Einstein＇s field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for the Bianchi type-I universe by assuming that the cosmological term is proportional...Einstein＇s field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for the Bianchi type-I universe by assuming that the cosmological term is proportional to R-m （R is a scale factor and m is a constant）.A variety of solutions are presented.The physical significance of the respective cosmological models are also discussed.展开更多
We consider spatially homogeneous and anisotropic Bianchi type V space- time with a bulk viscous fluid source, and time varying gravitational constant G and cosmological term A. The coefficient of bulk viscosity ζ is...We consider spatially homogeneous and anisotropic Bianchi type V space- time with a bulk viscous fluid source, and time varying gravitational constant G and cosmological term A. The coefficient of bulk viscosity ζ is assumed to be a simple linear function of the Hubble parameter H （i.e. ζ = ζ0 ＋ ζ1H, where ζ0 and ζ1 are constants）. The Einstein field equations are solved explicitly by using a law of varia- tion for the Hubble parameter, which yields a constant value of the deceleration pa- rameter. Physical and kinematical parameters of the models are discussed. The models are found to be compatible with the results of astronomical observations.展开更多
文摘Einstein＇s field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for the Bianchi type-I universe by assuming that the cosmological term is proportional to R-m （R is a scale factor and m is a constant）.A variety of solutions are presented.The physical significance of the respective cosmological models are also discussed.
文摘We consider spatially homogeneous and anisotropic Bianchi type V space- time with a bulk viscous fluid source, and time varying gravitational constant G and cosmological term A. The coefficient of bulk viscosity ζ is assumed to be a simple linear function of the Hubble parameter H （i.e. ζ = ζ0 ＋ ζ1H, where ζ0 and ζ1 are constants）. The Einstein field equations are solved explicitly by using a law of varia- tion for the Hubble parameter, which yields a constant value of the deceleration pa- rameter. Physical and kinematical parameters of the models are discussed. The models are found to be compatible with the results of astronomical observations.
