Matt's arXiv selection: week ending 2 February 2007.

From: Matthew Davis <>
Date: Fri, 2 Feb 2007 20:00:36 +1000 (EST)

The following message was sent to the matts_arxiv list by Matthew Davis <>

Hi all,

A special treat this week: the mailing is early. Although in principle I have
been on holiday this past week, next week I really will be away from work!

There are 24 new preprints this week:

Paper: cond-mat/0701647
Date: Fri, 26 Jan 2007 12:57:36 GMT (667kb)

Title: Vortex instability, generation of new vortices, and onset of turbulence
    in superfluid 3He-B
Authors: V.B. Eltsov, A.P. Finne, R. de Graaf, R. Hanninen, J. Kopu, M.
    Krusius, and R.E. Solntsev
Categories: cond-mat.soft cond-mat.supr-con
Subj-class: Soft Condensed Matter; Superconductivity
    Vortex dynamics in superfluid 3He-B is distinguished by an abrupt transition
to turbulence which is caused by a strongly temperature dependent mutual
friction dissipation. Above 0.6 Tc dynamic processes are vortex number
conserving. At lower temperatures a vortex moving in applied flow with respect
to the container walls may become unstable, create new vortices, and start
thereby turbulence. This single-vortex instability can be monitored in a
rotating long cylinder in the temperature regime where turbulence starts. By
comparing NMR measurements to numerical calculations, we study the expansion of
newly created vortices to rectilinear lines, while the instability generates
new vortices at a low rate ~ 1 vortex/s, before turbulence sets in.
\\ ( , 667kb)
Paper: cond-mat/0701649
Date: Fri, 26 Jan 2007 13:53:57 GMT (33kb)

Title: Cold Attractive Spin Polarized Fermi Lattice Gases and the Doped
    Positive U Hubbard Model
Authors: Adriana Moreo and D.J. Scalapino
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 pages, 2 figures
Subj-class: Strongly Correlated Electrons; Superconductivity
    Experiments on polarized fermion gases performed by trapping ultracold atoms
in optical lattices, allow the study of an attractive Hubbard model for which
the strength of the on site interaction is tuned by means of a Feshbach
resonance. Using a well-known particle-hole transformation we discuss how
results obtained for this system can be reinterpreted in the context of a doped
repulsive Hubbard model. In particular we show that the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state corresponds to the striped state
of the two-dimensional doped positive U Hubbard model. We then use the results
of numerical studies of the striped state to relate the periodicity of the FFLO
state to the spin polarization. We also comment on the relationship of the
$d_{x^2-y^2}$ superconducting phase of the doped 2D repulsive Hubbard model to
a d-wave spin density wave state for the attractive case.
\\ ( , 33kb)
Paper: cond-mat/0701668
Date: Fri, 26 Jan 2007 18:29:37 GMT (17kb)

Title: Bose-Einstein Condensate in a Harmonic Trap Decorated with Dirac Delta
Authors: Haydar Uncu, Devrim Tarhan, Ersan Demiralp, Ozgur E. Mustecaplioglu
Categories: cond-mat.other
Comments: 6 pages, 6 figures. submitted to Physical Review A
Subj-class: Other
    We study Bose-Einstein condensation in a harmonic trap with a dimple
potential. We specifically consider the case of a tight and deep dimple
potential and model it by using a Dirac delta function. This allows for
simpler, explicit numerical and analytical investigations of the system.
Calculating the atomic density, chemical potential, critical temperature and
the condensate fraction, the role of the relative depth of the dimple trap with
respect to the harmonic trap on large condensate formation at enhanced
temperatures is revealed clearly.
\\ ( , 18kb)
Paper: quant-ph/0701185
Date: Thu, 25 Jan 2007 21:34:14 GMT (16kb)

