Parameterizing the Effect of Dark Energy Perturbations on the Growth of Structures

TL;DR

This paper provides an analytical model for how dark energy perturbations influence the growth of cosmic structures, considering various dark energy parameters and their effects on the growth index.

Contribution

It introduces an analytical fit for the growth function that accounts for dark energy perturbations, incorporating dependencies on key dark energy parameters.

Findings

Growth index varies by ~5% with small sound speed and large deviations in w.

Analytical fit accurately models the impact of dark energy perturbations.

Dependence of growth on dark energy parameters is quantified.

Abstract

We present an analytical fit to the growth function of the dark matter perturbations when dark energy perturbations are present. The growth index depends upon the dark energy equation of state w, the speed of sound of the dark energy fluctuations, the dark matter abundance and the observed comoving scale. The growth index changes by ~5% for small speed of sound and large deviations of w from -1 with respect to its value in the limit of no dark energy perturbations.