Updated on 2025/04/03

写真a

 
KONDO Kei
 
Organization
Faculty of Environmental, Life, Natural Science and Technology Professor
Position
Professor
Profile

資格・免許:乗馬ライセンス5級(2023年5月取得)

External link

Degree

  • Doctor of Science ( 2003.3   Saga University )

  • Master of Science ( 2000.3   Sophia University )

Research Interests

  • Origami

  • Differentiable Geometry, Exotic Structure, Nonsmooth Analysis

  • Minimal Submanifolds via the PDE Aspects

  • Exotic Structures

  • Nonsmooth Analysis

  • Global Riemannian Geometry

Research Areas

  • Natural Science / Geometry  / Differential Geometry

Education

  • Saga University   大学院 工学系研究科 博士後期課程  

    2000.10 - 2003.3

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    Notes: 指導教官:塩濱勝博先生

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  • Sophia University   大学院 理工学研究科 博士後期課程  

    2000.4 - 2000.9

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    Notes: 指導教官:宮岡礼子先生 / 中退

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  • Sophia University   大学院 理工学研究科 博士前期課程  

    1998.4 - 2000.3

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    Notes: 指導教官:金行壯二先生

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  • Tokyo Gakugei University    

    1994.4 - 1998.3

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    Notes: 指導教官:関沢正躬先生

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  • 西南学院高等学校    

    1991.4 - 1994.3

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Research History

  • Okayama University   学術研究院 環境生命自然科学学域 理学系   Professor

    2023.4

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    Notes:理学部 数学科・大学院 環境生命自然科学研究科 環境生命自然科学専攻

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  • Okayama University   Faculty of Natural Science and Technology   Professor

    2021.4 - 2023.3

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  • Okayama University   The Graduate School of Natural Science and Technology   Professor

    2019.9 - 2021.3

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    Notes:理学部 数学科 兼担

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  • Yamaguchi University   大学院 創成科学研究科   Associate Professor

    2016.4 - 2019.8

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  • Kyushu University   大学院 数理学府

    2017.4 - 2017.9

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    Notes:集中講義

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Professional Memberships

Committee Memberships

  • Faculty of Science, Okayama University   Vice Dean  

    2025.4   

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  • The Mathematical Journal of Okayama University   Editor-in-Chief  

    2024.4   

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  • The American Mathematical Society   A reviewer for Mathematical Reviews  

    2022.10   

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    Committee type:Academic society

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  • Faculty of Natural Science and Technology, Okayama University   the Chairperson of Division of Mathematics and Physics (Doctor's Course)  

    2021.4 - 2022.3   

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  • Department of Mathematics, Faculty of Science, Okayama University   the Chairperson of Department of Mathematics  

    2021.4 - 2022.3   

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Papers

  • Approximations of Lipschitz maps via Ehresmann fibrations and Reeb's sphere theorem for Lipschitz functions Reviewed

    Kei KONDO

    Journal of the Mathematical Society of Japan   74 ( 2 )   521 - 548   2022.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Mathematical Society of Japan (Project Euclid)  

    DOI: 10.2969/jmsj/83448344

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  • On sufficient conditions to extend Huber's finite connectivity theorem to higher dimensions Reviewed

    Kei Kondo, Yusuke Shinoda

    TOHOKU MATHEMATICAL JOURNAL   73 ( 3 )   463 - 470   2021.9

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    Publishing type:Research paper (scientific journal)  

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  • Differentiable sphere theorems whose comparison spaces are standard spheres or exotic ones Reviewed

    Kei Kondo, Minoru Tanaka

    Kodai Mathematical Journal   43 ( 2 )   349 - 365   2020.6

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    Language:English   Publishing type:Research paper (scientific journal)  

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  • Approximations of Lipschitz maps via immersions and differentiable exotic sphere theorems Reviewed

    Kei Kondo, Minoru Tanaka

    NONLINEAR ANALYSIS-THEORY METHODS & APPLICATIONS   155   219 - 249   2017.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    As our main theorem, we prove that a Lipschitz map from a compact Riemannian manifold M into a Riemannian manifold N admits a smooth approximation via immersions if the map has no singular points on M in the sense of F.H. Clarke, where dim M <= dim N. As its corollary, we have that if a bi-Lipschitz homeomorphism between compact manifolds and its inverse map have no singular points in the same sense, then they are diffeomorphic. We have three applications of the main theorem: The first two of them are two differentiable sphere theorems for a pair of topological spheres including that of exotic ones. The third one is that a compact n-manifold M is a twisted sphere and there exists a bi-Lipschitz homeomorphism between M and the unit n-sphere S-n (1) which is a diffeomorphism except for a single point, if M satisfies certain two conditions with respect to critical points of its distance function in the Clarke sense. Moreover, we have three corollaries from the third theorem; the first one is that for any twisted sphere Sigma(n) of general dimension n, there exists a bi-Lipschitz homeomorphism between Sigma(n) and S-n (1) which is a diffeomorphism except for a single point. In particular, there exists such a map between an exotic n-sphere Sigma(n) of dimension n > 4 and S-n (1); the second one is that if an exotic 4-sphere Sigma(4) exists, then Sigma(4) does not satisfy one of the two conditions above; the third one is that for any Grove-Shiohama type n-sphere N, there exists a bi-Lipschitz homeomorphism between N and S-n (1) which is a diffeomorphism except for one of points that attain their diameters. (C) 2017 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.na.2017.01.022

