有序紧密超路径的图兰数

IF 1 3区 数学 Q1 MATHEMATICS
John P. Bright, Kevin G. Milans, Jackson Porter
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We find the Turán numbers for the <span><math><mi>r</mi></math></span>-uniform <span><math><mi>s</mi></math></span>-vertex tight path <span><math><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup></math></span> (with vertices in the natural order) exactly when <span><math><mrow><mi>r</mi><mo>≤</mo><mi>s</mi><mo>&lt;</mo><mn>2</mn><mi>r</mi></mrow></math></span> and <span><math><mi>n</mi></math></span> is even; our results imply <span><math><mrow><mover><mrow><mi>ex</mi></mrow><mo>→</mo></mover><mrow><mo>(</mo><mi>n</mi><mo>,</mo><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup><mo>)</mo></mrow><mo>=</mo><mrow><mo>(</mo><mn>1</mn><mo>−</mo><mfrac><mrow><mn>1</mn></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mi>s</mi><mo>−</mo><mi>r</mi></mrow></msup></mrow></mfrac><mo>+</mo><mi>o</mi><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mo>)</mo></mrow><mfenced><mrow><mfrac><mrow><mi>n</mi></mrow><mrow><mi>r</mi></mrow></mfrac></mrow></mfenced></mrow></math></span> when <span><math><mrow><mi>r</mi><mo>≤</mo><mi>s</mi><mo>&lt;</mo><mn>2</mn><mi>r</mi></mrow></math></span>. When <span><math><mrow><mi>s</mi><mo>≥</mo><mn>2</mn><mi>r</mi></mrow></math></span>, the asymptotics of <span><math><mrow><mover><mrow><mi>ex</mi></mrow><mo>→</mo></mover><mrow><mo>(</mo><mi>n</mi><mo>,</mo><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup><mo>)</mo></mrow></mrow></math></span> remain open. For <span><math><mrow><mi>r</mi><mo>=</mo><mn>3</mn></mrow></math></span>, we give a construction of an <span><math><mi>r</mi></math></span>-uniform <span><math><mi>n</mi></math></span>-vertex hypergraph not containing <span><math><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup></math></span> which we conjecture to be asymptotically extremal.</div></div>","PeriodicalId":50490,"journal":{"name":"European Journal of Combinatorics","volume":null,"pages":null},"PeriodicalIF":1.0000,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Turán numbers of ordered tight hyperpaths\",\"authors\":\"John P. Bright,&nbsp;Kevin G. 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We find the Turán numbers for the <span><math><mi>r</mi></math></span>-uniform <span><math><mi>s</mi></math></span>-vertex tight path <span><math><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup></math></span> (with vertices in the natural order) exactly when <span><math><mrow><mi>r</mi><mo>≤</mo><mi>s</mi><mo>&lt;</mo><mn>2</mn><mi>r</mi></mrow></math></span> and <span><math><mi>n</mi></math></span> is even; our results imply <span><math><mrow><mover><mrow><mi>ex</mi></mrow><mo>→</mo></mover><mrow><mo>(</mo><mi>n</mi><mo>,</mo><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup><mo>)</mo></mrow><mo>=</mo><mrow><mo>(</mo><mn>1</mn><mo>−</mo><mfrac><mrow><mn>1</mn></mrow><mrow><msup><mrow><mn>2</mn></mrow><mrow><mi>s</mi><mo>−</mo><mi>r</mi></mrow></msup></mrow></mfrac><mo>+</mo><mi>o</mi><mrow><mo>(</mo><mn>1</mn><mo>)</mo></mrow><mo>)</mo></mrow><mfenced><mrow><mfrac><mrow><mi>n</mi></mrow><mrow><mi>r</mi></mrow></mfrac></mrow></mfenced></mrow></math></span> when <span><math><mrow><mi>r</mi><mo>≤</mo><mi>s</mi><mo>&lt;</mo><mn>2</mn><mi>r</mi></mrow></math></span>. When <span><math><mrow><mi>s</mi><mo>≥</mo><mn>2</mn><mi>r</mi></mrow></math></span>, the asymptotics of <span><math><mrow><mover><mrow><mi>ex</mi></mrow><mo>→</mo></mover><mrow><mo>(</mo><mi>n</mi><mo>,</mo><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup><mo>)</mo></mrow></mrow></math></span> remain open. For <span><math><mrow><mi>r</mi><mo>=</mo><mn>3</mn></mrow></math></span>, we give a construction of an <span><math><mi>r</mi></math></span>-uniform <span><math><mi>n</mi></math></span>-vertex hypergraph not containing <span><math><msubsup><mrow><mover><mrow><mi>P</mi></mrow><mo>→</mo></mover></mrow><mrow><mi>s</mi></mrow><mrow><mrow><mo>(</mo><mi>r</mi><mo>)</mo></mrow></mrow></msubsup></math></span> which we conjecture to be asymptotically extremal.</div></div>\",\"PeriodicalId\":50490,\"journal\":{\"name\":\"European Journal of Combinatorics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2024-10-03\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"European Journal of Combinatorics\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0195669824001550\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"European Journal of Combinatorics","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0195669824001550","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0

摘要

有序超图是顶点集 V(G) 是线性有序的超图 G。当 r≤s<2r 且 n 为偶数时,我们精确地找到了 r-uniform s-vertex 紧路径 P→s(r)(顶点按自然顺序排列)的图兰数;当 r≤s<2r 时,我们的结果意味着 ex→(n,P→s(r))=(1-12s-r+o(1))nr。当 s≥2r 时,ex→(n,P→s(r)) 的渐近线仍未确定。对于 r=3,我们给出了一个不包含 P→s(r) 的 r-uniform n 顶点超图的构造,我们猜想它是渐近极值的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Turán numbers of ordered tight hyperpaths
An ordered hypergraph is a hypergraph G whose vertex set V(G) is linearly ordered. We find the Turán numbers for the r-uniform s-vertex tight path Ps(r) (with vertices in the natural order) exactly when rs<2r and n is even; our results imply ex(n,Ps(r))=(112sr+o(1))nr when rs<2r. When s2r, the asymptotics of ex(n,Ps(r)) remain open. For r=3, we give a construction of an r-uniform n-vertex hypergraph not containing Ps(r) which we conjecture to be asymptotically extremal.
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来源期刊
CiteScore
2.10
自引率
10.00%
发文量
124
审稿时长
4-8 weeks
期刊介绍: The European Journal of Combinatorics is a high standard, international, bimonthly journal of pure mathematics, specializing in theories arising from combinatorial problems. The journal is primarily open to papers dealing with mathematical structures within combinatorics and/or establishing direct links between combinatorics and other branches of mathematics and the theories of computing. The journal includes full-length research papers on important topics.
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