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

Date: Wed, 12 Dec 2007 22:46:21 +1000

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/ ========================================================================= Legal stuff: Unless stated otherwise, this e-mail represents only the views of the sender and not the views of the University of Queensland =========================================================================Received on Tue Dec 18 2007 - 08:22:20 EST

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