2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/44798We calculate the decay rate for a state prepared in a thermal density matrix centered on a metastable ground state. We find a rate that is intrinsically time {\it dependent}, as opposed to the {\it constant} rates of previous works. The rate vanishes at early times, rises to a maximum and eventually falls-off to zero as a consequence of unitary time evolution. Finally, we discuss extensions of this calculation to field theories and possible implications for both sphaleron mediated transitions and first order inflationary theories.LaTex, 14 pages, 3 figures (available upon request), CMU-HEP93-08, PITT-93-04High Energy Physics - PhenomenologyHigh Energy Physics - Theorytext