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

Date: Fri, 14 Sep 2007 15:05:15 +1000 (EST)

Date: Fri, 14 Sep 2007 15:05:15 +1000 (EST)

This week there were 18 new preprints and 6 replacements.

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arXiv:0708.3241

Date: Fri, 24 Aug 2007 13:44:06 GMT (283kb,D)

Title: Supersolid Bose-Fermi Mixtures in Optical Lattices

Authors: I. Titvinidze, M. Snoek, W. Hofstetter

Categories: cond-mat.other

Comments: 4 pages, 5 pictures

\\

We study a mixture of strongly interacting bosons and spinless fermions with

on-site repulsion in a three-dimensional optical lattice. In order to

investigate the regime of strong interactions, we develop and apply a

generalized DMFT (gDMFT) scheme, which consists of dynamical mean-field theory

(DMFT) for the fermions, combined with static Gutzwiller mean-field theory for

the bosons. We restrict ourselves to the case of half filling, where we find a

rich phase diagram. For weak Bose-Fermi repulsion a supersolid forms, in which

the bosons are superfluid and both fermions and bosons have a spatially

modulated density, i.e. charge-density wave order. For stronger interspecies

repulsion the bosons become localized while the charge density wave order

persists. The system is unstable against phase separation for weak repulsion

among the bosons.

\\ ( http://arxiv.org/abs/0708.3241 , 283kb)

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arXiv:0708.3265

Date: Fri, 24 Aug 2007 19:55:21 GMT (95kb)

Title: Time-dependent density-functional theory, Hubbard model, and exact

results for 1D contact-interacting fermions in a double well potential

Authors: R. J. Magyar

Categories: cond-mat.other cond-mat.mtrl-sci

\\

Two of the most popular quantum mechanical models of interacting fermions are

compared to each other and to potentially exact solutions for a pair of

contact-interacting fermions trapped in a 1D double-well potential, a model of

atoms in an optical lattice or electrons of a Hydrogen molecule in a strong

magnetic field. An exact few-body Hamiltonian is solved numerically in momentum

space yielding a highly-correlated eigenspectrum. Additionally, approximate

ground-state energies are obtained using both density functional theory (DFT)

with the exact-exchange / local correlation (EXX/LDA) functional and 2-site

Hubbard models. A 1D adiabatic LDA kernel is constructed for use in

time-dependent density functional theory (TDDFT), and the resulting

excited-state spectrum is compared to the exact and Hubbard results. TDDFT is

shown to provide exceptionally accurate results in the double-well range with

non-adiabatic effects accounting for deviations for stronger interactions. As

expected, the Hubbard model outperforms DFT at large separations but breaks

down at intermediate spacings due to improper scaling. A newly introduced

functional based on the effective local fermion number provides accurate

results for large spacings.

\\ ( http://arxiv.org/abs/0708.3265 , 95kb)

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arXiv:0708.3295

Date: Fri, 24 Aug 2007 09:16:11 GMT (230kb)

Title: Recent progress on the manipulation of single atoms in optical tweezers

for quantum computing

Authors: A. Browaeys, J. Beugnon, C. Tuchendler, H. Marion, A. Ga\"etan, Y.

Miroshnychenko, B. Darqui\'e, J. Dingjan, Y. R. P. Sortais, A. M. Lance, M.

P. A. Jones, G. Messin, P. Grangier

Categories: quant-ph

Comments: Proceedings of the ICOLS07 conference

\\

This paper summarizes our recent progress towards using single rubidium atoms

trapped in an optical tweezer to encode quantum information. We demonstrate

single qubit rotations on this system and measure the coherence of the qubit.

We move the quantum bit over distances of tens of microns and show that the

coherence is reserved. We also transfer a qubit atom between two tweezers and

show no loss of coherence. Finally, we describe our progress towards

conditional entanglement of two atoms by photon emission and two-photon

interferences.

