YOKOYAMA KEITA 横山啓太

… Alternative Names

YOKOYAMA Keita 横山啓太

横山啓太ヨコヤマケイタ

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Researcher Number	10534430
Other IDs	https://orcid.org/0000-0001-5329-3298
Affiliation (Current)	2025: 東北大学, 理学研究科, 教授
Affiliation (based on the past Project Information) *help	2021 – 2023: 東北大学, 理学研究科, 教授 2022: 東北大学, 理学(系)研究科(研究院), 教授 2021: 東北大学, 先端科学技術研究科, 講師 2018 – 2020: 北陸先端科学技術大学院大学, 先端科学技術研究科, 講師 2019: 東北大学, 先端科学技術研究科, 講師 … More 2016 – 2017: 北陸先端科学技術大学院大学, 先端科学技術研究科, 助教 2013 – 2015: 北陸先端科学技術大学院大学, 情報科学研究科, 助教 2011: Tohoku University, 理学(系)研究科(研究院), 助教 2009 – 2010: Tohoku University, 大学院・理学研究科, 助教 Less
Review Section/Research Field	Principal Investigator Basic Section 12030:Basic mathematics-related / Foundations of mathematics/Applied mathematics / Basic Section 12030:Basic mathematics-related / General mathematics (including Probability theory/Statistical mathematics) Except Principal Investigator Medium-sized Section 12:Analysis, applied mathematics, and related fields / Foundations of mathematics/Applied mathematics / General mathematics (including Probability theory/Statistical mathematics)
Keywords	Principal Investigator 逆数学 / 計算可能性理論 / 証明論 / ラムゼイの定理 / 数学基礎論 / 超準モデル / クリプキモデル / 組み合わせ論 / 算術 / 数理論理学 … More / 2階算術 / 非可述的公理 / 強制翻訳 / 決定可能性公理 / 算術の超準モデル / パラメータ付き計算量 / 反映原理 / 強制法 / 算術のモデル理論 / 計算可能性 / 組み合わせ理論 / 原始再帰的関数 / 指標関数 / Ekelandの定理 / 組み合わせ命題 / 証明の長さ / 計算量理論 / ２階算術 / 再帰理論 / 超準解析学 … More Except Principal Investigator 証明論 / 逆数学 / 数学基礎論 / 超準モデル / 計算可能性理論 / プログラム抽出・合成 / 構成的数学 / 超算術的公理 / 論理公理の階層 / 直観主義算術 / 構成的逆数学 / 算術的超限再帰 / 論理的公理の階層 / 構成的位相数学 / 構成的算術 / 構成的集合論 / ランダム決定木 / ゲームの決定性 / ランダム性 Less

New frontiers in reverse mathematics with the multidimensional perspectivePrincipal Investigator
- Principal Investigator
  
  横山啓太
- Project Period (FY)
  2023 – 2025
- Research Category
  
  Grant-in-Aid for Scientific Research (C)
- Review Section
  
  Basic Section 12030:Basic mathematics-related
- Research Institution
  Tohoku University
逆数学における分割順序数Principal Investigator
- Principal Investigator
  
  横山啓太
- Project Period (FY)
  2022 – 2023
- Research Category
  
  Grant-in-Aid for JSPS Fellows
- Review Section
  
  Basic Section 12030:Basic mathematics-related
- Research Institution
  Tohoku University
Constructive reverse mathematics and computational content of mathematical theorems
- Principal Investigator
  
  石原哉
- Project Period (FY)
  2021 – 2025
- Research Category
  
  Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))
- Review Section
  
  Medium-sized Section 12:Analysis, applied mathematics, and related fields
- Research Institution
  Toho University
  Japan Advanced Institute of Science and Technology
Approaching proof theory from the viewpoint of proof sizePrincipal Investigator
- Principal Investigator
  
  YOKOYAMA Keita
- Project Period (FY)
  2019 – 2023
- Research Category
  
  Grant-in-Aid for Scientific Research (C)
- Review Section
  
  Basic Section 12030:Basic mathematics-related
- Research Institution
  Tohoku University
  Japan Advanced Institute of Science and Technology
Expanding reverse mathematics with multiple viewpointsPrincipal Investigator
- Principal Investigator
  
  Yokoyama Keita
- Project Period (FY)
  2016 – 2019
- Research Category
  
  Grant-in-Aid for Young Scientists (B)
- Research Field
  
  Foundations of mathematics/Applied mathematics
- Research Institution
  Japan Advanced Institute of Science and Technology
Phase transitions of provability and supercritical propositions of reverse mathematics
- Principal Investigator
  
  Tanaka Kazuyuki
- Project Period (FY)
  2015 – 2019
- Research Category
  
  Grant-in-Aid for Scientific Research (B)
- Research Field
  
  Foundations of mathematics/Applied mathematics
- Research Institution
  Tohoku University
The start-up for reverse mathematics from various anglesPrincipal Investigator
- Principal Investigator
  
