Why does this term transform in this way?

Click For Summary

Discussion Overview

The discussion revolves around the transformation properties of the Dirac equation and the associated gamma matrices under Lorentz transformations. Participants explore the implications of these transformations on the spinor and the differential operator, addressing questions of invariance and the correct application of transformation rules.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the gamma matrices are not transformed alongside the derivative in the expression ##\gamma^{\mu} \partial_{\mu}##, suggesting they should form a Lorentz scalar.
  • Another participant clarifies that the gamma matrices are constant matrices in special relativity and do not transform like components of a 4-vector.
  • A participant expresses confusion about the Lorentz invariance of ##\gamma^{\mu} \partial_{\mu}##, noting that its transformation does not yield the same expression.
  • It is pointed out that the invariant quantity is actually ##\gamma^{\mu} \partial_{\mu} \psi##, where the spinor transforms appropriately to maintain invariance.
  • Concerns are raised about a potential typo in the transformation of the argument of ##\psi##, with a participant suggesting it reverts back in a later line.
  • Another participant questions the implications of the Dirac equation under Lorentz transformations, stating it does not imply invariance without additional conditions.
  • Discussion includes the commutation of the transformation matrix with the operator in the Dirac equation, leading to the original equation being recovered under certain transformations.
  • Participants debate the meaning of the transformation symbol ##\to##, with one expressing confusion about its interpretation in the context of Lorentz transformations.

Areas of Agreement / Disagreement

Participants express differing views on the transformation properties of the gamma matrices and the implications for Lorentz invariance. There is no consensus on the interpretation of the transformation symbol ##\to##, leading to further discussion and clarification.

Contextual Notes

Some participants highlight the potential for confusion regarding the transformation of the spinor and the implications of the Lorentz transformation being invertible. The discussion reflects varying levels of familiarity with the concepts involved, particularly among those self-studying.

  • #31
vanhees71 said:
A very good book about all the group-theoretical aspects is

R. U. Sexl, H. K. Urbantke, Relativity, Groups, Particles,
Springer, Wien (2001).

Thank you very much. I love those kinds of books. Have you read other books that belong to the same category as Relativity, Groups, Particles, meaning that they are meant to impart understanding? I only want books about "advanced" physics or mathematics like quantum field theory, general relativity, differential geometry, topology, and any other branches of pure mathematics.
 
Physics news on Phys.org
  • #32
MichaelJ12 said:
How did you go from the third line to the fourth line?
(A , B) \otimes (A^{\prime} , B^{\prime}) = (A + A^{\prime} , B + B^{\prime}) \oplus (A + A^{\prime} - 1 , B + B^{\prime}) \oplus \cdots \oplus (|A - A^{\prime}| , B + B^{\prime}) \oplus (A + A^{\prime} , B + B^{\prime} - 1) \oplus \cdots \oplus (|A - A^{\prime}| , |B - B^{\prime}|) .
Could you recommend a good book?
Almost all books on group representations in general and the representation theory of the Lorentz group \mbox{SL}(2 , \mathbb{C}) in particular teach you these stuff. The latter can be found in all textbooks on Supersymmetry.
 
  • #33
samalkhaiat said:
(A , B) \otimes (A^{\prime} , B^{\prime}) = (A + A^{\prime} , B + B^{\prime}) \oplus (A + A^{\prime} - 1 , B + B^{\prime}) \oplus \cdots \oplus (|A - A^{\prime}| , B + B^{\prime}) \oplus (A + A^{\prime} , B + B^{\prime} - 1) \oplus \cdots \oplus (|A - A^{\prime}| , |B - B^{\prime}|) .

Almost all books on group representations in general and the representation theory of the Lorentz group \mbox{SL}(2 , \mathbb{C}) in particular teach you these stuff. The latter can be found in all textbooks on Supersymmetry.

I meant where did you learn the physical meaning and significance of the gamma matrices projecting out certain spins.
 
  • #34
MichaelJ12 said:
I meant where did you learn the physical meaning and significance of the gamma matrices projecting out certain spins.
I have already said that you can learn about this stuff from all textbooks on supersymmetry. I just know this stuff because it is my business to know it.
 
  • Like
Likes   Reactions: MichaelJ12 and weirdoguy
  • #35
MichaelJ12 said:
Thank you very much. I love those kinds of books. Have you read other books that belong to the same category as Relativity, Groups, Particles, meaning that they are meant to impart understanding? I only want books about "advanced" physics or mathematics like quantum field theory, general relativity, differential geometry, topology, and any other branches of pure mathematics.
Then all textbooks by Weinberg are right for you :-)).
 
  • Like
Likes   Reactions: MichaelJ12

Similar threads

  • · Replies 3 ·
Replies
3
Views
621
Replies
3
Views
1K
  • · Replies 7 ·
Replies
7
Views
1K
  • · Replies 17 ·
Replies
17
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 14 ·
Replies
14
Views
4K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 16 ·
Replies
16
Views
2K