Dear all, The next date of the ItaCa Fest will be September 20, 2022 at 3 pm (Italian time): 3:00 - 3:45 pm: A. S. Cigoli - Groupal Pseudofunctors 4:00 - 4:45 pm: L. Reggio - Arboreal categories and homomorphism preservation theorems The zoom link is the following: https://cs-ox-ac-uk.zoom.us/j/97878376376?pwd=QithMyt5NzdOeE1EWGJRcjBxamxnUT... While the Fest website is this one: https://progetto-itaca.github.io/pages/fest22.html Join us (and bring a friend)! Cheers, Beppe, Ivan, Edoardo, Fosco, Paolo. ———————————————————————————————————— Alan S. Cigoli Title: Groupal Pseudofunctors Abstract: Let B be an additive category and let Set denote the category of sets. A finite product preserving functor F from B to Set necessarily factors through the category Ab of abelian groups. This simple and important observation has no straightforward generalization when F and Set are replaced by a pseudo-functor and the 2-category Cat of categories, respectively. The latter situation occurs precisely when B is the base category of an opfibration. In this talk, we will focus on pseudo-functors corresponding to cartesian monoidal opfibrations of codomain B. Among such, we will eventually characterize, in terms of oplax and lax monoidal structure, those factorizing through the bicategory of symmetric categorical groups. This is the case, for example, when the starting opfibration has groupoidal fibres. This is joint work with S. Mantovani and G. Metere. Luca Reggio Title: Arboreal categories and homomorphism preservation theorems Abstract: Game comonads, introduced by Abramsky, Dawar et al. in 2017, provide a categorical approach to (finite) model theory. In this framework one can capture, in a purely syntax-free way, various resource-sensitive logic fragments and corresponding combinatorial parameters. After an introduction to game comonads, I shall present an axiomatic framework which captures the essential common features of these constructions. This is based on the notion of arboreal category, in which every object is generated by its `paths’. I will then show how (resource-sensitive) homomorphism preservation theorems in logic can be recast and proved at this axiomatic level. This is joint work with Samson Abramsky. .ƸӜƷ.•°*”˜˜”*°•.ƸӜƷ.•°*”˜˜”*°•.ƸӜƷ. Giuseppe Metere, PhD Professore di Algebra Dipartimento di Matematica e Informatica Università degli Studi di Palermo [For admin and other information see: http://www.mta.ca/~cat-dist/ ]