From: Matthew Davis <mdavis_at_physics.uq.edu.au>

Date: Wed, 15 Sep 2010 23:03:49 +1000

Date: Wed, 15 Sep 2010 23:03:49 +1000

Dear subscribers,

This week's selection was compiled by Chao Feng, and contains 36 new

abstracts and 17 replacements.

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arXiv:1003.0854 (*cross-listing*)

Date: Wed, 3 Mar 2010 17:06:45 GMT (55kb,D)

Date (revised v2): Mon, 19 Jul 2010 18:12:41 GMT (94kb)

Title: Multiple scattering of matter waves: an analytic model of the refractive

index for atomic and molecular gases

Authors: Mikhail Lemeshko, Bretislav Friedrich

Categories: physics.atom-ph physics.chem-ph physics.optics quant-ph

Comments: 5 pages, 1 figure, 2 tables

\\

We present an analytic model of the refractive index for matter waves

propagating through atomic or molecular gases. The model, which combines a WKB

treatment of the long range attraction with the Fraunhofer model treatment of

the short range repulsion, furnishes a refractive index in compelling agreement

with recent experiments of Jacquey et al. [Phys. Rev. Lett. 98, 240405 (2007)]

on Li atom matter waves passing through dilute noble gases. We show that the

diffractive contribution, which arises from scattering by a two dimensional

"hard core" of the potential, is essential for obtaining a correct imaginary

part of the refractive index.

\\ ( http://arxiv.org/abs/1003.0854 , 94kb)

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arXiv:1007.2416 (*cross-listing*)

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 physics.atom-ph quant-ph

Comments: 4 pages, 4 figures

\\

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:1007.2652

Date: Thu, 15 Jul 2010 20:44:18 GMT (49kb)

Title: A Simple Quantum Model of Ultracold Polar Molecule Collisions

Authors: Zbigniew Idziaszek, Goulven Qu\'em\'ener, John L. Bohn, Paul S.

Julienne

Categories: quant-ph cond-mat.quant-gas

\\

We present a unified formalism for describing chemical reaction rates of

trapped, ultracold molecules. This formalism reduces the scattering to its

essential features, namely, a propagation of the reactant molecules through a

gauntlet of long-range forces before they ultimately encounter one another,

followed by a probability for the reaction to occur once they do. In this way,

the electric-field dependence should be readily parametrized in terms of a pair

of fitting parameters (along with a $C_6$ coefficient) for each asymptotic

value of partial wave quantum numbers $|L,M \rangle$. From this, the electric

field dependence of the collision rates follows automatically. We present

examples for reactive species such as KRb, and non-reactive species, such as

RbCs.

\\ ( http://arxiv.org/abs/1007.2652 , 49kb)

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arXiv:1007.2677 (*cross-listing*)

Date: Thu, 15 Jul 2010 23:10:10 GMT (786kb)

Title: Rotating Few-body Atomic Systems in the Fractional Quantum Hall Regime

Authors: Nathan Gemelke, Edina Sarajlic, and Steven Chu

Categories: cond-mat.quant-gas quant-ph

\\

Topologically-ordered matter is a novel quantum state of matter observed only

in a small number of physical systems, notably two-dimensional electron systems

exhibiting fractional quantum Hall effects. It was recently proposed that a

simple form of topological matter may be created in interacting systems of

rotating ultra-cold atoms. We describe ensemble measurements on small, rotating

clusters of interacting bosonic atoms, demonstrating that they can be induced

into quantum ground states closely analogous to topological states of

electronic systems. We report measurements of inter-particle correlations and

momentum distributions of Bose gases in the fractional quantum Hall limit,

making comparison to a full numerical simulation. The novel experimental

apparatus necessary to produce and measure properties of these deeply entangled

quantum states is described.

\\ ( http://arxiv.org/abs/1007.2677 , 786kb)

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arXiv:1007.2682

Date: Thu, 15 Jul 2010 23:51:48 GMT (355kb)

Title: Coherent control of diffuse light dynamics in an ultracold atomic gas

Authors: L.V. Gerasimov, I.M. Sokolov, D.V. Kupriyanov, R.G. Olave, and M.D.

Havey

Categories: quant-ph physics.atom-ph physics.optics

Comments: To appear, Optics Letters (2010)

\\

We show that diffuse light propagation in a disordered atomic medium,

prepared at ultra-low temperatures, can be be effectively delayed in the

presence of a strong control field initiating a stimulated Raman process. On a

time scale of a few milliseconds, when the atomic system can preserve its

configuration, the scattered signal pulse, diffusely propagating through the

medium, can be stored in the spin subsystem via its stimulated Raman-type

conversion into spin coherence. We demonstrate how this mechanism, potentially

interesting for developing quantum memories, would work for the example of a

coherent light pulse propagating through an alkali-metal atomic vapor under

typical conditions attainable in experiments with ultracold atoms.

\\ ( http://arxiv.org/abs/1007.2682 , 355kb)

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arXiv:1007.2690

Date: Fri, 16 Jul 2010 03:22:12 GMT (4468kb)

Title: Controlling phase separation of binary Bose-Einstein condensates via

mixed-spin-channel Feshbach resonance

Authors: Satoshi Tojo, Yoshihisa Taguchi, Yuta Masuyama, Taro Hayashi, Hiroki

Saito, and Takuya Hirano

Categories: cond-mat.quant-gas

Comments: 6 pages, 5 figures

\\

We investigate controlled phase separation of a binary Bose-Einstein

condensate (BEC) in the proximity of mixed-spin-channel Feshbach resonance in

the |F = 1, mF = +1> and |F = 2,mF = -1> states of 87Rb at a magnetic field of

9.10 G. Phase separation occurs on the lower magnetic-field side of the

Feshbach resonance while the two components overlap on the higher

magnetic-field side. The Feshbach resonance curve of the scattering length is

obtained from the shape of the atomic cloud by comparison with the numerical

analysis of coupled Gross-Pitaevskii equations.

