Heim–Neuhauser's log-concavity challenge for D'Arcais polynomials

From papers

Let Pnσ(X)=k=0npnσ(k)XkP_n^\sigma(X)=\sum_{k=0}^n p_n^\sigma(k)X^k be the D'Arcais polynomial defined by

m=1(1qm)X=n=0Pnσ(X)qn,\prod_{m=1}^\infty(1-q^m)^{-X}=\sum_{n=0}^\infty P_n^\sigma(X)q^n,

and call a sequence (ak)kN(a_k)_{k\in\mathbb{N}} log-concave at k1k\geq 1 when ak2ak1ak+1a_k^2\geq a_{k-1}a_{k+1}. Heim–Neuhauser's challenge. For every nNn\in\mathbb{N}, the sequence (pnσ(k))kN(p_n^\sigma(k))_{k\in\mathbb{N}} is log-concave at each k1k\geq 1. This is a proposed coefficient-growth property for the D'Arcais polynomials; the source supplies no resolution status.

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Sources & referencesView supporting material

Primary source

Johann Stumpenhusen, “On the Log-Concavity of the D'Arcais Polynomials for Normalised Functions”, arXiv:2607.14961 (2026).

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