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

Date: Fri, 17 Apr 2009 11:25:12 +1000

Date: Fri, 17 Apr 2009 11:25:12 +1000

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

No, you don't have a problem with your email. I really am 10 weeks behind. My

current batch of lectures ends shortly and I hope to catch up soon. There

doesn't seem to be much point in doing this if it is so late! :)

There are 39 new preprints and 11 replacements in this message.

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arXiv:0901.3555

Date: Thu, 22 Jan 2009 21:02:25 GMT (672kb)

Title: Density-Wave and Antiferromagnetic States of Fermionic Atoms in Optical

Lattices

Authors: Takuji Higashiyama, Kensuke Inaba, Sei-ichiro Suga

Categories: cond-mat.other cond-mat.supr-con

Comments: 7 pages, 7 figures

\\

We study the two-band effects on ultracold fermionic atoms in optical

lattices by means of dynamical mean-field theory. We find that at half-filling

the atomic-density-wave (ADW) state emerges owing to the two-band effects in

the attractive interaction region, while the antiferromagnetic state appears in

the repulsive interaction region. As the orbital splitting is increased, the

quantum phase transitions from the ADW state to the superfluid state and from

the antiferromagnetic state to the metallic state occur in respective regions.

Systematically changing the orbital splitting and the interaction, we obtain

the phase diagram at half-filling. The results are discussed using the

effective boson model derived for the strong attractive interaction.

\\ ( http://arxiv.org/abs/0901.3555 , 672kb)

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arXiv:0901.3625

Date: Fri, 23 Jan 2009 09:10:02 GMT (1185kb)

Title: Adiabatic cooling of a tunable Bose-Fermi mixture in an optical lattice

Authors: O. Soe Sorensen, N. Nygaard, P. B. Blakie

Categories: cond-mat.other

Comments: 9 pages, 7 figures

\\

We consider an atomic Fermi gas confined in a uniform optical lattice

potential, where the atoms can pair into molecules via a magnetic field

controlled narrow Feshbach resonance. Thus by adjusting the magnetic field the

portion of fermionic and bosonic particles in the system can be continuously

varied. We analyze the statistical mechanics of this system and consider the

interplay of the lattice physics with the atom-molecule conversion. We study

the entropic behavior of the system and characterize the temperature changes

that occur during adiabatic ramps across the Feshbach resonance. We show that

an appropriate choice of filling fraction can be used to reduce the system

temperature during such ramps.

\\ ( http://arxiv.org/abs/0901.3625 , 1185kb)

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arXiv:0901.3650

Date: Fri, 23 Jan 2009 13:56:38 GMT (6kb)

Title: Impossibility to describe repulsion with contact interaction

Authors: K. Morawetz, M. Maennel

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

Comments: 2 pages comment

\\

Contact interactions always lead to attractive behaviour. Arguments are

presented to show why a repulsive interacting system, e.g. Bose gases, cannot

be described by contact interactions and corresponding treatments are possibly

obscured by the appearance of bound states. The usually used cut-offs are

identified as finite range parameters.

\\ ( http://arxiv.org/abs/0901.3650 , 6kb)

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arXiv:0901.3696

Date: Fri, 23 Jan 2009 19:59:52 GMT (343kb)

Title: Theory of preparation and relaxation of a p-orbital atomic Mott

insulator

Authors: John H. Challis, S.M. Girvin, and L.I. Glazman

Categories: cond-mat.other

Comments: 27 pages, 23 figures

\\

We develop a theoretical framework to understand the preparation and

relaxation of a metastable Mott insulator state within the first excited band

of a 1D optical lattice. The state is loaded by "lifting" atoms from the ground

to the first excited band by means of a stimulated Raman transition. We

determine the effect of pulse duration on the accuracy of the state preparation

for the case of a Gaussian pulse shape. Relaxation of the prepared state occurs

in two major stages: double-occupied sites occurring due to quantum

fluctuations initially lead to interband transitions followed by a spreading of

particles in the trap and thermalization. We find the characteristic relaxation

times at the earliest stage and at asymptotically long times approaching

equilibrium. Our theory is applicable to recent experiments performed with 1D

optical lattices [T. M\"uller, S. F\"olling, A. Widera, and I. Bloch, Phys.

Rev. Lett. \textbf{99}, 200405 (2007)].

\\ ( http://arxiv.org/abs/0901.3696 , 343kb)

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arXiv:0901.3702

Date: Fri, 23 Jan 2009 15:49:34 GMT (577kb)

Title: Controlling spin current in a trapped Fermi gas

Authors: X. Du, Y. Zhang, J. Petricka, and J. E. Thomas

Categories: cond-mat.other

Comments: 4 pages, 3 figures

\\

We observe fundamental new features of spin current in a weakly interacting

Fermi gas of $^6$Li. By creating a spin current and then reversing its flow, we

demonstrate control of the spin current. This reversal is predicted by an

undamped spin wave theory, which we have developed to explain our previous

observation of spin segregation in a trapped Fermi gas. Numerical calculations

based on this theory are in very good agreement with the experimental results

both in amplitude and temporal evolution. The theory provides a simple physical

description of the origin of the spin current and suggests that broad control

of the spin current is possible.

\\ ( http://arxiv.org/abs/0901.3702 , 577kb)

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arXiv:0901.3767

Date: Fri, 23 Jan 2009 20:11:23 GMT (688kb)

Title: Transcritical flow of a Bose-Einstein condensate through a penetrable

barrier

Authors: A.M. Leszczyszyn, G.A. El, Yu.G. Gladush, A.M. Kamchatnov

Categories: cond-mat.other

Comments: 21 pages, 17 figures

\\

The problem of the transcritical flow of a Bose-Einstein condensate through a

wide repulsive penetrable barrier is studied analytically using the combination

of the localized "hydraulic" solution of the 1D Gross-Pitaevskii equation and

the solutions of the Whitham modulation equations describing the resolution of

the upstream and downstream discontinuities through dispersive shocks. It is

shown that within the physically reasonable range of parameters the downstream

dispersive shock is attached to the barrier and effectively represents the

train of very slow dark solitons, which can be observed in experiments. The

rate of the soliton emission, the amplitudes of the solitons in the train and

the drag force are determined in terms of the BEC oncoming flow velocity and

the strength of the potential barrier. Excellent agreement with direct

numerical solution is demonstrated. Connection with recent experiments is

discussed.

