Non-Linear Mean Field Dynamics in the Nuclear Spinodal Zone

We demonstrate, by numerical simulations, that the dynamics of nuclear matter mean field inside the spinodal region is chaotic. Spontaneous symmetry-breaking - no explicit fluctuating term is considered - occurs leading to wild unpredictable density fluctuations. A proper recipe to calculate an average Lyapunov exponent in this multidimensional phase space is introduced. The latter is calculated for different values of the density in order to characterize in a quantitative way the chaotic and regular regions. It is argued that the mean field chaoticity can be the main mechanism of the nuclear multifragmentation occurring in the intermediate energy reactions.