Matt's arXiv selection: week ending 28 March 2008.

From: Matthew Davis <>
Date: Fri, 04 Apr 2008 08:57:32 +1000

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

Hi all,

A slightly calmer week with 18 new preprints and 8 replacements. Our mail
server decided to delete all our incoming mail last Friday afternoon rather than
pass it on to the recipients, and so my incoming arXiv emails for that day were
lost. Hence I can to scour that days on the web, hence the different format for
the last four.

It's much more inconvenient that way!

Date: Fri, 21 Mar 2008 09:08:00 GMT (166kb)

Title: Phase diagram and momentum distribution of an interacting Bose gas in a
   bichromatic lattice
Authors: Xiaolong Deng (LP2MC, UJF, Grenoble) R. Citro (University of Salerno
   and LP2MC) A. Minguzzi (LP2MC) E. Orignac (ENS-Lyon)
Categories: cond-mat.other cond-mat.stat-mech
Comments: 10 pages, RevTeX 4, 9 Encapsulated Postscript figure files
   We determine the phase diagram and the momentum distribution for a
one-dimensional Bose gas with repulsive short range interactions in the
presence of a two-color lattice potential, with incommensurate ratio among the
respective wave lengths, by using a combined numerical (DMRG) and analytical
(bosonization) analysis. The system displays a delocalized (superfluid) phase
at small values of the intensity of the secondary lattice V2 and a localized
(Bose glass-like) phase at larger intensity V2. We analyze the localization
transition as a function of the height V2 beyond the known limits of free and
hard-core bosons. We find that weak repulsive interactions unfavor the
localized phase i. e. they increase the critical value of V2 at which
localization occurs. In the case of integer filling of the primary lattice, the
phase diagram at fixed density displays, in addition to a transition from a
superfluid to a Bose glass phase, a transition to a Mott-insulating state for
not too large V2 and large repulsion. We also analyze the emergence of a
Bose-glass phase by looking at the evolution of the Mott-insulator lobes when
increasing V2. The Mott lobes shrink and disappear above a critical value of
V2. Finally, we characterize the superfluid phase by the momentum distribution,
and show that it displays a power-law decay at small momenta typical of
Luttinger liquids, with an exponent depending on the combined effect of the
interactions and of the secondary lattice. In addition, we observe two side
peaks which are due to the diffraction of the Bose gas by the second lattice.
This latter feature could be observed in current experiments as characteristics
of pseudo-random Bose systems.
\\ ( , 166kb)
Date: Fri, 21 Mar 2008 15:05:17 GMT (269kb)

Title: Bose Fluids Above Tc
Authors: Philip W Anderson
Categories: cond-mat.stat-mech cond-mat.str-el
   This paper emphasizes that non-linear rotational or diamagnetic
susceptibility is characteristic of Bose fluids above their superfluid Tcs. For
sufficiently slow rotation or, for superconductors, weak B-fields this amounts
to an incompressible response to vorticity. The cause is that there are terms
missing in the conventionally accepted model Hamiltonian for quantized vortices
in the Bose fluid. The resulting susceptibility can account for recent
observations of Chan et al on solid He, and Ong et al on cuprate
\\ ( , 269kb)
Date: Fri, 21 Mar 2008 05:54:40 GMT (80kb)

Title: Tunneling and energy splitting in an asymmetric double-well potential
Authors: Dae-Yup Song
Categories: quant-ph
   An asymmetric double-well potential is considered, assuming that the minima
of the wells are quadratic with a frequency $\omega$ and the difference of the
minima is close to a multiple of $\hbar \omega$. A WKB wave function is
constructed on both sides of the local maximum between the wells, by matching
the WKB function to the exact wave functions near the classical turning points.
The continuities of the wave function and its first derivative at the local
maximum then give the energy-level splitting formula, which not only reproduces
the instanton result for a symmetric potential, but also elucidates the
appearance of resonances of tunneling in the asymmetric potential.
\\ ( , 80kb)
Date: Fri, 21 Mar 2008 17:13:23 GMT (50kb)
Date (revised v2): Fri, 21 Mar 2008 21:14:43 GMT (51kb)