\\ ( http://arxiv.org/abs/0901.3767 , 688kb)

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arXiv:0901.3770

Date: Fri, 23 Jan 2009 20:16:11 GMT (302kb,D)

Title: Three component fermions pairing in two dimensions

Authors: Theja N. De Silva

Categories: cond-mat.other

Comments: 5 pages and 5figures

\\

We study paring of interacting three component Fermi gases in two dimensions.

By using a mean field theory to decouple the interactions between different

components, we study the free energy landscapes as a function of various

parameters including chemical potentials, binding energies (interactions), and

temperature. We find series of second order thermal phase transitions and

series of first order quantum phase transitions for a homogenous system as we

change the parameters. In particular, we find the simultaneous existence of

three superfluid phases as well as re-entrant quantum phase transitions as we

tune the parameters appropriately.

\\ ( http://arxiv.org/abs/0901.3770 , 302kb)

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arXiv:0901.3654

Date: Fri, 23 Jan 2009 11:18:58 GMT (327kb)

Title: Ultra-low noise microwave generation with fiber-based optical frequency

comb and application to atomic fountain clock

Authors: J. Millo, M. Abgrall, M. Lours, E.M.L. English, H. Jiang, J. Guena, A.

Clairon, S. Bize, Y. Le Coq, G. Santarelli, M.E. Tobar

Categories: physics.atom-ph physics.optics

Comments: 3 pages, 3 figures

\\

We demonstrate the use of a fiber-based femtosecond laser locked onto an

ultra-stable optical cavity to generate a low-noise microwave reference signal.

Comparison with both a liquid Helium cryogenic sapphire oscillator (CSO) and a

Ti:Sapphire-based optical frequency comb system exhibit a stability about

$3\times10^{-15}$ between 1 s and 10 s. The microwave signal from the fiber

system is used to perform Ramsey spectroscopy in a state-of-the-art Cesium

fountain clock. The resulting clock system is compared to the CSO and exhibits

a stability of $3.5\times10^{-14}\tau^{-1/2}$. Our continuously operated

fiber-based system therefore demonstrates its potential to replace the CSO for

atomic clocks with high stability in both the optical and microwave domain,

most particularly for operational primary frequency standards.

\\ ( http://arxiv.org/abs/0901.3654 , 327kb)

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arXiv:0901.3800

Date: Sat, 24 Jan 2009 00:08:29 GMT (340kb)

Title: Crystalline Magnetic Order in a Dipolar Quantum Fluid

Authors: M. Vengalattore, J. Guzman, S. Leslie, F. Serwane, D. M. Stamper-Kurn

Categories: cond-mat.other

\\

We report on the magnetic phases of quasi-two dimensional $^{87}$Rb F=1

spinor gases produced by cooling unmagnetized gases into the regime of quantum

degeneracy. We find a robust low temperature magnetic phase characterized by

crystalline ordering of spin domains, an instance of spontaneously broken

translational symmetry in a quantum fluid. This phase displays an emergent

order parameter, a spin axis along which the magnetization shows the largest

variance.

\\ ( http://arxiv.org/abs/0901.3800 , 340kb)

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arXiv:0901.3627

Date: Fri, 23 Jan 2009 09:09:38 GMT (926kb)

Title: Observation of prolonged coherence time of the collective spin wave of

atomic ensemble in a paraffin coated Rb vapor cell

Authors: Shuo Jiang, Xiao-Ming Luo, Li-Qing Chen, Po-Ning, Shuai Chen,

Jing-Yang Wang, Zhi-Ping Zhong and Jian-Wei Pan

Categories: quant-ph

Comments: 4 pages, 4 figures

\\

We report a prolonged coherence time of the collective spin wave of a thermal

87Rb atomic ensemble in a paraffin coated cell. The spin wave is prepared

through a stimulated Raman Process. The long coherence time time is achieved by

prolonging the lifetime of the spins with paraffin coating and minimize

dephasing with optimal experimental configuration. The observation of the long

time delayed-stimulated Stokes signal in the writing process suggests the

prolonged lifetime of the prepared spins; a direct measurement of the decay of

anti-Stokes signal in the reading process shows the coherence time is up to 300

us after minimizing dephasing. This is one hundred times longer than the

reported coherence time in the similar experiments in thermal atomic ensembles

based on the Duan-Lukin-Cirac-Zoller (DLCZ) and its improved protocols. This

prolonged coherence time sets the upper limit of the memory time in quantum

repeaters based on such protocols, which is crucial for the realization of

long-distance quantum communication. The previous reported fluorescence

background in the writing process due to collision in a sample cell with buffer

gas is also reduced in a cell without buffer gas.

\\ ( http://arxiv.org/abs/0901.3627 , 926kb)

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arXiv:0901.3800

Date: Sat, 24 Jan 2009 00:08:29 GMT (340kb)

Title: Crystalline Magnetic Order in a Dipolar Quantum Fluid

Authors: M. Vengalattore, J. Guzman, S. Leslie, F. Serwane, D. M. Stamper-Kurn

Categories: cond-mat.other

\\

We report on the magnetic phases of quasi-two dimensional $^{87}$Rb F=1

spinor gases produced by cooling unmagnetized gases into the regime of quantum

degeneracy. We find a robust low temperature magnetic phase characterized by

crystalline ordering of spin domains, an instance of spontaneously broken

translational symmetry in a quantum fluid. This phase displays an emergent

order parameter, a spin axis along which the magnetization shows the largest

variance.

