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X-WR-CALDESC:Events for CMSA
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BEGIN:VTIMEZONE
TZID:America/New_York
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DTSTART:20210314T070000
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DTSTART:20211107T060000
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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220407T093000
DTEND;TZID=America/New_York:20220407T110000
DTSTAMP:20240301T063834Z
CREATED:20240214T102601Z
LAST-MODIFIED:20240301T063834Z
UID:10002669-1649323800-1649329200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Lattice Gauge Theory View of Toric Codes\, X-cube\, and More
DESCRIPTION:Youtube Video \n  \nAbstract: Exactly solvable spin models such as toric codes and X-cube model have heightened our understanding of spin liquids and topological matter in two and three dimensions. Their exact solvability\, it turns out\, is rooted in the existence of commuting generators in their parent lattice gauge theory (LGT). We can understand the toric codes as Higgsed descendants of the rank-1 U(1) LGT in two and three dimensions\, and the X-cube model as that of rank-2 U(1) LGT in three dimensions. Furthermore\, the transformation properties of the gauge fields in the respective LGT is responsible for\, and nearly determines the structure of the effective field theory (EFT) of the accompanying matter fields. We show how to construct the EFT of e and m particles in the toric codes and of fractons and lineons in the X-cube model by following such an idea. Recently we proposed some stabilizer Hamiltonians termed rank-2 toric code (R2TC) and F3 model (3D). We will explain what they are\, and construct their EFTs using the gauge principle as guidance. The resulting field theory of the matter fields are usually highly interacting and exhibit unusual conservation laws. Especially for the R2TC\, we demonstrate the existence of what we call the “dipolar braiding statistics” and outline the accompanying field theory which differs from the usual BF field theory of anyon braiding. \nReferences:\n[1] “Model for fractions\, fluxons\, and free verte excitations”\, JT Kim\, JH Han\, Phys. Rev. B 104\, 115128 (2021)\n[1] “Rank-2 toric code in two dimensions”\, YT Oh\, JT Kim\, EG Moon\, JH Han\, Phys. Rev. B 105\, 045128 (2022)\n[2] “Effective field theory for the exactly solvable stabilizer spin models”\, JT Kim\, YT Oh\, JH Han\, in preparation.\n[3] “Effective field theory of dipolar braiding statistics in two dimensions”\, YT Oh\, JT Kim\, JH Han\, in preparation.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/4-7-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-04.07.2022-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220406T213000
DTEND;TZID=America/New_York:20220406T223000
DTSTAMP:20240301T112919Z
CREATED:20240214T080706Z
LAST-MODIFIED:20240301T112919Z
UID:10002581-1649280600-1649284200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Gopakumar-Vafa type invariants of holomorphic symplectic 4-folds
DESCRIPTION:Abstract: Gromov-Witten invariants of holomorphic symplectic 4-folds vanish and one can consider the corresponding reduced theory. In this talk\, we will explain a definition of Gopakumar-Vafa type invariants for such a reduced theory. These invariants are conjectured to be integers and have alternative interpretations using sheaf theoretic moduli spaces. Our conjecture is proved for the product of two K3 surfaces\, which naturally leads to a closed formula of Fujiki constants of Chern classes of tangent bundles of Hilbert schemes of points on K3 surfaces. On a very general holomorphic symplectic 4-folds of K3^[2] type\, our conjecture provides a Yau-Zaslow type formula for the number of isolated genus 2 curves of minimal degree. Based on joint works with Georg Oberdieck and Yukinobu Toda.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/4-5-2022-joint-harvard-cuhk-ymsc-differential-geometry-seminar/
LOCATION:Virtual
CATEGORIES:Joint Harvard-CUHK-YMSC Differential Geometry
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/20220406_Yalong-CAO_poster.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220406T103000
DTEND;TZID=America/New_York:20220406T120000
DTSTAMP:20240301T064048Z
CREATED:20240214T102826Z
LAST-MODIFIED:20240301T064048Z
UID:10002671-1649241000-1649246400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Late time von Neumann entropy and measurement-induced phase transition
