The qq-rious unimodality conjecture

From papers

Let (a,b)(\boldsymbol{a},\boldsymbol{b}) be tuples of positive integers satisfying Landau's criterion, namely

iaixjbjx0for all x0.\sum_i\lfloor a_i x\rfloor-\sum_j\lfloor b_j x\rfloor\geqslant 0 \quad\text{for all }x\geqslant 0.

Let D(a,b;q)D(\boldsymbol{a},\boldsymbol{b};q) be the corresponding qq-factorial quotient, and write its coefficients as D(a,b;q)=i=0kciqiD(\boldsymbol{a},\boldsymbol{b};q)=\sum_{i=0}^k c_iq^i. qq-rious unimodality conjecture. The polynomial

(1+q)D(a,b;q)(1+q)D(\boldsymbol{a},\boldsymbol{b};q)

is unimodal. This is proposed as a stronger statement implying the qq-rious positivity conjecture, in a setting where the coefficient sequence of D(a,b;q)D(\boldsymbol{a},\boldsymbol{b};q) is symmetric.

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Sources & referencesView supporting material

Primary source

S. Ole Warnaar and Wadim Zudilin, “q-rious unimodality”, arXiv:2502.03993 (2025).

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