Perturbations on the antidiagonals of Hankel matrices

Given a strongly regular Hankel matrix, and its associated sequence of moments whichdefines a quasi-definite moment linear functional, we study the perturbation of a fixedmoment, i.e., a perturbation of one antidiagonal of the Hankel matrix. We define a linearfunctional whose action results in such a perturbation and establish necessary and sufficientconditions in order to preserve the quasi-definite character. A relation between thecorresponding sequences of orthogonal polynomials is obtained, as well as the asymptoticbehavior of their zeros. We also study the invariance of the Laguerre-Hahn class of linearfunctionals under such perturbation, and determine its relation with the so-called canonicallinear spectral transformations.The research of the first author was supported by Bolsa de Atração de Jovens Talentos CAPES/CNPq/FAPs of Brazil, Project 370291/2013 1 and Dirección General de Investigación, Ministerio de Economía y Competitividad of Spain, Grant MTM2012 36732 C03 0

MONOTONICITY AND ASYMPTOTICS OF ZEROS OF LAGUERRE-SOBOLEV-TYPE ORTHOGONAL POLYNOMIALS OF HIGHER ORDER DERIVATIVES

In this paper we analyze the location of the zeros of polynomials orthogonal with respect to the inner product (0.1) 〈p, q 〉 = p(x)q(x)x 0 α e −x dx + Np (j) (0)q (j) (0), where α>−1, N ≥ 0, and j ∈ N. In particular, we focus our attention on their interlacing properties with respect to the zeros of Laguerre polynomials as well as on the monotonicity of each individual zero in terms of the mass N. Finally, we give necessary and sufficient conditions in terms of N in order for the least zero of any Laguerre-Sobolev-type orthogonal polynomial to be negative

Monotonicity of zeros of Jacobi-Sobolev type orthogonal polynomials

Consider the inner product = Gamma(alpha + beta + 2)/2(alpha+beta+1) Gamma (alpha + 1)Gamma(beta +1) integral(t)(-t) p(x)q(x)(alpha) (1 + x)(beta) dx+ Mp(1)q(1)+ Np'(1)q'(1) + 1 (M) over tildep(-1)q(-1)+ (N) over tildep'(-1)q'(-1)where alpha, beta > -1 and M,N,(M) over tilde,(N) over tilde >= 0. If mu = (M,N,(M) over tilde,(N) over tilde), we denote by x(n,k)(mu)(alpha,beta), k =1,...n, the zeros of the n-th polynomial P(n)((alpha,beta,mu)) (x), orthogonal with respect to the above inner product. We investigate the location, interlacing properties, asymptotics and monotonicity of x(n,k)(mu)(alpha,beta) with respect to the parameters M, N,(M) over tilde,(N) over tilde in two important cases, when either i = N = 0 or N = 0. The results are obtained through careful analysis of the behavior and the asymptotics of the zeros of polynomials of the form p,,(x)= hn(x) + cgn(x) as functions of(C) 2010 IMACS. Published by Elsevier BA/. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Interlacing of zeros of orthogonal polynomials under modification of the measure

We investigate the mutual location of the zeros of two families of orthogonal polynomials. One of the families is orthogonal with respect to the measure dμ (x), supported on the interval (a, b) and the other with respect to the measure |x -c|τ|x -d|γdμ (x), where c and d are outside (a, b) We prove that the zeros of these polynomials, if they are of equal or consecutive degrees, interlace when either 0 < τ, γ ≤ 1 or γ = 0 and 0 < τ ≤ 2. This result is inspired by an open question of Richard Askey and it generalizes recent results on some families of orthogonal polynomials. Moreover, we obtain further statements on interlacing of zeros of specific orthogonal polynomials, such as the Askey-Wilson ones. © 2013 Elsevier Inc

Monotonicity and asymptotics of zeros of Sobolev type orthogonal polynomials: A general case

We investigate the location, monotonicity, and asymptotics of the zeros of the polynomials orthogonal with respect to the Sobolev type inner product (lambda,c.j) = integral(b)(a) p(x)q(x)mu(x) + lambda p((j))(c)q((j))(c),where mu is a positive Borel measure, lambda >= 0, j is an element of Z(+), and c is not an element of (a, b). We prove that these zeros are monotonic function of the parameter A and establish their asymptotics when either lambda converges to zero or to infinity. The precise location of the extreme zeros is also analyzed. (c) 2012 IMACS. Published by Elsevier B.V. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Monotonicity of zeros of Jacobi polynomials

Denote by x(nk)(alpha, beta), k = 1...., n, the zeros of the Jacobi polynornial P-n((alpha,beta)) (x). It is well known that x(nk)(alpha, beta) are increasing functions of beta and decreasing functions of alpha. In this paper we investigate the question of how fast the functions 1 - x(nk)(alpha, beta) decrease as beta increases. We prove that the products t(nk)(alpha, beta) := f(n)(alpha, beta) (1 - x(nk)(alpha, beta), where f(n)(alpha, beta) = 2n(2) + 2n(alpha + beta + 1) + (alpha + 1)(beta + 1) are already increasing functions of beta and that, for any fixed alpha > - 1, f(n)(alpha, beta) is the asymptotically extremal, with respect to n, function of beta that forces the products t(nk)(alpha, beta) to increase. (c) 2007 Elsevier B.V. All rights reserved

INEQUALITIES FOR ZEROS of JACOBI POLYNOMIALS VIA OBRECHKOFF'S THEOREM

In this paper we obtain sharp limits for all the zeros of Jacobi polynomials. We employ Obrechkoff's theorem on generalized Descartes' rule of signs and certain elaborated connection formulae which involve Jacobi and Laguerre polynomials.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP