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Involution matrix loci and orbit harmonics 卷积矩阵位置和轨道谐波
Pub Date : 2024-09-10 DOI: arxiv-2409.06175
Moxuan J. Liu, Yichen Ma, Brendon Rhoades, Hai Zhu
Let $mathrm{Mat}_{n times n}(mathbb{C})$ be the affine space of $n timesn$ complex matrices with coordinate ring $mathbb{C}[mathbf{x}_{n times n}]$.We define graded quotients of $mathbb{C}[mathbf{x}_{n times n}]$ which carryan action of the symmetric group $mathfrak{S}_n$ by simultaneous permutationof rows and columns. These quotient rings are obtained by applying the orbitharmonics method to matrix loci corresponding to all involutions in$mathfrak{S}_n$ and the conjugacy classes of involutions in $mathfrak{S}_n$with a given number of fixed points. In the case of perfect matchings on ${1,dots, n}$ with $n$ even, the Hilbert series of our quotient ring is relatedto Tracy-Widom distributions and its graded Frobenius image gives a refinementof the plethysm $s_{n/2}[s_2]$.
让 $mathrm{Mat}_{n times n}(mathbb{C})$ 是坐标环为 $mathbb{C}[mathbf{x}_{n times n}]$ 的 $n timesn$ 复矩阵的仿射空间。我们定义了$mathbb{C}[mathbf{x}_{n times n}]$的分级商,它通过行列的同时置换来承载对称组$mathfrak{S}_n$的作用。这些商环是通过对$mathfrak{S}_n$中所有渐开线对应的矩阵位置以及$mathfrak{S}_n$中具有给定定点数的渐开线共轭类应用轨道谐波方法得到的。在 $n$ 偶数的 ${1,dots, n}$ 上的完全匹配的情况下,我们商环的希尔伯特数列与特雷西-维多姆分布相关,而它的分级弗罗本尼乌斯像给出了褶的细化 $s_{n/2}[s_2]$。
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引用次数: 0
Deformed Homogeneous $(s,t)$-Rogers-Szegö Polynomials and the Deformed $(s,t)$-Exponential Operator e$_{s,t}(y{rm T}_a D_{s,t},v)$ 变形均质 $(s,t)$ 罗格斯-席格多项式与变形 $(s,t)$ 指数算子 e$_{s,t}(y{rm T}_a D_{s,t},v)$
Pub Date : 2024-09-10 DOI: arxiv-2409.06878
Ronald Orozco López
This article introduces the deformed homogeneous $(s,t)$-Rogers-Szeg"opolynomials h$_{n}(x,y;s,t,u,v)$. These polynomials are a generalization of theRogers-Szeg"o polynomials and the $(p,q)$-Rogers-Szeg"o polynomials definedby Jagannathan. By using the deformed $(s,t)$-exponential operator based onoperator T$_{a}D_{s,t}$ we find identities involving the polynomialsh$_{n}(x,y;s,t,u,v)$, together with generalizations of the Mehler and Rogersformulas. In addition, a generating function for the polynomialsh$_{n}(x,y;s,t,u,v)$ is found employing the deformed$frac{varphi}{u}$-commuting operators. A representation of deformed$(s,t)$-exponential function as the limit of a sequence of deformed$(s,t)$-Rogers-Szeg"o polynomials is obtained.
本文介绍了变形同质 $(s,t)$ 罗杰斯-赛格多项式 h$_{n}(x,y;s,t,u,v)$。这些多项式是 Jagannathan 定义的罗杰斯-赛格多项式和 $(p,q)$ 罗杰斯-赛格多项式的广义化。通过使用基于运算符 T$_{a}D_{s,t}$ 的变形 $(s,t)$-指数运算符,我们发现了涉及多项式sh$_{n}(x,y;s,t,u,v)$ 的常量,以及梅勒公式和罗杰斯公式的广义化。此外,还利用变形$frac{varphi}{u}$对换算子找到了多项式sh$_{n}(x,y;s,t,u,v)$的生成函数。得到了变形$(s,t)$-指数函数作为变形$(s,t)$-Rogers-Szeg"o 多项式序列的极限的表示。
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引用次数: 0
On the number of H-free hypergraphs 关于无 H 超图的数量
Pub Date : 2024-09-10 DOI: arxiv-2409.06810
Tao Jiang, Sean Longbrake
Two central problems in extremal combinatorics are concerned with estimatingthe number $ex(n,H)$, the size of the largest $H$-free hypergraph on $n$vertices, and the number $forb(n,H)$ of $H$-free hypergraph on $n$ vertices.While it is known that $forb(n,H)=2^{(1+o(1))ex(n,H)}$ for $k$-uniformhypergraphs that are not $k$-partite, estimates for hypergraphs that are$k$-partite (or degenerate) are not nearly as tight. In a recent breakthrough, Ferber, McKinley, and Samotij proved that for manydegenerate hypergraphs $H$, $forb(n, H) = 2^{O(ex(n,H))}$. However, there arefew known instances of degenerate hypergraphs $H$ for which$forb(n,H)=2^{(1+o(1))ex(n,H)}$ holds. In this paper, we show that $forb(n,H)=2^{(1+o(1))ex(n,H)}$ holds for a wideclass of degenerate hypergraphs known as $2$-contractible hypertrees. This isthe first known infinite family of degenerate hypergraphs $H$ for which$forb(n,H)=2^{(1+o(1))ex(n,H)}$ holds. As a corollary of our main results, weobtain a surprisingly sharp estimate of$forb(n,C^{(k)}_ell)=2^{(lfloorfrac{ell-1}{2}rfloor+o(1))binom{n}{k-1}}$for the $k$-uniform linear $ell$-cycle, for all pairs $kgeq 5, ellgeq 3$,thus settling a question of Balogh, Narayanan, and Skokan affirmatively for all$kgeq 5, ellgeq 3$. Our methods also lead to some related sharp results onthe corresponding random Turan problem. As a key ingredient of our proofs, we develop a novel supersaturation variantof the delta systems method for set systems, which may be of independentinterest.
