... ACKNOWLEDGENENTS I wish to sincerely thank Dr. Charles K. Chui for his suggestions and guidance concerning this thesis. I also am grateful to my husband, William H. Shull, for helping to type this thesis. TABLE OF CONTENTS CHAPTER INTRODUCTION. I. Uniform...

Shull, Carolyn Sue Flowers

2012-06-07

199

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

NASA Astrophysics Data System (ADS)

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

Baryshev, Yurij

2006-03-01

200

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

E-print Network

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

Baryshev, Y

2006-01-01

201

On the role of gravitational fields in some elementary particle processes  

Microsoft Academic Search

Summary  With the aid of a suitable perturbation formalism, the effect of an external gravitational field on elementary particle processes\\u000a is investigated. Electromagnetic bremsstrahlung by charged scalar particle waves is treated and the dependence of the result\\u000a on the inserted data and their empirical limits is analised. Application of the results to gravitational bremsstrahlung by\\u000a particles of vanishing rest-mass is made.

L. Halpern

1962-01-01

202

Plasma electron kinetics in a weak high-frequency field and magnetic field amplification.  

PubMed

We describe the linear stage of Weibel instability in a plasma heated via inverse bremsstrahlung absorption of a high-frequency, moderate intensity radiation field under conditions in which the plasma electron velocity distribution function is weakly anisotropic. We report on the possibility of a significant amplification of spontaneous magnetic fields both in the case of an electron distribution function slightly departing from a Maxwellian in the region of subthermal velocities, and in the case where the Langdon nonequilibrium distribution is formed. We show that the direct influence of collisions on the Weibel instability growth rate may be traced back to subthermal electrons, for which the effective collision frequency is large. PMID:11690157

Ferrante, G; Zarcone, M; Uryupin, S A

2001-10-01

203

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

SciTech Connect

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

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

2010-11-15

204

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

E-print Network

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 gravity, the equation of motion of a classical mass point in gravitational gauge field is given by Newton's second law of motion. A relativistic form of the gravitational force on a mass point is deduced in this paper. Based on the spherical symmetric solution of the field equation and Newton's second law of motion, we can discuss classical tests of gauge theory of gravity, including the deflection of light by the sun, the precession of the perihelia of the orbits of the inner planets and the time delay of radar echoes passing the sun. It is found that the theoretical predictions of these classical tests given by gauge theory of gravity are completely the same as those given by general relativity. From the study in this paper, an important qualitative conclusion on the nature of gravity is that gravity can be treated as a kind of physical interactions in flat Minkowski space-time, and the equation of motion of mass point in gravitational field can be given by Newton's second law of motion.

Ning Wu; Dahua Zhang

2005-08-01

205

Experimental study of the dynamic Newtonian field with a cryogenic gravitational wave antenna  

NASA Astrophysics Data System (ADS)

We present an experiment performed to study the behaviour of the dynamic gravitational interaction at laboratory scale. We used as field generator a mass quadrupole rotating in the range of 460 Hz and we detected the acceleration field with the cryogenic gravitational wave antenna Explorer of the Rome group. We report the measurements of this interaction as a function of the distance between the field source and the detector. An upper limit on the parameters of a Yukawa-like potential, modeling an hypotetic deviation from the Newtonian law of gravity, is derived.

Astone, P.; Bassan, M.; Bizzarri, R.; Bonifazi, P.; Brocco, L.; Carelli, P.; Coccia, E.; Cosmelli, C.; Degasperis, A.; Frasca, S.; Fafone, V.; Majorana, E.; Modena, I.; Modestino, G.; Moleti, A.; Pallottino, G. V.; Pizzella, G.; Puppo, P.; Rapagnani, P.; Ricci, F.; Terenzi, R.; Visco, M.

1998-10-01

206

Understanding possible electromagnetic counterparts to loud gravitational wave events: Binary black hole effects on electromagnetic fields  

SciTech Connect

In addition to producing loud gravitational waves, the dynamics of a binary black hole system could induce emission of electromagnetic radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as an enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.

Palenzuela, Carlos [Canadian Institute for Theoretical Astrophysics (CITA), Toronto, Ontario M5S 3H8 (Canada); Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Berlin, D-14476 Golm (Germany); Lehner, Luis [Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Canadian Institute For Advanced Research (CIFAR), Cosmology and Gravity Program (Canada); Yoshida, Shin [Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, University of Tokyo, Meguro, Tokyo 153-8902 (Japan)

2010-04-15

207

Genericity of black hole formation in the gravitational collapse of homogeneous self-interacting scalar fields  

Microsoft Academic Search

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

Roberto Giambò; Fabio Giannoni; Giulio Magli

2008-01-01

208

Dynamics of homogeneous scalar fields with general self-interaction potentials: cosmological and gravitational collapse models  

Microsoft Academic Search

The general relativistic dynamics of a wide class of self-interacting, self-gravitating homogeneous scalar fields models is analyzed. The class is characterized by certain general conditions on the scalar field potential, which 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

R. Giambò; FABIO GIANNONI; GIULIO MAGLI

2007-01-01

209

A scalar field matter model for dark halos of galaxies and gravitational redshift  

E-print Network

We analyze the spherically symmetric Einstein field equation with a massless complex scalar field. We can use the Newtonian solutions to fit the rotation curve data of spiral and dwarf galaxies. From the general relativistic solutions, we can derive high gravitational redshift values.

Franz E. Schunck

1998-02-19

210

Mapping Gravitational and Magnetic Fields with Children 9-11: Relevance, Difficulties and Prospects  

ERIC Educational Resources Information Center

This paper presents an investigation centered on a guided conceptual path concerning magnetic and gravitational fields, proposed for children aged 9-11. The goal is to appreciate to what extent the idea of "mapping" two fields of interaction is accessible and fruitful for children of that age. The conceptual target is to link magnetic and…

Bradamante, F.; Viennot, L.

2007-01-01

211

Wiggly tails: A gravitational wave signature of massive fields around black holes  

NASA Astrophysics Data System (ADS)

Massive fields can exist in long-lived configurations around black holes. We examine how the gravitational wave signal of a perturbed black hole is affected by such "dirtiness" within linear theory. As a concrete example, we consider the gravitational radiation emitted by the infall of a massive scalar field into a Schwarzschild black hole. Whereas part of the scalar field is absorbed/scattered by the black hole and triggers gravitational wave emission, another part lingers in long-lived quasibound states. Solving numerically the Teukolsky master equation for gravitational perturbations coupled to the massive Klein-Gordon equation, we find a characteristic gravitational wave signal, composed by a quasinormal ringing followed by a late time tail. In contrast to "clean" black holes, however, the late time tail contains small amplitude wiggles with the frequency of the dominating quasibound state. Additionally, an observer dependent beating pattern may also be seen. These features were already observed in fully nonlinear studies; our analysis shows they are present at linear level, and, since it reduces to a 1+1 dimensional numerical problem, allows for cleaner numerical data. Moreover, we discuss the power law of the tail and that it only becomes universal sufficiently far away from the dirty black hole. The wiggly tails, by constrast, are a generic feature that may be used as a smoking gun for the presence of massive fields around black holes, either as a linear cloud or as fully nonlinear hair.

Degollado, Juan Carlos; Herdeiro, Carlos A. R.

2014-09-01

212

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

E-print Network

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

Mei Xiaochun

2006-11-30

213

Wiggly tails: a gravitational wave signature of massive fields around black holes  

E-print Network

Massive fields can exist in long-lived configurations around black holes. We examine how the gravitational wave signal of a perturbed black hole is affected by such `dirtiness' within linear theory. As a concrete example, we consider the gravitational radiation emitted by the infall of a massive scalar field into a Schwarzschild black hole. Whereas part of the scalar field is absorbed/scattered by the black hole and triggers gravitational wave emission, another part lingers in long-lived quasi-bound states. Solving numerically the Teukolsky master equation for gravitational perturbations coupled to the massive Klein-Gordon equation, we find a characteristic gravitational wave signal, composed by a quasi-normal ringing followed by a late time tail. In contrast to `clean' black holes, however, the late time tail contains small amplitude wiggles with the frequency of the dominating quasi-bound state. Additionally, an observer dependent beating pattern may also be seen. These features were already observed in fully non-linear studies; our analysis shows they are present at linear level, and, since it reduces to a 1+1 dimensional numerical problem, allows for cleaner numerical data. Moreover, we discuss the power law of the tail and that it only becomes universal sufficiently far away from the `dirty' black hole. The wiggly tails, by constrast, are a generic feature that may be used as a smoking gun for the presence of massive fields around black holes, either as a linear cloud or as fully non-linear hair.

Juan Carlos Degollado; Carlos A. R. Herdeiro

2014-08-12

214

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

E-print Network

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

Li-Ming Cao; Yuxuan Peng; Jianfei Xu

2014-04-26

215

Two-stage magnetometer measures weak magnetic fields  

NASA Technical Reports Server (NTRS)

Sensitive magnetometer capable of measuring field strengths of 10 nanogauss is described. High permeability core is aligned parallel to magnetic field in first stage. In second stage, ferromagnetic toroid saturates rapidly. Adjustment of turns and area ratios of each stage provides wide range of sensitivities.

Buntenbach, R. W.

1972-01-01

216

Field-induced vortices in weakly anisotropic ferroelectrics  

NASA Astrophysics Data System (ADS)

In microscale and nanoscale ferroelectric samples, the formation and growth of domains are the usual stages of the polarization switching mechanism. By assuming weak polarization anisotropy and by solving the Ginzburg-Landau-Khalatnikov equation we have explored an alternative mechanism which consists in ferroelectric switching induced by vortex formation. We have studied the polarization dynamics inside a ferroelectric circular capacitor where switching leads to the formation of a metastable vortex state with a rotational motion of the polarization. Our results are consistent with recent first-principle simulations [I.I. Naumov, H.X. Fu, Phys. Rev. Lett. 98, 077603 (2007)] and with experiments on PbZr 0.2Ti 0.8O 3 [A. Gruverman, D. Wu, H.J. Fan, I. Vrejoiu, M. Alexe, R.J. Harrison, J.F. Scott, J. Phys. Condens. Matter 20 342201(2008)] and demonstrate that vortex-induced polarization switching can be an effective mechanism for circular nanocapacitors.

Sené, A.; Baudry, L.; Luk'yanchuk, I.; Lahoche, L.; El Amraoui, Y.

2011-03-01

217

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

E-print Network

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

Antonio Campos; B. L. Hu

1998-05-27

218

Orbital magnetism and transport phenomena in two-dimensional Dirac fermions in a weak magnetic field  

NASA Astrophysics Data System (ADS)

We discuss the orbital magnetism and the Hall effect in a weak magnetic field in two-dimensional Dirac fermion systems with an energy gap. This model is related to the graphene sheet, zero-gap organic conductors, and the d -density-wave state of cuprates. We found strong diamagnetism and anomalous Hall conductivity even in gapped systems. We also discuss the relation between results of the weak-magnetic-field formalism and those in a finite magnetic field with Landau quantization.

Nakamura, Masaaki

2007-09-01

219

Streamer Initiation from Hydrometeors in Weak Thundercloud Electric Fields  

NASA Astrophysics Data System (ADS)

How atmospheric lightning initiates in thunderclouds has been a scientific puzzle for decades. One theory of air electrical breakdown that has been applied to explaining the initiation of lightning discharges is the conventional breakdown theory [e.g., MacGorman and Rust, p. 86, 1998; Rakov and Uman, p. 121, 2003]. A critical component of this theory is to demonstrate that streamers are able to form and propagate in the field with a magnitude similar to the observed thundercloud electric fields. The observed maximum value of this field varies from 0.13-0.3E_k [Stolzenburg et al., 2007], where E_k is the conventional breakdown threshold field. This value fails to provide a sufficient condition for the initiation of electron avalanches and then the electrical breakdown process. To overcome this obstacle, the theory of streamer initiation from thundercloud hydrometeors (water drops, ice crystals, etc.) was brought forward [e.g., Dawson, JGR, 74 (28), 6859, 1969; Griffiths and Latham, Quart. J. Roy. Meteorol. Soc., 100, 163, 1974; Griffiths and Phelps, Quart. J. Roy. Meteorol. Soc., 102, 4019, 1976]. Hydrometeors are abundant in thunderclouds and they can cause significant field enhancement in their vicinity. For this study, the streamer discharge model reported by Liu and Pasko [JGR, 109, A04301, 2004] is utilized and modified to investigate whether streamers can successfully originate from isolated hydrometeors in the thundercloud electric field. The thundercloud hydrometeors are modeled using a neutral plasma column. Our simulation results show successful formation of streamers from model hydrometeors in a uniform applied electric field below the conventional breakdown threshold field. We report detailed modeling results at thundercloud altitude for the applied electric fields close to the observed maximum thundercloud field. It is demonstrated that the dimensions, i.e., length and radius, of the plasma column have a critical effect on the initiation of streamers. The results also show that at lower applied electric fields for certain initial conditions, branching structures easily appear at the tip of the hydrometeor. To reduce the effects of branching, we investigate the possibility of using other geometries, specifically an ellipsoid, for the initial ionization column. So far, the minimum electric field value required for the stable formation of streamers from hydrometeors without the occurrence of branching structures has been observed to be 0.3E_k at 7 km from our modeling results.

Sadighi, S.; Liu, N.; Dwyer, J. R.; Rassoul, H. K.

2011-12-01

220

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

E-print Network

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

Alexander A. Chernitskii

2006-09-28

221

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

E-print Network

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

A. DeBenedictis

1998-11-10

222

Gravitational Dynamics  

NASA Astrophysics Data System (ADS)

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.

Lahav, Ofer; Terlevich, Elena; Terlevich, Roberto J.

1996-07-01

223

Effects of electromagnetic field on the collapse and expansion of anisotropic gravitating source  

NASA Astrophysics Data System (ADS)

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 collapse there exits two horizons like in case of Reissner-Nordström metric.

Abbas, G.

2014-08-01

224

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

E-print Network

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

G. Abbas

2013-12-23

225

Electromgnetic-gravitational cross-sections in external elctromagnetic fields  

E-print Network

The classical processes: the conversion of photons into gravitons in the static electromagnetic fields are considered by using Feynman perturbation techniques. The differential cross sections are presented for the conversion in the electric field of the flat condesor and the magnetic field of the selenoid. A numerical evaluation shows that the cross sections may have the observable value in the present technical scenario.

Hoang Ngoc Long; Dang Van Soa; Tuan A. Tran

1994-10-03

226

Quasilinear Drift Of Cosmic Rays In Weak Turbulent Electromagnetic Fields  

E-print Network

A general quasilinear transport parameter for particle drift in arbitrary turbulence geometry is presented. The new drift coefficient is solely characterized by a nonresonant term and is evaluated for slab and two-dimensional turbulence geometry. The calculations presented here demonstrate that fluctuating electric fields are a key quantity for understanding quasilinear particle drift in slab geometry. It is shown that particle drift does not exist in unpolarized and purely magnetic slab fluctuations. This is in stark contrast to previous models, which are restricted to slab geometry and the field line random walk limit. The evaluation of the general transport parameter for two-dimensional turbulence geometry, presented here for the first time for dynamical magnetic turbulence, results in a drift coefficient valid for a magnetic power spectrum and turbulence decay rate varying arbitrarily in wavenumber. For a two-component, slab/two-dimensional turbulence model, numerical calculations are presented. The new q...

Stawicki, O

2005-01-01

227

Saturn's Gravitational Field, Internal Rotation, and Interior Structure  

NASA Astrophysics Data System (ADS)

Cassini gravitational data and Pioneer and Voyager radio occultation and wind data have been used to infer the rotation rate and structure of Saturn's deep interior. By minimizing the dynamical height excursions of the 100 mbar isosurface with respect to a reference geoid, we obtain a Saturnian rotation period of 10h 32m 35s ± 13s. This more rapid spin, compared with the rotation rate inferred from Saturn's kilometric radiation, implies a more benign atmospheric wind system than previously thought, with slower equatorial winds and both eastward and westward winds at higher latitudes, as on Jupiter. The reference geoid we obtain has an equatorial radius of 60,356.2 km ± 2.6 km and a mean polar radius of 54,437.6 km ± 1.9 km. The above data and inferred rotation rate are associated with an internal structure that we model with a sixth-degree polynomial in fractional radius. The polynomial representation of density and pressure versus depth yields an observational equation of state, density versus pressure, that has a molecular to metallic hydrogen transition about halfway to the planet's center. The polynomial smooths out any compositionally distinct core that might exist at the center of Saturn. This research was supported by NASA under grants from the Planetary Atmospheres and Planetary Geology and Geophysics Programs and by the Cassini Project through the Jet Propulsion Laboratory.

Schubert, Gerald; Anderson, J. D.

2007-10-01

228

Multiple Dp-branes in weak background fields  

Microsoft Academic Search

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

Washington Taylor IV; Mark Van Raamsdonkb

2000-01-01

229

Quasilinear Drift Of Cosmic Rays In Weak Turbulent Electromagnetic Fields  

E-print Network

A general quasilinear transport parameter for particle drift in arbitrary turbulence geometry is presented. The new drift coefficient is solely characterized by a nonresonant term and is evaluated for slab and two-dimensional turbulence geometry. The calculations presented here demonstrate that fluctuating electric fields are a key quantity for understanding quasilinear particle drift in slab geometry. It is shown that particle drift does not exist in unpolarized and purely magnetic slab fluctuations. This is in stark contrast to previous models, which are restricted to slab geometry and the field line random walk limit. The evaluation of the general transport parameter for two-dimensional turbulence geometry, presented here for the first time for dynamical magnetic turbulence, results in a drift coefficient valid for a magnetic power spectrum and turbulence decay rate varying arbitrarily in wavenumber. For a two-component, slab/two-dimensional turbulence model, numerical calculations are presented. The new quasilinear drift, induced by the magnetic perturbations, is compared with a standard drift expression related to the curvature and gradient of an unperturbed heliospheric background magnetic field. The considerations presented here offer a solid ground and natural explanation for the hitherto puzzling observation that drift models often describe observations much better when drift effects are reduced.

Olaf Stawicki

2005-01-13

230

Far fields, from electrodynamics to gravitation, and the dark matter problem  

E-print Network

Far fields, from electrodynamics to gravitation, and the dark matter problem A. Carati1 , S to make recourse to dark matter in order to explain the observed velocity dispersion in the Coma cluster that the existence of a dark matter may not be necessary in order to explain the phenomenology, at least

Carati, Andrea

231

Born--Infeld theory of electroweak and gravitational fields: Possible correction to Newton and Coulomb laws  

E-print Network

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.

