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1.
This paper deals with the general class of Bianchi cosmological models with bulk viscosity and particle creation described by full causal thermodynamics in Brans-Dicke theory. We discuss three types of average scale-factor solutions for the general class of Bianchi cosmological models by using a special law for the deceler- ation parameter which is linear in time with a negative slope. The exact solutions to the corresponding field equations are obtained in quadrature form and solutions to the Einstein field equations are obtained for three different physically viable cosmologies. All the physical parameters are calculated and discussed in each model. 相似文献
2.
C. P. Singh 《Astrophysics and Space Science》2011,331(1):337-342
The evolution and dynamics of a locally-rotationally-symmetric (LRS) Bianchi type-V space-time cosmological models are discussed
with variable gravitational and cosmological “constants” in context of the particle creation. We present the exact solutions
of Einstein field equations by using a power-law form of the average scale factor of the metric in the case of the particle
creation and in the absence of particle creation. The solution describes the particle and entropy generation in the anisotropic
cosmological models. The particle creation rate is uniquely determined by the variation of gravitational and cosmological
“constants”. We observe that the variable gravitational constant does not necessarily imply particle creation. In a generic
situation, models can be interpolated between different phases of the universe. The dynamical behaviors of the solutions and
kinematical parameters of the model are discussed in detail. 相似文献
3.
The solutions of Einstein’s equations with cosmological constant (Λ) in the presence of a creation field have been obtained for general class of anisotropic cosmological models. We have obtained the cosmological solutions for two different scenarios of average scale factor. In first case, we have discussed three different types of physically viable cosmological solutions of average scale factor for the general class of Bianchi cosmological models by using a special law for deceleration parameter which is linear in time with a negative slope. In second case, we have discussed another three different forms of cosmological solutions by using the average scale factor in three different scenarios like Intermediate scenario, Logamediate scenario and Emergent scenario. All physical parameters are calculated and discussed in each physical viable cosmological model. We examine the nature of creation field and cosmological constant is dominated the early Universe but they do not survive for long time and finally tends to zero for large cosmic time t. We have also discussed the all energy conditions in each cases. 相似文献
4.
C. P. Singh 《Astrophysics and Space Science》2009,323(2):197-203
In this paper we consider a locally-rotationally-symmetric (LRS) Bianchi type-V perfect fluid model with variable cosmological
‘constant’ representing the energy density of vacuum. The field equations are solved with and without heat conduction by using
a variation law for the mean Hubble parameter, which is related to the average scale factor of the metric and yields a constant
value of the deceleration parameter. A constant value of deceleration parameter generates power-law form of average scale
factor which is used to find the exact solutions with and without heat conduction with decaying vacuum density. The solutions
presented here satisfy all the necessary conditions for the physically acceptability. The thermodynamical relations in decaying
vacuum fluid model are also studied in detail. 相似文献
5.
A spatially homogeneous and anisotropic Bianchi type-V space–time is considered in the frame work of a scale covariant theory of gravitation proposed by Canuto et al. (Phys. Rev. Lett. 39:429, 1977) when the matter sources is a bulk viscous fluid containing one dimensional cosmic strings. Using some physically plausible conditions, we have obtained a determinate solution of the field equations of the theory which represents a Bianchi type-V bulk viscous string cosmological model in this theory. Some physical and kinematical properties of the model are also discussed. 相似文献
6.
V. U. M. Rao T. Vinutha M. Vijaya Shanthi G. Sree Devi Kumari 《Astrophysics and Space Science》2008,317(1-2):89-94
Exact Bianchi type-V cosmological models are presented in Einstein’s theory of gravitation with cosmological constant Λ in case of perfect fluid distribution. Also obtained Bianchi type-V cosmological models in a scalar-tensor theory of gravitation proposed by Saez and Ballester (1986) in case of perfect fluid distribution using and without using negative constant deceleration parameter. Some physical and geometrical properties of the models are also discussed. 相似文献
7.
