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- Summary
- Form Factors Of QED electron vertex function.

In Peskin book they calculate the QED Vertex Function named Gamma which depend on two scalar functions called form factors F1(q^2), F2(q^2).

they are calculating F1(q^2) and they do not really finish calculating for what I understand. They are just showing the Infrared divergent is cancelled by soft photons. Does it depend on the energy E_l of the largest energy measurable photon? and according to Wikipedia F1[0]=1 to all orders in perturbation theory , why is that?

And also, are there any physical quantities that are calculated due to F1[q^2] (I guess probably there are high energy physical quantities, but are there low energy ones such as g the anomalous magnetic moment?)

they are calculating F1(q^2) and they do not really finish calculating for what I understand. They are just showing the Infrared divergent is cancelled by soft photons. Does it depend on the energy E_l of the largest energy measurable photon? and according to Wikipedia F1[0]=1 to all orders in perturbation theory , why is that?

And also, are there any physical quantities that are calculated due to F1[q^2] (I guess probably there are high energy physical quantities, but are there low energy ones such as g the anomalous magnetic moment?)