Viscous Ricci Dark Energy

TL;DR

This paper explores how incorporating bulk viscosity into the Ricci dark energy model can resolve the age problem of the universe, particularly reconciling the age of old objects at high redshift.

Contribution

It introduces a viscous Ricci dark energy model and demonstrates that viscosity alleviates the universe's age problem present in the non-viscous model.

Findings

Viscosity extends the universe's age, resolving conflicts with old high-redshift objects.

The viscous RDE model better fits the age constraints of ancient objects.

Viscosity effects are significant in cosmological models with dark energy.

Abstract

We investigate the viscous Ricci dark energy (RDE) model by assuming that there is bulk viscosity in the linear barotropic fluid and the RDE. In the RDE model without bulk viscosity, the universe is younger than some old objects at some redshifts. Since the age of the universe should be longer than any objects in the universe, the RDE model suffers the age problem, especially when we consider the object APM 08279+5255 at $z=3.91$, whose age is $t = 2.1$ Gyr. In this letter, we find that once the viscosity is taken into account, this age problem is alleviated.