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Izvestiya: Mathematics, 1998, Volume 62, Issue 6, Pages 1095–1119
DOI: https://doi.org/10.1070/im1998v062n06ABEH000219
(Mi im219)
 

This article is cited in 11 scientific papers (total in 11 papers)

An exact Jackson–Stechkin inequality for $L^2$-approximation on the interval with the Jacobi weight and on projective spaces

A. G. Babenko

Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences
References:
Abstract: Let $L^2_{\alpha,\beta}$ be the Hilbert space of real-valued functions on $[0,\pi]$ with scalar product
$$ (F,G)=\int_{0}^{\pi}F(x)G(x)\biggl(\sin\dfrac{x}{2}\biggr)^{2\alpha+1} \biggl(\cos\dfrac{x}{2}\biggr)^{2\beta+1}\,dx,\qquad \alpha>-1,\quad \beta>-1, $$
and norm $\|F\|=(F,F)^{1/2}$. We prove in the case when $\alpha>\beta\geqslant-1/2$ the following exact Jackson–Stechkin inequality
$$ E_{n-1} (F)\leqslant\omega_r\bigl(F,2x_{n}^{\alpha,\beta}\bigr),\quad F\in L^2_{\alpha,\beta}, $$
between the best of $F$ by cosine-polynomials of order $n-1$ and its generalized modulus of continuity of (real) order $r\geqslant 1$: $n\geqslant\max\bigl\{2,1+ \frac{\alpha-\beta}{2}\bigr\}$ if $\beta>-\frac12$ , $n\geqslant 1$ if $\beta=-\frac12$ , where $x_{n}^{\alpha,\beta}$ is the first positive zero of the Jacobi cosine-polynomial $P_{n}^{(\alpha,\beta)}(\cos x)$. We deduce from this inequality similar inequalities for mean-square approximations of functions of several variables given on projective spaces.
Received: 30.09.1997
Bibliographic databases:
Language: English
Original paper language: Russian
Citation: A. G. Babenko, “An exact Jackson–Stechkin inequality for $L^2$-approximation on the interval with the Jacobi weight and on projective spaces”, Izv. Math., 62:6 (1998), 1095–1119
Citation in format AMSBIB
\Bibitem{Bab98}
\by A.~G.~Babenko
\paper An exact Jackson--Stechkin inequality for $L^2$-approximation on the interval with the Jacobi weight and on projective spaces
\jour Izv. Math.
\yr 1998
\vol 62
\issue 6
\pages 1095--1119
\mathnet{http://mi.mathnet.ru//eng/im219}
\crossref{https://doi.org/10.1070/im1998v062n06ABEH000219}
\mathscinet{http://mathscinet.ams.org/mathscinet-getitem?mr=1680874}
\zmath{https://zbmath.org/?q=an:0938.41015}
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\elib{https://elibrary.ru/item.asp?id=13284655}
\scopus{https://www.scopus.com/record/display.url?origin=inward&eid=2-s2.0-33747101252}
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  • https://www.mathnet.ru/eng/im/v62/i6/p27
  • This publication is cited in the following 11 articles:
    Citing articles in Google Scholar: Russian citations, English citations
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