Right angle crossing graphs and 1-planarity

  • Authors:
  • Peter Eades;Giuseppe Liotta

  • Affiliations:
  • School of Information Technologies, University of Sydney, Australia;Università degli Studi di Perugia, Italy

  • Venue:
  • GD'11 Proceedings of the 19th international conference on Graph Drawing
  • Year:
  • 2011

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Abstract

A Right Angle Crossing Graph (also called RAC graph for short) is a graph that has a straight-line drawing where any two crossing edges are orthogonal to each other. A 1-planar graph is a graph that has a drawing where every edge is crossed at most once. We study the relationship between RAC graphs and 1-planar graphs in the extremal case that the RAC graphs have as many edges as possible. It is known that a maximally dense RAC graph with n3 vertices has 4n --- 10 edges. We show that every maximally dense RAC graph is 1-planar. Also, we show that for every integer i such that i≥0, there exists a 1-planar graph with n=8+4i vertices and 4n --- 10 edges that is not a RAC graph.