The Black Hole Information Paradox Journal Club

Black Hole Information Journal Club Website

Included page "clone:kclstrings" does not exist (create it now) In the last year, our community has witnessed important developments in the context of black hole evaporation and the famous black hole information paradox. Given the relevance of these problems and the probable interest of many of the people in the London area, we decided to organise a joint journal club between KCL and QMUL to discuss the new literature. This journal club will be organised in a series of meetings, the first three happening at KCL and the following three at QMUL. Each meeting will be an hour and a half long. Given the broadness of the subject, we decided the format will be paper-based: for each meeting, we will provide a list of specific papers that we expect attendees to read beforehand in order to have interesting discussions during the journal club, which will be led by one of us. The first part of the journal club will take place on Fridays, February 14, 21 and 28, starting at 13:15hs at KCL. The second part will be at QMUL on March 11, 25 and April 1 starting at 16:00hs. If you would like to attend the journal club, please send an email to Damian (ku.ca.lck|etnalag.naimad#ku.ca.lck|etnalag.naimad). This is particularly important if you are not from KCL, as you won't be able to go through King's security if your name is not on the list of participants. If you have any questions or comments, please contact either David Vegh (ku.ca.lumq|hgev.d#ku.ca.lumq|hgev.d) or Damian Galante (ku.ca.lck|etnalag.naimad#ku.ca.lck|etnalag.naimad). THE BLACK HOLE INFORMATION PARADOX JOURNAL CLUB IS NOW BACK IN VIRTUAL FORMAT. Go directly to next meeting

Suggested topics for future meetings

A dynamical mechanism for the Page curve from quantum chaos (Hong Liu, Shreya Vardhan) JT gravity as a matrix integral (Saad, Shenker, Stanford) Fuzzball program The mini information paradox - Thermo-field dynamics of black holes (Israel), Eternal Black Holes in AdS (Maldacena), …

First Meeting - Basics of Hawking's Evaporation

Date: Friday February 14, 1:15PM. Venue: King's College London, K-1.56. Speaker: Sameer Murthy (KCL) References: Particle Creation by Black Holes (Hawking) On particle creation by black holes (Wald) Further references: Jerusalem Lectures on Black Holes and Quantum Information (Harlow) Breakdown of predictability in black hole collapse (Hawking)

Second Meeting - The Page Curve and Introduction to Entanglement Entropy

Date: Friday February 21, 1:15PM. Venue: King's College London, K0.16. Speaker: Sameer Murthy/Damian Galante (KCL) References: Page Curve: Information in black hole radiation (Page) Time dependence of Hawking radiation entropy (Page) Introduction to Entanglement Entropy: Entanglement Entropy in field theory and gravity (Iqbal) Holographic Entanglement Entropy Quantum corrections to holographic entanglement entropy (Faulkner, Lewkowycz, Maldacena) Quantum Extremal Surfaces: Holographic Entanglement Entropy beyond the Classical Regime (Engelhardt, Wall)

Third Meeting - Holographic Entanglement Entropy and the Page Curve

Date: Friday February 28, 1:15PM. Venue: King's College London, Franklin-Wilkins Building FWB 1.70, Waterloo campus. Speaker: Damian Galante (KCL) References: Entanglement Wedge Reconstruction and the Information Paradox (Penington) The entropy of bulk quantum fields and the entanglement wedge of an evaporating black hole (Almheiri, Engelhardt, Marolf, Maxfield) The Page curve of Hawking radiation from semiclassical geometry (Ahmed Almheiri, Raghu Mahajan, Juan Maldacena, Ying Zhao)

Fourth Meeting - Euclidean Quantum Gravity, Replica Wormholes and the Page Curve

Date: Wednesday March 4, 12:00-14:00 Venue: Queen Mary University of London, G.O. Jones Building, room 610 (6th floor) http://www.qmul.ac.uk/about/howtofindus/mileend Speaker: Edgar Shaghoulian (Cornell) References: A. Almheiri, T. Hartman, J. Maldacena, E. Shaghoulian and A. Tajdini, Replica Wormholes and the Entropy of Hawking Radiation, 1911.12333. G. Penington, S. H. Shenker, D. Stanford and Z. Yang, Replica wormholes and the black hole interior, 1911.11977.

Triangle Seminar

Date: Wednesday March 4, 16:30- Venue: Queen Mary University London, G.O. Jones Building, Lecture Theatre (ground floor) http://www.qmul.ac.uk/about/howtofindus/mileend Speaker: Edgar Shaghoulian (Cornell) Title: "Replica wormholes and the information paradox" Abstract: The information paradox can be realized in two-dimensional models of gravity. In this setting, we show that the large discrepancy between the von Neumann entropy as calculated by Hawking and the requirement of unitarity is fixed by including new saddles in the gravitational path integral. These saddles arise in the replica method as wormholes connecting different copies of the black hole.

