Journées de Probabilités 2024

The golf model on Z/nZ and on Z

13 juin 2024, 15:10

30m

Salle de Conférénces (Institut de mathématiques de Bordeaux)

Orateur

Zoé Varin (Univ. Bordeaux, CNRS, Bordeaux INP, LaBRI, UMR 5800, F-33400 Talence, France)

Description

We introduce a particle model, that we call the $\mathit{\text{golf model}}$. Initially, on a graph $G$, balls and holes are placed at random on some distinct vertices. Balls then move one by one, doing a random walk on $G$, starting from their initial vertex and stopping at the first empty hole they encounter, filling it. On finite graphs, under reasonable assumptions (if there are more holes than balls, and if the Markov chain characterizing the random walks is irreducible) a final configuration is reached almost surely. We are mainly interested in ${\mathbf{H}}^1$, the set of remaining holes. We give the distribution of ${\mathbf{H}}^1$ on $\mathbb{Z}/n\mathbb{Z}$, and describe a phase transition on the largest distance between two consecutive holes when the number of remaining holes has order $\sqrt{n}$. We show that the model on $\mathbb{Z}$ is well-defined when every vertex contains either a ball with probability $d_{\mathsf{b}}$, a hole with probability $d_{\mathsf{h}}$, or nothing, independently from the other vertices, as long as $d_{\mathsf{b}}\le d_{\mathsf{h}}$, and we describe the law of ${\mathbf{H}}^1$ in this case.