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:20260422T225927Z UID:IASQubit2023/1 DESCRIPTION:Title: Islands Far Outside the Horizon\nby Geoff Penington (University o f California\, Berkeley) as part of Workshop on Spacetime and Quantum Info rmation\n\n\nAbstract\nInformation located in an entanglement island in se miclassical gravity can be\nnonperturbatively reconstructed from distant r adiation\, implying a radical\nbreakdown of effective field theory. We sho w that this occurs well outside of\nthe black hole stretched horizon. We c ompute the island associated to\nlarge-angular momentum Hawking modes of a four-dimensional Schwarzschild black\nhole. These modes typically fall ba ck into the black hole but can be extracted\nto infinity by relativistic s trings or\, more abstractly\, by asymptotic boundary\noperators constructe d using the timelike tube theorem. Remarkably\, we find that\ntheir island can protrude a distance of order $\\sqrt{\\ell_p r_{\\rm hor}}$\noutside the horizon. This is parametrically larger than the Planck scale\n$\\ell_p $ and is comparable to the Bohr radius for supermassive black holes.\nTher efore\, in principle\, a distant observer can determine experimentally\nwh ether the black hole information information paradox is resolved by\ncompl ementarity\, or by a firewall.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/1/ END:VEVENT BEGIN:VEVENT SUMMARY:David Kolchmeyer (Massachusetts Institute of Technology) DTSTART:20231211T144500Z DTEND:20231211T153000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/2 DESCRIPTION:Title: Gravitational Algebras in (A)dS_2\nby David Kolchmeyer (Massachus etts Institute of Technology) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nTo construct interesting algebras in quantum g ravity\, one can dress local field operators to features of the spacetime. I will discuss this first in AdS JT gravity with matter\, where matter op erators may be dressed to the right or left AdS boundaries. Then\, I will consider a scalar field theory in dS2 together with two entangled observer s. Each observer carries a clock. As in the AdS example\, matter operators may be dressed to either of the two observers. The observers' degrees of freedom are exactly quantized. The algebra of dressed operators teaches us about a putative quantum-mechanical dual theory.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefan Hollands (Leipzig University) DTSTART:20231211T161500Z DTEND:20231211T170000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/3 DESCRIPTION:Title: Black Hole Interiors\nby Stefan Hollands (Leipzig University) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nKerr or Reissner-Nordström black holes have inner horizons which delineate the domain of predictability of solutions of wave equation type. Often\, thou gh not e.g. for certain (A)deSitter black holes\, these inner horizons are classically dynamically unstable\, and get turned into some sort of singu larity by perturbations\, and thus drastically changing the nature of the inner horizons relative to the underlying exact solutions\, and relegating the problem of predictability to the real of quantum gravity ("strong cos mic censorship"). Recent work has shown that semi-classical quantum effect s dominate classical ones very near the inner horizons\, and are expected lead to singularity in cases where the inner horizon is stable classically . I review recent progress surrounding these issues.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Eanna Flanagan (Cornell University) DTSTART:20231211T170000Z DTEND:20231211T174500Z DTSTAMP:20260422T225927Z UID:IASQubit2023/4 DESCRIPTION:Title: Horizon Phase Spaces in General Relativity\nby Eanna Flanagan (Co rnell University) as part of Workshop on Spacetime and Quantum Information \n\n\nAbstract\nWe discuss several different definitions of phase spaces a ssociated with horizons in general relativity\, and the associated symmetr y groups and charges. For stationary horizons we compute the symplectic f orm of the theory in terms of independent degrees of freedom\, by solving the constraint equations on the horizon.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Mikhail Lukin (Harvard University) DTSTART:20231211T194500Z DTEND:20231211T203000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/5 DESCRIPTION:Title: Scrambling and Quantum Error Correction Frontier\nby Mikhail Luki n (Harvard University) as part of Workshop on Spacetime and Quantum Inform ation\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/IASQubit2023/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Shunyu Yao (Stanford University) DTSTART:20231211T213000Z DTEND:20231211T221500Z DTSTAMP:20260422T225927Z UID:IASQubit2023/6 DESCRIPTION:Title: Scramblon Loops\nby Shunyu Yao (Stanford University) as part of W orkshop on Spacetime and Quantum Information\n\n\nAbstract\nOut of time or dered correlator(OTOC) is one signature of quantum chaos. In certain large N systems\, emergent scramblon-exchange modes dominate\, while scramblon interactions are suppressed by 1/N. However\, we are going to discuss cert ain types of scramblon loop corrections\, which cause a dramatic breakdown of scramblon exchange approximation\, much earlier than naive expectation . Interestingly\, while these effects are significant in high temperature/ saddle(stringy) dominant/incoherent systems\, they get cut off in low temp erature/pole(graviton) dominant/coherent systems by ballistic growth. This suggests a sharp distinction between coherent/incoherent scrambling could appear by studying quantum fluctuations. We will also comment on their re lation to wavefront broadening phenomena and gravitational high energy sca ttering.