\\ ( http://arxiv.org/abs/0901.3800 , 340kb)

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arXiv:0901.3846

Date: Sat, 24 Jan 2009 16:57:42 GMT (29kb)

Title: Ultracold molecules: new probes on the variation of fundamental

constants

Authors: Cheng Chin, V.V. Flambaum, K.G. Kozlov

Categories: cond-mat.other

\\

Ultracold molecules offer brand new opportunities to probe the variation of

fundamental constants with unprecedented sensitivity. This paper summarizes

theoretical background and current constraints on the variation of fine

structure constant and electron-to-proton mass ratio, as well as proposals and

experimental efforts to measure the variations based on ultracold molecules. In

particular, we describe two novel spectroscopic schemes on ultracold molecules

which have greatly enhanced sensitivity to fundamental constants: resonant

scattering near Feshbach resonances and spectroscopy on close-lying energy

levels of ultracold molecules.

\\ ( http://arxiv.org/abs/0901.3846 , 29kb)

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arXiv:0901.3850

Date: Sat, 24 Jan 2009 17:21:23 GMT (260kb)

Title: Efficient scheme for breeding beautiful Schr\"odinger cat in a

double-well potential

Authors: Gentaro Watanabe

Categories: cond-mat.other

Comments: 4 pages, 6 figures

\\

For trapped cold Bose gases in a double-well potential, we propose a new

scheme for creating the Schr\"odinger cat state in which all particles in the

right or left wells (so called NOON state). This scheme yields almost perfect

NOON states periodically. In this scheme, the formation time of the NOON state

is drastically reduced by sinusoidally modulating the tunneling matrix element.

For larger number of particles, further reduction is possible using more than

one frequencies. With this scheme, NOON state of larger number of particles can

be realized in current experiments.

\\ ( http://arxiv.org/abs/0901.3850 , 260kb)

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arXiv:0901.3862

Date: Sat, 24 Jan 2009 22:53:37 GMT (29kb)

Title: Excitation spectrum and effective interactions of highly-elongated Fermi

gas

Authors: D. Blume, D. Rakshit

Categories: cond-mat.other

Comments: 4 pages, 4 figures

\\

Full 3D calculations of small two-component Fermi gases under

highly-elongated confinement, in which unlike fermions interact through

short-range potentials with variable atom-atom s-wave scattering length, are

reported. The 3D excitation frequencies are compared with those determined from

atomic and molecular 1D model Hamiltonian. Our numerical results suggest that

the effective 1D atom-dimer and dimer-dimer interactions are to a good

approximation determined by simple analytical expressions. Implications for the

description of quasi-1D Fermi gases within strict 1D frameworks are discussed.

\\ ( http://arxiv.org/abs/0901.3862 , 29kb)

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arXiv:0901.3921

Date: Mon, 26 Jan 2009 19:04:26 GMT (761kb,D)

Title: Topological Insulators and Metals in Atomic Optical Lattices

Authors: Tudor D. Stanescu, Victor Galitski, J.Y. Vaishnav, Charles W. Clark

and S. Das Sarma

Categories: cond-mat.mes-hall

Comments: 4+ pages, 5 color figures

\\

We propose the realization of topological quantum states with cold atoms

trapped in an optical lattice. We discuss an experimental setup that generates

a two-dimensional hexagonal lattice in the presence of a light-induced periodic

vector potential, which represents a realization of the Haldane model with cold

atoms. We determine theoretically the conditions necessary for observing the

topological states and show that two of the key conditions are: 1) the

realization of sharp boundaries and 2) the minimization of any smoothly varying

component of the confining potential. We argue that, unlike their condensed

matter counterparts, cold atom topological quantum states can be i) "seen", by

mapping out the characteristic chiral edge states, and ii) controlled, by

controlling the periodic vector potential and the properties of the confining

potential.

\\ ( http://arxiv.org/abs/0901.3921 , 761kb)

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arXiv:0901.4062

Date: Mon, 26 Jan 2009 18:16:43 GMT (843kb,D)

Title: Wavepacket dynamics in energy space of a chaotic trimeric Bose-Hubbard

system

Authors: Moritz Hiller, Tsampikos Kottos, Theo Geisel

Categories: cond-mat.other

Comments: 18 pages, 19 figures

\\

We study the energy redistribution of interacting bosons in a ring-shaped

quantum trimer as the coupling strength between neighboring sites of the

corresponding Bose-Hubbard Hamiltonian undergoes a sudden change dk. Our

analysis is based on a three-fold approach combining linear response theory

calculations as well as semiclassical and random matrix theory considerations.

The dk-borders of applicability of each of these methods are identified by

direct comparison with the exact quantum mechanical results. We find that while

the variance of the evolving quantum distribution shows a remarkable

quantum-classical correspondence (QCC) for all dk-values, other moments exhibit

this QCC only in the non-perturbative dk-regime.

\\ ( http://arxiv.org/abs/0901.4062 , 843kb)

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arXiv:0901.3790

Date: Fri, 23 Jan 2009 21:36:22 GMT (496kb)

Title: Realistic theory of electromagnetically-induced transparency and slow

light in a hot vapor of atoms undergoing collisions

Authors: Joyee Ghosh, R. Ghosh, F. Goldfarb, J. L. Le Gou\"et, F. Bretenaker

Categories: quant-ph

\\

We present a realistic theoretical treatment of a three-level $\Lambda$

system in a hot atomic vapor interacting with a coupling and a probe field of

arbitrary strengths, leading to electromagnetically-induced transparency and

slow light under the two-photon resonance condition. We take into account all

the relevant decoherence processes including col5Blisions. Velocity-changing

collisions (VCCs) are modeled in the strong collision limit effectively, which

helps in achieving optical pumping by the coupling beam across the entire

Doppler profile. The steady-state expressions for the atomic density-matrix

elements are numerically evaluated to yield the experimentally measured

response characteristics. The predictions, taking into account a dynamic rate

of influx of atoms in the two lower levels of the $\Lambda$, are in excellent

agreement with the reported experimental results for $^4$He*. The role played

by the VCC parameter is seen to be distinct from that by the transit time or

Raman coherence decay rate.

