# Matt's arXiv selection: week ending 24 October 2008

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Wed, 29 Oct 2008 17:55:04 +1000

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

Hi everyone,

I'm back from Beijing this week, impressed by all the great work that everyone
is doing and slightly anxious I won't ever be able to keep up with it all. I
would like to acknowledge all the people I chatted to that thanked me for this
email service - positive feedback means it is more likely that it will continue
into the future!

This week there were 27 new preprints this week, yet only 3 YY replacements.

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arXiv:0810.3005
Date: Fri, 17 Oct 2008 12:26:15 GMT (75kb,D)

Title: Quantum criticality and black holes
Authors: Subir Sachdev and Markus Mueller
Categories: cond-mat.str-el hep-th
Comments: 12 pages, 2 figures; Talk at LT25, Amsterdam
\\
Many condensed matter experiments explore the finite temperature dynamics of
systems near quantum critical points. Often, there are no well-defined
quasiparticle excitations, and so quantum kinetic equations do not describe the
transport properties completely. The theory shows that the transport
co-efficients are not proportional to a mean free scattering time (as is the
case in the Boltzmann theory of quasiparticles), but are completely determined
by the absolute temperature and by equilibrium thermodynamic observables.
Recently, explicit solutions of this quantum critical dynamics have become
possible via the AdS/CFT duality discovered in string theory. This shows that
the quantum critical theory provides a holographic description of the quantum
theory of black holes in a negatively curved anti-de Sitter space, and relates
its transport co-efficients to properties of the Hawking radiation from the
black hole. We review how insights from this connection have led to new results
for experimental systems: (i) the vicinity of the superfluid-insulator
transition in the presence of an applied magnetic field, and its possible
application to measurements of the Nernst effect in the cuprates, (ii) the
magnetohydrodynamics of the plasma of Dirac electrons in graphene and the
prediction of a hydrodynamic cyclotron resonance.
\\ ( http://arxiv.org/abs/0810.3005 , 75kb)
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arXiv:0810.3051
Date: Fri, 17 Oct 2008 02:21:04 GMT (2kb)

Title: Comments on "Thermally induced rotons in two-dimensional dilute Bose
gases" [arXiv:cond-mat/0503523]
Authors: Sang-Hoon Kim
Categories: cond-mat.stat-mech
\\
A mistake of the effective interaction between D-dimensional Bose atoms
corrected.
\\ ( http://arxiv.org/abs/0810.3051 , 2kb)
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arXiv:0810.3061
Date: Fri, 17 Oct 2008 05:52:52 GMT (157kb)

Title: Quantum Nucleation and Macroscopic Quantum Tunneling in Cold-Atom
Boson-Fermion Mixtures
Authors: Dmitry Solenov and Dmitry Mozyrsky
Categories: cond-mat.mes-hall cond-mat.str-el
\\
Kinetics of phase separation transition in boson-fermion cold atom mixtures
is investigated. We identify the parameters at which the transition is governed
by quantum nucleation mechanism, responsible for the formation of critical
nuclei of a stable phase. We demonstrate that for low fermion-boson mass ratio
the density dependence of quantum nucleation transition rate is experimentally
observable. The crossover to macroscopic quantum tunneling regime is analyzed.
Based on a microscopic description of interacting cold atom boson-fermion
mixtures we derive an effective action for the critical droplet and obtain an
asymptotic expression for the nucleation rate in the vicinity of the phase
transition and near the spinodal instability of the mixed phase. We show that
dissipation due to excitations in fermion subsystem play a dominant role close
to the transition point.
\\ ( http://arxiv.org/abs/0810.3061 , 157kb)
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arXiv:0810.3088
Date: Fri, 17 Oct 2008 08:39:09 GMT (352kb)

