What is the relationship between eigenvalues and eigenvectors in 3x3 matrices?

In summary: Thus, the eigenvalues of A are the square roots of the eigenvalues of B, and the eigenvectors are the same. In summary, the eigenvalues of two 3x3 matrices A and B are related in that the eigenvalues of A are the square roots of the eigenvalues of B. Additionally, the eigenvectors of these matrices are the same. This means that the eigenvectors and eigenvalues of A and B are connected and can be easily determined from each other.
  • #1
hellomrrobot
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What does it mean when it says eigenvalues of Matrix (3x3) A are the square roots of the eigenvalues of Matrix (3x3) B and the eigenvectors are the same for A and B?
 
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  • #2
Seems simple to me.

You have two 3x3 matrices. Their eigenvectors are the same. The eigenvalues of one are the square roots of the eigenvalues of the other.
 
  • #3
Dr. Courtney said:
Seems simple to me.

You have two 3x3 matrices. Their eigenvectors are the same. The eigenvalues of one are the square roots of the eigenvalues of the other.
Yes, but what does that look like? It has been a while since I have even used the word eigenvalue/vector...
 
  • #5
Dr. Courtney said:
You have two 3x3 matrices. Their eigenvectors are the same. The eigenvalues of one are the square roots of the eigenvalues of the other.
So your question is really "what are eigenvalues and eigenvectors?". An "eigenvector for matrix A, corresponding to eigenvalue [itex]\lamba[/itex], is a vector, v, such that [itex]Av= \lambda v[/itex]".

Suppose [itex]A= \begin{bmatrix}3 & 0 & 0 \\ 0 & 2 & 0 \\ 0 & 0 & 6\end{bmatrix}[/itex]. Then it is easy to see that 3 is an eigenvalue of A with eigenvector any multiple of (1, 0, 0), 2 is an eigenvalue of A with eigenvector any multiple of (0, 1, 0), and 6 is an eigenvalue with eigenvector any multiple of (0, 0, 1).

Similarly, let [itex]B= \begin{bmatrix}9 & 0 & 0 \\ 0 & 4 & 0 \\ 0 & 0 & 36\end{bmatrix}[/itex]. Now, 9, 4, and 36 are eigenvalues of B with the same eigenvectors.
 

1. What are eigenvalues and eigenvectors?

Eigenvalues and eigenvectors are important concepts in linear algebra and matrix theory. They are used to describe the behavior of a linear transformation on a vector space. An eigenvector is a non-zero vector that, when transformed by a linear transformation, remains parallel to its original direction. An eigenvalue is a scalar that represents the amount by which the eigenvector is scaled during the transformation.

2. How are eigenvalues and eigenvectors calculated?

The process of finding eigenvalues and eigenvectors involves solving a system of equations known as the characteristic equation. This equation is formed by taking the determinant of a matrix and setting it equal to zero. The solutions to this equation are the eigenvalues, and the corresponding eigenvectors can be found by solving a system of linear equations.

3. What is the significance of eigenvalues and eigenvectors?

Eigenvalues and eigenvectors have many applications in mathematics and science. In linear algebra, they are used to understand the behavior of linear transformations and to solve systems of differential equations. In data analysis and machine learning, they are used in techniques such as principal component analysis and spectral clustering. They also have applications in physics, engineering, and computer graphics.

4. Can a matrix have more than one eigenvalue and eigenvector?

Yes, a matrix can have multiple eigenvalues and corresponding eigenvectors. In fact, the number of eigenvalues and eigenvectors of a square matrix is equal to its dimension. Additionally, some matrices may have repeated eigenvalues, meaning that there are multiple eigenvectors associated with the same eigenvalue.

5. How are eigenvalues and eigenvectors used in diagonalization?

Diagonalization is a process in linear algebra where a matrix is transformed into a diagonal matrix by using its eigenvalues and eigenvectors. This process is useful for simplifying calculations and solving problems involving matrices. The diagonal matrix can be easily raised to a power, which can be useful for solving systems of differential equations or finding the behavior of a linear transformation over multiple iterations.

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