\\ ( http://arxiv.org/abs/0901.3790 , 496kb)

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arXiv:0901.3868

Date: Sun, 25 Jan 2009 02:02:57 GMT (753kb)

Title: Regular and chaotic Bose-Einstein condensate in an accelerated

Wannier-Stark lattice

Authors: Wenhua Hai, Gengbiao Lu, Honghua Zhong

Categories: quant-ph

Comments: 5 pages, 3 figures

\\

We investigate a Bose-Einstein condensate held in a quasi-one-dimensional

Wannier-Stark lattice which is a combination of linear potential with an

accelerated optical lattice. It is demonstrated that the system can be reduced

to a periodically driven Gross-Pitaevskii one, in which we find the first exact

analytical solution and the regular and chaotic numerical solutions with

accelerated atomic flow densities. The results suggest an experimental scheme

for generating and controlling the accelerating regular and chaotic

matter-waves.

\\ ( http://arxiv.org/abs/0901.3868 , 753kb)

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arXiv:0901.3920

Date: Sun, 25 Jan 2009 20:48:35 GMT (1205kb,D)

Title: Global operations for protected quantum memories in atomic spin lattices

Authors: G.K. Brennen, K. Hammerer, L. Jiang, M. D. Lukin, and P. Zoller

Categories: quant-ph

Comments: 16 pages, 6 figures

\\

Quantum information processed in strongly correlated states of matter can

provide built in hardware protection against errors. We may encode information

in highly non local degrees of freedom, such as using three dimensional spin

lattices for subsystem codes or two dimensional spin lattices for topologically

ordered surface codes and measurement based codes. Recently, in [L. Jiang et

al., Nature Physics {\bf 4}, 482 (2008)] the authors showed how to manipulate

these global degrees of freedom using optical lattices coupled to a bosonic

degree of freedom via a cavity. We elaborate on these ideas and recapitulate

two approaches to implement many body gates necessary for quantum information

processing, both relying on controlled interactions of an ancillary cavity mode

with the spin system and single ancilla particles. The main focus of the

present paper is to analyze the effect of imperfections such a cavity decay and

collective and individual spin decoherence. We present strategies to fight

decoherence by monitoring cavity decay and show that high gate fidelities can

be achieved in the strong coupling regime of cavity-QED with state of the art

parameters.

\\ ( http://arxiv.org/abs/0901.3920 , 1205kb)

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arXiv:0901.3979

Date: Mon, 26 Jan 2009 15:58:26 GMT (2068kb,D)

Title: Intensity-field correlation of single-atom resonance fluorescence

Authors: S. Gerber, D. Rotter, L. Slodicka, J. Eschner, H. J. Carmichae, and R.

Blatt

Categories: quant-ph

Comments: 4 pages, 4 figures

\\

We report measurements of an intensity-field correlation function of the

resonance fluorescence of a single trapped Ba+ ion. Detection of a photon

prepares the atom in its ground state and we observe its subsequent evolution

under interaction with a laser field of well defined phase. We record the

regression of the resonance fluorescence source field. This provides a direct

measurement of the field of the radiating dipole of a single atom and exhibits

its strong non-classical behavior. In the experimental setup an interference

measurement is conditioned on a fluorescence photon detection. The third-order

correlation function thus recorded demonstrates an aspect of wave-particle

duality at the single-atom, single-photon level.

\\ ( http://arxiv.org/abs/0901.3979 , 2068kb)

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arXiv:0901.4008

Date: Mon, 26 Jan 2009 14:02:59 GMT (45kb)

Title: Large amplitude spin oscillations in a collisionless trapped atomic gas

Authors: F. Piechon, J.N. Fuchs, and F. Laloe

Categories: physics.atom-ph

\\

We propose an explanation of the recently observed strong spin segregation in

a trapped Fermi gas by Du et al. Numerical and analytical solutions of a spin

1/2 kinetic equation in a collisionless regime explain quantitatively the

observation of an "anomalous" large time scale and amplitude of the

segregation. The key difference with previous experiment on bosons rests more

in the diluteness of the gas than in the quantum statistics of the atoms. When

they undergo fast ballistic oscillations in the trap, they average the

inhomogeneous external field in an energy dependent way, so that their

transverse spin precession frequency becomes proportional to their energy.

Interactions between atoms of different energies and different spin directions

then involve the identical spin rotation effect (ISRE), which transfers atoms

to the up or down spin state in an energy dependent way. Since low energy atoms

are closer to the center of the trap than high energy atoms, which can visit

its edges, the final outcome is a strong correlation between spins and

positions.

\\ ( http://arxiv.org/abs/0901.4008 , 45kb)

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arXiv:0901.4103

Date: Tue, 27 Jan 2009 19:54:34 GMT (1480kb)

Title: Exotic phases and quantum phase transitions: model systems and

experiments

Authors: Subir Sachdev

Categories: cond-mat.str-el

Comments: 27 pages, 11 figures; Rapporteur talk at the 24th Solvay Conference

on Physics, "Quantum Theory of Condensed Matter", Brussels, Oct 2008

\\

I survey theoretical advances in our understanding of the quantum phases and

phase transitions of Mott insulators, and of allied conducting systems obtained

by doping charge carriers. A number of new experimental examples of Mott

insulators have appeared in recent years, and I critically compare their

observed properties with the theoretical expectations.

\\ ( http://arxiv.org/abs/0901.4103 , 1480kb)

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arXiv:0901.4110

Date: Tue, 27 Jan 2009 17:42:28 GMT (16kb)

Title: Generation of macroscopic singlet states in atomic ensembles

Authors: G\'eza T\'oth, Morgan W. Mitchell

Categories: quant-ph

Comments: 5 pages including 1 figure, revtex4

\\

We study squeezing of the spin uncertainties by quantum non-demolition (QND)

measurement in non-polarized spin ensembles. Unlike the case of polarized

ensembles, the QND measurements can be performed with negligible back-action

and produce squeezing even in the limit of strong measurement. Together these

allow, in principle, perfect spin squeezing as quantified by [G. Toth et al.,

Phys. Rev. Lett. 99, 250405 (2007)]. The generated spin states approach

many-body singlet states, and contain a macroscopic number of entangled

particles, even when individual spin is large. We estimate the achievable spin

squeezing for achievable experimental parameters. We introduce the Gaussian

treatment of unpolarized spin states.

