A Green function for the general self-dual gauge field

The recent general solution by Atiyah, Hitchin, Drinfeld and Manin of the self-duality equations for an arbitrary compact classical group is discussed. The Green function for a scalar field transforming as a vector under the group is shown to take an elegant form in the background field of the general self-dual solution. The massless solutions of the Dirac equation, for this representation of the group, are also explicitly exhibited. (Auth.)