Small-Scale Cosmology “Crisis” and Self-Interacting Right-Handed Neutrino Warm Dark Matter

Abstract

Abstract. In the lecture, I first review the basic problems of the ΛCDM model at small (galactic) scales, also known as "small-scale Cosmology crisis", namely discrepancies between theoretical simulations and observations. I then argue how systems of righthanded neutrinos (RHN) with masses of order 50 keV in the galaxies can tackle these problems, provided appropriately strong RHN self-interactions are included. Such models may constitute interesting minimal extensions of the Standard Model. Combining galactic phenomenology with other astroparticle physics considerations of such models, one arrives at a narrow range 47 keVc −2 ≤ m ≤ 50 keVc −2 for the allowed mass m of RHN, thereby pointing towards the rôle of such particles as interesteding warm dark matter components.