BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Mark van Raamsdonk (UBC) DTSTART:20200429T150000Z DTEND:20200429T170000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/1 DESCRIPTION:Title: Pushing boundaries in holography\nby Mark van Raamsdonk (UBC ) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nIn this talk\, I'll di scuss a variety of applications in AdS/CFT that make use of CFTs living on spacetimes with boundaries. The applications include the construction of black hole microstates whose behind-the-horizon geometries can be understo od explicitly\, constructing models of evaporating black holes in which th e Page curve can be understood through explicit CFT calculations\, providi ng a microscopic descriptions of certain Randall-Sundrum scenarios\, and p roviding a framework for holography where the CFT is replaced by a large n umber of non-interacting "bits".\n\nYou can access the recording right her e: https://www.youtube.com/watch?v=GSi4sE49gu0 .\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Manuela Kulaxizi (Trinity College Dublin) DTSTART:20200506T130000Z DTEND:20200506T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/2 DESCRIPTION:Title: Stress Tensor Sector of Conformal Correlators\nby Manuela Ku laxizi (Trinity College Dublin) as part of GQFI-UGent-WST Seminars\n\n\nAb stract\nAn important part of a CFT four-point function\, the stress tensor sector\, comprises the exchanges of the stress tensor and its composites. The OPE coefficients of these multi-stress tensor operators and consequen tly\, the complete stress tensor sector of four-point functions in CFTs wi th a large central charge\, can be determined by computing a heavy-heavy-l ight-light correlator. We show how one can make substantial progress in th is direction by bootstrapping a certain Ansatz for the stress tensor secto r of the correlator\, iteratively computing the OPE coefficients of multi- stress tensor operators with increasing twist. Some parameters are not fix ed by the bootstrap - they correspond to the OPE coefficients of multi-str ess tensors with spin zero and two. We further show that in holographic CF Ts one can use the phase shift computed in the dual gravitational theory t o reduce the set of undetermined parameters to the OPE coefficients of mul ti-stress tensors with spin zero. Finally\, we verify some of these result s using the Lorentzian OPE inversion formula and comment on its regime of applicability.\n\nCorrect link: https://mpi-aei.zoom.us/j/96444244925.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Nabil Iqbal (Durham) DTSTART:20200513T130000Z DTEND:20200513T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/3 DESCRIPTION:Title: Toward a 3d Ising Model with a weakly coupled string dual\nb y Nabil Iqbal (Durham) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI t has long been expected that the 3d Ising model can be thought of as a st ring theory\, where one interprets the domain walls that separate up spins from down spins as two-dimensional string worldsheets. I will revisit thi s 'string theory' from the modern point of view of higher form symmetries. The usual Ising Hamiltonian measures the area of these domain walls\; as there is no explicit dependence on the genus of the domain walls\, it can be thought of as a string theory with string coupling equal to unity. I di scuss how to add new local terms to the Ising Hamiltonian that further wei ght each spin configuration by a factor depending on the genus of the corr esponding domain wall\, resulting in a new 3d Ising model that has a tunab le bare string coupling. I will use a combination of analytical and numeri cal methods to analyze the phase structure of this model as this string co upling is varied. I will also describe statistical properties of the topol ogy of worldsheets and speculate on the prospects of using this new deform ation at weak string coupling to find a worldsheet description of the 3d I sing transition.\n\nZoom link: https://mpi-aei.zoom.us/j/91981837516 .\n\n 1) Please display your name when you join the seminar.\n\n2) Your micropho ne is muted by default. Please only unmute it if you wish to make a questi on or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Nick Hunter-Jones (IQI\, Perimeter) DTSTART:20200520T140000Z DTEND:20200520T153000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/4 DESCRIPTION:Title: Models of quantum complexity growth\nby Nick Hunter-Jones (I QI\, Perimeter) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nAbstract : The quantum complexity of a unitary or state is defined as the size of t he shortest quantum computation that implements the unitary or prepares th e state. The notion has far-reaching implications spanning computer scienc e\, quantum many-body physics\, and high energy theory. Complexity growth in time is a phenomenon expected to occur in holographic theories and stro ngly-interacting many-body systems more generally\, but explicitly computi ng the complexity of a given state or unitary is notoriously difficult. By considering an ensemble of systems\, and establishing a rigorous relation between complexity and unitary designs\, we will prove statements about c omplexity growth in various models. Specifically\, we prove a linear growt h of complexity in random quantum circuits\, using a recent result about t heir design growth. \n\nZoom Link: https://mpi-aei.zoom.us/j/99064635917\n \n-----\n1) Please display your name when you join the seminar.\n2) Your m icrophone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n------\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Ki-Seok Kim (POSTECH\, Pohang) DTSTART:20200527T130000Z DTEND:20200527T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/5 DESCRIPTION:Title: Emergent holographic dual effective field theory as a mean-field theory with all-loop quantum corrections in the large N limit\nby Ki- Seok Kim (POSTECH\, Pohang) as part of GQFI-UGent-WST Seminars\n\n\nAbstra ct\nHolographic duality conjecture states that a D-dimensional quantum fie ld theory can be duality-mapped into a (D+1)-dimensional quantum gravity t heory\, where the quantum gravity theory is a “hologram” of the quantu m field theory. Although this holographic duality conjecture serves as a n ovel non-perturbative theoretical framework for strongly coupled quantum f ield theories\, the duality transformation has not been clarified until no w. In this study we propose a prescription for the holographic duality tra nsformation based on Wilsonian recursive renormalization group (RG) transf ormations. As a result\, we manifest the RG flow of an effective field the ory with the introduction of an emergent extra dimensional space\, where R G $\\beta$-functions to describe the evolution of coupling functions appea r in the resulting effective action explicitly through the extra dimension al space. This microscopic construction of the dual holographic mapping su ggests that the origin of non-perturbative physics is in intertwined renor malization between dynamics and geometry.\n\n-----\n\n1) Please display yo ur name when you join the seminar.\n\n2) Your microphone is muted by defau lt. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n\n------\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Pascal Fries (Julius-Maximilians-Universität Würzburg) DTSTART:20200615T130000Z DTEND:20200615T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/6 DESCRIPTION:Title: Relative Entropy and Symmetry in QFT\nby Pascal Fries (Juliu s-Maximilians-Universität Würzburg) as part of GQFI-UGent-WST Seminars\n \n\nAbstract\nIn quantum information theory\, relative von Neumann entropy gives a quantitative meaning for the "distinguishability" of states by me asurements. In this talk\, I will introduce a variant of relative entropy which is compatible with the existence of conserved charges. I will show h ow to compute this "symmetry resolved relative entropy" in quantum field t heory and further present some analytic results for the free fermion CFT. This work is done in collaboration with Ignacio Reyes at AEI Potsdam.\n\n1 ) Please display your name when you join the seminar.\n\n2) Your microphon e is muted by default. Please only unmute it if you wish to make a questio n or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Kevin Grosvenor (Julius-Maximilians-Universität Würzburg) DTSTART:20200617T130000Z DTEND:20200617T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/7 DESCRIPTION:Title: Information geometry in QFT\nby Kevin Grosvenor (Julius-Maxi milians-Universität Würzburg) as part of GQFI-UGent-WST Seminars\n\n\nAb stract\nWe study the Fisher metrics associated with a variety of simple sy stems and derive some general lessons that may have important implications for the application of information geometry in holography. Some sample s ystems of interest are the classical 2d Ising model and the corresponding 1d free fermion theory\, the instantons in 3+1d massless phi-fourth theo ry\, and coherent states of free bosons and fermions.\n\nZoom Link: https: //mpi-aei.zoom.us/j/97089841078.\n\n-----\n\n1) Please display your name w hen you join the seminar.\n\n2) Your microphone is muted by default. Pleas e only unmute it if you wish to make a question or comment\, and then mute it back again.