Abstract
We show that there exist absolute constants $\delta > \delta > 0$ such that, for all $n \ge 2$, there exists a polynomial $P$ of degree $n$, with coefficients in $\{-1,1\}$, such that \[\delta\sqrt{n} \le |P(z)| \le \Delta \sqrt{n}\]for all $z \in \mathbb{C}$ with $|z|=1$. This confirms a conjecture of Littlewood from 1966.
Citation
Paul Balister. Béla Bollobás. Robert Morris. Julian Sahasrabudhe. Marius Tiba. "Flat Littlewood polynomials exist." Ann. of Math. (2) 192 (3) 977 - 1004, November 2020. https://doi.org/10.4007/annals.2020.192.3.6
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