Help with Lorentz Transformation Notation & Matrix Entries

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Discussion Overview

The discussion revolves around the notation and representation of Lorentz transformations, specifically focusing on the indices used in matrix form and their implications for covariant and contravariant vectors. It explores the conventions in physics regarding these transformations and their notation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that the notation for Lorentz transformations can vary, using symbols like Λαβ and Λμν, and question whether the upper index consistently denotes rows in both cases.
  • One participant suggests that the representation of Lorentz transformations in matrix form depends on the choice of covariant and contravariant vectors and how the transformation acts on them.
  • A question is raised about whether the interpretation of the indices changes depending on whether the transformation acts on a contravariant or covariant vector.
  • Another participant confirms that the logic regarding the indices is accepted but emphasizes the importance of spacing between the indices in notation.
  • Several participants mention the common practice of using a prime on one of the indices to indicate the frame of reference involved in the transformation.

Areas of Agreement / Disagreement

Participants express varying interpretations of the notation and its implications, indicating that multiple competing views remain on how to represent and understand Lorentz transformations in matrix form.

Contextual Notes

The discussion highlights the dependence on specific conventions in physics regarding the representation of indices and the potential for confusion in notation, particularly in distinguishing between frames of reference.

grzz
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The symbol for a Lorentz transformation is sometimes Λαβ and sometimes Λμν.

When Λαβ is shown by a matrix, the upper index denotes the entries in the rows and the lower index denotes the entries in the columns.

When Λμν is shown by a matrix, does the upper index still denotes the entries in the rows?

Any help is much appreciated.

Thanks.
 
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This depends on how you chose to represent the Lorentz transformation in matrix form, or more precisely, how you chose to represent covariant and contravariant vectors and how the Lorentz transformation acts on them.
 
Does it mean that when Λαβ acts on a contravariant vector xβ, then the upper index of Λ denotes the rows and when Λαβ acts on a covariant vector xβ, then it is the lower index which denotes the rows?
 
Yes, that's an accepted logic. Just remember that physicists don't put mu exactly over nu, it's always a space (it's either south-west-north-east or north west-south east, but never north south).
 
I'd like to also add that usually I see a prime on one of the indices to make it easier to figure out which frame to which the Lorentz transformation is transforming to.
 
Matterwave said:
I'd like to also add that usually I see a prime on one of the indices to make it easier to figure out which frame to which the Lorentz transformation is transforming to.

Thanks for all the replies!

Yes, 'Matterwave', I intended to put a prime on one of the indices of Λ to distinguish from which frame of reference and to which frame the Λ is transforming but I could not figure out the way to do it!
 

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