Conjectured chain decomposition of Dyck partitions

Fix kk and let λPar(k)\lambda\in\operatorname{Par}(k). A Dyck partition is a partition equipped with the Dyck-partition structure used in the paper; dpk(dyck(λ))\operatorname{dp}_k(\operatorname{dyck}(\lambda)) is the Dyck partition associated with λ\lambda. For a Dyck partition γ\gamma, R(γ)={νm(γ):0mρ(γ)}R(\gamma)=\{\nu^m(\gamma):0\leq m\leq\rho(\gamma)\} is its associated chain, and Δ\Delta and defc\operatorname{defc} are the paper's statistics.

Conjectured chain decomposition. There exists a sequence of Dyck partitions {γλ,i:iZ>0}\{\gamma_{\lambda,i}:i\in\mathbb{Z}_{>0}\} with strictly increasing sizes satisfying all five stated conditions: it contains dpk(dyck(λ))\operatorname{dp}_k(\operatorname{dyck}(\lambda)); its Δ\Delta values are weakly decreasing and then weakly increasing; all its elements have constant deficit statistic equal to

r=1(λ)1(1+λr)s=r+1(λ)λs;\sum_{r=1}^{\ell(\lambda)-1}(-1+\lambda_r)\sum_{s=r+1}^{\ell(\lambda)}\lambda_s;

for every dγλ,1d\geq|\gamma_{\lambda,1}|, exactly one element of the union of their chains has size dd; and the corresponding unions for λ\lambda and λ\lambda' are nn-opposite in every size nn.

This conjecture is presented as a stronger structural generalization of the hook and almost-hook results. Its general validity is not established in the supplied text.

Sources & referencesView supporting material

Primary source

Kyungyong Lee, Li Li and Nicholas A. Loehr, “A Combinatorial Approach to the Symmetry of q,t-Catalan Numbers”, arXiv:1602.01126 (2016).

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