{"title":"避免长度为 3 的模式或避免有限数量的简单模式的连续数字排列组合","authors":"","doi":"10.1016/j.disc.2024.114199","DOIUrl":null,"url":null,"abstract":"<div><p>For <span><math><mi>η</mi><mo>∈</mo><msub><mrow><mi>S</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span>, let <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span> denote the set of permutations in <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> that avoid the pattern <em>η</em>, and let <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span> denote the expectation with respect to the uniform probability measure on <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>. For <span><math><mi>n</mi><mo>≥</mo><mi>k</mi><mo>≥</mo><mn>2</mn></math></span> and <span><math><mi>τ</mi><mo>∈</mo><msubsup><mrow><mi>S</mi></mrow><mrow><mi>k</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>, let <span><math><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></msubsup><mo>(</mo><mi>σ</mi><mo>)</mo></math></span> denote the number of occurrences of <em>k</em> consecutive numbers appearing in <em>k</em> consecutive positions in <span><math><mi>σ</mi><mo>∈</mo><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>, and let <span><math><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>;</mo><mi>τ</mi><mo>)</mo></mrow></msubsup><mo>(</mo><mi>σ</mi><mo>)</mo></math></span> denote the number of such occurrences for which the order of the appearance of the <em>k</em> numbers is the pattern <em>τ</em>. We obtain explicit formulas for <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>;</mo><mi>τ</mi><mo>)</mo></mrow></msubsup></math></span> and <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></msubsup></math></span>, for all <span><math><mn>2</mn><mo>≤</mo><mi>k</mi><mo>≤</mo><mi>n</mi></math></span>, all <span><math><mi>η</mi><mo>∈</mo><msub><mrow><mi>S</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> and all <span><math><mi>τ</mi><mo>∈</mo><msubsup><mrow><mi>S</mi></mrow><mrow><mi>k</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>. These exact formulas then yield asymptotic formulas as <span><math><mi>n</mi><mo>→</mo><mo>∞</mo></math></span> with <em>k</em> fixed, and as <span><math><mi>n</mi><mo>→</mo><mo>∞</mo></math></span> with <span><math><mi>k</mi><mo>=</mo><msub><mrow><mi>k</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>→</mo><mo>∞</mo></math></span>. We also obtain analogous results for <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><msub><mrow><mi>η</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>⋯</mo><mo>,</mo><msub><mrow><mi>η</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>)</mo></mrow></msubsup></math></span>, the subset of <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> consisting of permutations avoiding the patterns <span><math><msubsup><mrow><mo>{</mo><msub><mrow><mi>η</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>}</mo></mrow><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>r</mi></mrow></msubsup></math></span>, where <span><math><msub><mrow><mi>η</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><msub><mrow><mi>S</mi></mrow><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>i</mi></mrow></msub></mrow></msub></math></span>, in the case that <span><math><msubsup><mrow><mo>{</mo><msub><mrow><mi>η</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>}</mo></mrow><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>n</mi></mrow></msubsup></math></span> are all simple permutations. A particular case of this is the set of separable permutations, which corresponds to <span><math><mi>r</mi><mo>=</mo><mn>2</mn></math></span>, <span><math><msub><mrow><mi>η</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>=</mo><mn>2413</mn><mo>,</mo><msub><mrow><mi>η</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>=</mo><mn>3142</mn></math></span>.</p></div>","PeriodicalId":50572,"journal":{"name":"Discrete Mathematics","volume":null,"pages":null},"PeriodicalIF":0.7000,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Clustering of consecutive numbers in permutations avoiding a pattern of length three or avoiding a finite number of simple patterns\",\"authors\":\"\",\"doi\":\"10.1016/j.disc.2024.114199\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>For <span><math><mi>η</mi><mo>∈</mo><msub><mrow><mi>S</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span>, let <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span> denote the set of permutations in <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> that avoid the pattern <em>η</em>, and let <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span> denote the expectation with respect to the uniform probability measure on <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>. For <span><math><mi>n</mi><mo>≥</mo><mi>k</mi><mo>≥</mo><mn>2</mn></math></span> and <span><math><mi>τ</mi><mo>∈</mo><msubsup><mrow><mi>S</mi></mrow><mrow><mi>k</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>, let <span><math><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></msubsup><mo>(</mo><mi>σ</mi><mo>)</mo></math></span> denote