Dmitriy Palatnik

2002-10-22

232

Stochastic gravitational fluctuations in a self-consistent mean field theory  

Microsoft Academic Search

A fully stochastic theory is formulated for the dynamical evolution of a gravitationally interacting stellar system. A given test star is assumed to experience a self-consistent mean field potential, and in addition to be subjected to random fluctuations. The general theory of random (Markoff) processes is briefly summarised, with emphasis upon the connections among the various fundamental equations: Kolmogorov-Feller, master,

Henry E. Kandrup

1980-01-01

233

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

SciTech Connect

Here we respond to the comment by Tsagas on our earlier paper. We show that the results in that comment are flawed and cannot be used for drawing conclusions about the nature of magnetic field amplification by gravitational waves and give further support that the results of our earlier paper are correct.

Betschart, Gerold [Racah Institute of Physics, Hebrew University of Jerusalem, Givat Ram, 91904 Jerusalem (Israel); Zunckel, Caroline [Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Dunsby, Peter K S [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); South African Astronomical Observatory, Observatory 7925, Cape Town (South Africa); Marklund, Mattias [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2007-04-15

234

Analysis of biological effects and limits of exposure to weak magnetic fields  

Microsoft Academic Search

Adverse biological outcomes due to thermal effects of exposure to high power magnetic fields are well understood and are the basis for standards for limiting human exposure to such fields. Over the past few decades a controversy has arisen over possible adverse biological effects due to exposure to weak, low frequency magnetic fields. This paper involves a critical analysis of

D. A. Chathurika; M. F. Peter; N. H. Malka

2010-01-01

235

Decay of weak poloidal magnetic fields in the liquid layer of neutron star envelopes  

Microsoft Academic Search

If a strong temperature gradient exists in the liquid layer of neutron star envelopes the interaction of the heat flux with the magnetic field is very effective. For weak magnetic fields the induction and heat transport equations describing this interaction can be linearized. In this case the poloidal magnetic field component is not influenced by the evolution of both the

U. Geppert; H.-L. Wiebicke

1992-01-01

236

Neuroendocrine and behavioral responses to weak electric fields in adult sea lampreys (Petromyzon marinus).  

PubMed

We characterized the behavioral and neuroendocrine responses of adult sea lampreys (Petromyzon marinus) to weak electric fields. Adult sea lampreys, captured during upstream spawning migration, exhibited limited active behaviors during exposure to weak electric fields and spent the most time attached to the wall of the testing arena near the cathode (-). For adult male sea lampreys, exposure to weak electric fields resulted in increased lamprey (l) GnRH-I mRNA expression but decreased lGnRH-I immunoreactivities in the forebrain, and decreased Jun (a neuronal activation marker) mRNA levels in the brain stem. Similar effects were not observed in the brains of female sea lampreys after weak electric field stimulation. The influence of electroreception on forebrain lGnRH suggests that electroreception may modulate the reproductive systems in adult male sea lampreys. The changes in Jun expression may be associated with swimming inhibition during weak electric field stimulation. The results for adult sea lampreys are the opposite of those obtained using parasitic-stage sea lampreys, which displayed increased activity during and after cathodal stimulation. Our results demonstrate that adult sea lampreys are sensitive to weak electric fields, which may play a role in reproduction. They also suggest that electrical stimuli mediate different behaviors in feeding-stage and spawning-stage sea lampreys. PMID:18329031

Chung-Davidson, Yu-Wen; Bryan, Mara B; Teeter, John; Bedore, Christine N; Li, Weiming

2008-06-01

237

Hermitian Dirac Hamiltonian in time dependent gravitational field  

E-print Network

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

M. Leclerc

2005-11-11

238

Zero Rest-Mass Fields Including Gravitation: Asymptotic Behaviour.  

National Technical Information Service (NTIS)

A zero rest-mass field of arbitrary spin s determines, at each event in space-time, a set of 2s principal null directions which are related to the radiative behaviour of the field. These directions exhibit the characteristic 'peeling-off' behaviour of Sac...

R. Penrose

1964-01-01

239

Some Consequences of the Law of Local Energy Conservation in the Gravitational Field  

E-print Network

At gravitational interactions of bodies and particles there appears the defect of masses, i.e. the energy yields since the bodies (or particles) are attracted. It is shown that this changing of the effective mass of the body (or the particle) in the external gravitational field leads to changes the measurement units: velocity and length (relative to the standard measurement units). The expression describing the advance of the perihelion of the planet (the Mercury) has been obtained. This expression is mathematically identical to Einstein's equation for the advance of the perihelion of the Mercury.

Kh. M. Beshtoev

2001-07-22

240

Impurity-Assisted Tunneling Magnetoresistance under a Weak Magnetic Field  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

241

Semiconductor artificial graphene: Effects in weak magnetic fields  

NASA Astrophysics Data System (ADS)

Two-dimensional quantum transport through the stripe of the hexagonal lattice of antidots built in the multimode channel in the GaAs/AlGaAs structure has been studied numerically. It has been found that the low perpendicular magnetic fields (˜3 mT) suppress the bulk currents and cause the appearance of the edge Landau states and high positive magnetic resistance on both sides of the Dirac point. Tamm edge states are present in some energy intervals; as a result, the 4 e 2/ h-amplitude oscillations caused by the quantization of these states on the lattice length are added to the steps of the conductance quantization G n = (2| n| + 1)2 e 2/ h.

Tkachenko, O. A.; Tkachenko, V. A.

2014-04-01

242

Mean-field universality class induced by weak hyperbolic curvatures  

NASA Astrophysics Data System (ADS)

Order-disorder phase transition of the ferromagnetic Ising model is investigated on a series of two-dimensional lattices that have negative Gaussian curvatures. Exceptional lattice sites of coordination number seven are distributed on the triangular lattice, where the typical distance between the nearest exceptional sites is proportional to an integer parameter n. Thus, the corresponding curvature is asymptotically proportional to -n-2. Spontaneous magnetization and specific heat are calculated by means of the corner transfer matrix renormalization group method. For all the finite n cases, we observe the mean-field-like phase transition. It is confirmed that the entanglement entropy at the transition temperature is linear in (c/6)lnn, where c =1/2 is the central charge of the Ising model. The fact agrees with the presence of the typical length scale n being proportional to the curvature radius.

Gendiar, Andrej; Daniška, Michal; Kr?már, Roman; Nishino, Tomotoshi

2014-07-01

243

Tunable slowing, storing, and releasing of a weak microwave field  

NASA Astrophysics Data System (ADS)

We study the slowing, storing, and releasing of microwave pulses in a superconducting circuit composed of two coplanar waveguide resonators and a superconducting transmon-type qubit. The quantum interference analogy to electromagnetically induced transparency is created in two coupled resonators. By tuning the resonance frequency of the transmon, we dynamically tune the effective coupling between the resonators. Via the modulation of the coupling, we show the tunable true time delay of microwave pulses at the single-photon level. We also store the microwave field in a high-Q resonator and release the signal from it to the output port. Our scheme promises applications in both quantum information processing and classical wireless communications.

Xia, Keyu

2014-02-01

244

The Relativistic Quantized Force: Newton's Second Law, Inertial and Gravitational; Generalization of Schwarzschild Metric for Strong and Weak Gravitational Field  

Microsoft Academic Search

In this paper we derived the relativistic Quantized force, where the force given as a function of frequency[1]. Where, in this paper we defined the relativistic momentum as a function of frequency equivalent to the energy held by a body, and time, and then the quantized force is given as the first derivative of the momentum with respect to time.

Azzam Almosallami

2011-01-01

245

The Effect of Weak Combined Magnetic Field on Root Gravitropism and a Role of Ca2+ Ions Therein  

NASA Astrophysics Data System (ADS)

At present, magnetic fields of different types are widely used to study gravity sensing in plants. For instance, magnetic levitation of amyloplasts caused by high gradient magnetic field enables us to alter the effective gravity sensed by plant cells. For the first time we showed that a weak combined magnetic field (CMF), that is the sum of collinear permanent and alternating magnetic fields ( 0.5 gauss, 0-100 Hz), changes a cress and pea root positive gravitropic reaction on a negative one. This effect has the form of resonance and occurs at the frequency of cyclotron resonance of calcium ions. What is especially interesting is that under gravistimulation in the CMF, the displacement of amylopasts in the root cap statocytes is directed to the upper wall of a cell, i.e. in the direction opposite to the gravitational vector. The displacement of amyloplasts, which contain the abundance of free Ca2+ ions in the stroma, is accompanied by Ca2+ redistribution in the same direction, and increasing in the cytosol around amyloplasts near ten times in the CMF in comparison with the state magnetic field. Earlier, we also observed the Ca2+ accumulation in the upper site of a root curvature in the elongation zone in the CMF unlike a positive gravitropic reaction. Thus, it should be stressed that a root is bending in the same direction in which amyloplasts are displacing: downwards when gravitropism is positive and upwards when gravitropism is negative. The obtained data confirm the amyloplast statolithic function and give another striking demonstration of a leading role of Ca2+ ions in root gravitropism. But these data bring the question: what forces can promote amyloplast displacement against gravity? The possible explanation of the effect found is discussed. It is based on the ion cyclotron resonance in biosystems proposed by Liboff.. The original approach based on the use of a weak CMF may be helpful for understanding the mechanisms of plant gravisensing

Kordyum, Elizabeth; Bogatina, Nina; Kondrachuk, A.

246

Temporal variations of the earth's gravitational field from satellite laser ranging to LAGEOS  

NASA Astrophysics Data System (ADS)

Monthly values of the J2 and J3 earth gravitational coefficients were estimated using LAGEOS satellite laser ranging data collected between 1980 and 1989. Monthly variations in gravitational coefficients caused by atmospheric mass redistribution were calculated using measurements of variations in surface atmospheric pressure. Results for correlation studies of the two time series are presented. The LAGEOS and atmospheric J2 time series agree well and it appears that variations in J2 can be attributed to the redistribution of atmospheric mass. Atmospheric and LAGEOS estimates for J3 show poorer agreement, J3 estimates appear to be very sensitive to unmodeled forces acting on the satellite. Results indicate that the LAGEOS data can be used to detect small variations in the gravitational field.

Nerem, R. S.; Chao, B. F.; Au, A. Y.; Chan, J. C.; Klosko, S. M.; Pavlis, N. K.; Williamson, R. G.

1993-04-01

247

Lorentz Covariant Theory of Light Propagation in Gravitational Fields of Arbitrary-Moving Bodies  

E-print Network

The Lorentz covariant theory of propagation of light in the gravitational fields of N-body systems consisting of arbitrarily moving point-like bodies with constant masses is constructed. The theory is based on the Lienard-Wiechert presentation of the metric tensor. A new approach for integrating the equations of motion of light particles depending on the retarded time argument is applied. In an approximation which is linear with respect to the universal gravitational constant, G, the equations of light propagation are integrated by quadratures and, moreover, an expression for the tangent vector to the perturbed trajectory of light ray is found in terms of instanteneous functions of the retarded time. General expressions for the relativistic time delay, the angle of light deflection, and gravitational red shift are derived. They generalize previously known results for the case of static or uniformly moving bodies. The most important applications of the theory are given. They include a discussion of the velocit...

Kopeikin, S M; Kopeikin, Sergei M.; Schafer, Gerhard

1999-01-01

248

Temporal variations of the earth's gravitational field from satellite laser ranging to LAGEOS  

NASA Technical Reports Server (NTRS)

Monthly values of the J2 and J3 earth gravitational coefficients were estimated using LAGEOS satellite laser ranging data collected between 1980 and 1989. Monthly variations in gravitational coefficients caused by atmospheric mass redistribution were calculated using measurements of variations in surface atmospheric pressure. Results for correlation studies of the two time series are presented. The LAGEOS and atmospheric J2 time series agree well and it appears that variations in J2 can be attributed to the redistribution of atmospheric mass. Atmospheric and LAGEOS estimates for J3 show poorer agreement, J3 estimates appear to be very sensitive to unmodeled forces acting on the satellite. Results indicate that the LAGEOS data can be used to detect small variations in the gravitational field.

Nerem, R. S.; Chao, B. F.; Au, A. Y.; Chan, J. C.; Klosko, S. M.; Pavlis, N. K.; Williamson, R. G.

1993-01-01

249

Effects of the Electromagnetic Field on Five-dimensional Gravitational Collapse  

E-print Network

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.

M. Sharif; G. Abbas

2010-01-29

250

Gravitational influences on magnetic field structure in accretion disks  

E-print Network

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

Schneck, Kristiana E. (Kristiana Elizabeth)

2010-01-01

251

Next-to-leading order gravitational spin-orbit coupling in an effective field theory approach  

SciTech Connect

We use an effective field theory (EFT) approach to calculate the next-to-leading order (NLO) gravitational spin-orbit interaction between two spinning compact objects. The NLO spin-orbit interaction provides the most computationally complex sector of the NLO spin effects, previously derived within the EFT approach. In particular, it requires the inclusion of nonstationary cubic self-gravitational interaction, as well as the implementation of a spin supplementary condition (SSC) at higher orders. The EFT calculation is carried out in terms of the nonrelativistic gravitational field parametrization, making the calculation more efficient with no need to rely on automated computations, and illustrating the coupling hierarchy of the different gravitational field components to the spin and mass sources. Finally, we show explicitly how to relate the EFT derived spin results to the canonical results obtained with the Arnowitt-Deser-Misner (ADM) Hamiltonian formalism. This is done using noncanonical transformations, required due to the implementation of covariant SSC, as well as canonical transformations at the level of the Hamiltonian, with no need to resort to the equations of motion or the Dirac brackets.

Levi, Michele [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)

2010-11-15

252

Embryological changes induced by weak, extremely low frequency electromagnetic fields.  

PubMed Central

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

Delgado, J M; Leal, J; Monteagudo, J L; Gracia, M G

1982-01-01

253

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

Microsoft Academic Search

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

John R. Spreiter; Wm. Prichard Jones

1963-01-01

254

Genericity of black hole formation in the gravitational collapse of homogeneous self-interacting scalar fields  

NASA Astrophysics Data System (ADS)

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.

Giambò, Roberto; Giannoni, Fabio; Magli, Giulio

2008-04-01

255

Genericity of blackhole formation in the gravitational collapse of homogeneous self-interacting scalar fields  

E-print Network

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.

Giambó, R; Magli, G

2008-01-01

256

Genericity of blackhole formation in the gravitational collapse of homogeneous self-interacting scalar fields  

Microsoft Academic Search

The gravitational collapse of a wide class of self-interacting homogeneous\\u000ascalar fields models is analyzed. The class is characterized by certain general\\u000aconditions on the scalar field potential, which, in particular, include both\\u000aasymptotically polynomial and exponential behaviors. Within this class, we show\\u000athat the generic evolution is always divergent in a finite time, and then make\\u000ause of this

R. Giambó; FABIO GIANNONI; GIULIO MAGLI

2008-01-01

257

Genericity of blackhole formation in the gravitational collapse of homogeneous self-interacting scalar fields  

E-print Network

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

258

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

SciTech Connect

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

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

2010-03-15

259

Why the gravitation of quasi-Casimir pressure in weak interaction is independent of the composition of matter  

Microsoft Academic Search

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

Shao-Guang Chen

2010-01-01

260

Evolution of Free Magnetic Fields. I. Neglecting Self-Gravitation  

Microsoft Academic Search

This paper gives the exact solutions, graphical and analytical, for an idealization of a phenomenon described in every textbook of physics: the decay of a magnetic field after its source current has ceased. The problem is solved for the cylindrically symmetric case where a uniform current in a long straight wire is suddenly brought to zero at an initial time

M. A. Melvin; J. S. Wallingford

1970-01-01

261

On the gravitational field induced by static electromagnetic sources  

E-print Network

It is argued that static electromagnetic sources induce Weyl-Majumdar-Papapetrou solutions for the spacetime metric. The acceleration in such fields has a term many orders of magnitude stronger than usual perturbative terms. Two electrostatic and two magnetostatic examples are given.

Boyko V. Ivanov

2005-02-10

262

Shapes and Gravitational Fields of Two-Layer Maclaurin Spheroids: Application to Planets and Satellites  

NASA Astrophysics Data System (ADS)

The shapes and gravitational fields of rotationally and tidally distorted planets and satellites depend on their interior mass distributions. Measurements of these observable characteristics are therefore used to infer the internal structure of planetary bodies. Interpretations are based on approximate formulae such as the Radau-Darwin relation derivable from the theory of figures or more accurate evaluations of the theory. The exact solution for the shape and gravitational field of the rotationally distorted constant density Maclaurin spheroid has, until now, provided one of the only ways to assess the accuracy and range of validity of approximate theory of figure predictions. We generalize the Maclaurin spheroid solution to a 2-layer core-envelope body, a more realistic model of a real planet or moon. The exact 2-layer Maclaurin spheroid solution, e. g., the shapes of the surface and core-envelope interface, depend on 3 parameters, the core-envelope density ratio, the fractional volume of the core, and ?2/2?G?2, where ? is the rotation rate, G is the gravitational constant, and ?2 is the envelope density. For realistic parameter values, the flattening of the interface is smaller than that of the surface. Results of the exact solution are compared with predictions of the theory of figures up to order 3 in the small rotational parameter of the theory. The exact solution serves as a benchmark for numerical models that attempt to invert gravitational and shape data to infer internal planetary structure.

Schubert, G.; Zhang, K.; Kong, D.; Anderson, J. D.; Helled, R.

