Matt's arXiv selection: week ending 27 May 2007

From: Matthew Davis <>
Date: Mon, 14 May 2007 09:54:15 +1000 (EST)

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

Hi all,

I think I've broken my previous record for the lateness of a week's mailing.
Thankfully by the time you finish reading this the following two weeks emails
will be sitting in your inbox ready to be enjoyed, and once again you will be
entirely up to date.

I've gone through so many papers in this scanning session that I can't even
remember the interesting ones. I'll have to revisit them again later. There are
28 new preprints and 14 replacements this week.

Date: Thu, 19 Apr 2007 22:11:20 GMT (413kb)

Title: Bragg spectroscopy of a superfluid Bose-Hubbard gas
Authors: X. Du, Shoupu Wan, Emek Yesilada, C. Ryu, D. J. Heinzen, Z. X. Liang,
   and Biao Wu
Categories: cond-mat.other
Comments: 11 pages, 4 figures
   Bragg spectroscopy is used to measure excitations of a trapped,
quantum-degenerate gas of 87Rb atoms in a 3-dimensional optical lattice. The
measurements are carried out over a range of optical lattice depths in the
superfluid phase of the Bose-Hubbard model. For fixed wavevector, the resonant
frequency of the excitation is found to decrease with increasing lattice depth.
A numerical calculation of the resonant frequencies based on Bogoliubov theory
shows a less steep rate of decrease than the measurements.
\\ ( , 413kb)
Date: Fri, 20 Apr 2007 07:10:25 GMT (54kb)

Title: Competing superfluid and density-wave ground-states of fermionic
   mixtures with mass imbalance in optical lattices
Authors: Tung-Lam Dao, Antoine Georges, Massimo Capone.
Categories: cond-mat.supr-con cond-mat.str-el
Comments: e.g.:4 pages, 3 figures
   We study the effect of mass imbalance on the phase diagram of a two-component
fermionic mixture with attractive interactions in optical lattices. Using
static and dynamical mean-field theories, we show that the pure superfluid
phase is stable for all couplings when the mass imbalance is smaller than a
limiting value. For larger imbalance, phase separation between a superfluid and
a charge-density wave takes place when the coupling exceeds a critical
strength. The harmonic trap induces a spatial segregation of the two phases,
with a rapid variation of the density at the boundary.
\\ ( , 54kb)
Date: Fri, 20 Apr 2007 14:45:33 GMT (211kb)

Title: Half-vortices in polariton condensates
Authors: Yuri Rubo
Categories: cond-mat.other
Comments: 4 pages, 3 figures
   It is shown that vortices in linearly polarized polariton condensates in
planar semiconductor microcavities carry two winding numbers (k,m). These
numbers can be either integer or half-integer simultaneously. Four half-integer
vortices (1/2,1/2), (-1/2,-1/2), (1/2,-1/2), and (-1/2,1/2) are anisotropic,
possess the smallest energy, and define the Kosterlitz-Thouless transition
temperature. The condensate concentration remains finite within the core of
half-vortex and the polarization becomes fully circular in the core center.
\\ ( , 211kb)
Date: Fri, 20 Apr 2007 02:31:21 GMT (19kb)

Title: Prospects for making polar molecules with microwave fields
Authors: Svetlana Kotochigova
Categories: quant-ph
Comments: 4 pages, 5 figures
   We propose a new mechanism to produce ultracold polar molecules with
microwave fields. The proposed mechanism converts trapped ultracold atoms of
different species into vibrationally excited molecules by a single microwave
transition and entirely depends on the existence of a permanent dipole moment
in the molecules. As opposed to production of molecules by photoassociation or
magnetic-field Feshbach resonances our method does not rely on the structure
and lifetime of excited states or existence of Feshbach resonances. In
addition, we determine conditions for optimal creation of polar molecules in
vibrationally excited states of the ground-state potential by changing
frequency and intensity of the microwave field. We also explore the possibility
to produce vibrationally cold molecules by combining the microwave field with
an optical Raman transition or by applying a microwave field to Feshbach
molecules. The production mechanism is illustrated for two polar molecules: KRb
and RbCs.
\\ ( , 19kb)
Date: Fri, 20 Apr 2007 17:16:45 GMT (259kb)

