The expansion factors of an outer automorphism and its inverse
نویسندگان
چکیده
A fully irreducible outer automorphism φ of the free group Fn of rank n has an expansion factor which often differs from the expansion factor of φ. Nevertheless, we prove that the ratio between the logarithms of the expansion factors of φ and φ is bounded above by a constant depending only on the rank n. We also prove a more general theorem applying to an arbitrary outer automorphism of Fn and its inverse and their two spectrums of expansion factors.
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