BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Edward Witten (IAS) DTSTART:20200413T190000Z DTEND:20200413T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/1 DESCRIPTION:Title: Vo lumes and random matrices\nby Edward Witten (IAS) as part of Western H emisphere colloquium on geometry and physics\n\n\nAbstract\nI will describ e recent results relating two-dimensional gravity and supergravity\; volum es of moduli spaces of Riemann surfaces and super Riemann surfaces\; and r andom matrix ensembles. See arX iv:1907.03363 by Saad\, Shenker\, and Stanford.\n LOCATION:https://researchseminars.org/talk/WHCGP/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Kevin Costello (Perimeter Institute) DTSTART:20200427T190000Z DTEND:20200427T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/2 DESCRIPTION:Title: To pological strings\, twistors\, and Skyrmions\nby Kevin Costello (Perim eter Institute) as part of Western Hemisphere colloquium on geometry and p hysics\n\n\nAbstract\nIt has long been known that holomorphic field theori es on twistor space lead to "physical" field theories on Minkowski space. In this talk I will discuss a type I (unoriented) version of the topologic al B model on twistor space. The corresponding theory on Minkowski space i s a sigma-model with target the group SO(8). This is a variant of the Skyr me model that appears as the low-energy effective theory of mesons in QCD. (The group SO(8) appears because of the Green-Schwarz mechanism in the to pological string). The origin of this model in the topological string impl ies many remarkable properties. For one thing\, the model is\, in a certai n sense\, integrable. Further\, although the Lagrangian is power-counting non-renormalizable\, counter-terms at all loops can be uniquely fixed.\n LOCATION:https://researchseminars.org/talk/WHCGP/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Miranda Cheng (University of Amsterdam) DTSTART:20200518T190000Z DTEND:20200518T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/3 DESCRIPTION:Title: Qu antum modularity from 3-manifolds\nby Miranda Cheng (University of Ams terdam) as part of Western Hemisphere colloquium on geometry and physics\n \n\nAbstract\nQuantum modular forms are functions on rational numbers that have rather mysterious weak modular properties. Mock modular forms and fa lse theta functions are examples of holomorphic functions on the upper-hal f plane which lead to quantum modular forms. Inspired by the 3d-3d corresp ondence in string theory\, a new topological invariants named homological blocks for (in particular plumbed) three-manifolds have been proposed a fe w years ago. My talk aims to explain the recent observations on the quantu m modular properties of the homological blocks\, as well as the relation t \n LOCATION:https://researchseminars.org/talk/WHCGP/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Davide Gaiotto (Perimeter Institute) DTSTART:20200601T190000Z DTEND:20200601T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/4 DESCRIPTION:Title: In tegrable Kondo problems and affine geometric Langlands\nby Davide Gaio tto (Perimeter Institute) as part of Western Hemisphere colloquium on geom etry and physics\n\n\nAbstract\nI will present some work on integrable lin e defects in WZW models and their relation to 4d CS theory\, the IM/ODe co rrespondence and affine generalizations of Geometric Langlands constructio ns.\n LOCATION:https://researchseminars.org/talk/WHCGP/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Maxim Kontsevich (IHES) DTSTART:20200615T190000Z DTEND:20200615T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/5 DESCRIPTION:Title: Sp ace-time analyticity in QFT\nby Maxim Kontsevich (IHES) as part of Wes tern Hemisphere colloquium on geometry and physics\n\n\nAbstract\nI will t alk on a joint work with Graeme Segal. We propose a new axiomatics for uni tary quantum field theory which includes both Lorentzian and Euclidean sig natures for curved space-time manifolds. The key to the definition is cert ain ope\n LOCATION:https://researchseminars.org/talk/WHCGP/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Anton Kapustin (Cal Tech) DTSTART:20200622T190000Z DTEND:20200622T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/6 DESCRIPTION:Title: Fr om gapped phases of matter to Topological Quantum Field Theory and back ag ain\nby Anton Kapustin (Cal Tech) as part of Western Hemisphere colloq uium on geometry and physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Nima Arkani-Hamed (IAS) DTSTART:20200706T190000Z DTEND:20200706T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/8 DESCRIPTION:Title: Sp acetime\, Quantum Mechanics and Clusterhedra at Infinity\nby Nima Arka ni-Hamed (IAS) as part of Western Hemisphere colloquium on geometry and ph ysics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Mina Aganagic (UC Berkeley) DTSTART:20200713T190000Z DTEND:20200713T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/9 DESCRIPTION:Title: Kn ot categorification from mirror symmetry\, via string theory\nby Mina Aganagic (UC Berkeley) as part of Western Hemisphere colloquium on geometr y and physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Laura Fredrickson (Stanford / U. Oregon) DTSTART:20200824T190000Z DTEND:20200824T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/10 DESCRIPTION:Title: T he asymptotic geometry of the Hitchin moduli space\nby Laura Fredricks on (Stanford / U. Oregon) as part of Western Hemisphere colloquium on geom etry and physics\n\n\nAbstract\nHitchin's equations are a system of gauge theoretic equations on a Riemann surface that are of interest in many area s including representation theory\, Teichmuller theory\, and the geometric Langlands correspondence. The Hitchin moduli space carries a natural hype rkahler metric. An intricate conjectural description of its asymptotic str ucture appears in the work of physicists Gaiotto-Moore-Neitzke and there h as been a lot of progress on this recently. I will discuss some recent res ults using tools coming out of geometric analysis which are well-suited fo r verifying these extremely delicate conjectures. This strategy often stre tches the limits of what can currently be done via geometric analysis\, an d simultaneously leads to new insights into these conjectures.