The universal expression for the amplitude square in quantum electrodynamics
arXiv:1507.03522 · doi:10.4236/jmp.2015.615226
Abstract
The universal expression for the amplitude square |u_f M u_i|^2 for any matrix of interaction M is derived. It has obvious covariant form. It allows the avoidance of calculation of products of the Dirac's matrices traces and allows easy calculation of cross-sections of any different processes with polarized and unpolarized particles.
4 pages