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Luca Ciambelli (Perimeter Institute) DTSTART:20231211T221500Z DTEND:20231211T230000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/7 DESCRIPTION:Title: Symplectic Analysis of Null Raychaudhuri\nby Luca Ciambelli (Peri meter Institute) as part of Workshop on Spacetime and Quantum Information\ n\n\nAbstract\nWorking intrinsically on a null hypersurface\, we first sho w that the Raychaudhuri constraint is the conservation law of a Carrollian stress tensor. After suitably dressing the diffeomorphisms with the inter nal boost symmetry\, we derive the full kinematical Poisson bracket. The d iffeomorphism boost charge turns out to be positive and monotonic in the d ressing time. We then perform a perturbative analysis in the weak gravity regime\, and show how the Raychaudhuri constraint can be interpreted as an equality of CFT stress tensors for the spin-0\, spin-2\, and matter syste ms. Finally\, we observe that the perturbative spin-0 stress tensor and Po isson bracket behave exactly like a curved beta-gamma CFT.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Harlow (Massachusetts Institute of Technology) DTSTART:20231212T140000Z DTEND:20231212T144500Z DTSTAMP:20260422T225927Z UID:IASQubit2023/8 DESCRIPTION:Title: Gauging Spacetime Inversions\nby Daniel Harlow (Massachusetts Ins titute of Technology) as part of Workshop on Spacetime and Quantum Informa tion\n\n\nAbstract\nSpacetime inversion symmetries such as parity and time reversal play a central role in physics\, but they are usually treated as global symmetries. In quantum gravity there are no global symmetries\, so any spacetime inversion symmetries must be gauge symmetries. In particula r this includes CRT symmetry (in even dimensions usually combined with a r otation to become CPT)\, which in quantum field theory is always a symmetr y and seems likely to be a symmetry of quantum gravity as well. I'll discu ss what it means to gauge a spacetime inversion symmetry\, and explain som e of the more unusual consequences of doing this. In particular I'll argue that the gauging of CRT is automatically implemented by the sum over topo logies in the Euclidean gravity path integral\, that in a closed universe the Hilbert space of quantum gravity must be a real vector space\, and tha t in Lorentzian signature manifolds which are not time-orientable must be included as valid configurations of the theory.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Eugenia Colafranceschi (University of California\, Santa Barbara) DTSTART:20231212T144500Z DTEND:20231212T153000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/9 DESCRIPTION:Title: Type I von Neumann Algebras from Gravitational Path Integrals: Ryu– Takayanagi as Entropy Without Holography\nby Eugenia Colafranceschi (U niversity of California\, Santa Barbara) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nRecent works by Chandrasekaran\, Pe nington and Witten have shown in various special contexts that the quantum -corrected Ryu-Takayanagi (RT) formula can be understood as computing an e ntropy on an algebra of bulk observables. These arguments do not rely on t he existence of a holographic dual field theory. We show that analogous-bu t-stronger results hold in any UV-completion of asymptotically anti-de Sit ter quantum gravity with a Euclidean path integral satisfying a simple and familiar set of axioms. In particular\, the path integral defines type I von Neumann algebras of bulk observables acting on compact closed codimens ion-2 asymptotic boundaries\, as well as entropies on these algebras. Such entropies can be written in terms of standard density matrices and standa rd Hilbert space traces\, and in appropriate semiclassical limits are comp uted by the RT-formula with quantum corrections. Our work thus provides a Hilbert space interpretation of the Ryu-Takayanagi entropy. Since our axio ms do not severely constrain UV bulk structures\, they may be expected to hold equally well for successful formulations of string field theory\, spi n-foam models\, or any other approach to constructing a UV-complete theory of gravity.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Faulkner (University of Illinois at Urbana-Champaign) DTSTART:20231212T161500Z DTEND:20231212T170000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/10 DESCRIPTION:Title: Vacuum Asymptotic Codes\nby Thomas Faulkner (University of Illin ois at Urbana-Champaign) as part of Workshop on Spacetime and Quantum Info rmation\n\n\nAbstract\nI will review asymptotically isometric codes - a to ol to take the large-N limit in holographic theories\, allowing for non-tr ivial von Neumann algebras to act on the code as well as on the physical H ilbert space. I will then discuss a relationship between the CFT thermal p artition function and the properties of entanglement wedges for disjoint b oundary regions in the vacuum. Our results suggest a characterization of a symptotic codes with emergent sub-AdS locality.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Alejandra Castro (University of Cambridge) DTSTART:20231212T170000Z DTEND:20231212T174500Z DTSTAMP:20260422T225927Z UID:IASQubit2023/11 DESCRIPTION:Title: Keeping Matter in the Loop in 3D Quantum Gravity\nby Alejandra C astro (University of Cambridge) as part of Workshop on Spacetime and Quant um Information\n\n\nAbstract\nIn this talk I will discuss a novel mechanis m that couples matter fields to three-dimensional quantum gravity. This co nstruction is based on the Chern-Simons formulation of three-dimensional g ravity\, and it centers on a collection of Wilson loops winding around spa cetime. We coin this object a Wilson spool. To construct the spool\, we bu ild take advantage of representation theory. To evaluate the spool\, we ad apt and exploit several known exact results in Chern-Simons theory. Our pr oposal correctly reproduces the one-loop determinant of a free massive sca lar field on S^3 and AdS_3 as G_N->0. Moreover\, allowing for quantum metr ic fluctuations\, it can be systematically evaluated to any order in pertu rbation theory.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Hsin-Yuan (Robert) Huang (Caltech) DTSTART:20231212T194500Z DTEND:20231212T203000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/12 DESCRIPTION:Title: Complexity of Learning and Creating Quantum Systems\nby Hsin-Yua n (Robert) Huang (Caltech) as part of Workshop on Spacetime and Quantum In formation\n\n\nAbstract\nThe complexity of a quantum system is a concept o f 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 quantum sys tems\, including (1) the minimum gates needed to create the state\, (2) th e minimum number of measurements needed to learn the state\, and (3) the m inimum computational time needed to learn the state. I will prove how thes e conceptually different notions closely relate to each other using techni ques from random scrambling\, learning theory\, and cryptography.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Ying Zhao (Kavli Institute for Theoretical Physics) DTSTART:20231212T213000Z DTEND:20231212T221500Z DTSTAMP:20260422T225927Z 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 of Works hop on Spacetime and Quantum Information\n\n\nAbstract\nMatter falling int o a Schwarzschild-AdS black hole from the left causes increased focussing of ingoing geodesics from the right\, and\, as a consequence\, they reach the singularity sooner. In a standard Penrose diagram\, the singularity "b ends down". We show how to detect this feature of the singularity holograp hically\, 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 rea d off from a novel analytic continuation of the boundary two-point functio n.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Luca Iliesiu (Stanford University & UC Berkeley) DTSTART:20231212T221500Z DTEND:20231212T230000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/14 DESCRIPTION:Title: The Non-Perturbative Hilbert Space of JT Gravity\nby Luca Iliesi u (Stanford University & UC Berkeley) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nWe propose a non-perturbative construc tion of the bulk Hilbert space of JT gravity. Within this Hilbert space\, we can non-perturbatively define and study observables that probe the blac k hole interior. To exemplify the power of this construction\, we discuss two related observables for two-sided black holes: one probes the length o f the black hole interior\, and the other probes the center of mass collis ion energy between an observer infalling from one side and a shockwave com ing from the opposite side. As we shall discuss\, both observables are str ongly affected by non-perturbative corrections at very late times\, servin g as useful probes for the presence of firewalls in very old black holes.\ n LOCATION:https://researchseminars.org/talk/IASQubit2023/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Ahmed Almheiri (New York University Abu Dhabi) DTSTART:20231213T140000Z DTEND:20231213T144500Z DTSTAMP:20260422T225927Z UID:IASQubit2023/15 DESCRIPTION:Title: Holography on the Quantum Disk\nby Ahmed Almheiri (New York Univ ersity Abu Dhabi) as part of Workshop on Spacetime and Quantum Information \n\n\nAbstract\nMotivated by recent observations in double-scaled SYK (DSS YK)\, this talk will feature work in progress analyzing holography on a no n-commutative analogue of the hyperbolic disk known as the quantum disk. I will briefly review hints of non-commutative geometry in the chord descri ption of DSSYK\, and point out how it lingers in the continuum limit at fi nite temperature on the recently studied “fake disk.” I’ll then intr oduce the quantum disk and derive its non-commutative nature\, and analyze the dynamics of fields propagating on the fixed quantum disk background. I will point out some notable features of this system including discretene ss of space and UV finiteness. I will also describe the implications of th e non-commutativity on properties of its putative boundary dual.