共查询到20条相似文献，搜索用时 15 毫秒
1.
Einstein field equations are considered for zero-curvature Robertson-Walker models in the case of a viscous fluid distribution interacting with zero-rest-mass scalar fields. Exact solutions are obtained for two different phases of the early universe viz. the inflationary phase and the radiation-dominated phase, by using the 'gamma-law' equation of state p = (-1). The index describing the material content varies continuously with cosmological time. The gravitational 'constant' and bulk viscosity are both allowed to depend on the cosmic time. Some physical properties of the cosmological models are also discussed. 相似文献
2.
Vladimir V. Sokolov 《Astrophysics and Space Science》1992,191(2):231-258
In the bounds of the consistent dynamic interpretation of gravitation (gravidynamics) a gravitational field has been divided into two components: scalar and tensor, each one interacting with its source by the same coupling constant. Consequently, a spherically-symmetrical gravitational field in vacuum generated by a massive object influences test bodies as an algebraic sum of attraction and repulsion. Field energy in vacuum around the source is also a sum of energies of two components — purely tensor and scalar ones of gravitation. At distances from a gravitating object much greater than its gravitational radius, energies of each separate field component are equal to each other at the same point of space.In the bounds of gravidynamics based on the so-called Einstein's linearized equation and proceeding from general principles of theory of classical fields a statement (a theorem) has been formulated on the static gravitational field of a collapsar: a spherically-symmetric object generating a static field in vacuum may always only occupy a finite, nonzero volume. 相似文献
3.
Quasinormal modes of a black hole with quintessence-like matter and a deficit solid angle: scalar and gravitational perturbations 总被引：1，自引：0，他引：1
Ping Xi 《Astrophysics and Space Science》2009,321(1):47-51
In the previous paper (Li et al. in Phys. Lett. B 666:125–130, 2008), we show the solutions of Einstein equations with static spherically-symmetric quintessence-like matter surrounding a global
monopole. Furthermore, this monopole become a black hole with quintessence-like matter and a deficit solid angle when it is
swallowed by an ordinary black hole. We study its quasinormal modes by WKB method in this paper. The numerical results show
that both the real part of the quasinormal frequencies and the imaginary part decrease as the state parameter w, for scalar and gravitational perturbations. And we also show variations of quasinormal frequencies of scalar and gravitational
fields via different ε (deficit solid angel parameter) and different ρ
0 (density of static spherically-symmetric quintessence-like matter at r=1), respectively. 相似文献
4.
M. Melek 《Astrophysics and Space Science》2000,272(4):417-421
Limits on cosmic time scale variations of gravitational and cosmological `constants' are studied. The study is based on a
function which can measure the temporal variation of the magnitude of the gradient of any scalar field defined inside a medium
exposed to a gravitational field. The cosmic time dependent scalar fields are taken to be the gravitational and cosmological
`constants'. The medium; in which those scalar fields are defined; is taken to be the spatially perturbed Friedman-Robertson-Walker
(FRW) expanding universe.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
L. C. Garcia de Andrade 《Astrophysics and Space Science》1992,198(1):79-83
The equivalence of Lagrangian containing gravitational, electromagnetic, scalar, and torsion fields is discussed. It is shown that the equation for the variation of the scalar field leads to a torsion wave equation generated by electromagnetic field leads to a torsion wave equation generated by electromagnetic fields. The system is proved to be equivalent to a Proca field coupling torsion non-minimally to a massive photon and having the scalar Higgs field as a strength of this photon-torsion coupling. The generalized Maxwell equations containing the scalar fields are obtained. The torsion potential around the Sun or a more massive collapsing star in the weak field limit is estimated. 相似文献
6.
It is shown that in the most general version of the bimetric scalar-tensor theory of gravitation, a spherically symmetric
vacuum gravitational field is static if the gravitational scalar does not depend on time. This result is generalized to certain
cases in which a source is present, including an electromagnetic field. Both branches of solutions with a variable and a constant
scalar field are considered.
Translated from Astrofizika, Vol. 40, No. 2, pp. 281–290, April–June, 1997. 相似文献
7.
It is show that axisymmetric stationary vacuum solutions of the general scalar tensor theory of gravitation proposed by Nordvedt and later discussed by Barker and others can be obtained from the solutions of the axisymmetric stationary Einstein vacuum fields and also from the axisymmetric static vacuum fields of the general scalar tensor theory. The scalar tensor analogue of the Kerr solution has been obtained. 相似文献
8.
The scalar field theory on the background of cosmological models with n(n ≥ 1) spaces of constant curvature is considered. We take the integrable case of Ricci flat internal spaces. The coupling between the scalar and the gravitational fields includes the minimal coupling as well as the conformal case. In the ground state of the scalar field we find the conditions for vacuum instability realized for most of the possible solutions to Einstein's equations if the coupling parameter takes appropriate values. For the excited states of the scalar field we show the induction of massive modes and discuss their properties. 相似文献
9.
R. W. John 《Astronomische Nachrichten》1987,308(1):9-26
First, in connection with their construction due to HADAMARD, the mathematical and physical meaning of covariant Green's functions in relativistic gravitational fields - according to EINSTEIN: on curved space-time - is discussed. Then, in the case of a general static spherically symmetric space-time the construction equations for a scalar Green's function are cast into symmetry-adapted form providing a convenient starting point for an explicit calculation of the Hadámard building elements. In applying the obtained basic scheme to a special one-parameter family of model metrics one succeeds in advancing to the explicit exact calculation of tail-term coefficients of a massless Green's function which are simultaneously coefficients in the Schwinger-De Witt expansion of the Feynman propagator for the corresponding massive Klein-Gordon equation on curved space-time. 相似文献
10.
