Discreteness effects, chaos, noise and the continuum limit of self gravitating models
by
Pierfrancesco di Cintio(CNR-ISC & NAF-OAA, Sesto Fiorentino, Italia)
→
Europe/Paris
Salle Fizeau (Valrose)
Salle Fizeau
Valrose
Description
In this talk I will review the role of discreteness effects and chaos on the relaxation of stellar systems. In particular, I will discuss the chaoticity of the N-body problem as a function of the particle number N and its implication on the validity of the continuum limit. Using direct N-body simulations of self-gravitating systems we study the dependence of dynamical chaos on the system size N. We find that the N-body chaos quantified in terms of the largest Lyapunov exponent Λmax decreases with N. The values of its inverse (the so-called Lyapunov time tλ) are found to be smaller than the two-body collisional relaxation time but larger than the typical violent relaxation time, thus suggesting the existence of another collective time scale connected to many-body chaos. Moreover, we introduce a simple model based on stochastic ODE for particle in time-dependent potentials aiming at investigating the interplay between micro- and macro-chaos in processes of Violent relaxation.
