October 2026 - Categories - categories.org.au

RAMiCS 2027 — Call for Papers
by Luigi Santocanale 21 Oct '26

21 Oct '26

Apologies for multiple copies of this email; please distribute as you see fit. CALL FOR PAPERS RAMiCS 2027 23rd International Conference on Relational and Algebraic Methods in Computer Science University of Johannesburg Wits Rural Facility, Hoedspruit, South Africa, 16-20 August 2027 https://ramics-conf.github.io/2027 The RAMiCS conference series is the main venue for research on relational algebras, Kleene algebras and similar algebraic formalisms, and their applications as conceptual and methodological tools in computer science and beyond. RAMiCS 2027 will be organized at the Wits Rural Facility, Hoedspruit, South Africa, and will feature both a classical conference and interactive sessions. IMPORTANT DATES * Abstract submission deadline: 8 January 2027 * Paper submission deadline: 22 January 2027 * Author notification: 26 March 2027 * Final version due: 23 April 2027 * Conference dates: 16-20 August 2027 PROGRAM COMMITTEE * Andrew Craig — South Africa (PC co-chair) * Roland Glück — Germany (PC co-chair) * Eugenia Ternovska — Canada (PC co-chair) * Henning Basold — The Netherlands * Paul Brunet — France * Uli Fahrenberg — France * Damas Gruska — Slovakia * Walter Guttmann — New Zealand * Robin Hirsch — United Kingdom * Peter Höfner — Australia * Marcel Jackson — Australia * Ali Jaoua — Qatar * Peter Jipsen — United States * Tomasz Kowalski — Poland * Arun Kumar — India * Sławomir Lasota — Poland * Ioana Leustean — Romania * Roger Maddux — United States * Brett McLean — Belgium * Nelma Moreira — Portugal * Luigi Santocanale — France * Jas Semrl — United Kingdom * Michael Winter — Canada * Krzysztof Ziemiański — Poland SCOPE Since 1994, the RAMiCS conference series has been the main venue for research on relational algebras, Kleene algebras and similar algebraic formalisms, and their applications as conceptual and methodological tools in computer science and beyond. Theoretical aspects include semigroups, residuated lattices, semirings, Kleene algebras, relation algebras, quantales and other algebras; their connections with program logics and other logics; their use in the theories of automata, concurrency, formal languages, games, networks and programming languages; the development of algebraic, algorithmic, category-theoretic, coalgebraic and proof-theoretic methods for these theories; their formalisation with theorem provers. Applications of these formalisms span a wide range of domains, including tools and techniques for program specification, verification, and correctness; qualitative and quantitative models of computing systems; algorithm design; automated reasoning; network protocol analysis; optimisation; control; and even social choice theory. We are calling for submission of original work not published or under review for publication elsewhere. The proceedings will be published as part of Springer LNCS. As for earlier RAMiCS conferences, we intend to publish a journal special issue with revised and extended versions of a selection of the best papers. Submissions must be in English using a PDF not exceeding 16 pages (excluding references and AI disclosure; see below) in LNCS style. Submission is via EasyChair at https://easychair.org/conferences/?conf=ramics2027 For more information, see https://ramics-conf.github.io/2027/ With regard to the recent developments in AI, there are the following guidelines for the use of AI: 1. Use of generative AI tools for conducting research must be disclosed in a submitted paper, with their specific uses described in detail. Such uses include the design of the research project, creation of theories and algorithms, designing experiments, generation and collection of data, coding, data analysis, testing, assisting with writing, or any aspects that are directly relevant to the conclusion of the research. This disclosure does not count for the page limit. We expect that contributions result mostly from human action. The PC may consider the usage of generative AI into account when assessing the novelty of submissions. 2. All named authors on a submission will be held responsible and accountable for any problematic content contained in the submission, regardless of its source. 3. PC members and subreferees must preserve confidentiality of the submitted material; in particular, it should not be passed to external AI tools. Please feel free to forward this announcement to interested colleagues. Best regards, the RAMiCS 2027 organizers: Andrew Craig, Roland Glück, and Eugenia Ternovska