\\ ( http://arxiv.org/abs/1007.2690 , 4468kb)

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arXiv:1007.2716

Date: Fri, 16 Jul 2010 08:26:37 GMT (281kb)

Title: Excitations in disordered bosonic optical lattices

Authors: Michael Knap, Enrico Arrigoni, Wolfgang von der Linden

Categories: cond-mat.quant-gas cond-mat.dis-nn

Comments: 6 pages, 6 figures

\\

Spectral excitations of ultracold gases of bosonic atoms trapped in one

dimensional optical lattices with disorder are investigated by means of the

variational cluster approach applied to the Bose-Hubbard model. In particular,

qualitatively different disorder distributions typically employed in

experiments are considered. The computed spectra exhibit a strong dependence on

both the shape of the disorder distribution and the disorder strength. We

compare alternative results for the Mott gap obtained from its formal

definition and from the minimum peak distance, which is the quantity available

from experiments.

\\ ( http://arxiv.org/abs/1007.2716 , 281kb)

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arXiv:1007.2807

Date: Fri, 16 Jul 2010 16:36:46 GMT (717kb)

Title: Disorder in quantum vacuum: Casimir-induced localization of matter waves

Authors: G. A. Moreno, R. Messina, D. A. R. Dalvit, A. Lambrecht, P. A. Maia

Neto and S. Reynaud

Categories: quant-ph cond-mat.quant-gas

\\

Disordered geometrical boundaries such as rough surfaces induce important

modifications to the mode spectrum of the electromagnetic quantum vacuum, and

may generate a disordered Casimir interaction between material bodies. In

analogy to Anderson localization of waves induced by a random potential, here

we show that the Casimir-Polder interaction between a cold atomic sample and a

rough surface also produces localization phenomena. These effects, that

represent a macroscopic manifestation of disorder in quantum vacuum, should be

observable with Bose-Einstein condensates expanding in proximity of rough

surfaces.

\\ ( http://arxiv.org/abs/1007.2807 , 717kb)

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arXiv:1007.2890

Date: Sat, 17 Jul 2010 00:56:54 GMT (169kb)

Title: Phonon-mediated Josephson oscillations in excitonic and polaritonic

condensates

Authors: E.B. Magnusson, H. Flayac, G. Malpuech and I.A. Shelykh

Categories: cond-mat.quant-gas

Comments: 10 pages, Submitted to Phys. Rev. B

\\

We analyze theoretically the role of the exciton-phonon interactions in

phenomena related to the Josephson effect between two spatially separated

exciton and exciton-polariton condensates. We consider the role of the

dephasing introduced by phonons in such phenomena as Josephson tunneling,

self-trapping and spontaneous polarization separation. In the regime of cw

pumping we find a remarkable bistability effect arising from exciton- exciton

interactions as well as regimes of self- sustained regular and chaotic

oscillations.

\\ ( http://arxiv.org/abs/1007.2890 , 169kb)

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arXiv:1007.2891

Date: Sat, 17 Jul 2010 01:03:37 GMT (1660kb)

Title: Rotons in a hybrid Bose-Fermi system

Authors: I.A. Shelykh, T. Taylor and A.V. Kavokin

Categories: cond-mat.quant-gas

Comments: 4 pages, submitted to Phys. Rev. Lett

\\

We calculate the spectrum of elementary excitations in a two-dimensional

exciton superfluid in the vicinity of a two-dimensional electron gas. We show

that attraction of excitons due to their scattering with free electrons may

lead to formation of a roton minimum. The energy of this minimum may go below

the ground state energy which manifests breaking of the superfluidity. The

Berezinsky-Kosterlitz-Thouless phase transition temperature decreases due to

the exciton-exciton attraction mediated by electrons.

\\ ( http://arxiv.org/abs/1007.2891 , 1660kb)

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arXiv:1007.2912 (*cross-listing*)

Date: Sat, 17 Jul 2010 08:49:07 GMT (518kb)

Title: Direct Forced Evaporative Cooling in Permanent Magnetic Microtraps

Authors: Amir Mohammadi, Saeed Ghanbari and Aref Pariz

Categories: cond-mat.quant-gas physics.atom-ph

Comments: 4 pages and 4 figures

\\

We propose two simple permanent magnetic micro-structures for creating single

Ioffe-Pritchard magnetic microtraps. Direct forced evaporative cooling of

neutral atoms without using spin flips can be implemented in these

microstructures to attain Bose-Einstein condensation (BEC). A BEC critical

temperature of $\sim 10 \mu$K is numerically obtained for $^{87}$Rb atoms in

the atom chips. A bias magnetic field is used to vary the depth of the trap,

frequencies and the minimum of the potential. Even without the external

magnetic field, it is possible to hold ultracold atoms in the microtraps.

Therefore, after achieving the BEC in the atom chips, the bias magnetic field

can be slowly removed to increase the trap barrier heights for more efficiently

holding the Bose-Einstein condensate.

\\ ( http://arxiv.org/abs/1007.2912 , 518kb)

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arXiv:1007.2936

Date: Sat, 17 Jul 2010 15:35:57 GMT (874kb)

Title: Optical probing of correlation driven liquid-to-insulator transition in

2D electron gas

Authors: F. Dionigi, F. Rossella, V. Bellani, M. Amado, E. Diez, K. Kowalik, G.

Biasiol and L. Sorba

Categories: cond-mat.str-el cond-mat.quant-gas

\\

We study the optical emission in an high mobility two dimensional electron

gas at intermediate density in the quantum Hall regime at the liquid-insulator

transition. For nu > 2 the emission from the liquid follows a Landau dispersion

with a screened magneto-Coulomb contribution while for 2 > nu > 1/3 the hidden

symmetry manifests. Above nu = 1/3 the electrons correlate into an insulating

phase with an increased renormalized mass, and the liquid-insulator transition

is coherent with a charge ordering driven by Coulomb correlations, which

conciliate the Wigner and Mott scenarios.

