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gerald V

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- TL;DR Summary
- How does the respective diagram look? How can the current conservation be seen?

The term for the electromagnetic interaction of a Fermion is ##g \bar{\Psi} \gamma_\mu \Psi A^\mu##, where ##g## is a dimensionless coupling constant, ##\Psi## is the wave function of the Fermion, ##\gamma## are the gamma matrices and ##A## is the electromagnetic field. One can quite simply see that in lowest order, one Fermion line goes in, one Fermion line goes out, and one electromagnetic line goes out or in.

In contrast, for charged scalars with complex wave function ##\varphi##, the interaction term reads ##g \varphi^* A^\mu \partial_\mu \varphi - cc.##. How does the interaction diagram look in this case, in particular the part encoding ##\partial_\mu \varphi##?

The electromagnetic current produced by the scalar field is conserved. How can this be seen from the diagram?I apologize if this is a stupid question. Thank you in advance.

In contrast, for charged scalars with complex wave function ##\varphi##, the interaction term reads ##g \varphi^* A^\mu \partial_\mu \varphi - cc.##. How does the interaction diagram look in this case, in particular the part encoding ##\partial_\mu \varphi##?

The electromagnetic current produced by the scalar field is conserved. How can this be seen from the diagram?I apologize if this is a stupid question. Thank you in advance.