Chiral gauge theory at the boundary between topological phases

Abstract

I demonstrate how chiral fermions with an exact gauge symmetry can appear on the d-dimensional boundary of a finite volume (d+1)-dimensional manifold, without any light mirror partners. The condition for the d-dimensional boundary theory to be local is that gauge anomalies cancel and that the volume be large. This can likely be achieved on a lattice and provides a new paradigm for the lattice regularization of chiral gauge theories.

Comments: V3: updated to version accepted for publication by Phys. Rev. Lett. on Jan. 21, 2024. Rendered more concise, no changes in the physics