Dear all Ross Street (Macquarie University) will give this month's online PCT seminar (https://pctseminar.github.io/) talk on Friday May 8 at 10am JST/11am AED (1am UTC). The zoom link to join the seminar is: https://kyoto-u-edu.zoom.us/j/82401794000?pwd=VjVmzVjmlgxhkdHES4xYeQBTpMzQkS... Title: Homodular pseudofunctors as objective invariants Abstract: As Riemann proved, a lot can come out of an 8 page paper! There are two techniques used in the paper [André Joyal, Calcul intégral combinatoire et homologie des groupes symétriques, C.R. Acad. Sci. Canada VII(6) (Dec. 1985) 337--342] which fascinate me. The author's goal is to prove something about how the homology of the symmetric group on n symbols sits in that on n+1 symbols. Rather than specify a particular homological functor, his first technique is to construct a universal one and prove the result for that. The property in question is preserved by additive functors and so holds for any homology. The second technique is to use his theory of (virtual) species of structure where passing from n to n+1 gives differentiation. My goal is to do something similar for the general linear groups over a fixed finite field. I have begun the adaptation of the two techniques and hope the results so far will be of independent interest. The two strands have yet to conflow into the desired application. We hope to see you there! Also reminder that recorded talks are posted afterwards on the seminar's youtube channel: https://www.youtube.com/@PCTSeminar Best wishes, Soichiro Fujii, Zeinab Galal, JS PL