Title: A statistical mechanics model for free-for-all airplane passenger
Authors: Jason H. Steffen (Fermilab Center for Particle Astrophysics)
Categories: physics.soc-ph physics.pop-ph
Comments: 4 pages 2 figures, submitted to AJP
Report-no: FERMILAB-PUB-08-068-A
   I present and discuss a model for the free-for-all passenger boarding which
is employed by some discount air carriers. The model is based on the principles
of statistical mechanics where each seat in the aircraft has an associated
binding energy which reflects the preferences of the population of air
travelers. As each passenger enters the airplane they select their seats using
Boltzmann statistics, proceed to that location, load their luggage, sit down,
and the partition function seen by remaining passengers is modified to reflect
this fact. I discuss the various model parameters and make qualtitative
comparisons of this passenger boarding model with models which involve assigned
seats. This model may be of value to industry professional as a useful
description of this boarding method. However, it also has significant value as
a pedagogical tool since it is a relatively unusual application of
undergraduate level physics and it describes a situation with which many
students and faculty may be familiar.
\\ ( , 51kb)
Date: Sun, 23 Mar 2008 18:36:56 GMT (2430kb,D)

Title: Turbulent dynamics in rotating helium superfluids
Authors: V.B. Eltsov, R. de Graaf, R. Hanninen, M. Krusius, R.E. Solntsev, V.S.
   L'vov, A.I. Golov, and P.M. Walmsley
Categories: cond-mat.other cond-mat.supr-con
Comments: 100 pages 47 figures. Submitted for publication in Progress in Low
   Temperature Physics, Vol. XVI
   New techniques, both for generating and detecting turbulence in the helium
superfluids 3He-B and 4He, have recently given insight in how turbulence is
started, what the dissipation mechanisms are, and how turbulence decays when it
appears as a transient state or when externally applied turbulent pumping is
switched off. Important simplifications are obtained by using 3He-B as working
fluid, where the highly viscous normal component is practically always in a
state of laminar flow, or by cooling 4He to low temperatures where the normal
fraction becomes vanishingly small. We describe recent studies from the low
temperature regime, where mutual friction becomes small or practically
vanishes. This allows us to elucidate the mechanisms at work in quantum
turbulence on approaching the zero temperature limit.
\\ ( , 2430kb)
Date: Fri, 21 Mar 2008 22:08:33 GMT (404kb)

Title: Quantum Monte Carlo Simulations of the BCS-BEC Crossover at Finite
Authors: Aurel Bulgac, Joaquin E. Drut, Piotr Magierski
Categories: cond-mat.stat-mech
Comments: 20 pages, 17 figures
   The Quantum Monte Carlo method for spin 1/2 fermions at finite temperature is
formulated for dilute systems with an s-wave interaction. The motivation and
the formalism are discussed along with descriptions of the algorithm and
various numerical issues. We report on results for the energy, entropy and
chemical potential as a function of temperature. We give upper bounds on the
critical temperature T_c for the onset of superfluidity, obtained by studying
the finite size scaling of the condensate fraction. All of these quantities
were computed for couplings around the unitary regime in the range -0.5 \le
(k_F a)^{-1} \le 0.2, where a is the s-wave scattering length and k_F is the
Fermi momentum of a non-interacting gas at the same density. In all cases our
data is consistent with normal Fermi gas behavior above a characteristic
temperature T_0 > T_c, which depends on the coupling and is obtained by
studying the deviation of the caloric curve from that of a free Fermi gas. For
T_c < T < T_0 we find deviations from normal Fermi gas behavior that can be
attributed to pairing effects. Low temperature results for the energy and the
pairing gap are shown and compared with Green Function Monte Carlo results by
other groups.
\\ ( , 404kb)
Date: Fri, 21 Mar 2008 22:12:53 GMT (742kb)

