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Logic Seminar

Monday, April 19, 2021
12:00pm to 1:00pm
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Online Event
A characterization of high transitivity for groups acting on trees
François Le Maître, Jussieu Mathematics Institute – PRG, University of Paris,

A countable group is highly transitive if it admits an embedding in the permutation group of the integers with dense image. I will present a joint work with Pierre Fima, Soyoung Moon and Yves Stalder where we show that a large class of groups acting on trees are highly transitive, which yields a characterization of high transitivity for groups admitting a minimal faithful action of general type on a tree thanks to the work of Le Boudec and Matte Bon. Our proof is new even for the free group on two generators and I will give a detailed overview in this very particular case, showing that the generic transitive action of the free group on two generators is highly transitive.

For more information, please email A. Kechris at kechris@caltech.edu.