2010-12-01

263

Cartographic generalization of urban street networks based on gravitational field theory  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

264

Horizon thermodynamics and gravitational field equations in Horava-Lifshitz gravity  

SciTech Connect

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

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

2010-04-15

265

Possible quantum gravity effects on the gravitational deflection of light  

E-print Network

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

Xin Li; Zhe Chang

2010-07-02

266

Magnetic Field Variations in the Near Geomagnetic Tail Associated with Weak Substorm Activity  

Microsoft Academic Search

Magnetic field observations obtained with the UCLA Ogo 5 fluxgate magnetometer on an inbound pass, during which the satellite remained close to the magnetic meridian and traveled almost parallel to and approximately 2 Rr above the expected position of the neutral sheet, are used to illustrate the variations in the configuration of the tail field during weak substorm activity. Beyond

C. T. Russell; R. L. McPherron; P. J. Coleman

1971-01-01

267

Influence of weak electric fields on Rydberg electron wavepacket dynamics in the radial coordinate  

Microsoft Academic Search

The spin–orbit autoionisation dynamics of Rydberg electron wavepackets in Ar are investigated in weak electric fields, where ???13.8 and ? is the scaled energy in atomic units. The electric field modifies both the interference pattern and revival time of the recurrence spectrum. By writing the energies of the eigenstates included in the superposition as a Taylor's expansion, a quantitative description

V. G. Stavros; H. H. Fielding

1998-01-01

268

Gravitational Field Equations and Theory of Dark Matter and Dark Energy  

E-print Network

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

Tian Ma; Shouhong Wang

2012-06-22

269

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

NASA Astrophysics Data System (ADS)

Concerns have been raised over the possibility that extremely-low-frequency (ELF) electromagnetic fields are carcinogenic and leukegenic. An examination of the physical interaction of such fields with the body shows that such interactions are too weak to have a significant effect on human biology at the cell level. Because of the high electrical conductivity of tissues, the coupling of external electric fields in air to tissue in the body is such that the effects of the internal fields on cells is smaller than thermal noise. Static magnetic fields smaller than the earth's field of 50 ?T and varying fields weaker than the 4-?T 60-Hz fields that are equivalent in effect to that from walking in the earth's field, cannot be expected to generate significant biological effects. Moreover, the interactions of such weak fields at the cell level are also small compared to thermal noise. These conclusions would be modified by 60-Hz cell resonances. But such resonances are shown to be incompatible with cell characteristics and the requirement from equipartition that the mean resonance energy must be kT. Hence, any biological effects of weak ELF fields on the cellular level must be found outside of the scope of conventional physics.

Adair, Robert K.

1991-01-01

270

The Dark Matter Halos of Moderate Luminosity X-ray AGN as Determined from Weak Gravitational Lensing and Host Stellar Masses  

E-print Network

Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modeling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to a fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z<1 fro...

Leauthaud, A; Civano, F; Coil, A L; Bundy, K; Massey, R; Schramm, M; Schulze, A; Capak, P; Elvis, M; Kulier, A; Rhodes, J

2014-01-01

271

Charged particles in higher dimensional homogeneous gravitational field: Self-energy and self-force  

E-print Network

A problem of self-energy and self-force for a charged point-like particle in a higher dimensional homogeneous gravitational field is considered. We study two cases, when a particle has usual electric charge and a case when it has a scalar charge, which is a source of a scalar massless minimally coupled field. We assume that a particle is at rest in the gravitational field, so that its motion is not geodesic and it has an acceleration a directed from the horizon. The self-energy of a point charge is divergent and the strength of the divergence grows with the number of dimensions. In order to obtain a finite contribution to the self- energy we use a covariant regularization method which is a modification of the proper time cut-off and other covariant regularizations. We analyze a relation between the self-energy and self-force and obtain explicit expressions for the self-forces for the electric and scalar charge in the spacetimes with the number of dimensions up to eight. General expressions for the case of higher dimensions are also obtained. We discuss special logarithmic factors ln(a), which are present both in the self-energy and self-force in odd dimensions. Finally, we compare the obtained results with the earlier known results both for the homogeneous gravitational field and for particles near black holes.

Valeri P. Frolov; Andrei Zelnikov

2014-07-11

272

Thick branes from self-gravitating scalar fields  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

273

Weak field magnetoresistance of narrow-gap semiconductors InSb  

E-print Network

The magnetoresistance of InSb has been intensively investigated. The experiments we perform here focus on weak field magnetoresistance of InSb thin film. We investigate the magnetoresistance of InSb films in perpendicular, tilted as well as parallel magnetic field. Our results verify the previous observations concerning weak localization effect in InSb thin film. Moreover, we systematically study the anisotropy of magnetoresistance of InSb. We find that the existence of in-plane field can effectively suppress the weak localization effect of InSb film. We fit the experimental data with two types of models, the match between data and model is excellent. From the fitting procedure, we get information about phase coherence time, spin-orbit scattering time. The information about Zeeman effect and sample roughness are also extracted from the fitting procedure.

R. Yang; G. L. Yu; Yanhui Zhang; P. P. Chen

2010-05-25

274

Weak field magnetoresistance of narrow-gap semiconductors InSb  

E-print Network

The magnetoresistance of InSb has been intensively investigated. The experiments we perform here focus on weak field magnetoresistance of InSb thin film. We investigate the magnetoresistance of InSb films in perpendicular, tilted as well as parallel magnetic field. Our results verify the previous observations concerning weak localization effect in InSb thin film. Moreover, we systematically study the anisotropy of magnetoresistance of InSb. We find that the existence of in-plane field can effectively suppress the weak localization effect of InSb film. We fit the experimental data with two types of models, the match between data and model is excellent. From the fitting procedure, we get information about phase coherence time, spin-orbit scattering time. The information about Zeeman effect and sample roughness are also extracted from the fitting procedure.

Yang, R; Zhang, Yanhui; Chen, P P

2010-01-01

275

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

NASA Technical Reports Server (NTRS)

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

Kopeikin, Sergei

2003-01-01

276

Development of the Evans Wave Equation in the Weak-Field Limit: The Electrogravitic Equation  

Microsoft Academic Search

The Evans wave equation [1-3] is developed in the weak-field limit to give the Poisson equation and an electrogravitic equation expressing the electric field strength E in terms of the acceleration g due to gravity and a fundamental scalar potential f(0) with the units of volts (joules per coulomb). The electrogravitic equation shows that an electric field strength can be

P. K. Anastasovski; P. Carpenter; C. Ciubotariu; W. T. Coffey; G. J. Evans; M. W. Evans; R. Flower; J. B. Hart; T. Kurata; A. Labounsky; B. Lehnert; J. K. Moscicki; S. Roy

2004-01-01

277

Self-gravitating systems in Extended Gravity  

E-print Network

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

Stabile, A

2014-01-01

278

Self-gravitating systems in Extended Gravity  

E-print Network

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

A. Stabile; S. Capozziello

2014-11-12

279

Effects of Electromagnetic Field on the Dynamical Instability of Expansionfree Gravitational Collapse  

E-print Network

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.

M. Sharif; M. Azam

2013-05-31

280

Contributions to the local gravitational field from beyond the local supercluster  

Microsoft Academic Search

IRAS 60 mu sources are used to map the local (⪅200 h-1Mpc, H0 = 100 h km s-1Mpc-1) gravitational field, and to determine its dipole component, on the assumption that the infrared radiation traces the matter. The dipole moment is found to point in the direction of the anisotropy of the microwave background radiation. Comparison of the two anisotropies, using

A. Yahil

1987-01-01

281

Analytical Solutions of the Gravitational Field Equations in de Sitter and Anti-de Sitter Spacetimes  

Microsoft Academic Search

The generalized Laplace partial differential equation, describing gravitational fields, is investigated in de Sitter spacetime from several metric approaches---such as the Riemann, Beltrami, Börner-Dürr, and Prasad metrics---and analytical solutions of the derived Riccati radial differential equations are explicitly obtained. All angular differential equations trivially have solutions given by the spherical harmonics and all radial differential equations can be written as

R. Da Rocha; E. Capelas Oliveira

2009-01-01

282

Analytical Solutions of the Gravitational Field Equations in de Sitter and Anti-de Sitter Spacetimes  

Microsoft Academic Search

The generalized Laplace partial differential equation, describing gravitational fields, is investigated in de Sitter spacetime\\u000a from several metric approaches—such as the Riemann, Beltrami, Börner-Dürr, and Prasad metrics—and analytical solutions of\\u000a the derived Riccati radial differential equations are explicitly obtained. All angular differential equations trivially have\\u000a solutions given by the spherical harmonics and all radial differential equations can be written as

R. da Rocha

2009-01-01

283

Separation of Polystyrene Microbeads Using Dielectrophoretic\\/Gravitational Field-Flow-Fractionation  

Microsoft Academic Search

The characterization of a dielectrophoretic\\/gravitational field-flow-fractionation (DEP\\/G-FFF) system using model polystyrene (PS) microbeads is presented. Separations of PS beads of different surface functionalization (COOH and none) and different sizes (6, 10, and 15?m in diameter) are demonstrated. To investigate the factors influencing separation performance, particle elution times were determined as a function of particle suspension conductivity, fluid flow rate, and

Xiao-Bo Wang; Jody Vykoukal; Frederick F. Becker; Peter R. C. Gascoyne

1998-01-01

284

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

E-print Network

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

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

2014-08-05

285

Semiclassical Ballistic Transport through a Circular Microstructure in Weak Magnetic Fields  

NASA Astrophysics Data System (ADS)

We study magneto-transport through a weakly open circular microstructure in the perpendicular weak magnetic fields by a semiclassical approximation within the framework of the Fraunhofer diffraction effect at the lead openings. It is found that the peak positions of the transmission power spectrum can be related to simple trajectories according to classical dynamics. Moreover, we formulate the fluctuations in the transmission amplitude as functions of both the wave number k and the magnetic field B in terms of different classical trajectories, and the Aharonov—Bohm phase of the directed areas enclosed by these trajectories that reflect the quantum interference effect.

Zhang, Yan-Hui; Cai, Xiang-Ji; Li, Zong-Liang; Jiang, Guo-Hui; Yang, Qin-Nan; Xu, Xue-You

2013-04-01

286

The Schrödinger-Newton equation as non-relativistic limit of self-gravitating Klein-Gordon and Dirac fields  

E-print Network

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.

Domenico Giulini; André Großardt

2012-06-19

287

Constrains on non-Newtonian gravity from the experiment on neutron quantum states in the Earth's gravitational field  

E-print Network

An upper limit to non-Newtonian attracive forces is obtained from the measurement of quantum states of neutrons in the Earth's gravitational field. This limit improves the existing constrains in the nanometer range.

V. V. Nesvizhevsky; K. V. Protasov

2004-01-23

288

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

SciTech Connect

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

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

1992-01-01

289

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

E-print Network

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

V. Majernik

2004-08-19

290

Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields  

E-print Network

Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields Chathurika D. Abeyrathne, Peter M. Farrell and Malka N. Halgamuge, Member, IEEE, Department of Civil and Environmental Engineering, Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville, VIC

Halgamuge, Malka N.

291

Toward Understanding Subtle Instrumentation Effects Associated with Weak Seismic Events in the Near Field  

E-print Network

of the quality of the instruments, many valuable near-fault records have also been obtained for weak earthquakes produce a long-period disturbance of this type. Users of near-fault broad- band velocigrams may Field by Jií Zahradník and Axel Plesinger Abstract Broadband observations of small earthquakes at short

Cerveny, Vlastislav

292

An efficient self-consistent field method for large systems of weakly interacting components  

E-print Network

An efficient self-consistent field method for large systems of weakly interacting components Rustam 2005; accepted 7 March 2006; published online 23 May 2006 An efficient method for removing the self, and govern physisorption in van der Waals systems.1 They also control self-assembly and self

Bell, Alexis T.

293

System based on fiber-optic gravimeters for a measurement of gravitational field gradient vector for navigation of flying objects  

Microsoft Academic Search

There are many tasks, which are required simultaneously to measure value and direction of gravitation field vector in 3D space. For instance, the task of flying objects navigation by measurement of full gravitation field vector horizontal gradient. To solve this problem is suggested the system, consists of two remote fiber-optic gravimeters, situated in different ends of flying object. Fiber-optic gravimeter

Yuri A. Bykovsky; Constantin A. Scvorchevsky; Andrey Y. Beskurnikov; Olga V. Poljakova; Alexander P. Grachev; Alexander V. Shutov

1997-01-01

294

Detecting weak magnetic fields in the central stars of planetary nebulae  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

295

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

E-print Network

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

Agathos, M.

296

The bioeffects of extremely weak power-frequency alternating magnetic fields  

Microsoft Academic Search

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

N. A. Belova; O. N. Ermakova; A. M. Ermakov; Z. Ye. Rojdestvenskaya; V. V. Lednev

2007-01-01

297

Inverse Square Law of Gravitation in (2+1)-Dimensional Space-Time as a Consequence of Casimir Energy  

E-print Network

The gravitational effect of vacuum polarization in space exterior to a particle in (2+1)-dimensional Einstein theory is investigated. In the weak field limit this gravitational field corresponds to an inverse square law of gravitational attraction, even though the gravitational mass of the quantum vacuum is negative. The paradox is resolved by considering a particle of finite extension and taking into account the vacuum polarization in its interior.

H. H. Soleng

1993-10-04

298

Decay of weak poloidal magnetic fields in the liquid layer of neutron star envelopes  

NASA Astrophysics Data System (ADS)

If a strong temperature gradient exists in the liquid layer of neutron star envelopes the interaction of the heat flux with the magnetic field is very effective. For weak magnetic fields the induction and heat transport equations describing this interaction can be linearized. In this case the poloidal magnetic field component is not influenced by the evolution of both the toroidal field and the temperature distribution. However, the strong radial temperature gradient inside the liquid layer acts on the poloidal field by the thermal drift velocity, which leads to a nonnegligible convective term in the induction equation. The hotter the neutron star surface is, the larger is the temperature gradient and the more slowly the poloidal field in this region decays. During typical time scales of small-scale toroidal field growth due to thermoelectricity the poloidal field is nearly stationary.

Geppert, U.; Wiebicke, H.-L.

1992-03-01

299

Weak field magnetoresistance of narrow-gap semiconductor InSb  

Microsoft Academic Search

The weak antilocalization effect of InSb film in perpendicular as well as\\u000atilted magnetic field is investigated. It is found that the InSb film has\\u000aquasi-two-dimensional feature and the Nyquist mechanism dominates decoherence.\\u000aThe two dimensionality is also verified further and the influence of roughness\\u000aeffect and Zeeman effect on weak antilocalization effect is studied by\\u000asystematically investigating the anisotropy

R. Yang; K. H. Gao; Y. H. Zhang; P. P. Chen; G. Yu; L. M. Wei; T. Lin; N. Dai; J. H. Chu

2010-01-01

300

Biological responses to weak 60-Hz electric and magnetic fields must vary as the square of the field strength.  

PubMed Central

Under quite general conditions, the biological response j(G) to a very weak continuous 60-Hz electric or magnetic field G is shown to be proportional to the square of the field strength. This conclusion follows from the continuity of the function j(G) and the first three derivatives of j(G) with respect to G over the amplitude of G. That continuity is ensured in nominally discontinuous systems by the presence of thermal noise. I argue the validity of the conjecture that all plausible biological responses to weak 60-Hz fields vary with the square of the field strength. A specific model is used to illustrate characteristic dependencies of biological responses to exposure times. PMID:7937782

Adair, R K

1994-01-01

301

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

E-print Network

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

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

2007-11-24

302

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

SciTech Connect

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

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

2008-02-15

303

Weak Field Approximation in a Model of de Sitter Gravity: Schwarzschild-De Sitter Solutions  

NASA Astrophysics Data System (ADS)

The weak field approximation in a model of de Sitter (dS) gravity is investigated in the static and spherically symmetric case, under the assumption that the vacuum spacetime without perturbations from matter fields is a torsion-free dS spacetime. It is shown on one the hand that any solution should be singular at the center of the matter field, if the exterior is described by a Schwarzschild-de Sitter (S-dS) spacetime and is smoothly connected to the interior. On the other, all the regular solutions are obtained, which might be used to explain the galactic rotation curves without involving dark matter.

Lu, Jia-An; Huang, Chao-Guang

2013-06-01

304

Reversing the weak measurement of an arbitrary field with finite photon number  

E-print Network

Reversing 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 2...; Level structure in step #1;II#2;. The classical field is #16;? polarized. #1;c#2; The profiles of the fields required for the adiabatic passages. #1;d#2; The system diagram. SUN, AL-AMRI, AND ZUBAIRY PHYSICAL REVIEW A 80, 033838 #1;2009#2; 033838...

Sun, Qingqing; Al-Amri, M.; Zubairy, M. Suhail.

2009-01-01

305

The Earth-Moon-Sun natural laboratory for testing of gravitational and electromagnetic fields coupling  

NASA Astrophysics Data System (ADS)

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.

Grunskaya, Lubov; Isakevich, Valiriy; Efimov, Vladislav; Zakirov, Alexander

306

TESTING WEAK-LENSING MAPS WITH REDSHIFT SURVEYS: A SUBARU FIELD  

SciTech Connect

We use a dense redshift survey in the foreground of the Subaru GTO2deg{sup 2} weak-lensing field (centered at {alpha}{sub 2000} = 16{sup h}04{sup m}44{sup s}; {delta}{sub 2000} = 43 Degree-Sign 11'24'') to assess the completeness and comment on the purity of massive halo identification in the weak-lensing map. The redshift survey (published here) includes 4541 galaxies; 4405 are new redshifts measured with the Hectospec on the MMT. Among the weak-lensing peaks with a signal-to-noise greater than 4.25, 2/3 correspond to individual massive systems; this result is essentially identical to the Geller et al. test of the Deep Lens Survey (DLS) field F2. The Subaru map, based on images in substantially better seeing than the DLS, enables detection of less massive halos at fixed redshift as expected. We demonstrate that the procedure adopted by Miyazaki et al. for removing some contaminated peaks from the weak-lensing map improves agreement between the lensing map and the redshift survey in the identification of candidate massive systems.

Kurtz, Michael J.; Geller, Margaret J.; Fabricant, Daniel G. [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States); Utsumi, Yousuke [Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo (Japan); Miyazaki, Satoshi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo (Japan); Dell'Antonio, Ian P., E-mail: mkurtz@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: dfabricant@cfa.harvard.edu, E-mail: yousuke.utsumi@nao.ac.jp, E-mail: satoshi@subaru.naoj.org, E-mail: ian@het.brown.edu [Department of Physics, Brown University, Box 1843, Providence, RI 02912 (United States)

2012-05-10

307

Separation of polystyrene microbeads using dielectrophoretic/gravitational field-flow-fractionation.  

