Matt's arXiv selection: week ending 9 November 2007.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Wed, 12 Dec 2007 22:46:21 +1000

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

Hi all,

Another long break between emails, partly I can blame the Quantum-Atom Optics
Downunder conference in Wollongong, Australia that happened last week, and the
related visitors to the University of Queensland the week before. A very
stimulating meeting.

I'll endeavour to be up to date by Christmas... 26 new preprints and 8
replacements this week.

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arXiv:0711.0268
Date: Fri, 2 Nov 2007 09:39:41 GMT (61kb)

Title: Phase space gaps and ergodicity breaking in systems with long range
   interactions
Authors: Freddy Bouchet (INLN, Phys-ENS), Thierry Dauxois (Phys-ENS), David
   Mukamel (Phys-ENS), Stefano Ruffo (Phys-ENS)
Categories: cond-mat.stat-mech
Proxy: ccsd ensl-00184817
\\
   We study a generalized isotropic XY-model which includes both two-spin and
four-spin mean-field interactions. This model can be solved in the
microcanonical ensemble. It is shown that in certain parameter regions the
model exhibits gaps in the magnetization at fixed energy, resulting in
ergodicity breaking. This phenomenon has previously been reported in
anisotropic and discrete spin models. The entropy of the model is calculated
and the microcanonical phase diagram is derived, showing the existence of first
order phase transitions from the ferromagnetic to a paramagnetic disordered
phase. It is found that ergodicity breaking takes place both in the
ferromagnetic and the paramagnetic phases. As a consequence, the system can
exhibit a stable ferromagnetic phase within the paramagnetic region, and
conversely a disordered phase within the magnetically ordered region.
\\ ( http://arxiv.org/abs/0711.0268 , 61kb)
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arXiv:0711.0318
Date: Fri, 2 Nov 2007 14:33:00 GMT (25kb)

Title: Exact solution of the extended Hubbard model in the atomic limit on the
   Bethe Lattice
Authors: F. Mancini, F. P. Mancini and A. Naddeo
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 9 pages,1 figure; presented at ESM '07
\\
   We study the phase diagram at finite temperature of a system of Fermi
particles on the sites of the Bethe lattice with coordination number z and
interacting through onsite U and nearest-neighbor V interactions. This is a
physical realization of the extended Hubbard model in the atomic limit. By
using the equations of motion method, we exactly solve the model. For an
attractive intersite potential, we find, at half filling, a phase transition
towards a broken particle-hole symmetry state. The critical temperature, as a
function of the relevant parameters, has a re-entrant behavior as already
observed in the equivalent spin-1 Ising model on the Bethe lattice.
\\ ( http://arxiv.org/abs/0711.0318 , 25kb)
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arXiv:0711.0375
Date: Fri, 2 Nov 2007 19:14:50 GMT (701kb)

Title: Dynamics of Vortex Formation in Merging Bose-Einstein Condensate
   Fragments
Authors: R. Carretero-Gonzalez, B.P. Anderson, P.G. Kevrekidis, D.J.
   Frantzeskakis, and C.N. Weiler
Categories: cond-mat.other
Comments: 11 pages, 11 figures (low res), submitted to Phys. Rev. A. November
   2007 Full resolution preprint available at:
   http://www-rohan.sdsu.edu/~rcarrete/publications/
\\
   We study the formation of vortices in a Bose-Einstein condensate (BEC) that
has been prepared by allowing isolated and independent condensed fragments to
merge together. We focus on the experimental setup of Scherer {\it et al.}
[Phys. Rev. Lett. {\bf 98}, 110402 (2007)], where three BECs are created in a
magnetic trap that is segmented into three regions by a repulsive optical
potential; the BECs merge together as the optical potential is removed. First,
we study the two-dimensional case, in particular we examine the effects of the
relative phases of the different fragments and the removal rate of the optical
potential on the vortex formation. We find that many vortices are created by
instant removal of the optical potential regardless of relative phases, and
that fewer vortices are created if the intensity of the optical potential is
gradually ramped down and the condensed fragments gradually merge. In all
cases, self-annihilation of vortices of opposite charge is observed. We also
find that for sufficiently long barrier ramp times, the initial relative phases
between the fragments leave a clear imprint on the resulting topological
configuration. Finally, we study the three-dimensional system and the formation
of vortex lines and vortex rings due to the merger of the BEC fragments; our
results illustrate how the relevant vorticity is manifested for appropriate
phase differences, as well as how it may be masked by the planar projections
observed experimentally.
\\ ( http://arxiv.org/abs/0711.0375 , 701kb)
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arXiv:0711.0263
Date: Fri, 2 Nov 2007 09:21:26 GMT (117kb)

Title: Three dimensional theory for light matter interaction
Authors: Martin W. S{\o}rensen and Anders S. S{\o}rensen
Categories: quant-ph
Comments: 32 pages, 2 figures
\\
   We present a full quantum mechanical three dimensional theory describing an
electromagnetic field interacting with an ensemble of identical atoms. The
theory is constructed such that it describes recent experiments on light-matter
quantum interfaces, where the quantum fluctuations of light are mapped onto the
atoms and back onto light. We show that the interaction of the light with the
atoms may be separated into a mean effect of the ensemble and a deviation from
the mean. The mean effect of the interaction effectively give rise to an index
of refraction of the gas. We formally change to a dressed state picture, where
the light modes are solutions to the diffraction problem, and develop a
perturbative expansion in the fluctuations. The fluctuations are due to quantum
fluctuations as well as the random positions of the atoms. In this perturbative
expansion we show how the quantum fluctuations are mapped between atoms and
light while the random positioning of the atoms give rise to decay due to
spontaneous emission. Furthermore we identify limits, where the full three
dimensional theory reduce to the one dimensional theory typically used to
describe the interaction.
\\ ( http://arxiv.org/abs/0711.0263 , 117kb)
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arXiv:0711.0264
Date: Fri, 2 Nov 2007 09:17:04 GMT (172kb)

