Matt's arXiv selection, Monday 27th March 2006.

From: Matthew Davis <>
Date: Mon, 27 Mar 2006 08:43:51 +1000 (EST)

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Dr M. J. Davis,               Senior Lecturer in Physics
School of Physical Sciences,  email:
University of Queensland,     ph   : +61 7 334 69824
Brisbane, QLD 4072,           fax  : +61 7 336 51242
Paper: cond-mat/0603454
Date: Fri, 17 Mar 2006 09:53:39 GMT   (463kb)
Title: Self-localized impurities embedded in a one dimensional Bose-Einstein
   condensate and their quantum fluctuations
Authors: Krzysztof Sacha and Eddy Timmermans
Comments: 7 pages, 5 figures
Subj-class: Other
   We consider the self-localization of neutral impurity atoms in a
Bose-Einstein condensate in a 1D model. Within the strong coupling approach, we
show that the self-localized state exhibits parametric soliton behavior. The
corresponding stationary states are analogous to the solitons of non-linear
optics and to the solitonic solutions of the Schroedinger-Newton equation
(which appears in models that consider the connection between quantum mechanics
and gravitation). In addition, we present a Bogoliubov-de~Gennes formalism to
describe the quantum fluctuations around the product state of the strong
coupling description. Our fluctuation calculations yield the excitation
spectrum and reveal considerable corrections to the strong coupling
description. The knowledge of the spectrum allows a spectroscopic detection of
the impurity self-localization phenomenon.
\\ ( ,  463kb)
Paper: cond-mat/0603458
Date: Fri, 17 Mar 2006 19:28:02 GMT   (100kb)
Title: Dynamic response of one-dimensional interacting fermions
Authors: M. Pustilnik, M. Khodas, A. Kamenev, L.I. Glazman
Subj-class: Mesoscopic Systems and Quantum Hall Effect; Strongly Correlated
   We evaluate the dynamic structure factor $S(q,\omega)$ of interacting
one-dimensional spinless fermions with a nonlinear dispersion relation. The
combined effect of the nonlinear dispersion and of the interactions leads to
new universal features of $S(q,\omega)$. The sharp peak $S\propto
q\delta(\omega-uq)$, characteristic for the Tomonaga-Luttinger model, broadens
up; $S(q,\omega)$ for a fixed $q$ becomes finite at arbitrarily large $\omega$.
The main spectral weight, however, is confined to a narrow frequency interval
of the width $\delta\omega\sim q^2/m$. At the boundaries of this interval the
structure factor exhibits power-law singularities with exponents depending on
the interaction strength and on the wave number $q$.
\\ ( ,  100kb)
Paper: cond-mat/0603461
Date: Fri, 17 Mar 2006 14:07:49 GMT   (559kb)
Title: Condensation of electron-hole pairs in a degenerate semiconductor at
   room temperature
Authors: Peter P. Vasil'ev and Igor V. Smetenin
Comments: 26 pages, 5 figures Submitted to Physical Review B
Subj-class: Strongly Correlated Electrons
   It has been theoretically shown that in large-density semiconductor plasma
there exist an energy level of a bound electron-hole pair (a composite boson)
at the band gap. Filling this level up occurs through the condensation of
electron-hole pairs with the use of mediating photons of a resonant
electromagnetic field. We have demonstrated that in the case of a strong
degeneracy of the plasma the critical temperature of the condensation is
determined by the Fermi energies of the plasma components rather than the order
parameter D. The critical temperature can exceed 300 K at electron-hole
densities as large as 6.1018 cm-3. The theoretical model is consistent with
available experimental data
\\ ( ,  559kb)
Paper: cond-mat/0603463
Date: Fri, 17 Mar 2006 15:08:23 GMT   (388kb)
Title: Low velocity quantum reflection of Bose-Einstein condensates
Authors: T. A. Pasquini, M. Saba, G. Jo, Y. Shin, W. Ketterle, D. E. Pritchard,
   T. A. Savas, N. Mulders
Comments: 4 figures
Subj-class: Other
   We studied quantum reflection of Bose-Einstein condensates at normal
incidence on a square array of silicon pillars. For incident velocities of
2.5-26 mm/s observations agreed with theoretical predictions that the
Casimir-Polder potential of a reduced density surface would reflect slow atoms
with much higher probability. At low velocities (0.5-2.5 mm/s), we observed
that the reflection probability saturated around 60% rather than increasing
towards unity. We present a simple model which explains this reduced
reflectivity as resulting from the combined effects of the Casimir-Polder plus
mean field potential and predicts the observed saturation. Furthermore, at low
incident velocities, the reflected condensates show collective excitations.
