Locality of the heat kernel on metric measure spaces

Abstract

We will discuss what it means for a general heat kernel on a metric measure space to be local. We show that the Wiener measure associated to Brownian motion is local. Next we show that locality of the Wiener measure plus a suitable decay bound of the heat kernel implies locality of the heat kernel. We define a class of metric spaces we call manifold-like that satisfy the prerequisites for these theorems. This class includes Riemannian manifolds, metric graphs, products and some quotients of these as well as a number of more singular spaces. There exists a natural Dirichlet form based on the Laplacian on manifold-like spaces and we show that the associated Wiener measure and heat kernel are both local. These results unify and generalise facts known for manifolds and metric graphs. They provide a useful tool for computing heat kernel asymptotics for a large class of metric spaces. As an application we compute the heat kernel asymptotics for two identical particles living on a metric graph.