Classical nonlinearity and quantum decay: The effect of classical phase-space structures

A numerical calculation of the decay from a potential well due to tunneling was carried out. It was found that in the presence of classical chaos, the decay can be strongly enhanced and that this enhancement depends on the system parameters in a resonantlike way. A qualitative inspection of the classical phase-space structure revealed a connection between the peaks in the decay probability and the presence of classical nonlinear resonances in the region of phase space occupied by the Husimi distribution of the initial state. This correspondence was quantitatively explained using a semiclassical result that was shown to be valid in the case of chaos-assisted tunneling.