45 research outputs found
Orthogonal Polynomials on the Unit Ball and Fourth-Order Partial Differential Equations
The purpose of this work is to analyse a family of mutually orthogonal
polynomials on the unit ball with respect to an inner product which includes an
additional term on the sphere. First, we will get connection formulas relating
classical multivariate orthogonal polynomials on the ball with our family of
orthogonal polynomials. Then, using the representation of these polynomials in
terms of spherical harmonics, algebraic and differential properties will be
deduced
Multivariate Orthogonal Polynomials and Modified Moment Functionals
Multivariate orthogonal polynomials can be introduced by using a moment
functional defined on the linear space of polynomials in several variables with
real coefficients. We study the so-called Uvarov and Christoffel modifications
obtained by adding to the moment functional a finite set of mass points, or by
multiplying it times a polynomial of total degree 2, respectively. Orthogonal
polynomials associated with modified moment functionals will be studied, as
well as the impact of the modification in useful properties of the orthogonal
polynomials. Finally, some illustrative examples will be given
Perturbations in the Nevai matrix class of orthogonal matrix polynomials
24 pages, no figures.-- MSC2000 codes: 15A54, 15A21, 42C05.MR#: MR1855403 (2002i:42037)Zbl#: Zbl 0992.15022In this paper we study a Jacobi block matrix and the behavior of the limit of its entries when a perturbation of its spectral matrix measure by the addition of a Dirac delta matrix measure is introduced.The work of the second author was supported by Dirección General de Enseñanza Superior (DGES) of Spain under grant PB96-0120-CO3-01 and INTAS Project INTAS-93-0219 Ext, and the work of the third author was supported by DGES under grant PB 95-1205, INTAS-93-0219-ext and Junta de Andalucía, Grupo de Investigación FQM 229.Publicad
What is beyond coherent pairs of orthogonal polynomials?
AbstractUsually, coherent pairs of orthogonal polynomials have been considered in the wider context of Sobolev orthogonality. In this paper, we focus our attention on the problem of coherence between two orthogonal polynomial sequences in terms of the corresponding linear functionals. We deduce some conditions about the linear functionals in order that the corresponding orthogonal polynomial sequences constitute a coherent pair
An asymptotic result for Laguerre-Sobolev orthogonal polynomials
AbstractLet {Sn} denote the sequence of polynomials orthogonal with respect to the Sobolev inner product (f,g)s = ∫0+∞ f(x)g(x)xαe−xdx+λ∫0+∞ f′(x)g′(x)xαe−xdx where α > − 1, λ > 0 and the leading coefficient of the Sn is equal to the leading coefficient of the Laguerre polynomial Ln(α). Then, if x∈Cß[0,+∞), limn→∞Sn(x)Ln(α−1)(x) is a constant depending on λ
Lax-type pairs in the theory of bivariate orthogonal polynomials
Sequences of bivariate orthogonal polynomials written as vector polynomials
of increasing size satisfy a couple of three term relations with matrix
coefficients. In this work, introducing a time-dependent parameter, we analyse
a Lax-type pair system for the coefficients of the three term relations. We
also deduce several characterizations relating the Lax-type pair, the shape of
the weight, Stieltjes function, moments, a differential equation for the
weight, and the bidimensional Toda-type systems