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