BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Bartek Czech (Tsinghua University) DTSTART:20201026T163000Z DTEND:20201026T174500Z DTSTAMP:20260422T212725Z UID:HET/1 DESCRIPTION:Title: Quer y complexity and cutoffs in AdS/CFT\nby Bartek Czech (Tsinghua Univers ity) as part of Purdue HET\n\n\nAbstract\nA quantum state is a map from op erators to real numbers that are their expectation values. Evaluating this map always entails using some algorithm\, for example contracting a tenso r network. I propose a novel way of quantifying the complexity of a quantu m state in terms of "query complexity": the number of times an efficient a lgorithm for computing correlation functions in the given state calls on a certain subroutine. I construct such an algorithm for a general "state at a cutoff" in 1+1-dimensional field theory. The algorithm scans cutoff-siz ed intervals for operators whose expectation values will be computed and t he relevant subroutine is a translation in the space of (cutoff-sized) int ervals. Query complexity then boils down to an appropriate notion of dista nce in the space of (cutoff-sized) intervals. A unique distance function i s consistent with the requisite notion of translations\; therefore the que ry complexity of a state at a cutoff is unambiguously defined. In holograp hic theories\, the query complexity evaluates to the integral of the Ricci scalar on a spatial slice enclosed by the bulk cutoff\, which in pure AdS 3 agrees with the volume proposal but otherwise departs from it.\n LOCATION:https://researchseminars.org/talk/HET/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Felix Haehl (IAS) DTSTART:20201102T173000Z DTEND:20201102T184500Z DTSTAMP:20260422T212725Z UID:HET/2 DESCRIPTION:Title: Comm ents on replica symmetry breaking in spin glasses and gravity\nby Feli x Haehl (IAS) as part of Purdue HET\n\n\nAbstract\nI will describe some pr ogress on understanding a model of bosonic spins with disorder averaged co uplings\, which is quite similar to the SYK model in many regards. What di stinguishes it from SYK is the appearance of a spin glass phase at low tem peratures\, where replica symmetry is broken. I will comment on possible i nterpretations in AdS2 gravity\, where a picture of fragmentation has been explored previously\, and a lot of progress has been made recently in und erstanding the relevance of wormhole geometries.\n LOCATION:https://researchseminars.org/talk/HET/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Sridip Pal (IAS\, Princeton) DTSTART:20201109T173000Z DTEND:20201109T184500Z DTSTAMP:20260422T212725Z UID:HET/3 DESCRIPTION:Title: Univ ersality in Asymptotic bounds and their saturation in 2D CFT\nby Sridi p Pal (IAS\, Princeton) as part of Purdue HET\n\n\nAbstract\nWe consider t he universality of existence and saturation of asymptotic bounds in variou s quantities in 2D CFT. In particular\, we focus on previously derived upp er and lower bounds on the number of operators in a window of scaling dime nsions [Δ−δ\,Δ+δ] at asymptotically large Δ in 2d unitary modular i nvariant CFTs. These bounds depend on a choice of functions that majorize and minorize the characteristic function of the interval [Δ−δ\,Δ+δ] and have Fourier transforms of finite support. The optimization of the bou nds over this choice turns out to be exactly the Beurling-Selberg extremiz ation problem\, widely known in analytic number theory. When the width of the interval is integer\, the bounds are saturated by known partition func tions with integer-spaced spectra. We further show with numerical assistan ce that one can see morally similar bounds and saturation in asymptotics o f various OPE coefficient. The talk will be based on arXiv:2003.14316 [hep -th] and arXiv: 2011.02482 [hep-th].\n LOCATION:https://researchseminars.org/talk/HET/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Junyu Liu (Caltech) DTSTART:20201130T173000Z DTEND:20201130T184500Z DTSTAMP:20260422T212725Z UID:HET/4 DESCRIPTION:Title: Quan tum computation and "cyberpunkian" quantum field theory\nby Junyu Liu (Caltech) as part of Purdue HET\n\n\nAbstract\nQuantum field theory is one of the greatest achievements by human beings in understanding the law of the universe. Almost all subjects in modern physics\, from condensed-matte r physics to string theory\, are closely related to the developments of qu antum field theory. However\, established in the infinite dimensional Hilb ert spaces\, quantum field theory is very hard to study\, especially when the theory is strongly coupled. This talk is a summary of quantum opportun ities for solving quantum field theory theoretically and numerically\, bas ed on a series of works by the speaker and collaborators. Specifically\, w e describe a digital quantum simulation algorithm for simulating domain wa ll scatterings in the 1+1 dimensional quantum field theory\, which could b e regarded as a toy version of cosmological false vacuum decay in the real universe\, as an example. We will discuss some potential fundamental limi tations of classical algorithms\, how quantum computers will help us solve the problem\, and how good quantum computers are (the quantum-extended Ch urch-Turing Thesis).\n LOCATION:https://researchseminars.org/talk/HET/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexander Zhiboedov (CERN) DTSTART:20201211T173000Z DTEND:20201211T184500Z DTSTAMP:20260422T212725Z UID:HET/5 DESCRIPTION:Title: Conf ormal collider physics: an update\nby Alexander Zhiboedov (CERN) as pa rt of Purdue HET\n\n\nAbstract\nI will describe recent progress in underst anding event shapes in conformal field theories. Familiar from the descrip tion of hadronic events at colliders\, these observables are computed by m atrix elements of the so-called light-ray operators. Characterizing the li ght-ray operators in a nonperturbative setting poses many theoretical chal lenges. I will describe some of the recently developed tools to perform co mputations of conformal event shapes and illustrate them using N=4 SYM. Fi nally\, I will explain how via holography some of the basic properties of conformal event shapes lead to nontrivial sum rules obeyed by possible UV completions of general relativity.\n LOCATION:https://researchseminars.org/talk/HET/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Aninda Sinha (Indian Insititute of Science) DTSTART:20210125T163000Z DTEND:20210125T174500Z DTSTAMP:20260422T212725Z UID:HET/6 DESCRIPTION:Title: Enta nglement in scattering and the S-matrix bootstrap\nby Aninda Sinha (In dian Insititute of Science) as part of Purdue HET\n\n\nAbstract\nI will ta lk about how relative entropy\, a concept in quantum information theory to distinguish two density matrices\, behaves in 2-2 scattering in quantum f ield theory\, string theory\, chiral perturbation theory and the numerical S-matrix bootstrap. In the context of massive quantum field theories\, I will derive high energy bounds on relative entropy as well as study the Re gge behavior. Then I will turn to the S-matrix bootstrap. I will give a br oad overview of what this program is about and how to constrain pion scatt ering with it. Here\, some insight from relative entropy will prove to be handy to constrain the space of S-matrices. I will discuss some ideas base d on minimization of total scattering cross-section to constrain pion S-ma trices further\; curious coincidences such as boundary of allowed S-matric es being close to the Lovelace-Shapiro model of early string theory\, emer ging linear Regge trajectories\, as well as reduction in Entanglement powe r near the standard model point will be discussed.\n LOCATION:https://researchseminars.org/talk/HET/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Hartman (Cornell University) DTSTART:20210208T173000Z DTEND:20210208T184500Z DTSTAMP:20260422T212725Z UID:HET/7 DESCRIPTION:Title: Isla nds in black holes and cosmology\nby Thomas Hartman (Cornell Universit y) as part of Purdue HET\n\n\nAbstract\nI will summarize recent developmen ts on the information paradox involving "islands" and replica wormholes\, and discuss the extent to which these ideas can be applied to cosmology.\n LOCATION:https://researchseminars.org/talk/HET/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Isaac Kim (Univeristy of Sydney) DTSTART:20210222T210000Z DTEND:20210222T221500Z DTSTAMP:20260422T212725Z UID:HET/8 DESCRIPTION:Title: Entr opy scaling law and the quantum (and classical) marginal problem\nby I saac Kim (Univeristy of Sydney) as part of Purdue HET\n\n\nAbstract\nQuant um (and classical) many-body states that appear in physics often obey an e ntropy scaling law\, meaning that an entanglement entropy of a subsystem c an be expressed as a sum of terms that scale linearly with its volume and area\, plus a correction term that is independent of its size. We conjectu re that these states have an efficient dual description in terms of a set of marginal density matrices on bounded regions\, obeying the same entropy scaling law locally. We prove a restricted version of this conjecture for translationally invariant systems in two spatial dimensions. Specifically \, we prove that a translationally invariant marginal obeying three non-li near constraints -- all of which follow from the entropy scaling law strai ghtforwardly -- must be consistent with some global state on an infinite l attice. Moreover\, we derive a closed-form expression for the maximum entr opy density compatible with those marginals\, deriving a variational upper bound on the thermodynamic free energy. Our construction's main assumptio ns are satisfied exactly by solvable models of topological order and appro ximately by finite-temperature Gibbs states of certain quantum spin Hamilt onians. To the best of our knowledge\, this is the first nontrivial soluti on to the quantum marginal problem in a many-body setting that lies strict ly outside the framework of mean-field theory.