Inhomogeneous early viscous fluid universe: A concrete model for dark energy

Abstract

In this paper the dynamical equation of the scale factor of the universe is investigated to describe the effect of bulk viscosity on the early evolution of the universe. We assume the inhomogeneous equation of state of the form [Formula: see text], where the adiabatic parameter [Formula: see text] varies with the scale factor [Formula: see text] proposed by Carvalho [Unified description of early universe, Int. J. Theor. Phys. 35 (1996) 2019] and [Formula: see text] is a time-dependent parameter in the framework of the flat FRW model. From this modified equation of state the exact solution of the field equations is obtained by considering the bulk viscosity is a linear combination of two terms of the form: [Formula: see text] and cosmological constant [Formula: see text], where [Formula: see text] and [Formula: see text] are constants, in which an inflationary phase is followed by the radiation dominated phase. For a special choice of the parameter we can explain the dark energy dominant universe and Friedmann equations are solved for two different phases of the universe and obtain the [Formula: see text]–[Formula: see text] relation.