\\ ( http://arxiv.org/abs/1007.2936 , 874kb)

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arXiv:1007.3063

Date: Mon, 19 Jul 2010 06:05:37 GMT (792kb)

Title: Synergy Dynamics of Vortices and Solitons in Atomic Bose-Einstein

Condensate Excited by an Oscillating Potential

Authors: Kazuya Fujimoto and Makoto Tsubota

Categories: cond-mat.quant-gas

Comments: 4 pages, 3 figures

\\

The hydrodynamics of quantized vortices and solitons in an atomic

Bose-Einstein condensate excited by an oscillating potential are studied by

numerically solving the two-dimensional Gross-Pitaevskii equation. The

oscillating potential keeps nucleating vortex dipoles, whose impulses

alternatively change their direction synchronously with the oscillation of the

potential. This leads to synergy dynamics of vortices and solitons which have

not been previously reported in quantum fluids.

\\ ( http://arxiv.org/abs/1007.3063 , 792kb)

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arXiv:1007.3180 (*cross-listing*)

Date: Mon, 19 Jul 2010 15:19:59 GMT (18kb)

Title: Variational methods with coupled Gaussian functions for Bose-Einstein

condensates with long-range interactions. I. General concept

Authors: Stefan Rau, J\"org Main, G\"unter Wunner

Categories: cond-mat.quant-gas nlin.CD quant-ph

Comments: 10 pages, submitted to Phys. Rev. A

\\

The variational method of coupled Gaussian functions is applied to

Bose-Einstein condensates with long-range interactions. The time-dependence of

the condensate is described by dynamical equations for the variational

parameters. We present the method and analytically derive the dynamical

equations from the time-dependent Gross-Pitaevskii equation. The stability of

the solutions is investigated using methods of nonlinear dynamics. The concept

presented in this paper will be applied to Bose-Einstein condensates with

monopolar 1/r and dipolar 1/r^3 interaction in the subsequent paper [S. Rau et

al., Phys. Rev. A, submitted], where we will present a wealth of new phenomena

obtained by using the ansatz with coupled Gaussian functions.

\\ ( http://arxiv.org/abs/1007.3180 , 18kb)

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arXiv:1007.3182 (*cross-listing*)

Date: Mon, 19 Jul 2010 15:25:04 GMT (1458kb,D)

Title: Variational methods with coupled Gaussian functions for Bose-Einstein

condensates with long-range interactions. II. Applications

Authors: Stefan Rau, J\"org Main, Holger Cartarius, Patrick K\"oberle, G\"unter

Wunner

Categories: cond-mat.quant-gas nlin.CD quant-ph

Comments: 14 pages, 14 figures, submitted to Phys. Rev. A

\\

Bose-Einstein condensates with an attractive 1/r interaction and with

dipole-dipole interaction are investigated in the framework of the Gaussian

variational ansatz introduced by S. Rau, J. Main, and G. Wunner [Phys. Rev. A,

submitted]. We demonstrate that the method of coupled Gaussian wave packets is

a full-fledged alternative to direct numerical solutions of the

Gross-Pitaevskii equation, or even superior in that coupled Gaussians are

capable of producing both, stable and unstable states of the Gross-Pitaevskii

equation, and thus of giving access to yet unexplored regions of the space of

solutions of the Gross-Pitaevskii equation. As an alternative to numerical

solutions of the Bogoliubov-de Gennes equations, the stability of the

stationary condensate wave functions is investigated by analyzing the stability

properties of the dynamical equations of motion for the Gaussian variational

parameters in the local vicinity of the stationary fixed points. For

blood-cell-shaped dipolar condensates it is shown that on the route to collapse

the condensate passes through a pitchfork bifurcation, where the ground state

itself turns unstable, before it finally vanishes in a tangent bifurcation.

\\ ( http://arxiv.org/abs/1007.3182 , 1458kb)

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arXiv:1007.3191

Date: Mon, 19 Jul 2010 15:54:34 GMT (3kb)

Title: On role of symmetries in Kelvin wave turbulence

Authors: V. V. Lebedev, V. S. L'vov and S. V. Nazarenko

Categories: cond-mat.other

\\

E.V. Kozik and B.V. Svistunov (KS) paper "Symmetries and Interaction

Coefficients of Kelvin waves", arXiv:1006.1789v1, [cond-mat.other] 9 Jun 2010,

contains a comment on paper "Symmetries and Interaction coefficients of Kelvin

waves", V. V. Lebedev and V. S. L'vov, arXiv:1005.4575, 25 May 2010. It relies

mainly on the KS text "Geometric Symmetries in Superfluid Vortex Dynamics}",

arXiv:1006.0506v1 [cond-mat.other] 2 Jun 2010. The main claim of KS is that a

symmetry argument prevents linear in wavenumber infrared asymptotics of the

interaction vertex and thereby implies locality of the Kelvin wave spectrum

previously obtained by these authors. In the present note we reply to their

arguments. We conclude that there is neither proof of locality nor any

refutation of the possibility of linear asymptotic behavior of interaction

vertices in the texts of KS.

\\ ( http://arxiv.org/abs/1007.3191 , 3kb)

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arXiv:1007.3200

Date: Mon, 19 Jul 2010 16:23:27 GMT (500kb,D)

Title: Bose-Einstein condensation at finite momentum and magnon condensation in

thin film ferromagnets

Authors: Johannes Hick, Francesca Sauli, Andreas Kreisel, Peter Kopietz

Categories: cond-mat.quant-gas cond-mat.str-el

Comments: 9 pages, 4 figures

\\

We use the Gross-Pitaevskii equation to determine the spatial structure of

the condensate density of interacting bosons whose energy dispersion epsilon_k

has two degenerate minima at finite wave-vectors q. We show that in general the

Fourier transform of the condensate density has finite amplitudes for all

integer multiples of q. If the interaction is such that many Fourier components

contribute, the Bose condensate is localized at the sites of a one-dimensional

lattice with spacing 2pi/q; in this case Bose-Einstein condensation resembles

the transition from a liquid to a crystalline solid. We use our results to

investigate the spatial structure of the Bose condensate formed by magnons in

thin films of ferromagnets with dipole-dipole interactions.

