[Matts-arxiv] Matt's arXiv selection: week ending 16 July 2010

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Fri, 10 Sep 2010 10:57:41 +1000

Dear subscribers,

This week's selection was compiled by Geoff Lee, and contains 31 new
abstracts and 18 replacements.

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arXiv:0910.5337 (*cross-listing*)
Date: Wed, 28 Oct 2009 10:51:07 GMT (242kb)
Date (revised v2): Thu, 15 Jul 2010 15:48:27 GMT (574kb)

Title: Fluctuations and stochastic processes in one-dimensional many-body
quantum systems
Authors: H.-P. Stimming, N. J. Mauser, J. Schmiedmayer, and I. E. Mazets
Categories: cond-mat.quant-gas quant-ph
Comments: 4 pages (revtex4), 4 color figures. Text substantially rewritten, two
Journal-ref: Phys. Rev. Lett. 105, 015301 (2010)
DOI: 10.1103/PhysRevLett.105.015301
\\
We study the fluctuation properties of a one-dimensional many-body quantum
system composed of interacting bosons, and investigate the regimes where
quantum noise or, respectively, thermal excitations are dominant. For the
latter we develop a semiclassical description of the fluctuation properties
based on the Ornstein-Uhlenbeck stochastic process. As an illustration, we
analyze the phase correlation functions and the full statistical distributions
of the interference between two one-dimensional systems, either independent or
tunnel-coupled and compare with the Luttinger-liquid theory.
\\ ( http://arxiv.org/abs/0910.5337 , 574kb)
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arXiv:0912.4493 (*cross-listing*)
Date: Tue, 22 Dec 2009 19:17:24 GMT (229kb)
Date (revised v2): Thu, 15 Jul 2010 16:59:19 GMT (231kb)

Title: Thermalization in a quasi-1D ultracold bosonic gas
Authors: I. E. Mazets and J. Schmiedmayer
Categories: cond-mat.quant-gas cond-mat.stat-mech quant-ph
Comments: revtex4, 3 figures. Final version of the text, accepted for
publication (see journal ref.)
Journal-ref: New J. Phys. 12 (2010) 055023
DOI: 10.1088/1367-2630/12/5/055023
\\
We study the collisional processes that can lead to thermalization in
one-dimensional systems. For two body collisions excitations of transverse
modes are the prerequisite for energy exchange and thermalzation. At very low
temperatures excitations of transverse modes are exponentially suppressed,
thermalization by two body collisions stops and the system should become
integrable. In quantum mechanics virtual excitations of higher radial modes are
possible. These virtually excited radial modes give rise to effective
three-body velocity-changing collisions which lead to thermalization. We show
that these three-body elastic interactions are suppressed by pairwise quantum
correlations when approaching the strongly correlated regime. If the relative
momentum $k$ is small compared to the two-body coupling constant $c$ the
three-particle scattering state is suppressed by a factor of $(k/c)^{12}$,
which is proportional to $\gamma ^{12}$, that is to the square of the
three-body correlation function at zero distance in the limit of the
Lieb-Liniger parameter $\gamma \gg 1$. This demonstrates that in one
dimensional quantum systems it is not the freeze-out of two body collisions but
the strong quantum correlations which ensures absence of thermalization on
experimentally relevant time scales.
\\ ( http://arxiv.org/abs/0912.4493 , 231kb)
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arXiv:1007.1458
Date: Thu, 8 Jul 2010 20:00:35 GMT (295kb)

Title: Dimensional crossover of a boson gas in multilayers
Authors: P. Salas, F.J. Sevilla, M. Fortes, M. de Llano, A. Camacho, and M.A.
Sol\'is
Categories: cond-mat.quant-gas
\\
We obtain the thermodynamic properties for a non-interacting Bose gas
constrained on multilayers modeled by a periodic Kronig-Penney delta potential
in one direction and allowed to be free in the other two directions. We report
Bose-Einstein condensation (BEC) critical temperatures, chemical potential,
internal energy, specific heat, and entropy for different values of a
dimensionless impenetrability $P\geqslant 0$ between layers. The BEC critical
temperature $T_{c}$ coincides with the ideal gas BEC critical temperature
$T_{0}$ when $P=0$ and rapidly goes to zero as $P$ increases to infinity for
any finite interlayer separation. The specific heat $C_{V}$ \textit{vs} $T$ for
finite $P$ and plane separation $a$ exhibits one minimum and one or two maxima
in addition to the BEC, for temperatures larger than $T_{c}$ which highlights
the effects due to particle confinement. Then we discuss a distinctive
dimensional crossover of the system through the specific heat behavior driven
by the magnitude of $P$. For $T<T_{c}$ the crossover is revealed by the change
in the slope of $\log C_{V}(T)$ and when $T>T_{c}$, it is evidenced by a broad
minimum in $C_{V}(T)$.
\\ ( http://arxiv.org/abs/1007.1458 , 295kb)
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arXiv:1007.1475
Date: Thu, 8 Jul 2010 21:41:36 GMT (276kb)

