{"title":"拉姆齐数和一般厄尔多斯-罗杰斯函数","authors":"","doi":"10.1016/j.disc.2024.114203","DOIUrl":null,"url":null,"abstract":"<div><p>Given a graph <em>F</em>, let <span><math><mi>L</mi><mo>(</mo><mi>F</mi><mo>)</mo></math></span> be a fixed finite family of graphs consisting of a <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span> and some bipartite graphs relying on an <em>s</em>-partite subgraph partitioning of edges of <em>F</em>. Define <span><math><mo>(</mo><mi>m</mi><mo>,</mo><mi>n</mi><mo>,</mo><mi>a</mi><mo>,</mo><mi>b</mi><mo>)</mo></math></span>-graph by an <span><math><mi>m</mi><mo>×</mo><mi>n</mi></math></span> bipartite graph with <span><math><mi>n</mi><mo>≥</mo><mi>m</mi></math></span> such that all vertices in the part of size <em>n</em> have degree <em>a</em> and all vertices in the part of size <em>m</em> have degree <span><math><mi>b</mi><mo>≥</mo><mi>a</mi></math></span>. In this paper, building upon the work of Janzer and Sudakov (2023<sup>+</sup>) and combining with the idea of Conlon, Mattheus, Mubayi and Verstraëte (2023<sup>+</sup>) we obtain that for each <span><math><mi>s</mi><mo>≥</mo><mn>2</mn></math></span>, if there exists an <span><math><mi>L</mi><mo>(</mo><mi>F</mi><mo>)</mo></math></span>-free <span><math><mo>(</mo><mi>m</mi><mo>,</mo><mi>n</mi><mo>,</mo><mi>a</mi><mo>,</mo><mi>b</mi><mo>)</mo></math></span>-graph, then there exists an <em>F</em>-free graph <span><math><msup><mrow><mi>H</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> with at least <span><math><mi>n</mi><msup><mrow><mi>a</mi></mrow><mrow><mo>−</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mi>s</mi><mo>−</mo><mn>1</mn></mrow></mfrac></mrow></msup><mo>−</mo><mn>1</mn></math></span> vertices in which every vertex subset of size <span><math><mi>m</mi><msup><mrow><mi>a</mi></mrow><mrow><mo>−</mo><mfrac><mrow><mi>s</mi></mrow><mrow><mi>s</mi><mo>−</mo><mn>1</mn></mrow></mfrac></mrow></msup><msup><mrow><mi>log</mi></mrow><mrow><mn>3</mn></mrow></msup><mo></mo><mo>(</mo><mi>a</mi><mi>n</mi><mo>)</mo></math></span> contains a copy of <span><math><msub><mrow><mi>K</mi></mrow><mrow><mi>s</mi></mrow></msub></math></span>. As applications, we obtain some upper bounds of general Erdős-Rogers functions for some special graphs of <em>F</em>. Moreover, we obtain the multicolor Ramsey numbers <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>(</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>5</mn></mrow></msub><mo>;</mo><mi>t</mi><mo>)</mo><mo>=</mo><mover><mrow><mi>Ω</mi></mrow><mrow><mo>˜</mo></mrow></mover><mo>(</mo><msup><mrow><mi>t</mi></mrow><mrow><mfrac><mrow><mn>3</mn><mi>k</mi></mrow><mrow><mn>7</mn></mrow></mfrac><mo>+</mo><mn>1</mn></mrow></msup><mo>)</mo></math></span> and <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>(</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>7</mn></mrow></msub><mo>;</mo><mi>t</mi><mo>)</mo><mo>=</mo><mover><mrow><mi>Ω</mi></mrow><mrow><mo>˜</mo></mrow></mover><mo>(</mo><msup><mrow><mi>t</mi></mrow><mrow><mfrac><mrow><mi>k</mi></mrow><mrow><mn>4</mn></mrow></mfrac><mo>+</mo><mn>1</mn></mrow></msup><mo>)</mo></math></span>, which improve that by Xu and Ge (2022) <span><span>[24]</span></span>.</p></div>","PeriodicalId":50572,"journal":{"name":"Discrete Mathematics","volume":null,"pages":null},"PeriodicalIF":0.7000,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Ramsey numbers and a general Erdős-Rogers function\",\"authors\":\"\",\"doi\":\"10.1016/j.disc.2024.114203\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Given a graph <em>F</em>, let <span><math><mi>L</mi><mo>(</mo><mi>F</mi><mo>)</mo></math></span> be a fixed finite family of graphs consisting of a <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>4</mn></mrow></msub></math></span> and some bipartite graphs relying on an <em>s</em>-partite subgraph partitioning of edges of <em>F</em>. Define <span><math><mo>(</mo><mi>m</mi><mo>,</mo><mi>n</mi><mo>,</mo><mi>a</mi><mo>,</mo><mi>b</mi><mo>)</mo></math></span>-graph by an <span><math><mi>m</mi><mo>×</mo><mi>n</mi></math></span> bipartite graph with <span><math><mi>n</mi><mo>≥</mo><mi>m</mi></math></span> such that all vertices in the part of size <em>n</em> have degree <em>a</em> and all vertices in the part of size <em>m</em> have degree <span><math><mi>b</mi><mo>≥</mo><mi>a</mi></math></span>. In this paper, building upon the work of Janzer and Sudakov (2023<sup>+</sup>) and combining with the idea of Conlon, Mattheus, Mubayi and Verstraëte (2023<sup>+</sup>) we obtain that for each <span><math><mi>s</mi><mo>≥</mo><mn>2</mn></math></span>, if there exists an <span><math><mi>L</mi><mo>(</mo><mi>F</mi><mo>)</mo></math></span>-free <span><math><mo>(</mo><mi>m</mi><mo>,</mo><mi>n</mi><mo>,</mo><mi>a</mi><mo>,</mo><mi>b</mi><mo>)</mo></math></span>-graph, then there exists an <em>F</em>-free graph <span><math><msup><mrow><mi>H</mi></mrow><mrow><mo>⁎</mo></mrow></msup></math></span> with at least <span><math><mi>n</mi><msup><mrow><mi>a</mi></mrow><mrow><mo>−</mo><mfrac><mrow><mn>1</mn></mrow><mrow><mi>s</mi><mo>−</mo><mn>1</mn></mrow></mfrac></mrow></msup><mo>−</mo><mn>1</mn></math></span> vertices in which every vertex subset of size <span><math><mi>m</mi><msup><mrow><mi>a</mi></mrow><mrow><mo>−</mo><mfrac><mrow><mi>s</mi></mrow><mrow><mi>s</mi><mo>−</mo><mn>1</mn></mrow></mfrac></mrow></msup><msup><mrow><mi>log</mi></mrow><mrow><mn>3</mn></mrow></msup><mo></mo><mo>(</mo><mi>a</mi><mi>n</mi><mo>)</mo></math></span> contains a copy of <span><math><msub><mrow><mi>K</mi></mrow><mrow><mi>s</mi></mrow></msub></math></span>. As applications, we obtain some upper bounds of general Erdős-Rogers functions for some special graphs of <em>F</em>. Moreover, we obtain the multicolor Ramsey numbers <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>(</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>5</mn></mrow></msub><mo>;</mo><mi>t</mi><mo>)</mo><mo>=</mo><mover><mrow><mi>Ω</mi></mrow><mrow><mo>˜</mo></mrow></mover><mo>(</mo><msup><mrow><mi>t</mi></mrow><mrow><mfrac><mrow><mn>3</mn><mi>k</mi></mrow><mrow><mn>7</mn></mrow></mfrac><mo>+</mo><mn>1</mn></mrow></msup><mo>)</mo></math></span> and <span><math><msub><mrow><mi>r</mi></mrow><mrow><mi>k</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>(</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>7</mn></mrow></msub><mo>;</mo><mi>t</mi><mo>)</mo><mo>=</mo><mover><mrow><mi>Ω</mi></mrow><mrow><mo>˜</mo></mrow></mover><mo>(</mo><msup><mrow><mi>t</mi></mrow><mrow><mfrac><mrow><mi>k</mi></mrow><mrow><mn>4</mn></mrow></mfrac><mo>+</mo><mn>1</mn></mrow></msup><mo>)</mo></math></span>, which improve that by Xu and Ge (2022) <span><span>[24]</span></span>.</p></div>\",\"PeriodicalId\":50572,\"journal\":{\"name\":\"Discrete Mathematics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.7000,\"publicationDate\":\"2024-08-12\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Discrete Mathematics\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0012365X24003340\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Discrete Mathematics","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0012365X24003340","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
摘要
给定一个图 F,让 L(F) 是一个固定的有限图族,由一个 C4 和一些依赖于 F 边的 s 部分子图分割的双部分图组成。定义(m,n,a,b)-图为 m×n 双部分图,n≥m,使得大小为 n 的部分中的所有顶点的度数为 a,大小为 m 的部分中的所有顶点的度数为 b≥a。本文以 Janzer 和 Sudakov (2023+) 的研究为基础,结合 Conlon、Mattheus、Mubayi 和 Verstraëte (2023+) 的想法,得出对于每个 s≥2,如果存在一个无 L(F)-free (m,n,a,b)-graph 图,那么存在一个至少有 na-1s-1-1 个顶点的无 F 图 H⁎,其中每个大小为 ma-ss-1log3(an) 的顶点子集都包含 Ks 的副本。此外,我们还得到了多色拉姆齐数 rk+1(C5;t)=Ω˜(t3k7+1) 和 rk+1(C7;t)=Ω˜(tk4+1) ,它们改进了徐和葛(2022)的结果[24]。
Ramsey numbers and a general Erdős-Rogers function
Given a graph F, let be a fixed finite family of graphs consisting of a and some bipartite graphs relying on an s-partite subgraph partitioning of edges of F. Define -graph by an bipartite graph with such that all vertices in the part of size n have degree a and all vertices in the part of size m have degree . In this paper, building upon the work of Janzer and Sudakov (2023+) and combining with the idea of Conlon, Mattheus, Mubayi and Verstraëte (2023+) we obtain that for each , if there exists an -free -graph, then there exists an F-free graph with at least vertices in which every vertex subset of size contains a copy of . As applications, we obtain some upper bounds of general Erdős-Rogers functions for some special graphs of F. Moreover, we obtain the multicolor Ramsey numbers and , which improve that by Xu and Ge (2022) [24].
期刊介绍:
Discrete Mathematics provides a common forum for significant research in many areas of discrete mathematics and combinatorics. Among the fields covered by Discrete Mathematics are graph and hypergraph theory, enumeration, coding theory, block designs, the combinatorics of partially ordered sets, extremal set theory, matroid theory, algebraic combinatorics, discrete geometry, matrices, and discrete probability theory.
Items in the journal include research articles (Contributions or Notes, depending on length) and survey/expository articles (Perspectives). Efforts are made to process the submission of Notes (short articles) quickly. The Perspectives section features expository articles accessible to a broad audience that cast new light or present unifying points of view on well-known or insufficiently-known topics.