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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:20190331T010000
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BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:20191027T010000
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TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:20200329T010000
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TZOFFSETTO:+0100
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DTSTART:20201025T010000
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BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20201113T103000
DTEND;TZID=Europe/Paris:20201113T115000
DTSTAMP:20260419T005941
CREATED:20201113T093000Z
LAST-MODIFIED:20211104T141149Z
UID:8559-1605263400-1605268200@www.math.ens.psl.eu
SUMMARY:Belles paires of valued fields and analytification
DESCRIPTION:In their work\, Hrushovski and Loeser proposed the space V̂ of generically stable types concentrating on V to study the homotopy type of the Berkovich analytification of V. An important feature of V̂ is that it is canonically identified as a projective limit of definable sets in ACVF\, which grants them tools from model theory. In this talk\, we will give a brief introduction to this object and present an alternative approach to internalize various spaces of definable types\, motivated by Poizat’s work on belles paires of stable theories. Several results of interest to model theorists will also be discussed. Particularly\, we recover the space V̂ is strict pro-definable and we propose a model-theoretic counterpart Ṽ of Huber’s analytification. Time permitting\, we will discuss some comparison and lifting results between V̂ and Ṽ. This is a joint project with Pablo Cubides Kovacsics and Martin Hils.
URL:https://www.math.ens.psl.eu/evenement/belles-paires-of-valued-fields-and-analytification/
LOCATION:Zoom
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20201113T090000
DTEND;TZID=Europe/Paris:20201113T102000
DTSTAMP:20260419T005941
CREATED:20201113T080000Z
LAST-MODIFIED:20211104T141207Z
UID:8558-1605258000-1605262800@www.math.ens.psl.eu
SUMMARY:The étale-open topology
DESCRIPTION:Fix an abstract field K. For each K-variety V\, we will define an étale-open topology on the set V(K) of rational points of V. This notion uniformly recovers (1) the Zariski topology on V(K) when K is algebraically closed\, (2) the analytic topology on V(K) when K is the real numbers\, (3) the valuation topology on V(K) when K is almost any henselian field. On pseudo-finite fields\, the étale-open topology seems to be new\, and has some interesting properties.The étale-open topology is mostly of interest when K is large (also known as ample). On non-large fields\, the étale-open topology is discrete. In fact\, this property characterizes largeness. Using this\, one can recover some well-known facts about large fields\, and classify the model-theoretically stable large fields. It may be possible to push these arguments towards a classification of NIP large fields. Joint work with Chieu-Minh Tran\, Erik Walsberg\, and Jinhe Ye.
URL:https://www.math.ens.psl.eu/evenement/the-etale-open-topology/
LOCATION:Zoom
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20201112T103000
DTEND;TZID=Europe/Paris:20201112T115000
DTSTAMP:20260419T005941
CREATED:20201112T093000Z
LAST-MODIFIED:20211104T121624Z
UID:14111-1605177000-1605181800@www.math.ens.psl.eu
SUMMARY:Cohomology of algebraic varieties over non-archimedean fields
DESCRIPTION:I will report on a joint work with Mário Edmundo and Jinhe Ye in which we introduced a sheaf cohomology theory for algebraic varieties over non-archimedean fields based on Hrushovski-Loeser spaces. After informally framing our main results with respect to classical statements\, I will discuss some details of our construction and the main difficulties arising in this new context. If time allows\, I will further explain how our results allow us to recover results of V. Berkovich on the sheaf cohomology of the analytification of an algebraic variety over a rank 1 complete non-archimedean field.
