English

On the speed of convergence in the strong density theorem

Functional Analysis 2019-05-22 v3

Abstract

For a compact set KRmK\subset \mathbb{R}^m, we have two indexes given under simple parameters of the set KK (these parameters go back to Besicovitch and Taylor in the late 50's). In the present paper we prove that with the exception of a single extreme value for each index, we have the following elementary estimate on how fast the ratio in the strong density theorem of Saks will tend to one RKR>1o(1logd(R))for a.e.  xK  and for  d(R)0 \frac{|R\cap K|}{|R|}>1-o\bigg(\frac{1}{|\log d(R)|}\bigg) \qquad \text{for a.e.} \ \ x\in K \ \ \text{and for} \ \ d(R)\to 0 (provided xRx\in R, where RR is an interval in Rm\mathbb{R}^m, dd stands for the diameter and |\cdot| is the Lebesgue measure). This work is a natural sequence of [3] and constitutes a contribution to Problem 146 of Ulam [5, p. 245] (see also [8, p.78]) and Erd\"{o}s' Scottish Book `Problems' [5, Chapter 4, pp. 27-33], since it is known that no general statement can be made on how fast the density will tend to one.

Keywords

Cite

@article{arxiv.1805.10035,
  title  = {On the speed of convergence in the strong density theorem},
  author = {Panagiotis Georgopoulos and Constantinos Gryllakis},
  journal= {arXiv preprint arXiv:1805.10035},
  year   = {2019}
}

Comments

A few typos corrected; enumeration of Propositions, Theorems, Relations, etc. according to the published version in RAE