Sterile Neutrinos in astrophysical and cosmological sauce

Abstract

The study of sterile neutrinos has recently acquired a different flavor: being now excluded as the dominant solution for the solar or atmospheric conversions, sterile neutrinos, still attractive for many other reasons, have thus become even more elusive. The present relevant questions are: which subdominant role can they have? Where (and how) can they show up? Cosmology and supernovae turn out to be powerful tools to address these issues. With the most general mixing scenarios in mind, I present the analysis of many possible effects on BBN, CMB, LSS, and in SN physics due to sterile neutrinos. I discuss the computational techniques, present the state-of-the-art bounds, identify the still allowed regions and study some of the most promising future probes. I show how the region of the LSND sterile neutrino is excluded by the constraints of standard cosmology.

Based on the published Proceedings for the 10th International Symposium on Particles, Strings and Cosmology (PASCOS '04), August 2004, Boston, USA and for the XVI Incontri sulla Fisica delle Alte Energie (IFAE), April 2004, Torino, Italy; with slightly expanded discussion and references. v2: some references corrected