Fachbereich Mathematik

Kolloquien WS 2023/24

Vorheriges Semester Nächstes Semester

Freitag, 20.10.2023: 50 Jahre AGFA


Kolloquium zum 50jährigen Jubiläum der Arbeitsgemeinschaft Funktionalanalysis AGFA

Uhrzeit: 14:00
Ort: TBD
Gruppe: Kolloquium
Einladender: R. Nagel

Freitag, 24.11.2023: Amenable group actions on spaces and operator algebras

Prof. Dr. Siegfried Echterhoff (Universität Münster)

16:00-16:45 Uhr Vor-Kolloquium im N14 für Studierende und Promovierende, moderiert von Dr. Rodrigo Avalos, Vortragender Prof. Dr. Siegfried Echterhoff The Banach-Tarski paradox and amenable groups The Banach-Tarski paradox states that the unit ball in three dimensional space can be partitioned into finitely many pieces in such way that we can resemble two full balls from these pieces. Hence we may double the unit ball. That this is possible is due to axiom of choice and the fact that the free group in two generators is not amenable. On the other hand, amenability of the circle group implies that similar partitions do not exist for the unit disc in the plane! We shall explain these facts. Kolloquium 17:15 Uhr Amenable group actions on spaces and operator algebras Motivated by the study of paradoxical decompositions (as in the Banach-Tarski paradoxon), the  notion of an amenable group has been introduced by von Neumann in the 1920’s. In the 1980’s Zimmer introduced  the concept of amenable group actions on measure spaces in order to study rigidity properties of lattices in Lie groups. In the meantime, various notions of amenability were introduced for actions on topological spaces and on operator algebras, where the latter can be viewed as non-commutative analogues of measure or topological spaces. They have important applications in the interplay between group theory and operator algebras. After a gentle introduction to various notions of amenable actions we want to give an overview over some exciting recent results.

Uhrzeit: 16:00
Ort: N14
Gruppe: Kolloquium
Einladender: Carla Cederbaum

Montag, 11.12.2023: Informationsveranstaltung zu Auslandsstudien (Erasmus, CIVIS, Trento, ...)

Daniele Agostini + FBZ

Die Veranstaltung richtet sich an Studierende in den Studiengängen des Fachbereich Mathematik, die sich über die Möglichkeiten für ein Auslandsstudium informieren möchten.

Uhrzeit: 16:00 - 17:30
Ort: N14
Gruppe: Kolloquium