LARGE FLUCTUATIONS IN A PERIODICALLY DRIVEN DYNAMICAL SYSTEM

Fluctuations in a periodically driven overdamped oscillator are studie d theoretically and experimentally in the limit of low noise intensity by investigation of their prehistory. It is shown that, for small noi se intensity, fluctuations to points in coordinate space that are remo te from the stable states occur along paths that form narrow tubes. Th e tubes are centered on the optimal paths corresponding to trajectorie s of an auxiliary Hamiltonian system. The optimal paths themselves, an d the tubes of paths around them, are visualized through measurements of the prehistory probability distribution for an electronic model. So me general features of fluctuations in nonequilibrium systems, such as singularities in the pattern of optimal paths, the corresponding nond ifferentiability of the generalized nonequilibrium potential, and the feasibility of their experimental investigation, are discussed.