Seminar

This reading group is aimed at understanding stacks in algebraic geometry, in particular the intersection theory on them as seen in e.g. Gromov-Witten theory.
The first few session will recall basic category theory and scheme theory. After this, we will get into defining stacks, using Vistoli's Notes on Grothendieck topologies, fibered categories and descent theory as a source. From there, we will introduce Deligne-Mumford stacks - using the moduli stacks of curves as an example - , their Chow groups, and virtual fundamental classes.

https://bbb.mpim-bonn.mpg.de/b/rei-xh2-kg6
Organiser: Reinier Kramer
Please send an email to rkramer@mpim... to get on the mailing list
(and in particular for the password for the sessions).

Seminar "Arithmetic of Algebraic Groups"
covering all of the winter term. The topics dealt with are centered around arithmetic groups, their cohomology groups [in various disguises] and their relation with the theory of automorphic forms. Some of the results obtained have interesting applications in the latter theory, and, more generally, in number theory. Since arithmetic groups have a very distinctive geometric flavour [via their action on suitable symmetric spaces or other geometric objects] we will also look at the resulting quotient spaces from a geometric point of view, for example, by studying the construction of geometric cycles and related questions.