Uniqueness of the infinite tree in low-dimensional random forests

Fuente: arXiv
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Autori principali: Halberstam, Noah, Hutchcroft, Tom
Natura: Preprint
Pubblicazione: 2023
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author Halberstam, Noah
Hutchcroft, Tom
author_facet Halberstam, Noah
Hutchcroft, Tom
contents The arboreal gas is the random (unrooted) spanning forest of a graph in which each forest is sampled with probability proportional to $β^{\# \text{edges}}$ for some $β\geq 0$, which arises as the $q\to 0$ limit of the Fortuin-Kastelyn random cluster model with $p=βq$. We study the infinite-volume limits of the arboreal gas on the hypercubic lattice $\mathbb{Z}^d$, and prove that when $d\leq 4$, any translation-invariant infinite volume Gibbs measure contains at most one infinite tree almost surely. Together with the existence theorem of Bauerschmidt, Crawford and Helmuth (2021), this establishes that for $d=3,4$ there exists a value of $β$ above which subsequential weak limits of the $β$-arboreal gas on tori have exactly one infinite tree almost surely. We also show that the infinite trees of any translation-invariant Gibbs measure on $\mathbb{Z}^d$ are one-ended almost surely in every dimension. The proof has two main ingredients: First, we prove a resampling property for translation-invariant arboreal gas Gibbs measures in every dimension, stating that the restriction of the arboreal gas to the trace of the union of its infinite trees is distributed as the uniform spanning forest on this same trace. Second, we prove that the uniform spanning forest of any translation-invariant random connected subgraph of $\mathbb{Z}^d$ is connected almost surely when $d\leq 4$. This proof also provides strong heuristic evidence for the conjecture that the supercritical arboreal gas contains infinitely many infinite trees in dimensions $d\geq 5$. Along the way, we give the first systematic and axiomatic treatment of Gibbs measures for models of this form including the random cluster model and the uniform spanning tree.
format Preprint
id arxiv_https___arxiv_org_abs_2302_12224
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Uniqueness of the infinite tree in low-dimensional random forests
Halberstam, Noah
Hutchcroft, Tom
Probability
Mathematical Physics
The arboreal gas is the random (unrooted) spanning forest of a graph in which each forest is sampled with probability proportional to $β^{\# \text{edges}}$ for some $β\geq 0$, which arises as the $q\to 0$ limit of the Fortuin-Kastelyn random cluster model with $p=βq$. We study the infinite-volume limits of the arboreal gas on the hypercubic lattice $\mathbb{Z}^d$, and prove that when $d\leq 4$, any translation-invariant infinite volume Gibbs measure contains at most one infinite tree almost surely. Together with the existence theorem of Bauerschmidt, Crawford and Helmuth (2021), this establishes that for $d=3,4$ there exists a value of $β$ above which subsequential weak limits of the $β$-arboreal gas on tori have exactly one infinite tree almost surely. We also show that the infinite trees of any translation-invariant Gibbs measure on $\mathbb{Z}^d$ are one-ended almost surely in every dimension. The proof has two main ingredients: First, we prove a resampling property for translation-invariant arboreal gas Gibbs measures in every dimension, stating that the restriction of the arboreal gas to the trace of the union of its infinite trees is distributed as the uniform spanning forest on this same trace. Second, we prove that the uniform spanning forest of any translation-invariant random connected subgraph of $\mathbb{Z}^d$ is connected almost surely when $d\leq 4$. This proof also provides strong heuristic evidence for the conjecture that the supercritical arboreal gas contains infinitely many infinite trees in dimensions $d\geq 5$. Along the way, we give the first systematic and axiomatic treatment of Gibbs measures for models of this form including the random cluster model and the uniform spanning tree.
title Uniqueness of the infinite tree in low-dimensional random forests
topic Probability
Mathematical Physics
url https://arxiv.org/abs/2302.12224