Hamiltonicity and Colorings of Arrangement Graphs

Stefan Felsner
Institut für Informatik
Freie Universität Berlin
Takustr. 9, D-14195 Berlin
email: felsner@inf.fu-berlin.de

Ferran Hurtado
Marc Noy
Dept. Matematica Aplicada 2
Universitat Politecnica de Catalunya
Pau Gargallo 5
Barcelona, Spain
email: name@ma2.upc.es.

Ileana Streinu
Dept. of Computer Science
Smith College
Northampton, MA 01063, USA
email: streinu@cs.smith.edu.

Report B-00-16

We study connectivity, Hamilton path and Hamilton cycle decomposition, 4-edge and 3-vertex coloring for geometric graphs arising from pseudoline (affine or projective) and pseudocircle (spherical) arrangements. While arrangements as geometric objects are well studied in discrete and computational geometry, their graph theoretical properties seem to have received little attention so far. In this paper we show that they provide well structured examples of families of planar and projective-planar graphs with very interesting properties. Most prominently, spherical arrangements admit decompositions into two Hamilton cycles and 4-edge colorings, but other classes have interesting properties as well: 4-connectivity, 3-vertex coloring or Hamilton paths and cycles. We show a number of negative results as well: there are projective arrangements which cannot be 3-vertex colored. A number of conjectures and open questions accompany our results.
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