BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Département de mathématiques et applications - ECPv6.2.2//NONSGML v1.0//EN CALSCALE:GREGORIAN METHOD:PUBLISH X-ORIGINAL-URL:https://www.math.ens.psl.eu X-WR-CALDESC:évènements pour Département de mathématiques et applications REFRESH-INTERVAL;VALUE=DURATION:PT1H X-Robots-Tag:noindex X-PUBLISHED-TTL:PT1H BEGIN:VTIMEZONE TZID:Europe/Paris BEGIN:DAYLIGHT TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST DTSTART:20180325T010000 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET DTSTART:20181028T010000 END:STANDARD TZID:UTC BEGIN:STANDARD TZOFFSETFROM:+0000 TZOFFSETTO:+0000 TZNAME:UTC DTSTART:20180101T000000 END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20181116T160000 DTEND;TZID=Europe/Paris:20181116T173000 DTSTAMP:20260422T033629 CREATED:20181116T150000Z LAST-MODIFIED:20211104T111157Z UID:8473-1542384000-1542389400@www.math.ens.psl.eu SUMMARY:Oscillatory integrals of subanalytic functions DESCRIPTION:In several papers\, R. Cluckers and D. Miller have built and investigated a class of real functions which contains the subanalytic functions and which is closed under parameterized integration. This class does not allow any oscillatory behavior\, nor stability under Fourier transform. On the other hand\, the behavior of oscillatory integrals\, in connection with singularity theory\, has been heavily investigated for decades. In this talk\, we explain how to build a class of complex functions\, which contains the subanalytic functions and their complex exponentials\, and which is closed under parameterized integration and under Fourier transform.Our techniques involve appropriate preparation theorems for subanalytic functions\, and some elements of the theory of uniformly distributed families of maps.(joint work with R. Clucker\, G. Comte\, D. Miller and T. Servi). URL:https://www.math.ens.psl.eu/evenement/oscillatory-integrals-of-subanalytic-functions/ LOCATION:ENS Salle W CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20181116T141500 DTEND;TZID=Europe/Paris:20181116T154500 DTSTAMP:20260422T033629 CREATED:20181116T131500Z LAST-MODIFIED:20211104T110958Z UID:8472-1542377700-1542383100@www.math.ens.psl.eu SUMMARY:First-order logic in finitely generated fields DESCRIPTION:The expressive power of first-order logic in the class of finitely generated fields\, as structures in the language of rings\, is relatively poorly understood. For instance\, Pop asked in 2002 whether elementarily equivalent finitely generated fields are necessarily isomorphic\, and this is still not known in the general case. On the other hand\, the related situation of finitely generated rings is much better understood by recent work of Aschenbrenner-Khélif-Naziazeno-Scanlon.Building on work of Pop and Poonen\, and using geometric results due to Kerz-Saito and Gabber\, I shall show that every infinite finitely generated field of characteristic not two admits a definable subring which is a finitely generated algebra over a global field. This implies that any such finitely generated field is biinterpretable with arithmetic\, and gives a positive answer to the question above in characteristic not two. URL:https://www.math.ens.psl.eu/evenement/first-order-logic-in-finitely-generated-fields/ LOCATION:ENS Salle W CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20181116T110000 DTEND;TZID=Europe/Paris:20181116T123000 DTSTAMP:20260422T033629 CREATED:20181116T100000Z LAST-MODIFIED:20211104T110958Z UID:8471-1542366000-1542371400@www.math.ens.psl.eu SUMMARY:Non-standard analysis and non-archimedean geometry DESCRIPTION:In this talk I will describe a joint work (still in progress) with E. Hrushovski