BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Henri Guenancia (CNRS - Univ. Toulouse) DTSTART:20200508T150000Z DTEND:20200508T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/1 DESCRIPTION:Title: F amilies of singular Kähler-Einstein metrics\nby Henri Guenancia (CNRS - Univ. Toulouse) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nI will outline the main results and ideas from a recent joint work with E. Di Nezza and V. Guedj. The general theme is as f ollows: let p:X\\to Y be a holomorphic\, proper surjective map from a comp lex Kähler space X and assume that the fibers X_y admit some (possibly tw isted) singular Kähler-Einstein metric. We show that the potentials of th ese metrics admit uniform bounds when y varies in compact subsets. If time permits\, I will mention a connection with an earlier work (joint with J. Cao and M. Paun) on the psh variation of the Kähler-Einstein metric on f amilies of manifolds of general type.\n LOCATION:https://researchseminars.org/talk/CIRGET/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Ekaterina Amerik (Univ. Paris Sud) DTSTART:20200515T150000Z DTEND:20200515T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/2 DESCRIPTION:Title: A round the cone conjecture for hyperkähler manifolds\nby Ekaterina Ame rik (Univ. Paris Sud) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nThe Morrison-Kawamata cone conjecture states t hat the automorphism group of a Calabi-Yau manifold acts with finitely man y orbits on the set of faces of its ample cone. I shall sketch its proof i n the hyperkähler case with some emphasis on a statement on Lie groups be hind it. All results\nare joint work with Misha Verbitsky.\n LOCATION:https://researchseminars.org/talk/CIRGET/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Patrick Orson (Boston College) DTSTART:20200522T150000Z DTEND:20200522T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/3 DESCRIPTION:Title: T opologically embedding spheres in knot traces\nby Patrick Orson (Bosto n College) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\n\nAbstract\nKnot traces are smooth 4-manifolds with boundary\, that a re homotopic to the 2-sphere\, and obtained by attaching a 2-handle to the 4-ball along a framed knot in the 3-sphere. I will give a complete charac terisation for when the generator of the second homotopy group of a knot t race can be represented by a locally flat embedded 2-sphere with abelian e xterior fundamental group. The answer is in terms of\nclassical and comput able invariants of the knot. This is a joint project with Feller\, Miller\ , Nagel\, Powell\, and Ray.\n LOCATION:https://researchseminars.org/talk/CIRGET/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Lukas Lewark (Univ. Regensburg) DTSTART:20200529T150000Z DTEND:20200529T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/4 DESCRIPTION:Title: S queezed knots\nby Lukas Lewark (Univ. Regensburg) as part of CRM - Sé minaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nA knot is call ed squeezed if it is a slice of a smooth cobordism of minimal genus betwee n a positive knot and a negative knot. Most small knots are squeezed\, as are many classes of knots\, such as alternating knots. However\, Khovanov homology and related tools may obstruct squeezedness. This is joint work i n progress with Peter Feller and Andrew Lobb.\n LOCATION:https://researchseminars.org/talk/CIRGET/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Ben Weinkove (Northwestern Univ.) DTSTART:20200605T150000Z DTEND:20200605T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/5 DESCRIPTION:Title: T he Chern-Ricci flow\nby Ben Weinkove (Northwestern Univ.) as part of C RM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nThe Ch ern-Ricci flow is a flow of Hermitian metrics by their Chern-Ricci form. It generalizes the Kahler-Ricci flow to the setting of non-Kahler metrics on complex manifolds. I will give an overview of known results for this f low and describe some open problems.\n LOCATION:https://researchseminars.org/talk/CIRGET/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Eiji Inoue (Tokyo Univ.) DTSTART:20200612T150000Z DTEND:20200612T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/6 DESCRIPTION:Title: m u-cscK metrics and muK-stability of polarized manifolds\nby Eiji Inoue (Tokyo Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topo logie\n\n\nAbstract\nI will talk about a framework unifying both the frame works on "cscK metrics and K-stability of polarized manifolds" and "Kahler -Ricci solitons and modified K-stability of Fano manifolds". There are two divided contents as follows. \n\n1. Formulation of mu-cscK metrics and br ief remarks on results parallel to the usual canonical metrics. On some at tractive special features/phenomenon of mu-cscK metrics\; "extremal limit" and "phase transition". On a little examples. \n\n2. How to formulate/der ive/express mu-Futaki invariant of test configurations with general singul arities. On a counterpart of CM line bundle for muK-stability. \n\nIf time permits\, I will also propose future problems/projects and its applicatio ns\, especially towards the algebraic moduli problems of Fano varieties ad mitting Kahler-Ricci solitons.\n LOCATION:https://researchseminars.org/talk/CIRGET/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Martin Bobb (UT Austin) DTSTART:20200626T150000Z DTEND:20200626T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/7 DESCRIPTION:Title: D ecomposition along flats for convex projective manifolds\nby Martin Bo bb (UT Austin) as part of CRM - Séminaire du CIRGET / Géométrie et Topo logie\n\n\nAbstract\nReal convex projective geometry generalizes hyperboli c geometry in a way that allows for interesting deformation theory and als o aspects of non-positive curvature. In this talk I will introduce convex projective geometry\, and we will discuss a natural decomposition of compa ct convex projective manifolds along their codimension-1 flat substructure s. This extends a celebrated 2006 result of Benoist: a 'geometric JSJ-deco mposition' for compact convex projective 3-manifolds to manifolds of every dimension (greater than 2).\n LOCATION:https://researchseminars.org/talk/CIRGET/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Vaibhav Gadre (Univ. of Glasgow) DTSTART:20200619T150000Z DTEND:20200619T163000Z DTSTAMP:20260422T225753Z UID:CIRGET/8 DESCRIPTION:Title: S tatistical hyperbolicity of Teichmuller spaces\nby Vaibhav Gadre (Univ . of Glasgow) as part of CRM - Séminaire du CIRGET / Géométrie et Topol ogie\n\n\nAbstract\nThe notion of statistical hyperbolicity introduced by Duchin-Lelievre-Mooney encapsulates whether a space is on average hyperbol ic at large scales\, that is\, whether average distance between pairs of p oints on large spheres of radius R is 2R. In this talk\, I will explain ho w Teichmuller spaces are statistically hyperbolic with respect to stationa ry measures arising random walks on mapping class groups. This is joint wo rk with Aitor Azemar and Luke Jeffreys and extends previous work of Dowdal l-Duchin-Masur.\n LOCATION:https://researchseminars.org/talk/CIRGET/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Gabriele Mondello (Univ. di Roma "Sapienza") DTSTART:20200710T150000Z DTEND:20200710T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/9 DESCRIPTION:Title: O n spherical surfaces of genus 1 with 1 conical point\nby Gabriele Mond ello (Univ. di Roma "Sapienza") as part of CRM - Séminaire du CIRGET / G éométrie et Topologie\n\n\nAbstract\nA spherical metric on a surface is a metric of constant curvature 1.\nSuch a metric has a conical point x of angle $2\\pi\\theta$ if it has vanishing order $(\\theta-1)$ at x.\nA sphe rical metric in an assigned conformal class can be viewed on one hand as a solution of a suitable singular Liouville equation.\nOn the other hand\, when the conformal class is not prescribed\, isotopy classes of spherical metrics can be considered as flat (SO(3\,R)\,S^2)-structure\, and so their moduli space has a natural finite-dimensional real-analytic structure.\n\ nI will discuss recent results on the topology of such moduli space of sph erical metrics with conical points of assigned angles.\nI will then focus on the case of genus 1 with 1 conical point.\n\nThis is joint work with Er emenko-Panov and with Eremenko-Gabrielov-Panov.\n LOCATION:https://researchseminars.org/talk/CIRGET/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Nicolina Istrati (Tel Aviv Univ.) DTSTART:20200703T150000Z DTEND:20200703T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/10 DESCRIPTION:Title: Variational problems in conformal geometry\nby Nicolina Istrati (Tel A viv Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\n\nAbstract\nI will present several natural functionals defined on a c onformal class of almost Hermitian metrics on a compact manifold\, and I w ill establish their Euler-Lagrange equations. I will show that the Gauduch on metrics appear naturally as the unique extremal metrics of one such fun ctional. Next\, a new class of metrics will be introduced\, also appearing as extremal in complex dimension two. I will show that these new metrics\ , while not Gauduchon in general\, give again unique representatives\, up to constant multiples\, of conformal classes of almost Hermitian metrics. This is joint work with D. Angella\, A. Otiman and N. Tardini.\n LOCATION:https://researchseminars.org/talk/CIRGET/10/ END:VEVENT BEGIN:VEVENT SUMMARY:Joshua Howie (UC Davis) DTSTART:20200717T150000Z DTEND:20200717T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/11 DESCRIPTION:by Joshua Howie (UC Davis) as part of CRM - Séminaire du CIRG ET / Géométrie et Topologie\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/11/ END:VEVENT BEGIN:VEVENT SUMMARY:Livio Liechti (Université de Fribourg) DTSTART:20200724T150000Z DTEND:20200724T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/12 DESCRIPTION:Title: Divide knots of maximal genus defect\nby Livio Liechti (Université de Fribourg) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/12/ END:VEVENT BEGIN:VEVENT SUMMARY:Andrew Lobb (University of Durham\, UK) DTSTART:20200911T150000Z DTEND:20200911T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/13 DESCRIPTION:Title: The rectangular peg problem\nby Andrew Lobb (University of Durham\, UK ) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nAbst ract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/13/ END:VEVENT BEGIN:VEVENT SUMMARY:Carlo Scarpa (SISSA\, Italy) DTSTART:20200918T150000Z DTEND:20200918T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/14 DESCRIPTION:Title: The Hitchin-cscK system\nby Carlo Scarpa (SISSA\, Italy) as part of CR M - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nA class ic result in the study of Kähler metrics with special curvature propertie s is that the cscK equation can be realized as the moment map equation for an infinite-dimensional Kähler reduction. We present a natural hyperkäh ler extension of this moment map picture\, obtaining a new system of equat ions reminiscent of Hitchin's equations for Higgs bundles. We will discuss some recent existence results\, particularly obstructions to solutions to the problem.\n LOCATION:https://researchseminars.org/talk/CIRGET/14/ END:VEVENT BEGIN:VEVENT SUMMARY:Jonathan Johnson (University of Texas at Austin\, US) DTSTART:20200925T150000Z DTEND:20200925T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/15 DESCRIPTION:Title: Bi-Orderability and Pretzel Knots\nby Jonathan Johnson (University of Texas at Austin\, US) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nThis talk concerns the bi-orderability of pret zel knot groups which appears to have a weird connection to the Heegaard F loer properties of the cyclic branched covers of the knots. In a recent pa per\, several new examples of bi-orderable pretzel knots are found. We\nwi ll discuss these results and some of their implications to this strange co incidence of orderability and Heegaard Floer.\n LOCATION:https://researchseminars.org/talk/CIRGET/15/ END:VEVENT BEGIN:VEVENT SUMMARY:Junyan Cao (Université de Nice\, France) DTSTART:20201002T150000Z DTEND:20201002T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/16 DESCRIPTION:Title: On the Ohsawa-Takegoshi extension theorem\nby Junyan Cao (Université de Nice\, France) as part of CRM - Séminaire du CIRGET / Géométrie et T opologie\n\n\nAbstract\nSince it was established\, the Ohsawa-Takegoshi ex tension theorem turned out to be a fundamental tool in complex geometry. W e establish a new extension result for twisted canonical forms defined on a hypersurface with simple normal crossings of a projective manifold with a control on its L^2 norme. It is a joint work with Mihai Pãun.\n LOCATION:https://researchseminars.org/talk/CIRGET/16/ END:VEVENT BEGIN:VEVENT SUMMARY:Christina Tonnesen-Friedman (Union College\, US) DTSTART:20201009T150000Z DTEND:20201009T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/17 DESCRIPTION:Title: Sasaki-Einstein metrics and the Iterated join\nby Christina Tonnesen-F riedman (Union College\, US) as part of CRM - Séminaire du CIRGET / Géom étrie et Topologie\n\n\nAbstract\nIn this talk\, which is based on joint works with Charles Boyer\, I will discuss the idea of using the join const ruction in Sasakian Geometry in a non-trivial iterative way in order to ar rive at some explicit Sasaki-Einstein examples in higher dimensions.\n LOCATION:https://researchseminars.org/talk/CIRGET/17/ END:VEVENT BEGIN:VEVENT SUMMARY:Yi Ni (Caltech\, US) DTSTART:20201016T150000Z DTEND:20201016T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/18 DESCRIPTION:Title: Seifert fibered surgeries on hyperbolic fibered knots\nby Yi Ni (Calte ch\, US) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\ n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/18/ END:VEVENT BEGIN:VEVENT SUMMARY:Aru Ray (MPIM Bonn\, Germany) DTSTART:20201023T150000Z DTEND:20201023T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/19 DESCRIPTION:Title: Embedding surfaces in 4-manifolds\nby Aru Ray (MPIM Bonn\, Germany) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstra ct\nI will present a surface embedding theorem for 4-manifolds with good f undamental group in the presence of potentially unframed\, immersed dual s pheres. The essential obstruction is the Kervaire-Milnor invariant and a g oal of the talk is to describe how it may be computed. This is based on jo int work with Daniel Kasprowski\, Mark Powell\, and Peter Teichner.\n LOCATION:https://researchseminars.org/talk/CIRGET/19/ END:VEVENT BEGIN:VEVENT SUMMARY:Hugues Auvray (Paris Orsay\, France) DTSTART:20201030T150000Z DTEND:20201030T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/20 DESCRIPTION:Title: Noyaux de Bergman sur les surfaces de Riemann épointées\nby Hugues A uvray (Paris Orsay\, France) as part of CRM - Séminaire du CIRGET / Géom étrie et Topologie\n\n\nAbstract\nDans des travaux en commun avec X. Ma ( Paris 7) et G. Marinescu (Cologne)\, nous obtenons des asymptotiques raffi nées pour des noyaux de Bergman calculées à partir de données singuli ères. On travaille sur le complémentaire d'un nombre fini de points\, vu s comme singularités\, dans une surface de Riemann compacte\, que l'on mu nit d'une métrique étendant la métrique cusp de Poincaré autour des si ngularités \; on se donne également un fibré en droites holomorphe pola risant pour cette métrique. J'expliquerai comment une description avancé e du modèle (sur le disque unité épointé) et des techniques de localis ation dans un contexte à poids permettent de décrire les noyaux de Bergm an associés à de telles surfaces de Riemann\, et ce jusque aux singulari tés. \n\nSi le temps le permet\, je préciserai également des interprét ations géométriques\, voire arithmétiques\, de tels résultats.\n LOCATION:https://researchseminars.org/talk/CIRGET/20/ END:VEVENT BEGIN:VEVENT SUMMARY:Philip Griffiths (Institute for Advanced Study\, University of Mia mi) DTSTART:20201106T160000Z DTEND:20201106T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/21 DESCRIPTION:Title: Some geometric applications of Hodge theory\nby Philip Griffiths (Inst itute for Advanced Study\, University of Miami) as part of CRM - Séminair e du CIRGET / Géométrie et Topologie\n\n\nAbstract\nModern Hodge theory is both a subject of study in its own right and a subject that is used in many areas of current mathematical research\, especially in but no means r estricted to algebraic geometry. This talk will be an informal and partial overview of some of its uses with emphasis on those in algebraic geometry . We will also discuss some of the historical development of the subject\; how did it originate and how did it get to its current state? Here the em phasis will be on the period up until the time of Hodge and will only touc h on a few of the major recent milestones.\n LOCATION:https://researchseminars.org/talk/CIRGET/21/ END:VEVENT BEGIN:VEVENT SUMMARY:Michelle Chu (University of Illinois at Chicago) DTSTART:20201113T160000Z DTEND:20201113T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/22 DESCRIPTION:Title: Prescribed virtual torsion in the homology of 3-manifolds\nby Michelle Chu (University of Illinois at Chicago) as part of CRM - Séminaire du CI RGET / Géométrie et Topologie\n\n\nAbstract\nHongbin Sun showed that a c losed hyperbolic 3-manifold virtually contains any prescribed torsion subg roup as a direct factor in homology. In this talk we will discuss joint wo rk with Daniel Groves generalizing Sun’s result to irreducible 3-manifol ds which are not graph-manifolds.\n LOCATION:https://researchseminars.org/talk/CIRGET/22/ END:VEVENT BEGIN:VEVENT SUMMARY:Neil Hoffman (Oklahoma State University) DTSTART:20201120T160000Z DTEND:20201120T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/23 DESCRIPTION:Title: Conjectures related to knot complement commensurability\nby Neil Hoffm an (Oklahoma State University) as part of CRM - Séminaire du CIRGET / Gé ométrie et Topologie\n\n\nAbstract\nTwo manifolds $M_1$ and $M_2$ are com mensurable if there is a third manifold $M_3$ that is a finite sheeted cov er of $M_1$ and $M_2$. Neumann and Reid conjecture that at most 3 hyperbol ic knot complements can be commensurable with each other. I will discuss w hat is known about the conjecture and open questions surrounding commensur able knot complements.\n LOCATION:https://researchseminars.org/talk/CIRGET/23/ END:VEVENT BEGIN:VEVENT SUMMARY:Mykola Matviichuk (McGill University) DTSTART:20201127T160000Z DTEND:20201127T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/25 DESCRIPTION:Title: A local Torelli theorem for log symplectic manifolds\nby Mykola Matvii chuk (McGill University) as part of CRM - Séminaire du CIRGET / Géométr ie et Topologie\n\n\nAbstract\nWe will discuss how to deform a holomorphic symplectic form that has logarithmic poles along a normal crossings divis or. We will introduce an appropriate deformation complex and explain how t o calculate its cohomology using natural local systems on the strata of th e polar divisor. An analysis of the L-infinity structure on the cohomology of the deformation complex leads to a simple combinatorial description of the deformation space in terms of the periods of the log symplectic form. As an application\, we construct new examples of log symplectic forms on $CP^4$ by deforming previously known ones. This is joint work with Brent P ym and Travis Schedler.