NEUTRINO ASYMMETRY AND OSCILLATIONS IN THE EARLY UNIVERSE

We consider oscillations of the electron neutrino ve into an inert neutrino species vx in the heat bath of the early universe. There thermal corrections dominate the oscillation patterns and give rise to resonant regions for a wide range in the parameter space. We show that the electron neutrino asymmetry will dynamically be adjusted to zero, provided the initial asymmetry is not very large. If B-L is conserved, neutrino oscillations cannot give rise to a large neutrino asymmetry during the onset of nucleosynthesis. © 1990.