Discrete & Computational Geometry

, Volume 39, Issue 4, pp 791–799 | Cite as

Note on the Pair-crossing Number and the Odd-crossing Number



The crossing number \({\mbox{\sc cr}}(G)\) of a graph G is the minimum possible number of edge-crossings in a drawing of G, the pair-crossing number \({\mbox{\sc pair-cr}}(G)\) is the minimum possible number of crossing pairs of edges in a drawing of G, and the odd-crossing number \({\mbox{\sc odd-cr}}(G)\) is the minimum number of pairs of edges that cross an odd number of times. Clearly, \({\mbox{\sc odd-cr}}(G)\le {\mbox{\sc pair-cr}}(G)\le {\mbox{\sc cr}}(G)\) . We construct graphs with \(0.855\cdot {\mbox{\sc pair-cr}}(G)\ge {\mbox{\sc odd-cr}}(G)\) . This improves the bound of Pelsmajer, Schaefer and Štefankovič. Our construction also answers an old question of Tutte.

Slightly improving the bound of Valtr, we also show that if the pair-crossing number of G is k, then its crossing number is at most O(k2/log 2k).


Drawings of a graph Crossing number 


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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  1. 1.Rényi InstituteHungarian Academy of SciencesBudapestHungary

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