USE OF HAMILTONIAN-MECHANICS IN SYSTEMS DRIVEN BY COLORED NOISE

The evaluation of the path-integral representation for stochastic processes in the weak-noise limit shows that these systems are governed by a set of equations which are those of a classical dynamics. We show that, even when the noise is colored, these may be put into a Hamiltonian form which leads to improved numerical treatments and to better insights. We concentrate on solving Hamilton's equations over an infinite time interval, in order to determine the leading order contribution to the mean escape time for a bistable potential. The paths may be oscillatory and inherently unstable, in which case one must use a multiple shooting numerical technique over a truncated time period in order to calculate the infinite time optimal paths to a given accuracy. We look at two systems in some detail: the underdamped Langevin equation driven by external exponentially correlated noise, and the overdamped Langevin equation driven by external quasimonochromatic noise. We deduce that the bifurcation of the optimal path in the latter case is due to singularities in the configuration space of the corresponding dynamical system. © 1995 The American Physical Society.