{"acronym":"qtcat2026","aspect_ratio":"16:9","created_at":"2026-08-09T15:19:57.389+02:00","updated_at":"2026-08-14T23:15:06.986+02:00","title":"Queer and Trans People in Category Theory 2026","schedule_url":"","slug":"conferences/qtcat/2026","event_last_released_at":"2026-08-14T00:00:00.000+02:00","link":"","description":"","webgen_location":"conferences/qtcat/2026","logo_url":"https://static.media.ccc.de/media/events/qtcat/2026/logo_light.png","images_url":"https://static.media.ccc.de/media/events/qtcat/2026","recordings_url":"https://cdn.media.ccc.de/events/qtcat/2026","url":"https://api.media.ccc.de/public/conferences/qtcat2026","events":[{"guid":"21c43923-3e01-550b-a793-829fc5564b28","title":"Closing/Closure/Completion","subtitle":null,"slug":"qtcat-2026-110779-closing-closure-completion","link":"https://pretalx.c3voc.de/qtcat-2026/talk/8FPG9V/","description":"A closing for QTCat, some closure for myself and maybe a bit about categorical completions.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Tessa Kammermeier"],"view_count":10,"promoted":false,"date":"2026-08-14T14:30:00.000+02:00","release_date":"2026-08-14T00:00:00.000+02:00","updated_at":"2026-08-14T22:00:07.806+02:00","tags":["8FPG9V","2026","qtcat2026","R. 221","qtcat2026-eng","Day 3"],"length":1276,"duration":1276,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110779-21c43923-3e01-550b-a793-829fc5564b28.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110779-21c43923-3e01-550b-a793-829fc5564b28_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110779-21c43923-3e01-550b-a793-829fc5564b28.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110779-21c43923-3e01-550b-a793-829fc5564b28.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110779-closing-closure-completion","url":"https://api.media.ccc.de/public/events/21c43923-3e01-550b-a793-829fc5564b28","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"1fc2e972-0a30-5c71-99e0-5f7771141096","title":"Parametrised Representability","subtitle":null,"slug":"qtcat-2026-110762-parametrised-representability","link":"https://pretalx.c3voc.de/qtcat-2026/talk/TB7KBX/","description":"Often we define functors F where each object F(A) satisfies a universal property; these could be products, limits, colimits, (co)ends, (co)free objects, kan extensions, exponential objects... Usually, existence and uniqueness of the mediating morphisms allow you to define the functorial action and verify functoriality, respectively. But as these constructions get more complicated, the diagram-chasing gets more and more tedious, and one gets the feeling that there should be some universal theorem giving functoriality for free.\n\nThis talk will show such a silver bullet _does_ exist! In these situations of a **parametrised family of universal properties** there is an economical, \"maximally lazy\" way to define your functors on objects, and deduce the action on morphisms.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Ruby Khondaker"],"view_count":2,"promoted":false,"date":"2026-08-14T14:00:00.000+02:00","release_date":"2026-08-14T00:00:00.000+02:00","updated_at":"2026-08-14T18:15:05.505+02:00","tags":["TB7KBX","2026","qtcat2026","R. 221","qtcat2026-eng","Day 3"],"length":1587,"duration":1587,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110762-1fc2e972-0a30-5c71-99e0-5f7771141096.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110762-1fc2e972-0a30-5c71-99e0-5f7771141096_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110762-1fc2e972-0a30-5c71-99e0-5f7771141096.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110762-1fc2e972-0a30-5c71-99e0-5f7771141096.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110762-parametrised-representability","url":"https://api.media.ccc.de/public/events/1fc2e972-0a30-5c71-99e0-5f7771141096","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"a89250a4-838a-565c-b9f4-a78acae20e60","title":"Cats and Types, Side by Side","subtitle":null,"slug":"qtcat-2026-110774-cats-and-types-side-by-side","link":"https://pretalx.c3voc.de/qtcat-2026/talk/WDTZ3Q/","description":"As a type theorist who hangs out with category theorists, I am always fascinated by what we share and by how we differ. What do some of us fuss over that others just take for granted? I gave a talk at Topos Institute with some observations in this area five years ago. In this talk, I'll look at what has changed, including me, in those five years. In particular, I have experienced the need to have more to say about monoidal structure - juxtaposition - as well as composition. I'll talk about opportunities and obstacles for using appropriate types to work with these cats.