Panyushev's order conjecture for the positive Panyushev map

Let WW be a finite, crystallographic Coxeter group with Coxeter number hh, let mm be the parameter from the preceding theorem, and let P+{\sf P}_+ be the positive Panyushev map on NN+(W)N\kern-1ptN_+(W). Write R\mathcal{R} for the set of reflections, S\mathcal{S} for the set of simple reflections, ψ\psi for the relevant involution, and ε\varepsilon for the identity map. Panyushev's conjecture. The order of P+{\sf P}_+ is given by

ord⁡(P+)={(m+1)h−2,if ψ∣R∖S≢ε,(m+1)h/2−1,if ψ∣R∖S≡ε.{\operatorname{ord}}({\sf P}_+) = \begin{cases} (m+1)h - 2, & \text{if } \psi|_{\mathcal{R} \setminus \mathcal{S}} \text{${}\not\equiv{}$} \varepsilon, \\ (m+1)h/2 - 1, & \text{if } \psi|_{\mathcal{R} \setminus \mathcal{S}} \equiv \varepsilon. \end{cases}

This is the positive analogue of Panyushev's conjecture on the order of the Panyushev map, whose non-positive version was proved by Armstrong, Stump, and Thomas. The supplied text does not establish whether this positive version has been resolved.

References

Primary source

Christian Krattenthaler and Christian Stump, “Positive m-divisible non-crossing partitions and their Kreweras maps”, arXiv:2506.14996 (2025).

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