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Kita Kosuke
| Faculty of Science Mathematics Mathematics | Assistant Professor |
Researcher basic information
■ Degree■ URL
researchmap URLホームページURL■ Various IDs
Researcher number
- 50962445
Research KeywordResearch Field■ Educational Organization
- Bachelor's degree program, School of Science
- Master's degree program, Graduate School of Science
- Doctoral (PhD) degree program, Graduate School of Science
Career
■ CareerCareer
- Apr. 2025 - Present
Hokkaido University, Faculty of Science Department of Mathematics, 助教 - Apr. 2024 - Mar. 2025
Tohoku University, 理学研究科, 特任研究員（日本学術振興会特別研究員PD） - Apr. 2023 - Mar. 2024
Shibaura Institute of Technology, College of Systems Engineering and Science, 非常勤講師 - Apr. 2023 - Mar. 2024
Tokyo University of Science, Faculty of Science and Technology Mathematics, 非常勤講師 - Apr. 2022 - Mar. 2024
Waseda University, Faculty of Science and Engineering, 講師 - Apr. 2020 - Mar. 2022
日本学術振興会 特別研究員 DC2
- Apr. 2019 - Mar. 2022, Waseda University, Graduate School of Advanced Science and Engineering, 物理学及応用物理学専攻 博士課程
- Apr. 2017 - Mar. 2019, Waseda University, Graduate School of Advanced Science and Engineering, 物理学及応用物理学専攻 修士課程
- Apr. 2013 - Mar. 2017, Waseda University, School of Advanced Science and Engineering, 応用物理学科
Research activity information
■ Awards■ Papers
- Optimal design problem with thermal radiation
Kosuke Kita; Kei Matsushima; Tomoyuki Oka
Partial Differential Equations in Applied Mathematics, 16, 101304, 101304, Elsevier BV, Dec. 2025, [Peer-reviewed]
Scientific journal - Weighted $L^\infty$-estimates for solutions of the damped wave equation in three space dimensions and its application
Vladimir Georgiev; Kosuke Kita
Nonlinear Analysis, 260, 113850, 113850, Elsevier BV, Nov. 2025, [Peer-reviewed]
English, Scientific journal - A remark on the blowing up of solutions to Nakao's problem
Kosuke Kita; Ryunosuke Kusaba
Journal of Mathematical Analysis and Applications, 513, 1, 126199, 126199, Elsevier BV, Sep. 2022, [Peer-reviewed]
Scientific journal - On a comparison theorem for parabolic equations with nonlinear boundary conditions
Kosuke Kita; Mitsuharu Ôtani
Advances in Nonlinear Analysis, 11, 1, 1165, 1181, Walter de Gruyter GmbH, 09 Mar. 2022, [Peer-reviewed]
Scientific journal, Abstract
In this article, a new type of comparison theorem for some second-order nonlinear parabolic systems with nonlinear boundary conditions is given, which can cover classical linear boundary conditions, such as the homogeneous Dirichlet or Neumann boundary condition. The advantage of our comparison theorem over the classical ones lies in the fact that it enables us to compare two solutions satisfying different types of boundary conditions. As an application of our comparison theorem, we can give some new results on the existence of blow-up solutions of some parabolic equations and systems with nonlinear boundary conditions. - Bounds for global solutions of nonlinear heat equations with nonlinear boundary conditions
Kosuke Kita; Mitsuharu Ôtani
Libertas Mathematica (new series), 41, 1, 1, 22, 2021, [Peer-reviewed]
Scientific journal - Bounds for global solutions of a reaction diffusion system with the Robin boundary conditions
Kosuke Kita; Mitsuharu Ôtani
