Séminaire Quid

by Mr Gabriel Duez

Wednesday May 7, 2025, 6:00 PM → 7:15 PM Europe/Paris

129 Room Picard (IMT 1R2)

`Quid of groupoid C*-algebras`

 

A groupoid is a generalization of a group in which multiplication is partially defined. This framework encompasses several familiar mathematical structures, including groups, transformation groups (arising from group actions on spaces) and equivalence relations. Since convolution algebras can be constructed for several of these examples — such as locally compact groups — it is natural to seek a similar construction for groupoids. In 1979, J. Renault first defined the C*-algebra of a groupoid, and this opened up a new chapter in the use of groupoids in operator algebras. In this talk, I propose to rediscover these objects and the construction of the C*-algebras, illustrating my point with several examples. If time allows, I will discuss a case in which a groupoid can be reconstructed from a C*-algebra.