{"title":"The saturation number for unions of four cliques","authors":"Ruo-Xuan Li, Rong-Xia Hao, Zhen He, Wen-Han Zhu","doi":"10.1016/j.disc.2025.114532","DOIUrl":null,"url":null,"abstract":"<div><div>A graph <em>G</em> is <em>H</em>-saturated if <em>G</em> does not contain a copy of <em>H</em>, but the addition of any edge <span><math><mi>e</mi><mo>∈</mo><mover><mrow><mi>G</mi></mrow><mo>‾</mo></mover></math></span> would create a copy of <em>H</em>. The saturation number <span><math><mi>s</mi><mi>a</mi><mi>t</mi><mo>(</mo><mi>n</mi><mo>,</mo><mi>H</mi><mo>)</mo></math></span> for a graph <em>H</em> is the minimal number of edges in any <em>H</em>-saturated graph of order <em>n</em>. The <span><math><mi>s</mi><mi>a</mi><mi>t</mi><mo>(</mo><mi>n</mi><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msub><mo>∪</mo><msub><mrow><mi>K</mi></mrow><mrow><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msub><mo>∪</mo><msub><mrow><mi>K</mi></mrow><mrow><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></msub><mo>)</mo></math></span> with <span><math><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>≥</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>+</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> was determined in [Discrete Math. 347 (2024) 113868]. In this paper, <span><math><mi>s</mi><mi>a</mi><mi>t</mi><mo>(</mo><mi>n</mi><mo>,</mo><msub><mrow><mi>K</mi></mrow><mrow><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msub><mo>∪</mo><msub><mrow><mi>K</mi></mrow><mrow><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></msub><mo>∪</mo><msub><mrow><mi>K</mi></mrow><mrow><msub><mrow><mi>p</mi></mrow><mrow><mn>3</mn></mrow></msub></mrow></msub><mo>∪</mo><msub><mrow><mi>K</mi></mrow><mrow><msub><mrow><mi>p</mi></mrow><mrow><mn>4</mn></mrow></msub></mrow></msub><mo>)</mo></math></span> with <span><math><msub><mrow><mi>p</mi></mrow><mrow><mi>i</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>−</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>≥</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> for <span><math><mn>2</mn><mo>≤</mo><mi>i</mi><mo>≤</mo><mn>3</mn></math></span> and <span><math><mn>4</mn><mo>≤</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>≤</mo><msub><mrow><mi>p</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> is determined.</div></div>","PeriodicalId":50572,"journal":{"name":"Discrete Mathematics","volume":"348 10","pages":"Article 114532"},"PeriodicalIF":0.7000,"publicationDate":"2025-04-10","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/S0012365X25001402","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 graph G is H-saturated if G does not contain a copy of H, but the addition of any edge would create a copy of H. The saturation number for a graph H is the minimal number of edges in any H-saturated graph of order n. The with was determined in [Discrete Math. 347 (2024) 113868]. In this paper, with for and is determined.
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.