\n\n------\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Arjun Kar (University of Pennsylvania) DTSTART:20200624T130000Z DTEND:20200624T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/8 DESCRIPTION:Title: Geometric secret sharing in a model of Hawking radiation\nby Arjun Kar (University of Pennsylvania) as part of GQFI-UGent-WST Seminars \n\n\nAbstract\nWe consider a black hole in three dimensional AdS space en tangled with an auxiliary radiation system. We model the microstates of th e black hole in terms of a field theory living on an end of the world bran e behind the horizon\, and allow this field theory to itself have a hologr aphic dual geometry. This geometry is also a black hole since entanglement of the microstates with the radiation leaves them in a mixed state. This "inception black hole" can be purified by entanglement through a wormhole with an auxiliary system which is naturally identified with the external r adiation\, giving a realization of the ER=EPR scenario. In this context\, we propose an extension of the Ryu-Takayanagi (RT) formula\, in which extr emal surfaces computing entanglement entropy are allowed to pass through t he brane into its dual geometry. This new rule reproduces the Page curve f or evaporating black holes\, consistently with the recently proposed "isla nd formula". We then separate the radiation system into pieces. Our extend ed RT rule shows that the entanglement wedge of the union of radiation sub systems covers the black hole interior at late times\, but the union of en tanglement wedges of the subsystems may not. This result points to a secre t sharing scheme in Hawking radiation wherein reconstruction of certain re gions in the interior is impossible with any subsystem of the radiation\, but possible with all of it.\n\n-----\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please on ly unmute it if you wish to make a question or comment\, and then mute it back again.\n\n------\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/8/ END:VEVENT BEGIN:VEVENT SUMMARY:David Kolchmeyer (Harvard) DTSTART:20200708T130000Z DTEND:20200708T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/9 DESCRIPTION:Title: Entanglement Entropy in Jackiw-Teitelboim Gravity\nby David Kolchmeyer (Harvard) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI w ill explain how to use the quantum Ryu-Takayanagi formula to compute entan glement entropies in pure JT gravity\, including all of the perturbative g raviton corrections. I will also explain why it is not possible to factori ze the gravity Hilbert space in a local way. The tension between defining a local and isometric factorization map motivates the insertion of a "defe ct operator" into the standard definition of the Renyi entropy. The defect operator has a clear interpretation in the Euclidean replica calculation of the entropy. The contribution of the defect operator to the entanglemen t entropy matches the area term in the quantum Ryu-Takayanagi formula.\n\n -----\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n\n------\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Edgar Shaghoulian (Cornell University) DTSTART:20200715T130000Z DTEND:20200715T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/10 DESCRIPTION:Title: Islands in asymptotically flat 2d gravity\nby Edgar Shaghou lian (Cornell University) as part of GQFI-UGent-WST Seminars\n\n\nAbstract \nAsymptotically flat two-dimensional dilaton gravity coupled to a conform al field theory of large central charge provides a useful toy model for se miclassical black holes and the information paradox. Analyses of the asymp totic information flux as given by the entanglement entropy show that it f ollows the Hawking curve\, indicating that information is destroyed in the se models. Recently\, motivated by developments in AdS/CFT\, a semiclassic al island rule for entropy has been proposed. We define and compute the is land rule entropy for black hole formation and evaporation in the large-N RST model of dilaton gravity and show that\, in contrast\, it follows the unitary Page curve.\n\n1) Please display your name when you join the semin ar.\n\n2) Your microphone is muted by default. Please only unmute it if yo u wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Marius Gerbershagen (Wuerzburg University) DTSTART:20200722T130000Z DTEND:20200722T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/11 DESCRIPTION:Title: Complexity measures from geometric actions on Virasoro coadjoin t orbits\nby Marius Gerbershagen (Wuerzburg University) as part of GQF I-UGent-WST Seminars\n\n\nAbstract\nWe explore connections between computa tional complexity in CFTs\, geometric actions on coadjoint orbits of the V irasoro group and Liouville theory. Previously\, it was shown in [arXiv:18 07.04422] that by choosing a suitable cost function\, the resulting comple xity functional is equivalent to a geometric action\, up to a term that or iginates from the central extension. We show that this term can be recover ed by modifying the cost function\, making the equivalence exact. We then determine the optimal circuits for these complexity measures and calculate the corresponding costs. We find that in most cases the complexity only m easures the cost associated to phase changes\, while assigning zero cost t o the non-phase changing part of the transformation. Furthermore\, we brie fly review how geometric actions arise from the gravity theory and derive an equivalence between the sum of two geometric actions and Liouville theo ry. From this equivalence statement\, we obtain a mapping of optimal circu its from the path integral optimization approach and from our complexity p roposal.\n\n1) Please display your name when you join the seminar.\n\n2) Y our microphone is muted by default. Please only unmute it if you wish to m ake a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Mario Flory (Jagiellonian University) DTSTART:20200909T130000Z DTEND:20200909T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/12 DESCRIPTION:Title: Geometry of Complexity in CFT2\nby Mario Flory (Jagiellonia n University) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\n"We study circuit and state complexity in the universal setting of (1+1)-dimensional conformal field theory and unitary transformations generated by the stres s-energy tensor. We provide a unifi​ed view of assigning a cost to circu its based on the Fubini-Study metric\, iteratively solve the emerging inte gro-diff​erential equation for sample optimal circuits and discuss the s ectional curvature of the underlying geometry. We also discuss the relatio n of our work to Euler-Arnold type equations such as the Korteweg-de Vries and Hunter-Saxton equations."\n\n1) Please display your name when you joi n the seminar.\n\n2) Your microphone is muted by default. Please only unmu te it if you wish to make a question or comment\, and then mute it back ag ain.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Pedro Jorge Martinez (Universidad Nacional de La Plata) DTSTART:20200916T130000Z DTEND:20200916T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/13 DESCRIPTION:Title: Modular Hamiltonian for (holographic) excited states\nby Pe dro Jorge Martinez (Universidad Nacional de La Plata) as part of GQFI-UGen t-WST Seminars\n\n\nAbstract\nWe study the Tomita-Takesaki construction fo r a family of excited states that\, in a strongly coupled CFT - at large N -\, correspond to coherent states in an asymptotically AdS spacetime geome try. We compute the modular flow and modular Hamiltonian associated to the se excited states in the Rindler wedge and for a ball shaped entangling su rface. Using holography\, one can compute the bulk modular flow and constr uct the Tomita-Takesaki theory for these cases. We also discuss generaliza tions of the entanglement regions in the bulk and how to estimate the modu lar Hamiltonian in a large N approximation. Finally we present a holograph ic formula\, based on the BDHM prescription\, to compute the modular evolu tion of operators in the corresponding CFT algebra.\n\n1) Please display y our name when you join the seminar.\n\n2) Your microphone is muted by defa ult. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexey Milekhin DTSTART:20200923T130000Z DTEND:20200923T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/14 DESCRIPTION:Title: Humanly Traversable Wormholes\nby Alexey Milekhin as part o f GQFI-UGent-WST Seminars\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Roberto Emparan (Universitat de Barcelona) DTSTART:20200930T130000Z DTEND:20200930T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/15 DESCRIPTION:Title: Quantum BTZ black hole\nby Roberto Emparan (Universitat de Barcelona) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI will begin by reviewing the framework of braneworld holography as a means of studying quantum effects on black holes including the gravitational backreaction o f strongly-coupled conformal fields. Then I will describe a holographic co nstruction of quantum rotating BTZ black holes (quBTZ) using an exact four -dimensional bulk solution. Besides yielding the quantum-corrected geometr y and the renormalized stress tensor of quBTZ\, we use it to show that the quantum black hole entropy\, which includes the entanglement of the field s outside the horizon\, rather non-trivially satisfies the first law of th ermodynamics\, while the Bekenstein-Hawking-Wald entropy does not.