Proof Vector Spaces: Unique Vector Satisfying "u + 0 = u

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Discussion Overview

The discussion revolves around proving the uniqueness of the zero vector in vector spaces, specifically addressing the equation "u + 0 = u" and the implications of this statement. Participants explore the axioms of vector spaces and the methods of proof, including the use of contradiction and the properties of additive inverses.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant attempts to prove the uniqueness of the zero vector using contradiction but questions the validity of concluding that two zero vectors are equal.
  • Another participant suggests that the uniqueness of the zero vector is an axiom of vector spaces and questions the need for proof.
  • A different participant clarifies that they are trying to prove the uniqueness of the identity element in summation, indicating a misunderstanding in their initial question.
  • Some participants assert that while uniqueness of the identity is an axiom in groups, it can also be proven in vector spaces, referencing the existence of additive inverses and commutativity of addition.
  • There is a contention regarding whether the axioms state that the zero vector must be unique or if it can be proven to be unique if it exists.
  • One participant expresses frustration, noting the lack of definitions and context provided in the original question, which complicates the discussion.

Areas of Agreement / Disagreement

Participants express differing views on whether the uniqueness of the zero vector is an axiom or requires proof, and there is no consensus on the necessity of definitions or the approach to the proof itself.

Contextual Notes

Some participants highlight the importance of defining the vector space and the axioms being used, indicating that the discussion may be limited by missing definitions and assumptions.

soul
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Hi eveyone,

I was trying to prove that for the vector spaces, there is a unique vector that satisfy "u + 0 = u" and I used contradiction technique. The last point that I reached is [tex]u + 0_1 = u + 0_2[/tex]. However, I don't know whether I can say [tex]0_1 = 0_2[/tex] after this statement or there are some other operations that I must do (like this statement needs a proof as well?).

Thank you.
 
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? Why do you need to prove that? Isn't that an axiom that every vector space has to satisfy? Namely that every vector space has a unique zero vector? What axioms do you start off with?

You can "prove" this by noting that along with your last step, -u also exists in the same vector space.
 
Sorry, I guess I wrote my question wrong. I was trying to prove there is a unique identitiy element in summation and what I did is to select two different vectors and at the end of it, to show they are the same. I used the axiom in the question.
 
Uniqueness of the identity is an axiom in groups but can be proved in a vector space.

In any vector space, there exist additive inverses and addition is commutative. Add the additive inverse of u to both sides of your equation.
 
HallsofIvy said:
Uniqueness of the identity is an axiom in groups but can be proved in a vector space.

In any vector space, there exist additive inverses and addition is commutative. Add the additive inverse of u to both sides of your equation.

Is this true? Almost every group theory book I have looked at proves the uniqueness of the identity as a theorem.
 
HallsofIvy said:
Uniqueness of the identity is an axiom in groups but can be proved in a vector space.

In any vector space, there exist additive inverses and addition is commutative. Add the additive inverse of u to both sides of your equation.

The axioms say there must exist a zero vector. It does not say it is unique or must be unique. You prove that it is unique if there exists such a vector.
 
It is impossible to reply. You do not said definition of the vector space, and do not said about preceding procedure.
 

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