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X-WR-CALNAME:Département de mathématiques et applications
X-ORIGINAL-URL:https://www.math.ens.psl.eu
X-WR-CALDESC:évènements pour Département de mathématiques et applications
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TZID:Europe/Paris
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:20170326T010000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:20171029T010000
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END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170428T141500
DTEND;TZID=Europe/Paris:20170428T141500
DTSTAMP:20260423T025015
CREATED:20170428T121500Z
LAST-MODIFIED:20211104T104241Z
UID:8379-1493388900-1493388900@www.math.ens.psl.eu
SUMMARY:Triangulation des ensembles semi-algébriques p-adiques
DESCRIPTION:On sait que les ensembles semi-algébriques p-adiques admettent une décomposition cellulaire semblable à celle des semi-algébriques réels (Denef 1984). On sait aussi les classifier à bijection semi-algébrique près (Cluckers 2001)\, mais pas à homéomorphismes semi-algébriques près. En introduisant une notion appropriée de simplexe sur les corps p-adiquement clos\, on peut montrer que tout ensemble semi-algébrique p-adique est semi-algébriquement homéomorphe à un complexe simplicial p-adique\, exactement comme dans le cas réel clos. C’est ce résultat récent de `triangulation p-adique’ que je tâcherai de présenter\, avec ses applications les plus directes (existence de découpages avec contraintes aux bords\, existence de rétractions\, etc).
URL:https://www.math.ens.psl.eu/evenement/triangulation-des-ensembles-semi-algebriques-p-adiques/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170428T110000
DTEND;TZID=Europe/Paris:20170428T110000
DTSTAMP:20260423T025015
CREATED:20170428T090000Z
LAST-MODIFIED:20211104T104241Z
UID:8378-1493377200-1493377200@www.math.ens.psl.eu
SUMMARY:Un théorème d'Ax-Lindemann non-archimédien
DESCRIPTION:On présentera un résultat de type Ax-Lindemann pour les produits de courbes de Mumford sur un corps p-adique. Notre preuve reprend en l’adaptant les grandes lignes de l’approche de Pila dans le cas archimédien. En particulier nous utilisons un théorème de Pila-Wilkie p-adique obtenu avec R. Cluckers et G. Comte. Il s’agit d’un travail en commun avec A. Chambert-Loir.
URL:https://www.math.ens.psl.eu/evenement/un-theoreme-dax-lindemann-non-archimedien/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170421T163000
DTEND;TZID=Europe/Paris:20170421T173000
DTSTAMP:20260423T025015
CREATED:20170421T143000Z
LAST-MODIFIED:20211104T104255Z
UID:8382-1492792200-1492795800@www.math.ens.psl.eu
SUMMARY:Groupe de Brauer invariant et obstruction de descente itérée
DESCRIPTION:Pour une variété quasi-projective\, lisse\, géométriquement intègre sur un corps de nombre k\, on montre que l’obstruction de descente itérée est équivalente à l’obstruction de descente. Ceci répond une question ouverte de Poonen. L’idée clé est la notion de sous-groupe de Brauer invariant et la notion d’obstruction de Brauer-Manin invariant étale pour une k-variété munie d’une action d’un groupe linéaire connexe.
URL:https://www.math.ens.psl.eu/evenement/groupe-de-brauer-invariant-et-obstruction-de-descente-iteree/
LOCATION:ENS Salle W
CATEGORIES:Variétés rationnelles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170421T150000
DTEND;TZID=Europe/Paris:20170421T160000
DTSTAMP:20260423T025015
CREATED:20170421T130000Z
LAST-MODIFIED:20211104T104242Z
UID:8381-1492786800-1492790400@www.math.ens.psl.eu
SUMMARY:Fields of definition and essential dimension in representation theory
DESCRIPTION:A classical theorem of Brauer asserts that every finite-dimensional non-modular representation p of a finite group G defined over a field K\, whose character takes values in a subfield k\, descends to k\, provided that k has suitable roots of unity. If k does not contain these roots of unity\, it is natural to ask how far p is from being definable over k. The classical answer is given by the Schur index of p\, which is the smallest degree of a finite field extension l/k such that p can be defined over l. In this talk\, based on joint work with Nikita Karpenko\, Julia Pevtsova and Dave Benson\, I will discuss another invariant\, the essential dimension of p\, which measures how far p is from being definable over k in a different way\, by using transcendental\, rather than algebraic field extensions. This invariant is of interest in both the modular and the non-modular settings. I will also consider the question of which representations of finite groups or finite-dimensional associative algebras have a minimal field of definition with respect to inclusion.
