Matt's arXiv selection: week ending 3 August 2007.

From: Matthew Davis <>
Date: Fri, 24 Aug 2007 09:30:12 +1000 (EST)

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

Hi everyone,

Firstly I would like to apologise for the delay in this posting, but for once I
have a good excuse. I usually try to compile this list on Monday mornings, but
not long after I arrived at work on August 6 my wife called me to say I
should get home quick and take her to the hospital. Less than three hours
later, Owen Joseph Davis made his way into the world. Hence I've had some time
off in the last couple of weeks :)

For those that are interested I've posted a few photos here

I should have you up to date fairly shortly. Here is the first week's worth
that you have no doubt been anticipating: 31 new papers and 17 replacements.

Date: Fri, 27 Jul 2007 08:17:15 GMT (91kb)

Title: Generation of mesoscopic superpositions of a binary Bose-Einstein
   condensate in a slightly asymmetric double well
Authors: Christoph Weiss (LKB - Lhomond), Niklas Teichmann (UMSIHP)
Categories: cond-mat.other
Comments: 5 pages, 4 figures, preprint-version
Proxy: ccsd hal-00165661
   A previous publication [Europhysics Letters 78, 10009 (2007)] suggested to
coherently generate mesoscopic superpositions of a two-component Bose-Einstein
condensate in a double well under perfectly symmetric conditions. However,
already tiny asymmetries can destroy the entanglement properties of the ground
state. Nevertheless, even under more realistic conditions, the scheme is
demonstrated numerically to generate mesoscopic superpositions.
\\ ( , 91kb)
Date: Fri, 27 Jul 2007 08:38:29 GMT (707kb)

Title: Fulde-Ferrell-Larkin-Ovchinnikov states in one-dimensional
   spin-polarized ultracold atomic Fermi gases
Authors: Xia-Ji Liu, Hui Hu, and Peter D. Drummond
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 23 papes, 19 figures, submitted to Phys. Rev. A
   We present a systematic study of quantum phases in a one-dimensional
spin-polarized Fermi gas. Three comparative theoretical methods are used to
explore the phase diagram at zero temperature: the mean-field theory with
either an order parameter in a single-plane-wave form or a self-consistently
determined order parameter using the Bogoliubov-de Gennes equations, as well as
the exact soluble Bethe ansatz method. We find that a spatially inhomogeneous
Fulde-Ferrell-Larkin-Ovchinnikov phase, which lies between the fully paired BCS
state and the fully polarized normal state, dominates most of the phase diagram
of a uniform gas. The phase transition from the BCS state to the
Fulde-Ferrell-Larkin-Ovchinnikov phase is of second order, and therefore there
are no phase separation states in one-dimensional homogeneous polarized gases.
This is in sharp contrast to the three-dimensional situation, where a phase
separation regime is predicted to occupy a very large space in the phase
diagram. We conjecture that the prediction of the dominance of the phase
separation phases in three dimension could be an artifact of the
non-self-consistent mean-field approximation, which is heavily used in the
study of three-dimensional polarized Fermi gases. We consider also the effect
of a harmonic trapping potential on the phase diagram, and find that in this
case the trap generally leads to phase separation, in accord with the
experimental observations for a trapped gas in three dimension. We finally
investigate the local fermionic density of states of the
Fulde-Ferrell-Larkin-Ovchinnikov ansatz. A two-energy-gap structure is shown
up, which could be used as an experimental probe of the
Fulde-Ferrell-Larkin-Ovchinnikov states.
\\ ( , 707kb)
Date: Fri, 27 Jul 2007 13:44:08 GMT (133kb)

Title: Mean-field description of ultracold Bosons on disordered two-dimensional
   optical lattices
Authors: P. Buonsante (1), Francesco Massel (1), Vittorio Penna (1), Alessandro
   Vezzani (2) ((1) Dipartimento di Fisica, Torino Politecnico (2) Dipartimento
   di Fisica, Universita' degli Studi di Parma)
Categories: cond-mat.dis-nn cond-mat.mes-hall
Comments: Accepted for publication on JPB-FTC
   In the present paper we describe the properties induced by disorder on an
ultracold gas of Bosonic atoms loaded into a two-dimensional optical lattice
with global confinement ensured by a parabolic potential. Our analysis is
centered on the spatial distribution of the various phases, focusing
particularly on the superfluid properties of the system as a function of
external parameters and disorder amplitude. In particular, it is shown how
disorder can suppress superfluidity, while partially preserving the system
\\ ( , 133kb)
Date: Fri, 27 Jul 2007 13:49:35 GMT (146kb)

