Effective interactions in N=4 super-Yang-Mills theory with spontaneously broken SU(2) gauge symmetry

Using N=1 supergraph techniques, we show that no dim. <= 6 effective operators can be generated at the one-loop level in N=4 super-Yang-Mills theory with the gauge group SU(2) spontaneously broken down to U(1). Moreover, all gauge-invariant three-point functions with external massless particles vanish identically while nongauge-invariant contributions vanish on-shell. We have also calculated an example of a nonvanishing four-point scattering amplitude, showing that the theory is perturbatively nontrivial. (orig.)