Survival probability of random walks leaping over traps

TL;DR

This paper analyzes the survival probability of one-dimensional random walks that can leap over traps, providing exact results for specific jump distributions and exploring effects of trap size, waiting times, and diffusive limits.

Contribution

It introduces a model of random walks with leap-over traps, deriving exact survival probabilities and extending to continuous-time and diffusive regimes with novel insights.

Findings

Survival probability decreases exponentially with steps, influenced by trap length and separation.

Exact mean first-passage time results for exponential jump distributions.

Algebraic decay of survival probability in continuous-time RWs with power-law waiting times.

Abstract

We consider one-dimensional discrete-time random walks (RWs) in the presence of finite size traps of length $\ell$ over which the RWs can jump. We study the survival probability of such RWs when the traps are periodically distributed and separated by a distance $L$. We obtain exact results for the mean first-passage time and the survival probability in the special case of a double-sided exponential jump distribution. While such RWs typically survive longer than if they could not leap over traps, their survival probability still decreases exponentially with the number of steps. The decay rate of the survival probability depends in a non-trivial way on the trap length $\ell$ and exhibits an interesting regime when $\ell\rightarrow 0$ as it tends to the ratio $\ell/L$, which is reminiscent of strongly chaotic deterministic systems. We generalize our model to continuous-time RWs, where we introduce a power-law distributed waiting time before each jump. In this case, we find that the survival probability decays algebraically with an exponent that is independent of the trap length. Finally, we derive the diffusive limit of our model and show that, depending on the chosen scaling, we obtain either diffusion with uniform absorption, or diffusion with periodically distributed point absorbers.