RESUMO
The implementation of Monte Carlo methods acting in the quantum phase space is hindered by the fact that quantum phase-space information is available only through quasiprobability densities. In this work, we present a first-principles Monte Carlo method employing a hidden variables representation. This allows the full quantum time evolution of an arbitrary initial quantum state to be calculated by a classical Monte Carlo algorithm, even for systems subjected to time-dependent potentials. Guidelines for implementing a practical algorithm are presented.
Assuntos
Algoritmos , Luz , Modelos Estatísticos , Método de Monte Carlo , Teoria Quântica , Simulação por Computador , Espalhamento de RadiaçãoRESUMO
We report experimental results concerning observation of a pattern forming system, subject to directional viscous fingering (printer's instability). This system was excited by a time-dependent, periodic perturbation. A variety of spatiotemporal effects was observed, including pattern transient dynamics, wave vector selection, and morphological transitions. Detailed measurement of pattern shape and its associated Fourier modes assured the detection of a crossover between different regimes of the pattern evolution.
RESUMO
A precursor is a kind of instability in a nonequilibrium system observed prior to a bifurcation. It has been observed in important natural phenomena such as earthquakes and epileptic seizures. In most cases just qualitative results were reported, with the exception of some quantitative observations of noisy precursors. We report the observation of precursors excited by a deterministic perturbation. Quantitative characterization of this type of precursor is important in predicting a bifurcation in advance. This predicting ability comes from a dynamical structure present on the perturbed system.