\n LOCATION:https://researchseminars.org/talk/HET/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Horacio Casini (Bariloche Atomic Centre) DTSTART:20210301T173000Z DTEND:20210301T184500Z DTSTAMP:20260422T212725Z UID:HET/9 DESCRIPTION:Title: Entr opic order parameters for symmetries in QFT\nby Horacio Casini (Barilo che Atomic Centre) as part of Purdue HET\n\n\nAbstract\nIn QFT there is an algebra of operators attached to any spacetime region. Simple degradation s of the most harmonious possible relation between algebras and regions ar e shown to encode generalized symmetries. Nets of algebras with these symm etries allow for a non uniqueness of the algebras that can be assigned to a given region. This non uniqueness suggests a simple geometrical order pa rameter in terms of a relative entropy. These satisfy a ''certainty relati on'' connecting the statistics of the order and disorder parameters for co mplementary regions. We describe how the lore about phases of theories wit h generalized symmetries is seen in this new picture.\n LOCATION:https://researchseminars.org/talk/HET/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Stefan Hollands (Leipzig University) DTSTART:20210217T163000Z DTEND:20210217T174500Z DTSTAMP:20260422T212725Z UID:HET/10 DESCRIPTION:Title: (In )determinism Inside Black Holes\nby Stefan Hollands (Leipzig Universit y) as part of Purdue HET\n\n\nAbstract\nIn classical General Relativity\, the values of fields on spacetime are\nuniquely determined by their initia l values within its 'domain of\ndependence'. However\, it may occur that t he\nspacetime under consideration extends beyond this domain\, and\nfields \, therefore\, are not entirely determined by their initial data. \nSuch a naive\nfailure of determinism occurs inside all physically relevant blac k holes.\n\nThe boundary of the region determined by the initial data is\n called the 'Cauchy horizon'. Penrose has proposed ('strong cosmic \ncenso rship conjecture')\nthat the Cauchy horizon is actually unstable in the se nse that the \nslightest perturbation caused\nby remnant fields convert i t to a final singularity. Whether or not \nthis is the case --\nand thus whether there is a real problem with determinism -- has been \ndebated re cently.\n\nIn this talk I ask whether quantum effects will come to the res cue of \nstrong cosmic censorship.\n LOCATION:https://researchseminars.org/talk/HET/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexandre Belin (CERN) DTSTART:20210315T163000Z DTEND:20210315T174500Z DTSTAMP:20260422T212725Z UID:HET/11 DESCRIPTION:Title: The OPE Randomness Hypothesis and Euclidean Wormholes\nby Alexandre Belin (CERN) as part of Purdue HET\n\n\nAbstract\nRecent developments in hologr aphy indicate that the semi-classical Euclidean path-integral of Einstein gravity is much more powerful than previously anticipated. It is capable o f reproducing a unitary Page curve for black hole evaporation\, and can ev en capture some features of the discrete nature of black hole microstates. Wormhole geometries play a key role in this context. I will propose a mec hanism to explain this in the CFT: the OPE Randomness Hypothesis. This ans atz is a generalization of the Eigenstate Thermalization Hypothesis which applies to chaotic CFTs\, and treats OPE coefficients of heavy operators a s random variables with a given probability distribution. I will present t wo applications of this framework: First\, it resolves a factorization puz zle in AdS_3/CFT_2 due to the genus-2 wormhole\, as raised by Maoz and Mal dacena. Second\, it provides an argument against global symmetries in quan tum gravity.\n LOCATION:https://researchseminars.org/talk/HET/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Nicholas LaRacuente (University of Chicago) DTSTART:20210118T173000Z DTEND:20210118T184500Z DTSTAMP:20260422T212725Z UID:HET/12 DESCRIPTION:Title: Mul tivariate Trace Inequalities\, p-Fidelity\, and Universal Recovery Beyond Tracial von Neumann Algebras\nby Nicholas LaRacuente (University of Ch icago) as part of Purdue HET\n\n\nAbstract\nTrace inequalities are powerfu l in quantum information theory\, often replacing classical functional cal culus in noncommutative settings. The physics of quantum field theory and holography\, however\, motivate entropy inequalities in von Neumann algebr as that lack a useful notion of a trace. The Haagerup and Kosaki Lp spaces enable re-expressing trace inequalities in non-tracial von Neumann algebr as. In particular\, we show this for the generalized Araki-Lieb-Thirring a nd Golden-Thompson inequalities from (Sutter\, Berta & Tomamichel 2017). T hen\, using the Haagerup approximation method\, we prove a general von Neu mann algebra version of the recovery map tightening of the data processing inequality for relative entropy. We also generalize via subharmonicity of a logarithmic p-fidelity of recovery. Furthermore\, we prove that non-dec rease of relative entropy is equivalent to existence of an L1-isometry imp lementing the channel on both input states.\n LOCATION:https://researchseminars.org/talk/HET/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Adam Levine (IAS Princeton) DTSTART:20210308T173000Z DTEND:20210308T184500Z DTSTAMP:20260422T212725Z UID:HET/13 DESCRIPTION:Title: Pro bing strings with quantum extremal surfaces\nby Adam Levine (IAS Princ eton) as part of Purdue HET\n\n\nAbstract\nWe drop a particle or string in to vacuum AdS and ask whether the excitation is in the entanglement wedge for a region composed of a Rindler wedge together with a small interval. W e compute the quantum fidelity between the state with a particle and the s tate without a particle\, which is a direct measure of whether the particl e is reconstructable from this region. We find that in a gravitational the ory and for a purely chiral probe particle\, the distinction of whether th e excitation is in the entanglement wedge or not is sharp\, corresponding precisely with when the excitation passes across the quantum extremal surf ace. For a theory with a non-zero string length\, we find that this distin ction between when the particle is inside or outside the entanglement wedg e becomes fuzzy and depends on the smearing scale of the particle creation operator. We comment on an interpretation of this phenomenon in terms of string spreading. Based upon forthcoming work with Ven Chandrasekaran and Tom Faulkner.\n LOCATION:https://researchseminars.org/talk/HET/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Shinsei Ryu (Princeton University) DTSTART:20211012T193000Z DTEND:20211012T204500Z DTSTAMP:20260422T212725Z UID:HET/14 DESCRIPTION:Title: Mul tipartitioning topological phases and quantum entangle\nby Shinsei Ryu (Princeton University) as part of Purdue HET\n\n\nAbstract\nWe discuss mu ltipartitions of the gapped ground states of (2+1)-dimensional topological liquids into three (or more) spatial regions that are adjacent to each ot her and meet at points. By considering the reduced density matrix obtained by tracing over a subset of the regions\, we compute various correlation measures\, such as entanglement negativity\, reflected entropy\, and ass ociated spectra. We utilize the bulk-boundary correspondence to achieve su ch multipartitions and construct the reduced density matrix near the entan gling boundaries. We find the fingerprints of topological liquid in these quantities\, such as (universal pieces in) the scaling of the entanglement negativity\, and a non-trivial distribution of the spectrum of the partia lly transposed density matrix. For reflected entropy\, we test the recent claim that states the difference between reflected entropy and mutual info rmation is given\, once short range correlations are properly removed\, by (|c|/3) ln 2 where c is the chiral central charge of the topological liqu id.\n LOCATION:https://researchseminars.org/talk/HET/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Raghu Mahajan (Stanford University) DTSTART:20210921T193000Z DTEND:20210921T204500Z DTSTAMP:20260422T212725Z UID:HET/15 DESCRIPTION:Title: Sph ere and disk partition functions in Liouville and in matrix integrals\ nby Raghu Mahajan (Stanford University) as part of Purdue HET\n\n\nAbstrac t\nWe compute the sphere and disk partition functions in semiclassical Lio uville string theory (without any vertex operator insertions) and analogou s quantities in double-scaled matrix integrals. The quantity sphere / disk ^2 is independent of the string coupling constant and we find a precise nu merical match between the Liouville answer and the matrix integral answer. \n\nThe main idea in the string theory computation is that the Liouville p ath integral has a noncompact family of saddle points that are related by the PSL(2\,C) and PSL(2\,R) conformal symmetries on the sphere and the dis k\, respectively. Faddeev-Popov gauge fixing then allows us to overcome th e usual difficulty associated with residual gauge symmetries on the sphere and the disk. \n\n(Based on joint work with Douglas Stanford and Cynthia Yan.)