\\ ( http://arxiv.org/abs/1007.3200 , 500kb)

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arXiv:1007.3245 (*cross-listing*)

Date: Mon, 19 Jul 2010 19:07:06 GMT (930kb,D)

Title: Anisotropic sub-Doppler laser cooling in dysprosium magneto-optical

traps

Authors: Seo Ho Youn, Mingwu Lu, and Benjamin L. Lev

Categories: physics.atom-ph quant-ph

Comments: 4 pages, 5 figures

\\

Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit

population-wide sub-Doppler cooling due to their near degeneracy of excited and

ground state Lande g factors. We discuss here an additional, unusual intra-MOT

sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser

intensity and magnetic quadrupole gradient increase beyond critical values.

Specifically, anisotropically sub-Doppler-cooled cores appear, and their

orientation with respect to the quadrupole axis flips at a critical ratio of

the MOT laser intensity along the quadrupole axis versus that in the plane of

symmetry. This phenomenon can be traced to a loss of the velocity-selective

resonance at zero velocity in the cooling force along directions in which the

atomic polarization is oriented by the quadrupole field. We present data

characterizing this anisotropic laser cooling phenomenon and discuss a

qualitative model for its origin based on the extraordinarily large Dy magnetic

moment and Dy's near degenerate g factors.

\\ ( http://arxiv.org/abs/1007.3245 , 930kb)

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arXiv:1007.3307

Date: Mon, 19 Jul 2010 23:28:10 GMT (148kb)

Title: Superfluid gap formation in a fermionic optical lattice with spin

imbalanced populations

Authors: Akihisa Koga and Philipp Werner

Categories: cond-mat.quant-gas

Comments: 4 pages, 1 figure, To appear in J. Phys.: Conf. Ser. for SCES2010

\\

We investigate the attractive Hubbard model in infinite spatial dimensions at

quarter filling. By combining dynamical mean-field theory with continuous-time

quantum Monte Carlo simulations in the Nambu formalism, we directly deal with

the superfluid phase in the population imbalanced system. We discuss the low

energy properties in the polarized superfluid state and the pseudogap behavior

in the vicinity of the critical temperature.

\\ ( http://arxiv.org/abs/1007.3307 , 148kb)

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arXiv:1007.3391

Date: Tue, 20 Jul 2010 10:48:31 GMT (260kb,D)

Title: Quantum memory for light via stimulated off-resonant Raman process:

beyond the three-level Lambda-scheme approximation

Authors: Alexandra S. Sheremet, Leonid V. Gerasimov, Igor M. Sokolov, Dmitriy

V. Kupriyanov (Department of Theoretical Physics, State Polytechnic

University, St.-Petersburg, Russia), Oxana S. Mishina, Elisabeth Giacobino,

Julien Laurat (Universite Pierre et Marie Curie, Ecole Normale Superieure,

CNRS, Case 74, Paris Cedex 05, France)

Categories: quant-ph

Comments: 8 pages, 6 figures

\\

We consider a quantum memory scheme based on the conversion of a signal pulse

into a long-lived spin coherence via stimulated off-resonant Raman process. For

a storing medium consisting of alkali atoms, we have calculated the

Autler-Townes resonance structure created by a strong control field. By taking

into account the upper hyperfine states of the D1 optical transition, we show

important deviations from the predictions of the usual three-level

Lambda-scheme approximation and we demonstrate an enhancement of the process

for particular detunings of the control. We estimate the memory efficiency one

can obtain using this configuration.

\\ ( http://arxiv.org/abs/1007.3391 , 260kb)

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arXiv:1007.3420

Date: Tue, 20 Jul 2010 13:33:37 GMT (392kb,D)

Title: Driven Dissipative d-Wave Pairing of Atomic Fermions

Authors: S. Diehl, W. Yi, A. J. Daley, P. Zoller

Categories: cond-mat.quant-gas cond-mat.str-el

Comments: 5 pages, 3 figures

\\

We show how dissipative dynamics can give rise to pairing for two-component

fermions on a lattice. In particular, we construct a "parent" Liouvillian

operator so that a BCS-type state of a given symmetry, e.g. a d-wave state, is

reached for arbitrary initial states in the absence of conservative forces. The

system-bath couplings describe single-particle, number conserving and

quasi-local processes. The pairing mechanism crucially relies on Fermi

statistics. We show how such Liouvillians can be realized via reservoir

engineering with cold atoms representing a driven dissipative dynamics.

\\ ( http://arxiv.org/abs/1007.3420 , 392kb)

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arXiv:1007.3432 (*cross-listing*)

Date: Tue, 20 Jul 2010 14:29:57 GMT (310kb)

Title: Toward large-scale Hybrid Monte Carlo simulations of the Hubbard model

on graphics processing units

Authors: Kyle A. Wendt, Joaqu\'{\i}n E. Drut, Timo A. L\"ahde

Categories: cond-mat.stat-mech physics.comp-ph

Comments: 8 pages, 5 figures

\\

The performance of the Hybrid Monte Carlo algorithm is determined by the

speed of sparse matrix-vector multiplication within the context of

preconditioned conjugate gradient iteration. We study these operations as

implemented for the fermion matrix of the Hubbard model in d+1 space-time

dimensions, and report a performance comparison between a 2.66 GHz Intel Xeon

E5430 CPU and an NVIDIA Tesla C1060 GPU using double-precision arithmetic. We

find speedup factors ranging between 30-350 for d = 1, and in excess of 40 for

d = 3. We argue that such speedups are of considerable impact for large-scale

simulational studies of quantum many-body systems.