Differential Equations & Applications, 11, 2, 227, 242, Element d.o.o., 2019, [Peer-reviewed]
Scientific journal - On some parabolic systems arising from a nuclear reactor model with nonlinear boundary conditions
Kosuke Kita; Mitsuharu Ôtani; Hiroki Sakamoto
Advances in Mathematical Sciences and Applications, 27, 2, 193, 224, 2018, [Peer-reviewed]
Scientific journal
- On a weighted estimate of solutions to the damped wave equation and its application to Nakao's problem in 3D
Kosuke Kita, RIMS Kôkyûroku, 2324, Jul. 2025 - 非線形境界条件を伴う非線形熱方程式の大域解の有界性について
喜多 航佑, 第41回発展方程式若手セミナー報告集, 259, 264, 2020
Japanese, Introduction other - 非線形境界条件に支配される放物型方程式に対する比較定理とその応用について
喜多 航佑, Hokkaido University technical report series in Mathematics, 176, 319, 324, 2019
Japanese - On some parabolic systems arising from a nuclear reactor model (Theory of Evolution Equation and Mathematical Analysis of Nonlinear Phenomena)
Kita, Kosuke, RIMS Kôkyûroku, 2090, 42, 59, Sep. 2018
京都大学数理解析研究所, English - The uniform boundedness of global solutions for a reaction diffusion system
喜多 航佑, 第40回発展方程式若手セミナー報告集, 121, 128, 2018
Japanese, Introduction other - 原子炉モデルに起因するある反応拡散系について
喜多 航佑, 第39回発展方程式若手セミナー報告集, 125, 134, 2017
Japanese, Introduction other
- 有限デバイ長エネルギーの特異極限問題
喜多航佑
ブラソフ方程式とマックスウェル方程式、プラズマの数理 V, 18 May 2026, Japanese - 〔Major achievements〕Existence of global solutions to Nakao's problem in three dimensions
Kosuke Kita
The 43th Kyushu Symposium on Partial Differential Equations, 27 Jan. 2026, English
[Invited] - 空間3次元における中尾の問題の時間大域解の存在とその減衰評価について
喜多航佑
第15回室蘭非線形解析研究会, 29 Nov. 2025, Japanese
[Invited] - 有界領域上の非線形熱方程式と放射型境界条件
喜多航佑
北海道大学 数学科 談話会, 27 Nov. 2025, Japanese, Oral presentation - Existence of global solutions to Nakao's problem in three dimensions
喜多 航佑
The 22nd Linear and Nonlinear Waves, 06 Nov. 2025
[Invited] - Existence of global solutions to a system of a semilinear damped wave equation and a semilinear wave equation
喜多 航佑
楕円型・放物型微分方程式研究集会, 31 Oct. 2025
[Invited] - On the global existence and decay estimates of solutions to Nakao’s problem in three space dimensions
喜多 航佑
第 2 回北見数理科学研究会, 05 Sep. 2025
[Invited] - 〔Major achievements〕On the existence of global solutions to Nakao's problem in 3D
Kosuke Kita
The first Japan-Spain forum on PDEs and their applications, 28 Aug. 2025, English, Oral presentation
[Invited] - 〔Major achievements〕On weighted estimates of solutions to the damped wave equation in lower dimensions
Kosuke Kita
Workshop on Nonlinear Wave Equations, 09 Jun. 2025, English, Oral presentation
[Invited] - On weighted estimates of solutions to the damped wave equation in lower dimensions and its applications
喜多 航佑
偏微分方程式セミナー, 18 Apr. 2025, Japanese, Oral presentation - 消散波動方程式の解の重み付き評価とその非線形問題への応用
喜多 航佑
第 14 回 福島応用数学研究集会, 24 Mar. 2025, Japanese, Oral presentation
[Invited] - Existence of global solutions to Nakao's problem in three dimensions
喜多 航佑
反応拡散方程式と非線形分散型方程式の解の挙動, Feb. 2025, Japanese, Oral presentation
[Invited] - 空間3次元における中尾の問題に対する時間大域解の存在とその減衰について
喜多 航佑
第４０回 松山キャンプ, 12 Jan. 2025, Japanese, Oral presentation - Global existence of small solutions to Nakao's problem in three dimensions
喜多 航佑
第 19 回浜松偏微分方程式研究集会, 24 Dec. 2024, Japanese, Oral presentation
[Invited] - Weighted estimates for solutions to the damped wave equation in 3D and its application