Title: Theory of Bose-Einstein condensation and superfluidity of
   two-dimensional polaritons in an in-plane harmonic potential
Authors: Oleg L. Berman, Yurii E. Lozovik and David W. Snoke
Categories: cond-mat.mes-hall cond-mat.str-el
Comments: 14 pages, 5 figures. Accepted for publication by Physical review B
   Recent experiments have shown that it is possible to create an in-plane
harmonic potential trap for a two-dimensional (2D) gas of exciton-polaritons in
a microcavity structure, and evidence has been reported of Bose-Einstein
condensation of polaritons accumulated in this type of trap. We present here
the theory of Bose-Einstein condensation (BEC) and superfluidity of the exciton
polaritons in a harmonic potential trap. Along the way, we determine a general
method for defining the superfluid fraction in a 2D trap, in terms of angular
momentum representation. We show that in the continuum limit, as the trap
becomes shallower the superfluid fraction approaches the 2D Kosterlitz-Thouless
limit, while the condensate fraction approaches zero, as expected.
\\ ( , 742kb)
Date: Sat, 22 Mar 2008 14:44:28 GMT (13kb)

Title: Virial theorems for trapped quantum gases
Authors: F\'elix Werner (LKB - Lhomond)
Categories: cond-mat.other
Proxy: ccsd hal-00266437
   We present a general virial theorem for quantum particles with arbitrary
zero-range or finite-range interactions in an arbitrary external potential. We
deduce virial theorems for several situations relevant to trapped gases:
zero-range interactions with and without Efimov effect, narrow resonances, and
finite-range interactions of infinite scattering length.
\\ ( , 13kb)
Date: Mon, 24 Mar 2008 20:01:41 GMT (22kb)

Title: Bose-Einstein condensation of indirect excitons in graphene bilayers
Authors: C.-H. Zhang, Yogesh N. Joglekar
Categories: cond-mat.mes-hall cond-mat.str-el
Comments: 4 pages, 3 figures
   Graphene, a single sheet of graphite with honeycomb lattice structure, has
massless carriers whose density and polarity can be tuned by external gate
voltage. We investigate the ground state phase diagram of graphene bilayers
separated by distance $d$ where the top layer has electrons and the bottom
layer has holes, using mean-field theory. We find that a uniform excitonic
condensate ground state occurs over a large range of carrier densities and is
(relatively) insensitive to the stacking. We obtain the quasiparticle spectrum,
renormalized quasiparticle speed, and calculate the quasiparticle density of
states. We discuss the implications of our results and present arguments which
suggest that the mass of these excitons, with massless particles as
constituents, is proportional to the square-root of the carrier density.
\\ ( , 22kb)
Date: Tue, 25 Mar 2008 19:55:22 GMT (7kb)

Title: Skepsis on the scenario of Biological Evolution provided by stochastic
Authors: Thomas Oikonomou
Categories: cond-mat.stat-mech
Comments: 8 pages
   Stochastic models, based on random processes, may lead to power law
distributions, which provide long range correlations. The observation of power
law behavior and the presence of long range correlations in biological systems
has been demonstrated in various studies. The combination of the two just
mentioned results, theoretical and experimental, supports strongly the scenario
of biological evolution across different organisms. In the current Letter we
explore in a general way, using the algebra of Nonextensive Statistics
introduced by Tsallis and coworkers, if the processes which are described by a
class of stochastic models are really random and discuss the results with
regard to a possible biological evolution.
\\ ( , 7kb)
Date: Tue, 25 Mar 2008 16:16:33 GMT (304kb)

