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Mercerian theorems

Published online by Cambridge University Press:  24 October 2008

H. R. Pitt
Affiliation:
Peterhouse

Extract

Suppose that k(x) is of bounded variation in (− ∞, ∞) and that s(x) is bounded and continuous in the same range. Let

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1938

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References

Integrals with unspecified limits are over (− ∞, ∞).

Pitt, H. R., “An extension of Wiener's general Tauberian theorem”, American Journal of Math. 60 (1938), 532–4CrossRefGoogle Scholar. We vise case (A) of the theorem.

A singular function is continuous, of bounded variation and not constant, and has zero derivative almost everywhere.

Wiener, N. and Pitt, H. R., “On absolutely convergent Fourier-Stieltjes transforms”, Duke Journal, 4 (1938), 420–36CrossRefGoogle Scholar, Theorem 1. When these Mercerian theorems were first proved I hoped that the class V* could be extended to include all functions of bounded variation. However, Theorem 3 of the above paper shows that some condition on the singular component of k(x) is essential, and it seems most natural to suppose that it vanishes altogether.

See, for example, Bochner, S., Vorlesungen fiber Fouriersche Integrate (Leipzig, 1932)Google Scholar, Satz 18.

The special case in which k(x) is absolutely continuous except at 0 has been treated by Paley, and Wiener, , “Fourier transforms in the complex domain”, American Math. Soc. Colloquium Publications, vol. 19 (New York, 1934)Google Scholar, Theorem XVII.

Hausdorff, F., “Summationsmethoden und Momentfolgen”, Math. Zeitschrift, 37 (1921), 74109.CrossRefGoogle Scholar

Pitt, H. R., “General Tauberian theorems”, Proc. London Math. Soc. (2), 44 (1938), 243–88CrossRefGoogle Scholar, § 4·3.

§ See, for example, Bieberbach, L., Lehrbuch der Funktionentheorie (Springer, 1931), p. 138.Google Scholar

Mercer, J., Proc. London Math. Soc. (2), 5 (1907), 206–24.CrossRefGoogle Scholar

See Pitt, H. R., “General Tauberian theorems”, Proc. London Math. Soc. (2), 44 (1938), 243–88CrossRefGoogle Scholar, § 2. The particular form of Tauberian theorem for Borel summation which we use below is contained in Theorem 16 of the same paper.