DESCRIPTION:Youtube Video \n  \nAbstract: Characterizing many-body entanglement is one of the most important problems in quantum physics. We present our studies on the steady state von Neumann entropy and its transition in Brownian SYK models. For unitary evolution\, we show that the correlations between different replicas account for the Page curve at late time\, and a permutation group structure emerges in the large-N calculation. In the presence of measurements\, we find a transition of von Neumann entropy from volume-law to area-law by increasing the measurement rate. We show that a proper replica limit can be taken\, which shows that the transition occurs at the point of replica symmetry breaking.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/4-6-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-04.06.2022-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220405T093000
DTEND;TZID=America/New_York:20220405T103000
DTSTAMP:20240304T082856Z
CREATED:20230825T075918Z
LAST-MODIFIED:20240304T082856Z
UID:10001293-1649151000-1649154600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Regularized integrals on Riemann surfaces and correlations functions in 2d chiral CFTs
DESCRIPTION:Abstract: I will report a recent approach of regularizing divergent integrals on configuration spaces of Riemann surfaces\, introduced by Si Li and myself in arXiv:2008.07503\, with an emphasis on genus one cases where modular forms arise naturally. I will then talk about some applications in studying correlation functions in 2d chiral CFTs\, holomorphic anomaly equations\, etc. If time permits\, I will also mention a more algebraic formulation of this notion of regularized integrals in terms of mixed Hodge structures. \nThe talk is partially based on joint works with Si Li.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/regularized-integrals-on-riemann-surfaces-and-correlations-functions-in-2d-chiral-cfts/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Algebraic-Geometry-in-String-Theory-04.05.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220404T100000
DTEND;TZID=America/New_York:20220404T230000
DTSTAMP:20240301T073634Z
CREATED:20230730T180720Z
LAST-MODIFIED:20240301T073634Z
UID:10001147-1649066400-1649113200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Causality constraints on corrections to Einstein gravity
DESCRIPTION:Swampland Seminar \nSpeakers: Simon Caron-Huot (McGill University) and Julio Parra (Caltech) \n\n\nTitle: Causality constraints on corrections to Einstein gravity \n\nAbstract: We study constraints from causality and unitarity on 2→2 graviton scattering in four-dimensional weakly-coupled effective field theories. Together\, causality and unitarity imply dispersion relations that connect low-energy observables to high-energy data. Using such dispersion relations\, we derive two-sided bounds on gravitational Wilson coefficients in terms of the mass M of new higher-spin states. Our bounds imply that gravitational interactions must shut off uniformly in the limit G→0\, and prove the scaling with M expected from dimensional analysis (up to an infrared logarithm). We speculate that causality\, together with the non-observation of gravitationally-coupled higher-spin states at colliders\, severely restricts modifications to Einstein gravity that could be probed by experiments in the near future.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/4-5-2022-swampland-seminar/
LOCATION:Virtual
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220401T090000
DTEND;TZID=America/New_York:20220401T103000
DTSTAMP:20240301T110938Z
CREATED:20240214T084536Z
LAST-MODIFIED:20240301T110938Z
UID:10002596-1648803600-1648809000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Diffusive growth sourced by topological defects
DESCRIPTION:Member Seminar \nSpeaker: Farzan Vafa \nTitle: Diffusive growth sourced by topological defects \nAbstract: In this talk\, we develop a minimal model of morphogenesis of a surface where the dynamics of the intrinsic geometry is diffusive growth sourced by topological defects. We show that a positive (negative) defect can dynamically generate a cone (hyperbolic cone). We analytically explain features of the growth profile as a function of position and time\, and predict that in the presence of a positive defect\, a bump forms with height profile h(t) ~ t^(1/2) for early times t. To incorporate the effect of the mean curvature\, we exploit the fact that for axisymmetric surfaces\, the extrinsic geometry can be deduced entirely by the intrinsic geometry. We find that the resulting stationary geometry\, for polar order and small bending modulus\, is a deformed football.\nWe apply our framework to various biological systems. In an ex-vivo setting of cultured murine neural progenitor cells\, we show that our framework is consistent with the observed cell accumulation at positive defects and depletion at negative defects. In an in-vivo setting\, we show that the defect configuration consisting of a bound +1 defect state\, which is stabilized by activity\, surrounded by two -1/2 defects can create a stationary ring configuration of tentacles\, consistent with observations of a basal marine invertebrate Hydra
