Matt's arXiv selection: week ending 23rd March 2007.

From: Matthew Davis <>
Date: Thu, 29 Mar 2007 13:37:09 +1000 (EST)

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

Another late mailing this week :(

A total of 27 new papers and 15 replacements:

Paper: cond-mat/0703433
Date: Fri, 16 Mar 2007 19:43:34 GMT (37kb)

Title: Spin-polarized Fermi superfluids as Bose-Fermi mixtures
Authors: E. Taylor, A. Griffin, and Y. Ohashi
Categories: cond-mat.other
Comments: 14 pages, 1 figure
Subj-class: Other
   In the strong-coupling BEC region where a Feshbach resonance gives rise to
tightly-bound dimer molecules, we show that a spin-polarized Fermi superfluid
reduces to a simple Bose-Fermi mixture of Bose-condensed dimers and the
leftover unpaired fermions. Using a many-body functional integral formalism,
the Gaussian fluctuations give rise to an induced dimer-dimer interaction
mediated by the unpaired fermions, with the dimer-fermion vertex being given by
the (mean-field) Born approximation. Treating the pairing fluctuations to
quartic order, we show how the action for a spin-polarized Fermi superfluid
reduces to one for a Bose-Fermi mixture at energies below the binding energy of
the dimers. This Bose-Fermi action includes an expression for the effective
dimer-unpaired fermion interaction in a spin-polarized Fermi superfluid beyond
the Born approximation, in the superfluid phase at finite temperatures. In the
low-density limit, we show how this dimer-fermion interaction gives the s-wave
scattering length $a_{BF}=1.18a_F$ ($a_F$ is the s-wave fermion scattering
length), a result first derived by Skorniakov and Ter-Martirosian in 1957 for
three interacting fermions.
\\ ( , 37kb)
Paper: cond-mat/0703443
Date: Fri, 16 Mar 2007 16:33:19 GMT (150kb)

Title: Spectral properties of a Rydberg atom immersed in a Bose-Einstein
Authors: Stephan Middelkamp, Igor Lesanovsky, and P. Schmelcher
Categories: cond-mat.other
Subj-class: Other
   The electronic spectrum of a Rydberg atom immersed in a Bose-Einstein
condensate is investigated. The Heisenberg equations of motions for the
condensate and the Rydberg atom are derived. Neglecting the backaction of the
Rydberg atom onto the condensate decouples the equations describing the
condensate and Rydberg atom. In this case the spectral structure of the Rydberg
atom is completely determined by an effective potential which depends on the
density distribution of the condensate. We study the spectral properties for
the situation of an isotropic harmonic and anharmonic as well as axially
symmetric confinement. In the latter case an intriguing analogy with Rydberg
atoms in magnetic fields is encountered.
\\ ( , 150kb)
Paper: cond-mat/0703449
Date: Fri, 16 Mar 2007 19:24:14 GMT (172kb)

Title: Open system of interacting fermions: Statistical properties of cross
   sections and fluctuations
Authors: G.L.Celardo, F.M.Izrailev, V.G. Zelevinsky, G.P.Berman
Categories: cond-mat.dis-nn cond-mat.stat-mech
Comments: 13 pages, 11 figures
Subj-class: Disordered Systems and Neural Networks; Statistical Mechanics
   Statistical properties of cross sections are studied for an open system of
interacting fermions. The description is based on the effective non-Hermitian
Hamiltonian that accounts for the existence of open decay channels preserving
the unitarity of the scattering matrix. The intrinsic interaction is modelled
by the two-body random ensemble of variable strength. In particular, the
crossover region from isolated to overlapping resonances accompanied by the
effect of the width redistribution creating super-radiant and trapped states is
studied in detail. The important observables, such as average cross section,
its fluctuations, autocorrelation functions of the cross section and scattering
matrix, are very sensitive to the coupling of the intrinsic states to the
continuum around the crossover. A detailed comparison is made of our results
with standard predictions of statistical theory of cross sections, such as the
Hauser-Feshbach formula for the average cross section and Ericson theory of
fluctuations and correlations of cross sections. Strong deviations are found in
the crossover region, along with the dependence on intrinsic interactions and
degree of chaos inside the system.
\\ ( , 172kb)
Paper (*cross-listing*): hep-ph/0703159
Date: Thu, 15 Mar 2007 07:58:06 GMT (71kb)

