[Matts-arxiv] Matt's arXiv selection: week ending 29 May 2009

From: Matthew Davis <mdavis_at_physics.uq.edu.au>
Date: Fri, 10 Jul 2009 14:35:14 +1000

Dear subscribers,

I'm still enlisting the help of my colleagues... today we can thank Geoff Lee
again. This mail contains 11 new preprints and 7 replacements.

Date: Mon, 18 May 2009 14:35:04 GMT (869kb)

Title: Single-laser, one beam, tetrahedral magneto-optical trap
Authors: Matthieu Vangeleyn, Paul F. Griffin, Erling Riis, Aidan S. Arnold
Categories: physics.atom-ph
Comments: 8 pages, 6 figures, 2 movies
   We have realised a 4-beam pyramidal magneto-optical trap ideally
suited for future microfabrication. Three mirrors split and steer a single
incoming beam into a tripod of reflected beams, allowing trapping in the
four-beam overlap volume. We discuss the influence of mirror angle on cooling
and trapping, finding optimum efficiency in a tetrahedral configuration. We
demonstrate the technique using an ex-vacuo mirror system to illustrate the
previously inaccessible supra-plane pyramid MOT configuration. Unlike standard
pyramidal MOTs both the pyramid apex and its mirror angle are non-critical and
our MOT offers improved molasses free from atomic shadows in the laser beams.
The MOT scheme naturally extends to a 2-beam refractive version with high
optical access. For quantum gas experiments, the mirror system could also be
used for a stable 3D tetrahedral optical lattice.
\\ ( http://arxiv.org/abs/0905.2897 , 869kb)
Date: Fri, 22 May 2009 13:49:31 GMT (362kb)

Title: Black hole radiation in Bose-Einstein condensates
Authors: Jean Macher and Renaud Parentani
Categories: cond-mat.quant-gas
Comments: revTeX 4, 55 pages single-column, 19 figures
   We study the phonon fluxes emitted when the condensate velocity crosses the
speed of sound, i.e., in backgrounds which are analogue to that of a black
hole. We focus on elongated one dimensional condensates, and on stationary
flows. Our theoretical analysis and numerical results are based on the
Bogoliubov-de-Gennes equation without any further approximation. The spectral
properties of the fluxes and of the long distance density-density correlations
are obtained, with and without an initial temperature. In realistic conditions,
we show that the condensate temperature dominates the fluxes, and thus hides
the presence of the spontaneous emission (the Hawking effect). We also explain
why the temperature amplifies the long distance correlations which are
intrinsic to this effect. This confirms that the correlations pattern offers a
neat signature of the Hawking effect. Optimal conditions to observe the pattern
are discussed.
\\ ( http://arxiv.org/abs/0905.3634 , 362kb)
Date: Fri, 22 May 2009 10:56:15 GMT (328kb)

Title: Collapse instability of solitons in the nonpolynomial Schr\"{o}dinger
   equation with dipole-dipole interactions
Authors: G. Gligoric, A. Maluckov, Lj. Hadzievski, and B. A. Malomed
Categories: cond-mat.quant-gas
Comments: 6 figures
   A model of the Bose-Einstein condensate (BEC) of dipolar atoms, confined in a
combination of a cigar-shaped trap and optical lattice acting in the axial
direction, is studied in the framework of the one-dimensional (1D)
nonpolynomial Schr\"{o}dinger equation (NPSE) with additional terms describing
long-range dipole-dipole (DD) interactions. The NPSE makes it possible to
describe the collapse of localized modes, which was experimentally observed in
the self-attractive BEC confined in tight traps, in the framework of the 1D
description. We study the influence of the DD interactions on the dynamics of
bright solitons, especially as concerns their collapse-induced instability.
Both attractive and repulsive contact and DD interactions are considered. The
results are summarized in the form of stability/collapse diagrams in a
respective parametric space. In particular, it is shown that the attractive DD
interactions may prevent the collapse instability in the condensate with
attractive contact interactions.
\\ ( http://arxiv.org/abs/0905.3660 , 328kb)
Date: Thu, 21 May 2009 18:20:05 GMT (152kb)

