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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250422T163000
DTEND;TZID=Europe/Paris:20250422T173000
DTSTAMP:20260419T001602
CREATED:20250415T114925Z
LAST-MODIFIED:20250424T084353Z
UID:13959-1745339400-1745343000@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Robert Szafarczyk (Université de Copenhague) : Ring quotients in homotopical algebra
DESCRIPTION:One of the hardest and most fundamental problems in topology is computing homotopy groups of spheres. One can simplify it a little by restricting to the stable range. This reveals a lot more structure: stable homotopy groups form a graded ring. We will argue that it is useful to make it into a « homotopical ring »\, where we do not phrase relations (like commutativity) in terms of equality\, but rather homotopy. We use this point of view to showcase a fundamental difference between algebra and homotopical algebra. In homotopical algebra\, ring quotients usually do not exist. This is an expository talk.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-robert-szafarczyk-universite-de-copenhague-ring-quotients-in-homotopical-algebra/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250408T163000
DTEND;TZID=Europe/Paris:20250408T173000
DTSTAMP:20260419T001602
CREATED:20250401T112859Z
LAST-MODIFIED:20250401T112859Z
UID:13933-1744129800-1744133400@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Davide Ricci (LMV) : Some ideas on étale and ℓ-adic cohomology
DESCRIPTION:La prochaine séance du séminaire des jeunes aura lieu le mardi 8 Avril de 16h30 à 17h30 dans la salle de séminaires du laboratoire.\n\nL’orateur sera Davide Ricci\, doctorant en première année de thése dans l’équipe Algèbre et Géometrie. \nSome ideas on étale and ℓ-adic cohomology\n\nDuring the last century\, the Weil conjectures motivated the need for new cohomology theories for algebraic varieties over positive characteristic fields. The desired “good” properties are summarized in the Weil cohomology theory axioms. In the sixties\, Grothendieck established the foundations of étale cohomology\, with Artin and Serre\, and later ℓ-adic cohomology\, which provides the first example of such a theory. This is not the only one known nowadays\, but it is still studied and useful for working over positive characteristic fields and for arithmetic problems.\nThere will be presented the motivations for étale and ℓ-adic cohomology\, the main ideas of the constructions\, and a nice example of a relatively recent application to arithmetic geometry by Esnault. The last concerns the existence of solutions for homogeneous polynomials over finite fields. \nI will try to make the imprint of the talk more popularizing than rigorous.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-davide-ricci-lmv-some-ideas-on-etale-and-%e2%84%93-adic-cohomology/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250325T163000
DTEND;TZID=Europe/Paris:20250325T173000
DTSTAMP:20260419T001602
CREATED:20250318T151246Z
LAST-MODIFIED:20250327T132257Z
UID:13894-1742920200-1742923800@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Aitor Iribar López (Université de Zurich) : Intersection theory on moduli spaces of abelian varieties
DESCRIPTION:Résumé :\nWe study A_g\, the moduli space of principally polarized abelian varieties of dimension g. The subring generated by the Chern classes of the Hodge bundle is called the tautological ring\, and it was fully determined by Gerard van der Geer in 1999\, but the question of which geometrically defined cycles belong to this subring remains open. In 2024\, Canning\, Oprea and Pandharipande showed that [A_1 × A_5] is not tautological in A_6\, and later I showed that [A_1 × A_{g-1}] is not tautological for g=12 or g ≥ 16 even.\nThe cycle [A_1 × A_{g-1}] is one of the Noether-Lefschetz cycles on the moduli spaces. With Greer and Lian\, we conjecture that these cycles are related to modular forms of weight 2g.\nA new technique\, which was not available in 1999 is the existence of a projection operator by Canning\, Oprea\, Molcho and Pandharipande onto the tautological ring. This leads to interesting conjectures about Gromov-Witten invariants on a moving elliptic curve\, which now have been proven in collaboration with Pandharipande and Tseng\, and are also connected to the failure of the λg conjecture on the moduli space of curves.\nThe talk will be an overview of the intersection theory of A_g and the moduli space of curves\, and I will explain briefly the ideas behind some proofs.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-aitor-iribar-lopez-universite-de-zurich-intersection-theory-on-moduli-spaces-of-abelian-varieties/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250218T163000
