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, Zurich, Switzerland;Department of Computer Science, Tufts University, Meford, USA;Department of Computer Science, Tufts University, Meford, USA;Department of Mathematics, University of Calgary, Calgary, Canada

  • Venue:
  • Journal of Combinatorial Optimization
  • Year:
  • 2011

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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 counterexamples to this conjecture, with n disjoint line segments for any n驴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.