New holographic dark energy model with bulk viscosity in f(R, T) gravity

Abstract

In this paper, we present the bulk viscous phenomena to mimic new holographic dark energy behavior in modified f(R, T) gravity. We assume the bulk viscosity coefficient, $$\zeta$$ in the form of $$\zeta = \zeta_{0} + \zeta_{1} H$$ , where $$\zeta_{0} , \zeta_{1}$$ are positive constants and H is the Hubble parameter. We obtain the exact solution of the scale factor and classify all the possible scenarios (deceleration, acceleration and their transition) of the evolution of the Universe. It is observed that the model transits from the decelerated phase to accelerated phase in early or late time depending on the values of viscous terms. For large values of viscous terms, the model always accelerates throughout the evolution. Furthermore, we also analyze two diagnostic parameters, statefinder $$\left\{ {r,s} \right\}$$ and Om to discriminate our model with the other existing dark energy models. The evolutions of these diagnostics are shown in $$r - s,r - q$$ and Om − z planes. It is found that the behavior of trajectories in different planes depends on the bulk viscous coefficients. A small combination of $$\zeta_{0}$$ and $$\zeta_{1}$$ gives the quintessence-like behavior, whereas a large combination gives Chaplygin gas-like model. However, the model approaches the ΛCDM model in the late time evolution of the Universe. The value of the effective equation of state parameter comes to be − 0.9745 which is very close to the observational data. The entropy and generalized second law of thermodynamics are valid under certain constraints. The analysis shows that the dark energy phenomena may be explained in the presence of bulk viscosity in the modified theory of gravity.