URL:https://live-hu-cmsa-222.pantheonsite.io/event/4-1-2022-member-seminar/
LOCATION:Virtual
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220330T140000
DTEND;TZID=America/New_York:20220330T150000
DTSTAMP:20240515T202223Z
CREATED:20230808T183529Z
LAST-MODIFIED:20240515T202223Z
UID:10001209-1648648800-1648652400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Memorizing Transformers
DESCRIPTION:Speaker: Yuhuai Wu\, Stanford and Google \nTitle: Memorizing Transformers \nAbstract: Language models typically need to be trained or fine-tuned in order to acquire new knowledge\, which involves updating their weights. We instead envision language models that can simply read and memorize new data at inference time\, thus acquiring new knowledge immediately. In this talk\, I will discuss how we extend language models with the ability to memorize the internal representations of past inputs. We demonstrate that an approximate NN lookup into a non-differentiable memory of recent (key\, value) pairs improves language modeling across various benchmarks and tasks\, including generic webtext (C4)\, math papers (arXiv)\, books (PG-19)\, code (Github)\, as well as formal theorems (Isabelle). We show that the performance steadily improves when we increase the size of memory up to 262K tokens. We also find that the model is capable of making use of newly defined functions and theorems during test time.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-30-2022-new-technologies-in-mathematics-seminar/
LOCATION:Virtual
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-NTM-Seminar-03.30.2022-1583x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220324T130000
DTEND;TZID=America/New_York:20220324T142000
DTSTAMP:20240122T085257Z
CREATED:20230824T173250Z
LAST-MODIFIED:20240122T085257Z
UID:10001309-1648126800-1648131600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Topological defects drive layer formation in gliding bacteria colonies
DESCRIPTION:Abstract: The developmental cycle of Myxococcus xanthus involves the coordination of many hundreds of thousands of cells aggregating to form mounds known as fruiting bodies. This aggregation process begins with the sequential formation of more and more cell layers. Using three-dimensional confocal imaging we study this layer formation process by observing the formation of holes and second layers within a base monolayer of M xanthus cells. We find that cells align with each other over the majority of the monolayer forming an active nematic liquid crystal with defect point where cell alignment is undefined. We find that new layers and holes form at positive and negative topological defects respectively. We model the cell layer using hydrodynamic modeling and find that this layer and hole formation process is driven by active nematic forces through cell motility and anisotropic substrate friction.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/topological-defects-drive-layer-formation-in-gliding-bacteria-colonies/
LOCATION:Virtual
CATEGORIES:Active Matter Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Active-Matter-Seminar-03.24.22.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220318T093000
DTEND;TZID=America/New_York:20220318T103000
DTSTAMP:20240301T111106Z
CREATED:20240214T084936Z
LAST-MODIFIED:20240301T111106Z
UID:10002599-1647595800-1647599400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Moduli Space of Metric SUSY Graphs
DESCRIPTION:Member Seminar \nSpeaker: Yingying Wu \nTitle: Moduli Space of Metric SUSY Graphs \nAbstract: SUSY curves are algebraic curves with additional supersymmetric or supergeometric structures. In this talk\, I will present the construction of dual graphs of SUSY curves with Neveu–Schwarz and Ramond punctures. Then\, I will introduce the concept of the metrized SUSY graph and the moduli space of the metric SUSY graphs. I will outline its geometric and topological properties\, followed by a discussion on the connection with the classical case.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-18-2022-member-seminar/
LOCATION:Virtual
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220316T103000
DTEND;TZID=America/New_York:20220316T120000
DTSTAMP:20240301T065907Z
CREATED:20240214T104642Z
LAST-MODIFIED:20240301T065907Z
UID:10002679-1647426600-1647432000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Summing Over Bordisms In 2d TQFT
DESCRIPTION:Abstract: Some recent work in the quantum gravity literature has considered what happens when the amplitudes of a TQFT are summed over the bordisms between fixed in-going and out-going boundaries. We will comment on these constructions. The total amplitude\, that takes into account all in-going and out-going boundaries can be presented in a curious factorized form. This talk reports on work done with Anindya Banerjee and is based on the paper on the e-print arXiv  2201.00903.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-16-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-03.16.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220315T093000
