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<< Oktober 2017

Veranstaltungskalender November 2017

Dezember 2017 >>

3 Einträge gefunden

  • 02. November
    17:00 - 18:00
    Ort: 48-436
    AG Algebra, Geometrie und Computer Algebra

    Caroline Lassueur: Lifting Morita equivalences with an endo-permutation source

    Motivated by current work of Boltje-Kessar-Linckelmann on the Picard group of Morita self-equivalences with endo-permutation source, we consider the problem of whether Morita equivalences with an endo-permutation source are liftable from positive characteristic to characteristic zero in general. The first part of the talk will give a gentle introduction to the concepts of vertices, sources and multiplicity modules in modular representation theory, while the second part of the talk will focus on the aforementioned lifting problem.

  • 16. November
    17:00 - 18:00
    Ort: 48-436
    AG Algebra, Geometrie und Computer Algebra

    Olivier Dudas, Université Paris Diderot: On the unitriangular shape of decomposition matrices for finite reductive group

    In order to classify the unipotent characters of finite reductive groups, Kawanaka constructed a family of representations induced from 'almost' unipotent groups, and conjectured a multiplicity formula for the unipotent constituents of these representations. I will explain how one can prove this formula providing some mild assumptions on unipotent classes. This can be used to show that the decomposition matrices of unipotent blocks have unitriangular shape. This is a joint work with O. Brunat and J. Taylor.

  • 23. November
    17:00 - 18:00
    Ort: 48-436
    AG Algebra, Geometrie und Computer Algebra

    Reda Chaneb, Université Paris Diderot: Basic sets for unipotent blocks of finite reductive groups

    Let G(q) be a finite group of Lie type and l be a prime number not dividing q. Geck and Hiss have proved that, if l is good, the restriction of unipotent characters to l-regular elements is a basic set for unipotent blocks of G(q). When l is bad, there are usually not enough unipotent characters to form a basic set. An alternative strategy to get a basic set is to construct projective characters satisfying some properties. For classical groups with connected center and l=2, by using a family of projective representations constructed by Kawanaka, Geck proved the existence of a basic set such that the decomposition matrix of the unipotent block has a unitriangular shape for this basic set. I will introduce those results and present generalizations of the results of Geck for the case of groups with disconnected center.