2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/180582The non-perturbative low energy effective action of N=2 SYM is studied within a microscopic string realization via D3/D-instanton systems. The localization deformation of instanton moduli space which has allowed the exact computation of multi-instanton contributions is, in this setting, due to a RR graviphoton background. The relation of deformed instanton contributions to topological string amplitudes on CY, argued by Nekrasov, appears quite natural in this framework. Based on arXiv:hep-th/0606013.5 pages, 3 fig.s, Latex, uses w-art class (included). To appear in the proceedings of the RTN workshop "ForcesUniverse", Naples, October 9-13, 2006High Energy Physics - Theorytext