Matt's arXiv selection, Monday 6th March 2006.

From: Matthew Davis <>
Date: Mon, 6 Mar 2006 09:30:10 +1000 (EST)

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Have a great week,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Paper: cond-mat/0602572
Date: Fri, 24 Feb 2006 01:24:49 GMT   (429kb)
Title: Dynamical Instability of a Rotating Dipolar Bose-Einstein Condensate
Authors: R.M.W. van Bijnen, D.H.J. O'Dell, N.G. Parker and A.M. Martin
Comments: 5 pages, including 3 figures
Subj-class: Other
   We calculate the static solutions of a rotating harmonically trapped dilute
gas Bose-Einstein condensate in the presence of long range dipolar
interactions, based on the hydrodynamic model. In particular we focus on the
dynamical instability of our solutions, for weakly anisotropic traps. When the
trap anisotropy is introduced adiabatically, at fixed rotation frequency,
$\Omega$, the upper bound for the unstable region in $\Omega$ is decreased in
the presence of dipolar interactions. By considering dynamical perturbations we
also find that for fixed trap anisotropy and adiabatically increasing
rotational frequency that the dynamically unstable region in $\Omega$ widens,
in a non-trivial manner, as the strength of the dipole interactions is
\\ ( ,  429kb)
Paper: cond-mat/0602582
Date: Fri, 24 Feb 2006 10:32:14 GMT   (338kb)
Title: Analysis of an atom laser based on the spatial control of the scattering
Authors: Alicia V. Carpentier, Humberto Michinel, Mar\'{\i}a I. Rodas-Verde,
   V\'{\i}ctor M. P\'erez-Garc\'{\i}a
Comments: Submitted to Phys. Rev. A
Subj-class: Other
   In this paper we analyze atom lasers based on the spatial modulation of the
scattering length of a Bose-Einstein Condensate. We demonstrate, through
numerical simulations and approximate analytical methods, the controllable
emission of matter-wave bursts and study the dependence of the process on the
spatial dependence of the scattering length along the axis of emission. We also
study the role of an additional modulation of the scattering length in time.
\\ ( ,  338kb)
Paper: cond-mat/0602525
replaced with revised version Thu, 23 Feb 2006 23:23:24 GMT   (429kb)
Title: Superfluid phases of the three-species fermion gas
Authors: Paulo F. Bedaque, Jos\'e P. D'Incao
Comments: 4 pages, 1 figure, typos corrected and references added
Subj-class: Other; Atomic Physics
\\ ( ,  429kb)
Paper: cond-mat/0602568
replaced with revised version Fri, 24 Feb 2006 03:54:50 GMT   (291kb)
Title: Homogeneous Fermion Superfluid with Unequal Spin Populations
Authors: Tin-Lun Ho and Hui Zhai
Comments: 4 pages, 3 figures
Subj-class: Superconductivity
\\ ( ,  291kb)
Paper: quant-ph/0602202
Date: Fri, 24 Feb 2006 09:54:22 GMT   (351kb)
Title: Non-Gaussian states from continuous-wave Gaussian light sources
Authors: Klaus Molmer
   We present a general analysis of the state obtained by subjecting the output
from a continuous-wave (cw) Gaussian field to non-Gaussian measurements. The
generic multimode state of cw Gaussian fields is characterized by an infinite
dimensional covariance matrix involving the noise correlations of the source.
Our theory extracts the information relevant for detection within specific
temporal output modes from these correlation functions . The formalism is
applied to schemes for production of non-classical light states from a squeezed
beam of light.
\\ ( ,  351kb)
Paper (*cross-listing*): hep-th/0602236
Date: Wed, 22 Feb 2006 20:32:10 GMT   (38kb)
Title: Nonlocality and quantum-like behavior from classical fields
Authors: B. Holdom
Comments: 19 pages, 5 figures
   By averaging over an ensemble of field configurations, a classical field
theory can display many of the characteristics of quantum field theory,
including Lorentz invariance, a loop expansion, and renormalization effects.