\\ ( http://arxiv.org/abs/1007.3432 , 310kb)

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arXiv:1007.3452

Date: Tue, 20 Jul 2010 15:40:41 GMT (7kb)

Title: Tan Relations in Dilute Bose Gasses

Authors: Adriaan M. J. Schakel

Categories: cond-mat.quant-gas

Comments: 4 pages, no figures

\\

The exact relations for strongly interacting Fermi gasses, recently derived

by Tan, are shown to first order in the loop expansion to also apply to dilute

Bose gasses. A simple thermodynamic argument is put forward to support their

validity. As an application, the second-order correction to the depletion of

the condensate is determined to logarithmic accuracy.

\\ ( http://arxiv.org/abs/1007.3452 , 7kb)

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arXiv:1007.3470 (*cross-listing*)

Date: Tue, 20 Jul 2010 17:51:16 GMT (41kb)

Title: On the numerical integration of the Gross-Pitaevskii equation using

Hermite-Fourier methods

Authors: Philipp Bader and Sergio Blanes

Categories: math.NA cond-mat.other math-ph math.MP

Comments: 9 pages of RevTex4-1, 6 figures; as submitted to journal

\\

We consider the numerical integration of the Gross-Pitaevskii equation with a

potential trap given by a harmonic potential or a small perturbation to it.

Splitting methods are frequently used with Fourier techniques since the system

can be split into the kinetic and remaining part, and each part can be solved

efficiently using Fast Fourier Transforms. To split the system into the quantum

harmonic oscillator problem and the remaining part allows to get higher

accuracies in many cases, but it requires to change between Hermite basis

functions and the coordinate space. We show how to build new methods which

combine the advantages of using Fourier methods while solving the harmonic

oscillator exactly.

\\ ( http://arxiv.org/abs/1007.3470 , 41kb)

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arXiv:1007.3513 (*cross-listing*)

Date: Tue, 20 Jul 2010 21:08:13 GMT (68kb)

Title: Status of the Radial Schrodinger Equation

Authors: Anzor A.Khelashvili and Teimuraz P. Nadareishvili

Categories: math-ph hep-th math.MP quant-ph

Comments: 6 pages

\\

We show that equation for radial wave function in its traditional form is

compatible with the full Schrodinger equation if and only if a definite

additional condition is required. This condition has a boundary condition form

at the origin. Some of consequences are also discussed.

\\ ( http://arxiv.org/abs/1007.3513 , 68kb)

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arXiv:1007.3529

Date: Tue, 20 Jul 2010 22:10:37 GMT (807kb)

Title: Measuring the equation of state of trapped ultracold bosonic systems in

an optical lattice with in-situ density imaging

Authors: Ping Nang Ma, Lode Pollet, Matthias Troyer

Categories: cond-mat.quant-gas

Comments: 8 pages, 10 figures

\\

We analyze quantitatively how imaging techniques with single-site resolution

allow to measure thermodynamical properties that cannot be inferred from

time-of-light images for the trapped Bose-Hubbard model. If the normal state

extends over a sufficiently large range, the chemical potential and the

temperature can be extracted from a single shot, provided the sample is in

thermodynamic equilibrium. When the normal state is too narrow, temperature is

low but can still be extracted using the fluctuation-dissipation theorem over

the entire trap range as long as the local density approximation remains valid,

as was recently suggested by Qi Zhou and Tin-Lun Ho [arXiv:0908.3015]. However,

for typical present-day experiments, the number of samples needed is of the

order of 1000 in order to get the temperature at least $10 \%$ accurate, but it

is possible to reduce the variance by 2 orders of magnitude if the

density-density correlation length is short, which is the case for the

Bose-Hubbard model. Our results provide further evidence that cold gases in an

optical lattices can be viewed as quantum analog computers.

\\ ( http://arxiv.org/abs/1007.3529 , 807kb)

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arXiv:1007.3547

Date: Wed, 21 Jul 2010 01:16:22 GMT (1241kb)

Title: Spectral Properties Near the Mott Transition in the One-Dimensional

Hubbard Model

Authors: Masanori Kohno

Categories: cond-mat.str-el cond-mat.stat-mech

Comments: 4 pages, 2 figures, accepted for publication in Physical Review

Letters

\\

Single-particle spectral properties near the Mott transition in the

one-dimensional Hubbard model are investigated using the dynamical

density-matrix renormalization group method and the Bethe ansatz. The

pseudogap, hole-pocket behavior, spectral-weight transfer, and upper Hubbard

band are explained in terms of spinons, holons, antiholons, and doublons. The

Mott transition is characterized by the emergence of a gapless mode whose

dispersion relation extends up to the order of hopping t (spin exchange J) in

the weak (strong) interaction regime caused by infinitesimal doping.

\\ ( http://arxiv.org/abs/1007.3547 , 1241kb)

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arXiv:1007.3548 (*cross-listing*)

Date: Wed, 21 Jul 2010 01:30:39 GMT (130kb,D)

Title: Kelvin-Tkachenko waves of few-vortex arrays in trapped Bose-Einstein

condensates

Authors: T.P. Simula and K. Machida

Categories: cond-mat.quant-gas quant-ph

Comments: 4 pages, 3 figures

\\

We have calculated the low-lying elementary excitations of three-dimensional

few-vortex arrays in trapped Bose-Einstein condensates. The number of different

Kelvin-Tkachenko vortex wave branches matches the number of vortices in the

condensate. The lowest odd-parity modes exhibit superfluid gyroscopic vortex

motion. Experimentally, these modes could be excited and observed individually

or in connection with the formation and decay of quantum turbulence.

\\ ( http://arxiv.org/abs/1007.3548 , 130kb)

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arXiv:1007.3551 (*cross-listing*)

Date: Wed, 21 Jul 2010 01:50:34 GMT (236kb,D)

Title: Rotating Dipolar Spin-1 Bose-Einstein Condensates

Authors: T. P. Simula, J. A. M. Huhtam\"aki, M. Takahashi, T. Mizushima, and K.

