Example of Set X with Two Topologies: Continuous But Not Homeomorphic

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Discussion Overview

The discussion revolves around finding an example of a set X with two topologies T and S such that the identity function from (X,T) to (X,S) is continuous but not homeomorphic. The scope includes conceptual understanding of topological properties and definitions related to continuity and homeomorphism.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant requests an example of a set X with two topologies T and S where the identity function is continuous but not homeomorphic, expressing feelings of being overwhelmed by the generality of the problem.
  • Another participant asks for definitions of "continuous" and "homeomorphic," suggesting the post belongs in the Homework Help section.
  • A participant provides standard definitions for continuity and homeomorphism, indicating that the identity function must fail at least one property of homeomorphism to not be homeomorphic.
  • One participant suggests that the identity function must fail to meet one of the four properties of homeomorphism while remaining continuous, prompting further exploration of which property that might be.
  • Another participant asserts that they are looking for a set X where the two topologies are never homeomorphic, indicating a belief that this is a general property of topological spaces.
  • A suggestion is made to consider a two-point set, implying that this could serve as a suitable example.
  • A participant inquires about the use of a particular point topology, seeking clarification on the approach being suggested.
  • A later reply indicates that the participant has resolved their question independently, expressing gratitude for the help received.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and approaches to the problem, with some disagreement on the complexity of the task and the definitions involved. The discussion does not reach a consensus on a specific example.

Contextual Notes

There are unresolved aspects regarding the specific properties of the topologies T and S that would lead to the identity function being continuous but not homeomorphic. The discussion also reflects varying interpretations of the definitions provided.

kiriyama
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Give an example of a set X with two topologies T and S such that the identity function from (X,T) to (X,S) is continuous but not homeomorphic.

I always struggle with these because I get overwhelmed by the generality that it has. Any ideas would be very much appreciated.
 
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What are the definitions of "continuous" and "homeomorphic"? Also, this post should be in the Homework Help section.
 
i apologize i am new here...just looked for the first place that seemed appropriate


and i assume the definitions to be the standard ones...

continuous:
T and S are topologies and F:X->Y; for each S open subset V of Y, f^-1(V) is a T open subset of X

and homeomorphic:
f is one to one, onto, continuous, and open
 
Okay, and if I is the identity function from (X,T) to (X,S), V is a subset of X, what is I-1(V)? If U is a subset X, what is I(U)? Now if I is not a homeomorphism, it has to fail to have at least one of the four properties you listed under the definition of homeomorphic. If we are trying to find an example when I is continuous, then there is in fact only one of those four properties of homeomorphism that I would fail to have. Which is it?
 
i believe youre over complicating this

im looking for an example of a set X that has two topologies T and S that has an identity function from (X,T) to (X,S) that is continuous but not homeomorphic

i already know that given any space X and two topologies T and S, (X,T) and (X,S) are never homeomorphic.

im just looking for an example of this
 
you are looking for a set with two topologies, one contained in the other. ho hum.

try a 2 point set.
 
using a particular point topology?

or what?

can you please explain

i mean i get where youre headed but I am trying to find the missing step in between
 
nvmd...i got it...took a little longer than i hoped but i got it now

thanks for the help
 

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