Title: Vortices and dynamics in trapped Bose-Einstein condensates
Authors: Alexander L. Fetter
Categories: cond-mat.quant-gas
Comments: Accepted for publication in Journal of Low Temperature Physics,
conference proceedings: Symposia on Superfluids under Rotation (Lammi,
Finland, April 2010)
\\
I review the basic physics of ultracold dilute trapped atomic gases, with
emphasis on Bose-Einstein condensation and quantized vortices. The hydrodynamic
form of the Gross-Pitaevskii equation (a nonlinear Schr{\"o}dinger equation)
illuminates the role of the density and the quantum-mechanical phase. One
unique feature of these experimental systems is the opportunity to study the
dynamics of vortices in real time, in contrast to typical experiments on
superfluid $^4$He. I discuss three specific examples (precession of single
vortices, motion of vortex dipoles, and Tkachenko oscillations of a vortex
array). Other unusual features include the study of quantum turbulence and the
behavior for rapid rotation, when the vortices form dense regular arrays.
Ultimately, the system is predicted to make a quantum phase transition to
various highly correlated many-body states (analogous to bosonic quantum Hall
states) that are not superfluid and do not have condensate wave functions. At
present, this transition remains elusive. Conceivably, laser-induced synthetic
vector potentials can serve to reach this intriguing phase transition.
\\ ( http://arxiv.org/abs/1007.1475 , 276kb)
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arXiv:1007.1480
Date: Thu, 8 Jul 2010 22:13:46 GMT (1561kb,D)

Title: Dysprosium magneto-optical traps
Authors: Seo Ho Youn, Mingwu Lu, Ushnish Ray, and Benjamin L. Lev
Categories: physics.atom-ph quant-ph
Comments: 13 pages, 12 figures, follow up material to Phys. Rev. Lett. 104,
063001 (2010)
\\
Magneto-optical traps (MOTs) of highly magnetic lanthanides open the door to
explorations of novel phases of strongly correlated matter such as lattice
supersolids and quantum liquid crystals. We recently reported the first MOTs of
the five high abundance isotopes of the most magnetic atom, dysprosium.
Described here are details of the experimental technique employed for
repumper-free Dy MOTs containing up to half a billion atoms. Extensive
metastable decay dynamics, trap dynamics---is provided.
\\ ( http://arxiv.org/abs/1007.1480 , 1561kb)
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arXiv:1007.1506
Date: Fri, 9 Jul 2010 03:54:20 GMT (39kb)

Title: Induced interaction in a spin-polarized Fermi gas
Authors: Zeng-Qiang Yu and Lan Yin
Categories: cond-mat.quant-gas cond-mat.str-el cond-mat.supr-con
Journal-ref: Phys. Rev. A 82, 013605 (2010)
DOI: 10.1103/Phys.Rev.A82.013605
\\
We study the effect of the induced interaction on the superfluidtransition
temperature of a spin-polarized Fermi gas. In the BCS limit, the polarization
is very small in the superfluid state, and the effect of the induced
interaction is almost the same as in the spin-balanced case. The temperature Tt
and the polarization Pt of the tricritical point are both reduced from
mean-field results by a factor about 2.22. This reduction is also significant
beyond the BCS limit. In the unitary limit, we find (Pt,Tt/TF)=(0.42,0.16), in
comparison with mean-field and experimental results.
\\ ( http://arxiv.org/abs/1007.1506 , 39kb)
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arXiv:1007.1534
Date: Fri, 9 Jul 2010 09:03:00 GMT (105kb)

Title: Stability of attractive bosonic cloud with van der Waals interaction
Authors: Anindya Biswas, Tapan Kumar Das, Luca Salasnich and Barnali
Chakrabarti
Categories: cond-mat.quant-gas
\\
We investigate the structure and stability of Bose-Einstein condensate of
$^{7}$Li atoms with realistic van der Waals interaction by using the potential
harmonic expansion method. Besides the known low-density metastable solution
with contact delta function interaction, we find a stable branch at a higher
density which corresponds to the formation of an atomic cluster. Comparison
with the results of non-local effective interaction is also presented. We
analyze the effect of trap size on the transition between the two branches of
solutions. We also compute the loss rate of a Bose condensate due to two- and
three-body collisions.
\\ ( http://arxiv.org/abs/1007.1534 , 105kb)
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arXiv:1007.1657 (*cross-listing*)
Date: Fri, 9 Jul 2010 19:47:47 GMT (102kb,D)

Title: Driving quantized vortices with quantum vacuum fluctuations
Authors: Fran\c{c}ois Impens, Ana M. Contreras-Reyes, Paulo A. Maia Neto, Diego
A. R. Dalvit, Romain Gu\'erout, Astrid Lambrecht, Serge Reynaud
Categories: cond-mat.quant-gas physics.atom-ph quant-ph
\\
We propose to use a rotating corrugated material plate in order to stir,
through the Casimir-Polder interaction, quantized vortices in an harmonically
trapped Bose-Einstein condensate. The emergence of such vortices within the
condensate appears as a genuine signature of non-trivial geometry effects on
the electromagnetic vacuum fluctuations which fully exploits the superfluid
nature of the sample. We calculate the exact non-perturbative Casimir-Polder
potential, valid to all orders of the corrugation amplitude, felt by the atoms
in front of the grating and show that the resulting quantum vacuum torque is
strong enough to provide a contactless transfer of angular momentum to the
condensate and generate quantized vortices under realistic experimental
conditions at separation distances around 3 microns.
\\ ( http://arxiv.org/abs/1007.1657 , 102kb)
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arXiv:1007.1796 (*cross-listing*)
Date: Sun, 11 Jul 2010 19:55:41 GMT (9kb)

Title: Localization of Multi-Dimensional Wigner Distributions
Authors: Elliott H. Lieb and Yaron Ostrover
Categories: math-ph math.MP quant-ph
MSC-class: 81S30, 81P15, 81P16
\\
A well known result of P. Flandrin states that a Gaussian uniquely maximizes
the integral of the Wigner distribution over every centered disc in the phase
plane. While there is no difficulty in generalizing this result to
higher-dimensional poly-discs, the generalization to balls is less obvious. In
this note we provide such a generalization.
\\ ( http://arxiv.org/abs/1007.1796 , 9kb)
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arXiv:1007.1847
Date: Mon, 12 Jul 2010 08:55:31 GMT (1377kb)

