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How to figure out Perturbed Lagrangians?

  1. Jun 23, 2009 #1
    I hope this is the right area to ask this, but does anyone know of a good link which describes perturbation theory? Or even a good book?

    I have a lagrangian that is a function of the vector potential and I need to figure out the perturbed lagrangian by perturbing the vector potential. That is, I need to figure out Delta of Lagrangian of Vector Potential. Or how to I figure out:

    dL = L(A+dA) - L(A) = ??? Say L = 2A + K

    Would it work the same way differentials are taken? How do you figure out:

    L(A+dA) ?????

    Clearly I'm missing something here!!!
  2. jcsd
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