Behavior of the Lyapunov exponent and phase transition in nuclei

Based on the quantum molecular dynamics model, we investigate the dynamical behaviors of the excited nuclear system to simulate the latter stage of he avy ion reactions, which associate with a liquid-gas phase transition. We t ry to search a microscopic way to describe the phase transition in real nuc lei. The Lyapunov exponent is employed and examined for our purpose. We fin d out that the Lyapunov exponent is one of good microscopic quantities to d escribe the phase transition in hot nuclei. Coulomb potential and the finit e size effect may give a strong influence on the critical temperature. Howe ver, the collision term plays a minor role in the process of the liquid-gas phase transition in finite systems.