\n LOCATION:https://researchseminars.org/talk/WHCGP/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Greg Moore (Rutgers) DTSTART:20200720T190000Z DTEND:20200720T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/11 DESCRIPTION:Title: B reaking News About\, Topologically Twisted Rank One N=2* Supersymmetric Ya ng-Mills Theory On Four-Manifolds\, Without Spin\nby Greg Moore (Rutge rs) as part of Western Hemisphere colloquium on geometry and physics\n\nAb stract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Sakura Schafer-Nameki (Oxford) DTSTART:20200803T190000Z DTEND:20200803T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/12 DESCRIPTION:Title: 5 d SCFTs: Symmetries and Moduli Spaces\nby Sakura Schafer-Nameki (Oxfor d) as part of Western Hemisphere colloquium on geometry and physics\n\nAbs tract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Marco Gualtieri (Univ. of Toronto) DTSTART:20200817T190000Z DTEND:20200817T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/13 DESCRIPTION:Title: B ranes in symplectic groupoids\nby Marco Gualtieri (Univ. of Toronto) a s part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstr act\nAfter reviewing coisotropic A-branes in symplectic manifolds and thei r role in mirror symmetry and geometric quantization\, I will explain how the problem of holomorphic quantization of Poisson brackets may be recast\ , and in some cases solved\, as a problem of computing morphisms between c oisotropic branes in symplectic groupoids. This is joint work with Franc is Bischoff and Joshua Lackman.\n LOCATION:https://researchseminars.org/talk/WHCGP/13/ END:VEVENT BEGIN:VEVENT SUMMARY:David Jordan (Edinburgh) DTSTART:20200914T190000Z DTEND:20200914T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/14 DESCRIPTION:Title: Q uantum geometric Langlands as a fully extended TFT\nby David Jordan (E dinburgh) as part of Western Hemisphere colloquium on geometry and physics \n\n\nAbstract\nI will survey several recent works realizing Betti geometr ic\nLanglands and its quantization as fully extended TFT's. In physics ter ms\nthis is most closely related to the Kapustin-Witten twist of N=4 d=4 S YM\nat generic values of \\Psi.\n\nI will outline numerous applications to quantum topology\, most notably\nto a conjecture of Witten on finite-dime nsionality of skein modules\, a\nconjecture of Bonahon-Wong concerning ske in modules at root-of-unity\nparameters\, a proposal of Ben-Zvi concerning cluster varieties and\nfactorization homology\, and an appearance of the type-A spherical DAHA\nfrom a once-marked torus.\n\nFinally\, I will prese nt a novel conjectural appearance of S-duality in\nthe study of skein modu les of 3-manifolds.\n LOCATION:https://researchseminars.org/talk/WHCGP/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Natalie Paquette (IAS) DTSTART:20201005T190000Z DTEND:20201005T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/15 DESCRIPTION:Title: B orcherds-Kac-Moody algebras\, 2d strings\, & other curiosities\nby Nat alie Paquette (IAS) as part of Western Hemisphere colloquium on geometry a nd physics\n\n\nAbstract\nIn this talk we will extol the virtues of compac tifying critical string theory down to few noncompact spacetime dimensions (particularly two). These string vacua possess rich groups of dualities. BPS-saturated quantities\, which mathematically are described by automorph ic forms\, are invariant under such duality transformations. Further\, suc h BPS states can furnish representations of interesting algebras\, such as infinite-dimensional Lie algebras. In this talk\, we explore some particu larly nice\, concrete examples\, which employ holomorphic super vertex ope rator algebras in our `compactification' theories. The BPS states in these models organize into representations of algebras\, which we prove are (ne w) examples of Borcherds-Kac-Moody superalgebras.\n LOCATION:https://researchseminars.org/talk/WHCGP/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Ben Webster (Waterloo) DTSTART:20200810T190000Z DTEND:20200810T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/16 DESCRIPTION:Title: 3 d mirror symmetry and its discontents\nby Ben Webster (Waterloo) as pa rt of Western Hemisphere colloquium on geometry and physics\n\nAbstract: T BA\n LOCATION:https://researchseminars.org/talk/WHCGP/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Lauren Williams (Harvard) DTSTART:20200921T190000Z DTEND:20200921T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/17 DESCRIPTION:Title: H ow is the hypersimplex related to the amplituhedron?\nby Lauren Willia ms (Harvard) as part of Western Hemisphere colloquium on geometry and phys ics\n\n\nAbstract\nIn 1987\, Gelfand-Goresky-MacPherson-Serganova made a b eautiful\nconnection between the geometry of the Grassmannian and convex p olytopes\, via\nthe moment map\; the moment map image of the Grassmannian Gr(k\,n) is a polytope\nknown as the hypersimplex Delta(k\,n). In 2013\, motivated by the desire to\ngive a geometric basis for the computation of scattering amplitudes in N=4\nSYM\, Arkani-Hamed and Trnka introduced the amplituhedron A(n\,k\,m) as the image\nof the positive Grassmannian Gr+(k\ ,n) under a linear map Z from R^n to R^{k+m}\nwhich is totally positive. While the case m=4 is most relevant to physics\,\nthe amplituhedron makes sense for any m. In my talk I will explain some\nstrange parallels betwee n the positroidal subdivisions of the hypersimplex\nDelta(k+1\,n) and the m=2 amplituhedron A(n\,k\,2). One link is provided by the\npositive tropi cal Grassmannian. Attributions: based on joint works with Tomek\nLukowski \, Matteo Parisi\, and David Speyer.\n\nDisclaimer: I'm neither a geometer nor a physicist.\n LOCATION:https://researchseminars.org/talk/WHCGP/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Gross (Cambridge) DTSTART:20200511T190000Z DTEND:20200511T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/18 DESCRIPTION:Title: I ntrinsic Mirror Symmetry\nby Mark Gross (Cambridge) as part of Western Hemisphere colloquium on geometry and physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Harold Williams (USC) DTSTART:20201214T200000Z DTEND:20201214T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/19 DESCRIPTION:Title: C anonical Bases for Coulomb Branches\nby Harold Williams (USC) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nFo llowing work of Kapustin-Saulina and Gaiotto-Moore-Neitzke\, one expects h alf-BPS line defects in a 4d N=2 field theory to form a monoidal category with a rich structure. In general\, a mathematical definition of this cate gory is not known. In this talk we discuss an algebro-geometric proposal i n the case of gauge theories with polarizable matter. The proposed categor y is the heart of a nonstandard t-structure on the dg category of coherent sheaves on the derived Braverman-Finkelberg-Nakajima space of triples. We refer to its objects as Koszul-perverse coherent sheaves\, as this t-stru cture interpolates between the perverse coherent t-structure and certain t -structures appearing in the theory of Koszul duality (specializing to the se in the case of a pure gauge theory and an abelian gauge theory\, respec tively). As a byproduct\, this defines a canonical basis in the associated quantized Coulomb branch by passing to classes of irreducible objects. Th is is joint work with Sabin Cautis.