Title: Polaron Physics in Optical Lattices
Authors: Martin Bruderer, Alexander Klein, Stephen R. Clark, and Dieter Jaksch
Categories: quant-ph
Comments: 5 pages, 4 figures
   We investigate the effects of a nearly-uniform Bose-Einstein condensate (BEC)
on the properties of immersed trapped impurity atoms. Using a weak-coupling
expansion in the BEC-impurity interaction strength we derive a model describing
polarons, i.e. impurities dressed by a coherent state of Bogoliubov phonons,
and apply it to ultra-cold bosonic atoms in an optical lattice. We show that
with increasing BEC temperature the transport properties of the impurities
change from coherent to diffusive. Furthermore, stable polaron clusters are
formed via a phonon-mediated off-site attraction.
\\ ( , 259kb)
Date: Thu, 19 Apr 2007 22:31:10 GMT (228kb)

Title: Atom-wave diffraction between the Raman-Nath and the Bragg regime:
   Effective Rabi frequency, losses, and phase shifts
Authors: Holger Mueller, Sheng-wey Chiow, and Steven Chu
Categories: physics.atom-ph
Comments: 21 pages, 10 figures
   We present an analytic theory of the diffraction of (matter) waves by a
lattice in the "quasi-Bragg" or "channelling" regime between the Bragg and the
short-interaction Raman-Nath regime. The Schroedinger equation is solved by
adiabatic expansion, using the conventional adiabatic approximation as a
starting point, and re-inserting the result into the Schroedinger equation to
yield a second order correction. Closed expressions for arbitrary pulse shapes
and diffraction orders are obtained and the losses of the population to output
states otherwise forbidden by the Bragg condition are derived. We consider the
phase shift due to couplings of the desired output to these states that depends
on the interaction strength and duration and show how these can be kept
negligible by a choice of smooth (e.g., Gaussian) envelope functions even in
situations that substantially violate the adiabaticity condition. We also give
an efficient method for calculating the effective Rabi frequency (which is
related to the eigenvalues of Mathieu functions) in the quasi-Bragg regime.
\\ ( , 228kb)
Date: Sun, 22 Apr 2007 00:21:54 GMT (421kb,D)

Title: State preparation and dynamics of ultracold atoms in higher lattice
Authors: Torben Mueller, Simon Foelling, Artur Widera, Immanuel Bloch
Categories: cond-mat.other cond-mat.str-el
Comments: 4 pages, 4 figures
   We report on the realization of a multi-orbital system with ultracold atoms
in the excited bands of a 3D optical lattice by selectively controlling the
band population along a given lattice direction. The lifetime of the atoms in
the excited band is found to be considerably longer (10-100 times) than the
characteristic time scale for inter-site tunneling, thus opening the path for
orbital selective many-body physics with ultracold atoms. Upon exciting the
atoms from an initial lowest band Mott insulating state to higher lying bands,
we observe the dynamical emergence of coherence in 1D (and 2D), compatible with
Bose-Einstein condensation to a non-zero momentum state.
\\ ( , 421kb)
Date: Mon, 23 Apr 2007 09:29:01 GMT (434kb)

Title: Superfluid-Insulator Transition of Strongly Interacting Fermi Gases in
   Optical Lattices
Authors: Hui Zhai and Tin-Lun Ho
Categories: cond-mat.supr-con
Comments: 4 pages, 4 figures
   We study a quantum phase transition from fermionic suerpfluid (SF) to
band-insulator (BI) of fermions in optical lattices. The destruction of the
band insulator is driven by the energy gain in promoting fermions in valance
band to various conducting bands to form Cooper pairs. We have obtained the
phase boundary of this transition for systems with two fermions per site using
mean-field theory, which is accurate at fermion side of a Feshbach resonance,
and should give qualitative correct results near resonance. As one moves across
resonance to the molecule side, the SF-BI transition evolves into the SF-Mott
insulator transition of bosonic molecules. The physics becomes more intriguing
at higher fermion densities, and we shall present a qualitative global phase
diagram for SF-Insulator transition for the entire BCS-BEC family. Our results
are directly related to the recent MIT experiment on lattices fermions.
\\ ( , 434kb)
Date: Sun, 22 Apr 2007 23:06:35 GMT (4810kb)