and F. Loeser\, in which we explain how the integrals I have defined with Chambert-Loir on Berkovich spaces can beseen (in the t-adic case) as limits of usual integrals on complex algebraic varieties URL:https://www.math.ens.psl.eu/evenement/non-standard-analysis-and-non-archimedean-geometry/ LOCATION:ENS Salle W CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20181113T160000 DTEND;TZID=Europe/Paris:20181113T173000 DTSTAMP:20260422T033629 CREATED:20181113T150000Z LAST-MODIFIED:20211104T110957Z UID:8469-1542124800-1542130200@www.math.ens.psl.eu SUMMARY:Groupes et anneaux oméga-catégoriques de fardeau fini DESCRIPTION:Les groupes de fardeau fini sont les groupes NTP_2 qui correspondent aux groupes stables ou simples de rang fini. Or\, le fardeau est plus difficile à manipuler car il n’est pas forcément additif par fibration. Nous montrons que ces groupes sont virtuellement abélien-par-fini\, et les anneaux sont virtuellement fini-par-nuls. Ceci améliore un résultat de Kaplan\, Levi et Simon qui avaient démontré qu’un groupe dp-minimal est virtuellement nilpotent.Travail en commun avec Jan Dobrowolski URL:https://www.math.ens.psl.eu/evenement/groupes-et-anneaux-omega-categoriques-de-fardeau-fini/ LOCATION:Salle 2015 Sophie Germain CATEGORIES:Théorie des Modèles et Groupes END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20181113T140000 DTEND;TZID=Europe/Paris:20181113T140000 DTSTAMP:20260422T033629 CREATED:20181113T130000Z LAST-MODIFIED:20211104T111158Z UID:8474-1542117600-1542117600@www.math.ens.psl.eu SUMMARY:Après-midi de théorie de groupes DESCRIPTION:Tuesday\, 13 November14.00-14.45 Miklos Abert (Renyi Institute Budapest)15.00-15.45 Arman Darbinyan (ENS Paris)15.45-15.15 coffee break16.15-17.00 Rachel Skipper (Göttingen and ENS Lyon) URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-de-groupes/ LOCATION:Salle W CATEGORIES:Séminaire de théorie des groupes à l’ENS END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20181009T140000 DTEND;TZID=Europe/Paris:20181009T170000 DTSTAMP:20260422T033629 CREATED:20181009T120000Z LAST-MODIFIED:20211119T102754Z UID:8468-1539093600-1539104400@www.math.ens.psl.eu SUMMARY:Après-midi de théorie des groupes DESCRIPTION:14.00-14.45 Martin Bridson (Oxford)\, Profinite rigidity and hyperbolic 3-orbifolds15.00-15.45 Arnaud Hilion (Marseille): Boundary of cyclic hyperbolic extensions of free groups15.45-16.15 pause café16.15-17.00 Damien Gaboriau (ENS Lyon)\, On non-vanishing of the cohomology of Aut(Fn) and Out(Fn) in top dimensions URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-des-groupes-2/ LOCATION:ENS 45 rue d’Ulm salle W toits du DMA CATEGORIES:Séminaire de théorie des groupes à l’ENS END:VEVENT BEGIN:VEVENT DTSTART;TZID=UTC:20180807T080000 DTEND;TZID=UTC:20180807T080000 DTSTAMP:20260422T033629 CREATED:20180807T060000Z LAST-MODIFIED:20211015T074123Z UID:557-1533628800-1533628800@www.math.ens.psl.eu SUMMARY:Science Nature Day DESCRIPTION:Lorem ipsum oin gravida nibh vel veliauctor aliquenean sollicitudin\, lorem quis bibendum auctor\, nisi elit consequat ipsutis sem nibh id elit. Duis sed odio sit amet nibh vulputate cursus a sit amet mauris. Morbi accumsan ipsum velit. Nam nec tellus a odio tincidunt auctor a ornare odio. Sed non mauris vitae erat consequat auctor eu in elit. Class aptent taciti sociosqu ad litora torquent per conubia nostra\, per inceptos himenaeos. Mauris in erat justo. Nullam ac urna eu felis dapibus condimentum sit amet a augue. Sed non neque elit. Sed ut imperdiet nisi. Proin condimentum fermentum nunc. URL:https://www.math.ens.psl.eu/evenement/science-nature-day/ CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=UTC:20180720T120000 