Two Dimensional QCD is a String Theory

TL;DR

This paper demonstrates that two-dimensional QCD can be interpreted as a closed string theory, with its partition function expansion directly related to sums over surface maps, revealing a deep string-theoretic structure.

Contribution

It establishes a precise correspondence between 2D QCD partition function coefficients and sums over surface maps, providing a string theory interpretation.

Findings

Partition function expanded in 1/N and area A

Coefficients determined by sums over surface maps

2D QCD interpreted as a closed string theory

Abstract

The partition function of two dimensional QCD on a Riemann surface of area $A$ is expanded as a power series in $1/N$ and $A$. It is shown that the coefficients of this expansion are precisely determined by a sum over maps from a two dimensional surface onto the two dimensional target space. Thus two dimensional QCD has a simple interpretation as a closed string theory.