590,050 research outputs found
Observable Dependent Quasi-Equilibrium in Slow Dynamics
We present examples demonstrating that quasi-equilibrium
fluctuation-dissipation behavior at short time differences is not a generic
feature of systems with slow non-equilibrium dynamics. We analyze in detail the
non-equilibrium fluctuation-dissipation ratio X(t,tw) associated with a
defect-pair observable in the Glauber-Ising spin chain. It turns out that throughout the short-time regime and in particular X(tw,tw) = 3/4 for
. The analysis is extended to observables detecting defects at a
finite distance from each other, where similar violations of quasi-equilibrium
behaviour are found. We discuss our results in the context of metastable
states, which suggests that a violation of short-time quasi-equilibrium
behavior could occur in general glassy systems for appropriately chosen
observables.Comment: 17 pages, 5 figures; substantially improved version of
cond-mat/040571
Generalized Elastic Model: thermal vs non-thermal initial conditions. Universal scaling, roughening, ageing and ergodicity
We study correlation properties of the generalized elastic model which
accounts for the dynamics of polymers, membranes, surfaces and fluctuating
interfaces, among others. We develop a theoretical framework which leads to the
emergence of universal scaling laws for systems starting from thermal
(equilibrium) or non-thermal (non-equilibrium) initial conditions. Our analysis
incorporates and broadens previous results such as observables' double scaling
regimes, (super)roughening and anomalous diffusion, and furnishes a new scaling
behavior for correlation functions at small times (long distances). We discuss
ageing and ergodic properties of the generalized elastic model in
non-equilibrium conditions, providing a comparison with the situation occurring
in continuous time random walk. Our analysis also allows to assess which
observable is able to distinguish whether the system is in or far from
equilibrium conditions in an experimental set-up
Non-equilibrium Anisotropic Phases, Nucleation and Critical Behavior in a Driven Lennard-Jones Fluid
We describe short-time kinetic and steady-state properties of the
non--equilibrium phases, namely, solid, liquid and gas anisotropic phases in a
driven Lennard-Jones fluid. This is a computationally-convenient
two-dimensional model which exhibits a net current and striped structures at
low temperature, thus resembling many situations in nature. We here focus on
both critical behavior and details of the nucleation process. In spite of the
anisotropy of the late--time spinodal decomposition process, earlier nucleation
seems to proceed by Smoluchowski coagulation and Ostwald ripening, which are
known to account for nucleation in equilibrium, isotropic lattice systems and
actual fluids. On the other hand, a detailed analysis of the system critical
behavior rises some intriguing questions on the role of symmetries; this
concerns the computer and field-theoretical modeling of non-equilibrium fluids.Comment: 7 pages, 9 ps figures, to appear in PR
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