DTEND;TZID=Europe/Paris:20250218T173000
DTSTAMP:20260419T001602
CREATED:20250214T154946Z
LAST-MODIFIED:20250221T084820Z
UID:13739-1739896200-1739899800@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Ricardo Canesin (Université Paris Cité) : Quiver Representations and Lie Theory
DESCRIPTION:Quiver representation theory is a fundamental tool in modern representation theory of associative algebras. A cornerstone of this field is Gabriel’s theorem\, which characterizes quivers with finitely many indecomposable representations as precisely those arising from Dynkin diagrams of type ADE. This result provided an early glimpse into a profound connection between quiver representations and Lie theory\, one that has since led to remarkable developments\, including Lusztig’s theory of canonical bases in quantum groups and Nakajima’s quiver varieties in geometric representation theory. In this talk\, we will give an accessible introduction to this interplay\, starting with the theorems of Gabriel and Kac and culminating in Ringel’s realization of the positive half of quantum groups through Ringel-Hall algebras.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-ricardo-canesin-universite-paris-cite-quiver-representations-and-lie-theory/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250204T163000
DTEND;TZID=Europe/Paris:20250204T173000
DTSTAMP:20260419T001602
CREATED:20250120T104925Z
LAST-MODIFIED:20250207T111928Z
UID:13595-1738686600-1738690200@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Danil Gubarevich (LMV) : Generalised wheel conditions for reductive groups
DESCRIPTION:Consider the variety Comm_n of pairs of commuting n by n matrices\, it is invariant under the action of GL_n on the space of pairs of all matrices\, by simultaneous conjunction. The natural algebraic structure to associate with is equivariant Borel-Moore homology (or K-theory) of the variety. It turns out the direct sum by n of homologies of varieties Comm_n is equipped with an associative multiplication\, given by convolution. The conjugation action has a fixed point (0\,0)\, it’s embedding induces the pullback map of the algebra in hand into the direct sum of algebras of symmetric polynomials\, equipped itself with a shuffle multiplication for which the map is an algebra homomorphism. In the paper (arXiv: 2108.08779)\, where one considers arbitrary finite quiver\, Neguţ proves the image of the morphism is given by polynomials satisfying certain vanishing conditions. In this talk I’ll give the overview of the subject and announce the computation made for general reductive groups. This is a work in progress.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20250121T163000
DTEND;TZID=Europe/Paris:20250121T173000
DTSTAMP:20260419T001602
CREATED:20250120T104821Z
LAST-MODIFIED:20250124T124336Z
UID:13593-1737477000-1737480600@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Antoine Galet (Jussieu) : Le principe local-global pour les espaces homogènes
DESCRIPTION:Un problème central en théorie des nombres est de déterminer si un système d’équations polynômiales à coefficients rationnels ou entiers a des solutions rationnelles ou entières. Pour traiter ce problème\, une approche historique et puissante est le principe local-global\, ou de Hasse\, consistant à comparer l’existence de solutions dans Q à celle dans chaque complété de Q : R et les corps p-adiques Q_p. Pour les variétés appelées espaces homogènes\, l’existence de points rationnels est entièrement caractérisée en termes local-global par l’obstruction de Brauer-Manin. Dans cette présentation\, j’essaierai d’expliquer le principe local-global et l’obstruction de Brauer-Manin\, et de donner l’idée des outils impliqués dans leur étude pour les espaces homogènes.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-antoine-galet-jussieu-le-principe-local-global-pour-les-espaces-homogenes/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241211T160000
