Ryuya Hora洞龍弥

Talks

Research talks, seminars and outreach lectures, newest first. Slides and recordings are attached where they exist.

2026

  1. 29 September 2026

    Title pending

    ItaCa Fest 2026 Online

  2. 12 September 2026

    Title pending

    数学カフェ 先端講演 Outreach

  3. 5 September 2026

    圏論は役に立つのか：数学者とエンジニアの対話から考える夜

    圏論NIGHT 学術バーQ, Tokyo With Kory Outreach

    A Categories in Tokyo collaboration event; a dialogue with Kory.

    • Category

  4. 17 July 2026

    AIについて数学者は(何を)考えるべきか

    AI for Math勉強会 第2回 12F, Kabukiza Tower, Tokyo Outreach

  5. 23 May 2026

    ベン図からトポスへ

    Math Space Topos 2026 new welcome event Outreach

    Slides (PDF)
    • Topos

  6. 6 April 2026

    A Rota-Baxter equation for winning games

    Differentiation in category theory and program semantics Room 420, RIMS, Kyoto University

    Slides (PDF)

    Paper: Differential calculus of impartial combinatorial games

    • Game

  7. 16 March 2026

    A space-time for Conway's game of life

    CSCAT 2026 Room 601A, AOSSA, Fukui

    Slides (PDF)

    Paper: Dynamical systems on pretopological spaces

    • Dynamics

  8. 11 March 2026

    Measure-theoretic closure operators on formal languages

    PPL 2026 Rexxam Hall, Takamatsu With Ryoma Sin'ya Poster

    Paper: A note on language measurability

    • Automaton

  9. 22 February 2026

    Turning lights out with the Snake Lemma

    20th CGP project The University of Electro-Communications, Chofu Presented by Kyosuke Higashida

    Slides (PDF)
    • Game

  10. 23 January 2026

    Connectedness and full subcategories of topoi

    Ph.D. thesis presentation Room 126, Graduate School of Mathematical Sciences, The University of Tokyo

    Papers: Grothendieck topoi with a left adjoint to a left adjoint to a left adjoint to the global sections functor · Solution to Lawvere's first problem: A Grothendieck topos that has proper class many quotient topoi · Lawvere's fourth open problem: Levels in the topos of symmetric simplicial sets

    • Topos
    • Category

2025

  1. 5 December 2025

    Local state classifier, The axiom of choice, and permutation model

    UTokyo Logic seminar Graduate School of Mathematical Sciences, The University of Tokyo

    Paper: Local state classifier, permutation model, and the internal axiom of choice

    • Topos
    • Logic

  2. 28 November 2025

    Connectedness and full subcategories of topoi

    UTokyo Logic seminar Graduate School of Mathematical Sciences, The University of Tokyo

    Papers: Grothendieck topoi with a left adjoint to a left adjoint to a left adjoint to the global sections functor · Solution to Lawvere's first problem: A Grothendieck topos that has proper class many quotient topoi · Lawvere's fourth open problem: Levels in the topos of symmetric simplicial sets

    • Topos
    • Category

  3. 31 October 2025

    Topoi of automata

    SLACS 2025 Shared Room 321, Akita University, Tegata Campus

    Paper: Topoi of automata I: Four topoi of automata and regular languages

    • Topos
    • Automaton

  4. 17 July 2025

    Topoi of automata

    CT 2025 Building B2, Faculty of Arts, Masaryk University, Brno

    Slides (PDF)

    Paper: Topoi of automata I: Four topoi of automata and regular languages

    • Topos
    • Automaton

  5. 11 June 2025

    A topos for regular language theory

    Theoretical Cosynus Seminar Henri Poincaré room, LIX, École polytechnique, Palaiseau

    Papers: Topoi of automata I: Four topoi of automata and regular languages · Internal parameterization of hyperconnected quotients

    • Topos
    • Automaton

  6. 5 June 2025

    Local state classifier for automata theory

    Séminaires du LIPN Salle B107, LIPN, Université Sorbonne Paris Nord, Villetaneuse

    Slides (PDF)

    Same slide deck as the IRIF Sémantique seminar.

    Papers: Topoi of automata I: Four topoi of automata and regular languages · Internal parameterization of hyperconnected quotients

    • Topos
    • Automaton

  7. 27 May 2025

    Local state classifier for automata theory

    IRIF Sémantique seminar Salle 3071, IRIF, Université Paris Cité

    Slides (PDF)

    Papers: Topoi of automata I: Four topoi of automata and regular languages · Internal parameterization of hyperconnected quotients

    • Topos
    • Automaton

  8. 16 May 2025

    Local state classifier for algebraic language theory

    Groupe de travail topossique Centre Lagrange, Paris

    Slides (PDF)

    Papers: Topoi of automata I: Four topoi of automata and regular languages · Internal parameterization of hyperconnected quotients