\\ ( http://arxiv.org/abs/0901.4110 , 16kb)

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arXiv:0901.4164

Date: Tue, 27 Jan 2009 03:00:47 GMT (382kb)

Title: Deceleration of continuous molecular beams

Authors: Eric R. Hudson

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

\\

A method for decelerating a continuous beam of neutral polar molecules is

theoretically demonstrated. This method utilizes non-uniform, static electric

fields and regions of adiabatic population transfer to generate a mechanical

force that opposes the molecular beam's velocity. By coupling this technique

with dissipative trap-loading, molecular densities $\geq10^{11}$ cm$^{-3}$ are

possible. When used in combination with forced evaporative cooling the proposed

method may represent a viable route to quantum degeneracy for a wide-class of

molecular species.

\\ ( http://arxiv.org/abs/0901.4164 , 382kb)

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arXiv:0901.4331

Date: Tue, 27 Jan 2009 20:39:03 GMT (338kb)

Title: Measurement of the trapping lifetime close to a cold metallic surface on

a cryogenic atom-chip

Authors: Andreas Emmert (LKB - Lhomond), Adrian Lupascu (LKB - Lhomond), Gilles

Nogues (LKB - Lhomond), Michel Brune (LKB - Lhomond), Jean-Michel Raimond

(LKB - Lhomond), Serge Haroche (LKB - Lhomond, CDF)

Categories: physics.atom-ph

Comments: 5 pages

\\

We have measured the trapping lifetime of magnetically trapped atoms in a

cryogenic atom-chip experiment. An ultracold atomic cloud is kept at a fixed

distance from a thin gold layer deposited on top of a superconducting trapping

wire. The lifetime is studied as a function of the distances to the surface and

to the wire. Different regimes are observed, where loss rate is determined

either by the technical current noise in the wire or the Johnson-Nyquist noise

in the metallic gold layer, in good agreement with theoretical predictions. Far

from the surface, we observe exceptionally long trapping times for an

atom-chip, in the 10-minutes range.

\\ ( http://arxiv.org/abs/0901.4331 , 338kb)

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arXiv:0901.4099

Date: Mon, 26 Jan 2009 21:00:03 GMT (29kb)

Title: BCS theory of superconductivity: the world's largest Madoff scheme?

Authors: J. E. Hirsch

Categories: physics.gen-ph

\\

The time-tested BCS theory of superconductivity is generally accepted to be

the correct theory of conventional superconductivity by physicists and, by

extension, by the world at large. In a different realm of human activity, until

very recently Bernard Madoff's time-tested investment operation was generally

accepted as true and legitimate in the financial world. Madoff's Ponzi scheme,

where old investors were being paid off by funds contributed by new investors,

was fundamentally flawed, yet was able to thrive for decades because of many

vested interests. `Red flags' suggesting its illegitimacy were ignored. Here I

suggest that the same is true of BCS theory. There are an increasing number of

`red flags' that strongly suggest the possibility that BCS theory may be

fundamentally flawed. For example, an ever-growing number of superconductors

are being classified as `unconventional', not described by the conventional BCS

theory and each requiring a different physical mechanism. In addition, I argue

that BCS theory is unable to explain the Meissner effect, $the$ most

fundamental property of superconductors. There are several other phenomena in

superconductors for which BCS theory provides no explanation, and BCS theory

has proven unable to predict any new superconducting compounds. From one day to

the next, Madoff's edifice came crashing down and a staggering 50 billion

dollars evaporated, and I suggest that this may also be the fate of BCS theory.

I outline an alternative theory to conventional BCS theory proposed to apply to

all superconductors, `conventional' as well as `unconventional', that offers an

explanation for the Meissner effect as well as for other puzzles and provides

clear guidelines in the search for new high temperature superconductors.

\\ ( http://arxiv.org/abs/0901.4099 , 29kb)

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arXiv:0901.4366

Date: Tue, 27 Jan 2009 22:30:12 GMT (154kb)

Title: Devil's staircases and supersolids in a one-dimensional dipolar Bose gas

Authors: F. J. Burnell, Meera M. Parish, N. R. Cooper, S. L. Sondhi

Categories: cond-mat.other

\\

We consider a single-component gas of dipolar bosons confined in a

one-dimensional optical lattice, where the dipoles are aligned such that the

long-ranged dipolar interactions are maximally repulsive. In the limit of zero

inter-site hopping and sufficiently large on-site interaction, the phase

diagram is a complete devil's staircase for filling fractions between 0 and 1,

wherein every commensurate state at a rational filling is stable over a finite

interval in chemical potential. We perturb away from this limit in two

experimentally motivated directions involving the addition of hopping and a

reduction of the onsite interaction. The addition of hopping alone yields a

phase diagram, which we compute in perturbation theory in the hopping, where

the commensurate Mott phases now compete with the superfluid. Further softening

of the onsite interaction yields alternative commensurate states with double

occupancies which can form a staircase of their own, as well as one-dimensional

"supersolids" which simultaneously exhibit discrete broken symmetries and

superfluidity.

