Cosmological simulations of a momentum coupling between dark matter and quintessence

TL;DR

This paper investigates how a momentum coupling between dark matter and quintessence affects non-linear structure formation, revealing scale-dependent impacts on cosmic structures through modified dynamics in simulations.

Contribution

It introduces a novel implementation of momentum coupling in N-body simulations and analyzes its effects on structure formation and halo properties.

Findings

Reduced small-scale structure with positive coupling

Enhanced large-scale structure due to coupling

Altered halo density profiles and velocity dispersions

Abstract

Dark energy is frequently modelled as an additional dynamical scalar field component in the Universe, referred to as "quintessence", which drives the late-time acceleration. Furthermore, the quintessence field may be coupled to dark matter and/or baryons, leading to a fifth force. In this paper we explore the consequences for non-linear cosmological structure formation arising from a momentum coupling between the quintessence field and dark matter only. The coupling leads to a modified Euler equation, which we implement in an N-body cosmological simulation. We then analyse the effects of the coupling on the non-linear power spectrum and the properties of the dark matter halos. We find that, for certain quintessence potentials, a positive coupling can lead to significantly reduced structure on small scales and somewhat enhanced structure on large scales, as well as reduced halo density profiles and increased velocity dispersions.