Talk:Compact space: Difference between revisions
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imported>Boris Tsirelson (→Properties: new section) |
imported>Boris Tsirelson (→Compactness axioms: new section) |
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:The image of a compact space under a continuous map to a Hausdorff space is compact." | :The image of a compact space under a continuous map to a Hausdorff space is compact." | ||
No, the matter is simpler: The image of a compact space under a continuous map is compact. [[User:Boris Tsirelson|Boris Tsirelson]] 15:10, 25 May 2010 (UTC) | No, the matter is simpler: The image of a compact space under a continuous map is compact. [[User:Boris Tsirelson|Boris Tsirelson]] 15:10, 25 May 2010 (UTC) | ||
== Compactness axioms == | |||
Why "compactum" redirects to "Compactness axioms" rather than here? And why the [[Compactness axioms]] page exists at all, separately from this page? [[User:Boris Tsirelson|Boris Tsirelson]] 15:53, 25 May 2010 (UTC) | |||
Revision as of 09:54, 25 May 2010
Compact set vs compact space
Don't you think this article should be rather a subsection in more general compact space? Wojciech Świderski 05:28, 12 July 2008 (CDT)
- The terms compact set and compact space mean almost the same to me. Could you please explain the difference? -- Jitse Niesen 09:33, 12 July 2008 (CDT)
- In general, a compact set is part of surrounding topological space that may not be compact - as closed and bounded subsets of R^n. Compact space is "compact in itself" - we don't think of it as of part of something greater. Compact manifold is a good example - if you don't consider it as embedded in anything else. See: [1] Wojciech Świderski 03:10, 13 July 2008 (CDT)
- Okay, then we're using the same definitions. I was a bit surprised by your statement that "compact space" is more general than "compact set", but I guess it depends on how you look at it. Anyway, feel free to extend the discussion in the article. I do believe that "compact space" and "compact set" mean more or less the same (at least, the definitions are the same). Every compact set can be viewed as a compact space, if you forget about the space it's embedded in; every compact space is also a compact set in the space itself. So I think it's best to discuss both concepts in the same article. -- Jitse Niesen 16:19, 13 July 2008 (CDT)
I would really like to retitle this as "compact space". Compactness is a property of a topological space, and it seems odd that the latter concept isn't even mentioned in the introduction. Richard Pinch 19:05, 30 October 2008 (UTC)
- Go ahead. -- Jitse Niesen 12:24, 31 October 2008 (UTC)
Properties
- "The quotient topology on an image of a compact space is compact.
- The image of a compact space under a continuous map to a Hausdorff space is compact."
No, the matter is simpler: The image of a compact space under a continuous map is compact. Boris Tsirelson 15:10, 25 May 2010 (UTC)
Compactness axioms
Why "compactum" redirects to "Compactness axioms" rather than here? And why the Compactness axioms page exists at all, separately from this page? Boris Tsirelson 15:53, 25 May 2010 (UTC)