平面图随机泛集的一个Omega(n^2)下界
An Omega(n^2) Lower Bound for Random Universal Sets for Planar Graphs
摘要:
一个集合$U\subseteq \reals^2$是$n$ -泛的,如果所有的$n$ -顶点平面图都有平面直线嵌入到$U$中.我们证明了,如果$Q \subseteq \reals^2$由随机和均匀地从单位正方形中选择的点组成,那么$Q$必须具有基数$Ω(n^2)$,以便以高概率成为$n$ -普适的。这表明,概率方法,至少在其基本形式,不能用于建立一个通用集上的$o(n^2)$上限。
英文摘要:
A set $U\subseteq \reals^2$ is $n$-universal if all $n$-vertex planar graphs have a planar straight-line embedding into $U$. We prove that if $Q \subseteq \reals^2$ consists of points chosen randomly and uniformly from the unit square then $Q$ must have cardinality $Ω(n^2)$ in order to be $n$-universal with high probability. This shows that the probabilistic method, at least in its basic form, cannot be used to establish an $o(n^2)$ upper bound on universal sets.
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