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

Date: Thu, 16 Oct 2008 10:01:30 +1000

Date: Thu, 16 Oct 2008 10:01:30 +1000

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

Hi everyone,

I'm off to the CASTU cold atom meeting in Beijing next week - I look forward to

seeing some of the subscribers to this list there, please come and say hello!

It was one of the quietest weeks I've seen for a while - this week there were 14

new preprints and 10 replacements.

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arXiv:0810.0600

Date: Fri, 3 Oct 2008 09:38:53 GMT (2437kb,D)

Title: Squeezing and entanglement in a Bose-Einstein condensate

Authors: J. Esteve, C. Gross, A. Weller, S. Giovanazzi, M.K. Oberthaler

(Kirchhoff Institut f\"ur Physik, Heidelberg, Germany)

Categories: cond-mat.other

DOI: 10.1038/nature07332

\\

Entanglement, a key feature of quantum mechanics, is a resource that allows

the improvement of precision measurements beyond the conventional bound

reachable by classical means. This is known as the standard quantum limit,

already defining the accuracy of the best available sensors for various

quantities such as time or position. Many of these sensors are interferometers

in which the standard quantum limit can be overcome by feeding their two input

ports with quantum-entangled states, in particular spin squeezed states. For

atomic interferometers, Bose-Einstein condensates of ultracold atoms are

considered good candidates to provide such states involving a large number of

particles. In this letter, we demonstrate their experimental realization by

splitting a condensate in a few parts using a lattice potential. Site resolved

detection of the atoms allows the measurement of the conjugated variables atom

number difference and relative phase. The observed fluctuations imply

entanglement between the particles, a resource that would allow a precision

gain of 3.8 dB over the standard quantum limit for interferometric

measurements.

\\ ( http://arxiv.org/abs/0810.0600 , 2437kb)

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arXiv:0810.0643

Date: Fri, 3 Oct 2008 14:10:56 GMT (28kb)

Title: Bose-Hubbard phase diagram with arbitrary filling

Authors: Niklas Teichmann, Dennis Hinrichs, Martin Holthaus, and Andre Eckardt

Categories: cond-mat.other

Comments: 4 pages, 4 figures

\\

We study the transition from a Mott insulator to a superfluid in both the

two- and the three-dimensional Bose-Hubbard model at zero temperature,

employing the method of the effective potential. Converting Kato's perturbation

series into an efficient numerical algorithm capable of reaching high orders,

we obtain accurate critical parameters for any filling factor. Our technique

allows us to monitor both the approach to the mean-field limit by considering

spatial dimensionalities $d > 3$, and to the quantum rotor limit of high

filling, which refers to an array of Josephson junctions.

\\ ( http://arxiv.org/abs/0810.0643 , 28kb)

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arXiv:0810.0686

Date: Fri, 3 Oct 2008 17:12:01 GMT (1465kb,D)

Title: Stability of a Bose-Einstein condensate revisited for composite bosons

Authors: M. Combescot and D.W. Snoke

Categories: cond-mat.other

\\

It is known that elementary bosons condense in a unique state, not so much

because this state has the lowest free particle energy but because it costs a

macroscopic amount of energy to put the particles into different states which

can then interact through quantum particle exchanges. Since individual

exchanges between the two fermions of a composite boson are ignored when

composite particles are replaced by elementary bosons, it is of importance to

reconsider the exchange energy argument for the stability of the Bose-Einstein

condensate in the case of composite bosons. We do this here in the light of the

new many-body theory which allows us to take exactly into account all possible

exchanges between the fermionic components of the composite bosons. We confirm

that the condensate of composite bosons is made of a unique state, this state

being moreover pure: a coherent superposition of states close in energy is

shown to be less favorable for both elementary and composite bosons.

\\ ( http://arxiv.org/abs/0810.0686 , 1465kb)

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arXiv:0810.0400 (*cross-listing*)

Date: Thu, 2 Oct 2008 12:15:51 GMT (96kb)

