On Instanton Calculations of N=2 Supersymmetric Yang-Mills Theory
  Instanton calculations are demonstrated from a viewpoint of twisted topological field theory. Various properties become manifest such that perturbative corrections are terminated at one-loop, and norm cancellations occur between bosonic and fermionic excitations in any instanton background. We can easily observe that for a suitable choice of Green functions the infinite dimensional path integration reduces to a finite dimensional integration over a supersymmetric instanton moduli space. 
Yuhsuke Yoshida