COMMENTS ON BLACK-HOLES IN MATRIX-THEORY

The recent suggestion that the entropy of Schwarzschild black holes ca n be computed in matrix theory using near-extremal D-brane thermodynam ics is examined. It is found that the regime in which this approach is valid actually describes black strings stretched across the longitudi nal direction, near the transition when black strings become unstable to the formation of black holes. It is argued that the appropriate dyn amics on the other (black hole) side of the transition is that of the zero modes of the corresponding super Yang-Mills theory. A suggestive mean field theory argument is given for the entropy of black holes in all dimensions. Consequences of the analysis for matrix theory and the holographic principle are discussed.