# Matt's arXiv selection: week ending 18 January 2008.

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Sun, 27 Jan 2008 22:13:27 +1000

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

Hi everyone,

A large email this week, with 32 new preprints and 16 replacements.

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arXiv:0801.1732
Date: Fri, 11 Jan 2008 08:37:46 GMT (109kb)

Title: Three-Body Recombination of Identical Bosons with a Large Positive
Scattering Length at Nonzero Temperature
Authors: Eric Braaten, H.-W. Hammer, Daekyoung Kang, Lucas Platter
Categories: cond-mat.other
Report-no: HISKP-TH-08-01
\\
For identical bosons with a large scattering length, the dependence of the
3-body recombination rate on the collision energy is determined by universal
functions of a single scaling variable. There are six scaling functions for
angular momentum zero and one scaling function for each higher partial wave. We
calculate these universal functions by solving the Skorniakov--Ter-Martirosian
equation. The results for the 3-body recombination as a function of the
collision energy are in good agreement with previous results from solving the
3-body Schroedinger equation for He-4 atoms. The universal scaling functions
can be used to calculate the 3-body recombination rate at nonzero temperature.
We obtain an excellent fit to the data from the Innsbruck group for Cs-133
atoms with a large positive scattering length.
\\ ( http://arxiv.org/abs/0801.1732 , 109kb)
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arXiv:0801.1743
Date: Fri, 11 Jan 2008 19:00:34 GMT (497kb)

Title: Temperature Effects in a Fermi Gas with Population Imbalance
Authors: Heron Caldas, and A. L. Mota
Categories: cond-mat.str-el cond-mat.supr-con
\\
We investigate temperature effects in a Fermi gas with imbalanced spin
populations. From the general expression of the thermal gap equation we find,
in {\it weak coupling limit}, an analytical expression for the transition
temperature $T_c$ as a function of various possibilities of chemical potential
and mass asymmetries between the two particle species. For a range of asymmetry
between certain specific values, this equation always has two solutions for
$T_c$ which has been interpreted as a reentrant phenomena or a pairing induced
by temperature effect. We show that the lower $T_c$ is never related to a
stable solution. The same results are obtained in {\it strong coupling limit}.
The thermodynamical potential is carefully analyzed to avoid the consideration
of the unstable solutions.
\\ ( http://arxiv.org/abs/0801.1743 , 497kb)
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arXiv:0801.1753
Date: Fri, 11 Jan 2008 10:57:49 GMT (269kb)

Title: Path Integral Ground State study of 2D solid 4He
Authors: E. Vitali, M. Rossi, F. Tramonto, D.E. Galli, L. Reatto
Categories: cond-mat.other cond-mat.stat-mech
\\
We have studied a two-dimensional triangular commensurate crystal of 4He with
the exact T=0 K Path Integral Ground State (PIGS) Monte Carlo method. We have
projected onto the true ground state both a Jastrow-Nosanow wave function, in
which equilibrium positions are explicitly given and no Bose-Einstein (BEC) is
present, and a translationally invariant shadow wave function, in which the
solid phase emerges through a spontaneously broken symmetry process and it has
BEC. We find a remarkable convergence to the same properties, both the diagonal
ones as well as the off-diagonal one-body density matrix rho_1. This supplies a
strong evidence that no variational bias are present in the PIGS method. We
find no BEC in the commensurate 2D 4He crystal at T=0 K, rho_1 shows an
exponential decay in the large distance range. The structure found in rho_1 is
due to virtual vacancy--interstitial pairs and this shows up in the momentum
distribution.
\\ ( http://arxiv.org/abs/0801.1753 , 269kb)
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arXiv:0801.1765
Date: Fri, 11 Jan 2008 12:18:09 GMT (74kb)

Title: The ALPS project release 1.3: open source software for strongly
correlated systems
Authors: A.F. Albuquerque, F. Alet, P. Corboz, P. Dayal, A. Feiguin, S. Fuchs,
L. Gamper, E. Gull, S. Guertler, A. Honecker, R. Igarashi, M. Koerner, A.
Kozhevnikov, A. Laeuchli, S.R. Manmana, M. Matsumoto, I.P. McCulloch, F.
Michel, R.M. Noack, G. Pawlowski, L. Pollet, T. Pruschke, U. Schollwock, S.
Todo, S. Trebst, M. Troyer, P. Werner, S. Wessel (for the ALPS collaboration)
Categories: cond-mat.str-el cond-mat.stat-mech
Journal-ref: Journal of Magnetism and Magnetic Materials 310, 1187 (2007)
DOI: 10.1016/j.jmmm.2006.10.304
\\
We present release 1.3 of the ALPS (Algorithms and Libraries for Physics
Simulations) project, an international open source software project to develop
libraries and application programs for the simulation of strongly correlated
quantum lattice models such as quantum magnets, lattice bosons, and strongly
correlated fermion systems. Development is centered on common XML and binary
data formats, on libraries to simplify and speed up code development, and on
full-featured simulation programs. The programs enable non-experts to start
carrying out numerical simulations by providing basic implementations of the
important algorithms for quantum lattice models: classical and quantum Monte
Carlo (QMC) using non-local updates, extended ensemble simulations, exact and
full diagonalization (ED), as well as the density matrix renormalization group
(DMRG). Changes in the new release include a DMRG program for interacting
models, support for translation symmetries in the diagonalization programs, the
ability to define custom measurement operators, and support for inhomogeneous
systems, such as lattice models with traps. The software is available from our
web server at http://alps.comp-phys.org/ .
\\ ( http://arxiv.org/abs/0801.1765 , 74kb)
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arXiv:0801.1815
Date: Fri, 11 Jan 2008 18:06:13 GMT (38kb)

