{"title":"概稳定一般Kneser超图的色数","authors":"A. Jafari","doi":"10.4310/joc.2022.v13.n3.a5","DOIUrl":null,"url":null,"abstract":"Let $n\\ge 1$ and $s\\ge 1$ be integers. An almost $s$-stable subset $A$ of $[n]=\\{1,\\dots,n\\}$ is a subset such that for any two distinct elements $i, j\\in A$, one has $|i-j|\\ge s$. For a family $\\cal F$ of subsets in $[n]$ and $r\\ge 2$, the chromatic number of the $r$-uniform Kneser hypergraph $\\mbox{KG}^r({\\cal F})$, whose vertex set is $\\cal F$ and whose edges set is the set of $\\{A_1,\\dots, A_r\\}$ of pairwise disjoint elements of $\\cal F$, has been studied extensively in the literature and Abyazi Sani and Alishahi were able to give a lower bound for it in terms of the equatable $r$-colorability defect, $\\mbox{ecd}^r({\\cal F})$. In this article, the methods of Chen for the special family of all $k$-subsets of $[n]$, are modified to give lower bounds for the chromatic number of almost stable general Kneser hypergraph $\\mbox{KG}^r({\\cal F}_s)$ in terms of $\\mbox{ecd}^s({\\cal F})$. Here ${\\cal F}_s$ is he collection of almost $s$-stable elements of $\\cal F$. We also, propose a generalization of conjecture of Meunier.","PeriodicalId":44683,"journal":{"name":"Journal of Combinatorics","volume":"23 1","pages":""},"PeriodicalIF":0.4000,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":"{\"title\":\"On the chromatic number of almost stable general Kneser hypergraphs\",\"authors\":\"A. Jafari\",\"doi\":\"10.4310/joc.2022.v13.n3.a5\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Let $n\\\\ge 1$ and $s\\\\ge 1$ be integers. An almost $s$-stable subset $A$ of $[n]=\\\\{1,\\\\dots,n\\\\}$ is a subset such that for any two distinct elements $i, j\\\\in A$, one has $|i-j|\\\\ge s$. For a family $\\\\cal F$ of subsets in $[n]$ and $r\\\\ge 2$, the chromatic number of the $r$-uniform Kneser hypergraph $\\\\mbox{KG}^r({\\\\cal F})$, whose vertex set is $\\\\cal F$ and whose edges set is the set of $\\\\{A_1,\\\\dots, A_r\\\\}$ of pairwise disjoint elements of $\\\\cal F$, has been studied extensively in the literature and Abyazi Sani and Alishahi were able to give a lower bound for it in terms of the equatable $r$-colorability defect, $\\\\mbox{ecd}^r({\\\\cal F})$. In this article, the methods of Chen for the special family of all $k$-subsets of $[n]$, are modified to give lower bounds for the chromatic number of almost stable general Kneser hypergraph $\\\\mbox{KG}^r({\\\\cal F}_s)$ in terms of $\\\\mbox{ecd}^s({\\\\cal F})$. Here ${\\\\cal F}_s$ is he collection of almost $s$-stable elements of $\\\\cal F$. We also, propose a generalization of conjecture of Meunier.\",\"PeriodicalId\":44683,\"journal\":{\"name\":\"Journal of Combinatorics\",\"volume\":\"23 1\",\"pages\":\"\"},\"PeriodicalIF\":0.4000,\"publicationDate\":\"2020-09-22\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Combinatorics\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.4310/joc.2022.v13.n3.a5\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"MATHEMATICS, APPLIED\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Combinatorics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.4310/joc.2022.v13.n3.a5","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATHEMATICS, APPLIED","Score":null,"Total":0}
On the chromatic number of almost stable general Kneser hypergraphs
Let $n\ge 1$ and $s\ge 1$ be integers. An almost $s$-stable subset $A$ of $[n]=\{1,\dots,n\}$ is a subset such that for any two distinct elements $i, j\in A$, one has $|i-j|\ge s$. For a family $\cal F$ of subsets in $[n]$ and $r\ge 2$, the chromatic number of the $r$-uniform Kneser hypergraph $\mbox{KG}^r({\cal F})$, whose vertex set is $\cal F$ and whose edges set is the set of $\{A_1,\dots, A_r\}$ of pairwise disjoint elements of $\cal F$, has been studied extensively in the literature and Abyazi Sani and Alishahi were able to give a lower bound for it in terms of the equatable $r$-colorability defect, $\mbox{ecd}^r({\cal F})$. In this article, the methods of Chen for the special family of all $k$-subsets of $[n]$, are modified to give lower bounds for the chromatic number of almost stable general Kneser hypergraph $\mbox{KG}^r({\cal F}_s)$ in terms of $\mbox{ecd}^s({\cal F})$. Here ${\cal F}_s$ is he collection of almost $s$-stable elements of $\cal F$. We also, propose a generalization of conjecture of Meunier.