Turbulence and Little Rip Cosmology

TL;DR

This paper explores conditions under which dark energy models can lead to Big Rip or Little Rip singularities, considering both one- and two-component fluids, including turbulence effects and their potential to prevent singularities.

Contribution

It introduces a novel decomposition of dark fluid into turbulent and non-turbulent components with distinct equations of state, analyzing their impact on cosmic singularities.

Findings

Both Big Rip and Little Rip scenarios are possible for dark energy.

Turbulence can prevent the universe from encountering a singularity.

A viscous era can evolve into a turbulent era, affecting cosmic fate.

Abstract

A variety of conditions is considered under which the cosmic dark fluid may be able to develop a future Big Rip or Little Rip singularity. Both one-component and two-component models are considered. In the last-mentioned case we present a way in which the fluid can be decomposed into two components, one non-turbulent (ideal) and one turbulent part, obeying two different equations of state. For the non-turbulent part, the thermodynamical parameter, commonly called w, is assumed to be less than -1 throughout. For the turbulent part, it turns out that it is sufficient that w{turb} lies in the quintessence region in order to lead to a singularity. Both Big Rip and Little Rip behaviour for dark energy are found. In the one-component case, we examine how the universe may develop from a viscous era with constant bulk viscosity into a turbulent era, the turbulence in effect protecting the universe from encountering the singularity at all. The equivalent description of the same cosmology in terms of inhomogeneous (imperfect) fluid is also presented.