Matt's arXiv selection: week ending 12 January 2007.

From: Matthew Davis <>
Date: Tue, 16 Jan 2007 09:25:04 +1000 (EST)

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

Things are still a bit slow, only 15 new papers last week.

The new abstracts:

Paper: cond-mat/0701098
Date: Fri, 5 Jan 2007 11:21:45 GMT (198kb)

Title: Fermi-Bose mixture across a Feshbach resonance
Authors: Luca Salasnich and Flavio Toigo
Categories: cond-mat.other cond-mat.stat-mech
Comments: 9 pages, 5 figures, to be published in Phys. Rev. A
Subj-class: Other; Statistical Mechanics
   We study a dilute mixture of degenerate bosons and fermions across a Feshbach
resonance of the Fermi-Fermi scattering length $a_F$. This scattering length is
renormalized by the boson-induced interaction between fermions and its value is
crucial to determine the phase diagram of the system. For the mixture in a box
and a positive Bose-Fermi scattering length, we show that there are three
possibilities: a single uniform mixed phase, a purely fermionic phase
coexisting with a mixed phase, and a purely fermionic phase coexisting with a
purely bosonic one. As $1/a_F$ is increased from a negative value to the
Feshbach resonance ($1/a_F=0$) the region of pure separation increases and the
other two regions are strongly reduced. Above the Feshbach resonance
($1/a_F>0$), pairs of Fermi atoms become Bose-condensed molecules. We find that
these molecules are fully spatially separated from the bosonic atoms when
$1/a_F$ exceedes a critical value. For a negative Bose-Fermi scattering length
we deduce the condition for collapse, which coincides with the onset of
dynamical instability of the fully mixed phase. We consider also the mixture in
a harmonic trap and determine the conditions for partial demixing, full
demixing and collapse. The experimental implications of our results are
investigated by analyzing mixtures of $^6$Li--$^{23}$Na and $^{40}$K--$^{87}$Rb
\\ ( , 198kb)
Paper (*cross-listing*): nlin.PS/0701011
Date: Thu, 4 Jan 2007 15:55:28 GMT (306kb)

Title: Nonstationary excitations in Bose-Einstein condensates under the action
   of periodically varying scattering length with time dependent frequencies
Authors: S. Rajendran, P. Muruganandam, and M. Lakshmanan
Categories: nlin.PS cond-mat.soft
Comments: 17 pages, 6 figures (to be published in Physica D)
Subj-class: Pattern Formation and Solitons; Soft Condensed Matter
   We investigate nonstationary excitations in 3D-Bose-Einstein condensates in a
spherically symmetric trap potential under the modulation of scattering length
with slowly varying frequencies (adiabatic modulation). By numerically solving
the Gross-Pitaevskii equation we observe a step-wise increase in the amplitude
of oscillation due to successive phase locking between driving frequency and
nonlinear frequency. Such a nonstationary excitation has been shown to exist by
an analytic approach using variational procedure and perturbation theory in the
action-angle variables. By using a canonical perturbation theory, we have
identified the successive resonance excitations whenever the driven frequency
matches the nonlinear frequency or its subharmonics.
\\ ( , 306kb)
Paper (*cross-listing*): nucl-th/0701006
Date: Tue, 2 Jan 2007 23:42:26 GMT (23kb)

Title: Spin 1/2 Fermions in the Unitary Limit
Authors: H.S. Kohler
Categories: nucl-th astro-ph cond-mat.other
Comments: 11 pages and 4 figures
Subj-class: Nuclear Theory; Other
   The energy shift due to the interaction of two particles in a large box is
proportional to the free particle scattering phase-shift. This provides an
approximation to the effective interaction referred to as the phase-shift
approximation. For a many-body fermion system this effective interaction has to
be corrected for the Pauli-blocking. It is used to calculate the energy of a
spin 1/2 fermion system as a function of the two-body scattering length and
effective range. In the unitary limit with scattering length going to infinity
and effective range going to zero the energy is 0.540 (in the units of the
non-interactiong fermi gas energy) with a pp-ladder summation. Including
hh-ladders the energy is 0.570. A smooth crossover from the BCS to the BEC
region is observed. Pairing is not included.
\\ ( , 23kb)
Paper: cond-mat/0701120
Date: Sat, 6 Jan 2007 03:12:14 GMT (115kb)

