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

Date: Thu, 14 Jan 2010 17:37:16 +1000

Date: Thu, 14 Jan 2010 17:37:16 +1000

Dear subscribers,

A happy new year to you all. It has been a fairly long absence, and there is a

fair bit of ground to catch up - we currently about three months behind. But we

haven't been entirely idle in the meantime: Chao Feng has authored a neat little

piece of software that allows the compilation of each weekly email to be sped up

by a factor of two. Over the next week or two I hope we will get back up to

speed, and we can start the new year as we intend to go on.

This week's selection was compiled by a Geoff Lee, and contains 16 new abstracts

and 5 replacements.

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arXiv:0910.0016 (*cross-listing*)

Date: Wed, 30 Sep 2009 20:13:03 GMT (1836kb)

Title: Long-distance entanglement in many-body atomic and optical systems

Authors: Salvatore M. Giampaolo, Fabrizio Illuminati

Categories: quant-ph cond-mat.other

Comments: 15 pages,

\\

We discuss the phenomenon of long-distance entanglement in the ground state

of quantum spin models, its use in high-fidelity and robust quantum

communication, and its realization in many-body systems of ultracold atoms in

optical lattices and in arrays of coupled optical cavities. We investigate

different patterns of site-dependent interaction couplings, singling out two

general settings: Patterns that allow for perfect long-distance entanglement

(LDE) in the ground state of the system, namely such that the end-to-end

entanglement remains finite in the thermodynamic limit, and patterns of quasi

long-distance entanglement (QLDE) in the ground state of the system, namely,

such such that the end-to-end entanglement vanishes with a very slow power-law

decay as the length of the spin chain is increased. We discuss physical

realizations of these models in ensembles of ultracold bosonic atoms loaded in

optical lattices. We show how, using either suitably engineered super-lattice

structures or exploiting the presence of edge impurities in lattices with

single periodicity, it is possible to realize models endowed with nonvanishing

LDE or QLDE. We then study how to realize models that optimize the robustness

of QLDE at finite temperature and in the presence of imperfections using

suitably engineered arrays of coupled optical cavities. We finally introduce

LDE-based schemes of long-distance quantum teleportation in linear arrays of

coupled cavities and show that they allow for high-fidelity and high success

rates even at moderately high temperatures.

\\ ( http://arxiv.org/abs/0910.0016 , 1836kb)

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arXiv:0910.0247

Date: Thu, 1 Oct 2009 20:00:09 GMT (75kb)

Title: Theory of Magnetic Field-Induce Bose-Einstein Condensation of Triplons

in Ba3Cr2O8

Authors: Tyler Dodds, Bohm-Jung Yang, and Yong Baek Kim

Categories: cond-mat.str-el

Comments: 10 pages, 13 figures

\\

Motivated by recent experiments on Ba$_{3}$Cr$_{2}$O$_8$, a new spin-dimer

compound with spin-1/2 moments of Cr$^{5+}$ ions, we theoretically investigate

the field-induced magnetic ordering in this material in view of the

Bose-Einstein condensation (BEC) of triplet excitations (triplons). We apply

the self-consistent Hartree-Fock-Popov (HFP) approach to a microscopic

Hamiltonian, using the realistic triplon dispersion measured in an inelastic

neutron scattering experiment. In particular, we ask to what extent the BEC of

dilute triplons near the critical field can explain the magnetic ordering in

this material. For example, we investigate the temperature range where the BEC

picture of triplons can be applied via the HFP approach. We also determine the

temperature regime where a quadratic approximation of the triplon dispersion

works. It is found that the strength of the effective repulsive interaction

between triplons is much weaker in Ba$_{3}$Cr$_{2}$O$_8$ than in the canonical

spin-dimer compound TlCuCl$_{3}$. Small effective repulsive interaction in

combination with the narrow band of triplons leads to higher density of

triplons $n_{cr}$ at the critical point. It turns out that the combined effect

points to a bigger HFP correction $U n_{cr}$ in Ba$_3$Cr$_2$O$_8$ than in

TlCuCl$_{3}$. Nonetheless, the HFP approach provides a reasonable explanation

of the transverse magnetization and the specific heat data of

Ba$_{3}$Cr$_{2}$O$_8$.

