Directed transport and localization in phase-modulated driven lattices

We explore the dynamics of non-interacting particles loaded into a phase-modulated one-dimensional lattice formed by laterally oscillating square barriers. Tuning the parameters of the driven unit cell of the lattice selected parts of the classical phase space can be manipulated in a controllable manner. We find superdiffusion in position space for all parameters regimes. A directed current of an ensemble of particles can be created through locally breaking the spatiotemporal symmetries of the time-driven potential. Magnitude and direction of the current are tunable. Several mechanisms for transient localization and trapping of particles in different wells of the driven unit cell are presented and analyzed

Dynamical trapping and chaotic scattering of the harmonically driven barrier

A detailed analysis of the classical nonlinear dynamics of a single driven square potential barrier with harmonically oscillating position is performed. The system exhibits dynamical trapping which is associated with the existence of a stable island in phase space. Due to the unstable periodic orbits of the KAM-structure, the driven barrier is a chaotic scatterer and shows stickiness of scattering trajectories in the vicinity of the stable island. The transmission function of a suitably prepared ensemble yields results which are very similar to tunneling resonances in the quantum mechanical regime. However, the origin of these resonances is different in the classical regime.Comment: 14 page

Transverse QCD Dynamics Near the Light Cone

Starting from the QCD Hamiltonian in near-light cone coordinates, we study the dynamics of the gluonic zero modes. Euclidean 2+1 dimensional lattice simulations show that the gap at strong coupling vanishes at intermediate coupling. This result opens the possibility to synchronize the continuum limit with the approach to the light cone.Comment: 15 pages, LaTeX, 3 figures (7 PS files

Low lying spectrum of weak-disorder quantum waveguides

We study the low-lying spectrum of the Dirichlet Laplace operator on a randomly wiggled strip. More precisely, our results are formulated in terms of the eigenvalues of finite segment approximations of the infinite waveguide. Under appropriate weak-disorder assumptions we obtain deterministic and probabilistic bounds on the position of the lowest eigenvalue. A Combes-Thomas argument allows us to obtain so-called 'initial length scale decay estimates' at they are used in the proof of spectral localization using the multiscale analysis.Comment: Accepted for publication in Journal of Statistical Physics http://www.springerlink.com/content/0022-471

Anti-ferromagnetic ordering in arrays of superconducting pi-rings

We report experiments in which one dimensional (1D) and two dimensional (2D) arrays of YBa2Cu3O7-x-Nb pi-rings are cooled through the superconducting transition temperature of the Nb in various magnetic fields. These pi-rings have degenerate ground states with either clockwise or counter-clockwise spontaneous circulating supercurrents. The final flux state of each ring in the arrays was determined using scanning SQUID microscopy. In the 1D arrays, fabricated as a single junction with facets alternating between alignment parallel to a [100] axis of the YBCO and rotated 90 degrees to that axis, half-fluxon Josephson vortices order strongly into an arrangement with alternating signs of their magnetic flux. We demonstrate that this ordering is driven by phase coupling and model the cooling process with a numerical solution of the Sine-Gordon equation. The 2D ring arrays couple to each other through the magnetic flux generated by the spontaneous supercurrents. Using pi-rings for the 2D flux coupling experiments eliminates one source of disorder seen in similar experiments using conventional superconducting rings, since pi-rings have doubly degenerate ground states in the absence of an applied field. Although anti-ferromagnetic ordering occurs, with larger negative bond orders than previously reported for arrays of conventional rings, long-range order is never observed, even in geometries without geometric frustration. This may be due to dynamical effects. Monte-Carlo simulations of the 2D array cooling process are presented and compared with experiment.Comment: 10 pages, 15 figure

Non Degenerate Dual Atomic Parametric Amplifier: Entangled Atomic Fields

In this paper, we investigate the dynamics of two coupled quantum degenerate atomic fields (BEC) interacting with two classical optical fields in the nonlinear atom optics regime. Two photon interaction produces entangled atom-atom pairs which exhibit nonclassical correlations. Since the system involves the creation of two correlated atom pairs, we call it the nondegenerate dual atomic parametric amplifier.Comment: 5 figure

Dynamical Color Correlations in a SU(2)cSU(2)_c Quark Exchange Model of Nuclear Matter

The quark exchange model is a simple realization of an adiabatic approximation to the strong-coupling limit of Quantum Chromodynamics (QCD): the quarks always coalesce into the lowest energy set of flux tubes. Nuclear matter is thus modeled in terms of its quarks. We wish to study the correlations imposed by total wavefunction antisymmetry when color degrees of freedom are included. To begin with, we have considered one-dimensional matter with a $SU(2)$ color internal degree of freedom only. We proceed by constructing a totally antisymmetric, color singlet {\it Ansatz} characterized by a variational parameter $\lambda$ (which describes the length scale over which two quarks in the system are clustered into hadrons) and by performing a variational Monte Carlo calculation of the energy to optimize $\lambda$ for a fixed density. We calculate the $q-q$ correlation function as well, and discuss the qualitative differences between the system at low and high density.Comment: 32 pages in REVTeX, IU/NTC 93-28, FSU-SCRI-93-161. The postscript file, including 12 figures, is available via anonymous ftp from ftp.scri.fsu.edu in /pub/jorgep/magic.p

Strange matter in the string-flip model

We employ variational Monte Carlo methods to study the transition to strange matter in a simple one-dimensional string-flip model with two flavors and two colors of quarks. The dynamics of the system are described in terms of a many-body potential that confines quarks within hadrons, yet enables the hadrons to separate without generating unphysical long-range van der Waals forces. The model has ``natural'' low- and high-density limits: it behaves as a system of isolated hadrons at low density and as a Fermi gas of quarks at high density. We show that the system exhibits a transition to strange matter characterized by an increase in the length-scale for confinement. Yet the small increase at the transition region --- of only ten percent --- suggests that clustering correlations remain strong well into the strange-matter domain. Our results put into question descriptions of strange matter in terms of noninteracting, or weakly interacting, quarks.Comment: 19 pages, 7 figure

SMEI observations of previously unseen pulsation frequencies in γ Doradus

Aims. As g-mode pulsators, gamma-Doradus-class stars may naïvely be expected to show a large number of modes. Taking advantage of the long photometric time-series generated by the solar mass ejection imager (SMEI) instrument, we have studied the star gamma Doradus to determine whether any other modes than the three already known are present at observable amplitude. Methods. High-precision photometric data from SMEI taken between April 2003 and March 2006 were subjected to periodogram analysis with the PERIOD04 package. Results. We confidently determine three additional frequencies at 1.39, 1.87, and 2.743 d−1. These are above and beyond the known frequencies of 1.320, 1.364, and 1.47 d−1. Conclusions. Two of the new frequencies, at 1.39 and 1.87 d−1, are speculated to be additional modes of oscillation, with the third frequency at 2.743−1 a possible combination frequency