DTEND;TZID=Europe/Paris:20241211T170000
DTSTAMP:20260419T001602
CREATED:20241206T143244Z
LAST-MODIFIED:20241212T144911Z
UID:13438-1733932800-1733936400@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Markus Kleinau (Université de Bonn) : Representation theory over F1
DESCRIPTION:Reinterpreting finite sets as vector spaces over F1 (the nonexistent field with one element) yields a combinatorial degeneration of linear algebra. Representation theory over these new vector spaces turns out to be closely related to graph theory. We will introduce this topic and give a graph theoretic criterion for when all scalar extensions of an F1-representation are indecomposable. Here the scalar extensions are representations over more familiar fields.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-markus-kleinau-universite-de-bonn-representation-theory-over-1/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241120T160000
DTEND;TZID=Europe/Paris:20241120T170000
DTSTAMP:20260419T001602
CREATED:20241129T130241Z
LAST-MODIFIED:20241129T130241Z
UID:13399-1732118400-1732122000@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Dzoara Núñez (Bergische Universität Wuppertal) : Cohomology of a certain wild quotient singularity
DESCRIPTION:Let k be an algebraically closed field. In characteristic 2\, the isolated wild quotient singularities arising from an action of the cyclic group Z/2Z on the power series ring in two variables k[[u\, v]]\, were completely described by Artin as an explicit hypersurface singularity. Peskin extended Artin’s result in characteristic 3. Moreover\, she developed canonical forms for certain p-cyclic automorphism of formal power series rings over fields in positive characteristic. More recently\, Schröer and Lorenzini introduced moderately ramified actions in any characteristic p > 0 on the formal power series ring k[[u_1\, . . . \, u_n]] with n ≥ 2\, which give rise to a new class of wild quotient singularities. Motivated by this construction\, we will describe in this talk the resolution of singularities of the singularity arising from the moderately ramified action on k[[u\, v]] in a particular case and we aim to compute the cohomology of the structure sheaf of this resolution which is an invariant of this singularity.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-dzoara-nunez-bergische-universitat-wuppertal-cohomology-of-a-certain-wild-quotient-singularity/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241106T160000
DTEND;TZID=Europe/Paris:20241106T170000
DTSTAMP:20260419T001602
CREATED:20241129T125935Z
LAST-MODIFIED:20241129T125935Z
UID:13397-1730908800-1730912400@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Elias Nohra (Université de Sorbonne) : Autour de la mesure de Yang—Mills en deux dimensions
DESCRIPTION:Résumé : La théorie de Yang-Mills est une théorie quantique des champs (QFT) qui vise à décrire les interactions entre les particules élémentaires. Comme toute QFT\, elle peut s’exprimer à l’aide d’intégrales de chemins de Feynman : des intégrales par rapport à des « mesures de probabilité » formelles sur des espaces de dimension infinie\, qui\, dans ce cas\, correspondent à l’espace des connexions modulo le groupe de jauge d’un fibré principal. La construction mathématique rigoureuse de ces mesures est souvent un véritable défi. \nDans cet exposé\, nous commencerons par une brève introduction à la théorie de Yang–Mills et à ses observables. Nous verrons ensuite comment\, en dimension 2\, cette mesure peut être construite rigoureusement comme la loi d’un processus de déplacements parallèles aléatoires\, suivant les travaux de Driver\, Lévy\, Sengupta\, etc. Enfin\, nous aborderons les travaux plus récents de Chevyrev\, qui définissent cette mesure comme la loi d’une variable aléatoire prenant ses valeurs dans un espace de connexions distributionnelles bien choisi.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-elias-nohra-universite-de-sorbonne-autour-de-la-mesure-de-yang-mills-en-deux-dimensions/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20241009T160000
DTEND;TZID=Europe/Paris:20241009T170000