Title: Unifying treatment of nonequilibrium and unstable dynamics of cold
bosonic atom system with time-dependent order parameter in Thermo Filed
Dynamics
Authors: Y. Nakamura and Y. Yamanaka
Categories: cond-mat.quant-gas cond-mat.other
\\
The coupled equations which describe the temporal evolution of the
Bose-Einstein condensed system are derived in the framework of nonequilibrium
Thermo Field Dynamics. The key element is that they are not the naive
assemblages of presumable equations, but are the self-consistent ones derived
by appropriate renormalization conditions. While the order parameter is
time-dependent, an explicit quasiparticle picture is constructed by a
time-dependent expansion. Our formulation is valid even for the system with a
unstable condensate, and describes the condensate decay caused by the Landau
instability as well as by the dynamical one.
\\ ( http://arxiv.org/abs/1007.1847 , 1377kb)
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arXiv:1007.1853
Date: Mon, 12 Jul 2010 09:44:30 GMT (31kb,D)

Title: Comment on "Feshbach-Einstein Condensates" by V. G. Rousseau and P. J.
H. Denteneer
Authors: Mar\'ia Eckholt, Tommaso Roscilde
Categories: cond-mat.quant-gas
\\
In a recent paper (Phys. Rev. Lett. 102, 015301 (2009), arXiv:0810.3763)
Rousseau and Denteneer claim that an unconventional "super-Mott" (SM) phase is
realized by bosons trapped in an optical lattice close to a Feshbach resonance
with a molecular state. The supposed SM phase, observed via quantum Monte Carlo
(QMC) simulations of an atom-molecule Bose-Hubbard model, is an incompressible
phase developing spontaneous atomic/molecular supercurrents which are perfectly
anticorrelated. Here we show that the identification of this phase is based on
a misinterpretation of the estimators of superfluidity in QMC, which break down
in the presence of coherent atom/molecule conversion. Our conclusion is that
the supposed SM phase is in fact a fully normal insulator.
\\ ( http://arxiv.org/abs/1007.1853 , 31kb)
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arXiv:1007.1884
Date: Mon, 12 Jul 2010 12:28:01 GMT (85kb)

Title: Feedback Cooling of a Single Neutral Atom
Authors: Markus Koch, Christian Sames, Alexander Kubanek, Matthias Apel,
Maximilian Balbach, Alexei Ourjoumtsev, Pepijn W.H. Pinkse and Gerhard Rempe
Categories: quant-ph
\\
We demonstrate feedback cooling of the motion of a single rubidium atom
trapped in a high-finesse optical resonator to a temperature of about 160 \mu
K. Time-dependent transmission and intensity-correlation measurements prove the
reduction of the atomic position uncertainty. The feedback increases the 1/e
storage time into the one second regime, 30 times longer than without feedback.
Feedback cooling therefore rivals state-of-the-art laser cooling, but with the
advantages that it requires less optical access and exhibits less optical
pumping.
\\ ( http://arxiv.org/abs/1007.1884 , 85kb)
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arXiv:1007.1892 (*cross-listing*)
Date: Mon, 12 Jul 2010 12:48:01 GMT (19kb)

Title: The ground state of the polar alkali-Strontium molecules: potential
energy curve and permanent dipole moment
Authors: Romain Gu\'erout (LKB - Jussieu), Mireille Aymar (LAC), Olivier Dulieu
(LAC)
Categories: physics.atm-clus quant-ph
\\
In this study, we investigate the structure of the polar alkali-Strontium
diatomic molecules as possible candidates for the realization of samples of new
species of ultracold polar molecules. Using a quantum chemistry approach based
on Effective Core Potentials and Core Polarization Potentials, we model these
systems as effective three valence electron systems, allowing for calculation
of electronic properties with Full Configuration Interaction. The potential
curve and the permanent dipole moment of the $^2\Sigma^+$ ground state are
determined as functions of the internuclear distances for LiSr, NaSr, KSr,
RbSr, and CsSr molecules. These molecules are found to exhibit a significant
permanent dipole moment, though smaller than those of the alkali-Rb molecules.
\\ ( http://arxiv.org/abs/1007.1892 , 19kb)
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arXiv:1007.1898
Date: Mon, 12 Jul 2010 13:24:08 GMT (3858kb)

Title: Vibrational stabilization of ultracold KRb molecules. A comparative
study
Authors: Mamadou Ndong and Christiane P. Koch
Categories: physics.atom-ph
Comments: 11 pages, 10 figures, 17 graphs
\\
The transfer of weakly bound KRb molecules from levels just below the
dissociation threshold into the vibrational ground state with shaped laser
pulses is studied. Optimal control theory is employed to calculate the pulses.
The complexity of modelling the molecular structure is successively increased
in order to study the effects of the long-range behavior of the excited state
potential, resonant spin-orbit coupling and singlet-triplet mixing.
\\ ( http://arxiv.org/abs/1007.1898 , 3858kb)
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arXiv:1007.1899
Date: Mon, 12 Jul 2010 13:29:53 GMT (201kb)

Title: Quantum imaging of spin states in optical lattices
Authors: James Douglas and Keith Burnett
Categories: quant-ph cond-mat.quant-gas
\\
We investigate imaging of the spatial spin distribution of atoms in optical
lattices using non-resonant light scattering. We demonstrate how scattering
spatially correlated light from the atoms can result in spin state images with
enhanced spatial resolution. Furthermore, we show how using spatially
correlated light can lead to direct measurement of the spatial correlations of
the atomic spin distribution.
\\ ( http://arxiv.org/abs/1007.1899 , 201kb)
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arXiv:1007.2015
Date: Tue, 13 Jul 2010 00:43:41 GMT (1211kb)