DTEND;TZID=UTC:20180720T120000 DTSTAMP:20260422T033629 CREATED:20180720T100000Z LAST-MODIFIED:20211015T074129Z UID:807-1532088000-1532088000@www.math.ens.psl.eu SUMMARY:Painting Festival DESCRIPTION:Lorem ipsum oin gravida nibh vel veliauctor aliquenean sollicitudin\, lorem quis bibendum auctor\, nisi elit consequat ipsutis sem nibh id elit. Duis sed odio sit amet nibh vulputate cursus a sit amet mauris. Morbi accumsan ipsum velit. Nam nec tellus a odio tincidunt auctor a ornare odio. Sed non mauris vitae erat consequat auctor eu in elit. Class aptent taciti sociosqu ad litora torquent per conubia nostra\, per inceptos himenaeos. Mauris in erat justo. Nullam ac urna eu felis dapibus condimentum sit amet a augue. Sed non neque elit. Sed ut imperdiet nisi. Proin condimentum fermentum nunc. URL:https://www.math.ens.psl.eu/evenement/painting-festival/ CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180626T140000 DTEND;TZID=Europe/Paris:20180626T180000 DTSTAMP:20260422T033629 CREATED:20180626T120000Z LAST-MODIFIED:20211104T110755Z UID:8464-1530021600-1530036000@www.math.ens.psl.eu SUMMARY:Après-midi de théorie des groupes DESCRIPTION:14.00-14.45 Pierre Pansu (Orsay) L^1 cohomology of Euclidean spaces andHeisenberg groups15.00-15.45  Tianyi Zhang  (UC San Diego) Growth of torsion Grigorchukgroups15.45-16.15 pause café16.15-17.00  Sergei Ivanov (St-Petersbourg)\, Transfinite invariants ofgroups and spaces17.15-18.00 Kate Juschenko (Northwestern University)\, On Liouvilleproperty of action of discrete groups URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-des-groupes/ LOCATION:Institut Henri Poincaré (11 rue Pierre et Marie Curie 75005 Paris) salle 01 CATEGORIES:Séminaire de théorie des groupes à l’ENS END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180619T160000 DTEND;TZID=Europe/Paris:20180619T173000 DTSTAMP:20260422T033629 CREATED:20180619T140000Z LAST-MODIFIED:20211104T110755Z UID:8463-1529424000-1529429400@www.math.ens.psl.eu SUMMARY:Corps interprétables dans ACVF DESCRIPTION:(Travail en commun avec E. Hrushovski)Le but de cet exposé sera de montrer qu’il n’y a que deux corps interprétables (à isomorphisme définissable près) dans ACVF. On commencera par rappeler des résultats de classification des groupes (abéliens) interprétables dans ACVF puis on appliquera ces résultats à l’étude des corps. URL:https://www.math.ens.psl.eu/evenement/corps-interpretables-dans-acvf/ LOCATION:Sophie Germain salle 1016 CATEGORIES:Théorie des Modèles et Groupes END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180518T160000 DTEND;TZID=Europe/Paris:20180518T173000 DTSTAMP:20260422T033629 CREATED:20180518T140000Z LAST-MODIFIED:20211104T110740Z UID:8460-1526659200-1526664600@www.math.ens.psl.eu SUMMARY:Doubling parametrizations and Remez-type inequalities DESCRIPTION:A doubling chart on an n-dimensional complex manifold Y is a univalent analytic mapping psi : B_1 URL:https://www.math.ens.psl.eu/evenement/doubling-parametrizations-and-remez-type-inequalities/ LOCATION:Jussieu salle 101 couloir 15-16 (1er étage)4 place Jussieu CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180518T141500 DTEND;TZID=Europe/Paris:20180518T154500 DTSTAMP:20260422T033629 CREATED:20180518T121500Z LAST-MODIFIED:20211104T110741Z UID:8461-1526652900-1526658300@www.math.ens.psl.eu SUMMARY:Isotrivial Mordell-Lang and finite automata DESCRIPTION:About fifteen years ago\, Thomas Scanlon and I gave a description of sets that arise as the intersection of a subvariety with a finitely generated subgroup inside a semiabelian variety over a finite field. Inspired by later work of Derksen on the positive characteristic Skolem-Mahler-Lech theorem\, which