Neutrino oscillations in the early universe. Resonant case

Abstract

Lepton asymmetry generated in the early universe by neutrino oscillations into sterile partners is calculated. Kinetic equations are analytically reduced to a simple form that permits an easy numerical treatment. Asymptotic values of the asymmetry are at the level of 0.2-0.3 and are reasonably close to those obtained by other groups, though the approach to asymptotics in some cases is noticeably slower. No chaoticity is observed.