Non-minimally coupled dark matter: effective pressure and structure formation

TL;DR

This paper introduces a phenomenological model where non-minimal gravity-dark matter coupling creates an effective pressure, potentially resolving small-scale issues in \\Lambda CDM by affecting structure growth and dark matter-baryon interactions.

Contribution

It presents a novel approach linking non-minimal coupling to effective dark matter pressure, impacting structure formation and galaxy dynamics.

Findings

Effective pressure reduces galactic scale structure growth.

Non-minimal coupling may explain dark matter-baryon correlations.

Model offers potential solutions to small-scale \\Lambda CDM problems.

Abstract

We propose a phenomenological model in which a non-minimal coupling between gravity and dark matter is present in order to address some of the apparent small scales issues of \lcdm model. When described in a frame in which gravity dynamics is given by the standard Einstein-Hilbert action, the non-minimal coupling translates into an effective pressure for the dark matter component. We consider some phenomenological examples and describe both background and linear perturbations. We show that the presence of an effective pressure may lead these scenarios to differ from \lcdm at the scales where the non-minimal coupling (and therefore the pressure) is active. In particular two effects are present: a pressure term for the dark matter component that is able to reduce the growth of structures at galactic scales, possibly reconciling simulations and observations; an effective interaction term between dark matter and baryons that could explain observed correlations between the two components of the cosmic fluid within Tully-Fisher analysis.