BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Renzo Cavalieri (Colorado State University) DTSTART:20200925T153000Z DTEND:20200925T170000Z DTSTAMP:20260422T225927Z UID:UBC-AG/1 DESCRIPTION:Title: T ropical Psi Classes\nby Renzo Cavalieri (Colorado State University) as part of UBC Vancouver Algebraic Geometry Seminar\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/UBC-AG/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Pierrick Bousseau (ETH Zürich) DTSTART:20201002T153000Z DTEND:20201002T170000Z DTSTAMP:20260422T225927Z UID:UBC-AG/2 DESCRIPTION:Title: T he skein algebra of the 4-punctured sphere from curve counting\nby Pie rrick Bousseau (ETH Zürich) as part of UBC Vancouver Algebraic Geometry S eminar\n\n\nAbstract\nThe Kauffman bracket skein algebra is a quantization of the algebra of regular functions on the SL_2 character variety of a to pological surface. I will explain how to realize the skein algebra of the 4-punctured sphere as the output of a mirror symmetry construction based o n higher genus Gromov-Witten invariants of a log Calabi-Yau cubic surface. This leads to a proof of a previously conjectured positivity property of the bracelets bases of the skein algebras of the 4-punctured sphere and of the 1-punctured torus.\n LOCATION:https://researchseminars.org/talk/UBC-AG/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Tony Yue Yu (Université Paris-Sud\, Paris-Saclay) DTSTART:20201009T153000Z DTEND:20201009T170000Z DTSTAMP:20260422T225927Z UID:UBC-AG/3 DESCRIPTION:Title: S econdary fan\, theta functions and moduli of Calabi-Yau pairs\nby Tony Yue Yu (Université Paris-Sud\, Paris-Saclay) as part of UBC Vancouver Al gebraic Geometry Seminar\n\n\nAbstract\nWe conjecture that any connected c omponent Q of the moduli space of triples (X\,E=E1+⋯+En\,Θ) where X is a smooth projective variety\, E is a normal crossing anti-canonical diviso r with a 0-stratum\, every Ei is smooth\, and Θ is an ample divisor not c ontaining any 0-stratum of E\, is \\emph{unirational}. More precisely: not e that Q has a natural embedding into the Kollár-Shepherd-Barron-Alexeev moduli space of stable pairs\, we conjecture that its closure admits a fin ite cover by a complete toric variety. We construct the associated complet e toric fan\, generalizing the Gelfand-Kapranov-Zelevinski secondary fan f or reflexive polytopes. Inspired by mirror symmetry\, we speculate a synth etic construction of the universal family over this toric variety\, as the Proj of a sheaf of graded algebras with a canonical basis\, whose structu re constants are given by counts of non-archimedean analytic disks. In the Fano case and under the assumption that the mirror contains a Zariski ope n torus\, we construct the conjectural universal family\, generalizing the families of Kapranov-Sturmfels-Zelevinski and Alexeev in the toric case. In the case of del Pezzo surfaces with an anti-canonical cycle of (−1)-c urves\, we prove the full conjecture. The reference is arXiv:2008.02299 jo int with Hacking and Keel.\n LOCATION:https://researchseminars.org/talk/UBC-AG/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Yan Soibelman (Kansas State University) DTSTART:20201016T153000Z DTEND:20201016T170000Z DTSTAMP:20260422T225927Z UID:UBC-AG/4 DESCRIPTION:Title: E xponential integrals\, Holomorphic Floer theory and resurgence\nby Yan Soibelman (Kansas State University) as part of UBC Vancouver Algebraic Ge ometry Seminar\n\n\nAbstract\nHolomorphic Floer theory is a joint project with Maxim Kontsevich\, which is devoted to various aspects of the Floer t heory in the framework of complex symplectic manifolds.\n\nIn my talk I wi ll consider an important special case of the general story. Exponential i ntegrals in finite and infinite dimension can be thought of generalization of the theory of periods (i.e variations of Hodge structure). In particu lar\, there are comparison isomorphisms between Betti and de Rham cohomolo gy in the exponential setting. These isomorphisms are corollaries of categ orical equivalences which are incarnations of our generalized Riemann-Hilb ert correspondence for complex symplectic manifolds.