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UMP: Elementary vs. Higher
by George Janelidze 21 Oct '26

21 Oct '26

Dear Colleagues, May I only make a comment on what Mr. Posina Venkata Rayudu says about Mac Lane's "Duality of Groups"? We all are humans, not computers, and in some cases we might miss some important references (I am sure I did it more than once). But I think we should be more careful in saying this about others, especially about those who are not with us anymore, and those who made a great contribution to mathematics and greatly helped many others to become excellent mathematicians. I am glad that "...UMP definition of product clearly(?) beats MacLane by at least 2 years..." at least contains a question mark, because the answer to that question is NO. But it is so because "beats" is wrong, sorry! Let me explain, speaking, for simplicity, about the binary product AxB. Put simply, Samuel says that, for various types of structures, the product structure on the product of underlying sets of A and B can be characterized by saying that (the projections preserve structure and) given structure preserving maps f:C—>A and g:C—>B, the map h:C—>AxB defined by h(c)=(f(a),g(c)) is also structure preserving. Needless to say, this is fundamentally different from defining products by the universal property (not to mention anything else, this cannot be used to define products of sets). Well, one might argue that universal properties in the sense of Bourbaki were predecessors of what we call universal properties today, but one might equally argue that Bourbaki structures and their axiomatically defined morphisms were predecessors of categories, but predecessors themselves had predecessors... Or, one might reformulate what Bourbaki used in terms of suitable forgetful functors into the category of sets, but that is another story. Sincerely, George Janelidze ________________________________ From: Posina Venkata Rayudu via Categories <categories-list(a)categories.org.au> Sent: Monday, October 19, 2026 19:18 To: Category Theory Mailing List <categories-list(a)categories.org.au> Cc: Posina Venkata Rayudu <posinavrayudu(a)gmail.com> Subject: [categories] UMP: Elementary vs. Higher CAUTION: This email originated outside the UCT network. Do not click any links or open attachments unless you know and trust the source. Dear All, I hope all is well. (Reading Advisory: Boring ;) In the case of the elementary universal mapping property (UMP) definitions (e.g., product, sum), wherein commutativity i.e., the isomorphism between, say, (A + B) and (B + A), makes the ordering boring (both at the level of listing summands A, B and also at that of the sum). However, in stating the definition of exponentiation or functor category as a higher UMP: For any pair of objects A, B of a category C, there is an object B^A called the object (or category) of all maps (functors) from A to B. This always seemed little like withholding the truth, albeit for a femtosec, in the sense of: given objects A, B, there's also the object A^B of maps from B to A. Is this asymmetry: product / sum vs. exponential, where switching around the objects doesn't matter vs. does matter (turning the whole thing upside down ;) the content of the contrast: elementary vs. higher (UMP definitions)? On a related note, MacLane (1950) Duality for Groups <https://www.ams.org/journals/bull/1950-56-06/S0002-9904-1950-09427-0/S0002-…<https://www.ams.org/journals/bull/1950-56-06/S0002-9904-1950-09427-0/S0002-…>> construes products and sums as universal mapping properties, but, for whatever reasons, doesn't cite [Bourbaki] Samuel (1948) Universal Mappings paper published in the very same Bulletin of the AMS <https://www.ams.org/journals/bull/1948-54-06/S0002-9904-1948-09052-8/S0002-…<https://www.ams.org/journals/bull/1948-54-06/S0002-9904-1948-09052-8/S0002-…>>, which with its UMP definition of product clearly(?) beats MacLane by at least 2 years. Then again, it's MacLane who, in his own admission, got to pick and choose editors and reviewers of his papers (e.g., Mackey); I wish I could (one invariant of the reviews I receive is that I didn't cite this or that or dem ;) Moving along to higher UMPs, the definition of truth value object / subobject classifier had to wait for Professor F. William Lawvere (cf. Grothendieck's "Lawvere element" <https://www.mat.uc.pt/~picado/lawvere/interview.pdf<https://www.mat.uc.pt/~picado/lawvere/interview.pdf>> p. 7). In my limited reading, it seems to me that even the aforementioned higher UMP definition of exponentiation also appears, for the first time(?), in the thesis of Professor F. William Lawere (cf. Functorial Semantics of Algebraic Theories <http://www.tac.mta.ca/tac/reprints/articles/5/tr5.pdf<http://www.tac.mta.ca/tac/reprints/articles/5/tr5.pdf>> p. 29). I look forward to your clarifications and corrections! Thanking you, Yours respectfully, posina P.S. As much as I hate watching people fight, I can't help but share an anecdote: A Frenchman, upon returning from a visit to the then blazing USA, quipped: Americans confuse plumbing for culture ;) On a related note, going by the "Emily in Paris", France has a long way to go (plumbing ;) Along these lines, even at the Harvard Medical School, it is understood and admitted by none other than Americans, based on the accumulating evidence in the discipline of neuroscience, that European science is solid, while Americans are good salesmen ;) _______________________________________________ Categories mailing list -- categories-list(a)categories.org.au To unsubscribe send an email to categories-list-leave(a)categories.org.au Disclaimer - University of Cape Town This email is subject to UCT policies and email disclaimer published on our website at https://www.uct.ac.za/main/email-disclaimer or obtainable from +27 21 650 9111. 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Postdoc at the CIRM (Marseille, France), Jan-Dec 2027
by Marcelo Fiore 21 Oct '26

