On N=2 supersymmetric QCD with four flavors

Seiberg and Witten's proposed solution of N=2 SQCD with N-c=2 and N-F=3 is known to conflict with instanton calculations in three distinct ways, Here we show how to resolve all three discrepancies, simply by reparametrizing the elliptic curve in terms of quantities tau(eff)((0)) and <(mu)over tilde> rather than tau and u=(Tr<(A)under tilde(2)>). SL(2, Z) invariance of the curve is preserved. However, there is now an infinite ambiguity in the relation between tau(eff)((0)) and tau and between <(mu)over tilde> and u, corresponding to an infinite number of unknown coefficients in the instanton expansion, Thus the reinterpreted curve (unlike the cases N-F <4) no longer determines the quantum modulus II as a function of the classical VEV a. (C) 1997 Elsevier Science B.V.