Title: Reversible Quantum Interface for Tunable Single-sideband Modulation
Authors: J. Cviklinski, J. Ortalo, A. Bramati, M. Pinard and E. Giacobino
Categories: quant-ph
Comments: 5 pages, 6 figures
\\
   Interaction of a control and a signal field with three-level atoms using
Electromagnetically Induced Transparency (EIT) allows direct mapping of the
quantum state of the signal field into long lived Zeeman coherences of an
atomic ground state. For a vapor of cesium atoms, we study the conditions in
which simultaneous storage of two non-commuting variables carried by light and
subsequent read-out is possible with good efficiency. We show that excess noise
associated with spontaneous emission and spin relaxation is negligible. We
compare the case where a tunable single side band is stored independently of
the other one to the case where the two symmetrical sidebands are stored using
the same EIT transparency window.
\\ ( http://arxiv.org/abs/0711.0264 , 172kb)
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arXiv:0711.0303
Date: Fri, 2 Nov 2007 13:18:07 GMT (129kb)

Title: Lossless Negative Refraction in An Active Dense Gas of Atoms
Authors: P. P. Orth, J. Evers, and C. H. Keitel
Categories: quant-ph
Comments: 4 figures
\\
   Current designs for negative index materials are passive, such that they
suffer from significant losses that prohibit applications, in particular
towards optical frequencies. We predict, based on nonlinear optical Bloch
equations, negative refraction with zero absorption in an active, i.e.,
amplifying, dense gas of atoms. External laser fields are used to tune the
medium's electromagnetic response and an additional weak pumping field controls
its absorption properties. Metastable Neon is identified as a suitable
experimental candidate at infrared frequencies to implement a lossless active
negative index material.
\\ ( http://arxiv.org/abs/0711.0303 , 129kb)
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arXiv:0711.0379
Date: Fri, 2 Nov 2007 19:32:31 GMT (462kb)

Title: Time-Domain Measurement of Spontaneous Vibrational Decay of Magnetically
   Trapped NH
Authors: Wesley C. Campbell, Gerrit C. Groenenboom, Hsin-I Lu, Edem Tsikata,
   John M. Doyle
Categories: physics.atom-ph physics.ao-ph
Comments: 10 pages + 3 figures (11 pages total)
\\
   The v = 1 -> 0 radiative lifetime of NH (X triplet-Sigma-, v=1,N=0) is
determined to be tau_rad,exp. = 37.0 0.5 stat +2.0 / -0.8 sys miliseconds,
corresponding to a transition dipole moment of |mu_10| = 0.0540 + 0.0009 /
-0.0018 Debye. To achieve the long observation times necessary for direct
time-domain measurement, vibrationally excited NH (X triplet-Sigma-, v=1,N=0)
radicals are magnetically trapped using helium buffer-gas loading. Simultaneous
trapping and lifetime measurement of both the NH(v=1, N=0) and NH(v=0,N=0)
populations allows for accurate extraction of tau_rad,exp. Background helium
atoms are present during our measurement of tau_rad,exp., and the rate constant
for helium atom induced collisional quenching of NH(v=1,N=0) was determined to
be k_q < 3.9 * 10-15 cm3/s. This bound on k_q yields the quoted systematic
uncertainty on tau_rad,exp. Using an ab initio dipole moment function and an
RKR potential, we also determine a theoretical value of 36.99 ms for this
lifetime, in agreement with our experimental value. Our results provide an
independent determination of tau_rad,10, test molecular theory, and furthermore
demonstrate the efficacy of buffer-gas loading and trapping in determining
metastable radiative and collisional lifetimes.
\\ ( http://arxiv.org/abs/0711.0379 , 462kb)
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arXiv:0711.0397
Date: Fri, 2 Nov 2007 20:59:19 GMT (303kb,D)

Title: Coherent, adiabatic and dissociation regimes in coupled atomic-molecular
   Bose-Einstein condensates
Authors: Pascal Naidon, Eite Tiesinga and Paul S. Julienne
Categories: cond-mat.other
Comments: 10 pages, 4 figures
\\
   We discuss the dynamics of a Bose-Einstein condensate of atoms which is
suddenly coupled to a condensate of molecules by an optical or magnetic
Feshbach resonance. Three limiting regimes are found and can be understood from
the transient dynamics occuring for each pair of atoms. This transient dynamics
can be summarised into a time-dependent shift and broadening of the molecular
state. A simple Gross-Pitaevskii picture including this shift and broadening is
proposed to describe the system in the three regimes. Finally, we suggest how
to explore these regimes experimentally.
\\ ( http://arxiv.org/abs/0711.0397 , 303kb)
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arXiv:0711.0425
Date: Sat, 3 Nov 2007 04:35:55 GMT (169kb)

