Hawking radiation, covariant boundary conditions, and vacuum states

Abstract

The basic characteristics of the covariant chiral current $⟨{J}_{\ensuremath{\mu}}⟩$ and the covariant chiral energy-momentum tensor $⟨{T}_{\ensuremath{\mu}\ensuremath{\nu}}⟩$ are obtained from a chiral effective action. These results are used to justify the covariant boundary condition used in recent approaches of computing the Hawking flux from chiral gauge and gravitational anomalies. We also discuss a connection of our results with the conventional calculation of nonchiral currents and stress tensors in different (Unruh, Hartle-Hawking and Boulware) states.