URL:https://www.math.ens.psl.eu/evenement/fields-of-definition-and-essential-dimension-in-representation-theory/
LOCATION:ENS Salle W
CATEGORIES:Variétés rationnelles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170418T160000
DTEND;TZID=Europe/Paris:20170418T173000
DTSTAMP:20260423T025015
CREATED:20170418T140000Z
LAST-MODIFIED:20211104T104205Z
UID:8376-1492531200-1492536600@www.math.ens.psl.eu
SUMMARY:Actions localement quadratiques de groupes de Chevalley\, et représentations minuscules
DESCRIPTION:Un très beau théorème de Timmesfeld caractérise\, sans hypothèse sur K\, la représentation naturelle de G = SL(2\,K) parmi les Z[G]-modules : c’est le seul Z[G]-module irréductible V où les sous-groupes unipotents de G agissent `quadratiquement’\, i.e. [U\, U\, V] = 0 (en itérant les commutateurs).Montrer ce théorème\, c’est essentiellement savoir reconstruire sur un Z[G]-module quadratique une structure de K-espace vectoriel compatible avec l’action de G.L’exposé présentera une généralisation de ce théorème aux autres groupes de Chevalley simples : si G est un tel groupe\, et V un Z[G]-module sur lequel chaque sous-groupe racine (aussi appelé sous-groupe à un paramètre) agit quadratiquement dans le sens précédent\, alors V est en effet un K-espace vectoriel construit à partir de représentations dites `minuscules’ (concept qui sera expliqué).Enfin il y aura une petite application symbolique aux représentations de rang de Morley fini des groupes algébriques.
URL:https://www.math.ens.psl.eu/evenement/actions-localement-quadratiques-de-groupes-de-chevalley-et-representations-minuscules/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170404T140000
DTEND;TZID=Europe/Paris:20170404T170000
DTSTAMP:20260423T025015
CREATED:20170404T120000Z
LAST-MODIFIED:20211104T104240Z
UID:8377-1491314400-1491325200@www.math.ens.psl.eu
SUMMARY:trois exposés en théorie des groupes
DESCRIPTION:https://sites.google.com/site/annaerschler/programtalks
URL:https://www.math.ens.psl.eu/evenement/trois-exposes-en-theorie-des-groupes-2/
LOCATION:Salle W DMA ENS
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170331T163000
DTEND;TZID=Europe/Paris:20170331T173000
DTSTAMP:20260423T025015
CREATED:20170331T143000Z
LAST-MODIFIED:20211104T104003Z
UID:8371-1490977800-1490981400@www.math.ens.psl.eu
SUMMARY:Finite descent obstruction and non-abelian reciprocity.
DESCRIPTION:For a nice algebraic variety X over a number field F\, one of the central problems of Diophantine Geometry is to locate precisely the set X(F) inside X(A)\, where A denotes the ring of adèles of F. One approach to this problem is provided by the finite descent obstruction\, which is defined to be the set of adelic points which can be lifted to twists of torsors for finite étale group schemes over F on X. More recently\, Kim proposed an iterative construction of another subset of X(A) which contains the set of rational points. In this talk\, we compare the two constructions. Our main result shows that the two approaches are equivalent.