Title: On the normal ordering of multi-mode boson operators
Authors: Toufik Mansour, Matthias Schork
Categories: quant-ph
    In this article combinatorial aspects of normal ordering annihilation and
creation operators of a multi-mode boson system are discussed. The modes are
assumed to be coupled since otherwise the problem of normal ordering is reduced
to the corresponding problem of the single-mode case. To describe the normal
ordering in the multi-mode case for each mode a colour is introduced and
coloured contractions are considered. A depiction for coloured contractions via
coloured linear representations is given. In analogy to the single-mode case
associated coloured Stirling numbers are defined as coefficients appearing in
the process of normal ordering powers of the number operators. Several
properties of these coloured Stirling numbers are discussed.
\\ ( , 16kb)
Paper: cond-mat/0701691
Date: Sun, 28 Jan 2007 17:20:18 GMT (141kb)

Title: Nature of Intermediate States between Superfluid and Mott insulator for
    Interacting Bosons in One-dimension with a Harmonic Trapping Potential
Authors: Shijie Hu, Yuchuan Wen, Xiaoqun Wang, Yue Yu
Categories: cond-mat.str-el
Comments: 4 pages, 5 figures
Subj-class: Strongly Correlated Electrons
    Successive quantum transitions in an intermediate regime are shown to exist
between the superfluid and Mott insulating states for interacting bosonic atoms
in one dimension with a trapping potential. These transitions, which are caused
by the interplay of the trapping potential with the competition between the
kinetic energy and the interaction, reveal novel many-body effects as reflected
by low-lying excitation behavior, unconventional long-range correlations and an
even-odd alternating squeezing process of superfluid bosons into the Mott
insulating state. These features, most likely being generic for all dimensions
when a trapping potential is involved, are relevant for both experimental
observations and physical interpretation of the Mott insulator transition.
\\ ( , 141kb)
Paper: cond-mat/0701692
Date: Sun, 28 Jan 2007 17:37:06 GMT (65kb)

Title: Spinodal decomposition in polarised Fermi superfluids
Authors: A. Lamacraft, F. M. Marchetti
Categories: cond-mat.supr-con
Comments: 5 pages, 3 eps figures
Subj-class: Superconductivity
    We discuss the dynamics of phase separation through the process of spinodal
decomposition in a Fermi superfluid with population imbalance. We discuss this
instability first in terms of a phenomenological Landau theory. Working within
the mean-field description at zero temperature, we then find the spinodal
region in the phase diagram of polarisation versus interaction strength, and
the spectrum of unstable modes in this region. After a quench, the spinodal
decomposition starts from the Sarma state, which is a minimum of the free
energy with respect to the order parameter at fixed density and polarisation
and a maximum at fixed chemical potentials. The possibility of observing
non-trivial domain structures in current experiments with trapped atomic gases
is discussed.
\\ ( , 65kb)
Paper: cond-mat/0701695
Date: Mon, 29 Jan 2007 00:36:28 GMT (46kb)

Title: Extension of the Thomas-Fermi approximation for trapped Bose-Einstein
    condensates with an arbitrary number of atoms
Authors: A. Mu\~{n}oz Mateo and V. Delgado (Univ. La Laguna)
Categories: cond-mat.other
Comments: 5 pages, 3 figures. Final version published in Phys. Rev. A
Subj-class: Other
Journal-ref: Phys. Rev. A 74, 065602 (2006)
DOI: 10.1103/PhysRevA.74.065602
    By incorporating the zero-point energy contribution we derive simple and
accurate extensions of the usual Thomas-Fermi (TF) expressions for the
ground-state properties of trapped Bose-Einstein condensates that remain valid
for an arbitrary number of atoms in the mean-field regime. Specifically, we
obtain approximate analytical expressions for the ground-state properties of
spherical, cigar-shaped, and disk-shaped condensates that reduce to the correct
analytical formulas in both the TF and the perturbative regimes, and remain
valid and accurate in between these two limiting cases. Mean-field quasi-1D and
-2D condensates appear as simple particular cases of our formulation. The
validity of our results is corroborated by an independent numerical computation
based on the 3D Gross-Pitaevskii equation.
\\ ( , 46kb)
Paper: quant-ph/0701204
Date: Mon, 29 Jan 2007 01:36:30 GMT (15kb)