\\ ( http://arxiv.org/abs/0901.4366 , 154kb)

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arXiv:0901.4385

Date: Wed, 28 Jan 2009 01:17:27 GMT (757kb)

Title: Metastable Quantum Phase Transitions in a Periodic One-dimensional Bose

Gas: Mean-Field and Bogoliubov Analyses

Authors: R. Kanamoto, L. D. Carr, M. Ueda

Categories: cond-mat.other

\\

We generalize the concept of quantum phase transitions, which is

conventionally defined for a ground state and usually applied in the

thermodynamic limit, to one for \emph{metastable states} in \emph{finite size

systems}. In particular, we treat the one-dimensional Bose gas on a ring in the

presence of both interactions and rotation. To support our study, we bring to

bear mean-field theory, i.e., the nonlinear Schr\"odinger equation, and linear

perturbation or Bogoliubov-de Gennes theory. Both methods give a consistent

result in the weakly interacting regime: there exist \emph{two topologically

distinct quantum phases}. The first is the typical picture of superfluidity in

a Bose-Einstein condensate on a ring: average angular momentum is quantized and

the superflow is uniform. The second is new: one or more dark solitons appear

as stationary states, breaking the symmetry, the average angular momentum

becomes a continuous quantity, and the phase of the condensate can be

continuously wound and unwound.

\\ ( http://arxiv.org/abs/0901.4385 , 757kb)

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\\

arXiv:0901.4437

Date: Wed, 28 Jan 2009 11:30:47 GMT (149kb)

Title: Momentum distribution of a freely expanding Lieb-Liniger gas

Authors: D. Juki\' c, B. Klajn and H. Buljan

Categories: cond-mat.other

\\

We numerically study free expansion of a few Lieb-Liniger bosons, which are

initially in the ground state of an infinitely deep hard-wall trap. Numerical

calculation is carried out by employing a standard Fourier transform, as

follows from the Fermi-Bose transformation for a time-dependent Lieb-Liniger

gas. We study the evolution of the momentum distribution, the real-space single

particle density, and the occupancies of natural orbitals. We find analytically

(by using the stationary phase approximation) that for sufficiently large times

the shape of the momentum distribution coincides (up to a simple scaling

transformation) with the shape of the real-space single-particle density. This

result is corroborated by our numerical simulations.

\\ ( http://arxiv.org/abs/0901.4437 , 149kb)

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\\

arXiv:0901.4391

Date: Wed, 28 Jan 2009 02:29:43 GMT (200kb,D)

Title: Stochastic Simulations of Conditional Master Equations

Authors: M. R. Hush, A. R. R. Carvalho, J. J. Hope

Categories: quant-ph

Comments: 5 pages, 2 figures

\\

We demonstrate a technique for performing stochastic simulations of

conditional master equations. This allows first-principles simulations of

continually measured quantum systems, such as those controlled by

measurement-based feedback. We show that the stochastic technique is nearly two

orders of magnitude faster than a Wigner function method by simulating a single

trapped particle undergoing position measurement and feedback control. More

importantly, we demonstrate that the method presented here scales almost

logarithmically with the size of the Hilbert space of the system, allowing

simulations of conditional dynamics of multimode bosonic quantum fields, which

were impractical using previous brute force methods.

\\ ( http://arxiv.org/abs/0901.4391 , 200kb)

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\\

arXiv:0901.4529

Date: Wed, 28 Jan 2009 18:55:57 GMT (263kb)

Title: Preparation of atomic Fock states by trap reduction

Authors: M. Pons, A. del Campo, J. G. Muga, M. G. Raizen

Categories: quant-ph

Comments: 5 pages, 5 figures

\\

We describe the preparation of atom-number states with strongly interacting

bosons in one dimension, or spin-polarized fermions. The procedure is based on

a combination of weakening and squeezing of the trapping potential. For the

resulting state, the full atom number distribution is obtained. Starting with

an unknown number of particles $N_i$, we optimize the sudden change in the

trapping potential which leads to the Fock state of $N_f$ particles in the

final trap. Non-zero temperature effects as well as different smooth trapping

potentials are analyzed. A simple criterion is provided to ensure the robust

preparation of the Fock state for physically realistic traps.

\\ ( http://arxiv.org/abs/0901.4529 , 263kb)

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\\

arXiv:0901.4584

Date: Wed, 28 Jan 2009 23:40:03 GMT (118kb)

Title: Observation of heteronuclear atomic Efimov resonances

Authors: G. Barontini, C. Weber, F. Rabatti, J. Catani, G. Thalhammer, M.

Inguscio, F. Minardi

Categories: cond-mat.other

Comments: 4 pages, 4 figures

\\

The Efimov effect represents a cornerstone in few-body physics. Building on

the recent experimental observation with ultracold atoms, we report the first

experimental signature of Efimov physics in a heteronuclear system. A mixture

of $^{41}$K and $^{87}$Rb atoms was cooled to few hundred nanoKelvins and

stored in an optical dipole trap. Exploiting a broad interspecies Feshbach

resonance, the losses due to three-body collisions were studied as a function

of the interspecies scattering length. We observe an enhancement of the

three-body collisions for three distinct values of the interspecies scattering

lengths, both positive and negative. We attribute the two features at negative

scattering length to the existence of two kind of Efimov trimers, namely KKRb

and KRbRb.

\\ ( http://arxiv.org/abs/0901.4584 , 118kb)

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\\

arXiv:0901.4600

Date: Thu, 29 Jan 2009 06:59:20 GMT (1998kb)

Title: Quantum turbulence: From superfluid helium to atomic Bose-Einstein

condensates

Authors: Makoto Tsubota

Categories: cond-mat.other

\\

This article reviews recent developments in quantum fluid dynamics and

quantum turbulence (QT) for superfluid helium and atomic Bose-Einstein

condensates. Quantum turbulence was discovered in superfluid $^4$He in the

1950s, but the field moved in a new direction starting around the mid 1990s.

Quantum turbulence is comprised of quantized vortices that are definite

topological defects arising from the order parameter appearing in Bose-Einstein

condensation. Hence QT is expected to yield a simpler model of turbulence than

does conventional turbulence. A general introduction to this issue and a brief

review of the basic concepts are followed by a description of vortex lattice

formation in a rotating atomic Bose-Einstein condensate, typical of quantum

fluid dynamics. Then we discuss recent developments in QT of superfluid helium

such as the energy spectra and dissipative mechanisms at low temperatures, QT

created by vibrating structures, and the visualization of QT. As an application

of these ideas, we end with a discussion of QT in atomic Bose-Einstein

condensates.

