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2020 Fiscal Year Annual Research Report

Gジップを用いた志村多様体の幾何と法p保型形式の研究

Research Project

Project/Area Number 18F18311
Research InstitutionSaitama University
Co-Investigator(Kenkyū-buntansha) Koskivirta Jean・Stefan  埼玉大学, 理工学研究科, 助教 (00897613)
Project Period (FY) 2018-11-09 – 2021-03-31
Keywords志村多様体 / Gジップのスタック / 法p保型形式
Outline of Annual Research Achievements

I conducted research in the field of Number theory and algebraic geometry. In particular, I studied the space of global sections of automorphic vector bundles on the stack of G-zips of Pink-Wedhorn-Ziegler. In a joint paper with Naoki Imai, we determined this space for a general reductive group in terms of the Brylinski-Kostant filtration. This paper was published in Forum of Mathematics, Sigma in April 2021. I also started several related projects with Imai and Goldring that will be submitted this month for publication. One project is related to the construction of partial Hasse invariants, the other has to do with understanding which weights admit nonzero automorphic forms in characteristic p. Specifically, we construct automorphic forms in characteristic p whose vanishing locus is a given codimension one stratum in the flag space of a Shimura variety. We show that this form always exists and lies in the subvector bundles attached to the socle of the representation. In the second project, we prove several results regarding the zip cone, that was introduced in a previous paper. In particular, we show that if a certain explicit condition on the Galois action is satisfied, then the zip cone is spanned over the positive rationals by the weights of partial Hasse invariants (constructed in the first paper). I presented my research at several institutions.

Research Progress Status

令和2年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

令和2年度が最終年度であるため、記入しない。

  • Research Products

    (4 results)

All 2021 2020

All Journal Article (1 results) (of which Peer Reviewed: 1 results) Presentation (3 results) (of which Invited: 3 results)

  • [Journal Article] Automorphic vector bundles on the stack of G-zips2021

    • Author(s)
      Imai, N., Koskivirta, J.-S.
    • Journal Title

      Forum of Mathematics, Sigma

      Volume: 9 Pages: 0-31

    • DOI

      10.1017/fms.2021.32

    • Peer Reviewed
  • [Presentation] Partial Hasse invariants on the flag space of Shimura varieties2020

    • Author(s)
      Koskivirta, J.-S.
    • Organizer
      Centre de Recherche Mathematique, University of Montreal. "Workshop on Serre weights conjectures and geometry of Shimura varieties" (via zoom)
    • Invited
  • [Presentation] Automorphic vector bundles and G-zips2020

    • Author(s)
      Koskivirta, J.-S.
    • Organizer
      University of Stockholm, Number Theory seminar (via Zoom)
    • Invited
  • [Presentation] Abelian varieties and stacks of G-zips2020

    • Author(s)
      Koskivirta, J.-S.
    • Organizer
      RIMS Conference "Theory and Applications of Supersingular Curves and Supersingular Abelian Varieties"
    • Invited

URL: 

Published: 2021-12-27  

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