The hardness of approximating the boxicity, cubicity and threshold dimension of a graph

  • Authors:
  • Abhijin Adiga;Diptendu Bhowmick;L. Sunil Chandran

  • Affiliations:
  • -;-;-

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2010

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Abstract

A k-dimensional box is the Cartesian product R"1xR"2x...xR"k where each R"i is a closed interval on the real line. The boxicity of a graph G, denoted as box(G), is the minimum integer k such that G can be represented as the intersection graph of a collection of k-dimensional boxes. A unit cube in k-dimensional space or a k-cube is defined as the Cartesian product R"1xR"2x...xR"k where each R"i is a closed interval on the real line of the form [a"i,a"i+1]. The cubicity of G, denoted as cub(G), is the minimum integer k such that G can be represented as the intersection graph of a collection of k-cubes. The threshold dimension of a graph G(V,E) is the smallest integer k such that E can be covered by k threshold spanning subgraphs of G. In this paper we will show that there exists no polynomial-time algorithm for approximating the threshold dimension of a graph on n vertices with a factor of O(n^0^.^5^-^@e) for any @e0 unless NP=ZPP. From this result we will show that there exists no polynomial-time algorithm for approximating the boxicity and the cubicity of a graph on n vertices with factor O(n^0^.^5^-^@e) for any @e0 unless NP=ZPP. In fact all these hardness results hold even for a highly structured class of graphs, namely the split graphs. We will also show that it is NP-complete to determine whether a given split graph has boxicity at most 3.