# Matt's arXiv selection: week ending 24 April 2009

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Fri, 29 May 2009 08:12:09 +1000

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

Dear subscribers,

Mike Garrett is the person to thank for helping edit this week's abstracts.
There are 34 new preprints and 15 replacements.

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arXiv:0904.2630
Date: Fri, 17 Apr 2009 04:32:53 GMT (34kb)

Title: Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover
Authors: Kun Huang, Zeng-Qiang Yu, Lan Yin
Categories: cond-mat.quant-gas cond-mat.supr-con
Comments: 16 pages, 2 figures, to be published in PRA
\\
The Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover is
derived by the path-integral method. In addition to the standard
Ginzburg-Landau equation, a second equation describing the total atom density
is obtained. These two coupled equations are necessary to describe both
homogeneous and inhomogeneous systems. The Ginzburg-Landau theory is valid near
the transition temperature $T_c$ on both sides of the crossover. In the
weakly-interacting BEC region, it is also accurate at zero temperature where
the Ginzburg-Landau equation can be mapped onto the Gross-Pitaevskii (GP)
equation. The applicability of GP equation at finite temperature is discussed.
On the BEC side, the fluctuation of the order parameter is studied and the
renormalization to the molecule coupling constant is obtained.
\\ ( http://arxiv.org/abs/0904.2630 , 34kb)
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arXiv:0904.2640
Date: Fri, 17 Apr 2009 06:29:08 GMT (171kb,D)

Title: Absence of Pressure-Driven Supersolid Flow at Low Frequency
Authors: Ann Sophie C. Rittner, Wonsuk Choi, Erich J. Mueller, and John D.
Reppy
Categories: cond-mat.other cond-mat.stat-mech
\\
We have conducted a low frequency (0.002 Hz) search for evidence of a
pressure-driven supersolid response, finding a null result. Our results set an
upper bound on the low frequency AC supersolid flow velocity of $3.3 \times 10^{-3}$ nm/s and on the AC displacement of 0.26 nm, a value roughly the size
of the $^4$He atom, and less than typical torsional oscillator amplitude of a
few nm. These findings, combined with related DC measurements by Day and
Beamish, suggest either that supersolid flow cannot be generated by pressure
gradients, or that supersolidity is a frequency dependent phenomenon that is
clearly evident at several hundred Hz, but undetectably small at mHz
frequencies.
\\ ( http://arxiv.org/abs/0904.2640 , 171kb)
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arXiv:0904.2729
Date: Fri, 17 Apr 2009 15:52:52 GMT (107kb)

Title: Dynamics and thermodynamics of systems with long-range interactions:
interpretation of the different functionals
Authors: Pierre-Henri Chavanis
Categories: cond-mat.stat-mech
Comments: Chapter of the volume "Dynamics and Thermodynamics of systems with
long range interactions: theory and experiments", A. Campa, A. Giansanti, G.
Morigi, F. Sylos Labini Eds., American Institute of Physics Conference
proceedings, 970 (2008)
Journal-ref: AIP Conf. Proc., 970, 39 (2008)
\\
We discuss the dynamics and thermodynamics of systems with weak long-range
interactions. Generically, these systems experience a violent collisionless
relaxation in the Vlasov regime leading to a (usually) non-Boltzmannian quasi
stationary state (QSS), followed by a slow collisional relaxation leading to
the Boltzmann statistical equilibrium state. These two regimes can be explained
by a kinetic theory, using an expansion of the BBGKY hierarchy in powers of
1/N, where N is the number of particles. We discuss the physical meaning of the
different functionals appearing in the analysis: the Boltzmann entropy, the
Lynden-Bell entropy, the "generalized" entropies arising in the reduced space
of coarse-grained distribution functions, the Tsallis entropy, the generalized
H-functions increasing during violent relaxation (not necessarily
monotonically) and the convex Casimir functionals used to settle the formal
nonlinear dynamical stability of steady states of the Vlasov equation. We show
the connection between the different variational problems associated with these
functionals. We also introduce a general class of nonlinear mean field
Fokker-Planck (NFP) equations that can be used as numerical algorithms to solve
these constrained optimization problems.
\\ ( http://arxiv.org/abs/0904.2729 , 107kb)
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arXiv:0904.2735
Date: Fri, 17 Apr 2009 16:03:41 GMT (590kb)

Title: Mesoscopic phases of dipolar ensembles with polar molecules and Rydberg
atoms
Authors: G. Pupillo, A. Micheli, M. Boninsegni, I. Lesanovsky, and P. Zoller
Categories: cond-mat.quant-gas cond-mat.stat-mech
\\
We discuss the realization of mesoscopic phases of dipolar gases relevant to
current experiments with cold polar molecules and Rydberg atoms confined to two
dimensions. We predict the existence of superfluid clusters, mesoscopic
supersolids, and crystals for a small number of trapped particles, with no
counterpart in the homogeneous situation. For certain strengths of the
dipole-dipole interactions, the stabilization of purely {\it non-classical
crystals} by quantum fluctuations is possible. We propose a magnification
scheme to detect the spatial structure of these crystalline phases.
\\ ( http://arxiv.org/abs/0904.2735 , 590kb)
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arXiv:0904.2616
Date: Fri, 17 Apr 2009 01:52:39 GMT (333kb)

Title: Strongly correlated quantum dynamics of multimode light coupled to a
two-level atom in a cavity
Authors: Tarun Kumar, Aranya B Bhattacherjee and ManMohan
Categories: quant-ph
\\
We study a composite multimode light-two-level atom system in a cavity. We
show that coupling of the two-level atom to multiple modes of the light
destroys the Mott phase of the composite system thus making the system less
useful platform for developing concepts in quantum information processing.
\\ ( http://arxiv.org/abs/0904.2616 , 333kb)
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arXiv:0904.2790
Date: Fri, 17 Apr 2009 22:05:16 GMT (431kb)

