The touchpoint 4-variable Catalan conjecture

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Let Cat⁡n,r(q,t,z,w)\operatorname{Cat}_{n,r}(q,t,z,w) and Cat⁡n,r′(q,t,z,w)\operatorname{Cat}'_{n,r}(q,t,z,w) be the refinements of the 4-variable Catalan polynomials obtained by summing over Dyck paths of order nn with exactly rr rows of area zero, with the rise and valley products defined in the source. Let En,rE_{n,r} be the polynomials defined in the cited Schröder-path reference, and let f(z,w)∣zkwℓ\left.f(z,w)\right|_{z^kw^\ell} denote coefficient extraction. Touchpoint 4-variable Catalan conjecture. For integers n≥kn\geq k, ℓ,r≥0\ell,r\geq0,

Cat⁡n,r(q,t,z,w)∣zkwℓ=Cat⁡n,r′(q,t,z,w)∣zkwℓ\left.\operatorname{Cat}_{n,r}(q,t,z,w)\right|_{z^kw^\ell}=\left.\operatorname{Cat}'_{n,r}(q,t,z,w)\right|_{z^kw^\ell} =⟨Δhℓ∇En−ℓ,r,sk+1,1n−k−ℓ−1⟩=\left\langle\Delta_{h_\ell}\nabla E_{n-\ell,r},s_{k+1,1^{n-k-\ell-1}}\right\rangle =⟨ΔhℓΔen−k−ℓ−1′En−ℓ,r,en−ℓ⟩.=\left\langle\Delta_{h_\ell}\Delta'_{e_{n-k-\ell-1}}E_{n-\ell,r},e_{n-\ell}\right\rangle.

The source notes that the polynomials En,rE_{n,r} are defined externally and that the equalities refine the 4-variable Catalan conjecture according to returns to the diagonal; it does not provide a resolution.

References

Primary source

James Haglund, Jeffrey Remmel and Andrew Timothy Wilson, “The Delta Conjecture”, arXiv:1509.07058 (2017).

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