Title: Spacetime analogue of Bose-Einstein condensates: Bogoliubov-de Gennes
formulation
Authors: Yasunari Kurita, Michikazu Kobayashi, Takao Morinari, Makoto Tsubota,
Hideki Ishihara
Categories: cond-mat.other
Report-no: OCU-PHYS-305, AP-GR-62, YITP-08-77
\\
We construct quantum field theory in an analogue curved spacetime in
Bose-Einstein condensates based on the Bogoliubov-de Gennes equations, by
identifying quantum particles in curved spacetime with Bogoliubov quasiparticle
excitations in Bose-Einstein condensates. Here, we derive a simple formula
relating the two, which can be used to calculate the particle creation spectrum
by solving the time-dependent Bogoliubov-de Gennes equations. Using our
formulation, we numerically investigate particle creation in an analogue
expanding Universe which can be expressed as Bogoliubov quasiparticles in an
expanding Bose-Einstein condensate. We obtain its spectrum, which follows the
thermal Maxwell-Boltzmann distribution, the temperature of which is
experimentally attainable. This is the first direct numerical simulation for
particle creation and its spectrum in analogue curved spacetime by using a
Bose-Einstein condensate system.
\\ ( http://arxiv.org/abs/0810.3088 , 352kb)
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arXiv:0810.3092
Date: Fri, 17 Oct 2008 08:50:12 GMT (10kb)

Title: Foundation of Statistical Mechanics under experimentally realistic
conditions
Authors: Peter Reimann
Categories: cond-mat.stat-mech
Comments: Accepted in Phys. Rev. Lett
\\
We demonstrate the equilibration of isolated macroscopic quantum systems,
prepared in non-equilibrium mixed states with significant population of many
energy levels, and observed by instruments with a reasonably bound working
range compared to the resolution limit. Both properties are fulfilled under
many, if not all, experimentally realistic conditions. At equilibrium, the
predictions and limitations of Statistical Mechanics are recovered.
\\ ( http://arxiv.org/abs/0810.3092 , 10kb)
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arXiv:0810.3036
Date: Thu, 16 Oct 2008 22:24:19 GMT (1687kb,D)

Title: Faddeev-Merkuriev integral equations for atomic three-body resonances
Authors: S Keller, A Marotta and Z Papp
Categories: physics.atom-ph
\\
Three-body resonances in atomic systems are calculated as complex-energy
integral equations are solved by approximating the potential terms in a
Coulomb-Sturmian basis. The Coulomb-Sturmian matrix elements of the three-body
Coulomb Green's operator has been calculated as a contour integral of two-body
Coulomb Green's matrices. This approximation casts the integral equation into a
matrix equation and the complex energies are located as the complex zeros of
the Fredholm determinant. We calculated resonances of the e-Ps system at higher
energies and for total angular momentum L=1 with natural and unnatural parity
\\ ( http://arxiv.org/abs/0810.3036 , 1687kb)
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arXiv:0810.3152
Date: Fri, 17 Oct 2008 13:03:07 GMT (374kb)

Title: Combination of Bloch oscillations with a Ramsey-Bord\'e interferometer :
new determination of the fine structure constant
Authors: Malo Cadoret (LKB - Jussieu), Estefania De Mirandes (LKB - Jussieu),
Pierre Clad\'e (LKB - Jussieu), Sa\"ida Guellati-Kh\'elifa (BNM-INM),
Catherine Schwob (LKB - Jussieu), Fran\c{c}ois Nez (LKB - Jussieu), Lucile
Julien (LKB - Jussieu), Fran\c{c}ois Biraben (LKB - Jussieu)
Categories: physics.atom-ph
\\
We report a new experimental scheme which combines atom interferometry with
Bloch oscillations to provide a new measurement of the ratio
$h/m_{\mathrm{Rb}}$. By using Bloch oscillations, we impart to the atoms up to
1600 recoil momenta and thus we improve the accuracy on the recoil velocity
measurement. The deduced value of $h/m_{\mathrm{Rb}}$ leads to a new
determination of the fine structure constant $\alpha^{-1}=137.035 999 45 (62)$
with a relative uncertainty of $4.6\times 10^{-9}$. The comparison of this
result with the value deduced from the measurement of the electron anomaly
provides the most stringent test of QED.
\\ ( http://arxiv.org/abs/0810.3152 , 374kb)
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arXiv:0810.3263
Date: Fri, 17 Oct 2008 22:00:19 GMT (246kb)

