Strong coefficientwise Hankel-total positivity conjecture for the GKP recurrence

About 6 years old · traced to

Let T(n,k)T(n,k) be defined by the shifted GKP recurrence

T(n,k)=[α~(n−1)+β~k+γ~]T(n−1,k)+[α~′(n−1)+β~′(k−1)+γ~′]T(n−1,k−1),T(n,k)=[\widetilde{\alpha}(n-1)+\widetilde{\beta}k+\widetilde{\gamma}]T(n-1,k)+[\widetilde{\alpha}'(n-1)+\widetilde{\beta}'(k-1)+\widetilde{\gamma}']T(n-1,k-1),

and let Pn(x;μ~)P_n(x;\widetilde{\bm{\mu}}) be its row-generating polynomials, where μ~=(α~,β~,γ~,α~′,β~′,γ~′)\widetilde{\bm{\mu}}=(\widetilde{\alpha},\widetilde{\beta},\widetilde{\gamma},\widetilde{\alpha}',\widetilde{\beta}',\widetilde{\gamma}'). A sequence is coefficientwise Hankel-totally positive when every minor of its Hankel matrix has nonnegative coefficients in the indicated indeterminates.

Strong coefficientwise Hankel-total positivity conjecture for the GKP recurrence. The sequence

P=(Pn(x;μ~))n≥0\bm{P}=(P_n(x;\widetilde{\bm{\mu}}))_{n\geq 0}

of row-generating polynomials of this shifted recurrence is coefficientwise Hankel-totally positive, jointly in the seven indeterminates x,α~,β~,γ~,α~′,β~′,γ~′x,\widetilde{\alpha},\widetilde{\beta},\widetilde{\gamma},\widetilde{\alpha}',\widetilde{\beta}',\widetilde{\gamma}'.

This is presented as a stronger version of the unshifted GKP positivity conjecture, obtained by an affine reparametrization, and remains unproved in the supplied text.

References

Primary source

Jesús Salas and Alan D. Sokal, “The Graham–Knuth–Patashnik recurrence: Symmetries and continued fractions”, arXiv:2008.03070 (2021).

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.