We present a study of the decay bf metastable states of a scalar field
via thermal activation, in the presence of a finite density of fermio
ns. The process we consider is the nucleation of ''droplets'' of true
vacuum inside the false one. We analyze a one-dimensional system of in
teracting bosons and fermions, considering the latter at finite temper
ature and with a given chemical potential. As a consequence of a noneq
uilibrium formalism previously developed, we obtain time-dependent dec
ay rates.