Note on Discrete Gauge Anomalies

TL;DR

This paper discusses the constraints on gauging discrete symmetries in low energy theories, emphasizing the role of instantons and the non-perturbative breaking of global discrete symmetries observed in string theory.

Contribution

It provides a framework to understand constraints on discrete gauge symmetries through instantons and highlights non-perturbative symmetry breaking in string perturbation theory.

Findings

Instantons impose constraints on gauging discrete symmetries.

Global discrete symmetries in string theory are broken non-perturbatively.

The paper clarifies the relationship between low energy constraints and string perturbation results.

Abstract

We consider the probem of gauging discrete symmetries. All valid constraints on such symmetries can be understood in the low energy theory in terms of instantons. We note that string perturbation theory often exhibits global discrete symmetries, which are broken non-perturbatively.