Evolution of density perturbations in decaying vacuum cosmology

TL;DR

This paper investigates how density perturbations evolve in a cosmological model where dark energy decays and produces matter, showing that homogeneous matter production affects structure growth but can still fit observations with adjusted parameters.

Contribution

It introduces a detailed analysis of perturbations in a decaying vacuum cosmology, highlighting the impact of homogeneous matter production on the matter power spectrum.

Findings

Homogeneous matter production suppresses matter contrast at late times.

Adjusting matter density improves agreement with observational data.

Homogeneous decay assumption may need relaxation for more accurate modeling.

Abstract

We study cosmological perturbations in the context of an interacting dark energy model, in which the cosmological term decays linearly with the Hubble parameter, with concomitant matter production. A previous joint analysis of the redshift-distance relation for type Ia supernovas, baryonic acoustic oscillations, and the position of the first peak in the anisotropy spectrum of the cosmic microwave background has led to acceptable values for the cosmological parameters. Here we present our analysis of small perturbations, under the assumption that the cosmological term, and therefore the matter production, are strictly homogeneous. Such a homogeneous production tends to dilute the matter contrast, leading to a late-time suppression in the power spectrum. Nevertheless, an excellent agreement with the observational data can be achieved by using a higher matter density as compared to the concordance value previously obtained. This may indicate that our hypothesis of homogeneous matter production must be relaxed by allowing perturbations in the interacting cosmological term.