Srednicki — Quantum Field Theory · Problem 80.3

Canonical Quantization of Scalar Fields — Mark Srednicki

Physics — QFT · feynman-rules-matrix-fields

Problem

Compute

\sum_{a_1,a_2,a_3,a_4} |\mathrm{Tr}(T^{a_1}T^{a_2}T^{a_3}T^{a_4})|^2

for the case of traceless

T^a

's.