We argue that states with nontrivial horizontal charges of a Bañados-Teitelboim-Zanelli (BTZ) black hole can be excited by ordinary falling matter including Hawking radiation. The matter effect does not break the integrability condition of the charges on the horizon. Thus we are able to trace the processes in which the matter imprints the information on the horizon by use of the charged states. It is naturally expected that in thermal equilibrium with the Hawking radiation the black hole wanders ergodically through different horizontal states due to thermal fluctuation of the incoming matter. This fact strengthens the plausibility of the basic part of Carlip’s idea. We also discuss some aspects of the quantum horizontal symmetry and conjecture how the precise black hole entropy will be given from our point of view.

• Received 26 June 2002

DOI:https://doi.org/10.1103/PhysRevD.66.124021