\\ ( http://arxiv.org/abs/0708.3295 , 230kb)

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arXiv:0708.3298

Date: Fri, 24 Aug 2007 19:25:31 GMT (11kb)

Title: Collapse times for attractive Bose-Einstein condensates

Authors: Esteban Calzetta

Categories: cond-mat.other

Comments: 12 pages

\\

We argue that the main mechanism for condensate collapse in an attractive

Bose-Einstein condensate is the loss of coherence between atoms a finite

distance apart, rather than the growth of the occupation number in

noncondensate modes. Since the former mechanism is faster than the latter by a

factor of approximately 3/2, this helps to dispell the apparent failure of

field theoretical models in predicting the collapse time of the condensate.

\\ ( http://arxiv.org/abs/0708.3298 , 11kb)

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arXiv:0708.3315

Date: Fri, 24 Aug 2007 11:30:36 GMT (232kb)

Title: Destruction of Anderson localization by a weak nonlinearity

Authors: A. S. Pikovsky and D. L. Shepelyansky

Categories: cond-mat.dis-nn

Comments: 4 pages, 5 figs

\\

We study numerically a spreading of an initially localized wave packet in a

one-dimensional discrete nonlinear Schr\"odinger lattice with disorder. We

demonstrate that above a certain critical strength of nonlinearity the Anderson

localization is destroyed and an unlimited subdiffusive spreading of the field

along the lattice occurs. The second moment grows with time $ \propto

t^\alpha$, with the exponent $\alpha$ being in the range $0.3 - 0.4$. For small

nonlinearities the distribution remains localized in a way similar to the

linear case.

\\ ( http://arxiv.org/abs/0708.3315 , 232kb)

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arXiv:0708.3320

Date: Fri, 24 Aug 2007 12:14:58 GMT (71kb)

Title: Optical polarizabilities of large molecules measured in near-field

interferometry

Authors: Lucia Hackermueller, Klaus Hornberger, Stefan Gerlich, Michael Gring,

Hendrik Ulbricht, Markus Arndt

Categories: quant-ph

Comments: 5 pages, 3 Figures

\\

We discuss a novel application of matter wave interferometry to characterize

the scalar optical polarizability of molecules at 532 nm. The interferometer

presented here consists of two material absorptive gratings and one central

optical phase grating. The interaction of the molecules with the standing light

wave is determined by the optical dipole force and is therefore directly

dependent on the molecular polarizability at the wavelength of the diffracting

laser light. By comparing the observed matter-wave interference contrast with a

theoretical model for several intensities of the standing light wave and

molecular velocities we can infer the polarizability in this first

proof-of-principle experiment for the fullerenes C60 and C70 and we find a good

agreement with literature values.

\\ ( http://arxiv.org/abs/0708.3320 , 71kb)

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arXiv:0708.3548

Date: Mon, 27 Aug 2007 08:42:01 GMT (111kb)

Title: One-dimensional fermionic gases with attractive p-wave interaction in a

hard-wall trap

Authors: Yajiang Hao, Yunbo Zhang, Shu Chen

Categories: cond-mat.other cond-mat.str-el

Comments: 6 pages, 5 figures

\\

We investigate the ground state of the one-dimensional fermionic system

enclosed in a hard-wall trap with attractive contact p-wave interactions. Based

on the Bethe ansatz method, the explicit wave function is derived by

numerically solving the Bethe ansatz equations for the full physical regimes

($-\infty \leq c_F\leq 0$). With the exact wave function some quantities which

are important in many-body physics are obtained, including the one-body density

matrix and the momentum distribution of the ground state for finite system. It

is shown that the shell structure of the density profiles disappears with the

increase of the interaction and in the fermionic Tonks-Girardeau (FTG) limit

the density distribution shows the same behavior as that of an ideal Bose gas.

However the one-body density matrix and the momentum distribution exhibit

completely different structures compared with their bosonic counterparts.