\n LOCATION:https://researchseminars.org/talk/CIRGET/25/ END:VEVENT BEGIN:VEVENT SUMMARY:Matei Toma (Univ. of Nancy) DTSTART:20201211T160000Z DTEND:20201211T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/26 DESCRIPTION:Title: Boundedness for sets of coherent analytic sheaves\nby Matei Toma (Univ . of Nancy) as part of CRM - Séminaire du CIRGET / Géométrie et Topolog ie\n\n\nAbstract\nA boundedness notion for sets of isomorphism classes of coherent algebraic sheaves as well as a boundedness criterion were introdu ced by Grothendieck in his 1961 paper on the construction of the Hilbert s cheme. In this talk we define boundedness for coherent analytic sheaves an d present a boundedness criterion in a complex geometric context. We then show how these apply to prove properties related to Douady spaces or to se mistability of coherent sheaves\, such as the existence of relative Harder -Narasimhan filtrations.\n LOCATION:https://researchseminars.org/talk/CIRGET/26/ END:VEVENT BEGIN:VEVENT SUMMARY:Mario Garcia-Fernandez (ICMAT\, Madrid) DTSTART:20210115T160000Z DTEND:20210115T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/27 DESCRIPTION:Title: Gravitating vortices with positive curvature\nby Mario Garcia-Fernande z (ICMAT\, Madrid) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIn this talk I will overview recent joint work wi th Vamsi \nPingali and Chengjian Yao in arXiv:1911.09616 about gravitating \nvortices. These equations couple a K\\"ahler metric on a compact \nRiem ann surface with a hermitian metric over a holomorphic line bundle \nequip ped with a fixed global section --- the Higgs field ---\, and have \na sym plectic interpretation as moment-map equations.\n\nIn our work we give a c omplete solution to the existence problem for \ngravitating vortices on th e Riemann sphere with positive topological \nconstant c > 0. Our main resu lt establishes the existence of solutions \nprovided that a GIT stability condition for an effective divisor on \nCP^1 is satisfied. To this end\, w e use a continuity path starting from \nYang's solution with c = 0. A sali ent feature of our argument is a new \nbound S \\geq c for the curvature o f gravitating\nvortices\, which we apply to construct a limiting solution along the \npath via Cheeger-Gromov theory.\n LOCATION:https://researchseminars.org/talk/CIRGET/27/ END:VEVENT BEGIN:VEVENT SUMMARY:Simone Diverio (SAPIENZA Università di Roma) DTSTART:20210205T160000Z DTEND:20210205T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/28 DESCRIPTION:Title: Pointwise universal Gysin formulae and positivity of some characteristic f orms\nby Simone Diverio (SAPIENZA Università di Roma) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIn the la st few years there has been a renewed interest around an old conjecture by Griffiths characterizing which should be the positive characteristic form s for any given Griffiths positive holomorphic Hermitian vector bundle. Ac cording to this conjecture\, they should be precisely the characteristic f orms belonging to the positive cone spanned by the Schur forms.\nAfter rec alling the various notions of positivity for holomorphic Hermitian vector bundles\, and how they are (or should be) related\, we shall explain a rec ent result obtained in collaboration with my PhD student F. Fagioli\, whic h gives a partial confirmation of the above conjecture.\nSuch a result is obtained as a consequence of a pointwise\, differential-geometric Gysin fo rmula for the push-forward of the curvature of the tautological line bundl es over flag bundles.\n LOCATION:https://researchseminars.org/talk/CIRGET/28/ END:VEVENT BEGIN:VEVENT SUMMARY:Yohan Brunebarbe (Univ. of Bordeaux) DTSTART:20210122T160000Z DTEND:20210122T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/29 DESCRIPTION:Title: Higher-dimensional Arakelov inequalities and applications to hyperbolicity \nby Yohan Brunebarbe (Univ. of Bordeaux) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIn this talk\, I will introduce the so-called Arakelov inequalities (due to Arakelov\, Faltings\ , Peters\, Deligne\, etc.) that one gets from an abelian scheme or more ge nerally from a variation of Hodge structures on a curve. I will then discu ss a generalization of these inequalities to higher-dimensional basis\, an d explain how they can be used to prove hyperbolicity properties of some m oduli spaces of varieties.\n LOCATION:https://researchseminars.org/talk/CIRGET/29/ END:VEVENT BEGIN:VEVENT SUMMARY:Tarik Aougab (Haverford College) DTSTART:20210129T160000Z DTEND:20210129T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/30 DESCRIPTION:Title: Statistics for random curves on surfaces\nby Tarik Aougab (Haverford C ollege) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n \nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/30/ END:VEVENT BEGIN:VEVENT SUMMARY:Allison Miller (Rice University) DTSTART:20210212T160000Z DTEND:20210212T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/31 DESCRIPTION:Title: Amphichiral knots with large 4-genera\nby Allison Miller (Rice Univers ity) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\ nAbstract\nAn oriented knot is called negative amphichiral if it is isotop ic to the reverse of its mirror image. Such knots have order at most two i n the concordance group\, and many modern concordance invariants vanish on them. Nevertheless\, we will see that there are negative amphichiral knot s with arbitrarily large 4-genera\, using Casson-Gordon signature invarian ts as a primary tool.\n LOCATION:https://researchseminars.org/talk/CIRGET/31/ END:VEVENT BEGIN:VEVENT SUMMARY:Michael Hallam (Oxford University) DTSTART:20210219T160000Z DTEND:20210219T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/32 DESCRIPTION:Title: Stability of fibrations through geodesic analysis\nby Michael Hallam ( Oxford University) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nA celebrated result in geometry is the Kobayashi- -Hitchin correspondence\, which states that a holomorphic vector bundle on a compact Kähler manifold admits a Hermite--Einstein metric if and only if the bundle is slope polystable. Recently\, Dervan and Sektnan have conj ectured an analogue of this correspondence for fibrations whose fibres are compact Kähler manifolds admitting Kähler metrics of constant scalar cu rvature. Their conjecture is that such a fibration is polystable in a suit able sense\, if and only if it admits an optimal symplectic connection. In this talk\, I will provide an introduction to this theory\, and describe my recent work on the conjecture. Namely\, I show that existence of an opt imal symplectic connection implies polystability with respect to a large c lass of fibration degenerations. The techniques used involve analysing geo desics in the space of relatively Kähler metrics of fibrewise constant sc alar curvature\, and convexity of the log-norm functional in this setting. This is work for my PhD thesis\, supervised by Ruadhaí Dervan and France s Kirwan.\n LOCATION:https://researchseminars.org/talk/CIRGET/32/ END:VEVENT BEGIN:VEVENT SUMMARY:Anthony Conway (MIT) DTSTART:20210312T160000Z DTEND:20210312T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/33 DESCRIPTION:Title: Knotted surfaces with infinite cyclic knot group\nby Anthony Conway (M IT) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\n Abstract\nThis talk will concern embedded surfaces in 4-manifolds for whic h the fundamental group of the complement is infinite cyclic. Working in t he topological category\, necessary and sufficient conditions will be give n for two such surfaces to be isotopic. This is based on joint work with M ark Powell.\n LOCATION:https://researchseminars.org/talk/CIRGET/33/ END:VEVENT BEGIN:VEVENT SUMMARY:Chris Kottke (New College of Florida) DTSTART:20210226T160000Z DTEND:20210226T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/34 DESCRIPTION:Title: Bigerbes and applications\nby Chris Kottke (New College of Florida) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstra ct\nGerbes are geometric objects on a space which represent degree 3 integ er cohomology\, in the same way that complex line bundles (classified by t he Chern class) represent cohomology in degree 2. Among other settings\, t hey arise naturally as obstructions to lifting the structure group of a pr incipal G-bundle to a U(1) central extension of G. \nHigher versions of ge rbes\, representing cohomology classes of degree 4 and up\, are typically complicated by higher categorical concepts (2-morphisms and so on) in thei r definition. In contrast\, bigerbes (and their higher cousins) admit a si mple\, geometric\, non-higher-categorical description\, and provide a sati sfactory account of the relationship between so-called `string structures' on a manifold and `fusion spin structures' on its loop space\, among othe r applications. This is based on recent joint work with Richard Melrose.\n LOCATION:https://researchseminars.org/talk/CIRGET/34/ END:VEVENT BEGIN:VEVENT SUMMARY:Philipp Naumann (Univ of Bayreuth) DTSTART:20210319T160000Z DTEND:20210319T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/35 DESCRIPTION:Title: Curvature formula for direct images of relative canonical bundles with a P oincaré type twist\nby Philipp Naumann (Univ of Bayreuth) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nAbstract: TBA\n\n We give a curvature formula of the L^2 metric on the direct image of the r elative canonical bundle twisted by a holomorphic line bundle endowed with a positive singular metric whose inverse has Poincaré type singularities along a relative snc divisor. The result applies to families of log canon ically polarized pairs. Moreover\, we show that it improves the general po sitivity result of Berndtsson-Paun in a special situation of a big line bu ndle.\n LOCATION:https://researchseminars.org/talk/CIRGET/35/ END:VEVENT BEGIN:VEVENT SUMMARY:Antonio Alfieri (University of British Columbia) DTSTART:20210326T150000Z DTEND:20210326T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/36 DESCRIPTION:Title: Symmetric knots and Floer homologies\nby Antonio Alfieri (University o f British Columbia) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nI will discuss some open problems\, and survey s ome classical material regarding symmetric knots\, and group actions on 3- and 4-manifolds. In the second part of the talk I will discuss how techni ques from Floer theory can be employed to approach some of these problems. Part of this is joint work with Irving Dai\, Abhishek Mallick\, and Sungk yung Kang.\n LOCATION:https://researchseminars.org/talk/CIRGET/36/ END:VEVENT BEGIN:VEVENT SUMMARY:Tye Lidman (North Carolina State University) DTSTART:20210507T150000Z DTEND:20210507T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/37 DESCRIPTION:Title: SU(2) representations for toroidal homology spheres\nby Tye Lidman (No rth Carolina State University) as part of CRM - Séminaire du CIRGET / Gé ométrie et Topologie\n\n\nAbstract\nThe three-dimensional Poincare conjec ture shows that any closed three-manifold other than the three-sphere has non-trivial fundamental group. A natural question is how to measure the no n-triviality of such a group\, and conjecturally this can be concretely re alized by a non-trivial representation to SU(2). We will show that the fun damental groups of three-manifolds with incompressible tori admit non-triv ial SU(2) representations. This is joint work with Juanita Pinzon-Caicedo and Raphael Zentner.\n LOCATION:https://researchseminars.org/talk/CIRGET/37/ END:VEVENT BEGIN:VEVENT SUMMARY:Johnny Nicholson (UCL) DTSTART:20210423T150000Z DTEND:20210423T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/38 DESCRIPTION:Title: Projective modules and exotic group presentations\nby Johnny Nicholson (UCL) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\ n\nAbstract\nTwo presentations for a group G which have the same deficienc y are called exotic if the corresponding presentation complexes are not ho motopy equivalent. The first examples of exotic presentations were found b y Dunwoody and Metzler in the 1970s but\, owing to the difficulty of the a lgebra involved\, few other examples have since been found.\nIn this talk\ , I will discuss a class of finite groups G for which these algebraic diff iculties can be largely reduced to a question about projective ZG modules which we resolve. I will also discuss applications to Wall’s D2 problem and the classification of 4-manifolds.\n LOCATION:https://researchseminars.org/talk/CIRGET/38/ END:VEVENT BEGIN:VEVENT SUMMARY:Marco Marengon (Max Planck Institute for Mathematics) DTSTART:20210409T150000Z DTEND:20210409T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/39 DESCRIPTION:Title: Relative genus bounds in indefinite 4-manifolds\nby Marco Marengon (Ma x Planck Institute for Mathematics) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nGiven a closed 4-manifold X with an indefinite intersection form\, we consider smoothly embedded surfaces in X-int(B^4)\, with boundary a given knot K in the 3-sphere.\nWe give sev eral methods to bound the genus of such surfaces in a fixed homology class . Our techniques include adjunction inequalities from Heegaard Floer homol ogy and the Bauer-Furuta invariants\, and the 10/8 theorem.\nIn particular \, we present obstructions to a knot being H-slice (that is\, bounding a n ull-homologous disc) in a 4-manifold and show that the set of H-slice knot s can detect exotic smooth structures on closed 4-manifolds.\nThis is join t work with Ciprian Manolescu and Lisa Piccirillo.\n LOCATION:https://researchseminars.org/talk/CIRGET/39/ END:VEVENT BEGIN:VEVENT SUMMARY:Wenhao Ou (Chinese Academy of Science) DTSTART:20210430T150000Z DTEND:20210430T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/41 DESCRIPTION:Title: Projective varieties whose tangent bundle contains certain positivity / Va riétés projectives dont le fibré tangent contient certaine positivité< /a>\nby Wenhao Ou (Chinese Academy of Science) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nSince the Frankel con jecture and the Hartshorne conjecture\, it turns out that the positivity o f tangent bundle imposes geometric constraints on the ambient manifold. In this talk\, I will introduce some classic results and my recent works on these structural theorems.\n\nDepuis la conjecture de Frankel et la conjec ture de Hartshorne\, il se trouve que la positivité du fibré tangent imp ose des contraintes géométriques sur la variété ambiante. Dans cet exp osé\, je vais introduire des résultats classiques et mes travaux récent s sur ce genre de théorèmes structurels.\n LOCATION:https://researchseminars.org/talk/CIRGET/41/ END:VEVENT BEGIN:VEVENT SUMMARY:Ziwen Zhu (Peking University) DTSTART:20210514T150000Z DTEND:20210514T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/42 DESCRIPTION:Title: Equivariant K-stability and valuative criteria\nby Ziwen Zhu (Peking U niversity) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\n\nAbstract\nEquivariant K-stability of Fano varieties is defined via equivariant test configurations. By definition it is weaker than usual K-s tability. However\, for Fano varieties with large symmetry\, it is often e asier to check equivariant K-stability. Valuative criterion is developed b y Chi Li and Kento Fujita to characterize K-stability using valuations. In this talk\, I will show that there is a parallel theory for equivariant K -stability by introducing pseudovaluations. As an application\, I will dis cuss how it can be applied to study K-stability of Fano varieties under fi nite group action. The talk is partially based on joint work with Yuchen L iu.\n LOCATION:https://researchseminars.org/talk/CIRGET/42/ END:VEVENT BEGIN:VEVENT SUMMARY:Alix Deruelle (Sorbonne Université) DTSTART:20210917T150000Z DTEND:20210917T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/43 DESCRIPTION:Title: A relative entropy for expanders of the Ricci flow (joint work with Felix Schulze\, Warwick University)\nby Alix Deruelle (Sorbonne Université) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbs tract\nExpanding self-similar solutions of the Ricci flow are solutions wh ich evolve by scaling and diffeomorphisms only. Such solutions are also ca lled expanding gradient Ricci solitons. These "canonical" metrics are pote ntial candidates for smoothing out isolated singularities instantaneously. These heuristics apply to the Kähler-Ricci flow too. In this talk\, we a sk the question of uniqueness of such self-similar solutions coming out of a given metric cone over a smooth link. As a first step\, we make sense o f a suitable Lyapunov functional also called relative entropy in this sett ing.\n LOCATION:https://researchseminars.org/talk/CIRGET/43/ END:VEVENT BEGIN:VEVENT SUMMARY:Xuwen Zhu (Northeastern University) DTSTART:20210924T150000Z DTEND:20210924T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/44 DESCRIPTION:Title: Constant curvature conical metrics\nby Xuwen Zhu (Northeastern Univers ity) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\ nAbstract\nThe problem of finding and classifying constant curvature metri cs with conical singularities has a long history bringing together several different areas of mathematics. This talk will focus on the particularly difficult spherical case where many new phenomena appear. When some of the cone angles are bigger than $2\\pi$\, uniqueness fails and existence is n ot guaranteed\; smooth deformation is not always possible and the moduli s pace is expected to have singular strata. I will give a survey of several recent results regarding this singular uniformization problem\, connecting microlocal techniques with complex analysis and synthetic geometry. Based on joint works with Rafe Mazzeo\, Bin Xu\, and Mikhail Karpukhin.\n LOCATION:https://researchseminars.org/talk/CIRGET/44/ END:VEVENT BEGIN:VEVENT SUMMARY:Peter Feller (ETH Zurich) DTSTART:20211015T150000Z DTEND:20211015T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/45 DESCRIPTION:Title: Braids\, quasimorphisms\, and slice-Bennequin inequalities\nby Peter F eller (ETH Zurich) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nThe writhe of a braid (=#pos crossing - #neg cro ssings) and the fractional Dehn twist coefficient of a braid (a rational n umber that measures "how much the braid twists") are the two most prominen t examples of what is known as a quasimorphism (a map that fails to be a g roup homomorphism by at most a bounded amount) from Artin's braid group on n-strands to the reals. We consider characterizing properties for such qu asimorphisms and talk about relations to the study of knot concordance. Fo r the latter\, we consider inequalities for quasimorphisms modelled after the so-called slice-Bennequin inequality: writhe(B) <= 2g_4(K) - 1 + n for all n-stranded braids B with closure a knot K. Based on work in progress. \n LOCATION:https://researchseminars.org/talk/CIRGET/45/ END:VEVENT BEGIN:VEVENT SUMMARY:Yang Li (MIT) DTSTART:20211022T150000Z DTEND:20211022T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/46 DESCRIPTION:Title: Metric SYZ conjecture\nby Yang Li (MIT) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nI will discuss my recent work on the metric aspect of the Strominger-Yau-Zaslow conjecture\, focus ing mostly on the Fermat family of hypersurfaces. The conjecture asks for the existence of special Lagrangian torus fibrations for Calabi-Yau manifo lds near the large complex structure limit\, at least in the generic regio n of the manifold. The key is to prove a metric asymptote in the limit\, a nd time permitting I will try to mention some ingredients.