URL:https://www.math.ens.psl.eu/evenement/finite-descent-obstruction-and-non-abelian-reciprocity/
LOCATION:ENS Salle W
CATEGORIES:Variétés rationnelles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170331T150000
DTEND;TZID=Europe/Paris:20170331T160000
DTSTAMP:20260423T025015
CREATED:20170331T130000Z
LAST-MODIFIED:20211104T104003Z
UID:8370-1490972400-1490976000@www.math.ens.psl.eu
SUMMARY:Wild ramification and K(pi\,1) spaces
DESCRIPTION:I will sketch the proof that every connected affine scheme in positivecharacteristic is a K(pi\,1) space for the etale topology.  The keytechnical ingredient is a ?RoeBertini-type?R statement regarding the wildramification of l-adic local systems on affine spaces. Its proof usesin an essential way recent advances in higher ramification theory dueto T. Saito.
URL:https://www.math.ens.psl.eu/evenement/wild-ramification-and-kpi1-spaces/
LOCATION:ENS Salle W
CATEGORIES:Variétés rationnelles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170328T160000
DTEND;TZID=Europe/Paris:20170328T160000
DTSTAMP:20260423T025015
CREATED:20170328T140000Z
LAST-MODIFIED:20211104T103601Z
UID:8360-1490716800-1490716800@www.math.ens.psl.eu
SUMMARY:NSOP_1\, Kim-independence\, and simplicity at a generic scale
DESCRIPTION:The class of NSOP_1 theories properly contains the simple theories and is contained in the class of theories without the tree property of the first kind. We will describe a notion of independence called Kim-independence\, which corresponds to non-forking independence ‘at a generic scale.’ In an NSOP_1 theory\, Kim-independence is symmetric and satisfies a version of Kim’s lemma and the independence theorem. Moreover\, these properties of Kim-independence individually characterize NSOP_1 theories. We will talk about what Kim-independence looks like in several concrete examples: parametrized equivalence relations\, Frobenius fields\, and vector spaces with a bilinear form. This is joint work with Itay Kaplan.
URL:https://www.math.ens.psl.eu/evenement/nsop_1-kim-independence-and-simplicity-at-a-generic-scale/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170321T140000
DTEND;TZID=Europe/Paris:20170321T170000
DTSTAMP:20260423T025015
CREATED:20170321T130000Z
LAST-MODIFIED:20211104T104202Z
UID:8372-1490104800-1490115600@www.math.ens.psl.eu
SUMMARY:Trois exposés en théorie des groupes
DESCRIPTION:14.00-14.45 Camille Horbez (Orsay): Boundary amenability of Out(Fn)15.00-15.45 Romain Tessera (Orsay): Poincaré profile in Hyperbolic groups15.45-16.15 pause café16.15-17.00 Yash Lodha (EPFL Lausanne): Nonamenable groups of piecewise projective homeomorphisms
URL:https://www.math.ens.psl.eu/evenement/trois-exposes-en-theorie-des-groupes/
LOCATION:ENS Toits du DMA salle W
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170314T000000
DTEND;TZID=Europe/Paris:20170314T000000
DTSTAMP:20260423T025015
CREATED:20170313T230000Z
LAST-MODIFIED:20211104T104002Z
UID:8369-1489449600-1489449600@www.math.ens.psl.eu
SUMMARY:Kappa-bounded exponential groups and exponential-logarithmic power series fields without log-atomic elements
DESCRIPTION:A divisible ordered abelian group is an exponential group if its rank as an ordered set is isomorphic to its negative cone. Exponential groups appear as the value groups of ordered exponential fields\, and were studied in [1]. In [2] we gave an explicit construction of exponential groups as Hahn groups of series with support bounded in cardinality by an uncountable regular cardinal kappa. An exp-log series s is said to be log atomic if the nth-iterate of log(s) is a monomial for all n in N. In this talk I will present a modified construction of kappa-bounded Hahn groups and exploit it to construct kappa bounded Hahn fields without log-atomic elements. This is ongoing joint work with Berarducci\, Mantova and Matusinski.[1] S. Kuhlmann\, Ordered exponential fields\, The Fields Institute Monograph Series\, vol 12. Amer. Math. Soc. (2000) [2] S. Kuhlmann and S. Shelah\, Kappa-bounded Exponential-Logarithmic power series fields\, Annals Pure and Applied Logic\, 136\, 284-296 (2005)