Title: Dirty Bosons: Twenty Years Later
Authors: Peter B. Weichman
Categories: cond-mat.dis-nn cond-mat.supr-con
Comments: 26 pages, 9 figures, submitted to Modern Physics Letters B (Brief
Reviews)
\\
A concise, somewhat personal, review of the problem of superfluidity and
quantum criticality in regular and disordered interacting Bose systems is
given, concentrating on general features and important symmetries that are
exhibited in different parts of the phase diagram, and that govern the
different possible types of critical behavior. A number of exact results for
various insulating phase boundaries, which may be used to constrain the results
of numerical simulations, can be derived using large rare region type
arguments. The nature of the insulator-superfluid transition is explored
through general scaling arguments, exact model calculations in one dimension,
numerical results in two dimensions, and approximate renormalization group
results in higher dimensions. Experiments on He-4 adsorbed in porous Vycor
glass, on thin film superconductors, and magnetically trapped atomic vapors in
a periodic optical potential, are used to illustrate many of the concepts.
\\ ( http://arxiv.org/abs/0810.3263 , 246kb)
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arXiv:0810.3379
Date: Sun, 19 Oct 2008 09:31:52 GMT (543kb)

Title: Making vortices in dipolar spinor condensates via rapid adiabatic
passage
Authors: J.-N. Zhang, L. He, H. Pu, C.-P. Sun, and S. Yi
Categories: cond-mat.other cond-mat.stat-mech
\\
We propose to the create vortices in spin-1 condensates via magnetic
dipole-dipole interaction. Starting with a polarized condensate prepared under
large axial magnetic field, we show that by gradually inverting the field,
population transfer among different spin states can be realized in a controlled
manner. Under optimal condition, we generate a doubly quantized vortex state
containing nearly all atoms in the condensate. The resulting vortex state is a
direct manifestation of the dipole-dipole interaction and spin textures in
spinor condensates. We also point out that the whole process can be
qualitatively described by a simple rapid adiabatic passage model.
\\ ( http://arxiv.org/abs/0810.3379 , 543kb)
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arXiv:0810.3545
Date: Mon, 20 Oct 2008 12:55:33 GMT (2425kb,D)

Title: Quantum noise squeezing and entanglement on the atomic clock transition
Authors: J. Appel, P.J. Windpassinger, D. Oblak, U.B. Hoff, N. Kjaergaard, E.S.
Polzik
Categories: quant-ph
\\
Squeezing of quantum fluctuations by means of entanglement is a well
recognized goal in the field of quantum information science and precision
measurements. In particular, squeezing the fluctuations via entanglement
between two-level atoms can improve the precision of atom clocks and of
spectroscopy in general. Here, we demonstrate 3.4 dB of metrologically relevant
squeezing and entanglement for 10^5 cold caesium atoms via a quantum
nondemolition (QND) measurement on the atom clock levels. We demonstrate the
effect of decoherence inherent to generation of entanglement via a QND
measurement and present a dichromatic QND scheme which allows to minimize the
effect of this decoherence in metrological applications. The spin squeezing
method demonstrated here on the microwave caesium clock transition is
potentially applicable to optical lattice atom clocks.
\\ ( http://arxiv.org/abs/0810.3545 , 2425kb)
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arXiv:0810.3288
Date: Sat, 18 Oct 2008 04:18:55 GMT (694kb)

