Violent Relaxation of Spherical Stellar Systems

Violent relaxation process of spherical stellar systems is examined by numerical simulations of shell model. The collapse of uniform density sphere both with and without external force is investigated. It is found that time variation of mean gravitational potential field induced by external force makes the system closer to Lynden-Bell distribution. Our result imply that systems which are gravitationary affected by other systems may approach the Lynden-Bell distribution.