AF/NT seminar

Organizers: Mikołaj Frączyk (UJ), Borys Kuca (UJ), Jolanta Marzec-Ballesteros (UAM) and Anna Szumowicz (UJ), Marcin Lara (IMPAN)

Automorphic Forms/ Number Theory seminar is a recurrent meeting wandering between Jagiellonian University in Krakow (JU)  and Adam Mickiewicz University in Poznań (AMU), typically on the first Monday of the month. We plan to have two invited speakers per session preceded by  introductory talks by junior faculty or graduate students. 

We have limited funds to support travel for the participants from Poland to the seminar venue. 

Talks in Krakow will take place in the Conference Hall B  under the library at the Faculty of Mathematics and Computer Science of JU . Talks in Poznań will take place in the seminar room B1-37 at the Faculty of Mathematics and Computer Science of AMU. 

If you would like to join one of the talks online, contact one of the organizers to obtain a link.

Upcoming Meetings

May 6th 2026 (Kraków)

13:15-14:00 Introductory talk: Thibault van den Hove (MPI Bonn) 

Title: Introduction to the geometric Satake equivalence

Abstract: In this introductory talk, I  will introduce and motivate the affine Grassmannian of a reductive group. I will then explain the geometric Satake equivalence, which is a fundamental tool in arithmetic geometry and representation theory, relating equivariant perverse sheaves on the affine Grassmannian to algebraic representations of the Langlands dual group.

14:00-14:30 Coffee break

14:30-15:30 Main talk: Thibault van den Hove (MPI Bonn) 

Title: Cycles on splitting models of Shimura varieties 

Abstract: I will explain how to construct examples of exotic Hecke correspondences between the special fibers of different Shimura varieties, at possibly ramified primes. These can be used to construct geometric realizations of the Jacquet-Langlands correspondence, and verify generic instances of the Tate conjecture for the special fibers of these Shimura varieties, generalizing the work of Xiao-Zhu in the unramified case. The key tools are (a ramified version of) the geometric Satake equivalence, and the resolutions of these special fibers given by the splitting models of Pappas-Rapoport.