BLACK-HOLE MICROSTRUCTURE

8 juin 2020, 11:50 → 12 juin 2020, 18:30 Europe/Paris

Via Zoom

Recorded Youtube links for all the talks can be found in the timetable

 

Conference:  June 8 - 12              

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The microscopic description of black holes has been a challenge for more that forty years.  There are now quite a number of promising approaches to solving this problem and the primary goal of this conference and workshop is to bring together experts in these areas to identify synergies, engage in constructive criticism and resolve apparent conflicts.  A significant focus will be the dynamics of black-hole microstructure: how infalling matter is scrambled and how information is recovered.

The conference will involve three talks a day and a panel discussion on the first four days of the conference.   All events will be held via Zoom.

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Organizers: Iosif Bena, Nick Warner

  

           

lundi 8 juin

11:50 → 12:00 Connecting. Welcome

All events are given in Paris time

Zoom Meeting ID: 989 6887 0177

12:00 → 13:00 Gravitational wave echoes, microstates and AdS/CFT

Recorded version: http://www.youtube.com/watch?v=bSJS8yWdnrA

Orateur: Bert Vercnocke

14:30 → 15:30 Making Microstate Geometries Spark Joy: Decluttering using Holomorphy and Dimensional Reduction

Microstates of the three-charge D1-D5-P black hole - superstrata - are complicated solutions in 6D supergravity. I will discuss two ways to make Marie Kondo proud by "decluttering" and simplifying these solutions. First, by a clever choice of complex variables, one can quickly generalize the existing (single mode) superstrata to contain arbitrary holomorphic functions of these variables. Second, some of these superstrata can be dimensionally reduced on a three-sphere to three dimensions, where they take on a much simpler form. I will also discuss why this should "spark joy", as these new tools and insights are a first steps on a path towards constructing and understanding more general three-charge microstates.

Recorded version: http://www.youtube.com/watch?v=Li7N8NUpAAw

Orateur: Daniel Mayerson

16:00 → 17:00 The VECRO hypothesis

We consider three fundamental issues in quantum gravity: (a) the black hole information paradox (b) the unboundedness of entropy that can be stored inside a black hole horizon (c) the relation between the black hole horizon and the cosmological horizon. With help from the small corrections theorem, we convert each of these issues into a sharp conflict. We then argue that all three conflicts can be resolved by the following hypothesis: The vacuum wavefunctional of quantum gravity contains a "vecro" component made of virtual fluctuations of configurations of the same type that arise in the fuzzball structure of black hole microstates. Further, if we assume that causality holds to leading order in gently curved spacetime, then we must necessarily have such a vecro component in order to resolve the above conflicts. The term vecro stands for `Virtual Extended Compression-Resistant Objects', and characterizes the nature of the vacuum fluctuations that resolve the puzzles. It is interesting that puzzle (c) may relate the role of quantum gravity in black holes to observations in the sky.

Recorded version: https://youtu.be/Li7N8NUpAAw?t=5409

Orateur: Samir Mathur

17:45 → 19:00 Panel: What does BMS and soft hair tell us about microstate structure?

Moderator: Guillaume Bossard

Recorded discussion: https://www.youtube.com/watch?v=NtQJsSiv4Fw

Orateurs: Andrea Puhm, Geoffrey Compère, Malcolm Perry

mardi 9 juin

11:50 → 12:00 Connecting: Zoom address

All events are given in Paris time

Zoom Meeting ID 957 9920 8880

12:00 → 13:00 Chaos at the rim of black hole and fuzzball shadows

We study the scattering of massless probes in the vicinity of the photon-sphere of asymptotically AdS/flat black holes and horizon-free microstate geometries (fuzzballs). We find that these exhibit a chaotic behaviour characterised by exponentially large deviations of nearby trajectories and compute the Lyapunov exponent \lambda governing the exponential growth. We find that fuzzballs and JMART geometries are characterised by Lyapunov exponents smaller than those associated to Black holes with the same mass providing evidence for the existence of a universal bound on chaos.

