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arXiv 2008.10225math.CO
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下确界闭集个数最少的树

Trees with minimum number of infima closed sets

Eric Ould Dadah Andriantiana, Stephan Wagner

摘要:

设$T$是一棵有根树,而$V(T)$是它的顶点集。$V(T)$的子集$X$称为$T$的下确界闭集,如果对于任何两个顶点$u,v\in X$,$u$和$v$的第一公共祖先也在$X$中。本文确定了给定阶的所有有根树中下确界闭集个数最少的树,从而回答了Klazar的一个问题。它表明,这些树基本上是完全的二叉树,在最后一级的顶点除外。此外,还给出了具有$n$顶点的树的最小下确界闭集个数的渐近估计。

英文摘要:

Let $T$ be a rooted tree, and $V(T)$ its set of vertices. A subset $X$ of $V(T)$ is called an infima closed set of $T$ if for any two vertices $u,v\in X$, the first common ancestor of $u$ and $v$ is also in $X$. This paper determines the trees with minimum number of infima closed sets among all rooted trees of given order, thereby answering a question of Klazar. It is shown that these trees are essentially complete binary trees, with the exception of vertices at the last levels. Moreover, an asymptotic estimate for the minimum number of infima closed sets in a tree with $n$ vertices is also provided.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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