DTEND;TZID=America/New_York:20220315T103000
DTSTAMP:20240304T082952Z
CREATED:20230825T075742Z
LAST-MODIFIED:20240304T082952Z
UID:10001292-1647336600-1647340200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:2-categorical 3d mirror symmetry
DESCRIPTION:Abstract: It is by now well-known that mirror symmetry may be expressed as an equivalence between categories associated to dual Kahler manifolds. Following a proposal of Teleman\, we inaugurate a program to understand 3d mirror symmetry as an equivalence between 2-categories associated to dual holomorphic symplectic stacks. We consider here the abelian case\, where our theorem expresses the 2-category of spherical functors as a 2-category of coherent sheaves of categories. Applications include categorifications of hypertoric category O and of many related constructions in representation theory. This is joint work with Justin Hilburn and Aaron Mazel-Gee.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-categorical-3d-mirror-symmetry/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220310T200000
DTEND;TZID=America/New_York:20220310T213000
DTSTAMP:20240813T163724Z
CREATED:20240214T104900Z
LAST-MODIFIED:20240813T163724Z
UID:10002680-1646942400-1646947800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Resonant side-jump thermal Hall effect of phonons coupled to dynamical defects
DESCRIPTION:Abstract: We present computations of the thermal Hall coefficient of phonons scattering off defects with multiple energy levels. Using a microscopic formulation based on the Kubo formula\, we find that the leading contribution perturbative in the phonon-defect coupling is of the ‘side-jump’ type\, which is proportional to the phonon lifetime. This contribution is at resonance when the phonon energy equals a defect level spacing. Our results are obtained for different defect models\, and include models of an impurity quantum spin in the presence of quasi-static magnetic order with an isotropic Zeeman coupling to the applied field. \nThis work is based on arxiv: 2201.11681
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-10-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-03.10.2022-1544x2048-1-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220309T103000
DTEND;TZID=America/New_York:20220309T120000
DTSTAMP:20240301T070302Z
CREATED:20240214T105142Z
LAST-MODIFIED:20240301T070302Z
UID:10002682-1646821800-1646827200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Anomalies\, topological insulators and Kaehler-Dirac fermions
DESCRIPTION:Abstract: Motivated by a puzzle arising from recent work on staggered lattice fermions we introduce Kaehler-Dirac fermions and describe their connection both to Dirac fermions and staggered fermions. We show that they suffer from a gravitational anomaly that breaks a chiral U(1) symmetry specific to Kaehler-Dirac fermions down to Z_4 in any even dimension. In odd dimensions we show that the effective theory that results from integrating out massive Kaehler-Dirac fermions is a topological gravity theory. Such theories generalize Witten’s construction of (2+1) gravity as a Chern Simons theory. In the presence of a domain wall massless modes appear on the wall which can be consistently coupled to gravity due to anomaly inflow from the bulk gravitational theory. Much of this story parallels the usual discussion of topological insulators. The key difference is that the twisted chiral symmetry and anomaly structure of Kaehler-Dirac theories survives intact under discretization and governs the behavior of the lattice models. $Z_4$ invariant four fermion interactions can be used to gap out states in such theories without breaking symmetries and in flat space yields the known constraints on the number of Majorana fermions needed symmetric mass generation namely eight and sixteen Majorana spinors in two and four dimensions.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-9-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-03.09.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220307T100000
DTEND;TZID=America/New_York:20220307T113000
DTSTAMP:20240301T073931Z
CREATED:20230730T175629Z
LAST-MODIFIED:20240301T073931Z
UID:10001144-1646647200-1646652600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:4d strings at strong coupling
DESCRIPTION:Speakers: Fernando Marchesano (UAM-CSIC\, Madrid)  and Max Wiesner (Harvard CMSA)\n\n\n\nTitle: 4d strings at strong coupling\n\n\nAs usual\, the format will be 45 min talk + 30 min discussion\, to encourage participation from the audience.\nLooking forward to seeing you there!
