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 A2〉 at the 1-instanton level, and find a discrepancy with Seiberg and Wittenʹs proposed exact solution. As in related models (N = 2, NF = 3 or 4), this discrepancy may be resolved by modifying their proposed relation between ũ (the parameter in the elliptic curve) and u.