{"title":"关于双星的拉姆齐数","authors":"Freddy Flores Dubó, Maya Stein","doi":"10.1016/j.disc.2024.114227","DOIUrl":null,"url":null,"abstract":"<div><p>The double star <span><math><mi>S</mi><mo>(</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span> is obtained from joining the centres of a star with <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> leaves and a star with <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>≤</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> leaves. We give a short proof of a new upper bound on the two-colour Ramsey number of <span><math><mi>S</mi><mo>(</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span> which holds for all <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> with <span><math><mfrac><mrow><msqrt><mrow><mn>5</mn></mrow></msqrt><mo>+</mo><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo><</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo><</mo><mn>3</mn><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>. Our result implies that for all positive <em>m</em>, the Ramsey number of the double star <span><math><mi>S</mi><mo>(</mo><mn>2</mn><mi>m</mi><mo>,</mo><mi>m</mi><mo>)</mo></math></span> is at most <span><math><mo>⌈</mo><mn>4.275</mn><mi>m</mi><mo>⌉</mo><mo>+</mo><mn>1</mn></math></span>.</p></div>","PeriodicalId":50572,"journal":{"name":"Discrete Mathematics","volume":"348 1","pages":"Article 114227"},"PeriodicalIF":0.7000,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0012365X24003583/pdfft?md5=141f97279491e2ead07751cfa50dfe96&pid=1-s2.0-S0012365X24003583-main.pdf","citationCount":"0","resultStr":"{\"title\":\"On the Ramsey number of the double star\",\"authors\":\"Freddy Flores Dubó, Maya Stein\",\"doi\":\"10.1016/j.disc.2024.114227\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>The double star <span><math><mi>S</mi><mo>(</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span> is obtained from joining the centres of a star with <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> leaves and a star with <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>≤</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> leaves. We give a short proof of a new upper bound on the two-colour Ramsey number of <span><math><mi>S</mi><mo>(</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>)</mo></math></span> which holds for all <span><math><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> with <span><math><mfrac><mrow><msqrt><mrow><mn>5</mn></mrow></msqrt><mo>+</mo><mn>1</mn></mrow><mrow><mn>2</mn></mrow></mfrac><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub><mo><</mo><msub><mrow><mi>m</mi></mrow><mrow><mn>1</mn></mrow></msub><mo><</mo><mn>3</mn><msub><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>. Our result implies that for all positive <em>m</em>, the Ramsey number of the double star <span><math><mi>S</mi><mo>(</mo><mn>2</mn><mi>m</mi><mo>,</mo><mi>m</mi><mo>)</mo></math></span> is at most <span><math><mo>⌈</mo><mn>4.275</mn><mi>m</mi><mo>⌉</mo><mo>+</mo><mn>1</mn></math></span>.</p></div>\",\"PeriodicalId\":50572,\"journal\":{\"name\":\"Discrete Mathematics\",\"volume\":\"348 1\",\"pages\":\"Article 114227\"},\"PeriodicalIF\":0.7000,\"publicationDate\":\"2024-08-30\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S0012365X24003583/pdfft?md5=141f97279491e2ead07751cfa50dfe96&pid=1-s2.0-S0012365X24003583-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Discrete Mathematics\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0012365X24003583\",\"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/S0012365X24003583","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
The double star is obtained from joining the centres of a star with leaves and a star with leaves. We give a short proof of a new upper bound on the two-colour Ramsey number of which holds for all with . Our result implies that for all positive m, the Ramsey number of the double star is at most .
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.