48 October 2021
Prague, Czech Republic  Online
This workshop is about the three different signs of the cosmological constant, the three resulting maximally symmetric spacetimes and their correspondence with conformal field theory. We are bringing together experts on these three aspects of holography to discuss and exchange ideas leading towards its broader understanding. The workshop targets a broad audience of senior researchers as well as postdocs and PhD students. We have scheduled four pedagogical review talks, six technical talks and four panel discussions on Zoom. Ample time has been set aside for discussion sessions using Zoom breakout rooms and Gather Town.
SPEAKER  INSTITUTE  TOPIC 

Dionysios Anninos  King's College, London 
Comments on de Sitter spacetimes
We discuss aspects of de Sitter spacetimes. We may touch upon and contrast features of the de Sitter horizon with the more standard cosmological description. Time permitting we will focus on various dimensionalities as well as the role of Euclidean signature.

Nicolas Boulanger  UMONS 
Unitary representations of the maximallysymmetric isometry algebras in arbitrary dimension
We will review the classification of the irreducible representations of the isometry algebras of the maximallysymmetric spacetimes in arbitrary dimension. Specific attention will be devoted to the unitary representations.

Tom Hartman  Cornell 
Wormholes in black holes and cosmology
I will give an overview and status report on the role of wormholes and ensemble averages in the gravitational path integral.

Andrea Puhm  CPHT, Inst. Polytechnique de Paris 
Recent advances in celestial holography
I will review current developments in celestial amplitudes and flat space holography.

SPEAKER  INSTITUTE  TOPIC 

Alexandre Belin  CERN 
Bootstrapping Quantum Extremal Surfaces
Quantum extremal surfaces are central to the connection between quantum information theory and quantum gravity and they have played a prominent role in the recent progress on the information paradox. In this talk, I will present a program to systematically link these surfaces to the microscopic data of the dual conformal field theory, namely the scaling dimensions of local operators and their OPE coefficients. I will consider CFT states obtained by acting on the vacuum with singletrace operators, which are dual to oneparticle states of the bulk theory. Focusing on AdS3/CFT2, I will compute the CFT entanglement entropy to second order in the large c expansion where quantum extremality becomes important and match it to the expectation value of the bulk area operator. I will show that to this order, the Virasoro identity block contributes solely to the area operator.

Laura Donnay  Vienna TU 
BMS flux algebra in celestial holography
In this talk, we construct the BMS momentum fluxes, which are given by nonlocal expressions of the solution space of asymptotically flat spacetimes. They transform in the coadjoint representation of the extended BMS group and correspond to Virasoro primaries under the action of bulk superrotations. We will also discuss their relation with celestial CFT currents and deduce the OPEs of the celestial CFT operators from the BMS flux algebra.

Austin Joyce  U. Chicago 
Inflation from the boundary
The largescale correlations that we observe in the distribution of matter in the universe have their origins in primordial perturbations produced prior to the hot big bang—likely during a period of inflationary expansion. Interestingly we do not directly observe the inflationary epoch, but instead infer its dynamics from correlations residing on the late time boundary of the inflationary spacetime, where the universe reheats. This motivates us to ask whether we can understand things directly on this asymptotic boundary, without making explicit reference to bulk time evolution. I will describe recent progress in this direction, including aspects of how the bulk dynamics is encoded on the boundary.

Toshifumi Noumi  Kobe University 
String Regge trajectories on de Sitter space
In string theory, higher spin Regge states are crucial for UV completion of gravitational scattering. In this talk, I will discuss similarity and difference of the spectrum of such string Regge states on flat space, antide Sitter space, and de Sitter space. In particular, I will demonstrate that each Regge trajectory on de Sitter space has a maximal spin due to causality and existence of the cosmological horizon, which could be a potential obstruction for string theory construction of de Sitter space. Further studies along this line would be useful for better understanding of de Sitter space and dS/CFT in the string theory context.

Romain Ruzziconi  Vienna TU 
Leaky boundary conditions in holography, BMS fluxes and flat limit
In this talk, I will explain the interest of considering leaky boundary conditions in holography. I will start by presenting generic boundary conditions in asymptotically locally (A)dS spacetimes that yield some flux through the conformal boundary. Then, I will provide a specific example that leads to BMSlike symmetries in presence of nonvanishing cosmological constant. In the flat limit, these symmetries and the associated phase space reduce to those of Generalized BMS in asymptotically flat spacetimes. Finally, I will discuss the BMS flux algebra that has recently been shown to be relevant in the context of celestial holography.