turns out to be a special case\, Jason Bell and I have recently recast those results in terms of finite automata. I will report on this work\, as well as on the work-in-progress it has engendered on an effective version of the isotrivial Mordell-Lang theorem. URL:https://www.math.ens.psl.eu/evenement/isotrivial-mordell-lang-and-finite-automata/ LOCATION:Jussieu salle 101 couloir 15-16 (1er étage)4 place Jussieu CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180518T110000 DTEND;TZID=Europe/Paris:20180518T123000 DTSTAMP:20260422T033629 CREATED:20180518T090000Z LAST-MODIFIED:20211104T110740Z UID:8459-1526641200-1526646600@www.math.ens.psl.eu SUMMARY:Groups and algebras DESCRIPTION:To every group G is associated an associative algebra\, namely its group ring kG. Which (geometric) properties are reflected in (algebraic) properties of kG? I will survey some results and conjectures in this area\, concentrating on specific examples: growth\, amenability\, torsion\, and filtrations. URL:https://www.math.ens.psl.eu/evenement/groups-and-algebras/ LOCATION:Jussieu salle 101 couloir 15-16 (1er étage)4 place Jussieu CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180515T140000 DTEND;TZID=Europe/Paris:20180515T170000 DTSTAMP:20260422T033629 CREATED:20180515T120000Z LAST-MODIFIED:20211104T110741Z UID:8462-1526392800-1526403600@www.math.ens.psl.eu SUMMARY:Mardi après-midi de théorie des groupes DESCRIPTION:14.00-14.45 Thomas Schick (Göttingen): Approximation of L2-Betti numbers and the algebraic Eigenvalue property (after Jaikin-Zaipirain)15.00-15.45 Jacques Darné (Lille): Variations autour du problème d’Andreadakis 15.45-16.15 pause café16.15-17.00 Volodymyr Nekrashevych (Texas A&M): Amenability of iterated monodromy groups URL:https://www.math.ens.psl.eu/evenement/mardi-apres-midi-de-theorie-des-groupes/ LOCATION:Salle W toits du DMA CATEGORIES:Séminaire de théorie des groupes à l’ENS END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180427T163000 DTEND;TZID=Europe/Paris:20180427T173000 DTSTAMP:20260422T033629 CREATED:20180427T143000Z LAST-MODIFIED:20211104T110739Z UID:8458-1524846600-1524850200@www.math.ens.psl.eu SUMMARY:Applications of Morava K-theory to algebraic groups and quadrics. DESCRIPTION:For a prime number p and a non-negative integer n we consider a Morava K-theory K(n) with the coefficient ring ?p. This is a universal oriented cohomology theory in the sense of Levine-Morel with a pn-typical formal group law which has height n modulo p. It turns out that K(n) is strongly related to cohomological invariants of algebraic groups in the sense of Serre. This is our starting point to compute the Chow groups of quadrics from the powers Im+2 of the fundamental ideal of the Witt ring up to codimension 2m. Moreover\, the Morava K-theory gives a conceptional explanation of the nature of the obtained answer. This is a joint work with Pavel Sechin. URL:https://www.math.ens.psl.eu/evenement/applications-of-morava-k-theory-to-algebraic-groups-and-quadrics/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180427T150000 DTEND;TZID=Europe/Paris:20180427T160000 DTSTAMP:20260422T033629 CREATED:20180427T130000Z LAST-MODIFIED:20211104T110540Z UID:8457-1524841200-1524844800@www.math.ens.psl.eu SUMMARY:Noyaux d'Albanese et groupes de Griffiths. DESCRIPTION:On décrit le groupe de Griffiths du produit d’une courbe C et d’une surface S comme un quotient du noyau d’Albanese de S pris sur le corps des fonctions de C. Quand C est une section hyperplane de S variant dans un pinceau de Lefschetz\, une modification convenable du graphe du plongement de C dans S a une classe dans Griff(CxS). On démontre que cette classe est non nulle pour