PDA

View Full Version : compact -> hausdorff


fallgesetz
Sep6-09, 01:39 PM
Is there a way to make a compact space hausdorff while preserving compactness?

0xDEADBEEF
Sep6-09, 02:57 PM
Specify what you mean.
A sphere is compact and Hausdorff.

fallgesetz
Sep6-09, 03:10 PM
I am not looking for an example of a compact & hausdorff space.

I am asking -- if I have a compact space, is there a process by which I can make it a hausdorff space while preserving compactness.

In a sense, I am looking for something like one point compactification(but not that, more like "hausdorffication").

0xDEADBEEF
Sep6-09, 03:21 PM
Just a thought... if the border of your compact set is a manifold, I think you can usually find a continuous mapping that extends the set into itself when going over the border. But since for example finite sets are compact, I don't see a sane way of making every compact set Hausdorff.

Hurkyl
Sep6-09, 03:21 PM
What are you looking to preserve? What is the application?

There are certainly things you can do: e.g. you can identify inseparable points. This works well for something like a Euclidean line with a double point at the origin (which gives you the Euclidean line). This doesn't work well for something like the Zariski plane over a field. (the result is the one-point space).

0xDEADBEEF
Sep6-09, 03:29 PM
But since for example finite sets are compact....

That statement sounds stupid in retrospective sorry...

g_edgar
Sep6-09, 04:37 PM
Perhaps he means this: Given a compact space X (not Hauseorff), can you enlarge the topology to make it a compact Hausdorff space? If that is what he means, then the answer is, in general, "no".