Laplacians on infinite graphs: discrete vs continuous

Abstract

There are two main notions of a Laplacian operator associated with graphs: discrete graph Laplacians and continuous Laplacians on metric graphs (widely known as quantum graphs). Both objects have a venerable history as they are related to several diverse branches of mathematics and mathematical physics. The existing literature usually treats these two Laplacian operators separately. In this overview, we will focus on the relationship between them (spectral and parabolic properties). Our main conceptual message is that these two settings should be regarded as complementary (rather than opposite) and exactly their interplay leads to important further insight on both sides.

arXiv commentThis is an extended version of the invited lecture of one of us (A.K.) at the 8th European Congress of Mathematics in Portorož, June 21-26, 2021. arXiv admin note: text overlap with arXiv:2105.09931

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