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X-WR-CALNAME:Laboratoire de Mathématiques de Versailles
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X-WR-CALDESC:Évènements pour Laboratoire de Mathématiques de Versailles
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260505T133000
DTEND;TZID=Europe/Paris:20260505T140000
DTSTAMP:20260507T114022Z
CREATED:20260430T161305Z
LAST-MODIFIED:20260507T114022Z
UID:15005-1777987800-1777989600@lmv.math.cnrs.fr
SUMMARY:AG : Lucas Pannier (LMV) : An effective proof of the p-curvature conjecture for first-order differential equations with rational coefficients
DESCRIPTION:Abstract: In 1974\, Honda proved the p-curvature conjecture for order one differential equations with rational coefficients over a number field. He demonstrated that in this setting\, the p-curvature conjecture was equivalent to a theorem due to Kronecker\, providing a local-global criterion for the splitting of polynomials over the rational numbers. In 1985 the Chudnovskys published another proof of Honda’s theorem (and of Kronecker’s theorem) by means of Padé approximation and elementary number theory\, thus paving the way to an effective version of these results. Here\, by « effective » we mean that we wish to obtain an explicit finite bound on the number of p-curvatures to be computed in order to decide the algebraicity of the solution of the differential equation. \nIn this talk\, I will explain how to obtain such a bound. \nThis is joint work with Florian Fürnsinn (University of Vienna).
URL:https://lmv.math.cnrs.fr/evenenement/ag-lucas-pannier-lmv-an-effective-proof-of-the-p-curvature-conjecture-for-first-order-differential-equations-with-rational-coefficients/
CATEGORIES:Séminaire AG
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260505T140000
DTEND;TZID=Europe/Paris:20260505T143000
DTSTAMP:20260507T114028Z
CREATED:20260430T161917Z
LAST-MODIFIED:20260507T114028Z
UID:15007-1777989600-1777991400@lmv.math.cnrs.fr
SUMMARY:AG : Davide Ricci (LMV) : The Mori cone of certain Hassett spaces
DESCRIPTION:Abstract: The talk will introduce the F-conjecture\, which states that the Mori cone of the moduli space of genus g stable curves ‾Mg\,n is generated by 1-dimensional strata. We will see that the question can be formulated on any Hassett space and has a positive answer when the universal family is a P1-bundle. In particular\, we review how these particular Hassett spaces are naturally isomorphic to certain GIT quotients (P1)n // PGL2\, and we characterize these spaces as the targets of the birational contractions of Bln-1Pn-3 with Q-factorial image.
URL:https://lmv.math.cnrs.fr/evenenement/ag-davide-ricci-lmv-the-mori-cone-of-certain-hassett-spaces/
CATEGORIES:Séminaire AG
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260519T133000
DTEND;TZID=Europe/Paris:20260519T143000
DTSTAMP:20260514T073238Z
CREATED:20260302T163943Z
LAST-MODIFIED:20260514T073238Z
UID:14829-1779197400-1779201000@lmv.math.cnrs.fr
SUMMARY:AG : Bernhard Keller (Université Paris Cité) : Catégorification du tressage grassmannien
DESCRIPTION:Résumé : En 2017\, Chris Fraser a découvert une action du groupe de tresses affine étendu à d brins sur la (grosse cellule de la) grassmannienne des sous-espaces de dimension k d’un espace de dimension n\, munie de sa structure d’algèbre amassée (cluster) due à Scott (2006). Ici\, l’entier d désigne le plus grand commun diviseur de k et n. Nous construisons un relèvement catégorique de cette action en utilisant la catégorification (additive) de la grassmannienne par Jensen\, King et Su via les modules de Cohen–Macaulay gradués sur une singularité de courbe plane. Un ingrédient essentiel est l’action du groupe de tresses de Seidel et Thomas (2000) sur la catégorie dérivée d’une algèbre de Calabi–Yau. Cet exposé est basé sur la thèse de doctorat en cours de Haoyu Wang.
