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Uniform chain decompositions and applications
Random Structures and Algorithms ( IF 0.9 ) Pub Date : 2021-07-12 , DOI: 10.1002/rsa.21034
Benny Sudakov 1 , István Tomon 1 , Adam Zsolt Wagner 2
Affiliation  

The Boolean lattice urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0001 is the family of all subsets of urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0002 ordered by inclusion, and a chain is a family of pairwise comparable elements of urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0003. Let urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0004, which is the average size of a chain in a minimal chain decomposition of urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0005. We prove that urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0006 can be partitioned into urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0007 chains such that all but at most urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0008 proportion of the chains have size urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0009. This asymptotically proves a conjecture of Füredi from 1985. Our proof is based on probabilistic arguments. To analyze our random partition we develop a weighted variant of the graph container method. Using this result, we also answer a Kalai-type question raised recently by Das, Lamaison, and Tran. What is the minimum number of forbidden comparable pairs forcing that the largest subfamily of urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0010 not containing any of them has size at most urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0011? We show that the answer is urn:x-wiley:rsa:media:rsa21034:rsa21034-math-0012. Finally, we discuss how these uniform chain decompositions can be used to optimize and simplify various results in extremal set theory.

中文翻译:

均匀链分解和应用

布尔格骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0001是按包含排序的所有子集的族骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0002,而链是 的成对可比元素的族骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0003。Let 骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0004,它是 的最小链分解中链的平均大小骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0005。我们证明骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0006可以划分成骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0007链,使得除了最多骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0008比例的链之外,所有链都具有大小骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0009。这渐近地证明了 Füredi 从 1985 年开始的猜想。我们的证明是基于概率论的。为了分析我们的随机分区,我们开发了图容器方法的加权变体。利用这个结果,我们还回答了 Das、Lamaison 和 Tran 最近提出的一个 Kalai 类型的问题。强迫最大亚科的禁止可比对的最小数量是多少骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0010不包含它们中的任何一个最多有大小骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0011吗?我们证明答案是骨灰盒:x-wiley:rsa:媒体:rsa21034:rsa21034-math-0012。最后,我们讨论了如何使用这些均匀链分解来优化和简化极值集理论中的各种结果。
更新日期:2021-07-12
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