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fxdung
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Is the expection value of expession in left hand side of motion equation of field(example: Klein-Gordon,Dirac...equations) equal zero or not?(left hand side of the equation equals zero when we put condition of mimimizing the action).If not,why we can say when expectation value of divergence of the current not equal zero then the symmetry be broken?The Lagrangian may still invariant because expectation values of both divergence of current and expression of the left hand side of Euler-Lagrange differ zero and the sum of them (equal Delta L(agrangian)) equal zero,so the symmetry still reserved.(But equation of motion be changed)
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