# Matt's arXiv selection: week ending 4 January 2008.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Tue, 08 Jan 2008 09:27:27 +1000

The following message was sent to the matts_arxiv list by Matthew Davis <mdavis_at_physics.uq.edu.au>

Hi all,

I'm off to a good start this year... it was a quiet week with only 15 new
preprints and 5 replacements... and even then a couple of them aren't actually
relevant to cold atoms but caught my eye anyway.

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arXiv:0712.4284
Date: Thu, 27 Dec 2007 21:29:46 GMT (493kb)

Title: The $p_{x,y}$-orbital counterpart of graphene: cold atoms in the
honeycomb optical lattice
Authors: Congjun Wu and S. Das Sarma
Categories: cond-mat.str-el cond-mat.mtrl-sci
\\
We study the ground state properties of the interacting spinless fermions in
the $p_{x,y}$-orbital bands in the two dimensional honeycomb optical lattice,
which exhibit different novel features from those in the $p_z$-orbital system
of graphene. In addition to two dispersive bands with Dirac cones, the
tight-binding band structure exhibits another two completely flat bands over
the entire Brillouin zone. With the realistic sinusoidal optical potential, the
flat bands acquire a finite but much smaller band width compared to the
dispersive bands. The band flatness dramatically enhanced interaction effects
giving rise to various charge and bond ordered states at commensurate fillings
of $n=\frac{i}{6} (i=1 \sim 6)$. At $n=1/6$, the many-body ground states can be
exactly solved as the close packed hexagon states which can be stabilized even
in the weak interacting regime. The dimerization of bonding strength occurs at
both $n=1/2$ and 5/6, and the latter case is accompanied with the charge
density wave of holes. The trimerization of bonding strength and charge
inhomogeneity appear at $n={1/3},{2/3}$. These crystalline orders exhibit
themselves in the noise correlations of the time of flight spectra.
\\ ( http://arxiv.org/abs/0712.4284 , 493kb)
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arXiv:0801.0009
Date: Fri, 28 Dec 2007 22:02:12 GMT (317kb,D)

Title: Non Perturbative Renormalization Group and Bose-Einstein Condensation
Authors: Jean-Paul Blaizot
Categories: cond-mat.stat-mech
Comments: Lectures given at the 2006 ECT* School "Renormalization Group and
Effective Field Theory Approaches to Many-Body Systems", Trento, Italy. Late
submission to arXiv
\\
These lectures are centered around a specific problem, the effect of weak
repulsive interactions on the transition temperature $T_c$ of a Bose gas. This
problem provides indeed a beautiful illustration of many of the techniques
which have been discussed at this school on effective theories and
renormalization group. Effective theories are used first in order to obtain a
simple hamiltonian describing the atomic interactions: because the typical
atomic interaction potentials are short range, and the systems that we consider
are dilute, these potentials can be replaced by a contact interaction whose
strength is determined by the s-wave scattering length. Effective theories are
used next in order to obtain a simple formula for the shift in $T_c$: one
exploits there the fact that near $T_c$ the physics is dominated by low
momentum modes whose dynamics is most economically described in terms of
classical fields; the ingredients needed to calculate the shift of $T_c$ can be
obtained from this classical field theory. Finally the renormalization group is
used both to obtain a qualitative understanding, and also as a non perturbative
tool to evaluate quantitatively the shift in $T_c$.
\\ ( http://arxiv.org/abs/0801.0009 , 317kb)
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arXiv:0801.0020
Date: Sat, 29 Dec 2007 01:26:48 GMT (96kb)