Title: The Design and Validation of the Quantum Mechanics Conceptual Survey
Authors: S. B. McKagan, K. K. Perkins, C. E. Wieman
Categories: physics.ed-ph
Comments: Submitted to Physical Review Special Topics: Physics Education
Research
\\
The Quantum Mechanics Conceptual Survey (QMCS) is a 12-question survey of
students' conceptual understanding of quantum mechanics. It is intended to be
used to measure the relative effectiveness of different instructional methods
in modern physics courses. In this paper we describe the design and validation
of the survey, a process that included observations of students, a review of
previous literature and textbooks and syllabi, faculty and student interviews,
and statistical analysis. We also discuss issues in the development of specific
questions, which may be useful both for instructors who wish to use the QMCS in
their classes and for researchers who wish to conduct further research of
student understanding of quantum mechanics. The QMCS has been most thoroughly
tested in, and is most appropriate for assessment of (as a posttest only),
sophomore-level modern physics courses. We also describe testing with students
in junior quantum courses and graduate quantum courses, from which we conclude
that the QMCS may be appropriate for assessing junior quantum courses, but is
not appropriate for assessing graduate courses. One surprising result of our
faculty interviews is a lack of faculty consensus on what topics should be
taught in modern physics, which has made designing a test that is valued by a
majority of physics faculty more difficult than expected.
\\ ( http://arxiv.org/abs/1007.2015 , 1211kb)
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arXiv:1007.2027
Date: Tue, 13 Jul 2010 03:30:10 GMT (789kb)

Title: Spin textures in condensates with large dipole moments
Authors: J. A. M. Huhtam\"aki, M. Takahashi, T. P. Simula, T. Mizushima, and K.
Machida
Categories: cond-mat.quant-gas
Journal-ref: Phys. Rev. A 81, 063623 (2010)
DOI: 10.1103/PhysRevA.81.063623
\\
We have solved numerically the ground states of a Bose-Einstein condensate in
the presence of dipolar interparticle forces using a semiclassical approach.
Our motivation is to model, in particular, the spontaneous spin textures
emerging in quantum gases with large dipole moments, such as 52Cr or Dy
condensates, or ultracold gases consisting of polar molecules. For a
pancake-shaped harmonic (optical) potential, we present the ground state phase
diagram spanned by the strength of the nonlinear coupling and dipolar
interactions. In an elongated harmonic potential, we observe a novel helical
spin texture. The textures calculated according to the semiclassical model in
the absence of external polarizing fields are predominantly analogous to
previously reported results for a ferromagnetic F = 1 spinor Bose-Einstein
condensate, suggesting that the spin textures arising from the dipolar forces
are largely independent of the value of the quantum number F or the origin of
the dipolar interactions.
\\ ( http://arxiv.org/abs/1007.2027 , 789kb)
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arXiv:1007.2056
Date: Tue, 13 Jul 2010 09:32:49 GMT (1584kb)

Title: Topology-induced phase transitions in quantum spin Hall lattices
Authors: D. Bercioux, N. Goldman, D.F. Urban
Categories: cond-mat.mes-hall cond-mat.quant-gas
\\
Physical phenomena driven by topological properties, such as the quantum Hall
effect, have the appealing feature to be robust with respect to external
perturbations. Lately, a new class of materials has emerged manifesting their
topological properties at room temperature and without the need of external
magnetic fields. These topological insulators are band insulators with large
spin-orbit interactions and exhibit the quantum spin-Hall (QSH) effect. Here we
investigate the transition between QSH and normal insulating phases under
topology deformations of a two-dimensional lattice. We demonstrate that the QSH
phase present in the honeycomb lattice looses its robustness as the occupancy
of extra lattice sites is allowed. Furthermore, we propose a method for
verifying our predictions with fermionic cold atoms in optical lattices. In
this context, the spin-orbit interaction is engineered via an appropriate
synthetic gauge field.
\\ ( http://arxiv.org/abs/1007.2056 , 1584kb)
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arXiv:1007.2136
Date: Tue, 13 Jul 2010 16:37:16 GMT (595kb)

Title: Improved detection of small atom numbers through image processing
Authors: C. F. Ockeloen, A. F. Tauschinsky, R. J. C. Spreeuw, and S. Whitlock
Categories: physics.atom-ph cond-mat.quant-gas
\\
We demonstrate improved detection of small trapped atomic ensembles through
advanced post-processing and optimal analysis of absorption images. A fringe
removal algorithm reduces imaging noise to the fundamental photon-shot-noise
level and proves beneficial even in the absence of fringes. A
maximum-likelihood estimator is then derived for optimal atom-number estimation
and is applied to real experimental data to measure the population differences
and intrinsic atom shot-noise between spatially separated ensembles each
comprising between 10 and 2000 atoms. The combined techniques improve our
signal-to-noise by a factor of 3, to a minimum resolvable population difference
of 17 atoms, close to our ultimate detection limit.
\\ ( http://arxiv.org/abs/1007.2136 , 595kb)
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arXiv:1007.2189 (*cross-listing*)
Date: Tue, 13 Jul 2010 20:05:09 GMT (372kb)

Title: Two-stage melting of solids in strongly interacting Rydberg atoms
Authors: Hendrik Weimer, Hans Peter B\"uchler
Categories: cond-mat.quant-gas physics.atom-ph quant-ph
\\
We analyze the ground state properties of a one-dimensional cold atomic
system in a lattice, where Rydberg excitations are created by an external laser
drive. In the classical limit, the ground state is characterized by a complete
devil's staircase for the commensurate solid structures of Rydberg excitations.
Using perturbation theory and a mapping onto an effective low energy
Hamiltonian, we find a transition of these commensurate solids into a floating
solid with algebraic correlations. For stronger quantum fluctuations the
floating solid eventually melts within a second quantum phase transition and
the ground state becomes paramagnetic.
\\ ( http://arxiv.org/abs/1007.2189 , 372kb)
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arXiv:1007.2245
Date: Wed, 14 Jul 2010 03:29:45 GMT (37kb)

