Date: Dec 12, 2012 12:31 PM
Author: Kaba
Subject: Re: Precompactness
12.12.2012 5:24, William Elliot wrote:

> On Tue, 11 Dec 2012, Kaba wrote:

>

>> Let X be a locally compact Hausdorff space. Is every open set of X

>> precompact (compact closure)?

>

> Yes. How would you prove it?

:)

Related, let X be a Hausdorff space. Royden (Real analysis) defines E

subset X to be _bounded_ if it is contained in a compact set. It seems

to me that precompact and bounded are equivalent properties.

Assume E is precompact. Then cl(E) is a compact set which contains E.

Therefore E is bounded. Assume E is bounded. Then there is a compact set

K such that E subset K. Since X is Hausdorff, K is closed. Therefore

cl(E) subset K. Since cl(E) is a closed subset of a compact set K, cl(E)

is compact. Therefore E is precompact.

Unless I am missing something?

--

http://kaba.hilvi.org