English

The polarization constant of finite dimensional complex spaces is one

Functional Analysis 2020-11-12 v2 Complex Variables

Abstract

The polarization constant of a Banach space XX is defined as c(X):=lim supkc(k,X)1k,\mathbf c(X):= \limsup\limits_{k\rightarrow \infty} \mathbf c(k, X)^\frac{1}{k}, where c(k,X)\mathbf c(k, X) stands for the best constant C>0C>0 such that PCP \Vert \overset{\vee}{P} \Vert \leq C \Vert P \Vert for every kk-homogeneous polynomial PP(kX)P \in \mathcal P(^kX). We show that if XX is a finite dimensional complex space then c(X)=1\mathbf c(X)=1. We derive some consequences of this fact regarding the convergence of analytic functions on such spaces.The result is no longer true in the real setting. Here we relate this constant with the so-called Bochnak's complexification procedure. We also study some other properties connected with polarization. Namely, we provide necessary conditions related with the geometry of XX for c(2,X)=1\mathbf c(2,X)=1 to hold. Additionally we link polarization's constants with certain estimates of the nuclear norm of the product of polynomials.

Keywords

Cite

@article{arxiv.1908.08107,
  title  = {The polarization constant of finite dimensional complex spaces is one},
  author = {Verónica Dimant and Daniel Galicer and Jorge Tomás Rodríguez},
  journal= {arXiv preprint arXiv:1908.08107},
  year   = {2020}
}

Comments

Math. Proc. Cambridge Philos. Soc., accepted