Coincidences of simplex centers and related facial structures.
Colouring polytopic partitions in
Colouring polytopic partitions in
We consider face-to-face partitions of bounded polytopes into convex polytopes in for arbitrary and examine their colourability. In particular, we prove that the chromatic number of any simplicial partition does not exceed . Partitions of polyhedra in into pentahedra and hexahedra are - and -colourable, respectively. We show that the above numbers are attainable, i.e., in general, they cannot be reduced.
Combinatorics, group theory and geometric models
Compact hyperbolic Coxeter -polytopes with facets.
Compact hyperbolic tetrahedra with non-obtuse dihedral angles.
Given a combinatorial description C of a polyhedron having E edges, the space of dihedral angles of all compact hyperbolic polyhedra that realize C is generally not a convex subset of RE. If C has five or more faces, Andreev's Theorem states that the corresponding space of dihedral angles AC obtained by restricting to non-obtuse angles is a convex polytope. In this paper we explain why Andreev did not consider tetrahedra, the only polyhedra having fewer than five faces, by demonstrating that the...
Comparing the relative volume with the relative inradius and the relative width.
Comparision of the length of infinite geodesics in manifolds with nonpositive curvature.
Computing a Centerpoint of a Finite Planar Set of Points in Linear Time.
Concerning the order and the semi-order of n-dimensional Euclidean space
Configuration spaces and limits of voronoi diagrams
The Voronoi diagram of n distinct generating points divides the plane into cells, each of which consists of points most close to one particular generator. After introducing 'limit Voronoi diagrams' by analyzing diagrams of moving and coinciding points, we define compactifications of the configuration space of n distinct, labeled points. On elements of these compactifications we define Voronoi diagrams.
Constructing non-regular algebraic spreads with asymplecticly complemented regulization.
Construction des regulären Sieben- und Dreizehn-Ecks
Construction of a line through a given point to divide a triangle into two parts with areas in a given ratio.
Correction to "On a functional equation arising from hyperbolic geometry", Volume 21 (1980), 113-116.
Countable Decompositions of R2 and R3 .
Countably convex sets
We investigate countably convex subsets of Banach spaces. A subset of a linear space is countably convex if it can be represented as a countable union of convex sets. A known sufficient condition for countable convexity of an arbitrary subset of a separable normed space is that it does not contain a semi-clique [9]. A semi-clique in a set S is a subset P ⊆ S so that for every x ∈ P and open neighborhood u of x there exists a finite set X ⊆ P ∩ u such that conv(X) ⊈ S. For closed sets this condition...
Counting all equilateral triangles in .
Counting Types of Rigid Frameworks.
Covering the plane with sprays
For any three noncollinear points c₀,c₁,c₂ ∈ ℝ², there are sprays S₀,S₁,S₂ centered at c₀,c₁,c₂ that cover ℝ². This improves the result of de la Vega in which c₀,c₁,c₂ were required to be the vertices of an equilateral triangle.