PubMed Central

The characterization of a dielectrophoretic/gravitational field-flow-fractionation (DEP/G-FFF) system using model polystyrene (PS) microbeads is presented. Separations of PS beads of different surface functionalization (COOH and none) and different sizes (6, 10, and 15 microm in diameter) are demonstrated. To investigate the factors influencing separation performance, particle elution times were determined as a function of particle suspension conductivity, fluid flow rate, and applied field frequency and voltage. Experimental data were analyzed using a previously reported theoretical model and good agreement between theory and experiment was found. It was shown that separation of PS beads was based on the differences in their effective dielectric properties. Particles possessing different dielectric properties were positioned at different heights in a fluid-flow profile in a thin chamber by the balance of DEP and gravitational forces, transported at different velocities under the influence of the fluid flow, and thereby separated. To explore hydrodynamic (HD) lift effects, velocities of PS beads were determined as a function of fluid flow rate in the separation chamber when no DEP field was applied. In this case, particle equilibrium height positions were governed solely by the balance of HD lift and gravitational forces. It was concluded that under the experimental conditions reported here, the DEP force was the dominant factor in controlling particle equilibrium height and that HD lift force played little role in DEP/G-FFF operation. Finally, the influence of various experimental parameters on separation performance was discussed for the optimization of DEP/G-FFF. PMID:9591693

Wang, X B; Vykoukal, J; Becker, F F; Gascoyne, P R

1998-01-01

308

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

E-print Network

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

J. C. Hafele

2011-05-19

309

A nonlinear multidimensional gravitational model R+R-1 with form fields and stabilized extra dimensions  

NASA Astrophysics Data System (ADS)

We studied multidimensional gravitational models with scalar curvature nonlinearity of the type R-1 and with form fields (fluxes) as a matter source. It is assumed that the higher-dimensional space-time undergoes Freund-Rubin-like spontaneous compactification to a warped product manifold. It is shown that for certain parameter regions the model allows for freezing stabilization of the internal space near the positive minimum of the effective potential, which plays the role of the positive effective cosmological constant. However, the parameters of model should be fine tuned to obtain the observable dark energy.

Saidov, T.; Zhuk, A.

2006-10-01

310

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

E-print Network

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

N. Ben-Amots

2008-08-19

311

Thermoelectric Magnetohydrodynamic Flow During Crystal Growth with a Moderate or Weak Magnetic Field  

NASA Technical Reports Server (NTRS)

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.

Khine, Y. Y.; Walker, John S.; Szofran, Frank R.; Rose, M. Franklin (Technical Monitor)

2000-01-01

312

Quantum fog and the degradation of information by the gravitational field  

SciTech Connect

In this paper the authors discuss how information transferred optically through a gravitational field is degraded as the quanta interact with the medium (vacuum state). The authors quantify information by means of Shannon's entropy, and consider information carriers that are quanta of some field. Next, the authors obtain the quantum noise ([open quote]quantum fog[close quote]) produced by the gravitational field and derive the appropriate [open quote]channel capacity[close quote] formula, which quantifies the maximum amount of information that can be transmitted per pulse, in the face of this noise. It is shown that the channel capacity formula vanishes if the source of information is a space-time singularity because a very intense noise is produced in the vicinity of the singularity. In other words, space-time singularities are hidden behind a very intense [open quote]quantum fog[close quote] and cannot be optically observed. A second consequence is that information is degraded as anisotropies (lumpiness) develop in the universe. 32 refs., 9 figs., 5 figs.

Sciffer, M. (CERN, Geneva (Switzerland))

1993-07-01

313

Gravitational waves from cosmic bubble collisions  

E-print Network

Cosmic bubbles are nucleated through the quantum tunneling process. After nucleation they would expand and undergo collisions with each other. In this paper, we focus in particular on collisions of two equal-sized bubbles and compute gravitational waves emitted from the collisions. First, we study the mechanism of the collisions by means of a real scalar field and a quartic potential of the field. Then, using this scalar field model, we compute gravitational waves from the collisions in a straightforward manner. In the quadrupole approximation, time-domain gravitational waveforms are directly obtained by integrating the energy-momentum tensors over the volume of the wave sources, where the energy-momentum tensors are expressed in terms of the scalar field, the local geometry and the potential; therefore, containing all information about the bubble collisions. We present gravitational waveforms emitted during (i) the initial-to-intermediate stage of strong collisions and (ii) the final stage of weak collisions...

Kim, Dong-Hoon; Lee, Wonwoo; Yang, Jongmann; Yeom, Dong-han

2014-01-01

314

MagnetoSperm: A microrobot that navigates using weak magnetic fields  

NASA Astrophysics Data System (ADS)

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.

Khalil, Islam S. M.; Dijkslag, Herman C.; Abelmann, Leon; Misra, Sarthak

2014-06-01

315

Searching For Weak Solar Magnetic Fields. What Can We Learn From the Hanle Effect?  

NASA Astrophysics Data System (ADS)

Many dynamical phenomena taking place in the solar atmosphere, such as flares and coronal mass ejections, are driven by the interplay between the magnetic field and the turbulent solar plasma. Long standing questions on the physical origin of coronal heating and solar wind acceleration are also probably related to magnetic mechanisms. So the issue of how to measure magnetic fields in the solar atmosphere, from the photosphere up to the corona, is of crucial importance in solar physics. Because of the high value of the Reynolds magnetic number in the solar atmosphere, magnetic structures may develop from large to very small spatial scales, typically ranging from the scale of the solar diameter down to few tens of kilometers. The magnetic field strength also shows a broad dispersion from several thousands of Gauss in active regions like sunspots, down to a few Gauss in the quiet Sun. The amount of magnetic energy stored in magnetic structures is still unkown, and, according to recent numerical simulations, a significant fraction may be stored in weak, small scale fields, which cover a large fraction of the solar surface. However these field are hardly detectable in magnetograms based on the Zeeman effect because of their limited performances both in terms of polarimetric sensitivity and of spatial resolution. The Hanle effect is a valuable alternative for the diagnostics of weak fields with mixed polarity at small scales. It affects the linear polarization of spectral lines formed by scattering of photons in the solar atmosphere. I will present how weak magnetic fields investigations have changed our vision of the solar magnetism and discuss future research directions, in the context of solar polarimetry projects with ground based or space based intruments.

Faurobert, M.

2012-12-01

316

On inhomogeneous magnetic seed fields and gravitational waves within the MHD limit  

E-print Network

In this paper we apply second-order gauge-invariant perturbation theory to investigate the possibility that the non-linear coupling between gravitational waves (GW) and a large scale inhomogeneous magnetic field acts as an amplification mechanism in an `almost' Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe. The spatial inhomogeneities in the magnetic field are consistently implemented using the magnetohydrodynamic (MHD) approximation, which yields an additional source term due to the interaction of the magnetic field with velocity perturbations in the plasma. Comparing the solutions with the corresponding results in our previous work indicates that, on super-horizon scales, the interaction with the spatially inhomogeneous field in the dust regime induces the same boost as the case of a homogeneous field, at least in the ideal MHD approximation. This is attributed to the observation that the MHD induced part of the generated field effectively only contributes on scales where the coherence length of the initial field is less than the Hubble scale. At sub-horizon scales, the GW induced magnetic field is completely negligible in relation to the MHD induced field. Moreover, there is no amplification found in the long-wavelength limit.

Caroline Zunckel; Gerold Betschart; Peter K S Dunsby; Mattias Marklund

2006-02-09

317

Inhomogeneous magnetic seed fields and gravitational waves within the magnetohydrodynamic limit  

SciTech Connect

In this paper we apply second-order gauge-invariant perturbation theory to investigate the possibility that the coupling between gravitational waves (GWs) and a large-scale inhomogeneous magnetic field acts as an amplification mechanism in an 'almost' Friedmann-Lemaitre-Robertson-Walker Universe. The spatial inhomogeneities in the magnetic field are consistently implemented using the magnetohydrodynamic (MHD) approximation, which yields an additional source term due to the interaction of the magnetic field with velocity perturbations in the plasma. Comparing the solutions with the corresponding results in our previous work indicates that, on superhorizon scales, the interaction with the spatially inhomogeneous field in the dust regime induces the same boost as the case of a homogeneous field, at least in the ideal MHD approximation. This is attributed to the observation that the MHD induced part of the generated field effectively only contributes on scales where the coherence length of the initial field is less than the Hubble scale. At subhorizon scales, the GW induced magnetic field is completely negligible in relation to the MHD induced field. Moreover, there is no amplification found in the long-wavelength limit.

Zunckel, Caroline [Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); Betschart, Gerold [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); Racah Institute of Physics, Hebrew University of Jerusalem, Givat Ram, 91904 Jerusalem (Israel); Dunsby, Peter K.S. [Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa); South African Astronomical Observatory, Observatory 7925, Cape Town (South Africa); Marklund, Mattias [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2006-05-15

318

Electron distribution function of a weakly ionized plasma in homogeneous and stationary external fields  

NASA Astrophysics Data System (ADS)

An analytical expression is obtained for the electron distribution function of a weakly ionized plasma in external homogeneous and stationary electric and magnetic fields, with allowance for the ionization of atoms due to electron impact and electron escape from the plasma. The electron distribution function is then used to find the mobility tensor components of the plasma electrons. The frequency and increment of the oscillations are determined through an expansion in plane waves.

Avtiushkov, A. P.; Stekolnikov, A. F.

319

Spectral Form Factor for Chaotic Dynamics in a Weak Magnetic Field  

E-print Network

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

Keiji Saito; Taro Nagao

2005-05-26

320

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

E-print Network

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

Richard G. Bower; Ian Smail

1996-12-16

321

Generation of upper-hybrid solitons in a weak magnetic field  

NASA Astrophysics Data System (ADS)

Attention is given to a simplified model which describes the effects of plasma nonuniformity, external pumping, and ion inertia in a weak magnetic field. The model predicts the space-time evolution of upper-hybrid waves excited in the mode-conversion process. The model results suggest that the ponderomotive force depresses the density which, in turn, reduces wave convection. The ion inertia forces the perturbed density to propagate, and the original state is recovered.

Sugai, H.; Niki, H.; Takeda, S.

1981-01-01

322

Unveiling chameleon fields in tests of the gravitational inverse-square law  

SciTech Connect

Scalar self-interactions are known to weaken considerably the current constraints on scalar-mediated fifth forces. We consider a scalar field with a quartic self-interaction and gravitation-strength Yukawa couplings to matter particles. After discussing the phenomenology of this scalar field, we assess the ability of ongoing and planned experiments to detect the fifth force mediated by such a field. Assuming that the quartic and matter couplings are of order unity, the current-generation Eoet-Wash experiment at the University of Washington will be able to explore an interesting subset of parameter space. The next-generation Eoet-Wash experiment is expected to be able to detect, or to rule out, the fifth force due to such a scalar with unit quartic and matter couplings at the 3{sigma} confidence level.

Upadhye, Amol; Gubser, Steven S. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Khoury, Justin [Perimeter Institute for Theoretical Physics, 31 Caroline St. N., Waterloo, ON, N2L 2Y5 (Canada)

2006-11-15

323

On observation of neutron quantum states in the Earth's gravitational field  

NASA Astrophysics Data System (ADS)

Observation of neutron gravitational quantum states En=mgzn in the peV energy range (z1 is about 10?m in the vertical direction) in the experiment conducted at Laue-Langevin Institute, Grenoble, with ultracold neutrons was recently reported in a series of publications. The purpose of the present work is to analyze the experiment. The experimental apparatus is designed to measure a transmission function T(za), namely, a horizontal flux of relatively fast neutrons (k?kz in wavelength terms) passing through a slit of variable height za of upper absorbing wall. The quantum states in question are defined by the so-called Airy functions, which are solutions to the stationary 1D equation for a neutron “bouncing” above the perfect mirror in a linear potential field. The Airy functions describe the quantum bouncer (QB), the concept of which is subject to theoretical study of toy 1D models of gravitationally bound particles in nonrelativistic quantum mechanics (QM). This is essentially different from the 3D nonstationary QM object, “the running QB,” investigated in the experiment. The authors assume that there is a connection between T(za) and the probability density distribution P(z,za) for QB states. They devised the “phenomenological model,” in which the quantum pattern should be visible in the transmission curve. We argue, however, that the measured curve T(za) is not sensitive to QB states. Instead, it is sensitive to dynamics of neutron horizontal transport inside the absorbing slit for neutrons of energy values about 105 times greater than eigenvalues En. The latter are related to the neutron transverse mode kz and cannot be termed “energies of neutron gravitational quantum states.” We conclude that the experiment setup and real conditions are not adequate to the claimed objective, and the methodology of measured data treatment is flawed. The authors’ claim that “neutron gravitational quantum states are observed” is neither theoretically nor experimentally substantiated. Final, statistically significant results of the experiment are consistent with our physical reasoning that the experiment is not sensitive to “neutron gravitational quantum states” (in terms of Airy mode) and does not prove even their existence in rigorous quantum-mechanical terms.

Vankov, Anatoli Andrei

2010-03-01

324

Gravitational anomaly and transport phenomena.  

PubMed

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

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

2011-07-01

325

Surface electrostatic field below weak precipitation and stratiform regions of mid-latitude storms  

NASA Astrophysics Data System (ADS)

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.

Soula, S.; Georgis, J. F.

2013-10-01

326

[Antitumor effect of a weak superlow frequency stochastic magnetic field with 1/f spectrum].  

PubMed

Antiblastomic effect of low strength low frequency fluctuating magnetic field with 1/f power spectrum (1/f MF) analogous to spectra of normal biological fluctuations is studied experimentally. For the first time it is demonstrated that stabilization of cell-cell surface interactions as well as suppression of mitotic activity of malignant cells exposed to 1/f MF may result in considerable inhibition of cancer growth in animals. These effects were shown to be absent in weak low frequency magnetic fields with spectra other than 1/f. PMID:9410023

Muzalevskaia, N I; Uritski?, V M

1997-01-01

327

The thermodynamic functions of plasma under the influence of a weak magnetic field  

NASA Astrophysics Data System (ADS)

The aim of this paper is to calculate the quantum thermodynamic functions until the third virial coefficient of plasma under the influence of a weak magnetic field. The calculation is based on the binary Slater sum in the case of a low density plasma, which is exact in a quadratic order with respect to the magnetic field. The method which was used is based on the Bloch equation. The second virial coefficient is obtained in the form of a convergent series expansion in terms of the interaction plasma parameter ?={eaeb}/{KT?} where ? being the thermal de Broglie wavelength between two particles. We compared our results with others.

Hussein, N. A.; Eisa, D. A.; Eldin, M. G.

2012-12-01

328

Time evolution and decay of an excited atom in a weak electric field  

SciTech Connect

A Mathematica notebook for describing the time evolution and decay of the hydrogen {ital n}=2 states in the presence of a weak external electric field is presented. The work involves (1) solving a set of differential equations coupled by the Hamiltonian of the external electric field and (2) deriving a set of formulas for a complete description of the polarization state of the emitted photons. It is demonstrated how problems with such complexity can be treated with ease and in an error-free manner by using symbolic software such as Mathematica. {copyright} {ital 1996 American Institute of Physics.}

Wang, J.B. [Center for Atomic, Molecular and Surface Physics, Physics Department, University of Western Australia, Perth 6009 (Australia)] [Center for Atomic, Molecular and Surface Physics, Physics Department, University of Western Australia, Perth 6009 (Australia)

1996-07-01

329

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

E-print Network

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

S. P. Dawson

2005-08-15

330

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

331

Effect of weak and ultraweak combined magnetic fields and low-intensity microwaves on regeneration in the planarian Dugesia tigrina  

Microsoft Academic Search

Regeneration (blastema growth) in Dugesia tigrina was accelerated if prior to transection the planarians were exposed to a weak constant magnetic field (42 ?T) combined with\\u000a an ultraweak alternating magnetic field (40 nT, 3.7 Hz); lesser stimulation was obtained with weak microwaves (100 ?W\\/cm2 at 36 GHz). Field exposure after transection produced only half of the effect (magnetic field) or

V. V. Novikov; I. M. Sheiman; A. V. Klyubin; E. E. Fesenko

2007-01-01

332

Sensitivity of calcium binding in cerebral tissue to weak environmental electric fields oscillating at low frequency.  

PubMed Central

Weak sinusoidal electric fields modify the calcium efflux from freshly isolated chick and cat cerebral tissues bathed in Ringer's solution, at 36 degrees. Following incubation (30 min) with radioactive calcium (45Ca2+), each sample, immersed in fresh solution, was exposed for 20 min to fields at 1, 6, 16, 32, or 75 Hz, with electric gradients of 5, 10, 56, and 100 V/m in air. 45Ca2+ efflux in the solution was then measured in 0.2 ml aliquots and compared with efflux from unexposed control samples. Field exposures resulted in a general trend toward a reduction in the release of the preincubated 45Ca2+. Both frequency and amplitude sensitivities were observed. Maximum decreases occurred at 6 and 16 Hz (12-15%). Thresholds were around 10 and 56 V/m for chick and cat tissues, respectively. Similar but nonsignificant trends occurred during other field exposures. All results were statistically compared with matched samples of controls. Tissue gradients could not be measured, but estimates were of the order of 0.1 muV/cm. The susceptibility of the electrochemical equilibrium in the neuronal membrane to small extracellular perturbations is discussed and a possible role for weak intrinsic cerebral fields in neuronal excitability is suggested. Images PMID:1064869

Bawin, S M; Adey, W R

1976-01-01

333

On the effects of a weak magnetic field on turbulent transport  

NASA Technical Reports Server (NTRS)

We discuss the effects of a weak large-scale magnetic field on turbulent transport. We show by means of a series of two-dimensional numerical experiments that turbulent diffusion can be effectively suppressed by a (large scale) magnetic field whose energy is small compared to equipartition. The suppression mechanism is associated with a subtle modification of the Lagrangian energy spectrum, and it does not require any substantial reduction of the turbulent amplitude. We exploit the relation between diffusion and random walking to emphasize that the effect of a large-scale magnetic field is to induce a long-term memory in the field of turbulence. The implications of the general case of three-dimensional transport are briefly discussed.

Cattaneo, F.

1994-01-01

334

Brain pathways and behavioral responses to weak electric fields in parasitic sea lampreys (Petromyzon marinus).  

