Scalar Field Cosmologies with Viscous Fluid

TL;DR

This paper explores cosmological models combining scalar fields and viscous fluids, providing exact solutions that include singular, bouncing, and stable de Sitter or power-law evolutions, depending on viscosity types.

Contribution

It introduces new exact solutions for scalar field cosmologies with both linear and nonlinear viscous pressures, analyzing their stability and evolution.

Findings

De Sitter stage is asymptotically stable with linear viscosity.

Power-law evolutions occur with nonlinear viscosity and zero cosmological constant.

Both viscosity types produce singular and bouncing cosmological solutions.

Abstract

We investigate cosmological models with a free scalar field and a viscous fluid. We find exact solutions for a linear and nonlinear viscosity pressure. Both yield singular and bouncing solutions. In the first regime, a de Sitter stage is asymptotically stable, while in the second case we find power-law evolutions for vanishing cosmological constant.