the number of occurrences of <em>k</em> consecutive numbers appearing in <em>k</em> consecutive positions in <span><math><mi>σ</mi><mo>∈</mo><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>, and let <span><math><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>;</mo><mi>τ</mi><mo>)</mo></mrow></msubsup><mo>(</mo><mi>σ</mi><mo>)</mo></math></span> denote the number of such occurrences for which the order of the appearance of the <em>k</em> numbers is the pattern <em>τ</em>. We obtain explicit formulas for <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>;</mo><mi>τ</mi><mo>)</mo></mrow></msubsup></math></span> and <span><math><msubsup><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup><msubsup><mrow><mi>N</mi></mrow><mrow><mi>n</mi></mrow><mrow><mo>(</mo><mi>k</mi><mo>)</mo></mrow></msubsup></math></span>, for all <span><math><mn>2</mn><mo>≤</mo><mi>k</mi><mo>≤</mo><mi>n</mi></math></span>, all <span><math><mi>η</mi><mo>∈</mo><msub><mrow><mi>S</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> and all <span><math><mi>τ</mi><mo>∈</mo><msubsup><mrow><mi>S</mi></mrow><mrow><mi>k</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><mi>η</mi><mo>)</mo></mrow></msubsup></math></span>. These exact formulas then yield asymptotic formulas as <span><math><mi>n</mi><mo>→</mo><mo>∞</mo></math></span> with <em>k</em> fixed, and as <span><math><mi>n</mi><mo>→</mo><mo>∞</mo></math></span> with <span><math><mi>k</mi><mo>=</mo><msub><mrow><mi>k</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>→</mo><mo>∞</mo></math></span>. We also obtain analogous results for <span><math><msubsup><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow><mrow><mtext>av</mtext><mo>(</mo><msub><mrow><mi>η</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><mo>⋯</mo><mo>,</mo><msub><mrow><mi>η</mi></mrow><mrow><mi>r</mi></mrow></msub><mo>)</mo></mrow></msubsup></math></span>, the subset of <span><math><msub><mrow><mi>S</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> consisting of permutations avoiding the patterns <span><math><msubsup><mrow><mo>{</mo><msub><mrow><mi>η</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>}</mo></mrow><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>r</mi></mrow></msubsup></math></span>, where <span><math><msub><mrow><mi>η</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>∈</mo><msub><mrow><mi>S</mi></mrow><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>i</mi></mrow></msub></mrow></msub></math></span>, in the case that <span><math><msubsup><mrow><mo>{</mo><msub><mrow><mi>η</mi></mrow><mrow><mi>i</mi></mrow></msub><mo>}</mo></mrow><mrow><mi>i</mi><mo>=</mo><mn>1</mn></mrow><mrow><mi>n</mi></mrow></msubsup></math></span> are all simple permutations. A particular case of this is the set of separable permutations, which corresponds to <span><math><mi>r</mi><mo>=</mo><mn>2</mn></math></span>, <span><math><msub><mrow><mi>η</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>=</mo><mn>2413</mn><mo>,</mo><msub><mrow><mi>η</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>=</mo><mn>3142</mn></math></span>.</p></div>\",\"PeriodicalId\":50572,\"journal\":{\"name\":\"Discrete Mathematics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.7000,\"publicationDate\":\"2024-08-08\",\"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/S0012365X24003303\",\"RegionNum\":3,\"RegionCategory\":\"数学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Discrete Mathematics","FirstCategoryId":"100","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0012365X24003303","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
摘要
对于η∈S3,让 Snav(η) 表示 Sn 中避免模式 η 的排列集合,让 Enav(η) 表示关于 Snav(η) 上均匀概率度量的期望。对于 n≥k≥2 且 τ∈Skav(η), 让 Nn(k)(σ) 表示连续 k 个数字出现在 σ∈Snav(η) 中连续 k 个位置的次数,让 Nn(k;τ)(σ) 表示 k 个数字出现的顺序为模式 τ 的次数。对于所有 2≤k≤n、所有 η∈S3 和所有 τ∈Skav(η) ,我们可以得到 Enav(η)Nn(k;τ) 和 Enav(η)Nn(k) 的明确公式。根据这些精确公式,我们可以得出 k 固定时 n→∞ 的渐近公式,以及 k=kn→∞ 时 n→∞ 的渐近公式。对于 Snav(η1,⋯,ηr),我们也得到了类似的结果,Sn 子集由避免 {ηi}i=1r 模式的排列组成,其中 ηi∈Smi, 在 {ηi}i=1n 都是简单排列的情况下。一个特殊的情况是可分离的排列集合,它对应于 r=2,η1=2413,η2=3142。
Clustering of consecutive numbers in permutations avoiding a pattern of length three or avoiding a finite number of simple patterns
For , let denote the set of permutations in that avoid the pattern η, and let denote the expectation with respect to the uniform probability measure on . For and , let denote the number of occurrences of k consecutive numbers appearing in k consecutive positions in , and let denote the number of such occurrences for which the order of the appearance of the k numbers is the pattern τ. We obtain explicit formulas for and , for all , all and all . These exact formulas then yield asymptotic formulas as with k fixed, and as with . We also obtain analogous results for , the subset of consisting of permutations avoiding the patterns , where , in the case that are all simple permutations. A particular case of this is the set of separable permutations, which corresponds to , .
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.