The Haglund–Morse–Zabrocki nabla conjecture for compositions

Let $c$ be a composition, let $\nabla$ be the nabla operator on symmetric functions, let $C_c=C_{c_1}\cdots C_{c_k}$ for $c=[c_1,\ldots,c_k]$, and let $\mathcal{A}_c$ be the set of parking functions with composition $c$. The Haglund–Morse–Zabrocki nabla conjecture.

$$\nabla C_c1=\sum_{PF\in\mathcal{A}_c}t^{\operatorname{area}(PF)}q^{\operatorname{dinv}(PF)}Q_{\operatorname{ides}(PF)}.$$

This conjecture connects the nabla action on modified Hall–Littlewood operator products with parking-function statistics and refines the shuffle-conjecture framework by composition. The source gives no resolution.