- Categories - Listes du LIPN

Room change
by Groupe de travail catégories 17 Jul '26

17 Jul '26

Hi, We're switching rooms to Seminar Room 4, on the 4th floor of the new building. Please send me a message if you are planning to come; I can come down to let people in if needed. Morgan

1 1

Retard
by Groupe de travail catégories 17 Jul '26

17 Jul '26

Hi, Unfortunately I'm running late because none of the people with keys for B107 are here... I'm looking for a solution. Morgan

1 0

GdT demain
by Groupe de travail catégories 16 Jul '26

16 Jul '26

Hi! There is still time for a meeting or two before August. Tomorrow I may continue the topos theory tutorial from last time, (unless someone has come across an interesting CT problem recently that they want some help in tackling). Either way, we'll meet at 10:30 in B107 as usual, and on BBB at the usual link (see email from last week). See you tomorrow, Morgan PS. Gautham, we'll need to postpone our meeting until after lunch.

1 0

DOUBLE GdT demain!
by Groupe de travail catégories 09 Jul '26

09 Jul '26

Hi! Two things tomorrow: 1. At 10:30am in B107, an interactive topos theory tutorial from me, as requested by some PhD students. The audience will likely be small, so come along if you have any questions about topos theory that you've not had a chance to ask before. 2. At 3pm in B107, a talk on categorical aspects of pomsets from one of the interns in the SAFER group, Maya Hayman. I'll send the abstract as soon as I receive it! The BBB link will be the same as usual for both sessions: https://bbb.lipn.univ-paris13.fr/b/rog-vao-uwm-s2j See you tomorrow :) Morgan

1 2

Pas de GdT demain, mais plans pour vendredi prochain!
by Groupe de travail catégories 02 Jul '26

02 Jul '26

Bonjour! J'avais prévu de lancer une petite série de tutoriels sur la pratique de travailler avec les faisceaux/topos, mais je serai en voyage demain toute la journée et le public sera apparemment petit par ailleurs. MAIS, pour la semaine prochaine (09/07), en supplément du plan ci-dessus dans le créneau usuel du matin, il y aura aussi une stagiaire entre les équipes LoCaL/SAFER qui nous présentera une approche algébrique/catégorique aux pomsets l'après-midi à 15h. En espérant vous voir la semaine prochaine, Morgan

1 0

No GdT tomorrow
by Groupe de travail catégories 17 Jun '26

17 Jun '26

Hi folks, Since many people are absent for the LHC days, there will again be no GdT tomorrow. See you next week, perhaps! Morgan

1 0

No GdT this morning
by Groupe de travail catégories 12 Jun '26

12 Jun '26

Hi! No GdT is planned for this morning. If you want to use the room to discuss something, it is booked anyway. Best, Morgan

1 0

GdT demain
by Groupe de travail catégories 05 Jun '26

05 Jun '26

Bonjour! Comme prévu, il y aura demain matin en B107 la continuation de l'exposé de Damiano. d'il y a deux semaines. Title: Constraint satisfaction problems: between complexity and categorical algebra Abstract: Constraint satisfaction problems (CSP) are a vast class of problems naturally arising in practical context, especially combinatorial optimization. In the early 90s, Feder and Vardi conjectured that CSPs enjoy a dichotomy: a CSP either admits a polynomial-time algorithm or can be proved to be NP-complete. Building on the work of several people spanning about 25 years, Bulatov and Zhuk indpendently proved the conjecture in 2017, and Feder and Vardi were awarded the Church Prize for starting this research area. The theory of CSPs heavily relies on tools from universal algebra. Very recently, Hadek, Jakl and Opršal found a categorical reformulation which neatly reorganizes and generalizes this theory. I will present my understanding of Hadek, Jakl and Opršal's paper (which has been accepted at LICS 2026) and I will introduce CSPs and their theory trying to keep as much as possible the parallel between the usual, combinatorial definitions and the categorical ones, and hopefully manage to give an idea of the proof of the hardness part of the dichotomy theorem, i.e., that "hard" CSPs are necessarily NP-complete. Pour rappel, le BBB sera celui de l'axe Complexités: https://bbb.lipn.univ-paris13.fr/b/mus-djh-bjk-ljz --- Hi! Tomorrow Damiano will continue his talk on CSPs. Details above. See you tomorrow, Morgan

1 2

GdT demain
by Groupe de travail catégories 28 May '26

28 May '26

Hi! My masters student Luc has offered to give us a primer on virtual equipments, including recent work of Arkor and McDermott on cocompletions in formal category theory. It will be at 10:30 in B107 and on BBB at the usual link (https://bbb.lipn.univ-paris13.fr/b/rog-vao-uwm-s2j) Next week at the same time and place, Damiano will give us a second part of his complexity theory talk from last week. See you there! Morgan

1 0

Reminder: Damiano's talk this morning
by Groupe de travail catégories 22 May '26

22 May '26

Hi! If you have come for Damiano's talk and need to enter the campus, give me a call at 0635326197. Morgan

1 1