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Systematic research for differential geometry of regular surfaces in a wider sense

Research Project

Project/Area Number 20K03617
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Review Section Basic Section 11020:Geometry-related
Research InstitutionTokyo Denki University

Principal Investigator

Kokubu Masatoshi  東京電機大学, 工学部, 教授 (50287439)

Project Period (FY) 2020-04-01 – 2025-03-31
Project Status Completed (Fiscal Year 2024)
Budget Amount *help
¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2022: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000)
Fiscal Year 2021: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2020: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Keywords微分幾何 / 広義の正則性 / 解析的拡張 / 特異点 / 曲率 / 平均曲率 / 平坦 / 波面 / 対称性 / 正則性 / 微分幾何学 / 曲面
Outline of Research at the Start

曲面に関する数学の研究は長い歴史を持ち,正則曲面(滑らかな曲面)について非常にたくさんの研究があります.その研究対象を少し広い範囲に拡げて,研究に取り組むことが目的です.現在,広義正則曲面(得点を持つ曲面,異質な性質の混在する曲面)については何人かの研究者により様々な興味深い結果が導かれているところです.それらの本質的な部分に着目して,より体系的な理論構築への寄与を目指します.

Outline of Final Research Achievements

In addition to ordinary smooth surfaces, we focused on surfaces containing singularities and studied them geometrically and analytically as regular surfaces in a wider sense.In particular, for a catenoid of mean curvature 1 in 3-dimensional de Sitter space, we showed the existence of analytic extensions beyond the constraints of space and that they are analytically maximal.
In hyperbolic spaces, flat wavefronts with regular polyhedral symmetry were constructed, and five specific examples and their geometric features were identified. Moreover, new concepts such as analytic completeness and double cone manifolds were introduced to deepen our understanding of the structure of surfaces with singularities. We also discovered surfaces for which Gauss curvature contours are concentric circles. These results were made public through papers and conference presentations.

Academic Significance and Societal Importance of the Research Achievements

本研究では、特異点を許容する広義の正則曲面という新たな視点を導入し、従来の滑らかな曲面理論を拡張した。特に、de Sitter 空間内のカテノイドの解析的極大性の証明や、双曲空間における対称性をもつ波面の構成は、曲面の微分幾何に新たな知見を加えるものである。また、「解析的完備性」や「二重錐多様体」といった概念の提案は、複素解析や位相幾何との接点を広げ、今後の理論展開の足がかりとなる。さらに、Gauss 曲率の等高線構造に注目した研究は、曲面分類への新たな手がかりを提供している。

Report

(6 results)
  • 2024 Annual Research Report   Final Research Report ( PDF )
  • 2023 Research-status Report
  • 2022 Research-status Report
  • 2021 Research-status Report
  • 2020 Research-status Report
  • Research Products

    (9 results)

All 2024 2022 Other

All Int'l Joint Research (2 results) Journal Article (4 results) (of which Int'l Joint Research: 2 results,  Peer Reviewed: 4 results,  Open Access: 1 results) Presentation (3 results) (of which Invited: 2 results)

  • [Int'l Joint Research] Korea University(韓国)

    • Country Name
      KOREA (REP. OF KOREA)
    • Counterpart Institution
      Korea University
    • Related Report
      2024 Annual Research Report
  • [Int'l Joint Research] TU Wien(オーストリア)

    • Country Name
      AUSTRIA
    • Counterpart Institution
      TU Wien
    • Related Report
      2024 Annual Research Report
  • [Journal Article] Surfaces with concentric or parallel K- contours2024

    • Author(s)
      Shoichi Fujimori, Yu Kawakami, Masatoshi Kokubu
    • Journal Title

      Journal of Geometry

      Volume: 115 Pages: -

    • DOI

      10.1007/s00022-024-00719-4

    • Related Report
      2024 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Surfaces with concentric or parallel K-contours2024

    • Author(s)
      Shoichi Fujimori, Yu Kawakami, Masatoshi Kokubu
    • Journal Title

      Journal of Geometry

      Volume: 115 Pages: -

    • DOI

      10.1007/s00022-024-00719-4

    • Related Report
      2023 Research-status Report
    • Peer Reviewed
  • [Journal Article] Analytic extensions of constant mean curvature one geometric catenoids in de Sitter 3-space2022

    • Author(s)
      Shoichi Fujimori, Yu Kawakami, Masatoshi Kokubu, Wayne Rossman, Masaaki Umehara, Kotaro Yamada and Seong-Deog Yang
    • Journal Title

      Differential Geometry and Its Applications

      Volume: 84 Pages: -

    • DOI

      10.1016/j.difgeo.2022.101924

    • Related Report
      2022 Research-status Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Flat fronts with polyhedral symmetry in hyperbolic three-space2022

    • Author(s)
      Masatoshi Kokubu
    • Journal Title

      Journal of Geometry

      Volume: 113 Pages: -

    • DOI

      10.1007/s00022-022-00633-7

    • Related Report
      2021 Research-status Report
    • Peer Reviewed / Open Access / Int'l Joint Research
  • [Presentation] 同心円状または平行直線状の等 K 線をもつ曲面について2024

    • Author(s)
      川上裕,國分雅敏,藤森祥一
    • Organizer
      日本数学会秋季総合分科会
    • Related Report
      2024 Annual Research Report
  • [Presentation] On flat fronts with symmetry2022

    • Author(s)
      Masatoshi Kokubu
    • Organizer
      Workshop on Surface Theory --UY60--
    • Related Report
      2021 Research-status Report
    • Invited
  • [Presentation] Flat fronts in hyperbolic three-space and related topics2022

    • Author(s)
      國分雅敏
    • Organizer
      日本数学会本会
    • Related Report
      2021 Research-status Report
    • Invited

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Published: 2020-04-28   Modified: 2026-01-16  

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