GRAVOTHERMAL EXPANSION IN N-BODY SYSTEMS

We investigated whether gravothermal expansion occurs in N-body system s. As the most idealized case, we studied the evolution of an N-body s ystem in a spherical adiabatic wall which is initially in thermal equi librium. Such a system is thermodynamically unstable if the central de nsity is more than 709 times higher than the density just inside the w all. We performed simulation of a 2048-body system with and without ar tificial perturbations. We found that gravothermal expansion took plac e as well as gravothermal contraction. Whether gravothermal expansion occurs or not is determined by the perturbation or statistical fluctua tion on the temperature structure in the initial model. The results we re compared with that of a self-gravitating gas system.