Geometry & Topology Monographs 1 (1998),
The Epstein Birthday Schrift,
paper no. 7, pages 139-158.
Folding sequences
M J Dunwoody
Abstract.
Bestvina and Feighn showed that a morphism S --> T between two
simplicial trees that commutes with the action of a group G can be
written as a product of elementary folding operations. Here a more
general morphism between simplicial trees is considered, which allow
different groups to act on S and T. It is shown that these morphisms
can again be written as a product of elementary operations: the
Bestvina-Feighn folds plus the so-called `vertex
morphisms'. Applications of this theory are presented. Limits of
infinite folding sequences are considered. One application is that a
finitely generated inaccessible group must contain an infinite torsion
subgroup.
Keywords.
Groups acting on trees, free groups
AMS subject classification.
Primary: 20E08. Secondary: 57M07.
E-print: arXiv:math.GT/9810192
Submitted: 27 October 1997.
Published: 26 October 1998.
Notes on file formats
M J Dunwoody
Faculty of Math.Studies
University of Southampton
Southampton, SO9 5NH, UK
Email: mjd@maths.soton.ac.uk
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