Strong synchronisation of alternating-group descent enumerators

From papers

Let An\mathcal{A}_n be the alternating group in Sn\mathfrak{S}_n, and let An,k+A_{n,k}^+ and An,kA_{n,k}^- denote the numbers of permutations with kk descents in An\mathcal{A}_n and SnAn\mathfrak{S}_n\setminus\mathcal{A}_n, respectively. Two sequences are strongly synchronised when each corresponding pair of terms satisfies the synchronisation inequalities defining this relation.

Strong-synchronisation conjecture. For every positive integer nn, the sequences (An,k+)k=0n1(A_{n,k}^+)_{k=0}^{n-1} and (An,k)k=0n1(A_{n,k}^-)_{k=0}^{n-1} are strongly synchronised.

This conjecture would imply log-concavity of both descent enumerator sequences. The surrounding discussion also relates it to conjectures on real-rootedness of the alternating-group descent polynomials, but no resolution is supplied here.

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Sources & referencesView supporting material

Primary source

Hiranya Kishore Dey, “Log-concavity of the Excedance Enumerators in positive elements of Type A and Type B Coxeter Groups”, arXiv:2009.10655 (2020).

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