Title: Enhanced phase sensitivity and soliton formation in an integrated BEC
Authors: Antonio Negretti and Carsten Henkel
Categories: quant-ph
Comments: 6 pages, 3 figures, Iop LaTex2e
Journal-ref: J. Phys. B: At. Mol. Opt. Phys. 37 No 23 (14 December 2004)
   We study the dynamics of Bose-Einstein condensates in time-dependent
microtraps for the purpose of understanding the influence of the mean field
interaction on the performance of interferometers. We identify conditions where
the non-linearity due to atom interactions increases the sensitivity of
interferometers to a phase shift. This feature is connected with the adiabatic
generation of a dark soliton. We analyze the robustness of this phenomenon with
respect to thermal fluctuations, due to excited near fields in an
electromagnetic surface trap.
\\ ( , 304kb)
Date: Wed, 26 Mar 2008 17:09:37 GMT (287kb)

Title: Optical lattice quantum Hall effect
Authors: Rebecca N. Palmer, Alexander Klein, Dieter Jaksch
Categories: cond-mat.mes-hall
Comments: 14 pages, 5 figures
   We explore the behavior of interacting bosonic atoms in an optical lattice
subject to a large artificial magnetic field. We extend earlier investigations
of this system where the number of magnetic flux quanta per unit cell alpha is
close to a simple rational number [Phys. Rev. Lett. 96, 180407 (2006)].
Interesting topological states such as the Laughlin and Read-Rezayi states can
occur even if the atoms experience a weak trapping potential in one direction.
An explicit numerical calculation near alpha = 1/2 shows that the system
exhibits a striped vortex lattice phase of one species, which is analogous to
the behavior of a two-species system for small alpha. We also investigate
methods to probe the encountered states. These include spatial correlation
functions and the measurement of noise correlations in time of flight expanded
atomic clouds. Characteristic differences arise which allow for an
identification of the respective quantum Hall states. We furthermore discuss
that a counterintuitive flow of the Hall current occurs for certain values of
\\ ( , 287kb)
Date: Wed, 26 Mar 2008 19:14:58 GMT (221kb)

Title: Condensate fraction in a 2D Bose gas measured across the Mott-insulator
Authors: I. B. Spielman, W. D. Phillips, and J. V. Porto
Categories: cond-mat.other
Comments: 4 pages, 3 figures
Journal-ref: Phys. Rev. Lett., 100, 120402 (2008)
   We realize a single-band 2D Bose-Hubbard system with Rb atoms in an optical
lattice and measure the condensate fraction as a function of lattice depth,
crossing from the superfluid to the Mott-insulating phase. We quantitatively
identify the location of the superfluid to normal transition by observing when
the condensed fraction vanishes. Our measurement agrees with recent quantum
Monte Carlo calculations for a finite-sized 2D system to within experimental
\\ ( , 221kb)
Date: Tue, 25 Mar 2008 18:30:23 GMT (325kb)

Title: Was There A Big Bang?
Authors: Robert K. Soberman, Maurice Dubin
Categories: physics.gen-ph
Comments: 9 pages, 4 figures
   The big bang hypothesis is widely accepted despite numerous physics
conflicts. It rests upon two experimental supports, galactic red shift and the
cosmic microwave background. Both are produced by dark matter, shown here to be
hydrogen dominated aggregates with a few percent of helium nodules. Scattering
from these non-radiating intergalactic masses produce a red shift that normally
correlates with distance. Warmed by our galaxy to an Eigenvalue of 2.735 K,
drawn near the Earth, these bodies, kept cold by ablation, resonance radiate
the Planckian microwave signal. Several tests are proposed that will
distinguish between this model and the big bang.
\\ ( , 325kb)
Supplementary Information to the paper ``Breakdown of the adiabatic limit in low
dimensional gapless systems''
Authors: A. Polkovnikov, V. Gritsev
(Submitted on 27 Mar 2008)

     Abstract: Here we give detailed derivations and provide additional examples
to the main paper: arXiv:0706.0212. In particular, we discuss the scaling
behavior of observables like correlation functions and density of excitations.
We also analyze effects of nonintegrability of the Bose-Hubbard model on the
long-time dynamics of the correlation functions. In addition we explicitly
consider several interacting models, where we are able to analyze slow dynamics
and classify it according to the regimes suggested in the main paper.

