2025 - T1 - Representation theory and noncommutative geometry

Collection 2025 - T1 - Representation theory and noncommutative geometry

Organizer(s) Afgoustidis, Alexandre ; Aubert, Anne-Marie ; Clare, Pierre ; Frahm, Jan ; Pasquale, Angela ; Şengün, Haluk

Date(s) 06/01/2025 - 04/04/2025

linked URL https://indico.math.cnrs.fr/event/10843/

65 112

Cuntz’ K-theoretic amenability revisited

In the early 1980’s, the question was raised of comparing the K-theory groups of the full and reduced $C^*$-algebras of a group $G$. J. Cuntz has described a condition ($K$-amenability) implying that they are isomorphic. Note that $K$-amenability is incompatible with Kazhdan’s property $T$, and is implied by the Haagerup property, a strong negation of property $T$. In this talk we shall explain that Cuntz’ condition relies on the construction of a $G$-Fredhom module. We shall give such a module in the example of $\mathrm{SL}_2$ on the fields of $p$-adics (Julg-Valette), of complex numbers (Kasparov) and of real numbers (Fox-Haskel and Julg-Kasparov).

Information about the video

Date of recording 28/01/2025
Date of publication 28/01/2025
Institution IHP
Licence CC BY NC ND
Language English
Audience Researchers
Director(s) Alexandre Duplessis
Format MP4
Venue IHP - Darboux Amphitheater

Domain(s)

Representation Theory

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