Title: Dispersive propagation of ultraslow light in an atomic Bose-Einstein
Authors: Devrim Tarhan, Seckin Sefi, and Ozgur E. Mustecaplioglu
Categories: physics.optics cond-mat.quant-gas quant-ph
Comments: 14 pages, 3 figures
   One dimensional propagation of ultraslow optical pulses in an atomic
Bose-Einstein condensate taking into account the dispersion and the spatial
inhomogeneity is investigated. Analytical and semi-analytical solutions of the
dispersive inhomogeneous wave equation modeling the ultraslow pulse propagation
are developed and compared against the standard wave equation solvers based
upon Cranck-Nicholson and pseudo-spectral methods. The role of curvature of the
trapping potential of the condensate on the amount of dispersion of the
ultraslow pulse is pointed out.
\\ ( http://arxiv.org/abs/0905.3541 , 152kb)
Date: Wed, 20 May 2009 20:00:28 GMT (452kb)

Title: Representation of quantum dynamics of interacting systems through
   classical trajectories
Authors: Anatoli Polkovnikov
Categories: cond-mat.stat-mech cond-mat.quant-gas hep-th quant-ph
Comments: 82 pages (single column), 17 figures
   We formulate representation of quantum dynamics of many-particle interacting
systems through classical trajectories as a perturbative expansion in quantum
fluctuations around the classical limit. We explicitly consider three different
classical limits in the coordinate-momentum representation (corpuscular
classical limit), coherent state representation (wave classical limit), and the
classical limit for spin systems. We describe how one recovers truncated Wigner
approximation (TWA) in the leading order in quantum fluctuations around each of
these limits. Further quantum corrections can be found either in the form of
non-linear response of observables to infinitesimal quantum jumps or
equivalently in terms of stochastic quantum jumps with non-positive weight. We
discuss how one can find both equal and non-equal time correlation functions
within this approach and which correlation functions have casual
representation. Our approach is closely related to phase space methods based on
Weyl quantization, coherent state phase space methods, and Keldysh diagrammatic
technique. We show how both new results and earlier concepts naturally emerge
from combining path-integral approach and the Heisenberg representation. We
illustrate this approach with various examples including sine-Gordon model,
one- and two-dimensional Bose Hubbard model, Dicke model and others.
\\ ( http://arxiv.org/abs/0905.3384 , 452kb)
Date: Sun, 24 May 2009 12:14:26 GMT (399kb)

Title: Anomalous scaling of fermions and order parameter fluctuations at
   quantum criticality
Authors: P. Strack, S. Takei, and W. Metzner
Categories: cond-mat.str-el cond-mat.stat-mech
Comments: 8 pages, 9 figures, submitted to Phys. Rev. B
   We analyze the quantum phase transition between a semimetal and a superfluid
in a model of attractively interacting fermions with a linear dispersion. The
quantum critical properties of this model cannot be treated by the Hertz-Millis
approach since integrating out the fermions leads to a singular Landau-Ginzburg
order parameter functional. We therefore derive and solve coupled
renormalization group equations for the fermionic degrees of freedom and the
bosonic order parameter fluctuations. In two spatial dimensions, fermions and
bosons acquire anomalous scaling dimensions at the quantum critical point,
associated with non-Fermi liquid behavior and non-Gaussian order parameter
\\ ( http://arxiv.org/abs/0905.3894 , 399kb)
Date: Mon, 25 May 2009 19:30:54 GMT (522kb)

Title: Superfluid--Mott Insulator Transition of Light in the Jaynes-Cummings
Authors: Jens Koch, Karyn Le Hur
Categories: cond-mat.other
Comments: 13 pages, 5 figures
   Regular arrays of electromagnetic resonators, in turn coupled coherently to
individual quantum two-level systems, exhibit a quantum phase transition of
polaritons from a superfluid phase to a Mott-insulating phase. The critical
behavior of such a Jaynes-Cummings lattice thus resembles the physics of the
Bose-Hubbard model. We explore this analogy by elaborating on the mean-field
theory of the phase transition, and by presenting several useful mappings which
pinpoint both similarities and differences of the two models. We show that a
field-theory approach can be applied to prove the existence of multicritical
curves analogous to the multicritical points of the Bose-Hubbard model, and we
provide analytical expressions for the position of these curves.
\\ ( http://arxiv.org/abs/0905.4005 , 522kb)
Date: Mon, 25 May 2009 09:00:16 GMT (829kb)

