Srinivasan Balaji ; Hosam Mahmoud - Urn-driven random walks

dmtcs:15546 - Discrete Mathematics & Theoretical Computer Science, April 15, 2026, vol. 28:2 - https://doi.org/10.46298/dmtcs.15546
Urn-driven random walksArticle

Authors: Srinivasan Balaji ; Hosam Mahmoud

The symmetric random walk is known to be recurrent in one and two dimensions, and becomes transient in three or higher dimensions. We compare the symmetric random walk to walks driven by certain \polya\ urns. We show that, in contrast, if the probabilities of the random walk are instead driven by a \polya-Eggenberger urn, the states are recurrent only in one dimension. Further consideration of exchangeability reveals that the walk is null recurrent. As soon as the underlying Markov chain of \polya\ walk gets in two dimensions or higher, there is a positive probability that the walker gets lost in the space, and the probability of her recurrence is less than 1.
On the other hand, a walk driven by Friedman urn behaves like the symmetric random walk, being recurrent in one and two dimensions and transient in higher dimensions. As Friedman urn scheme is not exchangeable, it is considerably harder to determine the nature of the recurrence in one and two dimensions. Empirical evidence through simulation suggests that in one dimension Friedman walk is positive recurrent.


Volume: vol. 28:2
Section: Combinatorics
Published on: April 15, 2026
Accepted on: March 25, 2026
Submitted on: April 23, 2025
Keywords: Probability