Title: Superfluidity and phase transitions in a resonant Bose gas
Authors: Leo Radzihovsky, Peter B. Weichman, Jae I. Park
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 55 pages, 18 eps figures, submitted to Annals of Physics
\\
   The atomic Bose gas is studied across a Feshbach resonance, mapping out its
phase diagram, and computing its thermodynamics and excitation spectra. It is
shown that such a degenerate gas admits two distinct atomic and molecular
superfluid phases, with the latter distinguished by the absence of atomic
off-diagonal long-range order, gapped atomic excitations, and deconfined atomic
pi-vortices. The properties of the molecular superfluid are explored, and it is
shown that across a Feshbach resonance it undergoes a quantum Ising transition
to the atomic superfluid, where both atoms and molecules are condensed. In
addition to its distinct thermodynamic signatures and deconfined half-vortices,
in a trap a molecular superfluid should be identifiable by the absence of an
atomic condensate peak and the presence of a molecular one.
\\ ( http://arxiv.org/abs/0711.0425 , 169kb)
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arXiv:0711.0459
Date: Sat, 3 Nov 2007 16:01:29 GMT (22kb)

Title: Rotating ground states of a one-dimensional spin-polarized gas of
   fermionic atoms with attractive p-wave interactions on a mesoscopic ring
Authors: M. D. Girardeau and E. M. Wright
Categories: cond-mat.other
Comments: 4 pages, 1 figure, revtex4. Submitted to Phys. Rev. Lett
\\
   The major finding of this paper is that a one-dimensional spin-polarized gas
comprised of an even number of fermionic atoms interacting via attractive
p-wave interactions and confined to a mesoscopic ring has a degenerate pair of
ground states that are oppositely rotating. In any realization the gas will
thus spontaneously rotate one way or the other in spite of the fact that there
is no external rotation or bias fields. Our goal is to show that this
counter-intuitive finding is a natural consequence of the combined effects of
quantum statistics, ring topology, and exchange interactions.
\\ ( http://arxiv.org/abs/0711.0459 , 22kb)
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arXiv:0711.0561
Date: Mon, 5 Nov 2007 02:30:43 GMT (169kb)

Title: Variational theory of two-fluid hydrodynamic modes at unitarity
Authors: Edward Taylor, Hui Hu, Xia-Ji Liu, Allan Griffin
Categories: cond-mat.other
Comments: 16 pages; 5 figures
\\
   We present the results of a variational calculation of the frequencies of the
low-lying Landau two-fluid hydrodynamic modes in a trapped Fermi superfluid gas
at unitarity. Landau's two-fluid hydrodynamics is expected to be the correct
theory of Fermi superfluids at finite temperatures close to unitarity, where
strong interactions give rise to collisional hydrodynamics. Two-fluid
hydrodynamics predicts the existence of in-phase modes in which the superfluid
and normal fluid components oscillate together, as well as out-of-phase modes
where the two components move against each other. We prove that at unitarity,
the dipole and breathing in-phase modes are locally isentropic. Their
frequencies are independent of temperature and are the same above and below the
superfluid transition. The out-of-phase modes, in contrast, are strongly
dependent on temperature and hence, can be used to test the thermodynamic
properties and superfluid density of a Fermi gas at unitarity. We give
numerical results for the frequencies of these new modes as function of
temperature in an isotropic trap at unitarity.
\\ ( http://arxiv.org/abs/0711.0561 , 169kb)
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arXiv:0711.0568
Date: Mon, 5 Nov 2007 06:26:49 GMT (156kb)

Title: Computing Ground States of Spin-1 Bose-Einstein Condensates by the
   Normalized Gradient Flow
Authors: Weizhu Bao and Fong Yin Lim
Categories: cond-mat.mtrl-sci
Comments: 25 pages, 12 figures
\\
   In this paper, we propose an efficient and accurate numerical method for
computing the ground state of spin-1 Bose-Einstein condensates (BEC) by using
the normalized gradient flow or imaginary time method. The key idea is to find
a third projection or normalization condition based on the relation between the
chemical potentials so that the three projection parameters used in the
projection step of the normalized gradient flow are uniquely determined by this
condition as well as the other two physical conditions given by the
conservation of total mass and total magnetization. This allows us to
successfully extend the most popular and powerful normalized gradient flow or
imaginary time method for computing the ground state of single component BEC to
compute the ground state of spin-1 BEC. An efficient and accurate
discretization scheme, the backward-forward Euler sine-pseudospectral method
(BFSP), is proposed to discretize the normalized gradient flow. Extensive
numerical results on ground states of spin-1 BEC with
ferromagnetic/antiferromagnetic interaction and harmonic/optical lattice
potential in one/three dimensions are reported to demonstrate the efficiency of
our new numerical method.
\\ ( http://arxiv.org/abs/0711.0568 , 156kb)
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arXiv:0711.0637
Date: Fri, 2 Nov 2007 22:41:45 GMT (1720kb,D)

