{"title":"Refined Enumeration of ({{varvec{k}}})-plane Trees and ({varvec{k}})-noncrossing Trees","authors":"Isaac Owino Okoth, Stephan Wagner","doi":"10.1007/s00026-023-00642-6","DOIUrl":"10.1007/s00026-023-00642-6","url":null,"abstract":"<div><p>A <i>k</i>-<i>plane tree</i> is a plane tree whose vertices are assigned labels between 1 and <i>k</i> in such a way that the sum of the labels along any edge is no greater than <span>(k+1)</span>. These trees are known to be related to <span>((k+1))</span>-ary trees, and they are counted by a generalised version of the Catalan numbers. We prove a surprisingly simple refined counting formula, where we count trees with a prescribed number of labels of each kind. Several corollaries are derived from this formula, and an analogous theorem is proven for <i>k</i>-<i>noncrossing trees</i>, a similarly defined family of labelled noncrossing trees that are related to <span>((2k+1))</span>-ary trees.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"28 1","pages":"121 - 153"},"PeriodicalIF":0.6,"publicationDate":"2023-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00026-023-00642-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41390405","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":"The Rank of the Sandpile Group of Random Directed Bipartite Graphs","authors":"Atal Bhargava, Jack DePascale, Jake Koenig","doi":"10.1007/s00026-023-00637-3","DOIUrl":"10.1007/s00026-023-00637-3","url":null,"abstract":"<div><p>We identify the asymptotic distribution of <i>p</i>-rank of the sandpile group of random directed bipartite graphs which are not too imbalanced. We show this matches exactly with that of the Erdös–Rényi random directed graph model, suggesting that the Sylow <i>p</i>-subgroups of this model may also be Cohen–Lenstra distributed. Our work builds on the results of Koplewitz who studied <i>p</i>-rank distributions for unbalanced random bipartite graphs, and showed that for sufficiently unbalanced graphs, the distribution of <i>p</i>-rank differs from the Cohen–Lenstra distribution. Koplewitz (sandpile groups of random bipartite graphs, https://arxiv.org/abs/1705.07519, 2017) conjectured that for random balanced bipartite graphs, the expected value of <i>p</i>-rank is <i>O</i>(1) for any <i>p</i>. This work proves his conjecture and gives the exact distribution for the subclass of directed graphs.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"27 4","pages":"979 - 992"},"PeriodicalIF":0.5,"publicationDate":"2023-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00026-023-00637-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46156088","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 Promotion and Quasi-Tangled Labelings of Posets","authors":"Eliot Hodges","doi":"10.1007/s00026-023-00646-2","DOIUrl":"10.1007/s00026-023-00646-2","url":null,"abstract":"<div><p>In 2022, Defant and Kravitz introduced extended promotion (denoted <span>( partial )</span>), a map that acts on the set of labelings of a poset. Extended promotion is a generalization of Schützenberger’s promotion operator, a well-studied map that permutes the set of linear extensions of a poset. It is known that if <i>L</i> is a labeling of an <i>n</i>-element poset <i>P</i>, then <span>( partial ^{n-1}(L) )</span> is a linear extension. This allows us to regard <span>( partial )</span> as a sorting operator on the set of all labelings of <i>P</i>, where we think of the linear extensions of <i>P</i> as the labelings which have been sorted. The labelings requiring <span>( n-1 )</span> applications of <span>( partial )</span> to be sorted are called <i>tangled</i>; the labelings requiring <span>( n-2 )</span> applications are called <i>quasi-tangled</i>. We count the quasi-tangled labelings of a relatively large class of posets called <i>inflated rooted trees with deflated leaves</i>. Given an <i>n</i>-element poset with a unique minimal element with the property that the minimal element has exactly one parent, it follows from the aforementioned enumeration that this poset has <span>( 2(n-1)!-(n-2)! )</span> quasi-tangled labelings. Using similar methods, we outline an algorithmic approach to enumerating the labelings requiring <span>( n-k-1 )</span> applications to be sorted for any fixed <span>( kin {1,ldots ,n-2} )</span>. We also make partial progress towards proving a conjecture of Defant and Kravitz on the maximum possible number of tangled labelings of an <i>n</i>-element poset.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"28 2","pages":"529 - 554"},"PeriodicalIF":0.6,"publicationDate":"2023-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47799232","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}