Title: Superfluid pairing between fermions with unequal masses
Authors: M.A. Baranov, C. Lobo, and G.V. Shlyapnikov
Categories: cond-mat.other cond-mat.supr-con
\\
We consider a superfluid state in a two-component gas of fermionic atoms with
equal densities and unequal masses in the BCS limit. We develop a perturbation
theory along the lines proposed by Gorkov and Melik-Barkhudarov and find that
for a large difference in the masses of heavy ($M$) and light ($m$) atoms one
has to take into account both the second-order and third-order contributions.
The result for the critical temperature and order parameter is then quite
different from the prediction of the simple BCS approach. Moreover, the small
parameter of the theory turns out to be $(p_{F}|a|)/\hbar)\sqrt{M/m}\ll1$,
where $p_{F}$ is the Fermi momentum, and $a$ the scattering length. Thus, for a
large mass ratio $M/m$ the conventional perturbation theory requires
significantly smaller Fermi momenta (densities) or scattering lengths than in
the case of $M\sim m$, where the small parameter is $(p_{F}|a|)/\hbar)\ll1$. We
show that 3-body scattering resonances appearing at a large mass ratio due to
the presence of 3-body bound Efimov states do not influence the result, which
in this sense becomes universal.
\\ ( http://arxiv.org/abs/0801.1815 , 38kb)
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arXiv:0801.1837
Date: Fri, 11 Jan 2008 20:53:44 GMT (10kb)

Title: A test of the g-ology model for one-dimensional interacting Fermi
systems
Authors: Andrey V. Chubukov, Dmitrii L. Maslov, and Fabian H.L. Essler
Categories: cond-mat.str-el
Comments: 4 pp, 1 fig, submitted to PRB RC
\\
Bosonization predicts that the specific heat, C(T), of a one-dimensional
interacting Fermi system is a sum of the specific heats of free collective
charge and spin excitations, plus the term with the running backscattering
amplitude which flows to zero logarithmically with decreasing T. We verify
whether this result is reproduced in the g-ology model. Of specific interest
are the anomalous terms in C(T) that depend on the bare backscattering
amplitude. We show that these terms can be incorporated into a renormalized
spin velocity. We do this by proving the equivalence of the results for C(T)
obtained within the g-ology model and by bosonization with velocities obtained
by the numerical solution of the Bethe-ansatz equations for the Hubbard model.
\\ ( http://arxiv.org/abs/0801.1837 , 10kb)
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arXiv:0801.1887
Date: Mon, 14 Jan 2008 19:25:48 GMT (120kb)

Title: Temperature changes when adiabatically ramping up an optical lattice
Authors: Lode Pollet, Corinna Kollath, Kris Van Houcke, Matthias Troyer
Categories: cond-mat.stat-mech
\\
When atoms are loaded into an optical lattice, the process of gradually
turning on the lattice is almost adiabatic. In this paper we investigate how
the temperature changes when going from the gapless superfluid phase to the
gapped Mott phase along isentropic lines. To do so we calculate the entropy in
the single-band Bose-Hubbard model for various densities, interaction strengths
and temperatures in one and two dimensions for homogeneous and trapped systems.
Our theory is able to reproduce the experimentally observed visibilities and
therefore strongly supports that current experiments remain in the quantum
regime for all considered lattice depths with low temperatures and minimal
heating.
\\ ( http://arxiv.org/abs/0801.1887 , 120kb)
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arXiv:0801.1916
Date: Sat, 12 Jan 2008 19:14:41 GMT (438kb)

Title: Quantised Vortices in an Exciton-Polariton Fluid
Authors: K. G. Lagoudakis, M. Wouters, M. Richard, A. Baas, I. Carusotto, R.
Andre, Le Si Dang, B. Deveaud-Pledran
Categories: cond-mat.other
\\
One of the most striking quantum effects in a low temperature interacting
Bose gas is superfluidity. First observed in liquid 4He, this phenomenon has
been intensively studied in a variety of systems for its amazing features such
as the persistence of superflows and the quantization of the angular momentum
of vortices. The achievement of Bose-Einstein condensation (BEC) in dilute
atomic gases provided an exceptional opportunity to observe and study
superfluidity in an extremely clean and controlled environment. In the solid
state, Bose-Einstein condensation of exciton polaritons has now been reported
several times. Polaritons are strongly interacting light-matter
quasi-particles, naturally occurring in semiconductor microcavities in the
strong coupling regime and constitute a very interesting example of composite
bosons. Even though pioneering experiments have recently addressed the
propagation of a fluid of coherent polaritons, still no conclusive evidence is
yet available of its superfluid nature. In the present Letter, we report the
observation of spontaneous formation of pinned quantised vortices in the
Bose-condensed phase of a polariton fluid by means of phase and amplitude
imaging. Theoretical insight into the possible origin of such vortices is
presented in terms of a generalised Gross-Pitaevskii equation. The implications
of our observations concerning the superfluid nature of the non-equilibrium
polariton fluid are finally discussed.
\\ ( http://arxiv.org/abs/0801.1916 , 438kb)
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arXiv:0801.1947
Date: Sun, 13 Jan 2008 11:08:46 GMT (431kb)