Title: Symmetry breaking and quantum correlations in finite systems: Studies of
   quantum dots and ultracold Bose gases and related nuclear and chemical
   methods
Authors: Constantine Yannouleas, Uzi Landman
Categories: cond-mat.mes-hall cond-mat.str-el
Comments: Review article published in Reports on Progress in Physics. REVTEX4.
   95 pages with 37 color figures. To download a copy with high-quality figures,
   go to publication #82 in http://www.prism.gatech.edu/~ph274cy/
Journal-ref: Rep. Prog. Phys. 70, 2067 (2007)
DOI: 10.1088/0034-4885/70/12/R02
\\
   Investigations of emergent symmetry breaking phenomena occurring in small
finite-size systems are reviewed, with a focus on the strongly correlated
regime of electrons in two-dimensional semicoductor quantum dots and trapped
ultracold bosonic atoms in harmonic traps. Throughout the review we emphasize
universal aspects and similarities of symmetry breaking found in these systems,
as well as in more traditional fields like nuclear physics and quantum
chemistry, which are characterized by very different interparticle forces. A
unified description of strongly correlated phenomena in finite systems of
repelling particles (whether fermions or bosons) is presented through the
development of a two-step method of symmetry breaking at the unrestricted
Hartree-Fock level and of subsequent symmetry restoration via post Hartree-Fock
projection techniques. Quantitative and qualitative aspects of the two-step
method are treated and validated by exact diagonalization calculations.
   Strongly-correlated phenomena emerging from symmetry breaking include: (I)
Chemical bonding, dissociation, and entanglement (at zero and finite magnetic
fields) in quantum dot molecules and in pinned electron molecular dimers formed
within a single anisotropic quantum dot. (II) Electron crystallization, with
particle localization on the vertices of concentric polygonal rings, and
formation of rotating electron molecules (REMs) in circular quantum dots. (III)
At high magnetic fields, the REMs are described by parameter-free analytic wave
functions, which are an alternative to the Laughlin and composite-fermion
approaches. (IV) Crystalline phases of strongly repelling bosons. In rotating
traps and in analogy with the REMs, such repelling bosons form rotating boson
molecules (RBMs).
\\ ( http://arxiv.org/abs/0711.0637 , 1720kb)
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arXiv:0711.0653
Date: Mon, 5 Nov 2007 14:49:25 GMT (262kb)

Title: Breaking superfluidity rotating a Fermi gas at unitarity
Authors: I. Bausmerth, A. Recati, S. Stringari
Categories: cond-mat.soft cond-mat.supr-con
Comments: 5 pages, 4 figures
\\
   We study the effect of the rotation on a harmonically trapped Fermi gas at
zero temperature under the assumption that vortices are not formed. We show
that at unitarity the rotation produces a phase separation between a non
rotating superfluid (S) core and a rigidly rotating normal (N) gas. The
interface between the two phases is characterized by a density discontinuity
$n_{\rm N}/n_{\rm S}= 0.85$, independent of the angular velocity. The depletion
of the superfluid and the angular momentum of the rotating configuration are
calculated as a function of the angular velocity. The conditions of energetic
and dynamic stability are also discussed.
\\ ( http://arxiv.org/abs/0711.0653 , 262kb)
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arXiv:0711.0688
Date: Mon, 5 Nov 2007 16:53:12 GMT (26kb)

Title: Statistical correlations in an ideal gas of particles obeying fractional
   exclusion statistics
Authors: F. M. D. Pellegrino, G. G. N. Angilella, N. H. March, R. Pucci
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: Accepted for publication in Phys. Rev. E
\\
   After a brief discussion of the concepts of fractional exchange and
fractional exclusion statistics, we report partly analytical and partly
numerical results on thermodynamic properties of assemblies of particles
obeying fractional exclusion statistics. The effect of dimensionality is one
focal point, the ratio mu/kB T of chemical potential to thermal energy being
obtained numerically as a function of a scaled particle density. Pair
correlation functions are also presented as a function of the statistical
parameter, with `Friedel' oscillations developing close to the fermion limit,
for sufficiently large density.
\\ ( http://arxiv.org/abs/0711.0688 , 26kb)
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arXiv:0711.0401
Date: Fri, 2 Nov 2007 21:25:29 GMT (582kb)

Title: Rabi flopping between ground and Rydberg states with dipole-dipole
   atomic interactions
Authors: T. A. Johnson, E. Urban, T. Henage, L. Isenhower, D. D. Yavuz, T. G.
   Walker, and M. Saffman
Categories: quant-ph
Comments: 4 pages, 6 figures
\\
   We demonstrate Rabi flopping of small numbers of $\rm{^{87}Rb}$ atoms between
ground and Rydberg states with $n\le 43$. Coherent population oscillations are
observed for single atom flopping, while the presence of two or more atoms
decoheres the oscillations. We show that these observations are consistent with
van der Waals interactions of Rydberg atoms.
\\ ( http://arxiv.org/abs/0711.0401 , 582kb)
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arXiv:0711.0663
Date: Mon, 5 Nov 2007 15:15:51 GMT (403kb)

Title: Averaging out magnetic forces with fast rf-sweeps in an optical trap for
   metastable chromium atoms
Authors: Q. Beaufils, R. Chicireanu, A. Pouderous, W. de Souza Melo, B.
   Laburthe-Tolra, E. Mar\'echal, L. Vernac, J. C. Keller, and O. Gorceix
Categories: quant-ph
Comments: 4 pages, 4 figures
\\
   We introduce a novel type of time-averaged trap, in which the internal state
of the atoms is rapidly modulated to modify magnetic trapping potentials. In
our experiment, fast radiofrequency (rf) linear sweeps flip the spin of atoms
at a fast rate, which averages out magnetic forces. We use this procedure to
optimize the accumulation of metastable chomium atoms into an optical dipole
trap from a magneto-optical trap. The potential experienced by the metastable
atoms is identical to the bare optical dipole potential, so that this procedure
allows for trapping all magnetic sublevels, hence increasing by up to 80
percent the final number of accumulated atoms.
\\ ( http://arxiv.org/abs/0711.0663 , 403kb)
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arXiv:0711.0823
Date: Tue, 6 Nov 2007 15:05:35 GMT (135kb)

