Convex Partitions with 2-Edge Connected Dual Graphs

  • Authors:
  • Marwan Al-Jubeh;Michael Hoffmann;Mashhood Ishaque;Diane L. Souvaine;Csaba D. Tóth

  • Affiliations:
  • Department of Computer Science, Tufts University, Meford, USA;Institute of Theoretical Computer Science, ETH Zürich, Switzerland;Department of Computer Science, Tufts University, Meford, USA;Department of Computer Science, Tufts University, Meford, USA;Department of Mathematics, University of Calgary, Canada

  • Venue:
  • COCOON '09 Proceedings of the 15th Annual International Conference on Computing and Combinatorics
  • Year:
  • 2009

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Abstract

It is shown that for every finite set of disjoint convex polygonal obstacles in the plane, with a total of n vertices, the free space around the obstacles can be partitioned into open convex cells whose dual graph (defined below) is 2-edge connected. Intuitively, every edge of the dual graph corresponds to a pair of adjacent cells that are both incident to the same vertex. Aichholzer et al. recently conjectured that given an even number of line-segment obstacles, one can construct a convex partition by successively extending the segments along their supporting lines such that the dual graph is the union of two edge-disjoint spanning trees. Here we present a counterexamples to this conjecture, with n disjoint line segments for any n *** 15, such that the dual graph of any convex partition constructed by this method has a bridge edge, and thus the dual graph cannot be partitioned into two spanning trees.