Small-Scale Crisis in Cosmology – Sterile Neutrinos to the Rescue?

Abstract

The ΛCDM standard model of cosmology is in excellent agreement with data on large scales but has difficulty explaining all observations on small scales. I discuss a simple particle physics model involving a new MeV-scale gauge boson that mediates dark matter self-interactions and dark matter interactions with a new light fermion. This allows to solve all small-scale problems of ΛCDM cosmology. It would be very attractive to identify the new light particle with a sterile neutrino, but it appears that this option is disfavored.