GAUGE TECHNIQUE

The gauge technique is a procedure whereby the Ward identities of a gauge theory are exatly solved to provide the longitudinal components of the Green's functions as functionals of the pure charged-line amplitudes. In quantum electrodinamics, for instance, the two-electron multiphoton amplitudes are determined by the electron propagator, which can itself be found via the Dyson-Schwinger equations: thus the procedure is gauge covariant and self-consistent. In this manner one readily obtains the infra-red properties of the amplitudes both for relativistic and nonrelativistic (axial) gauge-fixing schemes. The transverse components of the amplitudes are generated iteratively via the skeleton expansion using the gauge-covariant vertices and propagators determined by the gauge technique. As the method is nonperturbative, the prospect of applying it to the infra-red behaviour in chromodynamics looks promising. © 1979 Società Italiana di Fisica.