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A trace on fractal graphs and the Ihara zeta function

Daniele Guido·Tommaso Isola·Michel L. Lapidus
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Abstract

Starting with Ihara's work in 1968, there has been a growing interest in the study of zeta functions of finite graphs, by Sunada, Hashimoto, Bass, Stark and Terras, Mizuno and Sato, to name just a few authors. Then, Clair and Mokhtari-Sharghi have studied zeta functions for infinite graphs acted upon by a discrete group of automorphisms. The main formula in all these treatments establishes a connection between the zeta function, originally defined as an infinite product, and the Laplacian of the graph. In this article, we consider a different class of infinite graphs. They are fractal graphs, i.e. they enjoy a self-similarity property. We define a zeta function for these graphs and, using the machinery of operator algebras, we prove a determinant formula, which relates the zeta function with the Laplacian of the graph. We also prove functional equations, and a formula which allows approximation of the zeta function by the zeta functions of finite subgraphs.

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Daniele Guido, Tommaso Isola, Michel L. Lapidus. 2008-10-22. A trace on fractal graphs and the Ihara zeta function. https://doi.org/10.1090/s0002-9947-08-04702-8

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