Recorded version: http://www.youtube.com/watch?v=jAtq0gO9DSE

Orateur: Jose Morales

14:30 → 15:30 The Great Escape: Tunneling out of Microstate Geometries

We discuss the quasi-normal modes in asymptotically-flat microstate geometries that have the same charge as a D1-D5-P black hole, but whose long BTZ-like throat ends in a smooth cap. In general the wave equation is not separable, but we find a class of geometries in which the non-separable term is negligible and we can compute the quasi-normal frequencies using WKB methods. The long throats of these capped geometries generate large redshifts, which lead to exceptionally-low-energy states with extremely long decay times, set by the central charge of the dual CFT to the power of twice the dimension of the operator dual to the mode. While these decay times are extremely long, we also argue that the energy decay is bounded, at large t, by log(t)^-2 and is comparable with the behavior of ultracompact stars, as one should expect for microstate geometries.

Recorded Version: https://www.youtube.com/watch?v=MI5-c5-HLC0

Orateur: Pierre Heidmann

16:00 → 17:00 Stringy Structure at the BPS Bound

We explore the stringy structure of 1/2-BPS states in little string theory and its AdS3 limit using worldsheet techniques. Duality in the worldsheet theory maps the geometrical (Lunin-Mathur) description of these states to a non-compact Landau-Ginsburg model whose superpotential is determined by the fivebrane source configuration. Singular limits of the 1/2-BPS configuration space result when the fivebrane worldvolume self-intersects, as can be seen from both sides of the duality -- on the Landau-Ginsburg side from the degeneration of the superpotential, and on the geometrical side from an analysis of D-brane probes. These singular limits are a portal to black hole formation via the condensation of the W-branes that are becoming massless, and thus exhibit in the gravitational bulk description the central actors in the non-gravitational dual theory underlying black hole thermodynamics.

Recorded Version: https://youtu.be/MI5-c5-HLC0?t=5330

Orateur: Emil Martinec

17:45 → 19:00 Panel: Microstates and Chaos

Moderator: Costas Bachas

Recorded Version: https://youtu.be/MI5-c5-HLC0?t=11684

Orateurs: Ben Craps, Douglas Stanford, Emil Martinec, Iosif Bena

mercredi 10 juin

11:50 → 12:00 Connecting: Zoom address

All events are given in Paris time

Zoom Meeting ID 996 8098 6502

12:00 → 13:00 Session Cancelled

At the request of this morning’s speaker, and out of respect for our colleagues who are striking today to protest racial discrimination and institutional violence, we have cancelled this morning's session of the conference.

Orateur: Marika Taylor

14:30 → 15:30 What AdS_3 holography can tell us about black hole microstates?

Focusing on the paradigmatic example of the Strominger-Vafa black hole, I will review the insights on the gravitational description of black hole microstates coming from the dual 2D CFT. In particular I will discuss the correlators of "light" probe operators in the "heavy" states representing the microstates and their various limits.

Recorded Version: https://www.youtube.com/watch?v=31f_2G5DLaw

Orateur: Stefano Giusto

16:00 → 17:00 Gravity and randomness

Recorded Version: https://youtu.be/31f_2G5DLaw?t=5673

Orateur: Jan de Boer

17:45 → 19:00 Panel: Do typical states have horizons?

Moderator: David Turton

Recorded Version: https://youtu.be/31f_2G5DLaw?t=11367

Orateurs: Iosif Bena, Jan de Boer, Juan Maldacena, Samir Mathur, Suvrat Raju

jeudi 11 juin

11:50 → 12:00 Connecting: Zoom address

All events are given in Paris time

Zoom Meeting ID 988 2505 2011

12:00 → 13:00 Some comments on wormholes and factorization

Recorded Version: http://www.youtube.com/watch?v=zB99h7iWKOg

Orateur: Phil Saad

14:30 → 15:30 The unreasonable effectiveness of semi-classical gravity without microstructure.