  YOKOYAMA Keita
- Project Period (FY)
  2013 – 2014
- Research Category
  
  Grant-in-Aid for Research Activity Start-up
- Research Field
  
  Foundations of mathematics/Applied mathematics
- Research Institution
  Japan Advanced Institute of Science and Technology
Computational Aspects of Randomness and Their Structural Analysis via Nonstandard Methods
- Principal Investigator
  
  TANAKA Kazuyuki
- Project Period (FY)
  2011 – 2014
- Research Category
  
  Grant-in-Aid for Scientific Research (B)
- Research Field
  
  General mathematics (including Probability theory/Statistical mathematics)
- Research Institution
  Tohoku University
超準手法と算術の融合による逆数学プログラムと超準解析学の発展Principal Investigator
- Principal Investigator
  
  横山啓太
- Project Period (FY)
  2009 – 2011
- Research Category
  
  Grant-in-Aid for Young Scientists (B)
- Research Field
  
  General mathematics (including Probability theory/Statistical mathematics)
- Research Institution
  Tohoku University

[Journal Article] Erdos-Moser and ISigma_22024
- Author(s)
  Henry Towsner and Keita Yokoyama
- Journal Title
  
  Israel Journal of Mathematics
  
  Volume: -
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Journal Article] ON THE FIRST-ORDER PARTS OF PROBLEMS IN THE WEIHRAUCH DEGREES2024
- Author(s)
  DAMIR D. DZHAFAROV, REED SOLOMON, KEITA YOKOYAMA
- Journal Title
  
  Computability
  
  Volume: -
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Journal Article] An isomorphism theorem for models of Weak Konig's Lemma without primitive recursion2024
- Author(s)
  Marta Fiori-Carones, Leszek Aleksander Kolodziejczyk, Tin Lok Wong, Keita Yokoyama
- Journal Title
  
  Journal of European Mathematical Society
  
  Volume: -
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Journal Article] EXTENDED FRAMES AND SEPARATIONS OF LOGICAL PRINCIPLES2023
- Author(s)
  FUJIWARA MAKOTO、ISHIHARA HAJIME、NEMOTO TAKAKO、SUZUKI NOBU-YUKI、YOKOYAMA KEITA
- Journal Title
  
  The Bulletin of Symbolic Logic
  
  Volume: 29 Issue: 3 Pages: 311-353
- DOI
  10.1017/bsl.2023.29
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-21KK0045, KAKENHI-PROJECT-18K03392, KAKENHI-PROJECT-20K03716, KAKENHI-PROJECT-22K03400, KAKENHI-PROJECT-23K03205, KAKENHI-PROJECT-19K03601, KAKENHI-PROJECT-20K14354, KAKENHI-PROJECT-23K20588
[Journal Article] Ramsey's theorem for pairs, collection, and proof size2023
- Author(s)
  Kolodziejczyk Leszek Aleksander, Wong Tin Lok, Yokoyama Keita
- Journal Title
  
  Journal of Mathematical Logic
  
  Volume: - Issue: 02
- DOI
  10.1142/s0219061323500071
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601, KAKENHI-PROJECT-21KK0045
[Journal Article] The Paris-Harrington principle and second-order arithmetic--bridging the finite and infinite Ramsey theorem2023
- Author(s)
  Yokoyama Keita
- Journal Title
  
  Proceedings of the International Congress of Mathematics 2022
  
  Volume: - Pages: 1504-1528
- DOI
  10.4171/icm2022/106
- ISBN
  9783985470617, 9783985475612
- Open Access
- Data Source
  KAKENHI-PROJECT-19K03601
[Journal Article] Metric fixed point theory and partial impredicativity2023
- Author(s)
  Fernandez-Duque D., Shafer P., Towsner H., Yokoyama K.
- Journal Title
  
  Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
  
  Volume: 381 Issue: 2248
- DOI
  10.1098/rsta.2022.0012
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601, KAKENHI-PROJECT-21KK0045
[Journal Article] HOW STRONG IS RAMSEY’S THEOREM IF INFINITY CAN BE WEAK?2022
- Author(s)
  KOLODZIEJCZYK LESZEK ALEKSANDER, KOWALIK KATARZYNA W., YOKOYAMA KEITA
- Journal Title
  
  The Journal of Symbolic Logic
  
  Volume: - Issue: 2 Pages: 1-20
- DOI
  10.1017/jsl.2022.46
- Peer Reviewed / Open Access / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601, KAKENHI-PROJECT-21KK0045
[Journal Article] The reverse mathematics of theorems of Jordan and Lebesgue2021
- Author(s)
  Nies Andre、Triplett Marcus A.、Yokoyama Keita
- Journal Title
  