喜多 航佑
Okayama Workshop on Partial Differential Equations, 26 Oct. 2024, Japanese, Oral presentation
[Invited] - 〔Major achievements〕On nonlinear heat equations with nonlinear boundary conditions in a bounded domain
Kosuke Kita
日本数学会2024年度秋季総合分科会 実函数論分科会 特別講演, Sep. 2024, Japanese, Invited oral presentation
[Invited] - On a weighted estimate for the solution to the damped wave equation and its application to Nakao's problem in 3D
Kosuke Kita
International Meeting on Recent Developments in the Wave Equation and Related Evolution Equations, Aug. 2024, English, Oral presentation
[Invited] - 空間3次元における中尾の問題について
喜多 航佑
第2回 信州若里偏微分方程式セミナー, 23 Apr. 2024, Oral presentation
22 Apr. 2024 - 23 Apr. 2024, [Invited] - On Nakao's problem in three space dimensions
喜多 航佑
東北大学応用数理解析セミナー, 11 Apr. 2024, Oral presentation
[Invited] - On a weighted estimate for the solution to the damped wave equation in 3D
Kosuke Kita
Workshop on Nonlinear Hyperbolic PDEs. On the occasion of 60th birthday of Professor Yi Zhou, 25 Nov. 2023, English, Invited oral presentation
24 Nov. 2023 - 25 Nov. 2023, [Invited] - 3次元消散型波動方程式の解の重み付き各点評価について
喜多 航佑
鳥取PDE研究集会2023, 23 Nov. 2023, Japanese, Invited oral presentation
[Invited] - 〔Major achievements〕On critical phenomena for Fujita type equation on a bounded domain characterized by boundary conditions
Kosuke Kita
Workshop on Nonlinear Partial Differential Equations China-Japan Joint Project for Young Mathematicians 2023, 19 Nov. 2023, English, Invited oral presentation
19 Nov. 2023 - 20 Nov. 2023, [Invited] - 3次元消散型波動方程式の解の重み付き各点評価について
喜多 航佑
第１８９回神楽坂解析セミナー, 28 Oct. 2023, Japanese, Invited oral presentation
[Invited] - On global and blow-up solutions to nonlinear heat equations with nonlinear boundary conditions
喜多 航佑; 大谷 光春
日本数学会2023年度秋季総合分科会, Sep. 2023, Japanese, Oral presentation - Weighted pointwise estimates for the damped wave equation in three dimensions
Kosuke Kita
International Workshop on “Fundamental Problems in Mathematical and Theoretical Physics”, 28 Jul. 2023, English, Invited oral presentation
25 Jul. 2023 - 29 Jul. 2023, [Invited] - A new weighted L∞ estimate for the damped wave equation in three dimensions
喜多 航佑
秋田発展方程式小研究集会, 08 Jul. 2023, Japanese, Invited oral presentation
[Invited] - On critical phenomena for nonlinear heat equations on bounded domains characterized by nonlinear boundary conditions
Kosuke Kita
The 13th AIMS Conference on Dynamical Systems, Differential Equations and Applications, 01 Jun. 2023
31 May 2023 - 04 Jun. 2023, [Invited] - On critical phenomena for nonlinear heat equations on bounded domains
喜多 航佑
東京理科大学創域理工学部数理科学科談話会, 19 May 2023, Japanese, Invited oral presentation
[Invited] - Mosco convergence of functionals associated with Laplacian under nonlinear boundary conditions
喜多 航佑; 大谷 光春
日本数学会2023年度年会, 18 Mar. 2023, Oral presentation - Global existence and blow-up of solutions to nonlinear heat equations with nonlinear boundary conditions
喜多 航佑
第38回さいたま数理解析セミナー, 20 Feb. 2023, Invited oral presentation
[Invited] - Weighted L^∞ estimates for solutions to the damped wave equation in three space dimensions and its application
喜多 航佑
第15回実解析と函数解析による微分方程式セミナー, Dec. 2022, Invited oral presentation