\\ ( ,  388kb)
Paper: quant-ph/0603156
Date: Fri, 17 Mar 2006 17:10:59 GMT   (16kb)
Title: Exploring the Implementation of Quantum Random Walk using Bose-Enstein
Authors: C.M. Chandrashekar
Comments: 5 pages, 2 figures
   We propose a scheme to implement the simplest and best studied version of
quantum random walk, discrete Hadamard walk in one dimension using an
ultra-cold neutral atom, Bose-Einstein condensate (BEC). Implementation of
quantum walk using BEC gives access to the phenomena on a macroscopic scale.
Addressing BEC using lasers to implement quantum random walk appears less
complicated than addressing and analyzing quantum random walk using just cold
neutral atoms. This paper uses stimulated Raman transition technique as unitary
shift operator to impart momentum on coherent macroscopic sample of ultracold
atoms, BEC, which are in schr\"odinger cat state in a far detuned optical
dipole trap. The unitary shift operator followed by Hadamard rotation, rf pulse
for BEC, implements one step of the Hadamard walk and to realize a sizable
number of step, the process is iterated without restoring to intermediate
measurement. With current dipole trap technology for BEC, it should be possible
to implement enough steps to experimentally highlight the discrete quantum
random walk using a macroscopic wave-packet and lead to further exploration of
quantum random walks and its applications.
\\ ( ,  16kb)
Paper: quant-ph/0603158
Date: Fri, 17 Mar 2006 20:32:34 GMT   (41kb)
Title: N Identical Particles Under Quantum Confinement: A Many-Body Dimensional
   Perturbation Theory Approach II, The Lowest-Order Wave Function I
Authors: M. Dunn, D.K. Watson and J.G. Loeser
Comments: 52 pages
   In this paper we continue our development of a dimensional perturbation
theory (DPT) treatment of N identical particles under quantum confinement. DPT
is a beyond-mean-field method which is applicable to both weakly and
strongly-interacting systems and can be used to connect both limits. In a
previous paper we developed the formalism for low-order energies and excitation
frequencies. This formalism has been applied to atoms, Bose-Einstein
condensates and quantum dots. One major advantage of the method is that N
appears as a parameter in the analytical expressions for the energy and so
results for N up to a few thousand are easy to obtain. Other properties
however, are also of interest, for example the density profile in the case of a
BEC,and larger N results are desirable as well. The latter case requires us to
go to higher orders in DPT. These calculations require as input zeroth-order
wave functions and this paper, along with a subsequent paper, addresses this
\\ ( ,  41kb)
Paper: cond-mat/0603469
Date: Fri, 17 Mar 2006 22:49:54 GMT   (166kb)
Title: Dissociation dynamics of resonantly coupled bose-fermi mixtures in an
   optical lattice
Authors: Takahiko Miyakawa and Pierre Meystre
Comments: 9 pages, 10 figures
Subj-class: Other
   We consider the photodissociation of ground-state bosonic molecules trapped
in an optical lattice potential into two-component fermionic atoms. The system
is assumed to be described by a one-band resonantly-coupled Bose-Fermi Hubbard
model. We show that in the strong fermion-fermion interaction limit the
dissociation dynamics is governed by a spin-boson lattice Hamiltonian. In the
framework of a mean-field analysis based on the Gutzwiller ansatz, we then
examine the crossover of the dissociation from a regime of independent
single-site dynamics to a regime of cooperative dynamics as the molecular
tunneling increases. We also identify two types of self-trapping transitions, a
{\it coherent} and an {\it incoherent} one, depending on the ratio of the
repulsive molecule-molecule interaction strength to molecular tunneling.
Finally, we show that in the limits of weak and strong intersite tunneling the
mean-field solutions agree well with the results from the quantum optical
Jaynes-Cummings and Tavis-Cummings models, respectively.