\n\n1) P lease display your name when you join the seminar.\n\n2) Your microphone i s muted by default. Please only unmute it if you wish to make a question o r comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexandre Belin (CERN) DTSTART:20201007T130000Z DTEND:20201007T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/16 DESCRIPTION:Title: Gravitational path integral from the T^2 deformation\nby Al exandre Belin (CERN) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI w ill describe the $T^2$ deformation of large $N$ conformal field theories\, a higher dimensional generalization of the $TT$-deformation. The deformed partition function satisfies a flow equation of the diffusion type. I wil l explain how to solve this equation by finding its diffusion kernel\, whi ch is given by the Euclidean gravitational path integral in $d+1$ dimensio ns between two boundaries with Dirichlet boundary conditions for the metri c. An interesting output of the flow equation is the gravitational path in tegral measure which is consistent with a constrained phase space quantiza tion. Finally\, I will comment on the relation between the radial wave fun ction and the Hartle-Hawking wave functions dual to states in the CFT\, an d propose a way of obtaining the volume of the maximal slice from the $T^2 $ deformation.\n\n1) Please display your name when you join the seminar.\n \n2) Your microphone is muted by default. Please only unmute it if you wis h to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Horacio Casini (Centro Atomico Bariloche) DTSTART:20201014T130000Z DTEND:20201014T143000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/17 DESCRIPTION:Title: Entropic order parameters for the phases of QFT\nby Horacio Casini (Centro Atomico Bariloche) as part of GQFI-UGent-WST Seminars\n\n\ nAbstract\nWe propose entropic order parameters that capture the physics o f generalized symmetries and phases in QFT's. We do so by an analysis of s imple properties (additivity and Haag duality) of the net of operator alge bras attached to space-time regions. We observe that different types of sy mmetries are associated with the breaking of these properties in regions o f different non-trivial topologies. When such topologies are connected\, w e show the non locally generated operators generate an Abelian symmetry gr oup\, and their commutation relations are fixed. The existence of order pa rameters with area law\, like the Wilson loop for the confinement phase\, or the 't Hooft loop for the dual Higgs phase\, is shown to imply the exis tence of more than one possible choice of algebras for the same underlying theory. A natural entropic order parameter arises by this non-uniqueness. We display aspects of the phases of theories with generalized symmetries in terms of these entropic order parameters. In particular\, the connectio n between constant and area laws for dual order and disorder parameters is transparent in this approach\, new constraints arising from conformal sym metry are revealed\, and the algebraic origin of the Dirac quantization co ndition (and generalizations thereof) is described. A novel tool in this a pproach is the entropic certainty relation satisfied by the dual relative entropies associated with complementary regions\, which quantitatively rel ates the statistics of order and disorder parameters.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by de fault. Please only unmute it if you wish to make a question or comment\, a nd then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Jorrit Kruthoff (Stanford) DTSTART:20201021T150000Z DTEND:20201021T163000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/18 DESCRIPTION:Title: Bootstrapping Matrix Quantum Mechanics\nby Jorrit Kruthoff (Stanford) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nLarge N matri x quantum mechanics is central to holographic duality but not solvable in the most interesting cases. We show that the spectrum and simple expectati on values in these theories can be obtained numerically via a bootstrap me thodology. In this approach\, operator expectation values are related by s ymmetries\, such as time translation and SU(N) gauge invariance\, and then bounded with certain positivity constraints. We first demonstrate how thi s method efficiently solves the conventional quantum anharmonic oscillator . We then reproduce the known solution of large N single matrix quantum me chanics. Finally\, we present new results on the ground state of large N t wo matrix quantum mechanics.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back agai n.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Hugo Camargo (AEI Potsdam) DTSTART:20201112T140000Z DTEND:20201112T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/19 DESCRIPTION:by Hugo Camargo (AEI Potsdam) as part of GQFI-UGent-WST Semina rs\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Alice Di Tucci (AEI Potsdam) DTSTART:20201104T140000Z DTEND:20201104T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/20 DESCRIPTION:Title: Lessons for quantum cosmology from anti-de Sitter black holes\nby Alice Di Tucci (AEI Potsdam) as part of GQFI-UGent-WST Seminars\n\n \nAbstract\nIn this talk I will discuss gravitational path integrals in th e presence of negative and positive cosmological constant within the minis uperspace approximation\, putting special emphasis on boundary conditions and integration contours. I will show how the Hawking-Page transition is r ecovered in this setting. These findings have direct consequences for the no-boundary proposal in cosmology\, because the anti–de Sitter calculati on can be brought into one-to-one correspondence with a path integral for de Sitter space with Neumann conditions imposed at the nucleation of the U niverse.\n\n1) Please display your name when you join the seminar.\n\n2) Y our microphone is muted by default. Please only unmute it if you wish to m ake a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Victor Gorbenko (Stanford) DTSTART:20201111T160000Z DTEND:20201111T173000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/21 DESCRIPTION:Title: Bra-ket wormholes in gravitationally prepared states\nby Vi ctor Gorbenko (Stanford) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\ nWe consider two dimensional CFT states that are produced by a gravitation al path integral. As a first case\, we consider a state produced by Euclid ean AdS$_2$ evolution followed by flat space evolution. We use the fine gr ained entropy formula to explore the nature of the state. We find that the naive hyperbolic space geometry leads to a paradox. This is solved if we include a geometry that connects the bra with the ket\, a bra-ket wormhole . The semiclassical Lorentzian interpretation leads to CFT state entangled with an expanding and collapsing Friedmann cosmology. As a second case\, we consider a state produced by Lorentzian dS$_2$ evolution\, again follow ed by flat space evolution. The most naive geometry also leads to a simila r paradox. We explore several possible bra-ket wormholes. The most obvious one leads to a badly divergent temperature. The most promising one also l eads to a divergent temperature but by making a projection onto low energy states we find that it has features that look similar to the previous Euc lidean case. In particular\, the maximum entropy of an interval in the fut ure is set by the de Sitter entropy.\n\n1) Please display your name when y ou join the seminar.\n\n2) Your microphone is muted by default. Please onl y unmute it if you wish to make a question or comment\, and then mute it b ack again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Marina Huerta (Centro Atomico Bariloche) DTSTART:20201125T140000Z DTEND:20201125T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/22 DESCRIPTION:Title: Entanglement\, Global Symmetries and Topological contributions< /a>\nby Marina Huerta (Centro Atomico Bariloche) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nRecently it was shown that Entanglement Entropy f or theories based on algebras of operators invariant under a global symmet ry is non uniquely defined. This is a direct consequence of the fact that the algebra assigned to the region\, in case of regions with non-trivial t opology\, does not satisfy the expected property of additivity/duality. Th is can be understood by noticing the existence of operators which cannot b e locally generated within the region. These are called twists and intertw iners belonging to the region or its complement respectively. In this scen ario\, novel universal contributions\, topological in nature\, arise.\n\n1 ) Please display your name when you join the seminar.