极值组合学中有两个核心问题,一个是估计 $n$ 顶点上最大的无 H$ 超图的大小 $ex(n,H)$,另一个是估计 $n$ 顶点上无 H$ 超图的数量 $forb(n,H)$。虽然已知对于非 k$ 部分的 $k$ Uniformhypergraphs,$forb(n,H)=2^{(1+o(1))ex(n,H)}$,但对于 k$ 部分(或退化)的超图,估计值并不那么精确。在最近的一次突破中,费伯、麦金利和萨莫提证明,对于许多退化超图 $H$,$forb(n, H) = 2^{O(ex(n,H))}$ 。然而,对于退化超图 $H$,$forb(n,H)=2^{(1+o(1))ex(n,H)}$ 成立的已知实例很少。在本文中,我们证明了$forb(n,H)=2^{(1+o(1))ex(n,H)}$对于被称为$2$可收缩超树的一大类退化超图成立。这是第一个已知$forb(n,H)=2^{(1+o(1))ex(n,H)}$成立的无限退化超图$H$族。作为我们主要结果的一个推论,我们得到了$forb(n,C^{(k)}_ell)=2^{(lfloorfrac{ell-1}{2}rfloor+o(1))binom{n}{k-1}}$对$k$均匀线性$ell$循环的惊人的精确估计、对于所有对 $kgeq 5, ellgeq 3$,从而解决了 Balogh、Narayanan 和 Skokan 提出的一个问题,即对于所有 $kgeq 5, ellgeq 3$。我们的方法还引出了相应的随机图兰问题的一些相关的尖锐结果。作为我们证明的一个关键要素,我们发展了一种新颖的集合系统德尔塔系统方法的超饱和变体,这可能会引起一些独立的兴趣。
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引用次数: 0
The Converse of the Real Orthogonal Holant Theorem 实正交全等定理的逆定理
Pub Date : 2024-09-10 DOI: arxiv-2409.06911
Ben Young
The Holant theorem is a powerful tool for studying the computationalcomplexity of counting problems in the Holant framework. Due to the greatexpressiveness of the Holant framework, a converse to the Holant theorem woulditself be a very powerful counting indistinguishability theorem. The mostgeneral converse does not hold, but we prove the following, still highlygeneral, version: if any two sets of real-valued signatures areHolant-indistinguishable, then they are equivalent up to an orthogonaltransformation. This resolves a partially open conjecture of Xia (2010).Consequences of this theorem include the well-known result that homomorphismcounts from all graphs determine a graph up to isomorphism, the classicalsufficient condition for simultaneous orthogonal similarity of sets of realmatrices, and a combinatorial characterization of simultaneosly orthogonallydecomposable (odeco) sets of tensors.
