English

Minimal Fourier majorants in $L^p$

Functional Analysis 2021-12-28 v1

Abstract

Denote the coefficients in the complex form of the Fourier series of a function ff on the interval [π,π)[-\pi, \pi) by f^(n)\hat f(n). It is known that if p=2j/(2j1)p = 2j/(2j-1) for some integer j>0j>0, then for each function ff in LpL^p there exists another function FF in LpL^p that majorizes ff in the sense that F^(n)f^(n)\hat F(n) \ge |\hat f(n)| for all nn, and for which Fpfp\|F\|_p \le \|f\|_p. When j>1j > 1, the existence proofs for such small majorants do not provide constructions of them, but there is a unique majorant of minimal LpL^p norm. We modify previous existence proofs to say more about the form of that majorant.

Keywords

Cite

@article{arxiv.2112.13799,
  title  = {Minimal Fourier majorants in $L^p$},
  author = {John J. F. Fournier and Dean Vrecko},
  journal= {arXiv preprint arXiv:2112.13799},
  year   = {2021}
}