Index notation of matrix tranpose

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Discussion Overview

The discussion revolves around the interpretation of index notation in the context of matrix transposition as presented in a specific text. Participants explore the implications of index placement and its significance in tensor notation, particularly focusing on whether a statement regarding the transpose of a matrix is a typographical error or a valid representation.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant cites a definition of transpose from a text, questioning whether the notation used is a typo due to the positioning of indices.
  • Another participant argues that the notation is correct and clarifies the relationship between the indices in the expression provided.
  • A participant expresses confusion about the significance of the index positions and their implications for understanding upper and lower indices in tensor notation.
  • Further elaboration is provided on the importance of index order in matrix representation, indicating that the first index corresponds to the row and the second to the column.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the notation is a typo or correct. Multiple competing views remain regarding the interpretation of the index notation and its implications.

Contextual Notes

There are unresolved questions about the meaning of indices that are slightly shifted in position and how this affects the understanding of tensor notation. The discussion highlights the complexity of interpreting index placement without a clear resolution.

birulami
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Zee writes in Einstein Gravity in a nutshell page 186

"let us define the transpose by ##(\Lambda^T)_\sigma^\mu = \Lambda_\sigma^\mu##"

and even emphasizes the position of the indexes. Yes, they are not exchanged! This must be a typo, right?
 
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No, what he says is perfectly fine: he writes ##\Lambda^{\mu}{}{}_{\sigma} = (\Lambda^T)_{\sigma}{}{}^{\mu}## which is not what you wrote above.
 
And you are telling me now that this glitch in the typography of the slightly out of place indexes is the crucial point?:cry:

Oh my, I thought I understood why we have upper and lower indexes? But what is the meaning of an index slighly shifted to the right?
 
birulami said:
And you are telling me now that this glitch in the typography of the slightly out of place indexes is the crucial point?:cry:

Oh my, I thought I understood why we have upper and lower indexes? But what is the meaning of an index slighly shifted to the right?

The left-to-right order of the indices matters: in a matrix representation the first index is the row index and the second index is the column index.

[tex]A_\lambda{}^\mu = g_{\lambda\nu} \, A^{\nu\mu} = g_{\lambda\nu} \, g^{\mu\sigma} \, A^\nu{}_\sigma[/tex]
 

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