BPS SPECTRUM OF THE 5-BRANE AND BLACK-HOLE ENTROPY

We propose a formulation of 11-dimensional M-theory in terms of five-b ranes with closed strings on their world-volume, We use this descripti on to construct the complete spectrum of BPS states in compactificatio ns to six and five dimensions. We compute the degeneracy for fixed cha rge and find it to be in accordance with U-duality (which in our formu lation is manifest in six dimensions) and the statistical entropy form ula of the corresponding black hole. We also briefly comment on the co mpactification to four dimensions.