BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Geoff Penington (University of California\, Berkeley) DTSTART:20231211T140000Z DTEND:20231211T144500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/1 DESCRIPTION:Title: Islands Far Outside the Horizon\nby Geoff Penington (Unive rsity of California\, Berkeley) as part of Workshop on Spacetime and Quant um Information\n\n\nAbstract\nInformation located in an entanglement islan d in semiclassical gravity can be\nnonperturbatively reconstructed from di stant radiation\, implying a radical\nbreakdown of effective field theory. We show that this occurs well outside of\nthe black hole stretched horizo n. We compute the island associated to\nlarge-angular momentum Hawking mod es of a four-dimensional Schwarzschild black\nhole. These modes typically fall back into the black hole but can be extracted\nto infinity by relativ istic strings or\, more abstractly\, by asymptotic boundary\noperators con structed using the timelike tube theorem. Remarkably\, we find that\ntheir island can protrude a distance of order $\\sqrt{\\ell_p r_{\\rm hor}}$\no utside the horizon. This is parametrically larger than the Planck scale\n$ \\ell_p$ and is comparable to the Bohr radius for supermassive black holes .\nTherefore\, in principle\, a distant observer can determine experimenta lly\nwhether the black hole information information paradox is resolved by \ncomplementarity\, or by a firewall.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/1/ END:VEVENT BEGIN:VEVENT SUMMARY:David Kolchmeyer (Massachusetts Institute of Technology) DTSTART:20231211T144500Z DTEND:20231211T153000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/2 DESCRIPTION:Title: Gravitational Algebras in (A)dS_2\nby David Kolchmeyer (Ma ssachusetts Institute of Technology) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nTo construct interesting algebras in qu antum gravity\, one can dress local field operators to features of the spa cetime. I will discuss this first in AdS JT gravity with matter\, where ma tter operators may be dressed to the right or left AdS boundaries. Then\, I will consider a scalar field theory in dS2 together with two entangled o bservers. Each observer carries a clock. As in the AdS example\, matter op erators may be dressed to either of the two observers. The observers' degr ees of freedom are exactly quantized. The algebra of dressed operators tea ches us about a putative quantum-mechanical dual theory.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefan Hollands (Leipzig University) DTSTART:20231211T161500Z DTEND:20231211T170000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/3 DESCRIPTION:Title: Black Hole Interiors\nby Stefan Hollands (Leipzig Universi ty) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract \nKerr or Reissner-Nordström black holes have inner horizons which deline ate the domain of predictability of solutions of wave equation type. Often \, though not e.g. for certain (A)deSitter black holes\, these inner horiz ons are classically dynamically unstable\, and get turned into some sort o f singularity by perturbations\, and thus drastically changing the nature of the inner horizons relative to the underlying exact solutions\, and rel egating the problem of predictability to the real of quantum gravity ("str ong cosmic censorship"). Recent work has shown that semi-classical quantum effects dominate classical ones very near the inner horizons\, and are ex pected lead to singularity in cases where the inner horizon is stable clas sically. I review recent progress surrounding these issues.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Eanna Flanagan (Cornell University) DTSTART:20231211T170000Z DTEND:20231211T174500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/4 DESCRIPTION:Title: Horizon Phase Spaces in General Relativity\nby Eanna Flana gan (Cornell University) as part of Workshop on Spacetime and Quantum Info rmation\n\n\nAbstract\nWe discuss several different definitions of phase s paces associated with horizons in general relativity\, and the associated symmetry groups and charges. For stationary horizons we compute the sympl ectic form of the theory in terms of independent degrees of freedom\, by s olving the constraint equations on the horizon.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Mikhail Lukin (Harvard University) DTSTART:20231211T194500Z DTEND:20231211T203000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/5 DESCRIPTION:Title: Scrambling and Quantum Error Correction Frontier\nby Mikha il Lukin (Harvard University) as part of Workshop on Spacetime and Quantum Information\n\nAbstract: TBA\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Shunyu Yao (Stanford University) DTSTART:20231211T213000Z DTEND:20231211T221500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/6 DESCRIPTION:Title: Scramblon Loops\nby Shunyu Yao (Stanford University) as pa rt of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nOut of time ordered correlator(OTOC) is one signature of quantum chaos. In certai n large N systems\, emergent scramblon-exchange modes dominate\, while scr amblon interactions are suppressed by 1/N. However\, we are going to discu ss certain types of scramblon loop corrections\, which cause a dramatic br eakdown of scramblon exchange approximation\, much earlier than naive expe ctation. Interestingly\, while these effects are significant in high tempe rature/saddle(stringy) dominant/incoherent systems\, they get cut off in l ow temperature/pole(graviton) dominant/coherent systems by ballistic growt h. This suggests a sharp distinction between coherent/incoherent scramblin g could appear by studying quantum fluctuations. We will also comment on t heir relation to wavefront broadening phenomena and gravitational high ene rgy scattering.