Fifth Meeting - JT gravity

Date: Wednesday March 11, 4:00PM. Venue: Queen Mary University London, G.E. Fogg Building, Fogg Lecture Theatre http://www.qmul.ac.uk/about/howtofindus/mileend Speaker: Lorenzo Bianchi (QMUL) Title: "Jackiw–Teitelboim gravity" References: Conformal symmetry and its breaking in two dimensional Nearly Anti-de-Sitter space (Maldacena, Stanford, Yang) AdS2 holography and the SYK model (Sarosi)

Special Seminar

THIS EVENT HAS BEEN CANCELLED Date: Monday March 23, 4:30PM. Venue: Queen Mary University London, Engineering Building 2.09 http://www.qmul.ac.uk/about/howtofindus/mileend Speaker: Douglas Stanford (Stanford) References: A. Almheiri, T. Hartman, J. Maldacena, E. Shaghoulian and A. Tajdini, Replica Wormholes and the Entropy of Hawking Radiation, 1911.12333. G. Penington, S. H. Shenker, D. Stanford and Z. Yang, Replica wormholes and the black hole interior, 1911.11977.

Sixth Meeting - Information loss and 2d CFT

Date: Wednesday April 22nd, 15:00hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Tarek Anous (University of Amsterdam) Title: A status report on the island formula from the perspective of 2d CFT at large central charge Abstract: I will give an informal review of some of the recent developments on reproducing the page curve in semi-classical gravity. I will then compare and contrast these results to older results from the study of holographic 2d CFT with sparse spectra and large central charge. In these quantum systems, there is a natural understanding of the CFT duals of the bulk semiclassical classical saddles that are responsible for evading information loss. I will end with some cautionary remarks explaining why I believe it is too early to declare the information problem "solved".

Seventh Meeting - Fuzzballs

Date: Wednesday May 6th, 15:00hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Rodolfo Russo (QMUL) Title: A personal bird eye view of fuzzballs Abstract: There are indications that ‘traditional’ GR physics at the horizon and usual assumptions of locality cannot provide a consistent description of black holes. The fuzzball paradigm suggests that ‘traditional’ GR physics at the horizon should be relaxed and that string theory provides the right degrees of freedom to have a non-trivial structure at the scale of the horizon. I'll review how this idea has emerged from the analysis of the Strominger-Vafa black hole and its implication for the AdS3/CFT2 duality.

Eighth Meeting - Quenches and the Page curve

Date: Wednesday May 13th, 15hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Juan Pedraza (UCL/Brandeis) Title: Local quenches, bulk entanglement entropy and a unitary Page curve Abstract: Quantum corrections to the entanglement entropy of matter fields interacting with dynamical gravity have proven to be very important in the study of the black hole information problem. We consider a one-particle excited state of a massive scalar field infalling in a pure AdS3 geometry and compute these corrections for bulk subregions anchored on the AdS boundary. In the dual CFT2, the state is given by the insertion of a local primary operator and its evolution thereafter. We calculate the area and bulk entanglement entropy corrections at order O(N^0), both in AdS and its CFT dual. The two calculations match, thus providing a non-trivial check of the FLM formula in a dynamical setting. Further, we observe that the bulk entanglement entropy follows a Page curve. We explain the precise sense in which our setup can be interpreted as a simple model of black hole evaporation and comment on the implications for the information problem.

Ninth Meeting - Bulk Reconstruction

Date: Wednesday, June 3rd, 15:00hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Bartek Czech (IAS, Tsinghua U.) Title: From bulk reconstruction to Berry phases and back Abstract: The first half of the talk will be a review of the main ingredients of bulk reconstruction: the Ryu-Takayanagi formula and subregion duality, the JLMS theorem, error correction and the complexity conjecture. The second half will be about my recent and current work on "modular Berry phases"—a type of Berry phase which characterizes the entanglement structure of a quantum state. We will see that the bulk curvature in AdS is (up to an integral transform) a special case of the modular Berry phase, though the concept has many other applications which we may or may not discuss. References: (1) For the review part of the talk, a good reference is Matt Headrick's "Lectures on entanglement entropy in field theory and holography", https://arxiv.org/abs/1907.08126. (2) First description of modular Berry phases: https://arxiv.org/abs/1712.07123 (my work with Lampros Lamprou, Sam McCandlish, James Sully.) (3) A fuller treatment of modular Berry phases: https://arxiv.org/abs/1903.04493 (work with Jan de Boer, Dongsheng Ge, Lampros Lamprou.)

