9,364 research outputs found
Novel vortex structures in dipolar condensates
We investigate the properties of single vortices and of vortex lattice in a
rotating dipolar condensate. We show that vortices in this system possess many
novel features induced by the long-range anisotropic dipolar interaction
between particles. For example, when the dipoles are polarized along the
rotation axis, vortices may display a crater-like structure; when dipoles are
polarized orthogonal to the rotation axis, vortex cores takes an elliptical
shape and the vortex lattice no longer possesses hexagonal symmetry.Comment: 4 pages, 5 figure
Phase Separation in Bose-Fermi-Fermi Mixtures as a Probe of Fermi Superfluidity
We study the phase diagram of a mixture of Bose-Einstein condensate and a
two-component Fermi gas. In particular, we identify the regime where the
homogeneous system becomes unstable against phase separation. We show that,
under proper conditions, the phase separation phenomenon can be exploited as a
robust probe of Fermi superfluid
Effect of intense magnetic fields on reduced-MHD evolution in = 200 GeV Au+Au collisions
We investigate the effect of large magnetic fields on the dimensional
reduced-magnetohydrodynamical expansion of hot and dense nuclear matter
produced in = 200 GeV Au+Au collisions. For the sake of
simplicity, we consider the case where the magnetic field points in the
direction perpendicular to the reaction plane. We also consider this field to
be external, with energy density parametrized as a two-dimensional Gaussian.
The width of the Gaussian along the directions orthogonal to the beam axis
varies with the centrality of the collision. The dependence of the magnetic
field on proper time () for the case of zero electrical conductivity of
the QGP is parametrized following [Deng 2012], and for finite electrical
conductivity following [Tuchin 2013]. We solve the equations of motion of ideal
hydrodynamics for such an external magnetic field. For collisions with non-zero
impact parameter we observe considerable changes in the evolution of the
momentum eccentricities of the fireball when comparing the case when the
magnetic field decays in a conducting QGP medium and when no magnetic field is
present. The elliptic-flow coefficient of is shown to increase
in the presence of an external magnetic field and the increment in is
found to depend on the evolution and the initial magnitude of the magnetic
field.Comment: 12 pages, 6 figures, new discussion added, published in Phys.Rev.
Density oscillations in trapped dipolar condensates
We investigated the ground state wave function and free expansion of a
trapped dipolar condensate. We find that dipolar interaction may induce both
biconcave and dumbbell density profiles in, respectively, the pancake- and
cigar-shaped traps. On the parameter plane of the interaction strengths, the
density oscillation occurs only when the interaction parameters fall into
certain isolated areas. The relation between the positions of these areas and
the trap geometry is explored. By studying the free expansion of the condensate
with density oscillation, we show that the density oscillation is detectable
from the time-of-flight image.Comment: 7 pages, 9 figure
Oil spill: are we doing enough to avoid it?
YesThis paper reviews the recent studies on the identification and cleaning methods, as well as the consequences of oil spill. The future progression on oil spill prevention studies are also projected here
Turbulence modelling of shallow water flows using Kolmogorov approach
YesThis study uses an improved k –ε coupled shallow water equations (SWE) model that equipped with the numerical computation of the velocity fluctuation terms to investigate the turbulence structures of the open channel flows. We adapted the Kolmogorov K41 scaling model into the k –ε equations to calculate the turbulence intensities and Reynolds stresses of the SWE model. The presented model was also numerically improved by a recently proposed surface gradient upwind method (SGUM) to allow better accuracy in simulating the combined source terms from both the SWE and k –ε equations as proven in the recent studies. The proposed model was first tested using the flows induced by multiple obstructions to investigate the utilised k –ε and SGUM approaches in the model. The laboratory experiments were also conducted under the non-uniform flow conditions, where the simulated velocities, total kinetic energies (TKE) and turbulence intensities by the proposed model were used to compare with the measurements under different flow non-uniformity conditions. Lastly, the proposed numerical simulation was compared with a standard Boussinesq model to investigate its capability to simulate the measured Reynolds stress. The comparison outcomes showed that the proposed Kolmogorov k –ε SWE model can capture the flow turbulence characteristics reasonably well in all the investigated flows.The Major State Basic Research Development Program (973 program) of China (No. 2013CB036402
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