Title: Many-Body Physics with Ultracold Gases
Authors: Immanuel Bloch, Jean Dalibard, Wilhelm Zwerger
Categories: cond-mat.other
Comments: Article for Review of Modern Physics, 76 pages
   This article reviews recent experimental and theoretical progress on
many-body phenomena in dilute, ultracold gases. Its focus are effects beyond
standard weak-coupling descriptions, like the Mott-Hubbard-transition in
optical lattices, strongly interacting gases in one dimension or quasi
two-dimensional gases in fast rotation. Strong correlations in fermionic gases
are discussed in optical lattices or near Feshbach resonances in the BCS-BEC
\\ ( , 4810kb)
Date: Mon, 23 Apr 2007 07:16:20 GMT (274kb)

Title: Controlling statistical properties of stored light
Authors: A. Raczynski, K. Slowik, J. Zaremba, S. Zielinska-Kaniasty
Categories: quant-ph
Comments: 5 figures
   Statistical properties of outgoing light pulses are studies after they have
been stored in a medium of atoms in the tripod configuration. A generalized
Hong-Ou-Mandel interference, storing of squeezed states and homodyne signal
analysis are discussed in the context of their dependence on the parameters of
the control fields used for light storage and release.
\\ ( , 274kb)
Date: Mon, 23 Apr 2007 07:42:39 GMT (397kb)

Title: Formation of Ultracold Heteronuclear Dimers in Electric Fields
Authors: Rosario Gonz\'alez-F\'erez, Michael Mayle and Peter Schmelcher
Categories: quant-ph
   The formation of ultracold molecules via stimulated emission followed by a
radiative deexcitation cascade in the presence of a static electric field is
investigated. By analyzing the corresponding cross sections, we demonstrate the
possibility to populate the lowest rotational excitations via photoassociation.
The modification of the radiative cascade due to the electric field leads to
narrow rotational state distributions in the vibrational ground state. External
fields might therefore represent an additional valuable tool towards the
ultimate goal of quantum state preparation of molecules.
\\ ( , 397kb)
Date: Mon, 23 Apr 2007 19:31:05 GMT (437kb)

Title: Atom-atom correlations in spontaneous four wave mixing of two colliding
   Bose-Einstein Condensates
Authors: A. Perrin (LCFIO), H. Chang (LCFIO), V. Krachmalnicoff (LCFIO), M.
   Schellekens (LCFIO), D. Boiron (LCFIO), A. Aspect (LCFIO), C. I. Westbrook
Categories: quant-ph
Proxy: ccsd hal-00142991
   We have used a position sensitive, single atom detector to observe atom
scattering during the collision of two Bose-Einstein condensates. The process
can also be thought of as spontaneous, degenerate four wave mixing of deBroglie
waves. The observed two-particle correlation function shows a clear peak
corresponding to the production of back to back atom pairs. The correlation
function also exhibits a peak corresponding to pairs of atoms emitted in the
same direction, the Hanbury Brown-Twiss effect. Our experiment is in the regime
of well separated atom pairs, opening the route to the study of quantum atom
optics effects with individual entangled pairs.
\\ ( , 437kb)
Date: Mon, 23 Apr 2007 14:05:19 GMT (233kb)

Title: Ground-state magneto-optical resonances in Cesium vapour confined in an
   extremely thin cell
Authors: C. Andreeva, A. Atvars, M. Auzinsh, K.Bluss, S. Cartaleva, L. Petrov,
   and D. Slavov
Categories: physics.atom-ph
   Experimental and theoretical studies are presented related to the
ground-state magneto-optical resonance prepared in Cesium vapour confined in an
Extremely Thin Cell (ETC, with thickness equal to the wavelength of the
irradiating light). It is shown that the utilization of the ETC allows one to
examine the formation of a magneto-optical resonance on the individual
hyperfine transitions, thus distinguishing processes resulting in dark (reduced
absorption) or bright (enhanced absorption) resonance formation. We report on
an experimental evidence of the bright magneto-optical resonance sign reversal
in Cs atoms confined in the ETC. A theoretical model is proposed based on the
optical Bloch equations that involves the elastic interaction processes of
atoms in the ETC with its walls resulting in depolarization of the Cs excited
state which is polarized by the exciting radiation. This depolarization leads
to the sign reversal of the bright resonance. Using the proposed model, the
magneto-optical resonance amplitude and width as a function of laser power are
calculated and compared with the experimental ones. The numerical results are
in good agreement with the experiment.
\\ ( , 233kb)
Date: Tue, 24 Apr 2007 18:32:09 GMT (606kb)