\n LOCATION:https://researchseminars.org/talk/CIRGET/46/ END:VEVENT BEGIN:VEVENT SUMMARY:Marco Golla (University of Nantes) DTSTART:20211029T150000Z DTEND:20211029T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/47 DESCRIPTION:Title: 3-manifolds that bound no definite 4-manifold\nby Marco Golla (Univers ity of Nantes) as part of CRM - Séminaire du CIRGET / Géométrie et Topo logie\n\n\nAbstract\nAll 3-manifolds bound 4-manifolds\, and many construc tions of 3-manifolds automatically come with a 4-manifold bounding it. Oft entimes these 4-manifolds have definite intersection form. Using Heegaard Floer correction terms and an analysis of short characteristic covectors i n bimodular lattices\, we give an obstruction for a 3-manifold to bound a definite 4-manifold\, and produce some concrete examples. This is joint wo rk with Kyle Larson.\n LOCATION:https://researchseminars.org/talk/CIRGET/47/ END:VEVENT BEGIN:VEVENT SUMMARY:Ruadhai Dervan (University of Cambridge) DTSTART:20211112T160000Z DTEND:20211112T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/48 DESCRIPTION:Title: Stability conditions for polarised varieties\nby Ruadhai Dervan (Unive rsity of Cambridge) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nA central theme of complex geometry is the relat ionship between differential-geometric PDEs and algebro-geometric notions of stability. Examples include Hermitian Yang-Mills connections and Kähle r-Einstein metrics on the PDE side\, and slope stability and K-stability o n the algebro-geometric side. I will describe a general framework associat ing geometric PDEs on complex manifolds to notions of stability\, and will sketch a proof showing that existence of solutions is equivalent to stabi lity in a model case. The framework can be seen as an analogue in the sett ing of varieties of Bridgeland's stability conditions on triangulated cate gories.\n LOCATION:https://researchseminars.org/talk/CIRGET/48/ END:VEVENT BEGIN:VEVENT SUMMARY:Ya Deng (CNRS\, Université de Lorraine) DTSTART:20211119T160000Z DTEND:20211119T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/49 DESCRIPTION:Title: Big Picard theorem for varieties admitting nilpotent harmonic bundles\ nby Ya Deng (CNRS\, Université de Lorraine) as part of CRM - Séminaire d u CIRGET / Géométrie et Topologie\n\n\nAbstract\nThe big Picard theorem states that any holomorphic map from the punctured disk into the Riemann s phere avoiding three points must extend across the origin. In this talk I will explain a generalized big picard theorem for quasi-compact Kähler ma nifolds U endowed with a nilpotent harmonic bundle whose Higgs field is in jective at one point. Moreover\, we prove that there is a finite unramifi ed cover V of U from a quasi-projective manifold V so that the big Picard theorem holds for any projective compactification of V. This work is based on the joint work with Benoit Cadorel.\n LOCATION:https://researchseminars.org/talk/CIRGET/49/ END:VEVENT BEGIN:VEVENT SUMMARY:Gilles Carron (Université de Nantes) DTSTART:20211126T160000Z DTEND:20211126T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/50 DESCRIPTION:Title: Kato's Limits\nby Gilles Carron (Université de Nantes) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIt is a joint work with I. Mondello (Paris XII) and D. Tewodrose (UL Bruxelles\, N antes). A Kato bound on the Ricci curvature yields nice geometric properti es ( eigenvalue lower bound\, heat kernel estimates...)\; in particular it implies a doubling condition for the Riemannian volume and hence a precom pactness result in the Gromov-Hausdorff topology. We have obtained results that are generalization of the ones of Cheeger and Colding (where a unifo rm lower bound on the Ricci curvature is assumed).\n LOCATION:https://researchseminars.org/talk/CIRGET/50/ END:VEVENT BEGIN:VEVENT SUMMARY:Nathan Grieve (RMC/Carleton/UQAM) DTSTART:20211210T160000Z DTEND:20211210T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/51 DESCRIPTION:Title: On topics that surround the Cone Theorem\, K-stability and Diophantine Ari thmetic Geometry\nby Nathan Grieve (RMC/Carleton/UQAM) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nI will su rvey concepts that are near to the Cone Theorem and MMP (for klt pairs)\, the question of K-stability for polarized projective varieties and their D iophantine arithmetic consequences. In doing so\, I will report on some r ecent and ongoing work. As one example\, I intend to propose a concept of slope stability\, for polarized projective varieties\, from the viewpoint of the extremal ray theory. The idea is that it should extend the tradit ional concept of slope stability\, which is measured along a subvariety.\n LOCATION:https://researchseminars.org/talk/CIRGET/51/ END:VEVENT BEGIN:VEVENT SUMMARY:Sucharit Sarkar (UCLA) DTSTART:20211105T153000Z DTEND:20211105T164500Z DTSTAMP:20260422T225753Z UID:CIRGET/52 DESCRIPTION:Title: Mixed invariants in Khovanov homology for unorientable cobordisms\nby Sucharit Sarkar (UCLA) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\n** Note : the event will take place at 11.30 am and not 11 am as usual.\n** Attention : l'horaire est modifié à 11.30 exceptionnellement.\n\nUsing Bar-Natan's and Lee's deformations of Khovan ov homology of links\, we define minus\, plus\, and infinity versions of K hovanov homology. Given an unorientable cobordism in [0\,1]\\times S^3 fro m a link L_0 to a link L_1\, we define a mixed invariant as a map from the minus version of the Khovanov homology of L_0 to the plus version of the Khovanov homology of L_1. The construction is similar to the mixed invaria nt in Heegaard Floer homology. This invariant can be used to distinguish e xotic cobordisms\, that is\, two cobordisms which are topologically isotop ic but not smoothly isotopic. This is joint with Robert Lipshitz.\n LOCATION:https://researchseminars.org/talk/CIRGET/52/ END:VEVENT BEGIN:VEVENT SUMMARY:Adam Jacob (University of California Davis) DTSTART:20211217T160000Z DTEND:20211217T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/53 DESCRIPTION:Title: Special Lagrangian torus fibrations on Del Pezzo and Rational Elliptic Sur faces\nby Adam Jacob (University of California Davis) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIn this ta lk I will demonstrate the construction of mirror special Lagrangian torus fibrations on two non-compact spaces: A Del Pezzo surface with a smooth an ticanonical divisor removed\, and a rational elliptic surface minus a sing ular fiber of Kodaira type I_k. Special emphasis will be given to local ge ometric models\, and how the mean curvature flow provides a key step in th e construction. This is joint work with T.C. Collins and Y.-S. Lin\n LOCATION:https://researchseminars.org/talk/CIRGET/53/ END:VEVENT BEGIN:VEVENT SUMMARY:Steven Sivek (Imperial College) DTSTART:20211203T160000Z DTEND:20211203T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/54 DESCRIPTION:by Steven Sivek (Imperial College) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/54/ END:VEVENT BEGIN:VEVENT SUMMARY:Ethan Addison (Notre Dame Univ.) DTSTART:20220114T160000Z DTEND:20220114T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/55 DESCRIPTION:Title: Generalizing Poincaré-Type Kähler Metrics\nby Ethan Addison (Notre D ame Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\n\nAbstract\nPoincaré-type metrics are a type of complete cusp metric defined on the complement of a complex hypersurface $X$ in an ambient man ifold\, yet a result by Auvray shows that constant scalar curvature metric s of Poincaré-type always split into a product of cscK metrics in each of the ends\, inducing a cscK metric on $X$. We prove a result about \\emph{ gnarled} Poincaré-type metrics using holomorphic flows on $X$ to construc t complete cscK metrics near the ends which are perturbations of cscK Poin caré-type metrics\, even when the induced perturbed Kähler class on $X$ does not admit a cscK metric\, thus generalizing the initial flavor of met ric to one with fewer restrictions.\n LOCATION:https://researchseminars.org/talk/CIRGET/55/ END:VEVENT BEGIN:VEVENT SUMMARY:Francesco Lin (Columbia Univ.) DTSTART:20220121T160000Z DTEND:20220121T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/56 DESCRIPTION:Title: Closed geodesics and Frøyshov invariants of hyperbolic three-manifolds\nby Francesco Lin (Columbia Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nFrøyshov invariants are subtle numerical topological invariants of rational homology three-spheres deri ved from gradings in monopole Floer homology. In this talk I will look at their relation with invariants arising from hyperbolic geometry (such as volumes and lengths of closed geodesics)\, using an odd version of the S elberg trace formula and ideas from analytic number theory. In particular \, for the class of minimal L-spaces\, I will describe an effective proc edure to compute them taking as input explicit geometric data\, and show for example how this can be used to determine all the Frøyshov invariant s for the Seifert-Weber dodecahedral space. This is joint work with M. Li pnowski (McGill).\n LOCATION:https://researchseminars.org/talk/CIRGET/56/ END:VEVENT BEGIN:VEVENT SUMMARY:Xi Sisi Shen (Columbia Univ.) DTSTART:20220128T160000Z DTEND:20220128T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/57 DESCRIPTION:Title: A Chern-Calabi flow on Hermitian Manifolds\nby Xi Sisi Shen (Columbia Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\ n\nAbstract\nWe discuss the existence problem of constant Chern scalar cur vature metrics on a compact complex manifold and introduce a Hermitian ana logue of the Calabi flow on compact complex manifolds with vanishing first Bott-Chern class.\n LOCATION:https://researchseminars.org/talk/CIRGET/57/ END:VEVENT BEGIN:VEVENT SUMMARY:Kyle Hayden (Columbia Univ.) DTSTART:20220211T160000Z DTEND:20220211T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/59 DESCRIPTION:Title: Where are the complex curves in Khovanov homology?\nby Kyle Hayden (Co lumbia Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topol ogie\n\n\nAbstract\nSince the advent of gauge theory\, many modern tools e xhibit a close connection with complex curves and a heightened sensitivity to objects from the complex realm. Surprisingly\, this is true even for K hovanov homology\, whose construction is combinatorial rather than geometr ic. I will discuss this in the context of joint work with Isaac Sundberg t hat uses Khovanov homology to study knotted surfaces in 4-space\, especial ly (compact pieces of) complex curves in the 4-ball.\n LOCATION:https://researchseminars.org/talk/CIRGET/59/ END:VEVENT BEGIN:VEVENT SUMMARY:Ruiran Sun (UQAM) DTSTART:20220218T160000Z DTEND:20220218T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/60 DESCRIPTION:by Ruiran Sun (UQAM) as part of CRM - Séminaire du CIRGET / G éométrie et Topologie\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/60/ END:VEVENT BEGIN:VEVENT SUMMARY:Louis Ioos (Max Planck Institute\, Bonn) DTSTART:20220311T160000Z DTEND:20220311T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/61 DESCRIPTION:Title: Quantization methods in the Yau-Tian-Donaldson program\nby Louis Ioos (Max Planck Institute\, Bonn) as part of CRM - Séminaire du CIRGET / Géo métrie et Topologie\n\n\nAbstract\nA celebrated conjecture of Yau states that the existence of a Kähler metric\nwith constant scalar curvature on a projective manifold should be equivalent to a purely\nalgebraic stabilit y condition. Much progress has been done on this conjecture in the\npast d ecades\, culminating in what is now called the Yau-Tian-Donaldson program. \nIn this talk\, I will explain the key role played by quantization method s in this program\,\nand how they can be improved using a semiclassical es timate of the quantum noise of\nBerezin-Toeplitz quantization. This is par tly based on joint works in collaboration with\nVictoria Kaminker\, Leonid Polterovich and Dor Shmoish.\n LOCATION:https://researchseminars.org/talk/CIRGET/61/ END:VEVENT BEGIN:VEVENT SUMMARY:Jacob Caudell (Boston College) DTSTART:20220225T160000Z DTEND:20220225T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/62 DESCRIPTION:Title: Lens space surgeries\, lattices\, and the Poincaré homology sphere.\n by Jacob Caudell (Boston College) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nAbstract: TBA\n\nMoser's classification of Deh n surgeries on torus knots (1971) inspired a now fifty-years-old project t o classify "exceptional" Dehn surgeries on knots in the three-sphere. A pr ominent component of this project seeks to classify which knots admit surg eries to the "simplest" non-trivial 3-manifolds--lens spaces. By combining data from Floer homology and the theory of integer lattices into the noti on of a changemaker lattice\, Greene (2010) solved the lens space realizat ion problem: every lens space which may be realized as surgery on a knot i n the three-sphere may be realized by a knot already known to surger to th at lens space (i.e. a Berge knot). In this talk\, we present a survey of t echniques in Dehn surgery and their applications\, introduce a lattice the oretic construction in the spirit of Greene's changemaker lattices\, and d iscuss applications to surgeries on knots in the Poincaré homology sphere .\n LOCATION:https://researchseminars.org/talk/CIRGET/62/ END:VEVENT BEGIN:VEVENT SUMMARY:Alan Reid (Rice University) DTSTART:20220401T150000Z DTEND:20220401T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/63 DESCRIPTION:Title: Embedding and bounding geometrically rational homology 3-spheres\nby A lan Reid (Rice University) as part of CRM - Séminaire du CIRGET / Géomé trie et Topologie\n\n\nAbstract\nBordism properties of closed manifolds ha ve been a classical and important topic in topology\; for example it is a classical result of Rohklin that all closed orientable 3-manifolds bound a compact 4-manifold. In the context of hyperbolic manifolds\, a natural g eometric version of bordism is that of bounding geometrically: namely whet her a connected closed orientable hyperbolic n-manifold M could arise as the totally geodesic boundary of a compact hyperbolic (n+1)-manifold W. In work with Long (from 2000) we showed that there are infinitely many clos ed orientable hyperbolic n-manifolds that bound geometrically. One featu re of our construction is that all examples produced in dimension 3 have b_1>0. This led to the question of whether there are rational homology 3- spheres that bound geometrically. In this talk we describe a construction of infinitely many such rational homology 3-spheres.\n LOCATION:https://researchseminars.org/talk/CIRGET/63/ END:VEVENT BEGIN:VEVENT SUMMARY:Allison Moore (Virginia Commonwealth) DTSTART:20220408T150000Z DTEND:20220408T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/64 DESCRIPTION:Title: Cosmetic surgery\, cosmetic crossings\nby Allison Moore (Virginia Comm onwealth) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie \n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/64/ END:VEVENT BEGIN:VEVENT SUMMARY:Alexandre Girouard (Université de Laval) DTSTART:20220422T150000Z DTEND:20220422T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/65 DESCRIPTION:Title: Steklov eigenvalues\, homogenization and free boundary minimal surfaces\nby Alexandre Girouard (Université de Laval) as part of CRM - Séminair e du CIRGET / Géométrie et Topologie\n\n\nAbstract\nIt has been known si nce classical antiquity that disks have the largest area among planar figu res of prescribed perimeter. Nevertheless\, a rigorous proof was only give n around the end of the 19th century. During the 20th century\, area and p erimeter were replaced by many other analytic and geometric quantities\, a nd the geometric setting has been vastly enlarged. In this talk we will be interested in two such isoperimetric-type problems:\n\n(A) Free boundary minimal surfaces\nThe minimization of area for surfaces in balls\, with th eir boundary that are constrained to live on the boundary sphere (free bou ndary minimal surfaces).\n\nB) Isoperimetric problem for Steklov eigenvalu es\nThe maximization of the spectral gap of Dirichlet-to-Neumann operators for surfaces with prescribed perimeter.\n\nFor domains in the unit sphere and planar domains\, I will describe the complete solution of problem (B) . It is based on the theory of homogenization by perforation\, a topic whi ch comes from applied and industrial mathematics. Then\, using work of Fra ser and Schoen\, I will show how this solution leads to the construction o f new free boundary minimal surfaces in the unit 3-ball that have area lar ger than was previously thought possible.\n\nThis talk is based on joint w ork with Antoine Henrot\, Mikhail Karpukhin and Jean Lagacé.\n LOCATION:https://researchseminars.org/talk/CIRGET/65/ END:VEVENT BEGIN:VEVENT SUMMARY:Jean-Philippe Burelle (Univ. de Sherbrooke) DTSTART:20220429T150000Z DTEND:20220429T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/66 DESCRIPTION:Title: Piecewise circular curves and flag positivity.\nby Jean-Philippe Burel le (Univ. de Sherbrooke) as part of CRM - Séminaire du CIRGET / Géométr ie et Topologie\n\n\nAbstract\nIn this joint work with Ryan Kirk\, we inve stigate moduli spaces of closed piecewise circular curves. A curve is piec ewise circular if it is made of pieces which are circular arcs\, and these arcs are tangent at the intersection of pieces. We identify a special con nected component of these moduli spaces and prove that it is homeomorphic to an open ball of dimension 2n-10. We characterize this component as the subset of curves which have decreasing curvature in an appropriate sense. The proof involves "Lie circle geometry"\, a somewhat out of fashion theor y of the homogeneous spaces of Sp(4\,R)\, and Lusztig-Fock-Goncharov posit ivity.\n LOCATION:https://researchseminars.org/talk/CIRGET/66/ END:VEVENT BEGIN:VEVENT SUMMARY:Joel Kamnitzer (University of Toronto) DTSTART:20220506T150000Z DTEND:20220506T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/67 DESCRIPTION:Title: Symplectic duality and affine Grassmannian slices\nby Joel Kamnitzer ( University of Toronto) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nSymplectic resolutions are an exciting new fr ontier of research in geometry and representation theory. One of the most fascinating aspects of this study is symplectic duality: the observation that these resolutions come in pairs with matching properties. The Coulom b\nbranch construction allows us to produce and study many of these dual p airs. I will attempt to survey recent work in this area\, particularly f ocusing on ADE quiver varieties and affine Grassmannian slices.\n LOCATION:https://researchseminars.org/talk/CIRGET/67/ END:VEVENT BEGIN:VEVENT SUMMARY:Aldo Witte (KU Leuven) DTSTART:20220527T150000Z DTEND:20220527T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/68 DESCRIPTION:Title: Singular fibrations in toric and Poisson geometry\nby Aldo Witte (KU L euven) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\ n\nAbstract\nIn this talk I will present a class of singular fibrations ca lled boundary Lefschetz fibrations. These play important roles in the\, qu ite different\, fields of semi-toric and generalized complex geometry. Aft er describing how they can be studied using Lie algebroids\, I willshow th at they behave well with respect to blow-ups and connected sums. Finally\, I will show how they can be used in extending T-duality\, a version of mi rror symmetry. Joint work with Gil Cavalcanti and Ralph Klaasse.