[Invited] - Weighted \(L^\infty\) estimates for solutions to the damped wave equation in three space dimensions
喜多 航佑
The Second One Day Workshop on Hyperbolic PDE in Kushiro, 19 Nov. 2022, Invited oral presentation
[Invited] - Existence and nonexistence of global solutions to nonlinear diffusion equations on a bounded domain
喜多 航佑; 大谷 光春
日本数学会2022年度秋季総合分科会, 16 Sep. 2022, Japanese, Oral presentation - Existence and nonexistence of global solutions to nonlinear diffusion equations with nonlinear boundary conditions
喜多 航佑
応用解析研究会, 07 May 2022
[Invited] - Existence and nonexistence of global solutions for nonlinear heat equations with nonlinear boundary conditions
喜多 航佑
Critical Exponent and Nonlinear Partial Differential Equations 2022, 18 Mar. 2022
[Invited] - Existence and nonexistence of global solutions for nonlinear heat equations on a bounded domain
喜多 航佑
The 18th Mathematics Conference for Young Researchers, 04 Mar. 2022 - Qualitative theory of solutions to parabolic equations with nonlinear boundary conditions
喜多 航佑
大分解析セミナー, 19 Feb. 2022
[Invited] - On the global existence and blow-up of solutions for nonlinear heat equations on bounded domains
喜多 航佑
第47回発展方程式研究会, 26 Dec. 2021 - Convergence of functional associated with Laplacian under nonlinear boundary conditions
喜多 航佑
第42回発展方程式若手セミナー, 30 Aug. 2021 - 非線形境界条件を伴う非線形熱方程式に対する臨界現象について
喜多 航佑
One Day Workshop抽象発展方程式のこれまでとこれから -動的境界条件への応用を見据えて-, 26 Jan. 2021
[Invited] - Comparison theorem for parabolic equations governed by nonlinear boundary conditions and its applications
喜多 航佑
International Workshop on Multiphase Flows: Analysis, Modelling and Numerics, 01 Dec. 2020
[Invited] - Comparison theorem for parabolic equations governed by nonlinear boundary conditions and its applications
喜多 航佑
第7回 Elliptic and Parabolic Zoom Seminar, 12 Sep. 2020
[Invited] - On some nonlinear heat equations with nonlinear boundary conditions of radiation type
喜多 航佑
第9回非線形発展方程式セミナー, 26 May 2020
[Invited] - A bound for global solutions of some parabolic equation with nonlinear boundary conditions
喜多 航佑
第45回発展方程式研究会, 26 Dec. 2019 - On some parabolic equations with nonlinear boundary conditions of radiation type
喜多 航佑
東北大学OS特別セミナー, 01 Nov. 2019
[Invited] - On the uniform boundedness for global solutions of nonlinear heat equations with nonlinear boundary conditions in bounded domain
喜多 航佑; 大谷 光春
日本数学会2019年度秋季総合分科会, 20 Sep. 2019 - 非線形境界条件を伴う非線形熱方程式の大域解の有界性について
喜多 航佑
第41回発展方程式若手セミナー, 29 Aug. 2019 - On the comparison theorem for parabolic equations governed by nonlinear boundary conditions
喜多 航佑; 大谷 光春
日本数学会2019年度年会, 20 Mar. 2019 - An abstract comparison theorem for parabolic equations governed by nonlinear boundary conditions
喜多 航佑
第26回応用解析研究会シンポジウム, 11 Mar. 2019 - 非線形境界条件に支配される放物型方程式に対する比較定理とその応用について
喜多 航佑
The 15th Mathematics Conference for Young Researchers, 04 Mar. 2019 - 非線形境界条件に支配される放物型方程式の初期値境界値問題に対する比較定理とその応用
喜多 航佑
第44回発展方程式研究会, 26 Dec. 2018 - Bounds for global solutions of a reaction diffusion system
喜多 航佑; 大谷 光春
日本数学会2018年度秋季総合分科会, 27 Sep. 2018 - The uniform boundedness of global solutions for a reaction diffusion system
喜多 航佑
第40回発展方程式若手セミナー, 30 Aug. 2018 - On some parabolic systems arising from a nuclear reactor model with nonlinear boundary conditions
喜多 航佑
12th AIMS Conference Series on Dynamical Systems and Differential Equations, 08 Jul. 2018
