English

Do flat skew-reciprocal Littlewood polynomials exist?

Classical Analysis and ODEs 2020-07-09 v2

Abstract

Polynomials with coefficients in {1,1}\{-1,1\} are called Littlewood polynomials. Using special properties of the Rudin-Shapiro polynomials and classical results in approximation theory such as Jackson's Theorem, de la Vall\'ee Poussin sums, Bernstein's inequality, Riesz's Lemma, divided differences, etc., we give a significantly simplified proof of a recent breakthrough result by Balister, Bollob\'as, Morris, Sahasrabudhe, and Tiba stating that there exist absolute constants η2>η1>0\eta_2 > \eta_1 > 0 and a sequence (Pn)(P_n) of Littlewood polynomials PnP_n of degree nn such that η1nPn(z)η2n,zC,z=1,,\eta_1 \sqrt{n} \leq |P_n(z)| \leq \eta_2 \sqrt{n}\,, \qquad z \in \mathbb{C}\,, \, \, |z| = 1,, confirming a conjecture of Littlewood from 1966. Moreover, the existence of a sequence (Pn)(P_n) of Littlewood polynomials PnP_n is shown in a way that in addition to the above flatness properties a certain symmetry is satisfied by the coefficients of PnP_n making the Littlewood polynomials PnP_n close to skew-reciprocal.

Keywords

Cite

@article{arxiv.2001.08151,
  title  = {Do flat skew-reciprocal Littlewood polynomials exist?},
  author = {Tamás Erdélyi},
  journal= {arXiv preprint arXiv:2001.08151},
  year   = {2020}
}
R2 v1 2026-06-23T13:17:56.352Z