Multiple eigenvalues - any hints would be appreciated

In summary, in order to prove that a 4x4 matrix has 2 zero eigenvalues, the characteristic equation must be obtained by calculating the determinant of the matrix. This may be a daunting task, but there is no simple alternative method. Special matrices may have tricks to simplify the calculation, but without knowing the specific matrix, it is impossible to determine. The determinant of A- \lambda I must be set equal to 0, resulting in a fourth degree polynomial equation.
  • #1
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Homework Statement



I need to prove that a 4x4 matrix has 2 zero eignenvalues.

2. The attempt at a solution

I have tried to obtain the characteristic equation but calculating the determinant of a relevant 4x4 is rather daunting as there aren't many zeros.

I was wondering if there is any other way to prove the statement without resorting to this brute force approach.

Thank you in advance!
 
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  • #2
I assume you mean that you have a specific 4 by 4 matrix that you have not shown us. No, there is no 'simple' way to calculate eigenvalues except for special matrices. Whether or not there exist a special trick for your matrix, we cannot say because you do not show us the matrix. Just calculate the determinant of [itex]A- \lambda I[/itex] and set it equal to 0. With a f4 by 4 matrix that will give you a fourth degree polynomial equation.
 

1. What are eigenvalues and how do they relate to multiple eigenvalues?

Eigenvalues are a concept in linear algebra that are used to describe the behavior of a matrix. They represent the values that a matrix can be scaled by without changing the direction of its corresponding eigenvector. Multiple eigenvalues occur when a matrix has more than one eigenvector with the same eigenvalue.

2. How do you determine the number of eigenvalues a matrix has?

The number of eigenvalues a matrix has is equal to its dimension (or the number of rows/columns). However, not all matrices have distinct eigenvalues. Some may have repeated or multiple eigenvalues.

3. Can a matrix have multiple eigenvalues with different eigenvectors?

Yes, a matrix can have multiple eigenvalues with different eigenvectors. This means that there are different directions in which the matrix can be scaled without changing the corresponding eigenvector.

4. How do you solve for eigenvalues and eigenvectors of a matrix?

To solve for eigenvalues and eigenvectors, you need to first find the values of lambda (λ) that satisfy the equation (A-λI)x=0, where A is the matrix and I is the identity matrix. Once you have the values of λ, you can plug them back into the equation to solve for the corresponding eigenvectors.

5. Why are eigenvalues and eigenvectors important in mathematics and science?

Eigenvalues and eigenvectors are important because they provide a way to simplify complex systems and understand their behavior. They are used in various fields such as physics, engineering, and data analysis to solve problems and make predictions. They also have applications in computer graphics, quantum mechanics, and machine learning, among others.

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