Title: Improved Scaling for Periodic Matrix Product State Algorithms
Authors: Peter Pippan, Steven R. White, and Hans Gerd Evertz
Categories: cond-mat.str-el
\\
Recently, Verstraete et. al. proposed a matrix product state (MPS)
variational method for one dimensional systems with periodic boundary
conditions, for which the density matrix renormalization group (DMRG) does not
converge well. However, as Verstraete et. al. pointed out, while the dimension
m of the matrices could be made much smaller than in DMRG, the calculation time
scaled as m5 rather than m3. We modify the MPS method and we introduce a
factorization procedure which reduces the calculation time to m3, making MPS
calculations with periodic boundary conditions comparable in efficiency to DMRG
with open boundaries. We test the method on the S=1/2 and S=1 Heisenberg
chains. It is also applicable to non-translationally invariant cases.
\\ ( http://arxiv.org/abs/0801.1947 , 431kb)
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arXiv:0801.2002
Date: Mon, 14 Jan 2008 02:25:13 GMT (609kb)

Title: Efimov states embedded in the three-body continuum
Authors: N. P. Mehta, Seth T. Rittenhouse, J. P. D'Incao, Chris H. Greene
Categories: cond-mat.other
\\
We consider a multichannel generalization of the Fermi pseudopotential to
model low-energy atom-atom interactions near a magnetically tunable Feshbach
resonance, and calculate the adiabatic hyperspherical potential curves for a
system of three such interacting atoms. In particular, our model suggests the
existence of a series of quasi-bound Efimov states attached to excited
three-body thresholds, far above open channel collision energies. We discuss
the conditions under which such states may be supported, and identify which
interaction parameters limit the lifetime of these states. We speculate that it
may be possible to observe these states using spectroscopic methods, perhaps
allowing for the measurement of multiple Efimov resonances for the first time.
\\ ( http://arxiv.org/abs/0801.2002 , 609kb)
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arXiv:0801.2056
Date: Mon, 14 Jan 2008 12:06:09 GMT (205kb)

Title: Double and negative reflection of cold atoms in non-Abelian gauge
potentials
Authors: Gediminas Juzeliunas, Julius Ruseckas, Andreas Jacob, Luis Santos,
Patrik Ohberg
Categories: cond-mat.other
\\
Atom reflection is studied in the presence of a non-Abelian vector potential
proportional to a spin-1/2 operator. The potential is produced by a relatively
simple laser configuration for atoms with a tripod level scheme. We show that
the atomic motion is described by two different dispersion branches with
positive or negative chirality. As a consequence of that, atom reflection shows
unusual features, since an incident wave may split into two reflected ones at a
barrier, an ordinary specular reflection, and an additional non-specular one.
Remarkably, the latter wave can exhibit negative reflection and may become
evanescent if the angle of incidence exceeds a critical value. These reflection
properties are crucial for future designs in non-Abelian atom optics.
\\ ( http://arxiv.org/abs/0801.2056 , 205kb)
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arXiv:0801.2078
Date: Mon, 14 Jan 2008 14:02:33 GMT (11kb)

Title: On entropy growth and the hardness of simulating time evolution
Authors: Norbert Schuch, Michael M. Wolf, Karl Gerd H. Vollbrecht, J. Ignacio
Cirac
Categories: quant-ph
\\
The simulation of quantum systems is a task for which quantum computers are
believed to give an exponential speedup as compared to classical ones. While
ground states of one-dimensional systems can be efficiently approximated using
Matrix Product States (MPS), their time evolution can encode quantum
computations, so that simulating the latter should be hard classically.
However, one might believe that for systems with high enough symmetry, and thus
insufficient parameters to encode a quantum computation, efficient classical
simulation is possible. We discuss supporting evidence to the contrary: We
provide a rigorous proof of the observation that a time independent local
Hamiltonian can yield a linear increase of the entropy when acting on a product
state in a translational invariant framework. This challenges every classical
simulation method and it implies in particular that every global approximation
of the evolution requires exponential resources for any MPS based method.
\\ ( http://arxiv.org/abs/0801.2078 , 11kb)
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arXiv:0801.2324
Date: Tue, 15 Jan 2008 15:18:27 GMT (248kb)

Title: Spin-drag relaxation time in one-dimensional spin-polarized Fermi gases
Authors: Diego Rainis, Marco Polini, M.P. Tosi, and G. Vignale
Categories: cond-mat.str-el
Journal-ref: Phys. Rev. B 77, 035113 (2008)
DOI: 10.1103/PhysRevB.77.035113
\\
Spin propagation in systems of one-dimensional interacting fermions at finite
temperature is intrinsically diffusive. The spreading rate of a spin packet is
controlled by a transport coefficient termed "spin drag" relaxation time
$\tau_{\rm sd}$. In this paper we present both numerical and analytical
calculations of $\tau_{\rm sd}$ for a two-component spin-polarized cold Fermi
gas trapped inside a tight atomic waveguide. At low temperatures we find an
activation law for $\tau_{\rm sd}$, in agreement with earlier calculations of
Coulomb drag between slightly asymmetric quantum wires, but with a different
and much stronger temperature dependence of the prefactor. Our results provide
a fundamental input for microscopic time-dependent spin-density functional
theory calculations of spin transport in 1D inhomogeneous systems of
interacting fermions.
\\ ( http://arxiv.org/abs/0801.2324 , 248kb)
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arXiv:0801.2337
Date: Tue, 15 Jan 2008 16:58:18 GMT (48kb)

