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SIGMA, 2025 Volume 21, 083, 19 pp. (Mi sigma2199)

$q$-Hypergeometric Orthogonal Polynomials with $q=-1$

Luis Verde-Star

Department of Mathematics, Universidad Autónoma Metropolitana, Iztapalapa, Mexico City, Mexico

Abstract: We obtain some properties of a class $\mathcal{A}$ of $q$-hypergeometric orthogonal polynomials with $q=-1$, described by a uniform parametrization of the recurrence coefficients. We construct a class $\mathcal{C}$ of complementary $-1$ polynomials by means of the Darboux transformation with a shift. We show that our classes contain the Bannai–Ito polynomials and their complementary polynomials and other known $-1$ polynomials. We introduce some new examples of $-1$ polynomials and also obtain matrix realizations of the Bannai–Ito algebra.

Keywords: hypergeometric orthogonal polynomials, recurrence coefficients, $-1$ orthogonal polynomials, Bannai–Ito polynomials, Bannai–Ito algebra.

MSC: 33C45, 33D45

Received: October 31, 2024; in final form September 18, 2025; Published online October 2, 2025

Language: English

DOI: 10.3842/SIGMA.2025.083


ArXiv: 2410.14068


© Steklov Math. Inst. of RAS, 2025