Comments: 11 pages, 6 figures. The current version of the main paper
arXiv:0706.0212 is not up to date according to the Nature Physics editorial policy
Subjects: Statistical Mechanics (cond-mat.stat-mech); Mesoscopic Systems and
Quantum Hall Effect (cond-mat.mes-hall); Strongly Correlated Electrons
Cite as: arXiv:0803.3967v1 [cond-mat.stat-mech]

Quantum fluctuations, temperature and detuning effects in solid-light systems
Authors: Markus Aichhorn, Martin Hohenadler, Charles Tahan, Peter B. Littlewood
(Submitted on 27 Mar 2008)

     Abstract: The superfluid to Mott insulator transition in cavity polariton
arrays is analyzed using the variational cluster approach, taking into account
quantum fluctuations exactly on finite length scales. Phase diagrams in one and
two dimensions exhibit important non-mean-field features. Single-particle
excitation spectra in the Mott phase are dominated by particle and hole bands
separated by a Mott gap. In contrast to Bose-Hubbard models, detuning allows for
changing the nature of the bosonic particles from quasi-localized excitons to
polaritons to weakly interacting photons. The Mott state with density one exists
up to temperatures $T/g\gtrsim0.03$, implying experimentally accessible
temperatures for realistic cavity couplings $g$.

Comments: 5 pages, 4 figures
Subjects: Other (cond-mat.other)
Cite as: arXiv:0803.3963v1 [cond-mat.other]

The effects of next to nearest neighbor hopping on Bose-Einstein condensation in
cubic lattices
Authors: G. K. Chaudhary, R. Ramakumar
(Submitted on 27 Mar 2008 (v1), last revised 1 Apr 2008 (this version, v2))

     Abstract: In this brief report, we present results of our calculations on
the effects of next to nearest neighbor boson hopping ($t^{\prime}$) energy on
Bose-Einstein condensation in cubic lattices. We consider both non-interacting
and repulsively interacting bosons moving in the lowest Bloch band. The
interacting bosons are studied making use of the Bogoliubov method. We find that
the bose condensation temperature is enhanced with increasing $t^{\prime}$ for
bosons in a simple cubic (sc) lattice and decreases for bosons in body-centered
cubic (bcc) and face-centered cubic (fcc) lattices. We also find that
interaction induced depletion of the condensate is reduced for bosons in a sc
lattice while is enhanced for bosons in bcc and fcc lattices.

Comments: 4 pages including 6 figures, typos corrected
Subjects: Statistical Mechanics (cond-mat.stat-mech); Other (cond-mat.other)
Cite as: arXiv:0803.3888v2 [cond-mat.stat-mech]

Quantum Control of Ultra-cold Atoms: Uncovering a Novel Connection between Two
Paradigms of Quantum Nonlinear Dynamics
Authors: Jiao Wang, Anders S. Mouritzen, Jiangbin Gong (National. Univ. of
(Submitted on 27 Mar 2008)

     Abstract: Controlling the translational motion of cold atoms using optical
lattice potentials is of both theoretical and experimental interest. By
designing two on-resonance time sequences of kicking optical lattice potentials,
a novel connection between two paradigms of nonlinear mapping systems, i.e., the
kicked rotor model and the kicked Harper model, is established. In particular,
it is shown that Hofstadter's butterfly quasi-energy spectrum in periodically
driven quantum systems may soon be realized experimentally, with the effective
Planck constant tunable by varying the time delay between two sequences of
control fields. Extensions of this study are also discussed. The results are
intended to open up a new generation of cold-atom experiments of quantum
nonlinear dynamics

