QUANTUM BLACK-HOLE EVAPORATION

We investigate a recently proposed model for a full quantum descriptio n of two-dimensional black hole evaporation, in which a reflecting bou ndary condition is imposed in the strong-coupling region. It is shown that in this model each initial state is mapped to a well-defined asym ptotic out state, Provided one performs a certain projection in the gr avitational zero mode sector. We find that for an incoming localized e nergy pulse, the corresponding outgoing state contains approximately t hermal radiation, in accordance with semiclassical predictions. In add ition, our model allows for certain acausal strong-coupling effects ne ar the singularity that give rise to corrections to the Hawking spectr um and restore the coherence of the out state. To an asymptotic observ er these corrections appear to originate from behind the receding appa rent horizon and start to influence the outgoing state long before the black hole has emitted most of its mass. Finally, by putting the syst em in a finite box, we are able to derive some algebraic properties of the scattering matrix and prove that the final state contains all ini tial information.