  The Journal of Symbolic Logic
  
  Volume: - Issue: 4 Pages: 1-18
- DOI
  10.1017/jsl.2021.16
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601, KAKENHI-PROJECT-15H03634
[Journal Article] In search of the first-order part of Ramsey's theorem for pairs2021
- Author(s)
  Leszek Aleksander Kolodziejczyk and Keita Yokoyama
- Journal Title
  
  Lecture Notes in Computer Science
  
  Volume: 12183 Pages: 297-307
- DOI
  10.1007/978-3-030-80049-9_27
- ISBN
  9783030800482, 9783030800499
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Journal Article] Some upper bounds on ordinal-valued Ramsey numbers for colourings of pairs2020
- Author(s)
  Kolodziejczyk Leszek Aleksander、Yokoyama Keita
- Journal Title
  
  Selecta Mathematica
  
  Volume: 26 Issue: 4
- DOI
  10.1007/s00029-020-00577-3
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Journal Article] Ekeland's variational principle in weak and strong systems of arithmetic2020
- Author(s)
  Fernandez-Duque David、Shafer Paul、Yokoyama Keita
- Journal Title
  
  Selecta Mathematica
  
  Volume: 26 Issue: 5 Pages: 1-38
- DOI
  10.1007/s00029-020-00597-z
- Peer Reviewed / Open Access / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601, KAKENHI-PROJECT-15H03634
[Journal Article] Combinatorial principles equivalent to weak induction2019
- Author(s)
  Caleb Davis, Denis R. Hirschfeldt, Jeffry L. Hirst, Jake Pardo, Arno Pauly and Keita Yokoyama
- Journal Title
  
  Computability
  
  Volume: - Issue: 3-4 Pages: 1-12
- DOI
  10.3233/com-180244
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640, KAKENHI-PROJECT-15H03634
[Journal Article] The strength of Ramsey’s theorem for pairs and arbitrary many colors2018
- Author(s)
  Theodore A. Slaman and Keita Yokoyama
- Journal Title
  
  Journal of Symbolic Logic
  
  Volume: 印刷中
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Journal Article] A parameterized halting problem, the linear time hierarchy, and the MRDP theorem2018
- Author(s)
  Yijia Chen, Moritz Mueller and Keita Yokoyama
- Journal Title
  
  Proceedings of the 33rd Annual ACM/IEEE Symposium on Logic in Computer Science
  
  Volume: 33 Pages: 235-244
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Journal Article] A parameterized halting problem, the linear time hierarchy, and the MRDP theorem2018
- Author(s)
  Yijia Chen, Moritz Muller and Keita Yokoyama
- Journal Title
  
  Proceedings of the 33rd Annual ACM/IEEE Symposium on Logic in Computer Science
  
  Volume: - Pages: 235-244
- DOI
  10.1145/3209108.3209155
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Journal Article] The proof-theoretic strength of Ramsey’s theorem for pairs and two colors2018
- Author(s)
  Ludovic Patey and Keita Yokoyama
- Journal Title
  
  Advances in Mathematics
  
  Volume: 印刷中
- NAID
  120006874931
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Journal Article] The proof-theoretic strength of Ramsey's theorem for pairs and two colors2018
- Author(s)
  Ludovic Patey and Keita Yokoyama
- Journal Title
  
  Advances in Mathematics
  
  Volume: 330 Pages: 1034-1070
- DOI
  10.1016/j.aim.2018.03.035
- NAID
  120006874931
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Journal Article] The strength of SCT soundness2018
- Author(s)
  Emanuele Frittaion, Florian Pelupessy, Silvia Steila and Keita Yokoyama
- Journal Title
  
  Journal of Logic and Computation
  
  Volume: 印刷中 Issue: 6 Pages: 1217-1242
- DOI
  10.1093/logcom/exy003
- NAID
  120006725405
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634, KAKENHI-PROJECT-16K17640
[Journal Article] The strength of Ramsey's theorem for pairs and arbitrarily many colors2018
- Author(s)
  Theodore A. Slaman and Keita Yokoyama
- Journal Title
  
  Journal of Symbolic Logic
  
  Volume: 83 Issue: 04 Pages: 1610-1617
- DOI
  10.1017/jsl.2018.19
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Journal Article] The strength of the SCT criterion2017
- Author(s)
  Emanuele Frittaion, Silvia Steila and Keita Yokoyama
- Journal Title
  
  Lecture Notes in Computer Science
  
  Volume: 20185 Pages: 260-273
- DOI
  10.1007/978-3-319-55911-7_19
- ISBN
  9783319559100, 9783319559117
- Peer Reviewed / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Journal Article] Recent studies on the proof-theoretic strength of Ramsey's theorem for pairs2017
- Author(s)
  Keita Yokoyama
- Journal Title
  