Title: The Extended Bose Hubbard Model on the Two Dimensional Honeycomb Lattice
Authors: Jing Yu Gan, Wen Yu Chuan, Jin Wu Ye, Tao Li, Shi Jie Yang, and Yu Yue
Categories: cond-mat.other
Comments: 4pages, 5figures
Subj-class: Other
   We study the extended Bose Hubbard model on the two-dimensional honeycomb
lattice by using the quantum Monte Carlo simulations. We present the ground
state phase diagram for both of the hardcore and softcore case. We find that
the results of the honeycomb lattice are just similar to the square lattice.
For the hardcore case, the supersolid state is unstable towards the phase
separation. The transition between $\rho=1/2$ solid and the superfluid is of
first order. For the softcore case, due to the presence of the multiple
occupation, a stable supersolid phase emerges when $\rho>1/2$. We also study
the critical exponents of the transition between $\rho=1/2$ solid and
superfluid at the Heisenberg point. We find the dynamical critical exponent $z$
and the correlation length exponent $\nu$ are $z=0.15$ and $\nu=0.38$.
\\ ( , 115kb)
Paper: cond-mat/0701136
Date: Mon, 8 Jan 2007 07:43:42 GMT (820kb)

Title: Vortex density spectrum of quantum turbulence
Authors: Philippe-Emmanuel P.-E. Roche (NEEL), Pantxo Diribarne (NEEL,
   Phys-ENS), Thomas Didelot (NEEL), Olivier Fran\c{c}ais (GROUPE ESIEE, CNAM),
   Lionel Rousseau (GROUPE ESIEE), Herv\'{e} Willaime (ESPCI)
Categories: cond-mat.other
Comments: Submitted to Europhys. Lett
Proxy: ccsd hal-00122996
Subj-class: Other
   The fluctuations of the vortex density in a turbulent quantum fluid are
deduced from local second-sound attenuation measurements. These measurements
are performed with a micromachined open-cavity resonator inserted across a flow
of turbulent He-II near 1.6 K. The power spectrum of the measured vortex line
density is compatible with a (-5/3) power law. The physical interpretation,
still open, is discussed.
\\ ( , 820kb)
Paper: cond-mat/0701157
Date: Mon, 8 Jan 2007 23:02:24 GMT (59kb)

Title: Universality in the BCS - BEC Crossover in Cold Fermion Gases
Authors: S. Diehl
Categories: cond-mat.supr-con
Comments: 14 pages, 6 figures. Talk given at the 2006 ECT* School
   ``Renormalization Group and Effective Field Theory Approaches to Many-Body
   Systems'', Trento, Italy
Subj-class: Superconductivity
   We address the finite temperature phase diagram of ultracold fermionic atoms
across a Feshbach resonance based on a functional integral for an atom-molecule
model. This allows to fully exploit the presence of the global symmetry of
phase rotations, U(1). Both the equation of state and the classification of the
thermodynamic phases are obtained from a symmetry consideration. We focus on
the universal aspects associated to narrow and broad resonances, in turn
connected by an additional form of crossover. The narrow resonance limit can be
solved exactly above the critical temperature. We also assess deviations from
the broad resonance universality which have recently been probed
\\ ( , 59kb)
Paper: cond-mat/0701178
Date: Tue, 9 Jan 2007 16:38:22 GMT (101kb)

