Explicit construction of nilpotent covariants in N=4 SYM

Some aspects of correlation functions in N = 4 SYM are discussed. Using N = 4 harmonic superspace we study two and three-point correlation functions w hich are of contact type and argue that these contact terms will not affect the non-renormalization theorem for such correlators at non-coincident poi nts. We then present a perturbative calculation of a five-point function at two loops in N = 2 harmonic superspace and verify that it reproduces the d erivative of the previously found four-paint function with respect to the c oupling. The calculation of this four-point function via the five-point fun ction turns out to be significantly simpler than the original direct calcul ation. This calculation also provides an explicit construction of an N = 2 component of an N = 4 five-point nilpotent covariant that violates U(1)(Y) symmetry. (C) 2000 Elsevier Science B.V. All rights reserved.