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Luca Ciambelli (Perimeter Institute) DTSTART:20231211T221500Z DTEND:20231211T230000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/7 DESCRIPTION:Title: Symplectic Analysis of Null Raychaudhuri\nby Luca Ciambell i (Perimeter Institute) as part of Workshop on Spacetime and Quantum Infor mation\n\n\nAbstract\nWorking intrinsically on a null hypersurface\, we fi rst show that the Raychaudhuri constraint is the conservation law of a Car rollian stress tensor. After suitably dressing the diffeomorphisms with th e internal boost symmetry\, we derive the full kinematical Poisson bracket . The diffeomorphism boost charge turns out to be positive and monotonic i n the dressing time. We then perform a perturbative analysis in the weak g ravity regime\, and show how the Raychaudhuri constraint can be interprete d as an equality of CFT stress tensors for the spin-0\, spin-2\, and matte r systems. Finally\, we observe that the perturbative spin-0 stress tensor and Poisson bracket behave exactly like a curved beta-gamma CFT.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Harlow (Massachusetts Institute of Technology) DTSTART:20231212T140000Z DTEND:20231212T144500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/8 DESCRIPTION:Title: Gauging Spacetime Inversions\nby Daniel Harlow (Massachuse tts Institute of Technology) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nSpacetime inversion symmetries such as parity a nd time reversal play a central role in physics\, but they are usually tre ated as global symmetries. In quantum gravity there are no global symmetri es\, so any spacetime inversion symmetries must be gauge symmetries. In pa rticular this includes CRT symmetry (in even dimensions usually combined w ith a rotation to become CPT)\, which in quantum field theory is always a symmetry and seems likely to be a symmetry of quantum gravity as well. I'l l discuss what it means to gauge a spacetime inversion symmetry\, and expl ain some of the more unusual consequences of doing this. In particular I'l l argue that the gauging of CRT is automatically implemented by the sum ov er topologies in the Euclidean gravity path integral\, that in a closed un iverse the Hilbert space of quantum gravity must be a real vector space\, and that in Lorentzian signature manifolds which are not time-orientable m ust be included as valid configurations of the theory.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Eugenia Colafranceschi (University of California\, Santa Barbara) DTSTART:20231212T144500Z DTEND:20231212T153000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/9 DESCRIPTION:Title: Type I von Neumann Algebras from Gravitational Path Integrals: Ryu–Takayanagi as Entropy Without Holography\nby Eugenia Colafrance schi (University of California\, Santa Barbara) as part of Workshop on Spa cetime and Quantum Information\n\n\nAbstract\nRecent works by Chandrasekar an\, Penington and Witten have shown in various special contexts that the quantum-corrected Ryu-Takayanagi (RT) formula can be understood as computi ng an entropy on an algebra of bulk observables. These arguments do not re ly on the existence of a holographic dual field theory. We show that analo gous-but-stronger results hold in any UV-completion of asymptotically anti -de Sitter quantum gravity with a Euclidean path integral satisfying a sim ple and familiar set of axioms. In particular\, the path integral defines type I von Neumann algebras of bulk observables acting on compact closed c odimension-2 asymptotic boundaries\, as well as entropies on these algebra s. Such entropies can be written in terms of standard density matrices and standard Hilbert space traces\, and in appropriate semiclassical limits a re computed by the RT-formula with quantum corrections. Our work thus prov ides a Hilbert space interpretation of the Ryu-Takayanagi entropy. Since o ur axioms do not severely constrain UV bulk structures\, they may be expec ted to hold equally well for successful formulations of string field theor y\, spin-foam models\, or any other approach to constructing a UV-complete theory of gravity.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Faulkner (University of Illinois at Urbana-Champaign) DTSTART:20231212T161500Z DTEND:20231212T170000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/10 DESCRIPTION:Title: Vacuum Asymptotic Codes\nby Thomas Faulkner (University o f Illinois at Urbana-Champaign) as part of Workshop on Spacetime and Quant um Information\n\n\nAbstract\nI will review asymptotically isometric codes - a tool to take the large-N limit in holographic theories\, allowing for non-trivial von Neumann algebras to act on the code as well as on the phy sical Hilbert space. I will then discuss a relationship between the CFT th ermal partition function and the properties of entanglement wedges for dis joint boundary regions in the vacuum. Our results suggest a characterizati on of asymptotic codes with emergent sub-AdS locality.