Donaldson-Witten functions of massless N = 2 supersymmetric QCD Original Research Article

We study the Donaldson-Witten function in four-dimensional topological gauge theory which is constructed from N = 2 supersymmetric SU(2) gauge theory with Nf < 4 massless fundamental hypermultiplets. When Nf = 2, 3, the strong-coupling singularities with multiple massless monopoles appear in the moduli space (the u-plane) of the Coulomb branch. We show that the invariants made out of such singularities exhibit a property which is similar to the one expected for four-manifolds of generalized simple type.