The architecture of viral capsids based on tiling theory.
We prove that if a measurable domain tiles ℝ or ℝ² by translations, and if it is "close enough" to a line segment or a square respectively, then it admits a lattice tiling. We also prove a similar result for spectral sets in dimension 1, and give an example showing that there is no analogue of the tiling result in dimensions 3 and higher.
Suppose has a 2-dimensional expanding subspace , satisfies a regularity condition, called “good star”, and has , where is an oriented compound of . A morphism of the free group on is called a non-abelianization of if it has structure matrix . We show that there is a tiling substitution whose “boundary substitution” is a non-abelianization of . Such a tiling substitution leads to a self-affine tiling of with as its expansion. In the last section we find conditions on so...
Call a polygon rational if every pair of side lengths has rational ratio. We show that a convex polygon can be tiled with rational polygons if and only if it is itself rational. Furthermore we give a necessary condition for an arbitrary polygon to be tileable with rational polygons: we associate to any polygon a quadratic form , which must be positive semidefinite if is tileable with rational polygons.The above results also hold replacing the rationality condition with the following: a polygon...