Right Angle Crossing Graphs and 1-Planarity

  • Peter Eades
  • Giuseppe Liotta
Part of the Lecture Notes in Computer Science book series (LNCS, volume 7034)


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 n > 3 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.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Peter Eades
    • 1
  • Giuseppe Liotta
    • 2
  1. 1.School of Information TechnologiesUniversity of SydneyAustralia
  2. 2.Università degli Studi di PerugiaItaly

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