\n LOCATION:https://researchseminars.org/talk/CIRGET/68/ END:VEVENT BEGIN:VEVENT SUMMARY:Eric Finster (University of Birmingham) DTSTART:20220902T150000Z DTEND:20220902T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/70 DESCRIPTION:Title: Homotopy Theory and Constructive Mathematics\nby Eric Finster (Univers ity of Birmingham) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n\nAbstract\nConstructive mathematicians and computer scientis ts have long been\ninterested in logical theories in which all mathematica l statements\nhave computational content. In such systems\, any proof of the\nexistence of some natural number automatically gives an algorithm for \ncomputing the number. Most modern computer "proof assistants"\, that\ni s\, programs aimed at helping the user construct and verify the\ncorrectne ss of mathematical statements\, are based on a class of such\nsystems call *type theories*.\n\nAround 15 years ago\, however\, it was discovered tha t the way type\ntheories represent equality meant that\, rather than descr ibing\nconstructive *sets*\, these systems should more properly be thought of\nas describing constructive *homotopy types*. This has led to a numbe r\nof new connections between homotopy theory\, higher category theory\,\n computer science and logic. In this talk\, I will describe some of\nthese ideas and the results that they have led to.\n LOCATION:https://researchseminars.org/talk/CIRGET/70/ END:VEVENT BEGIN:VEVENT SUMMARY:Ruiran Sun (CIRGET) DTSTART:20220923T150000Z DTEND:20220923T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/71 DESCRIPTION:Title: On slope and valuative K-semistability for big and nef birational divisors \nby Ruiran Sun (CIRGET) as part of CRM - Séminaire du CIRGET / Géom étrie et Topologie\n\nLecture held in PK-5115.\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/71/ END:VEVENT BEGIN:VEVENT SUMMARY:Mathieu Anel (Carnegie Mellon University) DTSTART:20220930T150000Z DTEND:20220930T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/72 DESCRIPTION:Title: Introduction to non-separated topology\nby Mathieu Anel (Carnegie Mell on University) as part of CRM - Séminaire du CIRGET / Géométrie et Topo logie\n\nLecture held in PK-5115.\n\nAbstract\nClassically a topological s pace has a set of points. But non-separated spaces ( Shrinking Kahler-Ricci solitons\nby Ronan Conlan (University of Texas at Dallas) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\nLecture held in PK-5115.\n\nAbstract\nShrinking Kahler-Ricci solitons model finite-time singularities of the Kahler-Ricci flow\, hence the need for their classification. I will talk about the classification of such so litons in 4 real dimensions. This is joint work with Bamler-Cifarelli-Deru elle\, Cifarelli-Deruelle\, and Deruelle-Sun.\n LOCATION:https://researchseminars.org/talk/CIRGET/73/ END:VEVENT BEGIN:VEVENT SUMMARY:Carlo Scarpa (CIRGET) DTSTART:20221014T150000Z DTEND:20221014T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/74 DESCRIPTION:Title: Scalar curvature and deformations of complex structures\nby Carlo Scar pa (CIRGET) as part of CRM - Séminaire du CIRGET / Géométrie et Topolog ie\n\nLecture held in PK-5115.\n\nAbstract\nA classical problem in Kähler geometry is to choose\, among all the possible Kähler metrics on a manif old\, a canonical representative of each Kähler class. This is usually do ne by imposing curvature conditions on the metric\, such as Ricci-flat\, K ähler-Einstein\, or constant scalar curvature. In this talk\, I will desc ribe how the problem changes when we also consider deformations of the com plex structure\, introducing a partial differential equation which gives a canonical choice of a Kähler metric for each deformation class. Time per mitting\, I will examine the case of toric manifolds in more detail. The t alk is based on arxiv:2202.00429 and joint work with J. Stoppa.\n LOCATION:https://researchseminars.org/talk/CIRGET/74/ END:VEVENT BEGIN:VEVENT SUMMARY:Georg Biedermann (Universidad del Norte) DTSTART:20221021T150000Z DTEND:20221021T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/75 DESCRIPTION:Title: Calculus in homotopy theory\nby Georg Biedermann (Universidad del Nort e) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLec ture held in PK-5115.\n\nAbstract\n(joint with M. Anel\, E. Finster and A. Joyal)\nIn classical calculus one studies smooth functions via their Tayl or series. Its $n$-th homogeneous layer is governed by a single coefficien t: the $n$-th derivative. As part of his effort to relate algebraic K-theo ry to topological cyclic homology Goodwillie during the 90s introduced "Go odwillie calculus" to homotopy theory. A homotopy invariant functor is vie wed as an analogue of a smooth function and resolved into a tower whose $n $-th homogeneous layer is governed by a single coefficient: a spectrum (in the sense of homotopy theory) with $\\Sigma_n$-action. Goodwillie calculu s is now a central tool in homotopy theory.\nAround the same time (and inf luenced by Goodwillie) Michael Weiss constructed "orthogonal calculus": sp ace-valued functors from the category of finite dimensional Euclidean vect or spaces with morphism given by Stiefel manifolds are resolved into an or thogonal tower whose $n$-th homogeneous layer is governed by a spectrum wi th an action by $O(n)$. Weiss' theory has found many applications in diffe rential topology.\nPeople have wondered for a long time whether both theor ies have a common description. We can give one. In fact\, it turns out tha t the theory of $\\infty$-topoi is the perfect language. For any left exac t localization $L$ of an $\\infty$-topos we construct a tower $(P_n)_{n\\g e 0}$ of left exact localizations such that $P_0=L$. The pointed objects o f the layers form stable $\\infty$-categories. The tower is analogous to t he completion tower of a commutative ring with respect to an ideal. It spe cializes to Goodwillie's and Weiss' tower.\n\nI am going to tell you a bit about all these towers.\n LOCATION:https://researchseminars.org/talk/CIRGET/75/ END:VEVENT BEGIN:VEVENT SUMMARY:Clara Aldana (Universidad del Norte) DTSTART:20221028T150000Z DTEND:20221028T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/76 DESCRIPTION:Title: Polyakov Formulas for conical singularities in two dimensions.\nby Cla ra Aldana (Universidad del Norte) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nIn the f irst part of the talk I will introduce the regularized determinant of the Laplace operator on a Riemannian manifold and will explain the context and the motivation to consider Polyakov's formulas. Then\, I will present the formula for surfaces with conical singularities and smooth conformal fact ors\, and for polygonal domains in a Riemannian surface. I will mention ho w we obtain the so-called variational Polyakov formula for cones and secto rs and how in these cases we can obtain closed formulas for the determinan t of the Laplacian. The results presented in this talk are joint work with Klaus Kirsten and Julie Rowlett\, arxiv.org/abs/2010.02776.\n LOCATION:https://researchseminars.org/talk/CIRGET/76/ END:VEVENT BEGIN:VEVENT SUMMARY:Manh Tien Nguyen (Oxford University) DTSTART:20221104T150000Z DTEND:20221104T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/77 DESCRIPTION:Title: Monotonicity theorems and how to compare them\nby Manh Tien Nguyen (Ox ford University) as part of CRM - Séminaire du CIRGET / Géométrie et To pologie\n\nLecture held in PK-5115.\n\nAbstract\nI will present two result s. The first one concerns minimal surfaces of the hyperbolic space and is a relation between their renormalised area (in the sense of Graham and Wit ten) and the length of their ideal boundary measured in different metrics of the conformal infinity. The second result concerns minimal submanifolds of the sphere and is a relation between their volume and antipodal-ness. Both results were obtained from the same framework\, which involves new mo notonicity theorems and a comparison principle for them.\n LOCATION:https://researchseminars.org/talk/CIRGET/77/ END:VEVENT BEGIN:VEVENT SUMMARY:Takahiro Aoi (Abuno high school) DTSTART:20221111T160000Z DTEND:20221111T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/78 DESCRIPTION:Title: A conical approximation of constant scalar curvature K\\”{a}hler metrics of Poincar\\’{e} type and log K-semistability\nby Takahiro Aoi (Abu no high school) as part of CRM - Séminaire du CIRGET / Géométrie et Top ologie\n\nLecture held in PK-5115.\n\nAbstract\nGuenancia proved that a K\ \”{a}hler-Einstein metric of Poincar\\’{e} type is the limit of a sequ ence of K\\”{a}hler-Einstein metrics with cone singularities along a smo oth divisor. In this talk\, I will explain the recent result which is an a nalogue of Guenancia’s result for constant scalar curvature K\\”{a}hle r metrics. In addition\, I will explain that constant scalar curvature K\\ ”{a}hler metrics of Poincar\\’{e} type implies log K-semistability wit h angle 0.\n\nNote that the talk will take place in Boyer room PK-5675\n LOCATION:https://researchseminars.org/talk/CIRGET/78/ END:VEVENT BEGIN:VEVENT SUMMARY:Viktor Kalvin (Dawson College and Concordia Univ.) DTSTART:20221118T160000Z DTEND:20221118T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/79 DESCRIPTION:Title: Determinants of Laplacians on compact surfaces with conical singularities< /a>\nby Viktor Kalvin (Dawson College and Concordia Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-51 15.\n\nAbstract\nIn this talk I will discuss new anomaly formulae for the zeta regularized spectral determinants of Laplacians on compact Riemann su rfaces. These formulae are valid for the metrics with conical singularitie s and\, in particular\, show how the determinants of Laplacians depend on the orders (angles) of conical singularities. With a simple example I wil l show that the extremal properties of the determinants of Laplacians on s ingular metrics are very different from the classical results of Osgood\, Phillips\, and Sarnak for the smooth metrics. If time permits\, I will als o discuss how this is related to Kaehler potentials of metrics on moduli s paces\, the famous accessory parameters\, and the celebrated DOZZ formula from the Liouville conformal field theory. The talk is based on a series o f recent papers of mine.\n LOCATION:https://researchseminars.org/talk/CIRGET/79/ END:VEVENT BEGIN:VEVENT SUMMARY:Marcin Sroka (CIRGET) DTSTART:20221125T160000Z DTEND:20221125T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/80 DESCRIPTION:Title: Monge-Ampere equation in hypercomplex geometry\nby Marcin Sroka (CIRGE T) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLec ture held in PK-5115.\n\nAbstract\nI will outline the state of art concern ing the solvability of the so called quaternionic Monge-Ampere equation. T his second order\, elliptic\, nonlinear PDE was introduced by Alesker and Verbisty as a device for confirming the version of Calabi conjecture on hy percomplex manifolds. Its solvability has applications also for obtaining Calabi-Yau type theorems\nfor some classes of hermitian and hyperhermitian metrics.\n LOCATION:https://researchseminars.org/talk/CIRGET/80/ END:VEVENT BEGIN:VEVENT SUMMARY:Sally Collins (Georgia Tech) DTSTART:20221209T160000Z DTEND:20221209T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/81 DESCRIPTION:Title: Homology cobordism and knot concordance\nby Sally Collins (Georgia Tec h) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLec ture held in PK-5115.\n\nAbstract\nThe 0-surgeries of two knots K1 and K2 are homology cobordant rel meridians if there exists an integer homology c obordism X between them such that the two positive knot meridians are in t he same homology class of X. It is a natural question to ask: if two knots have the “same” 0-surgeries in this sense\, must they be smoothly con cordant? We give a pair of rationally slice knots as counterexample\, with one of concordance order two and the other of infinite order\, and along the way expand upon a Floer homology technique for obstructing torsion in the smooth concordance group first introduced by Hom\, Kang\, Park\, and S toffregen.\n LOCATION:https://researchseminars.org/talk/CIRGET/81/ END:VEVENT BEGIN:VEVENT SUMMARY:Paula Truöl (ETH Zurich) DTSTART:20221216T160000Z DTEND:20221216T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/82 DESCRIPTION:Title: Strongly quasipositive knots are concordant to infinitely many strongly qu asipositive knots\nby Paula Truöl (ETH Zurich) as part of CRM - Sémi naire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\n Abstract\nKnots are smooth embeddings of the (oriented) circle S^1 into th e 3-sphere S^3\, usually studied up to an equivalence relation called ambi ent isotopy. A natural generalization in dimension 4 of the question wheth er certain knots are isotopic to the trivial knot is the concept of concor dance\, another equivalence relation on the set of knots.\nWe show that ev ery non-trivial strongly quasipositive knot is (smoothly) concordant to in finitely many pairwise non-isotopic strongly quasipositive knots. In contr ast to our result\, it was conjectured by Baker that concordant strongly q uasipositive fibered knots are isotopic. Our construction uses a satellite operation whose companion is a slice knot with maximal Thurston-Bennequin number -1.\nIn the talk\, we will define the relevant terms necessary to understand the theorem in the title\, and explain the context of this resu lt. If time permits\, we will say a few words about how the construction e xtends to links.\n LOCATION:https://researchseminars.org/talk/CIRGET/82/ END:VEVENT BEGIN:VEVENT SUMMARY:Kaya Ferendo (Kaya Ferendo) DTSTART:20221212T160000Z DTEND:20221212T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/83 DESCRIPTION:Title: FI-calculus and representation stability\nby Kaya Ferendo (Kaya Ferend o) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLec ture held in PK-5115.\n\nAbstract\nFI is the category of finite sets and i njections. Representation stability is an appealing phenomenon enjoyed by certain functors from FI to\, for example\, rational vector spaces. The ra tional cohomology of certain families of moduli spaces is a key example. F unctor calculus is a family of techniques and structures that are useful i n the study of functors between certain infinity-categories. In this talk\ , we'll see that representation stability emerges as a facet of a new kind of functor calculus and discuss some of the features of this functor calc ulus.\n LOCATION:https://researchseminars.org/talk/CIRGET/83/ END:VEVENT BEGIN:VEVENT SUMMARY:Shih-Kai Chiu (Oxford University) DTSTART:20230127T160000Z DTEND:20230127T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/84 DESCRIPTION:Title: Calabi-Yau manifolds with maximal volume growth\nby Shih-Kai Chiu (Oxf ord University) as part of CRM - Séminaire du CIRGET / Géométrie et Top ologie\n\nLecture held in PK-5115.\n\nAbstract\nCalabi-Yau manifolds with maximal volume growth are complete Ricci-flat Kähler manifolds where any r-ball has volume at least r^m up to a uniform constant factor and m is th e real dimension of the manifold. Bishop-Gromov volume comparison theorem implies that such growth is indeed maximal. This notion generalizes the mo re well-known notion of asymptotically conical (AC) manifolds. Contrary to the AC case\, the asymptotic cones at infinity in general can have\nnon-i solated singularities. In this talk\, I will give a (biased) survey of the recent progress on this ongoing topic.\n LOCATION:https://researchseminars.org/talk/CIRGET/84/ END:VEVENT BEGIN:VEVENT SUMMARY:Yueqiao Wu (Michigan Univ) DTSTART:20230120T160000Z DTEND:20230120T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/85 DESCRIPTION:Title: A non-Archimedean characterization of local K-stability\nby Yueqiao Wu (Michigan Univ) as part of CRM - Séminaire du CIRGET / Géométrie et To pologie\n\nLecture held in PK-5115.\n\nAbstract\nLog Fano cone singulariti es are generalizations of cones over Fano varieties\, and have a local K-s tability theory extending the one for Fano varieties. In this talk\, we ai m to give a characterization for local K-stability from a non-Archimedean point of view. As a consequence of this characterization\, we can show tha t a log Fano cone singularity is K-polystable with respect to a larger cla ss of test configurations if it admits a Ricci-flat Kähler cone metric\, strengthening earlier results of Collins-Székelyhidi and Li.\n LOCATION:https://researchseminars.org/talk/CIRGET/85/ END:VEVENT BEGIN:VEVENT SUMMARY:Nicholas McCleerey (Michigan Univ) DTSTART:20230203T160000Z DTEND:20230203T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/86 DESCRIPTION:by Nicholas McCleerey (Michigan Univ) as part of CRM - Sémina ire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbst ract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/86/ END:VEVENT BEGIN:VEVENT SUMMARY:Tristan Ozuch (MIT) DTSTART:20230324T150000Z DTEND:20230324T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/88 DESCRIPTION:Title: 4-dimensional specific aspects of Ricci flows\nby Tristan Ozuch (MIT) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLectur e held in PK-5115.\n\nAbstract\nRicci flow has been extensively studied\, and most results are either true only in dimension 3 or hold in every dime nsion. However\, given the potential topological applications\, a theory s pecific to the 4-dimensional situation is desirable. In this discussion\, I will present tools and techniques that are unique to the 4-dimensional c ase.\n\nTogether with A. Deruelle\, we introduce a notion of stability for orbifold singularities. This notion helps to explain the formation of orb ifold singularities along Ricci flow. Moreover\, in collaboration with K. Naff\, we utilize self-duality in dimension 4 to simplify the evolution eq uations of curvature. This approach lets us uncover intriguing connections between Ricci flow and Yang-Mills flow.\n LOCATION:https://researchseminars.org/talk/CIRGET/88/ END:VEVENT BEGIN:VEVENT SUMMARY:Nathan Grieve (Carleton University) DTSTART:20230224T160000Z DTEND:20230224T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/89 DESCRIPTION:Title: On Harder-Narasimhan data and the Central Limit Theorem\nby Nathan Gri eve (Carleton University) as part of CRM - Séminaire du CIRGET / Géomét rie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nStarting with th e work of Harder and Narasimhan\, the concept of canonical (Harder and Nar asimhan) filtration emerged as a fundamental tool for measuring the extent to which a given object in a suitable category fails to be slope semistab le. In this lecture\, I will discuss an abstract concept of Harder and Na rasimhan data which I formulated as a tool for expanding on the key techni cal techniques of Codogni and Patakfalvi\, which arise in their work on we ak positivity of the CM line bundle over the moduli stack of K-semistable Fano varieties. Another source of motivation is Grayson's lattice reducti on theory via slope semistability. Finally\, via theory of Faltings and W ustholz\, for slope semistabilty of filtered vector spaces\, there is a st rong overlap with techniques from Diophantine approximation for linear ser ies. As application of this circle of ideas\, I will explain a recent res ult which gives a filtered vector space analogue to the above mentioned ke y technical result of Codogni and Patakfalvi.