2D DILATION GRAVITY IN A UNITARY GAUGE

Reduced phase space formulation of 2D dilaton gravity coupled to matter is studied in an extrinsic time gauge. The corresponding hamiltonian can be promoted into a hermitian operator acting in the physical Hilbert space, implying a unitary evolution for the system. Consequences for the black hole physics are discussed. In particular, this way of defining the quantum theory rules out the Hawking scenario for the endpoint of the black hole evaporation process.