On the Best Approximation in the Mean by Algebraic Polynomials with Weight and the Exact Values of Widths for the Classes of Functions

  • S. B. Vakarchuk Днепропетр. ун-т им. А. Нобеля
  • A. V. Shvachko

Abstract

The exact value of the extremal characteristic

is obtained on the class L 2 r (D ρ ), where r ∈+; \( {D}_{\rho} = \sigma (x)\frac{d^2}{d{ x}^2}+\tau (x)\frac{d}{d x} \) , σ and τ are polynomials of at most the second and first degrees, respectively, ρ is a weight function, 0 < p ≤ 2, 0 < h < 1, λ n (ρ) are eigenvalues of the operator D ρ , φ is a nonnegative measurable and summable function (in the interval (a, b)) which is not equivalent to zero, Ω k,ρ is the generalized modulus of continuity of the k th order in the space L 2,ρ (a, b), and E n (f)2,ρ is the best polynomial approximation in the mean with weight ρ for a function f ∈ L 2,ρ (a, b). The exact values of widths for the classes of functions specified by the characteristic of smoothness Ω k,ρ and the K-functional \( \mathbb{K} \) m are also obtained.

Published
25.12.2013
How to Cite
VakarchukS. B., and ShvachkoA. V. “On the Best Approximation in the Mean by Algebraic Polynomials With Weight and the Exact Values of Widths for the Classes of Functions”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 65, no. 12, Dec. 2013, pp. 1604–1621, http://umj.imath.kiev.ua/index.php/umj/article/view/2540.
Section
Research articles