10,017 research outputs found
Hidden symmetry and quantum phases in spin-3/2 cold atomic systems
Optical traps and lattices provide a new opportunity to study strongly
correlated high spin systems with cold atoms. In this article, we review the
recent progress on the hidden symmetry properties in the simplest high spin
fermionic systems with hyperfine spin , which may be realized with atoms
of Cs, Be, Ba, Ba, and Hg. A {\it generic}
SO(5) or isomorphically, ) symmetry is proved in such systems with the
s-wave scattering interactions in optical traps, or with the on-site Hubbard
interactions in optical lattices. Various important features from this high
symmetry are studied in the Fermi liquid theory, the mean field phase diagram,
and the sign problem in quantum Monte-Carlo simulations. In the s-wave quintet
Cooper pairing phase, the half-quantum vortex exhibits the global analogue of
the Alice string and non-Abelian Cheshire charge properties in gauge theories.
The existence of the quartetting phase, a four-fermion counterpart of the
Cooper pairing phase, and its competition with other orders are studied in one
dimensional spin-3/2 systems. We also show that counter-intuitively quantum
fluctuations in spin-3/2 magnetic systems are even stronger than those in
spin-1/2 systems
Breathing Oscillations in Bose - Fermi Mixing Gases with Yb atoms in the Largely Prolate Deformed Traps
We study the breathing oscillations in bose-fermi mixtures with Yb isotopes
in the largely prolate deformed trap, which are realized by Kyoto group. We
choose the three combinations of the Yb isotopes, Yb170-Yb171, Yb170-Yb173 and
Yb174-Yb173, whose boson-fermion interactions are weakly repulsive, strongly
attractive and strongly repulsive. The collective oscillations in the deformed
trap are calculated in the dynamical time-development approach, which is
formulated with the time-dependent Gross-Pitaevskii and the Vlasov equations.
We analyze the results in the time-development approach with the intrinsic
oscillation modes of the deformed system, which are obtained using the scaling
method, and show that the damping and forced-oscillation effects of the
intrinsic modes give time-variation of oscillations, especially, in the fermion
transverse mode.Comment: 27 pages, 12 figure
Minimization of deviations of gear real tooth surfaces determined by coordinate measurements
The deviations of a gear's real tooth surface from the theoretical surface are determined by coordinate measurements at the grid of the surface. A method was developed to transform the deviations from Cartesian coordinates to those along the normal at the measurement locations. Equations are derived that relate the first order deviations with the adjustment to the manufacturing machine-tool settings. The deviations of the entire surface are minimized. The minimization is achieved by application of the least-square method for an overdetermined system of linear equations. The proposed method is illustrated with a numerical example for hypoid gear and pinion
Dipole Oscillations in Bose - Fermi Mixture in the Time-Dependent Grosspitaevskii and Vlasov equations
We study the dipole collective oscillations in the bose-fermi mixture using a
dynamical time-dependent approach, which are formulated with the time-dependent
Gross-Pitaevskii equation and the Vlasov equation. We find big difference in
behaviors of fermion oscillation between the time-dependent approach and usual
approaches such as the random-phase approximation and the sum-rule approach.
While the bose gas oscillates monotonously, the fermion oscillation shows a
beat and a damping. When the amplitude is not minimal, the dipole oscillation
of the fermi gas cannot be described with a simple center-of-mass motion.Comment: 17 pages text, and 15 figure
Electrothermal flow in Dielectrophoresis of Single-Walled Carbon Nanotubes
We theoretically investigate the impact of the electrothermal flow on the
dielectrophoretic separation of single-walled carbon nanotubes (SWNT). The
electrothermal flow is observed to control the motions of semiconducting SWNTs
in a sizeable domain near the electrodes under typical experimental conditions,
therefore helping the dielectrophoretic force to attract semiconducting SWNTs
in a broader range. Moreover, with the increase of the surfactant
concentration, the electrothermal flow is enhanced, and with the change of
frequency, the pattern of the electrothermal flow changes. It is shown that
under some typical experimental conditions of dielectrophoresis separation of
SWNTs, the electrothermal flow is a dominating factor in determining the motion
of SWNTs.Comment: 5 pages, 4 figures, Submitted to PR
Atomic Hydrogen Cleaning of Polarized GaAs Photocathodes
Atomic hydrogen cleaning followed by heat cleaning at 450C was used
to prepare negative-electron-affinity GaAs photocathodes. When hydrogen ions
were eliminated, quantum efficiencies of 15% were obtained for bulk GaAs
cathodes, higher than the results obtained using conventional 600C heat
cleaning. The low-temperature cleaning technique was successfully applied to
thin, strained GaAs cathodes used for producing highly polarized electrons. No
depolarization was observed even when the optimum cleaning time of about 30
seconds was extended by a factor of 100
Quantum Molecular Dynamics Approach to the Nuclear Matter Below the Saturation Density
Quantum molecular dynamics is applied to study the ground state properties of
nuclear matter at subsaturation densities. Clustering effects are observed as
to soften the equation of state at these densities. The structure of nuclear
matter at subsaturation density shows some exotic shapes with variation of the
density.Comment: 21 pages of Latex (revtex), 9 Postscript figure
Quadrupole Oscillations in Bose-Fermi Mixtures of Ultracold Atomic Gases made of Yb atoms in the Time-Dependent Gross-Pitaevskii and Vlasov equations
We study quadrupole collective oscillations in the bose-fermi mixtures of
ultracold atomic gases of Yb isotopes, which are realized by Kyoto group. Three
kinds of combinations are chosen, Yb170-Yb171, Yb170-Yb173 and Yb174-Yb173,
where boson-fermion interactions are weakly repulsive, strongly attractive and
strongly repulsive respectively. Collective oscillations in these mixtures are
calculated in a dynamical time-evolution approach formulated with the
time-dependent Gross-Pitaevskii and the Vlasov equations. The boson
oscillations are shown to have one collective mode, and the fermions are shown
to have the boson-forced and two intrinsic modes, which correspond to the
inside- and outside-fermion oscillations for the boson-distributed regions. In
the case of the weak boson-fermion interactions, the dynamical calculations are
shown to be consistent with the results obtained in the small amplitude
approximations as the random phase approximation in early stage of oscillation,
but, in later stage, these two approaches are shown to give the different
results. Also, in the case of the strong boson-fermion interactions,
discrepancies appear in early stage of oscillation. We also analyze these
differences in two approaches, and show that they originated in the change of
the fermion distributions through oscillation
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