Accretion disks around Kerr black holes: vertical equilibrium reviseted
  We re-derive the equation for vertical hydrodynamical equilibrium of stationary thin and slim accretion disks in the Kerr spacetime. All the previous derivations have been unsatisfactory, yielding unphysical singularities. Our equation is non-singular, more general, and simpler than those previously derived. 
M.A. Abramowicz, A.Lanza, and M.J. Percival