Title: Topological Winding and Unwinding in Metastable Bose-Einstein
Authors: Rina Kanamoto, Lincoln D. Carr, Masahito Ueda
Categories: cond-mat.other
Comments: 4 pages, 4 figures,
   Topological winding and unwinding in a quasi-one-dimensional metastable
Bose-Einstein condensate are shown to be manipulated by changing the strength
of interaction or the frequency of rotation. Exact diagonalization analysis
reveals that quasidegenerate states emerge spontaneously near the transition
point, allowing a smooth crossover between topologically distinct states. On a
mean-field level, the transition is accompanied by formation of grey solitons,
or density notches, which serve as an experimental signature of this
\\ ( , 606kb)
Date: Tue, 24 Apr 2007 04:46:59 GMT (88kb)

Title: Combinatorics and Boson normal ordering: A gentle introduction
Authors: P. Blasiak (1), A. Horzela (1), K. A. Penson (2), A. I. Solomon (2),
   G. H. E. Duchamp (3), ((1) Polish Academy of Sciences, Krakow, Poland, (2)
   LPTMC, University of Paris VI, France, (3) Institut Galilee, University of
   Paris 13, France)
Categories: quant-ph
Comments: 8 pages, 1 figure
   We discuss a general combinatorial framework for operator ordering problems
by applying it to the normal ordering of the powers and exponential of the
boson number operator. The solution of the problem is given in terms of Bell
and Stirling numbers enumerating partitions of a set. This framework reveals
several inherent relations between ordering problems and combinatorial objects,
and displays the analytical background to Wick's theorem. The methodology can
be straightforwardly generalized from the simple example given herein to a wide
class of operators.
\\ ( , 88kb)
Date: Tue, 24 Apr 2007 07:58:46 GMT (169kb)

Title: Scanning magnetoresistance microscopy of atom chips
Authors: M. Volk, S. Whitlock, B. V. Hall, A. I. Sidorov
Categories: physics.atom-ph
Comments: 6 pages, 6 figures
   Surface based geometries of microfabricated wires or patterned magnetic films
can be used to magnetically trap and manipulate ultracold neutral atoms or
Bose-Einstein condensates. We investigate the magnetic properties of such atom
chips using a scanning magnetoresistive (MR) microscope with high spatial
resolution and high field sensitivity. We show that MR sensors are ideally
suited to observe small variations of the magnetic field caused by
imperfections in the wires or magnetic materials which ultimately lead to
fragmentation of ultracold atom clouds. Measurements are also provided for the
magnetic field produced by a thin current-carrying wire with small geometric
modulations along the edge. Comparisons of our measurements with a full numeric
calculation of the current flow in the wire and the subsequent magnetic field
show excellent agreement. Our results highlight the use of scanning MR
microscopy as a convenient and powerful technique for precisely characterizing
the magnetic fields produced near the surface of atom chips.
\\ ( , 169kb)
Date: Tue, 24 Apr 2007 21:20:57 GMT (187kb)

Title: Matter-wave interference in s-wave and p-wave Fermi condensates
Authors: Wei Zhang and C. A. R. Sa de Melo
Categories: cond-mat.str-el cond-mat.supr-con
Comments: extension of earlier work cond-mat/0603561. 8 pages, 5 figures
   We discuss the time evolution and matter-wave interference of Fermi
condensates on the BEC side of Feshbach resonances for $s$ and p-wave
superfluids, upon release from harmonic traps. In s-wave systems, where the
order parameter is a complex scalar, we find that the interference patterns
depend on the relative phase of the order parameters of the condensates. In
p-wave systems involving the mixture of two-hyperfine states, we show that the
interference pattern exhibits a polarization effect depending on the relative
orientation of the two vector order parameters. Lastly, we also point out that
p-wave Fermi condensates exhibit an anisotropic expansion, reflecting the
spatial anisotropy of the underlying interaction between fermions and the
orbital nature of the vector order parameter. Potential applications of our
results include systems of ultra-cold atoms that exhibit p-wave Feshbach
resonances such as $^6$Li or $^{40}$K.
\\ ( , 187kb)
Date: Wed, 25 Apr 2007 13:07:37 GMT (151kb)

