Effects of dark sectors' mutual interaction on the growth of structures

TL;DR

This paper develops a formalism to analyze how interactions between dark sectors influence the growth of cosmic structures, highlighting potential observational signatures of such interactions.

Contribution

It introduces a general framework for studying dark sector interactions and their impact on structure growth stability and observational signatures.

Findings

Dark sector interactions can significantly alter the growth index.

Stable structure growth constrains the form of dark sector coupling.

Interaction effects may be detectable with future large-scale structure observations.

Abstract

We present a general formalism to study the growth of dark matter perturbations when dark energy perturbations and interactions between dark sectors are present. We show that dynamical stability of the growth of structure depends on the type of coupling between dark sectors. By taking the appropriate coupling to ensure the stable growth of structure, we observe that the effect of the dark sectors' interaction overwhelms that of dark energy perturbation on the growth function of dark matter perturbation. Due to the influence of the interaction, the growth index can differ from the value without interaction by an amount within the observational sensibility, which provides a possibility to disclose the interaction between dark sectors through future observations on the growth of large structure.