URL:https://www.math.ens.psl.eu/evenement/cohomology-of-algebraic-varieties-over-non-archimedean-fields-2/
LOCATION:Zoom
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20201027T090000
DTEND;TZID=Europe/Paris:20201027T120000
DTSTAMP:20260419T005941
CREATED:20201027T080000Z
LAST-MODIFIED:20211104T134742Z
UID:8560-1603789200-1603800000@www.math.ens.psl.eu
SUMMARY:Une matinée de théorie de groupes
DESCRIPTION:https://us02web.zoom.us/j/86850693514The password is answer to the following question: What is the degree of the standard Cayely graph on 107 generators?09.00-09.45 Koji Fujiwara (Kyoto)\, The rates of growth in a hyperbolic group10.00-10.45 Macarena Arenas (Cambridge)\, Linear isoperimetric functions for surfaces in hyperbolic groups11.15-12.00 Indira Chatterji (Nice)\, Tangent bundles on hyperbolic spaces and proper actions on Lp spaces
URL:https://www.math.ens.psl.eu/evenement/une-matinee-de-theorie-de-groupes/
LOCATION:Zoom: https://us02web.zoom.us/j/86850693514
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20201016T103000
DTEND;TZID=Europe/Paris:20201016T115000
DTSTAMP:20260419T005941
CREATED:20201016T083000Z
LAST-MODIFIED:20211104T141411Z
UID:8557-1602844200-1602849000@www.math.ens.psl.eu
SUMMARY:Tame geometry and diophantine approximation
DESCRIPTION:Tame geometry is the study of structures where the definable sets admit finite complexity. Around 15 years ago Pila and Wilkie discovered a deep connection between tame geometry and diophantine approximation\, in the form of asymptotic estimates on the number of rational points in a tame set (as a function of height). This later led to deep applications in diophantine geometry\, functional transcendence and Hodge theory.I will describe some conjectures and a long-term project around a more effective form of tame geometry\, suited for improving the quality of the diophantine approximation results and their applications. I will try to outline some of the pieces that are already available\, and how they should conjecturally fit together. Finally I will survey some applications of the existing results around the Manin-Mumford conjecture\, the Andre-Oort conjecture\, Galois-orbit lower bounds in Shimura varieties\, unlikely intersections in group schemes\, and some other directions (time permitting).
URL:https://www.math.ens.psl.eu/evenement/tame-geometry-and-diophantine-approximation/
LOCATION:Zoom
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20201016T090000
DTEND;TZID=Europe/Paris:20201016T102000
DTSTAMP:20260419T005941
CREATED:20201016T070000Z
LAST-MODIFIED:20211104T141431Z
UID:8556-1602838800-1602843600@www.math.ens.psl.eu
SUMMARY:Complex Cellular Structures
DESCRIPTION:Real semialgebraic sets admit so-called cellular decomposition\, i.e. representation as a union of convenient semialgebraic images of standard cubes.\nThe Gromov-Yomdin Lemma (later generalized by Pila and Wilkie) proves that the maps could be chosen of C^r-smooth norm at most one\, and the number of such maps is uniformly bounded for finite-dimensional families. This number was not effectively bounded by Yomdin or Gromov\, but itnecessarily grows as r ? ?.\nIt turns out there is a natural obstruction to a naive holomorphic complexification of this result related to the natural hyperbolic metric of complex holomorphic sets.\nWe prove a lemma about holomorphic functions in annulii\, a quantitative version of the great Picard theorem. This lemma allowed us to construct an effective holomorphic version of the cellular decomposition results in all dimensions\, with explicit polynomial bounds on complexity for families of complex (sub)analytic and semialgebraic sets.\nAs the first corollary we get an effective version of Yomdin-Gromov Lemma with polynomial bounds on the complexity\, thus proving a long-standing Yomdin conjecture about tail entropy of analytic maps.Further connection to diophantine applications will be explained in Gal’s talk.