Title: Symbiotic gap and semi-gap solitons in Bose-Einstein condensates
Categories: cond-mat.other
\\
Using the variational approximation (VA) and numerical simulations, we study
one-dimensional gap solitons in a binary Bose-Einstein condensate trapped in an
optical-lattice potential. We consider the case of inter-species repulsion,
while the intra-species interaction may be either repulsive or attractive.
Several types of gap solitons are found: symmetric or asymmetric; %depending on
numbers of unsplit or split, if centers of the components coincide or separate;
intra-gap (with both chemical potentials falling into a single bandgap) or
inter-gap, otherwise. %We identify In the case of the intra-species attraction,
a smooth transition takes place between solitons in the semi-infinite gap, the
ones in the first finite bandgap, and \textit{semi-gap} solitons (with one
component in a bandgap and the other in the semi-infinite gap).
\\ ( http://arxiv.org/abs/0801.2337 , 48kb)
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arXiv:0801.2343
Date: Tue, 15 Jan 2008 17:21:14 GMT (301kb)

Title: Ultracold bosons in lattices with binary disorder
Authors: K.V.Krutitsky, M.Thorwart, R.Egger, R.Graham
Categories: cond-mat.dis-nn cond-mat.other
\\
Quantum phases of ultracold bosons with repulsive interactions in lattices in
the presence of quenched disorder are investigated. The disorder is assumed to
be caused by the interaction of the bosons with impurity atoms having a large
effective mass. The system is described by the Bose-Hubbard Hamiltonian with
random on-site energies which have a discrete binary probability distribution.
The phase diagram at zero temperature is calculated using several methods like
a strong-coupling expansion, an exact numerical diagonalization, and a
Bose-Fermi mapping valid in the hard-core limit. It is shown that the
Mott-insulator phase exists for any strength of disorder in contrast to the
case of continuous probablity distribution. We find that the compressibility of
the Bose glass phase varies in a wide range and can be extremely low.
Furthermore, we evaluate experimentally accessible quantities like the momentum
distribution, the static and dynamic structure factors and the density of
excited states. The influence of finite temperature is discussed as well.
\\ ( http://arxiv.org/abs/0801.2343 , 301kb)
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arXiv:0801.2364
Date: Tue, 15 Jan 2008 19:08:43 GMT (236kb)

Title: Bright solitary waves in a Bose-Einstein condensate and their
interactions
Authors: K. Karkkainen, A. D. Jackson, G. M. Kavoulakis
Categories: cond-mat.other
\\
We examine the dynamics of two bright solitary waves with a negative
nonlinear term. The observed repulsion between two solitary waves -- when these
are in an antisymmetric combination -- is attributed to conservation laws.
Slight breaking of parity, in combination with weak relaxation of energy, leads
the two solitary waves to merge. The effective repulsion between solitary waves
requires certain nearly ideal conditions and is thus fragile.
\\ ( http://arxiv.org/abs/0801.2364 , 236kb)
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arXiv:0801.2240
Date: Tue, 15 Jan 2008 09:50:12 GMT (218kb)

Title: High momentum entanglement of cold atoms generated by a single photon
scattering
Authors: Rui Guo, Xiaoji Zhou, Xuzong Chen
Categories: quant-ph
\\
With the mechanism of pairwise scattering of photons between two atoms, we
propose a novel scheme to highly entangle the motional state between two
ultracold neutral atoms by a single photon scattering and detection. Under
certain conditions, it is shown that an arbitrary amount of entanglement can be
obtained with this scheme.
\\ ( http://arxiv.org/abs/0801.2240 , 218kb)
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arXiv:0801.2223
Date: Tue, 15 Jan 2008 07:13:15 GMT (200kb)

Title: Cloaking of Matter Waves
Authors: Shuang Zhang, Dentcho A. Genov, Cheng Sun and Xiang Zhang
Categories: physics.optics physics.gen-ph
\\
Invariant transformation for quantum mechanical systems is proposed. A
cloaking of matter wave can be realized at given energy by designing the
potential and effective mass of the matter waves in the cloaking region. The
general conditions required for such a cloaking are determined and confirmed by
both the wave and particle (classical) approaches. We show that it may be
possible to construct such a cloaking system for cold atoms using optical
lattices.
\\ ( http://arxiv.org/abs/0801.2223 , 200kb)
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arXiv:0801.2500
Date: Wed, 16 Jan 2008 05:48:49 GMT (5513kb)

Title: Making, probing and understanding ultracold Fermi gases
Authors: Wolfgang Ketterle and Martin W. Zwierlein
Categories: cond-mat.other cond-mat.str-el
Comments: Long review article, 206 pages, 74 figures, to appear in Ultracold
Fermi Gases, Proceedings of the International School of Physics "Enrico
Fermi", Course CLXIV, Varenna, 20 - 30 June 2006, edited by M. Inguscio, W.
Ketterle, and C. Salomon (IOS Press, Amsterdam) 2008
\\
A review on superfluidity and the BEC-BCS crossover in ultracold Fermi gases.
\\ ( http://arxiv.org/abs/0801.2500 , 5513kb)
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arXiv:0801.2396
Date: Tue, 15 Jan 2008 22:08:40 GMT (25kb)

