Convex Embeddings and Bisections of 3-Connected Graphs1

  • Authors:
  • Hiroshi Nagamochi;Tibor Jordán;Yoshitaka Nakao;Toshihide Ibaraki

  • Affiliations:
  • Toyohashi University of Technology, Department of Information and Computer Sciences, Japan;Eötvös University, Department of Operations Research, Hungary;Mathematical Science Section, Sumitomo Metal Industries, LTD., Department of Operations Research, Japan;Kyoto University, Department of Applied Mathematics and Physics, Graduate School of Engineering, Japan

  • Venue:
  • Combinatorica
  • Year:
  • 2002

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Abstract

Given two disjoint subsets T 1 and T 2 of nodes in an undirected 3-connected graph G = (V, E) with node set V and arc set E, where $${\left| {T_{1} } \right|}{\kern 1pt}$$ and $${\left| {T_{2} } \right|}{\kern 1pt}$$ are even numbers, we show that V can be partitioned into two sets V1 and V2 such that the graphs induced by V1 and V2 are both connected and $${\left| {V_{1} \cap T_{j} } \right|} = {\left| {V_{2} \cap T_{j} } \right|} = {\left| {T_{j} } \right|}/2$$ holds for each j = 1,2. Such a partition can be found in $$O{\left( {{\left| V \right|}^{2} {\kern 1pt} \log {\kern 1pt} {\left| V \right|}} \right)}$$ time. Our proof relies on geometric arguments. We define a new type of ‘convex embedding’ of k-connected graphs into real space Rk-1 and prove that for k = 3 such an embedding always exists.