There is additional freedom in how the ensemble is chosen. When the field mode
amplitudes have a Gaussian distribution, and the mode phases are randomly
distributed, we review the known differences between the classical and quantum
theories. When the mode amplitudes are fixed, or have a nongaussian
distribution, the quartic and higher correlations among the free fields are
modified, seemingly in a nonlocal way. We show how this in turn affects the
perturbative expansion. We focus on $\lambda\phi^4$ theory in 1+1 dimensions
and use lattice simulations to augment our study. We give examples of how these
nonlocal correlations induce quantum-like behavior, at both weak and strong
\\ ( ,  38kb)
Paper: cond-mat/0602614
Date: Mon, 27 Feb 2006 01:34:48 GMT   (374kb)
Title: Phase Transitions in Ultra-Cold Two-Dimensional Bose Gases
Authors: D. A. W. Hutchinson and P. B. Blakie
Subj-class: Statistical Mechanics; Superconductivity
   We briefly review the theory of Bose-Einstein condensation in the
two-dimensional trapped Bose gas and, in particular the relationship to the
theory of the homogeneous two-dimensional gas and the
Berezinskii-Kosterlitz-Thouless phase. We obtain a phase diagram for the
trapped two-dimensional gas, finding a critical temperature above which the
free energy of a state with a pair of vortices of opposite circulation is lower
than that for a vortex-free Bose-Einstein condensed ground state. We identify
three distinct phases which are, in order of increasing temperature, a phase
coherent Bose-Einstein condensate, a vortex pair plasma with fluctuating
condensate phase and a thermal Bose gas. The thermal activation of
vortex-antivortex pair formation is confirmed using finite-temperature
classical field simulations.
\\ ( ,  374kb)
Paper: cond-mat/0602616
Date: Mon, 27 Feb 2006 04:07:49 GMT   (93kb)
Title: Commensurate mixtures of ultra-cold atoms in one dimension
Authors: L. Mathey
Comments: 4 pages, 2 figures
Subj-class: Other
   We study binary mixtures of ultra-cold atoms, confined to one dimension in an
optical lattice, with commensurate densities. Within a Luttinger liquid
description, which treats various mixtures on equal footing, we derive a system
of renormalization group equations at second order, from which we determine the
rich phase diagrams of these mixtures, which include charge/spin density wave
order, singlet and triplet pairing, polaron pairing, and a supersolid phase.
Various methods to detect our results experimentally are discussed.
\\ ( ,  93kb)
Paper: cond-mat/0602620
Date: Mon, 27 Feb 2006 10:20:34 GMT   (15kb)
Title: Composite-fermion description of rotating Bose gases at low angular
Authors: Nicolay Korslund and Susanne Viefers
Comments: 7 pages (RevTeX), 1 figure. Submitted to Phys Rev A
Report-no: OSLO-TP 1-06
Subj-class: Mesoscopic Systems and Quantum Hall Effect
   We study the composite fermion construction at and below the single vortex
($L=N$) state of weakly interacting rotating Bose gases, presenting a new
method for handling the large number of derivatives typically occurring via the
Slater determinant. Remarkably, the CF wave function at $L=N$ becomes {\em
exact} in the large $N$ limit, even though this construction is not, {\em a
priori}, expected to work in the low angular momentum regime. This implies an
interesting mathematical identity which may be useful in other contexts.
\\ ( ,  15kb)
Paper: cond-mat/0602622
Date: Mon, 27 Feb 2006 11:26:52 GMT   (67kb)
Title: Anderson localization of elementary excitations in a one dimensional
   Bose-Einstein condensate
Authors: Nicolas Bilas and Nicolas Pavloff
Comments: 11 pages, 6 figures
Subj-class: Other
   We study the elementary excitations of a transversely confined Bose-Einstein
condensate in presence of a weak axial random potential. We determine the
localization length (i) at low energy, for a domain of linear densities ranging
from the Tonks-Girardeau to the transverse Thomas-Fermi regime, in the case of
a white noise potential and (ii) for all the range of energies, in the
``one-dimensional mean field regime'', in the case where the randomness is
induced by a series of randomly placed point-like impurities.
\\ ( ,  67kb)
Paper: cond-mat/0602626
Date: Mon, 27 Feb 2006 13:12:53 GMT   (144kb)
Title: Bifurcations in Resonance Widths of an Open Bose-Hubbard Dimer
Authors: M. Hiller, T. Kottos, A. Ossipov
Comments: 4 pages, 3 figures
Subj-class: Other
   We investigate the structure of resonance widths of a Bose-Hubbard Dimer with
intersite hopping amplitude $k$, which is coupled to continuum at one of the
sites with strength $\gamma$. Using an effective non-Hermitian Hamiltonian
formalism, we show that by varying the on-site interaction term $\chi$ the
resonances undergo consequent bifurcations. For $\Lambda=k/\gamma\geq 0.5$, the
bifurcation points follow a scaling law ${\tilde \chi}_n \equiv \chi_n N/k =
f_{\Lambda}(n-0.5/\Lambda)$, where $N$ is the number of bosons. For the
function $f_{\Lambda}$ two different $\Lambda$ dependences are found around the
minimum and the maximum bifurcation point.