\n LOCATION:https://researchseminars.org/talk/WHCGP/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Christopher Beem (Oxford) DTSTART:20201102T200000Z DTEND:20201102T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/20 DESCRIPTION:Title: H all-Littlewood chiral rings and derived Higgs branches\nby Christopher Beem (Oxford) as part of Western Hemisphere colloquium on geometry and ph ysics\n\n\nAbstract\nI will discuss a relatively novel algebraic structure arising in four-dimensional N=2 superconformal field theories: the Hall-L ittlewood Chiral Ring (HLCR). The HLCR is an enhancement of the more famil iar Higgs branch chiral ring (which encodes the Higgs branch of the moduli space of vacua as an algebraic variety). The HLCR in gauge theories is co nstructed as the cohomology of a kind of BRST complex\, which allows it to be identified with the ring of functions on the derived Higgs branch (in the sense of derived algebraic geometry). I will describe the solution of the HLCR cohomology problem for a large class of Lagrangian theories (the class S theories of type A1)\, which illustrate some interesting phenomena . This talk is based on work in progress with Diego Berdeja Suárez.\n LOCATION:https://researchseminars.org/talk/WHCGP/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Sergei Gukov (Cal Tech) DTSTART:20201116T200000Z DTEND:20201116T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/21 DESCRIPTION:Title: R okhlin\, quantum groups\, and BPS states\nby Sergei Gukov (Cal Tech) a s part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstr act\nWhat do ADO polynomials\, cobordism invariants\, and affine Grassmann ians have in common? We will discuss how these seemingly different objects can be put under one roof of a BPS q-series that\, on the one hand\, can be thought of as a 3d analogue of the Vafa-Witten partition function and\, on the other hand\, is associated to quantum groups at generic q where Ve rma modules with arbitrary complex weights play an important role.\n LOCATION:https://researchseminars.org/talk/WHCGP/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Sourav Chatterjee (Stanford) DTSTART:20201130T200000Z DTEND:20201130T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/22 DESCRIPTION:Title: S trong mass gap implies quark confinement\nby Sourav Chatterjee (Stanfo rd) as part of Western Hemisphere colloquium on geometry and physics\n\n\n Abstract\nI will show that if a lattice gauge theory has exponential decay of correlations under arbitrary boundary conditions (which I call strong mass gap)\, and the gauge group has a nontrivial center\, then Wilson's ar ea law holds.\n LOCATION:https://researchseminars.org/talk/WHCGP/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Djordje Radicevic (Brandeis) DTSTART:20201019T190000Z DTEND:20201019T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/23 DESCRIPTION:Title: T he Lattice-Continuum Correspondence in Quantum Mechanics\nby Djordje R adicevic (Brandeis) as part of Western Hemisphere colloquium on geometry a nd physics\n\n\nAbstract\nIt is very well known that long-distance correla tion functions of many lattice systems can be calculated from continuum QF Ts. Making this correspondence more precise --- identifying continuum oper ators that correspond to individual lattice operators\, or exhibiting the lattice origins of subtler continuum phenomena like operator product expan sions --- has proven quite daunting. In this talk\, I will report on recen t progress in this direction\, using quantum mechanics (QFT in 0+1 dimensi ons) as an example. I will show how a finite but large quantum system can be systematically reduced to an Ersatz continuum theory\, using both Hamil tonian and path integral formalisms. Along the way I will point out the la ttice origins of several familiar continuum concepts\, including contact t erms\, scale invariance\, and the distinction between compact and noncompa ct theories. I will also stress the limitations imposed on the emergent co ntinuum theory by its lattice progenitor --- for instance\, any supersymme tric continuum theory emerging from a finite theory must have a vanishing Witten index.\n LOCATION:https://researchseminars.org/talk/WHCGP/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Mike Freedman (Microsoft Research/ UCSB) DTSTART:20210111T200000Z DTEND:20210111T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/24 DESCRIPTION:Title: Q uantum Codes and Systolic freedom\nby Mike Freedman (Microsoft Researc h/ UCSB) as part of Western Hemisphere colloquium on geometry and physics\ n\n\nAbstract\nIn work with Hastings we find a two-way street between quan tum\nerror correcting codes and Riemannian manifolds. A recent advance in coding\ntheory allows us to produce the first example of a manifolds with $Z_2$-power\nlaw-systolic freedom. Specifically we find\, for any$e>0$\, a sequence of\nappropriately scaled 11D Riemannian manifolds $M_i$\, so th at for any dual 4 and\n7 dimensional $Z_2$-cycles\, $X_i$ and $Y_i$\, resp .