Title: Particle-hole symmetric localization in optical lattices using time
modulated random on-site potentials
Authors: Yue Zou, Ryan Barnett, Gil Refael
Categories: cond-mat.quant-gas cond-mat.dis-nn
\\
The random hopping models exhibit many fascinating features, such as
diverging localization length and density of states as energy approaches the
bandcenter, due to its particle-hole symmetry. Nevertheless, such models are
yet to be realized experimentally because the particle-hole symmetry is easily
destroyed by diagonal disorder. Here we propose that a pure random hopping
model can be effectively realized in ultracold atoms by modulating a disordered
onsite potential in particular frequency ranges. This idea is motivated by the
recent development of the phenomena called "dynamical localization" or
"coherent destruction of tunneling". Investigating the application of this idea
in one dimension, we find that if the oscillation frequency of the disorder
potential is gradually increased from zero to infinity, one can tune a
non-interacting system from an Anderson insulator to a random hopping model
with diverging localization length at the band center, and eventually to a
uniform-hopping tight-binding model.
\\ ( http://arxiv.org/abs/1007.2245 , 37kb)
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arXiv:1007.2329 (*cross-listing*)
Date: Wed, 14 Jul 2010 13:41:50 GMT (117kb)

Title: Dynamics of bisolitonic matter waves in a Bose-Einstein condensate
subjected to an atomic beam splitter and gravity
Authors: Alain Moise Dikande, Isaiah Ndifon Ngek and Joseph Ebobenow
Categories: nlin.PS cond-mat.quant-gas physics.atom-ph physics.optics
Comments: 10 pages, 26 figures, to appear in Modern Physics Letters B (Accepted
12 July, 2010)
\\
A theoretical scheme for an experimental implementation involving bisolitonic
matter waves from an attractive Bose-Einstein condensate, is considered within
the framework of a non-perturbative approach to the associate Gross-Pitaevskii
equation. The model consists of a single condensate subjected to an expulsive
harmonic potential creating a double-condensate structure, and a gravitational
potential that induces atomic exchanges between the two overlapping post
condensates. Using a non-isospectral scattering transform method, exact
expressions for the bright-matter-wave bisolitons are found in terms of
double-lump envelopes with the co-propagating pulses displaying more or less
pronounced differences in their widths and tails depending on the mass of atoms
composing the condensate.
\\ ( http://arxiv.org/abs/1007.2329 , 117kb)
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arXiv:1007.2342 (*cross-listing*)
Date: Wed, 14 Jul 2010 14:18:02 GMT (1713kb)

Title: Spontaneous breaking of spatial and spin symmetry in spinor condensates
Authors: M. Scherer, B. L\"ucke, G. Gebreyesus, O. Topic, F. Deuretzbacher, W.
Ertmer, L. Santos, J.J. Arlt, C. Klempt
Categories: cond-mat.quant-gas quant-ph
\\
Parametric amplification of quantum fluctuations constitutes a fundamental
mechanism for spontaneous symmetry breaking. In our experiments, a spinor
condensate acts as a parametric amplifier of spin modes, resulting in a twofold
spontaneous breaking of spatial and spin symmetry in the amplified clouds. Our
experiments permit a precise analysis of the amplification in specific spatial
Bessel-like modes, allowing for the detailed understanding of the double
symmetry breaking. On resonances that create vortex-antivortex superpositions,
we show that the cylindrical spatial symmetry is spontaneously broken, but
phase squeezing prevents spin-symmetry breaking. If, however, nondegenerate
spin modes contribute to the amplification, quantum interferences lead to
spin-dependent density profiles and hence spontaneously-formed patterns in the
longitudinal magnetization.
\\ ( http://arxiv.org/abs/1007.2342 , 1713kb)
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arXiv:1007.2344 (*cross-listing*)
Date: Wed, 14 Jul 2010 14:27:04 GMT (2266kb,D)

Title: Emerging Bosons with Three-Body Interactions from Spin-1 Atoms in
Optical Lattices
Authors: Leonardo Mazza and Matteo Rizzi and Maciej Lewenstein and J.Ignacio
Cirac
Categories: cond-mat.quant-gas cond-mat.supr-con quant-ph
\\
We study two many-body systems of bosons interacting via an infinite
three-body contact repulsion in a lattice: a pairs quasi-condensate induced by
correlated hopping and the discrete version of the Pfaffian wavefunction. We
propose to experimentally realise systems characterized by such interaction by
means of a proper spin-1 lattice Hamiltonian: spin degrees of freedom are
locally mapped into occupation numbers of emerging bosons, in a fashion similar
to spin-1/2 and hardcore bosons. Such a system can be realized with ultracold
spin-1 atoms in a Mott Insulator with filling-factor one. The high versatility
of these setups allows us to engineer spin-hopping operators breaking the SU(2)
symmetry, as needed to approximate interesting bosonic Hamiltonians with
three-body hardcore constraint. For this purpose we combine bichromatic
spin-independent superlattices and Raman transitions to induce a different
hopping rate for each spin orientation. Finally, we illustrate how our setup
could be used to experimentally realize the first setup, i.e. the transition to
a pairs quasi-condensed phase of the emerging bosons. We also report on a route
towards the realization of a discrete bosonic Pfaffian wavefunction and list
some open problems to reach this goal.
\\ ( http://arxiv.org/abs/1007.2344 , 2266kb)
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arXiv:1007.2408
Date: Wed, 14 Jul 2010 19:59:13 GMT (328kb,D)

