# Matt's arXiv selection: week ending 13th April 2007.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Mon, 16 Apr 2007 10:08:44 +1000 (EST)

Hi everyone,

This week is relatively quiet with 16 new abstracts and 9 replacements. The one
to catch my eye was on the critical behaviour of the Bose gas from the ETH
Zurich group - published a couple of weeks ago but only just on the arXiv.

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arXiv:0704.0842
Date: Fri, 6 Apr 2007 05:08:44 GMT (103kb)

Title: Oscillation bands of condensates on a ring: Beyond the mean field theory
Authors: Chengguang Bao
Categories: cond-mat.other
Comments: 7 pages, 8 figures
\\
The Hamiltonian of a N-boson system confined on a ring with zero spin and
repulsive interaction is diagonalized. The excitation of a pair of
p-wave-particles rotating reversely appears to be a basic mode. The fluctuation
of many of these excited pairs provides a mechanism of oscillation, the states
can be thereby classified into oscillation bands. The particle correlation is
studied intuitively via the two-body densities. Bose-clustering originating
from the symmetrization of wave functions is found, which leads to the
appearance of 1-, 2-, and 3-cluster structures. The motion is divided into
being collective and relative, this leads to the establishment of a relation
between the very high vortex states and the low-lying states.
\\ ( http://arxiv.org/abs/0704.0842 , 103kb)
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arXiv:0704.0925
Date: Fri, 6 Apr 2007 19:48:17 GMT (576kb)

Title: Spinor Dynamics in an Antiferromagnetic Spin-1 Condensate
Authors: A.T. Black, E. Gomez, L.D. Turner, S. Jung, P.D. Lett
Categories: cond-mat.other cond-mat.soft cond-mat.stat-mech
Comments: 5 pages, 2 figures
\\
We observe coherent spin oscillations in an antiferromagnetic spin-1
Bose-Einstein condensate of sodium. The variation of the spin oscillations with
magnetic field shows a clear signature of nonlinearity, in agreement with
theory, which also predicts anharmonic oscillations near a critical magnetic
field. Measurements of the magnetic phase diagram agree with predictions made
in the approximation of a single spatial mode. The oscillation period yields
the best measurement to date of the sodium spin-dependent interaction
coefficient, determining that the difference between the sodium spin-dependent
s-wave scattering lengths $a_{f=2}-a_{f=0}$ is $2.47\pm0.27$ Bohr radii.
\\ ( http://arxiv.org/abs/0704.0925 , 576kb)
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arXiv:0704.0855
Date: Fri, 6 Apr 2007 08:06:59 GMT (314kb)

Title: Loading, cooling and trapping of Strontium using intercombinaison line
Authors: Thierry Chaneliere (LAC), Ling Xiang He, Robin Kaiser (INLN), David
Wilkowski (INLN)
Categories: physics.atom-ph
Comments: Submited to PRA (06/04/2007)
Proxy: ccsd hal-00140366
\\
The intercombinaison line of strontium at 689nm is successfully used in laser
cooling to reach the photon recoil limit with Doppler cooling in a
magneto-optical traps (MOT). In this paper we present a systematic study of the
loading efficiency of such a MOT. Comparing the experimental results to a
simple model allow us to discuss the actual limitation of our apparatus. We
also study in detail the final MOT regime emphasizing the role of the gravity
on the position, size and temperature along the vertical and horizontal
directions. At large laser detuning, one finds an unusual situation where
cooling and trapping occur in the presence of a high bias magnetic field.
\\ ( http://arxiv.org/abs/0704.0855 , 314kb)
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arXiv:0704.0912
Date: Fri, 6 Apr 2007 18:23:55 GMT (510kb)

Title: Nuclear Spin Effects in Optical Lattice Clocks
Authors: Martin M. Boyd, Tanya Zelevinsky, Andrew D. Ludlow, Sebastian Blatt,
Thomas Zanon-Willette, Seth M. Foreman, and Jun Ye
Categories: physics.atom-ph
Comments: 13 pages, 12 figures, submitted to PRA
\\
We present a detailed experimental and theoretical study of the effect of
nuclear spin on the performance of optical lattice clocks. With a state-mixing
theory including spin-orbit and hyperfine interactions, we describe the origin
of the $^1S_0$-$^3P_0$ clock transition and the differential $g$-factor between
the two clock states for alkaline-earth(-like) atoms, using $^{87}$Sr as an
example. Clock frequency shifts due to magnetic and optical fields are
discussed with an emphasis on those relating to nuclear structure. An
experimental determination of the differential $g$-factor in $^{87}$Sr is
performed and is in good agreement with theory. The magnitude of the tensor
light shift on the clock states is also explored experimentally. State specific
measurements with controlled nuclear spin polarization are discussed as a
method to reduce the nuclear spin-related systematic effects to below
10$^{-17}$ in lattice clocks.
\\ ( http://arxiv.org/abs/0704.0912 , 510kb)
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arXiv:0704.1089
Date: Mon, 9 Apr 2007 10:07:44 GMT (12kb)

