MathOverflow is a question and answer site for professional mathematicians. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

In the case where $E\subset\mathbb{R}^1$, a Besicovitch cover of $E$ is a cover by open intervals such that each point of $E$ is the center of some interval in the cover.

The Besicovitch Covering Theorem says that there exists some $n$ such that for any bounded set $E\subset\mathbb{R}$ with Besicovitch cover $F$, there exist $A_1,\ldots,A_n$ subsets of $F$ such that each is a disjoint collection of intervals and $\bigcup_{i=1}^nA_i$ covers $E$.

I have sketched out a proof that $n=2$ following the remark on page 10 of that this is trivial, and would like to use this fact in a paper of mine without pretending that the best constant is unknown, though including the proof would be irrelevant to the rest of the paper.

Does anyone know an appropriate citation or is it so universally accepted that nobody has bothered to publish it?

share|cite|improve this question

The statement of the Besicovitch Covering Theorem I've learned is a bit different, see Morgan "Geometric Measure Theory; a beginner's guide". The result you state is stated as a lemma there. As an example, the bound for $\mathbb{R}^2$ (18) is given, referring to Reifenberg, E.R. "A problem on circles" published in Math. Gazette 32 (1948), 290-292

The bound for $\mathbb{R}$ seems obvious to me. Probably this is easy to show by hand. I doubt if anyone will mind if you state this as a remark.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.