August 2026 - Categories - categories.org.au

Algebra Down Under 2026, the 10th Australian Algebra Conference (16-20 Nov 2026)
by JS Lemay 11 Sep '26

11 Sep '26

[[Send on behalf of the organisers]] Dear colleagues, We are pleased to announce Algebra Down Under 2026, the 10th Australian Algebra Conference, which will be held at Western Sydney University in Sydney, Australia, from 16–20 November 2026. The conference will bring together mathematicians working across a broad range of areas in algebra, including category theory, representation theory, K-theory, universal algebra, operator algebras, noncommutative algebra, group theory, algebraic geometry, semigroup theory, graph theory, and coding theory. Registration is now open through the conference website: https://adu2027.github.io/10thaac/ Early-bird registration closes on 30 September 2026. The early-bird fees are AUD 180 for academics and general participants, and AUD 100 for students, postdoctoral researchers, and early-career researchers. The submission link for contributed talks will be available shortly on the conference website. Talk submissions and conference registration will be handled separately, so those interested in presenting a talk are welcome to register now. Further information, including the list of invited speakers, is available on the conference website. Questions may be directed to adu(a)westernsydney.edu.au<mailto:adu@westernsydney.edu.au>. We would be grateful if you could share this announcement with interested colleagues and students. Best wishes, The Algebra Down Under 2026 Organising Committee

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ICLA 2027 - Submission deadline extended to September 3, 2026 AoE
by Abhisekh Sankaran 28 Aug '26

