BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Siegfried Echterhoff (WWU Münster\, Germany) DTSTART:20231204T150000Z DTEND:20231204T160000Z DTSTAMP:20260422T180050Z UID:QGS/103 DESCRIPTION:Title: Pr oper actions\, fixed-point algebras\, and deformation via coactions\nb y Siegfried Echterhoff (WWU Münster\, Germany) as part of Quantum Groups Seminar [QGS]\n\n\nAbstract\nThe notion of proper actions of groups on spa ces has various generalizations for group actions of noncommutative $C^*$- algebras $A$\, which all allow the construction of generalized fixed-point algebras $A^G$ which are Morita equivalent to ideals in the reduced cross ed products $A\\rtimes_rG$. The weakest version was introduced by Rieffel in 1990 and it played an important role in his theory of deformations vi a actions of $\\mathbb R^d$. In this talk we want to report on some joint work with Alcides Buss on a version of proper actions which allows the con struction of maximal (or exotic) generalized fixed-point algebras which ar e Morita equivalent to ideals in the maximal (resp. exotic) crossed produc ts. We will report on several applications including Landstad duality for coactions and deformation of C*-algebras via coactions in the sense of Kas przak and Bowmick\, Neshveyev\, and Sangha.\n LOCATION:https://researchseminars.org/talk/QGS/103/ END:VEVENT END:VCALENDAR