Comments: submitted to the special issue of "Quantum Control of Matter and
Light", Journal of Modern Optics
Subjects: Quantum Physics (quant-ph); Chaotic Dynamics (nlin.CD)
Cite as: arXiv:0803.3859v1 [quant-ph]

The replacments:

replaced with revised version Mon, 24 Mar 2008 16:22:52 GMT (919kb)

Title: Fully permanent magnet atom chip for Bose-Einstein condensation
Authors: T. Fernholz, R. Gerritsma, S. Whitlock, I. Barb, R. J. C. Spreeuw
Categories: cond-mat.other
Comments: changed title, substantial text modifications, journal reference
Journal-ref: Phys. Rev. A 77, 033409 (2008)
DOI: 10.1103/PhysRevA.77.033409
\\ ( , 919kb)
replaced with revised version Mon, 24 Mar 2008 16:52:50 GMT (236kb)

Title: Optimized Double-well quantum interferometry with Gaussian
Authors: Y. P. Huang and M. G. Moore
Categories: quant-ph
Comments: updated version
\\ ( , 236kb)
replaced with revised version Mon, 24 Mar 2008 16:49:41 GMT (105kb)

Title: On-demand generation of entanglement of atomic qubits via optical
Authors: Y. P. Huang and M. G. Moore
Categories: quant-ph
Comments: To be published in PRA
\\ ( , 105kb)
replaced with revised version Tue, 25 Mar 2008 01:19:05 GMT (169kb)

Title: Quantum dynamics of repulsively bound atom pairs in the Bose-Hubbard
Authors: Li Wang, Yajiang Hao, Shu Chen
Categories: cond-mat.other
Comments: 7 pages, 6 figures, significant changes made
\\ ( , 169kb)
replaced with revised version Tue, 25 Mar 2008 09:51:38 GMT (313kb)

Title: Density Correlations in Cold Atomic Gases: Atomic Speckles in the
   Presence of Disorder
Authors: P. Henseler and B. Shapiro
Categories: cond-mat.dis-nn cond-mat.mes-hall
Comments: 8 pages, 2 figures
Journal-ref: Phys. Rev. A 77, 033624 (2008)
\\ ( , 313kb)
replaced with revised version Wed, 26 Mar 2008 12:46:35 GMT (592kb)

Title: Solitons in coupled atomic-molecular Bose-Einstein condensates in a trap
Authors: B. Oles and K. Sacha
Categories: cond-mat.other cond-mat.stat-mech
Comments: 7 pages, 7 figures, published version
Journal-ref: J. Phys. B: At. Mol. Opt. Phys. 40 (2007) 1103-1116
\\ ( , 592kb)
replaced with revised version Wed, 26 Mar 2008 13:01:35 GMT (214kb)

Title: N-conserving Bogoliubov vacuum of a two component Bose-Einstein
   condensate: Density fluctuations close to a phase separation condition
Authors: Bartlomiej Oles, Krzysztof Sacha
Categories: cond-mat.other
Comments: 12 pages, 5 figures, published version
Journal-ref: J. Phys. A: Math. Theor. 41 (2008) 145005
\\ ( , 214kb)
arXiv:0711.3939 (*cross-listing*)
replaced with revised version Wed, 26 Mar 2008 02:40:32 GMT (539kb)

Title: Proposal of a Cold-atom Realization of Quantum Maps with Hofstadter's
   Butterfly Spectrum
Authors: Jiao Wang and Jiangbin Gong (National Univ. of Singapore)
Categories: quant-ph cond-mat.other nlin.CD
Comments: 5 pages, 4 figures, minor changes, to appear in Phys. Rev. A (Rapid
\\ ( , 539kb)

Till next time,

Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Matt's arXiv selection: weekly summary of cold-atom papers from
Legal stuff: Unless stated otherwise, this e-mail represents only the
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Received on Thu Apr 10 2008 - 09:27:39 EST

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