New agegraphic dark energy model with bulk viscosity

Abstract

New agegraphic dark energy (NADE) model with bulk viscosity is proposed by assuming that the universe is composed of the NADE and dark matter, and both the dark components have a bulk viscosity. At the matter-dominated epoch, the density parameter and the equation of state (EoS) of the viscous NADE are given by [Formula: see text] and [Formula: see text], respectively, where [Formula: see text] and [Formula: see text] are viscosity parameters. In the late time [Formula: see text], the NADE dominates [Formula: see text] and [Formula: see text]. Owing to the special analytic features at the matter-dominated epoch for the viscous NADE model, the initial condition [Formula: see text] at [Formula: see text] is used to solve the differential equation of [Formula: see text], and the other physical quantities can be obtained correspondingly. We also find that the viscosity of dark matter affects the current density and the start time of the cosmic acceleration. However, in the late time [Formula: see text] only depends on the viscosity of the dark energy. Furthermore, we investigate the viscous NADE model by means of statefinder diagnostic. The viscosity of dark matter significantly affects the evolution of the statefinder parameters. Therefore, the bulk viscosity plays a significant role in the cosmological evolution.