\\ ( http://arxiv.org/abs/0910.0247 , 75kb)

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arXiv:0910.0301

Date: Fri, 2 Oct 2009 05:05:15 GMT (265kb)

Title: Fast-forward of adiabatic dynamics in quantum mechanics

Authors: Shumpei Masuda and Katsuhiro Nakamura

Categories: cond-mat.mes-hall

\\

We propose a way to accelerate adiabatic dynamics of wave functions in

quantum mechanics to obtain a final adiabatic state except for the spatially

uniform phase in any desired short time. We develop the previous theory of

fast-forward (Masuda & Nakamura 2008) so as to derive a driving potential for

the fast-forward of the adiabatic dynamics. A typical example is the

fast-forward of adiabatic transport of a wave function which is the ideal

transport in the sense that a stationary wave function is transported to an

aimed position in any desired short time without leaving any disturbance at the

final time of the fast-forward. As other important examples we show accelerated

manipulations of wave functions such as their splitting and squeezing. The

theory is also applicable to macroscopic quantum mechanics described by the

nonlinear Schroedinger equation.

\\ ( http://arxiv.org/abs/0910.0301 , 265kb)

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arXiv:0910.0419

Date: Fri, 2 Oct 2009 15:14:49 GMT (14kb)

Title: Effects of disorder on quantum fluctuations and superfluid density of a

Bose-Einstein condensate in a two-dimensional optical lattice

Authors: Ying Hu, Zhaoxin Liang, and Bambi Hu

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

Comments: 8 pages, 0 figure. To appear in Physical Review A

\\

We investigate a Bose-Einstein condensate trapped in a 2D optical lattice in

the presence of weak disorder within the framework of the Bogoliubov theory. In

particular, we analyze the combined effects of disorder and an optical lattice

on quantum fluctuations and superfluid density of the BEC system. Accordingly,

the analytical expressions of the ground state energy and quantum depletion of

the system are obtained. Our results show that the lattice still induces a

characteristic 3D to 1D crossover in the behavior of quantum fluctuations,

despite the presence of weak disorder. Furthermore, we use the linear response

theory to calculate the normal fluid density of the condensate induced by

disorder. Our results in the 3D regime show that the combined presence of

disorder and lattice induce a normal fluid density that asymptotically

approaches 4/3 of the corresponding condensate depletion. Conditions for

possible experimental realization of our scenario are also proposed.

\\ ( http://arxiv.org/abs/0910.0419 , 14kb)

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arXiv:0910.0508

Date: Sat, 3 Oct 2009 08:54:11 GMT (356kb)

Title: D-wave bosonic pair in an optical lattice

Authors: Zi Cai, Lei Wang, Jian Li, Shu Chen, X. C. Xie, Yupeng Wang

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

Comments: 5 pages, 5 figures

\\

We present a bosonic model, in which two bosons may form a bound pair with

d-wave symmetry via the four-site ring exchange interaction. A d-wave pairing

superfluid as well as a d-wave density wave (DDW) state, are proposed to be

achievable in this system. This exotic bosonic system can be realized in the

BEC zone of a two-dimensional attractive p-band spinless fermionic system. By

the mean field approach, we find that at low densities, the d-wave pairs may

condensate, leading to a d-wave bosonic paired superfluid. At some particular

filling factors, a novel phase, d-wave density wave state, emerges. We study

this DDW state and its corresponding quantum phase transition in a two-leg

ladder by the time-evolving block decimation (TEBD) method.

\\ ( http://arxiv.org/abs/0910.0508 , 356kb)

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arXiv:0910.0564

Date: Mon, 5 Oct 2009 14:48:47 GMT (911kb)

Title: Adjustable microchip ring trap for cold atoms and molecules

Authors: Paul M. Baker, James A. Stickney, Matthew B. Squires, James A.

Scoville, Evan J. Carlson, Walter R. Buchwald, Steven M. Miller

Categories: physics.atom-ph

\\

We describe the design and function of a circular magnetic waveguide for

deBroglie waves produced from wires on a microchip. The guide is a

two-dimensional magnetic minimum for trapping weak-field seeking states of

atoms or molecules with a magnetic dipole moment. The design consists of seven

circular wires sharing a common radius. We describe the design, the

time-dependent currents of the wires and show that it is possible to form a

circular waveguide with adjustable height and gradient while minimizing

perturbation resulting from leads or wire crossings. This maximal area geometry

is suited for rotation sensing with atom interferometry via the Sagnac effect

using either cold atoms, molecules and Bose-condensed systems.

\\ ( http://arxiv.org/abs/0910.0564 , 911kb)

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arXiv:0910.0634

Date: Mon, 5 Oct 2009 17:26:24 GMT (403kb)

Title: Bose-Einstein Condensation of Strontium

Authors: Simon Stellmer, Meng Khoon Tey, Bo Huang, Rudolf Grimm, Florian

Schreck

Categories: cond-mat.quant-gas

Comments: 4 pages, 3 figures

\\

We report on the attainment of Bose-Einstein condensation (BEC) with

ultracold strontium atoms. We use the 84Sr isotope, which has a low natural

abundance but offers excellent scattering properties for evaporative cooling.