Title: Intrinsic relation between ground state fidelity and the
characterization of a quantum phase transition
Authors: Shu Chen, Li Wang, Yajiang Hao, Yupeng Wang
Categories: cond-mat.other cond-mat.stat-mech
Comments: 4 pages, 3 figures
\\
The notion of fidelity in quantum information science has been recently
applied to analyze quantum phase transitions from the viewpoint of the ground
state (GS) overlap for various many-body systems. In this work, we unveil the
intrinsic relation between the GS fidelity and the derivatives of GS energy and
find that they play equivalent role in identifying the quantum phase
transition. The general connection between the two approaches enables us to
understand the different singularity and scaling behaviors of fidelity
exhibited in various systems on general grounds. Our general conclusions are
illustrated via several quantum spin models which exhibit different kinds of
QPTs.
\\ ( http://arxiv.org/abs/0801.0020 , 96kb)
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arXiv:0801.0150
Date: Sun, 30 Dec 2007 18:02:15 GMT (164kb)

Title: Effects of strong correlations for 2D Bose-Einstein condensed dipolar
excitons
Authors: Yu. E. Lozovik, I. L. Kurbakov, G. E. Astrakharchik, J. Boronat, M.
Willander
Categories: cond-mat.str-el
Journal-ref: Sol.St.Comms., 144, 399-404 (2007)
\\
By doing quantum Monte Carlo ab initio simulations we show that dipolar
excitons, which are now under experimental study, actually are strongly
correlated systems. Strong correlations manifest in significant deviations of
excitation spectra from the Bogoliubov one, large Bose condensate depletion,
short-range order in the pair correlation function, and peak(s) in the
structure factor.
\\ ( http://arxiv.org/abs/0801.0150 , 164kb)
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arXiv:0801.0152
Date: Sun, 30 Dec 2007 18:06:09 GMT (75kb)

Title: Superfluidity of two- dimensional excitons in flat and harmonic traps
Authors: Yu. E. Lozovik, I. L. Kurbakov, M. Willander
Categories: cond-mat.str-el
Journal-ref: Phys. Lett. A 366, No. 4-5, 487-492 (2007)
\\
Superfluid exciton density and superfluid transition (crossover) temperature
are calculated for 2D excitons in large-size flat and harmonic traps. A
generalized local density approximation for the Kosterlitz-Thouless theory is
developed.
\\ ( http://arxiv.org/abs/0801.0152 , 75kb)
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arXiv:0801.0383
Date: Wed, 2 Jan 2008 13:44:40 GMT (424kb)

Title: Vortex-lattice formation and melting in a nonrotating Bose-Einstein
Condensate
Authors: Gary Ruben, David M. Paganin, and Michael J. Morgan (School of
Physics, Monash University)
Categories: cond-mat.other
Comments: 9 pages, 7 figures, REVTeX4
\\
Numerical simulations of the interference of a three-way segmented
nonrotating Bose-Einstein Condensate reveal the production of a honeycomb
vortex lattice containing significant numbers of vortices and antivortices
which, if confined within a trap, interact in complex ways over time. In
contrast with nonlinear vortex production mechanisms previously described for
BECs, the process here is primarily one of linear superposition, with initial
vortex locations described by a linear theory of wave packet interference. The
subsequent interaction dynamics, involving a rich vortex-antivortex chemistry,
reveal a phase transition from an ordered to a disordered state.
\\ ( http://arxiv.org/abs/0801.0383 , 424kb)
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arXiv:0801.0119
Date: Sun, 30 Dec 2007 09:59:27 GMT (627kb)

Title: Spectrum of coherently backscattered light from two atoms
Authors: Vyacheslav Shatokhin, Thomas Wellens, Beno\^it Gr\'emaud, Andreas
Buchleitner
Categories: quant-ph
Comments: 14 pages, 9 figures
Journal-ref: Phys. Rev. A 76, 043832 (2007)
\\
We present a detailed analytical and numerical analysis of the inelastic
coherent backscattering spectrum of laser light incident on cold atoms. We
identify frequency domains where the interference contribution can be positive
\emph{as well as} negative -- or exhibits dispersive character. These
distinctive features are explained by reciprocity arguments and dressed state
two-photon scattering amplitudes.
\\ ( http://arxiv.org/abs/0801.0119 , 627kb)
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arXiv:0801.0405
Date: Wed, 2 Jan 2008 15:17:10 GMT (610kb,D)

