# [Matts-arxiv] Matt's arXiv selection: week ending 5 June 2009

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Fri, 10 Jul 2009 14:37:39 +1000

Dear subscribers,

This week Simon Haine compiled the list of abstracts. There are 14 new
preprints and 10 replacements:

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arXiv:0905.4750
Date: Thu, 28 May 2009 21:09:05 GMT (301kb)

Title: Transport of ultracold Bose gases beyond the Gross-Pitaevskii
description
Authors: Thomas Ernst, Tobias Paul, and Peter Schlagheck
Categories: cond-mat.quant-gas
\\
We explore atom-laser-like transport processes of ultracold Bose-condensed
atomic vapors in mesoscopic waveguide structures beyond the Gross-Pitaevskii
mean-field theory. Based on a microscopic description of the transport process
in the presence of a coherent source which models the outcoupling from a
reservoir of perfectly Bose-Einstein condensed atoms, we derive a system of
coupled quantum evolution equations that describe the dynamics of a dilute
condensed Bose gas in the framework of the Hartree-Fock-Bogoliubov
approximation. We apply this method to study the transport of dilute Bose gases
through an atomic quantum dot and through waveguides with disorder. Our
numerical simulations reveal that the onset of an explictly time-dependent flow
corresponds to the appearance of strong depletion of the condensate on the
microscopic level and leads to a loss of global phase coherence.
\\ ( http://arxiv.org/abs/0905.4750 , 301kb)
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arXiv:0905.4783
Date: Fri, 29 May 2009 04:21:41 GMT (107kb)

Title: Critical temperature of a Bose gas in an optical lattice
Authors: D. Baillie and P. B. Blakie
Categories: cond-mat.quant-gas
\\
We present a theory for the critical temperature of a Bose gas in a combined
harmonic lattice potential based on a mean-field description of the system. We
develop practical expressions for the ideal-gas critical temperature, and
corrections due to interactions, the finite-size effect, and the occupation of
excited bands. We compare our expressions to numerical calculations and find
excellent agreement over a wide parameter regime.
\\ ( http://arxiv.org/abs/0905.4783 , 107kb)
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arXiv:0905.4817
Date: Fri, 29 May 2009 10:04:24 GMT (24kb)

Title: High-field instability of low-temperature magnon Bose-Einstein
condensate
Authors: Abdulla Rakhimov, E. Ya. Sherman and Chul Koo Kim
Categories: cond-mat.quant-gas cond-mat.stat-mech
Comments: 13 pages, 4 figures, Revtex
\\
We study the instability of the low-temperature Bose-Einstein condensation
(BEC) of magnons in magnetic dielectrics as a function of the temperature and
external magnetic field within the Hartree-Fock-Bogoliubov approach including
the anomalous density. We show that magnetization is continuous across the
transition, in agreement with the experiment. In sufficiently high fields the
condensate becomes unstable due to the magnon-magnon repulsion. As a result,
the system is characterized by two critical magnetic fields: one producing the
condensate and the other destroying it. We show that nonparabolic magnon
dispersion arising due to the gapped bare spectrum and the crystal structure
has the crucial influence on the magnon BEC phase diagram, making the stability
region smaller than it would be expected for the parabolic dispersion.
\\ ( http://arxiv.org/abs/0905.4817 , 24kb)
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arXiv:0905.4833
Date: Fri, 29 May 2009 11:29:35 GMT (52kb)

Title: Quantum quenches in the Dicke model: statistics of the work done and of
other observables
Authors: Francis N.C. Paraan, Alessandro Silva
Categories: cond-mat.stat-mech
\\
We study the statistics of the work done in a zero temperature quench of the
coupling constant in the Dicke model describing the interaction between a gas
of two level atoms and a single electromagnetic cavity mode. When either the
final or the initial coupling constants approach the critical coupling
$\lambda_c$ that separates the normal and superradiant phases of the system,
the probability distribution of the work done displays singular behavior. The
average work tends to diverge as the initial coupling parameter is brought
closer to the critical value $\lambda_c$. In contrast, for quenches ending
close to criticality, the distribution of work has finite moments but displays
a sequence of edge singularities. This contrasting behavior is related to the
difference between the processes of compression and expansion of a particle
subject to a sudden change of its confining potential. We confirm this by
studying in detail the time dependent statistics of other observables, such as
the quadratures of the photons and the total occupation of the bosonic modes.
\\ ( http://arxiv.org/abs/0905.4833 , 52kb)
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arXiv:0905.4880
Date: Fri, 29 May 2009 14:43:35 GMT (318kb,D)

