# FTheory: Electromagnetic Duality Anomaly in Curved Spacetimes

## Main Content

The source-free Maxwell's classical theory is invariant under electric-magnetic duality rotations. This is true even in the presence of an arbitrary gravitational background field. In this talk, I will discuss this symmetry and the associated Noether current and will show how the classical conversion law is broken once quantum mechanical effects are taken into account, as long as the (classical) gravitational background has a non-zero Chern-Pontryagin density. I will discuss the analogy with the well-known chiral anomaly of massless spin 1/2 fermions, as well as potential physical consequences.