Torsional Response, bulk-boundary correspondence, and Viscosity in Topological Insulators

We discuss the relationship between torsion and visco-elastic response of 2D time-reversal breaking topological insulators. We connect the bulk topological response to a new anomalies in the momentum current of the chiral edge theory that we have determined. We also discuss the implications for spectral flow and the emergence of a chiral-gravity type response theory.