Title: Dynamics of a strongly interacting Fermi gas: the radial quadrupole mode
Authors: A. Altmeyer (1), S. Riedl (1 and 2), M. J. Wright (1), C. Kohstall
   (1), J. Hecker Denschlag (1) and R. Grimm (1 and 2) ((1) Inst. of
   Experimental Physics and Center for Quantum Physics, Univ. Innsbruck,
   Technikerstra{\ss}e 25, Austria, (2) Inst. for Quantum Optics and Quantum
   Information, Acad. of Sciences, Austria)
Categories: cond-mat.other
Comments: 11 pages, 11 figures
   We report on measurements of an elementary surface mode in an ultracold,
strongly interacting Fermi gas of 6Li atoms. The radial quadrupole mode allows
us to probe hydrodynamic behavior in the BEC-BCS crossover without being
influenced by changes in the equation of state. We examine frequency and
damping of this mode, along with its expansion dynamics. In the unitarity limit
and on the BEC side of the resonance, the observed frequencies agree with
standard hydrodynamic theory. However, on the BCS side of the crossover, a
striking down shift of the oscillation frequency is observed in the
hydrodynamic regime as a precursor to an abrupt transition to collisionless
behavior; this indicates coupling of the oscillation to fermionic pairs.
\\ ( , 151kb)
Date: Wed, 25 Apr 2007 17:15:25 GMT (214kb)

Title: The effect of dipole-dipole interactions between atoms in an active
Authors: V.V.Berezovsky, L.I.Men'shikov, S.Oberg and C.D.Latham
Categories: cond-mat.str-el cond-mat.other
Comments: 8 pages, 7 figures
   Based on the results of numerical modeling, it is shown that dipole-dipole
interactions among atoms in the active medium influences strongly the character
of the associated superradiation. The main effect is to make the nuclear
subsystem behave chaotically. Its strength increases with the atom density, and
leads to the suppression of distant collective correlations and superradiation.
Near correlations between the atoms are established, causing a confinement
effect: a shielding of radiation in the active medium.
\\ ( , 214kb)
Date: Wed, 25 Apr 2007 19:28:34 GMT (273kb)

Title: Prospects for precision measurements of atomic helium using direct
   frequency comb spectroscopy
Authors: E. E. Eyler, D. E. Chieda, Matthew C. Stowe, Michael J. Thorpe, T. R.
   Schibli, and Jun Ye
Categories: physics.atom-ph
Comments: 14 pages, 6 figures
   We analyze several possibilities for precisely measuring electronic
transitions in atomic helium by the direct use of phase-stabilized femtosecond
frequency combs. Because the comb is self-calibrating and can be shifted into
the ultraviolet spectral region via harmonic generation, it offers the prospect
of greatly improved accuracy for UV and far-UV transitions. To take advantage
of this accuracy an ultracold helium sample is needed. For measurements of the
triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap
metastable $2 ^3S$ state atoms. We analyze schemes for measuring the two-photon
$2 ^3S \to 4 ^3S$ interval, and for resonant two-photon excitation to high
Rydberg states, $2 ^3S \to 3 ^3P \to n^3S,D$. We also analyze experiments on
the singlet-state spectrum. To accomplish this we propose schemes for producing
and trapping ultracold helium in the $1 ^1S$ or $2 ^1S$ state via
intercombination transition. A particularly intriguing scenario is the
possibility of direct singlet state spectroscopy, including a measurement of
the $1 ^1S \to 2 ^1S$ transition with extremely high accuracy by use of
two-photon excitation in a magic wavelength trap that operates identically for
both states. We predict a ``triple magic wavelength'' at 412 nm that could
facilitate numerous experiments on trapped helium atoms, because here the
polarizabilities of the $1 ^1S$, $2 ^1S$ and $2 ^3S$ states are all similar,
small, and positive.
\\ ( , 273kb)
Date: Tue, 24 Apr 2007 20:42:25 GMT (37kb)

