English

On a quantitative reversal of Alexandrov's inequality

Metric Geometry 2017-02-22 v2

Abstract

Alexandrov's inequalities imply that for any convex body AA, the sequence of intrinsic volumes V1(A),,Vn(A)V_1(A),\ldots,V_n(A) is non-increasing (when suitably normalized). Milman's random version of Dvoretzky's theorem shows that a large initial segment of this sequence is essentially constant, up to a critical parameter called the Dvoretzky number. We show that this near-constant behavior actually extends further, up to a different parameter associated with AA. This yields a new quantitative reverse inequality that sits between the approximate reverse Urysohn inequality, due to Figiel--Tomczak-Jaegermann and Pisier, and the sharp reverse Urysohn inequality for zonoids, due to Hug--Schneider. In fact, we study concentration properties of the volume radius and mean width of random projections of AA and show how these lead naturally to such reversals.

Keywords

Cite

@article{arxiv.1702.05762,
  title  = {On a quantitative reversal of Alexandrov's inequality},
  author = {Grigoris Paouris and Peter Pivovarov and Petros Valettas},
  journal= {arXiv preprint arXiv:1702.05762},
  year   = {2017}
}

Comments

Corrected the probability estimate in the lower small deviation inequality (1.12) in Theorem 1.2