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Lagrangian for the propagation of light in spacetime?

  1. Jul 4, 2011 #1
    Does anyone know the Lagrangian for the propagation of light in curved spacetime? I'm disappointed to discover that I don't actually know how to compute the action for a given null curve.
  2. jcsd
  3. Jul 4, 2011 #2


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    It's the same as for a massive object except instead of the proper time being your parameterization, you have to use just some random affine parameter.
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