Algebraic Multiplicity of an Eigenvalue

In summary, the conversation revolves around attempting a proof for the statement that the algebraic multiplicity of an eigenvalue λ is equal to the dimension of null [T - λ I] dim V. The reference provided suggests looking at an ebook on linear algebra for further understanding. There is a discussion about the difference between geometric and algebraic multiplicities, and the user shares their attempt at the proof but is stuck in the final stage.
  • #1
vish_maths
61
1
Please have a look at the attached images.I am attempting a proof for the statement : The algebraic multiplicity of an eigen value λ is equal to dim null [T - λ I] dim V.

Please advise me on how to move ahead. Apparently, I am at the final inference required for a proof but unable to move ahead. Thank you very much for your help in this regard.

Reference : To know how results (2) and (3) in the images come, you may please have a look at this ebook - pg 165, http://fetweb.ju.edu.jo/staff/EE/jrahhal/PDF/sc%20-%20Linear%20Algebra%20Done%20Right.pdf
 

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  • #2
In my experience, the definition you gave is of the _geometric _ multiplicity, not the algebraic one. The two multiplicities may or may not coincide.
 
  • #3
WWGD said:
In my experience, the definition you gave is of the _geometric _ multiplicity, not the algebraic one. The two multiplicities may or may not coincide.
Thank you for the answer. The notes which I have say that the number of times λ appears on the diagonal of an upper triangular matrix is equal to dim null [T - λ I] dim V. Do you think there is error in this statement as well?"

I have actually attempted the proof to prove this statement. Sorry about incorrectly saying it equal to algebraic multiplicity
 
  • #4
Ah, sorry, I did not see the exponent dimV in your post , at first. In my experience, the geometric multiplicity of ## \lambda ## is the dimension of null## [T- \lambda I] ##. The algebraic multiplicity of ## \lambda ## is the multiplicity of the exponent of ##\lambda## in the factorization of ## A-cI ##.
 
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  • #5
No problem :) . Do you think I made a good attempt at the proof? I just think i got stuck in the last stage of the proof
 

What is the algebraic multiplicity of an eigenvalue?

The algebraic multiplicity of an eigenvalue refers to the number of times an eigenvalue appears as a root of the characteristic polynomial of a matrix. It is also known as the multiplicity of an eigenvalue.

How is the algebraic multiplicity related to the geometric multiplicity?

The algebraic multiplicity is always greater than or equal to the geometric multiplicity. The geometric multiplicity refers to the number of linearly independent eigenvectors associated with an eigenvalue, while the algebraic multiplicity counts the total number of times the eigenvalue appears as a root of the characteristic polynomial.

Why is the algebraic multiplicity important?

The algebraic multiplicity provides important information about the properties of a matrix and its corresponding eigenvectors. It can help determine the diagonalizability of a matrix and the number of linearly independent eigenvectors associated with each eigenvalue.

How can the algebraic multiplicity be calculated?

The algebraic multiplicity can be calculated by finding the degree of the eigenvalue in the characteristic polynomial. For example, if an eigenvalue has a multiplicity of 3, it will appear 3 times in the characteristic polynomial as a root.

What is the significance of an eigenvalue with a multiplicity of 1?

An eigenvalue with a multiplicity of 1 is known as a simple eigenvalue and has only one corresponding eigenvector. This means that the eigenvector is unique and can be used to diagonalize the matrix. This is in contrast to an eigenvalue with a higher multiplicity, which may have multiple linearly independent eigenvectors associated with it.

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