Localized edge states, topology, and generalized Hall currents

Topological materials come in many forms with many different symmetries, with a common feature being topologically protected massless fermions stuck to edges, corners, vortices, etc. I discuss a relativistic quantum field theory approach that serves to unify them in a way that makes all of these systems look similar to the integer quantum Hall effect. The approach makes explicit the unique interplay between topology in both coordinate space and momentum space which underlies these systems.