Universality in Two Dimensional Gauge Theory.

TL;DR

This paper explores two-dimensional Yang-Mills theories with massless fermions, revealing that the massive states' physics depends only on the gauge group and anomaly, showing a form of universality, while massless physics is largely decoupled.

Contribution

It demonstrates that the spectrum and interactions of massive states in 2D gauge theories are universal, depending only on the gauge group and anomaly, regardless of detailed model structure.

Findings

Massive state physics depends only on gauge group and anomaly.

Massless physics decouples from massive physics.

Equivalence between different fermion representations in QCD2.

Abstract

We discuss two dimensional Yang -- Mills theories with massless fermions in arbitrary representations of a gauge group $G$. It is shown that the physics (spectrum and interactions) of the massive states in such models is independent of the detailed structure of the model, and only depends on the gauge group $G$ and an integer $k$ measuring the total anomaly. The massless physics, which does depend on the details of the model, decouples (almost) completely from that of the massive one. As an example, we discuss the equivalence of QCD$_2$ coupled to fermions in the adjoint, and fundamental representations.