7,907 research outputs found
Vortex stabilization in a small rotating asymmetric Bose-Einstein condensate
We use a variational method to investigate the ground-state phase diagram of
a small, asymmetric Bose-Einstein condensate with respect to the dimensionless
interparticle interaction strength and the applied external rotation
speed . For a given , the transition lines between no-vortex
and vortex states are shifted toward higher relative to those for the
symmetric case. We also find a re-entrant behavior, where the number of vortex
cores can decrease for large . In addition, stabilizing a vortex in a
rotating asymmetric trap requires a minimum interaction strength. For a given
asymmetry, the evolution of the variational parameters with increasing
shows two different types of transitions (sharp or continuous), depending on
the strength of the interaction. We also investigate transitions to states with
higher vorticity; the corresponding angular momentum increases continuously as
a function of
Stability of rotating states in a weakly-interacting Bose-Einstein condensate
We investigate the lowest state of a rotating, weakly-interacting
Bose-Einstein condensate trapped in a harmonic confining potential that is
driven by an infinitesimally asymmetric perturbation. Although in an
axially-symmetric confining potential the gas has an axially-symmetric
single-particle density distribution, we show that in the presence of the small
asymmetric perturbation its lowest state is the one given by the mean-field
approximation, which is a broken-symmetric state. We also estimate the rate of
relaxation of angular momentum when the gas is no longer driven by the
asymmetric perturbation and identify two regimes of "slow" and "fast"
relaxation. States of certain symmetry are found to be more robust.Comment: 6 pages, RevTe
Immediate effects of diamond burr debridement in patients with spontaneous chronic corneal epithelial defects, light and electron microscopic evaluation
Reactions to uncertainty and the accuracy of diagnostic mammography.
BackgroundReactions to uncertainty in clinical medicine can affect decision making.ObjectiveTo assess the extent to which radiologists' reactions to uncertainty influence diagnostic mammography interpretation.DesignCross-sectional responses to a mailed survey assessed reactions to uncertainty using a well-validated instrument. Responses were linked to radiologists' diagnostic mammography interpretive performance obtained from three regional mammography registries.ParticipantsOne hundred thirty-two radiologists from New Hampshire, Colorado, and Washington.MeasurementMean scores and either standard errors or confidence intervals were used to assess physicians' reactions to uncertainty. Multivariable logistic regression models were fit via generalized estimating equations to assess the impact of uncertainty on diagnostic mammography interpretive performance while adjusting for potential confounders.ResultsWhen examining radiologists' interpretation of additional diagnostic mammograms (those after screening mammograms that detected abnormalities), a 5-point increase in the reactions to uncertainty score was associated with a 17% higher odds of having a positive mammogram given cancer was diagnosed during follow-up (sensitivity), a 6% lower odds of a negative mammogram given no cancer (specificity), a 4% lower odds (not significant) of a cancer diagnosis given a positive mammogram (positive predictive value [PPV]), and a 5% higher odds of having a positive mammogram (abnormal interpretation).ConclusionMammograms interpreted by radiologists who have more discomfort with uncertainty have higher likelihood of being recalled
Weakly Interacting Bose-Einstein Condensates Under Rotation: Mean-field versus Exact Solutions
We consider a weakly-interacting, harmonically-trapped Bose-Einstein
condensed gas under rotation and investigate the connection between the
energies obtained from mean-field calculations and from exact diagonalizations
in a subspace of degenerate states. From the latter we derive an approximation
scheme valid in the thermodynamic limit of many particles. Mean-field results
are shown to emerge as the correct leading-order approximation to exact
calculations in the same subspace.Comment: 4 pages, RevTex, submitted to PR
Stability of small amplitude normal modes of a Bose-Einstein condensate with a singly quantized vortex confined in an optical lattice
We study the dynamics of a BEC with a singly quantized vortex, placed in the
combined potential of a 1-D (2-D) optical lattice and an axi-symmetric harmonic
trap. A time-dependent variational Lagrangian analysis shows that an optical
lattice helps to stabilize the vortex which in absence of the optical lattice
is unstable. We find that the normal modes are stable only if the depth of the
optical potential is more than a certain critical value. This critical value of
the optical potential depends on the interaction parameter.In general higher
the interaction parameter,lower the value of the optical potential required to
stabilize the vortex. The BEC with the singly quantized vortex is found to be
relatively more unstable in a 2-D optical lattice compared to a 1-D optical
lattice.Comment: Revised version with 11 pages including 1 figur
The Ellipticity and Orientation of Clusters of Galaxies from N-Body Experiments
In this study we use simulations of 128 particles to study the
ellipticity and orientation of clusters of galaxies in N-body simulations of
differing power-law initial spectra (P(k) \propto k^n ,n = +1, 0, -1, -2\Omega_0 = 0.2nD < 15 h^{-1}n-$dependent way.Comment: 22 pages, requires aaspp4.sty, flushrt.sty, and epsf.sty Revised
manuscript, accepted for publication in Ap
Analytical results for a trapped, weakly-interacting Bose-Einstein condensate under rotation
We examine the problem of a repulsive, weakly-interacting and harmonically
trapped Bose-Einstein condensate under rotation. We derive a simple analytic
expression for the energy incorporating the interactions when the angular
momentum per particle is between zero and one and find that the interaction
energy decreases linearly as a function of the angular momentum in agreement
with previous numerical and limiting analytical studies.Comment: 3 pages, RevTe
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