Poincaré invariance implies that only scalar combinations of field operators have non-vanishing (VEV) s. The (VEV) may break some of the internal symmetries of the Lagrangian of the field theory.
Poincaré invariance implies that only scalar combinations of field operators have non-vanishing VEV's. The VEV may break some of the internal symmetries of the Lagrangian of the field theory.