Title: Density correlations in ultracold Fermi systems within the exact
   Richardson solution
Authors: S. Staudenmayer, W. Belzig, C. Bruder
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 8 pages, 7 figures, submitted to PRA
\\
   We discuss the occupation number correlations in an ultracold system of
interacting fermionic atoms. For a system with a special energy-level
distribution, viz. two multiply-degenerate levels, explicit expressions for the
correlation functions are derived in a canonical approach using the exact
ground state wavefunction of the reduced BCS Hamiltonian. We evaluate the
correlators numerically for different interaction strength and find analytical
expressions in some limiting cases. Due to the underlying fermionic nature of
the pairs the occupations are predominantly anti-correlated and their
statistics is a multinomial distribution.
\\ ( http://arxiv.org/abs/0711.0823 , 135kb)
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arXiv:0711.0848
Date: Tue, 6 Nov 2007 11:59:59 GMT (22kb)

Title: Bose-Einstein condensation and gauge symmetry breaking
Authors: V.I. Yukalov
Categories: cond-mat.stat-mech
Comments: Latex file, 29 pages
Journal-ref: Laser Phys. Lett. 4 (2007) 632-647
\\
   The fundamental problem is analized, the relation between Bose-Einstein
condensation and spontaneous gauge symmetry breaking. This relation is largerly
misunderstood in physics community. Numerous articles and books contain the
statement that, though gauge symmetry breaking helps for describing
Bose-Einstein condensation, but the latter, in principle, does not require any
symmetry breaking. This, however, is not correct. The analysis is based on the
known mathematical theorems. But in order not to overcomplicate the
presentation and to make it accessible to all readers, technical details are
often omitted here. The emphasis is made on the following basic general facts:
Spontaneous breaking of gauge symmetry is the necessary and sufficient
condition for Bose-Einstein condensation. Condensate fluctuations, in
thermodynamic limit, are negligible. Their catastrophic behavior can arise only
as a result of incorrect calculations, when a Bose-condensed system is
described without gauge symmetry breaking. It is crucially important to employ
the representative statistical ensembles equipped with all conditions that are
necessary for a unique and mathematically correct description of the given
statistical system. Only then one is able to develop a self-consistent theory,
free of paradoxes.
\\ ( http://arxiv.org/abs/0711.0848 , 22kb)
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arXiv:0711.0853
Date: Tue, 6 Nov 2007 12:19:20 GMT (522kb)

Title: Anisotropic solitons in dipolar Bose-Einstein Condensates
Authors: I. Tikhonenkov, B. A. Malomed, and A. Vardi
Categories: cond-mat.other
Comments: 5 pages, 4 figures
\\
   Starting with a Gaussian variational ansatz, we predict anisotropic bright
solitons in quasi-2D Bose-Einstein condensates consisting of atoms with dipole
moments polarized \emph{perpendicular} to the confinement direction. Unlike
isotropic solitons predicted for the moments aligned with the confinement axis
[Phys. Rev. Lett. \textbf{95}, 200404 (2005)], no sign reversal of the
dipole-dipole interaction is necessary to support the solitons. Direct 3D
simulations confirm their stability.
\\ ( http://arxiv.org/abs/0711.0853 , 522kb)
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arXiv:0711.0854
Date: Tue, 6 Nov 2007 12:27:15 GMT (615kb)

Title: Matter-wave squeezing and the generation of SU(1,1) and SU(2)
   coherent-states via Feshbach resonances
Authors: I. Tikhonenkov, E. Pazy, Y. B. Band, and A. Vardi
Categories: cond-mat.other
Comments: 13 pages, 8 figures
\\
   Pair operators for boson and fermion atoms generate SU(1,1) and SU(2) Lie
algebras, respectively. Consequently, the pairing of boson and fermion atoms
into diatomic molecules via Feshbach resonances, produces SU(1,1) and SU(2)
coherent states, making bosonic pairing the matter-wave equivalent of
parametric coupling and fermion pairing equivalent to the Dicke model of
quantum optics. We discuss the properties of atomic states generated in the
dissociation of molecular Bose-Einstein condensates into boson or fermion
constituent atoms. The SU(2) coherent states produced in dissociation into
fermions give Poissonian atom-number distributions, whereas the SU(1,1) states
generated in dissociation into bosons result in super-poissonian distributions,
in analogy to two-photon squeezed states. In contrast, starting from an atomic
gas produces coherent number distributions for bosons and super-poissonian
distributions for fermions.
\\ ( http://arxiv.org/abs/0711.0854 , 615kb)
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arXiv:0711.0861
Date: Tue, 6 Nov 2007 12:38:41 GMT (88kb)