DTSTAMP:20260419T001602
CREATED:20241004T125621Z
LAST-MODIFIED:20241011T134319Z
UID:13197-1728489600-1728493200@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Judith Marquardt (LMV - IF Grenoble) : Nakayama algebras of small homological dimension and pattern avoiding permutations
DESCRIPTION:Abstract : In representation theory\, Nakayama algebras are a nice\, combinatorially described class of algebras that are often used as examples. We study when these algebras have small homological dimension (i.e. are shod). This can be done completely combinatorially\, by drawing a link to Dyck paths and 132-avoiding permutations. The classification of shod\, which corresponds to avoiding more patterns\, can then be done by drawing some very nice pictures. Come over\, there will be colour. This is a joint work with Viktória Klász and René Marczinzik.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-nakayama-algebras-of-small-homological-dimension-and-pattern-avoiding-permutations/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240422T163000
DTEND;TZID=Europe/Paris:20240422T173000
DTSTAMP:20260419T001602
CREATED:20240412T072359Z
LAST-MODIFIED:20240426T090526Z
UID:12640-1713803400-1713807000@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Taher Jalal (LMV) : Estimation non-paramétrique et processus de Lévy
DESCRIPTION:
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-taher-jalal-lmv/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240408T163000
DTEND;TZID=Europe/Paris:20240408T173000
DTSTAMP:20260419T001602
CREATED:20240404T150830Z
LAST-MODIFIED:20240411T124250Z
UID:12613-1712593800-1712597400@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Maria Abad-Aldonza (LMV) : Une introduction au groupe de Picard et à la Jacobienne d'une courbe
DESCRIPTION:Résumé: Les groupes de Picard\, originalement issus de la géométrie algébrique\, sont aujourd’hui utilisés dans des domaines aussi diverses que la théorie quantique des champs ou la cryptographie des courbes elliptiques. Dans cet exposé\, nous explorerons les différentes définitions de groupe de Picard et de Jacobienne associée à un courbe complexe lisse\, mettant en valeur pourquoi ces définitions sont équivalentes et les généralisations auxquelles elles donnent lieu.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-maria-abad-aldonza-lmv-une-introduction-au-groupe-de-picard-et-a-la-jacobienne-dune-courbe/
LOCATION:Bâtiment Fermat\, salle 2205\, 45 avenue des Etats-Unis\, Versailles\, 78000\, France
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240325T163000
DTEND;TZID=Europe/Paris:20240325T173000
DTSTAMP:20260419T001602
CREATED:20240322T111701Z
LAST-MODIFIED:20240328T084934Z
UID:12584-1711384200-1711387800@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Diego Sánchez Sanz (Sorbonne Université) : Van der Corput lemma and the study of oscillating integrals in several variables
DESCRIPTION:Abstract : \nVan der Corput lemma is an interesting tool to analyse in a quick and simple manner the rough behaviour of oscillatory integrals. However\, its original statement fails to work in the picture of several variables\, forcing us to use stationary phase approximation. In this talk\, we present both methods through the study of a particularly interesting exemple in two variables. In this exemple stationary phase methods fail to achieve the correct asymptotics\, but Van der Corput lemma can be adapted to capture the correct result.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-diego-sanchez-sanz-sorbonne-universite-van-der-corput-lemma-and-the-study-of-oscillating-integrals-in-several-variables/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240311T160000
DTEND;TZID=Europe/Paris:20240311T170000
DTSTAMP:20260419T001602
CREATED:20240314T122348Z
LAST-MODIFIED:20240314T122348Z
UID:12555-1710172800-1710176400@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Felipe Gambardella : Rational points and obstructions to their existence
