BEGIN:VCALENDAR VERSION:2.0 PRODID:-//132.216.98.100//NONSGML kigkonsult.se iCalcreator 2.20.4// BEGIN:VEVENT UID:20250801T195443EDT-6107jZ7mnj@132.216.98.100 DTSTAMP:20250801T235443Z DESCRIPTION:Title: Subgroups of Out(F_r) generated by Dehn (multi-)twists. \n\nAbstract: Pick two (multi)-curves on a surface. What can be said about the subgroup generated by powers of Dehn twists about the two curves? For twists about single curves a complete classification up to isomorphism is known and is determined by intersection number and twist power. For multi -curves with more components\, the fourth powers of the twists generate a free group. I will present analogous results for groups generated by two D ehn (multi-)twists in Out(F_r)\, where the analysis is complicated by the absence of a standard topological model.\n\n \n DTSTART:20180321T190000Z DTEND:20180321T200000Z LOCATION:Room 920\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue Sherbrooke Ouest SUMMARY:Edgar Bering (Temple University) URL:/mathstat/channels/event/edgar-bering-temple-unive rsity-285925 END:VEVENT END:VCALENDAR