Black holes

The difficulties that arise in formulating a theory of gravity according to the principles of quantum mechanics are longstanding, and manifest themselves most vividly in the conundrums related with the quantum properties of black holes. A naive description of the process of black hole evaporation via Hawking radiation seems to violate unitarity, a fundamental principle of quantum mechanics. The root of this difficulty lies in our lack of understanding of the nature of black hole microstates: the Bekenstein-Hawking entropy predicts an enormous number of states with fixed global charges, but these states are invisible in the spacetime picture of black holes implied by general relativity.

Holography relates the microstates of black holes to states of a dual Conformal Field Theory (CFT) and provides an invaluable tool to elucidate their properties and to formulate a consistent unitary description of their dynamics. Conversely, the identification of the microstates with explicit supergravity solutions can be used to extract non-trivial informations on the CFT. For instance, the study of small perturbations around the geometry of microstates leads to a novel way to compute dynamical correlators at strong coupling.