University of Cambridge > Talks.cam > Geometric Group Theory (GGT) Seminar > The abstract commensurator of Out(F_3)

The abstract commensurator of Out(F_3)

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  • UserRic Wade (Oxford)
  • ClockFriday 12 October 2018, 13:45-14:45
  • HouseCMS, MR13.

If you have a question about this talk, please contact Richard Webb.

A theorem of Farb and Handel states that when n is greater than or equal to 4, every isomorphism between two finite index subgroups of Out(F_n) is induced by conjugation in the group. In joint work with Camille Horbez, we show that this is also true in the case when n=3. The proof proceeds in the spirit of Ivanov’s work on the mapping class group and utilizes the action of Out(F_3) and its subgroups on relative free factor graphs and their boundaries. Time permitting, I will also discuss generalizations of the proof to other normal subgroups of Out(F_3) or in the case where n is arbitrary.

This talk is part of the Geometric Group Theory (GGT) Seminar series.

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