Title: Atoms in a radiofrequency-dressed optical lattice
Authors: N. Lundblad, P. J. Lee, I. B. Spielman, B. L. Brown, W. D. Phillips,
and J. V. Porto
Categories: quant-ph
Comments: 5 pages, 4 figures
\\
We load cold atoms into an optical lattice dramatically reshaped by
radiofrequency (rf) coupling of state-dependent lattice potentials. This rf
dressing changes the unit cell of the lattice at a subwavelength scale, such
that its curvature and topology departs strongly from that of a simple
sinusoidal lattice potential. Radiofrequency dressing has previously been
performed at length scales from mm to tens of microns, but not at the
single-optical-wavelength scale. At this length scale significant coupling
measure as a function of lattice depth and dressing frequency and amplitude. We
also investigate the dressing by measuring changes in the momentum distribution
of the dressed states.
\\ ( http://arxiv.org/abs/0801.0405 , 610kb)
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arXiv:0801.0028
Date: Sat, 29 Dec 2007 02:39:17 GMT (456kb)

Title: CODATA Recommended Values of the Fundamental Physical Constants: 2006
Authors: Peter J. Mohr, Barry N. Taylor, and David B. Newell
Categories: physics.atom-ph physics.gen-ph
Comments: 105 pages, 7 figures, 46 tables; describes in detail the 2006 CODATA
adjustment of the values of the constants
\\
This paper gives the 2006 self-consistent set of the basic constants and
conversion factors of physics and chemistry recommended by the Committee on
Data for Science and Technology (CODATA) for international use. Further, it
describes in detail the adjustment of the values of the constants, including
the selection of the final set of input data based on the results of
least-squares analyses. The 2006 adjustment takes into account the data
considered in the 2002 adjustment as well as the data that became available
between 31 December 2002, the closing date of that adjustment, and 31 December
2006, the closing date of the new adjustment. The new data have led to a
significant reduction in the uncertainties of many recommended values. The 2006
set replaces the previously recommended 2002 CODATA set and also may be found
on the World Wide Web at physics.nist.gov/constants.
\\ ( http://arxiv.org/abs/0801.0028 , 456kb)
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arXiv:0801.0589
Date: Thu, 3 Jan 2008 20:54:15 GMT (44kb)

Title: Orbital order in Mott insulators of spinless p-band fermions
Authors: Erhai Zhao and W. Vincent Liu
Categories: cond-mat.str-el cond-mat.other
\\
A gas of strongly interacting spinless p-orbital fermionic atoms in 2D
optical lattices is proposed and studied. Several interesting new features are
found. In the Mott limit on a square lattice, the gas is found to be described
effectively by an orbital exchange Hamiltonian equivalent to a pseudospin-1/2
XXZ model. For a triangular, honeycomb, or Kagome lattice, the orbital exchange
is geometrically frustrated and described by a new quantum 120 degree model. We
determine the orbital orderings on each lattice, and show how orbital wave
fluctuations select ground states via the order by disorder mechanism for the
honeycomb and triangular lattice. We discuss experimental signatures of various
orbital ordering.
\\ ( http://arxiv.org/abs/0801.0589 , 44kb)
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arXiv:0801.0132 (*cross-listing*)
Date: Sun, 30 Dec 2007 15:47:47 GMT (25kb)