\\ ( http://arxiv.org/abs/0708.3548 , 111kb)

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arXiv:0708.3638

Date: Mon, 27 Aug 2007 16:07:53 GMT (66kb)

Title: Spin dynamics in a one-dimensional ferromagnetic Bose gas

Authors: M. B. Zvonarev, V. V. Cheianov, T. Giamarchi

Categories: cond-mat.other

\\

We investigate the propagation of spin excitations in a one-dimensional (1D)

ferromagnetic Bose gas. While the spectrum of longitudinal spin waves in this

system is sound-like, the dispersion of transverse spin excitations is

quadratic making a direct application of the Luttinger Liquid (LL) theory

impossible. By using a combination of different analytic methods we derive the

large time asymptotic behavior of the spin-spin dynamical correlation function

for strong interparticle repulsion. The result has an unusual structure

associated with a crossover from the regime of trapped spin wave to an open

regime and does not have analogues in known low-energy universality classes of

quantum 1D systems.

\\ ( http://arxiv.org/abs/0708.3638 , 66kb)

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arXiv:0708.3646

Date: Mon, 27 Aug 2007 17:12:41 GMT (81kb)

Title: Complex solitons with power law behaviour in Bose-Einstein condensates

near Feshbach resonance

Authors: Utpal Roy, Rajneesh Atre, C. Sudheesh, C. Nagaraja Kumar, Prasanta K.

Panigrahi

Categories: cond-mat.other

Comments: 4 pages, 2 figures

\\

Complex, localized stable solitons, characterized by a power law behaviour,

are found for a quasi-one-dimensional Bose-Einstein condensate near Feshbach

resonance. Both dark and bright solitons can be excited in the experimentally

allowed parameter domain, when two and three-body interactions are respectively

repulsive and attractive. These solutions are obtained for non-zero chemical

potential, unlike their unstable real counterparts which exist in the limit of

vanishing $\mu$. The dark solitons travel with constant speed, which is quite

different from the Lieb mode, where profiles with different speeds, bounded

above by sound velocity can exist for specified interaction strengths.

\\ ( http://arxiv.org/abs/0708.3646 , 81kb)

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arXiv:0708.3657

Date: Mon, 27 Aug 2007 17:53:27 GMT (914kb)

Title: Hyperfine spectra of trapped Bosons in optical lattices

Authors: Kaden R.A. Hazzard and Erich J. Mueller

Categories: cond-mat.other

Comments: 7 pages, 5 figures, revtex4

\\

We calculate the interaction induced inhomogeneous broadening of spectral

lines in a trapped Bose gas as a function of the depth of a three-dimensional

cubic optical lattice. As observed in recent experiments, we find that the

terraced "wedding-cake" structure of Mott plateaus splits the spectrum into a

series of discrete peaks. The spectra are extremely sensitive to density

corrugations and trap anharmonicities. For example, even when the majority of

the cloud is superfluid the spectrum displays discrete peaks.

\\ ( http://arxiv.org/abs/0708.3657 , 914kb)

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arXiv:0708.3474

Date: Sun, 26 Aug 2007 09:50:32 GMT (69kb)

Title: Nonlinear control of chaotic walking of atoms in an optical lattice

Authors: Argonov V. Yu, S. V. Prants

Categories: quant-ph

Comments: 6 pages, 4 figures

\\

Centre-of-mass atomic motion in an optical lattice near the resonance is

shown to be a chaotic walking due to the interplay between coherent internal

atomic dynamics and spontaneous emission. Statistical properties of chaotic

atomic motion can be controlled by the single parameter, the detuning between

the atomic transition frequency and the laser frequency. We derive a

Fokker-Planck equation in the energetic space to describe the atomic transport

near the resonance and demonstrate numerically how to manipulate the atomic

motion varying the detuning.