PubMed

The authors characterized the behavioral and brain responses of parasitic sea lampreys (Petromyzon marinus) to weak electric fields. Lampreys showed preferences for the cathodal end of the testing aquarium after electric stimulation. Within a range of cathodal fields (-0.1 to -30.0 mu-V/cm), lampreys exhibited increased active behaviors. In contrast, anodal fields decreased most active behaviors below baseline. Exposure to electric fields resulted in changes in Western blot patterns for the neuronal activity markers Fos, Fos-B. and Jun in whole-brain homogenate. Electric stimulation also increased Fos-B immunoreactivity in the octavolateral and the habenula-fasciculus retroflexus-interpeduncular systems. These results confirm that the octavolateral system is associated with electroreception and suggest that the habenula-fasciculus retroflexus-interpeduncular system may be pan of the electroreceptive network. PMID:15174939

Chung-Davidson, Yu-Wen; Yun, Sang-Seon; Teeter, John; Li, Weiming

2004-06-01

335

Horizon thermodynamics and gravitational field equations in quasi-topological gravity  

NASA Astrophysics Data System (ADS)

In this paper we show that the gravitational field equations of -dimensional topological black holes with constant horizon curvature, in cubic and quartic quasi-topological gravity, can be recast in the form of the first law of thermodynamics, , at the black hole horizon. This procedure leads to extract an expression for the horizon entropy as well as the energy (mass) in terms of the horizon radius, which coincide exactly with those obtained in quasi-topological gravity by solving the field equations and using the Wald's method. We also argue that this approach is powerful enough to be extended to all higher order quasi-topological gravity for extracting the corresponding entropy and energy in terms of horizon radius.

Sheykhi, A.; Dehghani, M. H.; Dehghani, R.

2014-04-01

336

S-band transponder experiment. [measurement of lunar gravitational field during orbit of Apollo 17 spacecraft  

NASA Technical Reports Server (NTRS)

The purpose of this experiment was to measure the variations in the lunar gravitational field near the trajectory of orbiting space vehicles (the command and service module (CSM) and the small particles and fields subsatellites ejected from the Apollo 15 and 16 spacecraft). New information has been obtained from all Apollo orbiting spacecraft; however, this report shall be limited to the results from the Apollo 17 CSM and the Apollo 16 subsatellite. The data acquired are precise speed measurements of the orbiting spacecraft from which accelerations or gravity profiles may be inferred. Feature resolution is controlled by the spacecraft altitude and is almost a direct relationship (i.e., data taken from a 50-km altitude will resolve approximately a 50-km feature). Therefore, revolutions 3 to 12, when the CSM was in the low-altitude orbits, provided the clearest information.

Sjogren, W. L.; Wollenhaupt, W. R.; Wimberly, R. N.

1973-01-01

337

Conversion of relic gravitational waves into photons in cosmological magnetic fields  

SciTech Connect

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

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

2012-12-01

338

Shapes and gravitational fields of rotating two-layer Maclaurin ellipsoids: Application to planets and satellites  

NASA Astrophysics Data System (ADS)

The exact solution for the shape and gravitational field of a rotating two-layer Maclaurin ellipsoid of revolution is compared with predictions of the theory of figures up to third order in the small rotational parameter of the theory of figures. An explicit formula is derived for the external gravitational coefficient J2 of the exact solution. A new approach to the evaluation of the theory of figures based on numerical integration of ordinary differential equations is presented. The classical Radau-Darwin formula is found not to be valid for the rotational parameter ?2 = ?2/(2 ?G ?2) ? 0.17 since the formula then predicts a surface eccentricity that is smaller than the eccentricity of the core-envelope boundary. Interface eccentricity must be smaller than surface eccentricity. In the formula for ?2, ? is the angular velocity of the two-layer body, ?2 is the density of the outer layer, and G is the gravitational constant. For an envelope density of 3000 kg m -3 the failure of the Radau-Darwin formula corresponds to a rotation period of about 3 h. Application of the exact solution and the theory of figures is made to models of Earth, Mars, Uranus, and Neptune. The two-layer model with constant densities in the layers can provide realistic approximations to terrestrial planets and icy outer planet satellites. The two-layer model needs to be generalized to allow for a continuous envelope (outer layer) radial density profile in order to realistically model a gas or ice giant planet.

Schubert, Gerald; Anderson, John; Zhang, Keke; Kong, D.; Helled, Ravit

2011-08-01

339

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

SciTech Connect

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

White, D.H.; Sullivan, D.

1986-01-01

340

The proton-proton weak capture reaction within chiral effective field theory  

NASA Astrophysics Data System (ADS)

We review the results of the most recent calculation for the astrophysical S-factor of the weak proton-proton capture reaction, over a range for the center-of-mass relative energy of 0-100 keV. The so-called chiral effective field theory approach is used, where the chiral two- nucleon potential is derived up to next-to-next-to-next-to leading order and is augmented by the full electromagnetic interaction. The low-energy constants (LEC's) entering the weak current operators are fixed so as to reproduce the A = 3 binding energies and magnetic moments, and the Gamow-Teller matrix element in tritium ?-decay. Contributions from S and P partial waves in the incoming two-proton channel are retained. The S-factor at zero energy is found to be ~1% larger than the value reported in the literature, mostly due to the P-waves contributions.

Marcucci, Laura E.

2014-07-01

341

Non-linear evolution of the elliptical instability in the presence of weak magnetic fields  

NASA Astrophysics Data System (ADS)

We investigate whether the elliptical instability is important for tidal dissipation in gaseous planets and stars. In a companion paper, we found that the conventional elliptical instability results in insufficient dissipation because it produces long-lived vortices that then quench further instability. Here, we study whether the addition of a magnetic field prevents those vortices from forming, and hence leads to enhanced dissipation. We present results from magnetohydrodynamic simulations that evolve the elliptical instability in a local patch of a rotating planet or star, in the presence of a weak magnetic field. We find that magnetic fields do indeed prevent vortices from forming, and hence greatly enhance the steady-state dissipation rate. In addition, the resulting turbulence acts as a small-scale dynamo, amplifying the initially weak field. The inferred tidal dissipation is potentially important at short orbital periods. For example, it can circularize hot Jupiters with orbital periods shorter than 2.5 d and synchronize their spins with their orbits out to 6 d. However, it appears unable to account for the hot Jupiters that appear to have been circularized out to 6-10 d orbital periods. It also cannot account for the inferred circularization of many close binary stars.

Barker, Adrian J.; Lithwick, Yoram

2014-01-01

342

Application of the weak-field asymptotic theory to tunneling ionization of H2O  

NASA Astrophysics Data System (ADS)

The weak-field asymptotic theory of tunneling ionization in a static electric field is applied to H2O. The orientation dependence of the ionization rate is studied. The use of polarization-consistent basis sets with up to heptuble-zeta accuracy and variationally optimized exponents improves the asymptotic form of the wave function and allows for an accurate extraction of the structure factor defining the ionization rate. The results are presented based on Hartree-Fock wave functions and density functional theory. The density functional theory reproduces closely the experimental vertical ionization potential. We find that the rate peaks at an angle of 81? between the field and molecular principal inertial axis through the O atom. The predictions for the orientation dependence of the rate are compared to available theoretical results.

Madsen, Lars Bojer; Jensen, Frank; Tolstikhin, Oleg I.; Morishita, Toru

2014-03-01

343

Computer study of convection of weakly ionized plasma in a nonuniform magnetic field.  

NASA Technical Reports Server (NTRS)

A weakly ionized plasma in a strong and nonuniform magnetic field exhibits an instability analogous to the flute instability in a fully ionized plasma. The instability sets in at a critical magnetic field. To study the final state of the plasma after the onset of the instability, the plasma equations are integrated numerically assuming a certain initial spectrum of small disturbances. In the regime studied, numerical results indicate a final steadily oscillating state consisting of a single finite amplitude mode together with a time-independent modification of the original equilibrium. These results agree with the analytic results obtained by Simon in the slightly supercritical regime. As the magnetic field is increased further, the wavelength of the final oscillation becomes nonunique. There exists a subinterval in the unstable wave band. Final stable oscillation with a wavelength in this subinterval can be established if the initial disturbance has a sufficiently strong component at the particular wavelength.

Shiau, J. N.

1972-01-01

344

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

E-print Network

We treat a very crude model of an exploding star, in the weak field approximation of the Brans-Dicke theory, in a scenario that resembles some characteristics data of a Type Ia Supernova. The most noticeable feature, in the electromagnetic component, is the relationship between the absolute magnitude at maximum brightness of the star and the decline rate in one magnitude from that maximum. This characteristic has become one of the most accurate method to measure luminosity distances to objects at cosmological distances. An interesting result is that the active mass associated with the scalar field is totally radiated to infinity, representing a mass loss in the ratio of the "tensor" component to the scalar component of 1 to $(2 \\omega + 3)$ ($\\omega$ is the Brans-Dicke parameter), in agreement with a general result of Hawking. Then, this model shows explicitly, in a dynamical case, the mechanism of radiation of scalar field, which is necessary to understand the Hawking result.

Victor H. Hamity; Daniel E. Barraco

2005-04-21

345

Probing Gravitational Dark Matter  

E-print Network

So far all evidences of dark matter (DM) come from astrophysical and cosmological observations, due to the gravitational interactions of DM. It is possible that the true DM particle in the universe joins gravitational interactions only, but nothing else. Such a Gravitational DM (GDM) acts as a weakly interacting massive particle (WIMP), which is conceptually simple and attractive. In this work, we explore this direction by constructing the simplest scalar GDM particle $\\chi_s$. It is a $\\mathbb{Z}_2$ odd singlet under the standard model (SM) gauge group, and naturally joins the unique dimension-4 interaction with Ricci curvature, $\\xi_s\\chi_s^2{\\cal R}$, where $\\xi_s$ is the dimensionless nonminimal coupling. We demonstrate that this gravitational interaction $\\xi_s\\chi_s^2{\\cal R}$, together with Higgs-curvature nonminimal coupling term $\\xi_h H^\\dag H {\\cal R}$, induces effective couplings between $\\chi_s^2$ and SM fields which can account for the observed DM thermal relic abundance. We analyze the annihila...

Ren, Jing

2014-01-01

346

MTV-G experiment : probing a non-standard strong gravitational field at nuclear scale using geodetic precession  

NASA Astrophysics Data System (ADS)

The MTV-G project has started in 2011 to explore a strong gravitational field around nuclei utilizing an experimental technique developed to search time reversal symmetry violation in nuclear beta decay experiment at a radioactive beam facility. A large electron spin-precession due to a possible strong gravitational field, which has been predicted by a large extra dimension model, is investigated in an electron-nuclear scattering experiment at TRIUMF. The experimental design, which use a spin polarized electron source and a Mott-spin analyzer, the commissioning experiment, the preliminary results, together with an introduction to the next generation device, are described in this article.

Tanaka, Saki; Nakaya, Yusuke; Ninomiya, Kazufumi; Nishio, Hironori; Onishi, Junichi; Openshaw, Robert; Pearson, Matthew; Totsuka, Yumi; Murata, Jiro

2013-08-01

347

MTV-G experiment: Probing non-standard strong gravitational field at nuclear scale using geodetic precession  

NASA Astrophysics Data System (ADS)

A new experiment named MTV-G, probing a large electron spin-precession due to a possible strong gravitational field, which predicted by large extra dimension model, is started at TRIUMF from 2011. In an electron-nuclear scattering experiment, a strong gravitational field is tested as a large spin precession effect caused by geodetic precession predicted by general relativity theory as a result of a warped space-time around nuclei. Experimental design using spin polarized electron source and Mott-spin analyzer, commissioning experiment and the preliminary results are described.

Tanaka, Saki; Nakaya, Yusuke; Ninomiya, Kazufumi; Nishio, Hironori; Onishi, Junichi; Openshaw, Robert; Pearson, Matthew; Totsuka, Yumi; Murata, Jiro

2014-01-01

348

Superluminal Electromagnetic and Gravitational Fields Generated in the Nearfield of Dipole Sources  

E-print Network

In this paper the fields generated by an electric dipole and a gravitational quadrapole are shown to propagate superluminally in the nearfield of the source and reduce to the speed of light as the fields propagate into the farfield. A theoretical derivation of the generated fields using Maxwell's equations is presented followed by a theoretical analysis of the phase and group speed of the propagating fields. This theoretical prediction is then verified by a numerical simulation which demonstrates the superluminal propagation of modulated signals in the nearfield of their sources. An experiment using simple dipole antennas is also presented which verifies the theoretically expected superluminal propagation of transverse electromagnetic fields in the nearfield of the source. The phase speed, group speed, and information speed of these systems are compared and shown to differ. Provided the noise of a signal is small and the modulation method is known, it is shown that the information speed can be approximately the same as the superluminal group speed. According to relativity theory, it is known that between moving reference frames, superluminal signals can propagate backwards in time enabling violations of causality. Several explanations are presented which may resolve this dilemma.

William D. Walker

2006-03-28

349

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

NASA Astrophysics Data System (ADS)

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

Kirschvink, Joseph L.

1992-08-01

350

Lipid utilization in radish seedlings as affected by weak horizontal extremely low frequency magnetic field.  

PubMed

Composition and content of lipids were studied in 5-day-old radish seedlings (Raphanus sativus L. var. radicula DC.) grown in lowlight and darkness in an extremely low frequency (ELF) magnetic field characterized by 50?Hz frequency and ?500?µT flux density. The control seedlings were grown under the same conditions, but without exposure to the magnetic field. The products of lipid metabolism were compared with lipid composition in seeds. In control seedlings, reserve neutral lipids, mostly triacylglycerides, were utilized for the formation of polar lipids (PL). As a result, the amount of the latter doubled, particularly due to glycolipids (GL) and phospholipids (PhL) compared to their content in seeds. At 20-22?°C in light, magnetic field exposure increased the production of PL by threefold specifically, GL content increased fourfold and PhL content rose 2.5 times, compared to seeds. In darkness, the effect of magnetic field on lipids was weaker. At the lower temperature of 13-16?°C in light, the effect of the magnetic field was weak, but in the darkness, no magnetic field action was recorded. It is concluded that ELF magnetic field stimulated lipid synthesis in chloroplast, mitochondrial, and other cell membranes in radish seedlings grown in light at 20-22?°C and 13-16?°C. PMID:24123065

Novitskii, Yurii I; Novitskaya, Galina V; Serdyukov, Yurii A

2014-02-01

351

Weak extremely-low-frequency magnetic field-induced regeneration anomalies in the planarian, Dugesia tigrina  

SciTech Connect

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.

Jenrow, K.A.; Smith, C.H.; Liboff, A.R. [Oakland Univ., Rochester, MI (United States). Dept. of Physics] [Oakland Univ., Rochester, MI (United States). Dept. of Physics

1996-12-31

352

Bilayer graphene with long-range scatterers: Diamagnetism and weak-field Hall effect  

NASA Astrophysics Data System (ADS)

The diamagnetic susceptibility and the weak-field Hall conductivity are calculated for scatterers with nonzero range in bilayer graphene within a self-consistent Born approximation. The susceptibility exhibits a double-peak structure in the vicinity of zero energy. The Hall coefficient is given by the carrier concentration when the potential range is smaller or comparable to the Fermi wavelength, but becomes different when the range becomes larger than the Fermi wavelength. This deviation is not important in the case of charged impurities, but can become visible in the presence of environmental dielectric material.

Ando, Tsuneya

2014-04-01

353

Astronomers Use X-Rays To Probe Gravitational Field Of A Neutron Star  

NASA Astrophysics Data System (ADS)

With NASA's Chandra X-ray Observatory, astronomers have detected features that may be the first direct evidence of the effect of gravity on radiation from a neutron star. This finding, if confirmed, could enable scientists to measure the gravitational field of neutron stars and determine whether they contain exotic forms of matter not seen on Earth. A team led by George Pavlov of Penn State University in University Park observed 1E 1207.4-5209, a neutron star in the center of a supernova remnant about 7,000 light years from Earth. The results were presented on June 6, 2002, at the American Astronomical Society in Albuquerque, NM. Pavlov's group found two dips, or absorption features, in the spectrum of X-rays from the star. If these dips are due to the absorption of X-rays near the star by helium ions in a strong magnetic field, they indicate that the gravitational field reduces the energies of X-rays escaping from near the surface of a neutron star. "This interpretation is consistent with the data," said Pavlov, "but the features may be a blend of many other features. More precise measurements, preferably with Chandra's grating spectrometer, are needed." "These absorption features may be the first evidence of the effect of gravity on radiation near the surface of an isolated neutron star," said Pavlov. "This is particularly important because it would allow us to set limits on the type of matter that comprises this star." Neutron stars are formed when a massive star runs out of fuel and its core collapses. A supernova explosion occurs and the collapsed core is compressed to a hot object about 12 miles in diameter, with a thin atmosphere of hydrogen and possibly heavier ions in a gravitational field 100 billion times as strong as Earth's. These objects, which have a density of more than 1 billion tons per teaspoonful, are called neutron stars because they have been thought to be composed mostly of neutrons. Although neutron stars have been studied extensively for more than three decades, their exact nature is still unknown. "We are not even sure that neutron stars are composed of neutrons," said Divas Sanwal, also of Penn State, and lead author on a paper describing the team's results. "They could be largely composed of subatomic particles called pions or kaons, or even free quarks." One key to narrow the range of possibilities is to measure the strength of gravity on the surface of a neutron star by observing its effect on X-rays from very near the surface of the star. According to Einstein's theory of General Relativity, attraction of photons by a star's gravitational field results in a lower energy of the photon (longer wavelength of radiation) when detected by a distant observer. The measurement of this gravitational redshift relates the mass to the radius of the star, and it will test the theories for the various possible forms of dense matter. The team, which also includes Slava Zavlin of Max Plank Institute for Extraterrestrial Physics, Germany, and Marcus Teter of Penn State, considered several possible explanations for the absorption features observed from 1E 1207. The strength and X-ray energy of the features make it improbable that they are due to intervening interstellar material or absorption due to electrons or ions circling in a strong magnetic field. The most likely hypothesis, they conclude, is that the features are due to absorption by helium ions in a magnetic field about a hundred trillion times more intense than the Earth's magnetic field. In this case, the gravitational redshift reduces the energy of the X-rays by 17 percent. Pavlov and his colleagues observed 1E 1027 with Chandra's Advanced CCD Imaging Spectrometer on January 6, 2000, and again on January 5, 2002, each time for approximately 30,000 seconds. The ACIS instrument was built for NASA by Penn State and the Massachusetts Institute of Technology, Cambridge, Mass. under the leadership of Gordon Garmire of Penn State. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the

2002-06-01

354

``Faster than Light'' Photons in Gravitational Fields -- Causality, Anomalies and Horizons  

E-print Network

A number of general issues relating to superluminal photon propagation in gravitational fields are explored. The possibility of superluminal, yet causal, photon propagation arises because of Equivalence Principle violating interactions induced by vacuum polarisation in QED in curved spacetime. Two general theorems are presented: first, a polarisation sum rule which relates the polarisation averaged velocity shift to the matter energy-momentum tensor and second, a `horizon theorem' which ensures that the geometric event horizon for black hole spacetimes remains a true horizon for real photon propagation in QED. A comparision is made with the equivalent results for electromagnetic birefringence and possible connections between superluminal photon propagation, causality and the conformal anomaly are exposed.