URL:https://www.math.ens.psl.eu/evenement/complex-cellular-structures/
LOCATION:Zoom
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200324T160000
DTEND;TZID=Europe/Paris:20200324T173000
DTSTAMP:20260419T005941
CREATED:20200324T150000Z
LAST-MODIFIED:20211025T103827Z
UID:8548-1585065600-1585071000@www.math.ens.psl.eu
SUMMARY:Ensembles IP et ultraproduits de groupes finis
DESCRIPTION:Une sous-partie d’un groupe infini est IP si elle contient tous les produits finis (sans répétitions) d’un sous-ensemble infini. Le célèbre théorème de Hindman affirme que\, pour toute coloration finie des entiers positifs\, il existe un ensemble IP monochromatique. Au delà du cas abélien\, Bergelson et Tao ont repris un travail de Gowers pour montrer qu’une sous-partie `large’ dans un ultraproduit de groupes finis simples non-abéliens est IP.Dans un travail en commun avec D. Palacin (Freiburg)\, nous allons donner dans cet exposé une démonstration alternative du résultat précédent\, avec des techniques modèles-théoriques élémentaires.
URL:https://www.math.ens.psl.eu/evenement/ensembles-ip-et-ultraproduits-de-groupes-finis/
LOCATION:Sophie Germain Salle 2020
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200310T000000
DTEND;TZID=Europe/Paris:20200310T000000
DTSTAMP:20260419T005941
CREATED:20200309T230000Z
LAST-MODIFIED:20211025T103825Z
UID:8547-1583798400-1583798400@www.math.ens.psl.eu
SUMMARY:Théories non-équationnelles
DESCRIPTION:Une théorie est équationnelle\, si toute formule est combination booléenne d’équations. Une équation est une formule telle que la famille d’intersections finies d’instances n’admet aucune chaine infinie décroissante. Toute théorie équationnelle est stable\, mais la réciproque n’est pas vraie : Sela ainsi que Müller-Sklinos ont montré que le groupe libre non-abélien n’est pas équationnel. Malgré tout\, on connaît peu d’exemples de théories stables non-équationnelles.Dans cet exposé\, nous présenterons un travail en commun avec Martin Ziegler\, où nous exhiberons une infinité de nouvelles théories stables non-équationnelles\, à partir du pseudo-espace coloré de Hrushovski et Srour.
URL:https://www.math.ens.psl.eu/evenement/theories-non-equationnelles/
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200306T170000
DTEND;TZID=Europe/Paris:20200306T182000
DTSTAMP:20260419T005941
CREATED:20200306T160000Z
LAST-MODIFIED:20211025T103821Z
UID:8545-1583514000-1583518800@www.math.ens.psl.eu
SUMMARY:Constructing pseudo-algebraically closed fields
DESCRIPTION:A field K is called pseudo-algebraically closed (PAC) if every absolutely irreducible variety defined over K has a K-rational point. These fields were introduced by Ax in his characterization of pseudo-finite fields and have since become an important object of study in both model theory and field arithmetic. We will explain how the analysis of a PAC field often reduces to questions about the model theory of the absolute group and describe how these reductions combine with a graph-coding construction of Cherlin\, van den Dries\, and Macintyre together with to construct PAC fields with prescribed combinatorial properties.
URL:https://www.math.ens.psl.eu/evenement/constructing-pseudo-algebraically-closed-fields/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200306T110000
DTEND;TZID=Europe/Paris:20200306T122000
DTSTAMP:20260419T005941
CREATED:20200306T100000Z
LAST-MODIFIED:20211025T103823Z
UID:8546-1583492400-1583497200@www.math.ens.psl.eu
SUMMARY:Some remarks on complex analytic functions in a definable context
DESCRIPTION:We fix an o-minimal expansion of the real field\, M say. Definabilitynotions are with respect to M. Let F = {f_x : x in X} be a definable familyof (single valued) complex analytic functions\, each one having domain somedisk\, D_x say\, in ?\, where the parameter space X is a definable subset of ?^mfor some m. We present some finiteness theorems for such families F whichare uniform in parameters and give some applications.We also speculate on the notion of “definable” Riemann surface.