\\ ( http://arxiv.org/abs/0708.3474 , 69kb)

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arXiv:0708.3701

Date: Tue, 28 Aug 2007 00:38:12 GMT (402kb)

Title: Classical analogs for Rabi-oscillations, Ramsey-fringes, and spin-echo

in Josephson junctions

Authors: Jeffrey E. Marchese, Matteo Cirillo and Niels Gronbech-Jensen

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

Comments: 16 pages, 7 figures

\\

We investigate the results of recently published experiments on the quantum

behavior of Josephson circuits in terms of the classical modelling based on the

resistively and capacitively-shunted (RCSJ) junction model. Our analysis shows

evidence for a close analogy between the nonlinear behavior of a pulsed

microwave-driven Josephson junction at low temperature and low dissipation and

the experimental observations reported for the Josephson circuits.

Specifically, we demonstrate that Rabi-oscillations, Ramsey-fringes, and

spin-echo observations are not phenomena with a unique quantum interpretation.

In fact, they are natural consequences of transients to phase-locking in

classical nonlinear dynamics and can be observed in a purely classical model of

a Josephson junction when the experimental recipe for the application of

microwaves is followed and the experimental detection scheme followed. We

therefore conclude that classical nonlinear dynamics can contribute to the

understanding of relevant experimental observations of Josephson response to

various microwave perturbations at very low temperature and low dissipation.

\\ ( http://arxiv.org/abs/0708.3701 , 402kb)

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arXiv:0708.3750

Date: Tue, 28 Aug 2007 10:36:49 GMT (34kb)

Title: Entanglement and correlation functions following a local quench: a

conformal field theory approach

Authors: Pasquale Calabrese and John Cardy

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

Comments: 19 pages, 4 figures

\\

We show that the dynamics resulting from preparing a one-dimensional quantum

system in the ground state of two decoupled parts, then joined together and

left to evolve unitarily with a translational invariant Hamiltonian (a local

quench), can be described by means of quantum field theory. In the case when

the corresponding theory is conformal, we study the evolution of the

entanglement entropy for different bi-partitions of the line. We also consider

the behavior of one- and two-point correlation functions. All our findings may

be explained in terms of a picture, that we believe to be valid more generally,

whereby quasiparticles emitted from the joining point at the initial time

propagate semiclassically through the system.

\\ ( http://arxiv.org/abs/0708.3750 , 34kb)

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arXiv:0708.3840

Date: Tue, 28 Aug 2007 19:33:16 GMT (541kb)

Title: Formal analytical solutions for the Gross-Pitaevskii equation

Authors: C. Trallero-Giner, Julio C. Drake-Perez, V. Lopez-Richard, Joseph L.

Birman

Categories: cond-mat.other

Comments: 8 figures

\\

Considering the Gross-Pitaevskii integral equation we are able to formally

obtain an analytical solution for the order parameter $\Phi (x)$ and for the

chemical potential $\mu $ as a function of a unique dimensionless non-linear

parameter $\Lambda $. We report solutions for different range of values for the

repulsive and the attractive non-linear interactions in the condensate. Also,

we study a bright soliton-like variational solution for the order parameter for

positive and negative values of $\Lambda $. Introducing an accumulated error

function we have performed a quantitative analysis with other well-established

methods as: the perturbation theory, the Thomas-Fermi approximation, and the

numerical solution. This study gives a very useful result establishing the

universal range of the $\Lambda $-values where each solution can be easily

implemented. In particular we showed that for $\Lambda <-9$, the bright soliton

function reproduces the exact solution of GPE wave function.

