Browsing by Author "Huemer, Clemens"
Now showing items 1-20 of 37
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3-colorability of pseudo-triangulations
(2015)
Article
Open AccessDeciding 3-colorability for general plane graphs is known to be an NP-complete problem. However, for certain families of graphs, like triangulations, polynomial time algorithms exist. We consider the family of pseudo-tri ... -
4-Holes in point sets
(2014-08-01)
Article
Open AccessWe consider a variant of a question of Erdos on the number of empty k-gons (k-holes) in a set of n points in the plane, where we allow the k-gons to be non-convex. We show bounds and structural results on maximizing and ... -
4-labelings and grid embeddings of plane quadrangulations
(2009-06-03)
External research report
Open AccessWe show that each quadrangulation on $n$ vertices has a closed rectangle of influence drawing on the $(n-2) \times (n-2)$ grid. Further, we present a simple algorithm to obtain a straight-line drawing of a quadrangulation ... -
A new lower bound on the maximum number of plane graphs using production matrices
(2018)
Conference lecture
Restricted access - publisher's policyWe use the concept of production matrices to show that there exist sets of n points in the plane that admit ¿(41.77n) crossing-free geometric graphs. This improves the previously best known bound of ¿(41.18n) by Aichholzer ... -
Binary labelings for plane quadrangulations and their relatives
(2010)
Article
Open AccessMotivated by the bijection between Schnyder labelings of a plane triangulation and partitions of its inner edges into three trees, we look for binary labelings for quadrangulations (whose edges can be partitioned into two ... -
Carathodory's theorem in depth
(2017-07-01)
Article
Open AccessLet X be a finite set of points in RdRd . The Tukey depth of a point q with respect to X is the minimum number tX(q)tX(q) of points of X in a halfspace containing q. In this paper we prove a depth version of Carathéodory’s ... -
Characteristic polynomials of production matrices for geometric graphs
(2017-08-01)
Article
Open AccessAn n×n production matrix for a class of geometric graphs has the property that the numbers of these geometric graphs on up to n vertices can be read off from the powers of the matrix. Recently, we obtained such production ... -
Compatible spanning trees
(2014-07-01)
Article
Open AccessTwo plane geometric graphs are said to be compatible when their union is a plane geometric graph. Let S be a set of n points in the Euclidean plane in general position and let T be any given plane geometric spanning tree ... -
Edge-Removal and Non-Crossing Configurations in Geometric Graphs
(2010)
Article
Open AccessA geometric graph is a graph G = (V;E) drawn in the plane, such that V is a point set in general position and E is a set of straight-line segments whose endpoints belong to V . We study the following extremal problem for ... -
Empty monochromatic simplices
(2014-03-01)
Article
Open AccessLet S be a k-colored (finite) set of n points in , da parts per thousand yen3, in general position, that is, no (d+1) points of S lie in a common (d-1)-dimensional hyperplane. We count the number of empty monochromatic ... -
Empty non-convex and convex four-gons in random point sets
(2015-03-01)
Article
Open AccessLet S be a set of n points distributed uniformly and independently in a convex, bounded set in the plane. A four-gon is called empty if it contains no points of S in its interior. We show that the expected number of empty ... -
Large bichromatic point sets admit empty monochromatic 4-gons
(2009)
Conference report
Open AccessWe consider a variation of a problem stated by Erd˝os and Szekeres in 1935 about the existence of a number fES(k) such that any set S of at least fES(k) points in general position in the plane has a subset of k points that ... -
Lower bounds for the number of small convex k-holes
(2014-07-01)
Article
Open AccessLet S be a set of n points in the plane in general position, that is, no three points of S are on a line. We consider an Erdos-type question on the least number h(k)(n) of convex k-holes in S, and give improved lower bounds ... -
Lower bounds on the maximum number of non-crossing acyclic graphs
(2015-08-01)
Article
Open AccessThis paper is a contribution to the problem of counting geometric graphs on point sets. More concretely, we look at the maximum numbers of non-crossing spanning trees and forests. We show that the so-called double chain ... -
Matching points with diametral disks
(2017)
Conference report
Open AccessWe consider matchings between a set R of red points and a set B of blue points with diametral disks. In other words, for each pair of matched points p ¿ R and q ¿ B, we consider the diametral disk defined by p and q. We ... -
Maximizing maximal angles for plane straight-line graphs
(2013-01)
Article
Restricted access - publisher's policyLet G=(S,E) be a plane straight-line graph on a finite point set S⊂R2 in general position. The incident angles of a point p∈S in G are the angles between any two edges of G that appear consecutively in the circular order ... -
Modem illumination of monotone polygons
(2009)
Conference report
Open AccessWe study a generalization of the classical problem of illumination of polygons. Instead of modeling a light source we model a wireless device whose radio signal can penetrate a given number k of walls. We call these ... -
Moving rectangles
(2010)
Conference report
Open AccessConsider a set of n pairwise disjoint axis-parallel rectangles in the plane. We call this set the source rectangles S. The aim is to move S to a set of (pairwise disjoint) target rectangles T . A move consists in a ... -
New results on production matrices for geometric graphs
(2018-07-01)
Article
Restricted access - publisher's policyWe present novel production matrices for non-crossing partitions, connected geometric graphs, and k-angulations, which provide another way of counting the number of such objects. For instance, a formula for the number of ... -
Note on the number of obtuse angles in point sets
(2014-09)
Article
Open AccessIn $1979$ Conway, Croft, Erd\H{o}s and Guy proved that every set $S$ of $n$ points in general position in the plane determines at least $\frac{n^3}{18}-O(n^2)$ obtuse angles and also presented a special set of $n$ points ...