[Invited] - Some threshold property for a reaction diffusion system arising from a nuclear reactor model
喜多 航佑; 大谷 光春
日本数学会2018年度年会, 21 Mar. 2018 - Blow-up solutions for some parabolic systems arising from a nuclear reactor model
喜多 航佑
第25回応用解析研究会シンポジウム, 12 Mar. 2018 - 原子炉モデルに因る或る反応拡散系に対する解の時間大域挙動の閾値に就いて
喜多 航佑
第43回発展方程式研究会, 27 Dec. 2017 - On some parabolic systems arising from a nuclear reactor model
喜多 航佑
Theory of Evolution Equation and Mathematical Analysis of Nonlinear Phenomena, 18 Oct. 2017
[Invited] - On some elliptic systems arising from a nuclear reactor model
喜多 航佑; 大谷 光春
日本数学会2017年度秋季総合分科会, 14 Sep. 2017 - 原子炉モデルに起因するある反応拡散系について
喜多 航佑
第39回発展方程式若手セミナー, Sep. 2017 - 非線型境界条件を持つある反応拡散系の定常問題
喜多 航佑
第24回応用解析研究会シンポジウム, 13 Mar. 2017
■ Research Themes
- Mathematical analysis on nonlinear hyperbolic partial differential equations via lifespan estimates
二国間交流事業
Apr. 2025 - Dec. 2027
Takamura Hiroyuki; Kato Masakazu; Sasaki Takiko; Fujiwara Kazumasa; Wakasa Kouhei; Kita Kosuke; Lai Ning-An; Zhou Yi; Gao Junlei; Cai Lv; Fan Mengting; Zhou Jiang; Ren Cui; Zhou Kairui; Zhao Hongjie
JSPJ, Collaboration with China (NSFC), Tohoku University, Zhejiang Normal University, 120257401 - 時空重み付き評価を用いた消散型波動方程式に対する数学解析の新展開
科学研究費助成事業
Apr. 2024 - Mar. 2027
喜多 航佑
日本学術振興会, 特別研究員奨励費, 東北大学, 24KJ0010 - 拡散構造を持たない消散型波動方程式に対する大域可解性の理論の新展開
Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity Start-up
Aug. 2022 - Mar. 2024
喜多 航佑
Japan Society for the Promotion of Science, Grant-in-Aid for Research Activity Start-up, Waseda University, 22K20345 - 非線形境界条件を伴う反応拡散方程式系の数学解析
Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows
Apr. 2020 - Mar. 2022
喜多 航佑
本研究では有界領域における非線形境界条件を伴う非線形熱方程式の解の定性的性質に関する研究を実施した．特に，昨年度に構築した非線形境界条件を含むかなり一般の二階放物型方程式系に対する比較定理を応用し，有界領域における藤田型非線形熱方程式の大域解の存在に関する臨界現象が境界条件によって特徴付けられるという新たな結果を示した．即ち,全空間や半空間では，臨界現象が非線形項の冪の指数と空間次元によって特徴付けられるのに対して，有界領域では境界条件が支配的になるということを明らかにした．より具体的には種々の代表的な線形境界条件を含む非線形境界条件の枠組みにおいて，斉次ディリクレ境界条件と斉次ノイマン境界条件の中間に相当する臨界の境界条件を見出し，その境界条件よりも境界におけるエネルギー散逸が弱くなる境界条件でば全ての非負値非自明解が有限時間で爆発することを証明した．今後の展望としては，先ず1次元の有界区間の場合に上記の臨界境界条件の性質を詳細に調べ，より具体的な評価や爆発のプロファイルを導出することが挙げられる．
また，上記の臨界の境界条件を課した解は，冪乗型の非線形境界条件の解の冪に関する極限として実現されることを証明した．この結果は非線形発展方程式の主要部がなす汎函数がモスコ収束するときの解の収束に関する理論を摂動項付きの場合に拡張することで示した．その過程の中で，このモスコ収束と解の収束に関する抽象論は，具体的な放物型方程式(反応拡散方程式)に対する応用という観点からまだ不十分な箇所があると判明した．今後はこの抽象理論を自然な形で拡張することを計画している．
Japan Society for the Promotion of Science, Grant-in-Aid for JSPS Fellows, Waseda University, 20J11425
Industrial Property Rights
- The 51st Sapporo Symposium on Partial Differential Equations
05 Aug. 2026 - 07 Aug. 2026
Planning etc, Panel chair etc
Competition etc
Satoshi Masaki, Kosuke Kita
[Contributing to international academic research] - The 27th Northeastern Symposium on Mathematical Analysis
16 Feb. 2026 - 17 Feb. 2026
Planning etc
Academic society etc
Hideo Kubo, Kentaro Fujie, Kosuke Kita - One-day International Workshop on Dispersive Equations and Related Topics
09 Jan. 2026 - 09 Jan. 2026
Planning etc
Academic society etc
Satoshi Masaki, Kosuke Kita, Shun Tsuhara
46050669 - The 50th Sapporo Symposium on Partial Differential Equations
04 Aug. 2025 - 06 Aug. 2025
Planning etc, Panel chair etc
Competition etc
Hideo Kubo, Satoshi Masaki, Hirotoshi Kuroda, Nao Hamamuki, Kosuke Kita
