Near-critical Ornstein--Zernike theory for the planar random-cluster model

Fuente: arXiv
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Main Authors: D'Alimonte, Lucas, Manolescu, Ioan
Format: Preprint
Published: 2025
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author D'Alimonte, Lucas
Manolescu, Ioan
author_facet D'Alimonte, Lucas
Manolescu, Ioan
contents We develop an Ornstein--Zernike theory for the two-dimensional random-cluster model with $1 \leq q <4$ that also applies in its near-critical regime. In particular, we prove an asymptotic formula for the two-point function which holds uniformly for~$p < p_c$ and blends the subcritical and near-critical behaviours of the model. The analysis is carried out by studying the renewal properties of a subcritical percolation cluster, \emph{at the scale of the correlation length}. More precisely, we explore sequentially the cluster in a given direction, by slices of thickness comparable to the correlation length. We show that this exploration satisfies the properties of a {\em killed Markov renewal process} -- a class of processes that may be analysed independently and have Brownian behaviour. In addition to the two-point function estimate, we derive other consequences of the Ornstein--Zernike theory such as an invariance principle for the rescaled cluster and the strict convexity of the inverse correlation length -- all at the scale of the correlation length, uniformly in~$p<p_c$. Finally, our approach differs from that of earlier papers of Campanino, Ioffe, Velenik and others, with the cluster being dynamically explored rather than constructed from its diamond decomposition.
format Preprint
id arxiv_https___arxiv_org_abs_2510_13648
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Near-critical Ornstein--Zernike theory for the planar random-cluster model
D'Alimonte, Lucas
Manolescu, Ioan
Probability
Mathematical Physics
60K35, 82B20, 82B43
We develop an Ornstein--Zernike theory for the two-dimensional random-cluster model with $1 \leq q <4$ that also applies in its near-critical regime. In particular, we prove an asymptotic formula for the two-point function which holds uniformly for~$p < p_c$ and blends the subcritical and near-critical behaviours of the model. The analysis is carried out by studying the renewal properties of a subcritical percolation cluster, \emph{at the scale of the correlation length}. More precisely, we explore sequentially the cluster in a given direction, by slices of thickness comparable to the correlation length. We show that this exploration satisfies the properties of a {\em killed Markov renewal process} -- a class of processes that may be analysed independently and have Brownian behaviour. In addition to the two-point function estimate, we derive other consequences of the Ornstein--Zernike theory such as an invariance principle for the rescaled cluster and the strict convexity of the inverse correlation length -- all at the scale of the correlation length, uniformly in~$p<p_c$. Finally, our approach differs from that of earlier papers of Campanino, Ioffe, Velenik and others, with the cluster being dynamically explored rather than constructed from its diamond decomposition.
title Near-critical Ornstein--Zernike theory for the planar random-cluster model
topic Probability
Mathematical Physics
60K35, 82B20, 82B43
url https://arxiv.org/abs/2510.13648