\\ ( ,  166kb)
Paper: cond-mat/0603479
Date: Sun, 19 Mar 2006 00:29:25 GMT   (8kb)
Title: Study of the ground state energy density of a dilute Bose gas in the
   canonical transformation
Authors: Hyun Sik Noh, Sang-Hoon Kim, Chul Koo Kim, and Mukunda P. Das
Comments: 5 pages, 0 figure
Subj-class: Statistical Mechanics
   A ground state energy density of an interacting dilute Bose gas system is
studied in the canonical transformation scheme. It is shown that the
transformation scheme enables us to calculate a higher order correction of
order $n a^3$ in the particle depletion and ground state energy density of a
dilute Bose gas system, which corresponds to the density fluctuation
contribution from the excited states. The coefficient of $n a^3$ term is shown
to be $2(\pi - 8/3)$ for the particle depletion, and $16(\pi - 8/3)$ for the
ground state energy density.
\\ ( ,  8kb)
Paper: cond-mat/0603489
Date: Mon, 20 Mar 2006 04:02:37 GMT   (219kb)
Title: Comment on "Pairing and Phase Separation in a Polarized Fermi Gas" by G.
   B. Partridge, W. Li, R. I. Kamar, Y. Liao, R. G. Hulet, Science 311, 503
Authors: Martin W. Zwierlein and Wolfgang Ketterle
Comments: 5 pages, 2 figures
Subj-class: Superconductivity; Strongly Correlated Electrons
   We show that Partridge et al. (Science 311, 503 (2006)) used inconclusive and
incorrect criteria for superfluidity and phase separation. Simulations of their
experiment suggest that anharmoncities of the trapping potential have caused
the features which were interpreted as a signature of a quantum phase
\\ ( ,  219kb)
Paper: cond-mat/0603498
Date: Mon, 20 Mar 2006 08:55:37 GMT   (682kb)
Title: Pairing in a three component Fermi gas
Authors: T. Paananen, J.-P. Martikainen, and P. Torma
Comments: 10 pages, 3 figures
Subj-class: Superconductivity
   We consider pairing in a three-component gas of degenerate fermions. In
particular, we solve the finite temperature mean-field theory of an interacting
gas for a system where both interaction strengths and fermion masses can be
unequal. At zero temperature we find a a possibility of a quantum phase
transition between states associated with pairing between different pairs of
fermions. On the other hand, finite temperature behavior of the three-component
system reveals some qualitative differences from the two-component gas: for a
range of parameters it is possible to have two different critical temperatures.
The lower one corresponds to a transition between different pairing channels,
while the higher one corresponds to the usual superfluid-normal transition. We
discuss how these phase transitions could be observed in ultracold gases of
fermionic atoms.
\\ ( ,  682kb)
Paper: cond-mat/0603508
Date: Mon, 20 Mar 2006 11:10:42 GMT   (36kb)
Title: Comment on ``Sound velocity and multibranch Bogoliubov spectrum of an
   elongated Fermi superfluid in the BEC-BCS crossover"
Authors: P. Capuzzi, P. Vignolo, F. Federici, and M. P. Tosi
Comments: Comment on cond-mat/0510160
Subj-class: Other
   The work by T. K. Ghosh and K. Machida [cond-mat/0510160 and Phys. Rev. A 73,
013613 (2006)] on the sound velocity in a cylindrically confined Fermi
superfluid obeying a power-law equation of state is shown to make use of an
improper projection of the sound wave equation. This inaccuracy fully accounts
for the difference between their results and those previously reported by
Capuzzi et al. [cond-mat/0509323 and Phys. Rev. A 73, 021603(R) (2006)]. In
this Comment we show that both approaches lead exactly to the same result when
the correct weight function is used in the projection. Plots of the correct
behavior of the phonon and monopole-mode spectra in the BCS, unitary, and BEC
limits are also shown.
\\ ( ,  36kb)
Paper: cond-mat/0603513
Date: Mon, 20 Mar 2006 12:59:54 GMT   (70kb)
Title: Ultra Cold Atoms in Incommensurate 1D Optical Lattices - an Interacting
   Aubry-Andre Model
Authors: Nir Bar-Gill, Rami Pugatch, Eitan Rowen, Nadav Katz, and Nir Davidson 
Comments: 5 pages, 4 figures Subj-class: Disordered Systems and Neural Networks 
   We study theoretically a BEC loaded into an optical lattice in the
tight-binding regime, with a second, incommensurate lattice acting as a
perturbation. We find, using direct diagonalization of small systems and a
large scale, number conserving mean field approach, the phase diagram of the
model. We show that the superfluid, Mott-insulator and Bose-glass phases
familiar from disordered systems appear here as well, with a localization
transition occurring already in a 1D geometry, contrary to the well known
Anderson localization. These results, together with calculations we have
performed for realistic scenarios, suggest that this setup is well suited for
available experimental realizations.