  RIMS Kokyuroku
  
  Volume: 2050 Pages: 67-76
- Data Source
  KAKENHI-PROJECT-16K17640
[Journal Article] The strength of the SCT criterion2017
- Author(s)
  Emanuele Frittaion, Silvia Steila and Keita Yokoyama
- Journal Title
  
  Lecture Notes in Computer Science
  
  Volume: 10185
- Peer Reviewed / Acknowledgement Compliant / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Journal Article] On principles between Σ1- and Σ2-induction, and monotone enumerations2016
- Author(s)
  Alexander P. Kreuzer and Keita Yokoyama
- Journal Title
  
  Journal of Mathematical Logic
  
  Volume: 16 Issue: 01 Pages: 1650004-1650004
- DOI
  10.1142/s0219061316500045
- Peer Reviewed / Acknowledgement Compliant / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640, KAKENHI-PROJECT-15H03634
[Journal Article] Notes on various versions of Friedman's self-embedding theorem2016
- Author(s)
  Keita Yokoyama
- Journal Title
  
  in;Patrick Cegielski, Ali Enayat, and Roman Kossak (eds.): Studies in Weak Arithmetics
  
  Volume: 3
- Peer Reviewed / Acknowledgement Compliant
- Data Source
  KAKENHI-PROJECT-16K17640
[Journal Article] Reverse mathematical bounds for the Termination Theorem2016
- Author(s)
  Silvia Steila and Keita Yokoyama
- Journal Title
  
  Annals of Pure and Applied Logic
  
  Volume: 167 Issue: 12 Pages: 1213-1241
- DOI
  10.1016/j.apal.2016.06.001
- NAID
  120006478232
- Peer Reviewed / Acknowledgement Compliant / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640, KAKENHI-PROJECT-15H03634
[Journal Article] Categorical characterizations of the nat- ural numbers require primitive recursion2015
- Author(s)
  Leszek Aleksander Kolodziejczyk and Keita Yokoyama
- Journal Title
  
  Annals of Pure and Applied Logic
  
  Volume: 166 Issue: 2 Pages: 219-231
- DOI
  10.1016/j.apal.2014.10.003
- Peer Reviewed / Acknowledgement Compliant
- Data Source
  KAKENHI-PROJECT-25887026
[Journal Article] On the Ramseyan factorization theorem2014
- Author(s)
  S.Murakami, T.Yamazaki and K.Yokoyama
- Journal Title
  
  Lecture Notes in Computer Science
  
  Volume: 8493 Pages: 324-332
- DOI
  10.1007/978-3-319-08019-2_33
- NAID
  120005617819
- ISBN
  9783319080185, 9783319080192
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-23340020, KAKENHI-PROJECT-25887026
[Journal Article] Propagation of partial randomness2014
- Author(s)
  Kojiro Higuchi, Phil Hudelson, Stephen G. Simpson and Keita Yokoyama
- Journal Title
  
  Annals of Pure and Applied Logic
  
  Volume: 165 Issue: 2 Pages: 742-758
- DOI
  10.1016/j.apal.2013.10.006
- NAID
  120005473119
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-25887026
[Journal Article] Nonstandard second-order arithmetic and Riemann’s mapping theorem2014
- Author(s)
  Yoshihiro Horihata and Keita Yokoyama
- Journal Title
  
  Annals of Pure and Applied Logic
  
  Volume: 165 Issue: 2 Pages: 520-551
- DOI
  10.1016/j.apal.2013.06.022
- NAID
  120005425784
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-25887026
[Journal Article] Reverse mathematics and Peano categoricity2013
- Author(s)
  Stephen G. Simpson and Keita, Yokoyama
- Journal Title
  
  Annals of Pure and Applied Logic
  
  Volume: 164 Issue: 3 Pages: 284-293
- DOI
  10.1016/j.apal.2012.10.014
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-11J01045, KAKENHI-PROJECT-25887026
[Journal Article] Riceの定理のアナロジーについて2011
- Author(s)
  吉川紘史, 横山啓太
- Journal Title
  
  数理解析研究所講究録
  
  Volume: 1729 Pages: 163-166
- Data Source
  KAKENHI-PROJECT-21740061
[Journal Article] Nonstandard arguments and recursive arguments2011
- Author(s)
  横山啓太
- Journal Title
  
  数理解析研究所講究録
  
  Volume: 1729 Pages: 152-162
- Data Source
  KAKENHI-PROJECT-21740061
[Journal Article] Formalizing non-standard arguments in second-order arithmetic2010
- Author(s)
  Keita Yokoyama
- Journal Title
  
  The Journal of Symbolic Logic
  
  Volume: vol.75 Pages: 1199-1210
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-21740061
[Journal Article] Formalizing non-standard arguments in second-order arithmetic2010
- Author(s)
  Keita Yokoyama
- Journal Title
  
