Christopher Lazda: A Néron–Ogg–Shafarevich criterion for K3 surfaces
Time: Wed 2018-12-12 13.15
Lecturer: Christopher Lazda (University of Amsterdam)
Location: Room 306, House 6, Kräftriket, Department of Mathematics, Stockholm University
Abstract: The naive analogue of the Néron–Ogg–Shafarevich criterion fails for K3 surfaces, that is, there exist K3 surfaces over Henselian, discretely valued fields K, with unramified étale cohomology groups, but which do not admit good reduction over K. Assuming potential semi-stable reduction, I will show how to correct this by proving that a K3 surface has good reduction if and only if its second cohomology is unramified, and the associated Galois representation over the residue field coincides with the second cohomology of a certain “canonical reduction” of X. This is joint work with B. Chiarellotto and C. Liedtke.