Supersymmetric, rotating, asymptotically flat black holes with a regular horizon are rare configurations in string theory. One example is known in five spacetime dimensions, within the toroidal compactification of type IIB string theory. The existence of such special solution is allowed by the existence of a Chern-Simons coupling in the supergravity theory and by the possibility of imposing a self duality condition on the 'rotation 2-form'. We further exemplify the use of such duality condition by finding a new Brinkmann wave solution in D = 6 simple gravity, possessing Killing spinors, We then explore three peculiar features of the aforementioned black holes: (1) Oxidising to D = 10 the five-dimensional configuration may be interpreted as a system of D1-D5 branes with a Brinkmann wave propagating along their worldvolume. Unlike its five-dimensional Kaluza-Klein compactification, the universal covering space of this manifold has no causality violations, in other words, causal anomalies can be solved in higher dimensions. From the dual SCFT viewpoint, the causality bound for the compactified spacetime arises as the unitarity bound: (2) The vanishing of the scattering cross section for uncharged scalars and sufficiently high angular momentum of the background is shown still to hold at the level of charged interactions. The same is verified when a non-minimal coupling to the geometry is used. Therefore, the 'repulson' behaviour previously found is universal For non accelerated observers; (3) The solutions are shown to have a non-standard gyromagnetic ratio of 6 = 3, In contrast, the superpartners of a static, BPS, five-dimensional black hole have g = 1, At the semi-classical level, we find that a Dirac fermion propagating in the rotating hole background has g = 2 +/- 1, depending on the spinor direction of the fermion being parallel to Killing or 'anti-Killing' spinors. (C) 2000 Elsevier Science B.V. All rights reserved.
