AP2 - Neutrino Physics, Astrophysics and Cosmology |
Speaker_ |
Lattanzi, Massimiliano |
Co-autors |
R. Ruffini, G.V. Vereshchagin |
Talk _ |
Constraints on the neutrino asymmetry of the Universe from cosmological data |
Abstract _ |
The present amount of cosmological lepton asymmetry is unknown, and actually nothing, neither from a theoretical nor from an experimental point of view, prevents it to be much larger that the corresponding baryonic asymmetry. Since different models of baryogenesis produce different amount of lepton asymmetry, gathering information on the latter can in principle be used to discriminate between models of baryogenesis. The presence of a lepton asymmetry reflects in a non zero-chemical potential for the cosmological neutrino background (CNB). After discussing how this quantity affects the cosmological evolution, we will discuss the limits that the present cosmological data put on the lepton asymmetry. In particular we will show that CMB data alone cannot efficiently discriminate between models with large (of order 1) and small lepton asymmetry. This results also holds in the framework of cosmological models with non-standard structure of the neutrino sector, in which the nucleosynthesis bound can possibly be evaded. |