TEMPERATURE-DEPENDENT WAVE-FUNCTION RENORMALIZATION AND WEAK INTERACTION RATES PRIOR TO NUCLEOSYNTHESIS

We present a general prescription for the effects of medium-dependent wave function renormalization on rates of reactions involving a Dirac particle. The result is applied to the corrections of order e(2) to th e weak interaction rates prior to nucleosynthesis, due to the thermal photon and e(+)e(-) baths. The results coming from the standard ''fini te temperature'' corrections in the literature, a decrease of the pred icted He abundance by 0.16%, are found to be replaced by an increase o f 0.02%. But there are indications that plasma corrections that are no t included at the e(2) level may be more important than these correcti ons.