Instanton Approach to the Langevin Motion of a Particle in a Random Potential

We develop an instanton approach to the nonequilibrium dynamics in one-dimensional random environments. The long time behavior is controlled by rare fluctuations of the disorder potential and, accordingly, by the tail of the distribution function for the time a particle needs to propagate along the system (the delay time). The proposed method allows us to find the tail of the delay time distribution function and delay time moments, providing thus an exact description of the long time dynamics. We analyze arbitrary environments covering different types of glassy dynamics: dynamics in a short-range random field, creep, and Sinai's motion.