Zone diagrams in Euclidean spaces and in other normed spaces

  • Authors:
  • Akitoshi Kawamura;Jiři Matoušek;Takeshi Tokuyama

  • Affiliations:
  • University of Toronto, Toronto, ON, Canada;Charles University and and ETH Zurich, Prague, Czech Rep;Tohoku University, Sendai, Japan

  • Venue:
  • Proceedings of the twenty-sixth annual symposium on Computational geometry
  • Year:
  • 2010

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Abstract

Zone diagram is a variation on the classical concept of a Voronoi diagram. Given n sites in a metric space that compete for territory, the zone diagram is an equilibrium state in the competition. Formally it is defined as a fixed point of a certain "dominance" map. Asano, Matousek, and Tokuyama proved the existence and uniqueness of a zone diagram for point sites in Euclidean plane, and Reem and Reich showed existence for two arbitrary sites in an arbitrary metric space. We establish existence and uniqueness for n disjoint compact sites in a Euclidean space of arbitrary (finite) dimension, and more generally, in a finite-dimensional normed space with a smooth and rotund norm. The proof is considerably simpler than that of Asano et al. We also provide an example of non-uniqueness for a norm that is rotund but not smooth. Finally, we prove existence and uniqueness for two point sites in the plane with a smooth (but not necessarily rotund) norm.