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BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211102T130000
DTEND;TZID=America/New_York:20211102T140000
DTSTAMP:20260516T225324
CREATED:20240214T052811Z
LAST-MODIFIED:20240304T062921Z
UID:10002538-1635858000-1635861600@cmsa.fas.harvard.edu
SUMMARY:Gauss-Manin connection in disguise: Quasi Jacobi forms of index zero
DESCRIPTION:Abstract: We consider the moduli space of abelian varieties with two marked points and a frame of the relative de Rham cohomology with boundary at these points compatible with its mixed Hodge structure. Such a moduli space gives a natural algebro-geometric framework for higher genus quasi Jacobi forms of index zero and their differential equations which are given as vector fields. In the case of elliptic curves we compute explicitly the Gauss-Manin connection and such vector fields. This is a joint work with J. Cao and R. Villaflor. (arXiv:2109.00587)
URL:https://cmsa.fas.harvard.edu/event/gauss-manin-connection-in-disguise-quasi-jacobi-forms-of-index-zero/
LOCATION:MA
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211103T093000
DTEND;TZID=America/New_York:20211103T103000
DTSTAMP:20260516T225324
CREATED:20240212T104227Z
LAST-MODIFIED:20240502T152621Z
UID:10002003-1635931800-1635935400@cmsa.fas.harvard.edu
SUMMARY:Hitchin map as spectrum of equivariant cohomology
DESCRIPTION:Speaker: Tamás Hausel (IST Austria) \nTitle: Hitchin map as spectrum of equivariant cohomology \nAbstract: We will explain how to model the Hitchin integrable system on a certain Lagrangian upward flow as the spectrum of equivariant cohomology of a Grassmannian.
URL:https://cmsa.fas.harvard.edu/event/hitchin-map-as-spectrum-of-equivariant-cohomology/
LOCATION:MA
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-11.03.21-791x1024-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211103T140000
DTEND;TZID=America/New_York:20211103T153000
DTSTAMP:20260516T225324
CREATED:20240214T102259Z
LAST-MODIFIED:20240301T091205Z
UID:10002667-1635948000-1635953400@cmsa.fas.harvard.edu
SUMMARY:Non-Invertible Duality Defects in 3+1 Dimensions
DESCRIPTION:Speaker: Clay Cordova (U Chicago) \nTitle: Non-Invertible Duality Defects in 3+1 Dimensions \nAbstract:  For any quantum system invariant under gauging a higher-form global symmetry\, we construct a non-invertible topological defect by gauging in only half of spacetime. This generalizes the Kramers-Wannier duality line in 1+1 dimensions to higher spacetime dimensions. We focus on the case of a one-form symmetry in 3+1 dimensions and determine the fusion rule. From modular invariance and a direct analysis of one-form symmetry-protected topological phases\, we show that the existence of certain kinds of duality defects is intrinsically incompatible with a trivially gapped phase. By further assuming time-reversal symmetry\, we find that the presence of certain duality defects implies that the low-energy phase has to be gapless unless the one-form symmetry is spontaneously broken. We give an explicit realization of this duality defect in the free Maxwell theory where the duality defect is realized by a Chern-Simons coupling between the gauge fields from the two sides.
URL:https://cmsa.fas.harvard.edu/event/11-3-3021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211103T171200
DTEND;TZID=America/New_York:20211103T181200
DTSTAMP:20260516T225324
CREATED:20240214T094241Z
LAST-MODIFIED:20240813T155909Z
UID:10002643-1635959520-1635963120@cmsa.fas.harvard.edu
SUMMARY:When Computer Algebra Meets Satisfiability: A New Approach to Combinatorial Mathematics
DESCRIPTION:Speakers: Curtis Bright\, School of Computer Science\, University of Windsor and Vijay Ganesh\, Dept. of Electrical and Computer Engineering\, University of Waterloo \nTitle: When Computer Algebra Meets Satisfiability: A New Approach to Combinatorial Mathematics \nAbstract: Solvers for the Boolean satisfiability (SAT) problem have been increasingly used to resolve problems in mathematics due to their excellent search algorithms.  This talk will describe a new method for mathematical search that couples SAT solvers with computer algebra systems (CAS)\, thereby combining the expressiveness of CASs with the search power of SAT solvers.  This paradigm has led to a number of results on long-standing mathematical questions such as the first computer-verifiable resolution of Lam’s problem and the discovery of a new infinite class of Williamson matrices.