Title: Many-body dynamics of Rydberg excitation using the $\Omega$-expansion
Authors: J. Stanojevic and R. C\^ot\'e
Categories: quant-ph
Comments: 9 pages, 3 figures, 1 table
\\
We investigate the excitation dynamics of Rydberg atoms in ultracold atomic
samples by expanding the excitation probability and the correlation function
between excited atoms in powers of the isolated atom Rabi frequency $\Omega$.
In the Heisenberg picture, we give recurrence relations to calculate any order
of the expansions, which ere expected to be well-behaved for arbitrarily strong
interactions. For homogeneous large samples, we give the explicit form of the
expansions, up to $\Omega^4$, averaged over all possible random spatial
distributions of atoms, for the most important cases of excitation pulses and
interactions.
\\ ( http://arxiv.org/abs/0801.2396 , 25kb)
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arXiv:0801.2406
Date: Tue, 15 Jan 2008 22:50:12 GMT (21kb)

Title: Many-body Rabi oscillations of Rydberg excitation in small mesoscopic
samples
Authors: J. Stanojevic and R. C\^ot\'e
Categories: quant-ph
\\
We investigate the collective aspects of Rydberg excitation in ultracold
mesoscopic systems. Strong interactions between Rydberg atoms influence the
excitation process and impose correlations between excited atoms. The
manifestations of the collective behavior of Rydberg excitation are the
many-body Rabi oscillations, spatial correlations between atoms as well as the
fluctuations of the number of excited atoms. We study these phenomena in detail
by numerically solving the many-body Schr\"edinger equation.
\\ ( http://arxiv.org/abs/0801.2406 , 21kb)
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arXiv:0801.2440
Date: Wed, 16 Jan 2008 07:19:21 GMT (216kb)

Title: Subluminal to superluminal propagation of an optical pulse in an
f-deformed Bose- Einstein condensate
Authors: Z. Haghshenasfard, M. H. Naderi and M. Soltanolkotabi
Categories: quant-ph
\\
In this paper, we investigate the propagation of a weak optical probe pulse
in an f-deformed Bose- Einstein condensate (BEC) of a gas with the -type three-
level atoms in the electromagnetically induced transparency (EIT) regime. We
use an f- deformed generalization of an effective two- level quantum model of
the three- level configuration in which the Gardiner phonon operators for BEC
are deformed by an operator- valued function, f(n), of the particle- number
operator n. With making use of the quantum approach of the angular momentum
theory we obtain the eigenvalues and eigenfunctions of the system up to first
order approximation. We consider the collisions between the atoms as a special
kind of f- deformation. The collision rate k is regarded as the deformation
parameter and light propagation in the deformed BEC is analyzed. In particular,
we show that the absorptive and dispersive properties of the deformed
condensate can be controlled effectively by changing the deformation parameter
k and the total number of atoms. We find that by increasing the value of k the
group velocity of the probe pulse changes, through deformed condensate, from
subluminal to superluminal.
\\ ( http://arxiv.org/abs/0801.2440 , 216kb)
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arXiv:0801.2448
Date: Wed, 16 Jan 2008 08:32:21 GMT (256kb)

Title: Atom cooling with an atom-optical diode on a ring
Authors: A. Ruschhaupt, J. G. Muga
Categories: quant-ph
\\
We propose a method to cool atoms on a ring by combining an atom diode -a
laser valve for one-way atomic motion which induces robust internal state
excitation- and a trap. We demonstrate numerically that the atom is efficiently
slowed down at each diode crossing, and it is finally trapped when its velocity
is below the trap threshold.
\\ ( http://arxiv.org/abs/0801.2448 , 256kb)
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arXiv:0801.2449
Date: Wed, 16 Jan 2008 08:22:06 GMT (775kb)

Title: Entanglement renormalization in free bosonic systems: real-space versus
momentum-space renormalization group transforms
Authors: G. Evenbly, G. Vidal
Categories: quant-ph
\\
The ability of entanglement renormalization (ER) to generate a proper
real-space renormalization group (RG) flow in harmonic lattice systems of D=1
and D=2 spatial dimensions is analyzed. A conceptual overview of the steps
involved in momentum-space RG is provided and contrasted against the equivalent
steps in the real-space setting. The real-space RG flow, as generated by ER, is
compared with exact results from momentum space including an investigation of a
critical fixed points and examples with relevant/irrelevant perturbations.
\\ ( http://arxiv.org/abs/0801.2449 , 775kb)
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arXiv:0801.2514
Date: Wed, 16 Jan 2008 16:09:36 GMT (159kb)

Title: Trapping cold Atoms by Quantum Reflection
Authors: Alexander Jurisch, Jan-Michael Rost
Categories: quant-ph
\\
We examine the properties of a quantum reflection trap when
particle-interaction is included. We explore the influence of the
particle-interaction on the trapping for different regimes: repulsive
particle-interaction and attractive particle-interaction in its stable and
unstable limit. With variational techniques, we calculate the phase-diagram of
the quatum reflection trap and determine the stable and unstable regimes of the
system.
\\ ( http://arxiv.org/abs/0801.2514 , 159kb)
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arXiv:0801.2386
Date: Tue, 15 Jan 2008 21:15:38 GMT (178kb)

Title: Long-range potentials and $(n-1)d+ns$ molecular resonances in an
ultracold rydberg gas
Authors: J. Stanojevic, R. C\^ot\'e, D. Tong, E.E. Eyler, and P.L. Gould
Categories: physics.atom-ph
\\
We have calculated long-range molecular potentials of the $0_g^{+}$,
$0_u^{-}$ and $1_u$ symmetries between highly-excited rubidium atoms. Strong
$np+np$ potentials characterized by these symmetries are important in
describing interaction-induced phenomena in the excitation spectra of high $np$
Rydberg states. Long-range molecular resonances are such phenomena and they
were first reported in S.M. Farooqi {\it et al.}, Phys. Rev. Lett. {\bf 91}
183002. One class of these resonances occurs at energies corresponding to
excited atom pairs $(n-1)d+ns$. Such resonances are attributed to $\ell$-mixing
due to Rydberg-Rydberg interactions so that otherwise forbidden molecular
transitions become allowed. We calculate molecular potentials in Hund's case
(c), use them to find the resonance lineshape and compare to experimental
results.
\\ ( http://arxiv.org/abs/0801.2386 , 178kb)
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arXiv:0801.2580
Date: Wed, 16 Jan 2008 22:29:12 GMT (434kb,D)