\n\nFurthermore\, foma l series which appear e.g. in the stationary phase method or Feynman expan sions (in infinite dimensions) are Borel re-summable (resurgent). If time permits I will explain the underlying mathematical structure which we call analytic wall-crossing structure. From the perspective of Holomorphic Flo er theory it is related to the estimates for the number of pseudo-holomorp hic discs with boundaries on two given complex Lagrangian submanifolds.\n LOCATION:https://researchseminars.org/talk/UBC-AG/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Dragos Oprea (UCSD) DTSTART:20201023T153000Z DTEND:20201023T170000Z DTSTAMP:20260422T225927Z UID:UBC-AG/5 DESCRIPTION:Title: V irtual invariants of Quot schemes of surfaces\nby Dragos Oprea (UCSD) as part of UBC Vancouver Algebraic Geometry Seminar\n\n\nAbstract\nThe Quo t schemes of surfaces parametrizing quotients of dimension at most 1 of th e trivial sheaf carry 2-term perfect obstruction theories. Several generat ing series of associated virtual invariants are conjectured to be given by rational functions. We show this is the case for several geometries inclu ding all smooth projective surfaces with p_g>0. This talk is based on join t work with Noah Arbesfeld\, Drew Johnson\, Woonam Lim and Rahul Pandharip ande.\n LOCATION:https://researchseminars.org/talk/UBC-AG/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Halpern-Leistner (Cornell University) DTSTART:20201030T153000Z DTEND:20201030T170000Z DTSTAMP:20260422T225927Z UID:UBC-AG/6 DESCRIPTION:Title: D erived Theta-stratifications and the D-equivalence conjecture\nby Dani el Halpern-Leistner (Cornell University) as part of UBC Vancouver Algebrai c Geometry Seminar\n\n\nAbstract\nThe D-equivalence conjecture predicts th at birationally equivalent projective Calabi-Yau manifolds have equivalent derived categories of coherent sheaves. It is motivated by homological mi rror symmetry\, and has inspired a lot of recent work on connections betwe en birational geometry and derived categories. In dimension 3\, the conjec ture is settled\, but little is known in higher dimensions. I will discuss a proof of this conjecture for the class of Calab-Yau manifolds that are birationally equivalent to some moduli space of stable sheaves on a K3 sur face. This is the only class for which the conjecture is known in dimensio n >3. The proof uses a more general structure theory for the derived categ ory of an algebraic stack equipped with a Theta-stratification\, which we apply in this case to the Harder-Narasimhan stratification of the moduli o f sheaves.\n LOCATION:https://researchseminars.org/talk/UBC-AG/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Yifeng Huang (University of Michigan) DTSTART:20201106T170000Z DTEND:20201106T180000Z DTSTAMP:20260422T225927Z UID:UBC-AG/7 DESCRIPTION:Title: C ohomology of configuration spaces of punctured varieties\nby Yifeng Hu ang (University of Michigan) as part of UBC Vancouver Algebraic Geometry S eminar\n\n\nAbstract\nGiven a smooth complex variety $X$ (not necessarily compact)\, consider the unordered configuration space $Conf^n(X)$ defined as ${(x_1\,...\,x_n)\\in X^n: x_i \\neq x_j\\ \\text{for}\\ i\\neq j} / S_ n$. The singular cohomology of $Conf^n(X)$ has long been an active area of research. In this talk\, we investigate the following phenomenon: "punctu ring once more" seems to have a very predictable effect on the cohomology of configuration spaces when the variety we start with is noncompact. In s pecific\, a formula of Napolitano determines the Betti numbers of $Conf^n( X - {P})$ from the Betti numbers of $Conf^m(X)$ $(m \\leq n)$ if $X$ is a smooth *noncompact* algebraic curve and $P$ is a point. We present a new p roof using an explicit algebraic method\, which also upgrades this formula about Betti numbers into a formula about mixed Hodge numbers and generali zes this formula to certain cases where $X$ is of higher dimension.