URL:https://www.math.ens.psl.eu/evenement/some-remarks-on-complex-analytic-functions-in-a-definable-context/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200306T000000
DTEND;TZID=Europe/Paris:20200306T000000
DTSTAMP:20260419T005941
CREATED:20200305T230000Z
LAST-MODIFIED:20211025T103835Z
UID:8549-1583452800-1583452800@www.math.ens.psl.eu
SUMMARY:Exponential sums modulo powers of primes\, singularity theory\, and local global principles
DESCRIPTION:The theme of the talk is around the theory of Igusa’s local zeta functions\, his broader program on local global principles\, and recent progress on these via singularity theory and the minimal model program with M. Mustata and K. H. Nguyen. I will also present some new open questions that push Igusa’s program further\, and partial evidence obtained with K. H. Nguyen.
URL:https://www.math.ens.psl.eu/evenement/exponential-sums-modulo-powers-of-primes-singularity-theory-and-local-global-principles/
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200303T160000
DTEND;TZID=Europe/Paris:20200303T173000
DTSTAMP:20260419T005941
CREATED:20200303T150000Z
LAST-MODIFIED:20211104T113418Z
UID:8544-1583251200-1583256600@www.math.ens.psl.eu
SUMMARY:Les décompositions paradoxales et les théories simples
DESCRIPTION:Y-a-t-il une théorie des mesures de Keisler pour les théories simples? J’expliquerai quelques exemples\, suggérés par Hrushovski\, qui montrent que les mesures dans une théorie simple sont plus complexes que prévu. Ils sont basés sur des actions de groupes libres.Travail en commun avec plusieurs chercheurs.
URL:https://www.math.ens.psl.eu/evenement/les-decompositions-paradoxales-et-les-theories-simples/
LOCATION:Sophie Germain salle 2015
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200225T160000
DTEND;TZID=Europe/Paris:20200225T173000
DTSTAMP:20260419T005941
CREATED:20200225T150000Z
LAST-MODIFIED:20211025T103813Z
UID:8543-1582646400-1582651800@www.math.ens.psl.eu
SUMMARY:Autour d'un théorème d'approximation d'Artin
DESCRIPTION:(avec Tom Scanlon)J’exposerai un résultat d’élimination des quantificateurs pour les corps henséliens de degré d’imperfection fini\, relativement à la famille uniforme de tous les groupes RV_gamma = K^\,imes/1+gamma m. Ce résultat permet alors de démontrer que toute extension dense séparable de corps henséliens de même degré d’imperfection fini est élémentaire. En particulier\, l’extension F_p(t)^h leq  F_p((t)) est élémentaire. Ce dernier énoncé précise un résultat d’Artin selon lequel elle est existentiellement close.
URL:https://www.math.ens.psl.eu/evenement/autour-dun-theoreme-dapproximation-dartin/
LOCATION:Salle 2015 Sophie Germain
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200218T150000
DTEND;TZID=Europe/Paris:20200218T170000
DTSTAMP:20260419T005941
CREATED:20200218T140000Z
LAST-MODIFIED:20211104T134933Z
UID:8542-1582038000-1582045200@www.math.ens.psl.eu
SUMMARY:Après-midi de théorie de groupes
DESCRIPTION:14.00-14.45 David Hume (Oxford)\, Three dichotomies for connected unimodular Lie groups15.00-15.45 Nikolay Bogachev (Skoltech & MIPT)\, Arithmetic hyperbolic reflection groups16.15-17.00 Daniel Woodhouse (Oxford)\, Action rigidity of free products of hyperbolic manifold groups
URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-de-groupes-9/
LOCATION:Salle W (DMA ENS)
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200131T160000
DTEND;TZID=Europe/Paris:20200131T172000
DTSTAMP:20260419T005941
CREATED:20200131T150000Z
LAST-MODIFIED:20211025T103757Z
UID:8538-1580486400-1580491200@www.math.ens.psl.eu
SUMMARY:Geometric quadratic Chabauty.