\n LOCATION:https://researchseminars.org/talk/HET/15/ END:VEVENT BEGIN:VEVENT SUMMARY:David Kolchmeyer (Harvard University) DTSTART:20211005T193000Z DTEND:20211005T204500Z DTSTAMP:20260422T212725Z UID:HET/16 DESCRIPTION:Title: The Eigenstate Thermalization Hypothesis in JT gravity with matter\nby Da vid Kolchmeyer (Harvard University) as part of Purdue HET\n\n\nAbstract\nI will discuss ongoing efforts to find a two-matrix model dual to JT gravit y coupled to a free massive scalar field that admits an interpretation in terms of the Eigenstate Thermalization Hypothesis (ETH). The two Hermitian matrices\, H and O\, represent the boundary Hamiltonian and the boundary operator dual to the bulk scalar field. The gravitational path integral im plies that the matrix elements of O in the H eigenbasis obey a certain con straint. We use this constraint to make a conjecture about the form of the matrix model potential. This conjecture can be tested using a q-deformati on of JT gravity with matter. This talk is based on work in progress with Daniel Jafferis\, Baur Mukhametzhanov\, and Julian Sonner.\n LOCATION:https://researchseminars.org/talk/HET/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Kapec (IAS Princeton) DTSTART:20211019T193000Z DTEND:20211019T204500Z DTSTAMP:20260422T212725Z UID:HET/17 DESCRIPTION:Title: Sha dows and Soft Exchange in Celestial CFT\nby Daniel Kapec (IAS Princeto n) as part of Purdue HET\n\n\nAbstract\nI will discuss exponentiated soft exchange in (d+2)-dimensional gauge and gravitational theories using the c elestial CFT formalism. These models exhibit spontaneously broken asymptot ic symmetries generated by gauge transformations with non-compact support\ , and the effective dynamics of the associated Goldstone “edge” mode i s expected to be d-dimensional. The introduction of an infrared regulator also explicitly breaks these symmetries so the edge mode in the regulated theory is really a d-dimensional pseudo-Goldstone boson. Symmetry consider ations determine the leading terms in the effective action\, whose coeffic ients are controlled by the infrared cutoff. Computations in this model re produce the abelian infrared divergences in d=2\, and capture the re-summe d (infrared finite) soft exchange in higher dimensions. The model also rep roduces the leading soft theorems in gauge and gravitational theories in a ll dimensions. Interestingly\, we find that it is the shadow transform of the Goldstone mode that has local d-dimensional dynamics: the effective ac tion expressed in terms of the Goldstone mode is non-local for d>2. The an alysis demonstrates that symmetry principles suffice to calculate soft exc hange in gauge theory and gravity.\n LOCATION:https://researchseminars.org/talk/HET/17/ END:VEVENT BEGIN:VEVENT SUMMARY:James Sully (University of British Colombia) DTSTART:20211102T193000Z DTEND:20211102T204500Z DTSTAMP:20260422T212725Z UID:HET/18 DESCRIPTION:Title: Inn er Turmoil: Complexity\, Chaos\, and the Black Hole Interior\nby James Sully (University of British Colombia) as part of Purdue HET\n\n\nAbstrac t\nI will describe a precise and computationally tractable notion of opera tor complexity in quantum theories. In holographic theories\, this refined version of K-complexity exhibits exponential growth for a scrambling time \, followed by linear growth until saturation at a time exponential in the entropy—a behavior that is characteristic of chaos. I will explain how the linear growth regime implies a universal random matrix description of the operator dynamics after scrambling. Our main tool for establishing thi s connection is a “complexity renormalization group” where we integrat e out large K-complexities. Finally\, I will discuss a connection between the universal random matrix theory dynamics of operator growth after scram bling and the geometry of smooth black hole interiors.\n LOCATION:https://researchseminars.org/talk/HET/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Jennifer Lin (University of Oxford) DTSTART:20211026T153000Z DTEND:20211026T164500Z DTSTAMP:20260422T212725Z UID:HET/19 DESCRIPTION:Title: A n ew look at the gravitational entropy formula\nby Jennifer Lin (Univers ity of Oxford) as part of Purdue HET\n\n\nAbstract\nThe Ryu-Takayanagi for mula and its generalizations have led to a surprising amount of progress i n our understanding of quantum gravity in the last fifteen years\, culmina ting in the recent derivation of the Page curve in toy models of evaporati ng black holes. However\, we still don’t understand why these formulas are true from a canonical point of view. In this talk\, I will attempt to make progress on this problem by developing an analogy between gravitation al entropy formulas in low-dimensional examples of holography and similar- looking formulas that have appeared in the study of entanglement entropy i n emergent gauge theories. This talk will be based on 1807.06575\, 2107.11 872\, and 2107.12634.\n LOCATION:https://researchseminars.org/talk/HET/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Brian Swingle DTSTART:20210928T193000Z DTEND:20210928T204500Z DTSTAMP:20260422T212725Z UID:HET/20 DESCRIPTION:Title: Hyd rodynamics and the Spectral Form Factor\nby Brian Swingle as part of P urdue HET\n\n\nAbstract\nEnsembles of quantum chaotic systems are expected to exhibit random matrix universality in their energy spectrum. The prese nce of this universality can be diagnosed by looking for a linear in time 'ramp' in the spectral form factor\, but for realistic systems this featur e is typically only visible after a sufficiently long time. It is importan t to understand the emergence of this universality and how it connects to the larger body of phenomena associated with quantum chaos. This talk will present a hydrodynamic theory of the spectral form factor in systems with slow modes. The formalism predicts the linear ramp at sufficiently late t ime and gives a quantitative framework for computing the approach to ramp. \n LOCATION:https://researchseminars.org/talk/HET/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Ro Jefferson (NORDITA) DTSTART:20211109T203000Z DTEND:20211109T214500Z DTSTAMP:20260422T212725Z UID:HET/21 DESCRIPTION:Title: The edge of chaos: quantum field theory and deep neural networks\nby Ro J efferson (NORDITA) as part of Purdue HET\n\n\nAbstract\nThe nascent NN-QFT correspondence offers an interesting\, physics-based approach towards a t heoretical foundation for deep neural networks. In this talk\, I will disc uss recent work in which we explicitly construct the QFT corresponding to a general class of networks encompassing both recurrent and feedforward ar chitectures. The point at which the network exhibits critical behaviour ca n then be obtained by examining the largest Lyapunov exponent in a proper mean field theory treatment. However\, this and previous results in the li terature hold only at infinite width\, while empirical evidence suggests t hat the correlation length receives significant corrections in real-world (finite width) networks. Hence\, going beyond the mean field regime\, we d evelop a perturbative approach formally analogous to that in the O(N) vect or model\, in which the weight variance plays the role of the 't Hooft cou pling. In particular\, we compute both the O(1) corrections quantifying fl uctuations from typicality in the ensemble of networks\, and the subleadin g O(depth/width) corrections due to finite-width effects. I will introduce the use of Feynman diagrams in this context for linear models\, and discu ss the generalization to nonlinear models if time permits.\n LOCATION:https://researchseminars.org/talk/HET/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Pratik Rath (UCSB) DTSTART:20211116T203000Z DTEND:20211116T214500Z DTSTAMP:20260422T212725Z UID:HET/22 DESCRIPTION:Title: The Page curve for Reflected Entropy\nby Pratik Rath (UCSB) as part of Pu rdue HET\n\n\nAbstract\nReflected Entropy is a bipartite correlation measu re with a simple geometric holographic dual\, the minimal entanglement wed ge cross section. This duality further motivates the idea that spacetime e merges from entanglement and illustrates the richness of the multipartite entanglement structure of holographic systems. A particularly interesting feature that we focus on in this talk is the phase transition between a co nnected and disconnected entanglement wedge where the reflected entropy ju mps discontinuously. We explain how this phase transition is resolved in t ensor networks and a model of JT gravity which motivate a general ansatz f or the mechanism of the phase transition in AdS/CFT. We also demonstrate h ow the reflected entropy calculation motivates a procedure for building up geometry using tensor networks.