Note on a Compactification Due to Nielsen and Sloyer.
Let , be metric spaces and an injective mapping. We put , and (the distortion of the mapping ). We investigate the minimum dimension such that every -point metric space can be embedded into the space with a prescribed distortion . We obtain that this is possible for , where is a suitable absolute constant. This improves a result of Johnson, Lindenstrauss and Schechtman [JLS87] (with a simpler proof). Related results for embeddability into are obtained by a similar method.
We show that a compact space has a dense set of points if it can be covered by countably many Corson countably compact spaces. If these Corson countably compact spaces may be chosen to be dense in , then is even Corson.
In this note we are going to study dense covers in the category of locales. We shall show that any product of finitely regular locales with some dense covering property has this property as well.