{"title":"Spectral extrema of graphs: Forbidden star-path forests","authors":"Yanni Zhai , Xiying Yuan , Lihua You","doi":"10.1016/j.disc.2024.114351","DOIUrl":null,"url":null,"abstract":"<div><div>A path of order <em>n</em> is denoted by <span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span>, and a star of order <em>n</em> is denoted by <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub></math></span>. Recently, Fang and Yuan determined the Turán numbers of <span><math><mi>k</mi><msub><mrow><mi>S</mi></mrow><mrow><mi>ℓ</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>∪</mo><msub><mrow><mi>P</mi></mrow><mrow><mi>ℓ</mi></mrow></msub></math></span>, <span><math><msub><mrow><mi>k</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mi>S</mi></mrow><mrow><mn>2</mn><mi>ℓ</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>∪</mo><msub><mrow><mi>k</mi></mrow><mrow><mn>2</mn></mrow></msub><msub><mrow><mi>P</mi></mrow><mrow><mn>2</mn><mi>ℓ</mi></mrow></msub></math></span> and <span><math><mi>k</mi><msub><mrow><mi>S</mi></mrow><mrow><mn>4</mn></mrow></msub><mo>∪</mo><mn>2</mn><msub><mrow><mi>P</mi></mrow><mrow><mn>5</mn></mrow></msub></math></span> for <em>n</em> appropriately large. In this paper, we extend the results to the spectral counterpart. The graphs with maximum spectral radii among graphs containing no any copy of these three kinds of star-path forests are completely characterized.</div></div>","PeriodicalId":50572,"journal":{"name":"Discrete Mathematics","volume":"348 4","pages":"Article 114351"},"PeriodicalIF":0.7000,"publicationDate":"2024-12-10","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/S0012365X24004825","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
Abstract
A path of order n is denoted by , and a star of order n is denoted by . Recently, Fang and Yuan determined the Turán numbers of , and for n appropriately large. In this paper, we extend the results to the spectral counterpart. The graphs with maximum spectral radii among graphs containing no any copy of these three kinds of star-path forests are completely characterized.
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.