Polarization, sign sequences and isotropic vector systems

Abstract

We determine the order of magnitude of the $n$th ${\ell }_p$-polarization constant of the unit sphere $S^{d-1}$ for every $n,d\ge 1$ and $p>0$. For $p=2$, we prove that extremizers are isotropic vector sets, whereas for $p=1$, we show that the polarization problem is equivalent to that of maximizing the norm of signed vector sums. Finally, for $d=2$, we discuss the optimality of equally spaced configurations on the unit circle.

13 pages