# Tagged Questions

In first order of perturbation theory the S-matrix amplitude for electron scattering in the Coulomb field will be (up to normalization factors) $$S_{fi} = \frac{iZ q^2}{\sqrt{2E_{f}2E_{i}}}\bar ... 1answer 198 views ### Determinant of Dirac operator in flat space? How would you evaluate $$|iD\!\!\!\!/-m|$$ Where D_{\mu}=\partial_{\mu}-ieA_{\mu}. I have an idea of how to do this without the gauge field, because it's essentially ... 2answers 210 views ### A step in the derivation of the magnetic momentum of the electron in Zee's QFT book In chapter III.6 of his Quantum Field Theory in a Nutshell, A. Zee sets out to derive the magnetic moment of an electron in quantum electrodynamics. He starts by replacing in the Dirac equation the ... 2answers 149 views ### Spinors Under Spatial Reflection How eq(4.4) is a solution of eq(4.3) 2answers 298 views ### Energy spectrum of a Dirac electron How do you explain easily "The spectrum of an electron in a repulsive potential " and hence "bound state of charge conjugation" in Dirac hole theory ? 2answers 207 views ### numerical formulation of Dirac equation plus electromagnetic field I have the following equations describing the electron field in a (classic) electromagnetic field:$$ c\left(\alpha _i\right.{\cdot (P - q(A + A_b) + \beta mc) \psi = E \psi }  where $A_b$ is ...
EVERY QFT text I've ever examined states that if there is an external vector potential, $A_\mu$, then one writes the Dirac eq.(or Klein-Gordon eq.) using a covariant derivative to include this U(1) ...