English

Maximal surface area of polytopes with respect to log-concave rotation invariant measures

Classical Analysis and ODEs 2014-09-17 v1

Abstract

It was shown in \cite{GL} that the maximal surface area of a convex set in Rn\mathbb{R}^n with respect to a rotation invariant log-concave probability measure γ\gamma is of order nVarX4EX\frac{\sqrt{n}}{\sqrt[4]{Var|X|} \sqrt{\mathbb{E}|X|}}, where XX is a random vector in Rn\mathbb{R}^n distributed with respect to γ\gamma. In the present paper we discuss surface area of convex polytopes PKP_K with KK facets. We find tight bounds on the maximal surface area of PKP_K in terms of KK. We show that γ(PK)nEXlogKlogn\gamma(\partial P_K)\lesssim \frac{\sqrt{n}}{\mathbb{E}|X|}\cdot\sqrt{\log K}\cdot\log n for all KK. This bound is better then the general bound for all K[2,ecVarX]K\in [2,e^{\frac{c}{{\sqrt{Var|X|}}}}]. Moreover, for all KK in that range the bound is exact up to a factor of logn\log n: for each K[2,ecVarX]K\in [2,e^{\frac{c}{{\sqrt{Var|X|}}}}] there exists a polytope PKP_K with at most KK facets such that γ(PK)nEXlogK.\gamma(\partial P_K)\gtrsim \frac{\sqrt{n}}{\mathbb{E}|X|}\sqrt{\log K}. %For the measures γp\gamma_p with densities Cn,peyppC_{n,p} e^{-\frac{|y|^p}{p}} (where p>0p>0) we obtain: γp(PK)nEXlogK,\gamma_p(\partial P_K)\lesssim \frac{\sqrt{n}}{\mathbb{E}X}\sqrt{\log K}, which was obtained for the standard Gaussian measure γ2\gamma_2 by F. Nazarov.

Keywords

Cite

@article{arxiv.1409.4452,
  title  = {Maximal surface area of polytopes with respect to log-concave rotation invariant measures},
  author = {Galyna V. Livshyts},
  journal= {arXiv preprint arXiv:1409.4452},
  year   = {2014}
}