\n\n $ Vol_4(X_i)*Vol_7(Y_i) > (Vol_{11}(M_i))^{(5/4-e)} $. \n LOCATION:https://researchseminars.org/talk/WHCGP/24/ END:VEVENT BEGIN:VEVENT SUMMARY:Albrecht Klemm (Bonn) DTSTART:20210125T200000Z DTEND:20210125T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/25 DESCRIPTION:Title: C alabi-Yau modularity and Feynman graphs\nby Albrecht Klemm (Bonn) as p art of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract \nUsing the GKZ system for the primitive cohomology of an infinite series of complete intersection Calabi-Yau manifolds\, whose dimension is the loo p order minus one\, we completely clarify the analytic structure of all ba nana integrals with arbitrary masses. In particular\, we find that the lea ding logarithmic structure in the high energy regime\, which corresponds t o the point of maximal unipotent monodromy\, is determined by a novel \\ha t b-class evaluation in the ambient spaces of the mirror\, while the imagi nary part of the amplitude in this regime is determined by the Γb-clas s of the mirror Calabi-Yau manifold itself. We provide simple closed all l oop formulas for the former as well as for the Frobenius κ-constants\, which determine the behaviour of the amplitudes\, when the momentum square equals the sum of the masses squared\, in terms of zeta values. We find t he exact differential equation for the graph integrals with arbitrary valu e for the dimensional regularisation (d-\\epsilon) parameter and extend ou r previous work from three to four loops by providing for the latter case a complete set of (inhomogenous) Picard-Fuchs differential ideal for arbit rary masses. Using a recent p-adic analysis of the periods we determine th e value of the maximal cut equal mass four-loop amplitude at the attractor points in terms of periods of modular weight two and four Hecke eigenform s and the quasiperiods of their meromorphic cousins.\n LOCATION:https://researchseminars.org/talk/WHCGP/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Nikita Nekrasov (SCGP\, Stony Brook) DTSTART:20210208T200000Z DTEND:20210208T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/26 DESCRIPTION:Title: B eauty of the defects\nby Nikita Nekrasov (SCGP\, Stony Brook) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nSu rface and point-like defects in supersymmetric gauge theories in four dime nsions are studied with applications to quantum/classical correspondence. In particular\, the GIL formula for the tau-function of Painleve VI is exp lained using the blow-up method in the context of the BPS/CFT corresponden ce\, while the spin chain generalisation of Kharchev-Lebedev wavefunction of periodic Toda chain is obtained via wallcrossing. \n\nBased on several works\, in particular on papers in collaboration with Saebyeok Jeong\; Nor ton Lee\; Oleksandr Tsymbaliuk\; as well as S. Jeong and N. Lee\n LOCATION:https://researchseminars.org/talk/WHCGP/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Tamas Hausel (IST\, Austria) DTSTART:20210222T200000Z DTEND:20210222T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/27 DESCRIPTION:Title: M irror symmetry for Langlands dual Higgs bundles at the tip of the nilpoten t cone\nby Tamas Hausel (IST\, Austria) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nI will explain what we c an prove and what we conjecture about the mirror of Hecke transformed Hitc hin section motivated by symmetry ideas of Kapustin-Witten. The talk is ba sed on arXiv:2101.08583 joint with Hitchin.\n LOCATION:https://researchseminars.org/talk/WHCGP/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Dumitrescu (UCLA) DTSTART:20210308T200000Z DTEND:20210308T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/28 DESCRIPTION:Title: 2 -Group Global Symmetry in Quantum Field Theory\nby Thomas Dumitrescu ( UCLA) as part of Western Hemisphere colloquium on geometry and physics\n\n \nAbstract\nHigher-form generalizations of global symmetries play an impor tant role in Quantum Field Theory (QFT). In general\, symmetries of differ ent form degrees need not be independent\; instead\, they can form a highe r group. In this talk I will illustrate this phenomenon by explaining why many simple Lagrangian QFTs in four and six dimensions enjoy 2-group globa l symmetries. I will then apply this understanding to deduce new general r esults about (typically non-Lagrangian) SCFTs in six dimensions.\n LOCATION:https://researchseminars.org/talk/WHCGP/28/ END:VEVENT BEGIN:VEVENT SUMMARY:David Ben-Zvi (UT Austin) DTSTART:20210322T190000Z DTEND:20210322T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/29 DESCRIPTION:Title: E lectric-Magnetic Duality between Periods and L-functions\nby David Ben -Zvi (UT Austin) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nI will describe joint work with Yiannis Sakellaridi s and Akshay Venkatesh\, in\nwhich ideas originating in quantum field theo ry are applied to a problem in\nnumber theory.\n\nA fundamental tool in nu mber theory\, the relative Langlands program\, is\ncentered on the represe ntation of L-functions of Galois representations as\nintegrals of automorp hic forms. However\, the data that naturally index these\nperiod integrals (spherical varieties for a reductive group G) and the\nL-functions (repre sentations of the Langlands dual group G^) don't seem to line\nup\, making the search for integral representations somewhat of an art. \n\nWe presen t an approach to this problem via the Kapustin-Witten interpretation\nof t he [geometric] Langlands correspondence as electric-magnetic duality for\n 4-dimensional supersymmetric gauge theory. Namely\, we rewrite the relativ e \nLanglands program as duality in the presence of boundary conditions. A s a\nresult the partial correspondence between periods and L-functions is embedded\nin a natural duality between Hamiltonian actions of the dual gro ups.\n LOCATION:https://researchseminars.org/talk/WHCGP/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Arnav Tripathy (Harvard) DTSTART:20210405T190000Z DTEND:20210405T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/30 DESCRIPTION:Title: K 3 metrics\nby Arnav Tripathy (Harvard) as part of Western Hemisphere c olloquium on geometry and physics\n\n\nAbstract\nIt has long been an open problem to explicitly produce a\nRicci-flat metric on a (non-toroidal) com pact manifold. I'll discuss two\napproaches to this problem\, related by a version of 3d mirror symmetry\,\nfor K3 manifolds. This is joint work wit h M. Zimet.\n LOCATION:https://researchseminars.org/talk/WHCGP/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Cody Long/Cumrun Vafa (Harvard) DTSTART:20210419T190000Z DTEND:20210419T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/31 DESCRIPTION:Title: N on-Holomorphic Cycles and Non-BPS Black Branes\nby Cody Long/Cumrun Va fa (Harvard) as part of Western Hemisphere colloquium on geometry and phys ics\n\n\nAbstract\nWe discuss extremal non-BPS black holes and strings ari sing in M-theory compactifications on Calabi-Yau threefolds\, obtained by wrapping M2 branes on non-holomorphic 2-cycles and M5 branes on non-holomo rphic 4-cycles. Using the attractor mechanism we compute the black hole ma ss and black string tension\, leading to a conjectural formula for the asy mptotic volumes of connected\, locally volume-minimizing representatives o f non-holomorphic\, even-dimensional homology classes in the threefold\, w ithout knowledge of an explicit metric. In the case of divisors we find ex amples where the volume of the representative corresponding to the black s tring is less than the volume of the minimal piecewise-holomorphic represe ntative\, predicting recombination for those homology classes and leading to stable\, non-BPS strings. We also show how to compute the central charg es of non-BPS strings in F-theory via a near-horizon AdS3 limit in 6d whic h\, upon compactification on a circle\, account for the asymptotic entropy of extremal nonsupersymmetric 5d black holes (i.e.