Title: Phase diagram and thermodynamics of the three-dimensional Bose-Hubbard
Authors: B. Capogrosso-Sansone, N. V. Prokof'ev, B. V. Svistunov
Categories: cond-mat.other cond-mat.stat-mech
Comments: 11 pages, 13 figures
Subj-class: Other; Statistical Mechanics
   We report results of quantum Monte Carlo simulations of the Bose-Hubbard
model in three dimensions. Critical parameters for the
superfluid-to-Mott-insulator transition are determined with significantly
higher accuracy than it has been done in the past. In particular, the position
of the critical point at filling factor n=1 is found to be at (U/t)_c =
29.34(2), and the insulating gap Delta is measured with accuracy of a few
percent of the hopping amplitude t. We obtain the effective mass of particle
and hole excitations in the insulating state--with explicit demonstration of
the emerging particle-hole symmetry and relativistic dispersion law at the
transition tip--along with the sound velocity in the strongly correlated
superfluid phase. These parameters are the necessary ingredients to perform
analytic estimates of the low temperature (T << Delta) thermodynamics in
macroscopic samples. We present accurate thermodynamic curves, including these
for specific heat and entropy, for typical insulating (U/t=40) and superfluid
(t/U=0.0385) phases. Our data can serve as a basis for accurate experimental
thermometry, and a guide for appropriate initial conditions if one attempts to
use interacting bosons in quantum information processing.
\\ ( , 101kb)
Paper: cond-mat/0701180
Date: Tue, 9 Jan 2007 19:21:56 GMT (38kb)

Title: Twenty years of magnon Bose condensation and spin current superfluidity
   in 3He-B
Authors: G.E. Volovik
Categories: cond-mat.other
Comments: 12 pages, 1 figure
Subj-class: Other
   20 years ago a new quantum state of matter was discovered and identified. The
observed dynamic quantum state of spin precession in superfluid $^3$He-B bears
the properties of spin current superfluidity, Bose condensation of spin waves
-- magnons, off-diagonal long-range order and related phenomena of quantum
\\ ( , 38kb)
Paper: cond-mat/0701181
Date: Tue, 9 Jan 2007 17:25:21 GMT (301kb)

Title: Expansion of an ultra-cold lithium gas in the BEC-BCS crossover
Authors: Leticia Tarruell (LKB - Lhomond), Martin Teichmann (LKB - Lhomond),
   Jason Mckeever (LKB - Lhomond), Thomas Bourdel (LKB - Lhomond), Julien
   Cubizolles (LKB - Lhomond), Lev Khaykovich, Jing Zhang (SKLQOQOD), Nir Navon
   (LKB - Lhomond), Fr\'{e}d\'{e}ric Chevy (LKB - Lhomond), Christophe Salomon
   (LKB - Lhomond)
Categories: cond-mat.stat-mech cond-mat.mes-hall
Comments: 10 pages, to be published in the Proceddings of the 2006 Enrico Fermi
   summer school on Fermi gases
Proxy: ccsd hal-00123470
Subj-class: Statistical Mechanics; Mesoscopic Systems and Quantum Hall Effect
   We present an experimental study of the time of flight properties of a gas of
ultra-cold fermions in the BEC-BCS crossover. Since interactions can be tuned
by changing the value of the magnetic field, we are able to probe both non
interacting and strongly interacting behaviors. These measurements allow us to
characterize the momentum distribution of the system as well as its equation of
state. We also demonstrate the breakdown of superfluid hydrodynamics in the
weakly attractive region of the phase diagram, probably caused by pair breaking
taking place during the expansion.
\\ ( , 301kb)
Paper (*cross-listing*): nlin.CD/0612052
Date: Fri, 22 Dec 2006 18:50:39 GMT (365kb)

Title: Growing condensate in two-dimensional turbulence
Authors: M. Chertkov, C. Connaughton, I. Kolokolov, V. Lebedev
Categories: nlin.CD cond-mat.stat-mech physics.flu-dyn
Comments: 4 pages, 4 figures
Subj-class: Chaotic Dynamics; Statistical Mechanics; Fluid Dynamics
   We report a detailed numerical study of the phenomenon of ``energy
condensation'' in the inverse energy cascade of 2D turbulence in a biperiodic
box. Condensation is a finite size effect which occurs if the large scale
damping is weak enough to allow the inverse cascade to reach the size of the
system. It leads to the emergence of a coherent vortex dipole of a size
comparable to the box. We characterise the strongly inhomogeneous spatial
structure of the condensate and show that its time growth is self-similar. We
decompose the flow into a coherent and fluctuating component. The coherent
component, containing most of the energy, replaces the usual $k^{-5/3}$ inverse
cascade energy spectrum with a markedly steeper spectrum at large scales. Once
the coherent component is subtracted, however, we find that the fluctuations
have a spectrum close to $k^{-1}$. The fluctuations decay slowly as the
coherent part grows.
\\ ( , 365kb)
Paper: quant-ph/0701038
Date: Tue, 9 Jan 2007 06:06:23 GMT (172kb)