\n LOCATION:https://researchseminars.org/talk/CIRGET/89/ END:VEVENT BEGIN:VEVENT SUMMARY:Maxence Mayrand (Sherbrooke University) DTSTART:20230310T160000Z DTEND:20230310T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/90 DESCRIPTION:Title: Hyperkähler metrics via deformation theory\nby Maxence Mayrand (Sherb rooke University) as part of CRM - Séminaire du CIRGET / Géométrie et T opologie\n\nLecture held in PK-5115.\n\nAbstract\nHyperkähler structures are special holonomy metrics with a particularly rich geometry. I will dis cuss methods for constructing such metrics\, and the weaker notion of hype rcomplex structures\, using the theory of deformation of complex structure s. As a consequence\, we obtain new hyperkähler metrics on certain Lie gr oupoids\, namely\, integrations of holomorphic Poisson surfaces\, by using results on the deformation theory of such surfaces.\n LOCATION:https://researchseminars.org/talk/CIRGET/90/ END:VEVENT BEGIN:VEVENT SUMMARY:Emily Cliff (Sherbrooke University) DTSTART:20230421T140000Z DTEND:20230421T150000Z DTSTAMP:20260422T225753Z UID:CIRGET/91 DESCRIPTION:Title: Smooth 2-groups and their principal bundles\nby Emily Cliff (Sherbrook e University) as part of CRM - Séminaire du CIRGET / Géométrie et Topol ogie\n\nLecture held in PK-5115.\n\nAbstract\nA 2-group is a categorical g eneralization of a group: it's a category with a multiplication operation which satisfies the usual group axioms only up to coherent isomorphisms. I n this talk I will introduce the category of Lie groupoids and bibundles b etween them\, in order to provide the definition of a smooth 2-group. I wi ll define principal bundles for such a smooth 2-group\, and provide classi fication results that allow us to compare them to principal bundles for or dinary groups. As a consequence in specific settings\, we obtain a categor ification of the Freed--Quinn line bundle over the moduli stack Bun_G(X) f or a finite group G and Riemann surface X. This is a line bundle which pla ys an important role in Dijkgraaf--Witten theory (i.e. Chern--Simons theo ry for the finite group G). This talk is based on joint work with Dan Berw ick-Evans\, Laura Murray\, Apurva Nakade\, and Emma Phillips. I will not a ssume any previous background on 2-groups\, Lie groupoids\, or Dijkgraaf-- Witten theory.\n\nNote that we have 2 talks this week\, one at 10 am (E. C liff)\, another one at 11 am (A. Adem).\n LOCATION:https://researchseminars.org/talk/CIRGET/91/ END:VEVENT BEGIN:VEVENT SUMMARY:Maxime Fortier Bourque (Université de Montréal) DTSTART:20230217T160000Z DTEND:20230217T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/92 DESCRIPTION:Title: The systole of hyperbolic surfaces\nby Maxime Fortier Bourque (Univers ité de Montréal) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nThe systole of a Rieman nian manifold is defined as the infimal length of its closed geodesics tha t are not contractible and was studied by Berger and Gromov in the 70's an d 80's. In this talk\, I will survey recent results on the systole of clos ed hyperbolic surfaces. In particular\, I will explain how to construct a surface out of polygons glued along a graph in a way that we can determine its systole. Variants of this construction yield numerous local maxima fo r the systole\, critical points of lower index than expected\, and are use d to prove that the dimension of a certain set defined by Thurston is larg er than hoped.\n LOCATION:https://researchseminars.org/talk/CIRGET/92/ END:VEVENT BEGIN:VEVENT SUMMARY:Panagiotis Dimakis (Stanford University) DTSTART:20230317T150000Z DTEND:20230317T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/93 DESCRIPTION:Title: BAA branes on the Hitchin moduli space from solutions to the extended Bogo molny equations\nby Panagiotis Dimakis (Stanford University) as part o f CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nBAA branes are complex Lagrangian submanifolds of t he Hitchin space. Recently\, there has been interest in these objects due to their appearance in mirror symmetry conjectures and due to their intima te connection with the geometry of the Hitchin space. In this talk I will introduce the above notions. Then I will introduce the extended Bogomolny equations and explain how their solutions lead to holomorphic data associa ted with a Riemann surface. As long as the degree of a naturally occuring line bundle is not too negative\, I will show that the moduli of these hol omorphic data is a BAA brane. Some of the BAA branes obtained this way are known but some are new.\n LOCATION:https://researchseminars.org/talk/CIRGET/93/ END:VEVENT BEGIN:VEVENT SUMMARY:Mihai Paun (Universitat Bayreuth) DTSTART:20230331T150000Z DTEND:20230331T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/94 DESCRIPTION:Title: Infinitesimal extension of pluricanonical forms and injectivity.\nby M ihai Paun (Universitat Bayreuth) as part of CRM - Séminaire du CIRGET / G éométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nWe will p resent some of the main results obtained in collaboration with J. Cao in t he preprint arXiv:2012.05063.\n LOCATION:https://researchseminars.org/talk/CIRGET/94/ END:VEVENT BEGIN:VEVENT SUMMARY:Fraser Binns (Boston College) DTSTART:20230414T150000Z DTEND:20230414T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/95 DESCRIPTION:Title: Almost L-space knots\nby Fraser Binns (Boston College) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-51 15.\n\nAbstract\nHeegaard Floer homology is a powerful package of invarian ts in low dimensional topology due originally to Ozsváth-Szabó. An L-spa ce knot is a knot admitting surgeries to a manifold with Heegaard Floer ho mology of minimal rank. Ozsváth-Szabó classified the knot Floer homology of L-space knots from which it follows that L-space knots satisfy various strong topological conditions. I will discuss a generalization of Ozsvát h-Szabó's result to "almost L-space knots"\; i.e. knots which admit surge ries to manifolds with Heegaard Floer homology of next to minimal rank.\n LOCATION:https://researchseminars.org/talk/CIRGET/95/ END:VEVENT BEGIN:VEVENT SUMMARY:Alejandro Adem (University of British Columbia) DTSTART:20230421T150000Z DTEND:20230421T160000Z DTSTAMP:20260422T225753Z UID:CIRGET/96 DESCRIPTION:Title: Minimal Euler Characteristics for Even-Dimensional Manifolds with Finite F undamental Group\nby Alejandro Adem (University of British Columbia) a s part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nIn this talk we will discuss estimates for the minimal Euler characteristic of even dimensional manifolds with a give n finite fundamental group and a highly connected universal cover. In part icular we strengthen the Hausmann-Weinberger invariants and extend them to higher dimensions. As an application we obtain new restrictions for non-a belian finite groups arising as fundamental groups of rational homology 4 –spheres. This is joint work with Ian Hambleton.\n\nNote that we have 2 talks this week\, one at 10 am (E. Cliff)\, another one at 11 am (A. Adem) .\n LOCATION:https://researchseminars.org/talk/CIRGET/96/ END:VEVENT BEGIN:VEVENT SUMMARY:Xiaojun Wu (Universität Bayreuth) DTSTART:20230428T150000Z DTEND:20230428T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/97 DESCRIPTION:Title: Compact K\\"ahler threefold with nef anticanonical line bundle\nby Xia ojun Wu (Universität Bayreuth) as part of CRM - Séminaire du CIRGET / G éométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nIn my tal k\, I will discuss a recent collaboration with Shin-ichi Matsumura on comp act Kähler threefolds with nef anticanonical line bundles. Thanks to the breakthrough result of Cao-Höring\, we can focus on the non-projective ca se. Using the Kähler threefold MMP developed by Höring-Peternell\, we ha ve shown that there are only three possibilities for such manifolds: (1) C alabi-Yau manifolds\; (2) projectivizations of numerical flat vector bundl es over a torus\; (3) products of K3 surfaces with projective lines. I wil l begin by reviewing the arguments of Cao-Höring and then explain the dif ferent ingredients we used to establish our results in the Kähler setting .\n LOCATION:https://researchseminars.org/talk/CIRGET/97/ END:VEVENT BEGIN:VEVENT SUMMARY:Simon Jubert (UQAM & Université de Toulouse) DTSTART:20230512T150000Z DTEND:20230512T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/98 DESCRIPTION:Title: A Yau-Tian-Donaldson correspondence on a class of toric fibrations\nby Simon Jubert (UQAM & Université de Toulouse) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstr act\nThe Yau--Tian--Donaldson conjecture predicts that the existence of an \nextremal metric (in the sense of Calabi) in a given Kähler class of\nK ähler manifold is equivalent to a certain algebro-geometric notion of\nst ability of this class. In this talk\, we will discuss a resolution of\nthi s conjecture for a certain type of toric fibrations\, called\nsemisimple p rincipal toric fibrations. One of the main assets of these\nfibrations is that they come equipped with a connection which allows\ndefining\, from an y Kähler metrics on the toric fiber X\, a Kähler\nmetric on the total sp ace Y. After an introduction to the Calabi\nProblem for general compact K ähler manifolds\, we will focus on the\nweighted toric setting. Then\, I will explain how to translate the\nCalabi problem on Y\, to a weighted csc K problem on the corresponding\ntoric fiber X (arxiv paper: arXiv:2108.12 297).\n LOCATION:https://researchseminars.org/talk/CIRGET/98/ END:VEVENT BEGIN:VEVENT SUMMARY:Yoshinori Hashimoto (Osaka Metropolitan Univ) DTSTART:20230505T150000Z DTEND:20230505T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/99 DESCRIPTION:Title: Uniform Hörmander estimates for flat nontrivial line bundles\nby Yosh inori Hashimoto (Osaka Metropolitan Univ) as part of CRM - Séminaire du C IRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\n Hörmander’s $L^2$-estimates for the $\\bar{\\partial}$ operators on hol omorphic line bundles are of fundamental importance in complex analytic ge ometry\, whose conventional proof crucially relies on the positivity of th e line bundle. In this talk\, we prove the $L^2$-estimates for the solutio ns to the $\\bar{\\partial}$ equation that hold uniformly for all flat non trivial line bundles on compact Kähler manifolds\, whose main feature is the quantitative description of the blow-up behaviour as the line bundle a pproaches the trivial one. A key ingredient in the proof is the observatio n that line bundles with vanishing first Chern classes are topologically t rivial and can be identified with the trivial bundle with the "perturbed" $\\bar{\\partial}$ operator which we define in terms of coordinates on the Picard variety. This is a joint work with Takayuki Koike.\n LOCATION:https://researchseminars.org/talk/CIRGET/99/ END:VEVENT BEGIN:VEVENT SUMMARY:Daniel Litt (University of Toronto) DTSTART:20230915T150000Z DTEND:20230915T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/100 DESCRIPTION:Title: Hodge theory\, braid groups\, and some questions about 2x2 matrices\n by Daniel Litt (University of Toronto) as part of CRM - Séminaire du CIRG ET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nLet $X_n$ be the set of conjugacy classes of n-tuples of 2x2 matrices whose p roduct is the identity matrix--equivalently\, the character variety of a n -punctured sphere. There is a natural braid group action on $X_n$\, whose study goes back to work of Markoff in the late 19th century. The most basi c question one can ask about this action\, which dates to work of Painlev é\, Fuchs\, Schlesinger\, and Garnier in the beginning of the 20th centur y\, is: what are the finite orbits? I'll explain the history of this quest ion\, as well as some recent work\, joint with Lam and Landesman\, in whic h we give a complete classification of such finite orbits\, by algebro-geo metric methods\, when at least one of the matrices in question has infinit e order.\n LOCATION:https://researchseminars.org/talk/CIRGET/100/ END:VEVENT BEGIN:VEVENT SUMMARY:Masafumi Hattori (Kyoto University) DTSTART:20230922T150000Z DTEND:20230922T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/101 DESCRIPTION:Title: K-stability of CY fibrations over curves\nby Masafumi Hattori (Kyoto University) as part of CRM - Séminaire du CIRGET / Géométrie et Topolog ie\n\nLecture held in PK-5115.\n\nAbstract\nIn K-stability\, the character ization of K-stable varieties is well-studied when $K_X$ is ample or X is a Calabi-Yau or Fano variety. However\, K-stability of Fano fibrations or Calabi-Yau fibrations (i.e.\, $K_X$ is relatively trivial) is not known mu ch in algebraic geometry. On the other hand\, cscK problems on fibrations are studied by Fine\, Jian-Shi-Song and Dervan-Sektnan in Kahler geometry. We introduce adiabatic K-stability (If $f:(X\,H)\\to (B\,L)$ is a fibrati on of polarized varieties\, this means that K-stability of $(X\,aH+L)$ for sufficiently small a) and show that adiabatic K-semistability of Calabi-Y au fibration implies log-twisted K-semistability of the base variety by ap plying the canonical bundle formula and the result on J-stability. If the base is a curve\, we also obtain a partial converse. In this talk\, I woul d like to explain our main results.\n LOCATION:https://researchseminars.org/talk/CIRGET/101/ END:VEVENT BEGIN:VEVENT SUMMARY:Tian-Jun Li (University of Minnesota) DTSTART:20230928T173000Z DTEND:20230928T183000Z DTSTAMP:20260422T225753Z UID:CIRGET/102 DESCRIPTION:Title: Uniruled symplectic surfaces\nby Tian-Jun Li (University of Minnesota ) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLect ure held in PK-5675.\n\nAbstract\nWe survey several aspects of the geometr y of uniruled symplectic surfaces.\n\nRoom PK-5675\n LOCATION:https://researchseminars.org/talk/CIRGET/102/ END:VEVENT BEGIN:VEVENT SUMMARY:Claude LeBrun (Stony Brook) DTSTART:20231006T150000Z DTEND:20231006T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/103 DESCRIPTION:Title: Gravitational Instantons\, Weyl Curvature\, and Conformally Kahler Geomet ry\nby Claude LeBrun (Stony Brook) as part of CRM - Séminaire du CIRG ET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nThi s talk will describe my recent joint work with Olivier Biquard and Paul Ga uduchon on ALF Ricci-flat Riemannian 4-manifolds that are not hyper-Kahler . Our main result largely characterizes the known solutions in terms of an open\, purely Riemannian curvature condition.\n\nWe will have two seminar s on the 6th of October ! \n11 am : Claude Lebrun\n 2 pm : Simone Gutt\n LOCATION:https://researchseminars.org/talk/CIRGET/103/ END:VEVENT BEGIN:VEVENT SUMMARY:Simone Gutt (Université Libre de Bruxelles) DTSTART:20231006T180000Z DTEND:20231006T191500Z DTSTAMP:20260422T225753Z UID:CIRGET/104 DESCRIPTION:Title: Around almost complex structures\nby Simone Gutt (Université Libre d e Bruxelles) as part of CRM - Séminaire du CIRGET / Géométrie et Topolo gie\n\nLecture held in PK-5115.\n\nAbstract\nSmooth almost complex structu res on manifolds (in particular on symplectic manifolds) have various inte grability properties.\nWe have been interested in defining relevant prope rties which a non integrable almost complex structure may have\, in terms of its Nijenhuis tensor.\nIn particular\, we define the notions of minimal ly or maximally non integrable almost complex structures\, and the notion of transverse complex structure defined by an almost complex structure.\nW e review some Dolbeault-type cohomologies associated to an almost complex structure.\n LOCATION:https://researchseminars.org/talk/CIRGET/104/ END:VEVENT BEGIN:VEVENT SUMMARY:Thomas Barthelmé (Queen's University) DTSTART:20231013T150000Z DTEND:20231013T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/105 DESCRIPTION:Title: Group actions on bifoliated planes and classification of (pseudo)-Anosov flows in dimension 3\nby Thomas Barthelmé (Queen's University) as par t of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nAn old problem in dynamical systems is to try to classify Anosov flows up to orbit-equivalence. This question is particula rly interesting in dimension 3 where we both have lots of examples and a r ich\, but still poorly understood\, relationships between the dynamics of the flow and the topology of the manifold. By a result of T. Barbot\, clas sifying Anosov flows (or more general pseudo-Anosov flows) in dimension 3 up to orbit equivalence restricts to classifying\, up to conjugacy\, certa in actions of \\pi_1(M) on the orbit space\, a topological plane with two transverse foliations. \n\nIn this talk\, I will recall the above and dis cuss a new complete invariant for transitive (pseudo)-Anosov flows which o ften reduces to just knowing which conjugacy classes in \\pi_1(M) are repr esented by periodic orbits of the flow. \n\nIf time permits\, I’ll talk about some applications with link to contact geometry. This is all joint w ork with Kathryn Mann\, Steven Frankel and Sergio Fenley.\n LOCATION:https://researchseminars.org/talk/CIRGET/105/ END:VEVENT BEGIN:VEVENT SUMMARY:Abdellah Lahdili (UQAM) DTSTART:20231020T150000Z DTEND:20231020T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/106 DESCRIPTION:Title: The Einstein-Hilbert functional in Kähler and Sasaki geometry\nby Ab dellah Lahdili (UQAM) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nGiven a polarised K\ \"ahler manifold $(M\,L)$\, we consider the circle bundle associated to th e polarization with the induced transversal holomorphic structure. The spa ce of contact structures compatible with this transversal structure is nat urally identified with a bundle\, of infinite rank\, over the space of K\\ "ahler metrics in the first Chern class of $L$. We show that the Einstein- -Hilbert functional of the associated Tanaka--Webster connections is a fun ctional on this bundle\, whose critical points are constant scalar curvatu re Sasaki structures. In particular\, when the group of automorphisms of $ (M\,L)$ is discrete\, these critical points correspond to constant scalar curvature K\\"ahler metrics in the first Chern class of $L$. We show that the Einstein--Hilbert functional satisfies some monotonicity properties al ong some one-parameter families of CR-contact structures that are naturall y associated to test configurations\, and that its limit on the central fi ber of a test configuration is related to the Donaldson--Futaki invariant. As a by-product\, we show that the existence of cscK metrics on a polariz ed manifold implies K-semistability. This is a joint work with Eveline Leg endre and Carlo Scarpa.\n LOCATION:https://researchseminars.org/talk/CIRGET/106/ END:VEVENT BEGIN:VEVENT SUMMARY:Yann Rollin (Université de Nantes) DTSTART:20231027T150000Z DTEND:20231027T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/107 DESCRIPTION:Title: Moment maps in Symplectic geometry and applications to PL symplectic geom etry\nby Yann Rollin (Université de Nantes) as part of CRM - Séminai re du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbs tract\nClassical results of symplectic geometry\, like Darboux theorem\, a re open problems in piecewise linear symplectic geometry. This is notoriou sly due to the fact that diffeomorphisms flow techniques fail in this cont ext.