Kinetic Equation with Neutrino Oscillations in the Early Universe

Abstract

This paper considers the kinetic equation for interacting neutrino gas in the context of an expanding early universe. It is suggested that if neutrino oscillations are present and CP violations occur prior to the decoupling of the neutrino gas from the rest of the universe, then lepton number may not be conserved and, in principle, significant permanent neutrino chemical potentials may develop and survive until the present day. This would lead to the wen known effect that if the electron neutrino chemical potential is significantly non-zero, then the primordial abundances of the light elements are affected and differ from those of the standard model. Numerical computation is required to examine the parameter ranges leading to a significant non-zero electron neutrino chemical potential.