Title: Effect of resonant interactions on the stability of a three-state Fermi
gas
Authors: J. H. Huckans, J. R. Williams, E. L. Hazlett, R. W. Stites, and K. M.
O'Hara
Categories: physics.atom-ph
\\
We investigate the stability of a three spin state mixture of ultracold
fermionic $^6$Li atoms over a range of magnetic fields encompassing three
Feshbach resonances. For most field values, we attribute decay of the atomic
population to three-body processes involving one atom from each spin state and
find that the three-body loss coefficient varies by over four orders of
magnitude. We observe high stability when at least two of the three scattering
lengths are small, rapid loss near the Feshbach resonances, and two unexpected
resonant loss features. At our highest fields, where all pairwise scattering
lengths are approaching $a_t = -2140 a_0$, we measure a three-body loss
coefficient $L_3 \simeq 5\times 10^{-22} \mathrm{cm}^6/\mathrm{s}$ and a trend
toward lower decay rates for higher fields indicating that future studies of
color superfluidity and trion formation in a SU(3) symmetric Fermi gas may be
feasible.
\\ ( http://arxiv.org/abs/0810.3288 , 694kb)
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arXiv:0810.3720
Date: Tue, 21 Oct 2008 14:49:43 GMT (335kb)

Title: On quenches in non-integrable quantum many-body systems: the
one-dimensional Bose-Hubbard model revisited
Authors: Guillaume Roux
Categories: cond-mat.str-el cond-mat.stat-mech
\\
When a quantum many-body system undergoes a quench, the time-averaged
density-matrix $\rho$ governs the time-averaged expectation value of any
observable. It is consequently the key object to look at when comparing results
with equilibrium predictions. We show that the weights of $\rho$ can be
efficiently computed with Lanczos diagonalization for large Hilbert spaces,
giving a systematic method for studying quenches. As an application, the
non-integrable Bose-Hubbard model is shown to display two regimes: one with an
approximate Boltzmann distribution for small quench amplitudes, and one where
the distributions do not follow standard equilibrium predictions. Some
thermodynamics features of $\rho$, like the energy fluctuations and the
entropy, are also discussed.
\\ ( http://arxiv.org/abs/0810.3720 , 335kb)
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arXiv:0810.3763
Date: Tue, 21 Oct 2008 08:21:44 GMT (60kb)

Title: Feshbach-Einstein condensates
Authors: Valy G. Rousseau, Peter J.H. Denteneer
Categories: cond-mat.stat-mech
\\
We investigate the phase diagram of a two-species Bose-Hubbard model
describing atoms and molecules on a lattice, interacting via a Feshbach
resonance. We identify a region where the system exhibits an exotic super-Mott
phase and regions with phases characterized by atomic and/or molecular
condensates. Our approach is based on a recently developed exact quantum Monte
Carlo algorithm: the Stochastic Green Function algorithm with tunable
directionality. We confirm some of the results predicted by mean-field studies,
but we also find disagreement with these studies. In particular, we find a
phase with an atomic but no molecular condensate, which is missing in all
mean-field phase diagrams.
\\ ( http://arxiv.org/abs/0810.3763 , 60kb)
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arXiv:0810.3775
Date: Tue, 21 Oct 2008 09:45:37 GMT (321kb)

Title: Quantum phases of light coupled to a periodic Bose-Einstein condensate
in a cavity
Authors: Aranya B. Bhattacherjee and ManMohan
Categories: cond-mat.stat-mech
\\
We study a composite photon-Bose condensed atoms (BEC) system in an optical
lattice confined in a cavity. We show that the system is able to produce an
effective photon-photon repulsion in the presence of an external pump. We
predict for the first time zero-temperature quantum phases of light coupled to
BEC in the photon blockade regime in the presence of an external pump.
\\ ( http://arxiv.org/abs/0810.3775 , 321kb)
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arXiv:0810.3797
Date: Tue, 21 Oct 2008 10:50:33 GMT (26kb)

