How to find a basis for the vector space of real numbers over the field Q?

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Discussion Overview

The discussion revolves around finding a basis for the vector space of real numbers (R) over the field of rational numbers (Q). Participants explore the implications of the Axiom of Choice and the nature of transcendental numbers in this context, considering both theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asserts that the dimension of the vector space R over Q is infinite due to the existence of transcendental numbers that are not algebraic.
  • Another participant suggests that finding a basis for this vector space may not be possible without employing a weaker form of the Axiom of Choice.
  • A participant introduces the concept of the Vitali Set, proposing that selecting representatives from equivalence classes defined by rational differences might form a basis for R over Q, although they acknowledge the need for the Axiom of Choice in this construction.
  • Another participant agrees with the potential of the Vitali Set approach, discussing how it could span the interval [0,1] and questioning the linear independence of the proposed set.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of finding a basis for R over Q, with some supporting the Vitali Set approach while others emphasize the limitations imposed by the Axiom of Choice. The discussion remains unresolved regarding the validity and implications of these ideas.

Contextual Notes

Participants note the dependence on the Axiom of Choice for certain constructions and the implications of transcendental numbers on the dimensionality of the vector space. There are also unresolved questions about the linear independence of the proposed basis elements.

Arian.D
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So the title says everything. Let's assume R is a set equipped with vector addition the same way we add real numbers and has a scalar multiplication that the scalars come from the field Q. I believe the dimension of this vector space is infinite, and the reason is we have transcendental numbers that are not algebraic. On the other hand we know from the axiom of choice that any vector space has a basis, so is there a way to find a basis for this interesting one?

I hope my question isn't wrong.
 
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Probably, it is not possible to find such a basis without using at least some weaker form of the Axiom of Choice.
 
I might be way off here, but this is just a first thought. Have you heard of "the" (quotes because there is more than one) Vitali Set? The one I am thinking about is built like this: consider the interval [0,1]. Now, make an equivilence relation x~y iff x-y is rational. Now, pick one element from each equvilence class (you have to use the axiom of choice here.) This seems like it *might* form a basis for R over Q. But, like I said, this is one of the first things that popped in my mind so it might be wayyy off.
 
I think it might work. For example, if [r]_{\alpha} is the collection of equivilence classes, and if z \in [0,1] and z \in [r] for some r then r-z = q \in \mathbb{Q}. So that z = 1r + q1. So if we require that 1 be one of the numbers from the equivilency classes, then this set certainly spans [0,1]. And by taking q to be an integer + q it seems like this set will span the whole real line. Now, are they linearly independent?
 

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