Claudia Stadlmayr, "G-smooth RDP del Pezzo surfaces"

jeudi 7 mai 2026, 11:00 → 12:00 Europe/Paris

If f: X -> Y is a quotient by a free action of a finite group G, then X is smooth if and only if Y is smooth. Working in characteristic p > 0, one can replace G by a finite, not-necessarily reduced group scheme, and then X might be singular even if Y is smooth. Turning this around, this means that there are singular varieties X with a free action of a finite group scheme G such that the quotient of X by G is smooth. Following Brion, such varieties are called G-smooth, and they can be used to construct generically non-smooth fibrations between smooth varieties. In this talk, building on the classification of weak and RDP del Pezzo surfaces with global vector fields, I will report on work in progress with DongSeon Hwang and Gebhard Martin on the classification of G-smooth RDP del Pezzo surfaces.