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SUMMARY:Commensurating actions of groups of birational transformations - Y
 ves de Cornulier (CNRS (Centre national de la recherche scientifique)\; Un
 iversité Paris Saclay)
DTSTART:20170516T100000Z
DTEND:20170516T110000Z
UID:TALK72587@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:A commensurating action is an action of a group on a set along
  with a subset that is commensurated\, in the sense that it has finite sym
 metric difference with each of its translates. There are natural ways to g
 o from commensurating actions to actions on CAT(0) cube complexes and vice
  versa.  For each variety X\, we construct a natural commensurating action
  of the group of birational transformations of X. The commensurated subset
  turns out to be the set of irreducible hypersurfaces in X. Under the assu
 mption that the acting group has Property FW (which means that every actio
 n on a CAT(0) cube complex has a fixed point)\, we deduce restrictions on 
 its birational actions.  &nbsp\;  (Joint work with Serge Cantat)  <br><br>
 <br><br>
LOCATION:Seminar Room 2\, Newton Institute
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