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arXiv · 1806.10362

Intervals of permutations and the principal M\"{o}bius function

Robert Brignall·David Marchant
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Abstract

We show that the proportion of permutations of length $n$ with principal M\"{o}bius function equal to zero, $Z(n)$, is asymptotically bounded below by 0.3995. If a permutation $\pi$ contains two intervals of length 2, where one interval is an ascent and the other a descent, then we show that the value of the principal M\"{o}bius function $\mu [1, \pi]$ is zero, and we use this result to find the lower bound for $Z(n)$. We also show that if a permutation $\phi$ has certain properties, then any permutation $\pi$ which contains an interval order-isomorphic to $\phi$ has $\mu[1, \pi] = 0$.

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Robert Brignall, David Marchant. 2018-06-27. Intervals of permutations and the principal M\"{o}bius function. https://arxiv.org/abs/1806.10362

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