Fingerprinting dark energy

TL;DR

This paper develops simple approximations to characterize dark energy perturbations, enabling better differentiation between models with identical equations of state by analyzing their effects on cosmic structures and microwave background.

Contribution

It introduces accurate approximations for dark energy perturbations applicable to most scalar-field models, clarifying their influence on cosmological observations.

Findings

Dark energy perturbations significantly affect the dark matter power spectrum.

Perturbations impact the integrated Sachs-Wolfe effect in the CMB.

Approximations simplify analysis of dark energy models.

Abstract

Dark energy perturbations are normally either neglected or else included in a purely numerical way, obscuring their dependence on underlying parameters like the equation of state or the sound speed. However, while many different explanations for the dark energy can have the same equation of state, they usually differ in their perturbations so that these provide a fingerprint for distinguishing between different models with the same equation of state. In this paper we derive simple yet accurate approximations that are able to characterize a specific class of models (encompassing most scalar-field models) which is often generically called "dark energy". We then use the approximate solutions to look at the impact of the dark energy perturbations on the dark matter power spectrum and on the integrated Sachs-Wolfe effect in the cosmic microwave background radiation.