G. M. Shore

1995-04-25

355

Faster than Light Photons in Gravitational Fields II - Dispersion and Vacuum Polarisation  

E-print Network

Vacuum polarisation in QED in a background gravitational field induces interactions which effectively violate the strong equivalence principle and affect the propagation of light. In the low frequency limit, Drummond and Hathrell have shown that this mechanism leads to superluminal photon velocities. To confront this phenomenon with causality, however, it is necessary to extend the calculation of the phase velocity $\\vp(\\w)$ to high frequencies, since it is $\\vp(\\infty)$ which determines the characteristics of the effective wave equation and thus the causal structure. In this paper, we use a recently constructed expression, valid to all orders in a derivative expansion, for the effective action of QED in curved spacetime to determine the frequency dependence of the phase velocity and investigate whether superluminal velocities indeed persist in the high frequency limit.

G. M. Shore

2002-03-11

356

Transit time of a freely-falling quantum particle in a background gravitational field  

E-print Network

Using a model quantum clock, I evaluate an expression for the time of a non-relativistic quantum particle to transit a piecewise geodesic path in a background gravitational field with small spacetime curvature (gravity gradient), in the case that the apparatus is in free fall. This calculation complements and extends an earlier one (Davies 2004) in which the apparatus is fixed to the surface of the Earth. The result confirms that, for particle velocities not too low, the quantum and classical transit times coincide, in conformity with the principle of equivalence. I also calculate the quantum corrections to the transit time when the de Broglie wavelengths are long enough to probe the spacetime curvature. The results are compared with the calculation of Chaio and Speliotopoulos (2003), who propose an experiment to measure the foregoing effects.

P C W Davies

2004-07-05

357

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

NASA Technical Reports Server (NTRS)

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

Yuan, C.

1983-01-01

358

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

NASA Technical Reports Server (NTRS)

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

Nisbet, John S.

1989-01-01

359

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

NASA Astrophysics Data System (ADS)

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

Alsing, Paul M.; Cardimona, David A.; Huang, Danhong H.

2008-03-01

360

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

NASA Astrophysics Data System (ADS)

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

Alsing, P. M.; Cardimona, D. A.; Huang, D. H.

2007-10-01

361

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

362

Theory of tunneling ionization of molecules: Weak-field asymptotics including dipole effects  

SciTech Connect

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.

Tolstikhin, Oleg I. [National Research Center ''Kurchatov Institute'', Kurchatov Square 1, Moscow 123182 (Russian Federation); Morishita, Toru [Department of Engineering Science, The University of Electro-Communications, 1-5-1 Chofu-ga-oka, Chofu-shi, Tokyo 182-8585 (Japan); Madsen, Lars Bojer [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University (Denmark)

2011-11-15

363

[Cyclotron resonance as a cause of biological effects of weak electric and magnetic fields?].  

PubMed

Even weak electric and magnetic fields have been found to cause interaction effects in vitro only within small frequency ranges. The existence of such "frequency windows" may be explained by a cyclotron resonance model which also takes the influence of the earth's magnetic field into consideration. In this paper analytical relations are developed which permit the determination of energy uptake and motion curve diameter. On the basis of this calculations it can be concluded that, giving consideration to interparticle interactions and the limitations of motion curve dimensions due to the limited dimensions of cells and cellular interspaces, energy uptake in vivo is many orders of magnitude below thermal energy, and can therefore be neglected. PMID:2164850

Leitgeb, N

1990-06-01

364

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

NASA Astrophysics Data System (ADS)

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

Debnath, Ujjal; Rudra, Prabir; Biswas, Ritabrata

2012-05-01

365

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

E-print Network

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

Debnath, Ujjal; Biswas, Ritabrata

2012-01-01

366

Transformation of an Electromagnetic Field into Gravitational Field in Model of Extended Space:Prediction and Experiment  

E-print Network

Series of experiments were carried out to check the prediction concerning the possibility to generate gravitational field when charged massive particles decelerated in the in substance. As a source of the charged particles was used the accelerator of the electrons. The narrow bundle relativistic electrons (average power of a bundle 450 W, electrons energy about 30 MeV) were directed on a stopping target made from tungsten where electrons deceleration happened. The measurements have shown emerging statistically of authentic deviation of a rotating pendulum, one of which massive cargoes was near to the stopping target, in the moment when the bundle of relativistic electrons decelerated in the stopping target. Also was fixed changing of direction of the pendulum rotation when stopping target was shifted from one end of a pendulum to another. The magnitude of force that calls a deviation of the pendulum has upper limit 0,000001 N.

D. Yu. Tsipenyuk

2001-07-04

367

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

PubMed Central

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

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

1996-01-01

368

Models of magnetic field evolution and effective viscosity in weakly collisional extragalactic plasmas  

NASA Astrophysics Data System (ADS)

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.

Mogavero, Federico; Schekochihin, Alexander A.

2014-06-01

369

Self-gravitating instability of an annular fluid jet surrounding a mantle tar column upon oscillating periodical electric fields  

Microsoft Academic Search

The self-gravitating instability of an annular fluid jet surrounding a very dense mantle tar cylinder under oscillating periodical oblique electric fields has been developed. The potential and kinetic energies of the system are computed and the characteristic integral differential Mathieu equation is derived by utilizing the Lagrangian energy principle. Some reported works could be recovered as limiting cases. The model

Ahmed E. Radwan

1997-01-01

370

Stochastic gravitational fluctuations in a self-consistent mean field theory  

NASA Astrophysics Data System (ADS)

A fully stochastic theory is formulated for the dynamical evolution of a gravitationally interacting stellar system. A given test star is assumed to experience a self-consistent mean field potential, and in addition to be subjected to random fluctuations. The general theory of random (Markoff) processes is briefly summarised, with emphasis upon the connections among the various fundamental equations: Kolmogorov-Feller, master, and Fokker-Planck. In a first approximation, fluctuations may be viewed as a sum of random binary encounters in the spirit of the Boltzmann H-theorem. The advantages and difficulties of such a viewpoint are discussed. The full stochastic picture is then addressed. The nature of the stochastic force acting upon a test star is examined in detail, and an heuristic interpretation is discussed. A calculation is presented of the relative contribution to the total force resulting from field stars separated by a distance R from some origin. The effects of fluctuations are then discussed in a diffusion approximation as an application of the theory of the Brownian motion. The question of the actual validity of this self-consistent mean field picture is then discussed, and several of the more significant unresolved problems are stated.

Kandrup, Henry E.

1980-07-01

371

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

SciTech Connect

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

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

2009-05-15

372

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

PubMed

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

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

2013-12-01

373

Orbital diamagnetism of weakly doped bilayer graphene in a magnetic field.  

PubMed

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. PMID:21558597

Lv, Min; Wan, Shaolong

2011-06-01

374

Effect of weak static magnetic fields on the development of cultured skeletal muscle cells.  

PubMed

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. Bioelectromagnetics 35:537-546, 2014. © 2014 Wiley Periodicals, Inc. PMID:25266690

Surma, Sergei V; Belostotskaya, Galina B; Shchegolev, Boris F; Stefanov, Vasily E

2014-12-01

375

Chaotic transport in Hamiltonian systems perturbed by a weak turbulent wave field  

SciTech Connect

Chaotic transport in a Hamiltonian system perturbed by a weak turbulent wave field is studied. It is assumed that a turbulent wave field has a wide spectrum containing up to thousands of modes whose phases are fluctuating in time with a finite correlation time. To integrate the Hamiltonian equations a fast symplectic mapping is derived. It has a large time-step equal to one full turn in angle variable. It is found that the chaotic transport across tori caused by the interactions of small-scale resonances have a fractal-like structure with the reduced or zero values of diffusion coefficients near low-order rational tori thereby forming transport barriers there. The density of rational tori is numerically calculated and its properties are investigated. It is shown that the transport barriers are formed in the gaps of the density of rational tori near the low-order rational tori. The dependencies of the depth and width of transport barriers on the wave field spectrum and the correlation time of fluctuating turbulent field (or the Kubo number) are studied. These numerical findings may have importance in understanding the mechanisms of transport barrier formation in fusion plasmas.

Abdullaev, S. S. [Institute for Energy and Climate Research-Plasma Physics, Forschungszentrum Juelich GmbH, Association EURATOM-FZJ, Partner in the Trilateral Euregio Cluster, D-52425 Juelich (Germany)

2011-08-15

376

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

PubMed

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

Plocková, J; Chmelík, J

2001-05-25

377

Principles of gravitational biology  

NASA Technical Reports Server (NTRS)

Physical principles of gravitation are enumerated, including gravitational and inertial forces, weight and mass, weightlessness, size and scale effects, scale limits of gravitational effects, and gravity as biogenic factor. Statocysts, otolithic organs of vertebrates, gravity reception in plants, and clinostat studies for gravitation orientation are reviewed. Chronic acceleration is also studied, as well as physiology of hyper and hypodynamic fields. Responses of animals to a decreased acceleration field are examined, considering postural changes, work capacity, growth, and physiologic deadaptation.

Smith, A. H.

1975-01-01

378

Detection of a weak surface magnetic field on Sirius A: are all tepid stars magnetic?  

NASA Astrophysics Data System (ADS)

Aims: We aim at a highly sensitive search for weak magnetic fields in main sequence stars of intermediate mass, by scanning classes of stars with no previously reported magnetic members. After detecting a weak magnetic field on the normal, rapidly rotating A-type star Vega, we concentrate here on the bright star Sirius A, taken as a prototypical, chemically peculiar, moderately rotating Am star. Methods: We employed the NARVAL and ESPaDOnS high-resolution spectropolarimeters to collect 442 circularly polarized spectra, complemented by 60 linearly polarized spectra. Using a list of about 1100 photospheric spectral lines, we computed a cross correlation line profile from every spectrum, leading to a signal-to-noise ratio of up to 30 000 in the polarized profile. Results: We report the repeated detection of circularly polarized, highly asymmetric signatures in the line profiles, interpreted as Zeeman signatures of a large-scale photospheric magnetic field, with a line-of-sight component equal to 0.2 ± 0.1 G. Conclusions: This is the first polarimetric detection of a surface magnetic field on an Am star. Using rough estimates of the physical properties of the upper layers of Sirius A, we suggest that a dynamo operating in the shallow convective envelope cannot account for the field strength reported here. Together with the magnetic field of Vega, this result confirms that a new class of magnetic objects exists among non Ap/Bp intermediate-mass stars, and it may indicate that a significant fraction of tepid stars are magnetic. Based on observations obtained at the Bernard Lyot Telescope (TBL, Pic du Midi, France) of the Midi-Pyrénées Observatory, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

Petit, P.; Lignières, F.; Aurière, M.; Wade, G. A.; Alina, D.; Ballot, J.; Böhm, T.; Jouve, L.; Oza, A.; Paletou, F.; Théado, S.

2011-08-01

379

Black holes and fundamental fields: hair, kicks and a gravitational "Magnus" effect  

E-print Network

Scalar fields pervade theoretical physics and are a fundamental ingredient to solve the dark matter problem, to realize the Peccei-Quinn mechanism in QCD or the string-axiverse scenario. They are also a useful proxy for more complex matter interactions, such as accretion disks or matter in extreme conditions. Here, we study the collision between scalar "clouds" and rotating black holes. For the first time we are able to compare analytic estimates and strong field, nonlinear numerical calculations for this problem. As the black hole pierces through the cloud it accretes according to the Bondi-Hoyle prediction, but is deflected through a purely kinematic gravitational "anti-Magnus" effect, which we predict to be present also during the interaction of black holes with accretion disks. After the interaction is over, we find large recoil velocities in the transverse direction. The end-state of the process belongs to the vacuum Kerr family if the scalar is massless, but can be a hairy black hole when the fundamenta...

Okawa, Hirotada

2014-01-01

380

New Estimates of Hydrological and Oceanic Excitations of Variations of Earth's Rotation, Geocenter and Gravitational Field  

NASA Technical Reports Server (NTRS)

Hydrological mass transport in the geophysical fluids of the atmosphere-hydrosphere-solid Earth surface system can excite Earth's rotational variations in both length-of-day and polar motion. These effects can be computed in terms of the hydrological angular momentum by proper integration of global meteorological data. We do so using the 40-year NCEP data and the 18-year NASA GEOS-1 data, where the precipitation and evapotranspiration budgets are computed via the water mass balance of the atmosphere based on Oki et al.'s (1995) algorithm. This hydrological mass redistribution will also cause geocenter motion and changes in Earth's gravitational field, which are similarly computed using the same data sets. Corresponding geodynamic effects due to the oceanic mass transports (i.e. oceanic angular momentum and ocean-induced geocenter/gravity changes) have also been computed in a similar manner. We here compare two independent sets of the result from: (1) non-steric ocean surface topography observations based on Topex/Poseidon, and (2) the model output of the mass field by the Parallel Ocean Climate Model. Finally, the hydrological and the oceanic time series are combined in an effort to better explain the observed non-atmospheric effects. The latter are obtained by subtracting the atmospheric angular momentum from Earth rotation observations, and the atmosphere- induced geocenter/gravity effects from corresponding geodetic observations, both using the above-mentioned atmospheric data sets.

Chao, Benjamin F.; Chen, J. L.; Johnson, T.; Au, A. Y.

1998-01-01

381

Effect of H- ion extraction on a plasma sheath under an external weak magnetic field  

NASA Astrophysics Data System (ADS)

The extraction of negative ions inevitably leads to the destruction of the original plasma state. To understand the effect of extraction on a plasma sheath under a weak magnetic filter field, the time-dependent behavior of H- ion extraction from a negative ion source has been studied by particle-in-cell simulation in the collisionless limit. The simulation results have shown that the plasma sheath would undergo a transient process, in which there exists an edge electrostatic wave that propagates counterclockwise along the wall with a velocity of 4 mm/ns until it reaches the other side of extraction aperture. The thickness of the plasma sheath and the plasma potential both increase greatly at the final quasi-steady-state. For comparison, the results of extracting positive ions are also given.

Lan, Chao-Hui; Peng, Yu-Fei; Yang, Zhen; Long, Ji-Dong

2013-05-01

382

Temperature and magnetic field dependence of a Kondo system in the weak coupling regime  

PubMed Central

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. PMID:23817525

Zhang, Yong-hui; Kahle, Steffen; Herden, Tobias; Stroh, Christophe; Mayor, Marcel; Schlickum, Uta; Ternes, Markus; Wahl, Peter; Kern, Klaus

2013-01-01

383

Temporal variations of the earth's gravitational field from satellite laser ranging to LAGEOS  

Microsoft Academic Search

Monthly values of the J2 and J3 earth gravitational coefficients were estimated using LAGEOS satellite laser ranging data collected between 1980 and 1989. Monthly variations in gravitational coefficients caused by atmospheric mass redistribution were calculated using measurements of variations in surface atmospheric pressure. Results for correlation studies of the two time series are presented. The LAGEOS and atmospheric J2 time

R. S. Nerem; B. F. Chao; A. Y. Au; J. C. Chan; S. M. Klosko; N. K. Pavlis; R. G. Williamson

1993-01-01

384

The approximation of radiative effects in relativistic gravity - Gravitational radiation reaction and energy loss in nearly Newtonian systems  

NASA Technical Reports Server (NTRS)

An argument is presented to determine the accuracy with which a solution of Einstein's field equations of gravitation must be approximated in order to describe the dominant effects of gravitational radiation emission from weak-field systems. Several previous calculations are compared in the light of this argument, and some apparent discrepancies among them are resolved. The majority of these calculations support the 'quadrupole formulae' for gravitational radiation energy loss and radiation reaction.

Walker, M.; Will, C. M.

1980-01-01

385

YY Draconis and V709 Cassiopeiae two intermediate polars with weak magnetic fields  

E-print Network

We present data from long ROSAT HRI observations of the intermediate polars YY Dra and V709 Cas which show that V709 Cas, like YY Dra, exhibits a double-peaked X-ray pulse profile. Neither system shows evidence for X-ray beat period or orbital modulation, so both must be disc-fed accretors seen at low inclination angles. We argue that the short spin periods of the white dwarfs in these objects indicate that they have weak magnetic fields, so the radius at which material is captured by the field lines is relatively small. Consequently the footprints of the disc-fed accretion curtains on the white dwarf surface are large. The optical depths to X-ray emission within the accretion curtains are therefore lowest in the direction along the magnetic field lines, and highest in the direction parallel to the white dwarf surface, such that the emission from the two poles conspires to produce double-peaked X-ray pulse profiles. We emphasise that such a pulse profile is not a unique indicator of two-pole accretion however...

Norton, A J; Allan, A R; Hellier, C; Allan, Alasdair; Hellier, Coel

1999-01-01

386

Dynamics of a vertical flight in the stationary gravitational field of a celestial body: Post-newtonian corrections and gravitational redshift  

SciTech Connect

The standard problem of a radial motion of test particles in the stationary gravitational field of a spherically symmetric celestial body is solved and is used to determine the time features of this motion. The problem is solved for the equations of motion of general relativity (GR), and the time features are obtained in the post-Newtonian approximation, with linear GR corrections proportional to r{sub g}/r and {beta}{sup 2} (in the solution being considered, they are of the same order of smallness) being taken rigorously into account. Total times obtained by integrating the time differentials along the trajectories of motion are considered as the time features in question. It is shown that, for any parameters of the motion, the proper time (which corresponds to watches comoving with a test particle) exceeds the time of watches at rest (watches at the surface of the celestial body being considered). The mass and the radius of the celestial body, as well as the initial velocity of the test particle, serve as arbitrary parameters of the motion. The time difference indicated above implies a leading role of the gravitational redshift, which decreases somewhat because of the opposite effect of the Doppler shift. The results are estimated quantitatively for the important (from the experimental point of view) case of vertical flights of rockets starting from the Earth's surface. In this case, the GR corrections, albeit being extremely small (a few microseconds for several hours of the flight), aremeasurable with atomic (quantum) watches.

