Browsing by Author "Leung, K. T."
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- Effects of translational symmetry breaking induced by the boundaries in a driven diffusive systemAndersen, J. V.; Leung, K. T. (American Physical Society, 1991-04)We study the effects of the boundary conditions in a driven diffusive lattice-gas model which is known to display kinetic phase transitions. We find, in the case of attractive interaction, that a boundary-condition-induced symmetry breaking of the translational invariance, along the direction of the external field, destroys the second-order kinetic phase transition. This feature is absent in equilibrium systems. In the repulsive case, the phase diagram and critical properties are probably unaltered.
- Power spectrum of the current in systems with a conserved densityLeung, K. T. (American Physical Society, 1991-09)Motivated by recent studies of model sandpiles, the power spectrum S of the current in dissipative dynamical systems with a conserved density is investigated. In contrast to self-organized criticality exhibited in certain lattice gases and noisy Langevin equations, where power laws are described by universal, simple indices, the index of S(f) for small frequency f is determined at a second-order phase transition by nontrivial critical exponents. For systems with no external drive (i.e., model B), the exact result for the dynamic exponent z is rederived. With drive (driven diffusive systems), the index is given by the exponent of anisotropies. Simulation in two dimensions yields good agreements with theoretical predictions.
- Roughness, spatial, and temporal correlations of an interface in a driven nonequilibrium lattice gasLeung, K. T.; Mon, K. K.; Valles, J. L.; Zia, Royce K. P. (American Physical Society, 1989-05)The interface of a stochastic Ising lattice gas driven into a nonequilibrium steady state by a constant, uniform electric field E parallel to the interface is studied by extensive Monte Carlo simulation in two dimensions. Dependence on the system size and the field strength of the interface profile, roughness, time, and spatial correlation functions and structure factors are found numerically, by means of a coarse-graining method. The interface at zero field is shown to be rough by the divergence of both the interface width and correlation time. As soon as E is turned on, the interface becomes smooth. We argue that the general results may be extended to other similar nonequilibrium systems, and in higher dimensions.
- Trough models: Universality classes, distribution of avalanches, and cluster sizesLeung, K. T. (American Physical Society, 1992-11)Extensions of the one-dimensional two-state trough model introduced by Carlson, Chayes, Grannan, and Swindle (CCGS) [Phys. Rev. A 42, 2467 (1990)] are considered. In particular, I investigate what kinds of physical processes are relevant to its scaling behavior. Short-range rearrangements of trough positions (slide events), which were neglected by CCGS, are shown to be irrelevant. By a simple modification of the dynamics, however, I obtain universality classes characterized by a single parameter. For trough models in general, including the two-state and the "limited local" sandpile models, asymptotically exact relations between the distribution of trough-trough distances and that of the mass of avalanches are derived. They yield moment relations in agreement with Krug's [J. Stat. Phys. 66, 1635 (1992)]. All results are verified by simulations.
- Viability of competing field theories for the driven lattice gasSchmittmann, Beate; Janssen, H. K.; Täuber, Uwe C.; Zia, Royce K. P.; Leung, K. T.; Cardy, J. L. (American Physical Society, 2000-05)It has recently been suggested that the driven lattice gas should be described by an alternate held theory in the limit of infinite drive. We review the original and the alternate field theory, invoking several well-documented key features of the microscopics. Since the alternate field theory fails to reproduce these characteristics, we argue that it cannot serve as a viable description of the driven lattice gas. Recent results, for the critical exponents associated with this theory, are reanalyzed and shown to be incorrect.
- Viability of competing field theories for the driven lattice gasSchmittmann, Beate; Janssen, H. K.; Täuber, Uwe C.; Zia, Royce K. P.; Leung, K. T.; Cardy, J. L. (American Physical Society, 2000-05-01)