Title: Representative Ensembles in Statistical Mechanics
Authors: V.I. Yukalov
Categories: cond-mat.stat-mech
Comments: Latex file, 18 pages
Journal-ref: Int. J. Mod. Phys. B 21 (2007) 69-86
\\
The notion of representative statistical ensembles, correctly representing
statistical systems, is strictly formulated. This notion allows for a proper
description of statistical systems, avoiding inconsistencies in theory. As an
illustration, a Bose-condensed system is considered. It is shown that a
self-consistent treatment of the latter, using a representative ensemble,
always yields a conserving and gapless theory.
\\ ( http://arxiv.org/abs/0704.1089 , 12kb)
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arXiv:0704.1096
Date: Mon, 9 Apr 2007 11:29:32 GMT (14kb)

Title: Horizon formation in isotropically expanding Bose-Einstein condensates
Authors: Yasunari Kurita, Takao Morinari
Categories: cond-mat.other
Comments: 4 pages, 2 figures
Report-no: YITP-07-16, OCU-PHYS-264, AP-GR-40
\\
We propose a simple experiment to create a sonic horizon in isotropically
trapped cold atoms within currently available experimental techniques.
Numerical simulation of the Gross-Pitaevskii equation shows that the sonic
horizon should appear by making the condensate expand. The expansion is
triggered by changing the interaction which can be controlled by the Feshbach
resonance in real experiments. The sonic horizon is shown to be quasi-static
for sufficiently strong interaction. The characteristic temperature that is
associated with particle emission from the horizon, which corresponds to the
Hawking temperature in an ideal situation, is estimated to be 2nK.
\\ ( http://arxiv.org/abs/0704.1096 , 14kb)
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arXiv:0704.1037
Date: Sun, 8 Apr 2007 17:37:34 GMT (591kb)

Title: Controlled collisions of a single atom and ion guided by movable
trapping potentials
Authors: Z. Idziaszek, T. Calarco, P. Zoller
Categories: quant-ph
Comments: 16 pages, 16 figures
\\
We consider a system composed of a trapped atom and a trapped ion. The ion
charge induces in the atom an electric dipole moment, which attracts it with an
r^{-4} dependence at large distances. In the regime considered here, the
characteristic range of the atom-ion interaction is comparable or larger than
the characteristic size of the trapping potential, which excludes the
application of the contact pseudopotential. The short-range part of the
interaction is described in the framework of quantum-defect theory, by
introducing some short-range parameters, which can be related to the s-wave
scattering length. When the separation between traps is changed we observe
trap-induced shape resonances between molecular bound states and vibrational
states of the external trapping potential. Our analysis is extended to
quasi-one-dimensional geometries, when the scattering exhibit
confinement-induced resonances, similar to the ones studied before for
short-range interactions. For quasi-one-dimensional systems we investigate the
effects of coupling between the center of mass and relative motion, which
occurs for different trapping frequencies of atom and ion traps. Finally, we
show how the two types of resonances can be employed for quantum state control
and spectroscopy of atom-ion molecules.
\\ ( http://arxiv.org/abs/0704.1037 , 591kb)
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arXiv:0704.1283
Date: Tue, 10 Apr 2007 18:07:48 GMT (693kb)

Title: Scanning tunnelling microscopy for ultracold atoms
Authors: Corinna Kollath, Michael K\"ohl, Thierry Giamarchi
Categories: cond-mat.str-el
\\
We propose a novel experimental probe for cold atomic gases analogous to the
scanning tunnelling microscope (STM) in condensed matter. This probe uses the
coherent coupling of a single particle to the system. Depending on the
measurement sequence, our probe allows to either obtain the \emph{local}
density, with a resolution on the nanometer scale, or the single particle
correlation function in real time. We discuss applications of this scheme to
the various possible phases for a two dimensional Hubbard system of fermions in
an optical lattice.
\\ ( http://arxiv.org/abs/0704.1283 , 693kb)
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arXiv:0704.1292
Date: Tue, 10 Apr 2007 19:06:32 GMT (444kb)