Title: BEC-BCS Crossover in the Nambu--Jona-Lasinio Model of QCD
Authors: Gaofeng Sun, Lianyi He and Pengfei Zhuang
Categories: hep-ph cond-mat.supr-con nucl-th
Comments: 18 pages, 15 figures
Subj-class: High Energy Physics - Phenomenology; Superconductivity
   The BEC-BCS crossover in QCD at finite baryon and isospin chemical potentials
is investigated in the Nambu--Jona-Lasinio model. The diquark condensation in
two color QCD and the pion condensation in real QCD would undergo a BEC-BCS
crossover when the corresponding chemical potential increases. We determined
the crossover chemical potential as well as the BEC and BCS regions. The
crossover is not triggered by increasing the strength of attractive interaction
among quarks but driven by changing the charge density. The chiral symmetry
restoration at finite temperature and density plays an important role in the
BEC-BCS crossover. For real QCD, strong couplings in diquark and vector meson
channels can induce a diquark BEC-BCS crossover in color superconductor, and in
the BEC region the chromomagnetic instability is fully cured and the ground
state is a uniform phase.
\\ ( , 71kb)
Paper (*cross-listing*): nlin.PS/0703032
Date: Thu, 15 Mar 2007 19:11:50 GMT (391kb)

Title: Solitary Waves Bifurcated from Bloch Band Edges in Two-dimensional
   Periodic Media
Authors: Zuoqiang Shi, Jianke Yang
Categories: nlin.PS cond-mat.other physics.optics
Comments: 23 pages, 15 figures. To appear in Phys. Rev. E
Subj-class: Pattern Formation and Solitons; Optics; Other
   Solitary waves bifurcated from edges of Bloch bands in two-dimensional
periodic media are determined both analytically and numerically in the context
of a two-dimensional nonlinear Schr\"odinger equation with a periodic
potential. Using multi-scale perturbation methods, envelope equations of
solitary waves near Bloch bands are analytically derived. These envelope
equations reveal that solitary waves can bifurcate from edges of Bloch bands
under either focusing or defocusing nonlinearity, depending on the signs of
second-order dispersion coefficients at the edge points. Interestingly, at edge
points with two linearly independent Bloch modes, the envelope equations lead
to a host of solitary wave structures including reduced-symmetry solitons,
dipole-array solitons, vortex-cell solitons, and so on -- many of which have
never been reported before. It is also shown analytically that the centers of
envelope solutions can only be positioned at four possible locations at or
between potential peaks. Numerically, families of these solitary waves are
directly computed both near and far away from band edges. Near the band edges,
the numerical solutions spread over many lattice sites, and they fully agree
with the analytical solutions obtained from envelope equations. Far away from
the band edges, solitary waves are strongly localized with intensity and phase
profiles characteristic of individual families.
\\ ( , 391kb)
Paper: quant-ph/0703148
Date: Fri, 16 Mar 2007 10:29:20 GMT (990kb)

Title: Kicked Bose-Hubbard systems and kicked tops -- destruction and
   stimulation of tunneling
Authors: M P Strzys, E M Graefe and H J Korsch
Categories: quant-ph
   In the two-mode approximation Bose-Einstein condensates (BEC) in a
double-well potential can be described by a many particle Hamiltonian of
Bose-Hubbard type. We focus on such a BEC whose interatomic interaction
strength is modulated periodically with $\delta$-kicks. This System in fact
represents a model of a kicked top. The mean-field dynamics provide a rich
mixed phase space with regular and chaotic regions. By increasing the
kick-strength a bifurcation leads to the appearance of self-trapping states
localized in regular islands. This self-trapping is also found for the many
particle system, however in general suppressed by tunneling oscillations. We
show that the tunneling time can be calculated from the quasi-energy splitting
of the corresponding Floquet states. By varying the kick-strength these
quasi-energy levels undergo both avoided and even real crossings. Therefore
stimulation or actually complete destruction of tunneling is observed for this
many particle system.
\\ ( , 990kb)
Paper: quant-ph/0703155
Date: Fri, 16 Mar 2007 15:56:07 GMT (228kb)

Title: Trapping cold atoms near carbon nanotubes: thermal spin flips and
   Casimir-Polder potential
Authors: Rachele Fermani, Stefan Scheel, Peter L. Knight
Categories: quant-ph
Comments: 8 pages, 3 figures
   We investigate the possibility to trap ultracold atoms near the outside of a
metallic carbon nanotube (CN) which we imagine to use as a miniaturized
current-carrying wire. We calculate atomic spin flip lifetimes and compare the
strength of the Casimir-Polder potential with the magnetic trapping potential.
Our analysis indicates that the Casimir-Polder force is the dominant loss
mechanism and we compute the minimum distance to the carbon nanotube at which
an atom can be trapped.
\\ ( , 228kb)
Paper: physics/0703168
Date: Fri, 16 Mar 2007 16:46:59 GMT (30kb)

Title: Effects of nonintegrability on stabilization of Feshbach molecules in
   atom waveguides
Authors: V. A. Yurovsky
Categories: physics.atom-ph
Comments: 4 pages, 4 figures
Subj-class: Atomic Physics
   Deactivation of broad quasi-one-dimensional dibosonic molecules is analyzed.
Within integrable Lieb-Liniger-McGuire (LLMG) model an exact expression does
not demonstrate suppression of the deactivation at low collision energies.
Solution of Faddeev equations demonstrates that when a Feshbach resonance lifts
the symmetry of the LLMG model the deactivation becomes suppressed. This effect
shows a way for formation of a stable gas of dibosonic Feshbach molecules.
\\ ( , 30kb)
Paper: physics/0703172
Date: Fri, 16 Mar 2007 14:53:31 GMT (218kb)