Based on the three efficient stages of accumulation in a metastable state using

a magnetic trap, narrow-line cooling, and straightforward evaporative cooling

in an optical trap, we obtain pure condensates containing 1.5x10^5 atoms. This

puts 84Sr in a prime position for future experiments on quantum-degenerate

gases of atomic two-electron systems.

\\ ( http://arxiv.org/abs/0910.0634 , 403kb)

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arXiv:0910.0648

Date: Sun, 4 Oct 2009 22:22:39 GMT (34kb)

Title: Finite-Temperature Properties of Attractive Three-Component Fermionic

Atoms in Optical Lattices

Authors: Kensuke Inaba and Sei-ichiro Suga

Categories: cond-mat.quant-gas cond-mat.supr-con

Comments: 4 pages, 4 figures

\\

We investigate the finite-temperature properties of attractive

three-component (colors) fermionic atoms in optical lattices using a

self-energy functional approach. As the strength of the attractive interaction

increases in the low-temperature region, we observe a second-order transition

from a Fermi liquid to a color superfluid (CSF), where atoms from two of the

three colors form Cooper pairs. In the strong attractive region, we observe a

first-order transition from a CSF to a trionic state, where three atoms with

different colors form singlet bound states. A crossover between a Fermi liquid

and a trionic state is observed in the high-temperature region. We present a

phase diagram covering zero to finite temperatures. We demonstrate that the CSF

transition temperature is enhanced by the anisotropy of the attractive

interaction.

\\ ( http://arxiv.org/abs/0910.0648 , 34kb)

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arXiv:0910.0720

Date: Mon, 5 Oct 2009 10:55:11 GMT (32kb)

Title: Ultracold atoms at unitarity within quantum Monte Carlo

Authors: Andrew J. Morris, P. Lopez Rios and R. J. Needs

Categories: cond-mat.quant-gas

\\

Variational and diffusion quantum Monte Carlo (VMC and DMC) calculations of

the properties of the zero-temperature fermionic gas at unitarity are reported.

The ratio of the energy of the interacting to the non-interacting gas for a

system of 128 particles is calculated to be 0.4517(3) in VMC and 0.4339(1) in

the more accurate DMC method. The spherically-averaged pair-correlation

functions, momentum densities, and one-body density matrices are very similar

in VMC and DMC, but the two-body density matrices and condensate fractions show

some differences. Our best estimate of the condensate fraction of 0.51 is a

little smaller than values from other quantum Monte Carlo calculations.

\\ ( http://arxiv.org/abs/0910.0720 , 32kb)

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arXiv:0910.0788 (*cross-listing*)

Date: Mon, 5 Oct 2009 15:18:00 GMT (2015kb)

Title: Macroscopic entanglement between a Bose Einstein condensate and a

superconducting loop

Authors: Mandip Singh

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

Comments: 11 pages, 5 figures

Journal-ref: Optics Express, Vol. 17, Issue 4, pp. 2600-2610 (2009)

DOI: 10.1364/OE.17.002600

\\

We theoretically study macroscopic entanglement between a magnetically

trapped Bose-Einstein condensate and a superconducting loop. We treat the

superconducting loop in a quantum superposition of two different flux states

coupling with the magnetic trap to generate macroscopic entanglement. The

scheme also provides a platform to investigate interferometry with an entangled

Bose Einstein condensate and to explore physics at the quantum-classical

interface.

\\ ( http://arxiv.org/abs/0910.0788 , 2015kb)

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arXiv:0910.0953

Date: Tue, 6 Oct 2009 09:21:32 GMT (2598kb)

Title: Dynamics of reflection of ultracold atoms from a periodic 1D magnetic

lattice potential

Authors: Mandip Singh, Russell McLean, Andrei Sidorov and Peter Hannaford

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

Comments: 15 pages, 11 figures

Journal-ref: Phys. Rev. A 79, 053407 (2009)

DOI: 10.1103/PhysRevA.79.053407

\\

We report on an experimental study of the dynamics of the reflection of

ultracold atoms from a periodic one-dimensional magnetic lattice potential. The

magnetic lattice potential of period 10 \textmu m is generated by applying a

uniform bias magnetic field to a microfabricated periodic structure on a

silicon wafer coated with a multilayered TbGdFeCo/Cr magneto-optical film. The

effective thickness of the magnetic film is about 960 nm. A detailed study of

the profile of the reflected atoms as a function of externally induced periodic

corrugation in the potential is described. The effect of angle of incidence is

investigated in detail. The experimental observations are supported by

numerical simulations.

