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SUMMARY:Property (LR) for virtually free groups [MPIM]
DTSTART:20260618T113000Z
DTEND:20260618T130000Z
DTSTAMP:20260610T153700Z
UID:indico-event-1394@math-events.uni-bonn.de
DESCRIPTION:Speakers: Ashot Minasyan (MPIM/Southampton)\n\nOberseminar Dif
 ferentialgeometrie\nA classical theorem of M. Hall states that every finit
 ely generated subgroup of a free group is a free factor of a finite index 
 subgroup. Moreover\, the works of Brunner--Burns and Dunwoody\, imply that
  any finitely presented group satisfying this M. Hall's property must be v
 irtually free\, i.e.\, it must have a finite index free subgroup. However\
 , many virtually free groups fail to have M. Hall's property. In the talk 
 I will discuss the result that a weaker property (LR)\, defined by Long an
 d Reid\, does holds in all virtually free groups. Namely\, every finitely 
 generated subgroup of a virtually free group is a retract of a finite inde
 x subgroup. I will sketch the proof of this result\, which combines a new 
 embedding theorem for countable virtually free groups with a geometric arg
 ument using actions on trees.\n\nhttps://math-events.uni-bonn.de/event/139
 4/
LOCATION:MPIM\, Vivatsgasse\,  7 - Lecture Hall (Max Planck Institute for 
 Mathematics)
URL:https://math-events.uni-bonn.de/event/1394/
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