Gabor Sarosi  CERN 
The volume of the black hole interior at late times
The volume of the interior of a twosided eternal black hole classically grows forever. I will show that in JT gravity, summing the nonperturbative contribution of higher topologies leads to a saturation of the volume of the interior at times exponential in the entropy of the black hole. I will explain that this is evidence for the conjecture that the size of the interior is related to the complexity of the holographically dual quantum state.

TOPIC  PANELISTS  AFFILIATION 

AdS/CFT  ABSTRACT HERE  
Chair: Julian Sonner  University of Geneva 
Daniel Jafferis  Harvard University  
Jamie Sully  University of British Columbia  
Erik Verlinde  University of Amsterdam  
Flat space holography
Flat Space holography is understood as an attempt to rewrite the Quantum gravity S matrix in terms of Correlation functions of a field theory on the boundary. It thus aims to generalise Ads/CFT duality to spacetimes with vanishing cosmological constant. However an asymptotically flat spacetime can be conformally completed in many different ways and so there is no unique boundary manifold on which the sought after field theory lives. Part of the boundary which is universal is socalled Null infinity and a lot of effort has gone in developing flat space/field theory correspondence where the field theory lives on null infinity.
At a more fundamental level, holography is premised on the fact that the algebra of boundary observables is isomorphic to the algebra of all gravitational observables. In our Panel discussion, we will focus on both of these aspects of flat space holography and progress that is being made in these directions. 
Chair: Alok Laddha  Chennai Mathematical Institute (CMI), Chennai 
Jan de Boer  UvA, Amsterdam  
AnaMaria Raclariu  Perimeter Institute  
Suvrat Raju  ICTS, Bengaluru  
dS/CFT  ABSTRACT HERE  
Chair: Guilherme Pimentel  Leiden University and UvA, Amsterdam 
Paolo Benincasa  MaxPlanckInstitut für Physik  
Enrico Pajer  University of Cambridge  
Kostas Skenderis  University of Southampton  
All Lambdas
Holography has been most successful when the curvature of spacetime is negative. The boundary allows for a region where gravity turns off, giving us welldefined observables in the form of CFT correlation functions. In flat space and de Sitter, the problem is more difficult. In the former, it seems as though we need a theory of the Smatrix, whereas in the latter, gravity never seems to turn off. Gravity may still very well be emergent from a lower dimensional theory in these cases, but if so we need to understand the relevant observables in these more difficult cases. In our panel discussion we will discuss the issues of observables and other pertinent questions.

Chair: Tarek Anous  UvA, Amsterdam 
Eliot Hijano  Princeton University  
João Penedones  EPFL, Lausanne  
Loganayagam Ramalingam  ICTSTIFR 
NAME  INSTITUTE 

