Finite temperature radiative corrections to neutron decay and realted processes

We present a detailed calculation of the radiative corrections at finite temperature to the processes nν -><- pe, ne -><- pν and n -><- peν. The temperature range considered is approximately 100 keV to 3 MeV, which is the range relevant for nucleosynthesis calculations. Photon absorption and emission, photonic corrections to the vertex and fermion wave-function renormalizations, as well as the correction to the electron 'mass' are calculated explicitly. It is shown that infrared divergences are only cancelled when absorption and induced photon emission are included. We analyze the effect of these processes on the various reaction rates, and discuss the effects of these corrections on the calculated helium abundance in the universe. (orig.)