Title: Forward and non-forward symplectic integrators in solving classical
   dynamics problems
Authors: Siu A. Chin
Categories: physics.comp-ph physics.class-ph
Comments: 26 pages, 17 figures, to be published in a "Special Issue on
   Splitting Methods for Differential Equation", Intl. J. of Comp. Math
   Forward time step integrators are splitting algorithms with only positive
splitting coefficients. When used in solving physical evolution equations,
these positive coefficients correspond to positive time steps. Forward
algorithms are essential for solving time-irreversible equations that cannot be
evolved using backward time steps. However, forward integrators are also better
in solving time-reversible equations of classical dynamics by tracking as
closely as possible the physical trajectory. This work compares in detail
various forward and non-forward fourth-order integrators using three, fourth,
five and six force evaluations. In the case of solving the 2D Kepler orbit, all
non-forward integrators are optimized by simply minimizing the size of their
backward time steps.
\\ ( , 37kb)
Date: Wed, 25 Apr 2007 21:49:31 GMT (36kb)

Title: Dilute two-component Fermi superfluids and the symmetric heavy-light
Authors: Dean Lee (North Carolina State University)
Categories: cond-mat.supr-con
Comments: 32 pages, 6 figures
   The symmetric heavy-light ansatz is an approximate method for finding the
superfluid ground state of dilute fermions with two degenerate components.
While the Hamiltonian has an exact SU(2) symmetry, the heavy-light ansatz
breaks this symmetry by skewing the mass ratio of the two components. In the
limit where one component is infinitely heavy, the many-body problem can be
solved in terms of single-particle orbitals. The original SU(2) symmetry is
then reintroduced by requiring N-body density correlations for the two
components be equal for all N. In the simple approximation where only the
lowest orbitals are filled, the method is exact for the two-body system, exact
in the strong-coupling Bose gas limit, exact in the weak-coupling Fermi gas
limit, and in good agreement with recent lattice Monte Carlo results for the
ground state energy at unitarity.
\\ ( , 36kb)
Date: Wed, 25 Apr 2007 22:02:28 GMT (36kb)

Title: Dynamical models and the phase ordering kinetics of the s=1 spinor
Authors: Subroto Mukerjee Cenke Xu Joel E. Moore
Categories: cond-mat.stat-mech cond-mat.soft
Comments: 15 pages with 9 figures
   The $s=1$ spinor Bose condensate at zero temperature supports ferromagnetic
and polar phases that combine magnetic and superfluid ordering. We investigate
the formation of magnetic domains at finite temperature and magnetic field in
two dimensions in an optical trap. We study the general ground state phase
diagram of a spin-1 system and focus on a phase that has a magnetic Ising order
parameter and numerically determine the nature of the finite temperature
superfluid and magnetic phase transitions. We then study three different
dynamical models: model A, which has no conserved quantities, model F, which
has a conserved second sound mode and the Gross-Pitaevskii (GP) equation which
has a conserved density and magnetization. We find the dynamic critical
exponent to be the same for models A and F ($z=2$) but different for GP ($z
\approx 3$). Externally imposed magnetization conservation in models A and F
yields the value $z \approx 3$, which demonstrates that the only conserved
density relevant to domain formation is the magnetization density.
\\ ( , 36kb)
Date: Thu, 26 Apr 2007 07:18:31 GMT (35kb)

Title: Collective oscillations of a Bose-Fermi mixture: Effect of unequal mass
   of Bose and Fermi particles
Authors: Arup Banerjee
Categories: cond-mat.other cond-mat.mes-hall
Comments: 15 pages, 4 figures
   We investigate the effect of different mass of a Bose- and a Fermi-particle
on the collective oscillations of the degenerate boson-fermion mixtures. In
particular we consider the monopole and the quadrupole modes of the
oscillations and study their characters and the frequencies by using
variational-sum-rule approach. We find that for both the modes there exists a
critical value of the ratio of boson-fermion mass below and above which the
character and the frequency of the respective modes are significantly
\\ ( , 35kb)
Date: Thu, 26 Apr 2007 12:07:32 GMT (69kb)