\\ ( http://arxiv.org/abs/0708.3840 , 541kb)

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arXiv:0708.3826

Date: Tue, 28 Aug 2007 18:10:09 GMT (48kb)

Title: Trapping radioactive ^{82}Rb in an optical dipole trap and evidence of

spontaneous spin polarization

Authors: D. Feldbaum, H. Wang, J. Weinstein, D. Vieira and X. Zhao

Categories: quant-ph

Comments: 4 pages, 4 figures

\\

Optical trapping of selected species of radioactive atoms has great potential

in precision measurements for testing fundamental physics such as EDM, PNC and

parity violating beta-decay asymmetry correlation coefficients. We report

trapping of 10^4 radioactive ^{82}Rb atoms (t_{1/2}=75 s) with a trap lifetime

of ~55 seconds in an optical dipole trap. Transfer efficiency from the

magneto-optical trap was ~14%. We further report the evidence of spontaneous

spin polarization of the atoms in optical dipole trap loading. This advancement

is an important step towards a new generation of precision J-beta correlations

measurements with polarized ^{82}Rb atoms.

\\ ( http://arxiv.org/abs/0708.3826 , 48kb)

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arXiv:0708.3958

Date: Wed, 29 Aug 2007 13:59:41 GMT (273kb)

Title: Cruising through molecular bound state manifolds with radio frequency

Authors: F. Lang, P.v.d. Straten, B. Brandst\"atter, G. Thalhammer, K. Winkler,

P.S. Julienne, R. Grimm and J. Hecker Denschlag

Categories: quant-ph

Comments: 5 pages, 5 figures, submitted for publication

\\

The emerging field of ultracold molecules with their rich internal structure

is currently attracting a lot of interest. Various methods have been developed

to produce ultracold molecules in pre-set quantum states. For future

experiments it will be important to efficiently transfer these molecules from

their initial quantum state to other quantum states of interest. Optical Raman

schemes are excellent tools for transfer, but can be involved in terms of

equipment, laser stabilization and finding the right transitions. Here we

demonstrate a very general and simple way for transfer of molecules from one

quantum state to a neighboring quantum state with better than 99% efficiency.

The scheme is based on Zeeman tuning the molecular state to avoided level

crossings where radio-frequency transitions can then be carried out. By

repeating this process at different crossings, molecules can be successively

transported through a large manifold of quantum states. As an important

spin-off of our experiments, we demonstrate a high-precision spectroscopy

method for investigating level crossings.

\\ ( http://arxiv.org/abs/0708.3958 , 273kb)

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arXiv:0708.4124

Date: Thu, 30 Aug 2007 18:30:51 GMT (33kb)

Title: Shell Effects in the First Sound Velocity of an Ultracold Fermi Gas

Authors: Luca Salasnich and Flavio Toigo

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

Comments: 6 pages, 1 figure, submitted for the Proceedings of the International

Symposium on Quantum Fluids and Solids 2007, Kazan

\\

We investigate the first sound of a normal dilute and ultracold two-component

Fermi gas in a harmonic microtube, i.e. a cylinder with harmonic transverse

radial confinement in the length-scale of microns. We show that the velocity of

the sound that propagates along the axial direction strongly depends on the

dimensionality of the system. In particular, we predict that the first-sound

velocity display shell effects: by increasing the density, that is by inducing

the crossover from one-dimension to three-dimensions, the first-sound velocity

shows jumps in correspondence with the filling of harmonic modes. The

experimental achievability of these effects is discussed by considering 40K

atoms.

\\ ( http://arxiv.org/abs/0708.4124 , 33kb)

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arXiv:0708.4197

Date: Thu, 30 Aug 2007 16:28:24 GMT (489kb)

Title: Optimal transport of ultracold atoms in the non-adiabatic regime

Authors: A. Couvert (LKB - Lhomond), T. Kawalec (LKB - Lhomond), G. Reinaudi

(LKB - Lhomond), David Guery-Odelin (LKB - Lhomond)

Categories: cond-mat.other

Proxy: ccsd hal-00168928

\\

We report on the transport of ultracold atoms with optical tweezers in the

non-adiabatic regime i.e. on a time scale on the order of the oscillation

period. To quantitatively interpret our data, we provide a fruitful analogy

between the transport and the Fraunhofer diffraction of an object having a

transmittance with the same shape as the one of the velocity profile imposed on

center of the trap. The damping of the Kohn's mode due to the non-linear mixing

turns out to be reminiscent of the effect of a finite coherence source for its

optical counterpart.