Title: Signatures for generalized macroscopic superpositions
Authors: E. G. Cavalcanti and M. D. Reid
Categories: quant-ph
Comments: 4 pages, 2 figures, some changes made
Journal-ref: Phys. Rev. Lett. 97, 170405 (2006)
DOI: 10.1103/PhysRevLett.97.170405
    We develop criteria sufficient to enable detection of macroscopic coherence
where there are not just two macroscopically distinct outcomes for a pointer
measurement, but rather a spread of outcomes over a macroscopic range. The
criteria provide a means to distinguish a macroscopic quantum description from
a microscopic one based on mixtures of microscopic superpositions of
pointer-measurement eigenstates. The criteria are applied to Gaussian-squeezed
and spin-entangled states.
\\ ( , 15kb)
Paper: quant-ph/0701207
Date: Mon, 29 Jan 2007 10:47:59 GMT (861kb)

Title: Roughness suppression in an AC atom chip
Authors: Jean-Baptiste Trebbia (LCFIO), Carlos Leonardo Garrido (LCFIO), Alzar
    Ronald Cornelussen (LCFIO), Christopher Westbrook (LCFIO), Isabelle Bouchoule
Categories: quant-ph
Proxy: ccsd hal-00127098
Journal-ref: Physical review letters (29/01/2007) 4
    We present a method to suppress the potential roughness of a wire-based,
magnetic atom guide: modulating the wire current at a few tens of kHz, the
potential roughness, which is proportional to the wire current, averages to
zero. Using ultra-cold $^{87}{\rm Rb}$ clouds, we show experimentally that
modulation reduces the roughness by at least of a factor five without
measurable heating or atom loss. This roughness suppression results in a
dramatic reduction of the damping of center of mass oscillations.
\\ ( , 861kb)
Paper: quant-ph/0701215
Date: Mon, 29 Jan 2007 18:12:52 GMT (940kb)

Title: 'Designer atoms' for quantum metrology
Authors: C. F. Roos, M. Chwalla, K. Kim, M. Riebe, and R. Blatt
Categories: quant-ph
Journal-ref: Nature 443, 316 (2006)
DOI: 10.1038/nature05101
    Entanglement is recognized as a key resource for quantum computation and
quantum cryptography. For quantum metrology, the use of entangled states has
been discussed and demonstrated as a means of improving the signal-to-noise
ratio. In addition, entangled states have been used in experiments for
efficient quantum state detection and for the measurement of scattering
lengths. In quantum information processing, manipulation of individual quantum
bits allows for the tailored design of specific states that are insensitive to
the detrimental influences of an environment. Such 'decoherence-free subspaces'
protect quantum information and yield significantly enhanced coherence times.
Here we use a decoherence-free subspace with specifically designed entangled
states to demonstrate precision spectroscopy of a pair of trapped Ca+ ions; we
obtain the electric quadrupole moment, which is of use for frequency standard
applications. We find that entangled states are not only useful for enhancing
the signal-to-noise ratio in frequency measurements - a suitably designed pair
of atoms also allows clock measurements in the presence of strong technical
noise. Our technique makes explicit use of non-locality as an entanglement
property and provides an approach for 'designed' quantum metrology.
\\ ( , 940kb)
Paper: physics/0701311
Date: Sat, 27 Jan 2007 16:40:11 GMT (951kb)

Title: A quantitative analysis of measures of quality in science
Authors: S. Lehmann, A. D. Jackson, and B. E. Lautrup
Categories: physics.soc-ph
Comments: 11 pages, 8 figures, 4 tables
Subj-class: Physics and Society; Data Analysis, Statistics and Probability
    Condensing the work of any academic scientist into a one-dimensional measure
of scientific quality is a difficult problem. Here, we employ Bayesian
statistics to analyze several different measures of quality. Specifically, we
determine each measure's ability to discriminate between scientific authors.
Using scaling arguments, we demonstrate that the best of these measures require
approximately 50 papers to draw conclusions regarding long term scientific
performance with usefully small statistical uncertainties. Further, the
approach described here permits the value-free (i.e., statistical) comparison
of scientists working in distinct areas of science.
\\ ( , 951kb)
Paper: cond-mat/0701739
Date: Tue, 30 Jan 2007 10:19:07 GMT (30kb)

