Is the trace of a matrix independent of basis?

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Discussion Overview

The discussion centers around whether the trace of a matrix is independent of the basis used to represent it. Participants explore the relationship between the trace of a matrix and the eigenvalues of the corresponding operator, as well as the implications of changing bases on the representation of operators.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions if the trace of a matrix is independent of basis, noting that the trace equals the sum of the eigenvalues of the operator represented by the matrix.
  • Another participant suggests that the original question may already contain its own answer, implying that the trace should remain consistent across different bases.
  • A further contribution clarifies that while the trace may be the same in different bases, the matrices representing the operator will differ, indicating a distinction between the operator itself and its matrix representation.

Areas of Agreement / Disagreement

Participants express differing views on the independence of the trace from the basis, with some suggesting it is independent while others highlight the change in matrix representation across bases. The discussion remains unresolved regarding the implications of these points.

Contextual Notes

There is a potential ambiguity in the phrasing of the original question, particularly regarding the relationship between the operator and its matrix representations in different bases.

Trixie Mattel
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Hello,

Just wondering if the trace of a matrix is independent of basis, seeing as the trace of a matrix is equal to the sun of the eigenvalues of the operator that the matrix is a representation of.

Thank you
 
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mfb said:
I think you answered your own question, but a quick look at Wikipedia would lead to the same result.
Thank you mfb!
 
Trixie Mattel said:
Hello,

Just wondering if the trace of a matrix is independent of basis, seeing as the trace of a matrix is equal to the sun of the eigenvalues of the operator that the matrix is a representation of.

Thank you

What you might have meant is: if an operator is represented by a matrix ##M_1## in one basis, and ##M_2## in another basis, then is ##Tr(M_1) = Tr(M_2)##?

There is an important point that an operator does not change by a change of basis, but the matrix representing an operator may change from basis to basis.
 

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