\n LOCATION:https://researchseminars.org/talk/UBC-AG/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Emily Clader (San Francisco State University) DTSTART:20201120T170000Z DTEND:20201120T180000Z DTSTAMP:20260422T225927Z UID:UBC-AG/8 DESCRIPTION:Title: P ermutohedral Complexes and Curves With Cyclic Action\nby Emily Clader (San Francisco State University) as part of UBC Vancouver Algebraic Geomet ry Seminar\n\n\nAbstract\nAlthough the moduli space of genus-zero curves i s not a toric\nvariety\, it shares an intriguing amount of the combinatori al structure that a\ntoric variety would enjoy. In fact\, by adjusting the moduli problem slightly\,\none finds a moduli space that is indeed toric\ , known as Losev-Manin space. The\nassociated polytope is the permutohedro n\, which also encodes the\ngroup-theoretic structure of the symmetric gro up. Batyrev and Blume generalized\nthis story by constructing a "type-B" v ersion of Losev-Manin space\, whose\nassociated polytope is a signed permu tohedron that relates to the group of\nsigned permutations. In joint work in progress with C. Damiolini\, D. Huang\, S.\nLi\, and R. Ramadas\, we ca rry out the next stage of generalization\, defining a\nfamily of moduli sp ace of curves with Z_r action encoded by an associated\n"permutohedral com plex" for a more general complex reflection group\, which\nspecializes whe n r=2 to Batyrev and Blume's moduli space.\n LOCATION:https://researchseminars.org/talk/UBC-AG/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Dustin Ross (San Francisco State University) DTSTART:20201127T170000Z DTEND:20201127T180000Z DTSTAMP:20260422T225927Z UID:UBC-AG/9 DESCRIPTION:Title: P utting the "volume" back in volume polynomials\nby Dustin Ross (San Fr ancisco State University) as part of UBC Vancouver Algebraic Geometry Semi nar\n\n\nAbstract\nIt is a strange and wonderful fact that Chow rings of m atroids behave in many ways similarly to Chow rings of smooth projective v arieties. Because of this\, the Chow ring of a matroid is determined by a homogeneous polynomial called its volume polynomial\, whose coefficients r ecord the degrees of all possible top products of divisors. The use of the word "volume" is motivated by the fact that the volume polynomial of a sm ooth projective toric variety actually measures the volumes of certain pol ytopes associated to the variety. In the matroid setting\, on the other ha nd\, no such polytopes exist\, and the goal of our work was to find more g eneral polyhedral objects whose volume is measured by the volume polynomia l of matroids. In this talk\, I will motivate and describe these polyhedra l objects. This is joint work with Anastasia Nathanson.\n LOCATION:https://researchseminars.org/talk/UBC-AG/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Junliang Shen (MIT) DTSTART:20201204T163000Z DTEND:20201204T173000Z DTSTAMP:20260422T225927Z UID:UBC-AG/10 DESCRIPTION:Title: Intersection cohomology of the moduli of of 1-dimensional sheaves and the moduli of Higgs bundles\nby Junliang Shen (MIT) as part of UBC Vancouv er Algebraic Geometry Seminar\n\n\nAbstract\nIn general\, the topology of the moduli space of semistable sheaves on an algebraic variety relies heav ily on the choice of the Euler characteristic of the sheaves. We show a st riking phenomenon that\, for the moduli of 1-dimensional semistable sheave s on a toric del Pezzo surface (e.g. P^2) or the moduli of semistable Higg s bundles with respect to a divisor of degree > 2g-2 on a curve\, the inte rsection cohomology of the moduli space is independent of the choice of th e Euler characteristic. This confirms a conjecture of Bousseau for P^2\, and proves a conjecture of Toda in the case of local toric Calabi-Yau 3-fo lds. In the proof\, a generalized version of Ngô's support theorem plays a crucial role. Based on joint work in progress with Davesh Maulik.\n LOCATION:https://researchseminars.org/talk/UBC-AG/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Christopher Woodward (Rutgers University) DTSTART:20201113T163000Z DTEND:20201113T173000Z DTSTAMP:20260422T225927Z UID:UBC-AG/11 DESCRIPTION:Title: Quantum K-theory of git quotients\nby Christopher Woodward (Rutgers Un iversity) as part of UBC Vancouver Algebraic Geometry Seminar\n\n\nAbstrac t\n(w E. Gonzalez) I will discuss a generalization of the Kirwan map to q uantum K-theory\, a presentation of quantum K-theory of toric varieties\, and some open questions.\n LOCATION:https://researchseminars.org/talk/UBC-AG/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Ming Zhang (UBC) DTSTART:20201113T174500Z DTEND:20201113T184500Z DTSTAMP:20260422T225927Z UID:UBC-AG/13 DESCRIPTION:Title: Verlinde/Grassmannian Correspondence\nby Ming Zhang (UBC) as part of U BC Vancouver Algebraic Geometry Seminar\n\n\nAbstract\nIn the 90s'\, Witte n gave a physical derivation of an isomorphism between the Verlinde algebr a of $\\mathrm{GL}(n)$ of level l and the quantum cohomology ring of the G rassmannian $\\mathrm{Gr}(n\,n+l)$. In the joint work arXiv:1811.01377 wit h Yongbin Ruan\, we proposed a $K$-theoretic generalization of Witten's wo rk by relating the $\\mathrm{GL}_n$ Verlinde numbers to the level $l$ quan tum $K$-invariants of the Grassmannian $\\mathrm{Gr}(n\,n+l)$\, and refer to it as the Verlinde/Grassmannian correspondence. The correspondence was formulated precisely in the aforementioned paper\, and we proved the rank 2 case ($n$=2) there.\n\nIn this talk\, I will first explain the backgroun d of this correspondence and its interpretation in physics. Then I will di scuss the main idea of the proof for arbitrary rank. A new technical ingre dient is the virtual nonabelian localization formula developed by Daniel H alpern-Leistner.\n LOCATION:https://researchseminars.org/talk/UBC-AG/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Henry Liu (Columbia University) DTSTART:20210201T230000Z DTEND:20210202T000000Z DTSTAMP:20260422T225927Z UID:UBC-AG/14 DESCRIPTION:Title: Quasimaps and stable pairs\nby Henry Liu (Columbia University) as part of UBC Vancouver Algebraic Geometry Seminar\n\n\nAbstract\nI will explain an equivalence between a flavor of Donaldson-Thomas theory (due to Bryan and Steinberg) on ADE surface fibrations and quasimaps to Hilbert schemes of ADE surfaces. The proof involves an explicit combinatorial description of vertices. The equivalence can be used to relate machinery from both sid es\, notably an equivariant K-theoretic DT crepant resolution conjecture a nd 3d mirror symmetry.\n LOCATION:https://researchseminars.org/talk/UBC-AG/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Qile Chen (Boston College) DTSTART:20210322T220000Z DTEND:20210322T230000Z DTSTAMP:20260422T225927Z UID:UBC-AG/15 DESCRIPTION:Title: Counting curves in critical locus via logarithmic compactifications\nb y Qile Chen (Boston College) as part of UBC Vancouver Algebraic Geometry S eminar\n\n\nAbstract\nI will introduce some recent developments and work i n progress on\nstudying Gauged Linear Sigma Models using logarithmic compa ctifications.\n\nThese logarithmic compactifications admit two types of vi rtual cycles ---\nthe reduced virtual cycles that recover Gromov-Witten in variants of\ncomplete intersections\, and the canonical virtual cycles th at depend only\non the geometry of ambient spaces. These two types of virt ual cycles differ\nonly by a third virtual cycle of the boundary of the lo garithmic\ncompactifications. Using the punctured logarithmic maps of\nAbr amovich-Chen-Gross-Siebert\, these virtual cycles can be computed via the\ ntropical and equivariant geometry of the logarithmic compactifications.