URL:https://www.math.ens.psl.eu/evenement/kappa-bounded-exponential-groups-and-exponential-logarithmic-power-series-fields-without-log-atomic-elements/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170310T160000
DTEND;TZID=Europe/Paris:20170310T160000
DTSTAMP:20260423T025015
CREATED:20170310T150000Z
LAST-MODIFIED:20211104T104002Z
UID:8368-1489161600-1489161600@www.math.ens.psl.eu
SUMMARY:Satellites of spherical subgroups and Poincaré polynomials
DESCRIPTION:Let G be a connected reductive group over C. One can associate with every spherical homogeneous space G/H its lattice of weights X^*(G/H) and a subset S of M of linearly independent primitive lattice vectors which are called the spherical roots. For any subset I of S we define\, up to conjugation\, a spherical subgroup H_I in G such that dim H_I = dim H and X^*(G/H_I) = X^*(G/H). We call the subgroups H_I the satellites of the spherical subgroup H. Our interest in satellites H_I is motivated by the space of arcs of the spherical homogeneous space G/H.We show a close relation between the Poincaré polynomials of the two spherical homogeneous spaces G/H and G/H_I.All of this is useful for the computation of the stringy E-function of Q-Gorenstein spherical embeddings.The talk is based on joint works with Victor Batyrev.
URL:https://www.math.ens.psl.eu/evenement/satellites-of-spherical-subgroups-and-poincare-polynomials/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170310T141500
DTEND;TZID=Europe/Paris:20170310T141500
DTSTAMP:20260423T025015
CREATED:20170310T131500Z
LAST-MODIFIED:20211104T104001Z
UID:8367-1489155300-1489155300@www.math.ens.psl.eu
SUMMARY:Quasianalytic Ilyashenko algebras
DESCRIPTION:In 1923\, Dulac published a proof of the claim that every real analytic vector field on the plane has only finitely many limit cycles (now known as Dulac’s Problem). In the mid-1990s\, Ilyashenko completed Dulac’s proof
URL:https://www.math.ens.psl.eu/evenement/quasianalytic-ilyashenko-algebras/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170310T110000
DTEND;TZID=Europe/Paris:20170310T110000
DTSTAMP:20260423T025015
CREATED:20170310T100000Z
LAST-MODIFIED:20211104T103601Z
UID:8361-1489143600-1489143600@www.math.ens.psl.eu
SUMMARY:Rational points on families of curves
DESCRIPTION:The TAC (torsion anomalous conjecture) states that for an irreducible variety V embedded transversaly in an abelian variety A there are only finitely many maximal V-torsion anomalous varieties. It is well know that the TAC implies the Mordell-Lang conjecture. S. Checcole\, F. Veneziano and myself were trying to prove some new cases of the TAC. In this process we realised that some methods could be made not only effective but even explicit. So we analysed the implication of this explicit methods on the Mordell Conjeture. Namely: can we make the Mordell Conjecture explicit for some new families of curves and so determine all the rational points on these curves? Of course we started with the easiest situation\, that is curves in ExE for E an elliptic curve. We eventually could give some new families of curves of growing genus for which we can determine all the rational points. I will explain the difficulties and the ingredients of this result. I will then discuss the generalisations of the method and also its limits.