\\ ( ,  70kb)
Paper: cond-mat/0603523
Date: Mon, 20 Mar 2006 17:37:16 GMT   (168kb)
Title: The dynamics of superfluid 4He
Authors: Wouter Montfrooij, Eric Svensson, Rolf Verberg, Roelof Crevecoeur,
   Ignatz de Schepper
Comments: 12 pages, 4 figures. Material closely related to W. Montfrooij and
   E.C. Svensson, Journal of Low Temperature Physics, Vol. 121, p. 293-302
Subj-class: Other
   We present neutron scattering results for the dynamic response by superfluid
and normal-fluid 4He and the results of a simple perturbation-theory analysis
which allows us to describe all aspects of the observed behavior by considering
only density fluctuations. We show that the three key features that are
characteristic of the dynamic reponse of superfluid 4He, as well as their
dramatic variations with temperature, can be attributed predominantly to the
Bose statistics obeyed by all the 4He atoms. It appears that the presence of
the Bose condensate exerts at most a minor influence on the dynamic response.
\\ ( ,  168kb)
Paper: cond-mat/0512565
replaced with revised version Sat, 18 Mar 2006 19:09:40 GMT   (39kb)
Title: Asymmetries in the tunneling probability of Bose-Einstein condensate in
   an accelerating optical lattice
Authors: Valery S. Shchesnovich, Solange B. Cavalcanti
Comments: 23 pages, 7 figures. Revised section V and changed figure 7. To
   appear in J. Phys. B: Atomic, Molecular and Optical Physics
Subj-class: Other
\\ ( ,  39kb)
Paper: cond-mat/0603404
replaced with revised version Sat, 18 Mar 2006 00:38:53 GMT   (134kb)
Title: Dynamical vanishing of the order parameter in a fermionic condensate
Authors: Emil A. Yuzbashyan and Maxim Dzero
Comments: 4 pages, 3 figures, minor polishing
Subj-class: Superconductivity; Other
\\ ( ,  134kb)
Paper: physics/0603157
Date: Mon, 20 Mar 2006 02:21:10 GMT   (242kb)
Title: Electrodynamic trapping of spinless neutral atoms with an atom chip
Authors: T. Kishimoto, H. Hachisu, J. Fujiki, K. Nagato, M. Yasuda, and H.
Comments: 4pages, 4figures, to appear in Phys. Rev. Lett
Subj-class: Atomic Physics
   Three dimensional electrodynamic trapping of neutral atoms has been
demonstrated. By applying time-varying inhomogeneous electric fields with
micron-sized electrodes, nearly $10^2$ strontium atoms in the $^1S_0$ state
have been trapped with a lifetime of 80 ms. In order to design the electrodes,
we numerically analyzed the electric field and simulated atomic trajectories in
the trap, which showed reasonable agreement with the experiment.
\\ ( ,  242kb)
Paper: physics/0603145
Date: Fri, 17 Mar 2006 21:14:10 GMT   (268kb)
Title: Slow Light Propagation in a Linear-Response Three-Level Atomic Vapor
Authors: Wenhai Ji, Chunbai Wu and M. G. Raymer
Comments: 15 pages, 8 figures
Subj-class: Optics
   We observe pulse delays of up to twenty times the input pulse duration when
200-ps laser pulses pass through a hot Rb 85 vapor cell. The pulse peak travels
with a velocity equal to c/20, and the transmission is 5%. The measurements are
in good agreement with a three-level linear-dispersion calculation. We are able
to control the amount of delay by using a steady-state laser beam for optical
pumping of the ground states prior to sending in the test pulse.
