稀疏图形多副本的拉姆齐数

Pub Date : 2024-04-11 DOI:10.1002/jgt.23100
Aurelio Sulser, Miloš Trujić
{"title":"稀疏图形多副本的拉姆齐数","authors":"Aurelio Sulser,&nbsp;Miloš Trujić","doi":"10.1002/jgt.23100","DOIUrl":null,"url":null,"abstract":"<p>For a graph <span></span><math>\n \n <mrow>\n <mi>H</mi>\n </mrow></math> and an integer <span></span><math>\n \n <mrow>\n <mi>n</mi>\n </mrow></math>, we let <span></span><math>\n \n <mrow>\n <mi>n</mi>\n \n <mi>H</mi>\n </mrow></math> denote the disjoint union of <span></span><math>\n \n <mrow>\n <mi>n</mi>\n </mrow></math> copies of <span></span><math>\n \n <mrow>\n <mi>H</mi>\n </mrow></math>. In 1975, Burr, Erdős and Spencer initiated the study of Ramsey numbers for <span></span><math>\n \n <mrow>\n <mi>n</mi>\n \n <mi>H</mi>\n </mrow></math>, one of few instances for which Ramsey numbers are now known precisely. They showed that there is a constant <span></span><math>\n \n <mrow>\n <mi>c</mi>\n \n <mo>=</mo>\n \n <mi>c</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>H</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow></math> such that <span></span><math>\n \n <mrow>\n <mi>r</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mrow>\n <mi>n</mi>\n \n <mi>H</mi>\n </mrow>\n \n <mo>)</mo>\n </mrow>\n \n <mo>=</mo>\n \n <mrow>\n <mo>(</mo>\n \n <mrow>\n <mn>2</mn>\n \n <mo>∣</mo>\n \n <mi>H</mi>\n \n <mo>∣</mo>\n \n <mo>−</mo>\n \n <mi>α</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>H</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow>\n \n <mo>)</mo>\n </mrow>\n \n <mi>n</mi>\n \n <mo>+</mo>\n \n <mi>c</mi>\n </mrow></math>, provided <span></span><math>\n \n <mrow>\n <mi>n</mi>\n </mrow></math> is sufficiently large. Subsequently, Burr gave an implicit way of computing <span></span><math>\n \n <mrow>\n <mi>c</mi>\n </mrow></math> and noted that this long-term behaviour occurs when <span></span><math>\n \n <mrow>\n <mi>n</mi>\n </mrow></math> is triply exponential in <span></span><math>\n \n <mrow>\n <mo>∣</mo>\n \n <mi>H</mi>\n \n <mo>∣</mo>\n </mrow></math>. Very recently, Bucić and Sudakov revived the problem and established an essentially tight bound on <span></span><math>\n \n <mrow>\n <mi>n</mi>\n </mrow></math> by showing <span></span><math>\n \n <mrow>\n <mi>r</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mrow>\n <mi>n</mi>\n \n <mi>H</mi>\n </mrow>\n \n <mo>)</mo>\n </mrow>\n </mrow></math> follows this behaviour already when the number of copies is just a single exponential. We provide significantly stronger bounds on <span></span><math>\n \n <mrow>\n <mi>n</mi>\n </mrow></math> in case <span></span><math>\n \n <mrow>\n <mi>H</mi>\n </mrow></math> is a sparse graph, most notably of bounded maximum degree. These are relatable to the current state-of-the-art bounds on <span></span><math>\n \n <mrow>\n <mi>r</mi>\n \n <mrow>\n <mo>(</mo>\n \n <mi>H</mi>\n \n <mo>)</mo>\n </mrow>\n </mrow></math> and (in a way) tight. Our methods rely on a beautiful classic proof of Graham, Rödl and Ruciński, with an emphasis on developing an efficient absorbing method for bounded degree graphs.</p>","PeriodicalId":0,"journal":{"name":"","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jgt.23100","citationCount":"0","resultStr":"{\"title\":\"Ramsey numbers for multiple copies of sparse graphs\",\"authors\":\"Aurelio Sulser,&nbsp;Miloš Trujić\",\"doi\":\"10.1002/jgt.23100\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>For a graph <span></span><math>\\n \\n <mrow>\\n <mi>H</mi>\\n </mrow></math> and an integer <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow></math>, we let <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n \\n <mi>H</mi>\\n </mrow></math> denote the disjoint union of <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow></math> copies of <span></span><math>\\n \\n <mrow>\\n <mi>H</mi>\\n </mrow></math>. In 1975, Burr, Erdős and Spencer initiated the study of Ramsey numbers for <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n \\n <mi>H</mi>\\n </mrow></math>, one of few instances for which Ramsey numbers are now known precisely. They showed that there is a constant <span></span><math>\\n \\n <mrow>\\n <mi>c</mi>\\n \\n <mo>=</mo>\\n \\n <mi>c</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>H</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow></math> such that <span></span><math>\\n \\n <mrow>\\n <mi>r</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mrow>\\n <mi>n</mi>\\n \\n <mi>H</mi>\\n </mrow>\\n \\n <mo>)</mo>\\n </mrow>\\n \\n <mo>=</mo>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mrow>\\n <mn>2</mn>\\n \\n <mo>∣</mo>\\n \\n <mi>H</mi>\\n \\n <mo>∣</mo>\\n \\n <mo>−</mo>\\n \\n <mi>α</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>H</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow>\\n \\n <mo>)</mo>\\n </mrow>\\n \\n <mi>n</mi>\\n \\n <mo>+</mo>\\n \\n <mi>c</mi>\\n </mrow></math>, provided <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow></math> is sufficiently large. Subsequently, Burr gave an implicit way of computing <span></span><math>\\n \\n <mrow>\\n <mi>c</mi>\\n </mrow></math> and noted that this long-term behaviour occurs when <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow></math> is triply exponential in <span></span><math>\\n \\n <mrow>\\n <mo>∣</mo>\\n \\n <mi>H</mi>\\n \\n <mo>∣</mo>\\n </mrow></math>. Very recently, Bucić and Sudakov revived the problem and established an essentially tight bound on <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow></math> by showing <span></span><math>\\n \\n <mrow>\\n <mi>r</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mrow>\\n <mi>n</mi>\\n \\n <mi>H</mi>\\n </mrow>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow></math> follows this behaviour already when the number of copies is just a single exponential. We provide significantly stronger bounds on <span></span><math>\\n \\n <mrow>\\n <mi>n</mi>\\n </mrow></math> in case <span></span><math>\\n \\n <mrow>\\n <mi>H</mi>\\n </mrow></math> is a sparse graph, most notably of bounded maximum degree. These are relatable to the current state-of-the-art bounds on <span></span><math>\\n \\n <mrow>\\n <mi>r</mi>\\n \\n <mrow>\\n <mo>(</mo>\\n \\n <mi>H</mi>\\n \\n <mo>)</mo>\\n </mrow>\\n </mrow></math> and (in a way) tight. Our methods rely on a beautiful classic proof of Graham, Rödl and Ruciński, with an emphasis on developing an efficient absorbing method for bounded degree graphs.</p>\",\"PeriodicalId\":0,\"journal\":{\"name\":\"\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0,\"publicationDate\":\"2024-04-11\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://onlinelibrary.wiley.com/doi/epdf/10.1002/jgt.23100\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1002/jgt.23100\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"","FirstCategoryId":"100","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/jgt.23100","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0