Title: Effective theory for the Goldstone field in the BCS-BEC crossover at T=0
Authors: Juan L. Ma\~nes and Manuel A. Valle
Categories: cond-mat.other cond-mat.supr-con
\\
We perform a detailed study of the effective Lagrangian for the Goldstone
mode of a superfluid Fermi gas at zero temperature in the whole BCS-BEC
crossover. By using a derivative expansion of the response functions, we derive
the most general form of this Lagrangian at the next to leading order in the
momentum expansion in terms of four coefficient functions. This involves the
elimination of all the higher order time derivatives by careful use of the
leading order field equations. In the infinite scattering length limit where
conformal invariance is realized, we show that the effective Lagrangian must
contain an unnoticed invariant combination of higher spatial gradients of the
Goldstone mode, while explicit couplings to spatial gradients of the trapping
potential are absent. Across the whole crossover, we determine all the
coefficient functions at the one-loop level, taking into account the dependence
of the gap parameter on the chemical potential in the mean-field approximation.
These results are analytically expressed in terms of elliptic integrals of the
first and second kind. We discuss the form of these coefficients in the extreme
BCS and BEC regimes and around the unitary limit, and compare with recent work
by other authors.
\\ ( http://arxiv.org/abs/0810.3797 , 26kb)
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arXiv:0810.3812
Date: Tue, 21 Oct 2008 12:37:38 GMT (94kb)

Title: Anderson localization in a correlated fermionic mixture
Authors: O. Fialko and K. Ziegler
Categories: cond-mat.dis-nn
\\
A mixture of two fermionic species with different masses is studied in an
optical lattice. The heavy fermions are subject only to thermal fluctuations,
the light fermions also to quantum fluctuations. We derive the Ising-like
distribution for the heavy atoms and study the localization properties of the
light fermions numerically by a transfer-matrix method. In a two-dimensional
system one-parameter scaling of the localization length is found with a
transition from delocalized states at low temperatures to localized states at
high temperature. The critical exponent of the localization length is
$\nu\approx 0.88$.
\\ ( http://arxiv.org/abs/0810.3812 , 94kb)
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arXiv:0810.3833
Date: Tue, 21 Oct 2008 14:21:40 GMT (987kb)

Title: Unusual states of vortex matter in mixtures of Bose--Einstein
Condensates on rotating optical lattices
Authors: E. K. Dahl, E. Babaev, and A. Sudbo
Categories: cond-mat.stat-mech
Comments: 4 pages, 3 figures. Submitted to Physical Review
\\
A striking property of a single-component superfluid under rotation, is that
a broken symmetry in the order parameter results in a broken translational
symmetry, a vortex lattice. If translational symmetry is restored, the phase of
the order parameter disorders and the broken symmetry in the order parameter is
restored. We show that for Bose-Condensate mixtures on optical lattices (which
may possess a negative dissipationless intercomponent drag), a new situation
arises. A phase disordered nonsuperfluid component can break translational
symmetry in response to rotation due to interaction with a superfluid
component. This state is a modulated vortex liquid which breaks translational
symmetry in the direction transverse to the rotation vector.
\\ ( http://arxiv.org/abs/0810.3833 , 987kb)
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arXiv:0810.3841
Date: Tue, 21 Oct 2008 14:26:01 GMT (605kb)

Title: Quantum micro-mechanics with ultracold atoms
Authors: Thierry Botter, Daniel Brooks, Subhadeep Gupta, Zhao-Yuan Ma, Kevin L.
Moore, Kater W. Murch, Tom P. Purdy, and Dan M. Stamper-Kurn
Categories: quant-ph
Comments: Proceedings of International Conference on Atomic Physics (ICAP) 2008
\\
In many experiments isolated atoms and ions have been inserted into
high-finesse optical resonators for the study of fundamental quantum optics and
quantum information. Here, we introduce another application of such a system,
as the realization of cavity optomechanics where the collective motion of an
atomic ensemble serves the role of a moveable optical element in an optical
resonator. Compared with other optomechanical systems, such as those
incorporating nanofabricated cantilevers or the large cavity mirrors of
the quantum regime. We describe experimental investigations of optomechanical
effects, such as the bistability of collective atomic motion and the first
quantification of measurement backaction for a macroscopic object, and discuss
future directions for this nascent field.
\\ ( http://arxiv.org/abs/0810.3841 , 605kb)
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arXiv:0810.3854
Date: Tue, 21 Oct 2008 14:59:10 GMT (80kb)

