The black hole singularity in AdS/CFT

We explore physics behind the horizon in eternal AdS Schwarzschild black holes. In dimension d > 3, where the curvature grows large near the singularity, we find distinct but subtle signals of this singularity in the boundary CFT correlators. Building on previous work, we study correlation functions of operators on the two disjoint asymptotic boundaries of the spacetime by investigating the spacelike geodesics that join the boundaries. These dominate the correlators for large mass bulk fields. We show that the Penrose diagram for d > 3 is not square. As a result, the real geodesic connecting the two boundary points becomes almost null and bounces off the singularity at a finite boundary time t(c) not equal 0. If this geodesic were to dominate the correlator there would be a light cone singularity at t(c). However, general properties of the boundary theory rule this out. In fact, we argue that the correlator is actually dominated by a complexifted geodesic, whose properties yield the large mass quasinormal mode frequencies previously found for this black hole. We find a branch cut in the correlator at small time (in the limit of large mass), arising from coincidence of three geodesics. The t(c) singularity, a signal of the black hole singularity, occurs on a secondary sheet of the analytically continued correlator. Its properties are computationally accessible. The t(c) singularity persists to all orders in the 1/m expansion, for finite alpha', and to all orders in g(s). Certain leading nonperturbative effects can also be studied. The behavior of these boundary theory quantities near tc gives, in principle, significant information about stringy and quantum behavior in the vicinity of the black hole singularity.