Title: Solitons and solitary vortices in "pancake"-shaped Bose-Einstein
condensates
Authors: Luca Salasnich and Boris A. Malomed
Categories: cond-mat.quant-gas cond-mat.other
Comments: Phys. Rev. A, in press
\\
We study fundamental and vortical solitons in disk-morphed Bose-Einstein
condensates (BECs) subject to strong confinement along the axial direction.
Starting from the three-dimensional (3D) Gross-Pitaevskii equation (GPE), we
proceed to an effective 2D nonpolynomial Schroeodinger equation (NPSE) derived
by means of the integration over the axial coordinate. Results produced by the
latter equation are in very good agreement with those obtained from the full 3D
GPE, including cases when the formal 2D equation with the cubic nonlinearity is
unreliable. The 2D NPSE is used to predict density profiles and dynamical
stability of repulsive and attractive BECs with zero and finite topological
charge in various planar trapping configurations, including the axisymmetric
harmonic confinement and 1D periodic potential. In particular, we find a stable
dynamical regime that was not reported before, viz., periodic splitting and
recombination of trapped vortices with topological charge 2 or 3 in the
self-attractive BEC.
\\ ( http://arxiv.org/abs/0904.2790 , 431kb)
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arXiv:0904.2881
Date: Sun, 19 Apr 2009 05:23:58 GMT (1455kb)

Title: A supercritical superfluid and vortex unbinding following a quantum
quench
Authors: L. Mathey, A. Polkovnikov
Categories: cond-mat.quant-gas
\\
The technological advances of trapping and manipulating ultra-cold atom
systems provide an opportunity to study many-body dynamics with unprecedented
clarity. Here we study the dynamics of the relative phase of a bilayer of
two-dimensional superfluids after the two superfluids have been decoupled,
using truncated Wigner approximation. We find that on short time scales the
relative phase shows light cone' like thermalization and creates a metastable
superfluid state, which can be supercritical. On longer time scales this state
relaxes to a disordered state due to dynamical vortex unbinding. This scenario
of dynamically suppressed vortex proliferation constitutes an anti-Kibble-Zurek
effect. Our predictions are directly measurable in interference experiments, as
demonstrated in Ref. 1.
\\ ( http://arxiv.org/abs/0904.2881 , 1455kb)
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arXiv:0904.2927
Date: Sun, 19 Apr 2009 18:39:17 GMT (2173kb)

Title: Thermal effects in light scattering from ultracold bosons in an optical
lattice
Authors: Kazimierz {\L}akomy, Zbigniew Idziaszek, Marek Trippenbach
Categories: cond-mat.quant-gas quant-ph
\\
We study the scattering of a weak and far-detuned light from a system of
ultracold bosons in 1D and 3D optical lattices. We show the connection between
angular distributions of the scattered light and statistical properties of a
Bose gas in a periodic potential. The angular patterns are determined by the
Fourier transform of the second-order correlation function, and thus they can
be used to retrieve information on particle number fluctuations and
correlations. We consider superfluid and Mott insulator phases of the Bose gas
in a lattice, and we analyze in details how does the scattering depend on the
system dimensionality, temperature and atom-atom interactions.
\\ ( http://arxiv.org/abs/0904.2927 , 2173kb)
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arXiv:0904.2966
Date: Mon, 20 Apr 2009 08:15:56 GMT (42kb)

Title: Creation and detection of vortices in polariton condensates
Authors: Michiel Wouters and Vincenzo Savona
Categories: cond-mat.quant-gas
\\
We investigate theoretically the creation, persistence and detection of
quantized vortices in nonequilibrium polariton condensates within a stochastic
classical field model. The life time of the quantized vortices is shown to
increase with the spatial coherence and to depend on the geometry of the
condensate. The relation with superfluidity in conventional superfluids is
discussed. Three different ways to measure the vorticity of the polariton
condensate are proposed.
\\ ( http://arxiv.org/abs/0904.2966 , 42kb)
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arXiv:0904.3015
Date: Mon, 20 Apr 2009 12:10:07 GMT (118kb)

Title: Universal Spectra of Coherent Atoms in a Recurrent RandomWalk
Authors: R. Pugatch, O. Firstenberg, M. Shuker, N. Davidson
Categories: cond-mat.stat-mech
Journal-ref: Phys. Rev. Lett. vol. 102, p. 150602 (2009)
DOI: 10.1103/PhysRevLett.102.150602
\\
The probability of a random walker to return to its starting point in
dimensions one and two is unity, a theorem first proven by G. Polya. The
recurrence probability -- the probability to be found at the origin at a time
t, is a power law with a critical exponent d/2 in dimensions d=1,2. We report
an experiment that directly measures the Laplace transform of the recurrence
probability in one dimension using Electromagnetically Induced Transparency
(EIT) of coherent atoms diffusing in a vapor-cell filled with buffer gas. We
find a regime where the limiting form of the complex EIT spectrum is universal
and only depends on the effective dimensionality in which the random recurrence
takes place. In an effective one-dimensional diffusion setting, the measured
spectrum exhibits power law dependence over two decades in the frequency domain
with a critical exponent of 0.56 close to the expected value 0.5. Possible
extensions to more elaborate diffusion schemes are briefly discussed.
\\ ( http://arxiv.org/abs/0904.3015 , 118kb)
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arXiv:0904.3023
Date: Mon, 20 Apr 2009 14:53:34 GMT (20kb)

