Some functions that generalize the Krall-Laguerre polynomials

Grunbaum, FA;Haine, Luc;Horozov, E.
(1999) Journal of Computational and Applied Mathematics — Vol. 106, n° 2, p. 271-297 (1999)

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Authors
  • Grunbaum, FA
    Author
  • Haine, LucUCLouvain
    Author
  • Horozov, E.
    Author
Abstract
Let L(alpha) be the (semi-infinite) tridiagonal matrix associated with the three-term recursion relation satisfied by the Laguerre polynomials, with weight function 1/Gamma(alpha+1)z(alpha)e(-z), alpha>-1, on the interval [0, infinity]. We show that, when alpha is a positive integer, by performing at most alpha successive Darboux transformations from L(alpha), we obtain orthogonal polynomials on [0, infinity] with 'weight distribution' 1/Gamma(alpha-k+1)z(alpha-k)e(-z) + Sigma(j=1)(k) s(j)delta((k-j))(z), with 1 less than or equal to k less than or equal to alpha. We prove that, as a consequence of the rational character of the Darboux factorization, these polynomials are eigenfunctions of a (finite order) differential operator. Our construction calls for a natural bi-infinite extension of these results with polynomials replaced by functions, of which the semi-infinite case is a limiting situation. (C) 1999 Elsevier Science B.V. All rights reserved.
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Grunbaum, F., Haine, L., & Horozov, E. (1999). Some functions that generalize the Krall-Laguerre polynomials. Journal of Computational and Applied Mathematics, 106(2), 271-297. https://doi.org/10.1016/S0377-0427(99)00069-2 (Original work published 1999)