URL:https://www.math.ens.psl.eu/evenement/rational-points-on-families-of-curves/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170307T160000
DTEND;TZID=Europe/Paris:20170307T160000
DTSTAMP:20260423T025015
CREATED:20170307T150000Z
LAST-MODIFIED:20211104T103801Z
UID:8364-1488902400-1488902400@www.math.ens.psl.eu
SUMMARY:Elimination of imaginaries for differentially closed fields of finite characteristic
DESCRIPTION:All fields under discussion here are assumed to have finite characteristic p. This talk might be seen as a sequel to my survey talk at Françoise Delon’s conference in June 2016\, although it will not assume familiarity with this talk.Of interest here are two complete theories\, namely differentially closed fields (DCF) and separably closed fields (inf-SCF) with infinite degree of imperfection. These theories are related. For example\, the underlying field of a model of DCF is a model of inf-SCF\, and the constant field is also a model of inf-SCF. In each case\, there are natural choices of language in which the theory has quantifier elimination.We will consider ways in which the theories are not alike. In the mid 1980’s Gabriel Srour proved that DCF is equational\, and also that the theories of separably closed fields of finite degree of imperfection are equational. However\, to my knowledge\, the equationality of inf-SCF is still unknown.Delon proved that the finite imperfection separably closed fields have elimination of imaginaries (EI)
URL:https://www.math.ens.psl.eu/evenement/elimination-of-imaginaries-for-differentially-closed-fields-of-finite-characteristic/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170228T160000
DTEND;TZID=Europe/Paris:20170228T160000
DTSTAMP:20260423T025015
CREATED:20170228T150000Z
LAST-MODIFIED:20211104T141026Z
UID:8359-1488297600-1488297600@www.math.ens.psl.eu
SUMMARY:Expansions minimales de (Z\,+\,0)
DESCRIPTION:Cet exposé essayera de donner une vision d’ensemble des différentes choses connu à ce jour sur les expansions du groupes des entiers (Z\,+\,0) avec un accent sur les expansions dp-minimales. En particulier les deux structures (Z\,+\,0\,
URL:https://www.math.ens.psl.eu/evenement/expansions-minimales-de-z0/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170224T163000
DTEND;TZID=Europe/Paris:20170224T173000
DTSTAMP:20260423T025015
CREATED:20170224T153000Z
LAST-MODIFIED:20211104T103802Z
UID:8366-1487953800-1487957400@www.math.ens.psl.eu
SUMMARY:Actions de p-groupes sur les variétés projectives.
DESCRIPTION:Je discuterai des contraintes que la géométrie d’une variété projective fait peser sur les possibles actions de p-groupes sur cette dernière. J’expliquerai en particulier comment le calcul d’invariants numériques\, tels que les nombres caractéristiques\, peut permettre de prévoir l’existence de points fixes.
URL:https://www.math.ens.psl.eu/evenement/actions-de-p-groupes-sur-les-varietes-projectives/
LOCATION:ENS Salle W
CATEGORIES:Variétés rationnelles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170224T150000
DTEND;TZID=Europe/Paris:20170224T160000
DTSTAMP:20260423T025015
CREATED:20170224T140000Z
LAST-MODIFIED:20211104T103801Z
UID:8365-1487948400-1487952000@www.math.ens.psl.eu
SUMMARY:Brauer groups and the Brauer-Manin sets of Kummer varieties.
DESCRIPTION:This is a joint work with Yuri Zarhin. We study Kummer varieties attached to 2-coverings of abelian varieties of arbitrary dimension. Over a number field we show that the subgroup of odd order elements of the Brauer group does not obstruct the Hasse principle. Sufficient conditions for the triviality of the Brauer group can be given\, which allow us to give an example of a Kummer K3 surface of geometric Picard rank 17 over the rationals with trivial Brauer group. We establish the non-emptyness of the Brauer-Manin set of everywhere locally soluble Kummer varieties attached to 2-coverings of products of hyperelliptic Jacobians with large Galois action on 2-torsion.
URL:https://www.math.ens.psl.eu/evenement/brauer-groups-and-the-brauer-manin-sets-of-kummer-varieties/
LOCATION:ENS Salle W
CATEGORIES:Variétés rationnelles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170221T160000
DTEND;TZID=Europe/Paris:20170221T160000
DTSTAMP:20260423T025015
CREATED:20170221T150000Z
LAST-MODIFIED:20211104T103600Z
UID:8358-1487692800-1487692800@www.math.ens.psl.eu
SUMMARY:Equationalité des paires de corps
DESCRIPTION:Une théorie est équationelle si tout ensemble définissable est combinaison booléenne d’instances d’équations\, c’est-à-dire des formules telles que la famille des intersections finies d’instances ont la propriété de chaîne descendante. L’équationalité\, introduite par Srour et ensuite étudiée par Pillay et Srour\, entraîne la stabilité. Or\, le seul exemple algébrique naturel d’une théorie stable non-équationelle est la théorie du groupe non-abélien libre\, comme récemment montré par Sela. Cependant\, ce n’est pas évident de montrer qu’une théorie stable donnée est équationelle. Cet exposé présentera les idées d’un travail en commun avec Martin Ziegler sur l’équationalité de la théorie des belles paires de corps algébriquement clos en toute caractéristique.