Title: Dynamics of the attractive 1D Bose gas: analytical treatment from
Authors: P. Calabrese and J.-S. Caux
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 26 pages, 5 figures
   The physics of the attractive one-dimensional Bose gas (Lieb-Liniger model)
is investigated with techniques based on the integrability of the system.
Combining a knowledge of particle quasi-momenta to exponential precision in the
system size with determinant representations of matrix elements of local
operators coming from the Algebraic Bethe Ansatz, we obtain rather general
analytical results for the zero-temperature dynamical correlation functions of
the density and field operators. Our results thus provide quantitative
predictions for possible future experiments in atomic gases or optical
\\ ( , 146kb)
Date: Fri, 27 Jul 2007 14:01:28 GMT (8kb)

Title: Supersymmetry and Goldstino Mode in Bose-Fermi Mixtures
Authors: Yue Yu and Kun Yang
Categories: cond-mat.other cond-mat.str-el
Comments: 4 pages
   Supersymmetry is assumed to be a basic symmetry of the world in many high
energy theories, but none of the super partners of any known elementary
particle has been observed yet. We argue that supersymmetry can also be
realized and studied in ultracold atomic systems with a mixture of bosons and
fermions, with properly tuned interactions and single particle dispersion. We
further show that in such non-releativistic systems supersymmetry is either
spontaneously broken, or explicitly broken by a chemical potential difference
between the bosons and fermions. In both cases the system supports a sharp
fermionic collective mode or the so-called Goldstino, due to supersymmetry. We
also discuss possible ways to detect the Goldstino mode experimentally.
\\ ( , 8kb)
Date: Fri, 27 Jul 2007 21:51:27 GMT (104kb)

Title: Pairing states of a polarized Fermi gas trapped in a one-dimensional
   optical lattice
Authors: A.E. Feiguin, and F. Heidrich-Meisner
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 pages, 5 figs
   We study the properties of a one-dimensional (1D) gas of fermions trapped in
a lattice by means of the density matrix renormalization group method, focusing
on the case of unequal spin populations, and strong attractive interaction. In
the low density regime, the system phase-separates into a well defined
superconducting core and a fully polarized metallic cloud surrounding it. We
argue that the superconducting phase corresponds to a 1D analogue of the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, with a quasi-condensate of
tightly bound bosonic pairs with a finite center-of-mass momentum that scales
linearly with the magnetization. In the large density limit, the system allows
for four phases: in the core, we either find a Fock state of localized pairs or
a metallic shell with free spin-down fermions moving in a fully filled
background of spin-up fermions. As the magnetization increases, the Fock state
disappears to give room for a metallic phase, with a partially polarized
superconducting FFLO shell and a fully polarized metallic cloud surrounding the
\\ ( , 104kb)
Date: Fri, 27 Jul 2007 19:02:25 GMT (18kb)

Title: Any-order propagation of the nonlinear Schroedinger equation
Authors: Frederick W. Strauch
Categories: quant-ph
Comments: 10 pages, no figures, submitted to Phys. Rev. E
   We derive an exact propagation scheme for nonlinear Schroedinger equations.
This scheme is entirely analogous to the propagation of linear Schroedinger
equations. We accomplish this by defining a special operator whose algebraic
properties ensure the correct propagation. As applications, we provide a simple
proof of a recent conjecture regarding higher-order integrators for the
Gross-Pitaevskii equation, extend it to multi-component equations, and to a new
class of integrators.
\\ ( , 18kb)
Date: Sat, 28 Jul 2007 12:27:30 GMT (176kb)

Title: Superfluid-Insulator Transition and Fermion Pairing in Bose-Fermi
Authors: Kun Yang
Categories: cond-mat.supr-con cond-mat.str-el
Comments: 4 pages with 4 embedded figures
   It is well known that bosons on an optical lattice undergo a second-order
superfluid-insulator transition (SIT) when the lattice potential increases. In
this paper we study SIT when fermions coexist with the bosons. We find that the
critical properties of particle-hole symmetric SIT with dynamical exponent z=1
is modified when fermions are present; it either becomes a fluctuation-driven
first order transition or a different second-order transition. On the other
hand the more generic particle-hole asymmetric (with z=2) SIT is stable against
coupling with fermions. We also discuss pairing interaction between fermions
mediated by quantum critical fluctuations near SIT.
\\ ( , 176kb)
Date: Sat, 28 Jul 2007 20:04:56 GMT (23kb)

