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 break-out rooms and Gather Town.

Please be aware that talks will be recorded.

The recordings will be placed later at the YouTube channel "all lambda holography", that can be accessed any time.



Download schedule Programme


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 maximally-symmetric isometry algebras in arbitrary dimension We will review the classification of the irreducible representations of the isometry algebras of the maximally-symmetric 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.


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 single-trace operators, which are dual to one-particle 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 non-local 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 large-scale 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, anti-de 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 BMS-like symmetries in presence of non-vanishing 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 two-sided eternal black hole classically grows forever. I will show that in JT gravity, summing the non-perturbative 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.


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 re-write 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 space-time 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 so-called 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
Ana-Maria Raclariu Perimeter Institute
Suvrat Raju ICTS, Bengaluru
Chair: Guilherme Pimentel Leiden University and UvA, Amsterdam
Paolo Benincasa Max-Planck-Institut 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 well-defined 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 S-matrix, 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 ICTS-TIFR


anupam a hIMSc Chennai
Sreehari A PIndian Institute of Technology Madras
Haddad AbdelhamidAix-Marseille University
Giovanni AcquavivaArquimea Research Center
Preetham Kumar AdepuIndian Institute of Science, Bangalore
Mir AfrasiarIndian Institute of Technology Kanpur, India
Dmitry AgeevSteklov Mathematical Institute, RAS
Ankit AggarwalULB, UvA
Sergio Ernesto Aguilar GutierrezKU Leuven
Santiago Agüí SalcedoUniversity of Cambridge
Manu AkavoorChennai Mathematical Institute, India
Shabeeb AlalawiUniversity of Bonn
Soner AlbayrakUniversity of Amsterdam
Sevrin AlexanderVrije Universiteit Brussel
Yang AnZhejiang University of Technology
Raclariu Ana-MariaPerimeter Institute
Dionysios AnninosKing's College London
Tarek AnousUniversity of Amsterdam
Luis ApoloUniversity of Amsterdam
Delfante ArnaudUMONS
Taha AyferBogazici University
Sourish BanerjeeBITS Goa
Pinaki BanerjeeIAS Princeton
Jaydeep Kumar BasakIndian Institute of Technology, Kanpur, India
Ivano BasileUMONS
Debarshi BasuIndian Institute of Technology Kanpur
Marianthi BatakiUniversity of Cyprus
Teresa BautistaKing's College London
Alex BelinCERN
Aleksandr BelokonInstitute for Nuclear Research, Russian Academy of Sciences
Paolo BenincasaMax-Planck-Institut für Physik
Eric BergshoeffUniversity of Groningen
Klaus BeringMasaryk U
Alice BernamontiUniversity of Florence
Deepan BetalIndian Institute of Science Education and Research Bhopal
Budhaditya BhattacharjeeIndian Institute of Science
Arindam BhattacharjeeIISER Pune
Aranya BhattacharyaIndian Institute of Science
Parthajit BiswasIIT Kanpur
Eugenia BoffoCharles University Prague
James BonifacioUniversity of Cambridge
Nicolas BoulangerUMONS
Miguel CampigliaUdelaR
Andrea CampoleoniUniversity of Mons
Federico CaponeUniversity of Southampton
Percy CáceresPuc Rio de Janeiro
Subhroneel ChakrabartiCEICO, FZU, Prague
Tuneer ChakrabortyInternational Centre for Theoretical Sciences - TIFR
Ramesh ChandraUniversity of Amsterdam
Ashish chandraIIT Kanpur
Shira ChapmanBen Gurion University
Arghya ChattopadhyayUniversity of the Witwatersrand