\n LOCATION:https://researchseminars.org/talk/HET/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Michal P. Heller (Ghent University) DTSTART:20220125T203000Z DTEND:20220125T213000Z DTSTAMP:20260422T212725Z UID:HET/23 DESCRIPTION:Title: Ent anglement of Purification (and Reflected Entropy) in Conformal Field Theor y\nby Michal P. Heller (Ghent University) as part of Purdue HET\n\n\nA bstract\nQuantifying entanglement properties of mixed states in quantum fi eld theory via entanglement of purification and reflected entropy is a new and challenging subject. I will discuss universal CFT results on entangle ment of purification (and also on reflected entropy) in the paradigmatic e xample of two spherical subregions far away from each other in the vacuum of a conformal field theory. Based on 2009.11881\, 2102.00013 and work in progress.\n LOCATION:https://researchseminars.org/talk/HET/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Edgar Shaghoulian (University of Pennsylvania) DTSTART:20220301T203000Z DTEND:20220301T213000Z DTSTAMP:20260422T212725Z UID:HET/25 DESCRIPTION:Title: The central dogma and entanglement in de Sitter space\nby Edgar Shaghouli an (University of Pennsylvania) as part of Purdue HET\n\n\nAbstract\nThe c entral dogma of black hole physics – which says that from the outside a black hole can be described in terms of a quantum system with exp(Area/4G) states evolving unitarily – has recently been supported by computations indicating that the interior of the black hole is encoded in the Hawking radiation of the exterior. In this paper\, we probe whether such a dogma f or cosmological horizons has any support from similar computations. The fa ct that the de Sitter bifurcation surface is a minimax surface (instead of a maximin surface) causes problems with this interpretation when trying t o import calculations analogous to the AdS case. This suggests anchoring e xtremal surfaces to the horizon itself\, where we formulate a two-sided ex tremization prescription and find answers consistent with general expectat ions for a quantum theory of de Sitter space: vanishing total entropy\, an entropy of A/4G when restricting to a single static patch\, an entropy of a subregion of the horizon which grows with the region size and threatens the central dogma until an island-like transition at half the horizon siz e when the entanglement wedge becomes the entire static patch interior\, a nd a de Sitter version of the Hartman-Maldacena transition.\n LOCATION:https://researchseminars.org/talk/HET/25/ END:VEVENT BEGIN:VEVENT SUMMARY:John McGreevy (University of California San Diego) DTSTART:20220201T203000Z DTEND:20220201T213000Z DTSTAMP:20260422T212725Z UID:HET/26 DESCRIPTION:Title: Thr ee-manifolds and entanglement\nby John McGreevy (University of Califor nia San Diego) as part of Purdue HET\n\n\nAbstract\nThe Entanglement Boots trap is a program to understand liquid topological phases. The starting po int is a single wavefunction satisfying two simple and well-motivated axio ms about its entanglement structure. In 2+1 dimensions\, much of the alge braic theory of anyons has been derived from this starting point. In this talk\, based on work with Bowen Shi and Jin-Long Huang\, I'll describe so me consequences of this line of thought in 3+1 dimensions\, where the rich ness of low-dimensional topology plays a role.\n\nSome of this work has ap peared in https://arxiv.org/abs/2112.08398.\n LOCATION:https://researchseminars.org/talk/HET/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Alex May (Stanford University) DTSTART:20220208T203000Z DTEND:20220208T213000Z DTSTAMP:20260422T212725Z UID:HET/27 DESCRIPTION:Title: Tow ards quantum information processing in gravitating spacetimes\nby Alex May (Stanford University) as part of Purdue HET\n\n\nAbstract\nAside from quantum mechanics\, other areas in physics constrain information processi ng. From relativity\, we know information cannot move faster than the spee d of light. In quantum gravity\, we expect but don't fully understand addi tional constraints\, for instance on how densely information can be stored . Can we develop an understanding of information processing in the context of quantum gravity? Towards doing so\, we consider quantum information wi thin holographic spacetimes\, which have an alternative\, non-gravitationa l\, description. In that context questions about information processing in the presence of gravity can be translated to different questions about qu antum information without gravity. As a specific example\, we study constr aints on computation within a gravitating region\, and use the holographic description to argue that gravity constrains the complexity of operations that can happen inside the region. Along the way\, we are led to new conn ections relating quantum gravity\, position-based cryptography\, quantum s ecret sharing and complexity theory.\n LOCATION:https://researchseminars.org/talk/HET/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Mukund Rangamani (University of California\, Davis) DTSTART:20220215T203000Z DTEND:20220215T213000Z DTSTAMP:20260422T212725Z UID:HET/28 DESCRIPTION:Title: A p aradigm for open quantum systems with memory from holography\nby Mukun d Rangamani (University of California\, Davis) as part of Purdue HET\n\n\n Abstract\nThe late-time\, long-distance behaviour of gravitational perturb ations of planar AdS black holes is controlled by hydrodynamic quasinormal modes. In the dual CFT these are modes of the conserved currents which co ntrol the infra-red dynamics. While the on-shell structure of these modes has been understood for a long-time\, we have recently begun to understand how to construct an off-shell low energy effective action\, an effectiv e hydrodynamic field theory\, from holography. I will describe the general lessons learnt from the gravitational analysis\, sketching out a paradigm that provides a template for the analysis of general quantum systems with dissipation and long-time memory.\n LOCATION:https://researchseminars.org/talk/HET/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Nicole Yunger Halpern (QuICS\, NIST\, University of Maryland) DTSTART:20220308T203000Z DTEND:20220308T213000Z DTSTAMP:20260422T212725Z UID:HET/29 DESCRIPTION:Title: Lin ear growth of quantum circuit complexity\nby Nicole Yunger Halpern (Qu ICS\, NIST\, University of Maryland) as part of Purdue HET\n\n\nAbstract\n Quantifying quantum states' complexity is a key problem in various subfiel ds of science\, from quantum computing to black-hole physics. We prove a p rominent conjecture by Brown and Susskind about how random quantum circuit s' complexity increases. Consider constructing a unitary from Haar-random two-qubit quantum gates. Implementing the unitary exactly requires a circu it of some minimal number of gates—the unitary's exact circuit complexit y. We prove that this complexity grows linearly with the number of random gates\, with unit probability\, until saturating after exponentially many random gates. Our proof is surprisingly short\, given the established diff iculty of lower-bounding the exact circuit complexity. Our strategy combin es differential topology and elementary algebraic geometry with an inducti ve construction of Clifford circuits.\n\nReferences 1) Haferkamp\, Faist\, Kothakonda\, Eisert\, and NYH\, accepted by Nat. Phys. (in press) arXiv:2 106.05305. 2) NYH\, Kothakonda\, Haferkamp\, Munson\, Faist\, and Eisert\, arXiv:2110.11371 (2021).\n LOCATION:https://researchseminars.org/talk/HET/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Chris Akers (MIT) DTSTART:20220419T193000Z DTEND:20220419T203000Z DTSTAMP:20260422T212725Z UID:HET/30 DESCRIPTION:Title: Bla ck holes as non-isometric codes\nby Chris Akers (MIT) as part of Purdu e HET\n\n\nAbstract\nThe interior of an old black hole is encoded in the H awking radiation. Thisseems to be the implication of recent computations o f the Page curve. We takethis idea to its logical conclusion\, modeling ol d black holes as quantum codesembedding a large number of degrees of freed om (the interior and semiclassicalradiation) into a smaller number (the st retched horizon and physicalradiation). I will prove that such codes exist \, and discuss their novelproperties and what they can tell us about black holes. ​\n LOCATION:https://researchseminars.org/talk/HET/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Lampros Lamprou (University of British Columbia) DTSTART:20220315T193000Z DTEND:20220315T203000Z DTSTAMP:20260422T212725Z UID:HET/31 DESCRIPTION:Title: Fal ling inside holographic black holes\nby Lampros Lamprou (University of British Columbia) as part of Purdue HET\n\n\nAbstract\nI will present a b ulk reconstruction technique in AdS/CFT suitable for addressing a facet of the black hole information problem: how to unambiguously predict the resu lts of measurements accessible to an infalling observer in the black hole interior. I will explicitly apply the method in the AdS$_2$/SYK correspond ence and comment on its generalizations.