R. Chaubey

An interacting two-fluid scenario for dark energy in a Bianchi type-I cosmological model

We study the evolution of the dark energy parameter within a Bianchi type-I cosmological model filled with barotropic fluid and dark energy. The solutions have been obtained for power law and exponential forms of the expansion parameter (they correspond to a constant deceleration parameter in general relativity). After a long time, the models tend to be isotropic under certain conditions.

The general class of Bianchi cosmological models with viscous fluid and particle creation in Brans-Dicke theory

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 deceleration 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.

Bianchi type I cosmological model with a cosmological constant (Λ) in creation-field cosmology

Solutions of Einstein’s field equations with a cosmological constant Λ in the presence of a creation field have been obtained for Bianchi type I cosmological models in the Hoyle-Narlikar creation field theory. The cosmological parameters are calculated. We examine the nature of the creation field and the cosmological constant which dominate at the early stage of the universe, but they do not survive for a long time and finally tend to zero at large cosmic times.

Bianchi type-VIo Universe with wet dark fluid

The Bianchi type- VIo universe filled with dark energy from a wet dark fluid has been considered. A new equation of state for the dark energy component of the universe has been used. It is modeled on the equation of state p=γ(ρ-ρ﹡) which can describe a liquid, for example water. The exact solutions to the corresponding field equations are obtained in quadrature form. The solution for constant deceleration parameter have been studied in detail for power-law and exponential forms both. The case γ=0, γ=1, and γ=1/3 have been also analysed.

Kantowski-Sachs and Bianchi type models with a general non-canonical scalar field

The paper deals with spatially homogeneous and anisotropic Kantowski-Sachs and Bianchi universes with a general non-canonical scalar field with the Lagrangian L = F(X) − Ω(ϕ), where

Bianchi Type-III and Kantowski-Sachs Universes with Wet Dark Fluid

X = \frac{1}{2}{\phi _i}{\phi ^i}

Bouncing cosmologies in Brans–Dicke theory

X=12ϕiϕi. We discuss a general non-canonical scalar field in three different cosmologies: (i) cosmology with a constant potential, Ω(ϕ) = Ω0 = const, (ii) cosmology with a constant equation-of-state parameter, i.e., γϕ = const, and (iii) cosmology with a constant speed of sound, i.e., cs2 = const. For a constant potential, we have shown that the k-essence Lagrangian and the Lagrangian of the present model are equivalent. Dissipation of anisotropy, when the universe is filled with a general non-canonical scalar field, is investigated. The existence of an average bounce in Kantowski-Sachs and locally rotationally symmetric Bianchi-I and Bianchi-III models is discussed in detail.

k-essence cosmologies in Kantowski–Sachs and Bianchi space–times

We consider an anisotropic cosmological model with cold dark matter and a scalar field, where one component of the scale factor is taken in the framework of (i) a logamediate scenario (ii) an intermediate scenario, and (iii) an emergent scenario. In all cases we find expressions for the Chameleon field, Chameleon potential, the statefinder diagnostic pair, i.e., the {r, s} parameters, and the slow-roll parameters. All physical parameters are calculated and discussed in all three cases. It is also shown how the Chameleon field is directly affected by the role of curvature of space time. At large times (t→∞) the models tend asymptotically to an isotropic Friedmann–Robertson–Walker cosmological model.