Abstract
We investigate the zeros of a family of hypergeometric polynomials \(M_n(x;\beta ,c)=(\beta )_n\,{}_2F_1(-n,-x;\beta ;1-\frac{1}{c})\), \(n\in \mathbb N ,\) known as Meixner polynomials, that are orthogonal on \((0,\infty )\) with respect to a discrete measure for \(\beta >0\) and \(0<c<1.\) When \(\beta =-N\), \(N\in \mathbb N \) and \(c=\frac{p}{p-1}\), the polynomials \(K_n(x;p,N)=(-N)_n\,{}_2F_1(-n,-x;-N;\frac{1}{p})\), \(n=0,1,\ldots , N\), \(0<p<1\) are referred to as Krawtchouk polynomials. We prove results for the zero location of the orthogonal polynomials \(M_n(x;\beta ,c)\), \(c<0\) and \(n<1-\beta \), the quasi-orthogonal polynomials \(M_n(x;\beta ,c)\), \(-k<\beta <-k+1\), \(k=1,\ldots ,n-1\) and \(0<c<1\) or \(c>1,\) as well as the polynomials \(K_{n}(x;p,N)\) with non-Hermitian orthogonality for \(0<p<1\) and \(n=N+1,N+2,\ldots \). We also show that the polynomials \(M_n(x;\beta ,c)\), \(\beta \in \mathbb R \) are real-rooted when \(c\rightarrow 0\).
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Acknowledgments
The authors would like to thank Prof. Erik Koelink for the helpful comment and the anonymous referee for pertinent observations and remarks. The first two authors would like to thank the Institute for Biomathematics and Biometry at the Helmholtz Zentrum München for their support during a research visit.
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Research by K. Jordaan was partially supported by the National Research Foundation under grant number 2054423.
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Jooste, A., Jordaan, K. & Toókos, F. On the zeros of Meixner polynomials. Numer. Math. 124, 57–71 (2013). https://doi.org/10.1007/s00211-012-0504-6
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DOI: https://doi.org/10.1007/s00211-012-0504-6