The positive and negative-energy projection operators can be guessed from the Dirac equation in momentum space, equation 5.187,

(5.206) |

Applying the ``trial'' positive-energy projection operator to an arbitrary Dirac spinor and using equation 5.187, we have

(5.207) |

and similarly for the negative-energy operator, as required.

Applying the operator twice we have

(5.208) |

Since ,

(5.209) |

Therefore

(5.210) |

as required of a projection operator.

Also

(5.211) |

as required.

2004-03-18