Presented by:
Yves de Cornulier
Date:
Tuesday 16th May 2017 - 11:00 to 12:00
Venue:
INI Seminar Room 2
Abstract:
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
symmetric difference with each of its translates. There are natural ways to go
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
assumption that the acting group has Property FW (which means that every action
on a CAT(0) cube complex has a fixed point), we deduce restrictions on its
birational actions.
(Joint work with Serge Cantat)
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