URL:https://www.math.ens.psl.eu/evenement/equationalite-des-paires-de-corps/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170221T140000
DTEND;TZID=Europe/Paris:20170221T180000
DTSTAMP:20260423T025015
CREATED:20170221T130000Z
LAST-MODIFIED:20211104T103801Z
UID:8363-1487685600-1487700000@www.math.ens.psl.eu
SUMMARY:Quatre exposés en théorie des groupes
DESCRIPTION:
URL:https://www.math.ens.psl.eu/evenement/quatre-exposes-en-theorie-des-groupes/
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=Europe/Paris:20170210T160000
DTEND;TZID=Europe/Paris:20170210T160000
DTSTAMP:20260423T025015
CREATED:20170210T150000Z
LAST-MODIFIED:20211104T102728Z
UID:8343-1486742400-1486742400@www.math.ens.psl.eu
SUMMARY:Cell Decomposition for P-minimal structures: a story
DESCRIPTION:P-minimality is a concept that was developed by Haskell and Macpherson as a p-adic equivalent for o-minimality. For o-minimality\, the cell decomposition theorem is probably one of the most powerful tools\, so it is quite a natural question to ask for a p-adic equivalent of this.In this talk I would like to give an overview of the development of cell decomposition in the p-adic context\, with an emphasis on how questions regarding the existence of definable skolem functions have complicated things. The idea of p-adic cell decomposition was first developed by Denef\, for p-adic semi-algebraic structures\, as a tool to answer certain questions regarding quantifier elimination\, rationality and p-adic integration. This first version eventually resulted in a cell decomposition theorem for P-minimal structures. This theorem\, proven by Mourgues\, was however dependent on the existence of definable Skolem functions. The second part of the talk will focus a bit more on Skolem functions\, and sketch a generalized version of the Denef-Mourgues theorem that does not rely on the existence of such functions\, by introducing a notion of clustered cells. We will explain the notion\, give an informal sketch of the proof\, and compare with other versions of cell decomposition.
URL:https://www.math.ens.psl.eu/evenement/cell-decomposition-for-p-minimal-structures-a-story/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170210T141500
DTEND;TZID=Europe/Paris:20170210T141500
DTSTAMP:20260423T025015
CREATED:20170210T131500Z
LAST-MODIFIED:20211104T102727Z
UID:8342-1486736100-1486736100@www.math.ens.psl.eu
SUMMARY:Determining finite simple images of finitely presented groups
DESCRIPTION:I will discuss joint work with Martin Bridson and Martin Liebeck which addresses the question: for which collections of finite simple groups does there exist an algorithm that determines the images of an arbitrary finitely presented group that lie in the collection? We prove both positive and negative results. For a collection of finite simple groups that contains infinitely many alternating groups\, or contains classical groups of unbounded dimensions\, we prove that there is no such algorithm. On the other hand\, for a collection of simple groups of fixed Lie type we obtain positive results by using the model theory of finite fields.
