A phase space analysis for nonlinear bulk viscous cosmology

TL;DR

This paper uses phase space analysis to study nonlinear bulk viscous effects in cosmology, revealing different evolutionary behaviors depending on model parameters and extending previous findings.

Contribution

It introduces a dynamical systems approach to nonlinear bulk viscous cosmology, exploring new parameter regimes and their impact on cosmic evolution.

Findings

Trajectories evolve from singularity to de Sitter attractors for certain parameters.

Behavior differs from previous models for some parameter ranges.

Extends previous analyses with nonlinear viscous pressure dynamics.

Abstract

We consider a Friedmann-Robertson-Walker spacetime filled with both viscous radiation and nonviscous dust. The former has a bulk viscosity which is proportional to an arbitrary power of the energy density, i.e. $\zeta \propto \rho_v^{\nu}$, and viscous pressure satisfying a nonlinear evolution equation. The analysis is carried out in the context of dynamical systems and the properties of solutions corresponding to the fixed points are discussed. For some ranges of the relevant parameter $\nu$ we find that the trajectories in the phase space evolve from a FRW singularity towards an asymptotic de Sitter attractor, confirming and extending previous analysis in the literature. For other values of the parameter, instead, the behaviour differs from previous works.