\\ ( ,  144kb)
Paper: cond-mat/0602630
Date: Mon, 27 Feb 2006 14:11:14 GMT   (4kb)
Title: Relation between the thermodynamic Casimir effect in Bose-gas slabs and
   critical Casimir forces
Authors: A. Gambassi and S. Dietrich
Comments: Comment on cond-mat/0507263
Subj-class: Statistical Mechanics
   In a recent letter, Martin and Zagrebnov [Europhys. Lett., 73 (2006) 1]
discussed the thermodynamic Casimir effect for the ideal Bose gas confined in a
thin film. We point out that their findings can be expressed in terms of
previous general results for the Casimir effect induced by confined critical
fluctuations. This highlights the links between the Casimir effect in the
contexts of critical phenomena and Bose-Einstein condensation.
\\ ( ,  4kb)
Paper: cond-mat/0510214
replaced with revised version Mon, 27 Feb 2006 17:26:05 GMT   (21kb)
Title: Worm Algorithm for Continuous-space Path Integral Monte Carlo
Authors: M. Boninsegni, N. Prokof'ev and B. Svistunov
Comments: Fig. 2 differs from that of published version (includes data for
   larger system sizes)
Subj-class: Statistical Mechanics
Journal-ref: Phys. Rev. Lett. 96, 070601 (2006)
\\ ( ,  21kb)
Paper: cond-mat/0601432
replaced with revised version Fri, 24 Feb 2006 23:20:59 GMT   (456kb)
Title: Atomic matter of non-zero momentum Bose-Einstein condensation and
   orbital current order
Authors: W. Vincent Liu and Congjun Wu
Comments: 9 pages, 7 figures (with one in Appendix); Revised the experimental
   protocol for preparing the model system
Subj-class: Other; Strongly Correlated Electrons
\\ ( ,  456kb)
Paper: quant-ph/0508172
replaced with revised version Mon, 27 Feb 2006 08:51:20 GMT   (668kb)
Title: Cold atom dynamics in a quantum optical lattice potential
Authors: Christoph Maschler, Helmut Ritsch
Comments: 4 pages, 5 figures, corrected typos
Journal-ref: Phys. Rev. Lett. 95, 260401 (2005)
\\ ( ,  668kb)
Paper: physics/0602181
Date: Mon, 27 Feb 2006 14:33:25 GMT   (41kb)
Title: Control of Ultra-cold Inelastic Collisions by Feshbash Resonances and
   Quasi-One-Dimensional Confinement
Authors: V. A. Yurovsky (1) and Y. B. Band (2) ((1) Tel Aviv University,
   Israel, (2) Ben-Gurion University, Beer-Sheva, Israel)
Comments: 5 pages, 1 figure
Subj-class: Atomic Physics
   Cold inelastic collisions of atoms or molecules are analyzed using very
general arguments. In free space, the deactivation rate can be enhanced or
suppressed together with the scattering length of the corresponding elastic
collision via a Feshbach resonance, and by interference of deactivation of the
closed and open channels. In reduced dimensional geometries, the deactivation
rate decreases with decreasing collision energy and does not increase with
resonant elastic scattering length. This has broad implications; e.g.,
stabilization of molecules in a strongly confining two-dimensional optical
lattice, since collisional decay of the highly vibrationally excited states due
to inelastic collisions is suppressed. The relation of our results with those
based on the Lieb-Liniger model are addressed.
\\ ( ,  41kb)
Paper: cond-mat/0602670
Date: Tue, 28 Feb 2006 15:56:12 GMT   (90kb)
Title: Beyond Mean-Field Theory for Attractive Bosons under Transverse Harmonic
Authors: Luca Salasnich
Comments: To be published in J. Phys. B.: At. Mol. Opt. Phys
Subj-class: Statistical Mechanics; Other
   We study a dilute gas of attractive bosons confined in a harmonic cylinder,
i.e. under cylindric confinement due to a transverse harmonic potential. We
introduce a many-body wave function which extends the Bethe ansatz proposed by
McGuire (J. Math. Phys. {\bf 5}, 622 (1964)) by including a variational
transverse Gaussian shape. We investigate the ground state properties of the
system comparing them with the ones of the one-dimensional (1D) attractive Bose
gas. We find that the gas becomes ultra 1D as a consequence of the attractive
interaction: the transverse width of the Bose gas reduces by increasing the
number of particles up to a critical width below which there is the collapse of
the cloud. In addition, we derive a simple analytical expression for the
simmetry-breaking solitonic density profile of the ground-state, which
generalize the one deduced by Calogero and Degasperis (Phys. Rev. A {\bf 11},
265 (1975)). This bright-soliton analytical solution shows near the collapse
small deviations with respect to the 3D mean-field numerical solution. Finally,
we show that our variational Gauss-McGuire theory is always more accurate than
the McGuire theory. In addition, we prove that for small numbers of particles
the Gauss-McGuire theory is more reliable than the mean-field theory described
by the 3D Gross-Pitaevskii equation.
