Studies Of The Over-Rotating BMPV Solution
  We study unphysical features of the BMPV black hole and how each can be resolved using the enhancon mechanism. We begin by reviewing how the enhancon mechanism resolves a class of repulson singularities which arise in the BMPV geometry when D--branes are wrapped on K3. In the process, we show that the interior of an enhancon shell can be a time machine due to non-vanishing rotation. We link the resolution of the time machine to the recently proposed resolution of the BMPV naked singularity / "over-rotating" geometry through the expansion of strings in the presence of RR flux. We extend the analysis to include a general class of BMPV black hole configurations, showing that any attempt to "over-rotate" a causally sound BMPV black hole will be thwarted by the resolution mechanism. We study how it may be possible to lower the entropy of a black hole due to the non-zero rotation. This process is prevented from occurring through the creation of a family of resolving shells. The second law of thermodynamics is thereby enforced in the rotating geometry - even when there is no risk of creating a naked singularity or closed time-like curves. 
L. Dyson