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UID:20260601T025824EDT-91245HB9Xh@132.216.98.100
DTSTAMP:20260601T065824Z
DESCRIPTION:Title: Signature morphisms on the Cremona group.\n\nAbstract: T
 he Cremona group is the group of birational symmetries of the plane. This 
 is a rather huge group\, which is neither finitely generated nor finite di
 mensional. The abelianization of the Cremona group was recently studied: o
 ver the base field C\, the abelianization is trivial\, but over R\, the ab
 elianization is an uncountable direct sum of Z/2. I will discuss similar r
 esults over more general fields\, such as number fields or finite fields. 
 The key is to use a natural action on a square complex\, to exhibit variou
 s trees as quotients or subcomplexes\, and then to apply Bass-Serre theory
  (joint work with Susanna Zimmermann).\n\n \n
DTSTART:20170906T190000Z
DTEND:20170906T200000Z
LOCATION:Room 920\, Burnside Hall\, CA\, QC\, Montreal\, H3A 0B9\, 805 rue 
 Sherbrooke Ouest
SUMMARY:Stéphane Lamy\, Université Paul Sabatier
URL:/mathstat/channels/event/stephane-lamy-universite-
 paul-sabatier-269969
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