Imshennik, V. S., E-mail: imshennik@itep.r [Institute of Theoretical and Experimental Physics (Russian Federation)

2010-04-15

387

Detectors of gravitational waves  

NASA Astrophysics Data System (ADS)

Gravitational waves Motion of test bodies in a g.w. field Energy carried by gravitational waves Gravitational-wave sources Spinning star Double-star systems Fall into a Schwarzschild black hole Radiation from gravitational collapse Gravitational-wave detectors The nonresonant detectors The resonant detectors Electromechnical transducers Piezoelectric ceramic The capacitor The inductor Data analysis The Brownian noise The back-action The wide-band noise, data analysis and optimization The resonant transducer The Wiener-Kolmogoroff filter The cross-section and the effective temperature The antenna bandwidth The gravitational-wave experiments in the world The laser interferometers The resonant detectors

Pizzella, G.

388

Motion of the Three Viscoelastic Planets in Gravitational Field of the Mutual Attraction  

NASA Astrophysics Data System (ADS)

The translational-rotational motion of the three viscoelastic planets in gravitational field of the mutual attraction is studied. We model the planets by the homogeneous isotropic viscoelastic bodies, which in the natural non-deformed state occupy the spherical regions in the three-dimensional Eucliden space. The problem is being solved within the framework of the linear model of the theory of elasticity. The functional of the inner dissipative forces corresponds to the Kelvin-Voigt model. Each of the planets deforms due to its rotation around its mass center and its movement relative to the system's mass centre: the planet is being compressed endwise its axis of rotation and tidal humps appear aloud the lines binding the planet's mass centers. The changes in the planet's shape in their turn alter its translational-rotational movement. The system of equations of motion of the considered mechanical system is deduced from the D'Alembert-Lagrange variational principle and represents a complicated integro-differential system of equations in the banach space. The method of separation of motions is applied to the obtained system of equations and an approximate system of ordinary differential equations is deduced witch describes the translational-rotational motion of the planets, taking into account the perturbations caused by elasticity and dissipation. Unperturbed system of equations corresponds to the problem of the motion of the three rigid spheres interacting under the law of universal gravitation. Boundary problem of finding the vector of elastic displacement, describing forced oscillation of the planet under the influence of external forces and inertial forces of the translational motion is solved for each of the planets. Due to the planets' sphericity in their natural non-deformed state, the solutions of the boundary problems can be represented analytically as a sum of finite number of spherical functions. The solutions of the boundary problems are used to form the perturbing additives to the equations of motion. As a result of this procedure we get a vectorial perturbated system of ordinary differential equations on the radius of the planets' mass centers and the vectors of the planets' angular momentums. The stationary motion of the system of the three viscoelastic planets when the dissipative functional is equal to zero (the analogue of the triangular libration points in the classical three-body problem) is founded. According to this movement, the spheres move as one solid body with constant angular velocity, and the spheres' mass centers lie on a plan, orthogonal to the vector of angular velocity. If in unperturbed problem the mass centers of the planets form an equilateral triangle, the presence of perturbations leads to the emergence of the additives to stationary values of the triangle's side lengths, as the result of which the triangular in general case becomes inequilaterally. Due to the presence of dissipation of the system, the stationary triangular configuration is unsteady. This work is an extension of the series of articles [1-4] devoted to the problem of the viscoelastic spheres motion in gravitational field, the model problem for investigating the tidal evolution of the planets motion. The work is supported by RFBR, project 08-02-00367. References 1) Vilke V.G. The Motion of a Spherical Viscoelastic Body in the Central Newtonian Field of Forces // Appl. Math. Mech., 1980, Vol. 44, No 3, pp. 395-402. 2) Vilke V.G. Analytical and qualitative methods in the dynamics of the systems with infinite number of degrees of freedom. Moscow: Moscow State University, 1986. 3) Shatina A.V. Evolution of the Motion of a Viscoelastic Sphere in a Central Newtonian Field // Cosmic Research, 2001, Vol. 39, No 3, pp. 282-294. 4) Vilke V.G., Shatina A.V. Translational-Rotational Motion of a Viscoelastic Sphere in Gravitational Field of an Attracting Center and a Satellite // Cosmic Research, 2004, Vol. 42, No 1, pp. 95-106.

Vilke, V. G.; Shatina, A. V.; Shatina, L. S.

2009-04-01

389

Gravitational Lensing of Distant Field Galaxies by Rich Clusters: I. -- Faint Galaxy Redshift Distributions  

E-print Network

{}From deep optical images of three clusters selected by virtue of their X-ray luminosity and/or optical richness (1455+22; $z=0.26$, 0016+16; $z=0.55$ and 1603+43; $z=0.89$), we construct statistically-complete samples of faint field galaxies ($I \\leq 25$) suitable for probing the effects of gravitational lensing. By selecting clusters across a wide redshift range we separate the effects of the mean redshift distribution of the faint field population well beyond spectroscopic limits and the distribution of dark matter in the lensing clusters. A significant lensing signature is seen in the two lower redshift clusters whose X-ray properties are well-constrained. Based on these and dynamical data, it is straightforward to rule out field redshift distributions for $I \\leq 25$ which have a significant low redshift excess compared to the no evolution prediction, such as would be expected if the number counts at faint limits were dominated by low-$z$ dwarf systems. The degree to which we can constrain any high redshift tail to the no evolution redshift distribution depends on the distribution of dark matter in the most distant lensing cluster. In the second paper in this series, we use the lensing signal to reconstruct the full two-dimensional mass distribution in the clusters and, together with high resolution X-ray images, demonstrate that their structural properties are well-understood. The principal result is therefore the absence of a dominant low-$z$ dwarf population to $I \\leq25$.

Ian Smail; Richard S. Ellis; Michael J. Fitchett

1994-02-21

390

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

391

Effect of an AC magnetic field on the steady-state magnetization distribution in a weak ferromagnet  

Microsoft Academic Search

Possible steady-state magnetization distributions in a domain wall are found in a weak ferromagnet subjected to an ac magnetic\\u000a field. The character of the rotation of the magnetization vector in the domain wall is determined. It is predicted that domain\\u000a structures can be rearranged and reoriented under an ac magnetic field.

V. S. Gerasimchuk; A. A. Shitov

2008-01-01

392

Angular-spectral distribution of the emission of electrons moving in a plane weak-field magnetic undulator  

Microsoft Academic Search

The spontaneous emission of an electron moving in an infinite plane magnetic undulator is examined. The angular-spectral distribution of the emission is found in explicit form in the weak-field approximation for an arbitrary structure of the undulator field and is the product of a factor, which depends only on the harmonic, and a function of the angles and the velocity

Yu. M. Nikitina

1991-01-01

393

An Ensemble Solution for the Earth's time-varying gravitational field from the GRACE mission  

NASA Astrophysics Data System (ADS)

Several groups produce estimates of the Earth's time-varying gravitational field with data provided by the GRACE mission. While the solutions are similar, differences in processing strategies and tuning parameters result in solutions with regionally specific variations and error patterns. Thus it is unclear which solution is most suitable for different types of hydrological or oceanographic research. This project used four of the data center solutions to create an ensemble gravity model, attempting to harness the best characteristics of each solution to create an optimal model. Multiple methods were used to combine and analyze the individual and ensemble solutions. First a simple mean model was created; then the different solutions were weighted based on the formal error estimates published with the solutions as well as the monthly deviation from the simple mean. These ensemble models as well as the four individual data center solutions were evaluated with both statistical and external validation methods. The noise in the time series, scatter of solution over areas where little variation is expected, and comparison with hydrological models was examined. Initial results show that the ensemble models are effective at reducing noise in the models and better model hydrological processes. The ensemble models show slight differences, however all show improvement over any individual solution.

Sakumura, Carly; Bruinsma, Sean; Bettadpur, Srinivas

2013-04-01

394

Field Equation of Correlation Function of Mass Density Fluctuation for Self-Gravitating Systems  

E-print Network

We study the mass density distribution of the Newtonian self-gravitating system. Modeling the system either as a gas in thermal equilibrium, or as a fluid in hydrostatical equilibrium, we obtain the field equation of correlation function $\\xi(r)$ of the mass density fluctuation itself. It can apply to the study of galaxy clustering on Universe large scales. The observed $\\xi(r)\\simeq (r_0/r)^{1.7}$ follows from first principle. The equation tells that $\\xi(r)$ depends on the point mass $m$ and Jeans wavelength scale $\\lambda_{0}$, which are different for galaxies and clusters. It explains several longstanding, prominent features of the observed clustering: the profile of $\\xi_{cc}(r)$ of clusters is similar to $\\xi_{gg}(r)$ of galaxies but with a higher amplitude and a longer correlation length, the correlation length increases with the mean separation between clusters $r_0\\simeq 0.4d$ as the observed scaling, and on very large scales $\\xi_{cc}(r)$ exhibits periodic oscillations with a characteristic waveleng...

Zhang, Yang

2014-01-01

395

Magnetorotational instability of a weakly ionized accretion disk with vertical and azimuthal magnetic fields  

NASA Astrophysics Data System (ADS)

Magnetorotational instability of a weakly ionized accretion disk with an admixture of charged dust grains in a magnetic field with the axial and toroidal components is analyzed. The dispersion relation for perturbations perpendicular to the disk plane is derived with allowance for both the Hall current and the finite transverse plasma conductivity. It is shown that dust grains play an important role in the disk magnetic dynamics. Due to the effect of dust grains, the Hall current can reverse its direction as compared to the case of electron-ion plasma. As a result, the instability threshold shifts toward the short-wavelength range. Under certain conditions, electromagnetic fluctuations of any length can become unstable. It is established that the instability criterion for waves of any scale length is satisfied within a finite interval of the density ratio between the dust and electron plasma components. The width of this interval and the instability growth rate as functions of the plasma parameters and the configuration of the magnetic field in the disk are analyzed.

Prudskikh, V. V.

2014-05-01

396

Weak nonlinear analysis of magneto-convection under magnetic field modulation  

NASA Astrophysics Data System (ADS)

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

Bhadauria, B. S.; Kiran, Palle

2014-09-01

397

Weak lensing calibrated scaling relations for galaxy groups and clusters in the COSMOS and CFHTLS fields  

NASA Astrophysics Data System (ADS)

The outstanding problem in galaxy cluster count cosmology is to determine accurate scaling relations between survey observables and cluster mass. As indicated by the tension between Planck CMB and Sunya'ev-Zeldovich cluster count cosmology, the robustness of the cluster count results are dominated by the mass measurements used to calibrate the scaling relations. Here we present our work on the scaling of X-ray observables obtained with XMM-Newton to unbiased weak lensing masses in the COSMOS and CFHTLenS survey fields. Our recently published mass-temperature relation for low mass systems in the COSMOS field extended the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study. It showed that previous X-ray mass estimates can be biased low by up to 30-50%, which is the level required to bring Planck cosmology into consistency. We showed that the bias is not attributable to uncertainties in X-ray cross-calibration. Our recent inclusion of low mass clusters from CFHTLenS allows us to improve the constraint on the M-T relation and to study the effects of substucture. With the CFHTLenS extension, we also include the first lensing calibrated mass-luminosity relation for individual low mass systems.

Kettula, K.

2014-07-01

398

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

PubMed

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

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

2014-11-01

399

A New Jeans Resolution Criterion for (M)HD Simulations of Self-gravitating Gas: Application to Magnetic Field Amplification by Gravity-driven Turbulence  

Microsoft Academic Search

Cosmic structure formation is characterized by the complex interplay between gravity, turbulence, and magnetic fields. The processes by which gravitational energy is converted into turbulent and magnetic energies, however, remain poorly understood. Here, we show with high-resolution, adaptive-mesh simulations that MHD turbulence is efficiently driven by extracting energy from the gravitational potential during the collapse of a dense gas cloud.

Christoph Federrath; Sharanya Sur; Dominik R. G. Schleicher; Robi Banerjee; Ralf S. Klessen

2011-01-01

400

Non-Markovian analysis of the phase-damped Jaynes-Cummings model in the presence of a classical homogeneous gravitational field  

Microsoft Academic Search

In this paper, the non-Markovian dissipative dynamics of the phase-damped Jaynes-Cummings model in the presence of a classical homogeneous gravitational field will be analyzed. The model consists of a moving two-level atom simultaneously exposed to the gravitational field and a single-mode traveling radiation field in the presence of a non-Markovian phase damping mechanism. First, the non-Markovian master equation for the

M. Mohammadi

2009-01-01

401

ON THE GRAVITATIONAL FIELDS OF MACLAURIN SPHEROID MODELS OF ROTATING FLUID PLANETS  

SciTech Connect

Hubbard recently derived an important iterative equation for calculating the gravitational coefficients of a Maclaurin spheroid that does not require an expansion in a small distortion parameter. We show that this iterative equation, which is based on an incomplete solution of the Poisson equation, diverges when the distortion parameter is not sufficiently small. We derive a new iterative equation that is based on a complete solution of the Poisson equation and, hence, always converges when calculating the gravitational coefficients of a Maclaurin spheroid.

Kong, Dali; Zhang, Keke [Center for Geophysical and Astrophysical Fluid Dynamics and Department of Mathematical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom)] [Center for Geophysical and Astrophysical Fluid Dynamics and Department of Mathematical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom); Schubert, Gerald, E-mail: D.Kong@exeter.ac.uk, E-mail: kzhang@ex.ac.uk, E-mail: schubert@ucla.edu [Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA (United States)] [Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA (United States)

2013-02-10

402

Gravitational radiation fields in teleparallel equivalent of general relativity and their energies  

E-print Network

We derive two new retarded solutions in the teleparallel theory equivalent to general relativity (TEGR). One of these solutions gives a divergent energy. Therefore, we used the regularized expression of the gravitational energy-momentum tensor, which is a coordinate dependent. A detailed analysis of the loss of the mass of Bondi space-time is carried out using the flux of the gravitational energy-momentum.

G. G. L. Nashed

2011-01-05

403

Scalar Field as Dark Matter and Machian Cosmological Solution in the Generalized Scalar-Tensor Theory of Gravitation  

E-print Network

The Machian cosmological solution satisfying $\\phi =O(\\rho /\\omega)$ in the generalized scalar-tensor theory of gravitation with the varying cosmological constant is summarized. The scalar field $\\phi $ with the exponential potential is introduced as dark matter and the barotropic evolution of matter in the universe is discussed. As the universe expands, the coefficient $\\gamma $ of the equation of state approaches to -1/3 and the coupling function $\\omega (\\phi)$ diverges to $-\\infty $.

A. Miyazaki

2001-03-05

404

Transient gain property of a weak probe field in an asymmetric semiconductor coupled double quantum well structure  

NASA Astrophysics Data System (ADS)

The transient gain property of a weak probe field in an asymmetric semiconductor coupled double quantum well structure is reported. The transient process of the system, which is induced by the external coherent coupling field, shows the property of no inverse gain. We find that the transient behavior of the probe field can be tuned by the change of tunneling barrier. Both the amplitude of the transient gain and the frequency of the oscillation can be affected by the lifetime broadening.

Wang, Zhigang; Zheng, Zhiren; Yu, Junhua

2007-10-01

405

Constraints on strongly coupled chameleon fields from the experimental test of the weak equivalence principle for the neutron  

E-print Network

The chameleon scalar field is considered as a possible cause of accelerated expansion of the Universe. The chameleon field induces an interaction potential between a particle and a massive body. Previous experiments with falling cold neutrons intended to measure the neutron coherent scattering lengths and verification of the weak equivalence principle for the neutron are used to constrain the parameters characterizing the strength of the scalar chameleon fields.

Yu. N. Pokotilovski

2013-11-22

406

Relativistic Transverse Gravitational Redshift  

NASA Astrophysics Data System (ADS)

The parametrized post-Newtonian (PPN) formalism is a tool for quantitative analysis of the weak gravitational field based on the field equations of general relativity. This formalism and its ten parameters provide the practical theoretical foundation for the evaluation of empirical data produced by space-based missions designed to map and better understand the gravitational field (e.g., GRAIL, GRACE, GOCE). Accordingly, mission data is interpreted in the context of the canonical PPN formalism; unexpected, anomalous data are explained as similarly unexpected but apparently real physical phenomena, which may be characterized as ``gravitational anomalies," or by various sources contributing to the total error budget. Another possibility, which is typically not considered, is a small modeling error in canonical general relativity. The concept of the idealized point-mass spherical equipotential surface, which originates with Newton's law of gravity, is preserved in Einstein's synthesis of special relativity with accelerated reference frames in the form of the field equations. It was not previously realized that the fundamental principles of relativity invalidate this concept and with it the idea that the gravitational field is conservative (i.e., zero net work is done on any closed path). The ideal radial free fall of a material body from arbitrarily-large range to a point on such an equipotential surface (S) determines a unique escape-velocity vector of magnitude v collinear to the acceleration vector of magnitude g at this point. For two such points on S separated by angle d? , the Equivalence Principle implies distinct reference frames experiencing inertial acceleration of identical magnitude g in different directions in space. The complete equivalence of these inertially-accelerated frames to their analogous frames at rest on S requires evaluation at instantaneous velocity v relative to a local inertial observer. Because these velocity vectors are not parallel, a symmetric energy potential exists between the frames that is quantified by the instantaneous ? {v} = v\\cdot{d}? between them; in order for either frame to become indistinguishable from the other, such that their respective velocity and acceleration vectors are parallel, a change in velocity is required. While the qualitative features of general relativity imply this phenomenon (i.e., a symmetric potential difference between two points on a Newtonian `equipotential surface' that is similar to a friction effect), it is not predicted by the field equations due to a modeling error concerning time. This is an error of omission; time has fundamental geometric properties implied by the principles of relativity that are not reflected in the field equations. Where b is the radius and g is the gravitational acceleration characterizing a spherical geoid S of an ideal point-source gravitational field, an elegant derivation that rests on first principles shows that for two points at rest on S separated by a distance d << b, a symmetric relativistic redshift exists between these points of magnitude z = gd2/bc^2, which over 1 km at Earth sea level yields z ˜{10-17}. It can be tested with a variety of methods, in particular laser interferometry. A more sophisticated derivation yields a considerably more complex predictive formula for any two points in a gravitational field.

Mayer, A. F.

