Degeneracy between nonadiabatic dark energy models and $\Lambda$CDM: ISW effect and the cross correlation of CMB with galaxy clustering data

TL;DR

This paper investigates the difficulty in distinguishing nonadiabatic dark energy models from the standard Lambda Cold Dark Matter model using CMB observations, emphasizing the need for new observational probes.

Contribution

The study extends previous analyses to include CMB observables, specifically the ISW effect and its cross-correlation with galaxy data, highlighting persistent degeneracy.

Findings

Nonadiabatic dark energy models are nearly indistinguishable from Lambda CDM in CMB observations.

Current CMB probes are insufficient to detect nonadiabatic features in dark energy.

New observational strategies are required to differentiate these models.

Abstract

As recently pointed out in Ref. [Phys.\ Rev.\ D {\bf 96}, 8, 083502 (2017)] the evolution of the linear matter perturbations in nonadiabatic dynamical dark energy models is almost indistinguishable (quasi-degenerated) to the standard $\Lambda$CDM scenario. In this work we extend this analysis to CMB observables in particular the integrated Sachs-Wolfe effect and its cross-correlation with large scale structure. We find that this feature persists for such CMB related observable reinforcing that new probes and analysis are necessary to reveal the nonadiabatic features in the dark energy sector.