Matt's arXiv selection: week ending 4 May 2007.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Mon, 14 May 2007 09:54:31 +1000 (EST)

The following message was sent to the matts_arxiv list by Matthew Davis <mdavis_at_physics.uq.edu.au>

Another late mailing: 11 new preprints and 17 replacements

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arXiv:0704.3663
Date: Fri, 27 Apr 2007 05:43:00 GMT (315kb)

Title: Optimal conditions for quantum storage on subradiant states in an
extended atomic ensemble
Authors: Alexey Kalachev
Categories: quant-ph
\\
A scheme for coherent manipulation of collective atomic states is developed
such that total subradiant states, in which spontaneous emission is suppressed
for all spatial modes, can be created in an extended atomic ensemble. The
optimal conditions for quantum-state storage on such states are determined. It
is shown that the optimal shape of a light pulse to be stored and reconstructed
using a homogeneously broadened absorbtion line of an atomic system is the
time-reversed regular part of the response function of the system. In the limit
of high optical density, such pulses allow one to achieve maximum efficiency of
the light state mapping on the atomic system and its subsequent reconstruction.
\\ ( http://arxiv.org/abs/0704.3663 , 315kb)
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arXiv:0704.3774
Date: Sat, 28 Apr 2007 03:31:39 GMT (208kb)

Title: Mott Insulator - Superfluid Transitions in a Two Band Model at Finite
Temperature and Possible Application to Supersolid 4He
Authors: Huai-Bin Zhuang, Michael Ma, Xi Dai, Fu-Chun Zhang
Categories: cond-mat.stat-mech
\\
We study Mott insulator - superfluid transition in a two-band boson Hubbard
model, which can be mapped onto a spin-1/2 XY model with spins coupled to an
additional Ising degree of freedom. By using a modified mean field theory that
include the effects of phase fluctuations, we show that the transition is first
order at both zero and finite temperatures. On the Mott insulator side, there
may be reentrance in phase transition. These features are consequences of the
underlying transition between competing defect poor and defect rich phases. The
relevance of the model and our results to supersolid 4He and cold bosonic atoms
in optical lattices are discussed.
\\ ( http://arxiv.org/abs/0704.3774 , 208kb)
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arXiv:0704.3859
Date: Sun, 29 Apr 2007 20:15:42 GMT (53kb)

Title: Density waves and supersolidity in rapidly rotating atomic Fermi gases
Authors: Gunnar Moller, Nigel R. Cooper
Categories: cond-mat.mes-hall cond-mat.supr-con
Comments: 4 pages, 1 figure, uses feynmp.sty
\\
We study theoretically the low-temperature phases of a two-component atomic
Fermi gas with attractive s-wave interactions under conditions of rapid
rotation. We find that, in the extreme quantum limit, when all particles occupy
the lowest Landau level, the normal state is unstable to the formation of
"charge" density wave (CDW) order. At lower rotation rates, when many Landau
levels are occupied, we show that the low-temperature phases can be
supersolids, involving both CDW and superconducting order.
\\ ( http://arxiv.org/abs/0704.3859 , 53kb)
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arXiv:0704.3867
Date: Mon, 30 Apr 2007 01:14:30 GMT (213kb)

Title: Inhibited Feshbach Conversion of Atomic Fermions to Molecular Bosons due
to Molecular Interaction
Authors: Jie Liu, Li-Bin Fu, Bin Liu, Shi-Ping Yang and Biao Wu
Categories: cond-mat.mes-hall
\\
We show that the repulsive interaction between molecules can strongly
suppress the Feshbach conversion efficiency from atomic fermions to molecular
bosons, leading to a ceiling phenomenon that has been observed in recent
experiments. Our model predicts a power-law dependence of the remnant fraction
of unconverted atoms on the sweeping rates in the slow sweeping limit. Our
results agrees well with experimental data on $^6$Li and $^{40}$K.
\\ ( http://arxiv.org/abs/0704.3867 , 213kb)
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arXiv:0704.3868
Date: Mon, 30 Apr 2007 02:01:38 GMT (17kb)

