Dyck-path strengthening of the wreath conjecture

From papers

Let kk be a positive integer. Let Z2k+1\mathbb{Z}_{2k+1} be the integers modulo 2k+12k+1, let Dk\mathcal{D}_{k} be the set of Dyck kk-paths, and let CkC_k denote the kkth Catalan number. For a permutation π\pi of Z2k+1\mathbb{Z}_{2k+1}, let Fπ\mathcal{F}_{\pi} be its associated wreath.

Dyck-path strengthening. There exists a set Π={π1,π2,,πCk}\Pi=\{\pi_1,\pi_2,\ldots,\pi_{C_k}\} of CkC_k permutations of Z2k+1\mathbb{Z}_{2k+1}, each fixing 00, and a bijection φ:ΠDk\varphi:\Pi\to\mathcal{D}_k such that

Z2k+1(k)=i=1CkFπi,\mathbb{Z}_{2k+1}^{(k)}=\bigcup_{i=1}^{C_k}\mathcal{F}_{\pi_i},

and, for any ii and jj, the jjth step of φ(πi)\varphi(\pi_i) is a rise if and only if πi(j){1,2,,k}\pi_i(j)\in\{1,2,\ldots,k\}.

For n=2k+1n=2k+1, the original wreath conjecture requires CkC_k wreaths, and this statement strengthens it by indexing the wreaths with Dyck paths and prescribing the rise/value correspondence. The source reports computer verification for k4k\leq4, but no general proof.

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Primary source

Jan Petr and Pavel Turek, “Intervals in Dyck paths and the wreath conjecture”, arXiv:2501.07277 (2025).

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