Proper Function: Homeomorphism or Not?

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Discussion Overview

The discussion revolves around the conditions under which a proper injection F: X --> Y can be considered a homeomorphism, particularly focusing on the requirements of continuity and the properties of the spaces involved, such as being Hausdorff and compactly generated.

Discussion Character

  • Technical explanation, Conceptual clarification

Main Points Raised

  • One participant inquires if a proper injection F: X --> Y guarantees that F: X --> F(X) is a homeomorphism, under the assumption that F is proper.
  • Another participant asserts that F must be continuous and that Y needs to be Hausdorff and compactly generated for the homeomorphism to hold, referencing a specific corollary from Lee's work.
  • A later reply acknowledges the need for continuity and the Hausdorff condition, while also seeking clarification on the definition of compactly generated spaces.
  • One participant provides a link to a Wikipedia page for further information on compactly generated spaces.
  • Another participant confirms that Y is a locally compact space, thus qualifying it as a compactly generated space.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of continuity and the Hausdorff condition for Y, but there is no consensus on the implications of these conditions for establishing a homeomorphism.

Contextual Notes

The discussion does not resolve the specific definitions and implications of compactly generated spaces and their relationship to the properties of the function F.

Lie
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Hello!

F: X --> Y injection.

It is true that if F is proper (the inverse image of any compact set is compact) then F: X --> F(X) is a homeomorphism?

Thanks... :)
 
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You need F to be continuous and Y to be Hausdorff and compactly generated. See Corolarry 4.97 of Lee's Introduction to topological manifolds.
 
quasar987 said:
You need F to be continuous and Y to be Hausdorff and compactly generated. See Corolarry 4.97 of Lee's Introduction to topological manifolds.
Yes, I had forgotten: F to be continuous and Y (X and) to be Hausdorff. :)

Compactly generated = union of open compact ?

Thanks... :)
 
Thanks!

I showed that Y is locally compact space and therefore is compactly generated space.

Grateful.
 
You're welcome. :)
 

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