FRW Cosmology for Decay Law with Time-varying G, Λ & q

Abstract

In this paper, we study the Einstein’s field equations with time-dependant gravitational and cosmological constants in homogeneous and isotropic flat FRW metric containing the matter of the form perfect fluid which conserves the matter tensor. Solutions of the Einstein field equations are obtained by considering the time varying deceleration parameter q. For this we study the FRW mode with G and Λ by using decay laws Gρ ∝ Λ/8p and Λ ∝ H², and consider the γ-fluid equation of state. Numerical studies of the evolution of the scale-factor have tended to focus on the radiation like case (γ = ¾), the dust-like case (γ = 1) and stiff matter (γ = 1). Some physical and kinematical parameters are studied.