Bidiagonal matrix factorisations related to multiple orthogonal polynomials

Fuente: arXiv
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Autori principali: Branquinho, Amílcar, Díaz, Juan E. F., Foulquié-Moreno, Ana, Lima, Hélder, Mañas, Manuel
Natura: Preprint
Pubblicazione: 2024
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author Branquinho, Amílcar
Díaz, Juan E. F.
Foulquié-Moreno, Ana
Lima, Hélder
Mañas, Manuel
author_facet Branquinho, Amílcar
Díaz, Juan E. F.
Foulquié-Moreno, Ana
Lima, Hélder
Mañas, Manuel
contents We provide necessary and sufficient conditions for the Hessenberg recurrence matrix associated with a system of multiple orthogonal polynomials to admit a factorisation as a product of bidiagonal matrices. Using the Gauss-Borel factorisation of the moment matrix, we show that the nontrivial entries of those bidiagonal matrices can be expressed in terms of coefficients of type I or type II multiple orthogonal polynomials on the step-line with respect to the original system and its Christoffel transformations. Using the connection of multiple orthogonal polynomials with branched continued fractions, we show that the nontrivial entries of the bidiagonal matrices in the factorisation of the Hessenberg recurrence matrix correspond to the coefficients of a branched continued fraction associated with the given system of multiple orthogonal polynomials. As a case study, we present an explicit bidiagonal factorisation for the Hessenberg recurrence matrices of the Jacobi-Piñeiro polynomials and, as a limiting case, the multiple Laguerre polynomials of first kind.
format Preprint
id arxiv_https___arxiv_org_abs_2412_03694
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Bidiagonal matrix factorisations related to multiple orthogonal polynomials
Branquinho, Amílcar
Díaz, Juan E. F.
Foulquié-Moreno, Ana
Lima, Hélder
Mañas, Manuel
Classical Analysis and ODEs
15A23, 33C45, 42C05, 47B36. (Primary) 11J70, 33C20. (Secondary)
We provide necessary and sufficient conditions for the Hessenberg recurrence matrix associated with a system of multiple orthogonal polynomials to admit a factorisation as a product of bidiagonal matrices. Using the Gauss-Borel factorisation of the moment matrix, we show that the nontrivial entries of those bidiagonal matrices can be expressed in terms of coefficients of type I or type II multiple orthogonal polynomials on the step-line with respect to the original system and its Christoffel transformations. Using the connection of multiple orthogonal polynomials with branched continued fractions, we show that the nontrivial entries of the bidiagonal matrices in the factorisation of the Hessenberg recurrence matrix correspond to the coefficients of a branched continued fraction associated with the given system of multiple orthogonal polynomials. As a case study, we present an explicit bidiagonal factorisation for the Hessenberg recurrence matrices of the Jacobi-Piñeiro polynomials and, as a limiting case, the multiple Laguerre polynomials of first kind.
title Bidiagonal matrix factorisations related to multiple orthogonal polynomials
topic Classical Analysis and ODEs
15A23, 33C45, 42C05, 47B36. (Primary) 11J70, 33C20. (Secondary)
url https://arxiv.org/abs/2412.03694