Title: Implementation of a double-scanning technique for studies of the Hanle
   effect in Rubidium vapor
Authors: A. Atvars, M. Auzinsh, E. A. Gazazyan, A. V. Papoyan, S. V. Shmavonyan
Categories: physics.atom-ph
Subj-class: Atomic Physics
   We have studied the resonance fluorescence of a room-temperature rubidium
vapor exited to the atomic 5P3/2 state (D2 line) by powerful single-frequency
cw laser radiation (1.25 W/cm^2) in the presence of a magnetic field. In these
studies, the slow, linear scanning of the laser frequency across the hyperfine
transitions of the D2 line is combined with a fast linear scanning of the
applied magnetic field, which allows us to record frequency-dependent Hanle
resonances from all the groups of hyperfine transitions including V- and Lambda
- type systems. Rate equations were used to simulate fluorescence signals for
85Rb due to circularly polarized exciting laser radiation with different mean
frequency values and laser intensity values. The simulation show a dependance
of the fluorescence on the magnetic field. The Doppler effect was taken into
account by averaging the calculated signals over different velocity groups.
Theoretical calculations give a width of the signal peak in good agreement with
\\ ( , 218kb)
Paper: cond-mat/0703454
Date: Sat, 17 Mar 2007 01:41:48 GMT (268kb)

Title: Simulation and detection of Dirac fermions with cold atoms in an optical
Authors: Shi-Liang Zhu, Baigeng Wang, and L.-M. Duan
Categories: cond-mat.mtrl-sci
Comments: 4 pages
Subj-class: Materials Science
   We propose an experimental scheme to simulate and observe relativistic Dirac
fermions with cold atoms in a hexagonal optical lattice. By controlling the
lattice anisotropy, one can realize both massive and massless Dirac fermions
and observe the topological phase transition between them. Through explicit
calculations, we show that both the Bragg spectroscopy and the atomic density
profile in a trap can be used to demonstrate the Dirac fermions and the
associated phase transition.
\\ ( , 268kb)
Paper: cond-mat/0703465
Date: Mon, 19 Mar 2007 14:34:25 GMT (501kb)

Title: Unitary Fermi gas in the epsilon expansion
Authors: Yusuke Nishida
Categories: cond-mat.other
Comments: 103 pages, 29 figures; PhD thesis submitted to Univ. of Tokyo
   (supervisor: T. Hatsuda and D. T. Son)
Subj-class: Other
   We construct systematic expansions around four and two spatial dimensions for
a Fermi gas near the unitarity limit. Near four spatial dimensions such a Fermi
gas can be understood as a weakly-interacting system of fermionic and bosonic
degrees of freedom. To the leading and next-to-leading orders in the expansion
over \epsilon=4-d, with d being the dimensionality of space, we determine the
thermodynamic functions, the fermion quasiparticle spectrum, the critical
polarizations, and the critical temperature as functions of the binding energy
of the two-body state. We also show that the unitary Fermi gas near two spatial
dimensions reduces to a weakly-interacting Fermi gas and calculate the
thermodynamic functions and the fermion quasiparticle spectrum in the expansion
over \bar\epsilon=d-2. We discuss the matching of the two systematic expansions
around four and two spatial dimensions in order to extract physical observables
at d=3. We find good agreement of the results with those from recent Monte
Carlo simulations.
\\ ( , 501kb)
Paper: cond-mat/0703475
Date: Mon, 19 Mar 2007 02:39:37 GMT (11kb)

Title: Knotted Solitons in a Charged Two-Condensate Bose System
Authors: Yi-Shi Duan, Xin-Hui Zhang, Yu-Xiao Liu and Li Zhao
Categories: cond-mat.supr-con
Comments: 12 pages,0 figures
Subj-class: Superconductivity
Journal-ref: PHYSICAL REVIEW B 74, 144508 (2006)
   By making use of the decomposition of U(1) gauge potential theory and the
\phi mapping method, we propose that a charged two-condensate Bose system
possesses vortex lines and two classes of knotted solitons. The topological
charges of the vortex lines are characterized by the Hopf indices and the
Brower degrees of \phi-mapping, and the knotted solitons are described by the
nontrivial Hopf invariant and the BF action, respectively.
\\ ( , 11kb)
Paper: cond-mat/0703498
Date: Mon, 19 Mar 2007 19:44:04 GMT (239kb)

