Transient states in two-dimensional N-body systems

Tatekawa, Takayuki; Sakagami, Masaaki*; Taruya, Atsushi*; Okamura, Takashi*; Ruffo, S.*

We will discuss relaxation processes toward thermal equilibrium in the long-range interacting system by N-body simulations. In the early stage of its evolution, the system visits quasi-equilibrium state where the value of physical quantities such as mean kinetic energy are different from equilibrium ones. Then it gradually evolves toward thermal equilibrium. We find that this transient states can be described by the polytrope which is given by the one-particle distribution of the energy , , only when the system has the negative specific heat. The relaxation processes are characterized by increase of index n to infinity which corresponds the Boltzmann distribution. For dynamical evolution, we are trying to accelerate N-body simulations with General-Purpose computation on Graphics Processing Units (GPGPU). GPGPU can accelerate the computation of 2-body interactions.