254 research outputs found
Complements of tori and Klein bottles in the 4-sphere that have hyperbolic structure
Many noncompact hyperbolic 3-manifolds are topologically complements of links
in the 3-sphere. Generalizing to dimension 4, we construct a dozen examples of
noncompact hyperbolic 4-manifolds, all of which are topologically complements
of varying numbers of tori and Klein bottles in the 4-sphere. Finite covers of
some of those manifolds are then shown to be complements of tori and Klein
bottles in other simply-connected closed 4-manifolds. All the examples are
based on a construction of Ratcliffe and Tschantz, who produced 1171 noncompact
hyperbolic 4-manifolds of minimal volume. Our examples are finite covers of
some of those manifolds.Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol5/agt-5-41.abs.htm
Salem numbers and arithmetic hyperbolic groups
In this paper we prove that there is a direct relationship between Salem
numbers and translation lengths of hyperbolic elements of arithmetic hyperbolic
groups that are determined by a quadratic form over a totally real number
field. As an application we determine a sharp lower bound for the length of a
closed geodesic in a noncompact arithmetic hyperbolic n-orbifold for each
dimension n. We also discuss a "short geodesic conjecture", and prove its
equivalence with "Lehmer's conjecture" for Salem numbers.Comment: The exposition in version 3 is more compact; this shortens the paper:
26 pages now instead of 37. A discussion on Lehmer's problem has been added
in Section 1.2. Final version, to appear is Trans. AM
Matching theorems for systems of a finitely generated Coxeter group
In this paper we prove a series of matching theorems for two sets of Coxeter
generators of a finitely generated Coxeter group that identify common features
of the two sets of generators. As an application, we describe an algorithm for
finding a set of Coxeter generators of maximum rank for a finitely generated
Coxeter group.Comment: This paper replaces our earlier paper "On the isomorphism problem for
finitely generated Coxeter groups. I, Basic matching". 49 pages. Sections
7-10 are ne
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