Title: Mean-field stationary state of a Bose gas at a Feshbach resonance
Authors: Andrew Carmichael and Juha Javanainen
Categories: cond-mat.other
\\
We study the steady state of a zero-temperature Bose gas near a Feshbach or
photoassociation resonance using a two-channel mean-field model that
incorporates atomic and molecular condensates, as well as correlated atom pairs
originating from dissociation of molecules into pairs of atoms. We start from a
many-body Hamiltonian for atom-molecule conversion, and derive the time
dependent version of the mean-field theory. The stationary solution of the time
dependent model is rendered unique with an approximation that entails that all
noncondensate atoms are correlated, as if emerging from dissociation of
molecules. The steady state is solved numerically, but limiting cases are also
found analytically. The system has a phase transition in which the atomic
condensate emerges in a nonanalytic fashion. We quantify the scaling of the
observable quantities, such as fractions of atomic and molecular condensates,
with the detuning and the atom-molecule conversion strength. Qualitatively, the
dependence on detuning rounds out with increasing coupling strength. A study of
the thermodynamics shows that the pressure of the atom-molecule system is
negative, even on the molecule side of the resonance. This indicates the
possibility of mechanical instability.
\\ ( http://arxiv.org/abs/0801.2580 , 434kb)
------------------------------------------------------------------------------

\\
arXiv:0801.2640
Date: Thu, 17 Jan 2008 10:29:16 GMT (19kb)

Title: Two-component repulsive Fermi gases with population imbalance in
elongated harmonic traps
Authors: M. Colom\'e-Tatch\'e
Categories: cond-mat.str-el
\\
We study the two-component repulsive Fermi gas with imbalanced populations in
one dimension. Starting from the Bethe Ansatz solution we calculate
analytically the phase diagram for the homogeneous system. We show that two
phases appear: the fully polarised phase and the partially polarised phase. By
means of the local density approximation and the equation of state for the
homogeneous system we calculate the density profile for the harmonically
confined case. We show that a two-shell structure appears: at the center of the
cloud we find the partially polarised phase and at the edges the fully
polarised one. The radii of the inner and outer shells are calculated for
different values of the polarisation and the coupling strength. We calculate
the dependence of the magnetisation on the polarisation for different values of
the coupling strength and we show that the susceptibility is always finite.
\\ ( http://arxiv.org/abs/0801.2640 , 19kb)
------------------------------------------------------------------------------

\\
arXiv:0801.2747
Date: Thu, 17 Jan 2008 18:36:49 GMT (218kb)

Title: Energetics and Structural Properties of Trapped Two-Component Fermi
Gases
Authors: J. von Stecher, Chris H. Greene, D. Blume
Categories: cond-mat.other
\\
Using two different numerical methods, we study the behavior of two-component
Fermi gases interacting through short-range s-wave interactions in a harmonic
trap. A correlated Gaussian basis-set expansion technique is used to determine
the energies and structural properties, i.e., the radial one-body densities and
pair distribution functions, for small systems with either even or odd $N$, as
functions of the s-wave scattering length and the mass ratio $\kappa$ of the
two species. Particular emphasis is put on a discussion of the angular momentum
of the system in the BEC-BCS crossover regime. At unitarity, the excitation
spectrum of the four-particle system with total angular momentum L=0 is
calculated as a function of the mass ratio $\kappa$. The results are analyzed
from a hyperspherical perspective, which offers new insights into the problem.
Additionally, fixed-node diffusion Monte Carlo calculations are performed for
equal-mass Fermi gases with up to N=30 atoms. We focus on the odd-even
oscillations of the ground state energy of the equal-mass unitary system having
up to N=30 particles, which are related to the excitation gap of the system.
Furthermore, we present a detailed analysis of the structural properties of
these systems.
\\ ( http://arxiv.org/abs/0801.2747 , 218kb)
------------------------------------------------------------------------------

\\
arXiv:0801.2758
Date: Thu, 17 Jan 2008 20:20:33 GMT (600kb)

Title: Semiclassical theory of the quasi two-dimensional trapped Bose gas
Authors: Markus Holzmann, Maguelonne Chevallier, Werner Krauth
Categories: cond-mat.stat-mech
\\
We discuss the quasi two-dimensional trapped Bose gas where the thermal
occupation of excited states in the tightly confined direction is small but
remains finite in the thermodynamic limit. We show that the semiclassical
theory describes very accurately the density profile obtained by Quantum Monte
Carlo calculations in the normal phase above the Kosterlitz--Thouless
temperature T_KT, but differs strongly from the predictions of strictly
two-dimensional mean-field theory, even at relatively high temperature. We
discuss the relevance of our findings for analyzing ultra-cold-atom experiments
in quasi two-dimensional traps.
\\ ( http://arxiv.org/abs/0801.2758 , 600kb)
------------------------------------------------------------------------------

\\
arXiv:0801.2653
Date: Thu, 17 Jan 2008 11:45:51 GMT (306kb)

