Fluctuations of the Ising free energy on Erdős-Rényi graphs

Fuente: arXiv
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Auteurs principaux: Coja-Oghlan, Amin, Kaaser, Dominik, Rolvien, Maurice, Zakharov, Pavel, Zampetakis, Kostas
Format: Preprint
Publié: 2026
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author Coja-Oghlan, Amin
Kaaser, Dominik
Rolvien, Maurice
Zakharov, Pavel
Zampetakis, Kostas
author_facet Coja-Oghlan, Amin
Kaaser, Dominik
Rolvien, Maurice
Zakharov, Pavel
Zampetakis, Kostas
contents We investigate the ferromagnetic Ising model on the Erdős-Rényi random graph $\mathbb{G}(n,m)$ with bounded average degree $d=2m/n$. Specifically, we determine the limiting distribution of $\log Z_{\mathbb{G}(n,m)}(β,B)$, where $Z_{\mathbb{G}(n,m)}(β,B)$ is the partition function at inverse temperature $β>0$ and external field $B\geq0$. If either $B>0$, or $B=0$, $d>1$ and $β>\operatorname{ath}(1/d)$ the limiting distribution is a Gaussian whose variance is of order $Θ(n)$ and is described by a family of stochastic fixed point problems that encode the root magnetisation of two correlated Galton-Watson trees. By contrast, if $B=0$ and either $d\leq1$ or $β<\operatorname{ath}(1/d)$ the limiting distribution is an infinite sum of independent random variables and has bounded variance.
format Preprint
id arxiv_https___arxiv_org_abs_2601_08590
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Fluctuations of the Ising free energy on Erdős-Rényi graphs
Coja-Oghlan, Amin
Kaaser, Dominik
Rolvien, Maurice
Zakharov, Pavel
Zampetakis, Kostas
Combinatorics
Mathematical Physics
Probability
05C80, 82B44, 82B20
We investigate the ferromagnetic Ising model on the Erdős-Rényi random graph $\mathbb{G}(n,m)$ with bounded average degree $d=2m/n$. Specifically, we determine the limiting distribution of $\log Z_{\mathbb{G}(n,m)}(β,B)$, where $Z_{\mathbb{G}(n,m)}(β,B)$ is the partition function at inverse temperature $β>0$ and external field $B\geq0$. If either $B>0$, or $B=0$, $d>1$ and $β>\operatorname{ath}(1/d)$ the limiting distribution is a Gaussian whose variance is of order $Θ(n)$ and is described by a family of stochastic fixed point problems that encode the root magnetisation of two correlated Galton-Watson trees. By contrast, if $B=0$ and either $d\leq1$ or $β<\operatorname{ath}(1/d)$ the limiting distribution is an infinite sum of independent random variables and has bounded variance.
title Fluctuations of the Ising free energy on Erdős-Rényi graphs
topic Combinatorics
Mathematical Physics
Probability
05C80, 82B44, 82B20
url https://arxiv.org/abs/2601.08590