Magnetic charges in the AdS(4) superalgebra osp(4|2)

We discuss the issue of how to include magnetic charges in the AdS4 super-algebra osp(4|2). It is shown that the usual way of introducing a pseudoscalar central charge on the right hand side of the basic anticommutator does not work, because this breaks SO(2, 3) covariance. We propose a way out by promoting the magnetic charge to a vector charge, which amounts to enlarge osp(4|2) to the superconformal algebra su(2, 2|1). The conditions for 1/4, 1/2 and 3/4 BPS states are then analyzed. These states form the boundary of the convex cone associated with the Jordan algebra of 4×4 complex hermitian matrices. An Inönü-Wigner contraction of the constructed superalgebra yields a known extension of the Poincaré superalgebra containing electric and magnetic 0-brane charges as well as string-and space-filling 3-brane charges. As an example, we show how some supersymmetric AdS4 black holes fit into the classification scheme of BPS states.