\n\n2) Your microphon e is muted by default. Please only unmute it if you wish to make a questio n or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Xiao-Liang Qi (Stanford) DTSTART:20201216T160000Z DTEND:20201216T173000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/23 DESCRIPTION:Title: Effective entropy of quantum fields coupled with gravity\nb y Xiao-Liang Qi (Stanford) as part of GQFI-UGent-WST Seminars\n\n\nAbstrac t\nEntanglement entropy quantifies the amount of uncertainty of a quantum state. For quantum fields in curved space\, entanglement entropy of the qu antum field theory degrees of freedom is well-defined for a fixed backgrou nd geometry. In this paper\, we propose a generalization of the quantum fi eld theory entanglement entropy by including dynamical gravity. The genera lized quantity named effective entropy\, and its Renyi entropy generalizat ions\, are defined by analytic continuation of a gravitational path integr al on replica geometry with a co-dimension-2 brane at the boundary of regi on we are studying. We discuss different approaches to define the region i n a gauge invariant way\, and show that the effective entropy satisfies th e quantum extremal surface formula. When the quantum fields carry a signif icant amount of entanglement\, the quantum extremal surface can have a top ology transition\, after which an entanglement island region appears. Our result generalizes the Hubeny-Rangamani-Takayanagi formula of holographic entropy (with quantum corrections) to general geometries without asymptoti c AdS boundary\, and provides a more solid framework for addressing proble ms such as the Page curve of evaporating black holes in asymptotic flat sp acetime. We apply the formula to two example systems\, a closed two-dimens ional universe and a four-dimensional maximally extended Schwarzchild blac k hole. We discuss the analog of the effective entropy in random tensor ne twork models\, which provides more concrete understanding of quantum infor mation properties in general dynamical geometries. By introducing ancilla systems\, we show how quantum information in the entanglement island can b e reconstructed in a state-dependent and observer-dependent map. We study the closed universe (without spatial boundary) case and discuss how it is related to open universe.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\ n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Jamie Sully (University of British Columbia) DTSTART:20210120T150000Z DTEND:20210120T160000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/24 DESCRIPTION:Title: Sharp Holography for Boundary Conformal Field theory\nby Ja mie Sully (University of British Columbia) as part of GQFI-UGent-WST Semin ars\n\n\nAbstract\nOver the last decade we have learned a great deal about the conditions that allow a conformal field theory to have an effective d escription in terms of semiclassical gravity. But what about when we add d efects or boundaries to the CFT? Under what conditions can we expect those too to be described by gravity plus semiclassical branes? By examining ho lographic phase transitions in entanglement entropy\, I will show that the possible operator spectrum of BCFTs is constrained by agreement with the gravitational dual. And using techniques from the boundary bootstrap\, I w ill argue that even well-behaved holographic CFTs almost never have a good bulk dual once we add a boundary.\n\n1) Please display your name when you join the seminar.\n \n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it ba ck again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Johanna Erdmenger (University of Würzburg) DTSTART:20210127T140000Z DTEND:20210127T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/25 DESCRIPTION:Title: New materials for holographic hydrodynamics\nby Johanna Erd menger (University of Würzburg) as part of GQFI-UGent-WST Seminars\n\n\nA bstract\nMy talk will be devoted to an interdisciplinary project involving both holographers and condensed matter physicists. So far\, graphene is t he material of choice for experimentally realizing hydrodynamic behaviour of strongly coupled electrons in a solid. However\, in graphene the electr on-electron coupling is only of order one in suitable units\, still far aw ay from the infinite coupling limit studied in holographic hydrodynamics. Here we propose a new Dirac material\, Scandium-substituted Herbertsmithit e\, in which the electron-electron coupling is enhanced by a factor 3.2 as compared to graphene. Using a holographic approach that involves finite-c oupling higher-curvature corrections to the famous holographic result of 1 /4 pi for the ratio of shear viscosity over entropy density (eta/s)\, we e stimate eta/s in the coupling regime of the proposed new material. The ass ociated range of Reynolds numbers even puts turbulent behaviour within rea ch. In the talk I will give an introduction to the condensed matter aspect s of the project and present the holographic computations.\n\nBased on 191 1.06810 (Nature Communications 11 3997 (2020))\n\n----- 1) Please display your name when you join the seminar. 2) Your microphone is muted by defaul t. Please only unmute it if you wish to make a question or comment\, and t hen mute it back again. ------\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Joshua Kirklin (Okinawa Institute of Science and Technology) DTSTART:20210210T140000Z DTEND:20210210T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/26 DESCRIPTION:Title: Uhlmann Phase\, Black Hole Information and Holography\nby J oshua Kirklin (Okinawa Institute of Science and Technology) as part of GQF I-UGent-WST Seminars\n\n\nAbstract\nIn the 1980s\, Armin Uhlmann described a natural generalisation of Berry phase to mixed states which has come to be known as Uhlmann phase. I will describe a series of recent results cha racterising the Uhlmann phase of subsystems in quantum gravity. First\, as suming replica wormholes contribute to the path integral\, I will show tha t measurements of the Uhlmann phase of Hawking radiation allows one to rec onstruct the phase space of the interior of a black hole (past the Page ti me)\, providing a protocol for the recovery of all infalling classical inf ormation. This is a generalisation of a previous result concerning entangl ement wedges in holography. Next\, I describe a path integral formula for the Uhlmann phase of a generic highly entangled system\, explaining how it appears to inevitably involve an extra dimension generated by modular flo w\, despite a lack of any holographic assumptions. Finally\, I comment on the operational meaning of Uhlmann phase\, and how it's significance may r elate to decoherence.\n\n1) Please display your name when you join the sem inar.\n \n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Jean-Luc Lehners (AEI Potsdam) DTSTART:20210217T140000Z DTEND:20210217T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/27 DESCRIPTION:Title: Circuit complexity of primordial perturbations\nby Jean-Luc Lehners (AEI Potsdam) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI will discuss the quantum circuit complexity of cosmological perturbations in different models of the early universe. A natural measure for the comp lexity of cosmological perturbations is based on the symplectic group\, al lowing us to identify complexity with geodesics in the hyperbolic plane. W e investigate the complexity of both the mode functions and the physical p erturbations\, arguing that the latter often provides a more insightful de scription of the physics involved. In all models the total complexity reac hed is rather large. Inflationary perturbations may be represented by a co mparatively simple quantum circuit\, while the perturbations during a matt er-dominated contracting phase present the most rapid growth in complexity . Ekpyrotic perturbations reside in the middle and are distinguished by th e smallest growth of complexity before horizon exit. Our analysis serves t o highlight how different cosmological models achieve the same end result for the perturbations via different routes and how all models show a prono unced sensitivity to initial conditions.\n\n1) Please display your name wh en you join the seminar.\n \n2) Your microphone is muted by default. Pleas e only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Giuseppe Policastro (École Normale Supérieure) DTSTART:20210224T140000Z DTEND:20210224T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/28 DESCRIPTION:Title: Transport in TTbar-deformed conformal field theories\nby Gi useppe Policastro (École Normale Supérieure) as part of GQFI-UGent-WST S eminars\n\n\nAbstract\nI will discuss out of equilibrium properties of con formal field theories deformed by the TTbar deformation. Such theories are very interesting because they can describe the effect of an irrelevant pe rturbation of a critical system\, and they are exactly solvable\, to some extent. They can be approached from two different point of views: using in tegrability techniques and the holographic correspondence. I will focus on the energy and momentum Drude weights and diffusion constants\, as well a s the non equilibrium steady states which emerge after an inhomogeneous qu ench. The transport coefficients and non equilibrium steady state current admit closed form expressions\, whose universality is established by the a greement of the two approaches. I will finally discuss the prospects of fu rther extensions of our results.\n\n1) Please display your name when you j oin the seminar.