une infinité de membres du pinceau lorsque le corps de base k est de caractéristique 0\, que le genre géométrique de S est >0\, et que k est gros\, ou que S est de type abélien motivé. URL:https://www.math.ens.psl.eu/evenement/noyaux-dalbanese-et-groupes-de-griffiths/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180417T140000 DTEND;TZID=Europe/Paris:20180417T170000 DTSTAMP:20260422T033629 CREATED:20180417T120000Z LAST-MODIFIED:20211104T110540Z UID:8456-1523973600-1523984400@www.math.ens.psl.eu SUMMARY:3 exposés de dynamique et théorie des groupes DESCRIPTION:14.00-14.45 Omer Tamuz (Caltech): The Poisson boundary and the infinite conjugacy class property15.00-15.45 Yair Hartman (Northwestern University): Stationary C*-Dynamical Systems15.45-16.15 pause café16.15-17.00 Said Sidki (University of Brasilia): Self-similarity and finite presentability URL:https://www.math.ens.psl.eu/evenement/3-exposes-de-dynamique-et-theorie-des-groupes-2/ LOCATION:Salle W toits du DMA ENS CATEGORIES:Séminaire de théorie des groupes à l’ENS END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180323T160000 DTEND;TZID=Europe/Paris:20180323T173000 DTSTAMP:20260422T033629 CREATED:20180323T150000Z LAST-MODIFIED:20211104T110539Z UID:8455-1521820800-1521826200@www.math.ens.psl.eu SUMMARY:A model theoretic generalization of the one-dimensional case of the Elekes-Szabo theorem DESCRIPTION:(Joint work with A. Chernikov)Let V subseteq C^3 be a complex variety of dimension 2.The Elekes-Szabo Theorem says that if V contains `too many’ points on n x n x n Cartesian products then V has a special form: either V contains a cylinder over a curve or V is related to the graph of the multiplication of an algebraic group.In this talk we generalize the Elekes-Szabo Theorem to relations on strongly minimal sets interpretable in distal structures. URL:https://www.math.ens.psl.eu/evenement/a-model-theoretic-generalization-of-the-one-dimensional-case-of-the-elekes-szabo-theorem/ LOCATION:IHP amphitheatre Darboux CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180323T141500 DTEND;TZID=Europe/Paris:20180323T154500 DTSTAMP:20260422T033629 CREATED:20180323T131500Z LAST-MODIFIED:20211104T110538Z UID:8453-1521814500-1521819900@www.math.ens.psl.eu SUMMARY:The dynamical Mordell-Lang problem in positive characteristic DESCRIPTION:The dynamical Mordell-Lang conjecture in characteristic zero predicts that if f : X –> X is a map of algebraic varieties over a field K of characteristic zero\, Y subset X is a closed subvariety and a in X(K) is a K-rational point on X\, then the return set { n in N : f^n(a) in Y(K) } is a finite union of points and arithmetic progressions. For K a field of characteristic p > 0\, it is necessary to allow for finite unions with sets of the form { a + sum_{i=1}^m p^{n_i} : (n_1\, … \, n_m) in N^m } and one might conjecture that all return sets are finite unions of points\, arithmetic progressions and such p-sets. We studied the special case of the positive characteristic dynamical Mordell-Lang problem on semiabelian varieites and using our earlier results with Moosa on so-called F-sets reduced the problem to that of solving a class of exponential diophantine equations in characteristic zero. In so doing\, under the hypothesis that X is a semiabelian variety and either Y has small dimension or f is sufficiently general\, we prove the conjecture. However\, we also show that our reduction to the exponential diiophantine problems may be reversed so that the positive characteristic dynamical Mordell-Lang conjecture in general is equivalent to a class of hard exponential diophantine problems which the experts consider to be out of reach given our present