Making a Graph Crossing-Critical by Multiplying its Edges

  • Laurent Beaudou
  • César Hernández-Vélez
  • Gelasio Salazar


A graph is crossing-critical if the removal of any of its edges decreases its crossing number. This work is motivated by the following question: to what extent is crossing-criticality a property that is inherent to the structure of a graph, and to what extent can it be induced on a noncritical graph by multiplying (all or some of) its edges? It is shown that if a nonplanar graph $G$ is obtained by adding an edge to a cubic polyhedral graph, and $G$ is sufficiently connected, then $G$ can be made crossing-critical by a suitable multiplication of edges.

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