    Web of Science

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  • GROVE-SHIOHAMA TYPE SPHERE THEOREM IN FINSLER GEOMETRY Reviewed

    Kei Kondo

    OSAKA JOURNAL OF MATHEMATICS   52 ( 4 )   1143 - 1162   2015.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:OSAKA JOURNAL OF MATHEMATICS  

    From radial curvature geometry's standpoint, we prove a few sphere theorems of the Grove-Shiohama type for certain classes of compact Finsler manifolds.

    Web of Science

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Presentations

  • On the extension of Reeb-Milnor-Rosen's sphere theorem to Lipschitz functions, Pt.2 Invited

    Kei KONDO

    Tsukuba Global Riemannian Geometry  2023.3.7 

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    Event date: 2023.3.6 - 2023.3.7

    Presentation type:Oral presentation (invited, special)  

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  • On the extension of Reeb-Milnor-Rosen's sphere theorem to Lipschitz functions, Pt.1 Invited

    Kei KONDO

    Tsukuba Global Riemannian Geometry  2023.3.6 

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    Event date: 2023.3.6 - 2023.3.7

    Presentation type:Oral presentation (invited, special)  

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  • 特別講演:薄滑解析と微分球面定理 Invited

    近藤 慶

    日本数学会, 2016 年度 秋季総合分科会  2016.9.15  日本数学会

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:関西大学  

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  • Non-smooth analysis and differentiable sphere theorems Invited International conference

    KONDO Kei

    RIMS Project 2016: Differential Geometry and Geometric Analysis: Geometric analysis on Riemannian and metric spaces  2016.9.8 

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    Language:English   Presentation type:Oral presentation (invited, special)  

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  • 基調講演:フィンスラー多様体の旗曲率と位相の関係(角度の観点から) Invited

    近藤 慶

    第60 回幾何学シンポジウム  2013.8.25  日本数学会幾何分科会

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    Language:Japanese   Presentation type:Oral presentation (keynote)  

    Venue:東京工業大学  

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Works

  • 展覧会『すでにある秘密』–「放射曲率と位相の関係」

    近藤 慶

    2007.7.17
    -
    2007.7.24

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    Work type:Artistic work  

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Awards

  • 第6回写真新世紀展・奨励賞

    1997.12   Canon  

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  • 第15回写真新世紀公募・佳作入賞

    1997.2   Canon  

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Research Projects

  • Is it possible to mathematically formulate origami for materials with the property of stretching and shrinking?

    Grant number:22K03288  2022.04 - 2027.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    近藤 慶, 谷口 雅治, 物部 治徳

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    Authorship:Principal investigator 

    Grant amount:\3900000 ( Direct expense: \3000000 、 Indirect expense:\900000 )

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  • The application of nonsmooth analysis to the collapsing theory and exotic structure

    Grant number:17K05220  2017.04 - 2022.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    KONDO Kei

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    Authorship:Principal investigator 

    Grant amount:\4160000 ( Direct expense: \3200000 、 Indirect expense:\960000 )

    The aim of this study was to establish and develop the singularity theory of Lipschitz maps on Riemannian manifolds from the viewpoint of nonsmooth analysis. The results obtained in this study were: the intrinsic formulation and maintenance of various concepts in nonsmooth analysis on Riemannian manifolds (including a generalization of Clarke's inverse function theorem); the definition of the adjoint of the generalized differential of Lipschitz maps between Riemannian manifolds; the establishment of an approximation theorem for Lipschitz maps between Riemannian manifolds by locally trivial fibrations; and the generalization of Reeb's sphere theorem to general Lipschitz functions as an application of the approximation theorem. In relation to exotic structures, a new differential exotic sphere theorem was obtained from the standpoint of radial curvature geometry.

