Hello! Can someone explain to me the physical meaning of ##\bar{\psi}=\psi^\dagger\gamma^0## in the Dirac equation? For example when calculating propagation amplitude I see that what we calculate is ##<0|\psi(x)\bar{\psi(y)}|0>## and not ##<0|\psi(x)\psi(y)|0>## (as we do for KG equation) and I am not sure I understand why. Can someone explain? Thank you!(adsbygoogle = window.adsbygoogle || []).push({});

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# I Dirac vs KG propagation amplitude

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