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-7-2022-swampland-seminar/
LOCATION:Virtual
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220303T093000
DTEND;TZID=America/New_York:20220303T110000
DTSTAMP:20240813T163614Z
CREATED:20240214T105412Z
LAST-MODIFIED:20240813T163614Z
UID:10002684-1646299800-1646305200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Callan Rubakov Effect and Higher Charge Monopoles
DESCRIPTION:Abstract: In this talk we will discuss the interaction between magnetic monopoles and massless fermions. In the 1980’s Callan and Rubakov showed that in the simplest example and that fermion-monopole interactions catalyze proton decay in GUT completions of the standard model. Here we will explain how fermions in general representations interact with general spherically symmetric monopoles and classify the types of symmetries that are broken: global symmetries with ABJ-type anomalies.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-3-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-03.03.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220302T140000
DTEND;TZID=America/New_York:20220302T150000
DTSTAMP:20240517T193649Z
CREATED:20230808T182233Z
LAST-MODIFIED:20240517T193649Z
UID:10001206-1646229600-1646233200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Scaling Laws and Their Implications for Coding AI
DESCRIPTION:Speaker: Jared Kaplan\, Johns Hopkins Dept. of Physics & Astronomy \nTitle: Scaling Laws and Their Implications for Coding AI \nAbstract:  Scaling laws and associated downstream trends can be used as an organizing principle when thinking about current and future ML progress.  I will briefly review scaling laws for generative models in a number of domains\, emphasizing language modeling.  Then I will discuss scaling results for transfer from natural language to code\, and results on python programming performance from “codex” and other models.  If there’s time I’ll discuss prospects for the future — limitations from dataset sizes\, and prospects for RL and other techniques.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/3-2-2022-new-technologies-in-mathematics-seminar/
LOCATION:Virtual
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/03.2.2022-1553x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220302T093000
DTEND;TZID=America/New_York:20220302T103000
DTSTAMP:20240222T171906Z
CREATED:20240214T040557Z
LAST-MODIFIED:20240222T171906Z
UID:10002521-1646213400-1646217000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Dimers and webs
DESCRIPTION:Speaker: Richard Kenyon (Yale) \nTitle: Dimers and webs \nAbstract: We consider SL_n-local systems on graphs on surfaces and show how the associated Kasteleyn matrix can be used to compute probabilities of various topological events involving the overlay of n independent dimer covers (or “n-webs”). \nThis is joint work with Dan Douglas and Haolin Shi.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/dimers-and-webs/
LOCATION:Virtual
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/02CMSA-Colloquium-03.02.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220301T093000
DTEND;TZID=America/New_York:20220301T103000
DTSTAMP:20240304T083139Z
CREATED:20230825T075625Z
LAST-MODIFIED:20240304T083139Z
UID:10001291-1646127000-1646130600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Virtual localization for Artin stacks
DESCRIPTION:Abstract: This is a report about work in progress with: Adeel Khan\, Aloysha Latyntsev\, Hyeonjun Park and Charanya Ravi. We will describe a virtual Atiyah-Bott formula for Artin stacks.  In the Deligne-Mumford case our methods allow us to remove the global resolution hypothesis for the virtual normal bundle.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/virtual-localization-for-artin-stacks/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Algebraic-Geometry-in-String-Theory-02.22.2022-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220224T130000
DTEND;TZID=America/New_York:20220224T140000
DTSTAMP:20240304T051713Z
CREATED:20240214T080100Z
LAST-MODIFIED:20240304T051713Z
UID:10002576-1645707600-1645711200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Extreme Black Holes: Anabasis and Accidental Symmetry
DESCRIPTION:  \n \n  \nSpeaker: Achilleas Porfyriadis\, Harvard Black Hole Initiative \nTitle: Extreme Black Holes: Anabasis and Accidental Symmetry \nAbstract: The near-horizon region of black holes near extremality is universally AdS_2-like. In this talk I will concentrate on the simplest example of  AdS_2 x S^2 as the near-horizon of (near-)extreme Reissner-Nordstrom. I will first explain the SL(2)transformation properties of the spherically symmetric linear perturbations of  AdS_2 x S^2 and show how their backreaction leads to the Reissner-Nordstrom black hole. This backreaction with boundary condition change is called an anabasis. I will then show that the linear Einstein equation near AdS_2 x S^2\, with or without additional matter\, enjoys an accidental symmetry that may be thought of as an on-shell large diffeomorphism of AdS_2.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-24-2022-general-relativity-seminar/
LOCATION:Virtual
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220223T093000
DTEND;TZID=America/New_York:20220223T103000
DTSTAMP:20240501T204515Z
CREATED:20240214T040816Z
