The Hawking black-hole radiation spectrum has a short tail

Abstract

It is proved that the Hawking emission spectrum of a semiclassical Schwarzschild black hole of mass [Formula: see text] has a sharp cut at the frequency scale [Formula: see text]. In particular, taking into account the nonlinear gravitational coupling between the tunneled Hawking quanta and the emitting black hole, it is explicitly shown that the upper bound [Formula: see text] on the energies of the emitted Hawking quanta is a direct consequence of the famous Thorne hoop relation.