This talk will be about some surprising results from the semi-classical description of black holes. I will describe how this regime captures both the Hayden-Preskill protocol as well as the Page curve of evaporating black holes, indicative of unitary evaporation. The main tool will be the Island formula, as extension of the holographic entropy prescription to computing the entropy of the Hawking radiation. I will briefly mention how this formula is derived from a nonperturbative contributions to the replica trick.

Recorded version: https://youtu.be/wzVMDrfaRXA

Orateur: Ahmed Almheiri

16:00 → 17:00 Entropies of subregions in two dimensional cosmological models

We discuss a two dimensional cosmological model consisting of two dimensional de-Sitter JT gravity plus a CFT . We compute entropies of subregions of the future asymptotic region.

Recorded version: https://youtu.be/wzVMDrfaRXA?t=5406

Orateur: Juan Maldacena

17:45 → 19:00 Panel: Islands, JT Gravity, AdS2 holography and Microstate Structure.

Moderator: Marika Taylor

Recorded version: https://youtu.be/Vr61WnB6Ndw

Orateurs: Ahmed Almheiri, Juan Maldacena, Samir Mathur, Steve Shenker

vendredi 12 juin

11:50 → 12:00 Connecting: Zoom address

All events are given in Paris time

Zoom Meeting ID 987 8329 9477

12:00 → 13:00 Black Holes in string theory with duality twists.

We consider 5D supersymmetric black holes in string theory compactifications that partially break supersymmetry. We compactify type IIB on T^4 and then further compactify on a circle with a duality twist to give Minkowski vacua preserving partial supersymmetry (N=6,4,2,0) in five dimensions. The effective supergravity theory is given by a Scherk-Schwarz reduction with a Scherk-Schwarz supergravity potential on the moduli space, and the lift of this to string theory imposes a quantization condition on the mass parameters. In this theory, we study black holes with three charges that descend from various ten-dimensional brane configurations. For each black hole we choose the duality twist to be a transformation that preserves the solution, so that it remains a supersymmetric solution of the twisted theory with partially broken supersymmetry. We discuss the quantum corrections arising from the twist to the pure gauge and mixed gauge-gravitational Chern-Simons terms in the action and the resulting corrections to the black hole entropy.

Recorded version https://youtu.be/BMzNHx2wSWo

Orateur: Stefan Vandoren

14:30 → 15:30 Is structure at the horizon required to resolve the information paradox?

We will describe recent work on how quantum information is stored in quantum gravity in asymptotically flat space. We will argue that all information that is available on future null infinity can also be obtained from a small region near its past boundary. This can be physically understood as the statement that information about the black hole microstate is always available outside the black hole. We also show how one can sidestep the "small corrections theorem", and resolve the "bags of gold paradox". In particular, this means that the information paradox, by itself, cannot provide a reason for expecting "structure" near the black-hole horizon.

Recorded version https://youtu.be/7rvMkqVBhbY

Orateur: Suvrat Raju

16:00 → 17:00 JT, BTZ and the Island Phenomenon.

We study a simple model of black hole evaporation by considering a 1D QM system coupled to a 2D CFT on a strip, where both the 1D QM system and 2D CFT are chosen to have gravitational dual descriptions in terms of black holes in two and three dimensions respectively. By making use of the fact that JT gravity can be obtained via dimensional reduction of 3D gravity, the full system may be represented as a single BTZ geometry., in which the boundary of the strip is mapped on to end-of the world branes that extend to the horizon. This model exhibits and illuminates the notions of quantum entanglement, quantum extremal surfaces and the Island phenomenon in a simple and intuitive geometrical fashion.

Recorded version https://youtu.be/7rvMkqVBhbY?t=5773

Orateur: Erik Verlinde