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Kolmogorov lone fourier series diverges almost everywhere
Statement
Assume AC. There exists a complex-valued such that for almost every x. The torus has normalized measure and .
Facts & Assumptions
The explicit gliding-hump sequence has an limit with norm at most one Kolmogorov gliding hump series converges in lone.
Its symmetric Fourier partial sums are unbounded off a null set Kolmogorov block maxima diverge off a null limsup set.
Assume AC The Axiom of Choice.
Proof
Given: AC and normalized torus conventions.
Take f to be the limit supplied by F1, represented by the absolutely convergent block sum where defined and zero on its measurable null exceptional set. This is a complex integrable function with norm at most one, so all its Fourier coefficients are well defined.
F2 applies to exactly this sequence and limit. It gives outside a measurable null set. A convergent complex sequence is bounded: beyond some index it lies within one of its limit, and its finite initial segment has a finite maximum. Therefore these partial sums in particular fail to converge almost everywhere. The choice assumption is the one used for the countable norm-one block selection and the complex completeness supplier in F1.
Depends on
Used by
Dependency tree · two levels
10 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Grafakos, Classical Fourier Analysis, third edition (standard reference, not scraped)