21 Oct '26

Dear All, In the context of the Morlet Chair on “Two and Higher Dimensional Structure in Computation and Logic” [1] <https://www.chairejeanmorlet.com/2027-fiore-vaux-auclair-1st-semester.html> to be held at the CIRM (Marseille, France) during the first semester of 2027, we would like to advertise an offer for a 12-month postdoc position, starting January 2027. The details of the position are available on the CNRS job offer platform [2] <https://emploi.cnrs.fr/Offres/CDD/UAR822-SOPRIB-010/Default.aspx?lang=EN>. Applications must be submitted through this platform by the imminent deadline of November 9. Best regards, Marcelo Fiore and Lionel Vaux Auclair. [1] https://www.chairejeanmorlet.com/2027-fiore-vaux-auclair-1st-semester.html [2] https://emploi.cnrs.fr/Offres/CDD/UAR822-SOPRIB-010/Default.aspx?lang=EN

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UMP: Elementary vs. Higher
by Posina Venkata Rayudu 21 Oct '26

21 Oct '26

Dear All, I hope all is well. (Reading Advisory: Boring ;) In the case of the elementary universal mapping property (UMP) definitions (e.g., product, sum), wherein commutativity i.e., the isomorphism between, say, (A + B) and (B + A), makes the ordering boring (both at the level of listing summands A, B and also at that of the sum). However, in stating the definition of exponentiation or functor category as a higher UMP: For any pair of objects A, B of a category C, there is an object B^A called the object (or category) of all maps (functors) from A to B. This always seemed little like withholding the truth, albeit for a femtosec, in the sense of: given objects A, B, there's also the object A^B of maps from B to A. Is this asymmetry: product / sum vs. exponential, where switching around the objects doesn't matter vs. does matter (turning the whole thing upside down ;) the content of the contrast: elementary vs. higher (UMP definitions)? On a related note, MacLane (1950) Duality for Groups <https://www.ams.org/journals/bull/1950-56-06/S0002-9904-1950-09427-0/S0002-…> construes products and sums as universal mapping properties, but, for whatever reasons, doesn't cite [Bourbaki] Samuel (1948) Universal Mappings paper published in the very same Bulletin of the AMS <https://www.ams.org/journals/bull/1948-54-06/S0002-9904-1948-09052-8/S0002-…>, which with its UMP definition of product clearly(?) beats MacLane by at least 2 years. Then again, it's MacLane who, in his own admission, got to pick and choose editors and reviewers of his papers (e.g., Mackey); I wish I could (one invariant of the reviews I receive is that I didn't cite this or that or dem ;) Moving along to higher UMPs, the definition of truth value object / subobject classifier had to wait for Professor F. William Lawvere (cf. Grothendieck's "Lawvere element" <https://www.mat.uc.pt/~picado/lawvere/interview.pdf> p. 7). In my limited reading, it seems to me that even the aforementioned