Systems with long-range interactions display a short-time relaxation toward quasistationary states (QSSs) whose lifetime increases with system size. The application of Lynden-Bell’s theory of “violent relaxation” to the Hamiltonian Mean Field model leads to the prediction of out-of-equilibrium first- and second-order phase transitions between homogeneous (zero magnetization) and inhomogeneous (nonzero magnetization) QSSs, as well as an interesting phenomenon of phase re-entrances. We compare these theoretical predictions with direct N-body numerical simulations. We confirm the existence of phase re-entrance in the typical parameter range predicted from Lynden-Bell’s theory, but also show that the picture is more complicated than initially thought. In particular, we exhibit the existence of secondary re-entrant phases: we find unmagnetized states in the theoretically magnetized region as well as persisting magnetized states in the theoretically unmagnetized region. We also report the existence of a region with negative specific heats for QSSs both in the numerical and analytical caloric curves.

Out-of-equilibrium phase re-entrance(s) in long-range interacting systems / F. Staniscia; P. H. Chavanis; G. De Ninno; D. Fanelli. - In: PHYSICAL REVIEW E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS. - ISSN 1539-3755. - ELETTRONICO. - 80:(2009), pp. 0-0.

Out-of-equilibrium phase re-entrance(s) in long-range interacting systems

FANELLI, DUCCIO
2009

Abstract

Systems with long-range interactions display a short-time relaxation toward quasistationary states (QSSs) whose lifetime increases with system size. The application of Lynden-Bell’s theory of “violent relaxation” to the Hamiltonian Mean Field model leads to the prediction of out-of-equilibrium first- and second-order phase transitions between homogeneous (zero magnetization) and inhomogeneous (nonzero magnetization) QSSs, as well as an interesting phenomenon of phase re-entrances. We compare these theoretical predictions with direct N-body numerical simulations. We confirm the existence of phase re-entrance in the typical parameter range predicted from Lynden-Bell’s theory, but also show that the picture is more complicated than initially thought. In particular, we exhibit the existence of secondary re-entrant phases: we find unmagnetized states in the theoretically magnetized region as well as persisting magnetized states in the theoretically unmagnetized region. We also report the existence of a region with negative specific heats for QSSs both in the numerical and analytical caloric curves.
80
0
0
F. Staniscia; P. H. Chavanis; G. De Ninno; D. Fanelli
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2158/385173
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