OSCILLATING NEUTRINOS IN THE EARLY UNIVERSE

We investigate the physics of an ensemble of oscillating neutrinos in the primordial plasma of the early Universe. The result is a coupled s et of quantum kinetic equations both for the neutrino density operator and the momentum distributions of other species in the plasma. In the appropriate momentum-averaged limit, a comparable set of quantum rate equations arises. For the case of oscillations within the weakly inte racting sector we find surprising new contributions to the forward sca ttering effective potential, as well as new quantum contributions to t he kinetic and/or rate equations. The possibility that neutrino oscill ations might affect primordial nucleosynthesis is discussed.