URL:https://cmsa.fas.harvard.edu/event/11-3-21-cmsa-new-technologies-in-mathematics/
LOCATION:MA
CATEGORIES:New Technologies in Mathematics Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-NTM-Seminar-11.03.21.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211104T103000
DTEND;TZID=America/New_York:20211104T120000
DTSTAMP:20260516T225324
CREATED:20240214T101922Z
LAST-MODIFIED:20240301T091041Z
UID:10002665-1636021800-1636027200@cmsa.fas.harvard.edu
SUMMARY:Fusion Category Symmetries in Quantum Field Theory
DESCRIPTION:Speaker: Yifan Wang (NYU) \nTitle: Fusion Category Symmetries in Quantum Field Theory \nAbstract: Topological defects provide a modern perspective on symmetries in quantum field theory. They generalize the familiar inverti \n \nble symmetries described by groups to non-invertible symmetries described by fusion categories. Such generalized symmetries are ubiquitous in quantum field theory and provide new constraints on renormalization group flows and the IR phase diagram. In this talk I’ll review some recent progress in identifying and understanding fusion category symmetries in 1+1d conformal field theories. Time permitting\, I’ll also comment on higher dimensional generalizations.
URL:https://cmsa.fas.harvard.edu/event/11-4-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211104T130000
DTEND;TZID=America/New_York:20211104T140000
DTSTAMP:20260516T225324
CREATED:20240214T073728Z
LAST-MODIFIED:20240304T054749Z
UID:10002565-1636030800-1636034400@cmsa.fas.harvard.edu
SUMMARY:The stability of charged black holes
DESCRIPTION:Abstract: Black holes solutions in General Relativity are parametrized by their mass\, spin and charge. In this talk\, I will motivate why the charge of black holes adds interesting dynamics to solutions of the Einstein equation thanks to the interaction between gravitational and electromagnetic radiation. Such radiations are solutions of a system of coupled wave equations with a symmetric structure which allows to define a combined energy-momentum tensor for the system. Finally\, I will show how this physical-space approach is resolutive in the most general case of Kerr-Newman black hole\, where the interaction between the radiations prevents the separability in modes.
URL:https://cmsa.fas.harvard.edu/event/11-4-2021-general-relativity-seminar/
LOCATION:MA
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211104T184600
DTEND;TZID=America/New_York:20211104T204600
DTSTAMP:20260516T225324
CREATED:20240214T080650Z
LAST-MODIFIED:20240301T103919Z
UID:10002580-1636051560-1636058760@cmsa.fas.harvard.edu
SUMMARY:11/4/21 CMSA Interdisciplinary Science Seminar
DESCRIPTION:Title: Exploring Invertibility in Image Processing and Restoration \nAbstract: Today’s smartphones have enabled numerous stunning visual effects from denoising to beautification\, and we can share high-quality JPEG images easily on the internet\, but it is still valuable for photographers and researchers to keep the original raw camera data for further post-processing (e.g.\, retouching) and analysis. However\, the huge size of raw data hinders its popularity in practice\, so can we almost perfectly restore the raw data from a compressed RGB image and thus avoid storing any raw data? This question leads us to design an invertible image signal processing pipeline. Then we further explore invertibility in other image processing and restoration tasks\, including image compression\, reversible image conversion (e.g.\, image-to-video conversion)\, and embedding novel views in a single JPEG image. We demonstrate that customized invertible neural networks are highly effective in these inherently non-invertible tasks.
URL:https://cmsa.fas.harvard.edu/event/11-4-21-cmsa-interdisciplinary-science-seminar/
LOCATION:MA
CATEGORIES:Interdisciplinary Science Seminar
ATTACH;FMTTYPE=image/jpeg:https://cmsa.fas.harvard.edu/media/CMSA-Interdisciplinary-Science-Seminar-11.04.21-1583x2048-1-1.jpg
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211105T093000
DTEND;TZID=America/New_York:20211105T113000
DTSTAMP:20260516T225324
CREATED:20240214T073106Z
LAST-MODIFIED:20240301T111130Z
UID:10002562-1636104600-1636111800@cmsa.fas.harvard.edu
SUMMARY:The Greene-Plesser Construction Revisited
DESCRIPTION:Member Seminar  \nSpeaker: Chuck Doran \nTitle: The Greene-Plesser Construction Revisited \nAbstract: The first known construction of mirror pairs of Calabi-Yau manifolds was the Greene-Plesser “quotient and resolve” procedure which applies to pencils of hypersurfaces in projective space. We’ll review this approach\, uncover the hints it gives for some more general mirror constructions\, and describe a brand-new variant that applies to pencils of hypersurfaces in Grassmannians. This last is joint work with Tom Coates and Elana Kalashnikov (arXiv:2110.0727).
