Supersymmetric Gauge Theory on the Graph

TL;DR

This paper develops a graph-theoretic framework for discretized 2D supersymmetric gauge theories, revealing topological zero modes, anomalies as deficit angles, and simplifying path integrals via localization.

Contribution

It introduces a novel graph-based description of supersymmetric gauge theories on discretized surfaces, analyzing zero modes, anomalies, and localization in both Abelian and non-Abelian cases.

Findings

Fermionic zero modes relate to graph topology.

Anomalies correspond to deficit angles at vertices.

Path integrals localize to zero modes, simplifying calculations.

Abstract

We consider two-dimensional N=(2,2) supersymmetric gauge theory on discretized Riemann surfaces. We find that the discretized theory can be efficiently described by using graph theory, where the bosonic and fermionic fields are regarded as vectors on a graph and its dual. We first analyze the Abelian theory and identify its spectrum in terms of graph theory. In particular, we show that the fermions have zero modes corresponding to the topology of the graph, which can be understood as kernels of the incidence matrices of the graph and the dual graph. In the continuous theory, a scalar curvature appears as an anomaly in the Ward-Takahashi (WT) identity associated with a U(1) symmetry. We find that the same anomaly arises as the deficit angle at each vertex on the graph. By using the localization method, we show that the path integral on the graph reduces to an integral over a set of the zero modes. The partition function is then ill-defined unless suitable operators are inserted. We extend the same argument to the non-Abelian theory and show that the path integral reduces to multiple integrals of Abelian theories at the localization fixed points.