URL:https://www.math.ens.psl.eu/evenement/determining-finite-simple-images-of-finitely-presented-groups/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170210T110000
DTEND;TZID=Europe/Paris:20170210T110000
DTSTAMP:20260423T025015
CREATED:20170210T100000Z
LAST-MODIFIED:20211104T102528Z
UID:8341-1486724400-1486724400@www.math.ens.psl.eu
SUMMARY:Geometric invariants that are encoded in the Newton polygon
DESCRIPTION:Let k be a field and let P be a lattice polygon\, i.e. the convex hull in R^2 of finitely many non-collinear points of Z^2. Let C/k be the algebraic curve defined by a sufficiently generic Laurent polynomial that is supported on P. A result due to Khovanskii states that the geometric genus of C equals the number of Z^2-valued points that are contained in the interior of P. In this talk we will give an overview of various other curve invariants that can be told by looking at the combinatorics of P\, such as the gonality\, the Clifford index\, the Clifford dimension\, the scrollar invariants associated to a gonality pencil\, and in some special cases the canonical graded Betti numbers. This will cover joint work with Filip Cools\, Jeroen Demeyer and Alexander Lemmens.
URL:https://www.math.ens.psl.eu/evenement/geometric-invariants-that-are-encoded-in-the-newton-polygon/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170124T140000
DTEND;TZID=Europe/Paris:20170124T170000
DTSTAMP:20260423T025015
CREATED:20170124T130000Z
LAST-MODIFIED:20211104T102527Z
UID:8338-1485266400-1485277200@www.math.ens.psl.eu
SUMMARY:La propriété (T) et ses généralisations
DESCRIPTION:14.00-14.45 Marc Bourdon (Lille) : Espaces hyperboliques\, dimension conforme et cohomologie $ell _p$15.00-15.45 Masato Mimura (EPFL Lausanne) : Superintrinsic synthesis in fixed point properties15.45-16.15 pause café16.15-17.00 Mikael De La Salle (ENS Lyon) : Zuk’s criterion for actions on Banach spaces
URL:https://www.math.ens.psl.eu/evenement/la-propriete-t-et-ses-generalisations/
LOCATION:ENS Salle W (Toits du DMA)
CATEGORIES:Séminaire de théorie des groupes à l’ENS
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170120T163000
DTEND;TZID=Europe/Paris:20170120T173000
DTSTAMP:20260423T025015
CREATED:20170120T153000Z
LAST-MODIFIED:20211104T102528Z
UID:8340-1484929800-1484933400@www.math.ens.psl.eu
SUMMARY:Sous-groupes compacts d'un groupe algébrique linéaire sur un corps local.
DESCRIPTION:
URL:https://www.math.ens.psl.eu/evenement/sous-groupes-compacts-dun-groupe-algebrique-lineaire-sur-un-corps-local/
LOCATION:ENS salle Henri Cartan
CATEGORIES:Variétés rationnelles
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170120T150000
DTEND;TZID=Europe/Paris:20170120T160000
DTSTAMP:20260423T025015
CREATED:20170120T140000Z
LAST-MODIFIED:20211104T102527Z
UID:8339-1484924400-1484928000@www.math.ens.psl.eu
SUMMARY:Dualité et principe local-global sur des anneaux locaux henséliens de dimension 2.
DESCRIPTION:Sur les corps de nombres\, l’obstruction de Brauer-Manin est la seule obstruction au principe local-global pour les torseurs sous des groupes linéaires connexes. Dans un article récent\, Colliot-Thélène\, Parimala et Suresh ont introduit un nouveau type d’obstruction au principe local-global sur les corps de fonctions de schémas réguliers intègres de dimension quelconque\, et ils se demandent notamment si c’est la seule obstruction au principe local-global pour les torseurs sous des tores sur C((x\,y)). Dans cet exposé\, j’expliquerai pourquoi cette question admet une réponse affirmative.