URL:https://cmsa.fas.harvard.edu/event/11-5-2021-member-seminar/
LOCATION:MA
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211109T103000
DTEND;TZID=America/New_York:20211109T113000
DTSTAMP:20260516T225324
CREATED:20240213T062822Z
LAST-MODIFIED:20240304T062818Z
UID:10002112-1636453800-1636457400@cmsa.fas.harvard.edu
SUMMARY:Cosection localization for virtual fundamental classes of d-manifolds and Donaldson-Thomas invariants of Calabi-Yau fourfolds
DESCRIPTION:Abstract: Localization by cosection\, first introduced by Kiem-Li in 2010\, is one of the fundamental techniques used to study invariants in complex enumerative geometry. Donaldson-Thomas (DT) invariants counting sheaves on Calabi-Yau fourfolds were first defined by Borisov-Joyce in 2015 by combining derived algebraic and differential geometry.\nIn this talk\, we develop the theory of cosection localization for derived manifolds in the context of derived differential geometry of Joyce. As a consequence\, we also obtain cosection localization results for (-2)-shifted symplectic derived schemes. This provides a cosection localization formalism for the Borisov-Joyce DT invariant. As an immediate application\, the stable pair invariants of hyperkähler fourfolds\, constructed by Maulik-Cao-Toda\, vanish\, as expected.
URL:https://cmsa.fas.harvard.edu/event/cosection-localization-for-virtual-fundamental-classes-of-d-manifolds-and-donaldson-thomas-invariants-of-calabi-yau-fourfolds/
LOCATION:MA
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-Seminar-11.09.21-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211109T103000
DTEND;TZID=America/New_York:20211109T223000
DTSTAMP:20260516T225324
CREATED:20240304T062554Z
LAST-MODIFIED:20240304T062554Z
UID:10002897-1636453800-1636497000@cmsa.fas.harvard.edu
SUMMARY:Cosection localization for virtual fundamental classes of d-manifolds and Donaldson-Thomas invariants of Calabi-Yau fourfolds
DESCRIPTION:Speaker: Michail Savvas\, UT Austin \nTitle: Cosection localization for virtual fundamental classes of d-manifolds and Donaldson-Thomas invariants of Calabi-Yau fourfolds \nAbstract: Localization by cosection\, first introduced by Kiem-Li in 2010\, is one of the fundamental techniques used to study invariants in complex enumerative geometry. Donaldson-Thomas (DT) invariants counting sheaves on Calabi-Yau fourfolds were first defined by Borisov-Joyce in 2015 by combining derived algebraic and differential geometry.\nIn this talk\, we develop the theory of cosection localization for derived manifolds in the context of derived differential geometry of Joyce. As a consequence\, we also obtain cosection localization results for (-2)-shifted symplectic derived schemes. This provides a cosection localization formalism for the Borisov-Joyce DT invariant. As an immediate application\, the stable pair invariants of hyperkähler fourfolds\, constructed by Maulik-Cao-Toda\, vanish\, as expected. \n\n\n\nevent\n\n\nOrganizer: Seminars
URL:https://cmsa.fas.harvard.edu/event/11-9-21-cmsa-algebraic-geometry-in-string-theory-seminar/
LOCATION:MA
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211110T093000
DTEND;TZID=America/New_York:20211110T103000
DTSTAMP:20260516T225324
CREATED:20240212T104422Z
LAST-MODIFIED:20240502T153432Z
UID:10002006-1636536600-1636540200@cmsa.fas.harvard.edu
SUMMARY:Hypergraph decompositions and their applications
DESCRIPTION:Speaker: Peter Keevash\, Oxford \nTitle: Hypergraph decompositions and their applications \nAbstract: Many combinatorial objects can be thought of as a hypergraph decomposition\, i.e. a partition of (the edge set of) one hypergraph into (the edge sets of) copies of some other hypergraphs. For example\, a Steiner Triple System is equivalent to a decomposition of a complete graph into triangles. In general\, Steiner Systems are equivalent to decompositions of complete uniform hypergraphs into other complete uniform hypergraphs (of some specified sizes). The Existence Conjecture for Combinatorial Designs\, which I proved in 2014\, states that\, bar finitely many exceptions\, such decompositions exist whenever the necessary ‘divisibility conditions’ hold. I also obtained a generalisation to the quasirandom setting\, which implies an approximate formula for the number of designs; in particular\, this resolved Wilson’s Conjecture on the number of Steiner Triple Systems. A more general result that I proved in 2018 on decomposing lattice-valued vectors indexed by labelled complexes provides many further existence and counting results for a wide range of combinatorial objects\, such as resolvable designs (the generalised form of Kirkman’s Schoolgirl Problem)\, whist tournaments or generalised Sudoku squares. In this talk\, I plan to review this background and then describe some more recent and ongoing applications of these results and developments of the ideas behind them. \n 
URL:https://cmsa.fas.harvard.edu/event/hypergraph-decompositions-and-their-applications/
LOCATION:MA
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-11.10.21-791x1024-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211110T160000
DTEND;TZID=America/New_York:20211110T170000
DTSTAMP:20260516T225324
CREATED:20240213T063355Z
LAST-MODIFIED:20240213T063355Z
UID:10002116-1636560000-1636563600@cmsa.fas.harvard.edu
SUMMARY:Higher rank DT theory from rank 1
DESCRIPTION:Abstract: Fix a Calabi-Yau 3-fold X. Its DT invariants count stable bundles and sheaves on X. The generalised DT invariants of Joyce-Song count semistable bundles and sheaves on X. I will describe work with Soheyla Feyzbakhsh showing these generalised DT invariants in any rank r can be written in terms of rank 1 invariants. By the MNOP conjecture the latter are determined by the GW invariants of X. Along the way we also show they are determined by rank 0 invariants counting sheaves supported on surfaces in X. These invariants are predicted by S-duality to be governed by (vector-valued\, mock) modular forms.
