Algebra and Topology Seminar

4pm Tuesday 14 December 2004
Adam Piggott
University of Oxford

Detecting the growth of free-group automorphisms

Let f be a polynomially-growing automorphism of a finitely generated free group F. We present a theorem that there exists a charactersistic subgroup S F such that the induced automorphism (f|S)_ab of the abelianisation of S grows with the same polynomial degree as f:F ->F. The proof is geometric in nature and makes use of Bestvina-Feighn-Handel train track theory.




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