Title: Accurate determination of the superfluid-insulator transition in the
    one-dimensional Bose-Hubbard model
Authors: Jakub Zakrzewski and Dominique Delande
Categories: cond-mat.stat-mech cond-mat.other
Comments: 4pp. 3figs
Subj-class: Statistical Mechanics; Other
    The quantum phase transition point between the insulator and the superfluid
phase at unit filling factor of the infinite one-dimensional Bose-Hubbard model
is numerically computed with a high accuracy, better than current state of the
art calculations. The method uses the infinite system version of the time
evolving block decimation algorithm, here tested in a challenging case.
\\ ( , 30kb)
Paper: cond-mat/0701744
Date: Tue, 30 Jan 2007 12:02:18 GMT (169kb)

Title: Universal thermodynamics of strongly interacting Fermi gases
Authors: Hui Hu, Peter D. Drummond, and Xia-Ji Liu
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 5 pages + 3 figures, submitted for publication
Subj-class: Strongly Correlated Electrons; Superconductivity
    Strongly interacting Fermi gases are of great current interest. Not only are
fermions the most common particles in the universe, but they are also thought
to have a universal thermodynamic behavior for strong interactions
\cite{heiselberg,carlson,ho}. Recent experiments on ultra-cold Fermi gases
provide an unprecedented opportunity to test universality in the laboratory
\cite{hara,thomas,partridge,stewart,luo}. In principle this allows - for
example - the interior properties of hot, dense neutron stars to be
investigated on earth. Here we carry out a detailed test of this prediction. We
analyze results from three ultra-cold fermion experiments involving two
completely distinct atomic species in different kinds of atomic trap
environments \cite{partridge,stewart,luo}. The data is compared with the
predictions of a recent strong interaction theory \cite{hldepl,hldpra}.
Excellent agreement is obtained, with no adjustable parameters. By
extrapolating to zero temperature, we show that the experimental measurements
yield a many-body parameter} $\mathbf{\beta\simeq-0.59\pm.07}$,
\textbf{describing the universal energy of strongly interacting Fermi gases.
\\ ( , 169kb)
Paper: cond-mat/0701751
Date: Tue, 30 Jan 2007 14:29:41 GMT (380kb)

Title: Excitonic condensation under spin-orbit coupling and BEC-BCS crossover
Authors: Tu\u{g}rul Hakio\u{g}lu and Mehmet \c{S}ahin
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: Accepted for publication by Physical Review Letters
Subj-class: Strongly Correlated Electrons; Mesoscopic Systems and Quantum Hall
    The condensation of electron-hole (e-h) pairs is studied at zero temperature
and in the presence of a weak spin-orbit coupling (SOC) in the inversion-layer
quantum wells. Under realistic conditions, a perturbative SOC can have
observable effects in the order parameter of the experimentally
long-searched-for excitonic condensate. Firstly, the fermion exchange symmetry
is absent for the e-h pairs indicating a counterexample to the known
classification schemes of fermion pairing. With the lack of fermion exchange,
the condensate spin has no definite parity. Additionally, the excitonic SOC
breaks the rotational symmetry yielding a complex order parameter in an
unconventional way, i.e. the phase pattern of the order parameter is a function
of the condensate density. This is manifested through finite off diagonal
components of the static spin susceptibility, suggesting a new experimental
method to confirm an excitonic condensate.
\\ ( , 380kb)
Paper: cond-mat/0701752
Date: Tue, 30 Jan 2007 14:48:38 GMT (194kb)

Title: Self-bound droplet of Bose and Fermi atoms in one dimension: Collective
    properties in mean-field and Tonks-Girardeau regimes
Authors: Luca Salasnich, Sadhan K. Adhikari, and Flavio Toigo
Categories: cond-mat.other cond-mat.stat-mech
Comments: 9 pages, 5 figures, to be published in Phys. Rev. A
Subj-class: Other; Statistical Mechanics
    We investigate a dilute mixture of bosons and spin-polarized fermions in
one-dimension. With an attractive Bose-Fermi scattering length the ground-state
is a self-bound droplet, i.e. a Bose-Fermi bright soliton where the Bose and
Fermi clouds are superimposed. We find that the quantum fluctuations stabilize
the Bose-Fermi soliton such that the one-dimensional bright soliton exists for
any finite attractive Bose-Fermi scattering length. We study density profile
and collective excitations of the atomic bright soliton showing that they
depend on the bosonic regime involved: mean-field or Tonks-Girardeau.
\\ ( , 194kb)
Paper: cond-mat/0701756
Date: Tue, 30 Jan 2007 16:09:58 GMT (297kb)

