R. K. Tiwari

Bianchi type-I cosmological models with perfect fluid in general relativity

Einsteins field equations with variable gravitational and cosmological con- stants 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.

Noncommutative geometry inspired 3 -dimensional charged black hole solution in an anti-de Sitter background spacetime

We report a

Transit cosmological models with domain walls in f(R, T) gravity

3

Collineations of the curvature tensor in general relativity

3-D charged black hole solution in an anti-de Sitter space inspired by noncommutative geometry. In this construction, the black hole exhibits two horizons, which turn into a single horizon in the extreme case. We investigate the impacts of electromagnetic field on the location of the event horizon, mass and thermodynamic properties such as Hawking temperature, entropy, and heat capacity of the black hole. The geodesics of the charged black hole are also analyzed.

Some Bulk-Viscous Solutions in a First-Order Theory

A five dimensional Kaluza-Klein space-time is considered in the presence of a perfect fluid source with variable G and Λ. An expanding universe is found by using a relation between the metric potential and an equation of state. The gravitational constant is found to decrease with time as G∼t−(1−ω) whereas the variation for the cosmological constant follows as Λ∼t−2,

PERFECT FLUID BIANCHI TYPE I COSMOLOGICAL MODELS WITH TIME VARYING G AND Λ

\Lambda \sim (\dot{R}/R)^{2}

Some Robertson-Walker models with time dependent G and Λ

and

Bianchi type-I models in self-creation cosmology with constant deceleration parameter

\Lambda \sim \ddot{R}/R