Institut de Mathématiques de Toulouse

Les événements de la journée


6 événements


  • Séminaire de Probabilités

    Mardi 10 octobre 10:00-10:45 - Sylvie Méléard - Ecole Polytechnique

    The effect of competition and horizontal inheritance on invasion, fixation and evolution

    Résumé : In a large range of species, horizontal transfer of information, such as genetic mobile elements, plasmids, endosymbionts or cultural traits, affects the adaptation of populations and the evolution of species. Understanding how they are affected is a huge challenge, in particular for microorganisms since it plays a main role in the virulence evolution or in bacterial antibiotics resistances. We propose a general eco-evolutionary stochastic model of population dynamics with clonal reproduction and mutations, including competition for resources and exchange of genes, as in the conjugation for plasmids in bacteria cells. We study different asymptotics of this general birth and death process depending on the respective demographic, ecological and transfer time scales and on the population size. We show how the gene transfer can drastically affect the evolutionary outcomes.

    Lieu : Amphithéâtre Schwartz

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  • Séminaire de Géométrie et Topologie

    Mardi 10 octobre 11:00-12:00 - Arthur Renaudineau

    Topologie des courbes algébriques réelles planes et version tropicale du patchwork.

    Résumé : La méthode du patchwork a été inventé par Viro dans les années 80 et lui a permit notamment de finir la classification des courbes algébriques réelles planes de degré 7. Dans cet exposé, nous présenterons une version tropicale de la méthode du patchwork ainsi que quelques unes de ses conséquences (travail en commun avec B.Bertrand et E.Brugallé). Cette version tropicale apporte un nouvel éclairage à la méthode originelle et donne l’espoir d’avancer dans l’étude de la topologie des variétés algébriques réelles en dimension supérieure.

    Lieu : Salle Pellos (1R2, 207)

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  • Séminaire de Statistique

    Mardi 10 octobre 11:00-12:00 - Etienne Roquain - UPMC

    Post hoc inference via joint family-wise error rate control

    Résumé : We introduce a general methodology for post hoc inference in a large-scale multiple testing framework. The approach is called "user-agnostic" in the sense that the statistical guarantee on the number of correct rejections holds for any set of candidate items selected by the user (after having seen the data). This task is investigated by defining a suitable criterion, named the joint-family-wise-error rate (JER for short). We propose several procedures for controlling the JER, with a special focus on incorporating dependencies while adapting to the unknown quantity of signal (via a step-down approach). We show that our proposed setting incorporates as particular cases a version of the higher criticism as well as the closed testing based approach of Goeman and Solari (2011). Our theoretical statements are supported by numerical experiments.
    https://arxiv.org/abs/1703.02307

    Lieu : Salle 106, Bat 1R1

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  • Homotopie en Géométrie Algébrique

    Mardi 10 octobre 14:00-15:00 - Yonatan Harpaz - Paris 13, CNRS

    Quillen obstruction theory

    Résumé : Quillen’s abstract notion of cohomology, set up in Lurie’s infinity-categorical cotangent complex formalism, yields a natural form of cohomology which encompasses many classical well-studied invariants, including generalized cohomology of spaces, groups and various types of algebras. In addition, a relative variant of Quillen cohomology is the natural recipient for obstructions to the existence of lifts against a special class maps, known as small extensions. The notion of a small extension takes a variety of diverse forms in different contexts. For example, a torsor under an infinite loop space and a first order deformation of a dg-algebra are both examples of small extensions. This point of view allows one to study the classical Bousfield-Kan obstruction theory for maps between spaces, and the obstructions arising in deformation theory, in a unified setting. In this talk we will present joint work with Matan Prasma and Joost Nuiten whose goal is to make the above Quillen cohomology and associated obstruction theory accessible and computable in various higher categorical contexts of interest. This can be used, for example, to study the deformation theory of dg-categories with various types of monoidal structures, an application which is the topic of current work in progress.

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  • Homotopie en Géométrie Algébrique

    Mardi 10 octobre 15:30-16:30 - Massimo Pippi - IMT

    Rappels sur les catégories de modèles I

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