Gamma matrices and projection operator question on different representations

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Discussion Overview

The discussion revolves around the properties and interpretations of projection operators in the context of gamma matrices and their representations, particularly focusing on chirality and the implications of different representations on the nature of spinors. The scope includes theoretical aspects of quantum field theory and Clifford algebra.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that projection operators are defined as \( P_-=\frac{1}{2}(1-\gamma^5) \) and \( P_+=\frac{1}{2}(1+\gamma^5) \), with \( \gamma^5 \) defined as \( \gamma^5=i\gamma^0\gamma^1\gamma^2\gamma^3 \).
  • There is a suggestion that in different representations, the projection operators may not take a simple form, leading to questions about how to interpret chirality and the types of spinors.
  • One participant mentions that in some representations, left-handed and right-handed spinors can be mixed, and this is clearer in two-component notation.
  • Another participant states that left-handed and right-handed spinors are defined in a specific way, although they acknowledge this is not a rigorous definition.
  • It is noted that in any representation, the chiral basis is defined as the eigenvector of the projection operator, which may not always correspond to the simple forms like (1,0).

Areas of Agreement / Disagreement

Participants express varying views on the nature of chirality and the representation of spinors, indicating that multiple competing perspectives exist without a clear consensus on the implications of different representations.

Contextual Notes

There are limitations regarding the definitions and interpretations of chirality in different representations, as well as the rigor of the definitions provided by participants.

choongstring
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Typically I understand that projection operators are defined as

P_-=\frac{1}{2}(1-\gamma^5)
P_+=\frac{1}{2}(1+\gamma^5)

where typically also the fifth gamma matrices are defined as

\gamma^5=i\gamma^0\gamma^1\gamma^2\gamma^3

and.. as we choose different representations the projection operators are.. sometimes in nice form where there is only one identity element however what happens when in certain representations it doesn't come out nicely like that how do I interpret which type of spinors are which chiraliity and such. .. anyways and what are some good materials. (shorter the better) on something complete on clifford algebra and it's representations and all the other things like charge conjugation and such.
 
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choongstring said:
Typically I understand that projection operators are defined as

P_-=\frac{1}{2}(1-\gamma^5)
P_+=\frac{1}{2}(1+\gamma^5)

where typically also the fifth gamma matrices are defined as

\gamma^5=i\gamma^0\gamma^1\gamma^2\gamma^3

and.. as we choose different representations the projection operators are.. sometimes in nice form where there is only one identity element however what happens when in certain representations it doesn't come out nicely like that how do I interpret which type of spinors are which chiraliity and such. .. anyways and what are some good materials. (shorter the better) on something complete on clifford algebra and it's representations and all the other things like charge conjugation and such.

It's just that in other representations the left-handed and right-handed spinors are mixed. It's super clear if you use the two-component notation. For references you can read Srednicki's QFT book.
 
So even in other representations, left-handed and right-handed are defined as
(0,1) (1,0) kind of way? (although this is not a rigorous definition)
 
choongstring said:
So even in other representations, left-handed and right-handed are defined as
(0,1) (1,0) kind of way? (although this is not a rigorous definition)

In any representation, the chiral basis is defined as the eigenvector of the projection operator. So it won't always be like (1,0).
 

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