Studies of the over-rotating BMPV solution

We study unphysical features of the BMPV black hole and how each can beresolved using the enhancon mechanism. We begin by reviewing how the enhanconmechanism resolves a class of repulson singularities which arise in the BMPVgeometry when D--branes are wrapped on K3. In the process, we show that theinterior of an enhancon shell can be a time machine due to non-vanishingrotation. We link the resolution of the time machine to the recently proposedresolution of the BMPV naked singularity / "over-rotating" geometry through theexpansion of strings in the presence of RR flux. We extend the analysis toinclude a general class of BMPV black hole configurations, showing that anyattempt to "over-rotate" a causally sound BMPV black hole will be thwarted bythe resolution mechanism. We study how it may be possible to lower the entropyof a black hole due to the non-zero rotation. This process is prevented fromoccurring through the creation of a family of resolving shells. The second lawof thermodynamics is thereby enforced in the rotating geometry - even whenthere is no risk of creating a naked singularity or closed time-like curves