Title: Superradiance and multiple scattering of photons in atomic gases
Authors: A. Gero and E. Akkermans
Categories: cond-mat.mes-hall
Comments: 12 pages, 7 figures
   We study the influence of cooperative effects such as superradiance and
subradiance, on the scattering properties of dilute atomic gases. We show that
cooperative effects lead to an effective potential between pairs of atoms that
decays like $1/r$. In the case of superradiance, this potential is attractive
for close enough atoms and can be interpreted as a coherent mesoscopic effect.
We consider a model of multiple scattering of a photon among superradiant pairs
and calculate the elastic mean free path and the group velocity. We study first
the case of a scalar wave which allows to obtain and to understand basic
features of cooperative effects and multiple scattering. We then turn to the
general problem of a vector wave. In both cases, we obtain qualitatively
similar results and derive, for the case of a scalar wave, analytic expressions
of the elastic mean free path and of the group velocity for an arbitrary (near
resonance) detuning.
\\ ( , 69kb)
Date: Thu, 26 Apr 2007 01:05:34 GMT (909kb)

Title: Two-color atom guide and 1D optical lattice using evanescent fields of
   high-order transverse modes
Authors: Jian Fu, Xiang Yin, and Limin Tong
Categories: quant-ph
Comments: 18 pages, 12 figures, 1 table
   We propose a two-color scheme of atom guide and 1D optical lattice using
evanescent light fields of different transverse modes. The optical waveguide
carries a red-detuned light and a blue-detuned light, with both modes far from
resonance. The atom guide and 1D optical lattice potentials can be transformed
to each other by using a Mach-Zehnder interferometer to accurately control mode
transformation. This might provide a new approach to realize flexible
transition between the guiding and trapping states of atoms.
\\ ( , 909kb)

The replacements:

replaced with revised version Fri, 20 Apr 2007 18:18:23 GMT (51kb)

Title: Collective excitations of hard-core Bosons at half filling on square and
   triangular lattices: Development of roton minima and collapse of roton gap
Authors: Tyler Bryant and Rajiv R. P. Singh
Categories: cond-mat.str-el
Comments: 10 pages, 7 figures
\\ ( , 51kb)
replaced with revised version Fri, 20 Apr 2007 09:10:22 GMT (38kb)

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, 12 figures (revised and updated); to appear in Physical
   Review A
\\ ( , 38kb)
replaced with revised version Thu, 19 Apr 2007 21:37:16 GMT (321kb)

Title: Supersolids in confined fermions on one-dimensional optical lattices
Authors: F. Karim Pour, M. Rigol, S. Wessel, A. Muramatsu
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 pages, 5 figures, published version
Journal-ref: Phys. Rev. B 75, 161104(R) (2007)
DOI: 10.1103/PhysRevB.75.161104
\\ ( , 321kb)
replaced with revised version Thu, 19 Apr 2007 20:08:29 GMT (499kb)

Title: Excitations from a Bose-Einstein condensate of magnons in coupled spin
Authors: V. O. Garlea, A. Zheludev, T. Masuda, L.-P. regnault, E. Ressouche, B.
   Brenier, H. Manaka, J.-H. Chung, Y. Qiu, K. Habicht, K. Kiefer and M. Boehm
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 pages, 4 figures
Journal-ref: Phys. Rev. Lett. 98, 167202 (2007)
\\ ( , 499kb)
replaced with revised version Fri, 20 Apr 2007 16:51:44 GMT (66kb)

Title: Photon number states generated from a continuous-wave light source
Authors: Anne E. B. Nielsen and Klaus Molmer
Categories: quant-ph
Comments: 8 pages, 7 figures, v2: shortened version
Journal-ref: Phys. Rev. A 75, 043801 (2007)
\\ ( , 66kb)
replaced with revised version Tue, 24 Apr 2007 16:05:20 GMT (29kb)

