Universiteit Leiden Mathematisch Instituut
Geometry Seminar

Friday, 23 May 2008, 14:00–15:45, room TBA

Theo van den Bogaart: Cohomology of spaces whose number of points over finite fields is polynomial in the number of elements of the field

Abstract:

This talk is about the first two chapters of my thesis, with emphasis on the first. We will consider certain schemes or stacks over Z[1/r] whose number of points over F_q is polynomial in q, for any q satisfying (q,r)=1. Examples are provided by certain moduli spaces of curves. Our goal is to describe the cohomology of such spaces. For this talk, knowledge of stacks is unnecessary and I will try to make things intelligible to those having only a faint acquintance with étale cohomology.