Infinite q-log-convexity of the polynomial sequences in Example basic-qSM

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Let {fi(q)}i≥0\{f_i(q)\}_{i\geq 0} be any of the polynomial sequences defined in Example basic-qSM\mathrm{basic\text{-}qSM}. A sequence is infinitely qq-log-convex if every iterate under

L{fi(q)}i≥0={fi−1(q)fi+1(q)−fi(q)2}i≥1\mathcal{L}\{f_i(q)\}_{i\geq 0}=\{f_{i-1}(q)f_{i+1}(q)-f_i(q)^2\}_{i\geq 1}

has coefficientwise nonnegative polynomials. The infinite qq-log-convexity conjecture. Every sequence of polynomials in Example basic-qSM\mathrm{basic\text{-}qSM} is infinitely qq-log-convex. The paper notes that these sequences are already known to be 33-qq-log-convex and, for fixed nonnegative real qq, infinitely log-convex; the infinite qq-analogue remains proposed for further research.

References

Primary source

Bao-Xuan Zhu, “Positivity of iterated sequences of polynomials”, arXiv:1807.01062 (2018).

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