RUS  ENG
Full version
JOURNALS // Vladikavkazskii Matematicheskii Zhurnal // Archive

Vladikavkaz. Mat. Zh., 2022 Volume 24, Number 2, Pages 101–116 (Mi vmj817)

Approximation properties of polynomials $\hat{l}_{n,n}^\alpha(x),$ orthogonal on any sets

Z. M. Magomedovaa, A. A. Nurmagomedovb

a Branch of the Russian State University of Tourism and Service, 401 A--G. Akushinsky Ave., Makhachkala 367000, Russia
b M. M. Dzhambulatov Dagestan State Agrarian University, 180 M. Gadzhiev St., Makhachkala 367032, Russia

Abstract: Let $\Omega=\{x_0, x_1, \dots, x_j, \dots\}$ — discrete system of points such that $0=x_0<x_1<{x_2< \dots<x_j< \dots,}$ $\lim_{j\rightarrow\infty}x_j=+\infty$ and $\Delta{x_j}=x_{j+1}-x_j$, $\delta=\sup_{0\leq j<\infty}\Delta x_j<\infty,N=1/\delta.$ Asymptotic properties of polynomials $\hat{l}_{n,N}^\alpha(x)$ orthogonal with weight $\rho_1^\alpha(x_j)=e^{-x_j}(x_{j+1}^{\alpha+1}-x_j^{\alpha+1})/(\alpha+1)$ in the case $-1<\alpha\leq 0$ and $\rho_2^\alpha(x_j)=e^{-x_{j+1}}(x_{j+1}^{\alpha+1}-x_j^{\alpha+1}/(\alpha+1)$ in the case $\alpha>0$ on arbitrary grids consisting of an infinite many points on the semi-axis $[0, +\infty)$ are investigated. Namely an asymptotic formula is proved in which asymptotic behavior of these polynomials as $n$ tends to infinity together with $N$ is closely related to asymptotic behavior of the orthonormal Laguerre polynomials $\hat{L}_n^\alpha(x).$

Key words: polynomial, orthogonal system, set, weight, asymptotic formula.

UDC: 517.5

MSC: 33C45, 42Ñ05

Received: 08.12.2020

DOI: 10.46698/g5860-8517-3109-i



Bibliographic databases:


© Steklov Math. Inst. of RAS, 2025