Title: Bulk viscosities for cold Fermi superfluids close to the unitary limit
Authors: Miguel Angel Escobedo, Massimo Mannarelli, Cristina Manuel
Categories: cond-mat.quant-gas cond-mat.other
\\
We compute the coefficients of bulk viscosity for a non-relativistic
superfluid corresponding to a fermionic system close to the unitarity limit. We
consider the low temperature regime assuming that the transport properties of
the system are dominated by phonons. To compute the coefficients of bulk
viscosity we use kinetic theory in the relaxation time approximation and the
low energy effective field theory of the corresponding system. We show that the
three independent bulk viscosity coefficients, $\zeta_1, \zeta_2, \zeta_3$,
associated with irreversible flows vanish for phonons with a linear dispersion
law. Considering a phonon dispersion law with a cubic term in momentum we find
that in the conformal limit $\zeta_1 = \zeta_2=0$, while $\zeta_3$ is non-zero.
Including a conformal breaking term which arises for a large but finite s-wave
scattering length, $a$, at the leading order in $1/a$ we obtain that $\zeta_1 \propto 1/a$ and $\zeta_2 \propto 1/a^2$.
\\ ( http://arxiv.org/abs/0904.3023 , 20kb)
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arXiv:0904.3031
Date: Mon, 20 Apr 2009 13:35:47 GMT (258kb)

Title: Non-extensive entropy of bosonic Fibonacci oscillators
Authors: Abdullah Algin
Categories: cond-mat.stat-mech cond-mat.quant-gas
Comments: 30 pages, 2 figures, accepted on JSTAT
Journal-ref: J. Stat. Mech.: Ther. Exp. (2009) P04007
DOI: 10.1088/1742-5468/2009/04/P04007
\\
We discuss possible connections between the thermostatistical properties of a
gas of the two-parameter deformed bosonic particles called Fibonacci
oscillators and the properties of the Tsallis thermostatistics. In this
framework, we particularly focus on a comparison of the non-extensive entropy
functions expressed by these two generalized theories. We also show that the
thermostatistics of the two-parameter deformed bosons can be studied by the
formalism of Fibonacci calculus, which generalizes the recently proposed
formalism by Lavagno and Narayana Swamy of q-calculus for the one-parameter
deformed boson gas. As an application, we briefly summarize some of the recent
results on the Bose-Einstein condensation phenomenon for the present
two-parameter generalized boson gas.
\\ ( http://arxiv.org/abs/0904.3031 , 258kb)
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arXiv:0904.3065
Date: Mon, 20 Apr 2009 16:00:38 GMT (451kb)

Title: Symmetry breaking in quantum systems: the case study of vortex
nucleation
Authors: D. Dagnino, N. Barberan, M. Lewenstein, and J. Dalibard
Categories: cond-mat.quant-gas
\\
Mean field (MF) methods constitute a very powerful tool for investigations of
weakly interacting many-body systems in many branches of physics. In articular
they describe with an excellent accuracy trapped Bose-Einstein condensates. A
generic, but difficult question concerns the relation between the symmetry
properties of the true many-body state and its MF approximation. We address
this question by considering vortex nucleation in a rotating Bose-Einstein
condensate (BEC). A slow sweep of the rotation frequency changes the state of
the system from being at rest to the one containing one vortex. Within the MF
framework, the jump in the symmetry occurs through a turbulent phase around a
certain critical frequency. The exact many-body ground state at the critical
frequency corresponds to a fragmented condensate with strong correlations and
entanglement. We believe that this constitutes a paradigm example of symmetry
breaking/change in the adiabatic evolution of quantum many-body systems.
\\ ( http://arxiv.org/abs/0904.3065 , 451kb)
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arXiv:0904.3075
Date: Mon, 20 Apr 2009 17:24:55 GMT (218kb)

Title: Exact solution of the Bose-Hubbard model on the Bethe lattice
Authors: Guilhem Semerjian, Marco Tarzia and Francesco Zamponi
Categories: cond-mat.quant-gas cond-mat.other
\\
The exact solution of a quantum Bethe lattice model in the thermodynamic
limit amounts to resolve a functional self-consistent equation. In this paper
we obtain this equation for the Bose-Hubbard model on the Bethe lattice, under
two equivalent forms. The first one, based on a coherent state path integral,
leads in the large connectivity limit to the mean field treatment of Fisher et
al. [Phys. Rev. B 40, 546 (1989)] at the leading order, and to the bosonic
Dynamical Mean Field Theory as a first correction, as recently derived by
Byczuk and Vollhardt [Phys. Rev. B 77, 235106 (2008)]. We obtain an alternative
form of the equation using the occupation number representation, which can be
easily solved with an arbitrary numerical precision, for any finite
connectivity. We thus compute the transition line between the superfluid and
Mott insulator phases of the model, along with thermodynamic observables and
the space and imaginary time dependence of correlation functions. The finite
connectivity of the Bethe lattice induces a richer physical content with
respect to its mean-field counterpart: a notion of distance between sites of
the lattice is preserved, and the bosons are still weakly mobile in the Mott
insulator phase. The Bethe lattice construction can be viewed as an
approximation to the finite dimensional version of the model. We show indeed a
quantitatively reasonable agreement between our predictions and the results of
Quantum Monte Carlo simulations in two and three dimensions.
\\ ( http://arxiv.org/abs/0904.3075 , 218kb)
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arXiv:0904.2415
Date: Wed, 15 Apr 2009 23:41:30 GMT (170kb)

Title: Soliton Dynamics in Linearly Coupled Discrete Nonlinear Schr\"odinger
Equations
Authors: A. Trombettoni, H.E. Nistazakis, Z. Rapti, D.J. Frantzeskakis, P.G.
Kevrekidis
Categories: nlin.PS cond-mat.stat-mech
Comments: to be published in Mathematics and Computers in Simulation,
proceedings of the fifth IMACS International Conference on Nonlinear
Evolution Equations and Wave Phenomena: Computation and Theory (Athens,
Georgia - April 2007)
\\
We study soliton dynamics in a system of two linearly coupled discrete
nonlinear Schr\"odinger equations, which describe the dynamics of a
two-component Bose gas, coupled by an electromagnetic field, and confined in a
strong optical lattice. When the nonlinear coupling strengths are equal, we use
a unitary transformation to remove the linear coupling terms, and show that the
existing soliton solutions oscillate from one species to the other. When the
nonlinear coupling strengths are different, the soliton dynamics is numerically
investigated and the findings are compared to the results of an effective
two-mode model. The case of two linearly coupled Ablowitz-Ladik equations is
also investigated.
\\ ( http://arxiv.org/abs/0904.2415 , 170kb)
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arXiv:0904.3048
Date: Mon, 20 Apr 2009 14:47:16 GMT (24kb)

