Noise-induced escape of periodically modulated systems: from weak to strong modulation.

Noise-induced escape from a metastable state is studied for an overdamped periodically modulated system. We develop an asymptotic technique that gives both the instantaneous and period-average escape rates, including the prefactor, for an arbitrary modulation amplitude A . We find the parameter range where escape is strongly synchronized and the instantaneous escape rate displays sharp peaks. The peaks vary with increasing modulation frequency or amplitude from Gaussian to strongly asymmetric. The prefactor nu in the period-average escape rate depends on A nonmonotonically. Near the bifurcation amplitude A(c) it scales as nu approximately (A(c) - A)(zeta). We identify three scaling regimes, with zeta = 1/4, -1, and 1/2.