techniques. (This is a report on joint work with Pietro Corvaja\, Dragos Ghioca and Umberto Zannier available at arXiv:1802.05309.) URL:https://www.math.ens.psl.eu/evenement/the-dynamical-mordell-lang-problem-in-positive-characteristic/ LOCATION:IHP amphitheatre Darboux CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180323T110000 DTEND;TZID=Europe/Paris:20180323T110000 DTSTAMP:20260422T033629 CREATED:20180323T100000Z LAST-MODIFIED:20211104T110539Z UID:8454-1521802800-1521802800@www.math.ens.psl.eu SUMMARY:On a conjecture of Colliot-Thélène DESCRIPTION:Let f be a morphism of projective smooth varieties X\, Y defined over the rationals. The conjecture by Colliot-Thélène under discussion gives (conjectural) sufficient conditions which imply that for almost all rational prime numbers p\, the map f maps the p-adic points X(Q_p) surjectively onto Y(Q_p). The aim of the talk is to present some recent results by Denef\, Skorobogatov et al URL:https://www.math.ens.psl.eu/evenement/on-a-conjecture-of-colliot-thelene/ LOCATION:IHP amphitheatre Darboux CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180313T000000 DTEND;TZID=Europe/Paris:20180313T000000 DTSTAMP:20260422T033629 CREATED:20180312T230000Z LAST-MODIFIED:20211104T110338Z UID:8450-1520899200-1520899200@www.math.ens.psl.eu SUMMARY:3 exposés de dynamique et théorie des groupes DESCRIPTION:14.00-14.45 Julien Cassaigne (IML\, Marseille): A family of infinite words with complexity 2n+1 associated with a bidimensional continued fraction algorithm15.00-15.45 Milton Minervino (LaBRI\, Bordeaux): Fractals de Rauzy et substitutions d’arbre15.45-16.15 coffee break16.45-17.00 Nathalie Aubrun (ENS\, Lyon): Tilings problems on substitution orbits URL:https://www.math.ens.psl.eu/evenement/3-exposes-de-dynamique-et-theorie-des-groupes/ LOCATION:Salle W toits du DMA CATEGORIES:Séminaire de théorie des groupes à l’ENS END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180309T163000 DTEND;TZID=Europe/Paris:20180309T173000 DTSTAMP:20260422T033629 CREATED:20180309T153000Z LAST-MODIFIED:20211104T110339Z UID:8452-1520613000-1520616600@www.math.ens.psl.eu SUMMARY:Recollement sur les courbes de Berkovich et principe local-global DESCRIPTION:Le recollement a été introduit dans un cadre géométrique pour traiter le problème inverse de Galois. Par la suite\, la technique a été adaptée à un contexte plus algébrique par Harbater et Hartmann\, puis développée par Harbater\, Hartmann et Krashen. Nous commencerons par présenter une version de cette méthode sur les courbes de Berkovich. Ensuite\, nous l’utiliserons pour démontrer un résultat local-global sur les corps de fonctions de courbes de Berkovich et finirons en expliquant l’application aux formes quadratiques. Nos résultats généralisent ceux de Harbater\, Hartmann et Krashen. URL:https://www.math.ens.psl.eu/evenement/recollement-sur-les-courbes-de-berkovich-et-principe-local-global/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180309T150000 DTEND;TZID=Europe/Paris:20180309T160000 DTSTAMP:20260422T033629 CREATED:20180309T140000Z LAST-MODIFIED:20211104T110339Z UID:8451-1520607600-1520611200@www.math.ens.psl.eu SUMMARY:Introduction aux espaces de Berkovich DESCRIPTION:Il s’agira d’un exposé de survol de la théorie des espaces de Berkovich\, préparatoire à l’exposé suivant. URL:https://www.math.ens.psl.eu/evenement/introduction-aux-espaces-de-berkovich/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180220T140000 DTEND;TZID=Europe/Paris:20180220T170000 DTSTAMP:20260422T033629 CREATED:20180220T130000Z LAST-MODIFIED:20211104T110338Z UID:8449-1519135200-1519146000@www.math.ens.psl.eu SUMMARY:Un après-midi de marches aléatoires sur