{"title":"特异群中的元素顺序","authors":"M.-S Lazorec","doi":"10.1007/s10474-024-01454-7","DOIUrl":null,"url":null,"abstract":"<div><p>By using the structure and some properties of extraspecial and generalized/almost extraspecial <span>\\(p\\)</span>-groups, we explicitly determine the number of elements of specific orders in such groups. As a consequence, one may find the number of cyclic subgroups of any (generalized/almost) extraspecial group. For a finite group <span>\\(G\\)</span>, the ratio of the number of cyclic subgroups to the number of subgroups is called the cyclicity degree of <span>\\(G\\)</span> and is denoted by cdeg <span>\\((G)\\)</span>. We show that the set containing the cyclicity degrees of all finite groups is dense in <span>\\([0, 1]\\)</span>. This is equivalent to giving an affirmative answer to the following question posed by Tóth and Tărnăuceanu: “For every <span>\\(a\\in [0, 1]\\)</span>, does there exist a sequence <span>\\((G_n)_{n\\geq 1}\\)</span> of finite groups such that <span>\\( \\lim_{n\\to\\infty} \\text{cdeg} (G_n)=a\\)</span>?”. We show that such sequences are formed of finite direct products of extraspecial groups of a specific type. </p></div>","PeriodicalId":50894,"journal":{"name":"Acta Mathematica Hungarica","volume":"173 2","pages":"434 - 447"},"PeriodicalIF":0.6000,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Element orders in extraspecial groups\",\"authors\":\"M.-S Lazorec\",\"doi\":\"10.1007/s10474-024-01454-7\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>By using the structure and some properties of extraspecial and generalized/almost extraspecial <span>\\\\(p\\\\)</span>-groups, we explicitly determine the number of elements of specific orders in such groups. As a consequence, one may find the number of cyclic subgroups of any (generalized/almost) extraspecial group. For a finite group <span>\\\\(G\\\\)</span>, the ratio of the number of cyclic subgroups to the number of subgroups is called the cyclicity degree of <span>\\\\(G\\\\)</span> and is denoted by cdeg <span>\\\\((G)\\\\)</span>. We show that the set containing the cyclicity degrees of all finite groups is dense in <span>\\\\([0, 1]\\\\)</span>. This is equivalent to giving an affirmative answer to the following question posed by Tóth and Tărnăuceanu: “For every <span>\\\\(a\\\\in [0, 1]\\\\)</span>, does there exist a sequence <span>\\\\((G_n)_{n\\\\geq 1}\\\\)</span> of finite groups such that <span>\\\\( \\\\lim_{n\\\\to\\\\infty} \\\\text{cdeg} (G_n)=a\\\\)</span>?”. We show that such sequences are formed of finite direct products of extraspecial groups of a specific type. </p></div>\",\"PeriodicalId\":50894,\"journal\":{\"name\":\"Acta Mathematica Hungarica\",\"volume\":\"173 2\",\"pages\":\"434 - 447\"},\"PeriodicalIF\":0.6000,\"publicationDate\":\"2024-08-12\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Acta Mathematica Hungarica\",\"FirstCategoryId\":\"100\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s10474-024-01454-7\",\"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":"Acta Mathematica Hungarica","FirstCategoryId":"100","ListUrlMain":"https://link.springer.com/article/10.1007/s10474-024-01454-7","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"MATHEMATICS","Score":null,"Total":0}
By using the structure and some properties of extraspecial and generalized/almost extraspecial \(p\)-groups, we explicitly determine the number of elements of specific orders in such groups. As a consequence, one may find the number of cyclic subgroups of any (generalized/almost) extraspecial group. For a finite group \(G\), the ratio of the number of cyclic subgroups to the number of subgroups is called the cyclicity degree of \(G\) and is denoted by cdeg \((G)\). We show that the set containing the cyclicity degrees of all finite groups is dense in \([0, 1]\). This is equivalent to giving an affirmative answer to the following question posed by Tóth and Tărnăuceanu: “For every \(a\in [0, 1]\), does there exist a sequence \((G_n)_{n\geq 1}\) of finite groups such that \( \lim_{n\to\infty} \text{cdeg} (G_n)=a\)?”. We show that such sequences are formed of finite direct products of extraspecial groups of a specific type.
期刊介绍:
Acta Mathematica Hungarica is devoted to publishing research articles of top quality in all areas of pure and applied mathematics as well as in theoretical computer science. The journal is published yearly in three volumes (two issues per volume, in total 6 issues) in both print and electronic formats. Acta Mathematica Hungarica (formerly Acta Mathematica Academiae Scientiarum Hungaricae) was founded in 1950 by the Hungarian Academy of Sciences.