DESCRIPTION:Determining all rational points on a curve of genus at least 2 can be difficult. Chabauty’s method (1941) is to intersect\, for a prime number p\, in the p-adic Lie group of p-adic points of the jacobian\, the closure of the Mordell-Weil group with the p-adic points of the curve. If the Mordell-Weil rank is less than the genus then this method has never failed. Minhyong Kim’s non-abelian Chabauty programme aims to remove the condition on the rank. The simplest case\, called quadratic Chabauty\, was developed by Balakrishnan\, Dogra\, Mueller\, Tuitman and Vonk\, and applied in a tour de force to the so-called cursed curve (rank and genus both 3). This article aims to make the quadratic Chabauty method small and geometric again\, by describing it in terms of only `simple algebraic geometry’ (line bundles over the jacobian and models over the integers).
URL:https://www.math.ens.psl.eu/evenement/geometric-quadratic-chabauty/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200131T141500
DTEND;TZID=Europe/Paris:20200131T153500
DTSTAMP:20260419T005941
CREATED:20200131T131500Z
LAST-MODIFIED:20211104T141458Z
UID:8541-1580480100-1580484900@www.math.ens.psl.eu
SUMMARY:Quantitative Fundamental Theorem of Algebra
DESCRIPTION:Using subresultants\, we modify a recent real-algebraic proof due to Eisermann of the Fundamental Theorem of Algebra ([FTA]) to obtain the following quantitative information: in order to prove the [FTA] for polynomials of degree d\, the Intermediate Value Theorem ([IVT]) is requested to hold for real polynomials of degree at most d^2. We also explain that the classical algebraic proof due to Laplace requires [IVT] for real polynomials of exponential degree. These quantitative results highlight the difference in nature of these two proofs.
URL:https://www.math.ens.psl.eu/evenement/quantitative-fundamental-theorem-of-algebra/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200131T110000
DTEND;TZID=Europe/Paris:20200131T122000
DTSTAMP:20260419T005941
CREATED:20200131T100000Z
LAST-MODIFIED:20211025T103807Z
UID:8540-1580468400-1580473200@www.math.ens.psl.eu
SUMMARY:Classification des imaginaires dans VFA
DESCRIPTION:(travail en commun avec Silvain Rideau-Kikuchi)Les imaginaires (c’est-à-dire les quotients définissables) dans la théorie ACVF des corpsalgébriquement clos non-trivialement valués sont classifiés par les sortes “géométriques”.Ceci est un résultat fondamental dû à Haskell\, Hrushovski et Macpherson. En utilisantl’approche via la densité des types définissables/invariants\, nous donnons une réductiondes imaginaires dans des corps valués henséliens\, sous des hypothèses assez générales\,aux sortes géométriques et à des imaginaires de RV avec des sortes pour certains espacesvectoriels de dimension finie sur le corps résiduel.
URL:https://www.math.ens.psl.eu/evenement/classification-des-imaginaires-dans-vfa/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200121T150000
DTEND;TZID=Europe/Paris:20200121T170000
DTSTAMP:20260419T005941
CREATED:20200121T140000Z
LAST-MODIFIED:20211104T135010Z
UID:8539-1579618800-1579626000@www.math.ens.psl.eu
SUMMARY:Après-midi de théorie de groupes
DESCRIPTION:14.00-14.45 Francois Dahmani (Grenoble)\, Relative hyperbolicity of free-by-cyclic groups\, and conjugacy between automorphisms of free groups15.00-15.45 Tatiana Smirnova-Nagnibeda (Geneva)\, Various types of spectra and spectral measures on Schreier and Cayley graphs16.15-17.00 Urs Lang (ETH Zurich)\, Characterizations and asymptotic geometry of rank-n-hyperbolic spaces
URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-de-groupes-8/
LOCATION:Salle W (DMA ENS)
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20200107T160000
DTEND;TZID=Europe/Paris:20200107T173000
DTSTAMP:20260419T005941
CREATED:20200107T150000Z
LAST-MODIFIED:20211104T122755Z
UID:8536-1578412800-1578418200@www.math.ens.psl.eu
SUMMARY:Groupes de Lie et définissabilité le cas (non) linéaire.