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Conor Titania Mc Bride"],"view_count":60,"promoted":false,"date":"2026-08-13T14:00:00.000+02:00","release_date":"2026-08-14T00:00:00.000+02:00","updated_at":"2026-08-14T23:15:06.469+02:00","tags":["WDTZ3Q","2026","qtcat2026","R. 221","qtcat2026-eng","Day 2"],"length":3374,"duration":3374,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110774-a89250a4-838a-565c-b9f4-a78acae20e60.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110774-a89250a4-838a-565c-b9f4-a78acae20e60_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110774-a89250a4-838a-565c-b9f4-a78acae20e60.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110774-a89250a4-838a-565c-b9f4-a78acae20e60.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110774-cats-and-types-side-by-side","url":"https://api.media.ccc.de/public/events/a89250a4-838a-565c-b9f4-a78acae20e60","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"14a9ced8-f4d3-596b-b90a-41aa9d49614b","title":"Coinductive invertibility in higher categories","subtitle":null,"slug":"qtcat-2026-110772-coinductive-invertibility-in-higher-categories","link":"https://pretalx.c3voc.de/qtcat-2026/talk/LARUFT/","description":"Invertibility is a crucial notion in category theory, providing the correct notion of sameness for objects within a category and equivalences of categories. This notion readily generalises to finite-dimensional higher categories inductively by replacing equalities with higher dimensional isomorphisms. The situation becomes more subtle with infinite-dimensional categories where there are different notions of invertibility. In this talk, we will give an introduction to weak ω-categories and we will study coinductively invertible cells within them. We will then describe computads with invertible generators as data for freely generating ω-categories.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Ioannis Markakis"],"view_count":12,"promoted":false,"date":"2026-08-13T10:00:00.000+02:00","release_date":"2026-08-13T00:00:00.000+02:00","updated_at":"2026-08-14T18:30:04.374+02:00","tags":["LARUFT","2026","qtcat2026","R. 221","qtcat2026-eng","Day 2"],"length":3392,"duration":3392,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110772-14a9ced8-f4d3-596b-b90a-41aa9d49614b.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110772-14a9ced8-f4d3-596b-b90a-41aa9d49614b_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110772-14a9ced8-f4d3-596b-b90a-41aa9d49614b.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110772-14a9ced8-f4d3-596b-b90a-41aa9d49614b.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110772-coinductive-invertibility-in-higher-categories","url":"https://api.media.ccc.de/public/events/14a9ced8-f4d3-596b-b90a-41aa9d49614b","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"94cfe0a8-2a7d-58cc-9449-46949bc52126","title":"The fundamental theorem of deeper algebra","subtitle":null,"slug":"qtcat-2026-110773-the-fundamental-theorem-of-deeper-algebra","link":"https://pretalx.c3voc.de/qtcat-2026/talk/9QMSKT/","description":"Higher algebra is the algebra of (connective) spectra. Deeper algebra is the algebra of (coconnective) categorical spectra. Deeper algebra organizes and simplifies many phenomena, from Galois theory to the classification of phases of matter. I will introduce these areas, and I will report on joint work in progress with David Reutter.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Theo Johnson-Freyd"],"view_count":50,"promoted":false,"date":"2026-08-12T14:00:00.000+02:00","release_date":"2026-08-12T00:00:00.000+02:00","updated_at":"2026-08-14T23:15:06.982+02:00","tags":["9QMSKT","2026","qtcat2026","R. 221","qtcat2026-eng","Day 1"],"length":4268,"duration":4268,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110773-94cfe0a8-2a7d-58cc-9449-46949bc52126.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110773-94cfe0a8-2a7d-58cc-9449-46949bc52126_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110773-94cfe0a8-2a7d-58cc-9449-46949bc52126.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110773-94cfe0a8-2a7d-58cc-9449-46949bc52126.