38,861 research outputs found
Spinor Bose Condensates in Optical Traps
In an optical trap, the ground state of spin-1 Bosons such as Na,
K, and Rb can be either a ferromagnetic or a "polar" state,
depending on the scattering lengths in different angular momentum channel. The
collective modes of these states have very different spin character and spatial
distributions. While ordinary vortices are stable in the polar state, only
those with unit circulation are stable in the ferromagnetic state. The
ferromagnetic state also has coreless (or Skyrmion) vortices like those of
superfluid He-A. Current estimates of scattering lengths suggest that the
ground states of Na and Rb condensate are a polar state and a
ferromagnetic state respectively.Comment: 11 pages, no figures. email : [email protected]
Multiple Chern-Simons Fields on a Torus
Intertwined multiple Chern-Simons gauge fields induce matrix statistics among
particles. We analyse this theory on a torus, focusing on the vacuum structure
and the Hilbert space. The theory can be mimicked, although not completely, by
an effective theory with one Chern-Simons gauge field. The correspondence
between the Wilson line integrals, vacuum degeneracy and wave functions for
these two theories are discussed. Further, it is obtained in both of these
cases that the two total momenta and Hamiltonian commute only in the physical
Hilbert space.Comment: 20 pages, UMN-TH-1128/93, plain Te
Boundary Condition of Polyelectrolyte Adsorption
The modification of the boundary condition for polyelectrolyte adsorption on
charged surface with short-ranged interaction is investigated under two
regimes. For weakly charged Gaussian polymer in which the short-ranged
attraction dominates, the boundary condition is the same as that of the neutral
polymer adsorption. For highly charged polymer (compressed state) in which the
electrostatic interaction dominates, the linear relationship (electrostatic
boundary condition) between the surface monomer density and the surface charge
density needs to be modified.Comment: 4 page
High temperature expansion applied to fermions near Feshbach resonance
We show that, apart from a difference in scale, all of the surprising
recently observed properties of a degenerate Fermi gas near a Feshbach
resonance persist in the high temperature Boltzmann regime. In this regime, the
Feshbach resonance is unshifted. By sweeping across the resonance, a thermal
distribution of bound states (molecules) can be reversibly generated.
Throughout this process, the interaction energy is negative and continuous. We
also show that this behavior must persist at lower temperatures unless there is
a phase transition as the temperature is lowered. We rigorously demonstrate
universal behavior near the resonance.Comment: 4 pages, 4 figures (3 color, 1 BW), RevTeX4; ver4 -- updated
references, changed title -- version accepted for publication in Physical
Review Letter
Rapidly Rotating Fermi Gases
We show that the density profile of a Fermi gas in rapidly rotating potential
will develop prominent features reflecting the underlying Landau level like
energy spectrum. Depending on the aspect ratio of the trap, these features can
be a sequence of ellipsoidal volumes or a sequence of quantized steps.Comment: 4 pages, 1 postscript fil
Faddeev-type equations for three-body symmetry violating scattering amplitudes
The equations which relate three-body and two-body symmetry violating
scattering amplitudes are derived in the first order of symmetry violating
interactions. They can be used to obtain three-body symmetry violating
scattering amplitudes from two-body symmetry violating scattering amplitudes
calculated in low energy effective field theory
Efficient out-coupling and beaming of Tamm optical states via surface plasmon polariton excitation
We present evidence of optical Tamm states to surface plasmon polariton (SPP) coupling. We experimentally demonstrate that for a Bragg stack with a thin metal layer on the surface, hybrid Tamm-SPP modes may be excited when a grating on the air-metal interface is introduced. Out-coupling via the grating to free space propagation is shown to enhance the transmission as well as the directionality and polarization selection for the transmitted beam. We suggest that this system will be useful on those devices, where a metallic electrical contact as well as beaming and polarization control is needed
Anomaly-induced Quadrupole Moment of the Neutron in Magnetic Field
The neutrons cannot possess a quadrupole moment in the vacuum. Nevertheless,
we show that in the presence of an external magnetic field the neutrons acquire
a new type of quadrupole moment involving the
components of spin and magnetic field. This "chiral magnetic" quadrupole moment
arises from the interplay of the chiral anomaly and the magnetic field; we
estimate its value for the neutron in the static limit, and find . The detection of the quadrupole moment of the
neutron would provide a novel test of the role of the chiral anomaly in
low-energy QCD and can be possible in the presence of both magnetic and
inhomogeneous electric fields. The quadrupole moment of the neutron may affect
e.g. the properties of neutron stars and magnetars.Comment: 2 pages; extended versio
Investigation of defect cavities formed in three-dimensional woodpile photonic crystals
We report the optimisation of optical properties of single defects in
three-dimensional (3D) face-centred-cubic (FCC) woodpile photonic crystal (PC)
cavities by using plane-wave expansion (PWE) and finite-difference time-domain
(FDTD) methods. By optimising the dimensions of a 3D woodpile PC, wide photonic
band gaps (PBG) are created. Optical cavities with resonances in the bandgap
arise when point defects are introduced in the crystal. Three types of single
defects are investigated in high refractive index contrast (Gallium
Phosphide-Air) woodpile structures and Q-factors and mode volumes ()
of the resonant cavity modes are calculated. We show that, by introducing an
air buffer around a single defect, smaller mode volumes can be obtained. We
demonstrate high Q-factors up to 700000 and cavity volumes down to
. The estimates of and are then used to
quantify the enhancement of spontaneous emission and the possibility of
achieving strong coupling with nitrogen-vacancy (NV) colour centres in diamond.Comment: 12 pages, 11 figure
Time Reversal Invariance Violation in Neutron Deuteron Scattering
Time reversal invariance violating (TRIV) effects for low energy elastic
neutron deuteron scattering are calculated for meson exchange and EFT-type of
TRIV potentials in a Distorted Wave Born Approximation, using realistic
hadronic strong interaction wave functions, obtained by solving three-body
Faddeev equations in configuration space. The relation between TRIV and parity
violating observables are discussed
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