Viscous dark energy and phantom evolution

TL;DR

This paper explores how bulk viscosity in dark energy models can lead to a big rip singularity, showing that viscous effects can cause phantom energy behavior in flat FRW cosmologies.

Contribution

It compares Eckart and Israel-Stewart-Hiscock theories to analyze viscous effects and their role in inducing phantom energy and big rip singularities.

Findings

Bulk viscosity can induce a big rip singularity under certain conditions.

Viscous dark energy models can exhibit phantom behavior.

Negative pressure from viscosity cannot prevent phantom evolution.

Abstract

In order to study if the bulk viscosity may induce a big rip singularity on the flat FRW cosmologies, we investigate dissipative processes in the universe within the framework of the standard Eckart theory of relativistic irreversible thermodynamics, and in the full causal Israel–Stewart-Hiscock theory. We have found cosmological solutions which exhibit, under certain constraints, a big rip singularity. We show that the negative pressure generated by the bulk viscosity cannot avoid that the dark energy of the universe to be phantom energy.