LAST-MODIFIED:20240501T204515Z
UID:10002522-1645608600-1645612200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Holographic Cone of Average Entropies and Universality of Black Holes
DESCRIPTION:Speaker: Bartek Czech\, Tsinghua University \nTitle: Holographic Cone of Average Entropies and Universality of Black Holes \nAbstract:  In the AdS/CFT correspondence\, the holographic entropy cone\, which identifies von Neumann entropies of CFT regions that are consistent with a semiclassical bulk dual\, is currently known only up to n=5 regions. I explain that average\nentropies of p-partite subsystems can be checked for consistency with a semiclassical bulk dual far more easily\, for an arbitrary number of regions n. This analysis defines the “Holographic Cone of Average\nEntropies” (HCAE). I conjecture the exact form of HCAE\, and find that it has the following properties: (1) HCAE is the simplest it could be\, namely it is a simplicial cone. (2) Its extremal rays represent stages of thermalization (black hole formation). (3) In a time-reversed picture\, the extremal rays of HCAE represent stages of unitary black hole evaporation\, as stipulated by the island solution of the black hole information paradox. (4) HCAE is bound by a novel\, infinite family of holographic entropy inequalities. (5) HCAE is the simplest it could be also in its dependence on the number of regions n\, namely its bounding inequalities are n-independent. (6) In a precise sense I describe\, the bounding inequalities of HCAE unify (almost) all previously discovered holographic inequalities and strongly constrain future inequalities yet to be discovered. I also sketch an interpretation of HCAE in terms of error correction and the holographic Renormalization Group. The big lesson that HCAE seems to be teaching us is about the universality of black hole physics.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/collloquium_22323/
LOCATION:Virtual
CATEGORIES:Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220222T093000
DTEND;TZID=America/New_York:20220222T103000
DTSTAMP:20240304T083230Z
CREATED:20230825T075425Z
LAST-MODIFIED:20240304T083230Z
UID:10001290-1645522200-1645525800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Higgs-Coulomb correspondence in abelian GLSM
DESCRIPTION:Abstract: We construct a certain type of Gauged Linear Sigma Model quasimap invariants that generalize the original ones and are easier to compute. Higgs-Coulomb correspondence provides identification of generating functions of our invariants with certain analytic functions that can be represented as generalized inverse Mellin transforms. Analytic continuation of these functions provides wall-crossing results for GLSM and generalizes Landau- Ginzburg/Calabi-Yau correspondence. The talk is based on a joint work in progress with Melissa Liu.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/higgs-coulomb-correspondence-in-abelian-glsm/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Algebraic-Geometry-in-String-Theory-02.22.2022-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220217T093000
DTEND;TZID=America/New_York:20220217T110000
DTSTAMP:20240301T071849Z
CREATED:20240214T094917Z
LAST-MODIFIED:20240301T071849Z
UID:10002646-1645090200-1645095600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Spin-cobordisms\, surgeries and fermionic modular bootstrap
DESCRIPTION:Speaker: Andrea Grigoletto (SISSA & INFN) \nTitle: Spin-cobordisms\, surgeries and fermionic modular bootstrap \nAbstract: ‘tHooft anomalies of anomalous systems can be described via anomaly inflow by invertible theories living in one dimension higher. Thanks to this it is possible to provide a general method to determine modular transformations of anomalous 2d fermionic CFTs with general discrete symmetry group $G^f$. As a by-product\, one is able to determine explicit combinatorial expressions of spin-cobordism invariants in terms of Dehn-surgery representation of 3-manifolds. The same techniques also provide a method for evaluating the map from the group classifying free fermionic anomalies to the group of anomalies in interacting theories. As examples\, we work out the details for some symmetry groups\, including non-abelian ones\, and\, as an application\, we use these results to bootstrap the spectrum of the theories with a given anomaly.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-17-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-02.17.2022-1544x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220216T140000
DTEND;TZID=America/New_York:20220216T150000
DTSTAMP:20240515T205523Z
CREATED:20230808T181915Z
LAST-MODIFIED:20240515T205523Z
UID:10001205-1645020000-1645023600@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Bootstrapping hyperbolic manifolds