Title: Exact diagonalisation of 1-d interacting spinless Fermions
Authors: Heiner Kohler
Categories: math-ph cond-mat.str-el math.MP
MSC-class: 37K10; 37K15
\\
A new method of constructing an infinite set of exact eigenfunctions of 1-d
interacting spinless Fermionic systems is derived. Creation and annihilation
operators for the interacting system are found and thereby the many-body
Hamiltonian is diagonalised. The formalism is applied to several examples. One
instance is the theory of Jack polynomials. For the Calogero-Moser-Sutherland
Hamiltonian a direct proof of the correctness of the asymptotic Bethe Ansatz is
given.
\\ ( http://arxiv.org/abs/0801.0132 , 25kb)
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arXiv:0801.0577
Date: Thu, 3 Jan 2008 19:16:20 GMT (999kb,D)

Title: Magnetically-controlled velocity selection in a cold atom sample using
stimulated Raman transitions
Authors: Matthew L. Terraciano, Spencer E. Olson, Mark Bashkansky, Zachary
Dutton, Fredrik K. Fatemi
Categories: quant-ph
Comments: 5 pages, 6 figures
Journal-ref: Physical Review A 76, 053421 (2007)
DOI: 10.1103/PhysRevA.76.053421
\\
We observe velocity-selective two-photon resonances in a cold atom cloud in
the presence of a magnetic field. We use these resonances to demonstrate a
simple magnetometer with sub-mG resolution. The technique is particularly
useful for zeroing the magnetic field and does not require any additional laser
frequencies than are already used for standard magneto-optical traps. We verify
the effects using Faraday rotation spectroscopy.
\\ ( http://arxiv.org/abs/0801.0577 , 999kb)
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arXiv:0801.0475
Date: Thu, 3 Jan 2008 04:37:32 GMT (290kb)

Title: Observation of coherence revival and fidelity saturation in a
delta-kicked rotor potential
Authors: Saijun Wu, Alexey Tonyushkin, Mara G. Prentiss
Categories: physics.atom-ph physics.gen-ph
Comments: 10 pages, 3 figures
\\
We experimentally investigate the effect of atomic delta-kicked rotor
potentials on the mutual coherence between wavepackets in an atom
interferometer. The differential action of the kicked rotor degrades the mutual
coherence, leading to a reduction of the interferometry fringe visibility;
however, when the repetition rate of the kicked rotor is at or near the quantum
resonance, we observe revival of matter-wave coherence as the number of kicks
increases, resulting in non-vanishing coherence in the large kick number limit.
This coherence saturation effect reflects a fidelity saturation in phase-space
displacement echoes in deep quantum regime. The saturation effect is
accompanied with an invariant distribution of matter-wave coherence under the
kicked rotor perturbations.
\\ ( http://arxiv.org/abs/0801.0475 , 290kb)
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arXiv:0801.0524
Date: Thu, 3 Jan 2008 13:41:05 GMT (263kb)

Title: Self-citation as an impact-reinforcing mechanism in the science system
Authors: Anthony F.J. van Raan
Categories: physics.soc-ph physics.data-an
Comments: 22 pages, 18 figures, 4 tables
\\
In previous papers it was demonstrated that lower performance groups have a
larger size-dependent cumulative advantage for receiving citations than
top-performance groups. Furthermore, regardless of performance, larger groups
have less not-cited publications. Particularly for the lower performance groups
the fraction of not-cited publications decreases considerably with size. These
phenomena can be explained with a model in which self-citation acts as a
promotion mechanism for external citations. In this article we show that for
self-citations similar size-dependent scaling rules apply as for citations but
generally the power law exponents are higher for self-citations as compared to
citations. We also find that the fraction of self-citations is smaller for the
higher performance groups and this fraction decreases more rapidly with
increasing journal impact than for lower performance groups. An interesting
novel finding is that the variance in the correlation of the number of
self-citations with size is considerably less than the variance for external
citations. This is a clear indication that size is a stronger determinant for
self-citations than for external citations. Both higher and particularly lower
performance groups have a size-dependent cumulative advantage for
self-citations, but for the higher performance groups only in the lower impact
journals and in fields with low citation density.
\\ ( http://arxiv.org/abs/0801.0524 , 263kb)
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arXiv:0801.0253 (*cross-listing*)
Date: Mon, 31 Dec 2007 23:51:51 GMT (230kb,D)