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Clifford V. Johnson (University of California\, Santa Barbara) DTSTART:20231213T144500Z DTEND:20231213T153000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/16 DESCRIPTION:Title: New Non-Perturbative Results from a Random Matrix Model of N=2 JT Su pergravity\nby Clifford V. Johnson (University of California\, Santa B arbara) as part of Workshop on Spacetime and Quantum Information\n\n\nAbst ract\nBuilding on the work of Turiaci and Witten who proposed the perturba tive (in genus) matrix model of N=2 JT supergravity\, a non-perturbative d efinition has been constructed using scaled orthogonal polynomial technolo gy similar to that used for various N=1 and non-supersymmetric JT cases. T he analysis allows for the excavation of the underlying microscopic physic s. The spectrum of non-BPS states with zero threshold can be studied quite readily in this framework\, while the non-zero threshold sector requires more care. BPS states are naturally incorporated into the description due to the natural properties of the governing "string equation".\n LOCATION:https://researchseminars.org/talk/IASQubit2023/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefano Antonini (University of California\, Berkeley) DTSTART:20231213T164500Z DTEND:20231213T170000Z DTSTAMP:20260422T225927Z UID:IASQubit2023/17 DESCRIPTION:Title: Cosmology from Random Entanglement\nby Stefano Antonini (Univers ity of California\, Berkeley) as part of Workshop on Spacetime and Quantum Information\n\n\nAbstract\nObtaining a description of cosmology is a cent ral open problem in holography. Studying simple models can help us gain in sight on the generic properties of holographic cosmologies. In this talk I will describe the construction of entangled microstates of a pair of holo graphic CFTs whose dual semiclassical description includes big bang-big cr unch AdS cosmologies in spaces without boundaries. The cosmology is suppor ted by inhomogeneous heavy matter and it partially purifies the bulk entan glement of two auxiliary AdS spacetimes. In generic settings\, the cosmolo gy is an entanglement island contained in the entanglement wedge of one of the two CFTs. I will then describe the properties of the non-isometric bu lk-to-boundary encoding map and comment on an explicit\, state-dependent b oundary representation of operators acting on the cosmology. Finally\, I w ill discuss an ensemble interpretation of our results and other open quest ions.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Jinzhao Wang (Stanford University) DTSTART:20231213T170000Z DTEND:20231213T174500Z DTSTAMP:20260422T225927Z UID:IASQubit2023/18 DESCRIPTION:Title: What Exactly Does Bekenstein Bound?\nby Jinzhao Wang (Stanford U niversity) as part of Workshop on Spacetime and Quantum Information\n\n\nA bstract\nThe Bekenstein bound posits a maximum entropy for matter with fin ite energy confined to a spacetime region. It is often interpreted as a fu ndamental limit on the information that can be stored by physical objects. In this work\, we test this interpretation by asking whether the Bekenste in bound imposes constraints on a channel's communication capacity\, a con text in which information can be given a mathematically rigorous and opera tionally meaningful definition. We study specifically the Unruh channel th at describes a stationary Alice exciting different species of free scalar fields to send information to an accelerating Bob\, who is confined to a R indler wedge and exposed to the noise of Unruh radiation. We show that the classical and quantum capacities of the Unruh channel obey the Bekenstein bound that pertains to the decoder Bob. In contrast\, even at high temper atures\, the Unruh channel can transmit a large number of zero-bits\, whic h are quantum communication resources that can be used for quantum identif ication and many other primitive information processing protocols. Therefo re\, unlike classical bits and qubits\, zero-bits and their associated inf ormation processing capability are not constrained by the Bekenstein 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://researchseminars.org/talk/IASQubit2023/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Eric Perlmutter (IPhT Saclay/IHES) DTSTART:20231213T191500Z DTEND:20231213T203000Z DTSTAMP:20260422T225927Z 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 introd uce a framework for quantifying random matrix behavior of 2d CFTs and AdS3 quantum gravity. This is anchored by a 2d CFT trace formula\, analogous t o the Gutzwiller trace formula for chaotic quantum systems. We use this fr amework to understand the Cotler-Jensen torus wormhole of AdS3 pure gravit y from a microscopic CFT point of view. Factorizing the wormhole generates a new\, non-perturbative piece of the AdS3 pure gravity path integral wit h torus boundary\, containing fine-grained spectral data of pure gravity b lack hole microstates.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Edward Witten (Institute for Advanced Study) DTSTART:20231213T213000Z DTEND:20231213T221500Z DTSTAMP:20260422T225927Z UID:IASQubit2023/20 DESCRIPTION:Title: Background Independent Algebra for an Observer\nby Edward Witten (Institute for Advanced Study) as part of Workshop on Spacetime and Quant um Information\n\n\nAbstract\nI consider the operator product algebra alon g an observer's worldline as a background independent algebra in quantum g ravity.\n LOCATION:https://researchseminars.org/talk/IASQubit2023/20/ END:VEVENT END:VCALENDAR