Transition path time distributions for Levy flights

This paper presents a study of transition path time distributions for Levy noise-induced barrier crossing. Transition paths are short segments of the reactive trajectories and span the barrier region of the potential without spilling into the reactant/product wells. The time taken to traverse this segment is referred to as the transition path time. Since the transition path is devoid of excursions in the minimum, the corresponding time will give the exclusive barrier crossing time, unlike (rate constant)(-1). This work explores the distribution of transition path times for superdiffusive barrier crossing, analytically. This is made possible by approximating the barrier by an inverted parabola. Using this approximation, the distributions are evaluated in both over-and under-damped limits of friction. The short-time behaviour of the distributions, provide analytical evidence for single-step transition events-a feature in Levy-barrier crossing as observed in prior simulation studies. The average transition path time is calculated as a function of the Levy index (a), and the optimal value of a leading to minimum average transition path time is discussed, in both the limits of friction. Langevin dynamics simulations corroborating with the analytical results are also presented.