THE BACKGROUND FIELD METHOD FOR N=2 SUPER YANG-MILLS THEORIES IN HARMONIC SUPERSPACE

The background field method for N=2 super Yang-Mills theories in harmo nic superspace is developed, The ghost structure of the theory is inve stigated. It is shown that the ghosts include two fermionic real omega -hypermultiplets (Faddeev-Popov ghosts) and one bosonic real omega-hyp ermultiplet (Nielsen-Kallosh ghost), all in the adjoint representation of the gauge group. The one loop effective action is analysed in deta il and it is found that its structure is determined only by the ghost corrections in the pure super Yang-Mills theory. As applied to the cas e of N=4 super Yang-Mills theory, realized in terms of N=2 superfields , the latter result leads to the remarkable conclusion that the one-lo op effective action of the theory does not contain quantum corrections depending on the N=2 gauge superfield only. We show that the leading low-energy contribution to the one-loop effective action in the N=2 SU (2) super Yang-Mills theory coincides with Seiberg's perturbative holo morphic effective action. (C) 1998 Elsevier Science B.V.