共查询到20条相似文献，搜索用时 31 毫秒
1.
We present an exact solution of the Brans-Dicke equations for cosmological models of Bianchi type VI0 with stiff matter. The solution represents anisotropic universe which has its analogy in Einstein's theory. The corresponding result for a plane symmetry Bianchi type I model is obtained as a special case. 相似文献
2.
J. P. Singh 《Astrophysics and Space Science》2008,318(1-2):103-107
In this paper, we investigate a variation law for Hubble’s parameter in the curved, expanding background of spatially homogeneous, anisotropic Bianchi type I space-time. By choosing a particular form of the generalized Hubble’s parameter, which gives an early deceleration and late time acceleration for the anisotropic Bianchi type I cosmological model, we show that the model approaches isotropy and tends to a de Sitter universe at late times. The cosmological term asymptotically tends to a genuine cosmological constant and the solution is consistent with recent observations. 相似文献
3.
《New Astronomy》2022
In this study, we build up a general formalism for tilted N-component fluid form to investigate the isotropization features of the Bianchi-type models excluding Bianchi-IX. We applied this formalism to Bianchi type I and V models analytically and numerically using the metric approach of Einstein field equations. It is found that only the stiff fluid for Bianchi I model does not isotropize, in the absence of cosmological constant. Other Bianchi type I and V models become isotropic regardless of the type of the fluid or how much component it has. The result does not change with the existence of a cosmological constant. 相似文献
4.
An exact solution of the vacuum Brans-Dicke field equations is obtained for the metric tensor of a spatially-homogeneous and anisotropic Bianchi type I configuration. The solution has no analogy in Einstein's theory for the layer values of the BD parameter. Some properties of the solution are discussed. 相似文献
5.
Dieter Lorenz-Petzold 《Astrophysics and Space Science》1985,115(1):197-198
The inhomogeneous Bianchi type-VI0 perfect fluid solution given recently by Roy and Narain (1985) is shown to be identical with the solution first given by Tomita (1978). 相似文献
6.
G. Mukherjee 《Journal of Astrophysics and Astronomy》1983,4(4):295-300
The Bianchi type I cosmological models have been extensively studied in the past especially as examples of the homogeneous shearing universe. This paper presents a tilted universe solution admitting this group of motion where the velocity field is shear-free but there is an energy flux term. 相似文献
7.
We present exact solutions of a Bianchi type VI0 viscous fluid cosmological model. It is a generalization of the model proposed by Banerjee and Santos (1983) for Bianchi type I. 相似文献
8.
C. Lozanovski 《Astrophysics and Space Science》2014,351(1):371-376
A class of purely magnetic diagonal Bianchi type VI h Cosmologies is investigated. If the energy-momentum tensor is specialized to that of a perfect fluid with (non-zero) heat-flux, with respect to the co-moving fluid 4-velocity, then the only solution is of Bianchi type V and un-physical. Further, it is shown that if certain metric functions are functionally related then the spacetime is conformally flat. Unfortunately, all these results (somewhat indirectly) invalidate a claim by Kumar and Srivastava of finding a non-conformally flat purely magnetic diagonal Bianchi type V cosmology. Finally, we consider non-zero anisotropic pressure in place of non-zero heat flux. It is shown that these spacetimes are necessarily Bianchi type VI 0. We highlight the fact that there is a known solution that generalizes the purely magnetic perfect fluid Wylleman-Van den Bergh spacetime. Physical properties of this solution are discussed. 相似文献
9.
A procedure to generate new exact solutions to Einstein equations for perfect fluids is applied to LRS Bianchi type I line-element. Starting from some known solutions a class of new perfect fluid solutions of Bianchi type I are presented. The physical and kinematical properties of spatially homogeneous and anisotropic cosmological models are studied. 相似文献
10.
A. M. Anile 《Astrophysics and Space Science》1974,29(2):415-426
The relativistic transfer equation for polarised radiation is solved in an axisymmetric Bianchi type I universe. Previous
results concerning the linear polarisation induced in the cosmic microwave background radiation by Thomson scattering in an
anisotropically expanding universe are confirmed.
Work partly done at the Osservatorio Astrofisico, Catania (Italia). 相似文献
11.
Sigbjørn Hervik 《Astrophysics and Space Science》2003,283(4):673-678
The early time behaviour of brane-world models is analysed in the presence of anisotropic stresses. It is shown that that
the initial singularity cannot be isotropic, unless there is also an isotropic fluid stiffer than radiation present. Also,
a magnetic Bianchi type I brane-world is analysed in detail. It is known that the Einstein equations for the magnetic Bianchi
type I models are in general oscillatory and are believed to be chaotic, but in the brane-world model this chaotic behaviour
does not seem to be possible.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
In this note a new solution of the BD field equations, for a Bianchi type V space-time, is obtained. The solution has its general relativistic analogue. Some properties of the solution are also discussed. 相似文献
13.
We present a solution to the Einstein field equations for a massless scalar field in a Bianchi type-V spacetime, which can be interpreted as a solution for a perfect fluid with the equation of state of stiff matter. This solution complements a solution previously given by us for an anisotropic fluid. 相似文献
14.
Bianchi type I cosmological models are studied that contain a nonbarotropic relativistic Boltzmann gas. The effect of a cosmological
constant is considered too. In the limit of small temperatures the general solution of the Einstein gravitational field equations
can be expressed in an exact closed parametrical form. At final stages, depending on the presence or absence of the cosmological
constant, cosmologies are driven to an isotropic inflationary de Sitter Universe or to an isotropic Friedmann era.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
An LRS Bianchi type I string dust cosmological model with and without bulk viscosity following a method used by Letelier and
Stachel, is investigated. To get a determine solution, it is assumed that σ∝θ whereσ is shear and θ is scalar of expansion
and which leads to A =αBn were n is a constant. The physical and geometrical aspects of the model are also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
A class of exact solutions of Eistein's field equations with attractive massive scalar field in LRS Bianchi type I space time
is obtained. It is shown that how the dynamical importance of the scalar field and the shear change in the course of evolution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Bianchi type I, III, V, VI0, and Kantowski-Sachs type models have been investigated in a scalar tensor theory developed by Saez and Ballester (1985) and Saez (1985). The dynamical behaviour of the models has also been analyzed. 相似文献
18.
Astrophysics - We used modified holographic Ricci dark energy to find anisotropic LRS Bianchi type I cosmological model in five-dimensions based on Lyra geometry. The exact solutions of the... 相似文献
19.
Tilted Bianchi Type I cosmological model for perfect fluid distribution in presence of magnetic field, is investigated. To
get a determinate solution, it has been assumed that the universe is filled with stiff perfect fluid distribution together
with A=(BC)
n where A,B,C are metric potentials and n is a constant. The behaviour of the model in presence and absence of magnetic field is discussed. The various physical and
geometrical aspects of the model, is also discussed. It has been shown that tilted nature of the Bianchi Type I model is preserved
due to magnetic field.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
We obtain some cosmological models that are exact solutions of Einstein's field equations. The metric utilized is Marder's metric which is Bianchi Type I and the curvature source is a cloud of strings which are one dimensional objects. Bianchi type cosmological models play an important role in the study of the universe on a scale which anisotropy is not ignored. In this paper we have investigated the effect of cosmic strings on the cosmic microwave background anisotropy. Various physical and geometrical properties of the model are also discussed. The solutions have reported that the cosmic microwave background anisotropy may due to the cosmic strings. 相似文献