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Ariznabarreta, Gerardo and García Ardila, Juan and Mañas Baena, Manuel and Marcellan, Francisco (2019) Matrix biorthogonal polynomials on the real line: Geronimus transformations. Bulletin of mathematical sciences, 9 (2). ISSN 16643607

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Official URL: http://dx.doi.org/10.1142/S1664360719500073
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https://www.worldscientific.com/  Publisher 
Abstract
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 quasidefinite matrix of bivariate generalized functions with a welldefined 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 Christoffeltype formulas, which allow to express the perturbed matrix biorthogonal polynomials and its norms in terms of the original ones. The basic tool is the GaussBorel factorization of the Gram matrix, and particular attention is paid to the nonassociative character, in general, of the product of semiinfinite 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, ChristoffelGeronimus 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.
Item Type:  Article 

Additional Information:  © 2019 World Scientific Publishing Co Pte Ltd. 
Uncontrolled Keywords:  Valued orthogonal polynomials; Quasideterminant solutions; Darboux transformations; Determinants; Equations. 
Subjects:  Sciences > Physics > PhysicsMathematical models Sciences > Physics > Mathematical physics 
ID Code:  57186 
Deposited On:  04 Oct 2019 15:20 
Last Modified:  07 Oct 2019 07:26 
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