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On approximation in spaces of continuous functions

Published online by Cambridge University Press:  17 April 2009

Heinz H. Gonska
Affiliation:
University of Duisburg, Department of Mathematics, D-4100 Duisburg I, West Germany; Department of Mathematical Sciences, Drexel University, Philadelphia, Pennsylvania 19104, USA.
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Abstract

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This paper deals with approximation of certain operators defined on the space C(X) of real-valued continuous functions on an arbitrary compact metric space (X, d). In particular the problem of giving quantitative Korovkin type theorems for approximation by positive linear operators is solved. This is achieved by using a smoothing approach and the least concave majorant of the modulus of continuity of a function f in C(X). Several new estimates are given as applications, including such for Shepard's method of metric interpolation.

Type
Research Article
Copyright
Copyright © Australian Mathematical Society 1983

References

[1]Berens, H. and Lorentz, G.G., “Theorems of Korovkin type for positive linear operators on Banach lattices”, Approximation theory, 130 (Proc. Internat. Sympos. Austin, 1973. Academic Press, New York, San Francisco, London, 1973).Google Scholar
[2]Дзядык, В.К. [Dzjadyk, V.K.], Вєе∂енuе є mеорuо рєномерноо nрuблuxенuu nолuноммu [introduction to the theory of uniform approximation of functions by polynomials] (Izdat. “Nauka”, Moscow, 1977).Google Scholar
[3]Gonska, H., “On Mamedov estimates for the approximation of finitely defined operators”, Approximation theory III, 143448 (Proc. Internat. Sympos. Austin, 1980. Academic Press, New York, San Francisco, London, 1980).Google Scholar
[4]Gonska, Heinz H. and Meier, Jutta, “Quantitative theorems on approximation by Bernstein–Stancu operators”, Calcolo (to appear).Google Scholar
[5]Gordon, W.J. and Wixom, J.A., “Shepard's method of ‘metric interpolation’ to bivariate and multivariate interpolation”, Math. Comp. 32 (1978), 253264.Google Scholar
[6]Hermann, T. and Vértesi, P., “On an interpolatory operator and its saturation”, Acta Math. Acad. Sci. Hungar. 37 (1981), 19.CrossRefGoogle Scholar
[7]Pozo, M.A. Jiménez, “Sur les opérateurs linéraires positifs et la méthode des fonctions tests”, C.R. Acad. Sci. Paris Sér. A 278 (1974), 149152.Google Scholar
[8]Pozo, M.A. Jiménez, “On the problem of the convergence of a sequence of linear operators”, Moscow Univ. Math. Bull. 33 (1978), no. 4, 18.Google Scholar
[9]Pozo, M.A. Jiménez, “Deformation de la convexité et théorèmes du type Korovkin”, C.R. Acad. Sci. Paris Sér. A 290 (1980), 213215.Google Scholar
[10]Pozo, M.A. Jiménez, “Convergence of sequences of linear functionals”, Z. Angew. Math. Mech. 61 (1981), 495500.CrossRefGoogle Scholar
[11]Pozo, Miguel A. Jiménez, “Quantitative theorems of Korovkin type in bounded function spaces”, Constructive function theory (Proc. Internat. Conf., Varna, Bulgaria, 1981. To appear).Google Scholar
[12]Pozo, M.A. Jiménez y Baldet, M. Baile, “Estimados del orden de convergencia de una sucesion de operadores lineales en espacios de funciones con peso”, Cienc. Mat. (Havana) 2 (1981), 1628.Google Scholar
[13]Lehnhoff, H.G., “A simple proof of A.F. Timan's theorem“, J. Approx. Theory 38 (1983), 172176.CrossRefGoogle Scholar
[14]Мамедов, Р.Г. [Mamedov, R.G.], “О порядке приближения функций линейными положительными операторами” [On the order of approximation of functions by linear positive operators], Dokl. Akad. Nauk SSSR 128 (1959), 674676.Google ScholarPubMed
[15]Menger, K., “Untersuchungen über allgemeine Metrik”, Math. Ann. 100 (1928), 75163.CrossRefGoogle Scholar
[16]Mitjagin, B.S. and Semenov, E.M., “Lack of interpolation of linear operators in spaces of smooth functions”, Math. USSR-Izv. 11 (1977), 12291266.CrossRefGoogle Scholar
[17]Müller, M.W. and Walk, H., “Konvergenz- und Güteaussagen für die Approximation durch Folgen linearer positiver Operatoren”, Constructive theory of functions, 221233 (Proc. Internat. Conf. Varna, Bulgaria, 1970). Publishing House of the Bulgarian Academy of Sciences, Sofia, 1972).Google Scholar
[18]Newman, D.J. and Shapiro, H.S., “Jackson's theorem in higher dimension”, On approximation theory, 208219 (Proc. Conf. Math. Res. Inst. Oberwolfach, 1963. Birkhäuser, Basel, 1964).Google Scholar
[19]Nishishiraho, Toshihiko, “The rate of convergence of positive linear approximation processes”, Approximation theory IV (Proc. Internat. Sympos. College Station, 1983. Academic Press, New York, San Francisco, London, to appear).Google Scholar
[20]Nishishiraho, Toshihiko, “Convergence of positive linear approximation processes”, Tōhoku Math. J. (to appear).Google Scholar
[21]Shepard, D., “A two-dimensional interpolation function for irregularly spaced data”, Proc. 1968 ACM National Conference, 517524.Google Scholar
[22]Somorjai, G., “On a saturation problem”, Acta Math. Acad. Sci. Hungar. 32 (1978), 377381.CrossRefGoogle Scholar
[23]Stancu, D.D., “Approximation of bivariate functions by means of some Bernstein-type operators”, Multivariate approximation, 189208 (Proc. Sympos. Durham, 1977. Academic Press, New York, San Francisco, London, 1978).Google Scholar
[24]Szabados, J., “On a problem of R. DeVore”, Acta Math. Acad. Sci. Hungar. 27 (1976), 219223.CrossRefGoogle Scholar
[25]Wolff, M., “Über das Spektrum von Verbandshomomorphismen: in C(X)”, Math. Ann. 182 (1969), 161169.CrossRefGoogle Scholar