Title: Field Compensation of Field Frequency Shifts in the Ramsey Spectroscopy
of Clock Optical Transitions
Authors: A. V. Taichenachev, V. I. Yudin, C. W. Oates, Z. W. Barber and L.
Hollberg
Categories: physics.atom-ph physics.optics
Comments: 5 pages, 3 figures, RevTeX
\\
We develop the method of Ramsey spectroscopy with the use of an additional
field compensating the frequency shifts of clock optical transitions. This
method in combination with the method of magnetically induced excitation of
strongly forbidden transitions $^1S_0$$\to$$^3P_0$ [A.V. Taichenachev, et al.,
Phys. Rev. Lett. {\bf 96}, 083001 (2006)] allows the practically complete
compensation (down to the fractional level below 10$^{-17}$ with respect to the
unperturbed clock frequency) of field shifts of various origin for even
isotopes of alkaline-earth-like atoms confined to an optical lattice at magic
wavelength (lattice-based atomic clocks). Apart from this, the new method can
be used in the two-photon Doppler-free Ramsey spectroscopy of other forbidden
optical transitions (for example, $^1S_0$$\to$$^1S_0$ and $^1S_0$$\to$$^1D_2$)
and other atoms. This opens perspectives for development of principally new
variants of primary optical frequency standards based on free atoms. As a
whole, the method of the shift-compensating field is distinguished by
simplicity and high efficiency, and it can be applied for any transitions in
any atoms and ions.
\\ ( http://arxiv.org/abs/0810.3854 , 80kb)
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arXiv:0810.3876
Date: Tue, 21 Oct 2008 17:15:42 GMT (755kb)

Title: Four-body legacy of the Efimov effect
Authors: Javier von Stecher, Jose P. D'Incao, Chris H. Greene
Categories: physics.atom-ph
\\
Armed with a new solution to the four-body problem, we reanalyze the recent
Innsbruck observation of an Efimov resonance in three-body collisions of cesium
atoms, and show that it provides evidence of new, universal four-body physics
as well. Our theoretical treatment of four bosonic atoms in the limit of strong
two-body attraction suggests a ubiquitous result: namely, that resonantly-bound
states of all four atoms should occur whenever the two-body scattering length
is a specific fraction (0.43) of the value where a three-body Efimov resonance
occurs. A hitherto unanalyzed feature in the 2006 Innsbruck experiment supports
this universal prediction, and it provides the first known evidence to date
that a direct four-body recombination process plays a role. While we confirm
the conclusion reached previously by some studies that no true Efimov effect
exists for four particles, we demonstrate the existence of a universal class of
four-body states that are intimately connected with three-body Efimov states.
\\ ( http://arxiv.org/abs/0810.3876 , 755kb)
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arXiv:0810.4111
Date: Wed, 22 Oct 2008 17:06:26 GMT (1094kb)

Title: Sagnac effect in a chain of mesoscopic quantum rings
Authors: Chris P. Search, John R. E. Toland, and Marko Zivkovic
Categories: cond-mat.mes-hall
\\
The ability to interferometrically detect inertial rotations via the Sagnac
effect has been a strong stimulus for the development of atom interferometry
because of the potential 10^{10} enhancement of the rotational phase shift in
comparison to optical Sagnac gyroscopes. Here we analyze ballistic transport of
matter waves in a one dimensional chain of N coherently coupled quantum rings
in the presence of a rotation of angular frequency, \Omega. We show that the
transmission probability, T, exhibits zero transmission stop gaps as a function
of the rotation rate interspersed with regions of rapidly oscillating finite
transmission. With increasing N, the transition from zero transmission to the
oscillatory regime becomes an increasingly sharp function of \Omega with a
slope \partialT/\partial \Omega N^2. The steepness of this slope dramatically
enhances the response to rotations in comparison to conventional single ring
interferometers such as the Mach-Zehnder and leads to a phase sensitivity well
below the standard quantum limit.
\\ ( http://arxiv.org/abs/0810.4111 , 1094kb)
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arXiv:0810.4149
Date: Wed, 22 Oct 2008 23:05:08 GMT (275kb)