Title: Fermi-Polaron: Diagrammatic Monte Carlo for Divergent Sign-Alternating
Authors: Nikolay Prokof'ev and Boris Svistunov
Categories: cond-mat.stat-mech
Comments: 4 pages, 7 figures
   Diagrammatic Monte Carlo approach is applied to a problem of a single
spin-down fermion resonantly interacting with the sea of ideal spin-up
fermions. On one hand, we develop a generic, sign-problem tolerant, method of
exact numerical solution of polaron-type models. On the other hand, our
solution is important for understanding the phase diagram and properties of the
BCS-BEC crossover in the strongly imbalanced regime. This is the first, and
possibly characteristic, example of how the Monte Carlo approach can be applied
to a divergent sign-alternating diagrammatic series.
\\ ( , 23kb)
Date: Mon, 30 Jul 2007 12:31:02 GMT (152kb)

Title: Quantum rotor description of the Mott-insulator transition in the
   Bose-Hubbard model
Authors: T. P. Polak and T. K. Kope\'c
Categories: cond-mat.stat-mech
Comments: accepted to PRB
   We present the novel approach to the Bose-Hubbard model using the
$\mathrm{U}(1)$ quantum rotor description. The effective action formalism
allows us to formulate a problem in the phase only action and obtain an
analytical formulas for the critical lines. We show that the nontrivial
$\mathrm{U}(1)$ phase field configurations have an impact on the phase
diagrams. The topological character of the quantum field is governed by terms
of the integer charges - winding numbers. The comparison presented results to
recently obtained quantum Monte Carlo numerical calculations suggests that the
competition between quantum effects in strongly interacting boson systems is
correctly captured by our model.
\\ ( , 152kb)
Date: Mon, 30 Jul 2007 12:38:08 GMT (22kb)

Title: An Effective Low-Dimensional Hamiltonian for Strongly Interacting Atoms
   in a Transverse Trap
Authors: J. P. Kestner, L.-M. Duan
Categories: cond-mat.other
Comments: 4 pages, 1 figure
   We derive an effective low-dimensional Hamiltonian for strongly interacting
ultracold atoms in a transverse trapping potential near a wide Feshbach
resonance. The Hamiltonian includes crucial information about transverse
excitations in an effective model with renormalized interaction between atoms
and composite dressed molecules. We fix all the parameters in the Hamiltonian
for both one and two dimensional cases.
\\ ( , 22kb)
Date: Mon, 30 Jul 2007 13:44:10 GMT (76kb)

Title: Recent results from the Gaussian Quantum Monte Carlo method for fermions
   with symmetry projection
Authors: P. Corboz, A. Kleine, F. F. Assaad, I. P. McCulloch, U. Schollw\"ock,
   M. Troyer
Categories: cond-mat.str-el
Comments: 11 pages, 14 figures
   Gaussian Quantum Monte Carlo (GQMC) is a stochastic phase space method for
fermions with positive weights. In the example of the Hubbard model close to
half filling it fails to reproduce all the symmetries of the ground state
leading to systematic errors at low temperatures. In a previous work [Phys.
Rev. B {\bf 72}, 224518 (2005)] we proposed to restore the broken symmetries by
projecting the density matrix obtained from the simulation onto the ground
state symmetry sector. In this paper we present a systematic study of the
method for 2 and 3 leg Hubbard ladders for different fillings and on-site
repulsion strengths. We provide several indications that the systematic errors
stem from non-vanishing boundary terms in the partial integration step in the
derivation of the Fokker-Planck equation. Checking for spiking trajectories and
slow decaying probability distributions provides an important test of the
reliability of the results. Possible solutions to avoid boundary terms are
discussed. Furthermore we compare results obtained from two different sampling
methods: Reconfiguration of walkers and the Metropolis algorithm.
\\ ( , 76kb)
Date: Mon, 30 Jul 2007 14:09:23 GMT (64kb)

Title: Specific heat of a one-dimensional interacting Fermi system: the role of
Authors: Andrey V. Chubukov, Dmitrii L. Maslov, and Ronojoy Saha
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: 21 pages, 6 figures
   We re-visit the issue of the temperature dependence of the specific heat for
interacting fermions in 1D. Of particular interest is the spin component C_s(T)
of the specific heat. Unlike the charge component which scales linearly with T,
C_s(T) was shown by a variety of bosonization technique to contain a cube of
the running backscattering amplitude g_1(T), and eventually to scale down as
T/\log^3 T. On the other hand, a perturbative expansion of C_s (T) in powers of
the bare amplitude g_1 contains terms g_1, g^2_1, g^3_1, etc. We study in
detail why the running amplitude g_1 (T) appears in C_s(T) only at third order,
but not earlier. We consider a model with two cutoffs, fermionic and bosonic --
Lambda_f and Lambda_b-- set by the bandwidth and by the momentum-dependent
interaction, respectively. We show that for Lambda_f>Lambda_b (assumed in all
previous papers), C_s (T) does contains the running amplitude g_1 (T), but only
at intermediate temperatures: Lambda_b < T <Lambda_f. At lower T, g_1 in C_s
(T) freezes on the scale Lambda_b. We find that a physically distinct
contribution to C_s (T), emerging at third order, contains the running
amplitude g_1 (T) down to the lowest temperatures. We also show how to obtain
the same results within the sine-Gordon model.
\\ ( , 64kb)
Date: Mon, 30 Jul 2007 16:17:34 GMT (83kb)

