{"title":"Growth of products of subsets in finite simple groups","authors":"Daniele Dona, Attila Maróti, László Pyber","doi":"10.1112/blms.13093","DOIUrl":null,"url":null,"abstract":"<p>We prove that the product of a subset and a normal subset inside any finite simple non-abelian group <span></span><math>\n <semantics>\n <mi>G</mi>\n <annotation>$G$</annotation>\n </semantics></math> grows rapidly. More precisely, if <span></span><math>\n <semantics>\n <mi>A</mi>\n <annotation>$A$</annotation>\n </semantics></math> and <span></span><math>\n <semantics>\n <mi>B</mi>\n <annotation>$B$</annotation>\n </semantics></math> are two subsets with <span></span><math>\n <semantics>\n <mi>B</mi>\n <annotation>$B$</annotation>\n </semantics></math> normal and neither of them is too large inside <span></span><math>\n <semantics>\n <mi>G</mi>\n <annotation>$G$</annotation>\n </semantics></math>, then <span></span><math>\n <semantics>\n <mrow>\n <mrow>\n <mo>|</mo>\n <mi>A</mi>\n <mi>B</mi>\n <mo>|</mo>\n </mrow>\n <mo>⩾</mo>\n <msup>\n <mrow>\n <mo>|</mo>\n <mi>A</mi>\n <mo>|</mo>\n <mo>|</mo>\n <mi>B</mi>\n <mo>|</mo>\n </mrow>\n <mrow>\n <mn>1</mn>\n <mo>−</mo>\n <mi>ε</mi>\n </mrow>\n </msup>\n </mrow>\n <annotation>$|AB| \\geqslant |A||B|^{1-\\epsilon }$</annotation>\n </semantics></math> where <span></span><math>\n <semantics>\n <mrow>\n <mi>ε</mi>\n <mo>></mo>\n <mn>0</mn>\n </mrow>\n <annotation>$\\epsilon &gt;0$</annotation>\n </semantics></math> can be taken arbitrarily small. This is a somewhat surprising strengthening of a theorem of Liebeck, Schul, and Shalev.</p>","PeriodicalId":55298,"journal":{"name":"Bulletin of the London Mathematical Society","volume":"56 8","pages":"2704-2710"},"PeriodicalIF":0.8000,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Bulletin of the London Mathematical Society","FirstCategoryId":"100","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1112/blms.13093","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
We prove that the product of a subset and a normal subset inside any finite simple non-abelian group grows rapidly. More precisely, if and are two subsets with normal and neither of them is too large inside , then where can be taken arbitrarily small. This is a somewhat surprising strengthening of a theorem of Liebeck, Schul, and Shalev.