SEMINAIRE MERCREDI 19 DECEMBRE 2007
14 heures
Salle Séminaire 5
Centre de Physique Théorique
Marseille-Luminy

Stefano Ruffo
Dipartimento di Energetica "S. Stecco", Universita' di Firenze
INFN and CSDC, via s. Marta, 3 50139 Firenze, Italy

Title: Quasi-stationary states in mean-field dynamics

Abstract: Systems with mean-field like interactions display a short-time
relaxation towards Quasi Stationary States (QSSs), whose lifetime
increases with system size. Besides that, these states are
"attractive", since one observes convergence towards them from a
different generic initial state. They are robust to external and
stochastic perturbations and persist when a weak short-range
interaction is added. Examples of systems where such states appear
are: the Hamiltonian Mean-Field (HMF) model, the free-electron laser
and wave-particle Hamiltonians. Recently, the use of Lynden-Bell
entropy has been advocated to describe such states. In this talk, I
will discuss the merits and drawbacks of this approach.

Bibliography
-Y.Y. Yamaguchi, J. Barre', F. Bouchet, T. Dauxois,
S. Ruffo, "Stability criteria of the Vlasov equation and quasi-stationary
states of the HMF model", Physica A, 337, 36 (2004).
-A. Antoniazzi, F. Califano, D. Fanelli, S. Ruffo,
"Exploring the thermodynamic limit of Hamiltonian models, convergence to the
Vlasov equation", Phys. Rev. Lett, 98 150602 (2007).
-A. Antoniazzi, D. Fanelli, J. Barre', P.-H. Chavanis, T. Dauxois and S.
Ruffo, "A maximum entropy principle explains quasi-stationary states in
systems with long range interactions: the exemple of the HMF model",
Phys. Rev. E, 75, 011112 (2007).
-A. Antoniazzi, D. Fanelli, S. Ruffo and Y.Y. Yamaguchi,
"Non equilibrium tricritical point in a system with long-range interactions",
Phys. Rev. Lett., 99, 040601 (2007).