anupam a h  IMSc Chennai 
Sreehari A P  Indian Institute of Technology Madras 
Haddad Abdelhamid  AixMarseille University 
Giovanni Acquaviva  Arquimea Research Center 
Preetham Kumar Adepu  Indian Institute of Science, Bangalore 
Mir Afrasiar  Indian Institute of Technology Kanpur, India 
Dmitry Ageev  Steklov Mathematical Institute, RAS 
Ankit Aggarwal  ULB, UvA 
Sergio Ernesto Aguilar Gutierrez  KU Leuven 
Santiago Agüí Salcedo  University of Cambridge 
Manu Akavoor  Chennai Mathematical Institute, India 
Shabeeb Alalawi  University of Bonn 
Soner Albayrak  University of Amsterdam 
Sevrin Alexander  Vrije Universiteit Brussel 
Yang An  Zhejiang University of Technology 
Raclariu AnaMaria  Perimeter Institute 
Dionysios Anninos  King's College London 
Tarek Anous  University of Amsterdam 
Luis Apolo  University of Amsterdam 
Delfante Arnaud  UMONS 
Taha Ayfer  Bogazici University 
Sourish Banerjee  BITS Goa 
Pinaki Banerjee  IAS Princeton 
Jaydeep Kumar Basak  Indian Institute of Technology, Kanpur, India 
Ivano Basile  UMONS 
Debarshi Basu  Indian Institute of Technology Kanpur 
Marianthi Bataki  University of Cyprus 
Teresa Bautista  King's College London 
Alex Belin  CERN 
Aleksandr Belokon  Institute for Nuclear Research, Russian Academy of Sciences 
Paolo Benincasa  MaxPlanckInstitut für Physik 
Eric Bergshoeff  University of Groningen 
Klaus Bering  Masaryk U 
Alice Bernamonti  University of Florence 
Deepan Betal  Indian Institute of Science Education and Research Bhopal 
Budhaditya Bhattacharjee  Indian Institute of Science 
Arindam Bhattacharjee  IISER Pune 
Aranya Bhattacharya  Indian Institute of Science 
Parthajit Biswas  IIT Kanpur 
Eugenia Boffo  Charles University Prague 
James Bonifacio  University of Cambridge 
Nicolas Boulanger  UMONS 
Miguel Campiglia  UdelaR 
Andrea Campoleoni  University of Mons 
Federico Capone  University of Southampton 
Percy Cáceres  Puc Rio de Janeiro 
Subhroneel Chakrabarti  CEICO, FZU, Prague 
Tuneer Chakraborty  International Centre for Theoretical Sciences  TIFR 
Ramesh Chandra  University of Amsterdam 
Ashish chandra  IIT Kanpur 
Shira Chapman  Ben Gurion University 
Arghya Chattopadhyay  University of the Witwatersrand 
Sangmin Choi  Ecole Polytechnique 
Chandramouli Chowdhury  ICTSTIFR 
Enrico Cinti  University of Urbino/University of Geneva 
Suchetan Das  IIT Kanpur 
Jan de Boer  Institute of Theoretical Physics, University of Amsterdam 
Marchal Dominique  Université Libre de Bruxelles / Service Physique Mathématique / Ingénieur Civil Physicien 
Laura Donnay  TU Vienna 
Sarthak Duary  International Centre for Theoretical Sciences, Bangalore 
Sarthak Duary  International Centre for Theoretical Sciences, Bangalore 
Carlos Duaso Pueyo  University of Amsterdam 
Sudipta Dutta  IIT Kanpur 
Subham Dutta Chowdhury  Tata Institute of Fundamental Research 
Camille Eloy  VUB 
William Emond  CEICO, FZU 
Martin Enriquez Rojo  Arnold Sommerfeld Center  LMU Munich 
Cem Eröncel  DESY 
Ricardo Espindola Romero  University of Amsterdam 
Bobby Ezhuthachan  RKMVERI 
Kara Farnsworth  Case Western Reserve University 
Pau Figueras  Queen Mary University of London 
Adrien Fiorucci  TU Wien 
Daniel Flores  Cinvestav 
Thomas Flöss  University of Groningen 
Stefan Fredenhagen  University of Vienna 
Laurent Freidel  Perimeter institute 
Oscar Fuentealba  Université Libre de Bruxelles 
Damian Galante  King's College London 
Federico Galli  INFN Florence 
Bogdan Ganchev  IPhT, Saclay 
Compère Geoffrey  Université Libre de Bruxelles 
Silvia Georgescu  IPhT 
Masoud Ghezelbash  University of Saskatchewan 