Title: Theory of chaotic atomic transport in an optical lattice
Authors: V.Yu. Argonov and S.V. Prants
Categories: quant-ph
Comments: 14 pages, 8 figures
   A semiclassical theory of chaotic atomic transport in a one-dimensional
nondissipative optical lattice is developed. Using the basic equations of
motion for the Bloch and translational atomic variables, we derive a stochastic
map for the synchronized component of the atomic dipole moment that determines
the center-of-mass motion. We find the analytical relations between the atomic
and lattice parameters under which atoms typically alternate between flying
through the lattice and being trapped in the wells of the optical potential. We
use the stochastic map to derive formulas for the probability density functions
(PDFs) for the flight and trapping events. Statistical properties of chaotic
atomic transport strongly depend on the relations between the atomic and
lattice parameters. We show that there is a good quantitative agreement between
the analytical PDFs and those computed with the stochastic map and the basic
equations of motion for different ranges of the parameters. Typical flight and
trapping PDFs are shown to be broad distributions with power law ``heads'' with
the slope -1.5 and exponential ``tails''. The lengths of the power law and
exponential parts of the PDFs depend on the values of the parameters and can be
varied continuously. We find analytical conditions, under which deterministic
atomic transport has fractal properties, and explain a hierarchical structure
of the dynamical fractals.
\\ ( , 172kb)
Paper: quant-ph/0701049
Date: Tue, 9 Jan 2007 18:39:31 GMT (267kb)

Title: Electromagnetically Induced Transparency in optically trapped rubidium
Authors: Bernd Kaltenh\"{a}user, Harald K\"{u}bler, Andreas Chromik, J\"{u}rgen
   Stuhler, Tilman Pfau, Atac Imamoglu
Comments: 5 pages, 8 figures
   We demonstrate electromagnetically induced transparency (EIT) in a sample of
rubidium atoms, trapped in an optical dipole trap. Mixing a small amount of
$\sigma^-$-polarized light to the weak $\sigma^+$-polarized probe pulses, we
are able to measure the absorptive and dispersive properties of the atomic
medium at the same time. Features as small as 4 kHz have been detected on an
absorption line with 20 MHz line width.
\\ ( , 267kb)
Paper: cond-mat/0701198
Date: Wed, 10 Jan 2007 11:56:00 GMT (74kb)

Title: Flow Equations for the BCS-BEC Crossover
Authors: S. Diehl, H. Gies, J. M. Pawlowski, C. Wetterich
Categories: cond-mat.supr-con cond-mat.stat-mech
Comments: 4 pages, 4 figures
Report-no: HD-THEP-07-02
Subj-class: Superconductivity; Statistical Mechanics
   The functional renormalisation group is used for the BCS-BEC crossover in
gases of ultracold fermionic atoms. In a simple truncation, we see how
universality and an effective theory with composite bosonic di-atom states
emerge. We obtain a unified picture of the whole phase diagram. The flow
reflects different effective physics at different scales. In the BEC limit as
well as near the critical temperature, it describes an interacting bosonic
\\ ( , 74kb)
Paper: cond-mat/0701212
Date: Wed, 10 Jan 2007 16:52:13 GMT (268kb)

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: 11 pages, 5 figures
Subj-class: Other
   Two component Bose-Einstein condensates are considered within a number
conserving version of the Bogoliubov theory. We show that the Bogoliubov vacuum
state can be obtained in the particle representation in a simple form. The
formalism is used to analyze homogeneous condensates and condensates in a
double well potential. We show that for values of system parameters close to a
phase separation condition considerable density fluctuations appear. The
predicted fluctuations can be measured experimentally.
\\ ( , 268kb)
Paper: physics/0701123
Date: Wed, 10 Jan 2007 14:39:51 GMT (98kb)

