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Homework Help: Mandl & Shaw problem 14.2

  1. Aug 2, 2013 #1
    The problem is on pages 323 and 324 of the second edition.

    1. The problem statement, all variables and given/known data
    Given the lagrangian
    [tex]\mathcal{L} = -\frac{1}{4}F_{\mu\nu}(x)F^{\mu\nu}(x) - \frac{1}{2}(n_{\mu}A^{\mu})^2[/tex]
    show that the momentum space photon propoagator is given by
    [tex]D_F^{\mu\nu}(k) = \frac{-g^{\mu\nu} - k^{\mu}k^{\nu}(n^2 + k^2)/(kn)^2 + (n^{\mu}k^{\nu} + n^{\nu}k^{\mu})/(kn)}{k^2 + i\epsilon}[/tex]

    2. Relevant equations

    3. The attempt at a solution
    I can solve this problem if I replace the factor [itex](n^2 + k^2)[/itex] with [itex](n^2 - k^2)[/itex].

    My question is this:

    Should the book say [itex](n^2 - k^2)[/itex] and not [itex](n^2 + k^2)[/itex]?

    This question and this question only. The meat of the answer will be one word.
  2. jcsd
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