28 Aug '26

============== *Call for Papers* ============== --------------------------------------------------------------- ICLA 2027: Indian Conference on Logic and its Applications January 6 - 8, 2027 The Indian Institute of Science (IISc), Bangalore, India https://conf.researchr.org/home/icla-2027 *Extended submission deadline:* September 3, 2026 AoE Submission link: https://easychair.org/conferences/?conf=icla2027 Notification to authors: October 31, 2026 --------------------------------------------------------------- ICLA 2027 is the 12th edition of the biennial conference organised by the Association for Logic in India (ALI). It serves as a forum that brings together researchers from a variety of disciplines in which formal logic plays a significant, and often foundational, role, including Mathematics, Computer Science, Philosophy, Linguistics, and Cognitive Science. A distinctive feature of ICLA is its inclusion of research on systems of logic in the Indian tradition, as well as historical studies of logic. Details of ICLA 2025 can be found here, and information about earlier editions of the conference is available on the ALI website. https://logicindia.org/icla/icla2025/ https://logicindia.org/ ICLA 2027 will be held at the Indian Institute of Science (IISc), Bangalore, from January 6–8, 2027. Pre-conference workshops will be held on January 5, 2027. *List of Topics* Topics of interest include, but are not limited to, the following. Interdisciplinary submissions are especially encouraged. *Mathematical Logic and Foundations* Algorithmic randomness, category theory, descriptive set theory, foundations of mathematics, homotopy type theory, logical aspects of topology, model theory, recursion theory, reverse mathematics, universal algebra. *Modal, Epistemic, and Non-Classical Logics* Belief change and revision, deontic logics, description logics, dynamic epistemic logic, first-order modal logic, formal epistemology, imperative logics, interaction of classical logic with other logics, many-valued logics and their applications, modal logic: algebraic, algorithmic, category-theoretic, and model-theoretic aspects, non-monotonic logics, paraconsistency, particular systems of logic, provability logics, normative reasoning. *Logic in Computer Science* Automata theory and logic, category theory in computer science, logic and algebraic methods, logic and concurrency, logic and games, logic and quantum computing, probabilistic logics and stochastic processes, transductions, two-variable logics, well-quasi-orders. *Formal Methods, Verification, and Automated Reasoning* Automated reasoning, decision procedures for logics, formal analysis of programs, formal verification and synthesis, hyperproperties, logic in industrial applications, logic in security and privacy, programming language semantics, real-time logics, software tools and systems for logic, theory and applications of SAT and SMT solvers and theorem provers. *Finite Model Theory, Complexity, and Data* Algorithmic metatheorems, comonads in finite model theory, definable functions on relational structures, logic and computational complexity, logic and constraint satisfaction problems, logic and databases, logic and graph structure theory, many-valued logics in finite model theory, proof complexity, stability theory over finite structures. *Logic, Artificial Intelligence, and Multi-Agent Systems* Logic and artificial intelligence, logic and machine learning, logical aspects of Large Language Models (LLMs), logic for information, logic for probability and uncertainty, logic in decision and game theory, logic and social choice theory, logic and social cognition, logic and social software, logics for multi-agent systems. *History, Philosophy, Language, and Cognition* History of logic: Indian, Chinese, and Western traditions and comparative studies, Indian philosophical systems: Buddhism, Jainism, Mīmāṃsā, and Nyāya, logic and cognitive science, logic and education, logic and ethics in artificial intelligence, logic and law, logic and linguistics, logic and metaphysics, logic and philosophy of mathematics, logic and philosophy of science, philosophical issues concerning logical systems, philosophy of language. *Submission* Authors are invited to submit papers presenting original and unpublished research in any area of logic and its applications. Submissions must be written in English and should provide sufficient detail to enable the Programme Committee to assess the merits of the work. Papers may not exceed 12 pages, excluding references, and must be prepared using the Springer-Verlag Lecture Notes LaTeX2e style: https://link.springer.com/series/558/information-for-authors-and-editors If necessary, detailed proofs of technical results may be included in a clearly marked appendix, which may be consulted at the discretion of the Programme Committee. Submissions must be in PDF format. All submissions must be made electronically through the EasyChair conference management system using the following link: https://easychair.org/conferences/?conf=icla2027 Simultaneous submission to journals or to other conferences with published proceedings is not permitted. Submitted papers will undergo peer review, and accepted papers will be published in the conference proceedings, which will be available at the time of the conference. The proceedings will appear as a volume in the FoLLI Publications on Logic, Language and Information, a subseries of Springer LNCS. To be included in the proceedings, at least one author of each accepted paper must commit to presenting the paper at the conference. *Invited Speakers* - Anuj Dawar (University of Cambridge) - Andreas Herzig (IRIT, Toulouse) - Angelo Montanari (University of Udine) - Greg Restall (University of St Andrews) *Important Dates* ************************************************************************ Extended Submission Deadline: September 3, 2026 AoE Notification to Authors: October 31, 2026 Deadline for camera-ready papers: November 11, 2026 Pre-conference workshops: January 5, 2027 ICLA 2027: January 6-8, 2027 ************************************************************************ *Programme Committee* Sreejith A V [IIT Palakkad] Philippe Balbiani [IRIT, Toulouse] Nick Bezhanishvili [University of Amsterdam] Abhishek De [Krea University] Tim French [The University of Western Australia] Malvin Gattinger [University of Amsterdam] Sujata Ghosh [Indian Statistical Institute, Chennai] (co-chair) Shibashis Guha [Tata Institute of Fundamental Research] Eberhard Guhe [Fudan University] Yurii Khomskii [University of Amsterdam] Arun Kumar [Banaras Hindu University] Graham Leigh [University of Gothenburg] Dazhu Li [Chinese Academy of Sciences] Hitoshi Omori [Tohoku University] Anantha Padmanabha [IIT Madras] Sophie Pinchinat [IRISA, Universite de Rennes] Dilip Raghavan [National University of Singapore] Subhajit Roy [IIT Kanpur] Prakash Saivasan [Institute of Mathematical Sciences, Chennai] Manidipa Sanyal [University of Calcutta] Sunil Simon [IIT Kanpur] (co-chair) S P Suresh [Chennai Mathematical Institute] Ramanathan Thinniyam Srinivasan [Uppsala University] Sourav Tarafder [St. Xavier's College, Kolkata] Sara Uckelman [Durham University] Yanjing Wang [Peking University] *Organising Committee* Deepak D’Souza [Indian Institute of Science, Bangalore] Siddhartha Gadgil [Indian Institute of Science, Bangalore] Kamal Lodaya [BGVS Bangalore]

