BLACK-HOLES AS QUANTUM MEMBRANES

We propose a quantum description of black holes. The degrees of freedo m to be quantized are identified with the microscopic degrees of freed om of the horizon, and their dynamics is governed, at an effective lev el, by the action of the relativistic bosonic membrane in D = 4. We fi nd that quantum black holes are not characterized uniquely by mass, ch arge and angular momentum, but there is also a quasi-continuum of memb rane levels. In this approach, it is possible to assign a wave-functio n to the horizon, derive the Schrodinger equation that it obeys and di splay the solution explicitly. In general, it emerges a consistent and plausible description of black holes as objects which absorb, thermal ize and emit radiation in a way which is not fundamentally different f rom any other macroscopic object. The limits of validity of the membra ne approach rum out to coincide with the known limits of validity of t he thermodynamical description of black holes.