Proving kernel of matrix is isomorphic to 0 eigenvalue's eigenvectors

In summary, the conversation discusses the relationship between the eigenvectors corresponding to the 0 eigenvalue of a matrix and the kernel of the matrix. The attempt at a solution suggests that the eigenvectors corresponding to the 0 eigenvalue are the same as the nullspace, but this is not a sufficient proof. The nullspace is defined as the set of vectors that satisfy Ax=0, while the set of eigenvectors corresponding to zero is defined as the set of vectors that satisfy Ax=0 and L=0. Since both definitions are essentially the same, the relationship between the two is trivial.
  • #1
Coolphreak
46
0

Homework Statement


I want to prove that the eigenvectors corresponding to the 0 eigenvalue of hte matrix is the same thing as the kernel of the matrix.


Homework Equations


A = matrix.
L = lambda (eigenvalues)

Ax=Lx


The Attempt at a Solution



Ax = 0 is the nullspace.

Ax = Lx
Lx = 0.
L= 0.
the eigenvectors corresponding to the 0 eigenvalue are the same as the nullspace.

Is this a sufficient enough proof?
 
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  • #2
No, it's not. Maybe you have the right idea, but what you've written down doesn't make a lot of sense.

The nullspace is {x : Ax = 0}. Can you write down what the set of eigenvectors corresponding to zero is?
 
  • #3
Isn't the the set of eigenvectors which correspond to the 0 eigenvalue?
 
  • #4
What is the definition of the kernel of a matrix? What is the definition of the set of eigenvectors of a matrix with eigenvalue zero? Aren't they trivially the same?
 

1. How do you prove that the kernel of a matrix is isomorphic to the eigenvectors corresponding to the eigenvalue of 0?

In order to prove this, we first need to understand the concept of a kernel. The kernel of a matrix is the set of all vectors that, when multiplied by the matrix, result in the zero vector. In other words, the kernel is the set of all solutions to the equation Ax = 0, where A is the matrix and x is the vector. Now, since the eigenvalues of a matrix are the values that satisfy the equation Ax = λx, where λ is the eigenvalue, it follows that if the eigenvalue is 0, the corresponding eigenvectors must also satisfy the equation Ax = 0. Therefore, the eigenvectors corresponding to the eigenvalue of 0 are a subset of the kernel of the matrix.

2. Can you provide an example of a matrix where the kernel is isomorphic to the eigenvectors corresponding to the eigenvalue of 0?

Yes, consider the 2x2 matrix A = [0 1; 0 0]. The kernel of this matrix is the set of all vectors [x y] where x = 0. It can be easily verified that the eigenvectors corresponding to the eigenvalue of 0 are also of this form, making the two sets isomorphic.

3. Why is it important to prove that the kernel is isomorphic to the eigenvectors corresponding to the eigenvalue of 0?

This proof is important because it helps us understand the relationship between the kernel and the eigenvalues/eigenvectors of a matrix. It also allows us to make connections between different concepts in linear algebra and use them to solve problems.

4. What implications does this proof have in terms of the properties of a matrix?

This proof shows that a matrix with an eigenvalue of 0 has a non-trivial kernel, meaning that there are non-zero vectors that can be multiplied by the matrix to result in the zero vector. This has implications in terms of invertibility and the rank of the matrix, as a non-zero kernel implies that the matrix is not invertible and has a rank less than its dimensions.

5. Are there any other cases where the kernel is isomorphic to the eigenvectors of a matrix?

Yes, this is also true for matrices with an eigenvalue of 1. In this case, the eigenvectors corresponding to the eigenvalue of 1 are a subset of the kernel of the matrix, as they satisfy the equation Ax = x. This is because multiplying any vector by the identity matrix will result in the same vector, thus making them eigenvectors with an eigenvalue of 1.

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