Title: Re-examining Bogoliubov's theory of an interacting Bose gas
Authors: A.M. Ettouhami
Categories: cond-mat.stat-mech cond-mat.other
Comments: 17 pages, 7 figures
Subj-class: Statistical Mechanics; Other
   We point out a few questionable features of Bogoliubov's theory of an
interacting Bose gas. In this theory, one does not diagonalize the part
$\hat{H}_2$ of the Hamiltonian that is quadratic in the boson creation and
annihilation operators, but instead one diagonalizes the ``grand canonical
Hamiltonian" $\tilde{H}_2 = \hat{H}_2 - \mu \hat{N}_1$, where $\mu$ is the
chemical potential and the operator $\hat{N}_1$ counts the number of bosons
outside the condensate. We show that such a procedure leads to an energy cost
of exciting a single boson from the condensate to the single-particle state of
momentum ${\bf k}$ which diverges like $1/k$ in the long wavelength limit. We
also show that the above divergence does not occur if one diagonalizes
$\hat{H}_2$ directly, which results in a gapped excitation spectrum, both for
bosons and for quasiparticles. Gapped excitation spectra for bosons were
derived previously, by a number of authors, and were deemed unphysical on the
grounds that such spectra violate Goldstone's theorem. Here, we argue that such
an interpretation stems from an improper identification of the collective
Goldstone modes of the system, which have to do with fluctuations of the phase
of the condensate wavefunction. More importantly, we explicitly show that the
so-called "quasiparticle" modes of $\tilde{H}_2$ represent single-particle
excitations, {\em not} collective sound waves. Finally, we show that the
average interaction energy between condensed and depleted bosons is negative,
even for strictly repulsive interactions, which we argue seriously undermines
the validity of the present formulation of Bogoliubov's theory.
\\ ( , 239kb)
Paper: quant-ph/0703156
Date: Fri, 16 Mar 2007 20:45:28 GMT (255kb)

Title: Deterministic loading of individual atoms to a high-finesse optical
Authors: Kevin M. Fortier, Soo Y. Kim, Michael J. Gibbons, Peyman Ahmadi, and
   Michael S. Chapman
Categories: quant-ph
Comments: 10 pages, 5 figures, submitted to Phys. Rev. Lett
   Individual laser cooled atoms are delivered on demand from a single atom
magneto-optic trap to a high-finesse optical cavity using an atom conveyor.
Strong coupling of the atom with the cavity field allows simultaneous cooling
and detection of individual atoms for time scales exceeding 15 s. The single
atom scatter rate is studied as a function of probe-cavity detuning and probe
Rabi frequency, and the experimental results are in good agreement with
theoretical predictions. We demonstrate the ability to manipulate the position
of a single atom relative to the cavity mode with excellent control and
\\ ( , 255kb)
Paper: quant-ph/0703173
Date: Mon, 19 Mar 2007 14:50:21 GMT (92kb)

Title: Ultraslow propagation of matched pulses by four-wave mixing in an atomic
Authors: V. Boyer, C. F. McCormick, E. Arimondo, P. D. Lett
Categories: quant-ph
Comments: 5 pages, 4 figures
   We have observed the ultraslow propagation of matched pulses in nondegenerate
four-wave mixing in a hot atomic vapor. Probe pulses as short as 70 ns can be
delayed by a tunable time of up to 40 ns with little broadening or distortion.
During the propagation, a probe pulse is amplified and generates a conjugate
pulse which is faster and separates from the probe pulse before getting locked
to it at a fixed delay. The precise timing of this process allows us to
determine the key coefficients of the susceptibility tensor. The presence of
gain in this system makes this system very interesting in the context of
all-optical information processing.
\\ ( , 92kb)
Paper: quant-ph/0703177
Date: Mon, 19 Mar 2007 17:58:20 GMT (89kb)

Title: Transport and Entanglement Generation in the Bose-Hubbard Model
Authors: O. Romero-Isart, K. Eckert, C. Rod\'o, and A. Sanpera
Categories: quant-ph
Comments: 14 pages, 6 figures
   We study entanglement generation via particle transport across a
one-dimensional system described by the Bose-Hubbard Hamiltonian. We analyze
how the competition between interactions and tunneling affects transport
properties and the creation of entanglement in the occupation number basis.
Alternatively, we propose to use spatially delocalized quantum bits, where a
quantum bit is defined by the presence of a particle either in a site or in the
adjacent one. Our results can serve as a guidance for future experiments to
characterize entanglement of ultracold gases in one-dimensional optical
\\ ( , 89kb)
Paper: quant-ph/0703178
Date: Mon, 19 Mar 2007 19:09:33 GMT (57kb)