Title: Emulating Non-Abelian Topological Matter in Cold Atom Optical Lattices
Authors: V. W. Scarola and S. Das Sarma
Categories: cond-mat.other
   Certain proposed extended Bose-Hubbard models may exhibit topologically
ordered ground states with excitations obeying non-Abelian braid statistics. A
sufficient tuning of Hubbard parameters could yield excitation braiding rules
to allow implementation of a universal set of topologically protected quantum
gates. We discuss potential issues in realizing a model with a proposed
non-Abelian topologically ordered ground state using optical lattices
containing bosonic dipoles. Our direct implementation scheme does not realize
the necessary anisotropic hopping, anisotropic interactions, and low
temperatures. We briefly mention other implementation ideas which may alleviate
some of these problems.
\\ ( , 83kb)
Date: Mon, 30 Jul 2007 19:46:13 GMT (396kb)

Title: Bose-Einstein Condensates in Strongly Disordered Traps
Authors: T. Nattermann and V.L. Pokrovsky
Categories: cond-mat.stat-mech cond-mat.dis-nn
   A Bose-Einstein condensate in an external potential consisting of a
superposition of a harmonic and a random potential is considered theoretically.
   From a semi-quantitative analysis we find the size, shape and excitation
energy as a function of the disorder strength. For positive scattering length
and sufficiently strong disorder the condensate decays into fragments each of
the size of the Larkin length ${\cal L}$. This state is stable over a large
range of particle numbers. The frequency of the breathing mode scales as
$1/{\cal L}^2$. For negative scattering length a condensate of size ${\cal L}$
may exist as a metastable state. These finding are generalized to anisotropic
\\ ( , 396kb)
arXiv:0707.4397 (*cross-listing*)
Date: Mon, 30 Jul 2007 12:56:43 GMT (93kb)

Title: Ultracold collisions in magnetic fields: reducing inelastic cross
   sections near Feshbach resonances
Authors: R. Adam Rowlands, Maykel Leonardo Gonzalez-Martinez and Jeremy M.
Categories: physics.chem-ph physics.atm-clus physics.atom-ph
Comments: 9 pages, 9 figures
   We have carried out bound-state and low-energy quantum scattering
calculations on He + NH (triplet Sigma) in magnetic fields, with the NH
molecule in its n=1 rotationally excited states. We have explored the pattern
of levels as a function of magnetic field and identified the nearly good
quantum numbers in different regimes. We have used the bound-state calculations
to locate low-energy Feshbach resonances. When the magnetic field is used to
tune across such a resonance, the real and imaginary part of the scattering
length show asymmetric oscillations and peaks with amplitude between 1 and 3
Angstroms. The scattering length does not pass through a pole at resonance. The
resonant behavior is characterized by a complex resonant scattering length
a_res. The corresponding inelastic cross sections show troughs as well as peaks
near resonance. This may be important for efforts to achieve evaporative and
sympathetic cooling for molecules, because it offers the hope that inelastic
trap losses can be reduced by tuning close to a Feshbach resonance.
\\ ( , 93kb)
Date: Tue, 31 Jul 2007 01:33:17 GMT (100kb)

Title: Condensation Phenomena in the `Maxwell-Boltzmann' statistics
Authors: Jun Ohkubo
Categories: cond-mat.dis-nn cond-mat.stat-mech
Comments: 6 pages, 5 figures
   We study real-space condensation phenomena in a type of classical stochastic
processes (site-particle system), such as zero-range processes and urn models.
We here study a stochastic process in the Ehrenfest class, i.e., particles in a
site are distinguishable. In terms of the statistical mechanical analogue, the
Ehrenfest class obeys the Maxwell-Boltzmann statistics. It is revealed why the
condensation phenomenon is difficult to occur in the Ehrenfest class. In
addition, we discuss a model for the condensation phenomenon in the Ehrenfest
class. It becomes clear that the condensation phenomenon arises only in the
case with quenched disorder, and that the model shows three types of
condensation depending on the disorder parameters.
\\ ( , 100kb)
Date: Tue, 31 Jul 2007 01:43:15 GMT (21kb)