摘要

对于一个图和一个整数 ,我们用 表示其副本的不相交联合。 1975 年,伯尔、厄多斯和斯宾塞开始研究拉姆齐数,拉姆齐数是目前已知拉姆齐数的少数实例之一。他们证明,只要拉姆齐数足够大,就会有一个常数使得 , 。随后,伯尔给出了一种隐含的计算方法,并指出这种长期行为发生在......的三倍指数时。最近,布契奇和苏达科夫重新提出了这个问题,并建立了一个基本严密的约束,表明当副本数仅为单指数时,这种行为已经出现。在稀疏图的情况下,我们提供了明显更强的约束,最明显的是有界最大度。这些约束与当前最先进的约束是相关的,而且(在某种程度上)是紧密的。我们的方法依赖于 Graham、Rödl 和 Ruciński 的一个漂亮的经典证明,重点是为有界度图开发一种高效的吸收方法。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Ramsey numbers for multiple copies of sparse graphs

分享
查看原文
Ramsey numbers for multiple copies of sparse graphs

For a graph H and an integer n , we let n H denote the disjoint union of n copies of H . In 1975, Burr, Erdős and Spencer initiated the study of Ramsey numbers for n H , one of few instances for which Ramsey numbers are now known precisely. They showed that there is a constant c = c ( H ) such that r ( n H ) = ( 2 H α ( H ) ) n + c , provided n is sufficiently large. Subsequently, Burr gave an implicit way of computing c and noted that this long-term behaviour occurs when n is triply exponential in H . Very recently, Bucić and Sudakov revived the problem and established an essentially tight bound on n by showing r ( n H ) follows this behaviour already when the number of copies is just a single exponential. We provide significantly stronger bounds on n in case H is a sparse graph, most notably of bounded maximum degree. These are relatable to the current state-of-the-art bounds on r ( H ) and (in a way) tight. Our methods rely on a beautiful classic proof of Graham, Rödl and Ruciński, with an emphasis on developing an efficient absorbing method for bounded degree graphs.

求助全文
通过发布文献求助,成功后即可免费获取论文全文。 去求助
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信