Finding eigenvectors of similar matrices

In summary, to find an eigenvector w of PAP-1, you can use the fact about similarity by using Pv and PAP-1(Pv) = PAv = P \lambda v = \lambda Pv. This can also be thought of as a symmetry of Rn and the space of nxn matrices, where similar matrices represent the same linear operator in different bases. Hence, they have the same eigenvalues.
  • #1
Alupsaiu
13
0
If v is in Rn and is an eigenvector of matrix A, and P is an invertible matrix, how would you go about finding an eigenvector w of PAP-1?
I'm thinking you have to use a fact about similarity?
 
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  • #2
Just use Pv. Then PAP-1(Pv) = PAv = P [itex]\lambda[/itex] v = [itex]\lambda[/itex] Pv.
 
  • #3
Man I hate how painfully simple problems like these are when you see them done haha...thanks a bunch
 
  • #4
No problem. To give some intuition for this, you should think of an invertible matrix P as giving a "symmetry" of Rn. Then conjugation by P is the corresponding symmetry of the space of nxn matrices. That's really why people care about similar matrices. If two matrices are similar, then there is some "symmetry" that can transform one matrix into the other.
 
  • #5
Another way to think about it: two matrices are similar if and only if they represent the same linear operator, written in different bases (P is the "change of basis" matrix). They necessarily have the same eigenvalues since changing bases would only change vectors, not scalars.
 

FAQ: Finding eigenvectors of similar matrices

1. What are eigenvectors and why are they important in matrix operations?

Eigenvectors are special vectors that do not change direction when multiplied by a matrix. They are important in matrix operations because they represent the directions along which a matrix stretches or compresses, and they allow us to simplify complex matrix calculations.

2. How are similar matrices related to eigenvectors?

Similar matrices are matrices that have the same eigenvectors, although they may have different eigenvalues. This means that they represent the same linear transformation, but in different coordinate systems. Therefore, finding eigenvectors of similar matrices is important for understanding the properties of a linear transformation.

3. Can similar matrices have different eigenvectors?

No, similar matrices must have the same eigenvectors. This is because similar matrices represent the same linear transformation, and eigenvectors are the directions in which the transformation does not change. If the eigenvectors were different, it would mean the transformation is different.

4. How can I find eigenvectors of similar matrices?

To find eigenvectors of similar matrices, you can use the eigendecomposition method. This involves finding the eigenvalues and eigenvectors of one of the matrices, and then using those eigenvectors to create a transformation matrix that transforms the other matrix into its eigendecomposition form.

5. Are there any real-world applications of finding eigenvectors of similar matrices?

Yes, there are many real-world applications of finding eigenvectors of similar matrices. For example, in physics, eigenvectors are used to represent the different modes of vibration of a system. In engineering, they are used to understand the stability and performance of structures. In data analysis, they are used to reduce the dimensionality of a dataset and identify important features.

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