Title: Strongly interacting Fermi systems in 1/N expansion: From cold atoms to

color superconductivity

Authors: Hiroaki Abuki and Tomas Brauner

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

Comments: 13 pages, REVTeX4, 11 eps figures

\\

We investigate the 1/N expansion proposed recently as a strategy to include

quantum fluctuation effects in the nonrelativistic, attractive Fermi gas at and

near unitarity. We extend the previous results by calculating the

next-to-leading order corrections to the critical temperature along the whole

BCS-BEC crossover. We demonstrate explicitly that the extrapolation from the

mean-field approximation, based on the $1/N$ expansion, provides a useful

approximation scheme only on the BCS side of the crossover. We then apply the

technique to the study of strongly interacting relativistic many-fermion

systems. Having in mind the application to color superconductivity in cold

dense quark matter, we develop, within a simple model, a formalism suitable to

compare the effects of order parameter fluctuations in phases with different

pairing patterns. Our main conclusion is that the relative correction to the

critical temperature is to a good accuracy proportional to the mean-field ratio

of the critical temperature and the chemical potential. As a consequence, it is

significant even rather deep in the BCS regime, where phenomenologically

interesting values of the quark-quark coupling are expected. Possible impact on

the phase diagram of color-superconducting quark matter is discussed.

\\ ( http://arxiv.org/abs/0810.0400 , 96kb)

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arXiv:0810.0859

Date: Sun, 5 Oct 2008 21:35:39 GMT (565kb)

Title: Spontaneous symmetry breaking in a nonlinear double-well structure

Authors: Thawatchai Mayteevarunyoo (Department of Telecommunication

Engineering, Mahanakorn University of Technology, Bangkok, Thailand), Boris

A. Malomed (Department of Physical Electronics, School of Electrical

Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv, Israel),

and Guangjiong Dong (State Key Laboratory of Precision Spectroscopy and

Physics Department, East China Normal University, Shanghai, China)

Categories: cond-mat.other

Comments: submitted to Physical Review A

\\

We propose a model of a nonlinear double-well potential (NDWP), alias a

double-well pseudopotential, with the objective to study an alternative

implementation of the spontaneous symmetry breaking (SSB) in Bose-Einstein

condensates (BECs) and optical media, under the action of a potential with two

symmetric minima. In the limit case when the NDWP structure is induced by the

local nonlinearity coefficient represented by a set of two delta-functions, a

fully analytical solution is obtained for symmetric, antisymmetric and

asymmetric states. In this solvable model, the SSB bifurcation has a fully

subcritical character. Numerical analysis, based on both direct simulations and

computation of stability eigenvalues, demonstrates that, while the symmetric

states are stable up to the SSB bifurcation point, both symmetric and emerging

asymmetric states, as well as all antisymmetric ones, are unstable in the model

with the delta-functions. In the general model with a finite width of the

nonlinear-potential wells, the asymmetric states quickly become stable,

simultaneously with the switch of the SSB bifurcation from the subcritical to

supercritical type. Antisymmetric solutions may also get stabilized in the NDWP

structure of the general type, which gives rise to a bistability between them

and asymmetric states. The symmetric states require a finite norm for their

existence, an explanation to which is given. A full diagram for the existence

and stability of the trapped states in the model is produced. Experimental

observation of the predicted effects should be possible in BEC formed by

several hundred atoms.

\\ ( http://arxiv.org/abs/0810.0859 , 565kb)

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arXiv:0810.0900

Date: Mon, 6 Oct 2008 07:22:35 GMT (61kb)

Title: Supersolid Order of Frustrated Hard-Core Bosons in a Triangular Lattice

System

Authors: H. C. Jiang, M. Q. Weng, Z. Y. Weng, D. N. Sheng, and L. Balents

Categories: cond-mat.str-el

Comments: 4 pages, 4 figures

\\

We numerically demonstrate that a supersolid phase exists in a frustrated

hard-core boson system on a triangular lattice over a wide range of interaction

strength. In the infinite repulsion (Ising) limit, we establish a mapping to

the same problem with unfrustrated hopping, which connects the supersolid to

the known results in that case. The weak superfluidity can be destroyed or

strongly enhanced by a next nearest neighbor hopping term, which provides

valuable information for experimental realization of a supersolid phase on

optical lattice.

\\ ( http://arxiv.org/abs/0810.0900 , 61kb)

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arXiv:0810.1306

Date: Tue, 7 Oct 2008 22:58:53 GMT (548kb)

Title: Ultracold Heteronuclear Fermi-Fermi Molecules

Authors: A.-C. Voigt, M. Taglieber, L. Costa, T. Aoki, W. Wieser, T.W. H\"ansch

and K. Dieckmann

Categories: cond-mat.other

Comments: 5 figures

\\

We report on the first creation of ultracold bosonic heteronuclear molecules

of two fermionic species, 6Li and 40K, by a magnetic field sweep across an

interspecies s-wave Feshbach resonance. This allows us to associate up to

4x10^4 molecules with high efficiencies of up to 50%. Using direct imaging of

the molecules, we measure increased lifetimes of the molecules close to

resonance of more than 100 ms in the molecule-atom mixture stored in a harmonic

trap.

