eV-Scale Sterile Neutrinos and Cosmology - Compatible or Not?

by Mr Rasmus Hansen (Aarhus University, Denmark)

Thursday 19 Feb 2015, 11:15 → 12:15 Europe/Berlin

313

Several different experiments show anomalies that can be interpreted as hints for a sterile neutrino with a mass around 1eV, although this interpretation also leads to some mutual tension between the experiments. If such a sterile neutrino is introduced in cosmology, it has measurable consequences for both big bang nucleosynthesis, the cosmological microwave background radiation and large scale structure formation. When combining these different observables, the picture that emerges does not allow such a sterile neutrino to be fully thermalised as it would be via oscillations with active neutrinos assuming standard cosmology and the standard model for particle physics. This has lead to a rising interest in models where the bounds are either weakened or the thermalisation is avoided altogether. In my talk, I will review a few models where the thermalisation is suppressed - I will explain some of the nice features that they have and also discuss the strong constraints from various sources that must be considered.