Nonabelian Born-Infeld from Super-Yang-Mills effective action
  We discuss recent results on one-loop contributions to the effective action in {\cal N}=4 supersymmetric Yang-Mills theory in four dimensions. Contributions with five external vector fields are compared with corresponding ones in open superstring theory in order to understand the relation with the F^5 terms that appear in the nonabelian generalization of the Born-Infeld action. 
A.Refolli, A.Santambrogio, N.Terzi and D.Zanon