Generalizing Linear Independence: Beyond R^n and into Matrix Spaces

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Discussion Overview

The discussion revolves around the generalization of the concept of linear independence beyond vectors in R^n to other spaces, such as matrices in R^(mxn) and potentially to spaces of continuous functions and polynomials. Participants explore methods for testing linear independence in these broader contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that to test for linear independence in the space of mxn matrices, one can use a matrix of size (mxn)x(mxn) and apply determinant methods.
  • Another participant proposes using reduced-row echelon form to determine the rank of a matrix formed by the vectors, indicating that the rank reveals the number of linearly independent vectors.
  • A question is raised regarding the applicability of these methods to spaces of continuous functions and polynomials, prompting a discussion about potential limitations.
  • One participant clarifies that the standard definition of linear independence involves checking if a linear combination of vectors equals zero only when all coefficients are zero, though they express uncertainty about the case of infinitely many vectors.
  • Another participant acknowledges that the non-zero determinant condition is specific to R^n and may not apply universally.

Areas of Agreement / Disagreement

Participants express differing views on the generalization of linear independence to various spaces, with some methods being contested or requiring further clarification. There is no consensus on the applicability of the discussed methods to all types of vector spaces.

Contextual Notes

There are unresolved questions regarding the methods' applicability to infinite-dimensional spaces and the specific conditions under which the standard definitions hold true.

schaefera
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To text whether n vectors in R^n are linearly independent, you put those vectors in a matrix and take its determinant.

How can this be generalized beyond vectors in R^n-- say to the space of matrices in R^(mxn)?
 
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Hey schaefera.

In this new space do you have mxn vectors in mxn space? If so you do exactly the same thing except your matrix is (mxn)x(mxn).

If you want to check whether any set of vectors are linearly dependent (below the dimension of the space), simply put the vectors in a matrix and do a reduced-row echelon reduction on the matrix and see what it's rank is. The rank will give you the number of linearly independent vectors for that set that you entered in.
 
How about for the space of continuous functions? Polynomials? Does the method ever break down?
 
The question of linear independence of a finite amount of vectors can be thought of as asking about solutions to the equation: [tex]c_1\mathbf{v}_1+ c_2\mathbf{v}_2+...+c_n\mathbf{v}_n= \mathbf{0}[/tex] where [itex]\mathbf{v}_i \in V[/itex] are the vectors you are testing for linear independence and [itex]c_i \in F[/itex] are scalars in your field [itex]F[/itex]. The vectors [itex]\mathbf{v}_i[/itex] will be linearly independent if and only if all the scalars, [itex]c_1,c_2,...,c_n[/itex] are zero. Said another way: [tex]c_1\mathbf{v}_1+ c_2\mathbf{v}_2+...+c_n\mathbf{v}_n= \mathbf{0} \Rightarrow c_1,c_2,...,c_n=0[/tex] So to test a set of vectors for linear independence you set up the above equation and check to see if all the scalars [itex]c_i[/itex] are zero. How exactly you go about checking that is more or less dependent on what vector space you're dealing with. As for the case of infinitely many vectors I'm not 100% sure, so I won't comment.
 
What Gamble93 gives is the usual definition of "linear independence". Requiring that a matrix having non-zero determinant is a specific property.
 
I realized after my post that I should have included that a non zero determinant implying linear independence is a specific case that applies to [itex]\mathbb{R}^n[/itex] but I was late for class so it slipped my mind. Excuse my ignorance.
 

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