On the growth of perturbations in interacting dark energy and dark matter fluids

TL;DR

This paper investigates how certain models of interacting dark energy and dark matter influence the growth of cosmic perturbations, highlighting conditions that avoid early-time instabilities in strong coupling regimes.

Contribution

It provides a covariant framework for dark sector coupling and analyzes perturbation evolution, identifying models that remain stable under strong coupling.

Findings

Some models avoid early-time instabilities

Interaction rate proportional to dark matter and dark energy densities

Stable perturbation growth in strong coupling regimes

Abstract

The covariant generalizations of the background dark sector coupling suggested in G. Mangano, G. Miele and V. Pettorino, Mod. Phys. Lett. A 18, 831 (2003) are considered. The evolution of perturbations is studied with detailed attention to interaction rate that is proportional to the product of dark matter and dark energy densities. It is shown that some classes of models with coupling of this type do not suffer from early time instabilities in strong coupling regime.