On mass-deformed N=4 supersymmetric Yang-Mills theory

We construct the n-instanton action for the above model with gauge group SU(2), as a function of the collective coordinates of the general self-dual configurations of Atiyah, Drinfeld, Hitchin and Manin (ADHM). We calculate the quantum modulus u = (Tr A(2)) at the 1-instanton level, and find a discrepancy with Seiberg and Witten's proposed exact solution. As in related models (N = 2, N-F = 3 or 4), this discrepancy may be resolved by modifying their proposed relation between (u) over tilde (the parameter in the elliptic curve) and u. (C) 1997 Elsevier Science B.V.