Title: Bose-Einstein condensation of strongly interacting dipolar gases
Authors: Daw-Wei Wang
Categories: cond-mat.other cond-mat.supr-con
Comments: 5 pages and 1 figure
\\
We derive an effective many-body theory for bosonic dipolar atoms/molecules
in the regime of strong dipole interactions, where the conventionally used
first Born approximation for the scattering matrix elements fails to be
justified. We find that the effect of the anisotropic dipole interaction is
strongly reduced near the shape resonance regime and therefore stabilizes the
condensate ground state. In the 2D system with dipole moment perpendicular to
the plane, the Bogoliubov phonon excitation is modified to scale as
$\sqrt{|\bfp|}$ in the low momentum ($\bfp$) limit, showing the same low energy
properties as a 2D charged Bose gas with Coulomb ($1/r$) interactions.
\\ ( http://arxiv.org/abs/0704.3868 , 17kb)
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arXiv:0704.3984
Date: Mon, 30 Apr 2007 17:40:35 GMT (7kb)

Title: Exact renormalisation group flow for ultracold Fermi gases in unitary
limit
Authors: Boris Krippa
Categories: cond-mat.supr-con
\\
We study the exact renormalisation group flow for ultracold Fermi-gases in
unitary regime. We introduce a pairing field to describe the formation of the
Cooper pairs, and take a simple ansatz for the effective action. Set of
approximate flow equations for the effective couplings including boson and
fermionic fluctuations is derived. At some value of the running scale, the
system undergoes a phase transition to a gapped phase. The values of the energy
density, chemical potential, pairing gap and the corresponding proportionality
constants relating the interacting and non-interacting Fermi gases are
calculated. Standard mean field results are recovered if we omit the boson
loops.
\\ ( http://arxiv.org/abs/0704.3984 , 7kb)
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arXiv:0704.3823
Date: Sun, 29 Apr 2007 00:01:43 GMT (645kb)

Title: Effect of Decoherence on the Dynamics of Bose-Einstein Condensates in a
Double-well Potential
Authors: W. Wang, L. B. Fu, and X. X. Yi
Categories: quant-ph
Comments: for color figures, see PRA
Journal-ref: Phys. Rev. A 75,045601(2007)
\\
We study the dynamics of a Bose-Einstein condensate in a double-well
potential in the mean-field approximation. Decoherence effects are considered
by analyzing the couplings of the condensate to environments. Two kinds of
coupling are taken into account. With the first kind of coupling dominated, the
decoherence can enhance the self-trapping by increasing the damping of the
oscillations in the dynamics, while the decoherence from the second kind of
condensate-environment coupling leads to spoiling of the quantum tunneling and
self-trapping.
\\ ( http://arxiv.org/abs/0704.3823 , 645kb)
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arXiv:0704.3926
Date: Mon, 30 Apr 2007 12:23:24 GMT (9kb)

Title: Control of instability of one dimensional stationary state Bose-Einstein
condensates
Authors: Wenhua Hai, Guishu Chong
Categories: quant-ph
\\
We explore how to control the dynamical instability of a quasi-one
dimensional (1D) stationary state Bose-Einstein condensate (BEC) consisting of
fixed $N$ atoms with arbitrary time-independent external potential and atomic
scattering length. The dependence of the perturbed solutions on the velocity
field, external potential, condensed atom number, and the initial perturbations
is demonstrated analytically, that shows the stability, instability and
undetermined stability of the system. Some sufficient conditions on the
stability and controlling criteria to the instability are established. We take
a BEC held in an optical lattice potential as an example establishing the
stability regions on parameter space and illustrating the scheme for
controlling instability. The results contain the known stability assertions for
the lattice potential case and agree with the recent experimental findings
qualitatively.
\\ ( http://arxiv.org/abs/0704.3926 , 9kb)
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arXiv:0704.3959
Date: Mon, 30 Apr 2007 15:16:47 GMT (799kb)