\\ ( ,  90kb)
Paper: cond-mat/0503523
replaced with revised version Tue, 28 Feb 2006 15:34:42 GMT   (53kb)
Title: Thermally induced rotons in two-dimensional dilute Bose gases
Authors: Flavio S. Nogueira and Hagen Kleinert
Comments: 21 pages; 2 figures; v4: version accepted for publication in PRB; in
   this version Section IV is considerably extended
Subj-class: Other
\\ ( ,  53kb)
Paper: quant-ph/0602230
Date: Tue, 28 Feb 2006 10:35:10 GMT   (22kb)
Title: Ground state approximation for strongly interacting systems in arbitrary
Authors: S. Anders, M. B. Plenio, W. D\"ur, F. Verstraete, and H.-J. Briegel
Comments: 4 pages, 4 figures
   We introduce a variational method for the approximation of ground states of
strongly interacting spin systems in arbitrary geometries and spatial
dimensions. The approach is based on weighted graph states and superpositions
thereof. These states allow for the efficient computation of all local
observables (e.g. energy) and include states with diverging correlation length
and unbounded multi-particle entanglement. As a demonstration we apply our
approach to the Ising model on 1D, 2D and 3D square-lattices. We also present
generalizations to higher spins and continuous-variable systems, which allows
for the investigation of lattice field theories.
\\ ( ,  22kb)
Paper: quant-ph/0602236
Date: Tue, 28 Feb 2006 18:49:49 GMT   (14kb)
Title: Quantum Revivals in Periodically Driven Systems close to nonlinear
Authors: Farhan Saif and Mauro Fortunato
Comments: 14 pages, 1 figure
Journal-ref: Physical Review A 65, 013401 (2002)
   We calculate the quantum revival time for a wave-packet initially well
localized in a one-dimensional potential in the presence of an external
periodic modulating field. The dependence of the revival time on various
parameters of the driven system is shown analytically. As an example of
application of our approach, we compare the analytically obtained values of the
revival time for various modulation strengths with the numerically computed
ones in the case of a driven gravitational cavity. We show that they are in
very good agreement.
\\ ( ,  14kb)
Paper: cond-mat/0603004
Date: Tue, 28 Feb 2006 23:33:52 GMT   (11kb)
Title: Towards measuring Entanglement Entropies in Many Body Systems
Authors: Israel Klich, Gil Refael, Alessandro Silva
Subj-class: Statistical Mechanics
   We explore the relation between entanglement entropy of quantum many body
systems and the distribution of corresponding, properly selected, observables.
Such a relation is necessary to actually measure the entanglement entropy. We
show that in general, the Shannon entropy of the probability distribution of
certain symmetry observables gives a lower bound to the entropy. In some cases
this bound is saturated and directly gives the entropy. We also show other
cases in which the probability distribution contains enough information to
extract the entropy: we show how this is done in several examples including BEC
wave functions, the Dicke model, XY spin chain and chains with strong
\\ ( ,  11kb)
Paper: cond-mat/0603011
Date: Wed, 1 Mar 2006 08:26:39 GMT   (89kb)
Title: BCS-BEC crossover in an asymmetric two-component Fermi gas
Authors: Xia-Ji Liu and Hui Hu
Comments: 5 pages + 3 figures
Subj-class: Statistical Mechanics; Superconductivity
   We discuss the superfluid phase transition of a strongly interacting Fermi
gas with unequal (asymmetric) chemical potentials in two pairing hyperfine
states, and map out its phase diagram near the BCS-BEC crossover. Our approach
includes the fluctuation contributions of {}``preformed Cooper pairs'' to the
thermodynamic potential at finite temperature. We show that, below a critical
difference in chemical potentials between species, a normal gas is unstable
towards the formation of either a finite-momentum paired
Fulde-Ferrell-Larkin-Ovchinnikov superconducting phase or a uniform superfluid,
depending on the asymmetry and interaction strengths. We determine the value of
critical chemical potential mismatch, and find good qualitative agreement with
a recent measurement by Zwierlein \textit{et al.} {[}Science \textbf{311}, 492
\\ ( ,  89kb)
Paper: cond-mat/0603015
Date: Wed, 1 Mar 2006 09:47:39 GMT   (43kb)
Title: Collective modes of a quasi two-dimensional Bose condensate in large gas
   parameter regime
Authors: S.R. Mishra, S. P. Ram, Arup Banerjee
Comments: 10 pages, 2 figures
Subj-class: Other
   We have theoretically studied the collective modes of a quasi two-dimensional
(Q2D) Bose condensate in the large gas parameter regime by using a formalism
which treats the interaction energy beyond the mean-field approximation. In the
calculation we use the perturbative expansion for the interaction energy by
incorporating the Lee, Huang and Yang (LHY) correction term. The results show
that incorporation of this higher order term leads to detectable modifications
in the mode frequencies.
