Revealing the non-adiabatic nature of dark energy perturbations from galaxy clustering data

TL;DR

This paper investigates how non-adiabatic dark energy perturbations influence structure formation and finds that current data cannot distinguish non-adiabatic models from the standard b1CDM, highlighting the need for new observational probes.

Contribution

It demonstrates the impact of non-adiabatic dark energy perturbations on galaxy clustering and shows their effects are degenerate with b1CDM at linear order, emphasizing the necessity for novel detection methods.

Findings

Non-adiabatic dark energy models affect the growth rate observable.

Current data cannot distinguish non-adiabatic models from b1CDM.

New probes are required to detect non-adiabatic features.

Abstract

We study structure formation using relativistic cosmological linear perturbation theory in the presence of intrinsic and relative (with respect to matter) non-adiabatic dark energy perturbations. For different dark energy models we assess the impact of non-adiabaticity on the matter growth promoting a comparison with growth rate data. The dark energy models studied lead to peculiar signatures of the (non)adiabatic nature of dark energy perturbations in the evolution of the $f \sigma_{8}(z)$ observable. We show that non-adiabatic DE models become close to be degenerated with respect to the $\Lambda$CDM model at first order in linear perturbations. This would avoid the identification of the non-adiabatic nature of dark energy using current available data. Therefore, such evidence indicates that new probes are necessary to reveal the non-adiabatic features in the dark energy sector.