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3

Think I got it: One uses the anti-commutation relationship: $$\gamma^\nu \epsilon_\nu \gamma^\mu k'_\mu = 2\epsilon \cdot p - \gamma^\mu k'_\mu \gamma^\nu \epsilon_\nu$$ And then uses the fact that the spinors satisfy the Dirac equation, i.e: $$\bar{u} \gamma^\mu k'_\mu \approx 0$$ So that we are only left with $2\epsilon \cdot k'$ in the numerator. ...

2

First of all, these diagrams are no tadpole diagrams. A tadpole diagram is a diagram with exactly one external leg. Nevertheless, the QED diagram exists, of course. When you calculate it, you need to "connect" the electron propagator $S_F = \frac{i (\gamma \cdot p + m)}{p^2 - m^2}$ corresponding to the loop from both sides with the $\gamma^\mu$ from the ...

1

The problem with all the answers posted so far is that they are inconsistent with the historical narrative. There were three "nails in the coffin" of classical electromagnetism: namely, The black body spectrum The photo-electric effect The Compton effect. All of the critical experiments measuring these phenomena were done at the macroscopic level, with ...

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