  The Journal of Symbolic Logic 4(accepted)
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-21740061
[Journal Article] On Pi^1_1 conservativity of Pi^1_2 theories in second order arithmetic2009
- Author(s)
  Keita Yokoyama
- Journal Title
  
  Proceedings of the 10th Asian Logic Conference
  
  Pages: 375-386
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-21740061
[Journal Article] A nonstandard counterpart of WWKL
- Author(s)
  Stephen G.Simpson, Keita Yokoyama
- Journal Title
  
  Notre Dame Journal of Formal Logic
  
  Volume: (未定採用決定)
- Peer Reviewed
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] Weihrauch degrees above arithmetical transfinite recursion2023
- Author(s)
  Keita Yokoyama
- Organizer
  Computability and Combinatorics 2023
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-23K03193
[Presentation] Determinacy and reflection principles in second-order arithmetic2023
- Author(s)
  Keita Yokoyama
- Organizer
  From omega to Omega, Workshop on Computability Theory, Set Theory and their interactions
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-21KK0045
[Presentation] 自然数論のモデルと逆数学2023
- Author(s)
  横山啓太
- Organizer
  日本数学会数学基礎論および歴史分科会企画特別講演
- Invited
- Data Source
  KAKENHI-PROJECT-21KK0045
[Presentation] 算術の超準モデル論2023
- Author(s)
  横山啓太
- Organizer
  Logic Winter School 2023, 沖縄青年会館, 那覇, 2023年2月20-21日.
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Determinacy and reflection principles in second-order arithmetic2023
- Author(s)
  Keita Yokoyama
- Organizer
  From omega to Omega, Workshop on Computability Theory, Set Theory and their interactions
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-23K03193
[Presentation] Weihrauch degrees above arithmetical transfinite recursion2023
- Author(s)
  Keita Yokoyama
- Organizer
  Computability and Combinatorics 2023
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-21KK0045
[Presentation] 自然数論のモデルと逆数学2023
- Author(s)
  横山啓太
- Organizer
  日本数学会, 企画特別講演, 中央大学, 2023年3月.
- Invited
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Reverse mathematics from multiple points of view2022
- Author(s)
  Keita Yokoyama
- Organizer
  Japan forum associated with ICM 2022, RIMS Kyoto, Japan, June 13, 2022.
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Classifying theorems: reverse mathematics and its multiple viewpoints2022
- Author(s)
  Keita Yokoyama
- Organizer
  World Logic Day Workshop 2022
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Reverse mathematics from multiple points of view2022
- Author(s)
  Keita Yokoyama
- Organizer
  International Congress of Mathematics 2022, Sectional Speaker (Logic), online, July 13, 2022.
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Determinacy and reflection principles in second-order arithmetic2022
- Author(s)
  Leonardo Pacheco and Keita Yokoyama
- Organizer
  Workshop on Reverse Mathematics and its Philosophy, Paris, France, June 13-17, 2022
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Forcing interpretation, conservation and proof size2021
- Author(s)
  Keita Yokoyama
- Organizer
  Proof Theory Virtual Seminar (国際オンラインセミナー)
- Invited
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Reverse mathematics and proof and model theory of arithmetic2021
- Author(s)
  Keita Yokoyama
- Organizer
  Computability in Europe 2021
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] On the unique existence conservation theorem for WKL2021
- Author(s)
  Keita Yokoyama
- Organizer
  Workshop on Effective descriptive set theory, computable analysis and automata
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Automorphism argument and reverse mathematics2021
- Author(s)
  Keita Yokoyama
- Organizer
  Computability Theory and Applications Seminar (国際オンラインセミナー)
- Invited
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Recent struggling for the first-order part of Ramsey's theorem for pairs2019
- Author(s)
  Keita Yokoyama
- Organizer
  Reverse Mathematics of Combinatorial Principles, CMO-BIRS meeting (19w5111)
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] First-order parts of Weihrauch degrees2019
- Author(s)
  Keita Yokoyama
- Organizer
  Third Workshop on Mathematical Logic and its Applica- tions,
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Terrence Tao's finitary infinite pigeonhole principle and proof-theory2019
- Author(s)
  Keita Yokoyama
- Organizer
  2019 SJTU-JAIST-NU Follow-Up Workship on Formal Methods
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Weihrauch degrees of numerical problems2019
- Author(s)
  K. Yokoyama
- Organizer
  The 9th Computability Theory and Foundations of Mathematics 2019, Wuhan
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] On the first-order consequences of Ramsey's theorem over RCA_0*2019
- Author(s)
  Keita Yokoyama
- Organizer
  Workshop on Proof Theory, Modal Logic and Reflection Principles
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Finitary infinite pigeonhole principle and Ramsey’s theorem in reverse mathematics2019
- Author(s)
  Keita Yokoyama
- Organizer
  Computability in Europe 2019, Durham, July 15-19, 2019
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] Approaching the first-order part of Ramsey's theorem for pairs and two colors2019
- Author(s)
  Keita Yokoyama
- Organizer
  Workshop on Computability Theory 2019
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Weihrauch degrees of numerical problems2019
