First passage statistics of active random walks on one and two dimensional lattices

TL;DR

This paper analyzes the first passage statistics of active continuous time random walks on 1D and 2D lattices, revealing how activity influences return and passage probabilities beyond simple diffusion models.

Contribution

It provides a detailed analytical study of first passage probabilities for active random walks, highlighting effects of activity not captured by effective diffusion constants.

Findings

Activity increases the probability of return to the origin at late times.

First passage probabilities are not solely determined by an effective diffusion constant.

Analytical results are validated with kinetic Monte Carlo simulations.

Abstract

We investigate the first passage statistics of active continuous time random walks with Poissonian waiting time distribution on a one dimensional infinite lattice and a two dimensional infinite square lattice. We study the small and large time properties of the probability of the first return to the origin as well as the probability of the first passage to an arbitrary lattice site. It is well known that the occupation probabilities of an active particle resemble that of an ordinary Brownian motion with an effective diffusion constant at large times. Interestingly, we demonstrate that even at the leading order, the first passage probabilities are not given by a simple effective diffusion constant. We demonstrate that at late times, activity enhances the probability of the first return to the origin and the probabilities of the first passage to lattice sites close enough to the origin, which we quantify in terms of the P\'eclet number. Additionally, we derive the first passage probabilities of a symmetric random walker and a biased random walker without activity as limiting cases. We verify our analytic results by performing kinetic Monte Carlo simulations of an active random walker in one and two dimensions.