\n LOCATION:https://researchseminars.org/talk/HET/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Anthony Munson (University of Maryland) DTSTART:20220329T193000Z DTEND:20220329T203000Z DTSTAMP:20260422T212725Z UID:HET/32 DESCRIPTION:Title: Qua ntum (Un)complexity: A Resource for Quantum Computation\nby Anthony Mu nson (University of Maryland) as part of Purdue HET\n\n\nAbstract\nUnder r andom dynamics\, a system’s quantum complexity—which quantifies the di fficulty of preparing a desired state from a simple\, tensor-product state —increases linearly up to times exponential in the system’s size\, lon g after most physical observables have thermalized. The observation that c omplexity saturation is a late stage of quantum thermalization suggests th at a state’s lack of complexity\, or ``uncomplexity\,'' is a useful reso urce for quantum computation: Much as a system far from thermal equilibriu m can serve as a resource in information-processing tasks\, a state with h igh uncomplexity—i.e.\, a low-complexity state such as |0^n>—can be ut ilized as ``blank scrap paper'' for quantum computers. It is natural\, the refore\, to view uncomplexity through the lens of a resource theory. In a resource theory\, an agent can perform any operation subject to a fixed se t of simple rules\, and can identify which tasks are achievable under thes e rules and which tasks require additional resources. We define a resource theory of uncomplexity\, and then construct protocols in the resource the ory for extracting uncomplexity from a state and for expending uncomplexit y to imitate a state. Moreover\, we show that a new quantity\, the complex ity entropy\, quantifies the efficiencies with which we can perform uncomp lexity extraction and expenditure\, and thereby quantifies the resource re quirements for one-shot thermodynamic erasure (Landauer erasure) under com putational limitations.\n\nYunger Halpern\, Kothakonda\, Haferkamp\, Munso n\, Eisert\, and Faist (2021). https://arxiv.org/abs/2110.11371\n LOCATION:https://researchseminars.org/talk/HET/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexander Jahn (Caltech) DTSTART:20220510T193000Z DTEND:20220510T203000Z DTSTAMP:20260422T212725Z UID:HET/33 DESCRIPTION:Title: Hol ographic toy models with matchgate tensor networks\nby Alexander Jahn (Caltech) as part of Purdue HET\n\n\nAbstract\nMuch insight into the quant um information side of holographic dualities has come from studying simple toy models based on tensor networks. While these models have been shown t o realize properties such as entanglement and quantum error correction in line with continuum AdS/CFT\, their boundary states differ from those of s imple lattice discretizations of CFTs. In this talk\, I will introduce a c lass of tensor networks based on matchgate tensors for which such toy mode ls can be efficiently constructed. Within this class\, we will find simple solutions that are identified with a local\, critical boundary Hamiltonia n corresponding to a disordered version of the critical Ising model. Rathe r than just ground states\, we will find that the matchgate tensor ansatz can also reproduce low-energy excited states of the boundary Hamiltonian\, leading to a concrete bulk-boundary dictionary between bulk and boundary states. I will argue that this can be extended to a new class of holograph ic codes related to imaginary-time path integrals\, which serves as a prom ising avenue to study time dynamics in holographic tensor network models.\ n LOCATION:https://researchseminars.org/talk/HET/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Gabor Sarosi (CERN) DTSTART:20220628T193000Z DTEND:20220628T203000Z DTSTAMP:20260422T212725Z UID:HET/34 DESCRIPTION:Title: Com ments on the volume of the black hole interior in 2d gravity\nby Gabor Sarosi (CERN) as part of Purdue HET\n\n\nAbstract\nThe volume of the inte rior of a two-sided eternal black hole classically grows forever. I will d erive a microscopic formula for this volume in JT gravity by summing the n on-perturbative contribution of higher topologies. The non-perturbative co rrections lead to the saturation of the volume of the interior at times ex ponential in the entropy of the black hole. I will connect the microscopic formula for the volume with properties of a time averaged density matrix\ , in particular with its second Renyi entropy\, which I argue to measure t he number of nearly orthogonal states visited by time evolution. I will di scuss various problems with this interpretation.\n LOCATION:https://researchseminars.org/talk/HET/34/ END:VEVENT BEGIN:VEVENT SUMMARY:Cesar Agon (Instituto Balseiro) DTSTART:20220809T193000Z DTEND:20220809T203000Z DTSTAMP:20260422T212725Z UID:HET/35 DESCRIPTION:Title: On the N-partite information in Conformal Field Theory\nby Cesar Agon (In stituto Balseiro) as part of Purdue HET\n\n\nAbstract\nIn this talk\, I wi ll present a general procedure for computing the N-partite information in the ground state of a conformal field theory for N-disjoint spheres in the large separation regime. I will motive this computation as part of the ge neral program of describing the CFT from entanglement related quantities. Then\, I will apply the general procedure to rederive known formulas for t he mutual information and tri-partite information as well as to present a new result pertaining the four-partite information in the large separation regime. I then show good agreement between our analytic results and latti ce computations for the free scalar field in $d=3$. Finally\, I close with an explicit check within the context of our computations of the Faulkner\ , Lewkowycz and Maldacena (FLM) prescription in holographic conformal fiel d theories.\n LOCATION:https://researchseminars.org/talk/HET/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Keiichiro Furuya (Purdue University) DTSTART:20220816T193000Z DTEND:20220816T203000Z DTSTAMP:20260422T212725Z UID:HET/36 DESCRIPTION:Title: An Algebra of Observables for de Sitter Space\nby Keiichiro Furuya (Purdu e University) as part of Purdue HET\n\n\nAbstract\nIn this talk\, I will r eview the latest paper\, ``An Algebra of Observables for de Sitter Space ’’. Since Bekenstein studied the entropy associated with the black ho le\, the studies of the entropic structure of a system with gravity have b een developed. Especially\, the (entanglement) entropy of a quantum system of two different regions is important to explore the correlations in a sy stem. In a quantum mechanical system\, the (entanglement) entropy is a pr operty of the states of a given system. In quantum field theory\, it is in stead the property of the algebra of quantum field theory associated with a subregion of spacetime\, which we now call the local algebra. In particu lar\, the ultraviolet divergence is due to the property of the local algeb ra. Hence\, understanding the entropic structure of quantum field theory r equires you to investigate the structure of a local algebra. This paper sp ecifies the properties of the local algebra of quantum field theory in de Sitter space to seek its entropy.\n LOCATION:https://researchseminars.org/talk/HET/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Javier Magan (University of Pennsylvania) DTSTART:20221005T193000Z DTEND:20221005T203000Z DTSTAMP:20260422T212725Z UID:HET/37 DESCRIPTION:Title: A t ale of two hungarians: tridiagonalizing random matrices\nby Javier Mag an (University of Pennsylvania) as part of Purdue HET\n\n\nAbstract\nThe H ungarian physicist Eugene Wigner introduced random matrix models in physic s to describe the energy spectra of atomic nuclei. As such\, the main goal of Random Matrix Theory (RMT) has been to derive the eigenvalue statistic s of matrices drawn from a given distribution. The Wigner approach gives p owerful insights into the properties of complex\, chaotic systems in therm al equilibrium. Another Hungarian\, Cornelius Lanczos\, suggested a metho d of reducing the dynamics of any quantum system to a one-dimensional chai n by tridiagonalizing the Hamiltonian relative to a given initial state. I n the resulting matrix\, the diagonal and off-diagonal Lanczos coefficient s control transition amplitudes between elements of a distinguished basis of states. This method suggests a computable notion of complexity which we describe in detail. We then connect the Wigner/Lanczos approaches by anal yzing RMT in time-dependent scenarios. This is first accomplished by nume rically studying time-evolved thermofield double states in chaotic systems \, where our complexity measure shows parallel regimes as the Spectral For m Factor in RMT. Secondly\, to approach these problems analytically\, we i nitiate a novel approach to Random Matrix Theory based on matrix tridiagon zalition\, deriving the statistics of the tridiagonal matrix.\n LOCATION:https://researchseminars.org/talk/HET/37/ END:VEVENT BEGIN:VEVENT SUMMARY:Julian Sonner (University of Geneva) DTSTART:20221018T193000Z DTEND:20221018T203000Z DTSTAMP:20260422T212725Z UID:HET/38 DESCRIPTION:Title: Mat rix Models for Eigenstate Thermalization with applications to holography\nby Julian Sonner (University of Geneva) as part of Purdue HET\n\nAbstr act: TBA\n LOCATION:https://researchseminars.org/talk/HET/38/ END:VEVENT BEGIN:VEVENT SUMMARY:Samuel Leutheusser (MIT) DTSTART:20221025T193000Z DTEND:20221025T203000Z DTSTAMP:20260422T212725Z UID:HET/39 DESCRIPTION:Title: Sub region-subalgebra duality and the emergence of space and time in holograph y\nby Samuel Leutheusser (MIT) as part of Purdue HET\n\n\nAbstract\nIn holographic duality a higher dimensional quantum gravity system emerges f rom a lower dimensional conformal field theory (CFT) with a large number o f degrees of freedom\, N. Bulk geometric notions such as spacetime subregi ons\, extremal surfaces\, and causal structure are only sharply defined in the bulk G_N \\to 0 limit which corresponds to the boundary N \\to \\inft y limit. In this talk\, we will argue that geometric notions in the bulk e merge from the mathematical structure of the large N limit of the dual CFT \, which we have shown gives rise to the ubiquitous emergence of type III_ 1 von Neumann algebras. We explicitly construct the boundary subalgebras t hat describe bulk physics in most bulk subregions. We also comment on the relationship of our construction with quantum error correction\, subregion -subregion duality and the RT prescription.