- Author(s)
  Keita Yokoyama
- Organizer
  Computability Theory and Foundations of Mathematics 2019
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Finitary infinite pigeonhole principle and Ramsey's theorem in reverse mathematics2019
- Author(s)
  Keita Yokoyama
- Organizer
  Computability in Europe 2019
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Recent progress on the study of the first-order part of Ramsey's theorem for pairs2019
- Author(s)
  Keita Yokoyama
- Organizer
  Mathematical Logic and Constructivity
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-19K03601
[Presentation] Ramsey's theorem in arithmetic2018
- Author(s)
  Keita Yokoyama
- Organizer
  2018 Winter Meeting of the Association of Symbolic Logic
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Ekeland’s variational principle in reverse mathematics2018
- Author(s)
  Keita Yokoyama
- Organizer
  Symposium on Advances in Mathematical Logic 2018
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Ramsey's theorem and sizes of proofs2018
- Author(s)
  K. Yokoyama
- Organizer
  Workshop on Ramsey Theory and Computability, Rome
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] Ramsey’s theorem and sizes of proofs2018
- Author(s)
  Keita Yokoyama
- Organizer
  Workshop on Ramsey Theory and Computability
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Approaching the first-order strength of Hindman's theorem2018
- Author(s)
  Keita Yokoyama
- Organizer
  Workshop on Computability Theory and Foundations of Mathematics 2018
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Caristi's fixed point theorem in reverse mathematic2017
- Author(s)
  Keita Yokoyama
- Organizer
  Twelfth International Conference on Computability, Complexity and Randomness (CCR 2017)
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] On the first-order part of Ramsey's theorem for pairs2017
- Author(s)
  横山啓太
- Organizer
  CTFM 2017 at NUS
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] On the first-order strength of Ramsey's theorem in reverse mathematics2017
- Author(s)
  Keita Yokoyama
- Organizer
  Logic Colloquium 2017
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Konig's lemma for a tree which has at most finitely many paths in reverse mathematics2017
- Author(s)
  横山啓太
- Organizer
  日本数学会
- Place of Presentation
  首都大学東京(東京都八王子市)
- Year and Date
  2017-03-24
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Generalized indicator and forcing2017
- Author(s)
  Keita Yokoyama
- Organizer
  Oberwolfach Workshop: Mathematical Logic: Proof Theory, Constructive Mathematics
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] On the first-order part of Ramsey's theorem for pairs2017
- Author(s)
  Keita Yokoyama
- Organizer
  Computability Theory and Foundations of Mathematics 2017
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Nonstandard methods in combinatorics2016
- Author(s)
  Keita Yokoyama
- Organizer
  The 11th AIMS Conference on Dynamical Systems
- Place of Presentation
  Orlando, Florida, USA
- Year and Date
  2016-07-04
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Thoughts on indicators and density notions2016
- Author(s)
  Keita Yokoyama
- Organizer
  IMS-JSPS Joint Workshop on Mathematical Logic and the Foundations of Mathematics
- Place of Presentation
  シンガポール国立大学，シンガポール
- Year and Date
  2016-01-15
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] On the Proof-Theoretic Strength of Ramsey's Theorem for Pairs2016
- Author(s)
  Keita Yokoyama
- Organizer
  Mathematical Logic and Its Applications
- Place of Presentation
  京都大学(京都府京都市)
- Year and Date
  2016-09-26
- Invited / Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] On the Proof-Theoretic Strength of Ramsey's Theorem for Pairs2016
- Author(s)
  Keita Yokoyama
- Organizer
  2016 NFSC-JSPS computer science/joint research workshop
- Place of Presentation
  しいのき迎賓館(石川県金沢市)
- Year and Date
  2016-12-15
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] On the first-order strength of Ramsey's theorem for pairs and finitely many colors2016
- Author(s)
  Keita Yokoyama
- Organizer
  Association for Symbolic Logic 2016 Annual North American Meeting
- Place of Presentation
  University of Connecticut, Storrs, USA
- Year and Date
  2016-05-25
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Trees with at most finitely many paths in reverse mathematics2016
- Author(s)
  Keita Yokoyama
- Organizer
  CTFM2016
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] The proof-theoretic strength of Ramsey's theorem for pairs2016
- Author(s)
  Keita Yokoyama
- Organizer
  Mathematics for Computation
- Place of Presentation
  Lower Bavaria, DE, Germany
- Year and Date
  2016-05-09
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] On the proof-theoretic strength of Ramsey's theorem for pairs2016
- Author(s)
  横山啓太
- Organizer
  日本数学会
- Place of Presentation
  関西大学(大阪府吹田市)
- Year and Date
  2016-09-18
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] On the Proof-Theoretic Strength of Ramsey's Theorem for Pairs2016
- Author(s)
  Keita Yokoyama
- Organizer
  Mathematical Logic and Its Applications
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] Proof-theoretic strength and indicator arguments2016
- Author(s)
  Keita Yokoyama
- Organizer
  Workshop on Mathematical Logic and its Applications
- Place of Presentation