\n \n2) Your microphone is muted by default. Please only u nmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Dongsheng Ge (University of Warsaw) DTSTART:20210303T140000Z DTEND:20210303T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/29 DESCRIPTION:Title: Energy reflection and transmission at 2D holographic interfaces \nby Dongsheng Ge (University of Warsaw) as part of GQFI-UGent-WST Sem inars\n\n\nAbstract\nScattering from conformal interfaces in two dimension s is universal in that the flux of reflected and transmitted energy does n ot depend on the details of the initial state. In this talk\, we present t he first gravitational calculation of energy reflection and transmission c oefficients for interfaces with thin-brane holographic duals. Our result f or the reflection coefficient depends monotonically on the tension of the dual string anchored at the interface\, and obeys the lower bound recently derived from the ANEC in conformal field theory. The B(oundary)CFT limit is recovered for infinite ratio of the central charges.\n\n1) Please displ ay your name when you join the seminar.\n \n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\ , and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Ivan Munoz (Pontificia Universidad Catolica de Chile) DTSTART:20210317T140000Z DTEND:20210317T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/30 DESCRIPTION:Title: Loops in Holographic Correlators\nby Ivan Munoz (Pontificia Universidad Catolica de Chile) as part of GQFI-UGent-WST Seminars\n\n\nAb stract\nIn the early days of AdS/CFT correspondence\, it was already clear how to compute CFT correlators from the AdS side. Working at tree level i n the bulk\, and renormalizing the IR divergence properly due to the infin ite volume of AdS\, it is obtained the correct conformal correlator. We ex tend this treatment considering quantum corrections to the fields in the A dS and compute the holographic correlation function with loops in the bulk and study the role of IR divergences.\n\n1) Please display your name when you join the seminar.\n \n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute i t back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Ignacio Reyes (AEI Potsdam) DTSTART:20210324T140000Z DTEND:20210324T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/31 DESCRIPTION:Title: Moving mirrors\, Page curves and bulk entropies in AdS2\nby Ignacio Reyes (AEI Potsdam) as part of GQFI-UGent-WST Seminars\n\n\nAbstr act\nUnderstanding the entanglement of radiation in QFT has been a long st anding challenge\, with implications from black hole thermodynamics to qua ntum information. We demonstrate how the free fermion in 1+1-dimensions re veals the details of the density matrix of the radiation produced by a mov ing mirror. Using the resolvent method rather than standard boundary CFT t echniques we derive the Renyi entropies\, modular Hamiltonian and flow of the radiation\, and determine when mirrors generate unitary transformation s. Exploring the Renyi entropies on AdS2 with reflecting boundary conditio ns yields surprising consequences for quantum extremal surfaces in JT grav ity.\n\n1) Please display your name when you join the seminar.\n \n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Jan de Boer (University of Amsterdam) DTSTART:20210331T130000Z DTEND:20210331T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/32 DESCRIPTION:Title: The OPE Randomness Hypothesis\, Euclidean Wormholes\, and Effec tive Field Theory\nby Jan de Boer (University of Amsterdam) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nRecent developments in holography indicate that the semi-classical Euclidean path-integral of Einstein gravi ty is much more powerful than previously anticipated. It is capable of rep roducing a unitary Page curve for black hole evaporation\, and can even ca pture some features of the discrete nature of black hole microstates. Worm hole geometries play a key role in this context. I will propose a mechanis m to explain this in the CFT: the OPE Randomness Hypothesis. This ansatz i s a generalization of the Eigenstate Thermalization Hypothesis which appli es to chaotic CFTs\, and treats OPE coefficients of heavy operators as ran dom variables with a given probability distribution. I will present two ap plications of this framework: First\, it resolves a factorization puzzle i n AdS_3/CFT_2 due to the genus-2 wormhole\, as raised by Maoz and Maldacen a. Second\, it provides an argument against global symmetries in quantum g ravity. Based on arXiv:2006.05499 and arXiv:2012.07875.\n\n1) Please disp lay your name when you join the seminar.\n \n2) Your microphone is muted b y default. Please only unmute it if you wish to make a question or comment \, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Arjun Kar (University of British Columbia) DTSTART:20210421T150000Z DTEND:20210421T160000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/33 DESCRIPTION:Title: A hierarchy of complexity growth from integrability and chaos\nby Arjun Kar (University of British Columbia) as part of GQFI-UGent-WS T Seminars\n\n\nAbstract\nQuantum complexity has been conjectured to be re levant for black hole interiors.  In particular\, Susskind has conjecture d a generic form of complexity growth and saturation for maximally chaotic systems like black holes.  Using geodesic complexity techniques\, we stu dy the complexity of time evolution in free\, integrable\, and chaotic sys tems with N degrees of freedom.  We demonstrate that the growth rate of t his complexity is related to more familiar properties of physical theories like 1) the existence of creation/annihilation operators and 2) smeared t hermal two-point functions.  Using these properties\, we find that the co mplexity saturates in free\, integrable\, and chaotic theories at time sca les which are on the order of N^{1/2}\, polynomial in N\, and exponential in N\, respectively.  Our results in the free theory improve an existing bound in the complexity theory literature\, and our results in chaotic the ories are based only on coarse properties of the spectrum and eigenstates. \n\n1) Please display your name when you join the seminar.\n \n2) Your mic rophone is muted by default. Please only unmute it if you wish to make a q uestion or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Matthew Dodelson (Tokyo U.\, IPMU) DTSTART:20210428T130000Z DTEND:20210428T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/34 DESCRIPTION:Title: Singularities of thermal correlators at strong coupling\nby Matthew Dodelson (Tokyo U.\, IPMU) as part of GQFI-UGent-WST Seminars\n\n \nAbstract\nI will describe work with Ooguri on the singularities of the t wo point function at finite temperature in a conformal field theory in mor e than two dimensions. At weak coupling the only singularity is on the lig ht cone\, but in the large N\, large lambda regime a new singularity emerg es. This new singularity corresponds to a null geodesic in the AdS/Schwarz schild black hole\, which may wrap the photon sphere many times. After der iving this result\, I will discuss the resolution of these singularities by stringy tidal effects at finite lambda. The basic tool I will use is to take the Penrose limit around a given null geodesic\, and then use the so lubility of the string theory in this background. I will also discuss appl ications to rotating black holes.\n\n1) Please display your name when you join the seminar. 2) Your microphone is muted by default. Please only unmu te it if you wish to make a question or comment\, and then mute it back ag ain.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/34/ END:VEVENT BEGIN:VEVENT SUMMARY:Dionysios Anninos (King's College London) DTSTART:20210505T130000Z DTEND:20210505T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/35 DESCRIPTION:Title: Toward an infrared realisation of dS in AdS?\nby Dionysios Anninos (King's College London) as part of GQFI-UGent-WST Seminars\n\n\nAb stract\nWe explore the possibility of realising a portion of a two-dimensi onal de Sitter world in an asymptotically anti-de Sitter universe. We cons ider the question from both a macroscopic and microscopic perspective.\n\n 1) Please display your name when you join the seminar. 2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Jose Barbon (IFT-UAM/CSIC) DTSTART:20210519T130000Z DTEND:20210519T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/36 DESCRIPTION:Title: The complexity of gravitational clumping\nby Jose Barbon (I FT-UAM/CSIC) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWithin the holographic Complexity=Volume proposal\, we study correspondences between the rate of complexity growth and the degree of gravitational clumping in the bulk\, quantified as an average infall momentum. We show that such a c onnection is largely implicit in the CV proposal through the momentum cons traint of GR. We discuss generalisations of these momentum/complexity rela tions\, as well as some topological obstructions. (Work in collaboration w ith J. Martin-Garcia and M. Sasieta).\n\n1) Please display your name when you join the seminar.