DESCRIPTION:Abstract : Deciding if a system of polynomial equations has a solution over Q is one of the oldest questions in number theory and over the years it has proved to be a real challenge. One of the first     approaches to this question is to prove existence of solutions over bigger and  »simpler » fields (i.e. Q_p\, R) and then to try to  »restrict » the solutions\, this is known as the local-global principle. In         this talk\, I will present the local-global principle\, some counter examples to this principle\, and further approaches to finding rational solutions.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-felipe-gambardella-rational-points-and-obstructions-to-their-existence/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240226T160000
DTEND;TZID=Europe/Paris:20240226T170000
DTSTAMP:20260419T001602
CREATED:20240314T122153Z
LAST-MODIFIED:20240314T122153Z
UID:12552-1708963200-1708966800@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Margot Funk (LMV) : Outils pour la cryptanalyse de primitives symétriques
DESCRIPTION:Résumé: Le principal objectif de la cryptographie est de proposer des solutions algorithmiques pour permettre à deux parties de communiquer de manière sûre à travers un canal de communication non-sécurisé. Les primitives cryptographiques font office de briques élémentaires pour construire des cryptosystèmes complexes et doivent faire l’objet d’une étude constante et approfondie. Le but de cet exposé est de présenter des outils pour étudier la résistance des primitives symétriques contre certaines catégories d’attaques classiques. \nEn particulier\, l’exposé s’intéressera à des outils pour fournir des arguments de sécurité contre les attaques différentielles\, qui sont des attaques exploitant les statistiques de propagation d’une différence d’entrée vers une différence de sortie. Nous présenterons des algorithmes alternatifs aux outils génériques de recherche de chemins différentiels optimaux basés sur des solvers (MILP\, SAT…).\nEnfin\, une dernière partie exposera l’idée d’un travail en cours portant sur la résistance des primitives contre les attaques de type algébrique. Presque toute primitive symétrique peut être vue comme un système polynomial impliquant des variables publiques et privées. Les attaques algébriques tirent parti de faiblesses dans ces polynômes (faible degré\, absence d’un monôme de faible degré …). Ces polynômes sont bien trop grands pour être calculés de manière exacte. Le but de ce travail est de développer un outil pour étudier la répartition des monômes formant ces polynômes. The goal of this presentation will be to understand the construction of the Khovanov homology of a knot diagram.
URL:https://lmv.math.cnrs.fr/evenenement/seminaire-des-jeunes-margot-funk-lmv-outils-pour-la-cryptanalyse-de-primitives-symetriques/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20240205T163000
DTEND;TZID=Europe/Paris:20240205T173000
DTSTAMP:20260419T001602
CREATED:20240125T153441Z
LAST-MODIFIED:20240314T121914Z
UID:12404-1707150600-1707154200@lmv.math.cnrs.fr
SUMMARY:Séminaire des jeunes : Pierre Bodin (LMV) : Khovanov Homology : a categorification of the Jones polynomial
DESCRIPTION:Abstract : One of the main goal of Knot Theory is to develop tools allowing to tell apart different knots. Namely\, one wants to tell if two embedding K and K′ of the\ncircle \( S^1\) into \( R^3\) can be related by an ambient isotopy. Numerous invariants of knots have been developed since the 19th century and among them polynomial invariants form\nan important class. The Jones polynomial V (K) introduced in 1984 can be computed directly from a diagram of the knot K\, that is\, a (regular) projection of the knot K onto the plane \( R^2\). In 1999 Khovanov introduced a new invariant\, nowadays called Khovanov homology\, that refines the Jones polynomial. Given a diagram D of a knot K\, one can compute a complex C(D) of modules over an algebra A. The homology groups \(H^i(C(D))\) then form an invariant of K and one can recover the Jones polynomial by taking the\nalternating sum of the Euler characteristic of these groups. This is a particular instance of a categorification.\nThe goal of this presentation will be to understand the construction of the Khovanov homology of a knot diagram.
URL:https://lmv.math.cnrs.fr/evenenement/seminaires-des-jeunes-pierre-bodin-lmv-khovanov-homology-a-categorification-of-the-jones-polynomial/
LOCATION:Bâtiment Fermat\, salle 4205
CATEGORIES:Séminaire des jeunes
END:VEVENT
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