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BRST Symmetry and unphysical polarizations

  1. Jan 8, 2012 #1

    I am reading the BRST Symmetry section of Peskin and Schroeder but I can't find anywhere
    why the BRST transformation for the gauge vector,
    [tex] \delta A_\mu^a = \varepsilon \partial_\mu c^a [/tex]
    implies that only forward polarized states can create ghosts by applying Q, Q being define by
    [tex] \delta \phi = \varepsilon Q \phi [/tex]
    I saw in a paper that it's obvious when we go to momentum space, but unfortunately it's not for me...

    Thank you!
  2. jcsd
  3. Jan 10, 2012 #2
    I'm afraid I can't help, but one point about your post confuses me- why have you taken the [itex]D^{ab}[/itex] from Peskin and Schroeder's treatment to be diagonal? Isn't it the covariant derivative in the adjoint of the gauge group?
  4. Jan 10, 2012 #3
    Yes it is. But Peskin is considering the limit case where g is equal to zero
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