Title: Quantum particles from classical statistics
Authors: C.Wetterich
Categories: quant-ph
\\
Quantum particles and classical particles are described in a common setting
of classical statistical physics. Both correspond to isolated subsystems of
ensembles describing the particle and its environment. The property of a
particle being "classical" or "quantum" ceases to be a basic conceptual
difference. The dynamics differs, however, between quantum and classical
particles. We describe location, motion and correlations of a quantum particle
in terms of observables in a classical statistical ensemble. We also construct
explicitly the quantum mechanical Hamiltonian and wave function for classical
particles. Besides conceptual advances, the treatment of classical and quantum
particles in a common formalism could lead to interesting cross-fertilization
between classical statistics and quantum mechanics.
\\ ( http://arxiv.org/abs/0904.3048 , 24kb)
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arXiv:0904.3059
Date: Mon, 20 Apr 2009 15:43:01 GMT (79kb)

Title: Cooling of a particle by coupling to its own reflection
Authors: Peter Horak, Andr\'e Xuereb, Tim Freegarde
Categories: quant-ph
\\
We identify and explore a cooling force resulting from the retarded dipole
interaction between an illuminated particle and its reflection. For a
one-dimensional example, we find cooling times of milliseconds and limiting
temperatures in the millikelvin range. The force, which may be considered the
prototype for cavity-mediated cooling, may also be enhanced by plasmon and
cavity resonances at the mirror.
\\ ( http://arxiv.org/abs/0904.3059 , 79kb)
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arXiv:0904.3097
Date: Mon, 20 Apr 2009 20:06:42 GMT (409kb)

Title: Composite Fermion Theory for Bosonic Atoms in Optical Lattices
Authors: Gunnar Moller and Nigel R. Cooper
Categories: cond-mat.mes-hall cond-mat.quant-gas
\\
We study the groundstates of cold atomic gases on rotating optical lattices,
as described by the Bose-Hubbard model in a uniform effective magnetic field.
Mapping the bosons to composite fermions leads to the prediction of quantum
Hall fluids that have no counterpart in the continuum. We construct trial
wavefunctions for these phases, and perform numerical tests of the predictions
of the composite fermion model. Our results establish the existence of strongly
correlated phases beyond those in the continuum limit, and provide evidence for
a wider scope of the composite fermion approach beyond its application to the
lowest Landau-level.
\\ ( http://arxiv.org/abs/0904.3097 , 409kb)
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arXiv:0904.3131
Date: Mon, 20 Apr 2009 22:43:00 GMT (226kb)

Title: Fortran programs for the time-dependent Gross-Pitaevskii equation in a
fully anisotropic trap
Authors: P. Muruganandam and S. K. Adhikari
Categories: cond-mat.quant-gas physics.comp-ph
Comments: 34 pages, 11 figures, 18 Fortran programs with respective output
files included in 18 compressed tar files
\\
We develop simple numerical algorithms for both stationary and non-stationary
solutions of the time-dependent Gross-Pitaevskii (GP) equation describing the
properties of Bose-Einstein condensates at ultra low temperatures. In
particular, we consider algorithms involving real and imaginary-time
propagation based on a split-step Crank-Nicholson method. In a
one-space-variable form of the GP equation we consider the one-dimensional
linear, two-dimensional circularly symmetric, and the three-dimensional
spherically-symmetric traps. In the two-space-variable form we consider the GP
equation in two-dimensional anisotropic and three-dimensional axially-symmetric
traps. The fully-anisotropic three-dimensional GP equation is also considered.
Numerical results for the chemical potential and root-mean-square size of
stationary states are reported using imaginary-time propagation programs for
all the cases and compared with previously obtained results. Also presented are
numerical results of non-stationary oscillation for different trap symmetries
using real-time propagation programs. A set of convenient working codes
developed in Fortran 77 are also provided for all these cases (twelve programs
in all). In the case of two or three space variables, {Fortran 90/95 versions
provide some simplification over the Fortran 77 programs}, and these programs
are also included (six programs in all).
\\ ( http://arxiv.org/abs/0904.3131 , 226kb)
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arXiv:0904.3179
Date: Tue, 21 Apr 2009 09:03:10 GMT (2448kb)

Title: Instability of superfluid Fermi gases induced by a roton-like density
mode in optical lattices
Authors: Yoshihiro Yunomae, Daisuke Yamamoto, Ippei Danshita, Nobuhiko Yokoshi,
Shunji Tsuchiya
Categories: cond-mat.quant-gas cond-mat.other
\\
We study the stability of superfluid Fermi gases in deep one-dimensional (1D)
and two-dimensional (2D) optical lattices in the BCS-BEC crossover at zero
temperature. Within the tight-binding attractive Hubbard model, we calculate
the spectrum of the low-energy Anderson-Bogoliubov (AB) mode as well as the
single-particle excitations in the presence of superfluid flow in order to
determine the critical velocities. To obtain the spectrum of the AB mode, we
calculate the density response function in the generalized random phase
approximation (GRPA) applying the Green's function formalism developed by
C\^ot\'e and Griffin to the Hubbard model. We find that the spectrum of the AB
mode is separated from the particle-hole continuum having the characteristic
roton-like minimum at short wavelength due to the strong charge-density-wave
(CDW) fluctuations. The energy of the roton-like minimum decreases with
increasing the lattice velocity and it reaches zero at the critical velocity
which is smaller than the pair-breaking velocity. This indicates that the
superfluid state is energetically unstable due to the spontaneous emission of
the short wavelength roton-like excitations of the AB mode instead due to
pair-breaking. We determine the critical velocities as functions of the
interaction strength across the BCS-BEC crossover regime.
\\ ( http://arxiv.org/abs/0904.3179 , 2448kb)
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arXiv:0904.3221
Date: Tue, 21 Apr 2009 10:51:15 GMT (148kb)