\\ ( http://arxiv.org/abs/0810.1306 , 548kb)

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arXiv:0810.1321

Date: Wed, 8 Oct 2008 16:05:53 GMT (562kb)

Title: Induced p-wave superfluidity in two dimensions: Brane world in cold

atoms and nonrelativistic defect CFTs

Authors: Yusuke Nishida

Categories: cond-mat.other

Comments: 22 pages, 10 figures

Report-no: INT-PUB 08-46, MIT-CTP 3984

\\

We propose to use a two-species Fermi gas with the interspecies s-wave

Feshbach resonance to realize p-wave superfluidity in two dimensions. By

confining one species of fermions in a two-dimensional plane immersed in the

background three-dimensional Fermi sea of the other species, an attractive

interaction is induced between two-dimensional fermions. We compute the pairing

gap in the weak-coupling regime and show that it has the symmetry of p_x+ip_y.

Because the magnitude of the pairing gap increases toward the unitarity limit,

it is possible that the critical temperature for the p_x+ip_y-wave

superfluidity becomes within experimental reach. The resulting system has a

potential application to topological quantum computation using vortices with

non-Abelian statistics. We also discuss aspects of our system in the unitarity

limit as a "nonrelativistic defect conformal field theory (CFT)". The reduced

Schr\"odinger algebra, operator-state correspondence, scaling dimensions of

composite operators, and operator product expansions are investigated.

\\ ( http://arxiv.org/abs/0810.1321 , 562kb)

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arXiv:0810.1347

Date: Wed, 8 Oct 2008 02:54:51 GMT (141kb)

Title: Quantum fluctuations in trapped time-dependent Bose-Einstein condensates

Authors: Michael Uhlmann

Categories: cond-mat.other

\\

Quantum fluctuations in time-dependent, harmonically-trapped Bose-Einstein

condensates are studied within Bogoliubov theory. An eigenmode expansion of the

linear field operators permits the diagonalization of the Bogoliubov-de Gennes

equation for a stationary condensate. When trap frequency or interaction

strength are varied, the inhomogeneity of the background gives rise to

off-diagonal coupling terms between different modes. This coupling is

negligible for low energies, i.e., in the hydrodynamic regime, and an effective

space-time metric can be introduced. The influence of the inter-mode coupling

will be demonstrated in an example, where I calculate the quasi-particle number

for a quasi-one-dimensional Bose-Einstein condensate subject to an exponential

sweep of interaction strength and trap frequency.

\\ ( http://arxiv.org/abs/0810.1347 , 141kb)

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arXiv:0810.1555

Date: Wed, 8 Oct 2008 23:59:03 GMT (1178kb)

Title: Noise Correlations in low-dimensional systems of ultracold atoms

Authors: L. Mathey, A. Vishwanath, and E. Altman

Categories: cond-mat.other

Comments: 14 pages, 7 figures

\\

We derive relations between standard order parameter correlations and the

noise correlations in time of flight images, which are valid for systems with

long range order as well as low dimensional systems with algebraic decay of

correlations. Both Bosonic and Fermionic systems are considered. For one

dimensional Fermi systems we show that the noise correlations are equally

sensitive to spin, charge and pairing correlations and may be used to

distinguish between fluctuations in the different channels. This is in contrast

to linear response experiments, such as Bragg spectroscopy, which are only

sensitive to fluctuations in the particle-hole channel (spin or charge). For

Bosonic systems we find a sharp peak in the noise correlation at opposite

momenta that signals pairing correlations in the depletion cloud. In a

condensate with true long range order, this peak is a delta function and we can

use Bogoliubov theory to study its temperature dependence. Interestingly we

find that it is enhanced with temperature in the low temperature limit. In one

dimensional condensates with only quasi-long range (i.e. power-law) order the

peak in the noise correlations also broadens to a power-law singularity.

\\ ( http://arxiv.org/abs/0810.1555 , 1178kb)

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arXiv:0810.1593

Date: Thu, 9 Oct 2008 07:54:04 GMT (401kb)

Title: Nonlinear Ramsey interferometry with the Rosen-Zener pulses on a

two-component Bose-Einstein condensate

Authors: Sheng-Chang Li, Li-Bin Fu, Wen-Shan Duan, Jie Liu

Categories: cond-mat.other

Comments: 8 pages, 9 figures

\\

We propose a feasible scheme to realize nonlinear Ramsey interferometry with

a two-component Bose-Einstein condensate, where the nonlinearity arises from

the interaction between coherent atoms. In our scheme, two Rosen-Zener pulses

are separated by an intermediate holding period of variable duration and

through varying the holding period we have observed nice Ramsey interference

patterns in time domain. In contrast to the standard Ramsey fringes our

nonlinear Ramsey patterns display diversiform structures ascribed to the

interplay of the nonlinearity and asymmetry. In particular, we find that the

frequency of the nonlinear Ramsey fringes exactly reflects the strength of

nonlinearity as well as the asymmetry of system. Our finding suggests a

potential application of the nonlinear Ramsey interferometry in calibrating the

atomic parameters such as scattering length and energy spectrum.