{"title":"Arithmetic Properties of Certain t-Regular Partitions","authors":"Rupam Barman, Ajit Singh, Gurinder Singh","doi":"10.1007/s00026-023-00649-z","DOIUrl":"10.1007/s00026-023-00649-z","url":null,"abstract":"<div><p>For a positive integer <span>(tge 2)</span>, let <span>(b_{t}(n))</span> denote the number of <i>t</i>-regular partitions of a nonnegative integer <i>n</i>. Motivated by some recent conjectures of Keith and Zanello, we establish infinite families of congruences modulo 2 for <span>(b_9(n))</span> and <span>(b_{19}(n))</span>. We prove some specific cases of two conjectures of Keith and Zanello on self-similarities of <span>(b_9(n))</span> and <span>(b_{19}(n))</span> modulo 2. For <span>(tin {6,10,14,15,18,20,22,26,27,28})</span>, Keith and Zanello conjectured that there are no integers <span>(A>0)</span> and <span>(Bge 0)</span> for which <span>(b_t(An+ B)equiv 0pmod 2)</span> for all <span>(nge 0)</span>. We prove that, for any <span>(tge 2)</span> and prime <span>(ell )</span>, there are infinitely many arithmetic progressions <span>(An+B)</span> for which <span>(sum _{n=0}^{infty }b_t(An+B)q^nnot equiv 0 pmod {ell })</span>. Next, we obtain quantitative estimates for the distributions of <span>(b_{6}(n), b_{10}(n))</span> and <span>(b_{14}(n))</span> modulo 2. We further study the odd densities of certain infinite families of eta-quotients related to the 7-regular and 13-regular partition functions.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"28 2","pages":"439 - 457"},"PeriodicalIF":0.6,"publicationDate":"2023-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44349370","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}
Archit Agarwal, Subhash Chand Bhoria, Pramod Eyyunni, Bibekananda Maji
{"title":"Bressoud–Subbarao Type Weighted Partition Identities for a Generalized Divisor Function","authors":"Archit Agarwal, Subhash Chand Bhoria, Pramod Eyyunni, Bibekananda Maji","doi":"10.1007/s00026-023-00647-1","DOIUrl":"10.1007/s00026-023-00647-1","url":null,"abstract":"<div><p>In 1984, Bressoud and Subbarao obtained an interesting weighted partition identity for a generalized divisor function, by means of combinatorial arguments. Recently, the last three named authors found an analytic proof of the aforementioned identity of Bressoud and Subbarao starting from a <i>q</i>-series identity of Ramanujan. In the present paper, we revisit the combinatorial arguments of Bressoud and Subbarao, and derive a more general weighted partition identity. Furthermore, with the help of a fractional differential operator, we establish a few more Bressoud–Subbarao type weighted partition identities beginning from an identity of Andrews, Garvan and Liang. We also found a one-variable generalization of an identity of Uchimura related to Bell polynomials.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"28 2","pages":"555 - 574"},"PeriodicalIF":0.6,"publicationDate":"2023-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49518651","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}
{"title":"Congruence Modulo 4 for Andrews’ Even Parts Below Odd Parts Partition Function","authors":"Dandan Chen, Rong Chen","doi":"10.1007/s00026-023-00645-3","DOIUrl":"10.1007/s00026-023-00645-3","url":null,"abstract":"<div><p>We find and prove a class of congruences modulo 4 for Andrews’ partition with certain ternary quadratic form. We also discuss distribution of <span>(overline{mathcal{E}mathcal{O}}(n))</span> and further prove that <span>(overline{mathcal{E}mathcal{O}}(n)equiv 0pmod 4)</span> for almost all <i>n</i>. This study was inspired by similar congruences modulo 4 in the work by the second author and Garvan.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"27 2","pages":"269 - 279"},"PeriodicalIF":0.5,"publicationDate":"2023-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44237044","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}
Florian Frick, Mirabel Hu, Verity Scheel, Steven Simon