les groupes DESCRIPTION:14.00-14.45 François Ledrappier (Paris VI)\, Differentiability of the linear drift in negative curvature15.00-15.45 Johannes Cuno (ENS)\, Random walks on Baumslag-Solitar groups15.45-16.15 pause café16.15-17.00 Ariel Yadin (Ben Gurion University)\, Intersectional IRS and Furstenberg entropy realization URL:https://www.math.ens.psl.eu/evenement/un-apres-midi-de-marches-aleatoires-sur-les-groupes/ LOCATION:Toits du DMA salle W CATEGORIES:Séminaire de théorie des groupes à l’ENS END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180216T163000 DTEND;TZID=Europe/Paris:20180216T173000 DTSTAMP:20260422T033629 CREATED:20180216T153000Z LAST-MODIFIED:20211104T110337Z UID:8448-1518798600-1518802200@www.math.ens.psl.eu SUMMARY:Au sujet d'une conjecture de Voskresenskii DESCRIPTION:Dans cette collaboration avec M. Florence\, nous nous intéressons à la question de savoir quand les notions de rationalité et rationalité stable sont équivalentes. Nous traitons cette question dans le cas des tores\, où une réponse positive est conjecturée par Voskresenskii. Pour une certaine classe de tores\, cette conjecture est prouvée par Klyachko à l’aide de principes généraux. Nous donnons une nouvelle preuve explicite\, en passant par des morphismes simples\, menant à une application en cryptographie. URL:https://www.math.ens.psl.eu/evenement/au-sujet-dune-conjecture-de-voskresenskii/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180216T150000 DTEND;TZID=Europe/Paris:20180216T160000 DTSTAMP:20260422T033629 CREATED:20180216T140000Z LAST-MODIFIED:20211025T103328Z UID:8447-1518793200-1518796800@www.math.ens.psl.eu SUMMARY:Autour d'une conjecture de Kato et Kuzumaki DESCRIPTION:En 1986\, Kato et Kuzumaki ont émis des conjectures concernant les liensentre la dimension cohomologique des corps\, la K-théorie de Milnor etles hypersurfaces projectives de petit degré. Ces conjectures sontfausses en toute généralité\, mais elles restent ouvertes pour les corpsqui apparaissent usuellement en arithmétique et en géométrie algébrique.Dans cet exposé\, je présenterai plusieurs résultats en lien avec lesconjectures de Kato et Kuzumaki pour les corps globaux et pour certainscorps de fonctions. URL:https://www.math.ens.psl.eu/evenement/autour-dune-conjecture-de-kato-et-kuzumaki/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180126T163000 DTEND;TZID=Europe/Paris:20180126T173000 DTSTAMP:20260422T033629 CREATED:20180126T153000Z LAST-MODIFIED:20211104T110137Z UID:8444-1516984200-1516987800@www.math.ens.psl.eu SUMMARY:L'espace adélique d'un tore sur un corps de fonctions. DESCRIPTION:Soient k un corps de caractéristique zéro et K le corps des fonctions d’une courbe X sur k. Soient T un K-tore\, S un ensemble finide points fermés de X\, et T(A\,S) l’espace adélique de T hors de S. On démontre que l’ensemble des points rationnels T(K) estdiscret dans T(A\,S)\, puis on calcule le quotient T(A\,S)/T(K) en fonction de la cohomologie galoisienne de T dans les trois cassuivants : k algébriquement clos\, k=C((t))\, et k p-adique. URL:https://www.math.ens.psl.eu/evenement/lespace-adelique-dun-tore-sur-un-corps-de-fonctions/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180126T150000 DTEND;TZID=Europe/Paris:20180126T160000 DTSTAMP:20260422T033629 CREATED:20180126T140000Z LAST-MODIFIED:20211104T110136Z UID:8443-1516978800-1516982400@www.math.ens.psl.eu SUMMARY:Mauvaises places pour l'obstruction de Brauer-Manin dans les espaces homogènes. DESCRIPTION:L’obstruction de Brauer-Manin explique (en partie) le défaut de densité des points rationnels d’une variété X dans le produit des points sur les différents complétés du corps de base. Conjecturalement\, cette