The asymptotic consecutive-pattern distribution conjecture

For k3k\geq 3, let πSk\pi\in S_k be a consecutive pattern, let IZ+I\subseteq\mathbb{Z}^+ be finite, let Pπ(I,n)\mathcal{P}_{\pi}(I,n) be the set of permutations in SnS_n whose consecutive-pattern occurrence starting indices are exactly II, and write

pπ(I,n)=Pπ(I,n),pπ(n)=pπ(,n).p_{\pi}(I,n)=|\mathcal{P}_{\pi}(I,n)|,\qquad p_{\pi}(n)=p_{\pi}(\emptyset,n).

The asymptotic consecutive-pattern distribution conjecture. For any k3k\geq 3, any πSk\pi\in S_k, and any finite IZ+I\subseteq\mathbb{Z}^+, there are constants cπ,I,αRc_{\pi,I},\alpha\in\mathbb{R} with α>0\alpha>0 such that

pπ(I,n)=cπ,Ipπ(n)(1+O(nα)).p_{\pi}(I,n)=c_{\pi,I}p_{\pi}(n)\left(1+O\left(n^{-\alpha}\right)\right).

This conjectures that prescribing any finite set of consecutive-pattern occurrences changes the unrestricted count only by an asymptotically constant factor, with a power-saving error term. The source presents it as an analogue of an earlier theorem for decreasing patterns and states that the question remains open.

Sources & referencesView supporting material

Primary source

Kaarel Hänni, “Asymptotics of descent functions”, arXiv:2011.14360 (2020).

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