DESCRIPTION:Speaker: James Bonifacio\, Cambridge DAMTP \nTitle: Bootstrapping hyperbolic manifolds \nAbstract: Hyperbolic manifolds are a class of Riemannian manifolds that are important in mathematics and physics\, playing a prominent role in topology\, number theory\, and string theory. Associated with a given hyperbolic metric is a sequence of numbers corresponding to the discrete eigenvalues of the Laplace-Beltrami operator. While these eigenvalues usually cannot be calculated exactly\, they can be found numerically and must also satisfy various bounds. In this talk\, I will discuss a new approach for finding numerical bounds on the eigenvalues of closed hyperbolic manifolds using general consistency conditions and semidefinite programming\, inspired by the approach of the conformal bootstrap from physics. Although these bootstrap bounds follow from seemingly trivial consistency conditions\, they are surprisingly strong and are sometimes almost saturated by actual manifolds; for example\, one such bound implies that the first nonzero eigenvalue of a closed hyperbolic surface must be less than 3.83890\, and this is very close to being saturated by a particular genus-2 surface called the Bolza surface. I will show how to derive this and other bounds and will discuss some possible future directions for this approach.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-16-2022-new-technologies-in-mathematics-seminar/
LOCATION:Virtual
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-NTM-Seminar-02.16.2022-1553x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220216T103000
DTEND;TZID=America/New_York:20220216T120000
DTSTAMP:20240304T102225Z
CREATED:20240213T112617Z
LAST-MODIFIED:20240304T102225Z
UID:10002497-1645007400-1645012800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Topological Quantum Gravity and the Ricci Flow – Part I
DESCRIPTION:Speaker: Petr Hořava (UC Berkeley) \nTitle: Topological Quantum Gravity and the Ricci Flow – Part I \nAbstract: In this sequence of talks\, I will describe our work with Alexander Frenkel and Stephen Randall\, in which we presented a novel topological quantum gravity\, relating three previously unrelated fields:  Topological quantum field theories (of the cohomological type)\, the theory of Ricci flows on Riemannian manifolds\, and nonrelativistic quantum gravity.  The remarkable richness of results produced in the recent decades by mathematicians studying the Ricci flow promises to shed new light on the physics of the path integral in quantum gravity (at least in the topological regime).  In the opposite direction\, the techniques of quantum field theory and path integrals may end up putting some of the mathematical results in the Ricci flow theory in a new perspective as well.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-02.16.2022-1544x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220216T093000
DTEND;TZID=America/New_York:20220216T103000
DTSTAMP:20240425T182937Z
CREATED:20240213T112726Z
LAST-MODIFIED:20240425T182937Z
UID:10002499-1645003800-1645007400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Kobayashi-Hitchin correspondences for harmonic bundles and monopoles
DESCRIPTION:Speaker: Takuro Mochizuki (Kyoto University) \nTitle: Kobayashi-Hitchin correspondences for harmonic bundles and monopoles \nAbstract:  In 1960’s\, Narasimhan and Seshadri discovered the equivalence between irreducible unitary flat bundles and stable bundles of degree $0$ on compact Riemann surfaces. In 1980’s\, Donaldson\, Uhlenbeck and Yau generalized it to the equivalence between irreducible Hermitian-Einstein bundles and stable bundles on smooth projective varieties. This is a surprising bridge connecting differential geometry and algebraic geometry. Since then\, many interesting generalizations have been studied. \nIn this talk\, we would like to review a stream in the study of such correspondences for Higgs bundles\, integrable connections\, $D$-modules and periodic monopoles.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-16-2022-cmsa-colloquium/
LOCATION:Virtual
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-Colloquium-02.16.2022.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220215T093000
DTEND;TZID=America/New_York:20220215T103000
DTSTAMP:20240304T083319Z
CREATED:20230818T054001Z
LAST-MODIFIED:20240304T083319Z
UID:10001289-1644917400-1644921000@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Virtual Coulomb branch and quantum K-theory
DESCRIPTION:Abstract: In this talk\, I will introduce a virtual variant of the quantized Coulomb branch constructed by Braverman-Finkelberg-Nakajima\, where the convolution product is modified by a virtual intersection. The resulting virtual Coulomb branch acts on the moduli space of quasimaps into the holomorphic symplectic quotient T^*N//G. When G is abelian\, over the torus fixed points\, this representation is a Verma module. The vertex function\, a K-theoretic enumerative invariant introduced by A. Okounkov\, can be expressed as a Whittaker function of the algebra. The construction also provides a description of the quantum q-difference module. As an application\, this gives a proof of the invariance of the quantum q-difference module under variation of GIT.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/virtual-coulomb-branch-and-quantum-k-theory/
LOCATION:Virtual
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220210T093000
DTEND;TZID=America/New_York:20220210T110000
DTSTAMP:20240301T072127Z
CREATED:20240214T100805Z
LAST-MODIFIED:20240301T072127Z
UID:10002658-1644485400-1644490800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:The global structure of the Standard Model and new nonperturbative processes
