English

On the existence of universal series by trigonometric system

Functional Analysis 2011-09-20 v1

Abstract

In this paper we prove the following: let ω(t)\omega(t) be a continuous function, increasing in [0,)[0,\infty) and ω(+0)=0\omega(+0)=0. Then there exists a series of the formk=Ckeikx\sum_{k=-\infty}^\infty C_ke^{ikx} with k=Ck2ω(Ck)<\sum_{k=-\infty}^\infty C^2_k \omega(|C_k|)<\infty, Ck=CˉkC_{-k}=\bar{C}_k, with the following property: for each ϵ>0\epsilon>0 a weighted function μ(x),0<μ(x)1,{x[0,2π]:μ(x)1}<ϵ\mu(x), 0<\mu(x) \le1,| \{x\in[0,2\pi]: \mu(x)\not =1 \}| <\epsilon can be constructed, so that the series is universal in the weighted space Lμ1[0,2π]L_\mu^1[0,2\pi] with respect to rearrangements.

Keywords

Cite

@article{arxiv.1109.3805,
  title  = {On the existence of universal series by trigonometric system},
  author = {Sergo A. Episkoposian},
  journal= {arXiv preprint arXiv:1109.3805},
  year   = {2011}
}