On non-chiral extension of Kerr/CFT

We discuss possible non-chiral extension of the Kerr/CFT correspondence. We first consider the near horizon geometry of an extremal BTZ black hole and study the asymptotic symmetry. In order to define it properly, we introduce a regularization and show that the asymptotic symmetry becomes the desirable non-chiral Virasoro symmetry with the same central charges for both left and right sectors, which are independent of the regularization parameter. We then investigate the non-chiral extension for general extremal black holes in the zero entropy limit. Since the same geometric structure as above emerges in this limit, we identify non-chiral Virasoro symmetry by a similar procedure. This observation supports the existence of a hidden non-chiral CFT 2 structure with the same central charges for both left and right sectors dual to the rotating black holes.