URL:https://cmsa.fas.harvard.edu/event/higher-rank-dt-theory-from-rank-1/
LOCATION:MA
CATEGORIES:Joint Harvard-CUHK-YMSC Differential Geometry
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/20211110_Richard-Thomas_poster-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211111T130000
DTEND;TZID=America/New_York:20211111T140000
DTSTAMP:20260516T225324
CREATED:20240214T074127Z
LAST-MODIFIED:20240304T054620Z
UID:10002567-1636635600-1636639200@cmsa.fas.harvard.edu
SUMMARY:Sharp decay for Teukolsky equation in Kerr spacetimes
DESCRIPTION:Abstract: Teukolsky equation in Kerr spacetimes governs the dynamics of the spin $s$ components\, $s=0\, \pm 1\, \pm 2$ corresponding to the scalar field\, the Maxwell field\, and the linearized gravity\, respectively. I will discuss recent joint work with L. Zhang on proving the precise asymptotic profiles for these spin $s$ components in Schwarzschild and Kerr spacetimes.
URL:https://cmsa.fas.harvard.edu/event/11-11-2021-general-relativity-seminar/
LOCATION:MA
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211111T130000
DTEND;TZID=America/New_York:20211111T143000
DTSTAMP:20260516T225324
CREATED:20240213T112818Z
LAST-MODIFIED:20240304T084803Z
UID:10002501-1636635600-1636641000@cmsa.fas.harvard.edu
SUMMARY:Nonreciprocal matter: living chiral crystals
DESCRIPTION:Abstract: Active crystals are highly ordered structures that emerge from the nonequilibrium self-organization of motile objects\, and have been widely studied in synthetic and bacterial active matter. In this talk\, I will describe how swimming sea star embryos spontaneously assemble into chiral crystals that span thousands of spinning organisms and persist for tens of hours. Combining experiment\, hydrodynamic theory\, and simulations\, we demonstrate that the formation\, dynamics\, and dissolution of these living crystals are controlled by the natural development of the embryos. Remarkably\, due to nonreciprocal force and torque exchange between the embryos\, the living chiral crystals exhibit self-sustained oscillations with dynamic signatures recently predicted to emerge in materials with odd elasticity.
URL:https://cmsa.fas.harvard.edu/event/nonreciprocal-matter-living-chiral-crystals/
LOCATION:MA
CATEGORIES:Active Matter Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211111T142200
DTEND;TZID=America/New_York:20211111T152200
DTSTAMP:20260516T225324
CREATED:20240301T103744Z
LAST-MODIFIED:20240301T103744Z
UID:10002893-1636640520-1636644120@cmsa.fas.harvard.edu
SUMMARY:11/11/21 Interdisciplinary Science Seminar
DESCRIPTION:Title: The Kervaire conjecture and the minimal complexity of surfaces \nAbstract: We use topological methods to solve special cases of a fundamental problem in group theory\, the Kervaire conjecture.\nThe conjecture asserts that\, for any nontrivial group G and any element w in the free product G*Z\, the quotient (G*Z)/<<w>> is still nontrivial. We interpret this as a problem of estimating the minimal complexity (in terms of Euler characteristic) of surfaces in HNN extensions. This gives a conceptually simple proof of Klyachko’s theorem that confirms the Kervaire conjecture for any G torsion-free. I will also explain new results obtained using this approach.
