Neutrino Evolution in the Early Universe*

In the hot and dense early universe, neutrino evolution is driven by both the coherent development of quantum phase and the decoherent destruction of this phase through scattering.  In this environment, the quantum mechanical oscillation rate and kinetic scattering rate of neutrinos are affected by their interactions with a thermal background of the primordial soup of Standard Model particles; both these rates are large compared to the universal expansion rate.  We solve the Quantum Kinetic Equations for neutrino states in the early universe for a variety of scenarios and discuss the characteristics of their solutions.