204 research outputs found
Commensurations of Out(F_n)
Let \Out(F_n) denote the outer automorphism group of the free group
with . We prove that for any finite index subgroup \Gamma<\Out(F_n), the
group \Aut(\Gamma) is isomorphic to the normalizer of in
\Out(F_n). We prove that is {\em co-Hopfian} : every injective
homomorphism is surjective. Finally, we prove that the
abstract commensurator \Comm(\Out(F_n)) is isomorphic to \Out(F_n).Comment: Revised version, 43 pages. To appear in Publ. Math. IHE
Quasi-isometric rigidity for the solvable Baumslag-Solitar groups, II
Let BS(1,n)= . We prove that any finitely-generated
group quasi-isometric to BS(1,n) is (up to finite groups) isomorphic to
BS(1,n). We also show that any uniform group of quasisimilarities of the real
line is bilipschitz conjugate to an affine group.Comment: 42 pages. see also http://www.math.uchicago.edu/~far
Erratum for "The degree theorem in higher rank"
The purpose of this erratum is to correct a mistake in the proof of Theorem
4.1 of our paper \cite{CF}.Comment: Minor revisions suggested by refere
- …