Brenti's total-positivity conjecture for the clean Eulerian triangle

At least 9 years old · documented by

Let A=(⟨nk⟩clean)n,k≥0\bm{A}=\left(\left\langle\begin{matrix}n\\k\end{matrix}\right\rangle^{\rm clean}\right)_{n,k\geq 0} be the clean Eulerian triangle, where ⟨nk⟩clean\left\langle\begin{matrix}n\\k\end{matrix}\right\rangle^{\rm clean} counts permutations of [n+1][n+1] with kk excedances (equivalently, kk descents), and satisfies

⟨nk⟩clean=(n−k+1)⟨n−1k−1⟩clean+(k+1)⟨n−1k⟩clean\left\langle\begin{matrix}n\\k\end{matrix}\right\rangle^{\rm clean}=(n-k+1)\left\langle\begin{matrix}n-1\\k-1\end{matrix}\right\rangle^{\rm clean}+(k+1)\left\langle\begin{matrix}n-1\\k\end{matrix}\right\rangle^{\rm clean}

for n≥1n\geq 1, with ⟨0k⟩clean=δk0\left\langle\begin{matrix}0\\k\end{matrix}\right\rangle^{\rm clean}=\delta_{k0}. Brenti's conjecture. The clean Eulerian triangle A\bm{A} is totally positive. The conjecture is presented as an open problem; the source states that no proof was known there.

References

Primary source

Xi Chen, Bishal Deb, Alexander Dyachenko, Tomack Gilmore and Alan D. Sokal, “Coefficientwise total positivity of some matrices defined by linear recurrences”, arXiv:2012.03629 (2020).

Additional references

4 papers in this index state this conjecture (2016–2020). The statement above is taken from the most recent of them; the others are arXiv:2006.14485, arXiv:1807.08658, arXiv:1601.05645.

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.