图G的交叉数, 记作cr(G), 是把G画在平面上的所有画法中边与边产生交叉的最小数目, 它是拓扑图论中的一个热点问题。Klešč和 Petrillová刻画了当G1为圈且cr(G1□G2)=2时, 因子图G1和G2满足的充要条件。在此基础上, 本文研究当|V(G1)|≥3且cr(G1□G2)=2时, G1和G2应满足的充要条件。
The crossing number of a graph G, denoted by cr(G), is the minimum number of edge crossings in all drawings of G. The research on the crossing number of a graph is an active problem in topology graph theory. Klešč and Petrillová characterized graphs G1 and G2 for which the crossing number of G1□G2 is two if G1 is a cycle. This paper studies the necessary and sufficient conditions of G1 and G2 for which cr(G1□G2) = 2 if |V(G1)| > 3.
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