Title: Quantum phases of interacting phonons in ion traps
Authors: X.-L. Deng, D. Porras and J.I. Cirac
Categories: quant-ph
Comments: 10 pages
   The vibrations of a chain of trapped ions can be considered, under suitable
experimental conditions, as an ensemble of interacting phonons, whose quantum
dynamics is governed by a Bose--Hubbard Hamiltonian. In this work we study the
quantum phases which appear in this system, and show that thermodynamical
properties, such as critical parameters and critical exponents, can be measured
in experiments with a limited number of ions. Besides that, interacting phonons
in trapped ions offer us the possibility to access regimes which are difficult
to study with ultracold bosons in optical lattices, like models with attractive
or site--dependent phonon-phonon interactions.
\\ ( , 57kb)
Paper: cond-mat/0703500
Date: Mon, 19 Mar 2007 20:18:39 GMT (84kb)

Title: Non-equilibrium spin dynamics in a trapped Fermi gas with effective
   spin-orbit interaction
Authors: Tudor D. Stanescu, Chuanwei Zhang, and Victor Galitski
Categories: cond-mat.other
Comments: 5 pages, 3 figures
Subj-class: Other
   We consider a trapped atomic system in the presence of spatially varying
laser fields. The laser-atom interaction leads to an effective spin-orbit
coupling for the fermions in the trap. Reflections of the fermions from the
trap boundaries provide a physical mechanism for effective momentum relaxation
and non-trivial (pseudo)-spin dynamics due to the emergent spin-orbit coupling.
We explicitly consider evolution of an initially spin-polarized Fermi gas in a
two-dimensional harmonic trap and derive exact non-equilibrium behavior of the
spin polarization. %which shows interesting dynamic features. In a symmetric
harmonic trap, the spin polarization shows periodic echoes with a frequency
equal to the harmonic trapping frequency. Perturbations, such as an asymmetry
of the trap, lead to the suppression of the spin echo amplitudes. We discuss a
possible experimental setup to observe spin relaxation and spin echoes and
provide numerical estimates for the relevant parameters.
\\ ( , 84kb)
Paper: cond-mat/0703506
Date: Tue, 20 Mar 2007 05:02:38 GMT (168kb)

Title: Mott phases and quantum phase transitions of extended Bose-Hubbard
   models in 2+1 dimensions
Authors: K. Sengupta
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: Mini review; conference proceeeding for STATPHYS - KOLKATA V; to be
   published in Physica A
Subj-class: Strongly Correlated Electrons; Statistical Mechanics
   We review the recent theoretical developments towards understanding the Mott
phases and quantum phase transition of extended Bose-Hubbard models on lattices
in two spatial dimensions . We focuss on the description of these systems using
the dual vortex picture and point out the crucial role played by the geometry
of underlying lattices in determining the nature of both the Mott phases and
the quantum phase transitions. We also briefly compare the results of dual
vortex theory with quantum Monte Carlo results.
\\ ( , 168kb)
Paper: cond-mat/0703508
Date: Tue, 20 Mar 2007 07:45:08 GMT (177kb)

Title: Spatial Coherence of a Polariton Condensate
Authors: Hui Deng, Glenn S. Solomon, Rudolf Hey, Klaus H. Ploog, Yoshihisa
Categories: cond-mat.mes-hall
Subj-class: Mesoscopic Systems and Quantum Hall Effect
   We perform a Young's double-slit experiment to study the spatial coherence
properties of a two-dimensional Bose-Einstein condensate of semiconductor
microcavity polaritons. The coherence length of the system is measured as a
function of the pump rate, which confirms a spontaneous build-up of macroscopic
coherence at the BEC phase transition. An independent measurement reveals that
the position and momentum uncertainty product of the condensate is close to the
Heisenburg limit. An experimental realization of such a minimum uncertainty
wavepacket of the polariton condensate opens a door to coherent matter-wave
phenomena such as Josephson oscillation, superfluidity, and solitons in solid
state systems.
\\ ( , 177kb)
Paper: cond-mat/0703523
Date: Tue, 20 Mar 2007 17:04:53 GMT (8kb)

Title: Vortex mass in a superfluid at low frequencies
Authors: D. J. Thouless and J. R. Anglin
Categories: cond-mat.other
Comments: 4 pages
Subj-class: Other
   An inertial mass of a vortex can be calculated by driving it round in a
circle with a steadily revolving pinning potential. We show that in the low
frequency limit this gives precisely the same formula that was used by Baym and
Chandler, but find that the result is not unique and depends on the force field
used to cause the acceleration. We apply this method to the Gross-Pitaevskii
model, and derive a simple formula for the vortex mass. We study both the long
range and short range properties of the solution. We agree with earlier results
that the non-zero compressibility leads to a divergent mass. From the
short-range behavior of the solution we find that the mass is sensitive to the
form of the pinning potential, and diverges logarithmically when the radius of
this potential tends to zero.
\\ ( , 8kb)
Paper: cond-mat/0703526
Date: Tue, 20 Mar 2007 18:12:14 GMT (43kb)