Title: Optical Devices for Cold Atoms and Bose-Einstein Condensates
Telmini (LSAMA), Laurence Pruvost (LAC), Eric Charron (PPM)
Categories: quant-ph
Comments: Proceedings of the International Spectroscopy Conference ISC-2007,
Sousse, Tunisia
Proxy: ccsd hal-00144111
\\
The manipulation of cold atoms with optical fields is a very promising
technique for a variety of applications ranging from laser cooling and trapping
to coherent atom transport and matter wave interferometry. Optical fields have
also been proposed as interesting tools for quantum information processing with
cold atoms. In this paper, we present a theoretical study of the dynamics of a
cold 87Rb atomic cloud falling in the gravity field in the presence of two
crossing dipole guides. The cloud is either deflected or split between the two
branches of this guide. We explore the possibilities of optimization of this
device and present preliminary results obtained in the case of zero-temperature
dilute Bose-Einstein condensates.
\\ ( http://arxiv.org/abs/0704.3959 , 799kb)
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arXiv:0705.0064
Date: Tue, 1 May 2007 03:16:51 GMT (631kb)

Title: Bright solitary waves and trapped solutions in Bose-Einstein condensates
with attractive interactions
Authors: N. G. Parker, S. L. Cornish, C. S. Adams and A. M. Martin
Categories: cond-mat.other
\\
We analyse the static solutions of attractive Bose-Einstein condensates under
transverse confinement, both with and without axial confinement. By full
numerical solution of the Gross-Pitaevskii equation and variational methods we
map out the condensate solutions, their energetic properties, and their
critical points for instability. With no axial confinement a bright solitary
wave solution will tend to decay by dispersion unless the interaction energy is
close to the critical value for collapse. In contrast, with axial confinement
the only decay mechanism is collapse. The stability of a bright solitary wave
solution increases with higher radial confinement. Finally we consider the
stability of dynamical states containing up to four solitons and find good
agreement with recent experiments.
\\ ( http://arxiv.org/abs/0705.0064 , 631kb)
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arXiv:0705.0097
Date: Tue, 1 May 2007 11:46:07 GMT (36kb)

Title: Collective Oscillations in Trapped Bose-Einstein Condensed Gases in the
Presence of Weak Disorder
Authors: G.M. Falco, A. Pelster, R. Graham
Categories: cond-mat.other cond-mat.stat-mech
\\
The influence of a weak random potential on the collective modes of a trapped
interacting Bose-Einstein condensate at zero temperature is calculated in the
limit when the correlation length of the disorder is smaller than the healing
length of the superfluid. The problem is solved in the Thomas-Fermi limit by
generalizing the superfluid hydrodynamic equations to allow for the presence of
weak disorder. We find that the disorder-induced frequency-shifts of the
low-energy excitations can be of the same order of magnitude as the beyond
mean-field corrections in the normal interaction recently observed
experimentally.
\\ ( http://arxiv.org/abs/0705.0097 , 36kb)
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arXiv:0705.0058
Date: Tue, 1 May 2007 02:19:10 GMT (121kb)

Title: Exact Floquet states and spatiotemporal vortices of a driven condensate
Authors: Wenhua Hai, Chaohong Lee
Categories: quant-ph
\\
We investigate the exact Floquet states and spatiotemporal vortices of a
Gross-Pitaevskii equation, which describes an atomic Bose-Einstein condensate
in an optical lattice driven by a spatiotemporal periodic field, and analyze
their instabilities. The exact Floquet states can be prepared by adjusting the
lattice potential and the driving field to obey a balance condition. For small
driving field intensities, which are below a critical value related to the
lattice strength, the Floquet states are spatiotemporal vortices of nontrivial
phase structures and zero-density cores. Due to the velocity singularities of
vortex cores and the blowing-up of perturbations, the spatiotemporal vortices
are unstable. This instability is confirmed by the fast decay of fidelity
between the exact and numerical solutions. The results give a parametric region
of instability and suggest a method for suppressing the instability.
\\ ( http://arxiv.org/abs/0705.0058 , 121kb)
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arXiv:0705.0196
Date: Wed, 2 May 2007 03:01:32 GMT (111kb)

