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Universal interpolation. (English) Zbl 1292.41002

It was shown by P. Erdős and P. Vertesi [Acta Math. Acad. Sci. Hung. 36, 71–89 (1980; Zbl 0463.41002)] that for every system of nodes
\[ 0\leq x_1^n < x_2^n < \cdots < x_n^n \leq 1,\qquad n\in \mathbb{N}, \tag{1} \] there exists a continuous function \(f\) such that the corresponding sequence of interpolating polynomials \((p_n)_{n\in \mathbb{N}}\) on (1) diverges almost everywhere. In this paper the author shows that for every \(p\in [1,\infty)\), there exists an infinitely differentiable function \(f: [0, 1]\to \mathbb{R}\) and a system of nodes (1) with \[ \lim_{n\to \infty} \max\{x_1^n - 0, x_2^n - x_1^n, \ldots, x_n^n - x_{n-1}^n, 1 - x_n^n\} = 0, \] such that the polynomials \(p_n\) interpolating \(f\) on (1) have the following property: For every function \(g\in L_p\) there exists a subsequence \((n_k)_{k\in \mathbb{N}}\) of natural numbers with \(\lim_{k\to \infty} p_{n_k} = g\).

MSC:

41A05 Interpolation in approximation theory
41A10 Approximation by polynomials

Citations:

Zbl 0463.41002
Full Text: DOI

References:

[1] DOI: 10.1007/BF01457173 · JFM 46.0417.01 · doi:10.1007/BF01457173
[2] DOI: 10.1007/BF01897094 · Zbl 0463.41002 · doi:10.1007/BF01897094
[3] DOI: 10.1090/S0273-0979-99-00788-0 · Zbl 0933.47003 · doi:10.1090/S0273-0979-99-00788-0
[4] DOI: 10.1137/0114095 · Zbl 0173.06301 · doi:10.1137/0114095
[5] Herzog G., Analysis 11 pp 21– (1991) · Zbl 0729.41007 · doi:10.1524/anly.1991.11.1.21
[6] Marcinkiewicz J., Acta Sci. Math. Szeged 8 pp 131– (1937)
[7] Runge C., Zeitschrift für Mathematik und Physik 46 pp 224– (1901)
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