\n \n2) Your microphone is muted by default. Please o nly unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Erik Tonni (SISSA\, INFN) DTSTART:20210526T130000Z DTEND:20210526T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/37 DESCRIPTION:Title: Modular Hamiltonians for the massless Dirac field in the presen ce of a boundary or of a defect\nby Erik Tonni (SISSA\, INFN) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nThe reduced density matrix of a spatial subsystem can be written as the exponential of the modular Hamilto nian\, hence this operator contains a lot of information about the entangl ement of the corresponding spatial bipartition. First we consider the mass less Dirac field on the half-line\, imposing the most general boundary con ditions that ensure the global energy conservation. This leads to two ineq uivalent phases where either the vector or the axial symmetry is preserved . In these two phases\, we discuss the analytic expressions for the modula r Hamiltonians of an interval on the half-line when the system is in its g round state\, for the corresponding modular flows of the Dirac field and f or the corresponding modular correlators. The method allows to obtain anal ytic expressions also for the modular Hamiltonians\, the modular flows and the modular correlators for two disjoint equal intervals at the same dist ance from a point-like defect characterised by a unitary scattering matri x\, that allows both reflection and transmission.\n\n1) Please display you r name when you join the seminar.\n \n2) Your microphone is muted by defau lt. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/37/ END:VEVENT BEGIN:VEVENT SUMMARY:Onkar Parrikar (Stanford) DTSTART:20210602T130000Z DTEND:20210602T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/38 DESCRIPTION:Title: Building tensor networks for holographic states\nby Onkar P arrikar (Stanford) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWe di scuss a one-parameter family of states in two-dimensional holographic conf ormal field theories which are constructed via the Euclidean path integral of an effective theory on a family of hyperbolic slices in the dual bulk geometry. The effective theory in question is the CFT flowed under a TT*  deformation\, which "folds" the boundary CFT towards the bulk time-refle ction symmetric slice. We propose that these novel Euclidean path integral states in the CFT can be interpreted as continuous tensor network (CTN) s tates. We argue that these CTN states satisfy a Ryu-Takayanagi-like minima l area upper bound on the entanglement entropies of boundary intervals\, w ith the coefficient being equal to 1/4G_N\; the CTN corresponding to the bulk time-reflection symmetric slice saturates this bound.\n\n1) Please di splay your name when you join the seminar.\n \n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comme nt\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/38/ END:VEVENT BEGIN:VEVENT SUMMARY:Irene Valenzuela (Harvard) DTSTART:20210609T140000Z DTEND:20210609T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/39 DESCRIPTION:Title: A CFT Distance Conjecture\nby Irene Valenzuela (Harvard) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWe formulate a series of c onjectures relating the geometry of conformal manifolds to the spectrum of local operators in conformal field theories in d>2 spacetime dimensions. We focus on conformal manifolds with limiting points at infinite distance with respect to the Zamolodchikov metric. Our central conjecture is that a ll theories at infinite distance possess an emergent higher-spin symmetry\ , generated by an infinite tower of currents whose anomalous dimensions va nish exponentially in the distance. Stated geometrically\, the diameter of a non-compact conformal manifold must diverge logarithmically in the high er-spin gap. In the holographic context our conjectures are related to the Distance Conjecture in the swampland program. Interpreted gravitationally \, they imply that approaching infinite distance in moduli space at fixed AdS radius\, a tower of higher-spin fields becomes massless at an exponent ial rate that is bounded from below in Planck units. We discuss further im plications for conformal manifolds of superconformal field theories in thr ee and four dimensions.\n\n1) Please display your name when you join the s eminar.\n\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\ n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Janet Hung (Fudan University) DTSTART:20210616T130000Z DTEND:20210616T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/40 DESCRIPTION:Title: padic tensor network and emergent Einstein equation\nby Jan et Hung (Fudan University) as part of GQFI-UGent-WST Seminars\n\n\nAbstrac t\nWe take the tensor network describing explicit p-adic CFT partition fun ctions proposed in 1902.01411\, and consider boundary conditions of the ne twork describing a deformed Bruhat-Tits (BT) tree geometry. We demonstrate that this geometry satisfies an emergent graph Einstein equation in a uni que way that is consistent with the bulk effective matter action encoding the same correlation function as the tensor network\, at least in the pert urbative limit order by order away from the pure BT tree. Moreover\, the ( perturbative) definition of the graph curvature in the Mathematics literat ure naturally emerges from the consistency requirements of the emergent Ei nstein equation. This could provide new insights into the understanding of gravitational dynamics potentially encoded in more general tensor network s.\n\n1) Please display your name when you join the seminar.\n \n2) Your m icrophone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/40/ END:VEVENT BEGIN:VEVENT SUMMARY:Dominik Neuenfeld (Perimeter Institute) DTSTART:20211005T130000Z DTEND:20211005T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/41 DESCRIPTION:Title: Holonomy Constraints in Double Holography\nby Dominik Neuen feld (Perimeter Institute) as part of GQFI-UGent-WST Seminars\n\n\nAbstrac t\nI discuss the relation between the d-dimensional BCFT and CFT+gravity d escriptions of double holography. In both descriptions entropies can be co mputed using the RT formula in a (d+1)-dimensional bulk. However\, I argue that the standard assumptions about entanglement wedge reconstruction sug gest that the homology condition for RT surfaces depends on which of the " boundary" formulations is taken. After discussing implications for the rel ation between von Neumann entropy and the entropy computed using the islan d formula\, I will show how the island formula arises in a simple qubit mo del. Based on those results I speculate about the emergence of semi-classi cal gravity from quantum gravity.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only u nmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/41/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Mezei (SCGP\, Stony Brook) DTSTART:20211019T130000Z DTEND:20211019T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/42 DESCRIPTION:Title: The volume of the black hole interior at late times\nby Mar k Mezei (SCGP\, Stony Brook) as part of GQFI-UGent-WST Seminars\n\n\nAbstr act\nUnderstanding the fate of semi-classical black hole solutions at very late times is one of the most important open questions in quantum gravity . In this talk\, we provide a path integral definition of the volume of th e black hole interior and study it at arbitrarily late times for black hol es in various models of two-dimensional gravity. Because of a novel univer sal cancellation between the contributions of the semi-classical black hol e spectrum and some of its non-perturbative corrections\, we find that\, a fter a linear growth at early times\, the length of the interior saturates at a time\, and towards a value\, that is exponentially large in the entr opy of the black hole. This provides a non-perturbative confirmation of th e complexity equals volume proposal since complexity is also expected to p lateau at the same value and at the same time.\n\n1) Please display your n ame when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/42/ END:VEVENT BEGIN:VEVENT SUMMARY:Luca Delacretaz (University of Chicago) DTSTART:20211026T130000Z DTEND:20211026T140000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/43 DESCRIPTION:Title: Thermal aspects of 2d QFTs\nby Luca Delacretaz (University of Chicago) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI will prese nt general constraints on (1+1)d QFTs obtained by imposing causality in th e thermal state. One immediate consequence is the existence of a thermodyn amic C-function\, providing an alternative proof to Zamolodchikov's C-theo rem. Similar considerations fix the sign of the TT-bar correction in non-i ntegrable EFTs. Causality also severely constrains the out-of-equilibrium dynamics\, by placing a strong lower bound on the local equilibration time beyond which hydrodynamics emerges as an effective description. This esta blishes the conjectured "Planckian bound" on thermalization in the context of (1+1)d QFTs.\n\nBased on: arXiv:2105.02229 [hep-th].\n\n1) Please disp lay your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\ , and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/43/ END:VEVENT BEGIN:VEVENT SUMMARY:Tatsuma Nishioka (Yukawa Institute for Theoretical Physics) DTSTART:20211102T140000Z DTEND:20211102T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/44 DESCRIPTION:Title: Topological pseudo entropy\nby Tatsuma Nishioka (Yukawa Ins titute for Theoretical Physics) as part of GQFI-UGent-WST Seminars\n\n\nAb stract\nRecently\, a new quantum information measure called pseudo entropy was introduced as a generalization of entanglement entropy to quantify qu antum correlation between initial and final states in a time-dependent sys tem. In this talk\, I will examine some aspects of pseudo entropy in topol ogical field theory and conformal field theory (CFT). In three-dimensional Chern-Simons theory\, pseudo entropy can be given by a partition function on a three-sphere with Wilson loops in a similar manner to topological en tanglement entropy. I will also show that the pseudo entropy in a certain setup is equivalent to the interface entropy in two-dimensional CFTs\, and leverage the equivalence to calculate the pseudo entropies in particular examples. Furthermore\, I will define a pseudo entropy extension of the le ft-right entanglement entropy in two-dimensional boundary CFTs and derive a universal formula for a pair of arbitrary boundary states.