Title: Quantum Noise in the Coherent Matter-Wave Displacement Reaction
A+B2->AB+B
Authors: H. Jing, J. Cheng, and P. Meystre
Categories: quant-ph
Comments: 4 pages, 3 figures, submitted
\\
We demonstrate theoretically that the displacement reaction A+B2 ! AB+B
reaction can be realized efficiently with ultracold bosonic or fermionic matter
waves by using a generalized dark-state technique. We show that this reaction
is fundamentally different from the more familiar coherent atom-molecule
conversion (combination/decomposition reaction) in that quantum fluctuations
are critical in triggering its initial stages, with the appearacne of
non-classical correlations of the atomic and molecular fields as a result. This
study opens up a promising new research regime of ultracold matter-wave
superchemistry.
\\ ( http://arxiv.org/abs/0801.2653 , 306kb)
------------------------------------------------------------------------------

The replacements:

------------------------------------------------------------------------------
\\
arXiv:cond-mat/0703220
replaced with revised version Fri, 11 Jan 2008 11:13:46 GMT (385kb)

Title: Density and Stability in Ultracold Dilute Boson-Fermion Mixtures
Authors: Steffen Roethel and Axel Pelster
Categories: cond-mat.stat-mech
http://www.theo-phys.uni-essen.de/tp/ags/pelster_dir/
Journal-ref: European Physical Journal B 59, 343 (2007)
\\ ( http://arxiv.org/abs/cond-mat/0703220 , 385kb)
------------------------------------------------------------------------------
\\
arXiv:0711.3102
replaced with revised version Fri, 11 Jan 2008 16:29:08 GMT (202kb)

Title: Atom laser dynamics in a tight-waveguide
Authors: A. del Campo, I. Lizuain, M. Pons, J. G. Muga, M. Moshinsky
Categories: cond-mat.other cond-mat.soft
Comments: 6 pages, 5 figures, to be published in the Proceedings of the 395th
WE-Heraeus Seminar on "Time Dependent Phenomena in Quantum Mechanics ",
organized by T. Kramer and M. Kleber (Blaubeuren, Germany, September 2007)
\\ ( http://arxiv.org/abs/0711.3102 , 202kb)
------------------------------------------------------------------------------
\\
arXiv:0711.4065
replaced with revised version Fri, 11 Jan 2008 12:47:57 GMT (613kb)

Title: FFLO state in 1, 2, and 3 dimensional optical lattices combined with a
non-uniform background potential
Authors: T.K. Koponen, T. Paananen, J.-P. Martikainen, M.R. Bakhtiari, and P.
Torma
Categories: cond-mat.supr-con cond-mat.str-el
Comments: v2: minor revision, 18 pages, 10 figures
\\ ( http://arxiv.org/abs/0711.4065 , 613kb)
------------------------------------------------------------------------------
\\
arXiv:0712.4081
replaced with revised version Fri, 11 Jan 2008 18:29:36 GMT (13kb)

Title: Isospin excitations of a trapped 1D gas of attractively interacting
fermions
Authors: M. Colom\'e-Tatch\'e, G. V. Shlyapnikov and A. M. Tsvelik
Categories: cond-mat.str-el
Comments: 4 pages, 1 figure; minor corrections
\\ ( http://arxiv.org/abs/0712.4081 , 13kb)
------------------------------------------------------------------------------
\\
arXiv:0706.3360
replaced with revised version Mon, 14 Jan 2008 14:07:18 GMT (2141kb)

Title: Theory of ultracold Fermi gases
Authors: Stefano Giorgini, Lev P. Pitaevskii, Sandro Stringari
Categories: cond-mat.other
Comments: Revised and abridged version accepted for publication in Rev. Mod.
Phys.: 63 pages, 36 figures
\\ ( http://arxiv.org/abs/0706.3360 , 2141kb)
------------------------------------------------------------------------------
\\
arXiv:0708.2667
replaced with revised version Mon, 14 Jan 2008 15:07:46 GMT (196kb)

Title: Migration of bosonic particles across a Mott insulator to superfluid
phase interface
Authors: Michael J. Hartmann and Martin B. Plenio
Categories: cond-mat.str-el cond-mat.stat-mech quant-ph
Comments: 5 pages, 6 figures, to appear in Phys. Rev. Lett
\\ ( http://arxiv.org/abs/0708.2667 , 196kb)
------------------------------------------------------------------------------
\\
arXiv:0710.0521
replaced with revised version Mon, 14 Jan 2008 08:39:01 GMT (8kb)

Title: Kinetic Equationins in the Theory of Normal Fermi Liquid
Authors: I. Siddique, A.S. Kondratyev
Categories: cond-mat.stat-mech
\\ ( http://arxiv.org/abs/0710.0521 , 8kb)
------------------------------------------------------------------------------
\\
arXiv:0712.2495
replaced with revised version Sat, 12 Jan 2008 01:04:34 GMT (89kb)

Title: On the Quantum Instability of Attractive Bose Systems
Authors: George E. Cragg and Arthur K. Kerman
Categories: cond-mat.other cond-mat.stat-mech
typos
\\ ( http://arxiv.org/abs/0712.2495 , 89kb)
------------------------------------------------------------------------------
\\
arXiv:0801.0589
replaced with revised version Fri, 11 Jan 2008 22:31:55 GMT (39kb)

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
\\ ( http://arxiv.org/abs/0801.0589 , 39kb)
------------------------------------------------------------------------------
\\
arXiv:0801.1387
replaced with revised version Sat, 12 Jan 2008 13:27:01 GMT (53kb)