Title: Excitation of the dissipationless Higgs mode in a fermionic condensate
Authors: R. A. Barankov, L. S. Levitov
Categories: cond-mat.supr-con cond-mat.mes-hall
Comments: 4 pages, 4 figures
\\
The amplitude mode of a fermionic superfluid, analogous to the Higgs Boson,
becomes undamped in the strong coupling regime when its frequency is pushed
inside the BCS energy gap. We argue that this is the case in cold gases due to
the energy dispersion and nonlocality of the pairing interaction, and propose
to use the Feshbach resonance regime for parametric excitation of this mode.
The results presented for the BCS pairing dynamics indicate that even weak
dispersion suppresses dephasing and gives rise to persistent oscillations. The
frequency of oscillations extracted from our simulation of the BCS dynamics
agrees with the prediction of the many-body theory.
\\ ( http://arxiv.org/abs/0704.1292 , 444kb)
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arXiv:0704.1377
Date: Wed, 11 Apr 2007 09:05:29 GMT (723kb)

Title: Kibble-Zurek mechanism in a quenched ferromagnetic Bose-Einstein
condensate
Authors: Hiroki Saito, Yuki Kawaguchi, and Masahito Ueda
Categories: cond-mat.other
Comments: 11 pages, 7 figures
\\
The spin vortices are shown to be created through the Kibble-Zurek (KZ)
mechanism in a quantum phase transition of a spin-1 ferromagnetic Bose-Einstein
condensate, when the applied magnetic field is quenched below a critical value.
It is shown that the magnetic correlation functions have finite correlation
lengths, and magnetizations at widely separated positions grow in random
directions, resulting in spin vortices. We numerically confirm the scaling law
that the winding number of spin vortices is proportional to the square root of
the length of the closed path, and for slow quench, proportional to $\tau_{\rm Q}^{-1/6}$ with $\tau_{\rm Q}$ being the quench time. The relation between the
spin conservation and the KZ mechanism is discussed.
\\ ( http://arxiv.org/abs/0704.1377 , 723kb)
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arXiv:0704.1389
Date: Wed, 11 Apr 2007 10:18:22 GMT (125kb)

Title: Gutzwiller description of non-magnetic Mott insulators: a dimer lattice
model
Authors: Michele Fabrizio (SISSA and ICTP, Trieste, Italy)
Categories: cond-mat.str-el
Comments: 15 pages, 9 figures
\\
We introduce a novel extension of the Gutzwiller variational wavefunction
able to deal with insulators that escape any mean-field like description, as
for instance non-magnetic insulators. As an application, we study the Mott
transition from a paramagnetic metal into a non-magnetic Peierls, or
valence-bond, Mott insulator. We analyze this model by means of our Gutzwiller
wavefunction analytically in the limit of large coordination lattices, where we
find that: (1) the Mott transition is first order; (2) the Peierls gap is large
in the Mott insulator, although it is mainly contributed by the electron
repulsion; (3) singlet-superconductivity arises around the transition.
\\ ( http://arxiv.org/abs/0704.1389 , 125kb)
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arXiv:0704.1413
Date: Wed, 11 Apr 2007 14:14:28 GMT (351kb)

Title: Preparation and detection of magnetic quantum phases in optical
superlattices
Authors: A. M. Rey, V. Gritsev, I. Bloch, E. Demler and M.D. Lukin
Categories: cond-mat.other
Comments: 10 pages, 2 Figures
\\
We describe a novel approach to prepare, detect and characterize magnetic
quantum phases in ultra-cold spinor atoms loaded in optical superlattices. Our
technique makes use of singlet-triplet spin manipulations in an array of
isolated double well potentials in analogy to recently demonstrated quantum
control in semiconductor quantum dots. We also discuss the many-body
singlet-triplet spin dynamics arising from coherent coupling between nearest
neighbor double wells and derive an effective description for such system. We
use it to study the generation of complex magnetic states by adiabatic and
non-equilibrium dynamics.
\\ ( http://arxiv.org/abs/0704.1413 , 351kb)
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arXiv:0704.1439
Date: Wed, 11 Apr 2007 15:45:24 GMT