Title: Grid methods for cold molecules : determination of photoassociation
   lineshapes and rate constants
Authors: S. Kallush, R. Kosloff and F. Masnou-Seeuws
Categories: physics.chem-ph physics.atom-ph
Comments: Submitted to PRA
Subj-class: Chemical Physics; Atomic Physics
   A description of photoassociation by CW laser is formulated in the framework
of grid methods. The Hamiltonian describing one or several bound states coupled
to a multiple of continuum manifolds via a radiative field is written in the
energy representation and diagonalized. The generality of the treatment allows
to compute accurately and efficiently physical properties such as non-linear
high-intensity energy shifts, line shapes, and photoassociation rates both for
isolated and non-isolated resonances. Application is given to sodium
photoassociation in the experimental conditions of Mc Kenzie {\it et al} [Phys.
Rev. Lett. {\bf 88}, 090403 (2002)]. Inverted region for the dependency of the
rate vs. the intensity and non-symmetric lineshapes were predicted to occur
above the saturation limit. Comparison with the model of Bohn and Julienne
[Phys. Rev. A {\bf 60}, 414 (1999)] is discussed.
\\ ( , 98kb)
Paper: cond-mat/0701236
Date: Thu, 11 Jan 2007 09:01:49 GMT (7kb)

Title: Bogolyubov approximation for diagonal model of an interacting Bose gas
Authors: M.Corgini, D.P.Sankovich
Categories: cond-mat.stat-mech
Subj-class: Statistical Mechanics
   We study, using the Bogolyubov approximation, the thermodynamic behaviour of
a superstable Bose system whose energy operator in the second-quantized form
contains a nonlinear expression in the occupation numbers operators. We prove
that for all values of the chemical potential satisfying $\mu > \lambda(0)$,
where $\lambda (0)\leq 0$ is the lowest energy value, the system undergoes
Bose--Einstein condensation.
\\ ( , 7kb)
Paper: cond-mat/0701251
Date: Thu, 11 Jan 2007 18:37:48 GMT (44kb)

Title: The Shear Viscosity to Entropy Density Ratio of Trapped Fermions in the
   Unitarity Limit
Authors: Thomas Schaefer (North Carolina State University)
Categories: cond-mat.other
Comments: 4 pages, two figures
Subj-class: Other
   We extract the shear viscosity to entropy density ratio \eta/s of cold
fermionic atoms in the unitarity limit from experimental data on the damping of
collective excitations. We find that above the critical temperature \eta/s is
only weakly dependent on temperature and roughly equal to 1/3 in units of
\hbar/k_B. With the possible exception of the quark gluon plasma, this value is
closer to the conjectured lower bound 1/(4\pi) than any other known liquid.
\\ ( , 44kb)
Paper: quant-ph/0701060
Date: Thu, 11 Jan 2007 13:11:44 GMT (569kb)

Title: Quantum time of flight distribution for cold trapped atoms
Authors: Md. Manirul Ali, Dipankar Home, A. S. Majumdar, Alok K. Pan
Categories: quant-ph
Comments: 6 pages, RevTex, 4 eps figures
   The time of flight distribution for a cloud of cold atoms falling freely
under gravity is considered. We generalise the probability current density
approach to calculate the quantum arrival time distribution for the mixed state
describing the Maxwell-Boltzmann distribution of velocities for the falling
atoms. We find an empirically testable difference between the time of flight
distribution calculated using the quantum probability current and that obtained
from a purely classical treatment which is usually employed in analysing time
of flight measurements. The classical time of flight distribution matches with
the quantum distribution in the large mass and high temperature limits.
\\ ( , 569kb)

The replacements:

Paper (*cross-listing*): math-ph/0611043
replaced with revised version Mon, 8 Jan 2007 18:40:13 GMT (18kb)

Title: Interacting Bose and Fermi gases in low dimensions and the Riemann
Authors: Andr\'e LeClair
Categories: math-ph cond-mat.stat-mech math.MP math.NT
Comments: version 2: typos corrected
Subj-class: Mathematical Physics; Statistical Mechanics; Number Theory
\\ ( , 18kb)
Paper: cond-mat/0511721
replaced with revised version Tue, 9 Jan 2007 17:30:33 GMT (10kb)