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is mute d by default. Please only unmute it if you wish to make a question or comm ent\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/44/ END:VEVENT BEGIN:VEVENT SUMMARY:Olga Papadoulaki (Perimeter Institute) DTSTART:20211109T140000Z DTEND:20211109T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/45 DESCRIPTION:Title: Holography from the Wheeler-DeWitt equation\nby Olga Papado ulaki (Perimeter Institute) as part of GQFI-UGent-WST Seminars\n\n\nAbstra ct\nIn a theory of quantum gravity\, states can be represented as wavefunc tionals that assign an amplitude to a given configuration of matter fields and the metric on a spatial slice. These wavefunctionals must obey a set of constraints as a consequence of the diffeomorphism invariance of the th eory\, the most important of which is known as the Wheeler-DeWitt equation . I will present how to study these constraints perturbatively by expandin g them to leading nontrivial order in Newton’s constant about a backgrou nd AdS spacetime. It will become clear that in perturbation theory\, any w avefunctional that solves these constraints must have specific correlation s between a component of the metric at infinity and energetic excitations of matter fields or transverse-traceless gravitons. These correlations dis allow strictly localized excitations. I will prove perturbatively that two states or two density matrices that coincide at the boundary for an infin itesimal interval of time must coincide everywhere in the bulk. This analy sis establishes a perturbative version of holography for theories of gravi ty coupled to matter in AdS.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back agai n.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/45/ END:VEVENT BEGIN:VEVENT SUMMARY:Felix Haehl (IAS) DTSTART:20211116T140000Z DTEND:20211116T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/46 DESCRIPTION:Title: Spin glasses and holography\nby Felix Haehl (IAS) as part o f GQFI-UGent-WST Seminars\n\n\nAbstract\nThe connections between disordere d quantum systems (specifically the SYK model)\, ensemble averaging\, and two-dimensional dilaton gravity underlie much of the recent progress on ho lography and quantum gravity. While the SYK model is a 'spin liquid' even at low temperatures\, closely related disordered systems exhibit a 'spin g lass' phase\, characterized by ergodicity breaking and slow dynamics. I wi ll discuss simple spin glass models and some of their properties that are of interest from a gravitational point of view (such as thermodynamics and quantum chaos). I will propose a holographic interpretation of some cruci al features that relates to the fragmentation instability of AdS2 towards a geometry with multiple throats. Based on work with Tarek Anous\, Maine C hristos\, and Subir Sachdev.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back agai n.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/46/ END:VEVENT BEGIN:VEVENT SUMMARY:Nissan Itzhaki (Tel Aviv University) DTSTART:20211123T140000Z DTEND:20211123T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/47 DESCRIPTION:Title: Stringy Information and Black Holes\nby Nissan Itzhaki (Tel Aviv University) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWe sho w that in string theory\, due to non perturbative effects\, there are case s in which two states that semi classically are completely different\, are in fact the same. One state cannot be excited without exciting the other: they are two components of the same state in the exact theory. As a resul t\, in some situations that include black holes\, the nature of informatio n in string theory is dramatically different than in field theory. In part icular\, each general relativity state\, that lives in the atmosphere of b lack fivebranes\, is accompanied by an excitation that lives on folded str ings\, which fill the black hole interior. This is likely related to the w ay that information is extracted from black holes in string theory\, and w e refer to it as stringy information.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please on ly unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/47/ END:VEVENT BEGIN:VEVENT SUMMARY:Brian Swingle (Maryland University) DTSTART:20211130T140000Z DTEND:20211130T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/48 DESCRIPTION:Title: Effective Field Theory of Chaotic Spectral Correlations\nby Brian Swingle (Maryland University) as part of GQFI-UGent-WST Seminars\n\ n\nAbstract\nEnsembles of quantum chaotic systems are expected to exhibit random matrix universality in their energy spectrum. The presence of this universality can be diagnosed by looking for a linear in time 'ramp' in th e spectral form factor\, but for realistic systems this feature is typical ly only visible after a sufficiently long time. Given the wide prevalence of this random matrix behavior\, it is natural to ask for an effective fie ld theory which predicts the ramp and computes corrections to it arising f rom physical constraints. I will present such an effective theory based on fluctuating hydrodynamics. The theory can also be adapted to describe the effects of spontaneous symmetry breaking on spectral correlations.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/48/ END:VEVENT BEGIN:VEVENT SUMMARY:Juan Pedraza (ICC Barcelona) DTSTART:20211214T140000Z DTEND:20211214T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/49 DESCRIPTION:Title: Lorentzian Threads and Holographic Complexity\nby Juan Pedr aza (ICC Barcelona) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nThe continuous min flow-max cut principle is used to reformulate the 'complexi ty=volume' conjecture using Lorentzian flows. Conceptually\, discretized f lows are interpreted in terms of `gatelines'\, one-dimensional time-like c urves that connect layers of a tensor network grid in the bulk spacetime. We imagine each gateline represents a unitary operation such that the bulk calculation for complexity matches its information-theoretic definition. The bulk symplectic potential provides a 'canonical' flow configuration ch aracterizing perturbations around arbitrary CFT states. Its consistency re quires the bulk to obey linearized Einstein's equations\, which are shown to be equivalent to the holographic first law of complexity\, thereby advo cating a notion of 'spacetime complexity'. Finally\, we explain the need f or a more general measure of complexity that captures the role of suboptim al flows or tensor network configurations. Based on 2105.12735 and 2106.12 585.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/49/ END:VEVENT BEGIN:VEVENT SUMMARY:Rene Meyer (Würzburg U) DTSTART:20220111T140000Z DTEND:20220111T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/50 DESCRIPTION:Title: Symmetry-resolved quantum information measures for AdS gravity and beyond\nby Rene Meyer (Würzburg U) as part of GQFI-UGent-WST Semi nars\n\n\nAbstract\nQuantum entanglement is the key resource employed in m odern quantum computation. Different entanglement measures such as the ent anglement entropy and Renyi entropies also provide useful information abou t the entanglement structure of quantum field theories\, in particular at critical points. I will discuss the symmetry resolved entanglement and Ren yi entropies\, a fine-grained version of the usual entanglement and Renyi entropies\, both in the context of quantum field theory and AdS/CFT. In th e presence of global conserved charges\, they quantify the entanglement co ntent of the reduced density matrix in a fixed charge sector. These entang lement measures can in particular be calculated in two-dimensional conform al field theories with U(1) Kac-Moody structure at level k\, and are found to not depend on the value of the charge. This charge independence is cal led equipartition of entanglement\, and implies that no charge sector is d istinguished in terms of its entanglement content. Finally\, I will discus s the symmetry resolved entanglement in the AdS3/CFT2 dual of the U(1) Kac -Moody CFT. Agreement with CFT results provides a further test of the AdS3 /CFT2 correspondence. I finish with some results about the violation of th e equipartition property in CFTs with W3 symmetry. This talk is based on h ep-th/2012.11274 and hep-th/2108.09210.