霍兰德定理是研究霍兰德框架中计数问题计算复杂性的有力工具。由于霍兰德框架的巨大可扩展性,霍兰德定理的逆定理本身就是一个非常强大的计数无差别定理。最一般的逆定理并不成立,但我们证明了以下仍然非常一般的版本:如果任何两个实值符号集都是霍兰德不可区分的,那么它们在正交变换之前是等价的。这个定理的后果包括众所周知的结果:所有图的同态计数决定了一个图的同构性、实数集同时正交相似性的经典充分条件,以及同时正交可分解(odeco)张量集的组合特征。
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引用次数: 0
The asymptotic repetition threshold of sequences rich in palindromes 富含回文的序列的渐近重复阈值
Pub Date : 2024-09-10 DOI: arxiv-2409.06849
Lubomíra Dvořáková, Karel Klouda, Edita Pelantová
The asymptotic critical exponent measures for a sequence the maximumrepetition rate of factors of growing length. The infimum of asymptoticcritical exponents of sequences of a certain class is called the asymptoticrepetition threshold of that class. On the one hand, if we consider the classof all d-ary sequences with d greater than one, then the asymptotic repetitionthreshold is equal to one, independently of the alphabet size. On the otherhand, for the class of episturmian sequences, the repetition threshold dependson the alphabet size. We focus on rich sequences, i.e., sequences whose factorscontain the maximum possible number of distinct palindromes. The class ofepisturmian sequences forms a subclass of rich sequences. We prove that theasymptotic repetition threshold for the class of rich recurrent d-arysequences, with d greater than one, is equal to two, independently of thealphabet size.
渐近临界指数衡量的是一个序列中长度不断增长的因子的最大重复率。某类序列的渐近临界指数的最小值称为该类序列的渐近重复临界值。一方面,如果我们考虑所有 d 大于 1 的 dary 序列,那么渐近重复阈值等于 1,与字母表大小无关。另一方面,对于表观序列类,重复阈值取决于字母表的大小。我们关注的是富序列,即因子包含最大可能数量的不同回文的序列。episturmian序列类是富序列的一个子类。我们证明,d 大于 1 的富循环 dary 序列的渐近重复阈值等于 2,与字母大小无关。
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引用次数: 0
On the joint embedding property for cographs and trees 关于 cographs 和树的联合嵌入特性
Pub Date : 2024-09-10 DOI: arxiv-2409.06127
Daniel Carter
A family of graphs $mathcal{F}$ is said to have the joint embedding property(JEP) if for every $G_1, G_2in mathcal{F}$, there is an $Hin mathcal{F}$that contains both $G_1$ and $G_2$ as induced subgraphs. If $mathcal{F}$ isgiven by a finite set $S$ of forbidden induced subgraphs, it is known thatdetermining if $mathcal{F}$ has JEP is undecidable. We prove that this problemis decidable if $P_4in S$ and generalize this result to families of rootedlabeled trees under topological containment, bounded treewidth families underthe graph minor relation, and bounded cliquewidth families under the inducedsubgraph relation.
如果对于 $G_1, G_2in mathcal{F}$ 中的每一个 $G_1,$G_2,有一个 $Hin mathcal{F}$ 同时包含作为诱导子图的 $G_1$ 和 $G_2$,那么就可以说 $mathcal{F}$ 的图族具有联合嵌入属性(JEP)。如果$$mathcal{F}$是由一个有限的禁止诱导子图集$S$给出的,那么已知确定$$mathcal{F}$是否具有JEP是不可判定的。我们证明,如果 $P_4in S$,这个问题是可解的,并将这一结果推广到拓扑包含下的有根标记树族、图次要关系下的有界树宽族以及诱导子图关系下的有界剪辑宽族。
{"title":"On the joint embedding property for cographs and trees","authors":"Daniel Carter","doi":"arxiv-2409.06127","DOIUrl":"https://doi.org/arxiv-2409.06127","url":null,"abstract":"A family of graphs $mathcal{F}$ is said to have the joint embedding property\u0000(JEP) if for every $G_1, G_2in mathcal{F}$, there is an $Hin mathcal{F}$\u0000that contains both $G_1$ and $G_2$ as induced subgraphs. If $mathcal{F}$ is\u0000given by a finite set $S$ of forbidden induced subgraphs, it is known that\u0000determining if $mathcal{F}$ has JEP is undecidable. We prove that this problem\u0000is decidable if $P_4in S$ and generalize this result to families of rooted\u0000labeled trees under topological containment, bounded treewidth families under\u0000the graph minor relation, and bounded cliquewidth families under the induced\u0000subgraph relation.","PeriodicalId":501407,"journal":{"name":"arXiv - MATH - Combinatorics","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142197634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
New bounds for the optimal density of covering single-insertion codes via the Turán density 通过图兰密度计算覆盖单插码最优密度的新界限
Pub Date : 2024-09-10 DOI: arxiv-2409.06425
Oleg Pikhurko, Oleg Verbitsky, Maksim Zhukovskii
We prove that the density of any covering single-insertion code $CsubseteqX^r$ over the $n$-symbol alphabet $X$ cannot be smaller than $1/r+delta_r$ forsome positive real $delta_r$ not depending on $n$. This improves the volumelower bound of $1/(r+1)$. On the other hand, we observe that, for allsufficiently large $r$, if $n$ tends to infinity then the asymptotic upperbound of $7/(r+1)$ due to Lenz et al (2021) can be improved to $4.911/(r+1)$. Both the lower and the upper bounds are achieved by relating the code densityto the Tur'an density from extremal combinatorics. For the last task, we usethe analytic framework of measurable subsets of the real cube $[0,1]^r$.
