{"title":"具有有界周长的有限 4- 大地遍历图","authors":"Wei Jin, Li Tan","doi":"10.1007/s10801-024-01358-3","DOIUrl":null,"url":null,"abstract":"<p>Praeger and the first author in Jin and Praeger (J Combin Theory Ser A 178:105349, 2021) asked the following problem: classify <i>s</i>-geodesic-transitive graphs of girth <span>\\(2s-1\\)</span> or <span>\\(2s-2\\)</span>, where <span>\\(s=4,5,6,7,8\\)</span>. In this paper, we study the <span>\\(s=4\\)</span> case, that is, study the family of finite (<i>G</i>, 4)-geodesic-transitive graphs of girth 6 or 7 for some group <i>G</i> of automorphisms. A reduction result on this family of graphs is first given. Let <i>N</i> be a normal subgroup of <i>G</i> which has at least 3 orbits on the vertex set. We show that such a graph <span>\\(\\Gamma \\)</span> is a cover of its quotient <span>\\(\\Gamma _N\\)</span> modulo the <i>N</i>-orbits and either <span>\\(\\Gamma _N\\)</span> is (<i>G</i>/<i>N</i>, <i>s</i>)-geodesic-transitive where <span>\\(s=\\min \\{4,\\textrm{diam}(\\Gamma _N)\\}\\ge 3\\)</span>, or <span>\\(\\Gamma _N\\)</span> is a (<i>G</i>/<i>N</i>, 2)-arc-transitive strongly regular graph. Next, using the classification of 2-arc-transitive strongly regular graphs, we determine all the (<i>G</i>, 4)-geodesic-transitive covers <span>\\(\\Gamma \\)</span> when <span>\\(\\Gamma _N\\)</span> is strongly regular.</p>","PeriodicalId":14926,"journal":{"name":"Journal of Algebraic Combinatorics","volume":"32 1","pages":""},"PeriodicalIF":0.6000,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Finite 4-geodesic-transitive graphs with bounded girth\",\"authors\":\"Wei Jin, Li Tan\",\"doi\":\"10.1007/s10801-024-01358-3\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>Praeger and the first author in Jin and Praeger (J Combin Theory Ser A 178:105349, 2021) asked the following problem: classify <i>s</i>-geodesic-transitive graphs of girth <span>\\\\(2s-1\\\\)</span> or <span>\\\\(2s-2\\\\)</span>, where <span>\\\\(s=4,5,6,7,8\\\\)</span>. In this paper, we study the <span>\\\\(s=4\\\\)</span> case, that is, study the family of finite (<i>G</i>, 4)-geodesic-transitive graphs of girth 6 or 7 for some group <i>G</i> of automorphisms. A reduction result on this family of graphs is first given. Let <i>N</i> be a normal subgroup of <i>G</i> which has at least 3 orbits on the vertex set. We show that such a graph <span>\\\\(\\\\Gamma \\\\)</span> is a cover of its quotient <span>\\\\(\\\\Gamma _N\\\\)</span> modulo the <i>N</i>-orbits and either <span>\\\\(\\\\Gamma _N\\\\)</span> is (<i>G</i>/<i>N</i>, <i>s</i>)-geodesic-transitive where <span>\\\\(s=\\\\min \\\\{4,\\\\textrm{diam}(\\\\Gamma _N)\\\\}\\\\ge 3\\\\)</span>, or <span>\\\\(\\\\Gamma _N\\\\)</span> is a (<i>G</i>/<i>N</i>, 2)-arc-transitive strongly regular graph. Next, using the classification of 2-arc-transitive strongly regular graphs, we determine all the (<i>G</i>, 4)-geodesic-transitive covers <span>\\\\(\\\\Gamma \\\\)</span> when <span>\\\\(\\\\Gamma _N\\\\)</span> is strongly regular.</p>\",\"PeriodicalId\":14926,\"journal\":{\"name\":\"Journal of Algebraic Combinatorics\",\"volume\":\"32 1\",\"pages\":\"\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2024-09-09\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Algebraic Combinatorics\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://doi.org/10.1007/s10801-024-01358-3\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Algebraic Combinatorics","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1007/s10801-024-01358-3","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
摘要
Praeger 和第一作者在 Jin and Praeger (J Combin Theory Ser A 178:105349, 2021) 中提出了以下问题:分类周长为 \(2s-1\) 或 \(2s-2\) 的 s 节点变换图,其中 \(s=4,5,6,7,8\).在本文中,我们研究的是\(s=4\)的情况,也就是研究对于某个自动形群 G 而言周长为 6 或 7 的有限(G,4)-大地遍历图形族。首先给出这个图形族的还原结果。让 N 是顶点集上至少有 3 个轨道的 G 的正则子群。我们证明这样的图\(\Gamma \)是它的商\(\Gamma _N\)的覆盖,并且\(\Gamma _N\)是(G/N、s=min \{4,\textrm{diam}(\Gamma _N)\}ge 3\), 或者 \(\Gamma _N\) 是一个(G/N, 2)弧遍历强规则图。接下来,利用2-弧-传递强正则图的分类,我们确定了当\(\Gamma _N\)是强正则图时所有的(G,4)-大地-传递盖\(\Gamma \)。
Finite 4-geodesic-transitive graphs with bounded girth
Praeger and the first author in Jin and Praeger (J Combin Theory Ser A 178:105349, 2021) asked the following problem: classify s-geodesic-transitive graphs of girth \(2s-1\) or \(2s-2\), where \(s=4,5,6,7,8\). In this paper, we study the \(s=4\) case, that is, study the family of finite (G, 4)-geodesic-transitive graphs of girth 6 or 7 for some group G of automorphisms. A reduction result on this family of graphs is first given. Let N be a normal subgroup of G which has at least 3 orbits on the vertex set. We show that such a graph \(\Gamma \) is a cover of its quotient \(\Gamma _N\) modulo the N-orbits and either \(\Gamma _N\) is (G/N, s)-geodesic-transitive where \(s=\min \{4,\textrm{diam}(\Gamma _N)\}\ge 3\), or \(\Gamma _N\) is a (G/N, 2)-arc-transitive strongly regular graph. Next, using the classification of 2-arc-transitive strongly regular graphs, we determine all the (G, 4)-geodesic-transitive covers \(\Gamma \) when \(\Gamma _N\) is strongly regular.
期刊介绍:
The Journal of Algebraic Combinatorics provides a single forum for papers on algebraic combinatorics which, at present, are distributed throughout a number of journals. Within the last decade or so, algebraic combinatorics has evolved into a mature, established and identifiable area of mathematics. Research contributions in the field are increasingly seen to have substantial links with other areas of mathematics.
The journal publishes papers in which combinatorics and algebra interact in a significant and interesting fashion. This interaction might occur through the study of combinatorial structures using algebraic methods, or the application of combinatorial methods to algebraic problems.