  京都大学(京都府京都市)
- Year and Date
  2016-09-16
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] Computable analysis and reverse mathematics2016
- Author(s)
  Keita Yokoyama
- Organizer
  Algorithmic Randomness Interacts with Analysis and Ergodic Theory
- Place of Presentation
  The Casa Matematica Oaxaca (CMO), Mexico
- Year and Date
  2016-12-07
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-16K17640
[Presentation] A simple conservation proof for ADS2015
- Author(s)
  Keita Yokoyama
- Organizer
  Computability Theory and Foundations of Mathematics 2015
- Place of Presentation
  東京工業大学
- Year and Date
  2015-09-11
- Int'l Joint Research
- Data Source
  KAKENHI-PROJECT-15H03634
[Presentation] Proof transformations for nonstandard analysis2014
- Author(s)
  Keita Yokoyama
- Organizer
  The 10th AIMS Conference on Dynamical Sys- tems, Differential Equations and Applications, Special session 114: Nonstandard Analysis, Quan- tizations and Singular Perturbations
- Place of Presentation
  Madrid, Spain
- Year and Date
  2014-07-10
- Invited
- Data Source
  KAKENHI-PROJECT-25887026
[Presentation] The Dirac delta function in two settings of reverse mathematics2011
- Author(s)
  Keita Yokoyama, Sam Sanders
- Organizer
  日本数学会・数学基礎論及び歴史分科会
- Place of Presentation
  早稲田大学
- Year and Date
  2011-03-21
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] On Ramsey's theorem for pairs2011
- Author(s)
  Keita Yokoyama
- Organizer
  Workshop on Proof Theory and Computability Theory
- Place of Presentation
  Akiu Spa Hotel Iwanumaya, Sendai, Miyagi
- Year and Date
  2011-02-21
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] Reverse Mathematics for differential equations2010
- Author(s)
  横山啓太
- Organizer
  2009年度証明論シンポジウム
- Place of Presentation
  福島
- Year and Date
  2010-02-22
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] A nonstandard counterpart of DNR2010
- Author(s)
  Keita Yokoyama, Kojiro Higuchi
- Organizer
  Logic Colloquium 2010
- Place of Presentation
  Paris Diderot university, France
- Year and Date
  2010-07-27
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] Comparing non-standard axioms with axioms of second-order arithmetic2010
- Author(s)
  横山啓太
- Organizer
  Workshop on Constructive Aspects of Logic and Mathematics
- Place of Presentation
  金沢
- Year and Date
  2010-03-09
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] Nonstandard priority argument2010
- Author(s)
  横山啓太
- Organizer
  短期共同研究「形式体系と計算理論」
- Place of Presentation
  京都大学数理解析研究所
- Year and Date
  2010-09-14
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] 弱い公理系を用いた超準解析2010
- Author(s)
  横山啓太
- Organizer
  数学基礎論サマースクール-超準解析の基礎と応用-
- Place of Presentation
  名古屋大学
- Year and Date
  2010-08-25
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] Nonstandard counterparts of several weak axioms2010
- Author(s)
  横山啓太
- Organizer
  東北大学ロジックセミナー
- Place of Presentation
  東北大学
- Year and Date
  2010-07-23
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] The strength of transfer principles and Reverse Mathematics2010
- Author(s)
  横山啓太
- Organizer
  東北大学ロジックセミナー
- Place of Presentation
  東北大学
- Year and Date
  2010-04-06
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] 2階算術における超準解析学2009
- Author(s)
  横山啓太
- Organizer
  2009年度超準解析シンポジウム
- Place of Presentation
  名古屋
- Year and Date
  2009-11-08
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] 超準手法の逆数学と2階算術体系2009
- Author(s)
  横山啓太
- Organizer
  日本数学会・数学基礎論及び歴史分科会
- Place of Presentation
  大阪
- Year and Date
  2009-09-26
- Data Source
  KAKENHI-PROJECT-21740061
[Presentation] Use of nonstandard models in reverse mathematics
- Author(s)
  Keita Yokoyama
- Organizer
  Journees sur les Arithmetiques Faibles 33
- Place of Presentation
  University of Gothenburg, Gothenburg, Sweden
- Year and Date
  2014-06-16 – 2014-06-18
- Invited
- Data Source
  KAKENHI-PROJECT-25887026
[Presentation] Termination theorem and Ramsey's theorem
- Author(s)
  Keita Yokoyama
- Organizer
  IMS-JSPS Joint Workshop in Mathematical Logic and Foundations of Mathematics
- Place of Presentation
  National University of Singapore, Singapore
- Year and Date
  2014-09-01 – 2014-09-05
- Invited
- Data Source
  KAKENHI-PROJECT-25887026
[Presentation] The strength of Ramsey’s theorem from several different view points
- Author(s)
  Keita Yokoyama
- Organizer
  CORCON2014 Workshop
- Place of Presentation
  Genoa, Italy
- Year and Date
  2014-03-24 – 2014-03-27
- Data Source
  KAKENHI-PROJECT-25887026
[Presentation] What is needed to characterize the natural number system?
- Author(s)
  Keita Yokoyama
- Organizer
  Constructivizm and Computability 2015
- Place of Presentation
  Siinoki Cultural Complex, Kanazawa, Ishikawa, Japan
- Year and Date
  2015-03-02 – 2015-03-06
- Data Source
  KAKENHI-PROJECT-25887026
[Presentation] Reverse mathematics and termination analysis
- Author(s)
  Keita Yokoyama
- Organizer
  14th Asian Logic Conference
- Place of Presentation
  IIT Bombay, India
- Year and Date
  2015-01-05 – 2015-01-08
- Invited
- Data Source
  KAKENHI-PROJECT-25887026
[Presentation] Finite iterations of infinite and finite Ramsey's theorem
- Author(s)
  Keita Yokoyama
- Organizer
  Computability Theory and Foundations of Mathematics 2014
- Place of Presentation
  Tokyo Institute of Technology, Tokyo, Japan
- Year and Date
  2014-02-17 – 2014-02-20
- Data Source
  KAKENHI-PROJECT-25887026

