Perturbative construction of self-dual configurations on the torus
  We develop a perturbative expansion which allows the construction of non-abelian self-dual SU(2) Yang-Mills field configurations on the four-dimensional torus with topological charge 1/2. The expansion is performed around the constant field strength abelian solutions found by 't Hooft. Next to leading order calculations are compared with numerical results obtained with lattice gauge theory techniques. 
M. Garcia Perez, A. Gonzalez-Arroyo and C. Pena