\\ ( ,  268kb)
Paper: physics/0509211
replaced with revised version Fri, 17 Mar 2006 01:23:56 GMT   (1000kb)
Title: Trap-induced resonances in controlled collisions of cesium atoms
Authors: Rene Stock and Ivan H. Deutsch
Comments: 9 pages, 8 figures, 1 table
Subj-class: Atomic Physics; Other; Quantum Physics
Journal-ref: Physical Review A 73, 032701 (2006)
\\ ( ,  1000kb)
Paper: cond-mat/0603561
Date: Tue, 21 Mar 2006 20:14:13 GMT   (697kb)
Title: Time evolution and matter wave interference in Fermi condensates
Authors: Wei Zhang and C. A. R. Sa de Melo
Comments: 4 pages, 4 figures
Subj-class: Strongly Correlated Electrons
   We discuss matter wave interference of Fermi condensates in strongly coupled
s-wave and p-wave channels and the time evolution of a single cloud upon
release from trap. In s-wave systems, where the order parameter is a complex
scalar, we find that the interference patterns depend on the relative phase of
the order parameters of the condensates. In p-wave systems involving the
mixture of two-hyperfine states, we show that the interference pattern exhibits
a polarization effect depending on the relative orientation of the two vector
order parameters. However, in p-wave systems involving a single hyperfine
state, we show that this angular effect reduces to an overall phase difference
between the two interfering clouds, similar to s-wave. Lastly, we also point
out that p-wave Fermi condensates exhibit an anisotropic expansion, reflecting
the spatial anisotropy of the underlying interaction between fermions and the
orbital nature of the vector order parameter.
\\ ( ,  697kb)
Paper: cond-mat/0603190
replaced with revised version Tue, 21 Mar 2006 05:14:25 GMT   (18kb)
Title: Realization, Characterization, and Detection of Novel Superfluid Phases
   with Pairing between Unbalanced Fermion Species
Authors: Kun Yang
Comments: This is an invited contribution to a book titled "Pairing beyond BCS
   Theory in Fermionic Systems" (Mark Alford, John Clark and Armen Sedrakian,
   eds.), to be published by World Scientific. 21 pages. V4: added more
Subj-class: Superconductivity
\\ ( ,  18kb)
Paper: quant-ph/0603185 Date: Tue, 21 Mar 2006 19:17:15 GMT   (260kb)
Title: Lasing and cooling in a hot cavity
Authors: Thomas Salzburger Helmut Ritsch
Comments: 11 pages, 6 figures
   We present a microscopic laser model for many atoms coupled to a single
cavity mode, including the light forces resulting from atom-field momentum
exchange. Within a semiclassical description, we solve the equations for atomic
motion and internal dynamics to obtain analytic expressions for the optical
potential and friction force seen by each atom. When optical gain is maximum at
frequencies where the light field extracts kinetic energy from the atomic
motion, the dynamics combines optical lasing and motional cooling. From the
corresponding momentum diffusion coefficient we predict sub-Doppler
temperatures in the stationary state. This generalizes the theory of cavity
enhanced laser cooling to active cavity systems. We identify the gain induced
reduction of the effective resonator linewidth as key origin for the faster
cooling and lower temperatures, which implys that a bad cavity with a gain
medium can replace a high-Q cavity. In addition, this shows the importance of
light forces for gas lasers in the low-temperature limit, where atoms can
arrange in a periodic pattern maximizing gain and counteracting spatial hole
burning. Ultimately, in the low temperature limit, such a setup should allow to
combine optical lasing and atom lasing in single device.
\\ ( ,  260kb)
Paper: cond-mat/0603590
Date: Wed, 22 Mar 2006 19:46:54 GMT   (249kb)
Title: Adiabatic loading of a Bose-Einstein condensate in a 3D optical lattice
Authors: T. Gericke, F. Gerbier, A. Widera, S. Foelling, O. Mandel, and I.
Subj-class: Other
   We experimentally investigate the adiabatic loading of a Bose-Einstein
condensate into an optical lattice potential. The generation of excitations
during the ramp is detected by a corresponding decrease in the visibility of
the interference pattern observed after free expansion of the cloud. We focus
on the superfluid regime, where we show that the limiting time scale is related
to the redistribution of atoms across the lattice by single-particle tunneling.
