Tiling Polygons with Parallelograms.
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...
Cet article étudie, sur l’ensemble des points extrémaux d’un convexe compact , des topologies faciales dont les fermés sont les traces de faces “parallélisables” (il existe une plus grande face disjointe de , et tout de s’écrit , avec unique). Les topologies faciales uniformisables sont en bijection avec les sous-espaces réticulés fermés et contenant 1 de l’espace des fonctions affines continues sur . Ceci redonne des résultats classiques sur les simplexes, et permet une étude...
Continuing earlier work by Székelyhidi, we describe the topological and geometric structure of so-called T4-configurations which are the most prominent examples of nontrivial rank-one convex hulls. It turns out that the structure of T4-configurations in is very rich; in particular, their collection is open as a subset of . Moreover a previously purely algebraic criterion is given a geometric interpretation. As a consequence, we sketch an improved algorithm to detect T4-configurations. ...