arXiv subjects
Publications and source records attributed to T. Erdélyi.
We study the autocorrelation coefficients of the Rudin-Shapiro polynomials, proving in particular that their maximum on the interval $[1, 2^n)$ is bounded from below by $C_1 2^{αn}$ and is bounded from above by $C_2 2^{α' n}$ where $α= 0.7302852...$ and $α' = 0.7302867...$.
It is proven that for any system of n points z_1, ..., z_n on the (complex) unit circle, there exists another point z of norm 1, such that $$\sum 1/|z-z_k|^2 \leq n^2/4.$$ Equality holds iff the point system is a rotated copy of the nth unit roots. Two proofs are presented: one uses a characterisation of equioscillating rational functions, while the other is based on Bernstein's inequality.