Bulk Viscous Cosmology

TL;DR

This paper introduces a bulk viscous fluid model unifying dark matter and dark energy, analyzed through dynamical systems and tested against observational data, showing stability and competitiveness with existing models.

Contribution

It presents a novel bulk viscous cosmological model with non-adiabatic perturbations, analyzed via dynamical systems, and validated against supernova and matter power spectrum data.

Findings

Model exhibits stable matter power spectrum without instabilities.

Model is consistent with supernova and matter power spectrum observations.

Comparable performance to popular dark sector models.

Abstract

We propose a scenario in which the dark components of the Universe are manifestations of a single bulk viscous fluid. Using dynamical system methods, a qualitative study of the homogeneous, isotropic background scenario is performed in order to determine the phase space of all possible solutions. The specific model which we investigate shares similarities with a generalized Chaplygin gas in the background but is characterized by non-adiabatic pressure perturbations. This model is tested against supernova type Ia and matter power spectrum data. Different from other unified descriptions of dark matter and dark energy, the matter power spectrum is well behaved, i.e., there are no instabilities or oscillations on small perturbation scales. The model is competitive in comparison with the currently most popular proposals for the description of the cosmological dark sector.