\\ ( ,  249kb)
Paper: cond-mat/0511684
replaced with revised version Wed, 22 Mar 2006 04:26:54 GMT   (745kb)
Title: Critical fluctuations in a soliton formation of attractive Bose-Einstein
Authors: Rina Kanamoto, Hiroki Saito, Masahito Ueda
Comments: 14 pages, 13 figures
Subj-class: Other
Journal-ref: Phys. Rev. A 73, 033611 (2006)
\\ ( ,  745kb)
Paper: physics/0512151
replaced with revised version Wed, 22 Mar 2006 17:58:00 GMT   (448kb)
Title: Double-impulse magnetic focusing of launched cold atoms
Authors: Aidan S Arnold, Matthew J Pritchard, David A Smith and Ifan G Hughes
Comments: 14 pages, 6 figures. Accepted for publication in New Journal of
Subj-class: Atomic Physics; Optics
\\ ( ,  448kb)
Paper: cond-mat/0603601
Date: Thu, 23 Mar 2006 00:11:51 GMT   (32kb)
Title: Two-band superfluidity from the BCS to the BEC limit
Authors: M. Iskin and C. A. R. S{\'a} de Melo
Comments: 4 pages and 3 figures
Subj-class: Superconductivity; Other
   We analyze the evolution of two-band superfluidity from the weak coupling
Bardeen-Cooper-Schrieffer (BCS) to the strong coupling Bose-Einstein
condensation (BEC) limit. When the interband interaction is tuned from negative
to positive values, a quantum phase transition occurs from a 0-phase to a
$\pi$-phase state, depending on the relative phase of two order parameters.
Furthermore, population imbalances between the two bands can be created by
tuning the intraband or interband interactions. We also find two undamped low
energy collective excitations corresponding to in-phase and out-of-phase modes.
Lastly, we derive the coupled Ginzburg-Landau equations, and show that they
reduce to coupled Gross-Pitaevskii equations for two types of bosons in the BEC
\\ ( ,  32kb)
Paper: cond-mat/0603607
Date: Thu, 23 Mar 2006 05:57:26 GMT   (11kb)
Title: Enhancement of variation of fundamental constants in ultracold atom and
   molecule systems near Feshbach resonances
Authors: Cheng Chin, V.V. Flambaum
Subj-class: Other; Disordered Systems and Neural Networks
   Scattering length, which can be measured in Bose-Einstein condensate and
Feshbach molecule experiments, is extremely sensitive to the variation of
fundamental constants, in particular, the electron-to-proton mass ratio
(m_e/m_p or m_e/Lambda_{QCD}, where Lambda_{QCD} is the QCD scale). Based on
single- and two-channel scattering model, we show how the variation of the mass
ratio propagates to the scattering length. Our results suggest that variation
of m_e/m_p on the level of 10^{-11}~10^{-14} can be detected near a narrow
magnetic or an optical Feshbach resonance by monitoring the scattering length
on the 1% level. Derived formulae may also be used to estimate the isotopic
shift of the scattering length.
\\ ( ,  11kb)
Paper: cond-mat/0603631
Date: Thu, 23 Mar 2006 17:23:06 GMT   (511kb)
Title: Atom interferometer based on phase coherent splitting of Bose-Einstein
   condensates with an integrated magnetic grating
Authors: A. G\"unther, S. Kraft, C. Zimmermann, and J. Fort\'agh
Comments: 5 pages, 5 figures
Subj-class: Other
   We report the phase coherent splitting of Bose-Einstein condensates by means
of a phase grating produced near the surface of a micro-electronic chip. A
lattice potential with a period of $4\mu$m is generated by the superposition of
static and oscillating magnetic fields. Precise control of the diffraction is
achieved by controlling the currents in the integrated conductors. The
interference of overlapping diffraction orders is observed after 8ms of
propagation in a harmonic trap and subsequent ballistic expansion of the atomic
ensemble. By analyzing the interference pattern we show a reproducible phase
relation between the diffraction orders with an uncertainty given by the
resolution of the diffraction grating.
\\ ( ,  511kb)
Paper (*cross-listing*): gr-qc/0603089
Date: Wed, 22 Mar 2006 16:25:39 GMT   (671kb)
Title: Stability analysis of sonic horizons in Bose-Einstein condensates
Authors: C. Barcelo, A. Cano, L.J. Garay and G. Jannes
Comments: 14 pages, 7 figures (reduced resolution)
Subj-class: General Relativity and Quantum Cosmology; Other
   We examine the linear stability of various configurations in Bose-Einstein
condensates with sonic horizons. These configurations are chosen in analogy
with gravitational systems with a black hole horizon, a white hole horizon and
a combination of both. We discuss the role of different boundary conditions in
this stability analysis, paying special attention to their meaning in
gravitational terms. We highlight that the stability of a given configuration,
not only depends on its specific geometry, but especially on these boundary
conditions. Under boundary conditions directly extrapolated from those in
standard General Relativity, black hole configurations, white hole
configurations and the combination of both into a black hole--white hole
configuration are shown to be stable. However, we show that under other (less
stringent) boundary conditions, configurations with a single black hole horizon
remain stable, whereas white hole and black hole--white hole configurations
develop instabilities associated to the presence of the sonic horizons.