Title: Confinement controlled dissociation of a molecular Bose-Einstein
   condensate
Authors: I. Tikhonenkov and A. Vardi
Categories: cond-mat.other
Comments: 18 pages, 6 figures
Journal-ref: J. Phys. B 40, S299 (2007)
\\
   We study the collective two-channel dissociation dynamics of a molecular
Bose-Einstein condensate into bosonic fragments under tight harmonic
confinement. Bose-stimulated dissociation in either channel can only take place
provided that the respective trap size $l_i$ for the fragments is large with
respect to the healing length $\zeta_i$ of the atom-molecule resonance. Thus,
even when both channels are equally coupled, differences in mass or in
dynamical polarizability enable the control of the reaction outcome by
variation of the trap frequency. In particular, if $l_1>\zeta_1$ and
$l_2<\zeta_2$, only the first channel will be amplified. This behavior
demonstrate a unique feature of 'superchemistry' wherein a chemical reaction
may be controlled by the manipulation of the reaction vessel.
\\ ( http://arxiv.org/abs/0711.0861 , 88kb)
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arXiv:0711.0889
Date: Tue, 6 Nov 2007 14:59:49 GMT (110kb)

Title: Dipolar bosons in a planar array of one-dimensional tubes
Authors: C. Kollath, Julia S. Meyer, T. Giamarchi
Categories: cond-mat.other cond-mat.str-el
\\
   We investigate bosonic atoms or molecules interacting via dipolar
interactions in a planar array of one-dimensional tubes. We consider the
situation in which the dipoles are oriented perpendicular to the tubes by an
external field. We find various quantum phases reaching from a `sliding
Luttinger liquid' phase in which the tubes remain Luttinger liquids to a
two-dimensional charge density wave ordered phase. Two different kinds of
charge density wave order occur: a stripe phase in which the bosons in
different tubes are aligned and a checkerboard phase. We further point out how
to distinguish the occurring phases experimentally.
\\ ( http://arxiv.org/abs/0711.0889 , 110kb)
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arXiv:0711.0942
Date: Tue, 6 Nov 2007 18:33:39 GMT (94kb,D)

Title: Entanglement in the Bose-Einstein condensate phase transition
Authors: Libby Heaney
Categories: quant-ph
Comments: 9 pages, 5 figures
\\
   We determine the behaviour of entanglement between regions of space in a Bose
gas of fixed particle number around the critical temperature condensation.
Long-range correlations develop in the Bose-Einstein condensate (BEC) phase
transition and the aim here is to find out whether spatial coherence alone
implies entanglement. We use a purity measure of entanglement to derive an
entanglement witness that detects entanglement between two regions of space in
the BEC. It is shown that spatial coherence between the two regions is
necessary for entanglement with coherence and entanglement becoming equivalent
only when the regions occupy the entire confining volume of the gas. The
probabilities for Bosons to occupy the regions is the only other parameter that
influences the amount of entanglement. We calculate explicitly the amount of
entanglement between two regions for a cigar-shaped harmonic potential and find
that it increases with decreasing temperature. A second entanglement witness is
derived for entanglement between three regions of space, where again spatial
coherence between each pair of regions is precursor to entanglement. It is
shown that the state with the maximum amount of entanglement occurs when the
probabilities for the Bosons to occupy the three regions are equal.
\\ ( http://arxiv.org/abs/0711.0942 , 94kb)
------------------------------------------------------------------------------
\\
arXiv:0711.0968
Date: Tue, 6 Nov 2007 21:10:34 GMT (74kb)

Title: Quantum Monte Carlo study of the visibility of one-dimensional
   Bose-Fermi mixtures
Authors: C. N. Varney, V. G. Rousseau, R. T. Scalettar
Categories: cond-mat.other
Comments: 4 pages, 6 figures
\\
   We use quantum Monte Carlo simulations to evaluate the density profiles and
visibility ${\cal V}$ of mixtures of bosons and fermions in one-dimensional
optical lattices. We find that the bosonic ${\cal V}_b$ exhibits kinks which,
as in the pure case, are tied to the evolution of the superfluid and Mott
insulating domains on the lattice. However, additional kinks are caused by the
fermions and are tied to the formation of composite particles at the center of
the trap. For the parameters we study, the more generic behavior is that ${\cal
V}$ increases with the admixture of fermions, a phenomenon we show is
associated with the breakdown of Mott insulating behavior of the bosonic
species at the trap center caused by the attractive fermion-boson interaction.
In other regimes a decreased visibility results from the addition of fermions,
in agreement with recent experiments.
\\ ( http://arxiv.org/abs/0711.0968 , 74kb)
------------------------------------------------------------------------------
\\
arXiv:0711.0976
Date: Tue, 6 Nov 2007 22:10:55 GMT (53kb)

Title: Bose-Einstein condensation and superfluidity of magnetobiexcitons in
   quantum wells' and graphene superlattices
Authors: Oleg L. Berman, Roman Ya. Kezerashvili and Yurii E. Lozovik
Categories: cond-mat.mes-hall cond-mat.str-el
Comments: 4 pages, 2 figures
\\
   We propose the Bose-Einstein condensation (BEC) and superfluidity of
quasi-two-dimensional (2D) spatially indirect magnetobiexcitons in a slab of
superlattice with alternating electron and hole layers consisting from the
semiconducting quantum wells (QWs) and graphene superlattice in high magnetic
field. The two different Hamiltonians of a dilute gas of magnetoexcitons with a
dipole-dipole repulsion in superlattices consisting of both QWs and graphene
layers in the limit of high magnetic field have been reduced to one effective
Hamiltonian a dilute gas of two-dimensional excitons without magnetic field.
Moreover, for $N$ excitons we have reduced the problem of $2N\times 2$
dimensional space onto the problem of $N\times 2$ dimensional space by
integrating over the coordinates of the relative motion of an electron (e) and
a hole (h). The instability of the ground state of the system of interacting
two-dimensional indirect magnetoexcitons in a slab of superlattice with
alternating electron and hole layers in high magnetic field is established. The
stable system of indirect quasi-two-dimensional magnetobiexcitons, consisting
of pair of indirect excitons with opposite dipole moments is considered. The
density of superfluid component $n_{s}(T)$ and the temperature of the
Kosterlitz-Thouless phase transition to the superfluid state in the system of
two-dimensional indirect magnetobiexcitons, interacting as electrical
quadrupoles, are obtained for both QW and graphene realizations.
\\ ( http://arxiv.org/abs/0711.0976 , 53kb)
------------------------------------------------------------------------------