Title: Assessing the accuracy of projected entangled-pair states on infinite
lattices
Authors: Bela Bauer and Guifre Vidal and Matthias Troyer
Categories: cond-mat.str-el
\\
Generalizations of the density-matrix renormalization group method have long
been sought after. In this paper, we assess the accuracy of tensor-product
states/projected entangled-pair states on infinite lattices by comparing with
Quantum Monte Carlo results for several non-frustrated spin-1/2 systems.
Furthermore, we apply the method to a frustrated quantum system.
\\ ( http://arxiv.org/abs/0905.4880 , 318kb)
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arXiv:0905.4882
Date: Fri, 29 May 2009 14:44:19 GMT (1316kb)

Title: Suppression of the critical temperature for superfluidity near the Mott
transition: validating a quantum simulator
Authors: S. Trotzky, L. Pollet, F. Gerbier, U. Schnorrberger, I. Bloch, N.V.
Prokof'ev, B. Svistunov, M. Troyer
Categories: cond-mat.quant-gas
\\
Ultracold atomic gases in optical lattices have proven to be a controllable,
tunable and clean implementation of strongly interacting quantum many-body
systems. An essential prospect for such quantum simulators is their ability to
map out the phase diagram of fundamental many-body model Hamiltonians. However,
the results need to be validated first for representative benchmark problems
via state-of-the-art numerical methods of quantum many-body theory. Here we
present the first ab-initio comparison between experiments and quantum Monte
Carlo simulations for strongly interacting Bose gases on a lattice for large
systems (up to N = 3e5 particles). The comparison has enabled us to perform
thermometry for the interacting quantum gas and to experimentally determine the
finite temperature phase diagram for bosonic superfluids in an optical lattice.
Our results reveal a downshift of the critical temperature as the transition to
the Mott insulator is approached.
\\ ( http://arxiv.org/abs/0905.4882 , 1316kb)
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arXiv:0905.4780
Date: ?

Title: Mapping out atom-wall interaction with atomic clocks
Authors: A. Derevianko, B. Obreshkov, V. A. Dzuba
Categories: physics.atom-ph
\\
We explore a feasibility of measuring atom-wall interaction using atomic
clocks based on atoms trapped in engineered optical lattices. Optical lattice
is normal to the wall.
By monitoring the wall-induced clock shift at individual wells of the
lattice, one would measure a dependence of the atom-wall interaction on the
atom-wall separation. We rigorously evaluate the relevant clock shifts and show
that the proposed scheme may uniquely probe the long-range atom-wall
interaction in all three qualitatively-distinct regimes of the interaction: van
der Waals (image-charge interaction), Casimir-Polder (QED vacuum fluctuations)
and Lifshitz (thermal bath fluctuations). The analysis is carried out for atoms
Mg, Ca, Sr, Cd, Zn, and Hg, with a particular emphasis on Sr clock.
\\ ( http://arxiv.org/abs/0905.4780 , 1213kb)
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arXiv:0906.0016
Date: ?

Title: Entanglement Entropy and Mutual Information in Bose-Einstein Condensates
Authors: Wenxin Ding, Kun Yang
Categories: quant-ph
\\
In this paper we study the entanglement properties of free {\em
non-relativistic} Bose gases. At zero temperature, we calculate the bipartite
block entanglement entropy of the system, and find it diverges logarithmically
with the particle number in the subsystem. For finite temperatures, we study
the mutual information between the two blocks. We first analytically study an
infinite-range hopping model, then numerically study a set of long-range
hopping models in one-deimension that exhibit Bose-Einstein condensation. In
both cases we find that a Bose-Einstein condensate, if present, makes a
divergent contribution to the mutual information which is proportional to the
logarithm of the number of particles in the condensate in the subsystem. The
prefactor of the logarithmic divergent term is model dependent.
\\ ( http://arxiv.org/abs/0906.0016 , 125kb)
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arXiv:0906.0484
Date: Tue, 2 Jun 2009 13:54:35 GMT (71kb)

Title: Had the planet mars not existed: Kepler's equant model and its physical
consequences
Authors: Christian Bracco, Jean-Pierre Provost
Categories: physics.hist-ph physics.gen-ph
\\
We examine the equant model for the motion of planets, which has been the
starting point of Kepler's investigations before he modified it because of Mars
observations. We show that, up to first order in eccentricity, this model
implies for each orbit a velocity which satisfies Kepler's second law and
Hamilton's hodograph, and a centripetal acceleration with an inverse square
dependence on the distance to the sun. If this dependence is assumed to be
universal, Kepler's third law follows immediately. This elementary execice in
kinematics for undergraduates emphasizes the proximity of the equant model
coming from Ancient Greece with our present knowledge. It adds to its
historical interest a didactical relevance concerning, in particular, the
discussion of the Aristotelian or Newtonian conception of motion.
\\ ( http://arxiv.org/abs/0906.0484 , 71kb)
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arXiv:0906.0868
Date: Thu, 4 Jun 2009 09:57:44 GMT (969kb)

