Vincenzo Grecchi, Andrea Sacchetti Lifetime of the Wannier-Stark resonances and perturbation theory (266K, Postscript) ABSTRACT. We consider the small field asymptotics of the lifetime of metastable states in Wannier-Stark problems. Assuming that at zero field we have Bloch operators with only the first gap open and using the regular perturbation theory, we prove that the behavior of the lifetime computed by means of the Fermi Golden Rule is proportional to the correct one with the factor $(\pi /3)^2$. The connection with adiabatic problems is briefly discussed. --=====================_861042576==_ Content-Type: text/plain; charset="us-ascii"