Title: Local Density Functional Theory for Superfluid Fermionic Systems: The
   Unitary Gas
Authors: Aurel Bulgac
Categories: cond-mat.supr-con
Comments: 4 pages, 4 eps figures
Subj-class: Superconductivity
   The first detailed comparison between ab initio calculations of finite
fermionic superfluid systems performed recently by S.Y. Chang and G.F. Bertsch
and the extension of the density functional theory Superfluid Local Density
Approximation (SLDA) is presented. It is shown that SLDA reproduces the total
energies, number density distributions in inhomogeneous systems along with the
energy of the normal state in homogeneous systems. Since in SLDA the effective
fermion mass differs from the bare fermion mass, the spectrum of elementary
excitations is also reproduced.
\\ ( , 43kb)
Paper: quant-ph/0703185
Date: Tue, 20 Mar 2007 12:48:09 GMT (309kb)

Title: Addressing individual atoms in optical lattices with standing-wave
   driving fields
Authors: Jaeyoon Cho
Categories: quant-ph
Comments: 4 pages, 3 figures
   A scheme for addressing individual atoms in one- or two-dimensional optical
lattices loaded with one atom per site is proposed. The scheme is based on
position-dependent atomic population transfer induced by several standing-wave
driving fields. This allows various operations important in quantum information
processing, such as manipulation and measurement of any single atom, two-qubit
operations between any pair of adjacent atoms, and patterned loading of the
lattice with one atom per every nth site for arbitrary n. The proposed scheme
is robust against considerable imperfections and actually within reach of
current technology.
\\ ( , 309kb)
Paper: quant-ph/0703189
Date: Tue, 20 Mar 2007 18:55:24 GMT (84kb)

Title: Quantum synapse for cold atoms
Authors: G.A. Kouzaev
Categories: quant-ph
Comments: 3 figures
Journal-ref: 5th Int. Conf. Physics, Technology and Applications of Wave
   processes, Samara, Russia,Sept. 2006
   In this paper, the quantum synaptic effect is studied that arisen in the
system of two crossed wires excited by the static (DC) and radio-frequency (RF)
currents. The potential barrier between the two orthogonal atom streams is
controlled electronically and the atoms can be transferred from one wire to
another under certain critical values of the RF and DC currents. The results
are interesting in the study of quantum interferometry and quantum registering
of cold atoms.
\\ ( , 84kb)
Paper: physics/0703190
Date: Mon, 19 Mar 2007 21:43:52 GMT (21kb)

Title: Unitary Fermi Gas in a Harmonic Trap
Authors: S. Y. Chang, G. F. Bertsch
Categories: physics.atom-ph
Comments: 2 figures, 2 tables
Subj-class: Atomic Physics
   We present an {\it ab initio} calculation of small numbers of trapped,
strongly interacting fermions using the Green's Function Monte Carlo method
(GFMC). The ground state energy, density profile and pairing gap are calculated
for particle numbers $N = 2 \sim 22$ using the parameter-free "unitary"
interaction. Trial wave functions are taken of the form of correlated pairs in
a harmonic oscillator basis. We find that the lowest energies are obtained with
a minimum explicit pair correlation beyond that needed to exploit the
degeneracy of oscillator states. We find that energies can be well fitted by
the expression $a_{TF} E_{TF} + \Delta {\rm mod}(N,2)$ where $E_{TF}$ is the
Thomas-Fermi energy of a noninteracting gas in the trap and $\Delta$ is a
pairing gap. There is no evidence of a shell correction energy in the
systematics, but the density distributions show pronounced shell effects. We
find the value $\Delta= 0.7\pm 0.2\omega$ for the pairing gap. This is smaller
than the value found for the uniform gas at a density corresponding to the
central density of the trapped gas.
\\ ( , 21kb)
Paper: cond-mat/0204430
replaced with revised version Tue, 20 Mar 2007 20:49:51 GMT (9kb)

Title: Percolation transition in the Bose gas II
Authors: Andras Suto
Categories: cond-mat.stat-mech math-ph math.MP
Comments: The paper is completed with the proof of Eq. (34) and with a remark
   after Eq. (44) on the existence for any m>ln(rho/rho_0) of an infinite cycle
   which contains a fraction between exp{-(m+1)} and exp{-m} of the total number
   of particles
Subj-class: Statistical Mechanics; Mathematical Physics
Journal-ref: J. Phys. A: Math. Gen. 35 (2002) 6995-7002
\\ ( , 9kb)
Paper: cond-mat/0703573
Date: Thu, 22 Mar 2007 09:17:36 GMT (273kb)

Title: Tunnelling couplings in discrete lattices, single particle band
   structure and eigenstates of interacting atom pairs
Authors: Rune Piil and Klaus Molmer
Categories: cond-mat.other
Comments: 7 pages, 6 figures
Subj-class: Other
   By adjusting the tunnelling couplings over longer than nearest neighbor
distances it is possible in discrete lattice models to reproduce the properties
of the lowest energy band of a real, continuous periodic potential. We propose
to include such terms in problems with interacting particles and we show that
they have significant consequences for scattering and bound states of atom
pairs in periodic potentials.
\\ ( , 273kb)
Paper: cond-mat/0703585
Date: Thu, 22 Mar 2007 16:00:53 GMT (21kb)