Title: Cranked Hartree-Fock-Bogoliubov Calculation for Rotating Bose-Einstein
Condensates
Authors: Nobukuni Hamamoto, Makito Oi, Naoki Onishi
Categories: cond-mat.other
Comments: accepted to Phys. Rev. A
\\
A rotating bosonic many-body system in a harmonic trap is studied with the
3D-Cranked Hartree-Fock-Bogoliubov method at zero temperature, which has been
applied to nuclear many-body systems at high spin. This method is a variational
method extended from the Hartree-Fock theory, which can treat the pairing
correlations in a self-consistent manner. An advantage of this method is that a
finite-range interaction between constituent particles can be used in the
calculation, unlike the original Gross-Pitaevskii approach. To demonstrate the
validity of our method, we present a calculation for a toy model, that is, a
rotating system of ten bosonic particles interacting through the repulsive
yrast states, the lowest-energy states for the given total angular momentum,
does not correspond to the Bose-Einstein condensate, except a few special
cases. One of such cases is a vortex state, which appears when the total
angular momentum $L$ is twice the particle number $N$ (i.e., $L=2N$).
\\ ( http://arxiv.org/abs/0705.0196 , 111kb)
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arXiv:0705.0271
Date: Wed, 2 May 2007 12:52:29 GMT (18kb)

Title: Pairing based cooling of Fermi gases
Authors: M. J. Leskinen, J. Kinnunen, P. Torma
Categories: cond-mat.other cond-mat.supr-con
Report-no: NSF-KITP-07-101
\\
We propose a pairing-based method for cooling an atomic Fermi gas. A three
component (labels 1, 2, 3) mixture of Fermions is considered where the
components 1 and 2 interact and, for instance, form pairs whereas the component
3 is in the normal state. For cooling, the components 2 and 3 are coupled by an
electromagnetic field. Since the quasiparticle distributions in the paired and
in the normal states are different, the coupling leads to cooling of the normal
state even when initially $T_{paired}\geq T_{normal}$ (notation $T_S\geq T_N$).
The cooling efficiency is given by the pairing energy and by the linewidth of
the coupling field. No superfluidity is required: any type of pairing, or other
phenomenon that produces a suitable spectral density, is sufficient. In
principle, the paired state could be cooled as well but this requires
$T_N<T_S$. The method has a conceptual analogy to cooling based on
superconductor -- normal metal (SN) tunneling junctions. Main differences arise
from the exact momentum conservation in the case of the field-matter coupling
vs. non-conservation of momentum in the solid state tunneling process.
Moreover, the role of processes that relax the energy conservation requirement
in the tunneling, e.g. thermal fluctuations of an external reservoir, is now
played by the linewidth of the field. The proposed method should be
experimentally feasible due to its close connection to RF-spectroscopy of
ultracold gases which is already in use.
\\ ( http://arxiv.org/abs/0705.0271 , 18kb)
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arXiv:0705.0347
Date: Wed, 2 May 2007 19:23:31 GMT (333kb)

Title: Superfluidity and magnetism in multicomponent ultracold fermions
Authors: R. W. Cherng, Gil Refael, Eugene Demler
Categories: cond-mat.supr-con cond-mat.str-el
\\
We study the interplay between superfluidity and magnetism in a
multicomponent gas of ultracold fermions. Ward-Takahashi identities constrain
possible mean-field states describing order parameters for both pairing and
magnetization. The structure of global phase diagrams arises from competition
among these states as functions of anisotropies in chemical potential, density,
or interactions. They exhibit first and second order phase transition as well
as multicritical points, metastability regions, and phase separation. We
comment on experimental signatures in ultracold atoms.
\\ ( http://arxiv.org/abs/0705.0347 , 333kb)
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arXiv:0705.0322
Date: Wed, 2 May 2007 16:22:23 GMT (68kb,D)

