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JOURNALS // Daghestan Electronic Mathematical Reports // Archive

Daghestan Electronic Mathematical Reports, 2016 Issue 6, Pages 31–60 (Mi demr28)

This article is cited in 7 papers

Systems of functions orthogonal with respect to scalar products of Sobolev type with discrete masses generated by classical orthogonal systems

I. I. Sharapudinovab, Z. D. Gadzhievaab, R. M. Gadzhimirzaeva

a Daghestan Scientific Centre of Russian Academy of Sciences
b Daghestan State Pedagogical University

Abstract: For some natural number $r$ and a given system of functions $\left\{\varphi_k(x)\right\}_{k=0}^\infty$, orthonormal on $(a, b)$ with weight $\rho(x)$, we construct the new system of functions $\left\{\varphi_{r,k}(x)\right\}_{k=0}^\infty$, orthonormal with respect to the Sobolev type inner product of the following form
\begin{equation*} \langle f,g\rangle=\sum_{\nu=0}^{r-1}f^{(\nu)}(a)g^{(\nu)}(a)+\int_{a}^{b} f^{(r)}(t)g^{(r)}(t)\rho(t) dt. \end{equation*}
The convergence of the Fourier series by the system $\left\{\varphi_{r,k}(x)\right\}_{k=0}^\infty$ is investigated. Moreover, we consider some important special cases of systems of such type and obtain explicit representations for them, which can be used in the study of asymptotic properties of functions $\varphi_{r,k}(x)$ when $k\to\infty$ and the approximative properties of Fourier sums by the system $\left\{\varphi_{r,k}(x)\right\}_{k = 0}^\infty$.

Keywords: orthogonal polynomials, Sobolev orthogonal polynomials, Haar system, Jacobi polynomials, Ñhebyshev polynomials of the first kind, Laguerre polynomials, Hermite polynomials.

UDC: 517.538

Received: 29.07.2016
Revised: 07.09.2016
Accepted: 08.09.2016

DOI: 10.31029/demr.6.3



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