\n\nI will discuss certain moment map geometries of interest\, with ap plications to piecewise linear symplectic geometry. In particular the spac e of symplectic diffeomorphisms of the torus T^4 can be interpreted as the vanishing locus of a certain hyperKähler moment maps. An interesting mom ent map flow can be deduced as a key tool to compare homotopy properties o f the groups of diffeomorphisms and symplectomorphisms of the torus T^4.\n LOCATION:https://researchseminars.org/talk/CIRGET/107/ END:VEVENT BEGIN:VEVENT SUMMARY:Eva Miranda (Universitat Politècnica de Catalunya) DTSTART:20231103T150000Z DTEND:20231103T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/108 DESCRIPTION:Title: The Weinstein conjecture\, 44 years later\nby Eva Miranda (Universita t Politècnica de Catalunya) as part of CRM - Séminaire du CIRGET / Géo métrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nThe Weinstei n conjecture (1979) concerns the existence of periodic orbits of Reeb vect or fields. Over the years\, the conjecture has undergone significant devel opments. In this talk\, I will provide a historical overview of the Weinst ein conjecture and discuss variations for singular contact manifolds. I w ill relate the singular Weinstein conjecture with the existence of escape orbits in celestial mechanics and fluid dynamics. Time permitting\, I will conclude with a counterexample to the singular Weinstein conjecture.\n\nT his talk is based on joint works with Josep Fontana-McNally\, Cédric Oms\ , and Daniel Peralta-Salas (some of them ongoing).\n LOCATION:https://researchseminars.org/talk/CIRGET/108/ END:VEVENT BEGIN:VEVENT SUMMARY:Mike Wong (University of Ottawa) DTSTART:20231110T160000Z DTEND:20231110T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/109 DESCRIPTION:by Mike Wong (University of Ottawa) as part of CRM - Séminair e du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstra ct: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/109/ END:VEVENT BEGIN:VEVENT SUMMARY:Joe Boninger (Boston College) DTSTART:20231117T160000Z DTEND:20231117T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/110 DESCRIPTION:by Joe Boninger (Boston College) as part of CRM - Séminaire d u CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/110/ END:VEVENT BEGIN:VEVENT SUMMARY:Benoit Charbonneau (Waterloo Univ.) DTSTART:20240112T160000Z DTEND:20240112T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/111 DESCRIPTION:Title: Instantons symétriques\nby Benoit Charbonneau (Waterloo Univ.) as pa rt of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture hel d in PK-5115.\n\nAbstract\nSpencer Whitehead et moi avons développé une approche systématique pour étudier les instantons sur R4 qui sont invari ants sous l’action de groupes d’isométries de polyèdres. Dans cet ex posé\, je décrirai cette approche et quelques résultats obtenus en l’ utilisant.\n LOCATION:https://researchseminars.org/talk/CIRGET/111/ END:VEVENT BEGIN:VEVENT SUMMARY:Jarl G. Taxeras Flaten (Western Univ. Canada) DTSTART:20240119T160000Z DTEND:20240119T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/112 DESCRIPTION:Title: Central types and their bands\nby Jarl G. Taxeras Flaten (Western Uni v. Canada) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\nLecture held in PK-5115.\n\nAbstract\nWe will introduce and motivate the concept of a central type (or space) and explain their associated noti on of torsor\, called a band. Much like one can deloop a group G by its ty pe of torsors BG\, the type of bands of a central type A forms a delooping of A. Moreover\, we show that the delooping of A is itself central\, allo wing us to iterate. This procedure yields a new construction of Eilenberg- Mac Lane spaces\, which are examples of central types. We also produce a m ysterious formula for delooping pointed self-maps of A\, and study the mod uli space of H-space structures on a pointed type.\n\nOur results have bee n shown in homotopy type theory\, and most have been formalized using the Coq-HoTT library [1]. For this talk\, we do not assume familiarity with ty pe theory\; rather\, we will translate our results for topologists. This w ork is joint with Ulrik Buchholtz\, Dan Christensen\, and Egbert Rijke. [2 ]\n\n[1] https://github.com/jarlg/central-types\n[2] https://arxiv.org/abs /2301.02636\n LOCATION:https://researchseminars.org/talk/CIRGET/112/ END:VEVENT BEGIN:VEVENT SUMMARY:Ethan Ross (Toronto Univ.) DTSTART:20240126T160000Z DTEND:20240126T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/113 DESCRIPTION:Title: Reduction of Polarizations\nby Ethan Ross (Toronto Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in P K-5115.\n\nAbstract\nA polarization on a symplectic manifold $(M\,\\omega) $ is an involutive complex Lagrangian subbundle $P$ of the complexified ta ngent bundle $T^\\mathbb{C} M$. Kähler structures are special cases of po larizations which intersect their complex conjugates trivially. Much work has been done discussing how Kähler structures behave under symplectic re duction\, with only partial results for the reduction of more general pola rizations. In this talk\, I will discuss the reduction of polarizations an d also extend to the setting of singular reduction explored by Sjamaar-Ler man.\n LOCATION:https://researchseminars.org/talk/CIRGET/113/ END:VEVENT BEGIN:VEVENT SUMMARY:Chi Cheuk Tsang (UQAM) DTSTART:20240202T160000Z DTEND:20240202T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/114 DESCRIPTION:Title: Motivations and progress on the Fried-Ghys conjecture\nby Chi Cheuk T sang (UQAM) as part of CRM - Séminaire du CIRGET / Géométrie et Topolog ie\n\nLecture held in PK-5115.\n\nAbstract\nThe Fried-Ghys conjecture stat es that any two transitive Anosov flows with orientable stable and unstabl e foliations are almost equivalent\, i.e. they are the same up to homeomor phism and reparametrization after drilling out finitely many closed orbits . In this talk\, we will discuss some motivations underlying this conjectu re and some known partial results.\n LOCATION:https://researchseminars.org/talk/CIRGET/114/ END:VEVENT BEGIN:VEVENT SUMMARY:Charles Cifarelli (UQAM) DTSTART:20240209T160000Z DTEND:20240209T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/115 DESCRIPTION:Title: Steady gradient Kähler-Ricci solitons and Calabi-Yau metrics on C^n\ nby Charles Cifarelli (UQAM) as part of CRM - Séminaire du CIRGET / Géom étrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will presen t recent joint work with V. Apostolov on a new construction of complete st eady gradient Kähler-Ricci solitons on C^n\, using the theory of hamilton ian 2 forms\, introduced by Apostolov-Calderbank-Gauduchon-Tønnesen-Fried man\, as an Ansatz. The metrics come in families of two types with distinc t geometric behavior\, which we call Cao type and Taub-NUT type. In partic ular\, the Cao type and Taub-NUT type families have a volume growth rate o f r^n and r^{2n-1}\, respectively. Moreover\, each Taub-NUT type family co ntains a codimension 1 subfamily of complete Ricci-flat metrics.\n LOCATION:https://researchseminars.org/talk/CIRGET/115/ END:VEVENT BEGIN:VEVENT SUMMARY:Vamsi Pritham Pingali (Indian Institute of Science) DTSTART:20240315T150000Z DTEND:20240315T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/116 DESCRIPTION:Title: Ampleness of vector bundles and canonical metrics\nby Vamsi Pritham P ingali (Indian Institute of Science) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nHarts horne ampleness of vector bundles will be introduced and a generalisation of a criterion (due to Schneider and Tancredi) to recognise ample bundles will be presented. This work is joint with Indranil Biswas. We shall also introduce differentio-geometric positivity conditions and discuss PDE that are relevant for studying the Griffiths conjecture that asserts that Hart shorne ample bundles admit Griffiths positively curved metrics.\n\nBy zoom .\n LOCATION:https://researchseminars.org/talk/CIRGET/116/ END:VEVENT BEGIN:VEVENT SUMMARY:Bin Guo (Rutgers University) DTSTART:20240322T150000Z DTEND:20240322T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/117 DESCRIPTION:Title: Geometric estimates in Kahler geometry\nby Bin Guo (Rutgers Universit y) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLec ture held in PK-5115.\n\nAbstract\nWe will discuss the role of complex Mon ge-Ampere equations as auxiliary equations in deriving sharp analytic and geometric estimates in Kahler geometry. By studying Green's functions\, we will explore how to derive estimates for diameters and establish uniform Sobolev inequalities on Kähler manifolds\, which depend only on entropy o f the volume form and are independent of the lower bound of the Ricci curv ature. This talk is based on joint works with D. H. Phong\, J. Song\, and J. Sturm.\n LOCATION:https://researchseminars.org/talk/CIRGET/117/ END:VEVENT BEGIN:VEVENT SUMMARY:Federico Salmoiraghi (Queens Univ.) DTSTART:20240405T150000Z DTEND:20240405T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/118 DESCRIPTION:Title: Foliations\, contact structures and Anosov flows in dimension 3\nby F ederico Salmoiraghi (Queens Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nAnosov flows are an important class of dynamical systems due to their ergodic and geometric properties. Even though they represent examples of chaotic dyna mics\, they enjoy the remarkable property of being stable under small pert urbations. In this talk\, I will explain how\, perhaps surprisingly\, Anos ov flows are related to both integrable plane fields (foliations) and tota lly non-integrable plane fields (contact structures). The latter represent s a less-studied approach that has the potential to make new connections t o other branches of mathematics\, such as symplectic geometry and Hamilton ian dynamics. Along the way\, I will discuss some applications and example s with particular emphasis on the theory of surgery of Anosov flows.\n LOCATION:https://researchseminars.org/talk/CIRGET/118/ END:VEVENT BEGIN:VEVENT SUMMARY:Xuemiao Chen (Western Univ. Canada) DTSTART:20240412T150000Z DTEND:20240412T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/119 DESCRIPTION:Title: On Vafa-Witten equations over Kaehler manifolds\nby Xuemiao Chen (Wes tern Univ. Canada) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will talk about some analytic properties of solutions to the Vafa-Witten equations over compact Kaehler manifolds. Simple obstructions to the existence of nontrivial sol utions are identified. The gauge theoretical compactness for the C^* invar iant locus of the moduli space behaves similarly as the Hermitian-Yang-Mil ls connections. More generally\, this holds for solutions with uniformly b ounded spectral covers such as nilpotent solutions. When spectral covers a re unbounded\, we manage to take limits of the renormalized Higgs fields w hich are intrinsically characterized by the convergence of the associated spectral covers. This gives a simpler proof for Taubes’ results on rank two solutions over Kaehler surfaces together with a new complex geometric interpretation.\n LOCATION:https://researchseminars.org/talk/CIRGET/119/ END:VEVENT BEGIN:VEVENT SUMMARY:Andras Stipsicz (Renyi institute) DTSTART:20240419T150000Z DTEND:20240419T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/120 DESCRIPTION:by Andras Stipsicz (Renyi institute) as part of CRM - Séminai re du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstr act: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/120/ END:VEVENT BEGIN:VEVENT SUMMARY:Frédéric Rochon (UQAM) DTSTART:20240913T150000Z DTEND:20240913T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/121 DESCRIPTION:Title: Warped quasi-asymptotically conical Calabi-Yau metrics\nby Frédéric Rochon (UQAM) as part of CRM - Séminaire du CIRGET / Géométrie et Topo logie\n\nLecture held in PK-5115.\n\nAbstract\nWe will explain how to cons truct new examples of complete Calabi-Yau manifolds of maximal volume grow th on certain smoothings of Cartesian products of Calabi-Yau cones. A des cription of the geometry at infinity will be given in terms of a compactif ication by a manifold with corners obtained through a suitable sequence of blow-ups. A key analytical step in the construction of these Calabi-Yau metrics is to derive good mapping properties of the Laplacian on some suit able weighted Hölder spaces. Our methods also produce Calabi-Yau metric s with an isolated conical singularity modelled on a Calabi-Yau cone disti nct from the tangent cone at infinity\, in particular yielding a transitio n behavior between different Calabi-Yau cones as conjectured by Yang Li. This is used to exhibit many examples where the tangent cone at infinity d oes not uniquely specify a Calabi-Yau metric with exact Kähler form. Thi s is a joint work with Ronan Conlon.\n LOCATION:https://researchseminars.org/talk/CIRGET/121/ END:VEVENT BEGIN:VEVENT SUMMARY:Nathaniel Sagman (University of Luxembourg) DTSTART:20240927T150000Z DTEND:20240927T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/122 DESCRIPTION:Title: Labourie's conjecture and Higgs bundles at high energy\nby Nathaniel Sagman (University of Luxembourg) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nFor S a closed surface of genus at least 2\, Hitchin representations from pi_1(S) to PSL(n\,R) naturally generalize Fuchsian representations to PSL(2\,R). L abourie proved that every Hitchin representation comes with an invariant m inimal surface in the corresponding symmetric space. Motivated by the mapp ing class group action and potential Kahler metrics on the space of Hitchi n representations\, he conjectured that uniqueness holds as well. \n\nIn t his talk we'll explain how we used Higgs bundles to produce large area min imal surfaces that give counterexamples to Labourie's conjecture\, and we' ll overview related advances in the theory of Higgs bundles at high energy . This is all joint with Peter Smillie.\n LOCATION:https://researchseminars.org/talk/CIRGET/122/ END:VEVENT BEGIN:VEVENT SUMMARY:Julien Paupert (Arizona State) DTSTART:20241004T150000Z DTEND:20241004T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/123 DESCRIPTION:Title: Complex hyperbolic and projective deformations of Kleinian groups\nby Julien Paupert (Arizona State) as part of CRM - Séminaire du CIRGET / G éométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nWe consid er deformations of discrete subgroups (in particular lattices) of SO(3\,1) into the larger Lie groups SU(3\,1) and SL(4\,R). In particular\, when su ch deformations exist we would like to know whether or not they remain dis crete and faithful in some neighborhood of the inclusion. We will review r esults of Cooper-Long-Thistlethwaite and Ballas-Danciger-Lee in the manifo ld case\, then discuss recent joint work with Morwen Thistlethwaite for ce rtain Bianchi groups.\n LOCATION:https://researchseminars.org/talk/CIRGET/123/ END:VEVENT BEGIN:VEVENT SUMMARY:Chris Kottke (New College of Florida) DTSTART:20241018T150000Z DTEND:20241018T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/124 DESCRIPTION:Title: Geometric analysis on quasi-fibered boundary (QFB) manifolds\nby Chri s Kottke (New College of Florida) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nThe know n complete non-compact hyperkahler manifolds include several families of m oduli spaces\, including the moduli spaces of SU(2) monopoles on R^3 and t he Hilbert schemes of points on C^2\, among others. Beyond dimension 4\, t he asymptotic geometries of these spaces are not uniform\, but exhibit sin gularities `at infinity’\, presenting a challenge for geometric analysis . I will report on a framework for geometric analysis for a broad class of `quasi-fibered boundary’ (QFB) metrics. The point of view is to conside r compactifications of these spaces as manifolds with corners\, which can also be thought of as resolutions of certain stratified spaces. Through a pseudodifferential parametrix construction for the Hodge de Rham operator and an analysis relating weighted L2 cohomology with intersection cohomolo gy\, we prove a new case of Sen’s conjecture for the L2 cohomology of th e charge 3 monopole moduli space\, and of the Vafa-Witten conjecture for t he L2 cohomology of Hilbert schemes in all cases. This is joint work with F. Rochon\n LOCATION:https://researchseminars.org/talk/CIRGET/124/ END:VEVENT BEGIN:VEVENT SUMMARY:Freid Tong (University of Toronto) DTSTART:20241025T150000Z DTEND:20241025T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/125 DESCRIPTION:Title: Complete Calabi-Yau metrics and optimal transport problems\nby Freid Tong (University of Toronto) as part of CRM - Séminaire du CIRGET / Géom étrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nCalabi-Yau me trics are Ricci-flat and K\\"ahler metrics and they are a central part of K\\"ahler geometry. The construction of Calabi-Yau metrics on compact K\\" ahler manifolds has been understood since Yau's resolution of the Calabi c onjecture. By contrast\, the situation in the complete non-compact case is much more intricate and remains an active area of research. In this talk\ , I will discuss some recent developments in the study of complete Calabi- Yau metrics where the regularity theory of an optimal transport problem pl ays a big role. This is based on joint work with Tristan Collins and Shing -Tung Yau.\n LOCATION:https://researchseminars.org/talk/CIRGET/125/ END:VEVENT BEGIN:VEVENT SUMMARY:Bruno de Oliveira (Miami Univ) DTSTART:20241108T160000Z DTEND:20241108T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/127 DESCRIPTION:Title: Chern numbers ratios of surfaces with big cotangent bundle\nby Bruno de Oliveira (Miami Univ) as part of CRM - Séminaire du CIRGET / Géométr ie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nBigness of the co tangent bundle of a projective manifold is the condition that the growth o f the space of sections of the symmetric powers of the cotangent bundle is maximal. The condition implies that the manifold is of general type\, tha t is\, its canonical bundle $K_X$ satisfies the same condition. If an alge braic surface $X$ has a big cotangent bundle\, then $X$ satisfies Green-Gr iffiths-Lang conjecture. This talk examines the implication of our CMS-cri terion for bigness of the cotangent  bundle\, a condition about numerical invariants of $X$\, towards the possible ratios of the Chern numbers $c_1 ^2=K_X^2$ and $c_2=\\xi_{top}(X)$ of surfaces $X$ with big cotangent bundl e. We present several conjectures concerning  these ratios motivated by t he CMS-criterion and  examples supporting the conjectures.\n LOCATION:https://researchseminars.org/talk/CIRGET/127/ END:VEVENT BEGIN:VEVENT SUMMARY:Kathryn Mann (Cornell University) DTSTART:20241122T160000Z DTEND:20241122T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/128 DESCRIPTION:Title: (bi)-Foliations of the plane and laminations of the circle\nby Kathry n Mann (Cornell University) as part of CRM - Séminaire du CIRGET / Géom étrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nA "bifoliatio n" of a two-dimensional space is a way of covering it with local charts to the Euclidean plane R^2 so that overlap maps in R^2 match up the vertical and horizontal coordinate directions. Such objects arise naturally in ma ny dynamical contexts such as Anosov diffeomorphisms on surfaces\, or flow s on 3-manifolds.