Why the electromagn potential obeys Callan-Symazik equa like Green Function?

[ndung200790]

Please teach me this:
Why the electromagnetic potential obeys the Callan-Symazik equation in renormalization group theory like propagator functions.By the way,are there any relation between classical potential and interaction Haminton(the product of different field operators).
Thank you very much in advance.

 

[ndung200790]

Now I think that the Fourier transform of electromagnetic potential has form of scalar propagator(because the potential in momentum space has form:1/square(momentum)).Then it must obey the Callan-Symazik equation like the Green function.Is that correct?

 

[ndung200790]

At the moment,I think the Callan-Symazik describes the ''variable process'' under the change of renormalization condition with the ''terms'' that the Green function unchanging with bare parameter.The potential is also ''varied''similarly under changing renormalization.So it must be obeyed the Callan-Symazik like Green function
However,this Callan equation has not gamma function(relating with scale of fields in Green function case),because the potential is definite measurable,it does not shift from point to point of renormalization.Is that correct?