\, the asymptotic count of non-holomorphic minimal 2-cycles).\n LOCATION:https://researchseminars.org/talk/WHCGP/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Fei Yan (Rutgers) DTSTART:20210503T190000Z DTEND:20210503T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/32 DESCRIPTION:Title: T wo tales of networks and quantization\nby Fei Yan (Rutgers) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nI wi ll describe two quantization scenarios. The first scenario involves the co nstruction of a quantum trace map computing a new link "invariant" (with p ossible wall-crossing behavior) for links L in a 3-manifold M\, where M is a Riemann surface C times a real line. This construction computes familia r link invariants in a new way\, moreover it unifies that computation with the computation of protected spin characters counting ground states with spin for line defects in 4d N=2 theories of class-S. Certain networks on C play an important role in the construction. The second scenario concerns the study of Schroedinger equations and their higher order analogues\, whi ch could arise in the quantization of Seiberg-Witten curves in 4d N=2 theo ries. Here similarly certain networks play an important part in the exact WKB analysis for these Schroedinger-like equations. At the end of my talk I will also try to sketch a possibility to bridge these two quantization s cenarios. The first part of the talk is based on joint work with A. Neitzk e\; the final sketch is based on discussions with D. Gaiotto\, G. Moore an d A. Neitzke.\n LOCATION:https://researchseminars.org/talk/WHCGP/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Richard Thomas (Imperial College) DTSTART:20210517T190000Z DTEND:20210517T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/33 DESCRIPTION:Title: N onabelian DT theory from abelian DT theory\nby Richard Thomas (Imperia l College) as part of Western Hemisphere colloquium on geometry and physic s\n\n\nAbstract\nFix a Calabi-Yau 3-fold X. Its DT invariants count stable bundles and sheaves on X. Joyce's generalised DT invariants count semista ble sheaves on X.\n\nI will describe ongoing work with Soheyla Feyzbakhsh with the eventual aim of writing the generalised DT invariants in any rank r in terms of rank 1 invariants. By the MNOP conjecture the latter are de termined by the GW invariants of X.\n\nAlong the way we express rank r DT invariants in terms of rank 0 invariants counting D4-D2-D0 branes. These i nvariants are predicted by S-duality to be governed by (vector-valued mock ) modular forms.\n\nBased partly on arXiv:2007.03037 and arXiv:2103.02915 .\n LOCATION:https://researchseminars.org/talk/WHCGP/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Zohar Komargodski (SCGP\, Stony Brook) DTSTART:20210607T190000Z DTEND:20210607T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/35 DESCRIPTION:Title: H igher central charges and gapped boundaries\nby Zohar Komargodski (SCG P\, Stony Brook) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nThe chiral central charge is a famous diagnostic of edge modes on the boundary of 2+1 dimensional topological phases. We show that many theories with a vanishing chiral central charge nevertheless ca nnot admit a gapped boundary. We define higher chiral central charges and investigate their properties.\n LOCATION:https://researchseminars.org/talk/WHCGP/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Sarah Harrison (McGill University) DTSTART:20210712T190000Z DTEND:20210712T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/36 DESCRIPTION:Title: N ew BPS algebras from superstring compactifications\nby Sarah Harrison (McGill University) as part of Western Hemisphere colloquium on geometry a nd physics\n\n\nAbstract\nBorcherds Kac-Moody (BKM) algebras are a general ization of familiar Kac-Moody algebras with imaginary simple roots. On the one hand\, they were invented by Borcherds in his proof of the monstrous moonshine conjectures and have many interesting connections to new moonshi nes\, number theory and the theory of automorphic forms. On the other hand \, there is an old conjecture of Harvey and Moore that BPS states in strin g theory form an algebra that is in some cases a BKM algebra and which is based on certain signatures of BKMs observed in 4d threshold corrections a nd black hole physics. I will briefly review the construction of new BKMs superalgebras arising from self-dual vertex operator algebras of central c harge 12\, and then discuss recent work showing how they arise as algebras of BPS states in physical string theories in 2 dimensions\, as well as th eir connection with automorphic forms. Based on work with N. Paquette\, D. Persson\, and R. Volpato. This can be seen as a follow-up to a talk given by N. Paquette at this series this past October.\n LOCATION:https://researchseminars.org/talk/WHCGP/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Theo Johnson-Freyd (Perimeter/Dalhousie) DTSTART:20210726T190000Z DTEND:20210726T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/38 DESCRIPTION:Title: S emisimple higher categories\nby Theo Johnson-Freyd (Perimeter/Dalhousi e) as part of Western Hemisphere colloquium on geometry and physics\n\n\nA bstract\nSemisimple higher categories are a quantum version of topological spaces (behaving sometimes like homotopy types and sometimes like manifol ds) in which cells are attached along superpositions of other cells. Many operations from topology make sense for semisimple higher categories: they have homotopy sets (not groups)\, loop spaces\, etc. For example\, the ex tended operators in a topological sigma model form a semisimple higher cat egory that can be thought of as a type of "cotangent bundle" of the target space. The "symplectic pairing" on this "cotangent bundle" is measured an S-matrix pairing aka Whitehead bracket defined on the homotopy sets of an y (pointed connected) semisimple higher category\, and the nondegeneracy o f this pairing is a type of Poincare or Atiyah duality. This is joint work in progress with David Reutter.