Seminarios T. de Números
STATISTICS OF (ARAKELOV RAY) CLASS GROUPS AND ARITHMETICAL APPLICATIONS 
 
SPEAKER: Carlo Pagano (Max Planck Institute for Mathematics, Bonn) 
 
DATE & TIME: Tuesday, 19th November 2019 - 11:00 
 
VENUE: Aula 420, Departamento de Matemáticas, UAM 
 
ORGANISER: UAM - ICMAT 
 
ABSTRACT: I will survey some recent work triggered by the dramatic 
breakthrough of Alexander Smith on the Cohen--Lenstra and Goldfled's 
conjecture. I will give an overview of some new ideas and notions coming 
from Smith's work. From there I will explain a joint work with Peter 
Koymans where we use some of these innovations to generalize a classical 
result of Gauss on the 2-torsion of class groups from quadratic to 
multi-quadratic fields; a joint work with Chan, Koymans and Milovic on the 
Negative Pell equation; further progress on this and other Diophantine 
problems obtained jointly with Peter Koymans. I will finally explain how a 
non-archimedean version of Negative Pell leads naturally to wonder how 
to extend the Cohen--Lenstra heuristics from class groups to ray class 
groups. I will discuss the work I did on this topic for imaginary quadratic 
fields, jointly with Sofos, and present some ongoing work with Alex Bartel 
for more general families of number fields, where a notion of Arakelov ray 
class group plays a crucial role.