DESCRIPTION:Entre les catégories des groupes semialgébriques et des groupes de Lie se trouve la catégorie des groupes définissables dans une expansion o-minimale des réels (noté simplement définissables dans la suite). Puisque tout groupe définissable peut être équipé d’une structure de groupe de Lie (Pillay 1989)\, il est intéressant de savoir sous quelles conditions un groupe de Lie est isomorphe (au sens de Lie) à un groupe définissable. Starchenko\, Onshuus et Conversano ont répondu à cette question dans le cas où le groupe est résoluble (2016). Nous nous intéresserons ici au cas linéaire puis si le temps le permet au cas général.
URL:https://www.math.ens.psl.eu/evenement/groupes-de-lie-et-definissabilite-le-cas-non-lineaire/
LOCATION:Sophie Germain salle 2015
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191217T150000
DTEND;TZID=Europe/Paris:20191217T170000
DTSTAMP:20260419T005941
CREATED:20191217T140000Z
LAST-MODIFIED:20211104T135037Z
UID:8535-1576594800-1576602000@www.math.ens.psl.eu
SUMMARY:Après-midi de théorie de groupes
DESCRIPTION:15.00-15.45 Ashot Minasyan (Southampton)\, CAT(0) groups with exotic properties16.15-17.00 Assaf Naor (Princeton)\, Vertical-versus-horizontal isoperimetry*NOTE* Urs Lang’s talk has been moved to January 21
URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-de-groupes-7/
LOCATION:Salle W (DMA ENS)
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191112T140000
DTEND;TZID=Europe/Paris:20191112T170000
DTSTAMP:20260419T005941
CREATED:20191112T130000Z
LAST-MODIFIED:20211104T133906Z
UID:8533-1573567200-1573578000@www.math.ens.psl.eu
SUMMARY:Après-midi de théorie de groupes
DESCRIPTION:14.00-14.45 Peter Haissinsky (Université d’Aix-Marseille)\, Quasi-isometric rigidity of 3-manifold groups.15.00-15.45 Nima Hoda (ENS Paris)\, Shortcut graphs and groups.16.15-17.00 Elia Fioravanti (Oxford)\, Cross ratios on cube complexesand marked length-spectrum rigidity.
URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-de-groupes-6/
LOCATION:Salle W (DMA ENS)
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191110T110000
DTEND;TZID=Europe/Paris:20191110T123000
DTSTAMP:20260419T005941
CREATED:20191110T100000Z
LAST-MODIFIED:20211104T112900Z
UID:14071-1573383600-1573389000@www.math.ens.psl.eu
SUMMARY:A valuative approach to the inner geometry of surfaces
DESCRIPTION:Lipschitz geometry is a branch of singularity theory that studies the metric data of a germ of a complex analytic space.I will discuss a new approach to the study of such metric germs\, and in particular of an invariant called Lipschitz inner rate\, based on the combinatorics of a space of valuations\, the so-called non-archimedean link of the singularity. I will describe completely the inner metric structure of a complex surface germ showing that its inner rates both determine and are determined by global geometric data: the topology of the germ\, its hyperplane sections\, and its generic polar curves.This is a joint work with André Belotto and Anne Pichon.
URL:https://www.math.ens.psl.eu/evenement/a-valuative-approach-to-the-inner-geometry-of-surfaces-2/
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191108T160000
DTEND;TZID=Europe/Paris:20191108T172000
DTSTAMP:20260419T005941
CREATED:20191108T150000Z
LAST-MODIFIED:20211104T125730Z
UID:8532-1573228800-1573233600@www.math.ens.psl.eu
SUMMARY:Une construction d'extensions faiblement non ramifiées d'un anneau de valuation
DESCRIPTION:Étant donné un anneau de valuation V de corps résiduel F et contenant un corps k\, et une extension k’ de k\, on cherche à construire une extension V’ de V contenant k’\, d’idéal maximal engendré par celui de V\, et de corps résiduel composé de F et k’. On y parvient notamment si F ou k’ est séparable sur k.
