Gravothermal expansion in N-body systems

We investigated whether gravothermal expansion occurs in N-body systems. As the most idealized case, we studied the evolution of an N-body system in a spherical adiabatic wall which is initially in thermal equilibrium. Such a system is thermodynamically unstable if the central density is more than 709 times higher than the density just inside the wall. We performed simulation of a 2048-body system with and without artificial perturbations. We found that gravothermal expansion took place as well as gravothermal contraction. Whether gravothermal expansion occurs or not is determined by the perturbation or statistical fluctuation on the temperature structure in the initial model. The results were compared with that of a self-gravitating gas system.