Session D01: Holographic Developments in Quantum Black Hole Physics

Holographic Reconstruction of Black Hole Interiors

Holographic models can lead to preservation of quantum information when black holes evaporate. In this context, the magnitude of the corrections to semiclassical physics is quantified and refined. For certain quantities, such as those related to infalling observers, corrections to semiclassical quantities are shown to be negligible. This permits the holographic reconstruction of black hole interiors.   

Quantum Black Hole Physics from Random Matrix Models

A large N random matrix model's spectral density is generically a continuous function. In the context of various 2D quantum gravity models where the matrix model reproduces the sum over geometry and topology, this has been taken to mean that the holographic dual neccessarily involves an ensemble of Hamiltonians. This has led to a great deal of interesting activity, exploring the idea that gravity may fundamentally be an ensemble in more general contexts. However, a closer look at the matrix models shows that a discrete structure is in fact present in the spectrum. It is a sum of energy peaks that can be computed using Fredholm determinant techniques. It is suggested that this discrete structure reveals the spectrum of the single dual Hamiltonian of the gravity theory, and hence that gravity is not dual to an ensemble. Holography for 2D gravity then more closely resembles higher dimensional holography. An alternative interpretation of the matrix models' sum over topologies is given. Since some of these 2D gravity models arise from the low temperature physics of classes of higher dimensional black holes, these results also shed light on their low temperature physics.    

Classical Wormholes,Quenched Free Energy, and the Gravitational Replica Trick

Recent developments have revealed that at least in certain contexts, the gravitational path integral predicts unitary evolution of black hole evaporation as long as Euclidean wormholes are included.  The inclusion of such wormholes suggests an interpretation of the path integral as some kind of ensemble average.  In this talk, I'll discuss how the presence of these wormholes can make a contribution to the gravitational free energy, which can be computed from the path integral via a replica trick distinct from the more familiar one used to compute von Neumann entropies.  I'll sketch how this replica trick works using a two-dimensional model of dilaton gravity -- JT gravity -- as a prototypical example.  In pure JT gravity, the contributions of replica wormholes only affect the free energy at nonperturbatively small temperature.  In the case of JT coupled to matter, however, the replica wormholes can be stabilized even in a classical approximation; I'll report progress on understanding the contribution of these wormholes to the the gravitational generating functional in a classical limit.