Multi-instanton calculus in N = 2 supersymmetric QCD

Microscopic tests of the exact results are performed in N = 2 SU(2) supersymmetric QCD. We construct the multi-instanton solution in N = 2 supersymmetric QCD and calculate the two-instanton contribution F2 to the prepotential F explicitly. For Nf = 1,2, instanton calculus agrees with the prediction of the exact results, however, for Nf = 3, we find a discrepancy between them.