URL:https://www.math.ens.psl.eu/evenement/dualite-et-principe-local-global-sur-des-anneaux-locaux-henseliens-de-dimension-2/
LOCATION:ENS salle Henri Cartan
CATEGORIES:Variétés rationnelles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170113T160000
DTEND;TZID=Europe/Paris:20170113T160000
DTSTAMP:20260423T025015
CREATED:20170113T150000Z
LAST-MODIFIED:20211104T102526Z
UID:8337-1484323200-1484323200@www.math.ens.psl.eu
SUMMARY:Imaginaires dans les corps valués avec opérateurs
DESCRIPTION:Au début des années 2000\, Haskell\, Hrushovski and Macpherson ont décrit les ensembles interprétables dans un corps valué algébriquement clos à l’aide d’équivalents en plus grande dimension des boules. Plus précisément\, ils ont prouvé l’élimination des imaginaires dans le language géométrique. Pendant la même période\, l’intérêt des théoriciens des modèles pour les corps valués avec opérateurs s’est grandement développé. Les questions résolues pour ces structures tournent\, pour la plupart\, autour de l’élimination des quantificateurs et de la modération. Mais\, au vu des résultats de Haskell\, Hrushovski and Macpherson\, il est tentant de vouloir aussi classifier les ensembles interprétables.Dans cet exposé\, je traiterai des deux exemples les mieux compris: la modèle complétion de Scanlon des corps valués munis d’une dérivation contractive et les corps valués séparablement clos de degré d’imperfection fini. En particulier\, je montrerai comment l’élimination des imaginaires dans ces structures est liée à l’existence d’une base canonique pour les types définissables et comment la propriété d’indépendance (ou plutôt son absence) peut aider à contrôler ces bases canoniques.
URL:https://www.math.ens.psl.eu/evenement/imaginaires-dans-les-corps-values-avec-operateurs/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170113T141500
DTEND;TZID=Europe/Paris:20170113T141500
DTSTAMP:20260423T025015
CREATED:20170113T131500Z
LAST-MODIFIED:20211104T102327Z
UID:8336-1484316900-1484316900@www.math.ens.psl.eu
SUMMARY:Some Zilber-Pink-type problems
DESCRIPTION:I will discuss some problems which are analogous to\, but formally not comprehended within\, the Zilber-Pink conjecture\, involving collections of `special subvarieties’ connected with uniformization maps of suitable domains.
URL:https://www.math.ens.psl.eu/evenement/some-zilber-pink-type-problems/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170113T110000
DTEND;TZID=Europe/Paris:20170113T110000
DTSTAMP:20260423T025015
CREATED:20170113T100000Z
LAST-MODIFIED:20211104T102327Z
UID:8335-1484305200-1484305200@www.math.ens.psl.eu
SUMMARY:Wilkie's conjecture for restricted elementary functions
DESCRIPTION:Let X be a set definable in some o-minimal structure. The Pila-Wilkie theorem (in its basic form) states that the number of rational points in the transcendental part of X grows sub-polynomially with the height of the points. The Wilkie conjecture stipulates that for sets definable in R_exp\, one can sharpen this asymptotic to polylogarithmic.I will describe a complex-analytic approach to the proof of the Pila-Wilkie theorem for subanalytic sets. I will then discuss how this approach leads to a proof of the `restricted Wilkie conjecture’\, where we replace R_exp by the structure generated by the restrictions of exp and sin to the unit interval (both parts are joint work with Dmitry Novikov). If time permits I will discuss possible generalizations and applications.
URL:https://www.math.ens.psl.eu/evenement/wilkies-conjecture-for-restricted-elementary-functions/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170110T160000
DTEND;TZID=Europe/Paris:20170110T160000
DTSTAMP:20260423T025015
CREATED:20170110T150000Z
LAST-MODIFIED:20211104T102326Z
UID:8334-1484064000-1484064000@www.math.ens.psl.eu
SUMMARY:Mauvais groupes de rang de Morley 3
DESCRIPTION:Selon la conjecture d’algébricité de Cherlin-Zilber\, tout groupe simple et infini de rang de Morley fini est un groupe algébrique défini sur un corps algébriquement clos.Il y a presque 40 ans\, Cherlin avait montré que s’il existe un contre-exemple à cette conjecture\, alors il est de rang de Morley au moins 3. Il avait aussi montré que s’il est de rang 3\, alors c’est un mauvais groupe : ses sous-groupes définissables infinis propres sont de rang de Morley 1\, ils sont en particulier abéliens.Dans cet exposé\, nous montrerons pourquoi un tel mauvais groupe n’existe pas.
URL:https://www.math.ens.psl.eu/evenement/mauvais-groupes-de-rang-de-morley-3/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
END:VCALENDAR