Title: Critical Behavior of a Trapped Interacting Bose Gas
Authors: Tobias Donner, Stephan Ritter, Thomas Bourdel, Anton \"Ottl, Michael
K\"ohl, Tilman Esslinger
Categories: cond-mat.stat-mech
Comments: 4 pages, 3 figures, accepted version; published document available at
http://www.quantumoptics.ethz.ch/publications.html
Journal-ref: Science 315, 1556 (2007)
DOI: 10.1126/science.1138807
\\
The phase transition of Bose-Einstein condensation is studied in the critical
regime, when fluctuations extend far beyond the length scale of thermal de
Broglie waves. Using matter-wave interference we measure the correlation length
of these critical fluctuations as a function of temperature. The diverging
behavior of the correlation length above the critical temperature is observed,
from which we determine the critical exponent of the correlation length for a
trapped, weakly interacting Bose gas to be $\nu=0.67\pm 0.13$. This measurement
has direct implications for the understanding of second order phase
transitions.
\\ ( http://arxiv.org/abs/0704.1439 , )
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arXiv:0704.1539
Date: Thu, 12 Apr 2007 07:57:21 GMT (15kb)

Title: A New Monte Carlo Method and Its Implications for Generalized Cluster
Algorithms
Authors: C. H. Mak and Arun K. Sharma
Categories: cond-mat.soft cond-mat.stat-mech
Comments: 4 pages, 2 figures. Phys. Rev. Lett. (in press)
\\
We describe a novel switching algorithm based on a reverse'' Monte Carlo
method, in which the potential is stochastically modified before the system
configuration is moved. This new algorithm facilitates a generalized
formulation of cluster-type Monte Carlo methods, and the generalization makes
it possible to derive cluster algorithms for systems with both discrete and
continuous degrees of freedom. The roughening transition in the sine-Gordon
model has been studied with this method, and high-accuracy simulations for
system sizes up to $1024^2$ were carried out to examine the logarithmic
divergence of the surface roughness above the transition temperature, revealing
clear evidence for universal scaling of the Kosterlitz-Thouless type.
\\ ( http://arxiv.org/abs/0704.1539 , 15kb)
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arXiv:0704.1642
Date: Thu, 12 Apr 2007 18:49:58 GMT (51kb)

Title: Collective excitations of hard-core Bosons at half filling on square and
triangular lattices: Development of roton minima and collapse of roton gap
Authors: Tyler Bryant and Rajiv R. P. Singh
Categories: cond-mat.str-el
Comments: 10 pages, 7 figures
\\
We study ground state properties and excitation spectra for hard-core Bosons
on square and triangular lattices, at half filling, using series expansion
methods. Nearest-neighbor repulsion between the Bosons leads to the development
of short-range density order at the antiferromagnetic wavevector, and
simultaneously a roton minima in the density excitation spectra. On the
square-lattice, the model maps on to the well studied XXZ model, and the roton
gap collapses to zero precisely at the Heisenberg symmetry point, leading to
the well known spectra for the Heisenberg antiferromagnet. On the
triangular-lattice, the collapse of the roton gap signals the onset of the
supersolid phase. Our results suggest that the transition from the superfluid
to the supersolid phase maybe weakly first order. We also find several features
in the density of states, including two-peaks and a sharp discontinuity, which
maybe observable in experimental realization of such systems.
\\ ( http://arxiv.org/abs/0704.1642 , 51kb)
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arXiv:0704.1644
Date: Thu, 12 Apr 2007 18:55:27 GMT (164kb)

Title: Circulating Current States in Bilayer Fermionic and Bosonic Systems
Authors: Alexei Kolezhuk
Categories: cond-mat.other
Comments: 4 pages, 3 figures
\\
It is shown that fermionic polar molecules or atoms in a bilayer optical
lattice can undergo the transition to a state with circulating currents, which
spontaneously breaks the time reversal symmetry. Estimates of relevant
temperature scales are given and experimental signatures of the circulating
current phase are identified. Related phenomena in bosonic and spin systems
with ring exchange are discussed.
\\ ( http://arxiv.org/abs/0704.1644 , 164kb)
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Replacements:

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arXiv:quant-ph/0609208
replaced with revised version Fri, 6 Apr 2007 08:44:12 GMT (222kb)

Title: Continuous transfer and laser guiding between two cold atom traps
Authors: Emiliya Dimova (LAC), Olivier Morizot (LPL), Guillaume Stern (LAC),
Carlos L. Garrido Alzar (LPL), Andrea Fioretti (LAC), Vincent Lorent (LPL),
Daniel Comparat (LAC), H{\'e}l{\e}ne Perrin (LPL), Pierre Pillet (LAC)
Categories: quant-ph
Comments: 10 pages, 8 figures
Journal-ref: European physical Journal D 42 (2007) 299-308
DOI: 10.1140/epjd/e2007-00022-0
\\ ( http://arxiv.org/abs/quant-ph/0609208 , 222kb)
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arXiv:cond-mat/0608477
replaced with revised version Sat, 7 Apr 2007 20:24:23 GMT (48kb)

