Fluctuations of stochastic PDEs with long-range correlations
Luca Gerolla, Martin Hairer, Xue-Mei Li
TL;DR
This paper analyzes the large-scale fluctuations of a nonlinear stochastic heat equation in $d\ge 3$ subjected to long-range, non-integrable spatial noise with covariance decaying as $|x|^{-\kappa}$, $\kappa\in(2,d)$. By combining Malliavin calculus with Stein’s method and a Feynman-diagram framework, the authors show that diffusively scaled fluctuations persist in the limit and converge to an additive stochastic heat equation driven by a spatially colored noise with Riesz kernel $|x-y|^{-\kappa}$, with an effective variance $\nu_{\text{eff}}^2=|\mathbb{E}[\sigma(Z(0))]|^2$. They establish both finite-dimensional distribution convergence and tightness in negative Hölder spaces, and provide detailed bounds via diagrammatic estimates to control residual terms. The results extend the Edwards–Wilkinson-type limits to long-range correlated noise and quantify how correlation decay controls the scaling and effective variance, highlighting persistent spatial structure in the limit. This contributes to a deeper understanding of SPDE fluctuations under nonlocal spatial correlations and the robustness of Gaussian fluctuation limits beyond compactly supported noise.
Abstract
We study the large-scale dynamics of the solution to a nonlinear stochastic heat equation (SHE) in dimensions $d \geq 3$ with long-range dependence. This equation is driven by multiplicative Gaussian noise, which is white in time and coloured in space with non-integrable spatial covariance that decays at the rate of $|x|^{-κ}$ at infinity, where $κ\in (2, d)$. Inspired by recent studies on SHE and KPZ equations driven by noise with compactly supported spatial correlation, we demonstrate that the correlations persist in the large-scale limit. The fluctuations of the diffusively scaled solution converge to the solution of a stochastic heat equation with additive noise whose correlation is the Riesz kernel of degree $-κ$. Moreover, the fluctuations converge as a distribution-valued process in the optimal Hölder topologies.