The replacements:

------------------------------------------------------------------------------
\\
arXiv:physics/0607140
replaced with revised version Fri, 2 Nov 2007 16:13:24 GMT (50kb,D)

Title: Effective-range description of a Bose gas under strong one- or
   two-dimensional confinement
Authors: Pascal Naidon, Eite Tiesinga, William F. Mitchell, and Paul S.
   Julienne
Categories: physics.atom-ph
Comments: 6 pages, 3 figures
Journal-ref: New J. Phys. 9 No 1 (January 2007) 19
\\ ( http://arxiv.org/abs/physics/0607140 , 50kb)
------------------------------------------------------------------------------
\\
arXiv:0704.1096
replaced with revised version Sat, 3 Nov 2007 06:05:37 GMT (34kb)

Title: Formation of a sonic horizon in isotropically expanding Bose-Einstein
   condensates
Authors: Yasunari Kurita, Takao Morinari
Categories: cond-mat.other gr-qc hep-th
Comments: 7 pages, 8 figures; Final version, accepted to Phys.Rev. A
Report-no: YITP-07-16, OCU-PHYS-264, AP-GR-40
\\ ( http://arxiv.org/abs/0704.1096 , 34kb)
------------------------------------------------------------------------------
\\
arXiv:0710.3094
replaced with revised version Mon, 5 Nov 2007 14:53:45 GMT (38kb)

Title: Effect of the lattice alignment on Bloch oscillations of a Bose-Einstein
   condensate in a square optical lattice
Authors: M.-C. Chung and A. R. Kolovsky
Categories: cond-mat.supr-con cond-mat.mes-hall
Comments: 4 pages, 3 figures
\\ ( http://arxiv.org/abs/0710.3094 , 38kb)
------------------------------------------------------------------------------
\\
arXiv:cond-mat/0611295
replaced with revised version Mon, 5 Nov 2007 21:57:45 GMT (43kb)

Title: Oscillatory vortex interaction in a gapless fermion superfluid with spin
   population imbalance
Authors: Vladimir M. Stojanovic, W. Vincent Liu, Yong Baek Kim
Categories: cond-mat.supr-con cond-mat.other
Comments: 5 pages, 3 updated figures; a short version of arXiv:0710.2522
\\ ( http://arxiv.org/abs/cond-mat/0611295 , 43kb)
------------------------------------------------------------------------------
\\
arXiv:0706.3411 (*cross-listing*)
replaced with revised version Tue, 6 Nov 2007 14:00:38 GMT (877kb)

Title: Cavity QED with a Bose-Einstein condensate
Authors: Ferdinand Brennecke, Tobias Donner, Stephan Ritter, Thomas Bourdel,
   Michael K\"ohl and Tilman Esslinger
Categories: quant-ph cond-mat.other
Comments: 6 pages, 4 figures; version accepted for publication in Nature;
   updated Fig. 4; changed atom numbers due to new calibration
\\ ( http://arxiv.org/abs/0706.3411 , 877kb)
------------------------------------------------------------------------------
\\
arXiv:0704.3114
replaced with revised version Tue, 6 Nov 2007 21:33:36 GMT (629kb)

Title: Topological Winding and Unwinding in Metastable Bose-Einstein
   Condensates
Authors: Rina Kanamoto, Lincoln D. Carr, Masahito Ueda
Categories: cond-mat.other
Comments: 4 pages, 3 figures
\\ ( http://arxiv.org/abs/0704.3114 , 629kb)
------------------------------------------------------------------------------
\\
arXiv:0707.2918
replaced with revised version Wed, 7 Nov 2007 21:38:14 GMT (413kb)

Title: Anderson Localization of Bogolyubov Quasiparticles in Interacting
   Bose-Einstein Condensates
Authors: Pierre Lugan (LCFIO), David Cl\'ement (LCFIO), Philippe Bouyer
   (LCFIO), Alain Aspect (LCFIO), Laurent Sanchez-Palencia (LCFIO)
Categories: cond-mat.other
Comments: published version (no significant changes compared to last version)
Proxy: ccsd hal-00163902
Journal-ref: Physical Review Letters 99, 18 (2007) 180402
DOI: 10.1103/PhysRevLett.99.180402
\\ ( http://arxiv.org/abs/0707.2918 , 413kb)
------------------------------------------------------------------------------
\\
arXiv:0709.3463
replaced with revised version Wed, 7 Nov 2007 23:20:51 GMT (51kb)