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Alejandra Castro (University of Cambridge) DTSTART:20231212T170000Z DTEND:20231212T174500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/11 DESCRIPTION:Title: Keeping Matter in the Loop in 3D Quantum Gravity\nby Alej andra Castro (University of Cambridge) as part of Workshop on Spacetime an d Quantum Information\n\n\nAbstract\nIn this talk I will discuss a novel m echanism that couples matter fields to three-dimensional quantum gravity. This construction is based on the Chern-Simons formulation of three-dimens ional gravity\, and it centers on a collection of Wilson loops winding aro und spacetime. We coin this object a Wilson spool. To construct the spool\ , we build take advantage of representation theory. To evaluate the spool\ , we adapt and exploit several known exact results in Chern-Simons theory. Our proposal correctly reproduces the one-loop determinant of a free mass ive scalar field on S^3 and AdS_3 as G_N->0. Moreover\, allowing for quant um metric fluctuations\, it can be systematically evaluated to any order i n perturbation theory.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Hsin-Yuan (Robert) Huang (Caltech) DTSTART:20231212T194500Z DTEND:20231212T203000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/12 DESCRIPTION:Title: Complexity of Learning and Creating Quantum Systems\nby H sin-Yuan (Robert) Huang (Caltech) as part of Workshop on Spacetime and Qua ntum Information\n\n\nAbstract\nThe complexity of a quantum system is a co ncept of fundamental interest in quantum information\, quantum computing\, and\, more recently\, in the study of quantum black holes. In this talk\, I will present three notions of complexity for learning and creating quan tum systems\, including (1) the minimum gates needed to create the state\, (2) the minimum number of measurements needed to learn the state\, and (3 ) the minimum computational time needed to learn the state. I will prove h ow these conceptually different notions closely relate to each other using techniques from random scrambling\, learning theory\, and cryptography.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Ying Zhao (Kavli Institute for Theoretical Physics) DTSTART:20231212T213000Z DTEND:20231212T221500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/13 DESCRIPTION:Title: Boundary Signature of Singularity in the Presence of a Shock Wave\nby Ying Zhao (Kavli Institute for Theoretical Physics) as part o f Workshop on Spacetime and Quantum Information\n\n\nAbstract\nMatter fall ing into a Schwarzschild-AdS black hole from the left causes increased foc ussing of ingoing geodesics from the right\, and\, as a consequence\, they reach the singularity sooner. In a standard Penrose diagram\, the singula rity "bends down". We show how to detect this feature of the singularity h olographically\, using a boundary two-point function. We model the matter with a shock wave\, and show that this bending down of the singularity can be read off from a novel analytic continuation of the boundary two-point function.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Luca Iliesiu (Stanford University & UC Berkeley) DTSTART:20231212T221500Z DTEND:20231212T230000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/14 DESCRIPTION:Title: The Non-Perturbative Hilbert Space of JT Gravity\nby Luca Iliesiu (Stanford University & UC Berkeley) as part of Workshop on Spacet ime and Quantum Information\n\n\nAbstract\nWe propose a non-perturbative c onstruction of the bulk Hilbert space of JT gravity. Within this Hilbert s pace\, we can non-perturbatively define and study observables that probe t he black hole interior. To exemplify the power of this construction\, we d iscuss two related observables for two-sided black holes: one probes the l ength of the black hole interior\, and the other probes the center of mass collision energy between an observer infalling from one side and a shockw ave coming from the opposite side. As we shall discuss\, both observables are strongly affected by non-perturbative corrections at very late times\, serving as useful probes for the presence of firewalls in very old black holes.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Ahmed Almheiri (New York University Abu Dhabi) DTSTART:20231213T140000Z DTEND:20231213T144500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/15 DESCRIPTION:Title: Holography on the Quantum Disk\nby Ahmed Almheiri (New Yo rk University Abu Dhabi) as part of Workshop on Spacetime and Quantum Info rmation\n\n\nAbstract\nMotivated by recent observations in double-scaled S YK (DSSYK)\, this talk will feature work in progress analyzing holography on a non-commutative analogue of the hyperbolic disk known as the quantum disk. I will briefly review hints of non-commutative geometry in the chord description of DSSYK\, and point out how it lingers in the continuum limi t at finite temperature on the recently studied “fake disk.” I’ll th en introduce the quantum disk and derive its non-commutative nature\, and analyze the dynamics of fields propagating on the fixed quantum disk backg round. I will point out some notable features of this system including dis creteness of space and UV finiteness. I will also describe the implication s of the non-commutativity on properties of its putative boundary dual.