Double-vector multiplet and partially broken N=4, d=3 supersymmetry

We elaborate on a new N = 2, d = 3 supermultiplet (double-vector multiplet) with a non-trivial off-shell realization of the central charge. Its bosoni c sector comprises two abelian gauge vector fields forming an SO(2) vector. We present a superfield formulation of this multiplet in the central-charg e extended N = 2, d = 3 superspace and then employ it, in the framework of the nonlinear realizations approach, as the Goldstone one for the partial b reaking N = 4 --> N = 2 in three dimensions. The covariant equations of mot ion fur the self-interacting Goldstone superfield arise as a natural genera lization of the free ones and are interpreted as the worldvolume supersymme tric form of the equations of motion of a N = 4 D2-brane. For the vector fi elds we find a coupled nonlinear system of Born-Infeld type and demonstrate its dual equivalence to the d = 5 membrane. The double-vector multiplet ca n be fused with some extra N= 2, d = 3 multiplet to form an off-shell N = 4 , d = 3 supermultiplet. (C) 2000 Elsevier Science B.V. All rights reserved.