Tenth Meeting - Replica Wormholes

Date: Friday, June 12th, 16:30hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Douglas Stanford (Stanford University) Title: Discussion about replica wormholes and ensembles Abstract: The goal is to have a general discussion about replica wormholes and the black hole information problem. To start things off, we will discuss the question of whether an ensemble interpretation is necessary for the replica wormhole computations of the entropy.

11th Meeting - SYK

Date: Wednesday, June 17th, 17:00hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Josephine Suh (Caltech) Title: A new observable to decode emergent gravity Abstract: I review the emergence of JT gravity from the SYK model, and the calculation of correlation functions in JT gravity. I motivate the need for a new observable distinct from entanglement entropy to fully decode emergent gravity, and propose as such an observable a quantum generalization of the entropy of multiple measurements on a dynamical system.

12th Meeting - SYK and holography

Date: Wednesday, June 24th, 15:00hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Vladimir Rosenhaus (IAS) Title: A review of SYK and attempts at a bulk dual Abstract: Most recent discussions of holography in AdS_2/CFT_1 have focused on the Schwarzian and JT gravity. However, the AdS dual of SYK is expected to, in addition, contain an infinite tower of massive fields. The interactions for these fields are in principle fixed by the SYK correlation functions. We review the construction of all-point correlation functions in SYK. We comment on the difficulties in finding a coherent description of the bulk tower of fields.

13th Meeting - The Complex SYK

Date: Wednesday, July 8th, 15:00hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Grigory Tarnopolsky (Harvard) Title: Remarks on the complex SYK model Abstract: In this talk I will discuss new properties of the complex SYK model in comparison with the Majorana one. I’ll mostly focus on spectrum of operators and the effective low energy action of the complex SYK model. In this case the conserved U(1) charge contributes a compact scalar field to the effective action in addition to the Schwarzian term. References: Notes on the complex Sachdev-Ye-Kitaev model (Gu, Kitaev, Sachdev, Tarnopolsky)

14th Meeting - BFSS

Date: Wednesday, July 15th, 11:00hs (London time) Venue: Zoom (ID: 661 181 319) — Click here to join — Room will open half an hour before the talk starts. Speaker: Masanori Hanada Title: D0-brane matrix model and holography Abstract: The D0-brane matrix model (the BFSS matrix model and the BMN matrix model) can describe various objects including type IIA black zero-brane, M-theory black hole, M2-branes and M5-branes. We study this theory from several different angles. We put the emphasis on the importance of the dynamics of eigenvalues of matrices, and more generally, color degrees of freedom. Furthermore we explain how the Euclidean theory can be studied by using the Monte Carlo method, and discuss the future directions. If you have a good idea we can test it on computer together!

15th Meeting - Global charges

Date: Monday, November 2nd, 15:00hs (London time) Speaker: Daniel Harlow (MIT) Title: Global symmetry, Euclidean gravity, and the black hole information problem

16th Meeting - Page curve and baby universes

Date: Monday, November 23rd, 16:00hs (London time) Speaker: Henry Maxfield (UCSB) Title: Observations of Hawking radiation: the Page curve and baby universes Abstract: I'll discuss recent progress in black hole information, using semiclassical gravity to compute the entropy of Hawking radiation and finding the "Page curve" associated with a unitary quantum system with density of states given by the Bekenstein-Hawking formula. I will formulate this in terms of an operationally-defined notion of entropy, using a Lorentz-signature gravitational path integral in asymptotically flat spacetimes. I'll then explain the Hilbert space interpretation of these calculations, which requires the introduction of a Hilbert space of baby universes, and results in superselection sectors for asymptotic observers.

17th Meeting - Semi-classical black hole informatics

Date: Monday, February 8th, 16:00hs (London time) Speaker: Lárus Thorlacius (University of Iceland) Title: Semi-classical black hole informatics Abstract: Information about fine grained properties of the quantum state of a black hole appears to be encoded in the semiclassical black hole geometry. In particular, the Page curve governing the unitary evolution of the entanglement entropy between outgoing Hawking radiation and the remaining black hole is reproduced in semiclassical gravity by adopting a holographic prescription for the generalised entropy. This is verified for an evaporating black hole in asymptotically flat spacetime by analytic calculations in a two-dimensional dilaton gravity model. Another fine grained quantity, the holographic quantum complexity, can also be obtained analytically in this model and its rate of growth precisely tracks the shrinking number of degrees of freedom of the stretched horizon.