**Bits, Branes, Black Holes**

**Coordinators:** Vijay Balasubramanian, Alex Maloney, Donald Marolf, Joan Simon

**Scientific Advisors:** Joseph Polchinski, Theodore Jacobson

Over the last fifteen years, our understanding of quantum gravity in string theory has been transformed by the discovery and exploitation of D-branes and the AdS/CFT correspondence in string theory. Many problems that were thought insuperably difficult have been solved, at least partially: (i) the entropy and thermodynamic properties of many extremal and near-extremal black holes have been precisely explained in terms of microscopic degrees of freedom, (ii) light has been shed on the physics of spacetime singularities, (iii) the holographic principle, positing massive reduction of the degrees of freedom in quantum gravity, has been understood precisely in spacetimes with a negative cosmological constant via a duality between gravity and gauge theory. These results have been so powerful that it is now being used as a tool to shed light on otherwise intractable problems involving strongly coupled systems in other fields of physics.

Yet the fundamental mechanisms behind such holographic behaviors remain unclear. The goal of our program is to elucidate them and to understand the limits to (or generality of) their applicability. In particular, we will address the following points:

To what extent do the above lessons rely on the particular constructions used to date? Are they tied to stringy effects and to string theory in particular, or are they general lessons for quantum gravity?*How general is holography?:*Holography in string theory strongly suggests that information is not lost in black hole evaporation. Is it clear that this interpretation is correct? If so, how is this consistent with known bulk physics and the validity of Einstein gravity as a low-energy effective theory? How fast can information be extracted, under what conditions, and with what fidelity?*The information paradox:*Why is the entropy of a black hole proportional to horizon area, and not to some other geometrical construct? In holographic contexts, how does the interior of a black hole (where information about the microstate is hidden) get represented in its holographically dual description as a state in a non-gravitating field theory? How can the thermodynamic properties of black holes and gravity be explained in flat space, far from extremality?*The geometry of information:*In the context of the gauge/gravity duality, can we give a constructive description of the emergence of additional spacetime dimensions as the effective description of strongly coupled field theory dynamics? How does spacetime locality emerge in this formulation? Can spacetime always be regarded as an emergent concept, or is this special to some classes of universes? How is locality in gravitational physics to be understood more broadly?*Emergence of spacetime and locality:*Cosmological horizons in solutions to General Relativity admit a thermodynamic interpretation -- what is their microcanonical interpretation? Is there a dual field theoretic description of these systems? Can time be holographically reconstructed as space can when there is a negative cosmological constant?, Can the concepts/ideas of black hole physics shed light on cosmological singularities?*Holography & time:*The majority of developments to date have been in the context of asymptotically anti-de Sitter boundary conditions. To what extent do these lessons apply to systems with de Sitter or other cosmological asymptotics (or even to asymptotically flat spacetimes)?*Astrophysically relevant boundary conditions:*

This program will focus on these key questions in light of the progress achieved over the last decade.

There will be an associated conference **Black Holes and Information** to be held May 21-25, 2012. Further information will be posted when it becomes available. You need not be a program participant to attend the conference.