Title: Pairing instability driven by macroscopically degenerate collective
modes in two-dimensional rotating fermion liquids near unitarity
Authors: Predrag Nikolic
Categories: cond-mat.supr-con cond-mat.str-el
\\
Fermionic superfluids can undergo phase transitions into different kinds of
normal regimes, loosely characterized by whether Cooper pairs remain locally
stable. If the normal phase retains strong pairing fluctuations, it behaves
like a liquid of vortices, which has been observed in cuprate superconductors.
We argue that analogous strongly correlated normal states exist in
two-dimensional neutral fermion liquids near unitarity, where superfluid is
destroyed by fast rotation. These states have non-universal properties, and if
they develop as distinct thermodynamic phases they can be characterized as
quantum Hall states of Cooper pairs. The formal analysis is based on a model
with SP(2N) symmetry that describes the quantum critical region in the vicinity
of a broad Feshbach resonance. We explore the pairing phase diagram and
demonstrate that the considered model has macroscopically degenerate bosonic
modes in the normal phase, to all orders in 1/N. It takes finite-range
interactions to lift this degeneracy, making the Abrikosov flux lattice of the
superfluid particularly susceptible to quantum melting.
\\ ( http://arxiv.org/abs/0810.4149 , 275kb)
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arXiv:0810.4199
Date: Thu, 23 Oct 2008 02:38:23 GMT (407kb)

Title: Quantum dynamics of an instabiltiy-induced pulsation in a Bose-Einstein
condensate in an optical lattice
Authors: Uttam Shrestha, Juha Javanainen and Janne Ruostekoski
Categories: cond-mat.other
\\
We study the dynamics of a Bose-Einstein condensate (BEC) in a one
dimensional optical lattice in the limit of weak atom-atom interactions.
Numerically we find that a BEC may develop a pulsating instability in which
atoms nearly periodically collect themselves into a pulse and subsequently
disperse back into the initial homogeneous state. A qualitative explanation of
the quasi-periodic behavior is given by drawing an analogy with a double-well
system. In an extension we introduce quantum effects approximately within
Truncated Wigner Approximation (TWA). In pure classical mean field theory the
condensate shows an undamped pulsating instability, whereas we have observed a
damping in the oscillation when we average over many stochastic realizations.
\\ ( http://arxiv.org/abs/0810.4199 , 407kb)
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arXiv:0810.4207
Date: Thu, 23 Oct 2008 05:08:37 GMT (1065kb)

Title: Localized matter-waves patterns with attractive interaction in rotating
potentials
Authors: Hidetsgu Sakaguchi and Boris Malomed
Categories: cond-mat.stat-mech cond-mat.mes-hall
\\
We consider a two-dimensional (2D) model of a rotating attractive
Bose-Einstein condensate (BEC), trapped in an external potential. First, an
harmonic potential with the critical strength is considered, which generates
quasi-solitons at the lowest Landau level (LLL). We describe a family of the
LLL quasi-solitons using both numerical method and a variational approximation
(VA), which are in good agreement with each other. We demonstrate that kicking
the LLL mode or applying a ramp potential sets it in the Larmor (cyclotron)
motion, that can also be accurately modeled by the VA.
\\ ( http://arxiv.org/abs/0810.4207 , 1065kb)
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arXiv:0810.4206
Date: Thu, 23 Oct 2008 05:13:10 GMT (837kb)

