Black Hole Models and Quantum Interactions

Very often the basic problem of modern theoretical physics is identiffed with the task of quantizing gravity. In those cases, when only time and radius of a system are playing a role | hence for twodimensional theories of gravity | substantial progress could be made. For example, it turned out that after the collision of thin shells of matter this process can be attempted as passing through an intermediate Black Hole. Black Holes are wellknown solutions of Einstein theory with a very large mass so that within a certain "horizon" around that mass not even light rays are able to _ght the gravitational attraction { at least as long as no quantum effects come into play. In the course of these investigations it turned out that a new paper of S. Hawking (with R. Bousso) was affected by basic mistakes. In fact, their result would have led to physically completely unacceptable (and inconsistent) behaviour of a Black Hole when it emits quantum radiation ("Hawking radiation"). The correction of this work by the collaborators of the present project appeared in the same leading US journal (Physical Review D) as the original paper of Hawking and collaborator. Another, quite unexpected result concerned the so-called "supergravity" in two dimensions. Until the present work, the prevailing opinion implied that "ordinary" gravity had a unique supergravitational extension. Our results contradict this point of view; being able to construct the most general supergravity theory in two dimensions we show that these are highly ambiguous.