Making a eigenvector a linear combination of other eigenvectors

In summary, the conversation is about finding the eigenvector of \sigmax with a +1 eigenvalue as a linear combination of the eigenvectors of M. The conversation includes discussing the given equations for \sigmax and the attempt at a solution using arbitrary eigenvectors. However, the solution cannot be fully solved without knowing what M is.
  • #1
JordanGo
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Homework Statement


Write the eigenvector of [itex]\sigma[/itex]x with +1 eigenvalue as a linear combination of the eigenvectors of M.


Homework Equations



[itex]\sigma[/itex]x = (0,1),(1,0) (these are the columns)

The Attempt at a Solution



... Don't know what to do. Can someone show me how to do this using arbitrary eigenvectors, say (a,b) and (c,d)?
 
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  • #2
Can you find the eigenvector in question? Let's denote it by (v,w). Then you can write
(v,w) = C1(a,b) + C2(c,d) and solve the constant C's.
 
  • #3
Ok, that makes sense, thanks a lot!
 
  • #4
JordanGo said:

Homework Statement


Write the eigenvector of [itex]\sigma[/itex]x with +1 eigenvalue as a linear combination of the eigenvectors of M.


Homework Equations



[itex]\sigma[/itex]x = (0,1),(1,0) (these are the columns)
Okay, that's [itex]\sigma[/itex]. What is M? we can't write something "as a linear combination of the eigenvectors of M without knowing what M is!

The Attempt at a Solution



... Don't know what to do. Can someone show me how to do this using arbitrary eigenvectors, say (a,b) and (c,d)?
 

FAQ: Making a eigenvector a linear combination of other eigenvectors

1. What is an eigenvector?

An eigenvector is a vector that does not change its direction when multiplied by a given matrix. Instead, it only changes in length, which is represented by a scalar value known as the eigenvalue.

2. Why would I want to make an eigenvector a linear combination of other eigenvectors?

Making an eigenvector a linear combination of other eigenvectors can help simplify and generalize a problem. It can also help in solving systems of linear equations, diagonalizing matrices, and finding dominant eigenvalues and eigenvectors.

3. How do I make an eigenvector a linear combination of other eigenvectors?

To make an eigenvector a linear combination of other eigenvectors, you can use a method called diagonalization. This involves finding a matrix that is composed of the eigenvectors of the original matrix, as well as a diagonal matrix with the corresponding eigenvalues. Once these matrices are found, the original matrix can be written as a linear combination of the eigenvectors and eigenvalues.

4. Can any eigenvector be written as a linear combination of other eigenvectors?

Yes, any eigenvector can be written as a linear combination of other eigenvectors. This is because the eigenvectors of a matrix form a basis for the vector space, meaning that any vector in that space can be written as a linear combination of the eigenvectors.

5. Are there any limitations to making an eigenvector a linear combination of other eigenvectors?

One limitation is that the matrix must be diagonalizable, meaning that it must have a full set of linearly independent eigenvectors. Additionally, this method may not always be practical or useful in certain situations, as it may result in a large number of calculations and a more complex solution.

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