Title: Condensate density of interacting bosons: a functional renormalization
group approach
Authors: Christopher Eichler, Nils Hasselmann, and Peter Kopietz
Categories: cond-mat.quant-gas
\\
We calculate the temperature dependent condensate density $\rho^0 (T)$ of
interacting bosons in three dimensions using the functional renormalization
group (FRG). From the numerical solution of suitably truncated FRG flow
equations for the irreducible vertices we obtain $\rho^0 (T)$ for arbitrary
temperatures. We carefully extrapolate our numerical results to the critical
point and determine the order parameter exponent $\beta \approx 0.32$, in
reasonable agreement with the expected value $0.345$ associated with the
XY-universality class. We also calculate the condensate density in two
dimensions at zero temperature using a truncation of the FRG flow equations
based on the derivative expansion including cubic and quartic terms in the
expansion of the effective potential in powers of the density. As compared with
the widely used quadratic approximation for the effective potential, the
coupling constants associated with the cubic and quartic terms increase the
result for the condensate density by a few percent. However, the cubic and
quartic coupling constants flow to rather large values, which sheds some doubt
on FRG calculations based on a low order polynomial approximation for the
effective potential.
\\ ( http://arxiv.org/abs/0906.0868 , 969kb)
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arXiv:0906.0952
Date: Thu, 4 Jun 2009 18:35:43 GMT (13kb)

Title: The explicit expression of the fugacity for hard-sphere Bose and Fermi
gases
Authors: Wu-Sheng Dai, Mi Xie
Categories: cond-mat.stat-mech
\\
In this paper, we calculate the explicit expression for the fugacity for
three-dimensional hard-sphere Bose and Fermi gases from their equations of
state in isochoric and isobaric processes, respectively, based on the
mathematical result of the boundary problem of an analytic function -- the
homogeneous Riemann-Hilbert problem.
\\ ( http://arxiv.org/abs/0906.0952 , 13kb)
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arXiv:0906.0955
Date: Thu, 4 Jun 2009 18:21:50 GMT (40kb,D)

Title: Polarization Suppression and Nonmonotonic Local Two-Body Correlations in
the Two-Component Bose Gas in One Dimension
Authors: J.-S. Caux, A. Klauser and J. van den Brink
Categories: cond-mat.quant-gas
\\
We study the interplay of quantum statistics, strong interactions and finite
temperatures in the two-component (spinor) Bose gas with repulsive
delta-function interactions in one dimension. Using the Thermodynamic Bethe
Ansatz, we obtain the equation of state, population densities and local density
correlation numerically as a function of all physical parameters (interaction,
temperature and chemical potentials), quantifying the full crossover between
low-temperature ferromagnetic and high-temperature unpolarized regimes. In
contrast to the single-component, Lieb-Liniger gas, nonmonotonic behaviour of
the local density correlation as a function of temperature is observed.
\\ ( http://arxiv.org/abs/0906.0955 , 40kb)
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arXiv:0906.0962
Date: Thu, 4 Jun 2009 19:00:47 GMT (114kb)

Title: Quantum-limited metrology and Bose-Einstein condensates
Authors: Sergio Boixo, Animesh Datta, Matthew J. Davis, Anil Shaji, Alexandre
B. Tacla and Carlton M. Caves
Categories: quant-ph
\\
We discuss a quantum-metrology protocol designed to estimate a physical
parameter in a Bose-Einstein condensate of N atoms, and we show that the
measurement uncertainty can decrease faster than 1/N. The 1/N scaling is
usually thought to be the best possible in any measurement scheme. From the
perspective of quantum information theory, we outline the main idea that leads
to a measurement uncertainty that scales better than 1/N. We examine in detail
some potential problems and challenges that arise in implementing such a
measurement protocol using a Bose-Einstein condensate. We discuss how some of
these issues can be dealt with by using lower-dimensional condensates trapped
in nonharmonic potentials.
\\ ( http://arxiv.org/abs/0906.0962 , 114kb)
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arXiv:0906.0946
Date: Thu, 4 Jun 2009 17:13:04 GMT (1114kb,D)

Title: Magnetic trapping of ultracold Rydberg atoms in low angular momentum
states
Authors: Michael Mayle, Igor Lesanovsky, and Peter Schmelcher
Categories: physics.atom-ph
\\
We theoretically investigate the quantum properties of nS, nP, and nD Rydberg
atoms in a magnetic Ioffe-Pritchard trap. In particular, it is demonstrated
that the two-body character of Rydberg atoms significantly alters the trapping
properties opposed to point-like particles with identical magnetic moment.
Approximate analytical expressions describing the resulting Rydberg trapping
potentials are derived and their validity is confirmed for experimentally
relevant field strengths by comparisons to numerical solutions of the
underlying Schroedinger equation. In addition to the electronic properties, the
center of mass dynamics of trapped Rydberg atoms are studied. In particular, we
analyze the influence of a short-time Rydberg excitation, as required by
certain quantum-information protocols, on the center of mass dynamics of
trapped ground state atoms. A corresponding heating rate is derived and the
implications for the purity of the density matrix of an encoded qubit are
investigated.
\\ ( http://arxiv.org/abs/0906.0946 , 1114kb)
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The replacements:

