Application Of Orthogonal Polynomials Research Articles

Pastro polynomials and Sobolev-type orthogonal polynomials on the unit circle based on a q-difference operator

ABSTRACT Applications of orthogonal polynomials on the unit circle have attracted the attention of many researchers in recent years. Pastro polynomials, which are basic hypergeometric polynomials, are known to be biorthogonal polynomials on the unit circle. However, with special choice of parameters they provide one of the nicest examples of orthogonal polynomials on the unit circle. Our objective here is to consider some properties of three sequences of polynomials which are related to these Pastro orthogonal polynomials on the unit circle by a q-difference operator. We also provide information regarding connection formulas, bounds for the connection coefficients as well as outer relative asymptotics associated with these sequences of polynomials.

Applications of Orthogonal Polynomials in Simulations of Mass Transfer Diffusion Equation Arising in Food Engineering

In this paper, Chebyshev polynomials—which are ultraspherical in the first and second kind and hence symmetric, while the third and fourth order are not ultraspherical and are hence non-symmetric—are used for the simulation of two-dimensional mass transfer equation arising during the convective air drying processes of food products subject to Robin and Neumann boundary conditions. These simulations are used to improve the quality of dried food products and for prediction of the moisture distributions. The equation is discretized in both temporal and special variables by using the second order finite difference scheme and spectral method based on Chebyshev polynomial with the help of fast Fourier transform on tensor product grid, respectively. A system of algebraic equations is obtained after applying the proposed numerical scheme, which is then solved by an appropriate iterative method. The error analysis of the proposed scheme is provided. Some numerical examples are presented to confirm the numerical efficiency and theoretical justification of the proposed scheme. Our numerical scheme has an exponential rate of convergence, which means that one can achieve a very accurate solution using a few collocation points, as opposed to the other available techniques which are very slow in terms of convergence and consume a lot of time. In order to further validate the accuracy of our numerical method, a comparison is made with the exact solution using different norms.

Application of orthogonal polynomials for analysis of input numerical data in the problems of mass transfer

The investigations of the spectral methods are represented for solving applied tasks, in particular, the processing of digital information (problem of approximation, compression of information, filtration of signals, determination of nature of physical process which is modeled), also imposition of boundary conditions for the formulated problems of mathematical physics, etc. The essence of these methods consists in representation of known and required functions by orthogonal series in the chosen bases and construction of the algorithms for calculation of coefficients of these series (the generalized spectra). The methods of these calculation depend on the type of input information (analytic or discrete types). Approximation method for functions of two variables in domains of noncanonical form is suggested. Дослiджено спектральнi методи розв’язування прикладних задач, зокрема обробка цифрової iнформацiї (задачi апроксимацiї, стиску iнформацiї, фiльтрацiї сигналiв), визначення характеру фiзичного процесу, який моделюється, та побудови крайових умов пiд час формулювання задач математичної фiзики тощо. Суть цих методiв полягає в поданнi вiдомих i шуканих функцiй ортогональними рядами у вибраних базисах i побудовi алгоритмiв для обчислення коефiцiєнтiв цих рядiв (узагальнених спектрiв). Методи їх обчислення залежать вiд способу задання вхiдної iнформацiї (в дискретному або аналiтичному видах). Запропоновано спосiб апроксимацiї функцiй двох змiнних в областях неканонiчної форми.

Orthogonal polynomials, special functions and mathematical physics

In the 6th Int. Symposium on OPSFA there were several communications dealing with concrete applications of orthogonal polynomials to experimental and theoretical physics, chemistry, biology and statistics. Here I make suggestions concerning the use of powerful apparatus of orthogonal polynomials and special functions in several lines of research in mathematical physics