URL:https://www.math.ens.psl.eu/evenement/une-construction-dextensions-faiblement-non-ramifiees-dun-anneau-de-valuation/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191108T141500
DTEND;TZID=Europe/Paris:20191108T153500
DTSTAMP:20260419T005941
CREATED:20191108T131500Z
LAST-MODIFIED:20211104T125154Z
UID:8530-1573222500-1573227300@www.math.ens.psl.eu
SUMMARY:The Mumford-Tate conjecture implies the algebraic Sato-Tate conjecture
DESCRIPTION:The famous Mumford-Tate conjecture asserts that\, for every prime number l\, Hodge cycles are Q_l linear combinations of Tate cycles\, through Artin’s comparisons theorems between Betti and étale cohomology. The algebraic Sato-Tate conjecture\, introduced by Serre and developed by Banaszak and Kedlaya\, is a powerful tool in order to prove new instances of the generalized Sato-Tate conjecture. This previous conjecture is related with the equidistribution of Frobenius traces.Our main goal is to prove that the Mumford-Tate conjecture for an abelian variety A implies the algebraic Sato-Tate conjecture for A. The relevance of this result lies mainly in the fact that the list of known cases of the Mumford-Tate conjecture was up to now a lot longer than the list of known cases of the algebraic Sato-Tate conjecture. This is a joint work with Johan Commelin.
URL:https://www.math.ens.psl.eu/evenement/the-mumford-tate-conjecture-implies-the-algebraic-sato-tate-conjecture/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191108T110000
DTEND;TZID=Europe/Paris:20191108T122000
DTSTAMP:20260419T005941
CREATED:20191108T100000Z
LAST-MODIFIED:20211104T130247Z
UID:8531-1573210800-1573215600@www.math.ens.psl.eu
SUMMARY:Characterizing NIP henselian fields
DESCRIPTION:In this talk\, we characterize NIP henselian valued fields modulo the theory of their residue field. Assuming the conjecture that every infinite NIP field is either separably closed\, real closed or admits a non-trivial henselian valuation\, this allows us to obtain a characterization of all theories of NIP fields.
URL:https://www.math.ens.psl.eu/evenement/characterizing-nip-henselian-fields/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191105T160000
DTEND;TZID=Europe/Paris:20191105T173000
DTSTAMP:20260419T005941
CREATED:20191105T150000Z
LAST-MODIFIED:20211104T131047Z
UID:8527-1572969600-1572975000@www.math.ens.psl.eu
SUMMARY:Expansions de l'arithmétique de Presburger avec la propriété d'échange
DESCRIPTION:Soit G un groupe élémentairement équivalent à Z dans le langage de Presburger L_Pres. Soit L une expansion du langage L_Pres. On dit que la théorie de (G\, L) est L_Pres-minimale si tout sous-ensemble L-définissable de M est L_Pres-définissable (où M est un modèle de la théorie). Si G=Z\, des résultats de C. Michaux et R. Villemaire impliquent que Th(Z\, L) est L_Pres-minimale ssi la clôture algébrique a la propriété d’échange. Dans cet exposé\, je discuterai le cadre général. En particulier\, nous verrons que Th(G\,L) est L_Pres-minimale ssi la clôture algébrique a la propriété d’échange et tout sous-ensemble définissable borné de G a un maximum.
URL:https://www.math.ens.psl.eu/evenement/expansions-de-larithmetique-de-presburger-avec-la-propriete-dechange/
LOCATION:Sophie Germain salle 2015
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191029T160000
DTEND;TZID=Europe/Paris:20191029T173000
DTSTAMP:20260419T005941
CREATED:20191029T150000Z
LAST-MODIFIED:20211104T140810Z
UID:8529-1572364800-1572370200@www.math.ens.psl.eu
SUMMARY:Model theory of proalgebraic groups
DESCRIPTION:Inspired by the model theoretic study of profinite groups\, we discuss the foundations of a model theoretic approach to proalgebraic groups. Our axiomatization is based on the tannakian philosophy. Through a tensor analog of skeletal categories we are able to consider neutral tannakian categories with a fibre functor as many-sorted first order structures. The theory of a diagonalizable proalgebraic group is well understood. It is determined by the theory of the base field and the theory of its character group. This is joint work with Anand Pillay.
