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On the closure of

Published online by Cambridge University Press:  24 October 2008

W. H. J. Fuchs
Affiliation:
University CollegeSwansea

Extract

1. A set of functions {øν (t)} (ν = 1, 2, …) is said to be closed L2 in (a, b), if

implies f (t) = 0 p.p. in (a, b). It is well known that a set of functions is closed L2, if and only if every function of L2 (a, b) can be approximated in the mean square sense as closely as desired by finite linear combinations of the øν (t).

Type
Research Article
Copyright
Copyright © Cambridge Philosophical Society 1946

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References

Szàsz, O., Math. Ann. 77 (1916), 482–96.CrossRefGoogle Scholar

Hardy, G. H., Messenger of Math. 46 (1917), 175–82.Google Scholar

§ Boas, R. P., Trans. American Math. Soc. 46 (1939), 142–50.CrossRefGoogle Scholar

See, for example, Widder, D. V., The Laplace Transform, pp. 246–7.Google Scholar

See Levinson, N., Gap and Density Theorems 1 (New York, 1940), p. 425.Google Scholar

This follows from Lemma A by the limiting process T → ∞.

Nevanlinna, R., Eindeutige analytische Funktionen (Berlin, 1936), pp. 8992.CrossRefGoogle Scholar