Hawking radiation in large N strongly coupled field theories

Abstract

We consider strongly coupled field theories at large N on black hole backgrounds. At sufficiently high Hawking temperature TH, one expects a phase where the black hole is in equilibrium with a deconfined plasma. We explore this phase in the context of the AdS/CFT correspondence and argue that two possible behaviors may result. At a given Hawking temperature TH, field theories on large black hole backgrounds will result in a plasma that interacts strongly with the black hole. Such cases will be dual to novel bulk spacetimes having a single connected horizon which we dub black funnels. We construct examples of black funnels in low spacetime dimensions for different classes of field theory black holes. In this case, perturbing the equilibrium state results in the field theory exchanging heat with the black hole at a rate typical of conduction through deconfined plasma. In contrast, we argue that due to the finite physical size of plasma excitations, smaller black holes will couple only weakly to the field theory excitations. This situation is dual to bulk solutions containing two disconnected horizons which remain to be constructed. Here perturbations lead to heat exchange at a level typical of confined phases, even when TH remains far above any deconfinement transition. At least at large N and strong coupling, these two behaviors are separated by a sharp transition. Our results also suggest a richer class of braneworld black holes than hitherto anticipated.