Self-interacting dark matter as a solution to the problems in small-scale structures

Abstract

Dark matter self-interactions are a well-motivated solution to the core-vs.-cusp and the too-big-to-fail problems. They are commonly induced by means of a light mediator, that is also responsible for the dark matter freeze-out in the early universe. Motivated by the fact that such scenario is excluded in its simplest realizations, we will discuss the possibility that the relic density of a self-interacting dark matter candidate can proceed from the freeze-out of only annihilations into SM particles. We will argue that scalar and Majorana dark matter in the mass range of 10 to 500 MeV, coupled to a slightly heavier massive gauge boson, are the only candidates in agreement with multiple current experimental constraints. We will also discuss prospects of establishing or excluding these two scenarios in future experiments.