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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
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TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:20170326T010000
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TZOFFSETFROM:+0200
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DTSTART:20171029T010000
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20170307T160000
DTEND;TZID=Europe/Paris:20170307T160000
DTSTAMP:20260411T232249
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:20170310T110000
DTEND;TZID=Europe/Paris:20170310T110000
DTSTAMP:20260411T232249
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:20170310T141500
DTEND;TZID=Europe/Paris:20170310T141500
DTSTAMP:20260411T232249
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:20170310T160000
DTEND;TZID=Europe/Paris:20170310T160000
DTSTAMP:20260411T232249
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:20170314T000000
DTEND;TZID=Europe/Paris:20170314T000000
DTSTAMP:20260411T232249
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:20170321T140000
DTEND;TZID=Europe/Paris:20170321T170000
DTSTAMP:20260411T232249
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:20170328T160000
DTEND;TZID=Europe/Paris:20170328T160000
DTSTAMP:20260411T232249
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:20170331T150000
DTEND;TZID=Europe/Paris:20170331T160000
DTSTAMP:20260411T232249
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:20170331T163000
DTEND;TZID=Europe/Paris:20170331T173000
DTSTAMP:20260411T232249
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
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