English

John's Position is not good for approximation

Metric Geometry 2019-08-19 v3

Abstract

Recall that a convex body KK is in John's position if the unit Euclidean ball is the maximal volume ellipsoid contained in KK. Approximating convex body in John's position by polytopes we obtain the following results. 1. Let n>Rn1n>R_n\ge 1 be a sequence such that limnRnn=0\lim_{n\rightarrow \infty} \frac{R_n}{n}=0. For a sufficiently large nn, we can construct a convex body KRnK\subset \mathbb{R}^n in John's position such that there is no PP, polytope with a polynomial number of facets in nn such that KPRnKK\subset P\subset R_nK; 2. For a sufficiently large nn, there is a convex body KRnK\subset \mathbb{R}^n in John's position such that there is no PP, polytope that has less than exp(cn)\exp(cn) facets satisfies KPnKK\subset P \subset \sqrt{n}K.

Keywords

Cite

@article{arxiv.1703.02173,
  title  = {John's Position is not good for approximation},
  author = {Han Huang},
  journal= {arXiv preprint arXiv:1703.02173},
  year   = {2019}
}
R2 v1 2026-06-22T18:37:52.793Z