\n LOCATION:https://researchseminars.org/talk/WHCGP/38/ END:VEVENT BEGIN:VEVENT SUMMARY:Nathan Seiberg (IAS) DTSTART:20210927T190000Z DTEND:20210927T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/39 DESCRIPTION:Title: C omments on Lattice vs. Continuum Quantum Field Theory\nby Nathan Seibe rg (IAS) as part of Western Hemisphere colloquium on geometry and physics\ n\n\nAbstract\nThere is an interesting interplay between continuum quantum field theory (QFT) and lattice systems. First\, as in condensed-matter ph ysics\, we start at short distances (UV) with a lattice model and our goal is to find its long distance (IR) behavior. The lore is that this behavio r is captured by a continuum QFT. Conversely\, as is more common in high-e nergy physics and mathematical physics\, the lattice theory is a first ste p toward a rigorous definition of the continuum theory. Despite enormous p rogress over the past decades\, these two directions of the interplay betw een the lattice and the continuum face interesting challenges. \n\nHere\, motivated by recently discovered theoretical phases of matter (including t he XY-plaquette model and models of fractons)\, we will address two aspect s of the relation between the lattice in the UV and the continuum in the I R. We will present lattice models exhibiting topological properties of con tinuum theories\, like winding symmetries\, ‘t Hooft anomalies\, and dua lity. We will use this approach to clarify the subsystem global symmetries of some of the recently discovered exotic models. We will also discuss so me more dynamical aspects of these systems and in particular their enigmat ic UV/IR mixing\; i.e.\, some long-distance properties are sensitive to sh ort-distance details.\n LOCATION:https://researchseminars.org/talk/WHCGP/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Ryan Thorngren (Harvard University) DTSTART:20211011T190000Z DTEND:20211011T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/40 DESCRIPTION:Title: A Tour of Categorical Symmetry\nby Ryan Thorngren (Harvard University) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbst ract\nA categorical symmetry is a category acting as a symmetry of a QFT. These symmetries correspond to the topological operators in the QFT. I'll try to motivate this definition with some simple examples. Then I'll discu ss a bulk-boundary correspondence which in finite situations allows us to classify gapped phases with categorical symmetry and define things like an omalous symmetries and gauging. I'll conclude with some more examples of t opological operators in c = 1 CFTs and describe a Noether theorem for cont inuous categorical symmetries.\n LOCATION:https://researchseminars.org/talk/WHCGP/40/ END:VEVENT BEGIN:VEVENT SUMMARY:Ibrahima Bah (Johns Hopkins Univ.) DTSTART:20211025T190000Z DTEND:20211025T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/41 DESCRIPTION:Title: N on-supersymmetric smooth solitonic solutions in Einstein-Maxwell type theo ries\nby Ibrahima Bah (Johns Hopkins Univ.) as part of Western Hemisph ere colloquium on geometry and physics\n\n\nAbstract\nIn this talk I will present a recent framework to construct and study smooth horizon-less non- supersymmetric solutions in gravity with interesting topologies. These liv e in backgrounds that are 4d Minkowski with tori of various dimensions. I will discuss the physical mechanism that allows for their existence and co mment on their classical and thermodynamic stability. I will describe a fa mily of these constructions that resolve certain curvature singularities.\ n LOCATION:https://researchseminars.org/talk/WHCGP/41/ END:VEVENT BEGIN:VEVENT SUMMARY:Tony Pantev (University of Pennsylvania) DTSTART:20211108T200000Z DTEND:20211108T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/42 DESCRIPTION:Title: G eometry and topology of wild character varieties\nby Tony Pantev (Univ ersity of Pennsylvania) as part of Western Hemisphere colloquium on geomet ry and physics\n\n\nAbstract\nWild character varieties parametrize monodro my\nrepresentations of flat meromorphic connections on compact Riemann\nsu rfaces. They are classical objects with remarkable geometric and\ntopologi cal properties. \n\nI will recall how intrinsic geometric structures resol ve singularities\nof wild character varieties and will show that their al gebraic\nsymplectic structures extend naturally to the resolutions. This i s\nbased on a new universal method for producing symplectic structures\nwh ich is a joint work with Arinkin and Toen. I will also describe recent jo int works with\nChuang\, Diaconescu\, Donagi\, and Nawata in which we use string dualities \nto extract cohomological invariants of twisted wild cha racter\nvarieties from BPS counts on Calabi-Yau threefolds and refined\nC hern-Simons invariants of torus knots.\n LOCATION:https://researchseminars.org/talk/WHCGP/42/ END:VEVENT BEGIN:VEVENT SUMMARY:Lotte Hollands (Heriot-Watt University) DTSTART:20211122T200000Z DTEND:20211122T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/43 DESCRIPTION:Title: P artition functions\, BPS states and abelianization\nby Lotte Hollands (Heriot-Watt University) as part of Western Hemisphere colloquium on geome try and physics\n\n\nAbstract\nIn this talk I will re-express the Nekrasov -Shatashvili partition function for a four-dimensional N=2 gauge theory as an integral of a ratio of Wronskians of solutions to the relevant oper eq uation\, with the AD2 theory and the pure SU(2) theory as two main example s. This motivates the definition of a generalized Nekrasov-Shatashvili par tition function for any four-dimensional N=2 theory of class S\, and makes a connection with abelianization and exact WKB analysis. We will end with some remarks regarding the five-dimensional generalization and the relati on to similar mathematical structures underlying the topological string pa rtition function. This talk is based on 2109.14699 and work in progress.\n LOCATION:https://researchseminars.org/talk/WHCGP/43/ END:VEVENT BEGIN:VEVENT SUMMARY:Clay Córdova (University of Chicago) DTSTART:20211206T200000Z DTEND:20211206T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/44 DESCRIPTION:Title: N on-Invertible Duality Defects\nby Clay Córdova (University of Chicago ) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAb stract\nFor any quantum system invariant under gauging a higher-form globa l symmetry\, we construct a non-invertible topological defect by gauging i n only half of spacetime. This generalizes the Kramers-Wannier duality lin e in 1+1 dimensions to higher space- time dimensions. We focus on the case of a one-form symmetry in 3+1 dimensions\, and determine the fusion rule. From a direct analysis of one-form symmetry protected topological phases\ , we show that the existence of certain kinds of duality defects is intrin sically incompatible with a trivially gapped phase. We give an explicit re alization of this duality defect in the free Maxwell theory where it is re alized by a Chern-Simons coupling between the gauge fields from the two si des.