Lovász's Lemma for the Three-Dimensional K-Level of Concave Surfaces and its Applications

  • Authors:
  • Naoki Katoh;Takeshi Tokuyama

  • Affiliations:
  • -;-

  • Venue:
  • FOCS '99 Proceedings of the 40th Annual Symposium on Foundations of Computer Science
  • Year:
  • 1999

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Abstract

We show that for any line l in space, there are at most k(k+1) tangent planes through l to the k-level of an arrangement of concave surfaces. This is a generalization of Lovász's lemma, which is a key constituent in the analysis of the complexity of k-level of planes.Our proof is constructive, and finds a family of concave surfaces covering the "laminated at-most-k level" . As consequences, (1): we have an O((n-k)2/3 n2) upper bound for the complexity of the k-level of n triangles of space, and (2): we can extend the k-set result in space to the k-set of a system of subsets of n points.