higher UMP definition of exponentiation also appears, for the first time(?), in the thesis of Professor F. William Lawere (cf. Functorial Semantics of Algebraic Theories <http://www.tac.mta.ca/tac/reprints/articles/5/tr5.pdf> p. 29). I look forward to your clarifications and corrections! Thanking you, Yours respectfully, posina P.S. As much as I hate watching people fight, I can't help but share an anecdote: A Frenchman, upon returning from a visit to the then blazing USA, quipped: Americans confuse plumbing for culture ;) On a related note, going by the "Emily in Paris", France has a long way to go (plumbing ;) Along these lines, even at the Harvard Medical School, it is understood and admitted by none other than Americans, based on the accumulating evidence in the discipline of neuroscience, that European science is solid, while Americans are good salesmen ;)

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Universal Properties & Adjunctions
by Paul Taylor 20 Oct '26

20 Oct '26

Posina Venkata Rayudu observed: > MacLane (1950) Duality for Groups > ams.org/journals/bull/1950-56-06 ... > doesn't cite Samuel (1948) Universal Mappings ... > ams.org/journals/bull/1948-54-06 > with its Universal Mapping Property... Even more strange is that Mac Lane had REVIEWED Pierre Samuel's paper (needs an AMS login): mathscinet.ams.org/mathscinet-getitem?mr=0025152 Samuel probably also wrote the draft appendix to Bourbaki's "Algèbre" but it never appeared. This might be it: sites.mathdoc.fr/archives-bourbaki/PDF/041_iecnr_050.pdf Daniel Kan's 1958 paper "Adjoint Functors" was heavily citied withint a few years. Neither Kan nor Ehresmann cited Samuel. Google Scholar lists citations of Samuel in 1950+, 52, 57, 59+, 6-, 65+, 66, 70 (where + means twice) I haven't looked at all these but MacLane finally makes the connection with adjunctions in "Categorical algebra", Bull AMS 71 (1965) 40-106 pubs.ams.org/journals/bull/1965-71-01 These comments are based on fairly brief use of Google Scholar and other websites. It would be great if the few survivors from that time could correct me. Paul Taylor http://www.paultaylor.eu/delivery/261020-categories-history

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Final call for submissions - The Third Virtual Workshop on Double Categories
by Bryce Clarke 20 Oct '26

20 Oct '26

THE THIRD VIRTUAL WORKSHOP ON DOUBLE CATEGORIES Dates: Selected days from 2nd - 13th November 2026 Location: virtually on Zoom Dear colleagues, A reminder that submissions deadline for contributed talks to the Third Virtual Workshop on Double Categories is *Wednesday 21 October* (anywhere on earth <https://time.is/Anywhere_on_Earth>). Full information on the workshop including the form for talk proposals is available at the link below. https://bryceclarke.github.io/virtual-double-categories-workshop/index.html We look forward to your participation! Best regards, Bryce and Tim.