Title: From Feshbach-Resonance Managed Bose-Einstein Condensates to Anisotropic
    Universes: Some Applications of the Ermakov-Pinney equation with
    Time-Dependent Nonlinearity
Authors: G. Herring, P.G. Kevrekidis, F. Williams, T. Christodoulakis and D.J.
Categories: cond-mat.other
Comments: 9 pages, 4 figures
Subj-class: Other
    In this work we revisit the topic of two-dimensional Bose-Einstein
condensates under the influence of time-dependent magnetic confinement and
time-dependent scattering length. A moment approach reduces the examination of
moments of the wavefunction (in particular, of its width) to an Ermakov-Pinney
(EP) ordinary differential equation (ODE). We use the well-known structure of
the solutions of this nonlinear ODE to ``engineer'' trapping and interatomic
interaction conditions that lead to condensates dispersing, breathing or even
collapsing. The advantage of the approach is that it is fully tractable
analytically, in excellent agreement with our numerical observations. As an
aside, we also discuss how similar time-dependent EP equations may arise in the
description of anisotropic scalar field cosmologies.
\\ ( , 297kb)
Paper: cond-mat/0701758
Date: Tue, 30 Jan 2007 16:22:22 GMT (198kb)

Title: Shiva diagrams for composite-boson many-body effects : How they work
Authors: M. Combescot and O. Betbeder-Matibet
Categories: cond-mat.stat-mech
Comments: To be published in Eur. Phys. J. B
Subj-class: Statistical Mechanics
    The purpose of this paper is to show how the diagrammatic expansion in
fermion exchanges of scalar products of $N$-composite-boson (``coboson'')
states can be obtained in a practical way. The hard algebra on which this
expansion is based, will be given in an independent publication.
    Due to the composite nature of the particles, the scalar products of
$N$-coboson states do not reduce to a set of Kronecker symbols, as for
elementary bosons, but contain subtle exchange terms between two or more
cobosons. These terms originate from Pauli exclusion between the fermionic
components of the particles. While our many-body theory for composite bosons
leads to write these scalar products as complicated sums of products of ``Pauli
scatterings'' between \emph{two} cobosons, they in fact correspond to fermion
exchanges between any number P of quantum particles, with $2 \leq P\leq N$.
These $P$-body exchanges are nicely represented by the so-called ``Shiva
diagrams'', which are topologically different from Feynman diagrams, due to the
intrinsic many-body nature of Pauli exclusion from which they originate. These
Shiva diagrams in fact constitute the novel part of our composite-exciton
many-body theory which was up to now missing to get its full diagrammatic
representation. Using them, we can now ``see'' through diagrams the physics of
any quantity in which enters $N$ interacting excitons -- or more generally $N$
composite bosons --, with fermion exchanges included in an \emph{exact} -- and
transparent -- way.
\\ ( , 198kb)
Paper (*cross-listing*): hep-th/0308095
Date: Thu, 14 Aug 2003 00:45:51 GMT (2kb)

Title: Boson-Fermion Transmutation and the Statistics of Anyons
Authors: Wung-Hong Huang
Categories: hep-th cond-mat.mes-hall cond-mat.stat-mech
Subj-class: High Energy Physics - Theory; Statistical Mechanics; Mesoscopic
    Systems and Quantum Hall Effect
Journal-ref: Phys.Rev. E51 (1995) 3729
    It is shown that, by allowing a transmutation between a boson and a fermion,
the system with both bosons and fermions will have the statistical distribution
function of an anyon.
\\ ( , 2kb)
Paper: cond-mat/0701761
Date: Tue, 30 Jan 2007 21:00:30 GMT (37kb)

