M. A. Novotny

Suppressing Roughness of Virtual Times in Parallel Discrete-Event Simulations

In a parallel discrete-event simulation (PDES) scheme, tasks are distributed among processing elements (PEs) whose progress is controlled by a synchronization scheme. For lattice systems with short-range interactions, the progress of the conservative PDES scheme is governed by the Kardar-Parisi-Zhang equation from the theory of nonequilibrium surface growth. Although the simulated (virtual) times of the PEs progress at a nonzero rate, their standard deviation (spread) diverges with the number of PEs, hindering efficient data collection. We show that weak random interactions among the PEs can make this spread nondivergent. The PEs then progress at a nonzero, near-uniform rate without requiring global synchronizations.

Kinetic Ising Model in an Oscillating Field: Finite-Size Scaling at the Dynamic Phase Transition

We study hysteresis for a two-dimensional spin-1/2 nearest-neighbor kinetic Ising ferromagnet in an oscillating field using Monte Carlo simulations. The period-averaged magnetization is the order parameter for a proposed dynamic phase transition (DPT). To quantify the nature of this transition, we present the first finite-size scaling study of the DPT for this model. Evidence of a diverging correlation length is given, and we provide estimates of the transition frequency and the critical indices {beta} , {gamma} , and {nu} . {copyright} {ital 1998} {ital The American Physical Society}

Numerical study of a mixed Ising ferrimagnetic system

We present a study of a classical ferrimagnetic model on a square lattice in which the two interpenetrating square sublattices have spins one-half and one. This model is relevant for understanding bimetallic molecular ferrimagnets that are currently being synthesized by several experimental groups. We perform exact ground-state calculations for the model, and employ Monte Carlo and numerical transfer-matrix techniques to obtain the finite-temperature phase diagram for both the transition and compensation temperatures. When only nearest-neighbour interactions are included, our non-perturbative results indicate no compensation point or tricritical point at finite temperature, which contradicts earlier results obtained with mean-field analysis.

Dynamic phase transition, universality, and finite-size scaling in the two-dimensional kinetic Ising model in an oscillating field

We study the two-dimensional kinetic Ising model below its equilibrium critical temperature, subject to a square-wave oscillating external field. We focus on the multidroplet regime, where the metastable phase decays through nucleation and growth of many droplets of the stable phase. At a critical frequency, the system undergoes a genuine nonequilibrium phase transition, in which the symmetry-broken phase corresponds to an asymmetric stationary limit cycle for the time-dependent magnetization. We investigate the universal aspects of this dynamic phase transition at various temperatures and field amplitudes via large-scale Monte Carlo simulations, employing finite-size scaling techniques adopted from equilibrium critical phenomena. The critical exponents, the fixed-point value of the fourth-order cumulant, and the critical order-parameter distribution all are consistent with the universality class of the two-dimensional equilibrium Ising model. We also study the cross-over from the multidroplet regime to the strong-field regime, where the transition disappears.

Evidence for a dynamic phase transition in [ Co / Pt ] 3 magnetic multilayers

A dynamic phase transition (DPT) with respect to the period

Monte Carlo algorithms with absorbing Markov chains: Fast local algorithms for slow dynamics.

P

Absence of first-order transition and tricritical point in the dynamic phase diagram of a spatially extended bistable system in an oscillating field.

of an applied alternating magnetic field has been observed previously in numerical simulations of magnetic systems. However, experimental evidence for this DPT has thus far been limited to qualitative observations of hysteresis loop collapse in studies of hysteresis-loop area scaling. Here, we present significantly stronger evidence for the experimental observation of this DPT in a

Langevin simulation of thermally activated magnetization reversal in nanoscale pillars

{[\text{Co}(4\text{ }\text{\AA{}})/\text{Pt}(7\text{ }\text{\AA{}})]}_{3}

From massively parallel algorithms and fluctuating time horizons to nonequilibrium surface growth

-multilayer system with strong perpendicular anisotropy. We applied an out-of-plane time-varying (sawtooth) field to the

A Tutorial on Advanced Dynamic Monte Carlo Methods for Systems with Discrete State Spaces

{[\text{Co}/\text{Pt}]}_{3}