Title: Nonlocality of a single particle
Authors: Jacob Dunningham and Vlatko Vedral
Categories: quant-ph
\\
There has been a great deal of debate surrounding the issue of whether it is
possible for a single photon to exhibit nonlocality. A number of schemes have
been proposed that claim to demonstrate this effect, but each has been met with
significant opposition. The objections hinge largely on the fact that these
schemes use unobservable initial states and so, it is claimed, they do not
represent experiments that could actually be performed. Here we show how it is
possible to overcome these objections by presenting an experimentally feasible
scheme that uses realistic initial states. Furthermore, all the techniques
required for photons are equally applicable to atoms. It should, therefore,
also be possible to use this scheme to verify the nonlocality of a single
massive particle.
\\ ( http://arxiv.org/abs/0705.0322 , 68kb)
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arXiv:0705.0366
Date: Wed, 2 May 2007 20:29:19 GMT (3kb)

Title: Comment on Intensity correlations and mesoscopic fluctuations of
diffusing photons in cold atoms''
Authors: B. Gremaud, D. Delande, C.A. Muller, and C. Miniatura
Categories: cond-mat.mes-hall
Comments: 1 page. Comment submitted to PRL
\\
In a recent Letter (Phys. Rev. Lett. \textbf{98}, 083601 (2007),
arXiv:cond-mat/0610804), O. Assaf and E. Akkermans claim that the angular
correlations of the light intensity scattered by a cloud of cold atoms with
internal degeneracy (Zeeman sublevels) of the ground state overcome the usual
Rayleigh law. More precisely, they found that they become exponentially large
with the size of the sample. In what follows, we will explain why their results
are wrong and, in contrary, why the internal degeneracy leads to lower
intensity correlations.
\\ ( http://arxiv.org/abs/0705.0366 , 3kb)
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The replacements:

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arXiv:cond-mat/0609472
replaced with revised version Fri, 27 Apr 2007 14:59:29 GMT (548kb,D)

Title: Quantum Hall-like effect for cold atoms in non-Abelian gauge potentials
Authors: N. Goldman and P. Gaspard
Categories: cond-mat.mes-hall
\\ ( http://arxiv.org/abs/cond-mat/0609472 , 548kb)
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arXiv:cond-mat/0510111
replaced with revised version Mon, 30 Apr 2007 10:22:44 GMT (16kb)

Title: Particle correlations in a fermi superfluid
Authors: Austen Lamacraft
Categories: cond-mat.stat-mech
Journal-ref: Phys. Rev. A 73, 011602(R) (2006)
\\ ( http://arxiv.org/abs/cond-mat/0510111 , 16kb)
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arXiv:cond-mat/0609240
replaced with revised version Mon, 30 Apr 2007 15:18:30 GMT (398kb)

Title: Normal-Superfluid Interface Scattering For Polarized Fermion Gases
Authors: Bert Van Schaeybroeck and Achilleas Lazarides
Categories: cond-mat.other cond-mat.supr-con
Journal-ref: Phys. Rev. Lett. 98, 170402 (2007)
DOI: 10.1103/PhysRevLett.98.170402
\\ ( http://arxiv.org/abs/cond-mat/0609240 , 398kb)
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arXiv:cond-mat/0610389
replaced with revised version Mon, 30 Apr 2007 06:33:05 GMT (85kb)

Title: Ultracold Bose Gases in 1D Random Potentials: From Lifshits Glasses to
Bose-Einstein Condensates
Authors: Pierre Lugan (LCFIO), David Cl\'ement (LCFIO), Philippe Bouyer
(LCFIO), Alain Aspect (LCFIO), Maciej Lewenstein (ICFO), Laurent
Sanchez-Palencia (LCFIO)
Categories: cond-mat.other
Journal-ref: Physical Review Letters 98 (2007) 170403
DOI: 10.1103/PhysRevLett.98.170403
\\ ( http://arxiv.org/abs/cond-mat/0610389 , 85kb)
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arXiv:cond-mat/0611017
replaced with revised version Mon, 30 Apr 2007 10:02:42 GMT (505kb)

