Dynamical Evolution of Protoplanetary Disks
  This paper reviews the theory of protostellar debris disks. After a brief introduction to accretion disk physics, I describe coagulation models of planet formation in the outer regions of planetesimal disks. Coagulation models for the Kuiper Belt produce Pluto-sized objects on timescales of 10-40 Myr. These models yield size distributions which agree with observations of Kuiper Belt objects with red magnitudes, R = 20-27. Velocity stirring models for other debris disk systems demonstrate that 500 km or larger objects can stir the velocities of small objects up to the shattering limit needed to begin a collisional cascade. 
Scott J. Kenyon