On the convergence of Fourier series of computable Lebesgue integrable functions
β Scribed by Philippe Moser
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 130 KB
- Volume
- 56
- Category
- Article
- ISSN
- 0044-3050
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β¦ Synopsis
This paper studies how well computable functions can be approximated by their Fourier series. To this end, we equip the space of L p -computable functions (computable Lebesgue integrable functions) with a size notion, by introducing L p -computable Baire categories. We show that L p -computable Baire categories satisfy the following three basic properties. Singleton sets {f } (where f is L p -computable) are meager, suitable infinite unions of meager sets are meager, and the whole space of L p -computable functions is not meager. We give an alternative characterization of meager sets via Banach-Mazur games. We study the convergence of Fourier series for L p -computable functions and show that whereas for every p > 1, the Fourier series of every L p -computable function f converges to f in the L p norm, the set of L 1 -computable functions whose Fourier series does not diverge almost everywhere is meager.
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## Abstract Using Typeβ2 theory of effectivity, we define computability notions on the spaces of Lebesgueβintegrable functions on the real line that are based on two natural approaches to integrability from measure theory. We show that Fourier transform and convolution on these spaces are computabl