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Andrée Ehresmann (1935-2026)
by Isar Stubbe 25 Aug '26

25 Aug '26

Dear Colleagues, With great sadness, we inform you of the passing of Andrée Ehresmann (née Bastiani) on Friday, August 21, 2026, at her home in Amiens. Andrée Ehresmann played a major role in the category theory community for over sixty years. Born in Nice in 1935, she went as a young woman to Paris to study mathematics and Latin. She completed her doctoral thesis, and later her thèse d'État, in functional analysis, under the supervision of Gustave Choquet. From 1967, she was maître de conférences, and then professor, at the Université de Picardie in Amiens. It was Choquet who, already during her doctoral studies, encouraged her to take up category theory in the form that Charles Ehresmann was developing at that time. She later met Charles Ehresmann, who became her husband, and with whom she collaborated intensively until his death in 1979. Together they established the French school in category theory in Amiens, which became a vibrant research center, known internationally. From 1970 onwards, she was the driving force behind the Cahiers de Topologie et Géométrie Différentielle Catégoriques, which she directed until her passing. Andrée Ehresmann worked in various areas of category theory and pioneered the applications of categorical methods to the modeling of living and cognitive systems, mainly in collaboration with Jean-Paul Vanbremeersch. Her fundamental scientific contributions have been presented in an invited talk by René Guitart at the Séminaire Itinérant des Catégories held in Louvain-la-Neuve to celebrate her 90th birthday (https://www-lmpa.univ-littoral.fr/~sic/wordpress/?page_id=1609) The slides of René's talk are available here: https://www-lmpa.univ-littoral.fr/~sic/Louvain2025/Guitart.pdf On that occasion, she herself participated remotely and presented a talk, in French, about her scientific career: https://www-lmpa.univ-littoral.fr/~sic/Louvain2025/Ehresmann.pdf In the final months of her life, Andrée Ehresmann's health declined rapidly. Those who knew her personally appreciated her vision, leadership, generosity, and constant support of younger researchers. With her passing, the category theory community loses a prominent mathematician and a uniquely dedicated figure who contributed greatly to a historic era of French mathematics. Best regards, Isar Stubbe, Marino Gran, and René Guitart.

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Re: [cat.fr] Andrée Ehresmann (1935-2026)
by Ross Street 24 Aug '26