Title: Exact methods in analysis of nonequilibrium dynamics of integrable
models: application to the study of correlation functions in nonequilibrium
1D Bose gas
Authors: Vladimir Gritsev, Timofei Rostunov, Eugene Demler
Categories: cond-mat.quant-gas cond-mat.other
\\
In this paper we study nonequilibrium dynamics of one dimensional Bose gas
from the general perspective of dynamics of integrable systems. After outlining
and critically reviewing methods based on inverse scattering transform,
intertwining operators, q-deformed objects, and extended dynamical conformal
symmetry, we focus on the form-factor based approach. Motivated by possible
applications in nonlinear quantum optics and experiments with ultracold atoms,
we concentrate on the regime of strong repulsive interactions. We consider
dynamical evolution starting from two initial states: a condensate of particles
in a state with zero momentum and a condensate of particles in a gaussian
wavepacket in real space. Combining the form-factor approach with the method of
intertwining operator we develop a numerical procedure which allows explicit
summation over intermediate states and analysis of the time evolution of
non-local density-density correlation functions. In both cases we observe a
tendency toward formation of crystal-like correlations at intermediate time
scales.
\\ ( http://arxiv.org/abs/0904.3221 , 148kb)
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arXiv:0904.3314
Date: Tue, 21 Apr 2009 18:46:54 GMT (1683kb)

Title: Rapid production of $^{87}$Rb BECs in a combined magnetic and optical
potential
Authors: Y.-J. Lin, A. R. Perry, R. L. Compton, I. B. Spielman and J. V. Porto
Categories: cond-mat.quant-gas
\\
We describe an apparatus for quickly and simply producing $\Rb87$
Bose-Einstein condensates. It is based on a magnetic quadrupole trap and a red
detuned optical dipole trap. We collect atoms in a magneto-optical trap (MOT)
and then capture the atom in a magnetic quadrupole trap and force rf
evaporation. We then transfer the resulting cold, dense cloud into a spatially
below gravity. This technique combines the efficient capture of atoms from a
MOT into a magnetic trap with the rapid evaporation of optical dipole traps;
the approach is insensitive to the peak quadrupole gradient and the precise
trapping beam waist. Our system reliably produces a condensate with
$N\approx2\times10^6$ atoms every $16\second$.
\\ ( http://arxiv.org/abs/0904.3314 , 1683kb)
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arXiv:0904.2768 (*cross-listing*)
Date: Fri, 17 Apr 2009 19:26:12 GMT (288kb)

Title: The Bogoliubov/de Gennes system, the AKNS hierarchy, and nonlinear
quantum mechanical supersymmetry
Authors: Francisco Correa, Gerald V. Dunne and Mikhail S. Plyushchay
Categories: hep-th cond-mat.supr-con math-ph math.MP quant-ph
\\
We show that the Ginzburg-Landau expansion of the grand potential for the
Bogoliubov-de Gennes Hamiltonian is determined by the integrable nonlinear
equations of the AKNS hierarchy, and that this provides the natural
mathematical framework for a hidden nonlinear quantum mechanical supersymmetry
underlying the dynamics.
\\ ( http://arxiv.org/abs/0904.2768 , 288kb)
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arXiv:0904.3175
Date: Tue, 21 Apr 2009 07:09:33 GMT (1074kb)

Title: Cold and Ultracold Molecules: Science, Technology, and Applications
Authors: Lincoln D. Carr, David DeMille, Roman V. Krems, and Jun Ye
Categories: quant-ph
Comments: 82 pages, 9 figures, review article to appear in New Journal of
Physics Special Issue on Cold and Ultracold Molecules
\\
This article presents a review of the current state of the art in the
research field of cold and ultracold molecules. It serves as an introduction to
the Special Issue of the New Journal of Physics on Cold and Ultracold Molecules
and describes new prospects for fundamental research and technological
development. Cold and ultracold molecules may revolutionize physical chemistry
and few body physics, provide techniques for probing new states of quantum
matter, allow for precision measurements of both fundamental and applied
interest, and enable quantum simulations of condensed-matter phenomena.
Ultracold molecules offer promising applications such as new platforms for
quantum computing, precise control of molecular dynamics, nanolithography, and
Bose-enhanced chemistry. The discussion is based on recent experimental and
theoretical work and concludes with a summary of anticipated future directions
and open questions in this rapidly expanding research field.
\\ ( http://arxiv.org/abs/0904.3175 , 1074kb)
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arXiv:0904.3238
Date: Tue, 21 Apr 2009 12:45:51 GMT (20kb)

Title: Non-local quantum correlations and detection processes in QFT
Authors: Fabrizio Buscemi and Giuseppe Compagno
Categories: quant-ph
\\
Quantum detection processes in QFT must play a key role in the description of
quantum field correlations, such as the appearance of entanglement, and of
causal effects. We consider the detection in the case of a simple QFT model
with a suitable interaction to exact treatment, consisting of a quantum scalar
field coupled linearly to a classical scalar source. We then evaluate the
response function to the field quanta of two-level point-like quantum model
detectors, and analyze the effects of the approximation adopted in standard
detection theory. We show that the use of the RWA, that characterizes the
Glauber detection model, leads in the detector response to non-local terms
corresponding to an instantaneously spreading of source effects over the whole
space. Other detector models, obtained with non-standard or the no-application
of RWA, give instead local responses to field quanta, apart from source
independent vacuum contribution linked to preexisting correlations of
zero-point field.
\\ ( http://arxiv.org/abs/0904.3238 , 20kb)
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arXiv:0904.3266
Date: Tue, 21 Apr 2009 15:06:40 GMT (1952kb)

