Hostname: page-component-7bb8b95d7b-qxsvm Total loading time: 0 Render date: 2024-09-17T23:18:53.499Z Has data issue: false hasContentIssue false

On the divergence of Hermite-Fejér type interpolation with equidistant nodes

Published online by Cambridge University Press:  17 April 2009

T.M. Mills
Affiliation:
Department of Mathematics, La Trobe University, Bendigo, PO Box 199, Bendigo, Vic. 3550, Australia
Simon J. Smith
Affiliation:
Department of Mathematics, La Trobe University, Bendigo, PO Box 199, Bendigo, Vic. 3550, Australia
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

If f(x) is defined on [−1, 1], let 1 n(f, x) denote the Lagrange interpolation polynomial of degree n (or less) for f which agrees with f at the n+1 equally spaced points xk, n = −1 + (2k)/n (0 ≤ kn). A famous example due to S. Bernstein shows that even for the simple function h(x) = │x│, the sequence 1 n (h, x) diverges as n → ∞ for each x in 0 < │x│ < 1. A generalisation of Lagrange interpolation is the Hermite-Fejér interpolation polynomial mn (f, x), which is the unique polynomial of degree no greater than m(n + 1) – 1 which satisfies (f, Xk, n) = δo, pf(xk, n) (0 ≤ pm − 1, 0 ≤ kn). In general terms, if m is an even number, the polynomials mn(f, x) seem to possess better convergence properties than the 1 n (f, x). Nevertheless, D.L. Berman was able to show that for g(x) ≡ x, the sequence 2n(g, x) diverges as n → ∞ for each x in 0 < │x│. In this paper we extend Berman's result by showing that for any even m, H¯mn(g, x) diverges as n → ∞ for each x in 0 < │x│ < 1. Further, we are able to obtain an estimate for the error │mn(g, x) – g(x)│.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 1994

References

[1]Berman, D.L., ‘Divergence of the Hermite-Fejér interpolation process’, (in Russian), Uspehi Mat. Nauk. 13 (1958), 143148.Google Scholar
[2]Bernstein, S., ‘Quelques remarques sur l'interpolation’, Math. Ann. 79 (1918), 112.CrossRefGoogle Scholar
[3]Byrne, G.J., Mills, T.M. and Smith, S.J., ‘On Lagrange interpolation with equidistant nodes’, Bull. Austral. Math. Soc. 42 (1990), 8189.CrossRefGoogle Scholar
[4]Faber, G., ‘Über die interpolatorische Darstellung stetiger Funktionen’, Jahresber. Deutsch. Math. Verein. 23 (1914), 190210.Google Scholar
[5]Fejér, L., ‘Über interpolation’, Göttinger Nachrichten (1916), 6691.Google Scholar
[6]Li, X. and Mohapatra, R.N., ‘On the divergence of Lagrange interpolation with equidistant nodes’, Proc. Amer. Math. Soc. (to appear).Google Scholar
[7]Mendelevič, L.B., ‘Divergence of the Hermite interpolation polynomials with multiple equidistant nodes’, (in Russian), in Proceedings of the Central Regional Association of Mathematics Departments, Functional Analysis and the Theory of Functions 2 (Kalinin. Gos. Ped. Inst., Kalinin, 1971), pp. 136142.Google Scholar
[8]Szabados, J., ‘On the order of magnitude of fundamental polynomials of Hermite interpolation’, Acta Math. Hungar. (to appear).Google Scholar
[9]Whittaker, E.T. and Watson, G.N., A course of modern analysis, 4th edition (Cambridge Univ. Press, London, 1973).Google Scholar