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About Noether's theorem

  1. Mar 12, 2013 #1
    This question is from K. Huang, Quantum Field Theory: from operators to path integrals.

    He says that, under a continuous infinitesimal transformation,
    [itex]\phi[/itex](x)->[itex]\phi[/itex](x)+[itex]\delta\phi[/itex]
    the change of the Lagrangian density must be in the from
    [itex]\delta[/itex]L=[itex]∂^{\mu}[/itex][itex]W_{\mu}[/itex](x)

    It is easily understood that this quantity must be Lorentz-invariant, but why should only be this form, not others (e.g. without derivatives).
     
  2. jcsd
  3. Mar 12, 2013 #2
    because only in this way,it can not affect the action integral.It is 4 divergence,so it will vanish.
     
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