Title: Stability of the homogeneous Bose-Einstein condensate at large gas
parameter
Authors: Abdulla Rakhimov, Chul Koo Kim, Sang-Hoon Kim, and Jae Hyung Yee
Categories: cond-mat.stat-mech nucl-th physics.atom-ph
Comments: 9 pages, 3 figures, Revtex
\\ ( http://arxiv.org/abs/0801.1387 , 53kb)
------------------------------------------------------------------------------
\\
arXiv:0711.3116
replaced with revised version Mon, 14 Jan 2008 10:03:32 GMT (771kb)

Title: Seeking better times: atomic clocks in the generalized Tonks-Girardeau
regime
Authors: S. V. Mousavi, A. del Campo, I. Lizuain, M. Pons, J. G. Muga
Categories: quant-ph
Comments: Revised manuscript, 8 pages, 8 figures, proceedings of the 395th
WE-Heraeus Seminar on "Time Dependent Phenomena in Quantum Mechanics ",
Blaubeuren, Germany, September 2007
\\ ( http://arxiv.org/abs/0711.3116 , 771kb)
------------------------------------------------------------------------------
\\
arXiv:0710.2220
replaced with revised version Tue, 15 Jan 2008 08:39:07 GMT (69kb)

Title: Quantum phases of mixtures of atoms and molecules on optical lattices
Authors: V.G. Rousseau and P.J.H. Denteneer
Categories: cond-mat.stat-mech
Journal-ref: PRA 77, 013609 (2008)
DOI: 10.1103/PhysRevA.77.013609
\\ ( http://arxiv.org/abs/0710.2220 , 69kb)
------------------------------------------------------------------------------
\\
arXiv:0712.2978
replaced with revised version Tue, 15 Jan 2008 13:55:07 GMT (2kb)

Title: Comment on "Atom Interferometers"
Authors: V. A. Kuz'menko
Categories: physics.optics
Comments: 2 pages, other case discussed
\\ ( http://arxiv.org/abs/0712.2978 , 2kb)
------------------------------------------------------------------------------
\\
arXiv:0708.0894
replaced with revised version Wed, 16 Jan 2008 07:20:18 GMT (874kb)

Title: Density-Matrix Renormalization Group Study of Trapped Imbalanced Fermi
Condensates
Authors: Masaki Tezuka and Masahito Ueda
Categories: cond-mat.str-el
\\ ( http://arxiv.org/abs/0708.0894 , 874kb)
------------------------------------------------------------------------------
\\
arXiv:0710.3852
replaced with revised version Wed, 16 Jan 2008 03:59:35 GMT (191kb)

Title: Quantum Antiferromagnetism of Fermions in Optical Lattices with
Half-filled p-band
Authors: Kai Wu and Hui Zhai
Categories: cond-mat.str-el cond-mat.supr-con
Comments: 4 pages,2 figures; Revised version; Discussion on the Neel
temperature expanded
\\ ( http://arxiv.org/abs/0710.3852 , 191kb)
------------------------------------------------------------------------------
\\
arXiv:0711.0653
replaced with revised version Wed, 16 Jan 2008 16:48:45 GMT (336kb)

Title: Destroying superfluidity by rotating a Fermi gas at unitarity
Authors: I. Bausmerth, A. Recati, S. Stringari
Categories: cond-mat.soft cond-mat.supr-con
results; accepted for publication in Physical Review Letters
\\ ( http://arxiv.org/abs/0711.0653 , 336kb)
------------------------------------------------------------------------------

And seeing as you made it this far, have a look at this one for a bit of fun:

------------------------------------------------------------------------------
\\
arXiv:0801.1694
Date: Thu, 10 Jan 2008 23:23:53 GMT (835kb)

Title: Cheap Method for Shielding a City from Rocket and Nuclear Warhead
Impacts
Authors: Alexander Bolonkin
Categories: physics.gen-ph physics.soc-ph
Comments: 31 pages, 11 figures, 4 tables
\\
The author suggests a cheap closed AB-Dome which protects the densely
populated cities from nuclear, chemical, biological weapon (bombs) delivered by
warheads, strategic missiles, rockets, and various incarnations of aviation
technology. The offered AB-Dome is also very useful in peacetime because it
shields a city from exterior weather and creates a fine climate within the
AB-Dome. The hemispherical AB-Dome is the inflatable, thin transparent film,
located at altitude up to as much as 15 km, which converts the city into a
closed-loop system. The film may be armored the stones which destroy the
rockets and nuclear warhead. AB-Dome protects the city in case the World
nuclear war and total poisoning the Earth atmosphere by radioactive fallout
(gases and dust). Construction of the AB-Dome is easy; the enclosure film is
spread upon the ground, the air pump is turned on, and the cover rises to its
planned altitude and supported by a small air over-pressure. The offered method
is cheaper by thousand times than protection of city by current anti-rocket
systems. The AB-Dome may be also used (height up to 15 and more kilometers) for
TV, communication, telescope, long distance location, tourism, high placed
windmills (energy), illumination and entertainments. The author developed
theory of AB-Dome, made estimation, computation and computed a typical project.
Discussion and results are in the end of article.
\\ ( http://arxiv.org/abs/0801.1694 , 835kb)
------------------------------------------------------------------------------

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/
=========================================================================
Legal stuff: Unless stated otherwise, this e-mail represents only the
views of the sender and not the views of the University of Queensland
=========================================================================

Received on Fri Feb 01 2008 - 10:16:26 EST

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