次闭图类的k-顶点I.包围障碍物
k-apices of minor-closed graph classes. I. Bounding the obstructions
摘要:
设$\mathcal{G}$是一个次闭图类。我们称一个图$G$是$\mathcal{G}$的一个$k$ -顶点,如果$G$包含一个至多$k$顶点的集合$S$,使得$G\setminus S$属于$\mathcal{G}.$。我们用$\mathcal{A}_k (\mathcal{G})$表示所有是$\mathcal{G}.$的$k$ -顶点的图的集合。我们证明了$\mathcal{A}_k (\mathcal{G}),$的阻塞集中的每个图,即,不属于$\mathcal{A}_k (\mathcal{G}),$的图的次最小集合具有至多$2^{2^{2^{2^{\mathsf{poly}(k)}}}},$的大小,其中$\mathsf{poly}$是多项式函数,其次数取决于$\mathcal{G}.$的次障碍的大小。当$\mathcal{G}$排除某些顶点图作为次图时,该界限下降到$2^{2^{\mathsf{poly}(k)}}$。
英文摘要:
Let $\mathcal{G}$ be a minor-closed graph class. We say that a graph $G$ is a $k$-apex of $\mathcal{G}$ if $G$ contains a set $S$ of at most $k$ vertices such that $G\setminus S$ belongs to $\mathcal{G}.$ We denote by $\mathcal{A}_k (\mathcal{G})$ the set of all graphs that are $k$-apices of $\mathcal{G}.$ We prove that every graph in the obstruction set of $\mathcal{A}_k (\mathcal{G}),$ i.e., the minor-minimal set of graphs not belonging to $\mathcal{A}_k (\mathcal{G}),$ has size at most $2^{2^{2^{2^{\mathsf{poly}(k)}}}},$ where $\mathsf{poly}$ is a polynomial function whose degree depends on the size of the minor-obstructions of $\mathcal{G}.$ This bound drops to $2^{2^{\mathsf{poly}(k)}}$ when $\mathcal{G}$ excludes some apex graph as a minor.
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