\n LOCATION:https://researchseminars.org/talk/WHCGP/44/ END:VEVENT BEGIN:VEVENT SUMMARY:Pavel Etingof (MIT) DTSTART:20210913T190000Z DTEND:20210913T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/45 DESCRIPTION:Title: H ecke operators over local fields and an analytic approach to the geometric Langlands correspondence\nby Pavel Etingof (MIT) as part of Western H emisphere colloquium on geometry and physics\n\n\nAbstract\nI will review an analytic approach to the geometric Langlands correspondence\, following my work with E. Frenkel and D. Kazhdan\, arXiv:1908.09677\, arXiv:2103.01 509\, arXiv:2106.05243. This approach was developed by us in the last coup le of years and involves ideas from previous and ongoing works of a number of mathematicians and mathematical physicists\, Kontsevich\, Langlands\, Teschner\, and Gaiotto-Witten. One of the goals of this approach is to und erstand single-valued real analytic eigenfunctions of the quantum Hitchin integrable system. The main method of studying these functions is realizin g them as the eigenbasis for certain compact normal commuting integral ope rators the Hilbert space of L2 half-densities on the (complex points of) t he moduli space Bun_G of principal G-bundles on a smooth projective curve X\, possibly with parabolic points. These operators actually make sense ov er any local field\, and over non-archimedian fields are a replacement for the quantum Hitchin system. We conjecture them to be compact and prove th is conjecture in the genus zero case (with parabolic points) for G=PGL(2). I will first discuss the simplest non-trivial example of Hecke operators over local fields\, namely G=PGL(2) and genus 0 curve with 4 parabolic poi nts. In this case the moduli space of semistable bundles Bun_G^{ss} is P^1 \, and the situation is relatively well understood\; over C it is the theo ry of single-valued eigenfunctions of the Lame operator with coupling para meter -1/2 (previously studied by Beukers and later in a more functional-a nalytic sense in our work with Frenkel and Kazhdan). I will consider the c orresponding spectral theory and then explain its generalization to N>4 po ints and conjecturally to higher genus curves.\n LOCATION:https://researchseminars.org/talk/WHCGP/45/ END:VEVENT BEGIN:VEVENT SUMMARY:Hirosi Ooguri (Cal Tech) DTSTART:20220124T200000Z DTEND:20220124T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/46 DESCRIPTION:Title: S ymmetry in QFT and Gravity\nby Hirosi Ooguri (Cal Tech) as part of Wes tern Hemisphere colloquium on geometry and physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/46/ END:VEVENT BEGIN:VEVENT SUMMARY:Emily Cliff (Université de Sherbrooke) DTSTART:20220207T200000Z DTEND:20220207T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/47 DESCRIPTION:Title: M oduli spaces of principal 2-group bundles and a categorification of the Fr eed--Quinn line bundle\nby Emily Cliff (Université de Sherbrooke) as part of Western Hemisphere colloquium on geometry and physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/47/ END:VEVENT BEGIN:VEVENT SUMMARY:Heeyeon Kim (Rutgers University) DTSTART:20220509T190000Z DTEND:20220509T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/48 DESCRIPTION:Title: P ath integral derivations of K-theoretic Donaldson invariants\nby Heeye on Kim (Rutgers University) as part of Western Hemisphere colloquium on ge ometry and physics\n\n\nAbstract\nWe discuss path integral derivations of topologically twisted partition functions of 5d SU(2) supersymmetric Yang- Mills theory on M4 x S1\, where M4 is a smooth closed four-manifold. Mathe matically\, they can be identified with the K-theoretic version of the Don aldson invariants. In particular\, we provide two different path integral derivations of their wall-crossing formula for b_2^+(M4)=1\, first in the so-called U-plane integral approach\, and in the perspective of instanton counting. We briefly discuss the generalization to b_2^+(M4)>1.\n LOCATION:https://researchseminars.org/talk/WHCGP/48/ END:VEVENT BEGIN:VEVENT SUMMARY:Constantin Teleman (U. C. Berkeley) DTSTART:20220425T190000Z DTEND:20220425T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/49 DESCRIPTION:Title: C oulomb branches and Drinfeld centers\nby Constantin Teleman (U. C. Ber keley) as part of Western Hemisphere colloquium on geometry and physics\n\ n\nAbstract\nWe discuss a construction of Coulomb branches of a compact Li e group G from the Toda integrable systems and speculate on their origins as Drinfeld centers of modifications of (a variant of) the tensor category of topological representations of G.\n LOCATION:https://researchseminars.org/talk/WHCGP/49/ END:VEVENT BEGIN:VEVENT SUMMARY:Eric Zaslow (Northwestern University) DTSTART:20220228T200000Z DTEND:20220228T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/50 DESCRIPTION:Title: F raming Duality\nby Eric Zaslow (Northwestern University) as part of We stern Hemisphere colloquium on geometry and physics\n\n\nAbstract\nI will describe joint work in progress with Linhui Shen and Gus Schrader\, in whi ch we study moduli spaces of Fukaya objects and conjecture about their rel ationship to BPS and open Gromov-Witten invariants. This unabashedly synth esize previous works of many other groups\, whom I will credit in the talk . I will try to highlight some new aspects: 1) a definition of phases and framings and their combinatorial origins\; 2) conjectures on open Gromov-W itten invariants for Lagrangians bounding certain Legendrian surfaces\; 3) a “framing duality” relating Dondaldson-Thomas and open Gromov-Witten invariants.