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This article is cited in 3 scientific papers (total in 3 papers)
An Extremal Problem for Algebraic Polynomials in the Symmetric Discrete Gegenbauer–Sobolev Space
B. P. Osilenker Moscow State University of Civil Engineering
Abstract:
We study discrete Sobolev spaces with symmetric inner product
$$
\langle f,g\rangle_\alpha
=\int_{-1}^1fg\,d\mu_\alpha+M[f(1)g(1)+f(-1)g(-1)]+K[f'(1)g'(1)+f'(-1)g'(-1)],
$$
where $M\ge0$, $K\ge0$, and
$$
d\mu_\alpha(x)
=\frac{\Gamma(2\alpha+2)}
{2^{2\alpha+1}\Gamma^2(\alpha+1)}\,(1-x^2)^\alpha\,dx,\qquad
\alpha>-1,
$$
is the Gegenbauer probability measure. We obtain the solution of the following extremal problem: Calculate
$$
\inf_{a_0,a_1,\dots,a_{N-r}}\biggl\{
\langle P^{(r)}_N,P^{(r)}_N\rangle_\alpha,1\le r\le N-1,P^{(r)}_N(x)
=\sum_{j=N-r+1}^{N}a^0_j x^j+\sum_{j=0}^{N-r}a_j x^j\biggr\},
$$
where the $a^0_j$, $j=N-r+1,N-r+2,\dots,N-1,N$, $a^0_N>0$, are fixed numbers, and find the extremal polynomial.
Keywords:
algebraic polynomial, discrete Gegenbauer–Sobolev space, Gegenbauer probability measure, extremal problem, Hilbert space, Gram–Schmidt orthogonalization.
Received: 26.05.2006 Revised: 16.01.2007
Citation:
B. P. Osilenker, “An Extremal Problem for Algebraic Polynomials in the Symmetric Discrete Gegenbauer–Sobolev Space”, Mat. Zametki, 82:3 (2007), 411–425; Math. Notes, 82:3 (2007), 366–379
Linking options:
https://www.mathnet.ru/eng/mzm3843https://doi.org/10.4213/mzm3843 https://www.mathnet.ru/eng/mzm/v82/i3/p411
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