A Large-$N$ Phase Transition in a Finite Lattice Gauge Theory

TL;DR

This paper explores a large-$N$ phase transition in a 1+1D lattice gauge theory with a finite non-Abelian group, revealing a first-order transition analogous to confinement-deconfinement at infinite $N$.

Contribution

It introduces a new large-$N$ limit for finite group gauge theories and identifies a Gross-Witten-Wadia-like phase transition in the permutation group $S_N$.

Findings

Existence of a large-$N$ phase transition at $oxed{ ext{}\lambda=2}$

The transition is first order and resembles confinement-deconfinement

The string tension jumps from zero to finite at the transition

Abstract

We consider gauge theories of non-Abelian $finite$ groups, and discuss the 1+1 dimensional lattice gauge theory of the permutation group $S_N$ as an illustrative example. The partition function at finite $N$ can be written explicitly in a compact form using properties of $S_N$ conjugacy classes. A natural large-$N$ limit exists with a new 't Hooft coupling, $\lambda=g^2 \log N$. We identify a Gross-Witten-Wadia-like phase transition at infinite $N$, at $\lambda=2$. It is first order. An analogue of the string tension can be computed from the Wilson loop expectation value, and it jumps from zero to a finite value. We view this as a type of large-$N$ (de-)confinement transition. Our holographic motivations for considering such theories are briefly discussed.