\n This leads to a new method for computing Gromov-Witten invariants of\ncomp lete intersections.\n\nThe talk consists of joint work with Felix Janda\, Yongbin Ruan\, Adrien\nSauvaget and Rachel Webb.\n LOCATION:https://researchseminars.org/talk/UBC-AG/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Jack Petok (Dartmouth College) DTSTART:20210315T220000Z DTEND:20210315T230000Z DTSTAMP:20260422T225927Z UID:UBC-AG/16 DESCRIPTION:Title: Kodaira dimensions of some moduli spaces of hyperkähler fourfolds\nby Jack Petok (Dartmouth College) as part of UBC Vancouver Algebraic Geometr y Seminar\n\n\nAbstract\nWe use modular forms to study the birational geom etry of some moduli spaces of hyperkähler fourfolds. I'll review a bit of the algebraic geometry of these moduli spaces\, and then I'll explain som e methods\, due to Gritsenko\, Hulek\, and Sankaran\, for computing their Kodaira dimensions. These methods make use of special modular forms define d on high rank orthogonal groups. I'll also report on an ongoing project w ith Jen Berg applying related techniques to certain moduli spaces of Enriq ues surfaces.\n LOCATION:https://researchseminars.org/talk/UBC-AG/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Dylan G.L. Allegretti (UBC) DTSTART:20210118T230000Z DTEND:20210119T000000Z DTSTAMP:20260422T225927Z UID:UBC-AG/17 DESCRIPTION:Title: Wall-crossing and differential equations\nby Dylan G.L. Allegretti (UB C) as part of UBC Vancouver Algebraic Geometry Seminar\n\n\nAbstract\nThe Kontsevich-Soibelman wall-crossing formula describes the wall-crossing beh avior of BPS invariants in Donaldson-Thomas theory. It can be formulated a s an identity between (possibly infinite) products of automorphisms of a f ormal power series ring. In this talk\, I will explain how these same prod ucts also appear in the exact WKB analysis of Schrödinger's equation. In this context\, they describe the Stokes phenomenon for objects known as Vo ros symbols.\n LOCATION:https://researchseminars.org/talk/UBC-AG/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Arnav Tripathy (Harvard University) DTSTART:20210329T220000Z DTEND:20210329T230000Z DTSTAMP:20260422T225927Z UID:UBC-AG/18 DESCRIPTION:Title: K3s as Hyperkahler Quotients\nby Arnav Tripathy (Harvard University) a s part of UBC Vancouver Algebraic Geometry Seminar\n\n\nAbstract\nI'll exp lain how to construct K3 surfaces as hyperkahler quotients and\, as time p ermits\, our expected application to counting open GW invariants. This is all joint work with M. Zimet.\n LOCATION:https://researchseminars.org/talk/UBC-AG/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Yu-Wei Fan (UC Berkeley) DTSTART:20210208T230000Z DTEND:20210209T000000Z DTSTAMP:20260422T225927Z UID:UBC-AG/19 DESCRIPTION:Title: Stokes matrices\, character varieties\, and points on spheres\nby Yu-W ei Fan (UC Berkeley) as part of UBC Vancouver Algebraic Geometry Seminar\n \n\nAbstract\nModuli spaces of points on n-spheres carry natural actions o f braid groups. For n=0\,1\, and 3\, we prove that these symmetries extend to actions of mapping class groups of positive genus surfaces\, through e xceptional isomorphisms with certain character varieties. We also apply th e exceptional isomorphisms to the study of Stokes matrices and exceptional collections of triangulated categories. Joint work with Junho Peter Whang .\n LOCATION:https://researchseminars.org/talk/UBC-AG/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Mark Shoemaker (Colorado State University) DTSTART:20210222T230000Z DTEND:20210223T000000Z DTSTAMP:20260422T225927Z UID:UBC-AG/20 DESCRIPTION:Title: A mirror theorem for gauged linear sigma models\nby Mark Shoemaker (Co lorado State University) as part of UBC Vancouver Algebraic Geometry Semin ar\n\n\nAbstract\nLet G be a finite group acting on a smooth complex varie ty M. Let X —> M/G be a crepant resolution by a smooth variety X. The Crepant Resolution Conjecture predicts a complicated relationship between the Gromov—Witten invariants of X and the orbifold Gromov—Witten inva riants of the stack [M/G].