Affine Wa(A4), Quaternions, and Decagonal Quasicrystals

Abstract

We introduce a technique of projection onto the Coxeter plane of an arbitrary higher dimensional lattice described by the affine Coxeter group. The Coxeter plane is determined by the simple roots of the Coxeter graph I2 (h) where h is the Coxeter number of the Coxeter group W(G) which embeds the dihedral group Dh of order 2h as a maximal subgroup. As a simple application we demonstrate projections of the root and weight lattices of A4 onto the Coxeter plane using the strip (canonical) projection method. We show that the crystal spaces of the affine Wa(A4) can be decomposed into two orthogonal spaces whose point groups is the dihedral group D5 which acts in both spaces faithfully. The strip projections of the root and weight lattices can be taken as models for the decagonal quasicrystals. The paper also revises the quaternionic descriptions of the root and weight lattices, described by the affine Coxeter group Wa(A3), which correspond to the face centered cubic (fcc) lattice and body centered cubic (bcc) lattice respectively. Extensions of these lattices to higher dimensions lead to the root and weight lattices of the group Wa(An), n>=4 . We also note that the projection of the Voronoi cell of the root lattice of Wa(A4) describes a framework of nested decagram growing with the power of the golden ratio recently discovered in the Islamic arts.

26 pages, 17 figures

References in corpus (2)

• Catalan Solids Derived From 3D-Root Systems and Quaternions
• Bulk and surface structure of the clean and adsorbate-covered decagonal Al-Co-Ni quasicrystal

Cited by in corpus (5)

• Group Theoretical Analysis of Quasicrystallography from Projections of Higher Dimensional Lattices Bn
• Explicit Construction of the Voronoi and Delaunay Cells of W(An) and W(Dn) Lattices and Their Facets
• Prototiles and Tilings from Voronoi and Delone cells of the Root Lattice A_n
• SU(5) Grand Unified Theory, its Polytopes and 5-fold Symmetric Aperiodic Tiling
• From Affine $A_4$ to Affine $H_2$: Group Theoretical Analysis of Five-fold Tilings