Machida

Categories: cond-mat.quant-gas quant-ph

Comments: 4 pages, 4 figures

\\

We have computed phase diagrams for rotating spin-1 Bose-Einstein condensates

with long-range magnetic dipole-dipole interactions. Spin textures including

vortex sheets, staggered half-quantum- and skyrmion vortex lattices and higher

order topological defects have been found. These systems exhibit both

superfluidity and magnetic crystalline ordering and they could be realized

experimentally by imparting angular momentum in the condensate.

\\ ( http://arxiv.org/abs/1007.3551 , 236kb)

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\\

arXiv:1007.3561

Date: Wed, 21 Jul 2010 05:06:03 GMT (1003kb)

Title: Introduction to Xgrid: Cluster Computing for Everyone

Authors: Barbara J. Breen and John F. Lindner

Categories: physics.comp-ph cs.DC

\\

Xgrid is the first distributed computing architecture built into a desktop

operating system. It allows you to run a single job across multiple computers

at once. All you need is at least one Macintosh computer running Mac OS X v10.4

or later. (Mac OS X Server is not required.) We provide explicit instructions

and example code to get you started, including examples of how to distribute

your computing jobs, even if your initial cluster consists of just two old

laptops in your basement.

\\ ( http://arxiv.org/abs/1007.3561 , 1003kb)

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\\

arXiv:1007.3694

Date: Wed, 21 Jul 2010 17:03:26 GMT (87kb)

Title: Finite temperature damping of collective modes of a BCS-BEC crossover

superfluid

Authors: Zixu Zhang and W. Vincent Liu

Categories: cond-mat.quant-gas cond-mat.str-el

Comments: 8 pages, 4 figures

\\

A new mechanism is proposed to explain the puzzling damping of collective

excitations, which was recently observed in the experiments of strongly

interacting Fermi gases below the superfluid critical temperature on the

fermionic (BCS) side of Feshbach resonance. Sound velocity, superfluid density

and damping rate are calculated with effective field theory. We find that a

dominant damping process is due to the interaction between superfluid phonons

and thermally excited fermionic quasiparticles, in contrast to the previously

proposed pair-breaking mechanism. Results from our effective model are compared

quantitatively with recent experimental findings, showing a good agreement.

\\ ( http://arxiv.org/abs/1007.3694 , 87kb)

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\\

arXiv:1007.3713

Date: Wed, 21 Jul 2010 18:40:42 GMT (913kb)

Title: Probing three-body correlations in a quantum gas red using the

measurement of the third moment of density fluctuations

Authors: Julien Armijo (LCFIO), Thibaut Jacqmin (LCFIO), Karen Kheruntsyan,

Isabelle Bouchoule (LCFIO)

Categories: cond-mat.quant-gas

Comments:

\\

We perform measurements of the third moment of atom number fluctuations in

small slices of a very elongated weakly interacting degenerate Bose gas. We

find a positive skewness of the atom number distribution in the ideal gas

regime and a reduced skewness compatible with zero in the quasi-condensate

regime. For our parameters, the third moment is a thermodynamic quantity whose

measurement constitutes a sensitive test of the equation of state and our

results are in agreement with a modified Yang-Yang thermodynamic prediction.

Moreover, we show that the measured skewness reveals the presence of true three

body correlations in the system.

\\ ( http://arxiv.org/abs/1007.3713 , 913kb)

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\\

arXiv:1007.3828 (*cross-listing*)

Date: Thu, 22 Jul 2010 08:36:31 GMT (305kb)

Title: Phonon resonances in atomic currents through lattice Bose-Fermi mixtures

Authors: M. Bruderer, T. H. Johnson, S. R. Clark, D. Jaksch, A. Posazhennikova,

W. Belzig

Categories: cond-mat.quant-gas quant-ph

Comments: 8 pages, 5 figures

\\

We present an analysis of Bose-Fermi mixtures in optical lattices for the

case where the lattice potential of the fermions is tilted and the bosons (in

the superfluid phase) are described by Bogoliubov phonons. It is shown that the

Bogoliubov phonons enable hopping transitions between fermionic Wannier-Stark

states; these transitions are accompanied by energy dissipation into the

superfluid and result in a net atomic current along the lattice. We derive a

general expression for the drift velocity of the fermions and find that the

dependence of the atomic current on the lattice tilt exhibits negative

differential conductance (NDC) and phonon resonances. Numerical simulations of

the full dynamics of the system based on the time-evolving block decimation

(TEBD) algorithm reveal that the phonon resonances should be observable under

the conditions of a realistic measuring procedure.

\\ ( http://arxiv.org/abs/1007.3828 , 305kb)

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\\

arXiv:1007.3840

Date: Thu, 22 Jul 2010 09:47:18 GMT (1671kb)

Title: Superfluid density of states and pseudogap phenomenon in the BCS-BEC

crossover regime of a superfluid Fermi gas

Authors: Ryota Watanabe, Shunji Tsuchiya, and Yoji Ohashi

Categories: cond-mat.quant-gas

Comments: 22 pages, 8 figures

\\

We investigate single-particle excitations and strong-coupling effects in the

BCS-BEC crossover regime of a superfluid Fermi gas. Including phase and

amplitude fluctuations of the superfluid order parameter within a $T$-matrix

theory, we calculate the superfluid density of states (DOS), as well as

single-particle spectral weight, over the entire BCS-BEC crossover region below

the superfluid transition temperature $T_{\rm c}$. We clarify how the pseudogap

in the normal state evolves into the superfluid gap, as one passes through

$T_{\rm c}$. While the pseudogap in DOS continuously evolves into the

superfluid gap in the weak-coupling BCS regime, the superfluid gap in the

crossover region is shown to appear in DOS after the pseudogap disappears below

$T_{\rm c}$. In the phase diagram with respect to the temperature and

interaction strength, we determine the region where strong pairing fluctuations

dominate over single-particle properties of the system. Our results would be

useful for the study of strong-coupling phenomena in the BCS-BEC crossover

regime of a superfluid Fermi gas.