URL:https://lmv.math.cnrs.fr/evenenement/ag-bernhard-keller-imj-prg/
CATEGORIES:Séminaire AG
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260519T163000
DTEND;TZID=Europe/Paris:20260519T173000
DTSTAMP:20260522T070350Z
CREATED:20260518T072951Z
LAST-MODIFIED:20260522T070350Z
UID:15030-1779208200-1779211800@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Isabel Velazquez Contreras (LJLL\,LMO) : Singularity formation in binormal flow and nonlinear Schrödinger equations
DESCRIPTION:Abstract: The binormal flow\, which models the evolution of vortex filaments\, and the cubic nonlinear Schrödinger equation are deeply connected through the Hasimoto transform\, linking vortex filament dynamics with dispersive partial differential equations. In this talk\, I will give an overview of this connection and discuss the formation of corners in binormal flow\, as well as the role of Dirac masses in the nonlinear Schrödinger equation. I will present several results on corner formation in vortex filaments and singular NLS solutions\, illustrating some of the main ideas used to study these problems.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-isabel-velazquez-contreras-ljlllmo-singularity-formation-in-binormal-flow-and-nonlinear-schrodinger-equations/
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260521T133000
DTEND;TZID=Europe/Paris:20260521T170000
DTSTAMP:20260522T070343Z
CREATED:20260518T131737Z
LAST-MODIFIED:20260522T070343Z
UID:15040-1779370200-1779382800@lmv.math.cnrs.fr
SUMMARY:Soutenance de thèse : Danil Gubarevich : On Gromov-Witten invariants and the Hall induction
DESCRIPTION:Danil Gubarevich soutient sa thèse\,  intitulée « On Gromov-Witten invariants and the Hall induction » encadrée par Dimitri Zvonkine\, le jeudi 21 mai\, 13h30\, bâtiment Fermat\, salle 2201. \n  \nRésumé : \nThe first two chapters of the manuscript provide the motivation for the subjects we were studying in this thesis. First we discuss the relation between the Gromov-Witten and Donaldson-Thomas enumerative theories and explain how the DT-theory was categorified by means of perverse sheaves of vanishing cycles. This part aims to show the link between Chapters 3 and 4. \nFurther we review the generalities on genus 0 Gromov-Witten theory with the focus on smooth complete intersections\, relevant to Chapter 3. \nTo motivate Chapter 4\, we review the notions of the classical Hall algebra of a finitary hereditary category and its cohomological enhancement by the cohomological Hall algebra\, using quiver representations as a key example. These algebras serve as the primary inspiration for the constructions and theorems discussed in Chapter 4. \nFinally\, we state the results of our thesis. \nChapter 3 discusses GW-theory of even dimensional complete intersections X of two quadrics in CP^{m+2}. These varieties are exceptional from the point of view of the Gromov-Witten theory: they are (together with surfaces of degrees 2 and 3) the only complete intersections whose Gromov-Witten theory is not invariant under the full orthogonal or symplectic group acting on the primitive cohomology. The genus 0 Gromov-Witten theory of X was studied by Xiaowen Hu. He used geometric arguments and the associativity of quantum cohomology to compute all genus 0 correlators except one\, which cannot be determined by his methods. In our paper\, we use a different method\, based on Jun Li’s degeneration formula. We show [Theorem (??)] the existence of a basis in cohomology of X\, such that the remaining Gromov-Witten invariant in this basis vanishes. \nIn Chapter 4 we study an example of the Hall induction\, the natural analog of the Hall multiplication in situations where the moduli space at hand is not the moduli space of objects in some abelian category. We study the Hall induction for the moduli space T^*(V/G): the cotangent stack of the quotient stack V/G\, where V is a representation of a complex reductive group G. First we indicate how to define the Hall induction map via a representation of a Levi subgroup on the level of the critical Hall induction and then conjugate this map by the dimensional reduction isomorphism. We adapt a result proven for cohomological and K-theoretical Hall algebras of a quiver: the first is the torsion freeness of the Hall induction for the stack T^*(V/G) deformed by a certain torus T_s. This result is equivalent to an embedding of the Hall induction into the space of symmetric polynomials. As a corollary\, we prove that the T_s-equivariant Borel-Moore homology of T^*(V/G) is concentrated in even homological degrees.
URL:https://lmv.math.cnrs.fr/evenenement/soutenance-de-these-danil-gubarevich-on-gromov-witten-invariants-and-the-hall-induction/
CATEGORIES:Soutenance de thèse
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260521T140000
DTEND;TZID=Europe/Paris:20260521T150000
DTSTAMP:20260522T070335Z
CREATED:20260308T171641Z
LAST-MODIFIED:20260522T070335Z
UID:14846-1779372000-1779375600@lmv.math.cnrs.fr
SUMMARY:EDP : Daniel Han-Kwan (université de Nantes et CNRS) : Limite semiclassique de NLS cubique pour les états mixtes
DESCRIPTION:Résumé :\nOn considère la limite semiclassique de l’équation de Schrödinger cubique pour les états mixtes. La limite formelle est une équation de Vlasov singulière (Vlasov-Benney dans le cas défocalisant).\nCette limite est justifiée pour des données initiales à régularité finie\, vérifiant une condition de stabilité de type Penrose. \nIl s’agit d’une collaboration avec Frédéric Rousset (Orsay).