Title: Quantum Optomechanics with Single Atom
Authors: Yue Chang, H. Ian, and C. P. Sun
Categories: quant-ph
\\
The recently increasing explorations for cavity optomechanical coupling
assisted by a single atom or an atomic ensemble have opened an experimentally
accessible fashion to interface quantum optics and nano (micro) -mechanical
systems. In this paper, we study in details such composite quantum dynamics of
photon, phonon and atoms, specified by the triple coupling, which only exists
in this triple hybrid system: The cavity QED system with a movable end mirror.
We exactly diagonalize the Hamiltonian of the triple hybrid system under the
parametric resonance condition. We find that, with the rotating-wave
approximation, the hybrid system is modeled by a generalized spin-orbit
coupling where the orbital angular momentum operator is defined through a
Jordan-Schwinger realization with two bosonic modes, corresponding to the
mirror oscillation and the single mode photon of the cavity. In the
quasi-classical limit of very large angular momentum, this system will behave
like a standard cavity-QED system described by the Jaynes-Cummings model as the
angular momentum operators are transformed to bosonic operators of a single
mode. We test this observation with an experimentally accessible system with
the atom in the cavity with a moving mirror.
\\ ( http://arxiv.org/abs/0810.4206 , 837kb)
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arXiv:0810.4302
Date: Thu, 23 Oct 2008 15:31:18 GMT (308kb,D)

Title: Comparative study of semiclassical approaches to quantum dynamics
Authors: G.Schubert, V.S. Filinov, K. Matyash, R. Schneider, H. Fehske
Categories: quant-ph
Comments: 21 pages, 8 figures, submitted to J. Comp. Phys
\\
Quantum states can be described equivalently by density matrices, Wigner
functions or quantum tomograms. We analyze the accuracy and performance of
three related semiclassical approaches to quantum dynamics, in particular with
respect to their numerical implementation. As test cases, we consider the time
evolution of Gaussian wave packets in different one-dimensional geometries,
whereby tunneling, resonance and anharmonicity effects are taken into account.
The results and methods are benchmarked against an exact quantum mechanical
treatment of the system, which is based on a highly efficient Chebyshev
expansion technique of the time evolution operator.
\\ ( http://arxiv.org/abs/0810.4302 , 308kb)
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arXiv:0810.4208
Date: Thu, 23 Oct 2008 05:34:00 GMT (60kb)

Title: AC Stark shift of the Cs microwave atomic clock transitions
Authors: P. Rosenbusch, S. Ghezali, V. A. Dzuba, V. V. Flambaum, K. Beloy, A.
Derevianko
Categories: physics.atom-ph
\\
We analyze the AC Stark shift of the Cs microwave atomic clock transition
theoretically and experimentally. Theoretical and experimental data are in a
good agreement with each other. Results indicate the absence of a magic
wavelength at which there would be no differential shift of the clock states
having zero projections of the total angular momentum.
\\ ( http://arxiv.org/abs/0810.4208 , 60kb)
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The replacements:

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arXiv:0807.2979
replaced with revised version Mon, 20 Oct 2008 13:03:07 GMT (58kb)

Title: The two-body problem of ultra-cold atoms in a harmonic trap
Authors: Patrick Shea, Brandon P. van Zyl, Rajat K. Bhaduri
Categories: physics.atom-ph cond-mat.other
Comments: Final version accepted for publication in Am. Journ. Phys
\\ ( http://arxiv.org/abs/0807.2979 , 58kb)
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arXiv:0808.3552
replaced with revised version Mon, 20 Oct 2008 06:57:47 GMT (675kb,D)

Title: Dynamical thermalization and vortex formation in stirred 2D
Bose-Einstein condensates
Authors: T. M. Wright, R. J. Ballagh, A. S. Bradley, P. B. Blakie, and C. W.
Gardiner
Categories: cond-mat.other
Comments: 22 pages, 15 figures. v2: Minor refinements made at suggestion of
referee. Discussion of other treatments revised. To appear in Phys. Rev. A
\\ ( http://arxiv.org/abs/0808.3552 , 675kb)
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arXiv:0809.4652
replaced with revised version Tue, 21 Oct 2008 22:27:24 GMT (386kb)

Title: Condensation of ideal Bose gas from the analysis of canonical partition
function
Authors: Jeong-Hyuck Park and Sang-Woo Kim
Categories: cond-mat.stat-mech cond-mat.other
Comments: 5 pages, 1 color figure, computing code included; title changed,
presentation improved
\\ ( http://arxiv.org/abs/0809.4652 , 386kb)
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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/
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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 Thu Oct 30 2008 - 09:35:43 EST

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