Massimo Cerdonio Fabrizio De Marchi Roberto De Pietri Philippe Jetzer Francesco Marzari Giulio Mazzolo Antonello Ortolan Mauro Sereno 《Celestial Mechanics and Dynamical Astronomy》2010,107(1-2):255-264
The analysis of non-radiative sources of static or time-dependent gravitational fields in the Solar System is crucial to accurately estimate the free-fall orbits of the LISA space mission. In particular, we take into account the gravitational effects of Interplanetary Dust (ID) on the spacecraft trajectories. The perturbing gravitational field has been calculated for some ID density distributions that fit the observed zodiacal light. Then we integrated the Gauss planetary equations to get the deviations from the LISA Keplerian orbits around the Sun. This analysis can be eventually extended to Local Dark Matter (LDM), as gravitational fields are expected to be similar for ID and LDM distributions. Under some strong assumptions on the displacement noise at very low frequency, the Doppler data collected during the whole LISA mission could provide upper limits on ID and LDM densities. 相似文献
11.
Exact solutions are found for the static gravitational fields for a matter free space in a self-creation theory of gravitation proposed by G. A. Barber. 相似文献
12.
D. R. K. Reddy 《Astrophysics and Space Science》1988,140(1):161-164
A non-static plane-symmetric cosmological model in the presence of zero-mass scalar fields is obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density. Some properties of the model are discussed. 相似文献
13.
An exact Bianchi type-I cosmological model in the presence of zero-mass scalar fields is obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density. Some properties of the model are discussed. 相似文献
14.
An exact Bianchi type-III cosmological model in the presence of zero-mass scalar fields is obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density. Some properties of the model are also discussed. 相似文献
15.
Yu. V. Baryshev 《Astrophysics》1997,40(3):244-251
An equation is obtained for the cross section of a metal Weber cylinder for scalar gravitational waves, which are possible
within the framework of the field theory of gravitation. It is shown that the signals detected by the Amaldi and Weber antennas
during the explosion of supernova SN 1987A can be interpreted as the result of the action of scalar gravitational waves on
solid-state detectors. The required energy of the gravitational waves is about 1 M⊙c2. Together with the observed excess (about 1 %) of gravitational radiation from the binary system containing the pulsar PSR
1913+16, the signals from SN 1987A are the second piece of observational evidence for the actual existence of scalar gravitational
waves. The present-day, third-generation, solid-state antennas are capable of detecting scalar waves from events like SN 1987A
at a distance up to 5 Mpc. The expected level of the signal from SN 19931 is about 7 mK. An experimental test of the longitudinal
nature of scalar waves is possible using interferometric antennas based on free masses.
Translated from Astrofizika, Vol. 40, No. 3, pp. 377–389, August, 1997. 相似文献
16.
Self-consistent system of spinor, scalar and BI gravitational fields in presence of magneto-fluid and Λ term is considered.
Assuming that the expansion of the BI universe is proportional to the σ1 component of the shear tensor, exact solutions for the metric functions, as well as for scalar and spinor fields are obtained.
For a non-positive Λ, the initially anisotropic space–time becomes isotropic one in the process of expansion; whereas for
Λ > 0, an oscillatory mode of expansion of the BI model occurs.
PACS numbers: 03.65.Pm and 04.20.Ha 相似文献
17.
An exact Bianchi type-VI0 cosmological model in the presence of zero-mass scalar fields is obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density. Some physical properties of the model are discussed. 相似文献
18.
The environment, such as an accretion disk, could modify the signal of the gravitational wave from astrophysical black hole binaries. In this article, we model the matter field around intermediatemass binary black holes by means of an axion-like scalar field and investigate their joint evolution. In detail, we consider equal mass binary black holes surrounded by a shell of axion-like scalar field both in spherically symmetric and non-spherically symmetric cases, and with different strengths of the scalar field. Our result shows that the environmental scalar field could essentially modify the dynamics. Firstly,in the spherically symmetric case, with increase of the scalar field strength, the number of circular orbits for the binary black hole is reduced. This means that the scalar field could significantly accelerate the merger process. Secondly, once the scalar field strength exceeds a certain critical value, the scalar field could collapse into a third black hole with its mass being larger than that of the binary. Consequently,the new black hole that collapses from the environmental scalar field could accrete the binary promptly and the binary collides head-on with each other. In this process, there is almost no quadrupole signal produced, and, consequently, the gravitational wave is greatly suppressed. Thirdly, when the scalar field strength is relatively smaller than the critical value, the black hole orbit could develop eccentricity through accretion of the scalar field. Fourthly, during the initial stage of the inspiral, the gravitational attractive force from the axion-like scalar field could induce a sudden turn in the binary orbits, hence resulting in a transient wiggle in the gravitational waveform. Finally, in the non-spherical case, the scalar field could gravitationally attract the binary moving toward the center of mass for the scalar field and slow down the merger process. 相似文献
19.
Hiroshi Yoshida Kouji Nakamura Minoru Omote 《Monthly notices of the Royal Astronomical Society》2005,358(1):39-48
We study the continuous limit of the multiple gravitational lensing theory based on the thin lens approximation. We define a new, light-path dependent angular diameter distance and show that it satisfies the optical scalar equation. The distance provides relations between quantities used in gravitational lensing theory (the convergence, the shear and the twist terms) and those used in scalar optics theory (the rates of expansion, shear and rotation). 相似文献
20.
Exact Bianchi-type VIII and IX models in the presence of zero-mass scalar fields are presented, when the source of the gravitational field is a perfect fluid withP=. Some physical and geometrical properties of the models are also discussed. 相似文献