Finite temperature effects on decay rates in the real-time formalism

Abstract: This thesis work presents thermal decay rates for several reactions calculated within the framework of the real-time formalism. Processes considered are those of a neutral (pseudo)scalar decaying into two distinct (pseudo)scalars or into a fermion-antifermion pair. These processes are extended from earlier work to include chemical potentials and distinct species in the final state. A hypothetical (pseudo)scalar emission off a fermion line is also presented. The thermal decay rates at high temperature are found to be enhanced relative to zero-temperature theory in the case of (pseudo)scalar-(pseudo)scalar or (pseudo)scalar-fermion final state with quadratic and linear enhancement respectively. A suppression of the (pseudo)scalar decay rate into a fermion-antifermion final state, related to the Pauli principle, is found.