Proper Function: Homeomorphism or Not?

  • Thread starter Lie
  • Start date
In summary, the conversation discusses the conditions for a proper function F from X to Y to be a homeomorphism, which include F being continuous and Y being Hausdorff and compactly generated. The concept of compactly generated space is also briefly explained.
  • #1
Lie
15
0
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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  • #2
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.
 
  • #3
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... :)
 
  • #5
Thanks!

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

Grateful.
 
  • #6
You're welcome. :)
 

What is a proper homeomorphism?

A proper homeomorphism is a type of mathematical function that preserves the topological structure of a space. It is a continuous function that has a continuous inverse and maps open sets to open sets.

What are the properties of a proper homeomorphism?

A proper homeomorphism has the following properties:

  • It is a bijection, meaning it is both injective (one-to-one) and surjective (onto).
  • It is continuous, meaning small changes in the input result in small changes in the output.
  • It has a continuous inverse, meaning the inverse function is also continuous.
  • It preserves the topological structure of a space, meaning the open sets in the input space are mapped to open sets in the output space.
  • It is proper, meaning the preimage of a compact set is a compact set.

What is the difference between a proper homeomorphism and a homeomorphism?

A proper homeomorphism is a specific type of homeomorphism. While both are continuous functions with continuous inverses, a proper homeomorphism also has the property of being proper, meaning it maps compact sets to compact sets.

How can proper homeomorphisms be used in mathematics?

Proper homeomorphisms are useful in many areas of mathematics, including topology, geometry, and functional analysis. They are often used to define equivalence relations between spaces and to study the structure and properties of various mathematical objects.

Can proper homeomorphisms be generalized to other types of functions?

Yes, the concept of properness can be applied to other types of functions, such as proper mappings or proper embeddings. These functions also preserve the topological structure of a space and have properties similar to proper homeomorphisms.

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