CORRESPONDENCE PRINCIPLE FOR BLACK-HOLES AND STRINGS

For most black holes in string theory, the Schwarzschild radius in str ing units decreases as the string coupling is reduced. We formulate a correspondence principle, which states that (i) when the size of the h orizon drops below the size of a string, the typical black hole state becomes a typical state of strings and D-branes with the same charges, and (ii) the mass does not change abruptly during the transition. Thi s provides a statistical interpretation of black hole entropy. This ap proach does not yield the numerical coefficient, but gives the correct dependence on mass and charge in a wide range of cases, including neu tral black holes.