Title: Next-to-next-to-leading-order epsilon expansion for a Fermi gas at
infinite scattering length
Authors: Peter Arnold, Joaquin E. Drut, and Dam Thanh Son
Categories: cond-mat.other nucl-th
Comments: 28 pages, 14 figures
Report-no: INT PUB 06-12
Journal-ref: Phys.Rev. A75 (2007) 043605
DOI: 10.1103/PhysRevA.75.043605
\\ ( http://arxiv.org/abs/cond-mat/0608477 , 48kb)
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arXiv:cond-mat/0610079
replaced with revised version Mon, 9 Apr 2007 13:11:09 GMT (319kb)

Title: Adiabatic Phase Diagram of an Ultracold Atomic Fermi Gas with a Feshbach
Resonance
Authors: S. Watabe, T. Nikuni, N. Nygaard, J. E. Williams, and C. W. Clark
Categories: cond-mat.other
Comments: 13 pages, 8 figures. In press, "Journal of the Physical Society of
Japan", Vol.76, No.6
\\ ( http://arxiv.org/abs/cond-mat/0610079 , 319kb)
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arXiv:cond-mat/0610610
replaced with revised version Sun, 8 Apr 2007 13:57:38 GMT (304kb)

Title: Asymmetric Fermion Superfluid with Inter- and Intra-Species Pairings
Authors: Xuguang Huang, Xuewen Hao and Pengfei Zhuang
Categories: cond-mat.supr-con hep-ph
Comments: 4 pages, 4 figures
\\ ( http://arxiv.org/abs/cond-mat/0610610 , 304kb)
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arXiv:cond-mat/0701321
replaced with revised version Fri, 6 Apr 2007 21:38:18 GMT (14kb)

Title: Ultraslow optical waveguiding in an atomic Bose-Einstein condensate
Authors: Devrim Tarhan, Nazmi Postacioglu, Ozgur E. Mustecaplioglu
Categories: cond-mat.other quant-ph
Comments: 9 pages, 3 figures
Journal-ref: Opt. Lett. 32(9), 1038-1040 (2007)
\\ ( http://arxiv.org/abs/cond-mat/0701321 , 14kb)
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arXiv:0704.0289
replaced with revised version Tue, 10 Apr 2007 17:25:34 GMT (292kb)

Title: Kosterlitz-Thouless Crossover on a Two-Dimensional Lattice of
Josephson-Coupled Bose-Einstein Condensates
Authors: V. Schweikhard, S. Tung, and E. A. Cornell
Categories: cond-mat.mes-hall
Comments: corrected wording errors in introduction paragraph
\\ ( http://arxiv.org/abs/0704.0289 , 292kb)
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arXiv:cond-mat/0701751
replaced with revised version Tue, 10 Apr 2007 09:11:10 GMT (571kb)

Title: Excitonic condensation under spin-orbit coupling and BEC-BCS crossover
Authors: Tu\u{g}rul Hakio\u{g}lu and Mehmet \c{S}ahin
Categories: cond-mat.str-el cond-mat.mes-hall
Comments: Accepted for publication by Physical Review Letters
\\ ( http://arxiv.org/abs/cond-mat/0701751 , 571kb)
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arXiv:quant-ph/0612214
replaced with revised version Wed, 11 Apr 2007 01:54:11 GMT (500kb)

Title: Manipulation of the quantum state by Majorana transition in spinor
Bose-Einstein condensates
Authors: Lin Xia, Xu Xu, Fan Yang, Wei Xiong, Juntao Li, Qianli Ma, Xiaoji
Zhou, Hong Guo and Xuzong Chen
Categories: quant-ph cond-mat.other
Comments: 5 pages, 5 figures
\\ ( http://arxiv.org/abs/quant-ph/0612214 , 500kb)
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arXiv:0704.1413
replaced with revised version Thu, 12 Apr 2007 18:10:12 GMT (351kb)

Title: Preparation and detection of magnetic quantum phases in optical
superlattices
Authors: A. M. Rey, V. Gritsev, I. Bloch, E. Demler and M.D. Lukin
Categories: cond-mat.other
Comments: 5 pages, 2 Figures, reference added
\\ ( http://arxiv.org/abs/0704.1413 , 351kb)
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Till next week,
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 Mon Apr 16 2007 - 10:08:44 EST

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