2012-12-01

407

Simulation of the flyby anomaly by means of an empirical asymmetric gravitational field with definite spatial orientation  

E-print Network

All anomalous velocity increases until now observed during the Earth flybys of the spacecrafts Galileo, NEAR, Rosetta, Cassini and Messenger have been correctly calculated by computer simulation using an asymmetric field term in addition to the Newtonian gravitational field. The specific characteristic of this term is the lack of coupling to the rotation of the Earth or to the direction of other gravitational sources such as the Sun or Moon. Instead, the asymmetry is oriented in the direction of the Earth's motion within an assumed unique reference frame. With this assumption, the simulation results of the Earth flybys Galileo1, NEAR, Rosetta1 and Cassini hit the observed nominal values, while for the flybys Galileo2 and Messenger, which for different reasons are measured with uncertain anomaly values, the simulated anomalies are within plausible ranges. Furthermore, the shape of the simulated anomaly curve is in qualitative agreement with the measured Doppler residuals immediately following the perigee of the first Earth flyby of Galileo. Based on the simulation, an estimation is made for possible anomalies of the recently carried out flybys of Rosetta at Mars on 25.02.07 and at the Earth on 13.11.07, and for the forthcoming Earth flyby on 13.11.09. It is discussed, why a so modelled gravitational field has not been discovered until now by analysis of the orbits of Earth satellites, and what consequences are to be considered with respect to General Relativity.

Hans-Juergen Busack

2007-11-18

408

A three-dimensional multidimensional gas-kinetic scheme for the Navier Stokes equations under gravitational fields  

NASA Astrophysics Data System (ADS)

This paper extends the gas-kinetic scheme for one-dimensional inviscid shallow water equations (K. Xu, A well-balanced gas-kinetic scheme for the shallow-water equations with source terms, J. Comput. Phys. 178 (2002) 533-562) to multidimensional gas dynamic equations under gravitational fields. Four important issues in the construction of a well-balanced scheme for gas dynamic equations are addressed. First, the inclusion of the gravitational source term into the flux function is necessary. Second, to achieve second-order accuracy of a well-balanced scheme, the Chapman-Enskog expansion of the Boltzmann equation with the inclusion of the external force term is used. Third, to avoid artificial heating in an isolated system under a gravitational field, the source term treatment inside each cell has to be evaluated consistently with the flux evaluation at the cell interface. Fourth, the multidimensional approach with the inclusion of tangential gradients in two-dimensional and three-dimensional cases becomes important in order to maintain the accuracy of the scheme. Many numerical examples are used to validate the above issues, which include the comparison between the solutions from the current scheme and the Strang splitting method. The methodology developed in this paper can also be applied to other systems, such as semi-conductor device simulations under electric fields.

Tian, C. T.; Xu, K.; Chan, K. L.; Deng, L. C.

2007-10-01

409

Non-thermal mechanism of weak microwave fields influence on neurons  

NASA Astrophysics Data System (ADS)

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

Shneider, M. N.; Pekker, M.

2013-09-01

410

Sensory transduction of weak electromagnetic fields: role of glutamate neurotransmission mediated by NMDA receptors.  

PubMed

Subliminal electromagnetic fields (EMFs) triggered nonlinear evoked potentials in awake but not anesthetized animals, and increased glucose metabolism in the hindbrain. Field detection occurred somewhere in the head and possibly was an unrecognized function of sensory neurons in facial skin, which synapse in the trigeminal nucleus and project to the thalamus via glutamate-dependent pathways. If so, anesthetic agents that antagonize glutamate neurotransmission would be expected to degrade EMF-evoked potentials (EEPs) to a greater extent than agents having different pharmacological effects. We tested the hypothesis using ketamine which blocks N-methyl-d-aspartate (NMDA) receptors (NMDARs), and xylazine which is an ??-adrenoreceptor agonist. Electroencephalograms (EEGs) of rats were examined using recurrence analysis to observe EEPs in the presence and absence of ketamine and/or xylazine anesthesia. Auditory evoked potentials (AEPs) served as positive controls. The frequency of observation of evoked potentials in a given condition (wake or anesthesia) was compared with that due to chance using the Fisher's exact test. EEPs were observed in awake rats but not while they were under anesthesia produced using a cocktail of xylazine and ketamine. In another experiment each rat was measured while awake and while under anesthesia produced using either xylazine or ketamine. EEPs and AEPs were detected during wake and under xylazine (P<0.05 in each of the four measurements). In contrast, neither EEPs nor AEPs were observed when anesthesia was produced partly or wholly using ketamine. The duration and latency of the EEPs was unaltered by xylazine anesthesia. The afferent signal triggered by the transduction of weak EMFs was likely mediated by NMDAR-mediated glutamate neurotransmission. PMID:24239718

Frilot, C; Carrubba, S; Marino, A A

2014-01-31

411

Expressions for modelling the bathymetry-generated gravitational field quantities by means of the spherical bathymetric functions  

NASA Astrophysics Data System (ADS)

The currently available global geopotential models and the global elevation and bathymetry data allow modelling the topography corrected and bathymetry stripped reference gravity field to a very high spectral resolution (up to degree 2160 of spherical harmonics) using methods for a spherical harmonic analysis and synthesis of the gravity field. When modelling the topography corrected and crust density contrast stripped reference gravity field, additional stripping corrections are applied due to the ice, sediment and other major known density contrasts within the Earth's crust. The currently available data of global crustal density structures have, however, a very low resolution and accuracy. The compilation of the global crust density contrast stripped gravity field is thus limited to a low spectral resolution, typically up to degree 180 of spherical harmonics. In this study, we derive the expressions used in forward modelling of the bathymetry-generated gravitational field quantities and the corresponding bathymetric stripping corrections to gravity field quantities by means of the spherical bathymetric (ocean bottom depth) functions. The expressions for the potential and its radial derivative are formulated for the adopted constant (average) ocean saltwater density contrast and for the spherical approximation of the geoid surface. The numerical examples are given for the gravitational potential and attraction generated by the ocean density contrast. These gravitational field quantities are computed from the coefficients of the Global Bathymetric Model (GBM) complete to degree and order 180. The GBM numerical coefficients describe globally the depths of the sea floor. The mean value of the ocean saltwater density contrast 1640 kg m-3 (i.e., difference of the reference mean crustal density 2670 kg m-3 and the mean ocean saltwater density 1030 kg m-3) is adopted. The GBM coefficients are generated from the 5×5 arc-min global bathymetry data of the ETOPO5 (provided by the NOAA's National Geophysical Data Centre). The computation is realized globally on a 1×1 arc-deg geographical grid at the Earth's surface.

Tenzer, Robert; Vajda, Peter; H, Hamayun; Novák, Pavel

2010-05-01

412

Red Shift from Gravitational Back Reaction  

E-print Network

Deviations from geodesic motion caused by gravitational radiation have been discussed in the last decades to describe the motion of particles or photons in strong fields around collapsed objects. On cosmological scale this effect, which in the first order is caused by the finite speed of gravitational interaction, is important also in the weak field limit. In this paper the energy loss by transfer to the gravitational potential is determined in a quasi-Newtonian approximation for the examples of a static Einstein universe and for an expanding universe with flat metric. In both cases the resulting red shift is a considerable fraction of the total red shift and requires an adjustment of the age and the matter composition in our models of the universe.

Ernst Fischer

2007-03-30

413

On the Influence of Weak Magnetic and Electric Fields on the Fluctuations of Ionic Electric Currents in Blood Circulation  

E-print Network

An analysis of a variety of existing experimental data leads to the conclusion on the existence of a resonance mechanism allowing weak magnetic fields to affect biological processes. These fields may either be static magnetic fields comparable in magnitude with the magnetic field of the earth or weak ultra-low frequency time-dependent fields. So far, a generally accepted theoretical model allowing one to understand the effect of magnetic and electric fields on biological processes is not available. By this reason, it is not clear which characteristics of the fields, like magnetic and electric field strength, frequency of change of the field, shape of the electromagnetic wave, the duration of the magnetic or electric influence or some particular combination of them, are responsible for the biological effect. In the present analysis it is shown that external time-independent magnetic fields may cause a resonance amplification of ionic electric currents in biological tissues and, in particular, in the vasculature system due to a Brownian motion of charges. These resonance electric currents may cause necrotic changes in the tissues or blood circulation and in this way significantly affect the biological organism. The magnitude of the magnetic fields leading to resonance effects is estimated, it is shown that it depends significantly on the radius of the blood capillaries.

Zakirjon Kanokov; Juern W. P. Schmelzer; Avazbek K. Nasirov

2009-04-07

414

The Origin of Gravitation  

NASA Astrophysics Data System (ADS)

In the natural world, people have discovered four kinds of forces: electromagnetic force, gravitation, weak force, and strong force. Although the gravitation has been discovered more than three hundred years, its mechanism of origin is unclear until today. While investigating the origin of gravitation, I do some experiments discover the moving photons produce gravitation. This discovery shows the origin of gravitation. Meanwhile I do some experiments discover the light interference fringes are produced by the gravitation: my discovery demonstrate light is a particle, but is not a wave-particle duality. Furthermore, applications of this discovery to other moving particles show a similar effect. In a word: the micro particle moving produce gravitation and electromagnetic force. Then I do quantity experiment get a general formula: Reveal the essence of gravitational mass and the essence of electric charge; reveal the origin of gravitation and the essence of matter wave. Along this way, I unify the gravitation and electromagnetic force. Namely I find a natural law that from atomic world to star world play in moving track. See website: https://www.lap-publishing.com/catalog/details/store/gb/book/978-3-8473-2658-8/mechanism-of-interaction-in-moving-matter

Zheng, Sheng Ming

2012-10-01

415

Enhanced collective focusing of intense neutralized ion beam pulses in the presence of weak solenoidal magnetic fields  

E-print Network

applied magnetic field. VC 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4722999] I of Physics. Related Articles Perturbative analysis of sheared flow Kelvin­Helmholtz instability in a weakly information on Phys. Plasmas Journal Homepage: http://pop.aip.org/ Journal Information: http://pop.aip.org/about/about_the_journal

Kaganovich, Igor

416

Cavities of Weak Magnetic Field Strength in the Wake of FTEs: Results from Global Magnetospheric MHD Simulations  

NASA Technical Reports Server (NTRS)

We use the global magnetohydrodynamic (MHD) code BATS-R-US to model multipoint observations of Flux Transfer Event (FTE) signatures. Simulations with high spatial and temporal resolution predict that cavities of weak magnetic field strength protruding into the magnetosphere trail FTEs. These predictions are consistent with recently reported multi-point Cluster observations of traveling magnetopause erosion regions (TMERs).

Kuznetsova, M. M.; Sibeck, D. G.; Hesse, M.; Wang, Y.; Rastaetter, L.; Toth, G.; Ridley, A.

2009-01-01

417

The influence of extremely weak alternating magnetic fields on the regeneration of planarians and the gravitropic response of plants  

Microsoft Academic Search

The influence of extremely weak alternating magnetic fields (EW AMF) directed collinearly to the static Earth magnetic field\\u000a on the rate of regeneration of planarians and the rate of gravitropic response in the stem segments of flax has been studied.\\u000a The value of bioeffects of EW AMF is determined by the parameter ?B\\u000a AC\\/f, where ? is the gyromagnetic ratio

N. A. Belova; A. M. Ermakov; A. V. Znobishcheva; L. K. Srebnitskaya; V. V. Lednev

2010-01-01

418

Gravitation and electromagnetism  

E-print Network

Maxwell's equations comprise both electromagnetic and gravitational fields. The transverse part of the vector potential belongs to magnetism, the longitudinal one is concerned with gravitation. The Coulomb gauge indicates that longitudinal components of the fields propagate instantaneously. The delta-function singularity of the field of the divergence of the vector potential, referred to as the dilatation center, represents an elementary agent of gravitation. Viewing a particle as a source or a scattering center of the point dilatation, the Newton's gravitation law can be reproduced.

V. P. Dmitriyev

2002-07-23

419

Exponential Lagrangian for the Gravitational Field and the problem of Vacuum Energy  

E-print Network

We will analyze two particular features of an exponential gravitational Lagrangian. On the one hand, while this choice of the Lagrangian density allows for two free parameters, only one scale, the cosmological constant, arises as fundamental when the proper Einsteinian limit is to be recovered. On the other hand, the vacuum energy arising from $f(R)$ theories such that $f(0)\

O. M. Lecian; G. Montani

2008-03-11

420

Temporal variations of the Earth's gravitational field from satellite laser ranging to Lageos  

Microsoft Academic Search

We have estimated monthly values of the J2 and J3 Earth gravitational coefficients using LAGEOS satellite laser ranging (SLR) data collected between 1980 and 1989. For the same time period, we have also computed corresponding estimates of the variations in these coefficients caused by atmospheric mass redistribution using surface atmospheric pressure estimates from the European Center for Medium Range Weather

R. S. Nerem; B. F. Chao; A. Y. Au; J. C. Chan; S. M. Klosko; N. K. Pavlis; R. G. Williamson

1993-01-01

421

Ideal gas in a strong gravitational field: Area dependence of entropy  

SciTech Connect

We study the thermodynamic parameters like entropy, energy etc. of a box of gas made up of indistinguishable particles when the box is kept in various static background spacetimes having a horizon. We compute the thermodynamic variables using both statistical mechanics as well as by solving the hydrodynamical equations for the system. When the box is far away from the horizon, the entropy of the gas depends on the volume of the box except for small corrections due to background geometry. As the box is moved closer to the horizon with one (leading) edge of the box at about Planck length (L{sub p}) away from the horizon, the entropy shows an area dependence rather than a volume dependence. More precisely, it depends on a small volume A{sub perpendicular}L{sub p}/2 of the box, up to an order O(L{sub p}/K){sup 2} where A{sub perpendicular} is the transverse area of the box and K is the (proper) longitudinal size of the box related to the distance between leading and trailing edge in the vertical direction (i.e. in the direction of the gravitational field). Thus the contribution to the entropy comes from only a fraction O(L{sub p}/K) of the matter degrees of freedom and the rest are suppressed when the box approaches the horizon. Near the horizon all the thermodynamical quantities behave as though the box of gas has a volume A{sub perpendicular}L{sub p}/2 and is kept in a Minkowski spacetime. These effects are: (i) purely kinematic in their origin and are independent of the spacetime curvature (in the sense that the Rindler approximation of the metric near the horizon can reproduce the results) and (ii) observer dependent. When the equilibrium temperature of the gas is taken to be equal to the horizon temperature, we get the familiar A{sub perpendicular}/L{sub p}{sup 2} dependence in the expression for entropy. All these results hold in a D+1 dimensional spherically symmetric spacetime. The analysis based on methods of statistical mechanics and the one based on thermodynamics applied to the gas treated as a fluid in static geometry, lead to the same results showing the consistency. The implications are discussed.

Kolekar, Sanved; Padmanabhan, T. [IUCAA, Pune University Campus, Ganeshkhind, Pune 411007 (India)

2011-03-15

422

Endothelial Cell Morphology and Migration are Altered by Changes in Gravitational Fields  

NASA Technical Reports Server (NTRS)

Many of the physiological changes of the cardiovascular system during space flight may originate from the dysfunction of basic biological mechanisms caused by microgravity. The weightlessness affects the system when blood and other fluids move to the upper body causing the heart to enlarge to handle the increased blood flow to the upper extremities and decrease circulating volume. Increase arterial pressure triggers baroreceptors which signal the brain to adjust heart rate. Hemodynarnic studies indicate that the microgravity-induced headward fluid redistribution results in various cardiovascular changes such as; alteration of vascular permeability resulting in lipid accumulation in the lumen of the vasculature and degeneration of the the vascular wall, capillary alteration with extensive endothelial invagination. Achieving a true microgravity environment in ground based studies for prolonged periods is virtually impossible. The application of vector-averaged gravity to mammalian cells using horizontal clinostat produces alterations of cellular behavior similar to those observed in microgravity. Similarly, the low shear, horizontally rotating bioreactor (originally designed by NASA) also duplicates several properties of microgravity. Additionally, increasing gravity, i.e., hypcrgravity is easily achieved. Hypergravity has been found to increase the proliferation of several different cell lines (e.g., chick embryo fibroblasts) while decreasing cell motility and slowing liver regeneration following partial hepatectomy. The effect of altered gravity on cells maybe similar to those of other physical forces, i.e. shear stress. Previous studies examining laminar flow and shear stress on endothelial cells found that the cells elongate, orient with the direction of flow, and reorganize their F-actin structure, with concomitant increase in cell stiffness. These studies suggest that alterations in the gravity environment will change the behavior of most cells, including vascular cells. However, few studies have been directed at assessing the effect of altered gravitational field on vascular cell fiction and metabolism, Using image analysis we examined how bovine aortic endothelial cells altered their morphological characteristics and their response to a denudation injury when cells were subjected to simulated microgravity and hypergravity.

Melhado, Caroline; Sanford, Gary; Harris-Hooker, Sandra

1997-01-01

423

Perspectives on Measuring the PPN Parameters ? and ? in Earth's Gravitational Field to High Accuracy with Champ/grace Models  

NASA Astrophysics Data System (ADS)

The current bounds on the PPN parameters ? and ? are on the order of 10-4-10-5. Many missions aimed at improving such limits by several orders of magnitude have been proposed, including LATOR, ASTROD, BepiColombo and GAIA. They involve the use of various spacecraft, to be launched along interplanetary trajectories, for measuring the post-Newtonian effects induced by solar gravity on the propagation of electromagnetic waves. In this paper, we investigate the requirements needed to measure the combination ? = (2 + 2? - ?)/3 entering the post-Newtonian Einstein pericenter precession ? {? } of a test particle to an accuracy on the order of 10-5 with a pair of drag-free spacecraft in Earth's gravitational field. It turns out that the latest gravity models from the dedicated CHAMP and GRACE missions would allow the reduction of the systematic errors of gravitational origin to just this demanding level of accuracy. With regard to the non-gravitational errors, the spectral noise density of the required drag-free sensors amounts to 10-8-10-9 cm s-2 Hz-½ over very low frequencies. Although not yet attainable with present technologies, such a level of compensation is much less demanding than those required for LISA, for instance. As a by-product, an independent measurement of the post-Newtonian gravitomagnetic Lense-Thirring effect with a 1% accuracy will be possible as well. The forthcoming Earth gravity models from CHAMP and GRACE will further reduce the systematic bias of gravitational origin in both such tests.

Iorio, Lorenzo

424