2,847 research outputs found
Dynamical Casimir effect for magnons in a spinor Bose-Einstein condensate
Magnon excitation in a spinor Bose-Einstein condensate by a driven magnetic
field is shown to have a close analogy with the dynamical Casimir effect. A
time-dependent external magnetic field amplifies quantum fluctuations in the
magnetic ground state of the condensate, leading to magnetization of the
system. The magnetization occurs in a direction perpendicular to the magnetic
field breaking the rotation symmetry. This phenomenon is numerically
demonstrated and the excited quantum field is shown to be squeezed.Comment: 8 pages, 3 figure
Bloch Structures in a Rotating Bose-Einstein Condensate
A rotating Bose-Einstein condensate is shown to exhibit a Bloch band
structure without the need of periodic potential. Vortices enter the condensate
by a mechanism similar to the Bragg reflection, if the frequency of a rotating
drive or the strength of interaction is adiabatically changed. A localized
state analogous to a gap soliton in a periodic system is predicted near the
edge of the Brillouin zone.Comment: 4 pages, 3 figure
Rayleigh-Taylor instability and mushroom-pattern formation in a two-component Bose-Einstein condensate
The Rayleigh-Taylor instability at the interface in an immiscible
two-component Bose-Einstein condensate is investigated using the mean-field and
Bogoliubov theories. Rayleigh-Taylor fingers are found to grow from the
interface and mushroom patterns are formed. Quantized vortex rings and vortex
lines are then generated around the mushrooms. The Rayleigh-Taylor instability
and mushroom-pattern formation can be observed in a trapped system.Comment: 5 pages, 4 figure
In-plane deformation of a triangulated surface model with metric degrees of freedom
Using the canonical Monte Carlo simulation technique, we study a Regge
calculus model on triangulated spherical surfaces. The discrete model is
statistical mechanically defined with the variables , and , which
denote the surface position in , the metric on a two-dimensional
surface and the surface density of , respectively. The metric is
defined only by using the deficit angle of the triangles in {}. This is in
sharp contrast to the conventional Regge calculus model, where {} depends
only on the edge length of the triangles. We find that the discrete model in
this paper undergoes a phase transition between the smooth spherical phase at
and the crumpled phase at , where is the bending
rigidity. The transition is of first-order and identified with the one observed
in the conventional model without the variables and . This implies
that the shape transformation transition is not influenced by the metric
degrees of freedom. It is also found that the model undergoes a continuous
transition of in-plane deformation. This continuous transition is reflected in
almost discontinuous changes of the surface area of and that of ,
where the surface area of is conjugate to the density variable .Comment: 13 pages, 7 figure
Capillary instability in a two-component Bose-Einstein condensate
Capillary instability and the resulting dynamics in an immiscible
two-component Bose-Einstein condensate are investigated using the mean-field
and Bogoliubov analyses. A long, cylindrical condensate surrounded by the other
component is dynamically unstable against breakup into droplets due to the
interfacial tension arising from the quantum pressure and interactions. A
heteronuclear system confined in a cigar-shaped trap is proposed for realizing
this phenomenon experimentally.Comment: 7 pages, 6 figure
Novel Magnetic and Thermodynamic Properties of Thiospinel Compound CuCrZrS
We have carried out dc magnetic susceptibility, magnetization and specific
heat measurements on thiospinel CuCrZrS. Below 58 K, dc
magnetic susceptibility and magnetization data show ferromagnetic behavior with
a small spontaneous magnetization 0.27 f. u..
In dc magnetic susceptibility, large and weak irreversibilities are observed
below 6 K and in the range
respectively.
We found that there is no anomaly as a peak or step in the specific heat at
.Comment: 11 pages, 4 figure
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