  Dynamics of a system that performs a large fluctuation to a given state is
essentially deterministic: the distribution of fluctuational paths peaks
sharply at a certain optimal path along which the system is most likely to
move. For the general case of a system driven by colored Gaussian noise, we
provide a formulation of the variational problem for optimal paths. We also
consider the prehistory problem, which makes it possible to analyze the shape
of the distribution of fluctuational paths that arrive at a given state. We
obtain, and solve in the limiting case, a set of linear equations for the
characteristic width of this distribution.

Statistical Mechanics;Mesoscale and Nanoscale Physics