Title: Quantum Ratchets for Quantum Communication with Optical Superlattices
Authors: Oriol Romero-Isart and Juan Jose Garcia-Ripoll
Categories: quant-ph cond-mat.other
Comments: Published version, 9 pages, 5 figures
Journal-ref: Physical Review A 76, 052304 (2007)
DOI: 10.1103/PhysRevA.76.052304
\\ ( http://arxiv.org/abs/0709.3463 , 51kb)
------------------------------------------------------------------------------

The replacements:

------------------------------------------------------------------------------
\\
arXiv:physics/0607140
replaced with revised version Fri, 2 Nov 2007 16:13:24 GMT (50kb,D)

Title: Effective-range description of a Bose gas under strong one- or
   two-dimensional confinement
Authors: Pascal Naidon, Eite Tiesinga, William F. Mitchell, and Paul S.
   Julienne
Categories: physics.atom-ph
Comments: 6 pages, 3 figures
Journal-ref: New J. Phys. 9 No 1 (January 2007) 19
\\ ( http://arxiv.org/abs/physics/0607140 , 50kb)
------------------------------------------------------------------------------
\\
arXiv:0704.1096
replaced with revised version Sat, 3 Nov 2007 06:05:37 GMT (34kb)

Title: Formation of a sonic horizon in isotropically expanding Bose-Einstein
   condensates
Authors: Yasunari Kurita, Takao Morinari
Categories: cond-mat.other gr-qc hep-th
Comments: 7 pages, 8 figures; Final version, accepted to Phys.Rev. A
Report-no: YITP-07-16, OCU-PHYS-264, AP-GR-40
\\ ( http://arxiv.org/abs/0704.1096 , 34kb)
------------------------------------------------------------------------------
\\
arXiv:0710.3094
replaced with revised version Mon, 5 Nov 2007 14:53:45 GMT (38kb)

Title: Effect of the lattice alignment on Bloch oscillations of a Bose-Einstein
   condensate in a square optical lattice
Authors: M.-C. Chung and A. R. Kolovsky
Categories: cond-mat.supr-con cond-mat.mes-hall
Comments: 4 pages, 3 figures
\\ ( http://arxiv.org/abs/0710.3094 , 38kb)
------------------------------------------------------------------------------
\\
arXiv:cond-mat/0611295
replaced with revised version Mon, 5 Nov 2007 21:57:45 GMT (43kb)

Title: Oscillatory vortex interaction in a gapless fermion superfluid with spin
   population imbalance
Authors: Vladimir M. Stojanovic, W. Vincent Liu, Yong Baek Kim
Categories: cond-mat.supr-con cond-mat.other
Comments: 5 pages, 3 updated figures; a short version of arXiv:0710.2522
\\ ( http://arxiv.org/abs/cond-mat/0611295 , 43kb)
------------------------------------------------------------------------------
\\
arXiv:0706.3411 (*cross-listing*)
replaced with revised version Tue, 6 Nov 2007 14:00:38 GMT (877kb)

Title: Cavity QED with a Bose-Einstein condensate
Authors: Ferdinand Brennecke, Tobias Donner, Stephan Ritter, Thomas Bourdel,
   Michael K\"ohl and Tilman Esslinger
Categories: quant-ph cond-mat.other
Comments: 6 pages, 4 figures; version accepted for publication in Nature;
   updated Fig. 4; changed atom numbers due to new calibration
\\ ( http://arxiv.org/abs/0706.3411 , 877kb)
------------------------------------------------------------------------------
\\
arXiv:0704.3114
replaced with revised version Tue, 6 Nov 2007 21:33:36 GMT (629kb)

Title: Topological Winding and Unwinding in Metastable Bose-Einstein
   Condensates
Authors: Rina Kanamoto, Lincoln D. Carr, Masahito Ueda
Categories: cond-mat.other
Comments: 4 pages, 3 figures
\\ ( http://arxiv.org/abs/0704.3114 , 629kb)
------------------------------------------------------------------------------
\\
arXiv:0707.2918
replaced with revised version Wed, 7 Nov 2007 21:38:14 GMT (413kb)

Title: Anderson Localization of Bogolyubov Quasiparticles in Interacting
   Bose-Einstein Condensates
Authors: Pierre Lugan (LCFIO), David Cl\'ement (LCFIO), Philippe Bouyer
   (LCFIO), Alain Aspect (LCFIO), Laurent Sanchez-Palencia (LCFIO)
Categories: cond-mat.other
Comments: published version (no significant changes compared to last version)
Proxy: ccsd hal-00163902
Journal-ref: Physical Review Letters 99, 18 (2007) 180402
DOI: 10.1103/PhysRevLett.99.180402
\\ ( http://arxiv.org/abs/0707.2918 , 413kb)
------------------------------------------------------------------------------
\\
arXiv:0709.3463
replaced with revised version Wed, 7 Nov 2007 23:20:51 GMT (51kb)

Title: Quantum Ratchets for Quantum Communication with Optical Superlattices
Authors: Oriol Romero-Isart and Juan Jose Garcia-Ripoll
Categories: quant-ph cond-mat.other
Comments: Published version, 9 pages, 5 figures
Journal-ref: Physical Review A 76, 052304 (2007)
DOI: 10.1103/PhysRevA.76.052304
\\ ( http://arxiv.org/abs/0709.3463 , 51kb)
------------------------------------------------------------------------------

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/
=========================================================================
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Received on Tue Dec 18 2007 - 08:22:20 EST

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