Jewel Ghosh  Independent University Bangladesh (IUB) 
Marc Gillioz  SISSA 
Gaston Giribet  University of Buenos Aires 
Riccardo Gonzo  Trinity College Dublin 
Harry Goodhew  University of Cambridge 
Kaberi Goswami  PhD Student 
Tanguy Grall  University of Cambridge  DAMTP 
Daniel Grumiller  Institute for Theoretical Physics, TU Wien 
Philip Hacker  VUB 
Felix Haehl  IAS Princeton 
Eleanor Harris  King's College London 
Tom Hartman  Cornell 
Guzman HernandezChifflet  UdelaR 
Eliot Hijano  Princeton University 
Kurt Hinterbichler  Case Western Reserve University 
Jack Holden  University of Southampton 
Sk Jahanur Hoque  Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University, Prague. 
Anthony Houppe  IPhT, CEA Saclay 
Stanislav Hronek  Masaryk university 
Ondrej Hulik  VUB 
MINHAJUL ISLAM  IIT KANPUR 
Daniel Jafferis  Harvard 
Aditya Jain  Ashoka University 
Krishna Jalan  IMSc, Chennai 
Sadra Jazayeri  IAP, CNRS 
Hongliang Jiang  QMUL 
Laura Johnson  ETH Zurich 
Austin Joyce  University of Chicago 
Nirmalya Kajuri  IACS, Kolkata 
Alexandros Kanargias  Johannes Gutenberg University Mainz 
Sahaja Kanuri  University of Amsterdam 
Debanjan Karan  IIT Indore 
Yelda Kardaş  Boğaziçi University 
Dimitrios Katsinis  NKUA & NCSR Demokritos 
Mikhail Khramtsov  VUB 
Petr Kotlařík  Charles University 
Pavel Krtouš  ITP, FMP, Charles University 
Arpan Kundu  IMSc, Chennai 
Alok Laddha  Chennai Mathematical Institute 
Johannes Lahnsteiner  PhD Student 
Ricardo Landim  Technical University of Munich 
Ji Hoon Lee  Perimeter Institute 
Mang Hei Gordon Lee  University of Cambridge 
Yixuan Li  IPhT Saclay 
Arthur Lipstein  Durham University 
Yan LIU  University Libre de Bruxelles 
Quim Llorens  ICCUB, Barcelona 
Daniel Logares Álvarez  Ph.D Student 
Arshid Lone  Cluster University Of Srinagar Kashmir, India. 
Kevin Loo  Tsinghua University 
Sagar Kumar Maity  S N Bose National Center for Basic Sciences 
Pronobesh Maity  International Centre for Theoretical Sciences, India 
Sucheta Majumdar  Université Libre de Bruxelles 
Taniya Mandal  University of the Witwatersrand 
Arkajyoti Manna  IMSc. 
Knysh Maria  VUB 
De Clerck Marine  Vrije Universiteit Brussel 
Javier Matulich  Université Libre de Bruxelles 
Sabyasachi Maulik  Saha Institute of Nuclear Physics and Homi Bhabha National Institute 
Delaram Mirfendereski  University of Texas Rio Grande Valley 
ABDELMALEK MOHAMMED  Ecole Supérieure de Management de Tlemcen 
Sukrut Mondkar  Indian Institute of Technology Madras 
Takato Mori  SOKENDAI, KEK 
Edward Morvan  University of Amsterdam 
Beatrix Muhlmann  McGill University 
JYOTIRMOY MUKHERJEE  Indian Institute of Science 
Debangshu Mukherjee  IISER Thiruvananthapuram 
Ivan Munoz  Universidad Catolica de Chile 
Pratik Nandy  Indian Institute of Science 
Mrityunjay Nath  IIT Indore 
Turmoli Neogi  ULB 
Kevin Nguyen  King's College London 
Ruggero Noris  CEICO, Institute of Physics of the Czech Academy of Sciences 
Toshifumi Noumi  Kobe University 
Prafulla Oak  IACS 
Roberto Oliveri  CEICO 
Sergei Ovchinnikov  University of Edinburgh 
Ogan Özsoy  CEICO, Institute of Physics of the Czech Academy of Sciences 
Athira P V  Chennai Mathematical Institute 
enrico Pajer  University of Cambridge 
Yorgo Pano  CPHT  Ecole Polytechnique 
Himanshu Parihar  Indian Institute of Technology Kanpur, India 
Enrico Parisini  University of Southampton 
Andrei Parnachev  Trinity College Dublin 
Praneet Pathak  Indian Institute of Science Education and Research Mohali, India 
Dhruv Pathak  IISER Mohali 