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  • A construction of the thery of homogeneous surfaces in Riemannian symmetric spaces

    Grant number:16K05133  2016.04 - 2021.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Naitoh Hiroo

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    Authorship:Coinvestigator(s) 

    Grant amount:\3900000 ( Direct expense: \3000000 、 Indirect expense:\900000 )

    This research is positioned as the initial research of a research project that considers the classification of homogeneous submanifolds in the Riemannian symmetric spaces from the viewpoint of the Grassmann geometry of submanifolds, and
    the target submanifolds are limited to surfaces. The results obtained in this research led to the construction of a general theory regarding the framework of the Grassmann geometry of surfaces, and as a related research, gave the completion of the surface theory of Grassmann geometry in the three-dimensional Riemannian homogeneous space.

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  • A variational problem on conformality of maps and a variational problem on pullbacks of metrics

    Grant number:18K03280  2018.04 - 2022.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Nakauchi Nobumitsu

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    Authorship:Coinvestigator(s) 

    Grant amount:\4550000 ( Direct expense: \3500000 、 Indirect expense:\1050000 )

    A "manifold", or in particular "Riemannian manifold" is a general concept of "a (curved) space", and a "map" between manifolds gives a "relation" between them. The researcher in this research project introduced two new concepts "C-stationary maps" and "symphonic maps" for maps between Riemannian manifolds. In this project we give some new steps and results on these two concepts.

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  • Research on a variational problem related to conformal maps and a variational problem of pullback of metrics

    Grant number:15K04846  2015.04 - 2019.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Nakauchi Nobumitsu

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    Authorship:Coinvestigator(s) 

    Grant amount:\4680000 ( Direct expense: \3600000 、 Indirect expense:\1080000 )

    I focused on a covariant tensor for a smooth map f between Riemannian manifolds. This tensor vanishes if and only if such a map f is weakly conformal. I introduced an integral quantity and a concept of C-stationary map using this tensor and give some results on these maps. Furthermore I decomposed the quantity and obtained a functional of an integral of pullbacks of metrics. Using this functional, I introduced a concept of symphonic map, which is a counterpart of the concept of harmonic maps in a viewpoint of pullbacks of metrics. I give some results on these maps.

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Other research activities

  • 2016年度 山口大学理学部サイエンス・セッションU18,山口大学

    2017.03

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    本セッションは,山口県内および島根県の高校生が数学・理科に関する課題研究の成果を発表する山口大学理学部主催の研究発表会。本セッションにて数学部門の審査委員を勤めた。

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  • SSH (スーパー・サイエンス・スクール),山口大学

    2016.08

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    体験学習講師として,徳山高校の学生に対しn次元球面のオイラー標数 (公式) の求め方についての講義を行った。

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  • 第3回 山口県数理教育研究大会,山口県セミナーパーク,山口県

    2015.03

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    本大会は,山口県内の高校生が数学・理科に関する課題研究の成果を発表する山口県庁主催の研究発表会。本大会にて数学部門の審査委員を勤めた。

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  • やまぐちサイエンス・キャンプ–科学オリンピックへの道,山口県セミナーパーク,山口県

    2014.12

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    本キャンプは,科学オリンピックに向けて山口県内の高校生の論理的思考力・観察実験の技能の伸長を図ることを目的とした山口県庁主催のキャンプである。本キャンプにて数学部門の講師を勤めた。

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Class subject in charge

  • Advanced Practice in Global Riemannian Geometry 1 (2024academic year) Prophase  - その他

  • Advanced Practice in Global Riemannian Geometry 2 (2024academic year) Late  - その他

  • Advanced Practice in Global Riemannian Geometry 3 (2024academic year) Prophase  - その他

  • Advanced Practice in Global Riemannian Geometry 4 (2024academic year) Late  - その他

  • Advanced Lecture on Manifolds (2024academic year) Late  - 月5~6

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Academic Activities

  • 部分多様体幾何とリー群作用2023〜小池直之先生還暦記念研究集会〜

    Role(s):Planning, management, etc.

    小池 直之、田中 真紀子、馬場 蔵人(東京理科大学)  2023.11.20 - 2023.11.21

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  • The 23rd International Differential Geometry Workshop on Submanifolds in Homogeneous Spaces and Related Topics, The 19th RIRCM-OCAMI Joint Differential Geometry Workshop

    Role(s):Planning, management, etc.

    2021.7.2 - 2021.7.3

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  • The Cut Locus: A Bridge over Differentiable Geometry, Optimal Control, and Transport

    Role(s):Planning, management, etc., Panel moderator, session chair, etc., Supervision (editorial)

    2018.9.3 - 2018.9.6

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  • King Mongkut's Institute of Technology\\ \hspace{13.5mm}Ladkrabang,Bangkok,Thailand

    Role(s):Planning, management, etc., Panel moderator, session chair, etc., Supervision (editorial)

    2016.8.3 - 2016.8.6

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  • 内藤博夫先生退職記念研究集会(山口大学 理学部)

    Role(s):Planning, management, etc., Panel moderator, session chair, etc., Supervision (editorial)

    2016.3.5 - 2016.3.7

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