Title: Efimov states in atom-molecular collisions
Authors: M.A. Efremov, L. Plimak, B. Berg, M.Yu. Ivanov and W.P. Schleich
Categories: quant-ph
Comments: 4 pages, 2 figures
   We analyse scattering of a heavy atom off a weakly bound molecule comprising
an identical heavy and a light atom in the Born-Oppenheimer approximation. We
focus on the situation where the heavy atoms are bosons, which was realized in
several experiments. The elastic and inelastic cross sections for the
atom-molecular scattering exhibit a series of resonances corresponding to
three-body Efimov states. Resonances in elastic collisions are accessible
experimentally through thermalization rates, and thus constitute an alternative
way of observing Efimov states.
\\ ( http://arxiv.org/abs/0905.3974 , 829kb)
Date: Tue, 26 May 2009 16:50:06 GMT (65kb)

Title: Random Number Generators: A Survival Guide for Large Scale Simulations
Authors: Stephan Mertens
Categories: cond-mat.stat-mech physics.comp-ph
Comments: Lecture at the summer school "Modern Computation Science", 16-28
   August 2009, Oldenburg (Germany), see http://www.mcs.uni-oldenburg.de/
   Monte Carlo simulations are an important tool in statistical physics, complex
systems science, and many other fields. An increasing number of these
simulations is run on parallel systems ranging from multicore desktop computers
to supercomputers with thousands of CPUs. This raises the issue of generating
large amounts of random numbers in a parallel application. In this lecture we
will learn just enough of the theory of pseudo random number generation to make
wise decisions on how to choose and how to use random number generators when it
comes to large scale, parallel simulations.
\\ ( http://arxiv.org/abs/0905.4238 , 65kb)
Date: Tue, 26 May 2009 17:41:29 GMT (10kb)

Title: Fluctuation-dissipation theorem and harmonic oscillators
Authors: Vincenzo Branchina, Marco Di Liberto, Ivano Lodato
Categories: cond-mat.stat-mech
Comments: 11 pages, no figures
   The question of the "physical meaning" and "origin" of the Bose-Einstein (BE)
factor in the fluctuation-dissipation theorem (FDT) is often raised and this
term is sometimes interpreted as originating from a real harmonic oscillator
composition of the physical system. Such an interpretation, however, is not
really founded. Inspired by the famous work of Caldeira and Leggett, we have
been able to show that, whenever linear response theory is applicable, which is
the main hypothesis under which the FDT is established, any generic bosonic
and/or fermionic system at temperature $T$ can be mapped onto a fictitious
system of harmonic oscillators so that the suscettivity and the mean square of
the fluctuating observable of the real system coincide with the corresponding
quantities of the fictitious one. We claim that it is in this sense, and only
in this sense, that the BE factor can be interpreted in terms of harmonic
oscillators, no other physical meaning can be superimposed to it. At the best
of our knowledge, this is the first time that such a mapping is explicitly
worked out.
\\ ( http://arxiv.org/abs/0905.4254 , 10kb)
Date: Thu, 28 May 2009 13:38:09 GMT (325kb)

Title: Frequency matching in light storage spectroscopy of atomic Raman
Authors: Leon Karpa, Gor Nikoghosyan, Frank Vewinger, Michael Fleischhauer,
   Martin Weitz
Categories: physics.atom-ph physics.optics
Comments: 9 pages, 4 figures. submitted for publication
   We investigate the storage of light in an atomic sample with a lambda-type
coupling scheme driven by optical fields at variable two-photon detuning. In
the presence of electromagnetically induced transparency (EIT), light is stored
and retrieved from the sample by dynamically varying the group velocity. It is
found that for any two-photon detuning of the input light pulse within the EIT
transparency window, the carrier frequency of the retrieved light pulse matches
the two-photon resonance frequency with the atomic ground state transition and
the control field. This effect which is not based on spectral filtering is
investigated both theoretically and experimentally. It can be used for
high-speed precision measurements of the two-photon resonance as employed e.g.
in optical magnetometry.
\\ ( http://arxiv.org/abs/0905.4649 , 325kb)

