Normal approximation for total magnetization in subcritical long-range Ising models

Abstract

We establish Berry--Esseen bounds and 1-Wassershtein bounds for the total spin of strictly subcritical zero-field Ising models with summable interactions. Let $J:\mathbb Z^d\to[0,\infty)$ be symmetric, satisfy $J(0)=0$, and $\|J\|_1:=\sum_{x\in\mathbb Z^d}J(x)<\infty$. For a nonempty finite set $Λ\subset\mathbb Z^d$, consider zero-field Gibbs measure with free boundary conditions, in which a spin configuration $σ\in\{-1,+1\}^Λ$ has probability proportional to \[ \exp\!\left\{ β\sum_{x,y\inΛ} J(x-y)σ_xσ_y \right\}. \] Let $S_Λ:=\sum_{x\inΛ}σ_x$ be the total spin and $β_{\mathrm c}$ denote the critical inverse temperature. For every fixed $0\leqβ<β_{\mathrm c}$, we prove that \[ d_{\mathrm K}\!\left( \frac{S_Λ}{\sqrt{\operatorname{Var}(S_Λ)}},G \right) \leq C_{β,J}|Λ|^{-1/2}, \] where $d_{\mathrm K}$ is the Kolmogorov distance, $G\sim \mathcal{N}(0,1)$, and $C_{β,J}$ depends only on $β$ and $J$. For the fully periodized model on $(\mathbb Z/L\mathbb Z)^d$, the corresponding rate is $L^{-d/2}$, uniformly in $L$. For the classical nearest-neighbor model, the Kolmogorov bound also holds for $-β_{\mathrm c}<β<β_{\mathrm c}$, covering both ferromagnetic and antiferromagnetic interactions. We also obtain $1$-Wasserstein bounds with the same rates in the respective subcritical regimes. Both the Kolmogorov and $1$-Wasserstein bounds hold with the same rate under the corresponding infinite-volume free-boundary Gibbs measures.