URL:https://cmsa.fas.harvard.edu/event/11-11-21-interdisciplinary-science-seminar/
LOCATION:MA
CATEGORIES:Interdisciplinary Science Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Interdisciplinary-Science-Seminar-11.11.21.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211112T093000
DTEND;TZID=America/New_York:20211112T103000
DTSTAMP:20260516T225324
CREATED:20240214T072852Z
LAST-MODIFIED:20240301T111040Z
UID:10002561-1636709400-1636713000@cmsa.fas.harvard.edu
SUMMARY:Universal relations between entanglement\, symmetries\, and entropy
DESCRIPTION:Member Seminar \nSpeaker: Gabriel Wong  \nTitle: Universal relations between entanglement\, symmetries\, and entropy \nAbstract: Entanglement is an essential property of quantum systems that distinguishes them from classical ones.   It is responsible for the nonlocal character of quantum information and provides a resource for quantum teleportation and quantum computation. In this talk I will provide an introduction to quantum entanglement and explain the essential role it plays in two seemingly unrelated subjects: implementation of measurement-based quantum computation and microstate counting of black holes in quantum gravity.   Time permitting\, I will also discuss attempts to characterize entanglement in string theory. A unifying theme that illuminates the entanglement structure of these diverse systems is the role of surface symmetries and (entanglement) edge modes. We will explain how these universal aspects of entanglement are captured in the framework of extended topological quantum field theory.
URL:https://cmsa.fas.harvard.edu/event/11-12-2021-member-seminar/
LOCATION:MA
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211112T143000
DTEND;TZID=America/New_York:20211112T160000
DTSTAMP:20260516T225324
CREATED:20240214T101408Z
LAST-MODIFIED:20240301T090838Z
UID:10002663-1636727400-1636732800@cmsa.fas.harvard.edu
SUMMARY:A degeneracy bound for homogeneous topological order
DESCRIPTION:Speaker: Jeongwan Haah (Microsoft) \nTitle: A degeneracy bound for homogeneous topological order
URL:https://cmsa.fas.harvard.edu/event/11-12-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211115T130000
DTEND;TZID=America/New_York:20211115T140000
DTSTAMP:20260516T225324
CREATED:20240214T092545Z
LAST-MODIFIED:20240301T080852Z
UID:10002625-1636981200-1636984800@cmsa.fas.harvard.edu
SUMMARY:11/15/2021 – Swampland Seminar
DESCRIPTION:This week’s seminar will be an open mic discussion which will be led by Nima Arkani-Hamed (IAS)\, and by Gary Shiu (UW-Madison)\, and the topic will be “Swampland constraints\, Unitarity and Causality”. They will start with a brief introduction sharing their thoughts about the topic and moderate a discussion afterwards.
URL:https://cmsa.fas.harvard.edu/event/11-15-2021-swampland-seminar/
LOCATION:MA
CATEGORIES:Swampland Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T093000
DTEND;TZID=America/New_York:20211116T103000
DTSTAMP:20260516T225324
CREATED:20240213T063545Z
LAST-MODIFIED:20240223T111731Z
UID:10002118-1637055000-1637058600@cmsa.fas.harvard.edu
SUMMARY:11/16/21 Algebraic Geometry in String Theory
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/11-16-21-algebraic-geometry-in-string-theory/
LOCATION:MA
CATEGORIES:Algebraic Geometry in String Theory Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T093000
DTEND;TZID=America/New_York:20211116T103000
DTSTAMP:20260516T225324
CREATED:20240214T051424Z
LAST-MODIFIED:20240304T061932Z
UID:10002537-1637055000-1637058600@cmsa.fas.harvard.edu
SUMMARY:Gromov-Witten theory of complete intersections
DESCRIPTION:Abstract: I will describe an inductive algorithm computing Gromov-Witten invariants in all genera with arbitrary insertions of all smooth complete intersections in projective space. The main idea is to show that invariants with insertions of primitive cohomology classes are controlled by their monodromy and by invariants defined without primitive insertions but with imposed nodes in the domain curve. To compute these nodal Gromov-Witten invariants\, we introduce the new notion of nodal relative Gromov-Witten invariants. This is joint work with Hülya Argüz\, Rahul Pandharipande\, and Dimitri Zvonkine (arxiv:2109.13323).
