Spiral defect chaos in a model of Rayleigh-Benard convection

A numerical solution of a generalized Swift-Hohenberg equation in two dimensions reveals the existence of a spatio-temporal chaotic state comprised of a large number of rotating spirals. This state is observed for a reduced Rayleigh number $\epsilon=0.25$. The power spectrum of the state is isotropic, and the spatial correlation function decays exponentially, with an estimated decay length $\xi \approx 2.5 \lambda_{c}$, where $\lambda_{c}$ is the critical wavelength near the onset of convection. Our study suggests that this spiral defect state occurs for low Prandtl numbers and large aspect ratios.Comment: LaTeX. 4 PostScript figures. Appende

Study of spiral pattern formation in Rayleigh-Benard convection

We present a numerical study of a generalized two-dimensional Swift-Hohenberg model of spiral pattern formation in Rayleigh-B\'enard convection in a non-Boussinesq fluid. We demonstrate for the first time that a model for convective motion is able to predict in considerable dynamical detail the spontaneous formation of a rotating spiral state from an ordered hexagon state. Our results are in good agreement with recent experimental studies of $CO_{2}$ gas. The mean flow and non-Boussinesq effects are shown to be crucial in forming rotating spirals.Comment: 9 pages, 6 Figures (Postscript, appended

Transition from Tonks-Girardeau gas to super-Tonks-Girardeau gas as an exact many-body dynamics problem

We investigate transition of a one-dimensional interacting Bose gas from a strongly repulsive regime to a strongly attractive regime, where a stable highly excited state known as the super Tonks-Girardeau gas was experimentally realized very recently. By solving exact dynamics of the integrable Lieb-Liniger Bose gas, we demonstrate that such an excited gas state can be a very stable dynamic state. Furthermore we calculate the breathing mode of the super Tonks-Girardeau gas which is found to be in good agreement with experimental observation. Our results show that the highly excited super Tonks-Girardeau gas phase can be well understood from the fundamental theory of the solvable Bose gas.Comment: 4 pages, 4 figures, version to appear in Phys. Rev. A as a Rapid Communicatio

Quantum-State Engineering of Multiple Trapped Ions for Center-of-Mass Mode

We propose a scheme to generate a superposition with arbitrary coefficients on a line in phase space for the center-of-mass vibrational mode of N ions by means of isolating all other spectator vibrational modes from the center-of-mass mode. It can be viewed as the generation of previous methods for preparing motional states of one ion. For large number of ions, we need only one cyclic operatin to generate such a superposition of many coherent states.Comment: 14 pages, revte