Can you provide a reference to better solution for this problem? This one is from lecture notes.
This made me think, and i realized that I should use (fg)'=f'g+fg' to the first \partial _{\mu} not the second one. Now I get it.
Of course. I tried to transform \Psi twice.
Thank you...
Hello,
I don't understand two steps in solution to the problem:
I. Homework Statement
Show that QED action is invariant under gauge transformation.
II. Relevant equations
QED action:
S= \int{d^{4} x \left[\overline{\Psi}\left(i\gamma^{\mu} D_{\mu} -m \right)\Psi...