Title: Quantum quenches in a spinor condensate
Authors: Austen Lamacraft
Categories: cond-mat.stat-mech
Journal-ref: Phys. Rev. Lett. 98, 160404 (2007)
\\ ( http://arxiv.org/abs/cond-mat/0611017 , 505kb)
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arXiv:cond-mat/0611206
replaced with revised version Mon, 30 Apr 2007 08:59:20 GMT (812kb)

Title: Measuring the one-particle excitations of ultracold fermionic atoms by
stimulated Raman spectroscopy
Authors: Tung-Lam Dao, Antoine Georges, Jean Dalibard, Christophe Salomon,
Iacopo Carusotto
Categories: cond-mat.other
Comments: 5 pages, 3 figures, accepted for publication at Phys. Rev. Letters
\\ ( http://arxiv.org/abs/cond-mat/0611206 , 812kb)
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arXiv:cond-mat/0701668
replaced with revised version Sat, 28 Apr 2007 09:15:33 GMT (22kb)

Title: Bose-Einstein Condensate in a Harmonic Trap Decorated with Dirac Delta
Functions
Authors: Haydar Uncu, Devrim Tarhan, Ersan Demiralp, Ozgur E. Mustecaplioglu
Categories: cond-mat.other quant-ph
\\ ( http://arxiv.org/abs/cond-mat/0701668 , 22kb)
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arXiv:cond-mat/0605744
replaced with revised version Wed, 2 May 2007 07:00:09 GMT (63kb)

Title: Finite temperature phase diagram of a polarised Fermi condensate
Authors: M. M. Parish, F. M. Marchetti, A. Lamacraft and B. D. Simons
Categories: cond-mat.other
Comments: 6 pages, 4 figures. Manuscript extended and figures modified. For
final version, see Nature Physics
Journal-ref: Nature Physics 3, 124 (2007)
\\ ( http://arxiv.org/abs/cond-mat/0605744 , 63kb)
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arXiv:cond-mat/0608651
replaced with revised version Wed, 2 May 2007 06:48:55 GMT (84kb)

Title: Polarized Fermi condensates with unequal masses: Tuning the tricritical
point
Authors: M. M. Parish, F. M. Marchetti, A. Lamacraft, B. D. Simons
Categories: cond-mat.other
Journal-ref: Phys. Rev. Lett. 98 (2007) 160402
\\ ( http://arxiv.org/abs/cond-mat/0608651 , 84kb)
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arXiv:cond-mat/0610389
replaced with revised version Wed, 2 May 2007 07:08:17 GMT (85kb)

Title: Ultracold Bose Gases in 1D Disorder: From Lifshits Glass to
Bose-Einstein Condensate
Authors: Pierre Lugan (LCFIO), David Cl\'ement (LCFIO), Philippe Bouyer
(LCFIO), Alain Aspect (LCFIO), Maciej Lewenstein (ICFO), Laurent
Sanchez-Palencia (LCFIO)
Categories: cond-mat.other
Journal-ref: Physical Review Letters 98 (2007) 170403
DOI: 10.1103/PhysRevLett.98.170403
\\ ( http://arxiv.org/abs/cond-mat/0610389 , 85kb)
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arXiv:cond-mat/0612565
replaced with revised version Wed, 2 May 2007 13:10:44 GMT (162kb)

Title: Novel quantum phases of dipolar Bose gases in optical lattices
Authors: S. Yi, T. Li, C. P. Sun
Categories: cond-mat.other
\\ ( http://arxiv.org/abs/cond-mat/0612565 , 162kb)
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Till next time (which should only be a few minutes),
Matt.

--
=========================================================================
Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email: mdavis_at_physics.uq.edu.au
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Australia.                    http://www.physics.uq.edu.au/people/mdavis/
=========================================================================
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
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Received on Mon May 14 2007 - 09:54:31 EST

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