URL:https://cmsa.fas.harvard.edu/event/gromov-witten-theory-of-complete-intersections/
LOCATION:MA
CATEGORIES:Algebraic Geometry in String Theory Seminar
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Algebraic-Geometry-in-String-Theory-Seminar-11.16.21-1-1-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T150000
DTEND;TZID=America/New_York:20211116T163000
DTSTAMP:20260516T225324
CREATED:20240213T064804Z
LAST-MODIFIED:20240213T064804Z
UID:10002130-1637074800-1637080200@cmsa.fas.harvard.edu
SUMMARY:11/16/21 Quantum Matter in Mathematics and Physics
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/11-16-21-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211116T150000
DTEND;TZID=America/New_York:20211116T163000
DTSTAMP:20260516T225324
CREATED:20240214T101038Z
LAST-MODIFIED:20240301T090706Z
UID:10002660-1637074800-1637080200@cmsa.fas.harvard.edu
SUMMARY:Quantum Geometric Aspects of Chiral Twisted Graphene Models
DESCRIPTION:Speaker: Jie Wang (Simons Foundation) \nTitle: Quantum Geometric Aspects of Chiral Twisted Graphene Models \nAbstract: “Moire” materials produced by stacking monolayers with small relative twist angles are of intense current interest for the range of correlated electron phenomena they exhibit. The quench of the kinetic energy means that the interacting physics is controlled by the interplay between the interaction scale and intrinsic quantum geometries of the flat band states\, in particular the Berry curvature and the Fubini-Study metric\, which are in general spatially non-uniform. We show that the analytical solution of the twisted bilayer graphene wavefunction in the chiral limit has a special band geometry\, endowing the Brillouin zone with a complex structure. This talk focus on the origin of the momentum space complex structure\, concrete models that realize it\, and its implications to electron-electron interactions. We first show the momentum space complex structure in Chern number C=1 flatbands implies the Bloch wavefunction to exhibit an exact correspondence to the lowest Landau level in the dual momentum space [2]. We present a generalization of the Haldane pseudopotential concept to deal with interacting problems in these bands and discuss experimental implications [2]. We also present an analytically solvable multi-layer generalized chiral graphene model\, which exhibits arbitrarily high Chern number and ideal quantum geometries [3]. Numerical studies of interacting particles indicate model fractional Chern insulators without Landau level analogues\, characterized by exact degeneracies and infinite particle entanglement spectra gaps [3]. References: \n[1] Jie Wang\, Yunqin Zheng\, Andrew J. Millis\, Jennifer Cano (Phys. Rev. Research 3\, 023155)\n[2] Jie Wang\, Jennifer Cano\, Andrew J. Millis\, Zhao Liu\, Bo Yang (arXiv: 2105.07491\, to appear in PRL)\n[3] Jie Wang\, Zhao Liu (arXiv: 2109.10325)
URL:https://cmsa.fas.harvard.edu/event/11-16-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211117T093000
DTEND;TZID=America/New_York:20211117T103000
DTSTAMP:20260516T225324
CREATED:20240212T104547Z
LAST-MODIFIED:20240502T154225Z
UID:10002009-1637141400-1637145000@cmsa.fas.harvard.edu
SUMMARY:Curve counting on surfaces and topological strings
DESCRIPTION:Speaker: Andrea Brini\, U Sheffield \nTitle: Curve counting on surfaces and topological strings \nAbstract: Enumerative geometry is a venerable subfield of Mathematics\, with roots dating back to Greek Antiquity and a present inextricably linked with developments in other domains. Since the early 90s\, in particular\, the interaction with String Theory has sent shockwaves through the subject\, giving both unexpected new perspectives and a remarkably powerful\, physics-motivated toolkit to tackle several traditionally hard questions in the field.\nI will survey some recent developments in this vein for the case of enumerative invariants associated to a pair (X\, D)\, with X a complex algebraic surface and D a singular anticanonical divisor in it. I will describe a surprising web of correspondences linking together several a priori distant classes of enumerative invariants associated to (X\, D)\, including the log Gromov-Witten invariants of the pair\, the Gromov-Witten invariants of an associated higher dimensional Calabi-Yau variety\, the open Gromov-Witten invariants of certain special Lagrangians in toric Calabi–Yau threefolds\, the Donaldson–Thomas theory of a class of symmetric quivers\, and certain open and closed Gopakumar-Vafa-type invariants. I will also discuss how these correspondences can be effectively used to provide a complete closed-form solution to the calculation of all these invariants.
