Sharpness of the Percolation Phase Transition for the Contact Process on ${\mathbb{Z}}^d$

Abstract

We study percolation properties of the upper invariant measure of the contact process on ${\mathbb{Z}}^d$. Our main result is a sharp percolation phase transition with exponentially small clusters throughout the subcritical regime and a mean-field lower bound for the infinite cluster density in the supercritical regime. This generalizes and simplifies an earlier result of Van den Berg [Ann. App. Prob., 2011], who proved a sharp percolation phase transition on ${\mathbb{Z}}^2$. Our proof relies on the OSSS inequality for Boolean functions and is inspired by a series of papers by Duminil-Copin, Raoufi and Tassion in which they prove similar sharpness results for a variety of models.

Problem in third displayed equation of page 9