Milan Patra  National Institute of Science Education and Research, Bhubaneswar 
Priyadarshi Paul  International Centre for Theoretical Sciences 
Partha Paul  Chennai Mathematical Institute 
Simon Pekar  UMONS 
Joao Penedones  EPFL 
Benjamin Pethybridge  King's College London 
Spindel Philippe  UMONS & ULB 
Gui Pimentel  Leiden University and University of Amsterdam 
Aaron Poole  University of Southampton 
Nick Poovuttikul  Durham U. 
SOMNATH POREY  RKMVERI 
Siddharth Prabhu  Tata Institute of Fundamental Research 
Daniele Pranzetti  Perimeter Institute 
Aneesh Prema Balakrishnan  Institute of Mathematical Sciences, Chennai 
Tomas Prochazka  FZU 
Andrea Puhm  CPHT, Ecole Polytechnique 
Vasilii Pushkarev  unaffiliated 
Loganayagam R  ICTSTIFR 
Joris Raeymaekers  CEICO, FZU, Prague 
Tabasum Rahnuma  PhD Research scholar, IISER, Bhopal 
Vinayak Raj  Indian Institute of Technology Kanpur 
Suvrat Raju  International Centre for Theoretical Sciences (Bengaluru) 
Pabitra Ray  ICTSTIFR 
Anton Rebhan  TU Wien, Vienna, Austria 
Alan Rios Fukelman  ICC, University of Barcelona 
Lorenzo Rossi  Queen Mary University of London 
Paolo Rossi  Charles University 
Romain Ruzziconi  TU Vienna 
Muktajyoti Saha  IISER Bhopal 
SATYABRATA SAHOO  IIT INDORE 
Marco Sanchioni  University of Urbino 
Canberk Sanli  Bogazici University 
Debajyoti Sarkar  Indian Institute of Technology Indore (IITI) 
Gabor Sarosi  CERN 
Martin Sasieta  IFT UAM 
Ignacy Sawicki  CEICO, FZU 
Martin Schnabl  Ceico, FZU 
Bhim Sen  IIT INDORE 
Ali Seraj  ULB 
Roshan Shankar Kaundinya  IISER Mohali 
Punit Sharma  Indian Institute of Technology Kanpur, India 
Aditya Sharma  Indian Institute of Science Education and Research 
Sanjit Shashi  University of Texas at Austin 
Omkar Shetye  International Centre of theoretical Sciences 
Pushkal Shrivastava  Tata Institute of Fundamental Research, Mumbai 
VIBHOR SINGH  IIT Hyderabad 
VIBHOR SINGH  IIT HYDERABAD 
Rajeev Singh  Institute of Nuclear Physics Polish Academy of Sciences, Krakow Poland 
AKASH SINGH  IISER Mohali 
Kostas Skenderis  University of Southampton 
Constantinos Skordis  CEICO, Institute of Physics of the Czech Academy of Sciences 
Pavel Slepov  Steklov Mathematical Institute, RAS 
Julian Sonner  University of Geneva 
David Stefanyszyn  DAMTP, Cambridge 
Detournay Stephane  ULB 
Jamie Sully  University of British Columbia 
Adithya Suresh  IISER Pune 
Ryo Suzuki  ShingTung Yau Center of Southeast University 
Ota Svitek  Charles University, Prague 
Abinash Swain  IIT Gandhinagar 
Gizem Şengör  CEICO, Institute of Physics of the Czech Academy of Sciences 
Tayebeh Tahamtan  Charles University, Prague 
Luân Tăng Văn  Vietnam National University Hanoi 
Heckelbacher Till  LMU Munich 
Chiara Toldo  Amsterdam U. 
Marija Tomasevic  University of Barcelona 
DIEGO TRANCANELLI  USP and UniMORE and INFN Bologna 
Emilio Trevisani  CPhT Ecole Polytechnique 
Leonardo Trombetta  CEICO  FZU, Institute of Physics of the Czech Academy of Sciences 
Caner Unal  BenGurion University 
Pieter van der Hoek  UvA 
Erik Verlinde  University of Amsterdam 
Martin Vincze  Public 
Stathis Vitouladitis  University of Amsterdam 
Ward Vleeshouwers  Universiteit van Amsterdam, Universiteit Utrecht 
Gideon Vos  CEICO, Institute of Physics of the Czech Academy of Sciences 
Yiting Wang  University of WisconsinMadison 
Timm Wrase  Lehigh University 
Junbao Wu  Tianjin University 
Raphaela Wutte  TU Wien 
Jiabao Yang  Cornell University 
Nadir Yavuzkan  istanbul University 
HaiQing Zhang  Beihang University 
Xuao Zhang  KU Leuven 
Sofia Zhidkova  VUB 
Céline Zwikel  Perimeter Institute 