Title: Enhancing an Atom Interferometer Area using Double-diffraction
Authors: Thomas L\'ev\eque (SYRTE), A. Gauguet (SYRTE), Franck Michaud
(SYRTE), Franck Pereira Dos Santos (SYRTE), Arnaud Landragin (SYRTE)
Categories: physics.atom-ph
\\
In this paper we demonstrate a new scheme for Raman transitions which realize
a symmetric momentum-space splitting of $4 \hbar k$, deflecting the atomic
wave-packets into the same internal state. Combining the advantages of Raman
and Bragg diffraction, we achieve a three pulse state labelled interferometer,
intrinsically insensitive to the main systematics. This splitting scheme can be
extended to $4N \hbar k$ momentum transfer by a multipulse sequence and is
implemented on a $8 \hbar k$ interferometer. Measuring inertial phase shifts,
we demonstrate an area enhancement of a factor of 3.46 with respect to the
\\ ( http://arxiv.org/abs/0904.3266 , 1952kb)
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\\
arXiv:0904.3376
Date: Wed, 22 Apr 2009 02:50:40 GMT (247kb)

Title: Stability and chaotic behavior of Bose-Einstein condensates in optical
lattices with two- and three-body interactions
Authors: Yan Chen, Li-Bin Fu, Ke-Zhi Zhang, and Yong Chen
Categories: cond-mat.quant-gas
\\
The stability and chaotic behavior of Bose-Einstein condensates with two- and
three-atoms interactions in optical lattices are discussed with analytically
and numerically methods. It is demonstrated that the steady-state relative
population will appear tuning-fork bifurcation when the system parameters are
changed to certain critical values. In particular, the existence of three-body
interaction not only transform the bifurcation point of the system but also
affect greatly on the self-trapping behavior of the system associated with the
influence of the initial conditions, three-body interaction and the energy bias
on the macroscopic quantum self-trapping. Finally, by applying the periodic
modulation on the energy bias, we find that the relative population oscillation
can exhibit a process from order to chaos, through a series of period-doubling
bifurcations.
\\ ( http://arxiv.org/abs/0904.3376 , 247kb)
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\\
arXiv:0904.3440
Date: Wed, 22 Apr 2009 12:06:08 GMT (222kb,D)

Title: Numerical method for evolving the dipolar projected Gross-Pitaevskii
equation
Authors: P. B. Blakie, C. Ticknor, A. S. Bradley, A. M. Martin, M. J. Davis,
and Y. Kawaguchi
Categories: cond-mat.quant-gas cond-mat.stat-mech
\\
We describe a method for evolving the projected Gross-Pitaevskii equation
(PGPE) for an interacting Bose gas in a harmonic oscillator potential, with the
inclusion of a long-range dipolar interaction. The central difficulty in
solving this equation is the requirement that the field is restricted to a
small set of prescribed modes that constitute the low energy c-field region of
the system. We present a scheme, using a Hermite-polynomial based spectral
representation, that precisely implements this mode restriction and allows an
efficient and accurate solution of the dipolar PGPE. We introduce a set of
auxiliary oscillator states to perform a Fourier transform necessary to
evaluate the dipolar interaction in reciprocal space. We extensively
characterize the accuracy of our approach, and derive Ehrenfest equations for
the evolution of the angular momentum.
\\ ( http://arxiv.org/abs/0904.3440 , 222kb)
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\\
arXiv:0904.3477
Date: Wed, 22 Apr 2009 15:26:53 GMT (558kb,D)

Title: Feshbach resonant scattering of three fermions in one-dimensional wells
Authors: T. Duric, A. F. Ho, and D .K. K. Lee
Categories: cond-mat.quant-gas
\\
We study the weak-tunnelling limit for a system of cold 40K atoms trapped in
a one-dimensional optical lattice close to an s-wave Feshbach resonance. We
calculate the local spectrum for three atoms at one site of the lattice within
a two-channel model. Our results indicate that, for this one-dimensional
system, one- and two-channel models will differ close to the Feshbach
resonance, although the two theories would converge in the limit of strong
Feshbach coupling. We also find level crossings in the low-energy spectrum of a
single well with three atoms that may lead to quantum phase transition for an
optical lattice of many wells. We discuss the stability of the system to a
phase with non-uniform density.
\\ ( http://arxiv.org/abs/0904.3477 , 558kb)
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\\
arXiv:0904.3107 (*cross-listing*)
Date: Tue, 21 Apr 2009 01:15:58 GMT (435kb)

Title: Nearly Perfect Fluidity: From Cold Atomic Gases to Hot Quark Gluon
Plasmas
Authors: Thomas Schaefer (North Carolina State University), Derek Teaney (SUNY
Stony Brook and Riken-BNL)
Categories: hep-ph cond-mat.quant-gas hep-lat hep-th nucl-th
Comments: 69 pages, 9 figures, review article
\\
Quantum uncertainty suggests a lower bound on the internal friction -- shear
viscosity -- of a fluid. The shear viscosity of a nearly perfect fluid
approaches this bound. A measure of fluidity is provided by the ratio of shear
viscosity eta to entropy density s. In this review we summarize theoretical and
experimental information on the properties of the three main classes of quantum
fluids that are known to have values of eta/s that are smaller than hbar/k_B,
where hbar is Planck's constant and k_B is Boltzmann's constant. These fluids
are strongly coupled Bose fluids, in particular liquid helium, strongly
correlated ultracold Fermi gases, and the quark gluon plasma. We discuss the
main theoretical approaches to transport properties of these fluids: kinetic
theory, numerical simulations based on linear response theory, and holographic
dualities. We also summarize the experimental situation, in particular with
regard to the observation of hydrodynamic behavior in ultracold Fermi gases and
the quark gluon plasma.
\\ ( http://arxiv.org/abs/0904.3107 , 435kb)
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\\
arXiv:0904.3511
Date: Wed, 22 Apr 2009 17:32:19 GMT (230kb)

