English

Fourier transform inversion in the Alexiewicz norm

Classical Analysis and ODEs 2022-02-04 v1

Abstract

If fL1(R)f\in L^1({\mathbb R}) it is proved that limSffDS=0\lim_{S\to\infty}\lVert f-f\ast D_S\rVert=0, where DS(x)=sin(Sx)/(πx)D_S(x)=\sin(Sx)/(\pi x) is the Dirichlet kernel and f=supα<βαβf(x)dx\lVert f\rVert = \sup_{\alpha<\beta}|\int_{\alpha}^{\beta}f(x)\,dx| is the Alexiewicz norm. This gives a symmetric inversion of the Fourier transform on the real line. An asymmetric inversion is also proved. The results also hold for a measure given by dFdF where FF is a continuous function of bounded variation. Such measures need not be absolutely continuous with respect to Lebesgue measure. An example shows there is fL1(R)f\in L^1({\mathbb R}) such that limSffDS10\lim_{S\to\infty} \rVert f-f\ast D_S\lVert_1\neq 0.

Keywords

Cite

@article{arxiv.2202.01359,
  title  = {Fourier transform inversion in the Alexiewicz norm},
  author = {Erik Talvila},
  journal= {arXiv preprint arXiv:2202.01359},
  year   = {2022}
}
R2 v1 2026-06-24T09:16:57.904Z