Superfluorescence of Photonic Paint
  We consider the cooperative decay of incoherently pumped atoms in a disordered medium, where light undergoes multiple scattering. It is shown that the cooperation number, which determines the duration and amplitude of superfluorescent impulses, is given by the number of atoms along a diffusive trajectory of the light propagating through the medium. We also consider the problem of reflection of a probe wave during cooperative emission. 
Alexander Zyuzin (A.F.Ioffe Physical-Technical Institute,   St.Petersburg, Russia)