Formation of the Planetary Sequence in a Highly Flattened Disk of   Frequently Colliding Planetesimals
  The kinetic theory is used to study the evolution of the self-gravitating disk of planetesimals. The effects of frequent collisions between planetesimals are taken into account by using a Krook integral in the Boltzmann kinetic equation. It is shown that as a result of an aperiodic collision-dissipative instability of small gravity disturbances the disk is subdivided into numerous dense fragments. These can eventually condense into the planetary sequence. 
Evgeny Griv (1), Michael Gedalin (1), Edward Liverts (1), David   Eichler (1), and Chi Yuan (2) ((1) Department of Physics, ...