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arXiv 0909.4966math.CO
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交替排列和Young表的模式避免和类RSK算法

Pattern avoidance and RSK-like algorithms for alternating permutations and Young tableaux

Joel Brewster Lewis

摘要:

我们定义了一个类L_{n, k}的置换,推广交替(上下)置换,并给出了双射证明的某些模式,避免此类结果。作为我们结果的一个特例,我们给出了长度为2n且没有四项递增子序列的交替排列集合A_{2n}(1234)与形状为(3 ^n)的标准Young tableaux之间以及集合A_{2n + 1}(1234)与形状为(3^{n - 1},2,1)的标准Young tableaux之间的两个双射.这表示避免长度为4的模式的交替排列的第一次枚举。我们还扩展以前的工作双交替排列(交替排列的逆交替),我们更一般的情况下。集合L_{n, k}可以被看作是具有特定倾斜形状的标准杨氏表格的阅读单词的集合。在本文的最后一节中,我们扩大了我们的研究,考虑模式避免在阅读的话,标准的杨tableaux的任何歪斜的形状。我们双射表明,标准杨tableaux的形状lambda/mu的阅读单词避免213的数量是一个自然的mu模拟的加泰罗尼亚数字(特别是不依赖于lambda,一个简单的技术条件),并有类似的结果为模式132,231和312。

英文摘要:

We define a class L_{n, k} of permutations that generalizes alternating (up-down) permutations and give bijective proofs of certain pattern-avoidance results for this class. As a special case of our results, we give two bijections between the set A_{2n}(1234) of alternating permutations of length 2n with no four-term increasing subsequence and standard Young tableaux of shape (3^n), and between the set A_{2n + 1}(1234) and standard Young tableaux of shape (3^{n - 1}, 2, 1). This represents the first enumeration of alternating permutations avoiding a pattern of length four. We also extend previous work on doubly-alternating permutations (alternating permutations whose inverses are alternating) to our more general context. The set L_{n, k} may be viewed as the set of reading words of the standard Young tableaux of a certain skew shape. In the last section of the paper, we expand our study to consider pattern avoidance in the reading words of standard Young tableaux of any skew shape. We show bijectively that the number of standard Young tableaux of shape lambda/mu whose reading words avoid 213 is a natural mu-analogue of the Catalan numbers (and in particular does not depend on lambda, up to a simple technical condition), and that there are similar results for the patterns 132, 231 and 312.

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