Sangmin ChoiEcole Polytechnique
Chandramouli ChowdhuryICTS-TIFR
Enrico CintiUniversity of Urbino/University of Geneva
Suchetan DasIIT Kanpur
Jan de BoerInstitute of Theoretical Physics, University of Amsterdam
Marchal DominiqueUniversité Libre de Bruxelles / Service Physique Mathématique / Ingénieur Civil Physicien
Laura DonnayTU Vienna
Sarthak DuaryInternational Centre for Theoretical Sciences, Bangalore
Sarthak DuaryInternational Centre for Theoretical Sciences, Bangalore
Carlos Duaso PueyoUniversity of Amsterdam
Sudipta DuttaIIT Kanpur
Subham Dutta ChowdhuryTata Institute of Fundamental Research
Camille EloyVUB
William EmondCEICO, FZU
Martin Enriquez RojoArnold Sommerfeld Center - LMU Munich
Cem EröncelDESY
Ricardo Espindola RomeroUniversity of Amsterdam
Bobby EzhuthachanRKMVERI
Kara FarnsworthCase Western Reserve University
Pau FiguerasQueen Mary University of London
Adrien FiorucciTU Wien
Daniel FloresCinvestav
Thomas FlössUniversity of Groningen
Stefan FredenhagenUniversity of Vienna
Laurent FreidelPerimeter institute
Oscar FuentealbaUniversité Libre de Bruxelles
Damian GalanteKing's College London
Federico GalliINFN Florence
Bogdan GanchevIPhT, Saclay
Compère GeoffreyUniversité Libre de Bruxelles
Silvia GeorgescuIPhT
Masoud GhezelbashUniversity of Saskatchewan
Jewel GhoshIndependent University Bangladesh (IUB)
Marc GilliozSISSA
Gaston GiribetUniversity of Buenos Aires
Riccardo GonzoTrinity College Dublin
Harry GoodhewUniversity of Cambridge
Kaberi GoswamiPhD Student
Tanguy GrallUniversity of Cambridge - DAMTP
Daniel GrumillerInstitute for Theoretical Physics, TU Wien
Philip HackerVUB
Felix HaehlIAS Princeton
Eleanor HarrisKing's College London
Tom HartmanCornell
Guzman Hernandez-ChiffletUdelaR
Eliot HijanoPrinceton University
Kurt HinterbichlerCase Western Reserve University
Jack HoldenUniversity of Southampton
Sk Jahanur HoqueInstitute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University, Prague.
Anthony HouppeIPhT, CEA Saclay
Stanislav HronekMasaryk university
Ondrej HulikVUB
Daniel JafferisHarvard
Aditya JainAshoka University
Krishna JalanIMSc, Chennai
Sadra JazayeriIAP, CNRS
Hongliang JiangQMUL
Laura JohnsonETH Zurich
Austin JoyceUniversity of Chicago
Nirmalya KajuriIACS, Kolkata
Alexandros KanargiasJohannes Gutenberg University Mainz
Sahaja KanuriUniversity of Amsterdam
Debanjan KaranIIT Indore
Yelda KardaşBoğaziçi University
Dimitrios KatsinisNKUA & NCSR Demokritos
Mikhail KhramtsovVUB
Petr KotlaříkCharles University
Pavel KrtoušITP, FMP, Charles University
Arpan KunduIMSc, Chennai
Alok LaddhaChennai Mathematical Institute
Johannes LahnsteinerPhD Student
Ricardo LandimTechnical University of Munich
Ji Hoon LeePerimeter Institute
Mang Hei Gordon LeeUniversity of Cambridge
Yixuan LiIPhT Saclay
Arthur LipsteinDurham University
Yan LIUUniversity Libre de Bruxelles
Quim LlorensICCUB, Barcelona
Daniel Logares ÁlvarezPh.D Student
Arshid LoneCluster University Of Srinagar Kashmir, India.
Kevin LooTsinghua University
Sagar Kumar MaityS N Bose National Center for Basic Sciences
Pronobesh MaityInternational Centre for Theoretical Sciences, India
Sucheta MajumdarUniversité Libre de Bruxelles
Taniya MandalUniversity of the Witwatersrand
Arkajyoti MannaIMSc.
Knysh MariaVUB
De Clerck MarineVrije Universiteit Brussel
Javier MatulichUniversité Libre de Bruxelles
Sabyasachi MaulikSaha Institute of Nuclear Physics and Homi Bhabha National Institute
Delaram MirfendereskiUniversity of Texas Rio Grande Valley
ABDELMALEK MOHAMMEDEcole Supérieure de Management de Tlemcen
Sukrut MondkarIndian Institute of Technology Madras
Edward MorvanUniversity of Amsterdam
Beatrix MuhlmannMcGill University
JYOTIRMOY MUKHERJEEIndian Institute of Science
Debangshu MukherjeeIISER Thiruvananthapuram
Ivan MunozUniversidad Catolica de Chile
Pratik NandyIndian Institute of Science
Mrityunjay NathIIT Indore
Turmoli NeogiULB
