54 research outputs found
Bounding the gap between a free group (outer) automorphism and its inverse
For any finitely generated group , two complexity functions and
are defined to measure the maximal possible gap between the norm of
an automorphism (respectively outer automorphism) of and the norm of its
inverse. Restricting attention to free groups , the exact asymptotic
behaviour of and is computed. For rank ,
polynomial lower bounds are provided for and , and the
existence of a polynomial upper bound is proved for .Comment: 24 pages; To appear in Collectanea Mathematic
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