obstruction est la seule pour les variétés rationnellement connexes. Cela a pour conséquence l’existence d’un ensemble fini de mauvaises places en dehors desquelles on a en effet la densité souhaitée.Dans cet exposé\, je montrerai comment décrire explicitement un tel ensemble de mauvaises places pour un espace homogène d’un groupe semisimple et simplement connexe à stabilisateurs finis. Cela passe par une traduction du groupe de Brauer et de l’accouplement de Brauer-Manin en termes de cohomologie de groupes et d’un résultat qui généralise des travaux de Bogomolov et Colliot-Thélène permettant de décrire le sous-groupe des classes non ramifiées. URL:https://www.math.ens.psl.eu/evenement/mauvaises-places-pour-lobstruction-de-brauer-manin-dans-les-espaces-homogenes/ LOCATION:ENS Salle W CATEGORIES:Variétés rationnelles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180119T160000 DTEND;TZID=Europe/Paris:20180119T160000 DTSTAMP:20260422T033629 CREATED:20180119T150000Z LAST-MODIFIED:20211104T105937Z UID:8440-1516377600-1516377600@www.math.ens.psl.eu SUMMARY:Blurred Complex Exponentiation DESCRIPTION:Zilber conjectured that the complex field equipped with the exponential function is quasiminimal: every definable subset of the complex numbers is countable or co-countable. If true\, it would mean that the geometry of solution sets of complex exponential-polynomial equations and their projections is somewhat like algebraic geometry. If false\, it is likely that the real field is definable and there may be no reasonable geometric theory of these definable sets.I will report on some progress towards the conjecture\, including a proof when the exponential function is replaced by the approximate version given by exists q\,r in Q [y = e^{x+q+2pi i r}]. This set is the graph of the exponential function blurred by the group exp(Q + 2 pi i Q). We can also blur by a larger subgroup and prove a stronger version of the theorem. Not only do we get quasiminimality but the resulting structure is isomorphic to the analogous blurring of Zilber’s exponential field and to a reduct of a differentially closed field. Reference: Jonathan Kirby\, Blurred Complex Exponentiation\, arXiv:1705.04574 URL:https://www.math.ens.psl.eu/evenement/blurred-complex-exponentiation/ LOCATION:Amphitheatre Hermite IHP CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT BEGIN:VEVENT DTSTART;TZID=Europe/Paris:20180119T141500 DTEND;TZID=Europe/Paris:20180119T141500 DTSTAMP:20260422T033629 CREATED:20180119T131500Z LAST-MODIFIED:20211104T105936Z UID:8439-1516371300-1516371300@www.math.ens.psl.eu SUMMARY:Effective Chabauty and the Cursed Curve DESCRIPTION:The Chabauty method often allows one to find the rational points on curves of genus at least 2 over the rationals\, but has a lot of limitations. On a theoretical level\, the Mordell-Weil rank of the Jacobian of the curve has to be strictly smaller than its genus. In practice\, even when this condition is satisfied\, the relevant Coleman integrals can usually only be computed for hyperelliptic curves. We will report on recent work of ours (with different combinations of collaborators) on extending the method to more general curves. In particular\, we will show how one can use an extension of the Chabauty method by Kim to find the rational points on the split Cartan modular curve of level 13\, which is also known as the cursed curve. The talk will be aimed at non-specialists with an interest in number theory. URL:https://www.math.ens.psl.eu/evenement/effective-chabauty-and-the-cursed-curve/ LOCATION:Institut Henri Poincaré amphi Hermite CATEGORIES:Séminaire Géométrie et théorie des modèles END:VEVENT END:VCALENDAR