\\ ( http://arxiv.org/abs/0901.4600 , 1998kb)

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\\

arXiv:0901.4602

Date: Thu, 29 Jan 2009 05:14:53 GMT (159kb)

Title: Quantifying Finite Temperature Effects in Atom Chip Interferometry of

Bose-Einstein Condensates

Authors: R.G. Scott, D.A.W. Hutchinson, T.E. Judd, and T.M. Fromhold

Categories: cond-mat.other

Comments: 7 pages, 5 figures

\\

We quantify the effect of phase fluctuations on atom chip interferometry of

Bose-Einstein condensates. At very low temperatures, we observe small phase

fluctuations, created by mean-field depletion, and a resonant production of

vortices when the two clouds are initially in anti-phase. At higher

temperatures, we show that the thermal occupation of Bogoliubov modes makes

vortex production vary smoothly with the initial relative phase difference

between the two atom clouds. We also propose a technique to observe vortex

formation directly by creating a weak link between the two clouds. The position

and direction of circulation of the vortices is subsequently revealed by kinks

in the interference fringes produced when the two clouds expand into one

another. This procedure may be exploited for precise force measurement or

motion detection.

\\ ( http://arxiv.org/abs/0901.4602 , 159kb)

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\\

arXiv:0901.4631

Date: Thu, 29 Jan 2009 09:34:42 GMT (393kb)

Title: From Bogoliubov's approximation to Popov's hydrodynamic theory: a

unified picture of superfluidity

Authors: N. Dupuis

Categories: cond-mat.other

Comments: 4 pages, 4 figures

\\

Using a non-perturbative renormalization-group technique, we compute the

momentum and frequency dependence of the anomalous self-energy and the

one-particle spectral function of two-dimensional interacting bosons at zero

temperature. Below a characteristic momentum scale $k_G$, where the Bogoliubov

approximation breaks down, the anomalous self-energy develops a square root

singularity and the Goldstone mode of the superfluid phase (Bogoliubov sound

mode) coexists with a continuum of excitations, in agreement with the

predictions of Popov's hydrodynamic theory. Thus our results provide a unified

picture of superfluidity in interacting boson systems and connect Bogoliubov's

theory (valid for momenta larger than $k_G$) to Popov's hydrodynamic approach.

\\ ( http://arxiv.org/abs/0901.4631 , 393kb)

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\\

arXiv:0901.4641

Date: Thu, 29 Jan 2009 10:40:33 GMT (133kb)

Title: Stability and pairing in quasi-one-dimensional Bose-Fermi mixtures

Authors: F. M. Marchetti, Th. Jolicoeur, M. M. Parish

Categories: cond-mat.other

Comments: 4 pages, 2 figures

\\

We consider a mixture of single-component bosonic and fermionic atoms in an

array of coupled one-dimensional "tubes". For an attractive Bose-Fermi

interaction, we show that the system exhibits phase separation instead of the

usual collapse. Moreover, above a critical inter-tube hopping, all first-order

instabilities disappear in both attractive and repulsive mixtures. The

possibility of suppressing instabilities in this system suggests a route

towards the realization of paired phases, including a superfluid of p-wave

pairs unique to the coupled-tube system, and quantum critical phenomena.

\\ ( http://arxiv.org/abs/0901.4641 , 133kb)

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\\

arXiv:0901.4693

Date: Thu, 29 Jan 2009 14:44:18 GMT (1616kb)

Title: Topological Phase in Noncentrosymmetric S-Wave Superfluids of Ultracold

Fermionic Atoms

Authors: Masatoshi Sato, Yoshiro Takahashi, Satoshi Fujimoto

Categories: cond-mat.supr-con

Comments: 5 pages, 2 figures

\\

We show that in s-wave superfluids of cold fermionic atoms with laser-field

generated effective spin-orbit interactions, a topological phase with gapless

edge states and Majorana fermion quasiparticles obeying the non-Abelian

statistics is realized in the case with a large population imbalance of two

hyperfine states which form Cooper pairs.

\\ ( http://arxiv.org/abs/0901.4693 , 1616kb)

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\\

arXiv:0901.4769

Date: Thu, 29 Jan 2009 20:30:14 GMT (166kb)

Title: Induced interactions for ultra-cold Fermi gases in optical lattices

Authors: D.-H. Kim, P. Torma, J.-P. Martikainen

Categories: cond-mat.supr-con cond-mat.other

Comments: 4+ pages, 4 figures

\\

We investigate the effect optical lattices on the BCS superfluidity by using

the Gorkov-Melik-Barkhudarov (GMB) correction to the BCS mean-field theory for

a two-component Fermi gas. We find that the suppression of the order parameter

is strongly enhanced by the lattice effects. The predictions made by the GMB

corrections are in qualitative and, for the cases studied, in quantitative

agreement with previous quantum Monte Carlo results. We discuss how the GMB

correction extends the validity of the mean-field theory to a wider range of

tunable optical lattice systems in different dimensions.

\\ ( http://arxiv.org/abs/0901.4769 , 166kb)

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\\

arXiv:0901.4719

Date: Thu, 29 Jan 2009 16:55:59 GMT (359kb)

Title: Bloch oscillations of Bose-Einstein condensates: Quantum counterpart of

dynamical instability

Authors: Andrey R. Kolovsky, Hans J\"urgen Korsch, Eva-Maria Graefe

Categories: quant-ph

Comments: 12 pages, 14 figures

\\

We study the Bloch dynamics of a quasi one-dimensional Bose-Einstein

condensate of cold atoms in a tilted optical lattice modeled by a Hamiltonian

of Bose-Hubbard type: The corresponding mean-field system described by a

discrete nonlinear Schr\"odinger equation can show a dynamical (or modulation)

instability due to chaotic dynamics and equipartition over the quasimomentum

modes. It is shown, that these phenomena are related to a depletion of the

Floquet-Bogoliubov states and a decoherence of the condensate in the

many-particle description. Three different types of dynamics are distinguished:

(i) decaying oscillations in the region of dynamical instability, and (ii)

persisting Bloch oscillations or (iii) periodic decay and revivals in the

region of stability.

