Graph Zeta Functions and Wilson Loops in Kazakov-Migdal Model

TL;DR

This paper explores the extended Kazakov-Migdal model on arbitrary graphs, revealing connections to zeta functions and providing exact evaluations of the partition function at large N, with implications for Wilson loop contributions.

Contribution

It introduces a novel representation of the partition function using Bartholdi and Ihara zeta functions, and derives exact large N solutions on arbitrary graphs, extending previous models.

Findings

Partition function expressed via Bartholdi zeta function.

Exact evaluation of partition function on arbitrary graphs at large N.

Non-zero area Wilson loops contribute only at subleading order.

Abstract

In this paper, we consider an extended Kazakov-Migdal model defined on an arbitrary graph. The partition function of the model, which is expressed as the summation of all Wilson loops on the graph, turns out to be represented by the Bartholdi zeta function weighted by unitary matrices on the edges of the graph. The partition function on the cycle graph at finite $N$ is expressed by the generating function of the generalized Catalan numbers. The partition function on an arbitrary graph can be exactly evaluated at large $N$ which is expressed as an infinite product of a kind of deformed Ihara zeta function. The non-zero area Wilson loops do not contribute to the leading part of the $1/N$-expansion of the free energy but to the next leading. The semi-circle distribution of the eigenvalues of the scalar fields is still an exact solution of the model at large $N$ on an arbitrary regular graph, but it reflects only zero-area Wilson loops.