{"title":"Embedding Dimensions of Simplicial Complexes on Few Vertices","authors":"Florian Frick, Mirabel Hu, Verity Scheel, Steven Simon","doi":"10.1007/s00026-023-00644-4","DOIUrl":"10.1007/s00026-023-00644-4","url":null,"abstract":"<div><p>We provide a simple characterization of simplicial complexes on few vertices that embed into the <i>d</i>-sphere. Namely, a simplicial complex on <span>(d+3)</span> vertices embeds into the <i>d</i>-sphere if and only if its non-faces do not form an intersecting family. As immediate consequences, we recover the classical van Kampen–Flores theorem and provide a topological extension of the Erdős–Ko–Rado theorem. By analogy with Fáry’s theorem for planar graphs, we show in addition that such complexes satisfy the rigidity property that continuous and linear embeddability are equivalent.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"27 4","pages":"993 - 1003"},"PeriodicalIF":0.5,"publicationDate":"2023-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00026-023-00644-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41826685","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":"Strict Log-Subadditivity for Overpartition Rank","authors":"Helen W. J. Zhang, Ying Zhong","doi":"10.1007/s00026-023-00643-5","DOIUrl":"10.1007/s00026-023-00643-5","url":null,"abstract":"<div><p>Bessenrodt and Ono initially found the strict log-subadditivity of partition function <i>p</i>(<i>n</i>), that is, <span>(p(a+b)< p(a)p(b))</span> for <span>(a,b>1)</span> and <span>(a+b>9)</span>. Many other important partition statistics are proved to enjoy similar properties. Lovejoy introduced the overpartition rank as an analog of Dyson’s rank for partitions from the <i>q</i>-series perspective. Let <span>({overline{N}}(a,c,n))</span> denote the number of overpartitions with rank congruent to <i>a</i> modulo <i>c</i>. Ciolan computed the asymptotic formula of <span>({overline{N}}(a,c,n))</span> and showed that <span>({overline{N}}(a, c, n) > {overline{N}}(b, c, n))</span> for <span>(0le a<ble lfloor frac{c}{2}rfloor )</span> and <i>n</i> large enough if <span>(cge 7)</span>. In this paper, we derive an upper bound and a lower bound of <span>({overline{N}}(a,c,n))</span> for each <span>(cge 3)</span> by using the asymptotics due to Ciolan. Consequently, we establish the strict log-subadditivity of <span>({overline{N}}(a,c,n))</span> analogous to the partition function <i>p</i>(<i>n</i>).</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"27 4","pages":"799 - 817"},"PeriodicalIF":0.5,"publicationDate":"2023-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46460253","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}
{"title":"Dominance Regions for Rank Two Cluster Algebras","authors":"Dylan Rupel, Salvatore Stella","doi":"10.1007/s00026-023-00636-4","DOIUrl":"10.1007/s00026-023-00636-4","url":null,"abstract":"<div><p>We study the polygons defining the dominance order on <span>({varvec{g}})</span>-vectors in cluster algebras of rank 2 as in Fig. 1.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"27 4","pages":"873 - 894"},"PeriodicalIF":0.5,"publicationDate":"2023-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00026-023-00636-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48224641","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":"Berkovich–Uncu Type Partition Inequalities Concerning Impermissible Sets and Perfect Power Frequencies","authors":"Damanvir Singh Binner, Neha Gupta, Manoj Upreti","doi":"10.1007/s00026-023-00638-2","DOIUrl":"10.1007/s00026-023-00638-2","url":null,"abstract":"<div><p>Recently, Rattan and the first author (Ann. Comb. 25 (2021) 697–728) proved a conjectured inequality of Berkovich and Uncu (Ann. Comb. 23 (2019) 263–284) concerning partitions with an impermissible part. In this article, we generalize this inequality upon considering <i>t</i> impermissible parts. We compare these with partitions whose certain parts appear with a frequency which is a perfect <span>(t^{th})</span> power. In addition, the partitions that we study here have smallest part greater than or equal to <i>s</i> for some given natural number <i>s</i>. Our inequalities hold after a certain bound, which for given <i>t</i> is a polynomial in <i>s</i>, a major improvement over the previously known bound in the case <span>(t=1)</span>. To prove these inequalities, our methods involve constructing injective maps between the relevant sets of partitions. The construction of these maps crucially involves concepts from analysis and calculus, such as explicit maps used to prove countability of <span>(mathbb {N}^t)</span>, and Jensen’s inequality for convex functions, and then merge them with techniques from number theory such as Frobenius numbers, congruence classes, binary numbers and quadratic residues. We also show a connection of our results to colored partitions. Finally, we pose an open problem which seems to be related to power residues and the almost universality of diagonal ternary quadratic forms.</p></div>","PeriodicalId":50769,"journal":{"name":"Annals of Combinatorics","volume":"27 4","pages":"833 - 855"},"PeriodicalIF":0.5,"publicationDate":"2023-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00026-023-00638-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42684461","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}