Revealing the nonadiabatic nature of dark energy perturbations from galaxy clustering data

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 σ8(z) observable. We show that non-adiabatic DE models become close to be degenerated with respect to the ΛCDM 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.PACS numbers: 04.50. Kd, 95.36.+x,

Degeneracy between nonadiabatic dark energy models and ΛCDM : Integrated Sachs-Wolfe effect and the cross correlation of CMB with galaxy clustering data

“…Our findings can be interpreted in the same way as in Ref. [1], i.e., while adiabatic dark energy models differs substantially from the standard ΛCDM cosmology if the equation of state parameter departures from the constant value w DE = p DE /ρ DE = −1, there seems to exist a sort of quasi-degeneracy between nonadiabatic dark energy models and the ΛCDM model.…”

“…It has been found recently in Ref. [1] that nonadiabatic dark energy models are almost indistinguishable from the standard ΛCDM cosmology concerning the f σ 8 observable leading to an interesting degeneracy in the dark energy research context. Our focus in this work is to expand the analysis of Ref.…”

Cosmological constraints of phantom dark energy models

“…In [55] this method is applied and initial conditions are imposed at the radiation dominated epoch. On the other hand, in [56] the authors analyse the effects of non adiabaticity on the growth rate for several DE models and compute the observable f σ 8 .…”

A varying dark energy effective speed of sound parameter in the phantom Universe

“…Furthermore, in [47] the authors analyse the effects of a viscosity bulk within a modified gravity scenario endowed with the general action f (R, T ) and perform a test to check the validity of the studied models. The impact of the non adiabatic perturbations have been studied for example in [48,49]. In [48], the authors address a particular parametrisation of DE considering a linear combination of the intrinsic and entropy perturbations.…”

“…The impact of the non adiabatic perturbations have been studied for example in [48,49]. In [48], the authors address a particular parametrisation of DE considering a linear combination of the intrinsic and entropy perturbations. In the recent work [49], aside the non-adiabatic perturbations the non-vanishing anisotropic stress tensor is regarded as well.…”