URL:https://www.math.ens.psl.eu/evenement/model-theory-of-proalgebraic-groups/
LOCATION:Sophie Germain salle 2015
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191029T140000
DTEND;TZID=Europe/Paris:20191029T170000
DTSTAMP:20260419T005941
CREATED:20191029T130000Z
LAST-MODIFIED:20211104T135125Z
UID:8528-1572357600-1572368400@www.math.ens.psl.eu
SUMMARY:Après-midi de théorie de groupes
DESCRIPTION:14.00-14.45 Christophe Pittet (Genève)\, The exact convergence rate in the ergodic theorem of Lubotzky Phillips Sarnak.15.00-15.45 Thiebout Delabie (Orsay)\, High dimensional cuts and coarse embedding.16.15-17.00 Alina Vdovina (Newcastle)\, Ramanujan cubical complexes as higher-dimensional expanders.
URL:https://www.math.ens.psl.eu/evenement/apres-midi-de-theorie-de-groupes-5/
LOCATION:Salle W (DMA ENS)
CATEGORIES:Séminaire de théorie des groupes à l’ENS
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191022T160000
DTEND;TZID=Europe/Paris:20191022T173000
DTSTAMP:20260419T005941
CREATED:20191022T140000Z
LAST-MODIFIED:20211025T103725Z
UID:8526-1571760000-1571765400@www.math.ens.psl.eu
SUMMARY:The transitivity of Kim-independence
DESCRIPTION:The class of NSOP_1 theories contains the simple theories and many interesting non-simple theories\, such as the omega-free PAC fields or generic vector spaces with a non-degenerate bilinear form. With Itay Kaplan\, we introduced Kim-independence which agrees with non-forking independence within the simple theories and shares many of its nice properties within the simple NSOP_1 context. One very basic roadblock in lifting simplicity theory to the NSOP_1 setting\, however\, was transitivity: a free extension of a free extension should still be a free extension. This is almost immediate for non-forking extensions in a simple theory\, but becomes more involved for free extensions in the sense of Kim-independence. We will describe and motivate the basic theory\, and then discuss our recent proof of transitivity. This is joint with Itay Kaplan.
URL:https://www.math.ens.psl.eu/evenement/the-transitivity-of-kim-independence/
LOCATION:Sophie Germain salle 1016
CATEGORIES:Théorie des Modèles et Groupes
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Europe/Paris:20191011T160000
DTEND;TZID=Europe/Paris:20191011T173000
DTSTAMP:20260419T005941
CREATED:20191011T140000Z
LAST-MODIFIED:20211025T103721Z
UID:8524-1570809600-1570815000@www.math.ens.psl.eu
SUMMARY:H-minimality
DESCRIPTION:My goal\, in this talk\, is to explain a new notion of minimality for (characteristic zero) Henselian fields\, which generalizes C-minimality\, P-minimality and V-minimality and puts no restriction on the residue field or valued group contrary to these previous notions. This new notion\, h-minimality\, can be defined\, analogously to other minimality notions\, by asking that 1-types\, over algebraically closed sets\, are entirely determined by their reduct to some sublanguage – in that case the pure language of valued fields. However\, contrary to what happens with other minimality notions\, particular care has to be taken with regards to the parameters. In fact\, we define a family of notions: l-h-min for l a natural number or omega. My second goal in this talk will be to explain the various geometric properties that follow form h-minimality\, among which the well-known Jacobian property\, but also higher degree and higher dimensional versions of that property.
URL:https://www.math.ens.psl.eu/evenement/h-minimality/
LOCATION:ENS Salle W
CATEGORIES:Séminaire Géométrie et théorie des modèles
END:VEVENT
END:VCALENDAR