URL:https://lmv.math.cnrs.fr/evenenement/edp-daniel-han-kwan-universite-de-nantes-et-cnrs/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire EDP
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260521T153000
DTEND;TZID=Europe/Paris:20260521T163000
DTSTAMP:20260522T070323Z
CREATED:20260308T171802Z
LAST-MODIFIED:20260522T070323Z
UID:14848-1779377400-1779381000@lmv.math.cnrs.fr
SUMMARY:EDP : Philippe Souplet (université Sorbonne Paris Nord) : Classification of entire and ancient solutions of the diffusive Hamilton-Jacobi equation
DESCRIPTION:Abstract: (joint work with Loth Chabi) We study the Liouville type classification and symmetry properties\,\nin \(R^n\) and in a half-space with Dirichlet boundary conditions\, for entire and ancient solutions of the diffusive Hamilton-Jacobi equation\,\nwhich arises in optimal stochastic control\, in KPZ type models of surface growth and in studies of boundary gradient blow-up. \nIn particular we obtain optimal Liouville type theorems for ancient and entire solutions in \(R^n\) and we completely classify entire solutions in a half-space.\nThe proofs rely\, among other things\, on new and optimal\, local estimates of Bernstein and Li-Yau type.\nSuch Liouville type results are very useful in the qualitative analysis of blow-up singularities for this equation.
URL:https://lmv.math.cnrs.fr/evenenement/edp-philippe-souplet-universite-sorbonne-paris-nord/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire EDP
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260526T133000
DTEND;TZID=Europe/Paris:20260526T143000
DTSTAMP:20260529T083449Z
CREATED:20260305T161023Z
LAST-MODIFIED:20260529T083449Z
UID:14833-1779802200-1779805800@lmv.math.cnrs.fr
SUMMARY:AG : Sophie Morier-Genoud (Université de Reims) : q-analogues de nombres et théorie de Markov
DESCRIPTION:Résumé : Les suites classiques de nombres entiers ont pour la plupart des q-analogues bien établis. Les plus connus sont certainement les q-nombres entiers et les q-coefficients binomiaux qui apparaissent tout deux dans différents domaines de mathématique et physique. Avec Valentin Ovsienko nous avons récemment introduit des q-analogues de nombres rationnels et irrationnels. Notre approche est basée sur des propriétés combinatoires simples des nombres et des fractions continues. Les q-réels révèlent de nombreuses propriétés en lien avec des sujets variés (combinatoire des posets\, invariants de noeuds et tresses\, géométrie hyperbolique\, algèbre homologique\, algèbres amassées…) et permettent de revisiter des classiques.  Je ferai un petit tour d’horizon en donnant les constructions et les principales propriétés des q-réels et proposerai de revisiter la théorie d’approximation de Markov.
URL:https://lmv.math.cnrs.fr/evenenement/ag-sophie-morier-genoud-universite-de-reims/
CATEGORIES:Séminaire AG
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20260528T103000
DTEND;TZID=Europe/Paris:20260528T113000
DTSTAMP:20260529T083438Z
CREATED:20260522T073920Z
LAST-MODIFIED:20260529T083438Z
UID:15050-1779964200-1779967800@lmv.math.cnrs.fr
SUMMARY:Conférence exceptionnelle : Enkhbat Rentsen\, (Université Nationale de Mongolie) : Recent Advances in Sphere Packing Problems
DESCRIPTION:Enkhbat Rentsen\, professeur émérite à l'(Université Nationale de Mongolie et membre de l’académie des sciences de Mongolie\, donnera une conférence intitulée « Recent Advances in Sphere Packing Problems » le jeudi 28 mai à 10h30 en salle de séminaire du LMV \nLe résumé de la conférence est le suivant : \n« In this talk\, we consider a sphere-packing problem: packing nonoverlapping spheres of maximum volume into a convex set. We show that the problem reduces to a global optimization problem. Connections between the sphere packing problem and game theory\, multi-objective optimization\, and optimal control will be discussed. Finally\, applications of sphere packing problems in the mining industry and business have been given. »
URL:https://lmv.math.cnrs.fr/evenenement/conference-exceptionnelle-enkhbat-rentsen-universite-nationale-de-mongolie-recent-advances-in-sphere-packing-problems/
CATEGORIES:Evénement scientifique
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