Berlin-Hamburg-Hannover-Seminar am 29.05.2026

Simon Vialaret (Bochum) Systolic geometry of toric contact forms

In contact geometry, a systolic inequality is a uniform upper bound on the shortest period of closed Reeb orbits, involving the contact volume. This generalizes a well-studied notion in Riemannian geometry. It is known that there is no systolic inequality valid for all contact forms on any given contact manifold. In this talk I will state a sharp systolic inequality for T²-invariant contact forms on T³. In this setting, the systolic landscape is surprisingly complex, as the systolic ratio has infinitely many local maxima. The proof involves a reduction to a number-geometric problem, together with the classification of the local maximizers of the systolic ratio. This is a joint work with Florent Balacheff and Michael Vogel.

Sobhan Seyfaddini (ETH Zürich) The closing lemma and Lagrangian submanifolds

We will discuss the smooth closing lemma for Hamiltonian diffeomorphisms with invariant Lagrangians. Based on joint work with Erman Cineli & Shira Tanny.