Instantons, symmetries and anomalies in five dimensions

All five-dimensional non-abelian gauge theories have a U(1)(I) global symmetry associated with instantonic particles. We describe an obstruction to coupling U(1)(I) to a classical background gauge field that occurs whenever the theory has a one-form center symmetry. This is a finite-order mixed 't Hooft anomaly between the two symmetries. We also show that a similar obstruction takes place in gauge theories with fundamental matter by studying twisted bundles for the ordinary flavor symmetry. We explore some general dynamical properties of the candidate phases implied by the anomaly. Finally, we apply our results to supersymmetric gauge theories in five dimensions and analyze the symmetry enhancement patterns occurring at their conjectured RG fixed points.

Automated summary

This study reveals a finite-order mixed 't Hooft anomaly in five-dimensional non-abelian gauge theories, as well as an obstruction to coupling the U(1) global symmetry with a classical background gauge field associated with a one-form center symmetry. A similar obstruction is found to occur in gauge theories with fundamental matter. Furthermore, the general dynamical properties of the candidate phases implied by the anomaly are explored.