Year: 2026
Type: preprint
Abstract: In the paper, we prove a recursive version of the weighted Sidelnikov-Welch inequality for real and complex unit vectors. Unlike the classical form, which gives a direct lower bound for a fixed even power sum, our inequality relates two consecutive even power sums. Iteration yields the usual weighted Sidelnikov-Welch bound. We apply this estimate to maximal relative projection constants. If $\mathbb{K}^m$ admits a maximal equiangular tight frame with $M_{\mathbb K}$ vectors, then for every integer $k\geq1$, $$ λ_{\mathbb K}(kM_{\mathbb K}-m,kM_{\mathbb K}) = λ_{\mathbb K}(m)-\frac{2m}{kM_{\mathbb K}}+1. $$ Moreover, the maximal value is realized by an equiangular tight frame when $k=1$ and by a biangular tight frame when $k\geq2$.
Source: arXiv (Cornell University)
Authors: Deregowska, Beata, Lewandowska, Barbara
Language: English
Subfield: Applied Mathematics
Field: Mathematics
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214345996