’t Hooft Anomalies in Metals

Abstract

I review some recent results on understanding the physics of metals in an exact nonperturbative way through the powerful field-theoretic concepts of emergent symmetries and ’t Hooft anomalies. A ’t Hooft anomaly is a discrete topological property that quantum field theories with global symmetries can have. I explain how many of the properties of metals can in fact be viewed as direct consequences of the anomaly. This allows a structural understanding of metals, including non-Fermi liquids, to be obtained even in the absence of any exact solution for the strongly coupled dynamics. I then outline the main limitations and outstanding questions.