Running vacuum cosmology with bulk viscous matter

Abstract

In this paper, we study the late accelerating expansion of the universe by incorporating bulk viscous matter with the running vacuum. The running vacuum is assumed to be varied as the square of the Hubble parameter ([Formula: see text]), while the coefficient of bulk viscosity of matter is taken to be proportional to the Hubble parameter ([Formula: see text]). We have analytically solved for the Hubble parameter and estimated the model parameters using the combined data set [Formula: see text]. The evolution of the cosmological parameters was analyzed, and the universe’s age is estimated to be 13.94[Formula: see text]Gyr. The evolution of the universe in the present model marked considerable improvement compared to bulk viscous matter-dominated models. The transition from matter-dominated decelerated phase to vacuum energy-dominated accelerating phase occurred at a transition redshift, [Formula: see text], and the evolution asymptotically approaches a de Sitter epoch. We have obtained the coefficient of bulk viscosity of the matter component as [Formula: see text] which is two orders of magnitude less than the value predicted by most of the bulk viscous matter-dominated models. The statefinder analysis distinguishes our model from the [Formula: see text]CDM model at present, and the [Formula: see text] trajectory reveals the quintessence behavior of the vacuum energy. The model was found to satisfy the generalized second law of thermodynamics, and the entropy is maximized in the far future evolution.