EFFECTIVE ACTION OF THE N = 2 MAXWELL MULTIPLET IN HARMONIC SUPERSPACE

We present, in the N = 2, D = 4 harmonic superspace formalism, a gener al method for constructing the off-shell effective action of an N = 2 abelian gauge superfield coupled to matter hypermultiplets. Using mani festly N = 2 supersymmetric harmonic supergraph techniques, we calcula te the low-energy corrections to the renormalized one-loop effective a ction in terms of N = 2(anti)chiral superfield strengths. For a harmon ic gauge prepotential with vanishing vacuum expectation value, corresp onding to massless hypermultiplets, the only non-trivial radiative cor rections to appear are non-holomorphic. For a prepotential with non-ze ro vacuum value, which breaks the U(1)-factor in the N = 2 supersymmet ry automorphism group and corresponds to massive hypermultiplets, only non-trivial holomorphic [Bcorrections arise at leading order. These h olomorphic contribution are consistent with Seiberg's quantum correcti on to the effective action, while the first non-holomorphic contributi on in the massless case is the N = 2 supersymmetrization of the Heisen berg-Euler effective Lagrangian. (C) 1997 Elsevier Science B.V.