Title: Temperature Dependence of Critical Number of Particles for Attracting
   Atomic Bose Gas
Authors: Shyamal Biswas
Categories: cond-mat.stat-mech
Comments: 7 pages, 3 figures
Subj-class: Statistical Mechanics
   For an attractive two body interaction the collapse of the condensate in an
atomic Bose gas is experimentally observed if the number of atoms is greater
than a critical number. If the interaction is attractive, the density in the
central region of the trap tends to increase. This tendency is opposed by the
zero-point energy and by the thermal energy. If the number of atoms is greater
than a critical number, the central density increases very much and the
zero-point and thermal energy are no longer able to prevent the collapse of the
gas. We calculate the temperature dependence of the critical number particles
by a variational method within the Hartree-Fock approximation and find that
there is a dramatic increase in the critical number as the condensation point
is approached.
\\ ( , 21kb)
Paper: quant-ph/0703199
Date: Thu, 22 Mar 2007 18:13:52 GMT (453kb)

Title: A Bose-Einstein condensate coupled to a nanomechanical resonator on an
   atom chip
Authors: Philipp Treutlein, David Hunger, Stephan Camerer, Theodor W. H\"ansch,
   and Jakob Reichel
Categories: quant-ph
Comments: 5 pages, 3 figures
   We study the coupling of the spin of Bose-Einstein condensed atoms to the
mechanical oscillations of a nanoscale cantilever with a magnetic tip. This is
an experimentally viable hybrid quantum system which allows one to explore the
interface of quantum optics and condensed matter physics. We propose an
experiment where easily detectable atomic spin-flips are induced by the
cantilever motion. This can be used to probe thermal oscillations of the
cantilever with the atoms. At low cantilever temperatures, as realized in
recent experiments, back-action of the atoms onto the cantilever is significant
and the system represents a mechanical analog of cavity quantum
electrodynamics. With high but realistic cantilever quality factors, the strong
coupling regime can be reached, either with single atoms or collectively with
BECs. We discuss an implementation on an atom chip.
\\ ( , 453kb)

The replacements:

Paper: cond-mat/0508669
replaced with revised version Fri, 16 Mar 2007 07:27:02 GMT (140kb)

Title: Classical Region of a Trapped Bose Gas
Authors: P. Blair Blakie and Matthew J. Davis
Categories: cond-mat.other
Comments: 6 pages, 5 figures; updated to include new results with interactions
Subj-class: Other
\\ ( , 140kb)
Paper: cond-mat/0703282
replaced with revised version Fri, 16 Mar 2007 02:29:37 GMT (16kb)

Title: Temperature and scattering length dependent condensate fraction of
   trapped Bose atoms
Authors: Sang-Hoon Kim
Categories: cond-mat.stat-mech
Comments: 3 pages, 4 figures
Subj-class: Statistical Mechanics
\\ ( , 16kb)
Paper: cond-mat/0204430
replaced with revised version Sun, 18 Mar 2007 15:51:02 GMT (9kb)

Title: Percolation transition in the Bose gas II
Authors: Andras Suto
Categories: cond-mat.stat-mech math-ph math.MP
Comments: The paper is completed with the proof of Eq. (34) and with a remark
   after Eq. (44) on the existence for any m>ln(rho/rho_0) of an infinite cycle
   which contains a fraction between exp{-(m+1)} and exp{-m} of the total number
   of particles
Subj-class: Statistical Mechanics; Mathematical Physics
Journal-ref: J. Phys. A: Math. Gen. 35 (2002) 6995-7002
\\ ( , 9kb)
Paper: cond-mat/0510436
replaced with revised version Mon, 19 Mar 2007 19:58:44 GMT (31kb)

Title: A simple renormalization group approximation of the groundstate
   properties of interacting bosonic systems
Authors: Roman Werpachowski and Jerzy Kijowski
Categories: cond-mat.stat-mech
Comments: RevTex 4, 10 figures (revised and updated)
Subj-class: Statistical Mechanics
\\ ( , 31kb)
Paper: cond-mat/0609059
replaced with revised version Sat, 17 Mar 2007 16:10:58 GMT (413kb)

Title: Anomalous Heat Conduction in a Quasi One-Dimensional Gases
Authors: Taka H. Nishino
Categories: cond-mat.stat-mech
Comments: 8 pages, 2 figures
Subj-class: Statistical Mechanics
\\ ( , 413kb)
Paper: cond-mat/0609169
replaced with revised version Mon, 19 Mar 2007 15:31:14 GMT (124kb)

