1,356,327 research outputs found
Autocorrelation functions in 3D fully frustrated systems
No full textWe present a numerical study of autocorrelation functions of a 3D fully frustrated Ising model (FFIM) simulated by spin-flip Monte-Carlo dynamics finding simple exponential decay for all the temperature above the critical temperature T-c for the autocorrelation of squared magnetization and stretched exponential decay for the energy autocorrelation below a temperature T* with T-c < T* less than or equal to T-p where T-p is the Kasteleyn-Fortuin and Coniglio-Klein percolation temperature. The results are compared to those on 2D FFIM to make light on the relevant mechanism in the onset of stretched exponential relaxation functions. (C) 1998 Published by Elsevier Science B.V. All rights reserved
A Statistical Mechanics Approach to the Inherent States of Granular
No full textWe consider a Statistical Mechanics approach to granular systems by following the original ideas developed by Edwards. We use the concept of “inherent states”, deðned as the stable conðgurations in the potential energy landscape, introduced in the context of glasses. Under simplifying assumptions, the equilibrium inherent states can be characterized by a conðgura- tional temperature, 1=ð. We link ð to Edwards’ compactivity and address the problem of its experimental measure. We also discuss the possibility to describe the time dependent distribu- tion probability in the inherent states with an appropriate master equation
Relaxation properties in a lattice gas model with asymmetrical particles
No full textWe study the relaxation process in a two-dimensional lattice gas model, where the interactions originate from the excluded volume. In this model particles have three arms with an asymmetrical shape, which results in geometrical frustration that inhibits full packing. Relaxation functions are well fitted at long times by a stretched exponential form, with a exponent decreasing when the density is raised until the percolation transition is reached, and constant for higher densities. The structural arrest of the model seems to happen only at the maximum density of the model, where both the inverse diffusivity and the relaxation times diverge with a power law. The dynamical non-linear susceptibility, defined as the fluctuations of the self-overlap autocorrelation, exhibits a peak at some characteristic time, which also seems to diverge at the maximum density
Clusters and droplets in the q-state Potts model
No full textA Potts correlated polychromatic percolation is studied. The clusters are made of sites corresponding to a given value of the q-state Potts variables, connected by bonds being active with probability pB. To treat this problem an s-state Potts Hamiltonian diluted with q-state Potts variables (instead of lattice gas variables) is introduced to which the the Migdal-Kadanoff renormalisation group is applied. It is found for a particular choice of pB=1-e-K (where K is the Potts coupling constant divided by the Boltzmann factor) that these clusters, called droplets diverge at the Potts critical point with Potts exponents
FROM AN UNCONSTRAINED MODEL WITH QUENCHED INTERACTIONS TO A CONSTRAINED MODEL WITH ANNEALED INTERACTIONS
No full textThe frustrated lattice gas model is studied in the quenched version where the interactions are quenched random variables, and in the annealed version where the interactions are allowed to evolve in time with a suitable kinetic constraint. The dynamical nonlinear susceptibility, recently introduced by Donati et al, is evaluated. In the annealed version we observe a behaviour very similar to the results for the p-spin models in mean field, and those for a Lennard-Jones mixture as found by Donati et al. In the quenched version we observe a substantially different behaviour of the dynamical susceptibility. The results suggest that the behaviour of the dynamical susceptibility in the annealed model can be interpreted as the imprint of the thermodynamic transition present in the quenched model and signalled by the divergence of the static nonlinear susceptibility. A similar mechanism might also be present in glassy systems
Comment on Two Time Scales and Violation of the Fluctuation-Dissipation Theorem in a Finite Dimensional Model for Structural Glasses
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Macroscopic glassy relaxations and microscopic motions in a Frustrated Lattice Gas
No full textWe study microscopic and macroscopic dynamical properties of a frustrated lattice gas showing the violation of Stokes-Einstein law. Its glassy behaviors are analyzed and related with experimental results in glass former systems
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