Title: Competition between Vortex Unbinding and Tunneling in an Optical Lattice
Authors: M. A. Cazalilla, A. Iucci, and T. Giamarchi
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 4+ pages, 1 figure
Subj-class: Statistical Mechanics; Strongly Correlated Electrons
    We study a system of two-dimensional Bose gases trapped in minima of a deep
one-dimensional optical lattice potential. Increasing the tunneling amplitude
between adjacent gases drives a deconfinement transition to a phase where
coherence is established between neighboring two-dimensional gases. We compute
the signature of this transition in the interference pattern of the system as
well as in its rotational response, which provides a direct measurement of the
superfluidity in the system.
\\ ( , 37kb)
Paper: cond-mat/0701764
Date: Wed, 31 Jan 2007 02:28:02 GMT (53kb)

Title: Ground-state properties of trapped Bose-Einstein condensates. Extension
    of the Thomas-Fermi approximation
Authors: A. Mu\~{n}oz Mateo and V. Delgado (Univ. La Laguna)
Categories: cond-mat.other
Comments: 8 pages, 6 figures. This paper generalizes our previous work
Subj-class: Other
    We derive general approximate formulas that provide with remarkable accuracy
the ground-state properties of any mean-field scalar Bose-Einstein condensate
with short-range repulsive interatomic interactions, confined in arbitrary
cylindrically symmetric harmonic traps. Our formulation is even applicable for
condensates containing a multiply quantized axisymmetric vortex. We have
checked the validity of our formulas by numerically solving the 3D
Gross-Pitaevskii equation.
\\ ( , 53kb)
Paper: cond-mat/0701786
Date: Wed, 31 Jan 2007 20:36:49 GMT (69kb)

Title: Thermodynamics of a Trapped Unitary Fermi Gas
Authors: Aurel Bulgac, Joaquin E. Drut, Piotr Magierski
Categories: cond-mat.stat-mech
Comments: 4 pages, 4 figures
Subj-class: Statistical Mechanics
    We present the first model-independent comparison of recent measurements of
the entropy and of the critical temperature of a unitary Fermi gas, performed
by the Duke group, with the most complete results currently available from
finite temperature Monte Carlo calculations. The measurement of the critical
temperature in a cold fermionic atomic cloud is consistent with a value
$T_c=0.23(2)epsilon_F$ in the bulk, as predicted by the present authors in
their Monte Carlo calculations.
\\ ( , 69kb)
Paper: quant-ph/0701221
Date: Mon, 29 Jan 2007 21:08:12 GMT (455kb)

Title: Entanglement in continuous variable systems: Recent advances and current
Authors: Gerardo Adesso (University of Salerno), Fabrizio Illuminati
    (University of Salerno)
Categories: quant-ph cond-mat.stat-mech hep-th math-ph math.MP physics.optics
Comments: 61 pages, 7 figures, 3 tables
Subj-class: Quantum Physics; Mathematical Physics; Statistical Mechanics;
    We review the theory of continuous-variable entanglement with special
emphasis on foundational aspects, conceptual structures, and mathematical
methods. Much attention is devoted to the discussion of separability criteria
and entanglement properties of Gaussian states, for their great practical
relevance in applications to quantum optics and quantum information, as well as
for the very clean framework that they allow for the study of the structure of
nonlocal correlations. We give a self-contained introduction to phase-space and
symplectic methods in the study of Gaussian states of infinite-dimensional
bosonic systems. We review the most important results on the separability and
distillability of Gaussian states and discuss the main properties of bipartite
entanglement. These include the extremal entanglement, minimal and maximal, of
two-mode mixed Gaussian states, the ordering of two-mode Gaussian states
according to different measures of entanglement, the unitary (reversible)
localization, and the scaling of bipartite entanglement in multimode Gaussian
states. We then discuss recent advances in the understanding of entanglement
sharing in multimode Gaussian states, including the proof of the monogamy
inequality of distributed entanglement for all Gaussian states, and its
consequences for the characterization of multipartite entanglement. We finally
review recent advances and discuss possible perspectives on the qualification
and quantification of entanglement in non Gaussian states, a field of research
that is to a large extent yet to be explored.
\\ ( , 455kb)
Paper: cond-mat/0702002
Date: Wed, 31 Jan 2007 22:30:10 GMT (855kb)