Title: The new physics of non-equilibrium condensates: insights from classical
Authors: P. R. Eastham
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: 10 pages, 4 figures, submitted for a special issue of J. Phys.:
   Condensed Matter on "Optical coherence and collective phenomena in
   nanostructures". v2: added discussion of links to exact solutions
Subj-class: Strongly Correlated Electrons; Mesoscopic Systems and Quantum Hall
\\ ( , 124kb)
Paper: cond-mat/0612590
replaced with revised version Sat, 17 Mar 2007 10:44:58 GMT (104kb)

Title: Ground-State Fidelity and Bipartite Entanglement in the Bose-Hubbard
Authors: Pierfrancesco Buonsante and Alessandro Vezzani
Categories: cond-mat.other quant-ph
Comments: 7 pages, 5 figures (endfloats used due to problems with figures and
   latex. Sorry about that); final version, similar to the published one
Subj-class: Other
Journal-ref: Physical Review Letters 98, 11601 (2007)
DOI: 10.1103/PhysRevLett.98.110601
\\ ( , 104kb)
Paper: cond-mat/0703169
replaced with revised version Mon, 19 Mar 2007 19:11:37 GMT (235kb)

Title: Intrinsic Heating and Cooling in Adiabatic Processes for Bosons in
   Optical Lattices
Authors: Tin-Lun Ho and Qi Zhou
Categories: cond-mat.other
Comments: 4 pages, 3 figures, misprints are corrected and an additional
   acknowledgement is added
Subj-class: Other
\\ ( , 235kb)
Paper: cond-mat/0602237
replaced with revised version Mon, 19 Mar 2007 20:16:39 GMT (130kb)

Title: Zero-temperature Kosterlitz-Thouless transition in a two-dimensional
   quantum system
Authors: Claudio Castelnovo (1), Claudio Chamon (1), Christopher Mudry (2), and
   Pierre Pujol (3). ((1) Boston University, (2) Paul Scherrer Institut, (3)
   Ecole Normale Superieure)
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: (30 pages, 11 figures), v2 with minor corrections
Subj-class: Strongly Correlated Electrons; Statistical Mechanics
Journal-ref: Annals of Physics 322 (2007) 903-934
DOI: 10.1016/j.aop.2006.04.017
\\ ( , 130kb)
Paper: cond-mat/0611091
replaced with revised version Tue, 20 Mar 2007 11:13:02 GMT (242kb)

Title: Entanglement in extended Hubbard models and quantum phase transitions
Authors: Alberto Anfossi, Paolo Giorda, and Arianna Montorsi
Categories: cond-mat.str-el cond-mat.stat-mech quant-ph
Comments: 14 pages, 8 figures, 2 tables
Subj-class: Strongly Correlated Electrons; Statistical Mechanics
\\ ( , 242kb)
Paper: quant-ph/0402152
replaced with revised version Tue, 20 Mar 2007 18:34:06 GMT (336kb)

Title: Collective effects in the dynamics of driven atoms in a high-Q resonator
Authors: Stefano Zippilli, Giovanna Morigi, Helmut Ritsch
Categories: quant-ph
Comments: 12 pages, 13 figures, significantly extended version, slightly
   different from the published one
Journal-ref: Eur. Phys. J. D 31, 507 (2004)
\\ ( , 336kb)
Paper: quant-ph/0506030
replaced with revised version Tue, 20 Mar 2007 17:53:05 GMT (586kb)

Title: Cooling trapped atoms in optical resonators
Authors: Stefano Zippilli, Giovanna Morigi
Categories: quant-ph
Comments: 4 pages, 3 figures; version published in PRL
Journal-ref: Phys. Rev. Lett. 95, 143001 (2005)
\\ ( , 586kb)
Paper: cond-mat/0604164
replaced with revised version Wed, 21 Mar 2007 11:09:07 GMT (291kb)

Title: Fragmented superfluid due to frustration of cold atoms in optical
Authors: J. J. Garcia-Ripoll, J. Pachos
Categories: cond-mat.str-el quant-ph
Comments: New version, more results, about 20 pages
Subj-class: Strongly Correlated Electrons
\\ ( , 291kb)
Paper: quant-ph/0508075
replaced with revised version Wed, 21 Mar 2007 11:33:41 GMT (894kb)

Title: Mechanical effects of optical resonators on driven trapped atoms: Ground
   state cooling in a high finesse cavity
Authors: Stefano Zippilli, Giovanna Morigi
Categories: quant-ph
Comments: 17 pages, 6 figures
Journal-ref: Phys. Rev. A 72, 053408 (2005)
\\ ( , 894kb)
Paper: quant-ph/0611078
replaced with revised version Wed, 21 Mar 2007 19:13:15 GMT (86kb)

Title: Stability and entanglement in optical-atomic amplification of trapped
   atoms: the role of atomic collisions
Authors: V. V. Fran\c{c}a and G. A. Prataviera
Categories: quant-ph
Comments: 6 pages, 4 figures, accepted by PRA
\\ ( , 86kb)

Till next week,

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
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 Thu Mar 29 2007 - 13:37:09 EST

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