Validity of the zero-thermodynamic law in off-equilibrium coupled harmonic oscillators

In order to describe the thermodynamics of the glassy systems it has been recently introduced an extra parameter also called effective temperature which generalizes the fluctuation-dissipation theorem (FDT) to systems off-equilibrium and supposedly describes thermal fluctuations around the aging state. Here we investigate the applicability of a zero-th law for non-equilibrium glassy systems based on these effective temperatures by studying two coupled subsystems of harmonic oscillators with Monte Carlo dynamics. We analyze in detail two types of dynamics: 1) sequential dynamics where the coupling between the subsystems comes only from the Hamiltonian and 2) parallel dynamics where there is a further coupling between the subsystems arising from the dynamics. We show that the coupling described in the first case is not enough to make asymptotically the effective temperatures of two interacting subsystems coincide, the reason being the too small thermal conductivity between them in the aging state. This explains why different interacting degrees of freedom in structural glasses may stay at different effective temperatures without never mutually thermalizing.Comment: 23 pages, REVTeX, 4 eps figure

TEMPORAL CHAOS VIA PERIOD-DOUBLING ROUTE IN SINE-GORDON SYSTEM

On étudie l'équation de sine-Gordon perturbée par un terme de dissipation et un forçage périodique dans la limite Schrödinger nonlinéaire. On montre que l'évolution temporelle d'une condition initiale type breather devient chaotique via les cascades de doublement de periodes.The damped, driven sine-Gordon equation is investigated in the nonlinear Schrödinger limit. It is shown that the temporal evolution of a breather as initial data becomes chaotic via period-doubling cascades

CURVATURE EFFECTS IN LASER PLASMA INTERACTIONS

In laser plasma interactions, the strong self-generated magnetic field usually has a curvature which is of the same order as the temperature and density gradients. This curvature, together with the anisotropy in the electron temperature, are shown to result in a further reduction of the already inhibited electron heat transport across the magnetic field. We show that this situation leads to hot spot formation, occurrence of Weibel type instabilities, and eventual magnetic field break-up