The Role of Self Interactions in the Cosmological Evolution of Warm Dark Matter

TL;DR

This paper reviews how elastic self interactions in Warm Dark Matter models influence structure formation, cosmological perturbations, and halo development, suggesting they can resolve issues in standard cosmology and WDM models.

Contribution

It introduces the effects of self interactions in WDM, including vector field interactions, and modifies the CLASS code to simulate their impact on cosmological evolution.

Findings

Self interactions can alleviate tensions in standard CDM and WDM models.

Simulations show self interactions influence halo formation and perturbation evolution.

Results suggest self interactions are a promising extension to WDM theories.

Abstract

In this work we present a summary of recent studies on the effects of elastic self interactions in the evolution of Warm Dark Matter models (WDM), focusing on structure formation and the evolution of cosmological perturbations. We pay special attention to a particular class of sterile neutrino WDM known as $\nu$MSM and provide examples for the case of vector field self interactions. We calculate the effects of assuming self interacting dark matter in X-Ray astrophysical observations, in the formation of fermionic DM halos in (quasi) equilibrium states and in the evolution of DM perturbations in the early universe, assuming particle masses between $\mathcal{O}(1-100)$ keV. In the latter topic, we perform simulations using a modification to the public Boltzmann solver CLASS and compare our results with observations. We find self interactions to be an interesting addition to WDM models, which can alleviate tensions both present in standard CDM cosmology and regarding WDM itself, as well as provide an interesting avenue for DM halo formation.