Bonjour! Here are the title and abstract for Ivan's talk this *Friday at 10:30am* in *B107* of the *Institut Galilée* (at Villetaneuse), and on BBB, https://bbb.lipn.univ-paris13.fr/b/rog-vao-uwm-s2j Title: *The geometry of coherent topoi and ultrastructures.* Abstract: It is know that for T a first order theory we can construct ultraproducts of models along ultrafilters. From a topos theoretic point of view, this property should correspond to a geometric property of coherent topoi. We discover such a geometric property and we see how that impacts the behavior of coherent topoi. You should know what a Grothendieck topos is in advance for this talk (but Ivan will remind us what a coherent topos is). Some familiarity with Kan extensions (their universal property rather than their explicit construction) will make the talk more digestible too. For next week, I propose that we continue the reading group, but if someone has a suggestion for a talk (introductory or technical) or a guest speaker, that will take precedence. See you on Friday! Morgan On 13/10/2022 10:54, Morgan Rogers wrote:

Dear all,

A reminder for tomorrow and an announcement of the coming weeks' activities; as always we will meet on *Friday at 10:30am* in *B107* of the *Institut Galilée* (at Villetaneuse), and you may attend the talks remotely or access the recordings on BBB, https://bbb.lipn.univ-paris13.fr/b/rog-vao-uwm-s2j

Friday 14/10/22 Damiano Mazza will explain how algebra-geometry dualities are beginning to appear in his work on Boolean categories; this is an introduction to next week's reading group.

Friday 21/10/22 Damiano Mazza will kick off our first thread of reading groups on Topo-logie, Awodey's algebra/topology duality survey, and a little of Zhen Lin's thesis. At the end we will discuss which of the texts/aspects we will continue with in the eventual next session. /References at end of email./

Friday 28/10/22 Axel Osmond will give a talk on his work on abstract spectra or his more recent work (title TBA).

Friday 04/11/22 Ivan di Liberti will be visiting this week and will give a talk either at the GdT or at the LoVe seminar (title TBA).

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Un rappel pour demain et une annonce des activités des semaines à venir ; comme toujours nous nous retrouverons *vendredi**à 10h30 au B107 de l'Institut Galilée* (à Villetaneuse), et vous pourrez assister à distance ou accéder aux enregistrements sur BBB, https://bbb.lipn.univ-paris13.fr/b/rog-vao-uwm-s2j

vendredi 14/10/22 Damiano Mazza expliquera comment les dualités algèbro-géométriques commencent à apparaître dans ses travaux sur les catégories booléennes. Ceci est une introduction au groupe de lecture de la semaine prochaine.

vendredi 21/10/22 Damiano Mazza lancera notre premier fil de groupes de lecture sur Topo-logie, la revue sur la dualité algèbre/topologie d'Awodey, et un peu de la thèse de Zhen Lin. À la fin, nous discuterons les textes/aspects avec lesquels nous continuerons lors de l'éventuelle prochaine session. /References ci-dessous./

vendredi 28/10/22 Axel Osmond donnera un exposé sur les spectres abstraits ou sur ses travaux plus récents (titre TBA).

vendredi 04/11/22 Ivan di Liberti sera visitera cette semaine et donnera une conférence soit au GdT soit au séminaire du LoVe (titre TBA).

Amicalement, Morgan Rogers

Bibliographie pour le groupe de lecture de Damiano:

* Mathieu Anel and André Joyal,/Topo-logie/(http://mathieu.anel.free.fr/mat/doc/Anel-Joyal-Topo-logie.pdf <http://mathieu.anel.free.fr/mat/doc/Anel-Joyal-Topo-logie.pdf>) * Steve Awodey,/Sheaf Representations and Duality in Logic/(https://www.andrew.cmu.edu/user/awodey/preprints/lambek.pdf <https://www.andrew.cmu.edu/user/awodey/preprints/lambek.pdf>) * Zhen Lin Low,/Category of Spaces Built from Local Models/(https://www.repository.cam.ac.uk/handle/1810/256998 <https://www.repository.cam.ac.uk/handle/1810/256998>)

These two sets of slides can help reading Zhen Lin's thesis:

* /Generalising the functor of points approach/(preliminary work) :http://zll22.user.srcf.net/profile/slides/2015-06-16-ChartedSpaces.pdf <http://zll22.user.srcf.net/profile/slides/2015-06-16-ChartedSpaces.pdf> * The slides presenting the actual thesis :http://zll22.user.srcf.net/profile/slides/2015-06-16-ChartedSpaces.pdf <http://zll22.user.srcf.net/profile/slides/2015-06-16-ChartedSpaces.pdf>