Oscillating neutrinos in the early Universe

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Abstract
We investigate the physics of an ensemble of oscillating neutrinos in the primordial plasma of the early Universe. The result is a coupled set 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 interacting sector we find surprising new contributions to the forward scattering effective potential, as well as new quantum contributions to the kinetic and/or rate equations. The possibility that neutrino oscillations might affect primordial nucleosynthesis is discussed.