\\ ( http://arxiv.org/abs/0810.1593 , 401kb)

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arXiv:0810.1665

Date: Thu, 9 Oct 2008 14:45:40 GMT (1454kb)

Title: Dipole oscillations of confined lattice bosons in one dimension

Authors: Simone Montangero, Rosario Fazio, Peter Zoller, Guido Pupillo

Categories: cond-mat.other

Comments: 4 pages, 3 figures

\\

We study the dynamics of a non-integrable system comprising interacting cold

bosons trapped in an optical lattice in one-dimension by means of exact

time-dependent numerical DMRG techniques. Particles are confined by a parabolic

potential, and dipole oscillations are induced by displacing the trap center of

a few lattice sites. Depending on the system parameters this motion can vary

from undamped to overdamped. We study the dipole oscillations as a function of

the lattice displacement, the particle density and the strength of

interparticle interactions. These results explain the recent experiment C.D.

Fertig et al., Phys. Rev. Lett. 94, 120403 (2005).

\\ ( http://arxiv.org/abs/0810.1665 , 1454kb)

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arXiv:0810.1704

Date: Thu, 9 Oct 2008 17:47:36 GMT (76kb)

Title: DC and AC Josephson effects with superfluid Fermi atoms across a

Feshbach resonance

Authors: L. Salasnich, F. Ancilotto, N. Manini, and F. Toigo

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

Comments: 8 pages, 4 figures, presented at the Scientific Seminar on Physics of

Cold Trapped Atoms, 17th International Laser Physics Workshop (Trondheim,

June 30 - July 4, 2008)

\\

We show that both DC and AC Josephson effects with superfluid Fermi atoms in

the BCS-BEC crossover can be described at zero temperature by a nonlinear

Schrodinger equation (NLSE). By comparing our NLSE with mean-field extended BCS

calculations, we find that the NLSE is reliable in the BEC side of the

crossover up to the unitarity limit. The NLSE can be used for weakly-linked

atomic superfluids also in the BCS side of the crossover by taking the

tunneling energy as a phenomenological parameter.

\\ ( http://arxiv.org/abs/0810.1704 , 76kb)

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arXiv:0810.1720

Date: Thu, 9 Oct 2008 18:59:30 GMT (68kb)

Title: Momentum-space interferometry with trapped ultracold atoms

Authors: A. Ruschhaupt, A. del Campo, J. G. Muga

Categories: quant-ph

Comments: 8 pages

\\

Quantum interferometers are generally set so that phase differences between

paths in coordinate space combine constructive or destructively. Indeed, the

interfering paths can also meet in momentum space leading to momentum-space

fringes. We propose and analyze a method to produce interference in momentum

space by phase-imprinting part of a trapped atomic cloud with a detuned laser.

For one-particle wave functions analytical expressions are found for the fringe

width and shift versus the phase imprinted. The effects of unsharpness or

displacement of the phase jump are also studied, as well as many-body effects

to determine the potential applicability of momentum-space interferometry.

\\ ( http://arxiv.org/abs/0810.1720 , 68kb)

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The replacements:

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arXiv:0804.4003

replaced with revised version Thu, 2 Oct 2008 21:25:37 GMT (25kb)

Title: Adiabatic nonlinear probes of one-dimensional Bose gases

Authors: C. De Grandi, R. A. Barankov, A. Polkovnikov

Categories: cond-mat.other

Comments: 4+ pages, 4 figures, revised version

\\ ( http://arxiv.org/abs/0804.4003 , 25kb)

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arXiv:0809.1468

replaced with revised version Fri, 3 Oct 2008 09:10:10 GMT (0kb,I)

Title: Bose-Einstein condensation in an optical lattice: A perturbation

approach

Authors: C. Trallero-Giner, V. Lopez-Richard, Ming-Chiang Chung, Andreas

Buchleitner

Categories: cond-mat.other

Comments: the paper has been withdrawn

\\ ( http://arxiv.org/abs/0809.1468 , 0kb)

