Kinetic theory of stellar systems, two-dimensional vortices and HMF model

We discuss the kinetic theories of stellar systems, two-dimensional vortices and Hamiltonian mean field model, stressing their analogies and differences. We describe the evolution of the system as a whole and discuss the timescale of relaxation towards the Boltzmann distribution predicted by statistical mechanics. We also consider the relaxation of a test particle in a bath of field particles and analyze it with the aid of a Fokker-Planck equation involving a term of diffusion counterbalanced by a friction or a drift.