Title: Correlations Functions of One-Dimensional Lieb-Liniger Anyons
Authors: Ovidiu I. Patu, Vladimir E. Korepin, Dmitri V. Averin
Categories: cond-mat.stat-mech
Comments: 19 pages, RevTeX 4
   We have investigated the properties of a model of 1D anyons interacting
through a $\delta$-function repulsive potential. The structure of the
quasi-periodic boundary conditions for the anyonic field operators and the
many-anyon wavefunctions is clarified. The spectrum of the low-lying
excitations including the particle-hole excitations is calculated for periodic
and twisted boundary conditions. Using the ideas of the conformal field theory
we obtain the large-distance asymptotics of the density and field correlation
function at the critical temperature T=0 and at small finite temperatures. Our
expression for the field correlation function extends the results in the
literature obtained for harmonic quantum anyonic fluids.
\\ ( , 21kb)
Date: Tue, 31 Jul 2007 04:40:16 GMT (110kb)

Title: Stabilization of a Bose-Einstein droplet by hyperfine Rabi oscillations
Authors: Hiroki Saito, Randall G. Hulet, Masahito Ueda
Categories: cond-mat.other
Comments: 6 pages, 2 figures
   A self-trapped Bose-Einstein condensate is shown to be stabilized in
two-dimensional free space by Rabi oscillations between two hyperfine states
which make an effective interatomic interaction oscillate in time. The
stabilization mechanism is elucidated by using a two-component Gross-Pitaevskii
equation combined with a variational analysis. The parameter regime of
stability is investigated.
\\ ( , 110kb)
Date: Tue, 31 Jul 2007 14:44:08 GMT (192kb)

Title: Ground state properties of a homogeneous 2D system of Bosons with
   dipolar interactions
Authors: G.E. Astrakharchik, J. Boronat, J. Casulleras, I.L. Kurbakov, Yu.E.
Categories: cond-mat.other
Comments: Contribution to RPMBT14 conference. To be published in a volume of
   the Series on Advances in Quantum Many-Body by World Scientific
   The ground-state phase properties of a two-dimensional Bose system with
dipole-dipole interactions is studied by means of quantum Monte Carlo
techniques. Limitations of mean-field theory in a two-dimensional geometry are
discussed. A quantum phase transition from gas to solid is found. Crystal is
tested for existence of a supersolid in the vicinity of the phase transition.
Existence of mesoscopic analogue of the off-diagonal long-range order is shown
in the one-body density matrix in a finite-size crystal. Non-zero superfluid
fraction is found in a finite-size crystal, the signal being dramatically
increased in presence of vacancies.
\\ ( , 192kb)
Date: Tue, 31 Jul 2007 16:39:10 GMT (955kb)

Title: Laser tweezers for atomic solitons
Authors: Alicia V. Carpentier, Juan Belmonte-Beitia, Humberto Michinel, and
   Victor M. Perez-Garcia
Categories: cond-mat.other
Comments: 6 pages, 7 figures
   We describe a controllable and precise laser tweezers for Bose-Einstein
condensates of ultracold atomic gases. In our configuration, a laser beam is
used to locally modify the sign of the scattering length in the vicinity of a
trapped BEC. The induced attractive interactions between atoms allow to extract
and transport a controllable number of atoms. We analyze, through numerical
simulations, the number of emitted atoms as a function of the width and
intensity of the outcoupling beam. We also study different configurations of
our system, as the use of moving beams. The main advantage of using the control
laser beam to modify the nonlinear interactions in comparison to the usual way
of inducing optical forces, i.e. through linear trapping potentials, is to
improve the controllability of the outcoupled solitary wave-packet, which opens
new possibilities for engineering macroscopic quantum states.
\\ ( , 955kb)
Date: Tue, 31 Jul 2007 18:19:53 GMT (294kb)

Title: Atomic lattice excitons: from condensates to crystals
Authors: A. Kantian, A. J. Daley, P. Torma, P. Zoller
Categories: cond-mat.other
Comments: 19 pages, 15 figures
   We discuss atomic lattice excitons (ALEs), bound particle-hole pairs formed
by fermionic atoms in two bands of an optical lattice. Such a system provides a
clean setup to study fundamental properties of excitons, ranging from
condensation to exciton crystals (which appear for a large effective mass ratio
between particles and holes). Using both mean-field treatments and 1D numerical
computation, we discuss the properities of ALEs under varying conditions, and
discuss in particular their preparation and measurement.
\\ ( , 294kb)
Date: Tue, 31 Jul 2007 17:34:57 GMT (253kb)

