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arXiv · 1301.0430

Permutation statistics of products of random permutations

Axel Hultman
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Abstract

Given a permutation statistic $s : S_n \to \mathbb{R}$, define the mean statistic $\bar{s}$ as the statistic which computes the mean of $s$ over conjugacy classes. We describe a way to calculate the expected value of $s$ on a product of $t$ independently chosen elements from the uniform distribution on a union of conjugacy classes $\Gamma \subseteq S_n$. In order to apply the formula, one needs to express the class function $\bar{s}$ as a linear combination of irreducible $S_n$-characters. We provide such expressions for several commonly studied permutation statistics, including the excedance number, inversion number, descent number, major index and $k$-cycle number. In particular, this leads to formulae for the expected values of said statistics.

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Axel Hultman. 2013-01-03. Permutation statistics of products of random permutations. https://arxiv.org/abs/1301.0430

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