Scaling cosmology with variable dark-energy equation of state

TL;DR

This paper explores models of dark energy with a variable equation of state, analyzing their impact on cosmic evolution and the coincidence problem using observational data and statistical criteria.

Contribution

It extends previous models by incorporating a variable dark energy equation of state within the CPL parametrization and evaluates their effectiveness with observational data.

Findings

No significant evidence for alleviating the coincidence problem.

Analytic solutions for the Hubble rate are derived.

Models are classified using AIC and BIC criteria.

Abstract

Interactions between dark matter and dark energy which result in a power-law behavior (with respect to the cosmic scale factor) of the ratio between the energy densities of the dark components (thus generalizing the LCDM model) have been considered as an attempt to alleviate the cosmic coincidence problem phenomenologically. We generalize this approach by allowing for a variable equation of state for the dark energy within the CPL-parametrization. Based on analytic solutions for the Hubble rate and using the Constitution and Union2 SNIa sets, we present a statistical analysis and classify different interacting and non-interacting models according to the Akaike (AIC) and the Bayesian (BIC) information criteria. We do not find noticeable evidence for an alleviation of the coincidence problem with the mentioned type of interaction.