Instability in interacting dark sector: An appropriate Holographic Ricci dark energy model

TL;DR

This paper examines the instabilities caused by phantom crossing in interacting dark energy models, specifically holographic Ricci dark energy, and proposes modifications to mitigate these issues while maintaining observational consistency.

Contribution

It identifies the source of perturbative instabilities during phantom crossing and reconstructs the model to avoid them, altering the background parameters.

Findings

Instabilities are linked to phantom crossing in interacting dark energy models.

Reconstructed model avoids instabilities but modifies background parameters.

Significant parameter space changes occur when instabilities are mitigated.

Abstract

In this paper we investigate the consequences of phantom crossing considering the perturbative dynamics in models with interaction in their dark sector. By mean of a general study of gauge-invariant variables in comoving gauge, we relate the sources of instabilities in the structure formation process with the phantom crossing. In order to illustrate these relations and its consequences in more detail, we consider a specific case of an holographic dark energy interacting with dark matter. We find that in spite of the model is in excellent agreement with observational data at background level, however it is plagued of instabilities in its perturbative dynamics. We reconstruct the model in order to avoid these undesirable instabilities, and we show that this implies a modification of the concordance model at background. Also we find drastic changes on the parameters space in our model when instabilities are avoided.