Title: Nonlinear interference in a mean-field quantum model
Authors: Gilbert Reinisch and Vidar Gudmundsson
Categories: cond-mat.mes-hall cond-mat.quant-gas
Comments: RevTeX (pdfLaTeX), 7 pages with 5 png-figures included
\\
Using similar nonlinear stationary mean-field models for Bose-Einstein
Condensation of cold atoms and interacting electrons in a Quantum Dot, we
propose to describe the original many-particle ground state as a one-particle
statistical mixed state of the nonlinear eigenstates whose weights are provided
by the eigenstate non-orthogonality. We search for physical grounds in the
interpretation of our two main results, namely, quantum-classical nonlinear
transition and interference between nonlinear eigenstates.
\\ ( http://arxiv.org/abs/1007.2408 , 328kb)
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arXiv:1007.2416
Date: Wed, 14 Jul 2010 20:02:08 GMT (727kb)

Title: Quantum localization without disorder in interacting Bose-Einstein
condensates
Authors: Roberto Franzosi, Salvatore M. Giampaolo, Fabrizio Illuminati
Categories: cond-mat.quant-gas
\\
We discuss the possibility of exponential quantum localization in systems of
ultracold bosonic atoms with repulsive interactions in open optical lattices
without disorder. We show that exponential localization occur in the maximally
excited state of the lowest energy band. We establish the conditions under
which the presence of the upper energy bands can be neglected, determine the
successive stages and the quantum phase boundaries at which localization
occurs, and discuss how to detect it experimentally by visibility measurements.
The discussed mechanism is a bona fide type of quantum localization, solely due
to the interplay between nonlinearity and a bounded energy spectrum. In
particular, it does not require the presence of random disorder or other local
sources of noise, in striking contrast with Anderson localization.
\\ ( http://arxiv.org/abs/1007.2416 , 727kb)
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arXiv:1007.2544 (*cross-listing*)
Date: Thu, 15 Jul 2010 12:43:05 GMT (73kb)

Title: The three-site Bose-Hubbard model subject to atom losses: the boson-pair
dissipation channel and failure of the mean-field approach
Authors: V. S. Shchesnovich and D. S. Mogilevtsev
Categories: cond-mat.quant-gas cond-mat.other quant-ph
Comments: 9 pages; 3 figures in color; submitted to PRA
\\
We employ the perturbation series expansion for derivation of the reduced
master equations for the three-site Bose-Hubbard model subject to strong atom
losses from the central site. The model describes a condensate trapped in a
triple-well potential subject to externally controlled removal of atoms. We
find that the $\pi$-phase state of the coherent superposition between the side
wells decays via two dissipation channels, the single-boson channel (similar to
the externally applied dissipation) and the boson-pair channel. The quantum
derivation is compared to the classical adiabatic elimination within the
mean-field approximation. We find that the boson-pair dissipation channel is
not captured by the mean-field model, whereas the single-boson channel is
described by it. Moreover, there is a matching condition between the zero-point
energy bias of the side wells and the nonlinear interaction parameter which
separates the regions where either the single-boson or the boson-pair
dissipation channel dominate. Our results indicate that the $M$-site
Bose-Hubbard models, for $M>2$, subject to atom losses may require an analysis
which goes beyond the usual mean-field approximation for correct description of
their dissipative features. This is an important result in view of the recent
experimental works on the single site addressability of condensates trapped in
optical lattices.
\\ ( http://arxiv.org/abs/1007.2544 , 73kb)
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arXiv:1007.2568 (*cross-listing*)
Date: Thu, 15 Jul 2010 14:19:06 GMT (37kb)

Title: Atomic number fluctuations in a mixture of two spinor condensates
Authors: Jie Zhang, Z. F. Xu, L. You and Yunbo Zhang
Categories: cond-mat.quant-gas quant-ph
Comments: 5 pages, 2 figures, in press PRA
\\
We study particle number fluctuations in the quantum ground states of a
mixture of two spin-1 atomic condensates when the interspecies spin-exchange
coupling interaction $c_{12}\beta$ is adjusted. The two spin-1 condensates
forming the mixture are respectively ferromagnetic and polar in the absence of
an external magnetic (B-) field. We categorize all possible ground states using
the angular momentum algebra and compute their characteristic atom number
fluctuations, focusing especially on the the AA phase (when $c_{12}\beta >0$),
where the ground state becomes fragmented and atomic number fluctuations
exhibit drastically different features from a single stand alone spin-1 polar
condensate. Our results are further supported by numerical simulations of the
full quantum many-body system.
\\ ( http://arxiv.org/abs/1007.2568 , 37kb)
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\\
arXiv:1007.2591 (*cross-listing*)
Date: Thu, 15 Jul 2010 15:43:54 GMT (588kb)

Title: Probing magnetic order in ultracold lattice gases
Authors: G. De Chiara, O. Romero-Isart and A. Sanpera
Categories: cond-mat.quant-gas quant-ph
\\
The simulation of quantum magnetism with ultracold lattice gases is one of
the next challenges in the field of ultracold atoms. We propose a method to
measure directly the order parameter of non trivial antiferromagnetic quantum
phases in a non demolishing way. This atom-light interface gives access to
spatially resolved spin correlations. Such probing scheme allows one to
univocally characterize strongly correlated magnetic systems simulated with
ultracold atoms in optical lattices. As a proof of principle, we apply our
method to detect the complete phase diagram of the rotational invariant spin-1
chain.
\\ ( http://arxiv.org/abs/1007.2591 , 588kb)
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\\
arXiv:1007.2625
Date: Thu, 15 Jul 2010 18:10:27 GMT (29kb)

