Rooted $K_4$-Minors

[摘要] Let $a,b,c,d$ be four vertices in a graph $G$. A $K_4$ minor rooted at $a,b,c,d$ consists of four pairwise-disjoint pairwise-adjacent connected subgraphs of $G$, respectively containing $a,b,c,d$. We characterise precisely when $G$ contains a $K_4$-minor 

[学科分类] 离散数学和组合数学

[关键词] graph theory;graph minor;rooted minor;linkage