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Pacific Category Theory Seminar (Online) - Friday, October 23
by Zeinab Galal 20 Oct '26

20 Oct '26

Dear all, Nadish de Silva (Simon Fraser University) will give a talk for this month's PCT seminar (https://pctseminar.github.io/) on Friday October 23 at 10am JST/12pm AEDT (1am UTC). The zoom link to join the seminar is: https://kyoto-u-edu.zoom.us/j/82401794000?pwd=VjVmzVjmlgxhkdHES4xYeQBTpMzQk… Title: The Quantum Monad on Relational Structures Abstract: Homomorphisms between relational structures play a central role in finite model theory, constraint satisfaction and database theory. A central theme in quantum computation is to show how quantum resources can be used to gain advantage in information processing tasks. In particular, non local games have been used to exhibit quantum advantage in boolean constraint satisfaction, and to obtain quantum versions of graph invariants such as the chromatic number. We show how quantum strategies for homomorphism games between relational structures can be viewed as Kleisli morphisms for a quantum monad on the (classical) category of relational structures and homomorphisms. We show a general connection between these notions and state-independent quantum realizations of strong contextuality in the Abramsky-Brandenburger formulation of contextuality. We use these results to exhibit a wide range of examples of contextuality-powered quantum advantage, and to unify several apparently diverse strands of previous work. Co-authors: Samson Abramsky, Rui Soares Barbosa, Octavio Zapata We hope to see you there! Best wishes, Soichiro Fujii, Zeinab Galal, JS Lemay

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TS2027: Second Announcement – Registration is Open | Dedicated to Thomas Streicher’s Scientific Legacy
by Maria Emilia Maietti 20 Oct '26

20 Oct '26

Second Announcement [APOLOGIES FOR MULTIPLE POSTINGS] Dear all, This is the second announcement for the workshop Types and Structures (TS2027), which will be held in Padova during the week of 24–28 May 2027. The workshop will celebrate the scientific legacy of our friend and colleague Thomas Streicher. The event website can be found here: https://ulrikbuchholtz.dk/ts2027/ Registration for the event is now open. You can find a link to the registration form on the website. On the registration form, you can also indicate whether you are interested in giving a talk. We hope to be able to accommodate as many speakers as possible. We also expect to have some funds available to support junior researchers who wish to give a talk at the event. If you think you may be eligible for this support, please fill in the registration form and include a brief statement explaining your motivation for requesting funding. *Deadline for registration and funding requests for junior participants: 31 January 2027. * We encourage everyone to book accommodation as early as possible, as Padova is a popular destination in May. Finally, if you have any questions, please feel free to contact us at the following email address: typesandstructures2027(a)gmail.com We hope to see many of you at the event! Best wishes, Benno van den Berg Ulrik Buchholtz Jonas Frey Milly Maietti Jonathan Weinberger

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Cahiers LXVII-3
by Isar Stubbe 19 Oct '26

19 Oct '26

Dear Colleagues, We are pleased to inform you that a new issue of the Cahiers de Topologie et Géométrie Différentielle Catégoriques (Volume LXVII-3) is now freely available for download from the Cahiers website: https://cahierstgdc.com/ It contains contributions by T. Porter, by J.J. Xarez, by B. Strauss, and by J.-Y. Degos, and can be downloaded either as a complete volume or as individual articles. If you wish to submit an article for publication in the Cahiers, please send it to the Editor of your choice, with a copy to Isar Stubbe (isar.stubbe [at] univ-littoral.fr <http://univ-littoral.fr/>). With best regards, René Guitart, Marino Gran and Isar Stubbe.

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October/Novemberfest 2026 website now available
by Richard Blute 16 Oct '26

16 Oct '26

The 2026 Category Theory October/Novemberfest will be held on the weekend of October 31st through November 1st. The meeting will be virtual. The webpage is now live: https://richardblute.ca/october-novemberfest-2026/ At the moment, the only thing there is the schedule. Titles and abstracts will be available soon. Eventually slides and videos of the talks will be there as well. All talks will be 25 minutes with 5 minutes for questions. Note that all times are Eastern. But for added fun, in Ontario we set the clocks back at 2AM Sunday morning, November 1st. So Saturday’s talks will be Eastern Daylight Time (EDT) and Sunday’s talks will be Eastern Standard Time (EST).

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