A note on self-adjoint extensions of the Laplacian on weighted graphs

Abstract

We study the uniqueness of self-adjoint and Markovian extensions of the Laplacian on weighted graphs. We first show that, for locally finite graphs and a certain family of metrics, completeness of the graph implies uniqueness of these extensions. Moreover, in the case when the graph is not metrically complete and the Cauchy boundary has finite capacity, we characterize the uniqueness of the Markovian extensions.

17 pages. The assumption of "finite jump size" found in Theorems 1 and 2 in the previous version has been replaced by a weaker condition concerning the newly introduced notion of a "combinatorial neighborhood" in Theorem 1 and has been removed altogether from Theorem 2. Some references added. Final version to appear in J. Funct. Anal