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X-WR-CALDESC:évènements pour Département de mathématiques et applications
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TZID:Europe/Paris
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TZOFFSETFROM:+0100
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DTSTART:20180325T010000
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TZOFFSETFROM:+0200
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DTSTART:20181028T010000
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20180116T140000
DTEND;TZID=Europe/Paris:20180116T170000
DTSTAMP:20260410T174022
CREATED:20180116T130000Z
LAST-MODIFIED:20211025T103312Z
UID:8442-1516111200-1516122000@www.math.ens.psl.eu
SUMMARY:Trois exposés dans un après-midi de théorie des groupes
DESCRIPTION:https://sites.google.com/site/annaerschler/programtalks
URL:https://www.math.ens.psl.eu/evenement/trois-exposes-dans-un-apres-midi-de-theorie-des-groupes-3/
LOCATION:14:00-17:00 Salle W
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20180119T110000
DTEND;TZID=Europe/Paris:20180119T110000
DTSTAMP:20260410T174022
CREATED:20180119T100000Z
LAST-MODIFIED:20211104T105937Z
UID:8441-1516359600-1516359600@www.math.ens.psl.eu
SUMMARY:Spectral gap and definability
DESCRIPTION:Originating in the theory of unitary group representations\, the notion of spectral gap has played a huge role in many of the deep results in the theory of von Neumann algebras in the last couple of decades. Recently\, with my collaborators\, we are slowly understanding the model-theoretic significance of spectral gap\, in particular its connection with definability. In this talk\, I will discuss a few of our recent observations in this direction and speculate on some further possible developments. I will assume no knowledge of von Neumann algebras nor continuous logic. Various parts of this work are joint with Bradd Hart\, Thomas Sinclair\, and Henry Towsner.
URL:https://www.math.ens.psl.eu/evenement/spectral-gap-and-definability/
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:20260410T174022
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
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20180119T160000
DTEND;TZID=Europe/Paris:20180119T160000
DTSTAMP:20260410T174022
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:20180126T150000
DTEND;TZID=Europe/Paris:20180126T160000
DTSTAMP:20260410T174022
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:20180126T163000
DTEND;TZID=Europe/Paris:20180126T173000
DTSTAMP:20260410T174022
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
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