I will review several non-equilibrium dynamical effects
characteristic of systems with long-range interactions. In particular,
the intriguing formation of quasi-stationary states, which evolve to
equilibrium slower and slower as system size increases. In this
respect, I will discuss several models which show such features,
beginning with simple mean-field models of the Ising or the XY type.

References:
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 ``Statistical theory of high-gain free-electron laser saturation",
 Phys. Rev. E, Rapid Comm. {\bf 69}, 045501 (R) (2004).
-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, {\bf 337}, 36 (2004).
-D. Mukamel, S. Ruffo and N. Schreiber: 
 "Microcanonical dynamics and breaking of ergodicity in systems with long-range interactions",
 submitted to Phys. Rev. Lett., {\bf 95}, 240604 (2005).