Gravothermal Oscillations

We present the rst clear evidence that the gravothermal oscillation takes place in N-body systems. We performed direct N-body simulations of systems of point-mass particles with particle numbers from 2,048 to 32,768. In the simulation with 32,768 particles, the central density shows an oscillation with an amplitude of 10 3 , which is similar to what was observed in more approximate models such as a conducting gas sphere and one-dimensional Fokker-Planck calculations. The amplitude is smaller for a smaller number of particles. The number of particles in the core at the maximum contraction is 10 for all runs, while the number of particles at the maximum expansion is about 0:01N. For 16,384-and 32,768-body runs, the temperature inversion during the expansion phase is clearly visible.