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Computation of the effective action (Peskin 11.4)

  1. May 18, 2010 #1
    The generating functional Z[J] depends on [tex]\phi_{cl}[/tex] trough its dependence on J. At the lowest order in perturbation theory the relation between J(x) and [tex]\phi_{cl}[/tex] is just the classical field equation:

    [tex] \left(\frac{\delta L}{\delta \phi}\right)_{\phi=\phi_{cl}} + J(x) = 0 [/tex]

    The question is simple: why this expression for the field equation?

    Please help me
  2. jcsd
  3. May 29, 2010 #2
    Ah that's ok it's a functional derivative...
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