Twisted Kac–Moody algebras and the entropy of AdS3 black hole

We show that an SL(2,R)L×SL(2,R)R Chern–Simons theory coupled to a source on a manifold with the topology of a disk correctly describes the entropy of the AdS3 black hole. The resulting boundary WZNW theory leads to two copies of a twisted affine Kac–Moody algebra, for which the respective Virasoro algebras have the same central charge c as the corresponding untwisted theory. But the eigenvalues of the respective L0 operators are shifted. We show that the asymptotic density of states for this theory is, up to logarithmic corrections, the same as that obtained by Strominger using the asymptotic symmetry of Brown and Henneaux.