Title: Mixtures of Bose gases under rotation
Authors: S. Bargi, J. Christensson, G. M. Kavoulakis, and S. M. Reimann (LTH,
Categories: cond-mat.mes-hall
Comments: 4 pages, RevTex, 6 figures
Subj-class: Mesoscopic Systems and Quantum Hall Effect
    We examine the rotational properties of a mixture of two Bose gases.
Considering the limit of weak interactions between the atoms, we investigate
the behavior of the system under a fixed angular momentum. We demonstrate a
number of exact results in this many-body system.
\\ ( , 855kb)
Paper: cond-mat/0702004
Date: Thu, 1 Feb 2007 11:06:41 GMT (421kb)

Title: Negative magnetic susceptibility and nonequivalent ensembles for the
    mean-field $\phi^4$ spin model
Authors: A. Campa, S. Ruffo, H. Touchette
Categories: cond-mat.stat-mech
Comments: 14 pages, 4 figures, 2 appendices, REVTeX4
Subj-class: Statistical Mechanics
    We calculate the thermodynamic entropy of the mean-field $\phi^4$ spin model
in the microcanonical ensemble as a function of the energy and magnetization of
the model. The entropy and its derivative are obtained from the theory of large
deviations, as well as from Rugh's microcanonical formalism, which is
implemented by computing averages of suitable observables in microcanonical
molecular dynamics simulations. Our main finding is that the entropy is a
concave function of the energy for all values of the magnetization, but is
nonconcave as a function of the magnetization for some values of the energy.
This last property implies that the magnetic susceptibility of the model can be
negative when calculated microcanonically for fixed values of the energy and
magnetization. This provides a magnetization analog of negative heat
capacities, which are well-known to be associated in general with the
nonequivalence of the microcanonical and canonical ensembles. Here, the two
ensembles that are nonequivalent are the microcanonical ensemble in which the
energy and magnetization are held fixed and the canonical ensemble in which the
energy and magnetization are fixed only on average by fixing the temperature
and magnetic field.
\\ ( , 421kb)
Paper: quant-ph/0702002
Date: Wed, 31 Jan 2007 22:10:46 GMT (300kb)

Title: Preparation and probing of the ground state coherence in Rubidium
Authors: Martin Oberst, Frank Vewinger, A. I. Lvovsky
Categories: quant-ph
    We demonstrate the preparation and probing of the coherence between the
hyperfine ground states |5S_{1/2}, F=1> and |5S_{1/2}, F=2> of the Rubidium 87
isotope. The effect of various coherence control techniques, i.e. fractional
Stimulated Raman Adiabatic Passage and Coherent Population Return on the
coherence are investigated. These techniques are implemented using nearly
degenerate pump and Stokes lasers at 795nm (Rubidium D1 transition) which
couple the two hyperfine ground states via the excited state |5P_{1/2}, F=1>
through a resonant two-photon process, in which a coherent superposition of the
two hyperfine ground states is established. The medium is probed by an
additional weak laser, which generates a four-wave mixing signal proportional
to the ground state coherence, and allows us to monitor its evolution in time.
The experimental data are compared with numerical simulations.
\\ ( , 300kb)

The replacements:

Paper: cond-mat/0701506
replaced with revised version Fri, 26 Jan 2007 06:15:15 GMT (15kb)

Title: Fractional Spin Hall Effect in Bosonic Atomic Gas
Authors: Xiong-Jun Liu, Xin Liu, L. C. Kwek and C. H. Oh
Categories: cond-mat.mes-hall
Comments: 5 pages, 1 figure
Subj-class: Mesoscopic Systems and Quantum Hall Effect
\\ ( , 15kb)
Paper: quant-ph/0605231
replaced with revised version Fri, 26 Jan 2007 13:34:24 GMT (137kb)

Title: A single cold atom as efficient stationary source of EPR-entangled light
Authors: David Vitali, Giovanna Morigi, J\"urgen Eschner
Comments: 13 pages, 5 figures
Journal-ref: Phys. Rev. A 74, 053814 (2006)
\\ ( , 137kb)
Paper: cond-mat/0609219
replaced with revised version Mon, 29 Jan 2007 12:14:29 GMT (46kb)