\\ ( http://arxiv.org/abs/0910.0953 , 2598kb)

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arXiv:0910.1037

Date: Tue, 6 Oct 2009 15:44:42 GMT (2184kb)

Title: Cold and Ultracold Rydberg Atoms in Strong Magnetic Fields

Authors: T. Pohl, H. R. Sadeghpour, and P. Schmelcher

Categories: physics.atom-ph

Comments: 46 pages, 38 figures, to appear in Physics Reports

\\

Cold Rydberg atoms exposed to strong magnetic fields possess unique

properties which open the pathway for an intriguing many-body dynamics taking

place in Rydberg gases consisting of either matter or anti-matter systems. We

review both the foundations and recent developments of the field in the cold

and ultracold regime where trapping and cooling of Rydberg atoms have become

possible. Exotic states of moving Rydberg atoms such as giant dipole states are

discussed in detail, including their formation mechanisms in a strongly

magnetized cold plasma. Inhomogeneous field configurations influence the

electronic structure of Rydberg atoms, and we describe the utility of

corresponding effects for achieving tightly trapped ultracold Rydberg atoms. We

review recent work on large, extended cold Rydberg gases in magnetic fields and

their formation in strongly magnetized ultracold plasmas through collisional

recombination. Implications of these results for current antihydrogen

production experiments are pointed out, and techniques for trapping and cooling

of such atoms are investigated.

\\ ( http://arxiv.org/abs/0910.1037 , 2184kb)

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arXiv:0910.1073

Date: Tue, 6 Oct 2009 18:58:20 GMT (156kb)

Title: Radiative lifetime measurements of rubidium Rydberg states

Authors: Drew B. Branden, Tamas Juhasz, Tatenda Mahlokozera, Cristian Vesa, Roy

O. Wilson, Mao Zheng, Andrew Kortyna and Duncan A. Tate

Categories: physics.atom-ph

Comments: 6 figures

\\

We have measured the radiative lifetimes of ns, np and nd Rydberg states of

rubidium in the range 28 < n < 45. To enable long-lived states to be measured,

our experiment uses slow-moving Rb atoms in a magneto-optical trap (MOT). Two

experimental techniques have been adopted to reduce random and systematic

errors. First, a narrow-bandwidth pulsed laser is used to excite the target

Rydberg state, resulting in minimal shot-to-shot variation in the initial state

population. Second, we monitor the target state population as a function of

time delay from the laser pulse using a short-duration, millimetre-wave pulse

that is resonant with a one- or two-photon transition. We then selectively

field ionize the monitor state, and detect the resulting electrons with a

micro-channel plate. This signal is an accurate mirror of the target state

population, and is uncontaminated by contributions from other states which are

populated by black body radiation. Our results are generally consistent with

other recent experimental results obtained using a less sensitive method, and

are also in excellent agreement with theory.

\\ ( http://arxiv.org/abs/0910.1073 , 156kb)

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arXiv:0910.1382

Date: Thu, 8 Oct 2009 11:24:40 GMT (196kb)

Title: Cooling and Near-equilibrium Dynamics of Atomic Gases Across the

Superfluid-Mott Insulator Transition

Authors: Chen-Lung Hung, Xibo Zhang, Nathan Gemelke, Cheng Chin

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

\\

We study near-equilibrium thermodynamics of bosonic atoms in a

two-dimensional optical lattice by ramping up the lattice depth to convert a

superfluid into an inhomogeneous mixture of superfluid and Mott insulator.

Detailed study of in situ density profiles shows that, first, locally adiabatic

ramps do not guarantee global thermal equilibrium. Indeed, full thermalization

for typical parameters only occurs for experiment times which exceed one

second. Secondly, ramping non-adiabatically to the Mott insulator regime can

result in strong localized cooling at short times and global cooling once

equilibrated. For an initial temperature estimated as 20 nK, we observe local

temperatures as low as 1.5 nK, and a final global temperature of 9 nK. Possible

cooling mechanisms include adiabatic decompression, modification of the density

of states near the quantum critical regime, and the Joule-Thomson effect.