Title: Dynamical Aspects of Analogue Gravity: The Backreaction of Quantum
   Fluctuations in Dilute Bose-Einstein Condensates
Authors: Uwe R. Fischer
Categories: cond-mat.other gr-qc hep-th
Comments: 21+epsilon pages; has appeared in Springer Lecture Notes in Physics
Journal-ref: Lect. Notes Phys. 718, 93-113 (2007)
DOI: 10.1007/3-540-70859-6_5
\\ ( , 29kb)
replaced with revised version Tue, 24 Apr 2007 12:33:30 GMT (37kb)

Title: Phase diagram for interacting Bose gases
Authors: K. Morawetz, M. Maennel and M. Schreiber
Categories: cond-mat.stat-mech cond-mat.other
\\ ( , 37kb)
replaced with revised version Tue, 24 Apr 2007 13:16:31 GMT (229kb)

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 cond-mat.other
Comments: 8 pages, 3 figures
\\ ( , 229kb)
replaced with revised version Tue, 24 Apr 2007 19:20:24 GMT (248kb)

Title: Fast Quantum State Control of a Single Trapped Neutral Atom
Authors: Matthew P. A. Jones (LCFIO), Jerome Beugnon (LCFIO), Alpha Ga\"etan
   (LCFIO), Junxiang Zhang (LCFIO), Gaetan Messin (LCFIO), Antoine Browaeys
   (LCFIO), Philippe Grangier (LCFIO)
Categories: quant-ph
Journal-ref: Physical review A 75 (11/04/2007) 040301(R)
DOI: 10.1103/PhysRevA.75.040301
\\ ( , 248kb)
replaced with revised version Wed, 25 Apr 2007 14:23:35 GMT (413kb)

Title: Bragg spectroscopy of a superfluid Bose-Hubbard gas
Authors: X. Du, Shoupu Wan, Emek Yesilada, C. Ryu, D. J. Heinzen, Z. X. Liang,
   and Biao Wu
Categories: cond-mat.other
Comments: 11 pages, 4 figures
\\ ( , 413kb)
replaced with revised version Wed, 25 Apr 2007 17:45:39 GMT (119kb)

Title: Spin-correlation functions in ultracold paired atomic-fermion systems:
   sum rules, self-consistent approximations, and mean fields
Authors: Zhenhua Yu and Gordon Baym
Categories: cond-mat.other
Comments: 7 pages, 1 figure, content added
Journal-ref: Physical Review A 73, 063601 (2006)
\\ ( , 119kb)
replaced with revised version Wed, 25 Apr 2007 17:57:46 GMT (19kb)

Title: Quasi-Adiabatic Continuation in Gapped Spin and Fermion Systems:
   Goldstone's Theorem and Flux Periodicity
Authors: M. B. Hastings
Categories: cond-mat.stat-mech
Comments: 19 pages, 2 figures, final version in press at JSTAT
\\ ( , 19kb)
replaced with revised version Wed, 25 Apr 2007 15:47:22 GMT (177kb)

Title: Interaction-induced crossover versus finite-size condensation in a
   weakly interacting trapped one-dimensional Bose gas
Authors: Isabelle Bouchoule (LCFIO), Karen V. Kheruntsyan (ARC Centre of
   Excellence for Quantum-Atom Optics), Gora Shlyapnikov (LPTMS)
Categories: physics.atom-ph cond-mat.other cond-mat.stat-mech
Comments: 4 pages
Journal-ref: Physical Review A 75 (28/03/2007) 031606
\\ ( , 177kb)
replaced with revised version Thu, 26 Apr 2007 05:19:03 GMT (77kb)

Title: Bose-Einstein condensation of magnons in magnets with predominant
   ferromagnetic interaction
Authors: A. V. Syromyatnikov
Categories: cond-mat.str-el
Comments: 9 pages, 4 figure. The paper has been rewritten considerably. In
   particular, discussion of crossovers in the critical temperature in
   quasi-low-dimensional magnets is added
Journal-ref: Phys. Rev. B 75, 134421 (2007)
DOI: 10.1103/PhysRevB.75.134421
\\ ( , 77kb)

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Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from
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Received on Mon May 14 2007 - 09:54:15 EST

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