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110773-the-fundamental-theorem-of-deeper-algebra","url":"https://api.media.ccc.de/public/events/94cfe0a8-2a7d-58cc-9449-46949bc52126","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"25a00893-a118-5b86-8db3-85b06cbf1805","title":"Who cares about codensity monads?","subtitle":null,"slug":"qtcat-2026-110760-who-cares-about-codensity-monads","link":"https://pretalx.c3voc.de/qtcat-2026/talk/SBZJVC/","description":"Consider the category of groups with its forgetful functor down to Set. This functor is monadic, which tells us that groups are sets equipped with an algebraic structure. Now consider the category of finite sets, with its inclusion into Set. This functor is not monadic for many reasons, but what monadic functor best approximates it? In other words, finite sets are most like sets equipped with what algebraic structure? The answer to this question is given my the codensity monad of FinSet -\u003e Set. Quite surprisingly, this is the ultrafilter monad, whose algebras are compact Hausdorff spaces!\n\nThat's all well an good, but why should you care? Every monad is trivially the codensity monad of some functor. Does it matter if it is the codensity monad of a specially nice one, say a fully faithful one? It does! For example, if a polynomial monad T on Set restricts to FinSet, then a general theory guarantees that there is a unique distributive law of the ultrafilter monad over T, i.e. a unique monad on CHaus which lifts T.\n\nIn this talk I will tell you about this recent development about distributive laws involving codensity monads, and how they relate to the main subject of my thesis: pushforward monads. We will use the ulftrafilter monad as our central example.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Adrián Doña Mateo"],"view_count":40,"promoted":false,"date":"2026-08-12T12:00:00.000+02:00","release_date":"2026-08-12T00:00:00.000+02:00","updated_at":"2026-08-14T22:45:06.190+02:00","tags":["SBZJVC","2026","qtcat2026","R. 221","qtcat2026-eng","Day 1"],"length":1718,"duration":1718,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110760-25a00893-a118-5b86-8db3-85b06cbf1805.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110760-25a00893-a118-5b86-8db3-85b06cbf1805_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110760-25a00893-a118-5b86-8db3-85b06cbf1805.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110760-25a00893-a118-5b86-8db3-85b06cbf1805.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110760-who-cares-about-codensity-monads","url":"https://api.media.ccc.de/public/events/25a00893-a118-5b86-8db3-85b06cbf1805","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"2af093c5-e2e8-5299-a2e9-fb6d603d64c6","title":"The Road from Circuits to Category Theory","subtitle":null,"slug":"qtcat-2026-110765-the-road-from-circuits-to-category-theory","link":"https://pretalx.c3voc.de/qtcat-2026/talk/X8NKSX/","description":"String diagrams are often traced back to Richard Penrose's work in mathematical physics, but they also have an early and largely overlooked history in computer science through Günter Hotz. Following in the footsteps of Hotz, this talk will provide an introduction to string diagrams through the lens of circuit design.  Rather than beginning with category theory, we start from circuits and their computational properties, and then work backwards to the categorical structures they describe. For example, we will see how modelling feedback motivates compact closed categories and reversibility suggests the structure of a monoidal dagger category. We will then see how the ability to copy data gives rise to Cartesian categories, with the no-cloning theorem identifying precisely why quantum circuits lack this structure. When circuits are no longer Cartesian, basic operations such as conditional statements become harder to reason about graphically. We conclude with a look at ongoing work on controlled monoidal categories and controlled string diagrams, which aim to restore graphical reasoning for conditional statements in non-Cartesian circuits.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Scott Wesley"],"view_count":34,"promoted":false,"date":"2026-08-12T11:30:00.000+02:00","release_date":"2026-08-12T00:00:00.000+02:00","updated_at":"2026-08-14T20:00:06.245+02:00","tags":["X8NKSX","2026","qtcat2026","R. 221","qtcat2026-eng","Day 1"],"length":2049,"duration":2049,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110765-2af093c5-e2e8-5299-a2e9-fb6d603d64c6.