\\ ( http://arxiv.org/abs/0910.1382 , 196kb)

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arXiv:0910.1440

Date: Thu, 8 Oct 2009 08:25:28 GMT (683kb)

Title: Rayleigh-Taylor instability and mushroom-pattern formation in a

two-component Bose-Einstein condensate

Authors: Kazuki Sasaki, Naoya Suzuki, Daisuke Akamatsu, Hiroki Saito

Categories: cond-mat.quant-gas

Comments: 5 pages, 4 figures

\\

The Rayleigh-Taylor instability at the interface in an immiscible

two-component Bose-Einstein condensate is investigated using the mean-field and

Bogoliubov theories. Rayleigh-Taylor fingers are found to grow from the

interface and mushroom patterns are formed. Quantized vortex rings and vortex

lines are then generated around the mushrooms. The Rayleigh-Taylor instability

and mushroom-pattern formation can be observed in a trapped system.

\\ ( http://arxiv.org/abs/0910.1440 , 683kb)

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arXiv:0910.1518

Date: Thu, 8 Oct 2009 15:48:43 GMT (304kb)

Title: Quantum fluctuations and condensate fraction during the time-of-flight

expansion

Authors: Shiang Fang, Ray-Kuang Lee, and Daw-Wei Wang

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

Comments: 4 pages and 3 figures

\\

The quantum fluctuation effects in the time-of-flight (TOF) experiment for a

condensate released from a one-dimensional optical lattice potential is studied

within the truncated Wigner approximation. By investigating both the spatial

and momentum density distributions, we find that the condensate fraction

decreases as an algebraic function of time and hence cannot be measured in the

standard TOF image due to the interaction effect. We then suggest a scheme to

measure the true condensate fraction during the expansion and estimate its

value inside the optical lattice (before expansion), taking into account both

the finite time and finite interaction effects. Implication to the condensate

expansion in higher dimensional systems is also discussed.

\\ ( http://arxiv.org/abs/0910.1518 , 304kb)

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The replacements:

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arXiv:0905.3634

replaced with revised version Fri, 2 Oct 2009 15:32:15 GMT (400kb)

Title: Black-hole radiation in Bose-Einstein condensates

Authors: Jean Macher and Renaud Parentani

Categories: cond-mat.quant-gas gr-qc

Comments: revTeX 4, 55 pages single-column, 19 figures; v2: figure and refs

added, typos corrected; v3: twocolumn, refs added/updated, new results,

presentation clarified; v4: usefulness of white holes emphasized

\\ ( http://arxiv.org/abs/0905.3634 , 400kb)

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arXiv:0908.4336

replaced with revised version Sat, 3 Oct 2009 17:39:39 GMT (159kb)

Title: Rayleigh-Taylor instability of binary condensates

Authors: S. Gautam and D. Angom

Categories: cond-mat.quant-gas

Comments: 4 pages, 4figures, Extensive modifications including additional

figure and equations

\\ ( http://arxiv.org/abs/0908.4336 , 159kb)

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arXiv:0909.0489

replaced with revised version Fri, 2 Oct 2009 08:37:56 GMT (1515kb)

Title: Spin-dependent inelastic collisions in spin-2 Bose-Einstein condensates

Authors: Satoshi Tojo, Taro Hayashi, Tatsuyoshi Tanabe, Takuya Hirano, Yuki

Kawaguchi, Hiroki Saito, and Masahito Ueda

Categories: cond-mat.quant-gas

Comments: 7 pages, 5 figures

\\ ( http://arxiv.org/abs/0909.0489 , 1515kb)

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arXiv:0909.4072

replaced with revised version Mon, 5 Oct 2009 15:38:54 GMT (2369kb)

Title: Vortex Synchronization in Bose-Einstein Condensates: A Time-Dependent

Gross-Pitaevskii Equation Approach

Authors: Ryan Barnett, Edward Chen, and Gil Refael

Categories: cond-mat.quant-gas

Comments: 6.1 pages, 3 figures

\\ ( http://arxiv.org/abs/0909.4072 , 2369kb)

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arXiv:0910.0182

replaced with revised version Mon, 5 Oct 2009 20:17:59 GMT (28kb,D)

Title: A scalable Bose-Einstein condensate Sagnac interferometer in a linear

trap

Authors: J. H. T. Burke and C. A. Sackett

Categories: cond-mat.quant-gas

Comments: 4 pages, 2 figures. Added references

\\ ( http://arxiv.org/abs/0910.0182 , 28kb)

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Till next time,

Matt.

-- ========================================================================= Dr M. J. Davis, Associate Professor in Physics School of Mathematics and Physics, ph : +61 7 334 69824 The University of Queensland, fax : +61 7 336 51242 Brisbane, QLD 4072, mdavis_at_physics.uq.edu.au Australia. www.physics.uq.edu.au/people/mdavis/ ========================================================================= Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland ========================================================================= _______________________________________________ Matts-arxiv mailing list Matts-arxiv_at_lists.sps.uq.edu.auReceived on Thu Jan 14 2010 - 17:56:43 EST

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