\n LOCATION:https://researchseminars.org/talk/WHCGP/50/ END:VEVENT BEGIN:VEVENT SUMMARY:Joerg Teschner (DESY) DTSTART:20220314T190000Z DTEND:20220314T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/51 DESCRIPTION:Title: T he complex geometry of topological string partition functions\nby Joer g Teschner (DESY) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nThe goal of this talk will be to review some aspec ts of a program inspired by work of Tom Bridgeland aiming at a non-perturb ative characterisation of topological string partition functions. The prog ram is based on two main ingredients: The complex geometry of the underlyi ng moduli spaces on the one hand\, and cluster algebra structures defined by BPS- or DT-invariants on the other hand. The general picture is nicely illustrated by the Borel summation of the conifold partition functions rec ently studied with M. Alim\, A. Saha and I. Tulli\, with Stokes jumps of t he partition functions getting related to wall-crossing phenomena in the t heory of DT-invariants. Based on this and other examples we will propose a conjectural characterisation of the partition functions for local Calabi- Yau manifolds\, generalising earlier proposals by Marino and collaborators \, and related to earlier proposals by Alexandrov\, Pioline and collaborat ors based on the geometry of hypermultiplet moduli spaces.\n LOCATION:https://researchseminars.org/talk/WHCGP/51/ END:VEVENT BEGIN:VEVENT SUMMARY:Washington Taylor (MIT) DTSTART:20220328T190000Z DTEND:20220328T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/52 DESCRIPTION:Title: M iddle intersection forms on singular elliptic Calabi-Yau fourfolds\, and a pplications to the standard model and mirror symmetry\nby Washington T aylor (MIT) as part of Western Hemisphere colloquium on geometry and physi cs\n\n\nAbstract\nRecent work with Jefferson and Turner indicates that the intersection form on the vertical part of middle cohomology of singular e lliptic Calabi-Yau fourfolds is independent of resolution. This suggests t hat the intersection structure should have a natural definition even in th ese singular geometries. The resulting intersection form has a simple bloc k-diagonal structure in terms of Kodaira singularities and the geometry of the base of the elliptic fibration\; the talk will describe applications of this intersection form to analysis of chiral matter and standard model constructions in F-theory as well as new insights into mirror symmetry\, i n particular providing in some cases a complete description of the interse ction form on H_4 (X\, Z) for a smooth Calabi-Yau fourfold including both vertical and horizontal parts.\n LOCATION:https://researchseminars.org/talk/WHCGP/52/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Halpern-Leistner (Cornell) DTSTART:20220411T190000Z DTEND:20220411T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/53 DESCRIPTION:Title: I nfinite dimensional geometric invariant theory and gauged Gromov-Witten th eory\nby Daniel Halpern-Leistner (Cornell) as part of Western Hemisphe re colloquium on geometry and physics\n\n\nAbstract\nHarder-Narasimhan (HN ) theory gives a structure theorem for holomorphic vector bundles on a Rie mann surface. A bundle is either semistable\, or it admits a canonical fil tration whose associated graded bundle is semistable in a graded sense. Af ter reviewing recent advances in extending HN theory to arbitrary moduli p roblems in algebraic geometry I will discuss work in progress with Andres Fernandez Herrero and Eduardo Gonzalez to apply this general machinery to the moduli problem of gauged maps from a curve C to a G-variety X\, where G is a reductive group. Our main immediate application is to use HN theory for gauged maps to compute generating functions for K-theoretic gauged Gr omov-Witten invariants. This problem is interesting more broadly because i t can be formulated as an example of an infinite dimensional analog of the usual set up of geometric invariant theory\, which has applications to ot her moduli problems.\n LOCATION:https://researchseminars.org/talk/WHCGP/53/ END:VEVENT BEGIN:VEVENT SUMMARY:Nathan Seiberg (Institute for Advanced Study) DTSTART:20230911T190000Z DTEND:20230911T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/54 DESCRIPTION:Title: E manant Symmetries\nby Nathan Seiberg (Institute for Advanced Study) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstra ct\nBased on joint work with Meng Cheng (arXiv:2211.12543)\, with Shu-Heng Shao (arXiv: 2307.02534)\, and with Shu- Heng Shao and Sahand Seifnashri (to appear)\, we will discuss some aspects of global symmetries and their ‘t Hooft anomalies. We will define a notion of an emanant global symmetr y. It is not a symmetry of the UV theory\, but unlike emergent (accidental ) symmetries\, it is not violated by any relevant or irrelevant operators in the IR theory. It is an exact symmetry of the low-energy theory. We wil l demonstrate this notion in several well-known examples. We will discuss in detail the Majorana chain\, the transverse field Ising model\, a contin uum system with a chemical potential\, and the Heisenberg chain. In all th ese models\, we will find emanant symmetries. In one case\, it is a non-in vertible emanant symmetry.\n LOCATION:https://researchseminars.org/talk/WHCGP/54/ END:VEVENT BEGIN:VEVENT SUMMARY:John Pardon (Simons Center for Geometry and Physics) DTSTART:20231016T190000Z DTEND:20231016T200000Z DTSTAMP:20260422T225723Z UID:WHCGP/55 DESCRIPTION:Title: U niversally counting curves in Calabi--Yau threefolds\nby John Pardon ( Simons Center for Geometry and Physics) as part of Western Hemisphere coll oquium on geometry and physics\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/WHCGP/55/ END:VEVENT BEGIN:VEVENT SUMMARY:Sabrina Pasterski (Perimeter Institute) DTSTART:20231211T200000Z DTEND:20231211T210000Z DTSTAMP:20260422T225723Z UID:WHCGP/56 DESCRIPTION:Title: C elestial holography from bottom-up to top-down\nby Sabrina Pasterski ( Perimeter Institute) as part of Western Hemisphere colloquium on geometry and physics\n\n\nAbstract\nThe Celestial Holography program encompasses re cent efforts to understand the flat space hologram in terms of a CFT livin g on the celestial sphere. A key development instigating these efforts cam e from understanding how soft limits of scattering encode infinite dimensi onal symmetry enhancements corresponding to the asymptotic symmetry group of the bulk spacetime. Historically\, the construction of the bulk-boundar y dual pair has followed bottom up approach matching symmetries on both si des. Recently\, however\, there has been exciting progress in formulating top down descriptions using insights from twisted holography. In this talk we will cover salient aspects of the celestial construction\, the status of the dictionary\, and active research directions.\n LOCATION:https://researchseminars.org/talk/WHCGP/56/ END:VEVENT END:VCALENDAR