Title: Ground-state Competition of Two-Component Bosons in Optical Lattice near
    a Feshbach Resonance
Authors: Liping Guo, Yunbo Zhang, Shu Chen
Categories: cond-mat.other
Comments: Final version in PRA
Subj-class: Other
Journal-ref: Phys. Rev. A75, 013622(6) (2007)
DOI: 10.1103/PhysRevA.75.013622
\\ ( , 46kb)
Paper: cond-mat/0610623
replaced with revised version Mon, 29 Jan 2007 15:22:48 GMT (31kb)

Title: A number-conserving approach to a minimal self-consistent treatment of
    condensate and non-condensate dynamics in a degenerate Bose gas
Authors: S. A. Gardiner and S.A. Morgan
Categories: cond-mat.other
Comments: 20 pages, revised in response to referee's comments. Submitted to
    Phys. Rev. A
Subj-class: Other
\\ ( , 31kb)
Paper: cond-mat/0611450
replaced with revised version Mon, 29 Jan 2007 09:49:52 GMT (16kb)

Title: Bethe Ansatz for 1D interacting anyons
Authors: M.T. Batchelor, X.-W. Guan and J.-S. He
Categories: cond-mat.stat-mech
Comments: 22 pages, two references added, small improvements to text
Subj-class: Statistical Mechanics
\\ ( , 16kb)
Paper: cond-mat/0612670
replaced with revised version Mon, 29 Jan 2007 06:35:16 GMT (28kb)

Title: Anderson Localization of Expanding Bose-Einstein Condensates in Random
Authors: Laurent Sanchez-Palencia (LCFIO), David Cl\'{e}ment (LCFIO), Pierre
    Lugan (LCFIO), Philippe Bouyer (LCFIO), Georgy V. Shlyapnikov (LPTMS), Alain
    Aspect (LCFIO)
Categories: cond-mat.other
Comments: 4 pages, 2 figures; misprint corrected
Proxy: ccsd hal-00122278
Subj-class: Other
\\ ( , 28kb)
Paper: cond-mat/0603106
replaced with revised version Thu, 1 Feb 2007 14:43:45 GMT (101kb)

Title: Partially suppressed long-range order in the Bose-Einstein condensation
    of polaritons
Authors: Davide Sarchi, Vincenzo Savona
Categories: cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.other
Subj-class: Materials Science; Mesoscopic Systems and Quantum Hall Effect;
\\ ( , 101kb)
Paper: cond-mat/0606216
replaced with revised version Thu, 1 Feb 2007 16:38:34 GMT (462kb)

Title: The Mott insulator transition in two dimensions
Authors: I. B. Spielman, W. D. Phillips, and J. V. Porto
Categories: cond-mat.other
Comments: Expanded version of text accepted for publication in PRL. Changes:
    significant textual improvement, and corrected numerical transcription errors
    relevant to Figs 1. and 4
Subj-class: Other
\\ ( , 462kb)
Paper: cond-mat/0606471
replaced with revised version Thu, 1 Feb 2007 08:53:07 GMT (45kb)

Title: Studies of bosons in optical lattices in a harmonic potential
Authors: R. Ramakumar, A. N. Das, and S. Sil
Categories: cond-mat.stat-mech cond-mat.other
Comments: Revised version, References updated, a new section on Fermions added,
    14 pages, 16 figures
Subj-class: Statistical Mechanics; Other
\\ ( , 45kb)
Paper: cond-mat/0701751
replaced with revised version Thu, 1 Feb 2007 15:44:30 GMT (380kb)

Title: Excitonic condensation under spin-orbit coupling and BEC-BCS crossover
Authors: Tu\u{g}rul Hakio\u{g}lu and Mehmet \c{S}ahin
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: Accepted for publication by Physical Review Letters
Subj-class: Strongly Correlated Electrons; Mesoscopic Systems and Quantum Hall
\\ ( , 380kb)

Till next time,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from

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Received on Fri Feb 02 2007 - 20:00:36 EST

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