From Harnack inequality to heat kernel estimates on metric measure spaces and applications

TL;DR

This paper demonstrates that a dimension-free Harnack inequality on certain metric measure spaces implies sharp Gaussian heat kernel estimates, extending results to $RCD(K,\infty)$ spaces.

Contribution

It establishes a link between Harnack inequalities and heat kernel bounds in metric measure spaces, including new results for $RCD(K,\infty)$ spaces.

Findings

Dimension-free Harnack inequality implies Gaussian heat kernel estimates.

Proves local logarithmic Sobolev inequality in metric measure spaces.

Extends results to $RCD(K,\infty)$ spaces.

Abstract

Aim of this short note is to show that a dimension-free Harnack inequality on an infinitesimally Hilbertian metric measure space where the heat semigroup admits an integral representation in terms of a kernel is suffcient to deduce a sharp upper Gaussian estimate for such kernel. As intermediate step, we prove the local logarithmic Sobolev inequality (known to be equivalent to a lower bound on the Ricci curvature tensor in smooth Riemannian manifolds). Both results are new also in the more regular framework of $RCD(K,\infty)$ spaces.