Lepton Asymmetry and Neutrino Oscillations Interplay

TL;DR

This paper explores how lepton asymmetry and neutrino oscillations influence each other in the early Universe, affecting Big Bang nucleosynthesis constraints and the potential presence of additional relativistic particles.

Contribution

It provides a numerical analysis of lepton asymmetry enhancement via MSW resonant neutrino oscillations and discusses their combined impact on cosmological constraints and data.

Findings

L can suppress or enhance neutrino oscillations.

BBN constraints are highly sensitive to L in electron-sterile neutrino oscillations.

Active-sterile neutrino mixing and L may explain extra relativistic density evidence.

Abstract

We discuss the interplay between lepton asymmetry L and neutrino oscillations in the early Universe. Neutrino oscillations may suppress or enhance previously existing L. On the other hand L is capable to suppress or enhance neutrino oscillations. The mechanism of L enhancement in MSW resonant neutrino oscillations in the early Universe is numerically analyzed. L cosmological effects through neutrino oscillations are discussed. We discuss how L may change the cosmological BBN constraints on neutrino and show that BBN model with electron-sterile neutrino oscillations is extremely sensitive to L - it allows to obtain the most stringent constraints on L value. We discuss also the cosmological role of active-sterile neutrino mixing and L in connection with the indications about additional relativistic density in the early Universe, pointed out by BBN, CMB and LSS data and the analysis of global neutrino data.