相交超图中的破碎匹配

Q4 Mathematics
P. Frankl, J. Pach
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引用次数: 0

摘要

设$X$为一个包含$n$元素的集合,其中$n$为偶数。我们反驳了J. Gordon和Y. Teplitskaya的一个猜想,根据这个猜想,对于$X$的$\frac{n}2$ -元素子集的每一个最大相交族$\mathcal{F}$,人们可以将$X$划分为$\frac{n}2$不相交对,这样无论我们如何从每一个前$\frac{n}2 - 1$对中选取一个元素,它们所形成的集合总是可以通过添加最后一个元素来补全为$\mathcal{F}$的一个成员。上述问题与极值集合论中的经典问题有关。对于任意$t\ge 2$,我们称集合族$\mathcal{F}\subset 2^X${\em$t$为可分离的,}如果对于任意$X$的有序元素对$(x,y)$,存在$F\in\mathcal{F}$使得$F\cap\{x,y\}=\{x\}$。对于固定的$t, 2\le t\le 5$和$n\rightarrow\infty$,我们建立了最小整数$s=s(n,t)$的渐近紧估计,使得每个族$\mathcal{F}$与$|\mathcal{F}|\ge s$都是$t$可分的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Shattered matchings in intersecting hypergraphs
Let $X$ be an $n$-element set, where $n$ is even. We refute a conjecture of J. Gordon and Y. Teplitskaya, according to which, for every maximal intersecting family $\mathcal{F}$ of $\frac{n}2$-element subsets of $X$, one can partition $X$ into $\frac{n}2$ disjoint pairs in such a way that no matter how we pick one element from each of the first $\frac{n}2 - 1$ pairs, the set formed by them can always be completed to a member of $\mathcal{F}$ by adding an element of the last pair. The above problem is related to classical questions in extremal set theory. For any $t\ge 2$, we call a family of sets $\mathcal{F}\subset 2^X$ {\em $t$-separable} if for any ordered pair of elements $(x,y)$ of $X$, there exists $F\in\mathcal{F}$ such that $F\cap\{x,y\}=\{x\}$. For a fixed $t, 2\le t\le 5$ and $n\rightarrow\infty$, we establish asymptotically tight estimates for the smallest integer $s=s(n,t)$ such that every family $\mathcal{F}$ with $|\mathcal{F}|\ge s$ is $t$-separable.
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来源期刊
Moscow Journal of Combinatorics and Number Theory
Moscow Journal of Combinatorics and Number Theory Mathematics-Algebra and Number Theory
CiteScore
0.80
自引率
0.00%
发文量
21
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