Higher derivative terms in the effective action of N = 2 SUSY QCD from instantons

Abstract

We consider N = 2 SUSY QCD with gauge group SU(2) and N f flavours of matter with non-zero mass. Using the method of the instanton-induced effective vertex we calculate higher derivative corrections to the Seiberg-Witten result in the momuntum expansion of the low energy effective Lagrangian in various regions of the modular space. Then we focus on a certain higher derivative operator on the Higgs branch. We show that the singular behaviour of this operator comes from values of the mass of matter at which the charge singularity on the Coulomb branch collides with the monopole or dyon singularity. Given the behaviour of this operator at weak coupling coming from instantons as well as its behaviour near the points of colliding singularities we find the exact solution for this operator.