URL:https://cmsa.fas.harvard.edu/event/curve-counting-on-surfaces-and-topological-strings/
LOCATION:MA
CATEGORIES:Colloquium
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Colloquium-11.17.21-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T142500
DTEND;TZID=America/New_York:20211118T152500
DTSTAMP:20260516T225324
CREATED:20240214T075510Z
LAST-MODIFIED:20240301T103505Z
UID:10002572-1637245500-1637249100@cmsa.fas.harvard.edu
SUMMARY:11/18/2021 Interdisciplinary Science Seminar
DESCRIPTION:Title: Amplituhedra\, Scattering Amplitudes and Triangulations \nAbstract: In this talk I will discuss about Amplituhedra – generalizations of polytopes inside the Grassmannian – recently introduced by physicists as new geometric constructions encoding interactions of elementary particles in certain Quantum Field Theories. In particular\, I will explain how the problem of finding triangulations of Amplituhedra is connected to computing scattering amplitudes of N=4 super Yang-Mills theory. Triangulations of polygons are encoded in the associahedron studied by Stasheff in the sixties; in the case of polytopes\, triangulations are captured by secondary polytopes constructed by Gelfand et al. in the nineties. Whereas a “secondary” geometry describing triangulations of Amplituhedra is still not known\, and we pave the way for such studies. We will discuss how the combinatorics of triangulations interplays with T-duality from String Theory\, in connection with a dual object we define – the Momentum Amplituhedron. A generalization of T-duality led us to discover a striking duality between triangulations of Amplituhedra of “m=2” type and the ones of a seemingly unrelated object – the Hypersimplex. The latter is a polytope which has been central in many contexts\, such as matroid theory\, torus orbits in the Grassmannian\, and tropical geometry. Based on joint works with Lauren Williams\, Melissa Sherman-Bennett\, Tomasz Lukowski [arXiv:2104.08254\, arXiv:2002.06164].
URL:https://cmsa.fas.harvard.edu/event/11-18-2021-interdisciplinary-science-seminar/
LOCATION:MA
CATEGORIES:Interdisciplinary Science Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T143000
DTEND;TZID=America/New_York:20211118T160000
DTSTAMP:20260516T225324
CREATED:20240213T064124Z
LAST-MODIFIED:20240213T064401Z
UID:10002122-1637245800-1637251200@cmsa.fas.harvard.edu
SUMMARY:11/18/21 Quantum Matter in Mathematics and Physics
DESCRIPTION:
URL:https://cmsa.fas.harvard.edu/event/11-18-21-quantum-matter-in-mathematics-and-physics/
LOCATION:MA
CATEGORIES:Quantum Matter
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T143000
DTEND;TZID=America/New_York:20211118T160000
DTSTAMP:20260516T225324
CREATED:20240214T100731Z
LAST-MODIFIED:20240301T090528Z
UID:10002657-1637245800-1637251200@cmsa.fas.harvard.edu
SUMMARY:Exact Eigenstates in Non-Integrable Systems: A violation of the ETH
DESCRIPTION:Speaker: B. Andrei Bernevig (Princeton University) \nTitle: Exact Eigenstates in Non-Integrable Systems: A violation of the ETH \nAbstract: We find that several non-integrable systems exhibit some exact eigenstates that span the energy spectrum from lowest to the highest state. In the AKLT Hamiltonian and in several others “special” non-integrable models\, we are able to obtain the analytic expression of states exactly and to compute their entanglement spectrum and entropy to show that they violate the eigenstate thermalization hypothesis. This represented the first example of ETH violation in a non-integrable system; these types of states have gained notoriety since then as quantum Scars in the context of Rydberg atoms experiments. We furthermore show that the structure of these states\, in most models where they are found is that of an almost spectrum generating algebra which we call Restricted Spectrum Generating Algebra. This includes the (extended) Hubbard model\, as well as some thin-torus limits of Fractional Quantum Hall states. Yet in other examples\, such as the recently found chiral non-linear Luttinger liquid\, their structure is more complicated and not understood.
URL:https://cmsa.fas.harvard.edu/event/11-18-2021-quantum-matter-in-mathematics-and-physics/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Quantum-Matter-in-Mathematics-and-Physics-11.18.21-1583x2048-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211118T175200
DTEND;TZID=America/New_York:20211118T185200
DTSTAMP:20260516T225324
CREATED:20230801T181638Z
LAST-MODIFIED:20240304T065227Z
UID:10002545-1637257920-1637261520@cmsa.fas.harvard.edu
SUMMARY:Macroscopic properties of buyer-seller networks in online marketplaces
DESCRIPTION:Abstract:  Online marketplaces are the main engines of legal and illegal e-commerce\, yet the aggregate properties of buyer-seller networks behind them are poorly understood. We analyse two datasets containing 245M transactions (16B USD)  between 2010 and 2021 involving online marketplaces: 28 dark web marketplaces (DWM)\, unregulated markets whose main currency is Bitcoin\, and 144 product markets of one regulated e-commerce platform. We show how transactions in online marketplaces exhibit strikingly similar patterns of aggregate behavior despite significant differences in language\, products\, time\, regulation\, oversight\, and technology. We find remarkable regularities in the distributions of (i) transaction amounts\, (ii) number of transactions\, (iii) inter-event times\, (iv) time between first and last transactions. We then show how buyer behavior is affected by the memory of past interactions\, and draw on these observations to propose a model of network formation able to reproduce the main stylised facts of the data. Our findings have important implications for understanding market power on online marketplaces as well as inter-marketplace competition.
