Glassy phase in the Hamiltonian Mean Field model

Abstract

We study the relaxation dynamics of a Hamiltonian system of N fully-coupled XY spins. The thermodynamics of the system predicts a ferromagnetic and a paramagnetic phase. Starting from out-of-equilibrium initial conditions, the dynamics at constant energy drives the system into quasi-stationary states (QSS) characterized by dynamical frustration. We introduce the spin polarization as a new order parameter which allows to interpret the dynamically generated QSS regime as a glassy phase of the model.

Comments: Revtex4, 4 pages, 3 figures. New revised and improved version. Analogy with spin-glasses relativised, refs added, fig3 improved