Viscous cosmology with matter creation in modified f(R,T) gravity

Abstract

The Friedmann–Robertson–Walker Universe containing viscous fluid and matter creation is considered in the modified f(R,T) theory of gravitation, which is an arbitrary function of the Ricci scalar R and the trace T of the energy-momentum tensor. We assume the bulk viscosity and the matter creation as two independent processes as discussed by Progogine et al. (1988, 1989). The effects of bulk viscosity and matter creation are investigated by considering the general form of bulk viscous coefficient ζ=ζ0+ζ1H and particle creation rate Γ(t)=3βH. Assuming a particular class of f(R,T)=R+2f(T), where f(T)=αT, various forms of the scale factor are obtained with constant and time-dependent bulk viscous coefficient using equation of state p=(γ−1)ρ. All possible (deceleration, acceleration and their transitions) evolutions of the Universe are discussed by constraining the models on β, ζ0 and ζ1 in case of time-dependent deceleration parameter for positive and negative values of α. A big-rip singularity is observed for γ<0 at a finite value of cosmic time with some restrictions on parameters. It is also noted that the finite time big-rip singularity can be removed for a specific range of α in phantom region. The role of bulk viscosity and matter creation are discussed in detail through the tables and graphs of variation of deceleration parameter and the scale factor.