Prove or disprove: A and A transpose have the same eigenspaces

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Homework Help Overview

The discussion revolves around the relationship between a matrix \( A \) and its transpose \( A^T \) in terms of their eigenspaces. The original poster is tasked with proving or disproving the statement that \( A \) and \( A^T \) have the same eigenspaces.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to reason that since \( A \) and \( A^T \) share the same characteristic polynomial and eigenvalues, they might not have the same eigenspaces due to the swapping of elements in the transpose, unless \( A \) is symmetric. Some participants suggest creating a counterexample to explore the validity of the statement.

Discussion Status

The discussion is ongoing, with some participants indicating that they have found counterexamples that suggest the statement may not hold true unless \( A \) is symmetric. However, there is a call for specific counterexamples to solidify the disproof.

Contextual Notes

Participants are encouraged to provide specific examples to support their claims, and there is an emphasis on the need for clarity regarding the conditions under which the statement may or may not be true.

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Homework Statement



Prove or disprove: A and AT have the same eigenspaces.

Homework Equations





The Attempt at a Solution



I know that A and AT have the same determinant and so they have the same characteristic polynomial and eigenvalues, but then if they are transposed then the stuff above and below the main diagonal is swapped then they wouldn't have the same eigenspaces? Unless they were symmetric?
 
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If you don't think it's true, try and create a simple example to show it isn't true. That would be a disproof.
 
Okay so I did that and showed that its not true.. unless it was symmetric. Does that count as a disprove?
 
No, you will need to come up with a specific counterexample if you want to disprove it.
 

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