24 Aug '26

Thank you Camell. Thank you for the message Isar, Marino and René. Condolences to you all and to the category community. A solid pillar of category theory has moved on. It is hard to remember when I first became aware of Andrée, possibly from her joint publications such as [Bastiani, Andrée; Ehresmann, Charles Catégories de foncteurs structurés. Cahiers Topologie Géom. Différentielle 11 (1969), 329–384] with Charles. As mentioned in the message, Andrée did the total editing of the Cahiers for quite awhile. However, it was much more than normal editing. She rewrote all the papers herself (as I understood it) in the Cahiers style! She also acted as a referee and mentor providing corrections and suggestions. This applied to my two early papers "Two constructions on lax functors" and "Fibrations in bicategories". The first version of the latter did not detail the cofibrations for enriched categories at all. I am so glad Andrée pushed me into attending to that. I was honoured when she asked me to join the editorial board. Andrée's notes on Charles' complete works are invaluable. As many will know, Australia has a special connection with Amien. Imogen and Max Kelly came back from their visit glowing about what wonderful hosts the Ehresmanns were. I was fortunate enough to experience that and confirm it with two visits while Charles was still with us, one visit with family and one alone. Mme Ehresmann will be remembered as a pioneer of category theory, its communication, and its application. Very sadly, Ross On 23 Aug 2026, at 6:38 pm, Camell Kachour <camell.kachour(a)gmail.com> wrote: Dear Ross, Sad news, Andrée Ehersmann has passed away. With best regards, Camell. Le dim. 23 août 2026 à 12:54, Isar Stubbe <isar.stubbe(a)univ-littoral.fr<mailto:isar.stubbe@univ-littoral.fr>> a écrit : Chers collègues, C'est avec une grande tristesse que nous vous informons du décès d'Andrée Ehresmann (née Bastiani), survenu le vendredi 21 août 2026 à son domicile à Amiens. Andrée Ehresmann a joué un rôle majeur au sein de la communauté de la théorie des catégories pendant plus de soixante ans. Née à Nice en 1935, elle s'est rendue jeune femme à Paris pour y étudier les mathématiques et le latin. Elle a soutenu sa thèse de doctorat, puis plus tard sa thèse d'État, en analyse fonctionnelle, sous la direction de Gustave Choquet. À partir de 1967, elle a été maître de conférences, puis professeure, à l'Université de Picardie à Amiens. C'est Choquet qui, dès ses études doctorales, l'a encouragée à s'intéresser à la théorie des catégories sous la forme que Charles Ehresmann développait à cette époque. Elle a rencontré par la suite Charles Ehresmann, qui est devenu son époux et avec qui elle a collaboré intensément jusqu'à son décès en 1979. Ensemble, ils ont fondé l'école française de théorie des catégories à Amiens, qui est devenue un centre de recherche dynamique et de renommée internationale. À partir de 1970, elle a été la cheville ouvrière des Cahiers de Topologie et Géométrie Différentielle Catégoriques, qu'elle a dirigés jusqu'à son décès. Andrée Ehresmann a travaillé dans divers domaines de la théorie des catégories et a fait œuvre de pionnière dans l'application des méthodes catégoriques à la modélisation des systèmes vivants et cognitifs, principalement en collaboration avec Jean-Paul Vanbremeersch. Ses contributions scientifiques fondamentales ont été présentées lors d'un exposé invité par René Guitart au Séminaire Itinérant des Catégories organisé à Louvain-la-Neuve pour célébrer son 90e anniversaire (https://www-lmpa.univ-littoral.fr/~sic/wordpress/?page_id=1609<https://www-lmpa.univ-littoral.fr/~sic/wordpress/?page_id=1609>). Les diapositives de l'exposé de René sont disponibles ici : https://www-lmpa.univ-littoral.fr/~sic/Louvain2025/Guitart.pdf<https://www-lmpa.univ-littoral.fr/~sic/Louvain2025/Guitart.pdf> À cette occasion, elle a elle-même participé à distance et a présenté un exposé, en français, sur sa carrière scientifique : https://www-lmpa.univ-littoral.fr/~sic/Louvain2025/Ehresmann.pdf<https://www-lmpa.univ-littoral.fr/~sic/Louvain2025/Ehresmann.pdf> Au cours des derniers mois de sa vie, la santé d'Andrée Ehresmann s'est rapidement dégradée. Celles et ceux qui l'ont connue personnellement ont apprécié sa vision, son sens de la direction, sa générosité et son soutien constant aux jeunes chercheurs. Avec sa disparition, la communauté de la théorie des catégories perd une mathématicienne de premier plan et une figure d'un dévouement unique qui a grandement contribué à une époque historique des mathématiques françaises. Cordialement, Isar Stubbe, Marino Gran et René Guitart. Pour modifier votre abonnement : https://liste.univ-littoral.fr/sympa/info/cat.fr<https://liste.univ-littoral.fr/sympa/info/cat.fr> Pour vous désinscrire : https://liste.univ-littoral.fr/sympa/signoff/cat.fr/camell.kachour%40gmail.…<https://liste.univ-littoral.fr/sympa/signoff/cat.fr/camell.kachour%40gmail.…>

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Re: Andrée Ehresmann (1935-2026)
by Marco Grandis 23 Aug '26

