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Search Results: 1 - 10 of 297554 matches for " J. Kurchan "
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Tailoring symmetry groups using external alternate fields
I. Junier,J. Kurchan
Physics , 2002, DOI: 10.1209/epl/i2003-00583-2
Abstract: Macroscopic systems with continuous symmetries subjected to oscillatory fields have phases and transitions that are qualitatively different from their equilibrium ones. Depending on the amplitude and frequency of the fields applied, Heisenberg ferromagnets can become XY or Ising-like -or, conversely, anisotropies can be compensated -thus changing the nature of the ordered phase and the topology of defects. The phenomena can be viewed as a dynamic form of "order by disorder".
Canonically invariant formulation of Langevin and Fokker-Planck Equations
O. Cepas,J. Kurchan
Physics , 1997, DOI: 10.1007/s100510050243
Abstract: We present a canonically invariant form for the generalized Langevin and Fokker-Planck equations. We discuss the role of constants of motion, and the construction of conservative stochastic processes.
Fourier law in a momentum-conserving chain
C. Giardina',J. Kurchan
Physics , 2005, DOI: 10.1088/1742-5468/2005/05/P05009
Abstract: We introduce a family of Hamiltonian models for heat conduction with and without momentum conservation. They are analytically solvable in the high temperature limit and can also be efficiently simulated. In all cases Fourier law is verified in one dimension.
Microscopic realizations of the Trap Model
I. Junier,J. Kurchan
Mathematics , 2003, DOI: 10.1088/0305-4470/37/13/003
Abstract: Monte Carlo optimizations of Number Partitioning and of Diophantine approximations are microscopic realizations of `Trap Model' dynamics. This offers a fresh look at the physics behind this model, and points at other situations in which it may apply. Our results strongly suggest that in any such realization of the Trap Model, the response and correlation functions of smooth observables obey the fluctuation-dissipation theorem even in the aging regime. Our discussion for the Number Partitioning problem may be relevant for the class of optimization problems whose cost function does not scale linearly with the size, and are thus awkward from the statistical mechanic point of view.
Putting hydrodynamic interactions to work: tagged particle separation
J. L. Iguain,J. Kurchan
Physics , 2002, DOI: 10.1209/epl/i2003-00572-5
Abstract: Separation of magnetically tagged cells is performed by attaching markers to a subset of cells in suspension and applying fields to pull from them in a variety of ways. The magnetic force is proportional to the field gradient, and the hydrodynamic interactions play only a passive, adverse role. Here we propose using a homogeneous rotating magnetic field only to make tagged particles rotate, and then performing the actual separation by means of hydrodynamic interactions, which thus play an active role. The method, which we explore here theoretically and by means of numerical simulations, lends itself naturally to sorting on large scales.
On the Out of Equilibrium Relaxation of the Sherrington - Kirkpatrick model
L. F. Cugliandolo,J. Kurchan
Physics , 1993, DOI: 10.1088/0305-4470/27/17/011
Abstract: We derive analytical results for the large-time relaxation of the Sherrington - Kirkpatrick model in the thermodynamic limit, starting from a random configuration. The system never achieves local equilibrium in any fixed sector of phase-space, but remains in an asymptotic out of equilibrium regime. We propose as a tool, both numerical and analytical, for the study of the out of equilibrium dynamics of spin-glass models the use of `triangle relations' which describe the geometry of the configurations at three (long) different times.
Analytical Solution of the Off-Equilibrium Dynamics of a Long Range Spin-Glass Model
L. F. Cugliandolo,J. Kurchan
Physics , 1993, DOI: 10.1103/PhysRevLett.71.173
Abstract: We study the non-equilibrium relaxation of the spherical spin-glass model with p-spin interactions in the $N \rightarrow \infty$ limit. We analytically solve the asymptotics of the magnetization and the correlation and response functions for long but finite times. Even in the thermodynamic limit the system exhibits `weak' (as well as `true') ergodicity breaking and aging effects. We determine a functional Parisi-like order parameter $P_d(q)$ which plays a similar role for the dynamics to that played by the usual function for the statics.
Weak-ergodicity breaking in mean-field spin-glass models
L. F. Cugliandolo,J. Kurchan
Physics , 1994, DOI: 10.1080/01418639508238541
Abstract: We review the long-time off-equilibrium dynamical behaviour of two representative mean-field spin-glass models, namely the $p$-spin spherical and the Sherrington-Kirkpatrick models. We show how both models capture aging phenomena but with rather different characteristics. We discuss a scenario that allows for interpreting our results.
Evidence of aging in mean-field spin glass models
L. F. Cugliandolo,J. Kurchan,F. Ritort
Physics , 1993, DOI: 10.1103/PhysRevB.49.6331
Abstract: We study numerically the out of equilibrium dynamics of the hypercubic cell spin glass in high dimensionalities. We obtain evidence of aging effects qualitatively similar both to experiments and to simulations of low dimensional models. This suggests that the Sherrington-Kirkpatrick model as well as other mean-field finite connectivity lattices can be used to study these effects analytically.
Off equilibrium dynamics and aging in unfrustrated systems
L. F. Cugliandolo,J. Kurchan,G. Parisi
Physics , 1994, DOI: 10.1051/jp1:1994212
Abstract: We analyse the Langevin dynamics of the random walk, the scalar field, the X-Y model and the spinoidal decomposition. We study the deviations from the equilibrium dynamics theorems (FDT and homogeneity), the asymptotic behaviour of the systems and the aging phenomena. We compare the results with the dynamical behaviour of (random) spin-glass mean-field models.
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