Kevin NguyenKing's College London
Ruggero NorisCEICO, Institute of Physics of the Czech Academy of Sciences
Toshifumi NoumiKobe University
Prafulla OakIACS
Roberto OliveriCEICO
Sergei OvchinnikovUniversity of Edinburgh
Ogan ÖzsoyCEICO, Institute of Physics of the Czech Academy of Sciences
Athira P VChennai Mathematical Institute
enrico PajerUniversity of Cambridge
Yorgo PanoCPHT - Ecole Polytechnique
Himanshu PariharIndian Institute of Technology Kanpur, India
Enrico ParisiniUniversity of Southampton
Andrei ParnachevTrinity College Dublin
Praneet PathakIndian Institute of Science Education and Research Mohali, India
Dhruv PathakIISER Mohali
Milan PatraNational Institute of Science Education and Research, Bhubaneswar
Priyadarshi PaulInternational Centre for Theoretical Sciences
Partha PaulChennai Mathematical Institute
Simon PekarUMONS
Joao PenedonesEPFL
Benjamin PethybridgeKing's College London
Spindel PhilippeUMONS & ULB
Gui PimentelLeiden University and University of Amsterdam
Aaron PooleUniversity of Southampton
Nick PoovuttikulDurham U.
Siddharth PrabhuTata Institute of Fundamental Research
Daniele PranzettiPerimeter Institute
Aneesh Prema BalakrishnanInstitute of Mathematical Sciences, Chennai
Tomas ProchazkaFZU
Andrea PuhmCPHT, Ecole Polytechnique
Vasilii Pushkarevunaffiliated
Loganayagam RICTS-TIFR
Joris RaeymaekersCEICO, FZU, Prague
Tabasum RahnumaPhD Research scholar, IISER, Bhopal
Vinayak RajIndian Institute of Technology Kanpur
Suvrat RajuInternational Centre for Theoretical Sciences (Bengaluru)
Pabitra RayICTS-TIFR
Anton RebhanTU Wien, Vienna, Austria
Alan Rios FukelmanICC, University of Barcelona
Lorenzo RossiQueen Mary University of London
Paolo RossiCharles University
Romain RuzziconiTU Vienna
Muktajyoti SahaIISER Bhopal
Marco SanchioniUniversity of Urbino
Canberk SanliBogazici University
Debajyoti SarkarIndian Institute of Technology Indore (IITI)
Gabor SarosiCERN
Martin SasietaIFT UAM
Ignacy SawickiCEICO, FZU
Martin SchnablCeico, FZU
Ali SerajULB
Roshan Shankar KaundinyaIISER Mohali
Punit SharmaIndian Institute of Technology Kanpur, India
Aditya SharmaIndian Institute of Science Education and Research
Sanjit ShashiUniversity of Texas at Austin
Omkar ShetyeInternational Centre of theoretical Sciences
Pushkal ShrivastavaTata Institute of Fundamental Research, Mumbai
Rajeev SinghInstitute of Nuclear Physics Polish Academy of Sciences, Krakow Poland
Kostas SkenderisUniversity of Southampton
Constantinos SkordisCEICO, Institute of Physics of the Czech Academy of Sciences
Pavel SlepovSteklov Mathematical Institute, RAS
Julian SonnerUniversity of Geneva
David StefanyszynDAMTP, Cambridge
Detournay StephaneULB
Jamie SullyUniversity of British Columbia
Adithya SureshIISER Pune
Ryo SuzukiShing-Tung Yau Center of Southeast University
Ota SvitekCharles University, Prague
Abinash SwainIIT Gandhinagar
Gizem ŞengörCEICO, Institute of Physics of the Czech Academy of Sciences
Tayebeh TahamtanCharles University, Prague
Luân Tăng VănVietnam National University Hanoi
Heckelbacher TillLMU Munich
Chiara ToldoAmsterdam U.
Marija TomasevicUniversity of Barcelona
Emilio TrevisaniCPhT Ecole Polytechnique
Leonardo TrombettaCEICO - FZU, Institute of Physics of the Czech Academy of Sciences
Caner UnalBen-Gurion University
Pieter van der HoekUvA
Erik VerlindeUniversity of Amsterdam
Martin VinczePublic
Stathis VitouladitisUniversity of Amsterdam
Ward VleeshouwersUniversiteit van Amsterdam, Universiteit Utrecht
Gideon VosCEICO, Institute of Physics of the Czech Academy of Sciences
Yiting WangUniversity of Wisconsin-Madison
Timm WraseLehigh University
Junbao WuTianjin University
Raphaela WutteTU Wien
Jiabao YangCornell University
Nadir Yavuzkanistanbul University
Hai-Qing ZhangBeihang University
Xuao ZhangKU Leuven
Sofia ZhidkovaVUB
Céline ZwikelPerimeter Institute


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