English

Failure of Approximation of Odd Functions by Odd Polynomials

Functional Analysis 2020-07-01 v1 Classical Analysis and ODEs Complex Variables

Abstract

We construct a Hilbert holomorphic function space HH on the unit disk such that the polynomials are dense in HH, but the odd polynomials are not dense in the odd functions in HH. As a consequence, there exists a function ff in HH that lies outside the closed linear span of its Taylor partial sums sn(f)s_n(f), so it cannot be approximated by any triangular summability method applied to the sn(f)s_n(f). We also show that there exists a function ff in HH that lies outside the closed linear span of its radial dilates fr, r<1f_r, ~r<1.

Keywords

Cite

@article{arxiv.2006.16871,
  title  = {Failure of Approximation of Odd Functions by Odd Polynomials},
  author = {Javad Mashreghi and Pierre-Olivier Parisé and Thomas Ransford},
  journal= {arXiv preprint arXiv:2006.16871},
  year   = {2020}
}

Comments

8 pages. Submitted to Const.Approx. on the 2020/06/23

R2 v1 2026-06-23T16:44:24.846Z