Tidal heating in a Riemann-Cartan spacetime

We consider possible perturbations of the black hole event horizon induced by matter with spin, extending the derivation of the Hawking-Hartle formula (tidal heating) in the presence of torsion. When specialized to theories with a nonvanishing (pseudo-)traceless component of the (con)torsion tensor, we remarkably find that the tidal heating phenomenon gets modified by additional torsion-dependent terms, in agreement with previous investigations based on Jacobson's spacetime thermodynamics approach. These results lead to relevant phenomenological and theoretical consequences: modifications in the Hawking-Hartle term change the Bondi mass associated with the gravitational radiation observed at infinity, and modify the Hawking radiation spectrum of evaporating black holes.