The (i)Po(m)set Project

What

The (i)Po(m)set Project is a research project at the crossroads of concurrency theory, automata theory, algebra, and geometry. It aims to understand the basics of concurrency theory and develop its foundations.

Meetings

The Paris Automata and Concurrency Theory Seminar takes place for an afternoon every six-eight weeks, moving between LIX (École Polytechnique), LRE (EPITA Paris), and IRIF (Université Paris Cité).

The (i)Po(m)set Project Working Group meets twice a month in the Paris region:

• every first Tuesday at IRIF
• every third Thursday at LMF
• next meetings: 4/11, 20/11, 2/12, 18/12

The workshops on Pomsets and Related Structures (RaPS) take place irregularly:

1. Rennes, April 2024
2. Rzeszów, June 2025
3. Saclay, September 2025

The (i)Po(m)set Project Online Seminar used to take place about once a month, but has now been discontinued.

Who

Members:

• Uli Fahrenberg, Université Paris-Saclay, France
• Christian Johansen, NTNU, Gjøvik, Norway
• Georg Struth, University of Sheffield, UK
• Krzysztof Ziemiański, University of Warsaw, Poland

Associates:

• Amazigh Amrane, EPITA Paris, France
• Hugo Bazille, EPITA Rennes, France
• Paul Brunet, Université Paris-Est Créteil, France
• Emily Clement, Université Paris Nord, France
• Jérémy Dubut, École polytechnique, Paris, France
• Enzo Erlich, Université Paris Cité, France
• Marie Fortin, Université Paris Cité, France
• Eric Goubault, École polytechnique, Paris, France
• Roman Kniazev, Université de Bordeaux, France
• Jérémy Ledent, Université Paris Cité, France
• Philipp Schlehuber-Caissier, Télécom SudParis, France
• Safa Zouari, NTNU, Gjøvik, Norway

Interns:

• Timothée Fragnaud, EPITA Paris, France
• Rania Saadi, EPITA Paris, France

Former members, associates, or interns:

• Olavi Äikäs, Helsinki, Finland
• Ratan Bahadur Thapa, Oslo, Norway
• Clarisse Blanco, Rennes, France
• Cameron Calk, Paris, France
• Brieuc Crosson, EPITA Rennes, France
• Romane D'Ancona, EPITA Rennes, France
• Gurvan Estable, EPITA Rennes, France
• Paul Fournillon, EPITA Rennes, France
• Quentin Hay-Kergrohenn, EPITA Rennes, France
• Erwan Le Grand, EPITA Rennes, France
• Kévin Lubert, EPITA Rennes, France
• Luc Passemard, École polytechnique, Paris, France
• Dorian Peron, Rennes, France
• Christopher Trotter, Oslo, Norway

When

The (i)Po(m)set Project started sometime in 2018, but its name and this web site exist only since 21 May 2021.

Publications

Research papers published by the (i)Po(m)set Project:

1. Uli Fahrenberg, Christian Johansen, Christopher Trotter, Krzysztof Ziemiański: Sculptures in Concurrency. Logical Methods in Computer Science 17(2) (2021)
2. Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański: Domain Semirings United. Acta Cybernetica 25(3): 575-583 (2022)
3. Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański: Languages of Higher-Dimensional Automata. Mathematical Structures in Computer Science 31(5): 575-613 (2021)
4. Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański: Catoids and Modal Convolution Algebras. Algebra Universalis 84(10) (2023).
5. Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański: Posets with Interfaces as a Model for Concurrency. Information and Computation 285(B):104914 (2022)
6. Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański: Kleene Theorem for Higher-Dimensional Automata. Logical Methods in Computer Science20(4) (2024)
7. Uli Fahrenberg, Krzysztof Ziemiański: Myhill-Nerode Theorem for Higher-Dimensional Automata. Fundamenta Informaticae 192(3-4): 219-259 (2024)
8. Amazigh Amrane, Hugo Bazille, Uli Fahrenberg, Krzysztof Ziemiański: Closure and Decision Properties for Higher-Dimensional Automata. Theoretical Computer Science 1036 (2025)
9. Georg Struth, Krzysztof Ziemiański: Presheaf Automata. CoRR abs/2409.04612 (2024)
10. Amazigh Amrane, Hugo Bazille, Emily Clement, Uli Fahrenberg, Philipp Schlehuber-Caissier: Higher-Dimensional Timed Automata for Real-Time Concurrency. CoRR abs/2401.17444 (2025)
11. Amazigh Amrane, Hugo Bazille, Emily Clement, Uli Fahrenberg, Marie Fortin, Krzysztof Ziemiański: Büchi-Elgot-Trakhtenbrot Theorem for Higher-Dimensional Automata. CoRR abs/2505.10461 (2025)

Other publications

Conference contributions and others:

12. Uli Fahrenberg, Christian Johansen, Georg Struth, Ratan Bahadur Thapa: Generating Posets Beyond N. RAMiCS 2020: 82-99
13. Cameron Calk, Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański: lr-Multisemigroups, Modal Quantales and the Origin of Locality. RAMiCS 2021: 90-107
14. Olavi Äikäs, Uli Fahrenberg, Christian Johansen, Krzysztof Ziemiański: Generating Posets with Interfaces. CoRR abs/2203.02695 (2022)
15. Uli Fahrenberg, Christian Johansen, Georg Struth, Krzysztof Ziemiański: A Kleene Theorem for Higher-Dimensional Automata. CONCUR 2022: 29:1-29:18
16. Uli Fahrenberg, Krzysztof Ziemiański: A Myhill-Nerode Theorem for Higher-Dimensional Automata. PETRI NETS 2023: 167-188
17. Amazigh Amrane, Hugo Bazille, Uli Fahrenberg, Krzysztof Ziemiański: Closure and Decision Properties for Higher-Dimensional Automata. ICTAC 2023: 295-312
18. Amazigh Amrane, Hugo Bazille, Emily Clement, Uli Fahrenberg: Languages of Higher-Dimensional Timed Automata. PETRI NETS 2024: 197-219
19. Amazigh Amrane, Hugo Bazille, Emily Clement, Uli Fahrenberg, Krzysztof Ziemiański: Presenting Interval Pomsets with Interfaces. RAMiCS 2024
20. Amazigh Amrane, Hugo Bazille, Uli Fahrenberg, Marie Fortin: Logic and Languages of Higher-Dimensional Automata. DLT 2024
21. Safa Zouari, Krzysztof Ziemiański, Uli Fahrenberg: Bisimulations and Logics for Higher-Dimensional Automata. ICTAC 2024
22. Amazigh Amrane, Hugo Bazille, Uli Fahrenberg, Loïc Hélouët, Philipp Schlehuber-Caissier: Petri Nets and Higher-Dimensional Automata. PETRI NETS 2025
23. Luc Passemard, Amazigh Amrane, Uli Fahrenberg: Higher-Dimensional Automata: Extension to Infinite Tracks. FSCD 2025
24. Emily Clement, Enzo Erlich, Jérémy Ledent: Kamp Theorem for Higher Dimensional Automata. CSL 2026

Software and data

Software and data published by the (i)Po(m)set Project:

• Python code related to [RAMiCS 2020]
• Julia code related to [I&C 2022]
• Julia code related to [arxiv/2203.02695]
• Iposets and gp-iposets on up to 8 points, and forbidden substructures on up to 10 points

Contact

fahrenberg@gmail.com