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Clifford V. Johnson (University of California\, Santa Barbara) DTSTART:20231213T144500Z DTEND:20231213T153000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/16 DESCRIPTION:Title: New Non-Perturbative Results from a Random Matrix Model of N= 2 JT Supergravity\nby Clifford V. Johnson (University of California\, Santa Barbara) as part of Workshop on Spacetime and Quantum Information\n\ n\nAbstract\nBuilding on the work of Turiaci and Witten who proposed the p erturbative (in genus) matrix model of N=2 JT supergravity\, a non-perturb ative definition has been constructed using scaled orthogonal polynomial t echnology similar to that used for various N=1 and non-supersymmetric JT c ases. The analysis allows for the excavation of the underlying microscopic physics. The spectrum of non-BPS states with zero threshold can be studie d quite readily in this framework\, while the non-zero threshold sector re quires more care. BPS states are naturally incorporated into the descripti on due to the natural properties of the governing "string equation".\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefano Antonini (University of California\, Berkeley) DTSTART:20231213T164500Z DTEND:20231213T170000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/17 DESCRIPTION:Title: Cosmology from Random Entanglement\nby Stefano Antonini ( University of California\, Berkeley) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nObtaining a description of cosmology is a central open problem in holography. Studying simple models can help us gain insight on the generic properties of holographic cosmologies. In this talk I will describe the construction of entangled microstates of a pair of holographic CFTs whose dual semiclassical description includes big bang -big crunch AdS cosmologies in spaces without boundaries. The cosmology is supported by inhomogeneous heavy matter and it partially purifies the bul k entanglement of two auxiliary AdS spacetimes. In generic settings\, the cosmology is an entanglement island contained in the entanglement wedge of one of the two CFTs. I will then describe the properties of the non-isome tric bulk-to-boundary encoding map and comment on an explicit\, state-depe ndent boundary representation of operators acting on the cosmology. Finall y\, I will discuss an ensemble interpretation of our results and other ope n questions.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Jinzhao Wang (Stanford University) DTSTART:20231213T170000Z DTEND:20231213T174500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/18 DESCRIPTION:Title: What Exactly Does Bekenstein Bound?\nby Jinzhao Wang (Sta nford University) as part of Workshop on Spacetime and Quantum Information \n\n\nAbstract\nThe Bekenstein bound posits a maximum entropy for matter w ith finite energy confined to a spacetime region. It is often interpreted as a fundamental limit on the information that can be stored by physical o bjects. In this work\, we test this interpretation by asking whether the B ekenstein bound imposes constraints on a channel's communication capacity\ , a context in which information can be given a mathematically rigorous an d operationally meaningful definition. We study specifically the Unruh cha nnel that describes a stationary Alice exciting different species of free scalar fields to send information to an accelerating Bob\, who is confined to a Rindler wedge and exposed to the noise of Unruh radiation. We show t hat the classical and quantum capacities of the Unruh channel obey the Bek enstein bound that pertains to the decoder Bob. In contrast\, even at high temperatures\, the Unruh channel can transmit a large number of zero-bits \, which are quantum communication resources that can be used for quantum identification and many other primitive information processing protocols. Therefore\, unlike classical bits and qubits\, zero-bits and their associa ted information processing capability are not constrained by the Bekenstei n bound. Time permitting\, I’ll discuss what if one also restrains the encoder Alice. (Based on the joint work with Patrick Hayden https://arxiv. org/abs/2309.07436.)\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Eric Perlmutter (IPhT Saclay/IHES) DTSTART:20231213T191500Z DTEND:20231213T203000Z DTSTAMP:20260404T111333Z UID:IASQubit2023/19 DESCRIPTION:Title: AdS3/RMT2 Duality\nby Eric Perlmutter (IPhT Saclay/IHES) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nWe introduce a framework for quantifying random matrix behavior of 2d CFTs a nd AdS3 quantum gravity. This is anchored by a 2d CFT trace formula\, anal ogous to the Gutzwiller trace formula for chaotic quantum systems. We use this framework to understand the Cotler-Jensen torus wormhole of AdS3 pure gravity from a microscopic CFT point of view. Factorizing the wormhole ge nerates a new\, non-perturbative piece of the AdS3 pure gravity path integ ral with torus boundary\, containing fine-grained spectral data of pure gr avity black hole microstates.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Edward Witten (Institute for Advanced Study) DTSTART:20231213T213000Z DTEND:20231213T221500Z DTSTAMP:20260404T111333Z UID:IASQubit2023/20 DESCRIPTION:Title: Background Independent Algebra for an Observer\nby Edward Witten (Institute for Advanced Study) as part of Workshop on Spacetime an d Quantum Information\n\n\nAbstract\nI consider the operator product algeb ra along an observer's worldline as a background independent algebra in qu antum gravity.\n LOCATION:https://stable.researchseminars.org/talk/IASQubit2023/20/ END:VEVENT END:VCALENDAR