Title: Toward a statistical mechanics of four letter words
Authors: Greg J. Stephens and William Bialek
Categories: q-bio.NC cs.CL physics.data-an physics.soc-ph
\\
We consider words as a network of interacting letters, and approximate the
probability distribution of states taken on by this network. Despite the
intuition that the rules of English spelling are highly combinatorial (and
arbitrary), we find that maximum entropy models consistent with pairwise
correlations among letters provide a surprisingly good approximation to the
full statistics of four letter words, capturing ~92% of the multi-information
among letters and even "discovering" real words that were not represented in
the data from which the pairwise correlations were estimated. The maximum
entropy model defines an energy landscape on the space of possible words, and
local minima in this landscape account for nearly two-thirds of words used in
written English.
\\ ( http://arxiv.org/abs/0801.0253 , 230kb)
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The replacements:

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arXiv:cond-mat/0702183
replaced with revised version Fri, 28 Dec 2007 14:18:46 GMT (516kb)

Title: Coherent Matter Wave Transport in Speckle Potentials
Authors: R.C. Kuhn, O. Sigwarth, C. Miniatura, D. Delande, C.A. Mueller
Categories: cond-mat.other
Comments: 33 pages, minor corrections, published version
Journal-ref: New J. Phys. 9 (2007) 161
DOI: 10.1088/1367-2630/9/6/161
\\ ( http://arxiv.org/abs/cond-mat/0702183 , 516kb)
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arXiv:0708.3039
replaced with revised version Fri, 28 Dec 2007 18:36:17 GMT (279kb)

Title: Exact Solution of Strongly Interacting Quasi One-Dimensional Spinor Bose
Gases
Authors: Frank Deuretzbacher, Klaus Fredenhagen, Daniel Becker, Kai Bongs,
Klaus Sengstock, Daniela Pfannkuche
Categories: cond-mat.other
Comments: Revised to discuss large but finite interactions
\\ ( http://arxiv.org/abs/0708.3039 , 279kb)
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arXiv:0707.4172
replaced with revised version Wed, 2 Jan 2008 17:48:26 GMT (102kb)

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
Journal-ref: Phys. Rev. B 76, 220508(R) (2007)
DOI: 10.1103/PhysRevB.76.220508
\\ ( http://arxiv.org/abs/0707.4172 , 102kb)
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arXiv:0712.0205 (*cross-listing*)
replaced with revised version Sun, 30 Dec 2007 13:12:46 GMT (12kb)

Title: Self-consistent equations of unitary fermion thermodynamics with elusive
non-Gaussian correlations
Authors: Ji-sheng Chen, Jia-rong Li, Yan-ping Wang, Xiang-jun Xia
Categories: cond-mat.stat-mech hep-ph nucl-th quant-ph
Comments: Improved version with typos corrected
\\ ( http://arxiv.org/abs/0712.0205 , 12kb)
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arXiv:0707.0379
replaced with revised version Sun, 30 Dec 2007 21:49:38 GMT (228kb)

Title: Dependence of Resonant Absorption Linewidth on Atomic Vapour Column
Thickness for D1 Line of Cs Atoms Confined in Nano-Cell
Authors: A. Sargsyan, D. Sarkisyan, Y. Pashayan-Leroy, C. Leroy, P. Moroshkin,
A. Weis
Categories: physics.atom-ph
\\ ( http://arxiv.org/abs/0707.0379 , 228kb)
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Till next time,
Matt.

--
=========================================================================
Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email: mdavis_at_physics.uq.edu.au
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Australia.                    http://www.physics.uq.edu.au/people/mdavis/
=========================================================================
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
http://www.physics.uq.edu.au/people/mdavis/matts_arXiv/
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Received on Tue Jan 08 2008 - 10:01:09 EST

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