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arXiv:0805.3693
replaced with revised version Fri, 29 May 2009 10:59:56 GMT (355kb)

Title: Itinerant Ferromagnetism in an Atom Trap
Authors: Ilya Berdnikov, P. Coleman, Steven H. Simon
Categories: cond-mat.str-el
\\ ( http://arxiv.org/abs/0805.3693 , 355kb)
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arXiv:0905.1708
replaced with revised version Fri, 29 May 2009 01:40:17 GMT (108kb)

Title: Mesoscopic quantum switching of a Bose-Einstein condensate in an optical
lattice governed by the parity of the number of atoms
Authors: V. S. Shchesnovich
Categories: cond-mat.quant-gas
Comments: 4 pages, 3 figures in color
\\ ( http://arxiv.org/abs/0905.1708 , 108kb)
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arXiv:0905.4652
replaced with revised version Fri, 29 May 2009 17:20:08 GMT (86kb)

Title: Sudden Death and Birth of Entanglement Effects for Kerr-Nonlinear
Coupler
Authors: A. Kowalewska-Kud{\l}aszyk and W. Leo\'nski
Categories: quant-ph
Comments: 18 pages including 7 figures. Journal of the Optical Society of
America B - in press
\\ ( http://arxiv.org/abs/0905.4652 , 86kb)
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arXiv:0808.0479
replaced with revised version Fri, 29 May 2009 20:51:19 GMT (9kb)

Title: Dynamics of a one-dimensional spinor Bose liquid: a phenomenological
approach
Authors: A. Kamenev and L.I. Glazman
Categories: cond-mat.mes-hall cond-mat.other
\\ ( http://arxiv.org/abs/0808.0479 , 9kb)
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arXiv:0712.3466
replaced with revised version Sat, 30 May 2009 13:42:12 GMT (160kb)

Title: Interpretation of quantum theory - An overview
Authors: Dimitris Lazarou
Categories: quant-ph
\\ ( http://arxiv.org/abs/0712.3466 , 160kb)
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arXiv:0903.3194
replaced with revised version Tue, 2 Jun 2009 08:58:16 GMT (97kb)

Title: 60 years of Broken Symmetries in Quantum Physics (From the Bogoliubov
Theory of Superfluidity to the Standard Model)
Authors: D. V. Shirkov
Categories: physics.hist-ph cond-mat.supr-con hep-ph hep-th
Comments: 18 pages, 4 figures, to appear in Physics -- Uspekhi, June 2009. Two
figures are upgraded and small text modifications with few new references are
\\ ( http://arxiv.org/abs/0903.3194 , 97kb)
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arXiv:0902.0934
replaced with revised version Wed, 3 Jun 2009 05:25:04 GMT (2121kb)

Title: Interaction of dark-bright solitons in two-component Bose-Einstein
condensates
Authors: S. Rajendran, P. Muruganandam, M. Lakshmanan
Categories: cond-mat.other nlin.PS
\\ ( http://arxiv.org/abs/0902.0934 , 2121kb)
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arXiv:0904.1750
replaced with revised version Wed, 3 Jun 2009 18:53:27 GMT (17kb)

Title: The Yrast Line of a Rapidly Rotating Bose Gas: Gross-Pitaevskii Regime
Authors: Elliott H. Lieb, Robert Seiringer, Jakob Yngvason
Categories: cond-mat.quant-gas math-ph math.MP
Comments: RevTeX4, 9 pages; references added; to appear in Phys. Rev. A
\\ ( http://arxiv.org/abs/0904.1750 , 17kb)
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arXiv:0810.4982
replaced with revised version Thu, 4 Jun 2009 03:00:56 GMT (11kb)

Title: Feasibility of Experimental Realization of Entangled Bose-Einstein
Condensation
Authors: Yu Shi
Categories: cond-mat.other
\\ ( http://arxiv.org/abs/0810.4982 , 11kb)
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arXiv:0903.2796
replaced with revised version Thu, 4 Jun 2009 17:23:22 GMT (64kb)

Title: Cooling atoms into entangled states
Authors: Giovanni Vacanti and Almut Beige
Categories: quant-ph
\\ ( http://arxiv.org/abs/0903.2796 , 64kb)
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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/
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Received on Fri Jul 10 2009 - 16:01:05 EST

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