Namespaces
Variants
Actions

Lebesgue function

From Encyclopedia of Mathematics
Revision as of 17:05, 7 February 2011 by 127.0.0.1 (talk) (Importing text file)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

A function

where is a given system of functions, orthonormal with respect to the Lebesgue measure on the interval , . Lebesgue functions are defined similarly in the case when an orthonormal system is specified on an arbitrary measure space. One has

where

is the -th partial sum of the Fourier series of with respect to . In the case when is the trigonometric system, the Lebesgue functions are constant and reduce to the Lebesgue constants. They were introduced by H. Lebesgue.

References

[1] S. Kaczmarz, H. Steinhaus, "Theorie der Orthogonalreihen" , Chelsea, reprint (1951)
How to Cite This Entry:
Lebesgue function. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Lebesgue_function&oldid=47601
This article was adapted from an original article by B.S. Kashin (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article