Abstract
First we show that the quadratic decomposition of the Appell polynomials with respect to the q-divided difference operator is supplied by two other Appell sequences with respect to a new operator \(\mathcal{M}_{q;q^{-\varepsilon}}\), where ε represents a complex parameter different from any negative even integer number. While seeking all the orthogonal polynomial sequences invariant under the action of \(\mathcal{M}_{\sqrt{q};q^{-\varepsilon/2}}\) (the \(\mathcal{M}_{\sqrt{q};q^{-\varepsilon/2}}\)-Appell), only the Wall q-polynomials with parameter q ε/2+1 are achieved, up to a linear transformation. This brings a new characterization of these polynomial sequences.
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The first author was supported in part by FCT-Portugal through the Centro de Matemática da Universidade do Porto.
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Loureiro, A.F., Maroni, P. Around q-Appell polynomial sequences. Ramanujan J 26, 311–321 (2011). https://doi.org/10.1007/s11139-011-9336-8
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DOI: https://doi.org/10.1007/s11139-011-9336-8
Keywords
- Orthogonal polynomials
- Appell sequences
- Lowering operators
- q-derivative
- Hahn’s operator
- Quadratic decomposition