Simple question relating diffeomorphisms and homeomorphisms.

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Discussion Overview

The discussion revolves around the relationship between diffeomorphisms and homeomorphisms in the context of Euclidean spaces and manifolds. Participants explore whether the existence of a diffeomorphism between two regions implies that those regions are homeomorphic.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that if a diffeomorphism can be constructed between two regions, it implies they are homeomorphic.
  • Another participant confirms that every diffeomorphism is indeed a homeomorphism.
  • It is noted that the converse is not true, as a diffeomorphism requires a differentiable structure that an arbitrary topological space may lack.
  • A participant uses an analogy involving "ham and eggs" to question the clarity of the original inquiry, implying that understanding the terms is essential.
  • Another participant states that the continuity of a differentiable function underlies the relationship between diffeomorphisms and homeomorphisms.

Areas of Agreement / Disagreement

Participants generally agree that every diffeomorphism is a homeomorphism, but they acknowledge that the converse does not hold. The discussion remains unresolved regarding the implications of these relationships for arbitrary topological spaces.

Contextual Notes

The discussion highlights the dependence on the definitions of diffeomorphism and homeomorphism, as well as the necessity of a differentiable structure for diffeomorphisms, which may not apply to all topological spaces.

Pinu7
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Consider a Euclidean space or a manifold or whatever. Furthermore, consider two regions on this space. If one can construct a diffeomorphism between the points from one region to the other, does this imply that the two regions are homeomorphic?

My gut feeling is "yes," but I would like a confirmation with maybe an explanation.
 
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Every diffeomorphism is in particular a homeomorphism, yes.
 
though clearly not the converse. To have a diffeomorphism you need some sort of differentiable structure which an arbitrary topological space does not have.
 
if i have ham and eggs, does that mean i have eggs? i.e. you could only ask this question if you do not know what the words in it mean.
 
The explanation is the basic fact that a differentiable function is continuous.
 
mathwonk said:
if i have ham and eggs, does that mean i have eggs? i.e. you could only ask this question if you do not know what the words in it mean.
Ha, nice answer :)
 

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