Central limit conjecture for descents after stack-sorting

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For each n≥1n\geq 1, let DnD_n be the number of descents of the stack-sorted image of a uniformly random permutation in SnS_n, and define

Yn=Dn−(3−e)nn.Y_n=\frac{D_n-(3-e)n}{\sqrt{n}}.

Central limit conjecture. The sequence (Yn)n≥1(Y_n)_{n\geq 1} converges in distribution to a random variable YY such that

Y∼N(0,2+2e−e2).Y\sim N(0,2+2e-e^2).

The conjecture is motivated by the computed asymptotics of the first six central moments, which agree with those of an asymptotically normal distribution; its resolution is not given in the source.

References

Primary source

Colin Defant, “Troupes, Cumulants, and Stack-Sorting”, arXiv:2004.11367 (2022).

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