Matrix biorthogonal polynomials on the real line: Geronimus transformations
In this paper, Geronimus transformations for matrix orthogonal polynomials in the real line are studied. The orthogonality is understood in a broad sense, and is given in terms of a nondegenerate continuous sesquilinear form, which in turn is determined by a quasi-definite matrix of bivariate genera...
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World Scientific Publishing
2019-08-01
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| Series: | Bulletin of Mathematical Sciences |
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| Online Access: | http://www.worldscientific.com/doi/pdf/10.1142/S1664360719500073 |
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| author | Gerardo Ariznabarreta Juan C. García-Ardila Manuel Mañas Francisco Marcellán |
| author_facet | Gerardo Ariznabarreta Juan C. García-Ardila Manuel Mañas Francisco Marcellán |
| author_sort | Gerardo Ariznabarreta |
| collection | DOAJ |
| description | In this paper, Geronimus transformations for matrix orthogonal polynomials in the real line are studied. The orthogonality is understood in a broad sense, and is given in terms of a nondegenerate continuous sesquilinear form, which in turn is determined by a quasi-definite matrix of bivariate generalized functions with a well-defined support. The discussion of the orthogonality for such a sesquilinear form includes, among others, matrix Hankel cases with linear functionals, general matrix Sobolev orthogonality and discrete orthogonal polynomials with an infinite support. The results are mainly concerned with the derivation of Christoffel-type formulas, which allow to express the perturbed matrix biorthogonal polynomials and its norms in terms of the original ones. The basic tool is the Gauss–Borel factorization of the Gram matrix, and particular attention is paid to the non-associative character, in general, of the product of semi-infinite matrices. The Geronimus transformation in which a right multiplication by the inverse of a matrix polynomial and an addition of adequate masses are performed, is considered. The resolvent matrix and connection formulas are given. Two different methods are developed. A spectral one, based on the spectral properties of the perturbing polynomial, and constructed in terms of the second kind functions. This approach requires the perturbing matrix polynomial to have a nonsingular leading term. Then, using spectral techniques and spectral jets, Christoffel–Geronimus formulas for the transformed polynomials and norms are presented. For this type of transformations, the paper also proposes an alternative method, which does not require of spectral techniques, that is valid also for singular leading coefficients. When the leading term is nonsingular, a comparison of between both methods is presented. The nonspectral method is applied to unimodular Christoffel perturbations, and a simple example for a degree one massless Geronimus perturbation is given. |
| first_indexed | 2024-04-13T23:06:06Z |
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| issn | 1664-3607 1664-3615 |
| language | English |
| last_indexed | 2024-04-13T23:06:06Z |
| publishDate | 2019-08-01 |
| publisher | World Scientific Publishing |
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| series | Bulletin of Mathematical Sciences |
| spelling | doaj.art-5723753d857240999756c66ba5bba79b2022-12-22T02:25:41ZengWorld Scientific PublishingBulletin of Mathematical Sciences1664-36071664-36152019-08-01921950007-11950007-6810.1142/S166436071950007310.1142/S1664360719500073Matrix biorthogonal polynomials on the real line: Geronimus transformationsGerardo Ariznabarreta0Juan C. García-Ardila1Manuel Mañas2Francisco Marcellán3Departamento de Física Teórica II (Métodos Matemáticos de la Física), Universidad Complutense de Madrid, Ciudad Universitaria, Plaza de Ciencias 1, 28040 Madrid, SpainDepartamento de Matemáticas, Universidad Carlos III de Madrid, Avd/Universidad 30, 28911 Leganés, SpainDepartamento de Física Teórica II (Métodos Matemáticos de la Física), Universidad Complutense de Madrid, Ciudad Universitaria, Plaza de Ciencias 1, 28040 Madrid, SpainDepartamento de Matemáticas, Universidad Carlos III de Madrid, Avd/Universidad 30, 28911 Leganés, SpainIn this paper, Geronimus transformations for matrix orthogonal polynomials in the real line are studied. The orthogonality is understood in a broad sense, and is given in terms of a nondegenerate continuous sesquilinear form, which in turn is determined by a quasi-definite matrix of bivariate generalized functions with a well-defined support. The discussion of the orthogonality for such a sesquilinear form includes, among others, matrix Hankel cases with linear functionals, general matrix Sobolev orthogonality and discrete orthogonal polynomials with an infinite support. The results are mainly concerned with the derivation of Christoffel-type formulas, which allow to express the perturbed matrix biorthogonal polynomials and its norms in terms of the original ones. The basic tool is the Gauss–Borel factorization of the Gram matrix, and particular attention is paid to the non-associative character, in general, of the product of semi-infinite matrices. The Geronimus transformation in which a right multiplication by the inverse of a matrix polynomial and an addition of adequate masses are performed, is considered. The resolvent matrix and connection formulas are given. Two different methods are developed. A spectral one, based on the spectral properties of the perturbing polynomial, and constructed in terms of the second kind functions. This approach requires the perturbing matrix polynomial to have a nonsingular leading term. Then, using spectral techniques and spectral jets, Christoffel–Geronimus formulas for the transformed polynomials and norms are presented. For this type of transformations, the paper also proposes an alternative method, which does not require of spectral techniques, that is valid also for singular leading coefficients. When the leading term is nonsingular, a comparison of between both methods is presented. The nonspectral method is applied to unimodular Christoffel perturbations, and a simple example for a degree one massless Geronimus perturbation is given.http://www.worldscientific.com/doi/pdf/10.1142/S1664360719500073Matrix biorthogonal polynomialsspectral theory of matrix polynomialsquasi-definite matrix of generalized kernelsnondegenerate continuous sesquilinear formsGauss–Borel factorizationmatrix Geronimus transformationsmatrix linear spectral transformationsChristoffel-type formulasquasideterminantsspectral jetsunimodular matrix polynomials |
| spellingShingle | Gerardo Ariznabarreta Juan C. García-Ardila Manuel Mañas Francisco Marcellán Matrix biorthogonal polynomials on the real line: Geronimus transformations Bulletin of Mathematical Sciences Matrix biorthogonal polynomials spectral theory of matrix polynomials quasi-definite matrix of generalized kernels nondegenerate continuous sesquilinear forms Gauss–Borel factorization matrix Geronimus transformations matrix linear spectral transformations Christoffel-type formulas quasideterminants spectral jets unimodular matrix polynomials |
| title | Matrix biorthogonal polynomials on the real line: Geronimus transformations |
| title_full | Matrix biorthogonal polynomials on the real line: Geronimus transformations |
| title_fullStr | Matrix biorthogonal polynomials on the real line: Geronimus transformations |
| title_full_unstemmed | Matrix biorthogonal polynomials on the real line: Geronimus transformations |
| title_short | Matrix biorthogonal polynomials on the real line: Geronimus transformations |
| title_sort | matrix biorthogonal polynomials on the real line geronimus transformations |
| topic | Matrix biorthogonal polynomials spectral theory of matrix polynomials quasi-definite matrix of generalized kernels nondegenerate continuous sesquilinear forms Gauss–Borel factorization matrix Geronimus transformations matrix linear spectral transformations Christoffel-type formulas quasideterminants spectral jets unimodular matrix polynomials |
| url | http://www.worldscientific.com/doi/pdf/10.1142/S1664360719500073 |
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