\\ ( http://arxiv.org/abs/1007.3840 , 1671kb)

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\\

arXiv:1007.3895 (*cross-listing*)

Date: Thu, 22 Jul 2010 14:39:31 GMT (52kb,D)

Title: Atom-dimer scattering length for fermions with different masses:

analytical study of limiting cases

Authors: F. Alzetto, R. Combescot and X. Leyronas

Categories: cond-mat.quant-gas quant-ph

Comments: 15 pages, 4 figures

\\

We consider the problem of obtaining the scattering length for a fermion

colliding with a dimer, formed from a fermion identical to the incident one and

another different fermion. This is done in the universal regime where the range

of interactions is short enough so that the scattering length $a$ for non

identical fermions is the only relevant quantity. This is the generalization to

fermions with different masses of the problem solved long ago by Skorniakov and

Ter-Martirosian for particles with equal masses. We solve this problem

analytically in the two limiting cases where the mass of the solitary fermion

is very large or very small compared to the mass of the two other identical

fermions. This is done both for the value of the scattering length and for the

function entering the Skorniakov-Ter-Martirosian integral equation, for which

simple explicit expressions are obtained.

\\ ( http://arxiv.org/abs/1007.3895 , 52kb)

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The replacements:

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arXiv:1006.1269

replaced with revised version Mon, 19 Jul 2010 08:55:01 GMT (483kb)

Title: Incompressible states of a two-component Fermi gas in a double-well

optical lattice

Authors: Fran\c{c}ois Cr\'epin, Roberta Citro and Pascal Simon

Categories: cond-mat.quant-gas

Comments: 10 pages, 7 figures. Published in Phys. Rev. A

Journal-ref: Phys. Rev. A 82, 013613 (2010)

DOI: 10.1103/PhysRevA.82.013613

\\ ( http://arxiv.org/abs/1006.1269 , 483kb)

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\\

arXiv:0912.5022

replaced with revised version Mon, 19 Jul 2010 12:04:00 GMT (1577kb,D)

Title: Temporal coherence, anomalous moments, and pairing correlations in the

classical-field description of a degenerate Bose gas

Authors: T. M. Wright, P. B. Blakie, and R. J. Ballagh

Categories: cond-mat.quant-gas

Comments: 11 pages, 6 figures. v3: Final version. Typos fixed, and other minor

changes

Journal-ref: Phys. Rev. A 82, 013621 (2010)

DOI: 10.1103/PhysRevA.82.013621

\\ ( http://arxiv.org/abs/0912.5022 , 1577kb)

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\\

arXiv:1005.2420

replaced with revised version Mon, 19 Jul 2010 15:41:10 GMT (345kb)

Title: Comment on "Inequivalence between the Schrodinger equation and the

Madelung hydrodynamic equations"

Authors: Vel Hushwater

Categories: quant-ph

Comments: Paper was shortened - only one method of the proof was left.

Presentation was improved, some notations were corrected. Note [4] was

improved

\\ ( http://arxiv.org/abs/1005.2420 , 345kb)

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\\

arXiv:1002.3696

replaced with revised version Mon, 19 Jul 2010 15:47:50 GMT (168kb)

Title: Anderson localization vs. Mott-Hubbard metal-insulator transition in

disordered, interacting lattice fermion systems

Authors: K. Byczuk, W. Hofstetter, and D. Vollhardt

Categories: cond-mat.str-el cond-mat.dis-nn

Comments: 25 pages, 5 figures, typos corrected, references updated

Journal-ref: in "50 Years of Anderson Localization", ed. E. Abrahams (World

Scientific, Singapore, 2010), p. 473; reprinted in Int. J. Mod. Phys. B 24,

1727 (2010)

\\ ( http://arxiv.org/abs/1002.3696 , 168kb)

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\\

arXiv:1005.3541 (*cross-listing*)

replaced with revised version Mon, 19 Jul 2010 20:30:30 GMT (87kb)

Title: Nonlinear resonant tunneling of Bose-Einstein condensates in tilted

optical lattices

Authors: K. Rapedius, C. Elsen, D. Witthaut, S. Wimberger, and H. J. Korsch

Categories: cond-mat.quant-gas quant-ph

Comments: Revised and enlarged version, including 1 additional figure

\\ ( http://arxiv.org/abs/1005.3541 , 87kb)

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\\

arXiv:0911.5443

replaced with revised version Tue, 20 Jul 2010 01:26:30 GMT (817kb)

Title: Conformal invariance, multifractality, and finite-size scaling at

Anderson localization transitions in two dimensions

Authors: Hideaki Obuse, Arvind R. Subramaniam, Akira Furusaki, Ilya A.

Gruzberg, Andreas W. W. Ludwig

Categories: cond-mat.dis-nn cond-mat.mes-hall cond-mat.stat-mech

Comments: 13 pages, 7 figures

Journal-ref: Phys. Rev. B 82, 035309 (2010)

DOI: 10.1103/PhysRevB.82.035309

\\ ( http://arxiv.org/abs/0911.5443 , 817kb)

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\\

arXiv:0909.5615 (*cross-listing*)

replaced with revised version Tue, 20 Jul 2010 05:26:45 GMT (24kb)

Title: Pionic BEC--BCS crossover at finite isospin chemical potential

Authors: Masayuki Matsuzaki (Fukuoka Univ. of Education)

Categories: hep-ph cond-mat.quant-gas cond-mat.supr-con nucl-th

Comments: 17 pages, 3 figures, typos in eq.(6) and refs.[37] and [41] are

corrected, published in Phys. Rev. D

Journal-ref: Phys.Rev.D82:016005,2010

\\ ( http://arxiv.org/abs/0909.5615 , 24kb)

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\\

arXiv:1004.2925

replaced with revised version Tue, 20 Jul 2010 18:45:32 GMT (10kb)

Title: Two super Tonks-Girardeau states of a trapped 1D spinor Fermi gas

Authors: M.D. Girardeau

Categories: cond-mat.quant-gas

Comments: 4 pages, no figures, revtex4. Revised version, published in Phys.

