On the Particle Heating and Acceleration in Black Hole Accretion Systems
  The lack of our knowledge on how angular momentum is transported in accretion disks around black holes has prevented us from fully understanding their high energy emissions. We briefly highlight some theoretical models, emphasizing the energy flow and electron energization processes. More questions and uncertainties are raised from a plasma physics point of view. 
H. Li, S.A. Colgate (LANL), M. Kusunose (Japan), R.V.E. Lovelace   (Cornell)