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Reflection triangles in Coxeter groups and biautomaticity

  • Pierre-Emmanuel Caprace and Bernhard Mühlherr
Published/Copyright: November 18, 2005
Journal of Group Theory
From the journal Volume 8 Issue 4

Abstract

A Coxeter system (WS ) is called affine-free if its Coxeter diagram contains no affine subdiagram of rank ≥ 3. Let (WS ) be a Coxeter system of finite rank (i.e. |S | is finite). The main result is that W is affine-free if and only if W  has finitely many conjugacy classes of reflection triangles. This implies that the action of W  on its Coxeter cubing (defined by Niblo and Reeves [G. Niblo and L. Reeves. Coxeter groups act on CAT(0) cube complexes. J. Group Theory  6 (2003), 399–413]) is cocompact if and only if (WS ) is affine-free. This result was conjectured in loc. cit. As a corollary, we obtain that affine-free Coxeter groups are biautomatic.

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Published Online: 2005-11-18
Published in Print: 2005-07-20

Walter de Gruyter GmbH & Co. KG

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