We would like to invite you to the Mathematical-Physical Colloquium of the Faculty of Mathematics and Physics at Leibniz Universität Hannover:

**PD Dr. Jonathan Bowden (Universität Regensburg)**

speaks on the topic

**Automorphisms of Surfaces**

in Room B302 on Tuesday,** 13 December 2022** at **16:30.**

**Abstract: **The classification of compact topological surfaces goes back to the mid 19th century, in lieu of attempts to find counterexamples to Euler’s formulae for polyhedra, and is a landmark result in classical geometric topology. On the other hand the group of automorphisms of a surface is a very rich object and its study is still relevant today. The mapping class group of a surface, consisting of automorphisms up to deformation, appears naturally in many contexts Teichmüller theory, Thurston’s Geometrisation of 3-manifolds, stable homotopy theory (Madsen-Weiss’ proof of the Mumford Conjecture) to name a few. By contrast, the study of the full group of automorphisms, which is relevant in dynamics, is somewhat less understood and several natural questions remained open until recently. I will put these problems into context and indicate some recent progress concerning the geometry of this group in joint work with S. Hensel and R. Webb.

**Dr. Fabian Reede (Leibniz Universität Hannover)**

speaks on the topic

**New examples of stable bundles on hyperkähler manifolds of higher dimensions**

in Room B302 on Tuesday,** 24 January 2023** at **16:30.**

(Inaugural lecture within the habilitation procedure)

**Abstract: **Stable sheaves on K3 surfaces and their moduli spaces have been extensively studied. However, it is a challenging problem to construct non-trivial examples of stable sheaves on hyperkähler manifolds of higher dimensions let alone study their moduli spaces. In this talk I will present several constructions by applying techniques in derived categories which even produce irreducible components of the moduli spaces of such sheaves. This talk is based on joint work with Ziyu Zhang.