23 Aug '26

Dear All, I wish to express my deep gratitude to Andrée. Her drive in unfolding categorical visions in new fields have played and are playing an important role in category theory. Her kindness and devotion have made her contribution unique. Regards Marco Grandis

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First Central European Category Theory Seminar
by bourkej 22 Aug '26

22 Aug '26

Dear all, We are pleased to announce that the first Central European Category Theory Seminar will take place at Masaryk University, Brno on Friday November 20th 2026. The idea of the meeting is to bring together researchers in category theory and related areas from around the local region in an informal setting to meet and discuss their research. We have invited speakers from Prague, Vienna and Budapest and will also welcome short contributions from attendees. Further information is available on the webpage. https://centraleuropeanctseminar.github.io/CECTSeminarBrno2026/ Anyone is welcome to attend but we ask you to register by September 30th so we have an idea of the numbers. This is essential if you would like to contribute a short talk or apply for some financial support to make the trip (we expect to have some money available for train/bus transport and hotel). If you have any questions, feel free to email any of the organisers. Look forward to seeing you there, The Organisers (John Bourke, Mike Lieberman, Lukas Vokřínek).

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Do localizations of categories always preserve initial objects and terminal objects? If so, is this recorded?
by Yemon Choi 21 Aug '26

21 Aug '26

Hello everyone, This is primarily a reference request, but I would also welcome corrections or indications of "better ways to approach this". I am not a category-theorist by training! My current PhD student and I have been looking at the localization of a certain subcategory of Grp, with respect to a class of morphisms that satisfy some but not all of the conditions for a left/right calculus of fractions. The key feature is that in the localization, every abelian group becomes isomorphic to the trivial group. We then wanted to show that every abelian group behaves as a zero object in the localized category (initial and terminal), and verified this in an ad hoc way. However, inspecting our arguments, they seem to work in much greater generality, leading to: CLAIM: let C be any category with a terminal object 1, and let W be any class of morphisms in C. Then 1 is a terminal object in the localization C[W^{-1}]. Initially this seemed too good to be true, since localization "adds more morphisms", but at the time of writing I can't find a mistake in our argument. Q1. Does anyone know a reference for this result/claim? The sources that I have consulted so far mostly discuss localization in contexts where C or W satisfy additional conditions, and say very little about general properties of the localisation functor when W is arbitrary. In the general setting I see no reason for the localisation functor to admit a left adjoint, which would be the cheapest way to show that it preserves terminal objects. Q2. Assuming we haven't made an error: is there a "conceptual" reason or explanation for this result? Our current argument relies on the concrete model of C[W^{-1}] in terms of equivalence classes of zigzags (a la Gabriel-Zisman), and shows that any zigzag starting at an object A_0 and ending at 1 is equivalent to the unique C-morphism A_0 \to 1. The proof is "hacky": it works by performing an induction on the length of the zigzag, and requires a small but mildly annoying case-by-case analysis. I have often been told that a "true" categorical perspective should just use the appropriate universal property of localization (perhaps in a 2-categorical context), but at the moment I can't see a way to achieve this. Remark: essentially the same reasoning seems to show that localization preserves initial objects, so both Q1 and Q2 apply to that result/claim. Regards Yemon -- Dr. Y. Choi School of Mathematical Sciences Lancaster University Bailrigg, Lancaster Lancashire LA1 4YF

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RHPL@FSTTCS 2026: Call for Proposals
by Abhisekh Sankaran 21 Aug '26

