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Complete reducibility, geometric invariant theory, spherical buildings: a new approach to representations of algebraic groups

Research Project

Project/Area Number 19K14516
Research Category

Grant-in-Aid for Early-Career Scientists

Allocation TypeMulti-year Fund
Review Section Basic Section 11010:Algebra-related
Research InstitutionSoka University

Principal Investigator

Uchiyama Tomohiro  創価大学, 国際教養学部, 講師 (60822088)

Project Period (FY) 2019-04-01 – 2022-03-31
Project Status Completed (Fiscal Year 2021)
Budget Amount *help
¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
Fiscal Year 2021: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2020: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Keywords代数群 / 代数幾何学 / 組み合わせ幾何学 / 数論 / 幾何学的不変式論 / 球面式建物 / algebraic groups / invariant theory / spherical buildings / representation theory
Outline of Research at the Start

We study Serre's notion of complete reducibility of subgroups of reductive algebraic groups (matrix groups) via geometric invariant theory (a branch of algebraic geometry) and the theory of spherical buildings (highly combinatorial objects).

Outline of Final Research Achievements

In this project, we studied Serre's notion of complete reduciblity of subgroups of reductive algebraic groups using "geometric invariant theory" (a part of algebraic geometry) and "the theory of spherical buildings (highly symmetrical combinatorial objects). So far, the study of complete reducibility had been done by representation theoretic methods that were ad hoc, using different arguments depending on the "types" of reductive algebraic groups. In this research, I invented a unified method via geometric invariant theory and the theory of spherical buildings proving various results concerning complete reducibility in very short arguments.

Academic Significance and Societal Importance of the Research Achievements

これまでタイプ別に分析されていた代数群の構造に幾何学的不変式論を用いた統一的理解とビルディングの理論を用いたトポロジー的解釈を与え、より構造を理解しやすくした。またこれまでほとんど分析されてこなかったより複雑な代数群のケース(体がperfectでないケース)に幾何学的不変式論を適用するとこれまで通りの結果が成り立つ場合と成り立たない場合がある事を具体例を使ってその原因とともに示した。この結果は特に数論への応用に対して重要であると考えられ、今後の発展がより期待される。

Report

(4 results)
  • 2021 Annual Research Report   Final Research Report ( PDF )
  • 2020 Research-status Report
  • 2019 Research-status Report
  • Research Products

    (9 results)

All 2021 2019 Other

All Int'l Joint Research (6 results) Journal Article (2 results) (of which Int'l Joint Research: 2 results,  Peer Reviewed: 2 results) Presentation (1 results) (of which Int'l Joint Research: 1 results,  Invited: 1 results)

  • [Int'l Joint Research] University of Essex(英国)

    • Related Report
      2021 Annual Research Report
  • [Int'l Joint Research] Ruhr University Bochum(ドイツ)

    • Related Report
      2021 Annual Research Report
  • [Int'l Joint Research] University of Essex(英国)

    • Related Report
      2020 Research-status Report
  • [Int'l Joint Research] Ruhr university of Bochum(ドイツ)

    • Related Report
      2020 Research-status Report
  • [Int'l Joint Research] Ruhr University Bochum(ドイツ)

    • Related Report
      2019 Research-status Report
  • [Int'l Joint Research] University of Aberdeen/University of Essex(英国)

    • Related Report
      2019 Research-status Report
  • [Journal Article] Complete reducibility of subgroups of reductive algebraic groups over non-perfect fields IV: An F4 example2021

    • Author(s)
      Bannuscher Falk、Litterick Alastair、Uchiyama Tomohiro
    • Journal Title

      Journal of Group Theory

      Volume: 0 Issue: 3 Pages: 527-541

    • DOI

      10.1515/jgth-2020-0191

    • Related Report
      2021 Annual Research Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Complete reducibility of subgroups of reductive algebraic groups over non perfect fields III2019

    • Author(s)
      Tomohiro Uchiyama
    • Journal Title

      Communications in Algebra

      Volume: 47 Issue: 12 Pages: 49284944-49284944

    • DOI

      10.1080/00927872.2019.1602873

    • Related Report
      2019 Research-status Report
    • Peer Reviewed / Int'l Joint Research
  • [Presentation] Rationality problems for complete reducibility2019

    • Author(s)
      Tomohiro Uchiyama
    • Organizer
      Summer School: Perspectives in Linear Algebraic Groups
    • Related Report
      2019 Research-status Report
    • Int'l Joint Research / Invited

URL: 

Published: 2019-04-18   Modified: 2023-01-30  

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