Electronic Journal of Differential Equations, Conference 04 (2000), pp. 159-164. Title: The Bisognano-Wichmann theorem for charged states and the conformal boundary of a black hole Author: Roberto Longo (Univ. di Roma "Tor Vergata", Italy) Abstract: This note concerns the study of the incremental entropy of a quantum black hole, based on Operator Algebra methods. Our results are based on the results presented in the references [6,11,12,13]. Published July 12, 2000. Math Subject Classifications: 81T05, 46L60, 47L90, 83C57. Key Words: Bisognano-Wichmann Theorem; black hole; modular theory; KMS state.