A Note on the 4-Connected Line Graph of a Planar Triangulation Containing Two CISTs
摘要
Completely independent spanning trees (CISTs) in a graph G are spanning trees of G such that for any two distinct vertices of G, the paths between them in the spanning trees are pairwise edge-disjoint and internally vertex-disjoint. Hasunuma proved that there are two CISTs in any 4-connected planar triangulation and asked whether every 4-connected planar graph contains two CISTs. In this paper, we give a negative answer to this question and prove that every 4-connected line graph of a planar triangulation contains two CISTs.