Structure formation in Multiple Dark Matter cosmologies with long-range scalar interactions

TL;DR

This paper presents the first N-body simulations of multiple dark matter species with long-range scalar interactions, revealing unique nonlinear structure formation features that could distinguish these models from standard cosmology.

Contribution

It extends the study of multiple dark matter scenarios to the nonlinear regime, providing novel simulation results and identifying characteristic signatures of scalar interactions.

Findings

Formation of mirror cosmic structures in two dark matter species

Suppression of nonlinear matter power spectrum at high k

Fragmentation of collapsed halos due to scalar forces

Abstract

(Abridged) An interaction between Cold Dark Matter (CDM) and a classical scalar field playing the role of the cosmic dark energy (DE) might provide long-range dark interactions without conflicting with solar system bounds. Although presently available observations allow to constrain such interactions to a few percent of the gravitational strength, some recent studies have shown that if CDM is composed by two different particle species having opposite couplings to the DE field, such tight constraints can be considerably relaxed, allowing for long-range scalar forces of order gravity without significantly affecting observations both at the background and at the linear perturbations level. In the present work, we extend the investigation of such Multiple Dark Matter scenarios to the nonlinear regime of structure formation, by presenting the first N-body simulations ever performed for these cosmologies. Our results highlight some characteristic footprints of long-range scalar forces that arise only in the nonlinear regime for specific models that would be otherwise practically indistinguishable from the standard LCDM scenario both in the background and in the growth of linear density perturbations. Among these effects, the formation of "mirror" cosmic structures in the two CDM species, the suppression of the nonlinear matter power spectrum at k > 1 h/Mpc, and the fragmentation of collapsed halos, represent peculiar features that might provide a direct way to constrain this class of cosmological models.