1,922 research outputs found
Equilibrium vortex formation in ultrarapidly rotating two-component Bose-Einstein condensates
Equilibrium vortex formation in rotating binary Bose gases with a rotating
frequency higher than the harmonic trapping frequency is investigated
theoretically. We consider the system being evaporatively cooled to form
condensates and a combined numerical scheme is applied to ensure the binary
system being in an authentic equilibrium state. To keep the system stable
against the large centrifugal force of ultrafast rotation, a quartic trapping
potential is added to the existing harmonic part. Using the Thomas-Fermi
approximation, a critical rotating frequency \Omega_c is derived, which
characterizes the structure with or without a central density hole. Vortex
structures are studied in detail with rotation frequency both above and below
?\Omega_c and with respect to the miscible, symmetrically separated, and
asymmetrically separated phases in their nonrotating ground-state counterparts.Comment: 7 pages, 7 figure
Transcritical flow of a stratified fluid over topography: analysis of the forced Gardner equation
Transcritical flow of a stratified fluid past a broad localised topographic
obstacle is studied analytically in the framework of the forced extended
Korteweg--de Vries (eKdV), or Gardner, equation. We consider both possible
signs for the cubic nonlinear term in the Gardner equation corresponding to
different fluid density stratification profiles. We identify the range of the
input parameters: the oncoming flow speed (the Froude number) and the
topographic amplitude, for which the obstacle supports a stationary localised
hydraulic transition from the subcritical flow upstream to the supercritical
flow downstream. Such a localised transcritical flow is resolved back into the
equilibrium flow state away from the obstacle with the aid of unsteady coherent
nonlinear wave structures propagating upstream and downstream. Along with the
regular, cnoidal undular bores occurring in the analogous problem for the
single-layer flow modeled by the forced KdV equation, the transcritical
internal wave flows support a diverse family of upstream and downstream wave
structures, including solibores, rarefaction waves, reversed and trigonometric
undular bores, which we describe using the recent development of the nonlinear
modulation theory for the (unforced) Gardner equation. The predictions of the
developed analytic construction are confirmed by direct numerical simulations
of the forced Gardner equation for a broad range of input parameters.Comment: 34 pages, 24 figure
Influence of temperature, light and plant growth regulators on germination of black pepper (Piper nigrum L.) seeds
Effects of temperature, light and different concentrations of plant growth regulators on germination of Piper nigrum L. seeds was studied under controlled environmental conditions. Black pepper seeds were placed inPetri dishes with filtration papers and the germination and radical  development followed during eighteen days periods. The seeds generally germinated within six or seven days. There was no difference in percentgermination between dark and light treatments, but the development of radical length was significantly influenced by both light and temperature. Germination was highest at 30°C, but seeds also germinated at 25and 35°C. No germination was observed at low (20°C) and high (40 and 45°C) temperatures. The plant growth regulators enhanced the seeds germination and radical length different degree. The results are consistent with the Piper nigrum L. being recalcitrant species need a certain environment condition to germinate
Spontaneous Crystallization of Skyrmions and Fractional Vortices in the Fast-rotating and Rapidly-quenched Spin-1 Bose-Einstein Condensates
We investigate the spontaneous generation of crystallized topological defects
via the combining effects of fast rotation and rapid thermal quench on the
spin-1 Bose-Einstein condensates. By solving the stochastic projected
Gross-Pitaevskii equation, we show that, when the system reaches equilibrium, a
hexagonal lattice of skyrmions, and a square lattice of half-quantized vortices
can be formed in a ferromagnetic and antiferromagnetic spinor BEC, respetively,
which can be imaged by using the polarization-dependent phase-contrast method
Ground state energy of the spinor Bose-Einstein condensates
We calculate, in the standard Bogoliubov approximation, the ground state
energy of the spinor BEC with hyperfine spin where the two-body repulsive
hard-core and spin exchange interactions are both included. The coupling
constants characterized these two competing interactions are expressed in terms
of the corresponding s-wave scattering lengths using second-order perturbation
methods. We show that the ultraviolet divergence arising in the ground state
energy corrections can be exactly eliminated.Comment: 14 pages, no figures, submitted to PR
An adjustable law of motion for relativistic spherical shells
A classical and a relativistic law of motion for an advancing shell are
deduced applying the thin layer approximation. A new parameter connected with
the quantity of absorbed matter in the expansion is introduced; this allows of
matching theory and observation.Comment: 15 pages, 10 figures and article in press; Central European Journal
of Physics 201
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KurSL: model of anharmonic coupled oscillations based on Kuramoto coupling and Sturm–Liouville problem
Physiological signaling is often oscillatory and shows nonlinearity due to complex interactions of underlying processes or signal propagation delays. This is particularly evident in case of brain activity which is subject to various feedback loop interactions between different brain structures, that coordinate their activity to support normal function. In order to understand such signaling in health and disease, methods are needed that can deal with such complex oscillatory phenomena. In this paper, a data-driven method for analyzing anharmonic oscillations is introduced. The KurSL model incorporates two well-studied components, which in the past have been used separately to analyze oscillatory behavior. The Sturm–Liouville equations describe a form of a general oscillation, and the Kuramoto coupling model represents a set of oscillators interacting in the phase domain. Integration of these components provides a flexible framework for capturing complex interactions of oscillatory processes of more general form than the most commonly used harmonic oscillators. The paper introduces a mathematical framework of the KurSL model and analyzes its behavior for a variety of parameter ranges. The significance of the model follows from its ability to provide information about coupled oscillators’ phase dynamics directly from the time series. KurSL offers a novel framework for analyzing a wide range of complex oscillatory behaviors, such as the ones encountered in physiological signals
Nonlinear Decoherence in Quantum State Preparation of a Trapped Ion
We present a nonlinear decoherence model which models decoherence effect
caused by various decohereing sources in a quantum system through a nonlinear
coupling between the system and its environment, and apply it to investigating
decoherence in nonclassical motional states of a single trapped ion. We obtain
an exactly analytic solution of the model and find very good agreement with
experimental results for the population decay rate of a single trapped ion
observed in the NIST experiments by Meekhof and coworkers (D. M. Meekhof, {\it
et al.}, Phys. Rev. Lett. {\bf 76}, 1796 (1996)).Comment: 5 pages, Revte
The Nature and Cause of Spectral Variability in LMC X-1
We present the results of a long-term observation campaign of the
extragalactic wind-accreting black-hole X-ray binary LMC X-1, using the
Proportional Counter Array on the Rossi X-Ray Timing Explorer (RXTE). The
observations show that LMC X-1's accretion disk exhibits an anomalous
temperature-luminosity relation. We use deep archival RXTE observations to show
that large movements across the temperature-luminosity space occupied by the
system can take place on time scales as short as half an hour. These changes
cannot be adequately explained by perturbations that propagate from the outer
disk on a viscous timescale. We propose instead that the apparent disk
variations reflect rapid fluctuations within the Compton up-scattering coronal
material, which occults the inner parts of the disk. The expected relationship
between the observed disk luminosity and apparent disk temperature derived from
the variable occultation model is quantitatively shown to be in good agreement
with the observations. Two other observations support this picture: an inverse
correlation between the flux in the power-law spectral component and the fitted
inner disk temperature, and a near-constant total photon flux, suggesting that
the inner disk is not ejected when a lower temperature is observed.Comment: 35 pages, 10 figures, to be published in Ap
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