An easy question about cartesian product

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    Cartesian Product
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Discussion Overview

The discussion revolves around the concept of the Cartesian product of sets, specifically exploring the relationships between different forms of Cartesian products and their representations in the context of functions and vector spaces.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant defines the Cartesian product of two sets A and B and questions whether (A^2)*B is equivalent to A*A*B, using the example of (R^2)*R and R*R*R.
  • Another participant asserts that they are isomorphic as vector spaces, suggesting they are the same under certain conditions.
  • A different participant clarifies that for any two sets, there exists a one-to-one and onto mapping between (A^2)xB and AxAxB.
  • One participant connects the discussion to the graph of a function, questioning if the representation of points in 3D space aligns with the Cartesian product notation.
  • Another participant agrees with the previous points, suggesting that the two representations are simply different perspectives on the same concept.
  • A later reply introduces the idea of associativity in Cartesian products, noting natural isomorphisms between different product forms.

Areas of Agreement / Disagreement

Participants express varying degrees of agreement on the relationships between the Cartesian products and their representations, but there is no consensus on the implications of these relationships in all contexts.

Contextual Notes

Some assumptions about the nature of the sets and the context of the functions are not explicitly stated, and the discussion does not resolve whether the equivalences hold in all mathematical contexts.

C0nfused
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Hi everybody,
When we have two sets A and B , we define the cartesian product of A and B as the set A*B={(x,y): (x element of A) and (y element of B)}. We also define A*A*...*A (n factors)=A^n. So when we write (A^2)*B, this is the same as A*A*B? I mean, for example (R^2)*R is the same as R*R*R, or ((1,2),3)=(1,2,3) ?
Thanks
 
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They're isomorphic as vector spaces, i.e. they are the same. (unless you want to get hyper formal, in which case I think you need to stick with just isomorphic).
 
Hum, I answered for R as a vector space, sorry. Given any 2 sets, then you have a 1-1 and onto mapping between (A^2)xB and AxAxB.
 
Thanks for your answer. Actually i am asking this question because I read somewhere that the graph of a function f (if it's called this way) is the set G={(x,f(x)):x element of f's domain}. So if f: (R^2) -> R then the vectors (x,y,f(x,y) that are points of f's 3D representation must be the same as ((x,y),f(x,y)). ( I hope u understood what i am asking).

Thanks again
 
Yes, I think I do.
And yes, they are the same. Eventually, it's just 2 different ways of looking at it- just like thinking of f(x,y) as a function of 2 scalar variables or of 1 vector variable.
I hope you understand what I'm trying to say.:)
 
To put in "proper" terms (ie ones that might help you search for other things on it) you're getting towards the idea that the cartesian product is associative: that is there are natural isomorphisms from (AxB)xC to Ax(BxC)
 

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