\\ ( http://arxiv.org/abs/0708.4197 , 489kb)

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The replacments:

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arXiv:cond-mat/0701668

replaced with revised version Fri, 24 Aug 2007 21:30:51 GMT (22kb)

Title: Bose-Einstein condensate in a harmonic trap decorated with Dirac delta

functions

Authors: Haydar Uncu, Devrim Tarhan, Ersan Demiralp, Ozgur E. Mustecaplioglu

Categories: cond-mat.other quant-ph

Comments: 8 pages, 8 figures

Journal-ref: PHYSICAL REVIEW A 76, 013618 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0701668 , 22kb)

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arXiv:cond-mat/0702223

replaced with revised version Sun, 26 Aug 2007 10:00:11 GMT (117kb)

Title: Coherent state path integral and super-symmetry for condensates composed

of bosonic and fermionic atoms

Authors: Bernhard Mieck

Categories: cond-mat.stat-mech

Journal-ref: Fortschr. Phys. ("Progress of Physics") Vol. 55, (No. 9-10), pp.

989-1120 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0702223 , 117kb)

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arXiv:cond-mat/0604162

replaced with revised version Tue, 28 Aug 2007 14:13:09 GMT (33kb)

Title: Thermodynamical Properties of a Rotating Ideal Bose Gas

Authors: Sebastian Kling, Axel Pelster

Categories: cond-mat.stat-mech

Comments: Author Information under

http://www.theo-phys.uni-essen.de/tp/ags/pelster_dir/

Journal-ref: Phys. Rev. A 76, 023609 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0604162 , 33kb)

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arXiv:cond-mat/0609685

replaced with revised version Wed, 29 Aug 2007 17:45:47 GMT (267kb)

Title: Criterion for bosonic superfluidity in an optical lattice

Authors: Roberto B. Diener, Qi Zhou, Hui Zhai, and Tin-Lun Ho

Categories: cond-mat.other

Comments: 4 pages, 2 figures; published version

Journal-ref: Physical Review Letters, 98, 180404 (2007)

\\ ( http://arxiv.org/abs/cond-mat/0609685 , 267kb)

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arXiv:0704.1096

replaced with revised version Wed, 29 Aug 2007 03:50:02 GMT (34kb)

Title: Formation of sonic horizon in isotropically expanding Bose-Einstein

condensates

Authors: Yasunari Kurita, Takao Morinari

Categories: cond-mat.other gr-qc hep-th

Comments: 7 pages, 8 figures, section 3 extended, figures and references added

Report-no: YITP-07-16, OCU-PHYS-264, AP-GR-40

\\ ( http://arxiv.org/abs/0704.1096 , 34kb)

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arXiv:0704.2280 (*cross-listing*)

replaced with revised version Thu, 30 Aug 2007 07:40:41 GMT (201kb)

Title: Full-time dynamics of modulational instability in spinor Bose-Einstein

condensates

Authors: Evgeny V. Doktorov, Vassilis M. Rothos and Yuri S. Kivshar

Categories: nlin.SI cond-mat.other

Comments: 6 pages, 2 figures, text slightly extended, a reference added

Journal-ref: Physical Review A 76, 013626 (2007)

\\ ( http://arxiv.org/abs/0704.2280 , 201kb)

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Till next time,

Mat.

-- ========================================================================= Dr M. J. Davis, Senior Lecturer in Physics School of Physical Sciences, email: mdavis_at_physics.uq.edu.au University of Queensland, ph : +61 7 334 69824 Brisbane, QLD 4072, fax : +61 7 336 51242 Australia. http://www.physics.uq.edu.au/people/mdavis/ ========================================================================= Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/ ========================================================================= 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 Sep 14 2007 - 15:05:15 EST

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