\\ ( http://arxiv.org/abs/0901.4719 , 359kb)

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The replacements:

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\\

arXiv:0805.3388

replaced with revised version Fri, 23 Jan 2009 17:25:09 GMT (53kb)

Title: Threshold for Chaos and Thermalization in One-Dimensional Mean-Field

Bose-Hubbard Model

Authors: Amy C. Cassidy, Douglas Mason, Vanja Dunjko, Maxim Olshanii

Categories: cond-mat.other cond-mat.stat-mech

Comments: 4 pages, 3 figures, published version

Journal-ref: Phys. Rev. Lett. 102, 025302 (2009)

DOI: 10.1103/PhysRevLett.102.025302

\\ ( http://arxiv.org/abs/0805.3388 , 53kb)

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\\

arXiv:0811.1873

replaced with revised version Fri, 23 Jan 2009 09:59:09 GMT (1305kb)

Title: Density profiles of polarized Fermi gases confined in harmonic traps

Authors: G. Bertaina and S. Giorgini

Categories: cond-mat.other cond-mat.supr-con

Comments: 6 pages, 4 figures. We added references and modified the figures

Journal-ref: Phys. Rev. A 79, 013616 (2009)

DOI: 10.1103/PhysRevA.79.013616

\\ ( http://arxiv.org/abs/0811.1873 , 1305kb)

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\\

arXiv:0901.3303

replaced with revised version Mon, 26 Jan 2009 08:33:18 GMT (459kb)

Title: Atom chips and one-dimensional Bose gases

Authors: Isabelle Bouchoule (LCFIO), N. J. Van Druten, Christoph I. Westbrook

(LCFIO)

Categories: physics.atom-ph

\\ ( http://arxiv.org/abs/0901.3303 , 459kb)

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\\

arXiv:0805.3226

replaced with revised version Tue, 27 Jan 2009 16:08:26 GMT (377kb)

Title: Thermodynamics of a trapped unitary Fermi gas

Authors: R. Haussmann and W. Zwerger

Categories: cond-mat.stat-mech

Comments: 10 pages, 5 figures

Report-no: KN-08-05

Journal-ref: Phys. Rev. A 78, 063602 (2008)

\\ ( http://arxiv.org/abs/0805.3226 , 377kb)

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\\

arXiv:0811.2139

replaced with revised version Tue, 27 Jan 2009 11:11:02 GMT (1293kb,D)

Title: Coherent state approach to the cross collisional effects in the

population dynamics of a two-mode Bose-Einstein condensate

Authors: Thiago F. Viscondi, K. Furuya and M. C. de Oliveira

Categories: quant-ph

Comments: 19 pages, 8 figures. Added some references, remarks on LMG model and

acknowledgments

\\ ( http://arxiv.org/abs/0811.2139 , 1293kb)

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\\

arXiv:0811.2479

replaced with revised version Tue, 27 Jan 2009 17:24:57 GMT (233kb)

Title: Negative-index media for matter-wave optics

Authors: J. Baudon, M. Hamamda, J. Grucker, F. Perales, G. Dutier, M. Boustimi

and M. Ducloy

Categories: quant-ph physics.optics

Comments: 4 pages, 4 figures, submitted at PRL 4 November 2008

\\ ( http://arxiv.org/abs/0811.2479 , 233kb)

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\\

arXiv:0804.1850

replaced with revised version Wed, 28 Jan 2009 03:38:36 GMT (260kb)

Title: Realizing and Detecting the Haldane's Quantum Hall effect with Ultracold

Atoms

Authors: L. B. Shao, Shi-Liang Zhu, L. Sheng, D. Y. Xing, and Z. D. Wang

Categories: cond-mat.mes-hall

Comments: 5 pages

Journal-ref: Phys. Rev. Lett.101,246810 (2008)

\\ ( http://arxiv.org/abs/0804.1850 , 260kb)

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\\

arXiv:0812.0239

replaced with revised version Wed, 28 Jan 2009 15:18:44 GMT (61kb)

Title: Collective modes of trapped Fermi gases with in-medium interaction

Authors: S.Chiacchiera, T.Lepers, M.Urban, D.Davesne

Categories: cond-mat.other nucl-th

Comments: 17 pages

\\ ( http://arxiv.org/abs/0812.0239 , 61kb)

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\\

arXiv:0812.1977

replaced with revised version Wed, 28 Jan 2009 16:46:40 GMT (653kb)

Title: Kinetic quantum phase transition in bosonic superfluids on a lattice

Authors: A. S. Alexandrov and I. O. Thomas

Categories: cond-mat.other

Comments: 4 pages, 3 figures. Submitted to Physical Review Letters Revised

version has additional results and a clarification regarding the

applicability of the values of the hopping parameters

\\ ( http://arxiv.org/abs/0812.1977 , 653kb)

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\\

arXiv:0811.4696

replaced with revised version Thu, 29 Jan 2009 13:42:20 GMT (21kb)

Title: Hubbard model calculations of phase separation in optical lattices

Authors: H. Heiselberg

Categories: cond-mat.supr-con cond-mat.str-el

\\ ( http://arxiv.org/abs/0811.4696 , 21kb)

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\\

arXiv:0805.3083

replaced with revised version Thu, 29 Jan 2009 12:25:21 GMT (77kb)

Title: Generation of nonground-state Bose-Einstein condensates by modulating

atomic interactions

Authors: E. R. F. Ramos, E. A. L. Henn, J. A. Seman, M. A. Caracanhas, K. M. F.

Magalh\~aes, K. Helmerson, V. I. Yukalov, V. S. Bagnato

Categories: quant-ph

Comments: 6 pages, 2 figures, 1 table

Journal-ref: Phys. Rev. A 78, 063412 (2008)

DOI: 10.1103/PhysRevA.78.063412

\\ ( http://arxiv.org/abs/0805.3083 , 77kb)

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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 =========================================================================Received on Fri May 01 2009 - 15:51:04 EST

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