Title: Conceptual Design of a Micron-Scale Atomic Clock
Authors: Eric C. Hannah, Michael A. Brown
Categories: physics.atom-ph physics.ins-det
Comments: Submitted to the Journal of Applied Physics
   A theoretical proposal for reducing an entire atomic clock to micron
dimensions. A phosphorus or nitrogen atom is introduced into a fullerene cage.
This endohedral fullerene is then coated with an insulating shell and a number
of them are deposited as a thin layer on a silicon chip. Next to this layer a
GMR sensor is fabricated which is close to the endohedral fullerenes. This GMR
sensor measures oscillating magnetic fields on the order of micro-gauss from
the nuclear spins varying at the frequency of the hyperfine transition (413 MHz
frequency). Given the micron scale and simplicity of this system only a few
transistors are needed to control the waveforms and to perform digital
clocking. This new form of atomic clock exhibits extremely low power (nano
watts), high vibration and shock resistance, stability on the order of 10^{-9},
and is compatible with MEMS fabrication and chip integration. As GMR sensors
continue to improve in sensitivity the stability of this form of atomic clock
will increase proportionately.
\\ ( , 253kb)
Date: Wed, 1 Aug 2007 19:54:15 GMT (206kb)

Title: One-dimensional quantum wires: A pedestrian approach to bosonization
Authors: Sebastian Eggert
Categories: cond-mat.str-el
Comments: 47 pages, 18 figures, lecture notes (A3 Foresight Summer School,
   Korea, 2006). The most recent version can be found at
   In these lecture notes we will consider systems in which the motion of
electrons is confined to one dimension (1D). In these so-called quantum wires
electron-electron interaction effects play an important role because the
restricted dimensions enhance the scattering between the electrons and
completely destroy the quasi-particle picture. New density wave excitations
appear that are described by bosonic operators. Here, we will develop this
bosonic description, following a pedestrian approach which does not require any
previous knowledge in field theory methods. These notes therefore serve as a
detailed introduction into bosonization by carefully deriving the most
fundamental formulas.
\\ ( , 206kb)
Date: Wed, 1 Aug 2007 08:51:33 GMT (297kb)

Title: Bistability and fluctuations of a weakly interacting Bose-Einstein
Authors: Z. Idziaszek, L. Zawitkowski, M. Gajda, K. Rzazewski
Categories: cond-mat.stat-mech
Comments: 4 pages, 4 figures
   Fluctuations of the number of condensed atoms in a finite-size, weakly
interacting Bose gas confined in a box potential are investigated for
temperatures up to the critical region. We develop a recursive scheme that
allows to calculate condensate statistics for systems of few hundred particles
and an approximate approach applicable to systems with N~10000 particles. We
point out the importance of particle-number constrain for the statistics near
the critical region, which reveal a novel bistable phase of the condensate. Our
analysis is performed in the canonical ensemble and the excitations are
described in a self-consistent way within the Bogoliubov-Popov approximation.
\\ ( , 297kb)
Date: Wed, 1 Aug 2007 13:55:55 GMT (26kb)

Title: Upper limit on the transition temperature for non-ideal Bose gases
Authors: Wu-Sheng Dai and Mi Xie
Categories: cond-mat.stat-mech cond-mat.supr-con
Comments: 7 pages, 1 figure
Journal-ref: Ann. Phys. (New York) 322, 1771-1775 (2007)
   In this paper we show that for a non-ideal Bose gas there exists an upper
limit on the transition temperature above which Bose-Einstein condensation
cannot occur regardless of the pressure applied. Such upper limits for some
realistic Bose gases are estimated. This result implies that there may also
exist an upper limit on the transition temperature of superconductors.
\\ ( , 26kb)
Date: Wed, 1 Aug 2007 18:15:42 GMT (497kb)

Title: Collective oscillations in optical matter
Authors: F. J. Garcia de Abajo
Categories: cond-mat.soft cond-mat.other
Comments: 4 figures. Optics Express (in press)
   Atom and nanoparticle arrays trapped in optical lattices are shown to be
capable of sustaining collective oscillations of frequency proportional to the
strength of the external light field. The spectrum of these oscillations
determines the mechanical stability of the arrays. This phenomenon is studied
for dimers, strings, and two-dimensional planar arrays. Laterally confined
particles free to move along an optical channel are also considered as an
example of collective motion in partially-confined systems. The fundamental
concepts of dynamical response in optical matter introduced here constitute the
basis for potential applications to quantum information technology and signal
processing. Experimental realizations of these systems are proposed.
\\ ( , 497kb)
Date: Wed, 1 Aug 2007 10:48:34 GMT (214kb)