我们证明,对于某个不依赖于 $n$ 的正实数 $delta_r$,在 $n$ 符号字母表 $X$ 上的任何覆盖单插入代码 $CsubseteqX^r$ 的密度不可能小于 $1/r+delta_r$。这改进了$1/(r+1)$的体积下限。另一方面,我们观察到,对于所有足够大的 $r$,如果 $n$ 趋于无穷大,那么 Lenz 等人(2021 年)提出的渐近上限 $7/(r+1)$ 可以提高到 $4.911/(r+1)$。下限和上限都是通过将代码密度与极值组合学中的 Tur'an 密度相关联来实现的。对于最后一项任务,我们使用了实立方$[0,1]^r$的可测子集的分析框架。
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引用次数: 0
A Systematic Approach to Crossing Numbers of Cartesian Products with Paths 直角坐标积与路径交叉数的系统方法
Pub Date : 2024-09-10 DOI: arxiv-2409.06755
Zayed Asiri, Ryan Burdett, Markus Chimani, Michael Haythorpe, Alex Newcombe, Mirko H. Wagner
Determining the crossing numbers of Cartesian products of small graphs witharbitrarily large paths has been an ongoing topic of research since the 1970s.Doing so requires the establishment of coincident upper and lower bounds; theformer is usually demonstrated by providing a suitable drawing procedure, whilethe latter often requires substantial theoretical arguments. Many such papershave been published, which typically focus on just one or two small graphs at atime, and use ad hoc arguments specific to those graphs. We propose a generalapproach which, when successful, establishes the required lower bound. Thisapproach can be applied to the Cartesian product of any graph with arbitrarilylarge paths, and in each case involves solving a modified version of thecrossing number problem on a finite number (typically only two or three) ofsmall graphs. We demonstrate the potency of this approach by applying it toCartesian products involving all 133 graphs $G$ of orders five or six, and showthat it is successful in 128 cases. This includes 60 cases which a recentsurvey listed as either undetermined, or determined only in journals withoutadequate peer review.
自 20 世纪 70 年代以来,确定具有任意大路径的小型图的笛卡尔积的交叉数一直是一个持续的研究课题。要做到这一点,需要建立重合的上限和下限;前者通常通过提供合适的绘制过程来证明,而后者通常需要大量的理论论证。已发表的许多此类论文通常同时只关注一两个小图形,并使用针对这些图形的特别论证。我们提出了一种通用方法,一旦成功,就能建立所需的下界。这种方法可以应用于任何具有任意大路径的图的笛卡尔积,并且在每种情况下都涉及在有限数量(通常只有两到三个)的小图上求解修正版的交叉数问题。我们将这种方法应用于涉及所有 133 个五阶或六阶图 $G$ 的笛卡尔积,证明了它的威力,并证明它在 128 个案例中取得了成功。其中有 60 个案例在最近的调查中被列为未确定或仅在未经同行充分评议的期刊中确定。
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引用次数: 0
Hamilton cycles in vertex-transitive graphs of order $6p$ 阶$6p$顶点变换图中的汉密尔顿循环
Pub Date : 2024-09-10 DOI: arxiv-2409.06138
Shaofei Du, Tianlei Zhou
It was shown that every connected vertex-transitive graph of order $6p$,where $p$ is a prime, contains a Hamilton path cite{KS09}. It will be shown inthis paper that every such graph contains a Hamilton cycle, except for thetriangle-replaced graph of the Petersen graph.
研究表明,每一个阶数为 $6p$(其中 $p$ 是素数)的连通顶点-传递图都包含一条汉密尔顿路径 (cite{KS09})。本文将证明,除了彼得森图的三角重置图之外,每个这样的图都包含一个汉密尔顿循环。
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引用次数: 0
Generalized Diagonals in Positive Semi-Definite Matrices 正半有限矩阵中的广义对角线
Pub Date : 2024-09-10 DOI: arxiv-2409.06907
Robert Angarone, Daniel Soskin
We describe all inequalities among generalized diagonals in positivesemi-definite matrices. These turn out to be governed by a simple partial orderon the symmetric group. This provides an analogue of results of Drake, Gerrish,and Skandera on inequalities among generalized diagonals in totally nonnegativematrices.
我们描述了正半定矩阵中广义对角线之间的所有不等式。结果表明,这些不等式受对称群上一个简单偏序的支配。这与 Drake、Gerrish 和 Skandera 关于完全非负矩阵中广义对角线间不等式的结果类似。
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引用次数: 0
期刊
arXiv - MATH - Combinatorics
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