Title: Capture into Rydberg states and momentum distributions of ionized
electrons
Authors: N.I. Shvetsov-Shilovski (1), S.P. Goreslavski (1), S.V. Popruzhenko
(1), and W. Becker (2) ((1) Moscow State Engineering Physics Institute,
Moscow, Russia (2) Max-Born-Institut, Berlin, Germany)
Categories: physics.atom-ph physics.atm-clus
Comments: 9 pages, 8 figures in one zip-archive
\\
The yield of neutral excited atoms and low-energy photoelectrons generated by
the electron dynamics in the combined Coulomb and laser field after tunneling
is investigated. We present results of Monte-Carlo simulations built on the
two-step semiclassical model, as well as analytic estimates and scaling
relations for the population trapping into the Rydberg states. It is shown that
mainly those electrons are captured into bound states of the neutral atom that
due to their initial conditions (i) have moderate drift momentum imparted by
the laser field and (ii) avoid strong interaction ("hard" collision) with the
ion. In addition, it is demonstrated that the channel of capture, when
accounted for in semiclassical calculations, has a pronounced effect on the
momentum distribution of electrons with small positive energy. For the
parameters that we investigated its presence leads to a dip at zero momentum in
the longitudinal momentum distribution of the ionized electrons.
\\ ( http://arxiv.org/abs/0904.3511 , 230kb)
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\\
arXiv:0904.3643
Date: Thu, 23 Apr 2009 10:12:21 GMT (29kb)

Title: The superfluid-Bose glass transition in a 1-D weakly interacting Bose
gas
Authors: Luca Fontanesi, Michiel Wouters, Vincenzo Savona
Categories: cond-mat.quant-gas cond-mat.dis-nn
\\
We study the one-dimensional Bose gas in spatially correlated disorder at
T=0, using an extended density-phase Bogoliubov method. The decay of the
one-body density matrix is analyzed and particular attention is paid to the
behavior of the low-energy Bogoliubov excitations across the phase boundary. We
have observed that the transition to the Bose glass phase is marked by a
divergence in the density of states together with a 1/E behaviour of the
localization length of the Bogoliubov modes. Finally we draw the phase diagram
of the superfluid-insulator transition in the limit of small interaction
strength.
\\ ( http://arxiv.org/abs/0904.3643 , 29kb)
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\\
arXiv:0904.3738
Date: Thu, 23 Apr 2009 19:24:02 GMT (458kb)

Title: p-wave resonant Bose gas: a "spinor supersolid"
Categories: cond-mat.quant-gas cond-mat.other
\\
We show that a degenerate gas of two-species bosonic atoms interacting
through a p-wave Feshbach resonance (as e.g., realized in a 85Rb-87Rb mixture)
exhibits an atomic-molecular supersolid phase (AMSF), sandwiched by a molecular
p-wave (orbital spinor) superfluid and by an s-wave atomic superfluid at large
negative and positive detunings, respectively. The magnetic field can be used
to tune the modulation wavevector of the AMSF state, as well as to drive
quantum phase transitions in this rich system.
\\ ( http://arxiv.org/abs/0904.3738 , 458kb)
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\\
arXiv:0904.3617
Date: Thu, 23 Apr 2009 08:08:05 GMT (595kb,D)

Title: Entanglement assisted spin-wave atom interferometer
Authors: Yu-Ao Chen, Xiao-Hui Bao, Zhen-Sheng Yuan, Shuai Chen, Bo Zhao,
Jian-Wei Pan
Categories: quant-ph
Comments: 6 pages, 5 figures (including appendix)
\\
We report the observation of phase-super resolution in a motion-sensitive
spin-wave (SW) atom interferometer utilizing a NOON-type entanged state. The SW
interferometer is implemented by generating a superposition of two SWs and
observing the interference between them, where the interference fringe is
sensitive to the atomic collective motion. By heralded generation of a second
order NOON state in the SW interferometer, we clearly observe the interference
pattern with phase super-resolution. The demonstrated SW interferometer can in
principle be scaled up to highly entangled quantum state, and thus is of
fundamental importance to implement quantum-enhanced-measurement.
\\ ( http://arxiv.org/abs/0904.3617 , 595kb)
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The replacements:

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\\
arXiv:0812.1782
replaced with revised version Fri, 17 Apr 2009 14:53:39 GMT (211kb)

Title: Relativistic BCS-BEC crossover of a two-species Fermi gas with number
density asymmetry at zero temperature
Authors: Hao Guo, Chih-Chun Chien and Yan He
Categories: hep-ph cond-mat.other
Journal-ref: Nuclear Physics A 823, 83 (2009)
\\ ( http://arxiv.org/abs/0812.1782 , 211kb)
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\\
arXiv:0903.1639
replaced with revised version Thu, 16 Apr 2009 20:12:40 GMT (488kb)

Title: Angle resolved photon spectrum and quasiparticle excitation spectrum in
an exciton superfluid
Authors: Jinwu Ye, T. Shi and Longhua Jiang
Categories: cond-mat.mes-hall cond-mat.mtrl-sci physics.atom-ph physics.optics
Comments: 4+ \epsilon pages, 2 color figures, REVTEX4
Report-no: NSF-KITP 09-42
\\ ( http://arxiv.org/abs/0903.1639 , 488kb)
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\\
arXiv:0903.2254
replaced with revised version Mon, 20 Apr 2009 14:58:21 GMT (498kb,D)

Title: Emergent superfluid crystals, frustration, and topologically defected
states in multimode cavity QED
Authors: Sarang Gopalakrishnan, Benjamin L. Lev, and Paul M. Goldbart
Categories: cond-mat.other quant-ph
\\ ( http://arxiv.org/abs/0903.2254 , 498kb)
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\\
arXiv:0904.2399
replaced with revised version Sun, 19 Apr 2009 22:15:31 GMT (118kb)