Rev. A 82, 011607(R) (2010)

\\ ( http://arxiv.org/abs/1004.2925 , 10kb)

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arXiv:1004.1891

replaced with revised version Tue, 20 Jul 2010 21:44:12 GMT (2468kb)

Title: Dissipative Transport of a Bose-Einstein Condensate

Authors: D. Dries and S. E. Pollack and J. M. Hitchcock and R. G. Hulet

Categories: physics.atom-ph cond-mat.dis-nn cond-mat.quant-gas

Comments: 14 pages, 20 figures

\\ ( http://arxiv.org/abs/1004.1891 , 2468kb)

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arXiv:0804.0782

replaced with revised version Wed, 21 Jul 2010 03:31:28 GMT (106kb)

Title: Collective modes in asymmetric ultracold Fermi systems

Authors: Elena Gubankova, Massimo Mannarelli and Rishi Sharma

Categories: cond-mat.supr-con cond-mat.stat-mech hep-ph

Comments: 41 pages, 6 figures. Expanded introduction, improved figures,

conclusions unchanged. Version to match the published version

DOI: 10.1016/j.aop.2010.05.001

\\ ( http://arxiv.org/abs/0804.0782 , 106kb)

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arXiv:0709.1293

replaced with revised version Wed, 21 Jul 2010 03:55:37 GMT (166kb,D)

Title: Weakly interacting Bose gases below the critical temperature

Authors: E. Kovalchuk and R. Kobes

Categories: cond-mat.other

Comments: 15 pages, 9 figures, uses revtex4-1. Added references and

clarification of the nature and validity of the assumptions used

\\ ( http://arxiv.org/abs/0709.1293 , 166kb)

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\\

arXiv:1005.0463

replaced with revised version Wed, 21 Jul 2010 10:38:34 GMT (22kb)

Title: Mott Insulator to Superfluid transition in Bose-Bose mixtures in a

two-dimensional lattice

Authors: M. Guglielmino, V. Penna and B. Capogrosso-Sansone

Categories: cond-mat.quant-gas

Comments: 4 pages, 3 figures, accepted as PRA Rapid Communication

\\ ( http://arxiv.org/abs/1005.0463 , 22kb)

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\\

arXiv:0908.2026

replaced with revised version Wed, 21 Jul 2010 13:35:09 GMT (214kb)

Title: Interacting trapped bosons yield fragmented condensate states in low

dimensions

Authors: Uwe R. Fischer and Philipp Bader

Categories: cond-mat.quant-gas

Comments: 9 pages of RevTex4, 4 figures; as published in Physical Review A

Journal-ref: Phys. Rev. A 82, 013607 (2010)

DOI: 10.1103/PhysRevA.82.013607

\\ ( http://arxiv.org/abs/0908.2026 , 214kb)

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arXiv:1003.3355

replaced with revised version Wed, 21 Jul 2010 19:07:49 GMT (770kb)

Title: Quantum Classical Correspondence for a non-Hermitian Bose-Hubbard Dimer

Authors: Eva-Maria Graefe, Hans J\"urgen Korsch, and Astrid Elisa Niederle

Categories: quant-ph cond-mat.quant-gas

Comments: 17 pages, 17 figures; bibliography updated, typos corrected,

published version

Journal-ref: Phys. Rev. A 82, 013629 (2010)

DOI: 10.1103/PhysRevA.82.013629

\\ ( http://arxiv.org/abs/1003.3355 , 770kb)

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arXiv:0912.0092

replaced with revised version Wed, 21 Jul 2010 23:27:18 GMT (835kb)

Title: Spin-Imbalance in a One-Dimensional Fermi Gas

Authors: Yean-an Liao, Ann Sophie C. Rittner, Tobias Paprotta, Wenhui Li,

Guthrie B. Partridge, Randall G. Hulet, Stefan K. Baur, Erich J. Mueller

Categories: physics.atom-ph cond-mat.quant-gas

Comments: 30 pages, 7 figures

\\ ( http://arxiv.org/abs/0912.0092 , 835kb)

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arXiv:1005.3239

replaced with revised version Thu, 22 Jul 2010 02:26:19 GMT (599kb)

Title: Competition between Normal Superfluidity and Larkin-Ovchinnikov Phases

of Polarized Fermi Gases in Elongated Traps

Authors: J.C. Pei, J. Dukelsky, W. Nazarewicz

Categories: cond-mat.quant-gas nucl-th

Comments: 4 pages, 4 figures; revision; accepted for publication in Phys.Rev.A

(Rapid Communication)

\\ ( http://arxiv.org/abs/1005.3239 , 599kb)

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arXiv:1007.0840 (*cross-listing*)

replaced with revised version Thu, 22 Jul 2010 09:35:26 GMT (1082kb)

Title: Entanglement spectrum: Identification of the transition from

vortex-liquid to vortex-lattice state in a weakly interacting rotating

Bose-Einstein condensate

Authors: Zhao Liu, Hong-Li Guo, Vlatko Vedral and Heng Fan

Categories: cond-mat.quant-gas quant-ph

Comments: 4 pages, 5 figures, comments are welcome. The title is changed.

Reference is added and reordered

\\ ( http://arxiv.org/abs/1007.0840 , 1082kb)

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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/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland ========================================================================= _______________________________________________ Matts-arxiv mailing list Matts-arxiv_at_lists.sps.uq.edu.auReceived on Wed Oct 20 2010 - 09:28:34 EST

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