Bm. Pimentel et Jl. Tomazelli, PATH-ORDERED PHASE-FACTORS IN SCALAR QUANTUM ELECTRODYNAMICS, Progress of theoretical physics, 93(6), 1995, pp. 1105-1112
Starting from linear equations for the complex scalar field, the two-
and three-point Green's functions are obtained in the infrared approxi
mation. We show that the infrared singularity factorizes in the vertex
function as in spinor QED, reproducing in a simple and straightforwar
d way the result of lengthy perturbative calculations.