# Jeroen Sijsling: Endomorphisms and decompositions of Jacobians

**Time: **
Wed 2019-11-06 11.00 - 12.00

**Location: **
F11, KTH

**Participating: **
Jeroen Sijsling, Ulm

### Abstract

Let \(C\) be a curve over a number field, with Jacobian \(J\), and let \(\operatorname{End} (J)\) be the endomorphism ring of \(J\). The ring \(\operatorname{End} (J)\) is typically isomorphic to \(\mathbb Z\), but the cases where it is larger are interesting for many reasons, most of all because the corresponding curves can then often be matched with relatively simple modular forms.