862 research outputs found
Chirality and projective linear groups
AbstractIn recent years the term ‘chiral’ has been used for geometric and combinatorial figures which are symmetrical by rotation but not by reflection. The correspondence of groups and polytopes is used to construct infinite series of chiral and regular polytopes whose facets or vertex-figures are chiral or regular toroidal maps. In particular, the groups PSL2(Zm) are used to construct chiral polytopes, while PSL2(Zm[i]) and PSL2(Zm[ω]) are used to construct regular polytopes
Chiral extensions of chiral polytopes
Given a chiral d-polytope K with regular facets, we describe a construction
for a chiral (d + 1)-polytope P with facets isomorphic to K. Furthermore, P is
finite whenever K is finite. We provide explicit examples of chiral 4-polytopes
constructed in this way from chiral toroidal maps.Comment: 21 pages. [v2] includes several minor revisions for clarit
Mixing Chiral Polytopes
An abstract polytope of rank n is said to be chiral if its automorphism group
has two orbits on the flags, such that adjacent flags belong to distinct
orbits. Examples of chiral polytopes have been difficult to find. A "mixing"
construction lets us combine polytopes to build new regular and chiral
polytopes. By using the chirality group of a polytope, we are able to give
simple criteria for when the mix of two polytopes is chiral
Constructing Self-Dual Chiral Polytopes
An abstract polytope is chiral if its automorphism group has two orbits on
the flags, such that adjacent flags belong to distinct orbits. There are still
few examples of chiral polytopes, and few constructions that can create chiral
polytopes with specified properties. In this paper, we show how to build
self-dual chiral polytopes using the mixing construction for polytopes.Comment: 16 page
Hereditary Polytopes
Every regular polytope has the remarkable property that it inherits all
symmetries of each of its facets. This property distinguishes a natural class
of polytopes which are called hereditary. Regular polytopes are by definition
hereditary, but the other polytopes in this class are interesting, have
possible applications in modeling of structures, and have not been previously
investigated. This paper establishes the basic theory of hereditary polytopes,
focussing on the analysis and construction of hereditary polytopes with highly
symmetric faces.Comment: Discrete Geometry and Applications (eds. R.Connelly and A.Ivic
Weiss), Fields Institute Communications, (23 pp, to appear
Problems on Polytopes, Their Groups, and Realizations
The paper gives a collection of open problems on abstract polytopes that were
either presented at the Polytopes Day in Calgary or motivated by discussions at
the preceding Workshop on Convex and Abstract Polytopes at the Banff
International Research Station in May 2005.Comment: 25 pages (Periodica Mathematica Hungarica, Special Issue on Discrete
Geometry, to appear
Polygonal Complexes and Graphs for Crystallographic Groups
The paper surveys highlights of the ongoing program to classify discrete
polyhedral structures in Euclidean 3-space by distinguished transitivity
properties of their symmetry groups, focussing in particular on various aspects
of the classification of regular polygonal complexes, chiral polyhedra, and
more generally, two-orbit polyhedra.Comment: 21 pages; In: Symmetry and Rigidity, (eds. R.Connelly, A.Ivic Weiss
and W.Whiteley), Fields Institute Communications, to appea
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