arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1309.4643math.CO
收藏

含有多个极大链的集合系统

Set Systems Containing Many Maximal Chains

J. Robert Johnson, Imre Leader, Paul A. Russell

摘要:

这篇简短的问题论文的目的是提出一个关于集合系统的极值问题,这个问题似乎是自然和吸引人的。我们的问题是:哪个给定大小的集合系统使幂集$\mathcal{P}(\{1,2,\dots,n\})$中的$(n+1)$ -元素链的数目最大化?我们将证明,对于每个固定的$α>0$有一个家庭的$α2^n$集包含$(α+o(1))n!$这样的链,这是渐近最好的可能。对于较小的集合系统,我们无法回答这个问题。我们猜想一个“立方塔”的结构是极值的。最后,我们简要地提到一个连接到一个极值问题的偏序集和一个变种,我们的问题的网格图。

英文摘要:

The purpose of this short problem paper is to raise an extremal question on set systems which seems to be natural and appealing. Our question is: which set systems of a given size maximise the number of $(n+1)$-element chains in the power set $\mathcal{P}(\{1,2,\dots,n\})$? We will show that for each fixed $α>0$ there is a family of $α2^n$ sets containing $(α+o(1))n!$ such chains, and that this is asymptotically best possible. For smaller set systems we are unable to answer the question. We conjecture that a `tower of cubes' construction is extremal. We finish by mentioning briefly a connection to an extremal problem on posets and a variant of our question for the grid graph.

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。

↑