Title: Observation of Universal Temperature Scaling in the Quantum Viscosity of
a Unitary Fermi Gas
Authors: C. Cao, E. Elliott, J. Joseph, H. Wu, J. Petricka, T. Schaefer, and J.
E.Thomas
Categories: cond-mat.quant-gas
\\
A Fermi gas of atoms tuned near a Feshbach resonance should obey universal
hydrodynamics, where the shear viscosity and other transport coefficients are
universal functions of the density and temperature. At temperatures well above
the superfluid transition, the viscosity has a universal quantum scale
$p_T^3/\hbar^2$, where $p_T$ is the thermal momentum. We observe the expansion
of a unitary Fermi gas in this regime and show that the slowing of the dynamics
with increasing temperature $T$ is explained by a shear viscosity that scales
precisely as $T^{3/2}$. These results are important for measurement of the
shear viscosity just above the critical temperature, where the ratio of the
shear viscosity to the entropy density is expected to exhibit a minimum that
can be compared to a recent conjecture regarding perfect normal fluids.
\\ ( http://arxiv.org/abs/1007.2625 , 29kb)
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\\
arXiv:1007.2638
Date: Thu, 15 Jul 2010 19:47:34 GMT (782kb)

Title: Collisional-inhomogeneity-induced generation of matter-wave dark
solitons
Authors: C. Wang, P.G. Kevrekidis, T.P. Horikis and D.J. Frantzeskakis
Categories: cond-mat.quant-gas nlin.PS
Comments: 8 pages, 5 Figures, Physics Letters A (in press)
\\
We propose an experimentally relevant protocol for the controlled generation
of matter-wave dark solitons in atomic Bose-Einstein condensates (BECs). In
particular, using direct numerical simulations, we show that by switching-on a
spatially inhomogeneous (step-like) change of the s-wave scattering length, it
is possible to generate a controllable number of dark solitons in a
quasi-one-dimensional BEC. A similar phenomenology is also found in the
two-dimensional setting of "disk-shaped" BECs but, as the solitons are subject
to the snaking instability, they decay into vortex structures. A detailed
investigation of how the parameters involved affect the emergence and evolution
of solitons and vortices is provided.
\\ ( http://arxiv.org/abs/1007.2638 , 782kb)
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The replacements:

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arXiv:0905.3384 (*cross-listing*)
replaced with revised version Fri, 9 Jul 2010 06:27:20 GMT (462kb)

Title: Phase space representation of quantum dynamics
Authors: Anatoli Polkovnikov
Categories: cond-mat.stat-mech cond-mat.quant-gas hep-th quant-ph
Comments: 92 pages, typos corrected, published version
Journal-ref: Annals of Phys. 325, 1790 (2010)
DOI: 10.1016/j.aop.2010.02.006
\\ ( http://arxiv.org/abs/0905.3384 , 462kb)
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arXiv:1006.3008
replaced with revised version Fri, 9 Jul 2010 13:17:49 GMT (132kb)

Title: Comparing cavity and ordinary laser cooling
Authors: Tony Blake, Andreas Kurcz, and Almut Beige
Categories: quant-ph
Comments: 11 pages, 8 figures, substantially revised version, submitted to
Journal of Modern Optics (Special Issue on New cooling mechanisms for atoms
and molecules)
\\ ( http://arxiv.org/abs/1006.3008 , 132kb)
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\\
arXiv:1003.1403
replaced with revised version Fri, 9 Jul 2010 19:57:03 GMT (360kb)

Title: Quantum chaos and thermalization in gapped systems
Authors: Marcos Rigol and Lea F. Santos
Categories: cond-mat.stat-mech cond-mat.quant-gas
Comments: 8 pages, 8 figures, as published
Journal-ref: Phys. Rev. A 82, 011604(R) (2010)
DOI: 10.1103/PhysRevA.82.011604
\\ ( http://arxiv.org/abs/1003.1403 , 360kb)
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arXiv:0912.3559 (*cross-listing*)
replaced with revised version Fri, 9 Jul 2010 20:00:06 GMT (2189kb,D)

Title: Topological states in two-dimensional optical lattices
Authors: Tudor D. Stanescu, Victor Galitski and S. Das Sarma
Categories: cond-mat.quant-gas cond-mat.mes-hall quant-ph
version)
Journal-ref: Phys. Rev. A 82, 013608 (2010)
DOI: 10.1103/PhysRevA.82.013608
\\ ( http://arxiv.org/abs/0912.3559 , 2189kb)
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arXiv:1004.4134
replaced with revised version Mon, 12 Jul 2010 14:33:08 GMT (231kb)

Title: Oscillating solitons in a three component BEC
Authors: Piotr Szankowski, Eryk Infeld, Marek Trippenbach, George Rowlands
Categories: cond-mat.quant-gas
\\ ( http://arxiv.org/abs/1004.4134 , 231kb)
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\\
arXiv:0906.4584
replaced with revised version Mon, 12 Jul 2010 23:22:51 GMT (222kb)

Title: Phases of a bilayer Fermi gas
Authors: Yusuke Nishida
Categories: cond-mat.quant-gas nucl-th
Comments: 5 pages, 5 figures; (v2) stability of trimer is emphasized; (v3)
published version
Report-no: MIT-CTP 4048
Journal-ref: Phys. Rev. A 82, 011605(R) (2010)
DOI: 10.1103/PhysRevA.82.011605
\\ ( http://arxiv.org/abs/0906.4584 , 222kb)
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arXiv:1006.0181 (*cross-listing*)
replaced with revised version Tue, 13 Jul 2010 10:04:50 GMT (197kb,D)

Title: The two faces of quantum sound
Authors: C. Barcelo, L.J. Garay, G. Jannes
Categories: gr-qc cond-mat.quant-gas
(secs. V.C-D,VI), some other minor changes, this version accepted for
publication in PRD
\\ ( http://arxiv.org/abs/1006.0181 , 197kb)
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arXiv:1007.0840 (*cross-listing*)
replaced with revised version Tue, 13 Jul 2010 11:01:43 GMT (1083kb)

