Srednicki — Quantum Field Theory · Problem 62.3

Canonical Quantization of Scalar Fields — Mark Srednicki

Physics — QFT · four-photon-loop-gauge-invariance

Problem

Consider the six one-loop diagrams with four external photons (and no external fermions). Show that, even though each diagram is logarithmically divergent, their sum is finite. Use gauge invariance to explain why this must be the case.

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