\n\nIn this talk I will describe an analogous co njecture involving Landau—Ginzburg (LG) models. An LG model is\, roughl y\, a smooth complex variety Y together with a regular function w: Y—> \ \CC. LG models can be used to give alternate “resolutions” of hypersu rface singularities in a certain sense and are related to so-called noncom mutative resolutions. I will briefly discuss the gauged linear sigma model \, which is used to define curve counting invariants for LG models\, and d escribe a new technique for computing these invariants.\n LOCATION:https://researchseminars.org/talk/UBC-AG/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Yefeng Shen (University of Oregon) DTSTART:20210301T230000Z DTEND:20210302T000000Z DTSTAMP:20260422T225927Z UID:UBC-AG/21 DESCRIPTION:Title: Virasoro constraints in quantum singularity theory\nby Yefeng Shen (Un iversity of Oregon) as part of UBC Vancouver Algebraic Geometry Seminar\n\ n\nAbstract\nIn this talk\, we introduce Virasoro operators in quantum sin gularity theories for nondegenerate quasi-homogeneous polynomials with non trivial diagonal symmetries. Using Givental's quantization formula of quad ratic Hamiltonians\, these operators satisfy the Virasoro relations. Inspi red by the famous Virasoro conjecture in Gromov-Witten theory\, we conject ure that the genus g generating functions arise in quantum singularity the ories are annihilated by the Virasoro operators. We verify the conjecture in various examples and discuss the connections to mirror symmetry of LG m odels and LG/CY correspondence. This talk is based on work joint with Weiq iang He.\n LOCATION:https://researchseminars.org/talk/UBC-AG/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Davesh Maulik (MIT) DTSTART:20210308T230000Z DTEND:20210309T000000Z DTSTAMP:20260422T225927Z UID:UBC-AG/22 DESCRIPTION:Title: Cohomology of the moduli of Higgs bundles and the Hausel-Thaddeus conjectu re\nby Davesh Maulik (MIT) as part of UBC Vancouver Algebraic Geometry Seminar\n\n\nAbstract\nIn this talk\, I will discuss some results on the structure of the cohomology of the moduli space of stable SL_n Higgs bundl es on a curve. One consequence is a new proof of the Hausel-Thaddeus conje cture proven previously by Groechenig-Wyss-Ziegler via p-adic integration. We will also discuss connections to the P=W conjecture if time permits. B ased on joint work with Junliang Shen.\n LOCATION:https://researchseminars.org/talk/UBC-AG/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Zijun Zhou (IPMU) DTSTART:20210412T220000Z DTEND:20210412T230000Z DTSTAMP:20260422T225927Z UID:UBC-AG/23 DESCRIPTION:Title: 3d mirror symmetry\, vertex function\, and elliptic stable envelope\nb y Zijun Zhou (IPMU) as part of UBC Vancouver Algebraic Geometry Seminar\n\ n\nAbstract\n3d mirror symmetry is a duality in physics\, where Higgs and Coulomb branches of certain pairs of 3d N=4 SUSY gauge theories are exchan ged with each other. Motivated from this\, M. Aganagic and A. Okounkov int roduced the enumerative geometric conjecture that the vertex functions of the mirror theories are related to each other. The two sets of q-differenc e equations satisfied by the vertex functions\, in terms of the K\\"ahler and equivariant parameters\, are expected to exchange with each other. The conjecture therefore leads to a nontrivial relation between their monodro my matrices\, the so-called elliptic stable envelopes. In this talk\, I wi ll discuss the proof in several cases of the conjecture for both vertex fu nctions and elliptic stable envelopes. This is based on joint works with R . Rim\\'anyi\, A. Smirnov\, and A. Varchenko.\n LOCATION:https://researchseminars.org/talk/UBC-AG/23/ END:VEVENT END:VCALENDAR