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Archimedean actions on median pretrees

Published online by Cambridge University Press:  18 May 2001

BRIAN H. BOWDITCH
Affiliation:
Faculty of Mathematical Studies, University of Southampton, Southampton, SO17 1BJ. e-mail: [email protected]
JOHN CRISP
Affiliation:
Laboratoire de Topologie, Université de Bourgogne, UMR 5584 du CNRS, B.P. 47 870, 21078 Dijon, France

Abstract

In this paper we consider group actions on generalized treelike structures (termed ‘pretrees’) defined simply in terms of betweenness relations. Using a result of Levitt, we show that if a countable group admits an archimedean action on a median pretree, then it admits an action by isometries on an ℝ-tree. Thus the theory of isometric actions on ℝ-trees may be extended to a more general setting where it merges naturally with the theory of right-orderable groups. This approach has application also to the study of convergence group actions on continua.

Type
Research Article
Copyright
2001 Cambridge Philosophical Society

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