A panorama of L^2-invariants (Wolfgang LÜCK, University of Bonn)

21.05.2026 16:15

Betti numbers of closed manifolds or finite simplicial complexes are classical invariants in algebraic topology. Atiyah proposed an L^2-version obtained from the universal covering and the action of the fundamental group using von Neumann algebras.
We will present the basic properties of these L^^2-Betti numbers without going into technical details and discuss interesting and striking applications to topology, algebra, group theory, and geometry which are both interesting for and easy to explain to a general audience. If time allows, we will also introduce L^2-torsion which is the analogue of the classical Reidemeister torsion.

Le colloque sera suivi d'un apéritif

Lieu

Bâtiment: Conseil Général 7-9

Salle 1-15, Colloque de mathématiques

entrée libre