BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Ralf Meyer (Goettingen) DTSTART:20200827T100000Z DTEND:20200827T110000Z DTSTAMP:20260419T060157Z UID:CRMDS/16 DESCRIPTION:Title: A periodicity and related properties for crossed product inclusions\nby Ralf Meyer (Goettingen) as part of Western Sydney University Abend Seminar s\n\n\nAbstract\nIn recent work with Bartosz Kwa?niewski\, we have vastly generalised the condition that was introduced by Kishimoto in order to pro ve that reduced crossed products for outer group actions on simple C*-alge bras are again simple. We call this condition aperiodicity\, and it appli es to arbitrary inclusions of C*-algebras\, without requiring a crossed pr oduct structure. We relate this to topological non-triviality conditions in the special case of actions of inverse semigroups or étale groupoids ( which are possibly non-Hausdorff). In that generality\, we define an esse ntial crossed product\, which is a quotient of the reduced crossed product . If the action satisfies Kishimoto's condition\, then the coefficient al gebra detects ideals in this essential crossed product. And in the simple case\, we also get criteria for the essential crossed product to be simpl e. We also relate aperiodicity to other properties that have been used to study the ideal structure of crossed products. This includes unique pseu do-expectations and the almost extension property\, which assume that the set of pure states on the coefficient algebra that extend uniquely to the crossed product is dense.\n LOCATION:https://researchseminars.org/talk/CRMDS/16/ END:VEVENT END:VCALENDAR