A Gravitational Instability-Driven Viscosity in Self-Gravitating   Accretion Disks
  We derive a viscosity from gravitational instability in self-gravitating accretion disks, which has the required properties to account for the observed fast formation of the first super-massive black holes in highly redshifted quasars and for the cosmological evolution of the black hole-mass distribution. 
Wolfgang J. Duschl (1,2,3) and Markward Britsch (1) ((1) Institut   f\"ur Theoretische Astrophysik, Universit\"at Heidelberg...