Note: Edge intersection graphs of systems of paths on a grid with a bounded number of bends

  • Authors:
  • Andrei Asinowski;Andrew Suk

  • Affiliations:
  • Caesarea Rothschild Institute, University of Haifa, Haifa 31905, Israel;Courant Institute, New York University, New York, NY 10012, United States

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2009

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Abstract

We answer some of the questions raised by Golumbic, Lipshteyn and Stern and obtain some other results about edge intersection graphs of paths on a grid (EPG graphs). We show that for any d=4, in order to represent every n vertex graph with maximum degree d as an edge intersection graph of n paths on a grid, a grid of area @Q(n^2) is needed. We also show several results related to the classes B"k-EPG, where B"k-EPG denotes the class of graphs that have an EPG representation such that each path has at most k bends. In particular, we prove: For a fixed k and a sufficiently large n, the complete bipartite graph K"m","n does not belong to B"2"m"-"3-EPG (it is known that this graph belongs to B"2"m"-"2-EPG); for any odd integer k we have B"k-EPG @?B"k"+"1-EPG; there is no number k such that all graphs belong to B"k-EPG; only 2^O^(^k^n^l^o^g^(^k^n^)^) out of all the 2^n^2 labeled graphs with n vertices are in B"k-EPG.