Ημερομηνία: Παρασκευή, 18 Ιανουαρίου 2023
Ώρα: 11:00
Τόπος: Αίθουσα A31
Oμιλητής: Dr. Paolo Sentinelli, Politecnico di Milano
Τίτλος: Linear extensions and shelling orders
Περίληψη: We will explore the Bruhat order on the set of facets of a pure simplicial complex (viewed as Grassmannian permutations) and its barycentric subdivision (viewed in a non-standard ambient, a quotient of a symmetric group). We are led to the results that linear extensions of order ideals of the first ambient poset are shelling orders and that that linear extensions of order ideals of the second ambient poset are flag shelling orders, a notion which will be introduced in the talk. Similar results hold for matroids and some other Coxeter matroids. We end by defining promotion and evacuation operators on shelling orders.