2,548 research outputs found
Expansion of matter waves in static and driven periodic potentials
We study the non-equilibrium dynamics of cold atoms held in an optical
lattice potential. The expansion of an initially confined atom cloud occurs in
two phases: an initial quadratic expansion followed by a ballistic behaviour at
long times. Accounting for this gives a good description of recent experimental
results, and provides a robust method to extract the effective intersite
tunneling from time-of-flight measurements.Comment: 4 pages, 3 eps figure
Time-resolved measurement of Landau--Zener tunneling in different bases
A comprehensive study of the tunneling dynamics of a Bose--Einstein
condensate in a tilted periodic potential is presented. We report numerical and
experimental results on time-resolved measurements of the Landau--Zener
tunneling of ultracold atoms introduced by the tilt, which experimentally is
realized by accelerating the lattice. The use of different protocols enables us
to access the tunneling probability, numerically as well as experimentally, in
two different bases, namely, the adiabatic basis and the diabatic basis. The
adiabatic basis corresponds to the eigenstates of the lattice, and the diabatic
one to the free-particle momentum eigenstates. Our numerical and experimental
results are compared with existing two-state Landau--Zener models
Possibility of Measuring Azimuthal Anisotropy in Absorption in the ALICE Experiment
The absorption of J/ψ by comovers in the forward rapidity region is predicted to be azimuthally anisotropic as compared to an isotropic Glauber absorption. In the framework of a fast simulation we investigate the possibility of measuring this anisotropy within the ALICE experiment for the J/ψ 's detected in the Di-Muon Spectrometer using the event plane provided by the Photon Multiplicity Detector(PMD). The effect of limitations in the event plane determination on measured J/ψ anisotropy is also investigated
Evolution of a coherent array of Bose-Einstein Condensates in a magnetic trap
We investigate the evolution process of the interference pattern for a
coherent array of Bose-Einstein condensates in a magnetic trap after the
optical lattices are switched off. It is shown that there is a decay and
revival of the density oscillation for the condensates confined in the magnetic
trap. We find that, due to the confinement of the magnetic trap, the
interference effect is much stronger than that of the experiment induced by
Pedri et al. (Phys. Rev. Lett, {\bf 87}, 220401), where the magnetic trap is
switched off too. The interaction correction to the interference effect is also
discussed for the density distribution of the central peak.Comment: RevTex, 17 pages,9 figures. E-mail: [email protected]
Statics, Dynamics and Manipulations of Bright Matter-Wave Solitons in Optical Lattices
Motivated by recent experimental achievement in the work with Bose-Einstein
condensates (BECs), we consider bright matter-wave solitons, in the presence of
a parabolic magnetic trap and a spatially periodic optical lattice (OL), in the
attractive BEC. We examine pinned states of the soliton and their stability by
means of perturbation theory. The analytical predictions are found to be in
good agreement with numerical simulations. We then explore possibilities to use
a time-modulated OL as a means of stopping and trapping a moving soliton, and
of transferring an initially stationary soliton to a prescribed position by a
moving OL. We also study the emission of radiation from the soliton moving
across the combined magnetic trap and OL. We find that the soliton moves freely
(without radiation) across a weak lattice, but suffers strong loss for stronger
OLs.Comment: 7 pages, 5 figs, Phys Rev A in Press (2005
Effect of the lattice alignment on Bloch oscillations of a Bose-Einstein condensate in a square optical lattice
We consider a Bose-Einstein condensate of ultracold atoms loaded into a
square optical lattice and subject to a static force. For vanishing atom-atom
interactions the atoms perform periodic Bloch oscillations for arbitrary
direction of the force. We study the stability of these oscillations for
non-vanishing interactions, which is shown to depend on an alignment of the
force vector with respect to the lattice crystallographic axes. If the force is
aligned along any of the axes, the mean field approach can be used to identify
the stability conditions. On the contrary, for a misaligned force one has to
employ the microscopic approach, which predicts periodic modulation of Bloch
oscillations in the limit of a large forcing.Comment: 4 pages, 3 figure
The Virtual Monte Carlo
The concept of Virtual Monte Carlo (VMC) has been developed by the ALICE
Software Project to allow different Monte Carlo simulation programs to run
without changing the user code, such as the geometry definition, the detector
response simulation or input and output formats. Recently, the VMC classes have
been integrated into the ROOT framework, and the other relevant packages have
been separated from the AliRoot framework and can be used individually by any
other HEP project. The general concept of the VMC and its set of base classes
provided in ROOT will be presented. Existing implementations for Geant3, Geant4
and FLUKA and simple examples of usage will be described.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 8 pages, LaTeX, 6 eps figures. PSN
THJT006. See http://root.cern.ch/root/vmc/VirtualMC.htm
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