\nA trick due to Mather lets one compactify a bifoliated plane with a "circle at infinity" using the data of the bifoliation. In r ecent work with Barthelmé and Bonatti\, we studied the inverse question: what is the minimum amount of data from infinity that allows one to revers e this procedure and uniquely reconstruct a bifoliation of the plane? Th is talk will explain the answer! While our motivation for this question w as the problem of classifying pseudo-Anosov flows\, the problem and soluti on are entirely in the realm of low-dimensional topology.\n LOCATION:https://researchseminars.org/talk/CIRGET/128/ END:VEVENT BEGIN:VEVENT SUMMARY:Olivier Martin (IMPA) DTSTART:20241213T160000Z DTEND:20241213T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/129 DESCRIPTION:Title: Isotrivial Lagrangian fibrations of hyper-Kähler manifolds of K3^[n] and Kum_n type\nby Olivier Martin (IMPA) as part of CRM - Séminaire du C IRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\n I will present a classification result for Lagrangian fibrations of hyper- Kähler manifolds of K3^[n] and Kum_n types up to Tate-Shafarevich twist/d egenerate twistor deformation. This improvement on the work of Markman is made possible by a recent breakthrough of Verbitsky-Soldatenkov which ensu res that a degenerate twistor deformation of a Lagrangian fibration is Kä hler. As a consequence\, we prove that the only isotrivial Lagrangian fibr ations of hyper-Kähler manifolds of K3^[n] and Kum_n type are the obvious ones. This is joint work with Yoonjoo Kim and Radu Laza.\n LOCATION:https://researchseminars.org/talk/CIRGET/129/ END:VEVENT BEGIN:VEVENT SUMMARY:Panos Dimakis DTSTART:20241129T160000Z DTEND:20241129T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/130 DESCRIPTION:Title: On a conjecture of Simpson\nby Panos Dimakis as part of CRM - Sémina ire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAb stract\nOn a compact Riemann surface $\\Sigma$ of genus $g>1$ equipped wit h a complex vector bundle $E$ of rank two and degree zero\, let $M_H$ be t he moduli space of Higgs bundles. $M_H$ admits a $\\mathbb C^{\\star}$-act ion and to each stable $\\mathbb C^{\\star}$-fixed point $[(\\bar\\partial _0\,\\Phi_0)]$ is associated a holomorphic Lagrangian submanifold $W^1(\\b ar\\partial_0\,\\Phi_0)$ inside the de Rham moduli space $M_{dR}$ of compl ex flat connections on $E$. In this talk I will give a proof of a conjectu re of Simpson stating that $W^1(\\bar\\partial_0\,\\Phi_0)$ is closed insi de $M_{dR}$.\n LOCATION:https://researchseminars.org/talk/CIRGET/130/ END:VEVENT BEGIN:VEVENT SUMMARY:Caleb Jonker DTSTART:20241206T160000Z DTEND:20241206T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/131 DESCRIPTION:Title: Curvatures in generalized Kähler geometry\nby Caleb Jonker as part o f CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nGeneralized Kähler geometry is an extension of Kä hler geometry\, with origins in supersymmetric string theory\, which invol ves a pair of Hermitian complex structures on a Riemannian manifold or\, e quivalently\, a pair of generalized complex structures on an exact Courant algebroid. I will introduce the various curvatures that appear in general ized Kähler geometry\, and give some relations between them. In particula r\, I will explain how the generalized Kähler-Ricci flow is related to th e canonical bundles of the two generalized complex structures.\n LOCATION:https://researchseminars.org/talk/CIRGET/131/ END:VEVENT BEGIN:VEVENT SUMMARY:Chung-Ming Pan (UQAM) DTSTART:20250110T160000Z DTEND:20250110T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/132 DESCRIPTION:Title: Singular Gauduchon metrics and Hermite-Einstein problem on non-Kähler va rieties\nby Chung-Ming Pan (UQAM) as part of CRM - Séminaire du CIRGE T / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nGaud uchon metrics are very useful generalizations of Kähler metrics in non-K ähler geometry\, as Gauduchon proved that these special metrics always ex ist on compact complex manifolds. One of their important applications is d efining the notion of stability for vector bundles/sheaves on non-Kähler manifolds. It also leads the study of the existence of Hermite-Einstein me trics and the classification of non-Kähler surfaces. In this talk\, I wil l first introduce the singular version of Gauduchon's theorem and its appl ication to the Hermite-Einstein problem for stable reflexive sheaves on no n-Kähler normal varieties. Then\, I will explain one of the main technica l points that lies in obtaining uniform Sobolev inequalities for perturbed hermitian metrics on a resolution of singularities.\n LOCATION:https://researchseminars.org/talk/CIRGET/132/ END:VEVENT BEGIN:VEVENT SUMMARY:Patricia Sorya (UQAM) DTSTART:20250117T160000Z DTEND:20250117T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/133 DESCRIPTION:Title: Borner les chirurgies de Dehn non caractérisantes non entières\nby Patricia Sorya (UQAM) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nNous discutons d'ava ncées vers une conjecture de McCoy stipulant que tout nœud ne possède q u'au plus un nombre fini de chirurgies de Dehn non entières qui ne le car actérisent pas. En combinant des idées de topologie géométrique et des calculs de complexes de Floer de nœuds\, nous trouvons une région born ée contenant tous les coefficients de chirurgie de Dehn non entiers non c aractérisants pour la vaste majorité des 1 701 935 nœuds avec au plus 1 6 croisements.\n LOCATION:https://researchseminars.org/talk/CIRGET/133/ END:VEVENT BEGIN:VEVENT SUMMARY:Katherine Goldman (McGill Univ.) DTSTART:20250207T160000Z DTEND:20250207T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/134 DESCRIPTION:Title: Residual properties of 2-dimensional Artin groups\nby Katherine Goldm an (McGill Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et T opologie\n\nLecture held in PK-5115.\n\nAbstract\nIt is a longstanding ope n question to determine which Artin groups are residually finite. Past res ults have followed from linearity (e.g.\, for spherical-type or virtually cocompact special Artin groups) or product decompositions in rank 3. We pr esent a new approach to this problem using intermediate quotients to so-ca lled Shephard groups. These Shephard groups possess their own interesting (and sometimes counterintuitive) geometry which we can leverage to give ne w information about their corresponding Artin groups in some cases. As a h ighlight of this connection\, we show that an Artin group which is simulta neously 2-dimensional\, hyperbolic-type\, and FC-type is residually finite . One of the key features of the proof we will discuss is the fact that hy perbolic-type 2-dimensional Shephard groups are relatively hyperbolic\, wh ich is almost never true of Artin groups.\n LOCATION:https://researchseminars.org/talk/CIRGET/134/ END:VEVENT BEGIN:VEVENT SUMMARY:Jean Pierre Mutanguha (McGill Univ.) DTSTART:20250131T160000Z DTEND:20250131T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/135 DESCRIPTION:Title: Canonically decomposing fibrations: 3-manifolds & groups\nby Jean Pie rre Mutanguha (McGill Univ.) as part of CRM - Séminaire du CIRGET / Géom étrie et Topologie\n\nLecture held in PK-5115.\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/135/ END:VEVENT BEGIN:VEVENT SUMMARY:Ana Balibanu (Louisiana State Univ.) DTSTART:20250221T160000Z DTEND:20250221T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/136 DESCRIPTION:Title: Transversal slices in quasi-Poisson manifolds\nby Ana Balibanu (Louis iana State Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et T opologie\n\nLecture held in PK-5115.\n\nAbstract\nQuasi-Poisson manifolds are multiplicative generalizations of ordinary Poisson manifolds in which the Jacobi identity is twisted by the action of a group. We study a class of transversal slices to this group action which are motivated by geometri c representation theory. We show that these transversal slices can be thou ght of as Hamiltonian reductions of the ambient quasi-Poisson structure\, and we use this to construct examples of old and new Poisson structures in representation theory. This is joint work with Maxence Mayrand.\n LOCATION:https://researchseminars.org/talk/CIRGET/136/ END:VEVENT BEGIN:VEVENT SUMMARY:Yannick Sire (John Hopkins Univ.) DTSTART:20250404T150000Z DTEND:20250404T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/137 DESCRIPTION:Title: Harmonic maps between singular spaces\nby Yannick Sire (John Hopkins Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\ nLecture held in PK-5115.\n\nAbstract\nAfter reviewing briefly the classic al theory of harmonic maps between smooth manifolds\, I will describe some recent results related to harmonic maps with  free boundary\, emphasizin g on two different approaches based on recent developments by Da Lio and R iviere. This latter approach allows in particular to give another formulat ion which is well-suited for such maps between singular spaces. After the works of Gromov\, Korevaar and Schoen\, harmonic maps between singular spa ces have been instrumental to investigate super-rigidity in geometry. I wi ll report on recent results where we introduce a new energy between singul ar spaces and prove a version of Takahashi’s theorem (related to minimal immersions by eigenfunctions) on RCD spaces.\n LOCATION:https://researchseminars.org/talk/CIRGET/137/ END:VEVENT BEGIN:VEVENT SUMMARY:Mehdi Lejmi (CUNY) DTSTART:20250411T150000Z DTEND:20250411T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/138 DESCRIPTION:Title: Balanced HKT metrics.\nby Mehdi Lejmi (CUNY) as part of CRM - Sémi naire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\n Abstract\nBalanced HKT metrics in hypercomplex geometry are thought to b e the quaternionic analog of Calabi-Yau metrics in Kahler geometry. In thi s talk\, first we prove the openness of balanced HKT cone inside the con e of HKT structures on a compact hypercomplex manifold. We also study th e Lie algebra of hyperholomorphic vector fields. For instance\, we prove a harmonicity property for forms dual to hyperholomorphic vector fields. Th is is a joint with Giovanni Gentili.\n LOCATION:https://researchseminars.org/talk/CIRGET/138/ END:VEVENT BEGIN:VEVENT SUMMARY:Richard Melrose (MIT) DTSTART:20250425T150000Z DTEND:20250425T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/139 DESCRIPTION:by Richard Melrose (MIT) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/139/ END:VEVENT BEGIN:VEVENT SUMMARY:François Nicoleau (Univ. de Nantes) DTSTART:20250502T150000Z DTEND:20250502T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/140 DESCRIPTION:Title: Global counterexamples to uniqueness  for a Calder\\'on problem with smo oth conductivities.\nby François Nicoleau (Univ. de Nantes) as part o f CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nLet $\\Omega \\subset \\R^n$\, $n \\geq 3$\, be a fixed smooth bounded domain\, and let $\\gamma$ be a smooth conductivity i n $\\overline{\\Omega}$. Consider a non-zero frequency\n$\\lambda_0$ which does not belong to the Dirichlet spectrum of $L_\\gamma = -{\\rm div} (\\ gamma \\nabla \\cdot)$. Then\, there exists an infinite number of pairs of smooth non-isometric conductivities $(\\gamma_1\, \\gamma_2)$ on $\\overl ine{\\Omega}$\, which are close to $\\gamma$ and such that the associated DN maps at frequency $\\lambda_0$ are identical.\n\nThis is a joint work with Thierry Daudé\, Bernard Helffer and Niky Kamran.\n LOCATION:https://researchseminars.org/talk/CIRGET/140/ END:VEVENT BEGIN:VEVENT SUMMARY:Xi Chen (Univ of Alberta) DTSTART:20250314T150000Z DTEND:20250314T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/141 DESCRIPTION:Title: Cuspidal curves on K3 surfaces\nby Xi Chen (Univ of Alberta) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held i n PK-5115.\n\nAbstract\nA cusp is a curve singularity that is locally irre ducible. A\ncuspidal curve is a curve with only cusps as singularities.\nT opologically\, a cuspidal curve is homeomorphic to its normalization.\nRat ional cuspidal curves on the projective plane have been extensively\nstudi ed classically. Rational curves with one\, two and three cusps\nwere expli citly constructed. It is known that the number of cusps of\nthese curves a re bounded\, regardless of the degree of the curve. It is\nconjectured tha t there are no rational cuspidal plane curves with 5 or\nmore cusps. On th e other hand\, the degrees of these curves are\nunbounded. We will study r ational cuspidal curves on K3 surfaces. On\nK3 surfaces\, there is actuall y an upper bound for the degree of these\ncurves. This is a joint work wit h Frank Gounelas.\n LOCATION:https://researchseminars.org/talk/CIRGET/141/ END:VEVENT BEGIN:VEVENT SUMMARY:Roberto Albesiano (Univ. of Waterloo) DTSTART:20250328T150000Z DTEND:20250328T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/142 DESCRIPTION:Title: From division to extension\nby Roberto Albesiano (Univ. of Waterloo) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLectur e held in PK-5115.\n\nAbstract\nExtending holomorphic data from subvarieti es (L2 extension) and lifting holomorphic sections of quotient bundles (L2 division) are fundamental problems in complex geometry and several comple x variables. They are also intimately related: in fact\, Ohsawa showed th at a version of the L2 division theorem can be proved as a corollary of th e L2 extension theorem. We will see how\, conversely\, a version of the e xtension theorem can be obtained as an easy corollary of a division theore m with bounded generators.\n LOCATION:https://researchseminars.org/talk/CIRGET/142/ END:VEVENT BEGIN:VEVENT SUMMARY:Kuan-Hui Lee (Univ. California\, Irvine) DTSTART:20250509T150000Z DTEND:20250509T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/143 DESCRIPTION:Title: The stability of steady pluriclosed soliton\nby Kuan-Hui Lee (Univ. C alifornia\, Irvine) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nNon-Kähler Calabi-Yau theory is a newly developed subject and it arises naturally in mathematic al physics and generalized geometry. The relevant geometries are pluriclos ed metrics which are critical points of the generalized Einstein–Hilbert action which is an extension of Perelman’s F-functional. In this talk\, we studied the non-Kähler Calabi-Yau through pluriclosed flow which was first introduced by Streets and Tian a few years ago. We study the critica l points of the generalized Einstein-Hilbert action and discuss the stabil ity of critical points which are defined as pluriclosed steady solitons. W e proved that all compact Bismut–Hermitian–Einstein metrics are linear ly stable.\n LOCATION:https://researchseminars.org/talk/CIRGET/143/ END:VEVENT BEGIN:VEVENT SUMMARY:Changjie Chen (Université de Montréal) DTSTART:20250919T150000Z DTEND:20250919T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/144 DESCRIPTION:Title: Morse theory on moduli spaces\nby Changjie Chen (Université de Montr éal) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\n Lecture held in PK-5115.\nAbstract: TBA\n\nSarnak conjectured in the 1990s that the determinant of the Laplacian is a Morse function on the space of unit area Riemannian metrics on a given surface\, and hence induces a Mor se function on the moduli space of Riemann surfaces.\n\nIt is known that t he systole function\, defined as the length of a shortest closed geodesic with respect to the base metric\, is topologically Morse on the moduli spa ce M_{g\,n}. However\, it does not generate a Morse theory.\n\nIn this tal k\, I will introduce a family of Morse functions\, defined as weighted exp onential averages of all geodesic-length functions\, on the Deligne-Mumfor d compactification (M_{g\,n} bar). These functions are compatible with the Deligne-Mumford stratification and the Weil-Petersson metric\, and their critical points can be characterized by a combinatorial property.\n\nI wil l finally talk about homological consequences of hyperbolic geometry resul ts via Morse theory\, including a stability theorem. If time permits\, I w ill explain how these Morse functions connect to Sarnak’s conjecture.\n LOCATION:https://researchseminars.org/talk/CIRGET/144/ END:VEVENT BEGIN:VEVENT SUMMARY:Mike Roth (Queens University) DTSTART:20251003T150000Z DTEND:20251003T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/145 DESCRIPTION:Title: Reduced Čech complexes and computing higher direct images under toric fi brations.\nby Mike Roth (Queens University) as part of CRM - Séminair e du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbst ract\nLet $X$ be a topological space\, $F$ a sheaf of abelian groups on $X $\, and $\\{ U_{\\alpha}\\}_{\\alpha\\in I\\}$ an open cover of $X$. Then one can form a Čech complex\, a complex of groups built from the values of $F$ on the open sets and their intersections. \n\nIf the higher coho mology of $F$ vanishes on all these open sets\, then it is a well-known th eorem of Leray that this complex computes the cohomology of $F$ on $X$. For instance\, if $X$ is a manifold and the $U_{\\alpha}$ form a `good cov er’ (all the $U_{\\alpha}$ and their intersections are homeomorphic to $ \\mathbb{R}^n$)\, then the Čech complex can be used to compute the topolo gical cohomology of $X$.\n\nFor special kinds of toric varieties — those whose fans are `simplicial’ -- it is known how to construct smaller ( “reduced”) complexes which still correctly compute cohomology of sheav es.\n\nThis talk has three main goals : (1) To give an axiomatization of ‘reduced Čech complexes’\, valid for any topological space\; (2) To extend the previous construction of reduced Čech complexes to all compact toric varieties (not just simplicial ones)\, and more generally to ’sem i-proper’ toric varieties\; (3) To use the previous method to give an al gorithm for computing higher direct images (roughly the `cohomology along the fibres’) of line bundles for toric fibrations between smooth toric v arieties.\n\nNo previous knowledge of toric varieties is required.\nThis i s joint work with Sasha Zotine.\n LOCATION:https://researchseminars.org/talk/CIRGET/145/ END:VEVENT BEGIN:VEVENT SUMMARY:Dylan Cant (Université de Montréal) DTSTART:20251017T150000Z DTEND:20251017T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/146 DESCRIPTION:Title: Equivariant quantum cohomology for Lagrangian submanifolds\nby Dylan Cant (Université de Montréal) as part of CRM - Séminaire du CIRGET / G éométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nSuppose t hat M is a symplectic manifold equipped with an involution preserving the symplectic structure\, and suppose L is a compact Lagrangian submanifold o f M preserved by the involution. A central question in symplectic topology concerns the existence of intersections between L and f(L)\, where f is a Hamiltonian motion (the time 1 map of a Hamiltonian isotopy). We will exp lore additional rigidity exhibited by Hamiltonian motions which are equiva riant with respect to the involution. As an example\, we show the product of the n unit circles (in R2n) is not displaceable by a Hamiltonian motion commuting with the antipodal map z→-z.