Complex Jacobi matrices and quadrature rules

Given any sequence of orthogonal polynomials, satisfying the three term recurrence relation xpn(x) = ?n+1pn+1(x) + ?npn(x) + ?npn-1(x), p-1(x)=0 po(x)=1 with ?n ? 0, n ? N, ?0 = 1, an infinite Jacobi matrix can be associated in the following way ? ? ??0 ?1 0...? ? ? ??1 ?1 ?2...? ? ? J = ?0 ?2 ?2...? ?.... ? ?.... ? ?....? ? ? In the general case if the sequences {?n} or {?n} are complex the associated Jacobi matrix is complex. Under the condition that both sequences {?n}and {?n} are uniformly bounded, the associated Jacobi matrix can be understood as a linear operator J acting on ?2, the space of all complex square-summable sequences, where the value of the operator J at the vector x is a product of an infinite vector x and an infinite matrix J in the matrix sense. The case when the sequences {?n} and {?n} are not uniformly bounded, an operator acting on ?2 can not be defined that easily. Additional properties of the sequence of orthogonal polynomials are needed in order to be able to define the operator uniquely. The case when the sequences ?n and ?n are real is very well understood. The spectra of the Jacobi matrix J equals the support of the measure of orthogonality for the given sequence of orthogonal polynomials. All zeros of orthogonal polynomials are real, simple and interlace, contained in the convex hull of the spectra of the Jacobi operator associated with the infinite Jacobi matrix J. Every point in ?(J) attracts zeros of orthogonal polynomials. An application of orthogonal polynomials is the construction of quadrature rules for the approximation of integration with respect to the measure of orthogonality. For arbitrary sequences {?n} and {?n} the situation is changed dramatically. Zeros of orthogonal polynomials need not be simple; they are not real and they do not necessarily lie in the convex hull of ?(J). There is also a little known about convergence results of related quadrature rule. Only in recent years a connection between complex Jacobi matrices and related orthogonal polynomials is interesting again (see [2]). Studies of complex Jacobi operators should lead to a better understanding of related orthogonal polynomials, but also the study of orthogonal polynomials with the complex Jacobi matrices should put more light on the non-hermitian banded symmetric matrices. In this lecture some results are given about complex Jacobi matrices and related quadrature rules, and also some interesting examples are presented.

Application of Orthogonal Polynomials to Diffraction Problems

Application of Orthogonal Polynomials to Diffraction Problems

New applications of orthogonal polynomials to some problem of the antennas theory

In this paper we show that orthogonal polynomials can be applied to study some old and new problems of the antennas theory. Some new approaches to the applications of orthogonal polynomials to the antennas theory is considered.

Summation of slowly convergent series

Among the applications of orthogonal polynomials described briefly on my previous visit to this Center [9, §3.2] were slowly convergent series whose terms could be represented in terms of the Laplace transform at integer arguments. We proposed to sum such

An approximate analysis of transient response of time-dependent linear systems by use of orthogonal polynomials

The paper deals with the approximate analysis of second order linear systems with variable coefficients through the application of orthogonal polynomials. The time-dependent functions appearing as coefficients in the system equations may be periodic, non-periodic or can have multiple turning points. These variable coefficients are replaced by simple functions, viz. a constant, a linear or a quadratic function, and orthogonal polynomial expansions are used in the desired time interval, such that the approximate differential equations thus obtained have known closed form solutions. In particular, expansions in ultraspherical polynomials have been treated in detail, which include the Chebyshev and Legendre polynomials as special cases. If the time-function is approximated by a constant, the approximate solutions are the sine and cosine functions, while a linear approximation leads to a solution in terms of Bessel functions of 1 3 order or Airy functions. The quadratic approximation of the function results in Weber's equations and the solutions are parabolic cylindrical functions. In the case of periodic coefficients, the functions are approximated such that the periods of the original and the approximate functions remain the same. The method has been applied to an equation with two turning points and to Mathieu's equation and the results are compared with numerical solutions. The well-known WKBJ results are also presented for comparison. Results obtained by the present approach agree with numerical solutions to a better accuracy depending on the choice of orthogonal polynomials used in the expansions. Moreover, in the case of turning point problems the approach is simpler as compared to other methods available in the literature and uniformly valid solutions are obtained without any difficulty.

The application of orthogonal polynomials to cubature formulae

The application of orthogonal polynomials to cubature formulae