RH Ryuya Hora洞龍弥

Ryuya Hora — Curriculum Vitae

Assistant Professor, ZEN University

horaryuya38@gmail.com · https://ryuyahora.jp · Tokyo, Japan

Education

Research Interests

Papers

Published

  1. Ryuya Hora and Yuhi Kamio, “Quotient toposes of discrete dynamical systems,” Journal of Pure and Applied Algebra 228(8), 107657, 2024.
  2. Ryuya Hora, “Internal parameterization of hyperconnected quotients,” Theory and Applications of Categories 42(11), 263-313, 2024.
  3. Ryuya Hora, “Grothendieck topoi with a left adjoint to a left adjoint to a left adjoint to the global sections functor,” Proceedings of the American Mathematical Society 154, 567-584, 2026.
  4. Yuhi Kamio and Ryuya Hora, “Solution to Lawvere's first problem: A Grothendieck topos that has proper class many quotient topoi,” Advances in Mathematics 487, 110751, 2026.

Preprints

  1. Ryuya Hora, “Topoi of automata I: Four topoi of automata and regular languages,” arXiv:2411.06358, 2024.
  2. Ryuya Hora, Yuhi Kamio, and Yuki Maehara, “Lawvere's fourth open problem: Levels in the topos of symmetric simplicial sets,” arXiv:2503.03439, 2025.
  3. Ryuya Hora, “Games as recursive coalgebras: A categorical view on the Nim-sum,” arXiv:2510.22886, 2025.
  4. Ryuya Hora, “Normalization of a subgroup, in a topos, and of a word-congruence,” arXiv:2511.05012, 2025.

Talks and Presentations

2023

  1. Internal parameterization of hyperconnected quotients, at CSCAT 2023, 9 March 2023, Room 478, Research Building 2, Kyoto University.
  2. Internal parameterization of hyperconnected quotients, at Australian Category Seminar, 19 April 2023, online.
  3. Grundy Numbers and Categories, at Japan Combinatorial Game Theory Mini-Workshops, 12 May 2023, NII, Tokyo.
  4. Internal parameterization of hyperconnected quotients, at Category Theory 2023, 6 July 2023, Auditoires des Sciences, UCLouvain.
  5. Category Theory and Combinatorial Game Theory, at 7th Japan Combinatorial Game Theory Conference, 21 August 2023, NII, Tokyo.
  6. Constructive mathematics and representation theory, at 数学基礎論若手の会2023, 10 December 2023, Chiba.

2024

  1. Combinatorial games as recursive coalgebras, at CSCAT 2024, 15 March 2024, Multimedia Room 1, Science Building 4, Chiba University.
  2. Introduction to topos theory, at 代数トポロジー若手の会, 16 March 2024, Nagoya University.
  3. 圏論の利用と濫用, at 18th AFSA Colloquium, 24 April 2024, NII Kanda Lab, Tokyo.
  4. Quotient toposes of discrete dynamical systems, at CT 2024, 28 June 2024, Facultade de Matemáticas, Universidade de Santiago de Compostela.
  5. Topos theory as a tool of automata theory, at Young Automata Theorists Gathering in Japan, 29 August 2024, Room 305, Akita University.
  6. The colimit of all monomorphisms classifies hyperconnected geometric morphisms, at Toposes in Mondovì, 10 September 2024, Circolo di Lettura, Palazzo del Governatore.
  7. Quotient topoi and geometry of computation, at AFSA area meeting, 30 November 2024, TKP Kanda Business Center, Tokyo.

2025

  1. Topoi of automata, at CMUP SAL seminar, 28 February 2025, Zoom.
  2. Topoi of automata, at CSCAT 2025, 12 March 2025, Room F203, Sojo University, Kumamoto.
  3. Topoi of automata, at Groupe de travail topossique, 30 April 2025, Centre Lagrange, Paris.
  4. Topoi of automata, at Categories for Automata and Language Theory, 6 May 2025, IRIF, Paris.
  5. Local state classifier for algebraic language theory, at Groupe de travail topossique, 16 May 2025, Centre Lagrange, Paris.
  6. Local state classifier for automata theory, at IRIF Sémantique seminar, 27 May 2025, Salle 3071, IRIF, Paris.
  7. Local state classifier for automata theory, at Séminaires du LIPN, 5 June 2025, LIPN, Villetaneuse.
  8. A topos for regular language theory, at Theoretical Cosynus Seminar, 11 June 2025, LIX, Ecole polytechnique, Palaiseau.
  9. Topoi of automata, at CT 2025, 17 July 2025, Building B2, Faculty of Arts, Masaryk University, Brno.
  10. Topoi of automata, at SLACS 2025, 31 October 2025, Shared Room 321, Akita University.
  11. Connectedness and full subcategories of topoi, at UTokyo Logic seminar, 28 November 2025, Graduate School of Mathematical Sciences, The University of Tokyo.
  12. The axiom of choice and local state classifier, at UTokyo Logic seminar, 5 December 2025, Graduate School of Mathematical Sciences, The University of Tokyo.

2026

  1. Connectedness and full subcategories of topoi, at Ph.D. thesis presentation, 23 January 2026, Room 126, Graduate School of Mathematical Sciences, The University of Tokyo.
  2. (Joint work with and talk given by Kyosuke Higashida) Turning lights out with the Snake Lemma, at 20th CGP project, 22 February 2026, The University of Electro-Communications, Chofu.
  3. (Joint work with Ryoma Sin'ya) Measure-theoretic closure operators on formal languages, at PPL 2026, 11 March 2026, Rexxam Hall, Takamatsu.
  4. A space-time for Conway's game of life, at CSCAT 2026, 17 March 2026, AOSSA Room 601A, Fukui.
  5. A Rota-Baxter equation for winning games, at Differentiation in category theory and program semantics, 6 April 2026, Room 420, RIMS, Kyoto University.
  6. AI for Mathについて数学者は(何を)考えるべきか, at AI for Math勉強会 第2回, 17 July 2026, Kabukiza Tower 12F, Tokyo.

Awards

Grants/Fellowships

Academic Positions and Activities

Other Activities