Title: Bose-Einstein and Fermi-Dirac distributions in nonextensive quantum
statistics: An exact approach
Authors: Hideo Hasegawa (Tokyo Gakugei Univ.)
Categories: cond-mat.stat-mech cond-mat.other
Comments: 23 pages, 11 figures; revised the text
\\ ( http://arxiv.org/abs/0904.2399 , 118kb)
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\\
arXiv:0901.3268
replaced with revised version Sat, 18 Apr 2009 07:31:38 GMT (45kb)

Title: Two-level atom at finite temperature
Authors: Tomasz Sowinski
Categories: quant-ph
\\ ( http://arxiv.org/abs/0901.3268 , 45kb)
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\\
arXiv:0903.4401
replaced with revised version Mon, 20 Apr 2009 14:00:48 GMT (303kb)

Title: Photoassociation and coherent transient dynamics in the interaction of
ultracold rubidium atoms with shaped femtosecond pulses - II. Theory
Authors: Andrea Merli, Frauke Eimer, Fabian Weise, Albrecht Lindinger, Wenzel
Salzmann, Terry Mullins, Simone Gotz, Roland Wester, Matthias Weidemuller,
Ruzin Aganoglu, Christiane P. Koch
Categories: physics.atom-ph physics.chem-ph
\\ ( http://arxiv.org/abs/0903.4401 , 303kb)
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\\
arXiv:0809.0350
replaced with revised version Tue, 21 Apr 2009 07:14:25 GMT (927kb)

Title: Stability of superfluid Fermi gases in optical lattices
Authors: Yoshihiro Yunomae, Ippei Danshita, Daisuke Yamamoto, Nobuhiko Yokoshi,
and Shunji Tsuchiya
Categories: cond-mat.other
Comments: 4 pages, 4 figures, conference proceeding for ISQM-TOKYO'08
\\ ( http://arxiv.org/abs/0809.0350 , 927kb)
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\\
arXiv:0901.2295
replaced with revised version Tue, 21 Apr 2009 10:12:42 GMT (1414kb)

Title: Photonic spectrum of bichromatic optical lattices
Authors: Stefan Rist, Patrizia Vignolo, Giovanna Morigi
Categories: quant-ph cond-mat.other
Comments: 10 pages, 10 figures, to appear in PRA
\\ ( http://arxiv.org/abs/0901.2295 , 1414kb)
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\\
arXiv:0901.3979
replaced with revised version Tue, 21 Apr 2009 14:28:20 GMT (2032kb,D)

Title: Intensity-field correlation of single-atom resonance fluorescence
Authors: S. Gerber, D. Rotter, L. Slodicka, J. Eschner, H. J. Carmichael, and
R. Blatt
Categories: quant-ph
Comments: 4 pages, 4 figures, accepted in PRL
\\ ( http://arxiv.org/abs/0901.3979 , 2032kb)
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\\
arXiv:0902.4818
replaced with revised version Wed, 22 Apr 2009 15:31:14 GMT (12kb)

Title: Hyperfine frequency shift in two-dimensional atomic hydrogen
Authors: A.I.Safonov, I.I.Safonova and I.S.Yasnikov
Categories: quant-ph cond-mat.soft
\\ ( http://arxiv.org/abs/0902.4818 , 12kb)
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\\
arXiv:0904.3015
replaced with revised version Wed, 22 Apr 2009 08:04:36 GMT (118kb)

Title: Universal Spectra of Coherent Atoms in a Recurrent Random Walk
Authors: R. Pugatch, O. Firstenberg, M. Shuker, N. Davidson
Categories: cond-mat.stat-mech
Journal-ref: Phys. Rev. Lett. vol. 102, p. 150602 (2009)
DOI: 10.1103/PhysRevLett.102.150602
\\ ( http://arxiv.org/abs/0904.3015 , 118kb)
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\\
arXiv:0806.2960
replaced with revised version Thu, 23 Apr 2009 12:37:50 GMT (30kb)

Title: Systematic Semiclassical Expansion for Harmonically Trapped Ideal Bose
Gases
Authors: Ben Kl\"under and Axel Pelster
Categories: cond-mat.stat-mech
http://www.theo-phys.uni-essen.de/tp/ags/pelster_dir
Journal-ref: European Physical Journal B 68, 457-465 (2009)
\\ ( http://arxiv.org/abs/0806.2960 , 30kb)
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\\
arXiv:0901.4008
replaced with revised version Thu, 23 Apr 2009 18:01:05 GMT (51kb)

Title: Cumulative identical spin rotation effects in collisionless trapped
atomic gases
Authors: F. Piechon, J.N. Fuchs, and F. Laloe
Categories: physics.atom-ph cond-mat.other
\\ ( http://arxiv.org/abs/0901.4008 , 51kb)
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\\
arXiv:0902.4653
replaced with revised version Wed, 22 Apr 2009 22:51:48 GMT (402kb)

Title: FFLO vs Bose-Fermi mixture in polarized 1D Fermi gas on a Feshbach
resonance: a 3-body study
Authors: Stefan K. Baur, John Shumway, Erich J. Mueller
Categories: cond-mat.supr-con
\\ ( http://arxiv.org/abs/0902.4653 , 402kb)
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\\
arXiv:0903.0884
replaced with revised version Thu, 23 Apr 2009 15:28:38 GMT (169kb)

Title: Prediction of Feshbach resonances from three input parameters
Authors: Thomas M. Hanna, Eite Tiesinga, Paul S. Julienne
Categories: cond-mat.other
Comments: 5 pages, 2 figures, revised version
\\ ( http://arxiv.org/abs/0903.0884 , 169kb)
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Till next time,
Matt.

--
=========================================================================
Dr M. J. Davis,                      Associate Professor in Physics
School of Mathematics and Physics,   ph  : +61 7 334 69824
The University of Queensland,        fax : +61 7 336 51242
Brisbane, QLD 4072,                  mdavis_at_physics.uq.edu.au
Australia.                           www.physics.uq.edu.au/people/mdavis/
=========================================================================
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
=========================================================================
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Received on Fri May 29 2009 - 09:16:09 EST

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