Multi-instanton calculus in N=2 supersymmetric gauge theory

The Seiberg-Witten solution of N = 2 supersymmetric SU(2) gauge theory may be viewed as a prediction for the infinite family of constants {F-n} measuring the n-instanton contribution to the prepotential F. Here we examine the instanton physics directly, in particular the contribution of the general self-dual solution of topological charge n constructed by Atiyah, Drinfeld, Hitchin, and Manin (ADHM). In both the bosonic and supersymmetric cases, we determine both the large- and short-distance behavior of all the fields in this background. This allows us to construct the exact classical interaction between n ADHM (super)instantons mediated by the adjoint Higgs bosons. We calculate the one- and two-instanton contributions to the low-energy Seiberg-Witten effective action and find precise agreement with their predicted values of F-1 and F-2.