\n LOCATION:https://researchseminars.org/talk/HET/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Antony Speranza (UIUC) DTSTART:20221115T203000Z DTEND:20221115T213000Z DTSTAMP:20260422T212725Z UID:HET/40 DESCRIPTION:Title: Com plexity = (Anything)^2\nby Antony Speranza (UIUC) as part of Purdue HE T\n\nLecture held in Room 242\, Department of Physics and Astronomy\, Purd ue University.\n\nAbstract\nI will describe an infinite class of gravitati onal observables that can serve as measures of holographic complexity. Th ese observables are constructed relationally by extremizing a surface with respect to one functional\, and evaluating a second functional on that su rface. We show that classical Poisson brackets of these observables can b e computed via the Peierls construction\, and demonstrate that the extrema lity conditions follow naturally from diffeomorphism invariance. A wide c lass of these observables can be shown to exhibit universal properties of complexity measures\, including linear growth at late times in thermal sta tes and the switchback effect. By taking distinct limits\, specific obser vables can be shown to reduce to the standard holographic complexity measu res such as volume or action.\n LOCATION:https://researchseminars.org/talk/HET/40/ END:VEVENT BEGIN:VEVENT SUMMARY:Pawel Caputa (University of Warsaw) DTSTART:20221101T193000Z DTEND:20221101T203000Z DTSTAMP:20260422T212725Z UID:HET/41 DESCRIPTION:Title: Qua ntum Complexity in the Krylov basis\nby Pawel Caputa (University of Wa rsaw) as part of Purdue HET\n\n\nAbstract\nI will review some recent progr ess on defining a universal measure of quantum complexity based on the so- called Krylov basis. After introducing Krylov basis techniques\, I will di scuss the “Spread Complexity” measure for quantum states with some exp licit examples its general properties. The talk will be based on:\nhttps:/ /arxiv.org/abs/2202.06957\nhttps://arxiv.org/abs/2109.03824\n LOCATION:https://researchseminars.org/talk/HET/41/ END:VEVENT BEGIN:VEVENT SUMMARY:Erik Tonni (SISSA and INFN Sezione di Trieste) DTSTART:20221122T203000Z DTEND:20221122T213000Z DTSTAMP:20260422T212725Z UID:HET/42 DESCRIPTION:Title: Ent anglement entropies for Lifshitz fermionic fields at finite density\nb y Erik Tonni (SISSA and INFN Sezione di Trieste) as part of Purdue HET\n\n \nAbstract\nThe entanglement entropies of an interval for the free fermion ic spinless Schroedinger field theory at finite density and zero temperatu re are investigated. The interval is either on the line or at the beginnin g of the half line\, when either Neumann or Dirichlet boundary conditions are imposed at the origin. We show that the entanglement entropies are fin ite functions of a dimensionless parameter proportional to the area of the rectangular region in the phase space identified by the Fermi momentum an d the length of the interval. \nFor the interval on the line\, the entangl ement entropy is a monotonically increasing function. Instead\, for the in terval on the half line\, it displays an oscillatory behaviour related to the Friedel oscillations of the mean particle density at the entangling po int. \nBy employing the properties of the prolate spheroidal wave function s or the expansions of the tau functions of the kernels occurring in the s pectral problems\, determined by the two point function\, we find analytic expressions for the expansions of the entanglement entropies in the asymp totic regimes of small and large area of the rectangular phase space regio n. Extending our analysis to a class of free fermionic Lifshitz models\, w e find that the parity of the Lifshitz exponent determines the properties of the bipartite entanglement.\n LOCATION:https://researchseminars.org/talk/HET/42/ END:VEVENT BEGIN:VEVENT SUMMARY:Marco Tomamichel (National University of Singapore) DTSTART:20220920T140000Z DTEND:20220920T150000Z DTSTAMP:20260422T212725Z UID:HET/43 DESCRIPTION:Title: Qua ntum Rényi divergence and beyond\nby Marco Tomamichel (National Unive rsity of Singapore) as part of Purdue HET\n\n\nAbstract\nI will give a tou r of quantum generalisations of Rényi's entropy and divergence and variou s notions of conditional entropy and mutual information based on Rényi di vergence. A particular focus will be on the non-uniqueness of such general isations and interesting questions that arise from it\, as well as operati onal interpretations of some Rényi information measures.\n LOCATION:https://researchseminars.org/talk/HET/43/ END:VEVENT BEGIN:VEVENT SUMMARY:Shoy Ouseph (Purdue University) DTSTART:20221108T203000Z DTEND:20221108T213000Z DTSTAMP:20260422T212725Z UID:HET/44 DESCRIPTION:Title: Rec ent developments in generalizing symmetries\nby Shoy Ouseph (Purdue Un iversity) as part of Purdue HET\n\n\nAbstract\nI will be reviewing the rec ent developments in understanding symmetries in quantum many body systems and generalizing the Landau theory for phase transitions based on the revi ew paper https://arxiv.org/abs/2204.03045 and https://arxiv.org/abs/1412.5 148.\n LOCATION:https://researchseminars.org/talk/HET/44/ END:VEVENT BEGIN:VEVENT SUMMARY:Prashanth Raman (Indian Institute of Science) DTSTART:20220927T193000Z DTEND:20220927T203000Z DTSTAMP:20260422T212725Z UID:HET/45 DESCRIPTION:Title: Pos itivity Constraints on EFT’s and Geometric Function Theory\nby Prash anth Raman (Indian Institute of Science) as part of Purdue HET\n\nLecture held in Room 242\, Department of Physics and Astronomy.\n\nAbstract\nIn th is talk\, we shall look at the implications of crossing symmetry\, localit y\, and unitarity in the UV on low-energy EFT’s. We will begin by lookin g at 2-2scattering amplitudes with identical external particles and introd uce a crossing symmetric dispersive representation (CSDR) of the amplitude that makes full (s\,t\,u)-crossing symmetry manifest\, unlike the usual f ixed-t dispersion relations. Though the CSDR makes crossing symmetry manif est\, locality is lost and has to be restored by demanding that certain sp urious singularities cancel in the low energy expansion of the amplitude l eading to locality constraints. \n\nFor massive external particles\, the C SDR and unitarity make a certain analytic property of the amplitude called typically-realness manifest and enables us to use techniques from the geo metric function theory of typically-real functions to show that the low en ergy Wilson coefficients have to be o(1) numbers and that the space of the se Wilson coefficients is finite. \nFor massless external particles with massive exchanges we look at the celestial amplitude (CA) corresponding to our original 2-2 scattering amplitude and show that the locality constrai nts imply an infinite linear system of equations that the partial wave mom ents of any local theory need to satisfy. By additionally imposing linear unitarity (positivity of partial wave moments)\, we show that these natura lly lead to the phenomenon of low-spin dominance (LSD). Finally\, we show that the crossing symmetric partial waves with spurious singularities rem oved\, dubbed as Feynman blocks are typically-real and using this we obtai n two-sided bounds on low-energy Wilson coefficients for this case.\nThis is based on work with Sudip Ghosh and Aninda Sinha.\n\nHost: Martin Krucze nski\n LOCATION:https://researchseminars.org/talk/HET/45/ END:VEVENT BEGIN:VEVENT SUMMARY:Nathan Benjamin (CalTech) DTSTART:20221129T203000Z DTEND:20221129T213000Z DTSTAMP:20260422T212725Z UID:HET/46 DESCRIPTION:Title: Sca lar Modular Bootstrap and Zeros of the Riemann Zeta Function\nby Natha n Benjamin (CalTech) as part of Purdue HET\n\nLecture held in Room 242\, D epartment of Physics and Astronomy.\n\nAbstract\nWe derive a crossing equa tion that acts only on the scalar primary operators of any 2d CFT with U(1 )^c symmetry. We derive bounds on the scalar gap of all such theories. Rat her remarkably\, our crossing equation contains information about all nont rivial zeros of the Riemann zeta function. As a result\, we rephrase the R iemann hypothesis as a statement about the asymptotic density of scalar op erators in certain theories. We discuss generalizations to theories with o nly Virasoro symmetry. Based on 2208.02259 with C.-H. Chang.\n LOCATION:https://researchseminars.org/talk/HET/46/ END:VEVENT BEGIN:VEVENT SUMMARY:Roy Araiza (UIUC) DTSTART:20230404T193000Z DTEND:20230404T203000Z DTSTAMP:20260422T212725Z UID:HET/47 DESCRIPTION:Title: An index for inclusions of operator systems\nby Roy Araiza (UIUC) as part of Purdue HET\n\nLecture held in Room 242\, Department of Physics and Ast ronomy.