21 Aug '26

TCS Confidential ============================================================= CALL FOR PROPOSALS RHPL@FSTTCS 2026: Workshop on Research Highlights in Programming Languages + Dates: December 16 - 18, 2026 + Venue: IIT Delhi, co-located with FSTTCS 2026 + Website: https://fmindia.cmi.ac.in/rhpl2026/ + Submission deadline: September 28, 2026 IST ============================================================= Dear Colleague, As you may know, FSTTCS 2026 (https://www.fsttcs.org.in/2026/) will be held at IIT Delhi (https://home.iitd.ac.in/) during December 16 - 18, 2026. The conference is organized by IARCS, the Indian Association for Research in Computing Science (https://www.iarcs.org.in/) in association with ACM India (https://india.acm.org/) It is a very visible forum for presenting original results in foundational aspects of Computer Science and Software Technology. As in previous years, the Workshop on Research Highlights in Programming Languages (RHPL) will be co-located with the main FSTTCS conference. The workshop is organized jointly by IARCS and iPLAN (the India Chapter of ACM SIGPLAN; https://india.acm.org/chapters) The focus of the workshop will be on all areas of Programming Languages. The objective of RHPL is to foster interactions between the attendees of the workshop, and more broadly researchers working on Programming Languages, and the traditional FSTTCS community of researchers working on Theoretical Computer Science and Formal Methods. We invite proposals for: + Talks: based on recent work that has been published in reputed venues, or is mature in terms of approach and evaluation. + Posters: - Regular: Based on early ideas that are promising but have not been developed fully. Selections of these proposals will be made based on the promise of research possibilities and their novelty. - Student: Based on unpublished work at any stage. Selected proposals will be included in a student poster competition that will be judged by a panel of experts. More details on the submission topics, submission guidelines and the student poster competition can be found below. --------------- Websites: --------------- RHPL 2026: https://fmindia.cmi.ac.in/rhpl2026/ RHPL 2025: https://fmindia.cmi.ac.in/rhpl2025/ ============= Important Dates ============= All dates below are in Indian Standard Time (IST). - Submission portal opens: August 21, 2026 - Submission deadline: September 28, 2026 - Notification: October 7, 2026 - Early registration deadline: TBA - RHPL@FSTTCS: December 16 - 18, 2026 =============== Submission Topics =============== The submission topics include, but are not limited to, the following: - Applied formal methods - Automated and interactive theorem provers - Compilers - Concurrency and memory models - Domain and type theories - Program analysis and verification - Program sketching, synthesis, and repair - Programming language design and semantics Further, in view of the increasing role of Artificial Intelligence (AI) and Machine Learning (ML) in PL theory and practice, the workshop explicitly includes in its scope themes at this intersection. Of particular interest are the roles of Large Language Models (LLMs) in PL, such as in design and code synthesis, as well as broader mutual influences between AI/ML and PL; for instance, probabilistic programming languages. ==================== Student Poster Competition ==================== We invite students at all stages, from undergraduate to PhD, to submit poster proposals based on their unpublished work. For graduate students, only individual work is allowed to be presented. If the work is being done as part of a group, then the presenters must focus on their individual contributions. Undergraduates can present their individual work and also work done in (undergraduate) team projects. The evaluation of the posters will be on the basis of the technical strength of the work, the presenter's awareness of related literature, and the quality of the poster and presentation. The results will be announced on the RHPL 2026 website following the competition. ================ Submission Guidelines ================ Proposals to the workshop may be submitted using the form below. https://forms.fillout.com/t/7ePHh773f2us Proposals for talks may be based on published or unpublished work. Proposals for posters are only for unpublished work. For both formats, submissions may present either a single study, such as in an individual paper or an unpublished manuscript, or a body of research. Multiple proposal submissions are allowed. Each proposal must be submitted as a single PDF file. Any reasonable style file can be chosen. The proposal page limits are as below; the page counts exclude references. Appendices are to be avoided, and references may contain pointers to papers, preprints, technical reports, or manuscripts under progress that the proposal is based on. + Talks: - Proposals based on work that is published: 2 pages - Proposals based solely on unpublished work: 4 pages + Posters: - Regular (non-student) proposals: 2 pages - Student proposals: 4 pages Talk proposals based on unpublished work and student poster proposals will be provided short referee reports along with their decision notifications. There are no publications of the workshop. Accepted proposals may be compiled into a booklet of abstracts/proposals to be made available on the RHPL 2026 website. ======= Contact ======= For any queries, feel free to write to us at the addresses below. - pankaj.kumar.kalita(a)ibm.com<mailto:pankaj.kumar.kalita@ibm.com> - abhisekh.sankaran(a)tcs.com<mailto:abhisekh.sankaran@tcs.com> We look forward to receiving your talk/poster proposals to the workshop. On behalf of the RHPL@FSTTCS workshop organizing committee: Pankaj Kumar Kalita (IBM Research) (co-Chair) Abhisekh Sankaran (TCS Research) (co-Chair) Deepak D'Souza (IISc Bangalore) Uday Khedker (IIT Bombay) Kumar Madhukar (IIT Delhi) Kartik Nagar (IIT Madras) Ganesan Ramalingam (Microsoft) Abhik Roychoudhury (National University of Singapore) Divyesh Unadkat (Synopsys) =====-----=====-----===== Notice: The information contained in this e-mail message and/or attachments to it may contain confidential or privileged information. If you are not the intended recipient, any dissemination, use, review, distribution, printing or copying of the information contained in this e-mail message and/or attachments to it are strictly prohibited. If you have received this communication in error, please notify us by reply e-mail or telephone and immediately and permanently delete the message and any attachments. Thank you

