- #1
AlbertEi
- 27
- 0
Hi,
In QFT we define the projection operators:
\begin{equation}
P_{\pm} = \frac{1}{2} ( 1 \pm \gamma^5)
\end{equation}
and define the left- and right-handed parts of the Dirac spinor as:
\begin{align}
\psi_R & = P_+ \psi \\
\psi_L & = P_- \psi
\end{align}
I was wondering if the left- and right-handed parts of the Dirac spinor are dependent on the representation of the gamma matrices (for instant Dirac representation, Weyl representation or Majorana representation)?
For instance, a general solution of the Dirac equation (following the book "Symmetry and the Standard Model" by Matthew Robinson who works with the signature (-,+,+,+)) is given by:
\begin{equation}
\psi(x) = a v(\mathbf{p}) e^{i p_\mu x^\mu} + b u(\mathbf{p}) e^{- i p_\mu x^\mu} \label{15.1}
\end{equation}
Then, it is not too difficult to show that for a particle at rest using the Weyl representation this results in:
\begin{equation}
v_L=-v_R
\end{equation}
and:
\begin{equation}
u_L=u_R
\end{equation}
Subsequently, he derives that in the Dirac representation the above two equations also hold. However, I do not agree with his derivation and his result, and according to my derivation the above two equations do not hold in the Dirac representation. So my question is: do the above two equations must hold for any representation (i.e. is my derivation definitely wrong)?
In QFT we define the projection operators:
\begin{equation}
P_{\pm} = \frac{1}{2} ( 1 \pm \gamma^5)
\end{equation}
and define the left- and right-handed parts of the Dirac spinor as:
\begin{align}
\psi_R & = P_+ \psi \\
\psi_L & = P_- \psi
\end{align}
I was wondering if the left- and right-handed parts of the Dirac spinor are dependent on the representation of the gamma matrices (for instant Dirac representation, Weyl representation or Majorana representation)?
For instance, a general solution of the Dirac equation (following the book "Symmetry and the Standard Model" by Matthew Robinson who works with the signature (-,+,+,+)) is given by:
\begin{equation}
\psi(x) = a v(\mathbf{p}) e^{i p_\mu x^\mu} + b u(\mathbf{p}) e^{- i p_\mu x^\mu} \label{15.1}
\end{equation}
Then, it is not too difficult to show that for a particle at rest using the Weyl representation this results in:
\begin{equation}
v_L=-v_R
\end{equation}
and:
\begin{equation}
u_L=u_R
\end{equation}
Subsequently, he derives that in the Dirac representation the above two equations also hold. However, I do not agree with his derivation and his result, and according to my derivation the above two equations do not hold in the Dirac representation. So my question is: do the above two equations must hold for any representation (i.e. is my derivation definitely wrong)?
Last edited: