Combinatorial formulas for the coefficients of the Al-Salam-Chihara polynomials
Abstract
The Al-Salam-Chihara polynomials are an important family of orthogonal polynomials in one variable x depending on 3 parameters α, β and q. They are closely connected to a model from statistical mechanics called the partially asymmetric simple exclusion process (PASEP) and they can be obtained as a specialization of the Askey-Wilson polynomials. We give two different combinatorial formulas for the coefficients of the (transformed) Al-Salam-Chihara polynomials. Our formulas make manifest the fact that the coefficients are polynomials in α, β and q with positive coefficients.
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