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arXiv · 1508.07637

Explicit Expressions for the Variance and Higher Moments of the Size of a Simultaneous Core Partition and its Limiting Distribution

Shalosh B. Ekhad·Doron Zeilberger
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Abstract

Jaclyn Anderson proved that if s and t are relatively prime positive integers, then there are exactly (s+t-1)!/(s!t!) partitions whose set of hook-lengths is disjoint from the set {s,t}. Drew Armstrong conjectured (and Paul Johnson, and a bit later, Victor Wang, proved) a beautiful expression for the average size, namely (s-1)(t-1)(s+t+1)/24 . In the present article, we go far beyond the average, and state absolutely certain expressions (but "officially" still conjectures) for the variance (showing in particular that it is rather large, and there is no "concentration about the mean"), and the third through the sixth moments. For the special case of (s,s+1)-core partitions, we go all the way to the 9th moment. We pose two challenges, and will be glad to donate 100 dollars each, to the OEIS foundation in honor of the first provers, regarding a "soft" and "global", yet rigorous, justification of our empirical approach, and for proving an intriguing conjecture about the limiting distribution. This version reports (thanks to Marko Thiel and Nathan Williams) that the second challenge mentioned above has been done by Paul Johnson (but not in two pages). A donation to the OEIS was made. The first challenge is still wide open.

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Shalosh B. Ekhad, Doron Zeilberger. 2015-09-01. Explicit Expressions for the Variance and Higher Moments of the Size of a Simultaneous Core Partition and its Limiting Distribution. https://arxiv.org/abs/1508.07637

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