The astrophysics of rotational energy extraction from a black hole
  Recent work has called into question whether nature can extract the
rotational energy of a black hole via electromagnetic fields by appealing to an
alleged ability to absorb current. We describe the strategies needed to
properly treat the astrophysics in curved spacetime near black holes, showing
that while the Blandford-Znajek effect is sound, the deeper nature of the
electric nature of black holes remains unresolved.
