- #1
synoe
- 23
- 0
I have a question about chirality.
When a spinor [itex]\psi[/itex] have plus chirality, namely
[tex]
\gamma_5\psi=+\psi,
[/tex]
how can I write this condition for the Dirac adjoint [itex]\bar{\psi}=\psi^\dagger i\gamma^0[/itex]?
Let me choose the signature as [itex]\eta_{\mu\nu}=\mathrm{diag}(-,+,+,+)[/itex] and define [itex]\gamma_5\equiv i\gamma^0\gamma^1\gamma^2\gamma^3[/itex]. Taking the Dirac adjoint of the left hand side of the above equation,
[tex]
(\gamma_5\psi)^\dagger i\gamma^0=\psi^\dagger\gamma^\dagger_5i\gamma^0\\
=\psi^\dagger(-\gamma^0\gamma^0)\gamma_5i\gamma^0\\
=\bar{\psi}\gamma^0\gamma^0\\
=-\bar{\psi}\gamma_5,
[/tex]
so the chirality condition seems to be rewritten as
[tex]
\bar{\psi}\gamma_5=-\bar{\psi}.
[/tex]
However, for example, considering a quantity [itex]\bar{\psi}\gamma_5\psi[/itex], this result is inconsistent. Where is wrong in the above calculation?
When a spinor [itex]\psi[/itex] have plus chirality, namely
[tex]
\gamma_5\psi=+\psi,
[/tex]
how can I write this condition for the Dirac adjoint [itex]\bar{\psi}=\psi^\dagger i\gamma^0[/itex]?
Let me choose the signature as [itex]\eta_{\mu\nu}=\mathrm{diag}(-,+,+,+)[/itex] and define [itex]\gamma_5\equiv i\gamma^0\gamma^1\gamma^2\gamma^3[/itex]. Taking the Dirac adjoint of the left hand side of the above equation,
[tex]
(\gamma_5\psi)^\dagger i\gamma^0=\psi^\dagger\gamma^\dagger_5i\gamma^0\\
=\psi^\dagger(-\gamma^0\gamma^0)\gamma_5i\gamma^0\\
=\bar{\psi}\gamma^0\gamma^0\\
=-\bar{\psi}\gamma_5,
[/tex]
so the chirality condition seems to be rewritten as
[tex]
\bar{\psi}\gamma_5=-\bar{\psi}.
[/tex]
However, for example, considering a quantity [itex]\bar{\psi}\gamma_5\psi[/itex], this result is inconsistent. Where is wrong in the above calculation?