Encounter-based model of a run-and-tumble particle
File(s)
Accepted version
Author(s)
Bressloff, Paul C
Type
Journal Article
Abstract
In this paper we extend the encounter-based model of diffusion-mediated surface absorption to the case of an unbiased run-and-tumble particle (RTP) confined to a finite interval [0, L] and switching between two constant velocity states ±v at a rate α. The encounter-based formalism is motivated by the observation that various surface-based reactions are better modeled in terms of a reactivity that is a function of the amount of time that a particle spends in a neighborhood of an absorbing surface, which is specified by a functional known as the boundary local time. The effects of surface reactions are taken into account by identifying the first passage time (FPT) for absorption with the event that the local time crosses some random threshold $\hat{\ell }$. In the case of a Brownian particle, the local time ℓ(t) is a continuous non-decreasing function of the time t. Taking ${\Psi}(\ell )\equiv \mathbb{P}[\hat{\ell } > \ell ]$ to be an exponential distribution, ${\Psi}[\ell ]={\mathrm{e}}^{-{\kappa }_{0}\ell }$, is equivalent to imposing a Robin boundary condition with a constant rate of absorption κ0. One major difference in the encounter-based model of an RTP is that the boundary local time ℓ(t) is a now a discrete random variable that counts the number of collisions of the RTP with the boundary. Given this modification, we show that in the case of a geometric distribution Ψ(ℓ) = zℓ, z = 1/(1 + κ0/v), we recover the RTP analog of the Robin boundary condition. This allows us to solve the boundary value problem (BVP) for the joint probability density for particle position and the local time, and thus incorporate more general models of absorption based on non-geometric distributions Ψ(ℓ). We illustrate the theory by calculating the mean FPT (MFPT) for absorption at x = L given a totally reflecting boundary at x = 0. We also determine the splitting probability for absorption at x = L when the boundary at x = 0 is totally absorbing.
Date Issued
2022-11-01
Date Acceptance
2022-11-01
Citation
Journal of Statistical Mechanics: Theory and Experiment, 2022, 2022 (11)
ISSN
1742-5468
Publisher
IOP Publishing
Journal / Book Title
Journal of Statistical Mechanics: Theory and Experiment
Volume
2022
Issue
11
Copyright Statement
Copyright © 2022 IOP Publishing Ltd. This is an author-created, un-copyedited version of an article published in Journal of Statistical Mechanics: Theory and Experiment. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at 10.1088/1742-5468/aca0ed
Identifier
http://dx.doi.org/10.1088/1742-5468/aca0ed
Publication Status
Published
Article Number
113206
Date Publish Online
2022-11-24