Title: A case study of the Hirsch index for 26 non-prominent physicists
Authors: Michael Schreiber
Categories: physics.soc-ph
Comments: 13 pages, 3 figures, accepted for publication in Annalen der Physik
   (Ann. Phys.)
   The h index was introduced by Hirsch to quantify an individual's scientific
research output. It has been widely used in different fields to show the
relevance of the research work of prominent scientists. I have worked out 26
practical cases of physicists which are not so prominent. Therefore this case
study should be more relevant to discuss various features of the Hirsch index
which are interesting or disturbing or both for the more average situation. In
particular, I investigate quantitatively some pitfalls in the evaluation and
the influence of self-citations.
\\ ( , 214kb)
Date: Thu, 2 Aug 2007 01:01:23 GMT (63kb)

Title: Many-Body Quantum and Thermal Fluctuations in Josephson-Linked
Authors: Chaohong Lee, Libin Fu, Yuri S. Kivshar
Categories: quant-ph
Comments: 4 pages, 4 figures
   We analyze many-body quantum and thermal fluctuations of phase coherence
between two Josephson-linked Bose-Einstein condensates with repulsive
interaction. For zero temperature, we find that the coherence fluctuations of
symmetric systems grow as $\sim E_C/E_J$ and the number squeezing increases as
$\sim N^2 E_C/E_J$, where E_C is the interaction energy, E_J is the tunneling
energy, and N is the total particle number. The coherence fluctuations are
suppressed dramatically due to an interplay between the system asymmetry and
interaction revealing interesting resonance effects. For finite temperatures,
the coherence fluctuations grow, and the formation of self-trapped states
causes an anomalous behavior. The results are in a good qualitative agreement
with the experimental data.
\\ ( , 63kb)
Date: Thu, 2 Aug 2007 14:46:05 GMT (8kb)

Title: Quantum phase diffusion of a Bose system: beyond the
   Hartree-Fock-Bogoliubov approximation
Authors: Ferdinando de Pasquale, Gian Luca Giorgi
Categories: quant-ph
   A diffusion process is usually assumed for the phase of the order parameter
of a Bose system of finite size. The theoretical basis is limited to the so
called Bogoliubov approximation. We show that a suitable generalization of the
Hartree-Fock-Bogoliubov approach recovers phase diffusion.
\\ ( , 8kb)
Date: Thu, 2 Aug 2007 14:51:19 GMT (176kb)

Title: Entanglement, BEC, and superfluid-like behavior of two-mode photon
Authors: Ferdinando de Pasquale, Gian Luca Giorgi
Categories: quant-ph
   A system of two interacting photon modes, without constraints on the photon
number, in the presence of a Kerr nonlinearity, exhibits BEC if the transfer
amplitude is greater than the mode frequency. A symmetry-breaking field (SBF)
can be introduced by taking into account a classical electron current. The
ground state, in the limit of small nonlinearity, becomes a squeezed state, and
thus the modes become entangled. The smaller is the SBF, the greater is
entanglement. Superfluid-like behavior is observed in the study of entanglement
growth from an initial coherent state, since in the short-time range the growth
does not depend on the SBF amplitude, and on the initial state amplitude. On
the other hand, the latter is the only parameter which determines entanglement
in the absence of the SBF.
\\ ( , 176kb)

The replacements:

replaced with revised version Fri, 27 Jul 2007 15:50:09 GMT (251kb)

Title: Vortex quantum creation and winding number scaling in a quenched spinor
   Bose gas
Authors: Michael Uhlmann, Ralf Sch\"utzhold and Uwe R. Fischer
Categories: cond-mat.other
Comments: 4+epsilon pages of RevTex4, 2 figures; to appear in Physical Review
\\ ( , 251kb)
replaced with revised version Mon, 30 Jul 2007 10:27:50 GMT (22kb)

Title: Thermodynamic properties of a trapped Bose gas : A diffusion Monte Carlo
Authors: S Datta
Categories: cond-mat.stat-mech
Comments: 19 pages, 12 figures
\\ ( , 22kb)
replaced with revised version Sat, 28 Jul 2007 19:45:08 GMT (36kb)

Title: Bold Diagrammatic Monte Carlo: When Sign Problem is Welcome
Authors: Nikolay Prokof'ev and Boris Svistunov
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 4 pages, 2 figures, revtex4
\\ ( , 36kb)
replaced with revised version Tue, 31 Jul 2007 03:01:07 GMT (22kb)

Title: Thermodynamic properties of a trapped Bose gas : A diffusion Monte Carlo
Authors: S Datta
Categories: cond-mat.stat-mech
Comments: 19 pages, 12 figures
\\ ( , 22kb)
replaced with revised version Tue, 31 Jul 2007 11:28:40 GMT (193kb)

