C. Yeung | Searcharxiv

arXiv1999

Triangular anisotropies in Driven Diffusive Systems: reconciliation of Up and Down

Deterministic coarse-grained descriptions of driven diffusive systems (DDS) have been hampered by apparent inconsistencies with kinetic Ising models of DDS. In the evolution towards the driven steady-state, ``triangular'' anisotropies in the two systems point in opposite directions with respect to the drive field. We show that this is non-universal behavior in the sense that the triangular anisotropy ``flips'' with local modifications of the Ising interactions. The sign and magnitude of the triangular anisotropy also vary with temperature. We have also flipped the anisotropy of coarse-grained models, though not yet at the latest stages of evolution. Our results illustrate the comparison of deterministic coarse-grained and stochastic Ising DDS studies to identify universal phenomena in driven systems. Coarse-grained systems are particularly attractive in terms of analysis and computational efficiency.

cond-mat.stat-mech↗

arXiv1993

Possibilities and Limitations of Gaussian Closure Approximations for Phase Ordering Dynamics

The nonlinear equations describing phase ordering dynamics can be closed by assuming the existence of an underlying Gaussian stochastic field which is nonlinearly related to the observable order parameter field. We discuss the relation between different implementations of the Gaussian assumption and consider the limitations of this assumption for phase ordering dynamics. The fact that the different approaches gives different results is a sign of the breakdown of the Gaussian assumption. We concentrate on the non-conserved order parameter case but also touch on the conserved order parameter case. We demonstrate that the Gaussian assumption is fundamentally flawed in the latter case.

cond-mat↗