Conjectured chain decomposition of Dyck partitions

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Fix kk and let λ∈Par⁡(k)\lambda\in\operatorname{Par}(k). A Dyck partition is a partition equipped with the Dyck-partition structure used in the paper; dp⁡k(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):0≤m≤ρ(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:i∈Z>0}\{\gamma_{\lambda,i}:i\in\mathbb{Z}_{>0}\} with strictly increasing sizes satisfying all five stated conditions: it contains dp⁡k(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=1ℓ(λ)−1(−1+λr)∑s=r+1ℓ(λ)λs;\sum_{r=1}^{\ell(\lambda)-1}(-1+\lambda_r)\sum_{s=r+1}^{\ell(\lambda)}\lambda_s;

for every d≥∣γλ,1∣d\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.

References

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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