Redshift space distortions in the presence of non-minimally coupled dark matter

TL;DR

This paper explores how non-minimal couplings between dark matter and scalar fields affect redshift space distortions, modifying growth rate measurements and impacting cosmological parameter constraints.

Contribution

It provides a detailed analysis of the effects of conformal and disformal couplings on redshift space distortions and forecasts observational constraints.

Findings

Growth rate differs from uncoupled models

Kaiser formula is modified by coupling terms

Future surveys can constrain coupling parameters

Abstract

In this paper, we fully investigate cosmological scenarios in which dark matter is non-minimally coupled to an extra scalar degree of freedom. The interaction is realized by means of conformal and disformal terms in the transformed gravitational metric. Considering linear perturbation theory, we show that the growth rate of dark matter differs from the uncoupled case and that the well-known Kaiser formula undergoes modification. As a result, redshift space distortion measurements cease to be a direct probe of the linear growth rate of total matter, since the distortion factor has an extra, coupling-dependent term. We study the effect of the coupling in three cosmological models, two conformally and one disformally coupled, and forecast the constraints on the coupling, and other cosmological parameters, from future galaxy surveys.