\\ ( ,  43kb)
Paper: cond-mat/0603016
Date: Wed, 1 Mar 2006 10:15:34 GMT   (22kb)
Title: Feynman-Kac path integral approach for the energy spectrum of many boson
Authors: S .Datta
Comments: 24 pages, 12 Figures
Subj-class: Statistical Mechanics
   We study the ground and excited states of weakly interacting Bose gases (with
positive and negative scattering lengths) in connection with Bose Einstein
Condensation.. They behave as new quantum fluids (a gas in the weak limit and a
liquid in the dense limit and we study their many body physics in the dilute
limit within the realistic potential model (Morse type) by Feynman-Kac path
integral technique. Within numerical limitations, this method is exact in
principle and turns out to be a better alternative to GP as all the ground and
excited state properties can be calculated in a much simpler way.
\\ ( ,  22kb)
Paper: cond-mat/0501058
replaced with revised version Wed, 1 Mar 2006 12:31:55 GMT   (182kb)
Title: First-principles quantum dynamics in interacting Bose gases II:
   stochastic gauges
Authors: P. Deuar and P. D. Drummond
Comments: 39 pages, 11 figures, 2 tables. Major revision, especially Section 6
   (convergence issues) which is almost all new, and also introduction. Now in J
   phys A format
Subj-class: Other
Journal-ref: J. Phys. A: Math. Gen. 39 (2006) 2723-2755
\\ ( ,  182kb)
Paper: cond-mat/0603030
Date: Thu, 2 Mar 2006 02:37:11 GMT   (19kb)
Title: The Mott insulator phase of the one dimensional Bose-Hubbard model
Authors: Bogdan Damski and Jakub Zakrzewski
Comments: 4 pages, 4 figures, 1 table
Report-no: LAUR-06-1357
Subj-class: Other
   The one dimensional Bose-Hubbard model at a unit filling factor is
considered. We do a very high order symbolic perturbative expansion in hopping
(tunneling) coupling. Analytical expressions are presented for different ground
state quantities: energy per site, variance of on-site occupation, correlation
functions: <a_j^\dag a_{j+r}> and <n_j n_{j+r}>. Perturbative predictions are
compared to numerical findings and good agreement is found in the Mott
insulator phase. These results are of direct relevance to future experiments in
ultra cold atomic gases placed in homogeneous lattices.
\\ ( ,  19kb)
Paper: quant-ph/0603016
Date: Thu, 2 Mar 2006 12:38:36 GMT   (255kb)
Title: Quantum correlations of two optical fields close to electromagnetically
   induced transparency
Authors: Alice Sinatra (LKB - Lhomond)
Comments: 4 pages, 6 figures
Proxy: ccsd ccsd-00019947
   For two cavity modes exciting a $\Lambda$ transition close to
electromagnetically induced transparency we show the existence of a universal
dispersive bistability curve dividing the parameter space into two regions in
which the system acts either as an ideal "squeezer" or a quantum non demolition
device. We use a fully quantum 3-level model including cavity losses and
spontaneous emission to calculate mean field intensities and quantum
fluctuations as a function of the cavity length that could be directly compared
with experiment. Simple analytical predictions are obtained in the good cavity
limit in which the atomic variables are adiabatically eliminated.
\\ ( ,  255kb)
Received on Mon Mar 06 2006 - 09:30:10 EST

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