- #1
synoe
- 23
- 0
In four dimensions, left and right chiral fermion can be written as
[tex]
\psi_L=
\begin{pmatrix}
\psi_+\\
0
\end{pmatrix},\qquad
\psi_R=
\begin{pmatrix}
0\\
\psi_-
\end{pmatrix},
[/tex]
respectively, where [itex]\psi_+[/itex] and [itex]\psi_-[/itex] are some two components spinors(Weyl spinors?). In this representation, the chirality operator [itex]\gamma_5[/itex] is written as
[tex]
\gamma_5=
\begin{pmatrix}
\mathbb{1}&0\\
0&-\mathbb{1}
\end{pmatrix}.
[/tex]
In five dimensions, the fifth [itex]\gamma[/itex]-matrix [itex]\Gamma^4[/itex] can coincide with the four dimensional chiral operator [itex]\gamma_5[/itex]. The other matrices are same as four dimensional ones:
[tex]
\Gamma^\mu=\gamma^\mu\qquad\mu=0,1,2,3\\
\Gamma^4=\gamma_5.
[/tex]
In this representation, a five dimensional fermion [itex]\Psi=\psi_L[/itex] seems to be "chiral" if I define the chiral operator as [itex]\Gamma_6=\Gamma^4=\gamma_5[/itex].
However in general, there is no notion of chirality in odd dimensions. Why the above [itex]\Psi[/itex] cannot be a chiral fermion?
[tex]
\psi_L=
\begin{pmatrix}
\psi_+\\
0
\end{pmatrix},\qquad
\psi_R=
\begin{pmatrix}
0\\
\psi_-
\end{pmatrix},
[/tex]
respectively, where [itex]\psi_+[/itex] and [itex]\psi_-[/itex] are some two components spinors(Weyl spinors?). In this representation, the chirality operator [itex]\gamma_5[/itex] is written as
[tex]
\gamma_5=
\begin{pmatrix}
\mathbb{1}&0\\
0&-\mathbb{1}
\end{pmatrix}.
[/tex]
In five dimensions, the fifth [itex]\gamma[/itex]-matrix [itex]\Gamma^4[/itex] can coincide with the four dimensional chiral operator [itex]\gamma_5[/itex]. The other matrices are same as four dimensional ones:
[tex]
\Gamma^\mu=\gamma^\mu\qquad\mu=0,1,2,3\\
\Gamma^4=\gamma_5.
[/tex]
In this representation, a five dimensional fermion [itex]\Psi=\psi_L[/itex] seems to be "chiral" if I define the chiral operator as [itex]\Gamma_6=\Gamma^4=\gamma_5[/itex].
However in general, there is no notion of chirality in odd dimensions. Why the above [itex]\Psi[/itex] cannot be a chiral fermion?