1. TANAKA Kazuyuki (70188291)

# of Collaborated Projects: 2 results

# of Collaborated Products: 0 results
2. 根元多佳子 (20546155)

# of Collaborated Projects: 2 results

# of Collaborated Products: 1 results
3. YAMAZAKI Takeshi (30336812)

# of Collaborated Projects: 1 results

# of Collaborated Products: 1 results
4. SUZUKI Toshio (30235973)

# of Collaborated Projects: 1 results

# of Collaborated Products: 0 results
5. TADAKI Kohtaro (70407881)

# of Collaborated Projects: 1 results

# of Collaborated Products: 0 results
6. KURODA Satoru (30300586)

# of Collaborated Projects: 1 results

# of Collaborated Products: 0 results
7. 木原貴行 (80722701)

# of Collaborated Projects: 1 results

# of Collaborated Products: 0 results
8. 石原哉 (10211046)

# of Collaborated Projects: 1 results

# of Collaborated Products: 1 results
9. 河井達治 (00824343)

# of Collaborated Projects: 1 results

# of Collaborated Products: 0 results
10. 藤原誠 (20779095)

# of Collaborated Projects: 1 results

# of Collaborated Products: 1 results
11. SOLDA GIOVANNI

# of Collaborated Projects: 1 results

# of Collaborated Products: 0 results

YOKOYAMA KEITA 横山 啓太

YOKOYAMA Keita 横山 啓太

横山 啓太 ヨコヤマ ケイタ

Research Projects

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Co-Researchers

New frontiers in reverse mathematics with the multidimensional perspectivePrincipal Investigator

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逆数学における分割順序数Principal Investigator

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Constructive reverse mathematics and computational content of mathematical theorems

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Approaching proof theory from the viewpoint of proof sizePrincipal Investigator

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Expanding reverse mathematics with multiple viewpointsPrincipal Investigator

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Phase transitions of provability and supercritical propositions of reverse mathematics

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The start-up for reverse mathematics from various anglesPrincipal Investigator

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Computational Aspects of Randomness and Their Structural Analysis via Nonstandard Methods

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超準手法と算術の融合による逆数学プログラムと超準解析学の発展Principal Investigator

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[Journal Article] Erdos-Moser and ISigma_22024

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[Journal Article] ON THE FIRST-ORDER PARTS OF PROBLEMS IN THE WEIHRAUCH DEGREES2024

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[Journal Article] An isomorphism theorem for models of Weak Konig's Lemma without primitive recursion2024

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[Journal Article] EXTENDED FRAMES AND SEPARATIONS OF LOGICAL PRINCIPLES2023

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[Journal Article] Ramsey's theorem for pairs, collection, and proof size2023

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YOKOYAMA KEITA 横山啓太

YOKOYAMA Keita 横山啓太

横山啓太ヨコヤマケイタ