Robustness of the Blandford-Znajek mechanism
  The Blandford-Znajek mechanism has long been regarded as a key ingredient in models attempting to explain powerful jets in AGNs, quasars, blazzars etc. In such mechanism, energy is extracted from a rotating black hole and dissipated at a load at far distances. In the current work we examine the behaviour of the BZ mechanism with respect to different boundary conditions, revealing the mechanism robustness upon variation of these conditions. Consequently, this work closes a gap in our understanding of this important scenario. 
Carlos Palenzuela, Carles Bona, Luis Lehner and Oscar Reula
astro-ph.HE gr-qc