Symmetries, anomalies, and dualities of two-dimensional Non-Linear Sigma Models

Abstract

We analyse the global symmetry structure of two-dimensional Non-Linear Sigma Models with Wess-Zumino term. When the target space has a compact isometry without fixed points, the theory has a pair of (group-like) global symmetries and many such theories also have non-invertible symmetries. We describe how the topology of the target space and Wess-Zumino term determine whether the group-like symmetries are continuous or discrete, and study their pure and mixed 't Hooft anomalies. We also revisit the construction of the non-invertible symmetries, which are associated with possible self-dualities under discrete gauging, and show how the global symmetry structure is left invariant by this gauging.