منابع مشابه
Reflection subgroups of Coxeter groups
We use geometry of Davis complex of a Coxeter group to investigate finite index reflection subgroups of Coxeter groups. The main result is the following: if G is an infinite indecomposable Coxeter group and H ⊂ G is a finite index reflection subgroup then the rank of H is not less than the rank of G. This generalizes results of [7]. We also describe some properties of the nerves of the group an...
متن کاملOn finite index reflection subgroups of discrete reflection groups
Let G be a discrete group generated by reflections in hyperbolic or Euclidean space, and H ⊂ G be a finite index subgroup generated by reflections. Suppose that the fundamental chamber of G is a finite volume polytope with k facets. In this paper, we prove that the fundamental chamber of H has at least k facets. 1. Let X be hyperbolic space H, Euclidean space E or spherical space S . A polytope...
متن کاملReflection subgroups of odd-angled Coxeter groups
We give a criterion for a finitely generated odd-angled Coxeter group to have a proper finite index subgroup generated by reflections. The answer is given in terms of the least prime divisors of the exponents of the Coxeter relations.
متن کاملImaginary Cone and Reflection Subgroups of Coxeter Groups
The imaginary cone of a Kac-Moody Lie algebra is the convex hull of zero and the positive imaginary roots. This paper studies the imaginary cone for a class of root systems of general Coxeter groups W . It is shown that the imaginary cone of a reflection subgroup of W is contained in that of W , and that for irreducible infinite W of finite rank, the closed imaginary cone is the only non-zero, ...
متن کاملOn Reflection Length in Reflection Groups
Let W be the Weyl group of a connected reductive group over a finite field. It is a consequence of the Borel-Tits rational conjugacy theorem for maximal split tori that for certain reflection subgroups W1 of W (including all parabolic subgroups), the elements of minimal reflection length in any coset wW1 are all conjugate, provided w normalises W1. We prove a sharper and more general result of ...
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ژورنال
عنوان ژورنال: Functional Analysis and Its Applications
سال: 2004
ISSN: 0016-2663,1573-8485
DOI: 10.1007/s10688-005-0011-y