\n\nAbstract\nMotivated by the initial work of Jones\, Pimsner\, an d Popa in studying the index of inclusions of II_1 factors\, I will presen t an analogue to the ``classical index'' in the operator system category. After going through some background and initial motivation\, our goal will be to connect this new ``completely positive index’’ of operator syst ems arising from finite graphs\, to the Lovasz theta invariant.\n LOCATION:https://researchseminars.org/talk/HET/47/ END:VEVENT BEGIN:VEVENT SUMMARY:Yidong Chen (UIUC) DTSTART:20230411T193000Z DTEND:20230411T203000Z DTSTAMP:20260422T212725Z UID:HET/48 DESCRIPTION:Title: Non commutative Poisson Random Measure and its Applications in AQFT and Quantu m Chaos\nby Yidong Chen (UIUC) as part of Purdue HET\n\n\nAbstract\nOn e of the important problems in modern mathematical physics is to understan d quantization - both quantizing classical systems to quantum systems and quantizing one-particle systems to many-body systems. Up to now\, the math ematical second quantization relies on the Gaussian functor and produces g eneralized free theories. Interactions are generally modeled by perturbati on theories (a la Glimm and Jaffe). In this talk\, we take a new approach to second quantization by constructing a noncommutative analog of the clas sical Poisson random measure. This construction produces a functor which s hall be called Poissonization. The analog of correlation functions in this construction cannot be factorized into the sum of products of two-point f unctions. After we outlined the main ideas of Poissonization\, we will cle arly state the construction and its functorial properties. Moreover\, we w ill discuss the main properties of this construction\, emphasizing on its versatility and physical relevance. Subsequently\, we will focus on two ma in areas of physical applications. On one hand\, we will discuss how Poiss onization can be used to produce examples of algebraic quantum field theor ies starting from the data of unitary representations of real semisimple L ie groups (single particles a la Weinberg). On the other hand\, we will di scuss how Poissonization can be used to rigorously calculate quantum infor mation quantities (e.g. relative entropy\, tripartite information\, out-of -time-order correlation etc.) in type III von Neumann algebras. In many to y examples\, these quantities have the right quanlitative behaviors as con jectured in physics literature. Lastly\, we will briefly discuss future di rections\, emphasizing on why we cannot yet claim to have constructed an i nteracting CFT in dimensions larger than 2 and how we can achieve this goa l using Poissonization.\n LOCATION:https://researchseminars.org/talk/HET/48/ END:VEVENT BEGIN:VEVENT SUMMARY:Nicholas LaRacuente (University of Chicago) DTSTART:20230418T193000Z DTEND:20230418T203000Z DTSTAMP:20260422T212725Z UID:HET/49 DESCRIPTION:Title: Com plexity and Purity Over Time in Quantum Dynamics\nby Nicholas LaRacuen te (University of Chicago) as part of Purdue HET\n\nLecture held in Room 2 42\, Department of Physics and Astronomy.\n\nAbstract\nA quantum system's time-evolution usually combines internal\, coherent dynamics with environm ental noise. Combined dynamics may converge to mixed equilibria\, reduce t o classical determinism for long times\, or maintain non-classicality. The first regime is well-explained in quantum Markov semigroup theory. The se cond is well-established in classical mechanics\, though its emergence fro m quantum dynamics still yields mysteries. The third regime of persistent quantum complexity is a key goal\, often proposed achievable through activ e error correction. I will present results on the capabilities for quantum quench dynamics to innately manifest non-classical complexities and maint ain classical or quantum purity without intervention. Of particular intere st are chaotic quantum systems and related conjectures about natural pheno mena seeming to require non-classical capabilities.\n LOCATION:https://researchseminars.org/talk/HET/49/ END:VEVENT BEGIN:VEVENT SUMMARY:Jonah Kudler-Flam (IAS Princeton) DTSTART:20230425T193000Z DTEND:20230425T203000Z DTSTAMP:20260422T212725Z UID:HET/50 DESCRIPTION:Title: Hor izons as eavesdroppers: decoherence from soft radiation\nby Jonah Kudl er-Flam (IAS Princeton) as part of Purdue HET\n\n\nAbstract\nRecently\, Da nielson\, Satishchandran\, and Wald proposed a novel mechanism for decoher ence in spacetimes with Killing horizons. When Alice performs a Stern-Gerl ach type experiment outside the horizon\, there is a fundamental rate of d ecoherence due to the emission of soft gravitons/photons that radiate away information. In this talk\, I will sharpen and generalize this mechanism by recasting the gedankenexperiment in the language of (approximate) quant um error correction. By explicitly computing the quantum fidelity between the vacuum state on the horizon and the state with soft radiation propagat ing through the horizon\, we characterize how much an eavesdropper (Eve) b ehind the horizon is able to learn about Alice's experiment. From the info rmation-disturbance tradeoff\, there is a direct relation between the info rmation gained by Eve and the decoherence of Alice's generalized experimen t. I will comment on how an information-theoretic language may lead to new insights on energy/entropy inequalities\, islands\, and the central dogma of black holes.\n LOCATION:https://researchseminars.org/talk/HET/50/ END:VEVENT BEGIN:VEVENT SUMMARY:Dalimil Mazac (IAS Princeton) DTSTART:20230502T193000Z DTEND:20230502T203000Z DTSTAMP:20260422T212725Z UID:HET/51 DESCRIPTION:Title: Con formal measure spaces\nby Dalimil Mazac (IAS Princeton) as part of Pur due HET\n\n\nAbstract\nThe conformal bootstrap equations in the general di mension are an infinite set of coupled non-linear equations in infinitely many variables. According to the lore\, the solutions of the full set of e quations correspond to physical CFTs. At the same time\, the only solution s truly known to exist above two dimensions are the mean field theories. I n this talk\, I will define conformal measure spaces\, which are mathemati cal objects guaranteed to produce solutions of the conformal bootstrap in any dimension. I will review why hyperbolic manifolds give rise to a parti cular class of conformal measure spaces\, and use the bootstrap equations to prove new bounds on their spectra. Finally\, I will discuss the similar ities and differences between these solutions\, and those that are believe d to arise in physical CFTs.\n LOCATION:https://researchseminars.org/talk/HET/51/ END:VEVENT BEGIN:VEVENT SUMMARY:Samuel Goldman (UIUC) DTSTART:20230509T193000Z DTEND:20230509T203000Z DTSTAMP:20260422T212725Z UID:HET/52 DESCRIPTION:Title: Exa ct Renormalization and its Application to Quantum States\nby Samuel Go ldman (UIUC) as part of Purdue HET\n\n\nAbstract\nThe exact renormalizatio n group (ERG) is a general tool for implementing the Wilsonian idea that p hysics is independent of our parametrization of the degrees of freedom. In its original formulation\, it is simply a manifestation of the invariance of path integrals with respect to the choice of field variable. More rece ntly\, ERG methods have been generalized to objects derived from path inte grals\, such as wavefunctionals. We extend these ideas in two complementar y ways which demonstrate the flexibility of ERG\n\nin the context of quant um states. In one scheme which uses multiple regulators\, we obtain a clas s of unitary wavefunctional flows\, a subset of which are the so-called co ntinuous MERA networks. In a parallel investigation\, we consider the ERG for density operators and find that the non-locality generated along flows introduces non-unitary contributions to the state. The description of thi s non-unitarity takes the form of a quantum Markov semigroup. These result s have a variety of potential applications\, such as the construction of i nteracting and non-unitary cMERA networks\, as well as extending our under standing of emergent geometry and renormalization in both holographic and non-holographic contexts.\n LOCATION:https://researchseminars.org/talk/HET/52/ END:VEVENT BEGIN:VEVENT SUMMARY:Zhencheng Wang (UIUC) DTSTART:20240123T203000Z DTEND:20240123T213000Z DTSTAMP:20260422T212725Z UID:HET/53 DESCRIPTION:Title: Typ e I von Neumann algebras from gravitational path integrals\nby Zhenche ng Wang (UIUC) as part of Purdue HET\n\nLecture held in Room 242 in the De partment of Physics and Astronomy.\n\nAbstract\nIn this talk\, I will desc ribe a construction of Hilbert spaces and von Neumann algebras from any UV -completion of asymptotically anti-de Sitter quantum gravity with a Euclid ean path integral satisfying a simple and familiar set of axioms. We consi der a quantum context in which a standard Lorentz-signature classical bulk limit would have Cauchy slices with two asymptotic boundaries (left and r ight)\, both of which are compact manifolds without boundary. Our main res ult is then that the quantum gravity path integral defines (left and right ) type I von Neumann algebras of observables acting respectively at the le ft and right boundaries\, such that the two algebras are commutants. The p ath integral also defines entropies on the von Neumann algebras. The entro pies can also be written in terms of standard density matrices and standar d Hilbert space traces.