Title: Entanglement Spectrum Identifying Transition from Vortex Liquid to
Vortex Lattice
Authors: Zhao Liu, Hong-Li Guo, Vlatko Vedral and Heng Fan
Categories: cond-mat.quant-gas quant-ph
\\ ( http://arxiv.org/abs/1007.0840 , 1083kb)
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\\
arXiv:1007.1743
replaced with revised version Tue, 13 Jul 2010 13:29:58 GMT (696kb)

Title: Dynamical instability of a spin spiral in an interacting Fermi gas as a
probe of the Stoner transition
Authors: G.J. Conduit and Ehud Altman
Categories: cond-mat.quant-gas cond-mat.other cond-mat.str-el
\\ ( http://arxiv.org/abs/1007.1743 , 696kb)
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\\
arXiv:1003.2757
replaced with revised version Wed, 14 Jul 2010 01:29:09 GMT (639kb)

Title: Spontaneous inhomogeneous phases in ultracold dipolar Fermi gases
Authors: Kai Sun and Congjun Wu and S. Das Sarma
Categories: cond-mat.quant-gas
\\ ( http://arxiv.org/abs/1003.2757 , 639kb)
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\\
arXiv:1005.4076
replaced with revised version Wed, 14 Jul 2010 10:27:33 GMT (188kb)

Title: Observation of a two-dimensional Fermi gas of atoms
Authors: Kirill Martiyanov, Vasiliy Makhalov, Andrey Turlapov
Categories: cond-mat.quant-gas
\\ ( http://arxiv.org/abs/1005.4076 , 188kb)
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\\
arXiv:1001.1918
replaced with revised version Wed, 14 Jul 2010 11:05:53 GMT (22kb)

Title: Controlled hole doping of a Mott insulator of ultracold fermionic atoms
Authors: Andre Eckardt and Maciej Lewenstein
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 4-5 pages, accepted for publication as a Rapid Communication in
Physical Review A
\\ ( http://arxiv.org/abs/1001.1918 , 22kb)
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\\
arXiv:1007.0922 (*cross-listing*)
replaced with revised version Wed, 14 Jul 2010 15:13:24 GMT (1760kb,D)

Title: Atom-light crystallization of BECs in multimode cavities: Nonequilibrium
classical and quantum phase transitions, emergent lattices, supersolidity,
and frustration
Authors: Sarang Gopalakrishnan, Benjamin L. Lev, Paul M. Goldbart
Categories: cond-mat.quant-gas quant-ph
Comments: 34 pages, 13 figures; follow up to Nat. Phys. 5, 845 (2009)
\\ ( http://arxiv.org/abs/1007.0922 , 1760kb)
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arXiv:0910.1803
replaced with revised version Wed, 14 Jul 2010 16:15:25 GMT (424kb,D)

Title: Pi-phases in balanced fermionic superfluids on spin-dependent optical
lattices
Authors: I. Zapata and B. Wunsch and N. T. Zinner and E. Demler
Categories: cond-mat.quant-gas cond-mat.mes-hall cond-mat.str-el
Comments: 4.2 pages, 4 figures, revised version, accepted by PRL
\\ ( http://arxiv.org/abs/0910.1803 , 424kb)
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arXiv:1005.0428
replaced with revised version Thu, 15 Jul 2010 13:17:13 GMT (2318kb)

Title: An Artificial Frustrated System: Cold Atoms in 2D Triangular Optical
Lattice
Authors: Yao-Hua Chen, Wei Wu, Hong-Shuai Tao, and Wu-Ming Liu
Categories: cond-mat.quant-gas
\\ ( http://arxiv.org/abs/1005.0428 , 2318kb)
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arXiv:1003.4887
replaced with revised version Thu, 15 Jul 2010 13:42:56 GMT (32kb)

Title: Identification of the critical temperature from non-equilibrium
time-dependent quantities
Authors: Eugenio Lippiello and Alessandro Sarracino
Categories: cond-mat.stat-mech
Journal-ref: EPL 90 (2010) 60001
\\ ( http://arxiv.org/abs/1003.4887 , 32kb)
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arXiv:1003.4790 (*cross-listing*)
replaced with revised version Thu, 15 Jul 2010 14:13:07 GMT (83kb)

Title: Hard-core Bose-Fermi mixture in one-dimensional split traps
Authors: Xiaolong L\"u, Xiangguo Yin, Yunbo Zhang
Categories: cond-mat.quant-gas quant-ph
Comments: 6 pages, 4 figures, PRA in press
Journal-ref: Phys. Rev. A 81, 043607 (2010)
DOI: 10.1103/PhysRevA.81.043607
\\ ( http://arxiv.org/abs/1003.4790 , 83kb)
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arXiv:1004.3060
replaced with revised version Thu, 15 Jul 2010 15:56:45 GMT (1484kb)

Title: Controlling the transverse instability of dark solitons and nucleation
of vortices by a potential barrier
Authors: Manjun Ma, R. Carretero-Gonzalez, P. G. Kevrekidis, D. J.
Frantzeskakis, and B. A. Malomed
Categories: cond-mat.quant-gas nlin.PS
Comments: 10 pages, 7 figures. To appear on Phys. Rev. A, 2010
\\ ( http://arxiv.org/abs/1004.3060 , 1484kb)
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Till next time,
Matt.

--
--
=========================================================================
Dr M. J. Davis,                      Associate Professor in Physics
School of Mathematics and Physics,   ph  : +61 7 334 69824
The University of Queensland,        fax : +61 7 336 51242
Brisbane, QLD 4072,                  mdavis_at_physics.uq.edu.au
Australia.                           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 Wed Oct 20 2010 - 09:28:33 EST

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