\n LOCATION:https://researchseminars.org/talk/CIRGET/146/ END:VEVENT BEGIN:VEVENT SUMMARY:Octav Cornea (Université de Montréal) DTSTART:20251107T160000Z DTEND:20251107T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/147 DESCRIPTION:Title: Approximability and Gromov width of Lagrangians\nby Octav Cornea (Uni versité de Montréal) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will describe rec ent work joint with Giovanni Ambrosioni and\nPaul Biran ( both from ETH) t hat ties certain bounds of Lagrangian Gromov \nwidth to a categorified   notion of approximability first introduced by Alan\nTuring in the study of Lie groups.\n LOCATION:https://researchseminars.org/talk/CIRGET/147/ END:VEVENT BEGIN:VEVENT SUMMARY:Steven Rayan DTSTART:20251117T160000Z DTEND:20251117T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/148 DESCRIPTION:Title: Hyperbolic Band Structures and Moduli Spaces\nby Steven Rayan as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5675.\n\nAbstract\nI will discuss my recent works involving the use of ideas from differential and complex algebraic geometry to anticipate ne w models of 2-dimensional quantum materials\, generalizing topological mat erials\, with an emphasis on the development of a hyperbolic analogue of e lectronic band theory.  In the process\, we will develop a dictionary bet ween well-known moduli spaces of data on Riemann surfaces on the one side and condensed matter properties on the other\, with a view to invariants e ncoding physical behaviours. I will briefly outline recent attempts to syn thesize such materials in my recent collaborations with experimental and e ngineering physicists.\n\nNote : The room is PK-5675 and the date : Monday 17th of November.\n LOCATION:https://researchseminars.org/talk/CIRGET/148/ END:VEVENT BEGIN:VEVENT SUMMARY:Shih-Kai Chiu (University of California\, Irvine) DTSTART:20251121T160000Z DTEND:20251121T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/149 DESCRIPTION:Title: Special Lagrangian submanifolds from tropical-like data\nby Shih-Kai Chiu (University of California\, Irvine) as part of CRM - Séminaire du CI RGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nS pecial Lagrangian submanifolds are volume-minimizing Lagrangians in Calabi -Yau manifolds. Their existence not only provides a rich source of higher- codimensional minimal submanifolds\, but also plays a central role in the SYZ picture of mirror symmetry. However\, existence results remain scarce\ , especially in the compact case. In this talk\, I will present two gluing constructions: (1) special Lagrangians in K3-fibered Calabi-Yau 3-folds\, and (2) special Lagrangians in the simplest SYZ fibration\, $T^*T^n$. In both cases\, the starting point is a tropical-like graph in the base of th e fibration\, which guides the gluing of local models. Based on joint work s with Yang Li and Yu-Shen Lin.\n LOCATION:https://researchseminars.org/talk/CIRGET/149/ END:VEVENT BEGIN:VEVENT SUMMARY:Tristan Collins (University of Toronto) DTSTART:20251128T160000Z DTEND:20251128T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/150 DESCRIPTION:Title: Complete Calabi-Yau Manifolds and Optimal Transportation\nby Tristan Collins (University of Toronto) as part of CRM - Séminaire du CIRGET / G éométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI will di scuss some geometric\, analytic and algebraic\, aspects of complete Calabi -Yau metrics on pairs (X\,D) where X is Fano and D is an ample anti-canoni cal divisor with simple normal crossings. I will highlight the connection between existence of such Calabi-Yau metrics and optimal boundary regular ity theory for optimal transportation.\nThis talk is based on joint works with Y. Li\, F. Tong\, S.-T. Yau\, and H. Guenancia\n LOCATION:https://researchseminars.org/talk/CIRGET/150/ END:VEVENT BEGIN:VEVENT SUMMARY:Junsheng Zhang (Courant Institute\, NYU) DTSTART:20251205T160000Z DTEND:20251205T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/151 DESCRIPTION:Title: Diameter lower bounds for the Kähler–Ricci flow at finite-time singula rities\nby Junsheng Zhang (Courant Institute\, NYU) as part of CRM - S éminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115. \n\nAbstract\nWe establish a uniform lower bound for the diameter along th e Kähler–Ricci flow up to the first finite-time singularity for non-Fan o initial data. The argument is based on a weak transcendental base-point- freeness result on compact Kähler manifolds and a generalized Schwarz-typ e lemma.\n LOCATION:https://researchseminars.org/talk/CIRGET/151/ END:VEVENT BEGIN:VEVENT SUMMARY:Christophe Mourougane (Université de Rennes) DTSTART:20251024T150000Z DTEND:20251024T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/152 DESCRIPTION:Title: Jet differentials and applications\nby Christophe Mourougane (Univers ité de Rennes) as part of CRM - Séminaire du CIRGET / Géométrie et Top ologie\n\nLecture held in PK-5115.\n\nAbstract\nJet differentials on compl ex manifolds are geometric objects that formalize algebraic differential e quations. \nThey are useful in Kobayashi's theory of hyperbolicity\, where we seek\, for example\, to show the algebraic degeneration of entire curv es on projective manifolds of general type.\nIn this talk\, based on work in progress with Pierre-Emmanuel Chaput and Lionel Darondeau\, I will pres ent a construction of jet differentials and some ideas to prove the comple teness of the resulting system.\n LOCATION:https://researchseminars.org/talk/CIRGET/152/ END:VEVENT BEGIN:VEVENT SUMMARY:Jérôme Vétois (McGill) DTSTART:20260116T160000Z DTEND:20260116T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/153 DESCRIPTION:Title: Nonexistence of extremals for the second conformal eigenvalue in low dime nsions\nby Jérôme Vétois (McGill) as part of CRM - Séminaire du CI RGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nI n this talk\, we will consider the second conformal eigenvalue on a closed Riemannian manifold of positive Yamabe type and dimension greater than or equal to 3. The second conformal eigenvalue is defined as the infimum of the second eigenvalue of the conformal Laplacian in a conformal class of m etrics with renormalized volume. We will discuss a recent result showing t hat this infimum is not attained for metrics close to the round metric on the sphere in dimensions 3 to 10\, which contrasts sharply with the situat ion in dimensions greater than or equal to 11\, where Ammann and Humbert o btained the existence of minimizers on any closed nonlocally conformally f lat manifold. This is a joint work with Bruno Premoselli (Université Libr e de Bruxelles).\n LOCATION:https://researchseminars.org/talk/CIRGET/153/ END:VEVENT BEGIN:VEVENT SUMMARY:Chenxi Yin (UQAM) DTSTART:20260130T160000Z DTEND:20260130T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/154 DESCRIPTION:Title: Relative uniform Yau-Tian-Donaldson correspondence for projective bundles over a curve\nby Chenxi Yin (UQAM) as part of CRM - Séminaire du CIR GET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nIn this talk\, I will present recent joint work with Simon Jubert on a versi on of the Yau–Tian–Donaldson correspondence for projective bundles Y=P (E) over a curve. By earlier work of Apostolov–Keller\, if a Kähler cla ss on Y admits an extremal Kähler metric\, then E must split as a direct sum of stable vector bundles. We show that\, for such E\, a Kähler class on Y admits an extremal Kähler metric if and only if it is relatively uni formly K-stable. The proof uses a distinguished family of test configurati ons\, called compatible test configurations\, constructed from the horosph erical symmetry of the fibers\, together with the framework of weighted co nstant scalar curvature Kähler metrics.\n LOCATION:https://researchseminars.org/talk/CIRGET/154/ END:VEVENT BEGIN:VEVENT SUMMARY:Tyrone Ghaswala (University of Waterloo) DTSTART:20260213T160000Z DTEND:20260213T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/155 DESCRIPTION:Title: Big mapping class groups and uniqueness of Polish structures\nby Tyro ne Ghaswala (University of Waterloo) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract\nSuppo se you are given a topological group. You may wonder about how much the gr oup structure determines the topology. At first glance\, the answer appear s to be "not very much at all"\, since every topological group admits the discrete topology\, and the trivial topology\, both of which are compatibl e with the group operation. \n\nMapping class groups of infinite-type surf aces are humungous (not a technical term)\, and come equipped with a Polis h topology. We can ask a refinement of the above question: How much does t he group structure of a mapping class group determine its Polish topology? In this talk we'll investigate this question\, leading to a perhaps surpr ising answer.\n\nThis is joint work with Sumun Iyer\, Robbie Lyman\, and N ick Vlamis.\n LOCATION:https://researchseminars.org/talk/CIRGET/155/ END:VEVENT BEGIN:VEVENT SUMMARY:Robert Harris (UQAM) DTSTART:20260220T160000Z DTEND:20260220T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/156 DESCRIPTION:Title: Recipes for exotic definite 4-manifolds\nby Robert Harris (UQAM) as p art of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture he ld in PK-5115.\n\nAbstract\nIt is an ongoing search to find an exotic mani fold which is homeomorphic to a sum of complex projective planes (or a su m with only oppositely oriented projective planes). Relaxing this conditio n\, a smooth definite manifold is one with an intersection form at least i somorphic to that of such a space. The door into the study of definite exo tica was first opened by the discovery of examples with a fundamental gr oup of order two by Levine\, Lidman and Piccirillo and further advancement s have since been made to construct examples with larger fundamental group s. We will discuss the general recipe for constructing these manifolds\, a s well as the specific ingredients that different researchers have been us ing. This is based on joint work with Patrick Naylor and B. Doug Park.\n LOCATION:https://researchseminars.org/talk/CIRGET/156/ END:VEVENT BEGIN:VEVENT SUMMARY:Ronan Conlan (UT Dallas) DTSTART:20260227T160000Z DTEND:20260227T171500Z DTSTAMP:20260422T225753Z UID:CIRGET/157 DESCRIPTION:Title: On Toric Shrinking Gradient Kähler-Ricci Solitons\nby Ronan Conlan ( UT Dallas) as part of CRM - Séminaire du CIRGET / Géométrie et Topologi e\n\nLecture held in PK-5115.\n\nAbstract\nShrinking gradient Kähler-Ricc i solitons model finite-time singularities of the Kähler-Ricci flow on co mpact Kähler manifolds. I will discuss the existence problem for shrinkin g gradient Kähler-Ricci solitons in the non-compact toric setting. This t alk is based on joint work with Ivin Babu and Alix Deruelle\, and with Cha rles Cifarelli and Alix Deruelle.\n LOCATION:https://researchseminars.org/talk/CIRGET/157/ END:VEVENT BEGIN:VEVENT SUMMARY:Mauricio Bustamente (UQAM) DTSTART:20260313T150000Z DTEND:20260313T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/158 DESCRIPTION:Title: Strict hyperbolization of flat manifolds\nby Mauricio Bustamente (UQA M) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLec ture held in PK-5115.\n\nAbstract\nCharney–Davis strict hyperbolization is a construction that takes a nonpositively curved cube complex and conve rts it into a negatively curved space. In this talk\, I’ll explain how s trict hyperbolization can be used to produce closed hyperbolic manifolds w ith interesting topological features\, by applying it to a suitable class of flat manifolds. This leads to new examples of closed hyperbolic manifol ds with nontrivial Pontryagin and Stiefel–Whitney classes\, hyperbolic m anifolds that arise as totally geodesic boundaries of other hyperbolic man ifolds\, and aspherical topological manifolds that admit no smooth structu re. This is joint work with Eduardo Reyes and Stefano Riolo.\n LOCATION:https://researchseminars.org/talk/CIRGET/158/ END:VEVENT BEGIN:VEVENT SUMMARY:Yu-Chi Hou (Univ. of Maryland) DTSTART:20260327T150000Z DTEND:20260327T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/159 DESCRIPTION:Title: Kähler Quantization in Degenerate Setting\nby Yu-Chi Hou (Univ. of M aryland) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\ n\nLecture held in PK-5115.\n\nAbstract\nKähler quantization provides a b ridge between infinite-dimensional geometric objects in Kähler geometry a nd finite-dimensional data arising from spaces of holomorphic sections. In this talk\, I will first review this correspondence in the ample case\, w here it is well understood and plays a central role in the study of canoni cal metrics.\nI will then explain how this picture can be extended beyond the ample setting\, where smooth positively curved metrics are no longer a vailable. In particular\, I will describe how the Monge–Ampère energy c an still be recovered from finite-dimensional approximations in the semipo sitive and big setting. Finally\, if time permits\, I will outline the ide a of the proof.\n LOCATION:https://researchseminars.org/talk/CIRGET/159/ END:VEVENT BEGIN:VEVENT SUMMARY:Hans Boden (McMaster Univ.) DTSTART:20260417T150000Z DTEND:20260417T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/160 DESCRIPTION:Title: Mock Seifert matrices and concordance of virtual knots\nby Hans Boden (McMaster Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et T opologie\n\nLecture held in PK-5115.\n\nAbstract\nWe generalize the Gordon -Litherland pairing to homologically trivial knots in thickened surfaces\, and use it to define new knot invariants with applications to concordance of virtual knots.\n\nThis talk is a report on joint papers with Homayun K arimi.\n LOCATION:https://researchseminars.org/talk/CIRGET/160/ END:VEVENT BEGIN:VEVENT SUMMARY:Mike Miller Eismeier (Vermont Univ.) DTSTART:20260424T150000Z DTEND:20260424T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/161 DESCRIPTION:Title: Mod-2 instanton homology and Dehn surgery\nby Mike Miller Eismeier (V ermont Univ.) as part of CRM - Séminaire du CIRGET / Géométrie et Topol ogie\n\nInteractive livestream: https://uqam.zoom.us/j/88383789249\nLectur e held in PK-5115.\n\nAbstract\nKim Froyshov has introduced new homology c obordism invariants q2(Y)\, q3(Y) coming from the study of mod-2 instanton homology. q3\, in particular\, has some remarkable properties: if Y\, Y' cobound a 4-manifold W\, then |q3(Y) - q3(Y')| is bounded in terms of homo logical invariants of W. I will explain the origin of this bound\, how it leads to a resolution of the surgery number question\, and directions for further inquiry.\n\nThis talk is based on forthcoming joint work with Ali Daemi and Xingpei Liu.\n LOCATION:https://researchseminars.org/talk/CIRGET/161/ URL:https://uqam.zoom.us/j/88383789249 END:VEVENT BEGIN:VEVENT SUMMARY:Charlie Cifarelli (Stony Brook University) DTSTART:20260320T150000Z DTEND:20260320T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/162 DESCRIPTION:Title: K-polystability of asymptotically conical Kähler-Ricci shrinkers\nby Charlie Cifarelli (Stony Brook University) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nLecture held in PK-5115.\n\nAbstract \nShrinking gradient Kähler-Ricci solitons (Kähler-Ricci shrinkers) are fundamental objects in the study of the Kähler-Ricci flow\, characterizin g much of the behavior of finite-time singularities. Recently\, Sun--Zhang have developed an algebraic theory for Kähler-Ricci shrinkers\, which in particular implies that such spaces are naturally quasiprojective varieti es. Moreover\, they propose a YTD correspondence between the existence of such a metric and an algebro-geometric notion of K-stability\, analogous t o and in fact extending the well-known situations for Fano manifolds and K ähler cones. In this talk\, I will discuss the proof of one direction of the correspondence\, namely that the existence of a Kähler-Ricci shrinke r metric implies K-polystability\, in the case that the Ricci curvature de cays at infinity. This is joint work with Carlos Esparza.\n LOCATION:https://researchseminars.org/talk/CIRGET/162/ END:VEVENT BEGIN:VEVENT SUMMARY:Bob Olivier (Université Sorbonne Paris Nord) DTSTART:20260529T150000Z DTEND:20260529T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/164 DESCRIPTION:Title: The local structure of finite groups and of their classifying spaces\ nby Bob Olivier (Université Sorbonne Paris Nord) as part of CRM - Sémina ire du CIRGET / Géométrie et Topologie\n\nInteractive livestream: https: //uqam.zoom.us/j/88383789249\nLecture held in PK-5115.\n\nAbstract\nFix a prime ${p}$. We say that two finite groups $G$ and\n$H$ are ``${p}$-equiva lent'' if there is an isomorphism between\nSylow $p$-subgroups $S \\in Syl _p(G)$ and $T\\in \nSyl_p({H})$ that preserves all $G-$ and\n${H}-$conjuga cy relations among elements and subgroups of $S$\nand $T$. We say that two topological spaces ${X}$ and ${Y}$ are ``${p}$-equivalent'' if there is a third space ${Z}$\, and maps $X\\to Z \\leftarrow Y$ that induce isomorph isms in homology\nwith coefficients in $\\mathbb{Z}/p$. (Both of these are equivalence\nrelations.) The main theorem I want to describe says that fi nite groups ${G}$ and ${H}$ are\n$p$-equivalent (as groups) if and only if their classifying spaces\nare ${p}$-equivalent (as spaces).\n\n\nI will s tart by defining in more detail classifying spaces of discrete\ngroups and the two kinds of ${p}$-equivalence described above\, and\nalso saying a l ittle about the background of the theorem. I then plan to\ngive some examp les of finite groups that are ${p}$-locally equivalent\nbut not isomorphic \, and say something about ideas that went into the\nproof of the theorem (carried out by several different people over a\nperiod of 10--15 years).\ n LOCATION:https://researchseminars.org/talk/CIRGET/164/ URL:https://uqam.zoom.us/j/88383789249 END:VEVENT BEGIN:VEVENT SUMMARY:Qi Yao (Stony Brook) DTSTART:20260508T150000Z DTEND:20260508T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/165 DESCRIPTION:by Qi Yao (Stony Brook) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nInteractive livestream: https://uqam.zoom.us /j/88383789249\nLecture held in PK-5115.\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/CIRGET/165/ URL:https://uqam.zoom.us/j/88383789249 END:VEVENT BEGIN:VEVENT SUMMARY:Niky Kamran (Univ. McGill) DTSTART:20260501T150000Z DTEND:20260501T161500Z DTSTAMP:20260422T225753Z UID:CIRGET/166 DESCRIPTION:Title: Logarithmic stability in the inverse Steklov problem on warped products\nby Niky Kamran (Univ. McGill) as part of CRM - Séminaire du CIRGET / Géométrie et Topologie\n\nInteractive livestream: https://uqam.zoom.us/j /88383789249\nLecture held in PK-5115.\n\nAbstract\nWe study the amount of information contained in the Steklov spectrum of some compact manifolds w ith connected boundary equipped with a warped product metric. Examples of such manifolds include deformed balls in R^d. We first show that the Stekl ov spectrum determines uniquely the warping function and also show that th e approximate knowledge (in a given technical sense) of the Steklov spectr um is enough to determine uniquely the warping function in a neighbourhood of the boundary. Second\, we provide logarithmic stability estimates on t he warping function from the Steklov spectrum. The key element of these st ability results relies on a formula that\, roughly speaking\, connects the inverse data (the Steklov spectrum) to the Laplace transform of the diffe rence of the two warping factors.\n LOCATION:https://researchseminars.org/talk/CIRGET/166/ URL:https://uqam.zoom.us/j/88383789249 END:VEVENT END:VCALENDAR