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arXiv:0801.0635

replaced with revised version Sun, 5 Oct 2008 19:42:05 GMT (215kb)

Title: Phase separation and collapse in Bose-Fermi mixtures with a Feshbach

resonance

Authors: F. M. Marchetti, C. Mathy, M. M. Parish, D. A. Huse

Categories: cond-mat.other

Comments: 7 pages, 3 figures. Extended version

\\ ( http://arxiv.org/abs/0801.0635 , 215kb)

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arXiv:0807.2954

replaced with revised version Sat, 4 Oct 2008 15:26:37 GMT (2757kb)

Title: Long-range correlations of density in a Bose-Einstein condensate

expanding in a random potential

Authors: N. Cherroret, S.E. Skipetrov

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

Comments: 4 pages, 5 figures

\\ ( http://arxiv.org/abs/0807.2954 , 2757kb)

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arXiv:0808.0120

replaced with revised version Mon, 6 Oct 2008 14:11:35 GMT (398kb,D)

Title: Scattering and binding of different atomic species in a one-dimensional

optical lattice

Authors: R. T. Piil, N. Nygaard, and K. Molmer

Categories: cond-mat.other

Comments: 5 pages, 4 figures

Journal-ref: Phys. Rev. A 78, 033611 (2008)

\\ ( http://arxiv.org/abs/0808.0120 , 398kb)

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arXiv:0806.2862

replaced with revised version Tue, 7 Oct 2008 12:57:26 GMT (24kb)

Title: Microscopic diagonal entropy and its connection to basic thermodynamic

relations

Authors: Roman Barankov and Anatoli Polkovnikov

Categories: cond-mat.stat-mech hep-th quant-ph

Comments: minor revisions, 4. pages 2 figures. Added numerical example and

discussion of ergodicity

\\ ( http://arxiv.org/abs/0806.2862 , 24kb)

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arXiv:0808.4147

replaced with revised version Tue, 7 Oct 2008 01:15:12 GMT (732kb,D)

Title: Heteronuclear quantum gas mixtures

Authors: C. Ospelkaus, S. Ospelkaus

Categories: cond-mat.other cond-mat.stat-mech physics.atom-ph

Comments: 72 pages, updated to published version

Journal-ref: J. Phys. B: At. Mol. Opt. Phys. 41, 203001 (2008)

DOI: 10.1088/0953-4075/41/20/203001

\\ ( http://arxiv.org/abs/0808.4147 , 732kb)

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arXiv:cond-mat/0702462

replaced with revised version Wed, 8 Oct 2008 15:44:06 GMT (50kb)

Title: Efimov states near a Feshbach resonance

Authors: P. Massignan and H. T. C. Stoof

Categories: cond-mat.other

Comments: Version accepted for publication: minor revisions concerning the

comparison with the cesium experiment

Journal-ref: Phys. Rev. A 78, 030701(R) (2008)

DOI: 10.1103/PhysRevA.78.030701

\\ ( http://arxiv.org/abs/cond-mat/0702462 , 50kb)

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arXiv:0805.4198

replaced with revised version Thu, 9 Oct 2008 16:11:46 GMT (40kb)

Title: Realizing the strongly correlated $d$-Mott state in a fermionic cold

atom optical lattice

Authors: Michael R. Peterson, Chuanwei Zhang, Sumanta Tewari, S. Das Sarma

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

Comments: 4 pages, 5 figures

Journal-ref: Phys. Rev. Lett. 101, 150406 (2008) v2 is final version

\\ ( http://arxiv.org/abs/0805.4198 , 40kb)

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arXiv:0803.4069

replaced with revised version Thu, 9 Oct 2008 08:14:25 GMT (535kb,D)

Title: Engineering the quantum transport of atomic wavefunctions over

macroscopic distances

Authors: A. Alberti, V. V. Ivanov, G. M. Tino and G. Ferrari

Categories: quant-ph

Comments: 5 pages, 5 figures

\\ ( http://arxiv.org/abs/0803.4069 , 535kb)

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Till next time,

Matt.

-- ========================================================================= Dr M. J. Davis, Senior Lecturer in Physics School of Physical Sciences, email: mdavis_at_physics.uq.edu.au University of Queensland, ph : +61 7 334 69824 Brisbane, QLD 4072, fax : +61 7 336 51242 Australia. http://www.physics.uq.edu.au/people/mdavis/ ========================================================================= Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/ ========================================================================= 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 Wed Oct 29 2008 - 09:15:09 EST

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