URL:https://cmsa.fas.harvard.edu/event/macroscopic-properties-of-buyer-seller-networks-in-online-marketplaces/
LOCATION:MA
CATEGORIES:Special Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211119T093000
DTEND;TZID=America/New_York:20211119T103000
DTSTAMP:20260516T225324
CREATED:20240214T072706Z
LAST-MODIFIED:20240301T110941Z
UID:10002560-1637314200-1637317800@cmsa.fas.harvard.edu
SUMMARY:China’s financial regulatory reform\, financial opening-up\, and Central Bank Digital Currency (CBDC)
DESCRIPTION:Member Seminar \nSpeaker: Kan Lin \nTitle: China’s financial regulatory reform\, financial opening-up\, and Central Bank Digital Currency (CBDC) \nAbstract: In this talk\, I will explain the overall situation of China’s financial industry and review the development of China’s financial regulatory system reform from 1949 to 2021. Then\, I will explain the policies of the 3 stages of financial opening-up\, 2001–08\, 2008–18\, 2018≠present. In particular\, the latest round of opening-up from 2018 has brought great opportunities for foreign institutions. China has the world’s largest banking industry with assets totaling $53 trillion\, and accounts for 1/3 of the growth in global insurance premiums over the next 10 years. I will also introduce the progress of research & development of China’s Central Bank Digital Currency (CBDC\, or E-CNY). By October 2021\, 140 million people had opened E-CNY wallets\, and 1.6 million merchants could accept payments using eCNY wallets\, including utilities\, catering services\, transportation\, retail\, and government services.
URL:https://cmsa.fas.harvard.edu/event/11-19-2021-member-seminar/
LOCATION:MA
CATEGORIES:Member Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211119T130000
DTEND;TZID=America/New_York:20211119T140000
DTSTAMP:20260516T225324
CREATED:20240214T074604Z
LAST-MODIFIED:20240304T053957Z
UID:10002570-1637326800-1637330400@cmsa.fas.harvard.edu
SUMMARY:On Curvature Propagation and ‘Breakdown’ of the Einstein Equations on U(1) Symmetric Spacetimes
DESCRIPTION:strong>Abstract: The analysis of global structure of the Einstein equations for general relativity\, in the context of the initial value problem\, is a difficult and intricate mathematical subject. Any additional structure in their formulation is welcome\, in order to alleviate the problem.  It is expected that the initial value problem of the Einstein equations on spacetimes admitting a translational\, fixed-point free\, spatial U(1) isometry group are globally well-posed. In our previous works\, we discussed the special structure provided by the dimensional reduction of 3+1 dimensional U(1) symmetric Einstein equations to 2+1 Einstein-wave map system and demonstrated global existence in the equivariant case for large data.  In this talk\, after discussing some preliminaries and background\, we shall discuss about yet another structure of the U(1) symmetric Einstein equations\, namely the analogy with Yang-Mills theory via the Cartan formalism and reconcile with the dimensionally reduced field equations. We shall also discuss implications for ‘breakdown’ criteria of U(1) symmetric Einstein equations.
URL:https://cmsa.fas.harvard.edu/event/11-19-2021-general-relativity-seminar/
LOCATION:MA
CATEGORIES:General Relativity Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20211122T130000
DTEND;TZID=America/New_York:20211122T140000
DTSTAMP:20260516T225324
CREATED:20240214T091807Z
LAST-MODIFIED:20240301T075427Z
UID:10002616-1637586000-1637589600@cmsa.fas.harvard.edu
SUMMARY:Taming the Landscape
DESCRIPTION:Abstract: In this talk I will introduce a generalized notion of finiteness that provides a structural principle for the set of effective theories that can be consistently coupled to quantum gravity. More concretely\, I will propose a ‘tameness conjecture’ that states that all scalar field spaces and coupling functions that appear in such an effective theory must be definable in an o-minimal structure. The fascinating field of tame geometry has seen much recent progress and I will argue that the results can be used to support the above swampland conjecture. The strongest evidence arises from a new finiteness theorem for the flux landscape which is shown using the tameness of the period map.
URL:https://cmsa.fas.harvard.edu/event/11-22-2021-swampland-seminar/
LOCATION:MA
CATEGORIES:Swampland Seminar
END:VEVENT
END:VCALENDAR