Andrzej Dudek, Jarosław Grytczuk, Andrzej Ruciński
{"title":"Long Twins in Random Words","authors":"Andrzej Dudek, Jarosław Grytczuk, Andrzej Ruciński","doi":"10.1007/s00026-023-00651-5","DOIUrl":"10.1007/s00026-023-00651-5","url":null,"abstract":"<div><p><i>Twins</i> in a finite word are formed by a pair of identical subwords placed at disjoint sets of positions. We investigate the maximum length of twins in <i>a random</i> word over a <i>k</i>-letter alphabet. The obtained lower bounds for small values of <i>k</i> significantly improve the best estimates known in the deterministic case. Bukh and Zhou in 2016 showed that every ternary word of length <i>n</i> contains twins of length at least 0.34<i>n</i>. Our main result states that in a random ternary word of length <i>n</i>, with high probability, one can find twins of length at least 0.41<i>n</i>. In the general case of alphabets of size <span>(kgeqslant 3)</span> we obtain analogous lower bounds of the form <span>(frac{1.64}{k+1}n)</span> which are better than the known deterministic bounds for <span>(kleqslant 354)</span>. In addition, we present similar results for <i>multiple</i> twins in random words.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00026-023-00651-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46164776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"On the Subdivision Algebra for the Polytope $$mathcal {U}_{I,overline{J}}$$","authors":"Matias von Bell, Martha Yip","doi":"10.1007/s00026-023-00650-6","DOIUrl":"https://doi.org/10.1007/s00026-023-00650-6","url":null,"abstract":"","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45728539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}