Leading Large N Modification of QCD_2 on a Cylinder by Dynamical Fermions

TL;DR

This paper analyzes 2D QCD on a cylindrical space with massless fermions, revealing how dynamical quarks modify the large N saddle point through eigenvalue decompactification, affecting vacuum energy and Wilson loops.

Contribution

It introduces a novel analysis of large N QCD_2 on a cylinder with dynamical fermions, highlighting the decompactification phenomenon and its impact on the gauge theory's vacuum structure.

Findings

Eigenvalue decompactification due to fermion coupling

Nontrivial dependence of vacuum energy on quark flavors

Altered Wilson loop expectation values

Abstract

We consider 2-dimensional QCD on a cylinder, where space is a circle. We find the ground state of the system in case of massless quarks in a $1/N$ expansion. We find that coupling to fermions nontrivially modifies the large $N$ saddle point of the gauge theory due to the phenomenon of `decompactification' of eigenvalues of the gauge field. We calculate the vacuum energy and the vacuum expectation value of the Wilson loop operator both of which show a nontrivial dependence on the number of quarks flavours at the leading order in $1/N$.