Belgian-Dutch Algebraic Geometry day

On Friday November 22, 2013 we will have the next Belgian-Dutch Algebraic Geometry day. This edition will take place at:



Ben Moonen (Nijmegen)
Johannes Nicaise (Leuven)
Lenny Taelman (Leiden)



The lectures are given in the Huygens Building, room HG00.071 on the ground floor. Address: Heyendaalseweg 135, Nijmegen. The Huygens building is approximately 250 meters from train station Nijmegen Heyendaal. From Nijmegen central station it can also be reached by taking bus number 10, which takes only 5 minutes to the University. (Recommended stop: Huygensgebouw.) See also the map of the campus.

Programme (click titles for the abstracts)

13:00-14:00 Nero Budur (Leuven) Cohomology jump loci
Abstract: In practice, any deformation problem over fields of characteristic zero is governed by a differential graded Lie algebra (DGLA). Following Deligne, Goldman-Millson and Simpson described the local structure of deformation spaces for various geometric situations. Given an object with a notion of cohomology theory, how can one describe all its deformations subject to cohomology constraints? We will present an approach via DGLA pairs. As applications we discuss the structure of cohomology jump loci of vector bundles and of local systems. This is joint work with Botong Wang.
14:00-14:30 Coffee break
14:30-15:30 Stefan Schröer (Düsseldorf) Wild quotient surface singularities
Abstract: I will discuss joint work with Hiroyuki Ito concerning wild quotient surface singularities. The main topic is the structure of the dual graph describing the exceptional divisor on the resolution of singularities. The results answers some questions posed by Lorenzini.
15:30-16:00 Coffee break
16:00-17:00 René Schoof (Rome) Finite group schemes and abelian varieties with good reduction outside one prime
Abstract: The Jacobian J0(23) of the modular curve X0(23) is a semi-stable abelian variety over Q with good reduction outside 23. It is simple. We prove that every simple semi-stable abelian variety over Q with good reduction outside 23 is isogenous over Q to J0(23).

As usual, after the lectures we intend to go for an informal dinner in town.

Further information

For further information, please contact Ben Moonen, b.moonen at, or +31 (0)24 3653220. We hope to see you on November 22!