A. Zee, Quantum Field Theory in a Nutshell · Problem III.6.3

Field Theory Redux

Physics — QFT

Problem

By Lorentz invariance the right hand side of (7) has to be a vector. The only possibilities are

\gamma^\mu \bar{u}u

(p + p')^\mu\bar{u}u

, and

(p - p')^\mu\bar{u}u

. The last term is ruled out because it would not be consistent with current conservation. Show that the form given in (7) is in fact the most general allowed.

Browse the problem library