Title: Vanishing bulk viscosities and conformal invariance of unitary Fermi gas
Authors: D.T. Son
Categories: cond-mat.other cond-mat.supr-con
Comments: 4 pages
Report-no: INT-PUB 05-29
Subj-class: Other; Superconductivity
\\ ( , 10kb)
Paper: cond-mat/0610575
replaced with revised version Tue, 9 Jan 2007 14:50:24 GMT (16kb)

Title: Probing Anomalous Longitudinal Fluctuations of the Interacting Bose Gas
   via Bose-Einstein Condensation of Magnons
Authors: Andreas Kreisel, Nils Hasselmann, and Peter Kopietz
Categories: cond-mat.stat-mech cond-mat.str-el
Comments: 4 pages, 1 figure, revised version. To appear in Physical Review
Subj-class: Statistical Mechanics; Strongly Correlated Electrons
\\ ( , 16kb)
Paper: cond-mat/0612268
replaced with revised version Tue, 9 Jan 2007 08:01:20 GMT (164kb)

Title: Fermionic superfluidity: From high Tc superconductors to ultracold Fermi
Authors: Qijin Chen, Chih-Chun Chien, Yan He, and K. Levin
Categories: cond-mat.str-el cond-mat.supr-con
Comments: Expanded version, invited talk at the 5th International Conference on
   Complex Matter -- Stripes 2006, 6 pages, 6 figures
Subj-class: Strongly Correlated Electrons; Superconductivity
\\ ( , 164kb)
Paper: cond-mat/0612522
replaced with revised version Tue, 9 Jan 2007 13:43:27 GMT (24kb)

Title: Mott-insulator phases of non-locally coupled 1D dipolar Bose gases
Authors: A. Arguelles and L. Santos
Categories: cond-mat.other
Comments: 4 pages, 4 eps figures; minor changes, reference added
Subj-class: Other
\\ ( , 24kb)
Paper: quant-ph/0612200
replaced with revised version Wed, 10 Jan 2007 11:05:46 GMT (254kb)

Title: Coherent optical detection of highly excited Rydberg states using
   electromagnetically induced transparency
Authors: A. K. Mohapatra, T. R. Jackson, C. S. Adams
Categories: quant-ph
Comments: Comments removed
\\ ( , 254kb)
Paper: cond-mat/0611487
replaced with revised version Thu, 11 Jan 2007 08:16:01 GMT (471kb)

Title: Time modulation of atom sources
Authors: A. del Campo, J. G. Muga, M. Moshinsky
Categories: cond-mat.other
Comments: 13 pages, 8+1 figures, references added, minor corrections
Subj-class: Other
\\ ( , 471kb)

And if you're still reading at this stage, here's one just for fun:

Paper: physics/0701130
Date: Thu, 11 Jan 2007 03:27:13 GMT (145kb)

Title: NASA's astonishing evidence that c is not constant: The pioneer anomaly
Authors: E. D. Greaves
Categories: physics.gen-ph
Comments: 5 pages, 2 figures, 1 table; Submitted to Astrophysical Journal
Subj-class: General Physics; Space Physics
   For over 20 years NASA has struggled to find an explanation to the Pioneer
anomaly. Now it becomes clear the solution to the riddle is that they have
uncovered evidence that c, the speed of light, is not quite a universal
constant. Using J. C. Cure s hypothesis that the index of refraction is a
function of the gravitational energy density of space and straightforward
Newtonian mechanics, NASA s measurements provide compelling evidence that the
speed of light depends on the inverse of the square root of the gravitational
energy density of space. The magnitude of the Pioneer anomalous acceleration
leads to the value of the primordial energy density of space due to faraway
stars and galaxies: 1.0838. x 10^15 Joule/m3. A value which almost miraculously
coincides with the same quantity: 1.09429 x 10^15 Joule/m3 derived by J. C.
Cure from a completely different phenomenon: the bending of starlight during
solar eclipses.
\\ ( , 145kb)

Till next 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
Matt's arXiv selection: weekly summary of cold-atom papers from
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Received on Tue Jan 16 2007 - 09:25:04 EST

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