Long turns, INP's and index for free group automorphisms Auteur(s): Coulbois T., Lustig M. (Document sans référence bibliographique) 2015-06-15 Ref HAL: hal-01318378_v1 Ref Arxiv: 1506.04532 Ref. & Cit.: NASA ADS Exporter : BibTex | endNote Résumé: The goal of this paper is to introduce a new tool, called {\em long turns}, which is a useful addition to the train track technology for automorphisms of free groups, in that it allows one to control periodic INPs in a train track map and hence the index of the induced automorphism. Commentaires: 25 pages