Geometry & Topology Monographs 1 (1998) 139–158

DOI: 10.2140/gtm.1998.1.139

arXiv: math.GT/9810192

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

Mathematical Subject Classification

Primary: 20E08

Secondary: 57M07

References

Publication

Received: 27 October 1997
Published: 22 October 1998

Authors