\n LOCATION:https://researchseminars.org/talk/HET/53/ END:VEVENT BEGIN:VEVENT SUMMARY:Ning Bao (Northeastern University) DTSTART:20240220T203000Z DTEND:20240220T213000Z DTSTAMP:20260422T212725Z UID:HET/54 DESCRIPTION:Title: An Exponential Speedup in Contraction Maps for Holographic Entanglement Entro py\nby Ning Bao (Northeastern University) as part of Purdue HET\n\n\nA bstract\nIn this talk\, I will go over the basic concepts of contraction m ap proof methods for holographic entanglement entropy\, and comment on rec ent advances in dramatically improving the proving power of such inequalit ies. In addition\, I will prove the completeness of such methods.\n LOCATION:https://researchseminars.org/talk/HET/54/ END:VEVENT BEGIN:VEVENT SUMMARY:Arvin Shahbazi-Moghaddam (Stanford) DTSTART:20240305T203000Z DTEND:20240305T213000Z DTSTAMP:20260422T212725Z UID:HET/55 DESCRIPTION:Title: Sin gular inner horizons\nby Arvin Shahbazi-Moghaddam (Stanford) as part o f Purdue HET\n\nLecture held in Room 242 in the Department of Physics and Astronomy.\n\nAbstract\nAn often overlooked problem in black hole physics is that the inner horizon of stationary black holes do not (generically) e xist even in the equilibrium state (i.e. the Hartle-Hawking state)\, due t o the divergence of quantum fields. Even though this behavior has been obs erved numerically in 2+1 and 3+1 dimensions for free fields\, a universal and analytic understanding of it is lacking. I will discuss work in progre ss on trying to fill this gap.\n LOCATION:https://researchseminars.org/talk/HET/55/ END:VEVENT BEGIN:VEVENT SUMMARY:Sridip Pal (Caltech) DTSTART:20240312T193000Z DTEND:20240312T203000Z DTSTAMP:20260422T212725Z UID:HET/56 DESCRIPTION:Title: Uni versality in Spin-resolved High-Energy CFT data\nby Sridip Pal (Caltec h) as part of Purdue HET\n\nLecture held in Room 242 in the Department of Physics and Astronomy.\n\nAbstract\nI will discuss the universal behavior of spin-resolved data of conformal field theory (CFT) at high energies. Us ing a technique\, called thermal effective field theory\, we derive\, for d>2 CFTs\, the universal high temperature behavior of grand-canonical part ition function with finite angular fugacity turned on. This result can be considered a higher-dimensional version of a similar formula for 2d CFTs\, generally derived using modular invariance. I will also discuss holograph ic interpretations of this result.\n LOCATION:https://researchseminars.org/talk/HET/56/ END:VEVENT BEGIN:VEVENT SUMMARY:Agnese Bissi (ICTP Trieste) DTSTART:20240326T183000Z DTEND:20240326T193000Z DTSTAMP:20260422T212725Z UID:HET/57 DESCRIPTION:Title: Mul ti-trace operators in CFTs\nby Agnese Bissi (ICTP Trieste) as part of Purdue HET\n\n\nAbstract\nIn this talk I will discuss how to deal with mul ti-trace operators\, in particular in the context of N=4 Super Yang Mills. I will review their relevance in computing holographic correlators and di scuss recent developments on how to treat them.\n LOCATION:https://researchseminars.org/talk/HET/57/ END:VEVENT BEGIN:VEVENT SUMMARY:Anatoly Dymarsky (University of Kentucky) DTSTART:20240402T193000Z DTEND:20240402T203000Z DTSTAMP:20260422T212725Z UID:HET/58 DESCRIPTION:Title: Cla ssical and quantum codes\, 2d CFTs and holography\nby Anatoly Dymarsky (University of Kentucky) as part of Purdue HET\n\nLecture held in Room 24 2 in the Department of Physics and Astronomy.\n\nAbstract\nThere is a rich connection between classical and quantum codes and holographic correspond ence connecting 2d CFTs and abelian 3d Chern-Simons theories. In the 3d la nguage the codes emerge as a way to parametrize condensable anyons. Upon c ondensation 3d topological field theory gives rise to 2d CFT at\n the boun dary. This provides a way to construct 2d CFTs from codes - the so-called "code CFTs". This construction has a natural interpretation in terms of a CSS quantum code (defined in terms of the original classical code\, defini ng the CFT). From the holographic point of view a particularly interesting question is that of an ensemble of codes and associated code CFTs. The en semble of boundary theories is holographically dual to "Chern-Simons gravi ty"\, a topological field theory that sums over 3d topologies.\n LOCATION:https://researchseminars.org/talk/HET/58/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Green (UCSD) DTSTART:20240430T193000Z DTEND:20240430T203000Z DTSTAMP:20260422T212725Z UID:HET/59 DESCRIPTION:Title: Cos mic Surveys and the Quantum Universe\nby Daniel Green (UCSD) as part o f Purdue HET\n\nLecture held in Room 242.\n\nAbstract\nUnderstanding the q uantum nature of accelerating cosmologies is essential to making sense of the past\, present\, and future of our Universe. One important quantity re levant to the dynamics of these epoches is the spectrum of quantum fluctua tions\, organized by scaling dimensions that control how these fluctuation s redshift away. When these fluctuations are coupled to the inflaton in t he early universe\, this scaling behavior appears in the statistics of the density fluctuations and can be measured with galaxy surveys. Remarkably\ , self-consistency of these late universe observations with the symmetries of the early universe place non-trivial constraints on both the dynamics of inflation and the statistics of galaxies. In this talk\, I will explain how these connections arise\, what they can tell us about the Universe\, and the current constraints and future prospects for measuring these dimen sions with cosmic surveys.\n LOCATION:https://researchseminars.org/talk/HET/59/ END:VEVENT BEGIN:VEVENT SUMMARY:Yikun Jiang (Northeastern University) DTSTART:20240507T193000Z DTEND:20240507T203000Z DTSTAMP:20260422T212725Z UID:HET/60 DESCRIPTION:Title: Bui lding up quantum spacetimes with BCFT Legos\nby Yikun Jiang (Northeast ern University) as part of Purdue HET\n\nLecture held in Room 350 in the D epartment of Physics and Astronomy.\n\nAbstract\nIs it possible to read of f the quantum gravity dual of a CFT directly from its operator algebra? In this talk\, I will present a step-by-step recipe for building up 3D quant um spacetimes dual to 2D CFTs\, synthesizing results and techniques from c onformal bootstrap\, topological symmetries\, real-space tensor network re normalization\, and the asymptotics of quantum 6j symbols. Quantum Liouvil le theory serves as a simple and explicit example\, illustrating how the e xact CFT/gravitational path integral can be built up from triangulation an d local pieces of BCFT correlation functions\, which we call the ``BCFT Le gos''. This is essentially a tensor network that admits an interpretation of a state-sum of a 3D topological theory constructed with quantum 6j symb ols of Uq(SL(2\,R)) with non-trivial boundary conditions\, and it reduces to a sum over 3D geometries weighted by the Einstein-Hilbert action to lea ding order in large c. The triangulation coincides with producing a networ k of geodesics in the AdS bulk\, which can be changed making use of the pe ntagon identity and orthogonality condition satisfied by the 6j symbols\, and arranged into a precise holographic tensor network. The constructive m ap between gravity and CFT naturally and explicitly bridges local geometri cal data\, algebraic structures\, and quantum entanglement.\n LOCATION:https://researchseminars.org/talk/HET/60/ END:VEVENT BEGIN:VEVENT SUMMARY:Gautam Satishchandran (Princeton University) DTSTART:20250305T181500Z DTEND:20250305T193000Z DTSTAMP:20260422T212725Z UID:HET/61 DESCRIPTION:Title: Gen eralized Entropy is von Neumann Entropy: Black Holes and Cosmology\nby Gautam Satishchandran (Princeton University) as part of Purdue HET\n\nLec ture held in Room 242 in the Department of Physics and Astronomy.\nAbstrac t: TBA\n LOCATION:https://researchseminars.org/talk/HET/61/ END:VEVENT BEGIN:VEVENT SUMMARY:Jonathan Sorce (MIT) DTSTART:20250326T171500Z DTEND:20250326T183000Z DTSTAMP:20260422T212725Z UID:HET/62 DESCRIPTION:Title: Gra vitational constraints\, modular flow\, and the information theory of UV d ivergences\nby Jonathan Sorce (MIT) as part of Purdue HET\n\nLecture h eld in Room 242 in the Department of Physics and Astronomy.\nAbstract: TBA \n LOCATION:https://researchseminars.org/talk/HET/62/ END:VEVENT BEGIN:VEVENT SUMMARY:Benoit Collins (Kyoto University) DTSTART:20250402T140000Z DTEND:20250402T151500Z DTSTAMP:20260422T212725Z UID:HET/63 DESCRIPTION:Title: Fre e probability and its applications to quantum information theory\nby B enoit Collins (Kyoto University) as part of Purdue HET\n\nLecture held in Room 242 in the Department of Physics and Astronomy.\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/HET/63/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Kapec (Harvard University) DTSTART:20250423T171500Z DTEND:20250423T183000Z DTSTAMP:20260422T212725Z UID:HET/64 DESCRIPTION:by Daniel Kapec (Harvard University) as part of Purdue HET\n\n Lecture held in Room 242 in the Department of Physics and Astronomy.\nAbst ract: TBA\n LOCATION:https://researchseminars.org/talk/HET/64/ END:VEVENT END:VCALENDAR