\n\n1) Please display your name whe n you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute i t back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/50/ END:VEVENT BEGIN:VEVENT SUMMARY:Martin Sasieta (Madrid IFT) DTSTART:20220118T140000Z DTEND:20220118T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/51 DESCRIPTION:Title: Holographic Complexity of Quantum Black Holes\nby Martin Sa sieta (Madrid IFT) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nIn th is talk\, I will describe a way to characterize the bulk quantum correctio ns to holographic complexity proposals for the state of a black hole using double holography. The specific setup is the quantum BTZ black hole\, whi ch encompasses in an exact manner the effects of conformal fields with lar ge central charge in the presence of the black hole\, including the backre action corrections to the BTZ metric. I will show how the Volume Complexit y admits a consistent quantum expansion\, while the Action Complexity fail s to account for the additional contributions from bulk quantum fields and does not lead to the correct classical limit.\n\n1) Please display your n ame when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/51/ END:VEVENT BEGIN:VEVENT SUMMARY:Rob Myers (Perimeter Institute) DTSTART:20220125T140000Z DTEND:20220125T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/52 DESCRIPTION:Title: Complexity=Anything\nby Rob Myers (Perimeter Institute) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nMotivated by holographic co mplexity\, we examine a new class of gravitational observables in asymptot ically AdS space associated with codimension-one slices or with codimensio n-zero regions. We argue that any of these observables is an equally viab le candidate as the extremal volume for a gravitational dual of complexity .\n\n1) Please display your name when you join the seminar.\n\n2) Your mic rophone is muted by default. Please only unmute it if you wish to make a q uestion or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/52/ END:VEVENT BEGIN:VEVENT SUMMARY:Sridip Pal (IAS) DTSTART:20220201T140000Z DTEND:20220201T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/53 DESCRIPTION:Title: Automorphic Spectra and the Conformal Bootstrap\nby Sridip Pal (IAS) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nWe point out t hat the spectral geometry of hyperbolic manifolds provides a remarkably pr ecise model of the modern conformal bootstrap. As an application\, we use conformal bootstrap techniques to derive rigorous computer-assisted upper bounds on the lowest positive eigenvalue $\\lambda_1(X)$ of theLaplace-Bel trami operator on closed hyperbolic surfaces and 2-orbifolds $X$. In a num ber of notable cases\, our bounds are nearly saturated by known surfaces a nd orbifolds. For instance\, our bound on all genus-2 surfaces $X$ is $\\l ambda_1(X)\\leq 3.8388976481$\, while the Bolza surface has $\\lambda_1(X) \\approx 3.838887258$.\n\nI will explain that hyperbolic surface are of th e form \\Gamma\\G/K with G=PSL(2\,R)\, K=SO(2) /{\\pm I} and \\Gamma being Fuchsian group. For a given hyperbolic surface\, one can define a Hilbert space of local operators\, transforming under unitary irreps of a conform al group (PSL(2\,R)) and introduce a notion of operator product expanion ( OPE). The associativity of this OPE reflects the associativity of function multiplication on the space \\Gamma\\G and leads to the bootstrap equatio ns. Now the functions on \\Gamma\\G can be thought of automorphic forms on the surface \\Gamma\\G/K and I will show that the scaling dimensions of t hese operators are in fact related to the automorphic spectra in particula r the Laplacian eigenvalues on the surface. Hence the bootstrap equations imply bound on the Laplacian eigenvalues.\n\nFinally\, I will make some re marks about how our methods can be generalized to higher-dimensional hyper bolic manifolds (or orbifolds) and to yield stronger bounds in the two-dim ensional case. This is based on a work (arXiv:2111.12716) with P. Kravchuk and D. Mazac.\n\n1) Please display your name when you join the seminar.\n \n2) Your microphone is muted by default. Please only unmute it if you wis h to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/53/ END:VEVENT BEGIN:VEVENT SUMMARY:Shota Komatsu (CERN) DTSTART:20220208T150000Z DTEND:20220208T160000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/54 DESCRIPTION:Title: Crosscap States in Integrable Field Theories and Spin Chains\nby Shota Komatsu (CERN) as part of GQFI-UGent-WST Seminars\n\n\nAbstrac t\nCrosscap states have been extensively studied in two-dimensional confor mal field theory in the past\, where part of the motivations came from the ir connection to orientifolds in string theory. Surprisingly however\, ana logous studies in (massive) integrable theories have been lacking. In this talk\, I will fill this gap by presenting a systematic study of crosscap states in integrable field theories and spin chains. First\, I derive an e xact formula for overlaps between the crosscap state and any excited state in integrable field theories with diagonal scattering. Using the formula\ , I compute the crosscap entropy i.e. the overlap with the ground state in several examples\, and find that it decreases monotonically along the ren ormalization group flow except in cases where the discrete symmetry is spo ntaneously broken in the infrared. We next introduce crosscap states in in tegrable spin chains and obtain exact determinant expressions for overlaps with energy eigenstates. These states are long-range entangled and provid e interesting initial conditions for the quantum quench protocol\, which a re quite distinct from short-range entangled states corresponding to the b oundary states. As a side result\, I will also briefly comment on the inte rplay between fermionization and Bethe ansatz.\n\n1) Please display your n ame when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/54/ END:VEVENT BEGIN:VEVENT SUMMARY:Dalimil Mazac (IAS) DTSTART:20220215T140000Z DTEND:20220215T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/55 DESCRIPTION:Title: Bootstrapping Boundaries and Branes\nby Dalimil Mazac (IAS) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nI will discuss bootstra p constraints on conformal boundary conditions in 2D CFTs. In particular\, I will explain how to derive bounds on the boundary entropy starting from the consistency of the annulus partition function. In the context of stri ng theory\, these imply a universal upper bound on the tension of stable D -branes. It turns out that our bounds are often saturated by interesting b oundary conditions in rational CFTs. In some cases\, the exact saturation can be proven using analytic functionals\, which is closely related to the solution of the sphere packing problem in 8 and 24 dimensions. Our bounds at large central charge have potential implications for end-of-the-world branes in pure gravity on AdS_3. The talk will be based on https://arxiv.o rg/pdf/2112.00750.pdf\, which is joint work with Scott Collier and Yifan W ang.\n\n1) Please display your name when you join the seminar.\n\n2) Your microphone is muted by default. Please only unmute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/55/ END:VEVENT BEGIN:VEVENT SUMMARY:Nima Lashkari (Purdue University) DTSTART:20220222T140000Z DTEND:20220222T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/56 DESCRIPTION:Title: Renormalization Group and Error Correction\nby Nima Lashkar i (Purdue University) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nIn renormalization group (RG) flow\, the low energy states form a code subsp ace that is protected against the local short-distance errors. We will dis cuss the similarities and differences between this approximate error corre ction code and the classical and quantum codes that appear in the degenera te vacua of local many-body quantum systems. We will consider continuous M ERA as a concrete example and discuss how well the low-energy operators ar e protected. The trade-off bounds set a bound on the amount of quantum inf ormation at a scale. Finally\, we will comment on the connections to the q uantum error correction codes in holography.\n\n1) Please display your nam e when you join the seminar.\n\n2) Your microphone is muted by default. Pl ease only unmute it if you wish to make a question or comment\, and then m ute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/56/ END:VEVENT BEGIN:VEVENT SUMMARY:Jacopo Viti (IIP) DTSTART:20220301T140000Z DTEND:20220301T150000Z DTSTAMP:20260422T215007Z UID:Holography_AdSCFT/57 DESCRIPTION:Title: The Classical Limit of the Entanglement Entropy\nby Jacopo Viti (IIP) as part of GQFI-UGent-WST Seminars\n\n\nAbstract\nIt may be nai vely assumed that certain entanglement measures\, like the entanglement en tropy of a pure state\, approach zero in the classical limit. In this talk \, we show that the limit (when properly defined) is both well-behaved and nonzero: for a bipartite system of N particles\, it coincides with the Sh annon entropy of N bits. These results have been demonstrated previously i n the context of quantum field theory\, but here we derive them in an elem entary way and also provide a physical interpretation.\n\nWork in collabor ation with G. Mussardo\, to be published in PRA as Editor suggestion\, see https://arxiv.org/abs/2112.06840.\n\n1) Please display your name when you join the seminar. 2) Your microphone is muted by default. Please only un mute it if you wish to make a question or comment\, and then mute it back again.\n LOCATION:https://researchseminars.org/talk/Holography_AdSCFT/57/ END:VEVENT END:VCALENDAR