Sterile neutrinos and low reheating temperature

Abstract

Cosmological and astrophysical constraints on the mixings of sterile neutrinos are commonly much more stringent than the ones coming from laboratory searches. Within the standard cosmological picture, this mixing needs to be very small to prevent the cosmological overabundance of sterile neutrinos. We present here a scenario, based on a low reheating temperature TRH << 100 MeV at the end of (the last episode of) inflation or entropy creation, and show that the production of sterile neutrinos becomes largely suppressed with respect to what happens in the standard framework. In this case, the dominant constraints come from laboratory measurements, which may render sterile neutrinos to be ‘visible’ in future experiments.