In the present paper we study some new aspects of the Bianchi type-V space time. The Electric and Magnetic parts of Weyl tensors are calculated in terms of tilted congruence and discussed the purely magnetic Weyl tensor. Einstein field equations for purely magnetic space time are obtained and solution of such field equations called purely magnetic solution. To get deterministic solutions of the field equations we consider a new law of variation of average scale factor which yields time dependent deceleration parameter. Certain physical and geometrical properties of the model are also discussed. 相似文献
8.
In this paper an exact solution of the Brans-Dicke field equations in the presence of stiff matter is obtained for the Bianchi type-I cosmological space-time. The new solution represents an anisotropic homogeneous cosmological model which tends to anisotropic expansion. The behaviour of the solution near the singularities and late stages of the expansion is discussed. 相似文献
9.
10.
J. K. Singh 《Astrophysics and Space Science》2008,314(4):361-365
Bianchi type-V anisotropic cosmological models have been studied in the theory based on Lyra’s geometry in normal gauge. The
physical and kinematical behaviors of the models have been discussed in the presence and absence of the magnetic field.
相似文献
11.
We have studied anisotropic and homogeneous Locally Rotationally Symmetric (LRS) Bianchi type-I, Bianchi type-V, Bianchi type-III, Bianchi type-VI0, and Kantowaski–Sachs space-times with variable equation of state (EoS) parameter (w) in General Relativity. A special form of deceleration parameter (q) which gives an early deceleration and late time accelerating cosmological model has been utilized to solve the field equations. The geometrical and physical aspects of the models are also studied. 相似文献
12.
R. K. Tiwari 《Astrophysics and Space Science》2008,318(3-4):243-247
Einstein field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for Bianchi type-I universe by assuming the cosmological term proportional to the Hubble parameter. This variation law for vacuum density has recently been proposed by Schützhold on the basis of quantum field estimations in the curved and expanding background. The model obtained approaches isotropy. The cosmological term tends asymptotically to a genuine cosmological constant, and the model tends to a deSitter universe. We obtain that the present universe is accelerating with a large fraction of cosmological density in the form of cosmological term. 相似文献
13.
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
14.
The spatially-homogeneous and anisotropic cosmological model in self-creation theory of gravitation proposed by Barber, is obtained in the presence of perfect fluid with disordered radiation and the metric is of Bianchi type-V. Some physical properties of the model are discussed. 相似文献
15.
Solutions of Brans-Dicke field equations are obtained when the source of the gravitational field is a perfect fluid with pressure equal to energy density and the metric is cylindrically symmetric of Marder-type. Various physical and geometrical properties of the model have been discussed. Finally the solutions have been transformed to the original form of Brans-Dicke (1961) theory and then through unit transformation to a general form. 相似文献
16.
Exact solutions for Bianchi type-II cosmological model in the Jordan Brans-Dicke scalar-tensor theory of gravilation are obtained. We discuss the behaviour of these solutions and compare them with others recently published.Supported in part by DGICSA SEP grant C90-03-0347. 相似文献
17.
Aroonkumar Beesham 《Astrophysics and Space Science》1993,203(1):169-170
In a recent paper, the general vacuum Bianchi type-V solution in Brans-Dicke theory was presented and the isotropization of the model was discussed. It is pointed out that this solution was derived previously. Some remarks are made about the isotropization of the model. 相似文献
18.
Field equations are obtained with the aid of higher dimensional Bianchi type-I cosmological model in scale covariant theory
of gravitation in the context of cosmic strings. We present here isotropic and anisotropic solutions of the field equations
and some physical implications of these solutions are briefly discussed. 相似文献
19.
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
20.
J.K. Singh 《Astrophysics and Space Science》2002,281(3):585-594
The Bianchi type-V cosmological solutions of massive strings in the presence and absence of the magnetic field are investigated.
The physical behavior of these models are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献