DESCRIPTION:Speaker: Mohamed Anber (Durham University) \nTitle: The global structure of the Standard Model and new nonperturbative processes \nAbstract: It is well-established that the Standard Model (SM) of particle physics is based on su(3)Xsu(2)Xu(1) Lie-algebra. What is less appreciated\, however\, is that SM accommodates a Z_6 1-form global symmetry.  Gauging this symmetry\, or a subgroup of it\, changes the global structure of the SM gauge group and amounts to summing over sectors of instantons with fractional topological charges. After a brief review of the concept of higher-form symmetries\, I will explain the origin of the Z_6 1-form symmetry and construct the explicit fractional-instanton solutions on compact manifolds. The new instantons mediate baryon-number and lepton-number violating processes\, which can win over the weak BPST-instanton processes\, provided that SM accommodates extra hyper-charged particles above the TeV scale. I will also comment on the cosmological aspects of the new solutions.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-10-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-02.10.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220209T200000
DTEND;TZID=America/New_York:20220209T213000
DTSTAMP:20240301T072509Z
CREATED:20240214T103129Z
LAST-MODIFIED:20240301T072509Z
UID:10002674-1644436800-1644442200@live-hu-cmsa-222.pantheonsite.io
SUMMARY:On the absence of global anomalies of heterotic string theories
DESCRIPTION:Speaker: Yuji Tachikawa (Kavli IPMU\, U Tokyo) \nTitle: On the absence of global anomalies of heterotic string theories \nAbstract: Superstring theory as we know it started from the discovery by Green and Schwarz in 1984 that the perturbative anomalies of heterotic strings miraculously cancel. But the cancellation of global anomalies of heterotic strings remained an open problem for a long time. \nIn this talk\, I would like to report how this issue was finally resolved last year\, by combining two developments outside of string theory. Namely\, on one hand\, the study of topological phases in condensed matter theory has led to our vastly improved understanding of the general form of global anomalies. On the other hand\, the study of topological modular forms in algebraic topology allows us to constrain the data of heterotic worldsheet theories greatly\, as far as their contributions to the anomalies are concerned. Putting them together\, it is possible to show that global anomalies of heterotic strings are always absent. \nThe talk is based on https://arxiv.org/abs/2103.12211 and https://arxiv.org/abs/2108.13542 \, in collaboration with Mayuko Yamashita.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-9-2022-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/jpeg:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-QMMP-02.09.2022-1544x2048-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220209T140000
DTEND;TZID=America/New_York:20220209T150000
DTSTAMP:20240517T193404Z
CREATED:20230808T181534Z
LAST-MODIFIED:20240517T193404Z
UID:10001204-1644415200-1644418800@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Toward Demystifying Transformers and Attention
DESCRIPTION:Speaker: Ben Edelman\, Harvard Computer Science \nTitle: Toward Demystifying Transformers and Attention \nAbstract: Over the past several years\, attention mechanisms (primarily in the form of the Transformer architecture) have revolutionized deep learning\, leading to advances in natural language processing\, computer vision\, code synthesis\, protein structure prediction\, and beyond. Attention has a remarkable ability to enable the learning of long-range dependencies in diverse modalities of data. And yet\, there is at present limited principled understanding of the reasons for its success. In this talk\, I’ll explain how attention mechanisms and Transformers work\, and then I’ll share the results of a preliminary investigation into why they work so well. In particular\, I’ll discuss an inductive bias of attention that we call sparse variable creation: bounded-norm Transformer layers are capable of representing sparse Boolean functions\, with statistical generalization guarantees akin to sparse regression.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/2-9-2022-new-technologies-in-mathematics-seminar/
LOCATION:Virtual
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/png:https://live-hu-cmsa-222.pantheonsite.io/media/CMSA-NTM-Seminar-02.09.2022-1553x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20220208T213000
DTEND;TZID=America/New_York:20220208T223000
DTSTAMP:20240501T205116Z
CREATED:20240214T041520Z
LAST-MODIFIED:20240501T205116Z
UID:10002524-1644355800-1644359400@live-hu-cmsa-222.pantheonsite.io
SUMMARY:Tetrahedron instantons and M-theory indices
DESCRIPTION:Colloquium \nSpeaker: Wenbin Yan (Tsinghua University) \nTitle: Tetrahedron instantons and M-theory indices \nAbstract: We introduce and study tetrahedron instantons. Physically they capture instantons on $\mathbb{C}^{3}$ in the presence of the most general intersecting codimension-two supersymmetric defects. In this talk\, we will review instanton moduli spaces\, explain the construction\, moduli space and partition functions of tetrahedron instantons. We will also point out possible relations with M-theory index which could be a generalization of Gupakuma-Vafa theory.
URL:https://live-hu-cmsa-222.pantheonsite.io/event/tetrahedron-instantons-and-m-theory-indices/
LOCATION:Virtual
CATEGORIES:Colloquium
END:VEVENT
END:VCALENDAR