Maximal index automorphisms of free groups with no attracting fixed points on the boundary are Dehn twists
نویسنده
چکیده
In this paper we define a quantity called the rank of an outer automorphism of a free group which is the same as the index introduced in [3] without the count of fixed points on the boundary. We proceed to analyze outer automorphisms of maximal rank and obtain results analogous to those in [5]. We also deduce that all such outer automorphisms can be represented by Dehn twists, thus proving the converse to a result in [4], and indicate a solution to the conjugacy problem when such automorphisms are given in terms of images of a basis, thus providing a moderate extension to the main theorem of [4] by somewhat different methods.
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