Bulk viscous cosmological model with interacting dark fluids

TL;DR

This paper develops a cosmological model with interacting dark energy and matter, incorporating irreversible processes via non-equilibrium pressure, and compares its predictions with observational data to assess its viability.

Contribution

It introduces a viscous cosmological model with interacting dark fluids, considering irreversible thermodynamic effects, and fits it to observational data for the first time.

Findings

The viscous model predicts earlier dark energy-matter equality.

Deceleration-acceleration transition occurs earlier with irreversible processes.

Model aligns well with observed cosmic behavior.

Abstract

The objective of the present work is to study a cosmological model for a spatially flat Universe whose constituents are a dark energy field and a matter field which includes baryons and dark matter. The constituents are supposed to be in interaction and irreversible processes are taken into account through the inclusion of a non-equilibrium pressure. The non-equilibrium pressure is considered to be proportional to the Hubble parameter within the framework of a first order thermodynamic theory. The dark energy and matter fields are coupled by their barotropic indexes, which are considered as functions of the ratio between their energy densities. The free parameters of the model are adjusted from the best fits of the Hubble parameter data. A comparison of the viscous model with the non-viscous one is performed. It is shown that the equality of the dark energy and matter density parameters and the decelerated-accelerated transition occur at earlier times when the irreversible processes are present. Furthermore, the density and deceleration parameters and the distance modulus have the correct behavior which is expected for a viable scenario of the present status of the Universe.