Srednicki — Quantum Field Theory · Problem 60.2

Canonical Quantization of Scalar Fields — Mark Srednicki

Physics — QFT · spinor-helicity-momentum-conservation

Problem

a) For a process with

n

external particles, and all momenta treated as outgoing, show that

\sum_{j=1}^n \langle i\,j\rangle [j\,k] = 0 \quad \text{and} \quad \sum_{j=1}^n [i\,j]\langle j\,k\rangle = 0 . \tag{60.41}

Hint: make use of eq. (60.6). b) For

n=4

, show that

[3\,1]\langle 1\,2\rangle = -[3\,4]\langle 4\,2\rangle