The replacements:

replaced with revised version Fri, 22 May 2009 11:43:02 GMT (393kb)

Title: Unified picture of superfluidity: From Bogoliubov's approximation to
   Popov's hydrodynamic theory
Authors: N. Dupuis
Categories: cond-mat.other
Comments: v2) 4 pages, 4 figures v3) Revised title + minor changes
Journal-ref: Phys. Rev. Lett. 102, 190401 (2009)
DOI: 10.1103/PhysRevLett.102.190401
\\ ( http://arxiv.org/abs/0901.4631 , 393kb)
replaced with revised version Fri, 22 May 2009 07:57:03 GMT (114kb)

Title: Multimode quantum memory based on atomic frequency combs
Authors: Mikael Afzelius, Christoph Simon, Hugues de Riedmatten, and Nicolas
Categories: quant-ph
Comments: Final version: 9 pages, 3 figures
Journal-ref: Phys. Rev. A 79, 052329 (2009)
\\ ( http://arxiv.org/abs/0805.4164 , 114kb)
replaced with revised version Fri, 22 May 2009 10:03:43 GMT (1138kb,D)

Title: Quantum resonances in an atom-optical delta-kicked harmonic oscillator
Authors: T. P. Billam and S. A. Gardiner
Categories: quant-ph
Comments: 10 pages, 6 figures. Manuscript revised and extended
\\ ( http://arxiv.org/abs/0809.4373 , 1138kb)
replaced with revised version Tue, 26 May 2009 09:31:34 GMT (27kb)

Title: Superfluid Pairing in the Three Component Fermi Gas
Authors: S. Y. Chang, V. R. Pandharipande
Categories: physics.atom-ph
Comments: 4
\\ ( http://arxiv.org/abs/physics/0607008 , 27kb)
replaced with revised version Wed, 27 May 2009 18:45:29 GMT (14kb)

Title: Absence of a Direct Superfluid to Mott Insulator Transition in
   Disordered Bose Systems
Authors: L. Pollet, N.V. Prokof'ev, B. V. Svistunov, M. Troyer
Categories: cond-mat.stat-mech cond-mat.other
Comments: 4 pages, 3 figures; replaced with resubmitted version
\\ ( http://arxiv.org/abs/0903.3867 , 14kb)
replaced with revised version Wed, 27 May 2009 21:24:28 GMT (404kb)

Title: The Finite Temperature Pairing Gap of a Unitary Fermi Gas by Quantum
   Monte Carlo
Authors: P. Magierski, G. Wlazlowski, A. Bulgac and J.E. Drut
Categories: cond-mat.stat-mech nucl-th
Comments: 4 pages, 5 figures. New material, substantial changes
\\ ( http://arxiv.org/abs/0801.1504 , 404kb)
replaced with revised version Thu, 28 May 2009 04:58:07 GMT (1527kb,D)

Title: Suppression of collisional decoherence
Authors: Yoav Sagi, Ido Almog and Nir Davidson
Categories: quant-ph
Comments: 4 pages, 5 figures, typos corrected and a few minor changes
\\ ( http://arxiv.org/abs/0905.0286 , 1527kb)

Till next time,

Dr M. J. Davis,                      Associate Professor in Physics
School of Mathematics and Physics,   ph  : +61 7 334 69824
The University of Queensland,        fax : +61 7 336 51242
Brisbane, QLD 4072,                  mdavis_at_physics.uq.edu.au
Australia.                           www.physics.uq.edu.au/people/mdavis/
Matt's arXiv selection: weekly summary of cold-atom papers from arXiv.org
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Received on Fri Jul 10 2009 - 16:01:01 EST

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