    • Topos
    • Automaton
    • Algebra

  9. 6 May 2025

    Topoi of automata

    Categories for Automata and Language Theory Salle 3071, IRIF, Université Paris Cité

    Slides (PDF)

    Paper: Topoi of automata I: Four topoi of automata and regular languages

    • Topos
    • Automaton

  10. 30 April 2025

    Topoi of automata

    Groupe de travail topossique Centre Lagrange, Paris

    Slides (PDF)

    Paper: Topoi of automata I: Four topoi of automata and regular languages

    • Topos
    • Automaton

  11. 12 March 2025

    Topoi of automata

    CSCAT 2025 Room F203, Sojo University, Kumamoto

    Slides (PDF)

    Paper: Topoi of automata I: Four topoi of automata and regular languages

    • Topos
    • Automaton

  12. 28 February 2025

    Topoi of automata

    CMUP SAL seminar Online

    Event flyer

    Paper: Topoi of automata I: Four topoi of automata and regular languages

    • Topos
    • Automaton

2024

  1. 30 November 2024

    Quotient topoi and geometry of computation

    AFSA area meeting Hall 401, TKP Kanda Business Center, Tokyo Outreach

    • Topos
    • Geometry

  2. 10 September 2024

    The colimit of all monomorphisms classifies hyperconnected geometric morphisms

    Toposes in Mondovì Circolo di Lettura, Palazzo del Governatore, Mondovì

    Video

    Paper: Internal parameterization of hyperconnected quotients

    • Topos

  3. 29 August 2024

    Topos theory as a tool of automata theory

    Young Automata Theorists Gathering in Japan Room 305, Akita University, Tegata Campus

    Paper: Topoi of automata I: Four topoi of automata and regular languages

    • Topos
    • Automaton

  4. 28 June 2024

    Quotient toposes of discrete dynamical systems

    CT 2024 Facultade de Matemáticas, Universidade de Santiago de Compostela

    Paper: Quotient toposes of discrete dynamical systems

    • Topos
    • Dynamics

  5. 18 May 2024

    アイゼンシュタイン整数と組合せ論

    Math Space Topos 2024 new welcome event Outreach

    Slides (PDF)
    • Algebra
    • Combinatorics

  6. 24 April 2024

    圏論の利用と濫用

    18th AFSA Colloquium NII Kanda Lab, Tokyo

    • Category

  7. 16 March 2024

    Introduction to topos theory

    代数トポロジー若手の会 Nagoya University

    • Topos

  8. 15 March 2024

    Combinatorial games as recursive coalgebras

    CSCAT 2024 Multimedia Room 1, Science Building 4, Chiba University, Nishi-Chiba Campus

    Slides (PDF)

    Paper: Games as recursive coalgebras: A categorical view on the Nim-sum

    • Game
    • Coalgebra
    • Algebra

2023

  1. 10 December 2023

    Constructive mathematics and representation theory

    数学基礎論若手の会2023 Multipurpose Room Nalu, Sunset Breeze Hota, Kyonan, Chiba

    Slides (PDF)

    Paper: A topos-theoretic view on Gabriel's theorem

    • Logic
    • Algebra

  2. 21 August 2023

    Category Theory and Combinatorial Game Theory

    7th Japan Combinatorial Game Theory Conference National Institute of Informatics, Tokyo

    Paper: Games as recursive coalgebras: A categorical view on the Nim-sum

    • Game
    • Category

  3. 15 July 2023

    母関数の種

    Math Space Topos 2023 new welcome event Outreach

    Slides (PDF)
    • Combinatorics

  4. 6 July 2023

    Internal parameterization of hyperconnected quotients

    Category Theory 2023 Auditoires des Sciences, UCLouvain, Louvain-la-Neuve

    Video

    Paper: Internal parameterization of hyperconnected quotients

    • Topos

  5. 12 May 2023

    Grundy Numbers and Categories

    Japan Combinatorial Game Theory Mini-Workshops with Urban Larsson National Institute of Informatics, Tokyo

    Paper: Games as recursive coalgebras: A categorical view on the Nim-sum

    • Game
    • Category

  6. 19 April 2023

    Internal parameterization of hyperconnected quotients

    Australian Category Seminar Online

    Paper: Internal parameterization of hyperconnected quotients

    • Topos

  7. 9 March 2023

    Internal parameterization of hyperconnected quotients

    CSCAT 2023 Room 478, Research Building 2, Kyoto University, Yoshida Campus

    Paper: Internal parameterization of hyperconnected quotients

    • Topos

2022

  1. 4 June 2022

    順序集合で遊ぶKan拡張

    Math Space Topos 2022 new welcome event Outreach

    Slides (PDF)
    • Category

2021

  1. 4 December 2021

    ゼータ関数とメビウス反転

    Math Space Topos 2021 new welcome event Outreach

    Slides (PDF)
    • Combinatorics