{"title":"3均匀紧循环的余度Turán密度","authors":"Simón Piga, Nicolás Sanhueza-Matamala, Mathias Schacht","doi":"10.1016/j.jctb.2025.07.007","DOIUrl":null,"url":null,"abstract":"Given any <mml:math altimg=\"si1.svg\"><mml:mi>ε</mml:mi><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">></mml:mo><mml:mn>0</mml:mn></mml:math> we prove that every sufficiently large <ce:italic>n</ce:italic>-vertex 3-graph <ce:italic>H</ce:italic> where every pair of vertices is contained in at least <mml:math altimg=\"si2.svg\"><mml:mo stretchy=\"false\">(</mml:mo><mml:mn>1</mml:mn><mml:mo stretchy=\"false\">/</mml:mo><mml:mn>3</mml:mn><mml:mo linebreak=\"badbreak\" linebreakstyle=\"after\">+</mml:mo><mml:mi>ε</mml:mi><mml:mo stretchy=\"false\">)</mml:mo><mml:mi>n</mml:mi></mml:math> edges contains a copy of <mml:math altimg=\"si3.svg\"><mml:msub><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:mn>10</mml:mn></mml:mrow></mml:msub></mml:math>, i.e. the tight cycle on 10 vertices. In fact we obtain the same conclusion for every cycle <mml:math altimg=\"si36.svg\"><mml:msub><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow></mml:msub></mml:math> with <mml:math altimg=\"si5.svg\"><mml:mi>ℓ</mml:mi><mml:mo>≥</mml:mo><mml:mn>19</mml:mn></mml:math>.","PeriodicalId":54865,"journal":{"name":"Journal of Combinatorial Theory Series B","volume":"27 1","pages":"1-6"},"PeriodicalIF":1.2000,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"The codegree Turán density of 3-uniform tight cycles\",\"authors\":\"Simón Piga, Nicolás Sanhueza-Matamala, Mathias Schacht\",\"doi\":\"10.1016/j.jctb.2025.07.007\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Given any <mml:math altimg=\\\"si1.svg\\\"><mml:mi>ε</mml:mi><mml:mo linebreak=\\\"goodbreak\\\" linebreakstyle=\\\"after\\\">></mml:mo><mml:mn>0</mml:mn></mml:math> we prove that every sufficiently large <ce:italic>n</ce:italic>-vertex 3-graph <ce:italic>H</ce:italic> where every pair of vertices is contained in at least <mml:math altimg=\\\"si2.svg\\\"><mml:mo stretchy=\\\"false\\\">(</mml:mo><mml:mn>1</mml:mn><mml:mo stretchy=\\\"false\\\">/</mml:mo><mml:mn>3</mml:mn><mml:mo linebreak=\\\"badbreak\\\" linebreakstyle=\\\"after\\\">+</mml:mo><mml:mi>ε</mml:mi><mml:mo stretchy=\\\"false\\\">)</mml:mo><mml:mi>n</mml:mi></mml:math> edges contains a copy of <mml:math altimg=\\\"si3.svg\\\"><mml:msub><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:mn>10</mml:mn></mml:mrow></mml:msub></mml:math>, i.e. the tight cycle on 10 vertices. In fact we obtain the same conclusion for every cycle <mml:math altimg=\\\"si36.svg\\\"><mml:msub><mml:mrow><mml:mi>C</mml:mi></mml:mrow><mml:mrow><mml:mi>ℓ</mml:mi></mml:mrow></mml:msub></mml:math> with <mml:math altimg=\\\"si5.svg\\\"><mml:mi>ℓ</mml:mi><mml:mo>≥</mml:mo><mml:mn>19</mml:mn></mml:math>.\",\"PeriodicalId\":54865,\"journal\":{\"name\":\"Journal of Combinatorial Theory Series B\",\"volume\":\"27 1\",\"pages\":\"1-6\"},\"PeriodicalIF\":1.2000,\"publicationDate\":\"2025-08-07\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Combinatorial Theory Series B\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://doi.org/10.1016/j.jctb.2025.07.007\",\"RegionNum\":1,\"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":"Journal of Combinatorial Theory Series B","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1016/j.jctb.2025.07.007","RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
The codegree Turán density of 3-uniform tight cycles
Given any ε>0 we prove that every sufficiently large n-vertex 3-graph H where every pair of vertices is contained in at least (1/3+ε)n edges contains a copy of C10, i.e. the tight cycle on 10 vertices. In fact we obtain the same conclusion for every cycle Cℓ with ℓ≥19.
期刊介绍:
The Journal of Combinatorial Theory publishes original mathematical research dealing with theoretical and physical aspects of the study of finite and discrete structures in all branches of science. Series B is concerned primarily with graph theory and matroid theory and is a valuable tool for mathematicians and computer scientists.