N-Body Simulations of Open, Self-Gravitating Systems

Astrophysical systems differ often in two points from classical thermodynamical systems: 1.) They are open and 2.) gravity is a dominant factor. Both modifies the homogeneous equilibrium structure, known from classical thermodynamics. In order to study the consequence for structure formation in astrophysical systems, we carry out N-body simulations of self-gravitating systems, subjected to an energy-flow. The simulations show that physically realistic, time-dependent boundary conditions can maintain a molecular cloud in a statistically steady state, out of thermodynamic equilibrium. Moreover we perform some simple "gravo-thermal" N-body experiments and compare them with theoretical results. We find negative specific heat in an energy range predicted by Follana and Laliena (1999).