Can one condition a killed random walk to survive?
Abstract
We consider the simple random walk on killed with probability at site for a function decaying at infinity. Due to recurrence in dimension , the killed random walk (KRW) dies almost surely if is positive, while in dimension it is known that the KRW dies almost surely if and only if , under mild technical assumptions on . In this paper we consider, for any , functions for which the KRW dies almost surely and we ask ourselves if the KRW conditioned to survive is well-defined. More precisely, given an exhaustion of , does the KRW conditioned to leave before dying converges in distribution towards a limit which does not depend on the exhaustion? We first prove that this conditioning is well-defined for , and that it is not for for . This question is connected to branching random walks and the infinite snake. More precisely, in dimension , the infinite snake is related to the KRW with , therefore our results imply that the infinite snake conditioned to avoid the origin in four dimensions is well-defined.
Cite
@article{arxiv.2406.12328,
title = {Can one condition a killed random walk to survive?},
author = {Lucas Rey and Augusto Teixeira},
journal= {arXiv preprint arXiv:2406.12328},
year = {2025}
}
Comments
37 pages, 2 figures