Is Dimension 3 Enough to Prove Isomorphism Between Spaces?

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Discussion Overview

The discussion revolves around the relationship between the dimension of a vector space and isomorphism, specifically questioning whether a 3-dimensional space can be equated to ℝ^3 and the implications of such statements in the context of linear transformations and homomorphisms.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that a 3-dimensional space E is isomorphic to ℝ^3, while others argue that stating E = ℝ^3 is incorrect.
  • One participant questions the notation used in their textbook, where the image of a homomorphism with dimension 3 is stated to be ℝ^3.
  • Another participant suggests that if a linear transformation has a codomain of ℝ^3 and its image has dimension 3, then the image is indeed ℝ^3.
  • It is noted that sometimes the equality sign is used to imply "isomorphic to," which could clarify the confusion regarding notation.
  • A later reply mentions that the notation in the textbook may be a slight abuse but is commonly accepted.

Areas of Agreement / Disagreement

Participants do not reach a consensus; there are competing views regarding the correct interpretation of the relationship between dimension, isomorphism, and notation in mathematical texts.

Contextual Notes

There are unresolved issues regarding the definitions of isomorphism and equality in the context of vector spaces, as well as the implications of dimensionality in linear transformations.

Daaavde
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Is it correct to state that if a space E has dimension 3 then:
E = ℝ^{3} and that the two spaces are isomorph?
 
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If E is a 3-dimensional real vector space, then yes E is isomorphic as a vector space to R3. The statement that E = R3 is false however.
 
Then I wonder why in my textbook, every time there is an omomorphism f whose image Im(f) (row space) has dimension 3 it writes Im(f) = ℝ^3.

Am I missing something?
 
Two possibilities for this: First if your linear transformation has codomain R3 and its image has dimension 3, then its image literally is R3. And two sometimes the equality sign is used to mean "isomorphic to" and in that case I am f is definitely isomorphic to R3.
 
I think I should have add that all the homomorphisms in the textbook are always f : ℝ^m \rightarrow ℝ^n
 
In that case it is a slight abuse of notation to write I am f = R3, but also a very common one.
 
I see, thank you for your answer.
 

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