\\ ( ,  671kb)
Paper: cond-mat/0508106
replaced with revised version Thu, 23 Mar 2006 11:38:56 GMT   (245kb)
Title: Splitting and merging an elongated Bose-Einstein condensate at finite
Authors: A. Mebrahtu, A. Sanpera and M. Lewenstein
Comments: 8 pages, 6 figures
Subj-class: Other
Journal-ref: Phys. Rev. A 73, 033601 (2006)
DOI: 10.1103/PhysRevA.73.033601
\\ ( ,  245kb)
Paper: cond-mat/0512556
replaced with revised version Thu, 23 Mar 2006 10:30:00 GMT   (23kb)
Title: Strongly interacting Fermi gases with density imbalance
Authors: J. Kinnunen, L. M. Jensen, and P. Torma
Comments: Added one reference. Published in PRL
Subj-class: Strongly Correlated Electrons; Other; Superconductivity
Journal-ref: Phys. Rev. Lett. 96, 110403 (2006)
\\ ( ,  23kb)
Paper: quant-ph/0603214
Date: Thu, 23 Mar 2006 18:05:40 GMT   (51kb)
Title: Generation of a squeezed vacuum resonant on Rubidium D_1 line with
   periodically-poled KTiOPO_4
Authors: Takahito Tanimura, Daisuke Akamatsu, Yoshihiko Yokoi, Akira Furusawa,
   and Mikio Kozuma
Comments: 4 pages, 4 figures
   We report generation of a continuous-wave squeezed vacuum resonant on the Rb
D_1 line (795 nm) using periodically poled KTiOPO_4 (PPKTP) crystals. With a
frequency doubler and an optical parametric oscillator based on PPKTP crystals,
we observed a squeezing level of -2.75 +- 0.14 dB and an anti-squeezing level
of +7.00 +- 0.13 dB. This system could be utilized for demonstrating storage
and retrieval of the squeezed vacuum, which is important for the ultra-precise
measurement of atomic spins as well as quantum information processing.
\\ ( ,  51kb)
Paper: quant-ph/0603216
Date: Thu, 23 Mar 2006 18:34:06 GMT   (584kb)
Title: Fourier-limited Raman velocimetry of laser-cooled, polarized, cesium
Authors: Julien Chab\'{e} (PhLAM, CERLA), Hans Lignier (PhLAM, CERLA), Pascal
   Szriftgiser (PhLAM, CERLA), Jean Claude Garreau (PhLAM, CERLA)
Comments: 7 pages, 8 figures, revtex4, submitted to Phys. Rev. A
Proxy: ccsd ccsd-00021689
   We describe and test experimentally a setup allowing efficient optical
pumping of laser-cooled cesium atoms into the F=4, m=0 ground-state Zeeman
sublevel, which is insensitive to magnetic perturbations. High resolution Raman
stimulated spectroscopy is shown to produce Fourier-limited lines, allowing, in
realistic experimental conditions, atomic velocity selection to one-fifth of a
recoil velocity.
\\ ( ,  584kb)
Paper: quant-ph/0603218
Date: Thu, 23 Mar 2006 19:05:47 GMT   (214kb)
Title: A Stern-Gerlach experiment for slow light
Authors: Leon Karpa and Martin Weitz
Comments: 11 pages, 3 figures. Nature Physics, in press
   Electromagnetically induced transparency allows for light transmission
through dense atomic media by means of quantum interference. Media exhibiting
electromagnetically induced transparency have very interesting properties, such
as extremely slow group velocities. Associated with the slow light propagation
are quasiparticles, the so-called dark polaritons, which are mixtures of a
photonic and an atomic contribution. We here demonstrate that these excitations
behave as particles with a nonzero magnetic moment, which is in clear contrast
to the properties of a free photon. It is found that light passing through a
rubidium gas cell under the conditions of electromagnetically induced
transparency is deflected by a small magnetic field gradient. The deflection
angle is proportional to the optical propagation time through the cell. The
observed beam deflection can be understood by assuming that dark state
polaritons have an effective magnetic moment. Our experiment can be described
in terms of a Stern-Gerlach experiment for the polaritons.
\\ ( ,  214kb)
Received on Mon Mar 27 2006 - 08:43:51 EST

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