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110765-2af093c5-e2e8-5299-a2e9-fb6d603d64c6_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110765-2af093c5-e2e8-5299-a2e9-fb6d603d64c6.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110765-2af093c5-e2e8-5299-a2e9-fb6d603d64c6.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110765-the-road-from-circuits-to-category-theory","url":"https://api.media.ccc.de/public/events/2af093c5-e2e8-5299-a2e9-fb6d603d64c6","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"030bbd5a-36ca-58c3-847f-5c42016f0f27","title":"Category theory, formalised humanely","subtitle":null,"slug":"qtcat-2026-110771-category-theory-formalised-humanely","link":"https://pretalx.c3voc.de/qtcat-2026/talk/9F8KNH/","description":"Formalisation is the process of expressing mathematical ideas in the\nlanguage understood by a proof assistant, a computer program that\nenables the interactive construction of verified mathematical\ndefinitions, theorems, and proofs.\n\nThe stereotypical understanding of formalisation is as the rote\ntranslation of pre-existing mathematics to a cumbersome formal language,\ndone primarily as a means of certifying the correctness of an argument.\nThis memetic conception as a chore standing in the way of a coveted\nresult (guaranteed correctness) has long allowed the aesthetics of\nformalisation to be appropriated by adversarial actors to further their\nfinancial interests (\"get paid for proving lemmas on the\nblockchain\"/\"our new LLM will totally solve All Of Maths, and we have\nthe Lean to prove it\").\n\nI aim to challenge this understanding, presenting the process of\nformalisation, in itself, as a force for good. I will share some of my\nown experiences with free-and-libre, community-supported proof\nassistants as a tool for independent study; genuine mathematical\ninsights revealed by developing category theory within formal univalent\ntype theory; and a few challenges that come with maintaining a library\nof formalised mathematics.\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Amélia Liao"],"view_count":627,"promoted":true,"date":"2026-08-12T10:00:00.000+02:00","release_date":"2026-08-12T00:00:00.000+02:00","updated_at":"2026-08-14T23:15:06.159+02:00","tags":["9F8KNH","2026","qtcat2026","R. 221","qtcat2026-eng","Day 1"],"length":3842,"duration":3842,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110771-030bbd5a-36ca-58c3-847f-5c42016f0f27.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110771-030bbd5a-36ca-58c3-847f-5c42016f0f27_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110771-030bbd5a-36ca-58c3-847f-5c42016f0f27.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110771-030bbd5a-36ca-58c3-847f-5c42016f0f27.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110771-category-theory-formalised-humanely","url":"https://api.media.ccc.de/public/events/030bbd5a-36ca-58c3-847f-5c42016f0f27","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]},{"guid":"41953ecd-0a67-58e4-a9e0-d409daab9640","title":"Opening","subtitle":null,"slug":"qtcat-2026-110775-opening","link":"https://pretalx.c3voc.de/qtcat-2026/talk/G8V7E7/","description":"Opening of QTCat!\n\nLicensed to the public under https://creativecommons.org/licenses/by/4.0/","original_language":"eng","persons":["Tessa Kammermeier"],"view_count":57,"promoted":false,"date":"2026-08-12T09:45:00.000+02:00","release_date":"2026-08-12T00:00:00.000+02:00","updated_at":"2026-08-14T23:00:06.312+02:00","tags":["G8V7E7","2026","qtcat2026","R. 221","qtcat2026-eng","Day 1"],"length":241,"duration":241,"thumb_url":"https://static.media.ccc.de/media/events/qtcat/2026/110775-41953ecd-0a67-58e4-a9e0-d409daab9640.jpg","poster_url":"https://static.media.ccc.de/media/events/qtcat/2026/110775-41953ecd-0a67-58e4-a9e0-d409daab9640_preview.jpg","timeline_url":"https://static.media.ccc.de/media/events/qtcat/2026/110775-41953ecd-0a67-58e4-a9e0-d409daab9640.timeline.jpg","thumbnails_url":"https://static.media.ccc.de/media/events/qtcat/2026/110775-41953ecd-0a67-58e4-a9e0-d409daab9640.thumbnails.vtt","frontend_link":"https://media.ccc.de/v/qtcat-2026-110775-opening","url":"https://api.media.ccc.de/public/events/41953ecd-0a67-58e4-a9e0-d409daab9640","conference_title":"Queer and Trans People in Category Theory 2026","conference_url":"https://api.media.ccc.de/public/conferences/qtcat2026","related":[]}]}