Title: Quantum liquid of repulsively bound pairs of particles in a lattice
Authors: David Petrosyan, Bernd Schmidt, James R. Anglin, Michael Fleischhauer
Categories: cond-mat.other quant-ph
Comments: Modified, expanded text, added figures
\\ ( , 193kb)
replaced with revised version Tue, 31 Jul 2007 02:37:46 GMT (8kb)
Title: Discontinuity in the specific heat of a weakly interacting Bose gas
Authors: Sang-Hoon Kim
Categories: cond-mat.stat-mech
Comments: 2 pages, 2 figures
\\ ( , 8kb)
replaced with revised version Wed, 1 Aug 2007 09:21:22 GMT (67kb)

Title: Meissner effect in a charged Bose gas with short-range repulsion
Authors: Shun-ichiro Koh
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 8 pages, 3 figures
Journal-ref: Physical Review B 68,144502(2003)
DOI: 10.1103/PhysRevB.68.144502
\\ ( , 67kb)
replaced with revised version Wed, 1 Aug 2007 12:31:50 GMT (482kb)

Title: The ground state of a mixture of two species of fermionic atoms in 1D
   optical lattice
Authors: Shi-Jian Gu, Rui Fan, and Hai-Qing Lin
Categories: cond-mat.str-el quant-ph
Comments: 9 pages, 10 figures, extended version
\\ ( , 482kb)
replaced with revised version Wed, 1 Aug 2007 02:43:02 GMT (9kb)

Title: Ground state energy density of a dilute Bose gas in the canonical
Authors: Sang-Hoon Kim, Chul Koo Kim, and Mukunda P. Das
Categories: cond-mat.stat-mech
Comments: 5 pages, 0 figure
\\ ( , 9kb)
replaced with revised version Wed, 1 Aug 2007 08:56:09 GMT (173kb)

Title: Ultracold atoms in radio-frequency-dressed potentials beyond the
   rotating wave approximation
Authors: S. Hofferberth, B. Fischer, T. Schumm, J. Schmiedmayer, and I.
Categories: quant-ph
Comments: 6 pages, 4 figures
Journal-ref: Phys. Rev. A 76, 013401 (2007)
\\ ( , 173kb)
replaced with revised version Thu, 2 Aug 2007 05:46:16 GMT (169kb)

Title: Universal thermodynamics of strongly interacting Fermi gases
Authors: Hui Hu, Peter D. Drummond, and Xia-Ji Liu
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 5 pages + 3 figures, submitted for publication
Journal-ref: Nature Physics, Vol 3 (2007)469
\\ ( , 169kb)
replaced with revised version Thu, 2 Aug 2007 04:04:31 GMT (23kb)

Title: Quantum rearrangement and self-consistent BCS-BEC crossover
Authors: Ji-sheng Chen, Chuan-ming Cheng, Jia-rong Li, Yan-ping Wang
Categories: cond-mat.stat-mech hep-ph nucl-th
Comments: published version revised according to comments; a few typos fixed
   and references updated
\\ ( , 23kb)
replaced with revised version Thu, 2 Aug 2007 00:27:14 GMT (15kb)

Title: Fermionic stabilization and density-wave ground state of a polar
Authors: O.Dutta R. Kanamoto and P.Meystre
Categories: cond-mat.other
\\ ( , 15kb)
replaced with revised version Thu, 2 Aug 2007 08:26:42 GMT (138kb)

Title: Non-equilibrium coherence dynamics in one-dimensional Bose gases
Authors: S. Hofferberth, I. Lesanovsky, B. Fischer, T. Schumm, J. Schmiedmayer
Categories: cond-mat.other cond-mat.supr-con
Comments: to appear in nature
\\ ( , 138kb)
replaced with revised version Thu, 2 Aug 2007 18:38:26 GMT (104kb)

Title: Pairing states of a polarized Fermi gas trapped in a one-dimensional
   optical lattice
Authors: A.E. Feiguin, and F. Heidrich-Meisner
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 pages, 5 figs
\\ ( , 104kb)
replaced with revised version Thu, 2 Aug 2007 18:45:29 GMT (114kb)

Title: Preparing and probing atomic number states with an atom interferometer
Authors: J. Sebby-Strabley, B. L. Brown, M. Anderlini, P. J. Lee, P. R.
   Johnson, W. D. Phillips, and J. V. Porto
Categories: quant-ph
Journal-ref: Phys. Rev. Lett. 98 200405 (2007)
DOI: 10.1103/PhysRevLett.98.200405
\\ ( , 114kb)
replaced with revised version Thu, 2 Aug 2007 17:10:50 GMT (99kb)

Title: Chaos in kicked Bose-Einstein condensates: Bogoliubov resonances
Authors: J. Reslen, C.E. Creffield, and T.S. Monteiro
Categories: quant-ph
Comments: 5 pages
\\ ( , 99kb)

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 Fri Aug 24 2007 - 09:30:12 EST

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