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Pacific Category Theory Seminar (Online) - Friday, August 28
by JS Lemay 20 Aug '26

20 Aug '26

Dear all, Alyssa Renata (Imperial College London) will give a talk for a second edition of this month's PCT seminar (https://pctseminar.github.io/) on Friday August 28 at 10am JST/11am AED (1am UTC). The zoom link to join the seminar is: https://kyoto-u-edu.zoom.us/j/82401794000?pwd=VjVmzVjmlgxhkdHES4xYeQBTpMzQk… Title: The Game Spectrum of a Monad? Abstract: In recent work joint with Richard Garner and my supervisor Nicolas Wu, inspired by the computational effects interpretation of monads and algebraic theories due to Moggi, Plotkin and Power, we constructed an adjunction between the category of monads on set and the category of small categories and retrofunctors/cofunctors. Under the computational effects interpretation, the monad encodes computations which may interact with or affect some environment. The left adjoint to this construction assigns to each monad what is called its **behaviour category**, which may be seen as a model of the environment itself: the objects are the possible states, and the morphisms transitions between states. This adjunction ought to be seen as a kind of duality, with the behaviour category acting as the spectrum of a monad. The first half of the talk will be dedicated to reviewing this construction and its surrounding adjunction. The second half of the talk is about my recent attempt with Richard at rectifying a defect of the theory: many monads have trivial behaviour category! This is undesirable because of an analogy we want to develop with schemes: the monads replace the (commutative) rings, while the behaviour category should replace the affine schemes. But of course, an affine scheme/spectrum should faithfully encode its corresponding ring/monad, and this is evidently not so for the behaviour category. Our proposal then is to replace the behaviour category by a particular 2-player game (between the program and the environment), from which the data of the behaviour category can be extracted by inspecting its (winning) strategies. The point is that the behaviour category is trivial when there are no winning strategies, but this need not imply triviality of the game itself. To be more precise, we will investigate the relationship with the template games of Paul-Andre Mellies, which he used to build higher-dimensional models of linear logic. We hope to see you there! Talks after posted on youtube afterwards: https://www.youtube.com/@PCTSeminar Best wishes, Soichiro Fujii, Zeinab Galal, JS PL

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PhD and Postdoc in the theory of comonads
by Tomáš Jakl 19 Aug '26

19 Aug '26

Dear All, I'm looking for a postdoc and PhD student to work with me on the study of both the theory and applications of comonads. We aim to build the theory of presentations of comonads to be able to specify computational resources in a principal way. Therefore, the project is in the intersections of category theory, linear type theory, programming language semantics and potentially also finite model theory (via game comonads), theory of concurrency and so on. For details, see https://tomas.jakl.one/projects/unicator Feel free to pass my announcement to potential candidates, should you know any. Thank you, Tomas

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