Student Friendly Introduction to QFT · Problem 8.1

The Vacuum Revisited

Physics — QFT · qed-s-operator-sub-terms

Problem

Show that the sub-term S2(1)=ie∫d4x1N{ψˉ−A+ψ+}x1S_2^{(1)} = ie\int d^4x_1 N\left\{\bar{\psi}^- \mathcal{A}^+ \psi^+\right\}_{x_1} represents destruction of an initial electron and an initial photon, followed by creation of another electron. Draw the Feynman diagram for this process. Evaluate the integral to the point where you can show that outgoing 4-momentum for the final electron equals incoming 4-momentum of the initial multi-particle state.

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