2,097 research outputs found
Unearthing wave-function renormalization effects in the time evolution of a Bose-Einstein condensate
We study the time evolution of a Bose-Einstein condensate in an accelerated
optical lattice. When the condensate has a narrow quasimomentum distribution
and the optical lattice is shallow, the survival probability in the ground band
exhibits a steplike structure. In this regime we establish a connection between
the wave-function renormalization parameter and the phenomenon of
resonantly enhanced tunneling.Comment: 12 pages, 3 figures. arXiv admin note: substantial text overlap with
arXiv:1201.628
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
Frenkel-Kontorova model with cold trapped ions
We study analytically and numerically the properties of one-dimensional chain
of cold ions placed in a periodic potential of optical lattice and global
harmonic potential of a trap. In close similarity with the Frenkel-Kontorova
model, a transition from sliding to pinned phase takes place with the increase
of the optical lattice potential for the density of ions incommensurate with
the lattice period. Quantum fluctuations lead to a quantum phase transition and
melting of pinned instanton glass phase at large values of dimensional Planck
constant. The obtained results are also relevant for a Wigner crystal placed in
a periodic potential.Comment: RevTeX, 5 pages, 11 figures, research at
http://www.quantware.ups-tlse.f
Mechanism of Pion Production in p Scattering at 1 GeV/nucleon
The one-pion and two-pion production in the p(alpha, alpha prime)X reaction
at an energy of E{alpha} = 4.2 GeV has been studied by simultaneous
registration of the scattered alpha particles and the secondary pion or proton.
The obtained results demonstrate that the inelastic alpha-particle scattering
on the proton at the energy of the experiment proceeds either through
excitation and decay of Delta resonance in the projectile or through excitation
in the target proton of the Roper resonance, which decays mainly on a nucleon
and a pion or a nucleon and a sigma meson - system of two pions in the isospin
I = 0, S-wave.Comment: 16 pages, 10 figures. Submitted to Proceedings of the XX
International Baldin Seminar on High - Energy Physics Problems, Dubna,
October 4 - 9, 201
Stability of small amplitude normal modes of a Bose-Einstein condensate with a singly quantized vortex confined in an optical lattice
We study the dynamics of a BEC with a singly quantized vortex, placed in the
combined potential of a 1-D (2-D) optical lattice and an axi-symmetric harmonic
trap. A time-dependent variational Lagrangian analysis shows that an optical
lattice helps to stabilize the vortex which in absence of the optical lattice
is unstable. We find that the normal modes are stable only if the depth of the
optical potential is more than a certain critical value. This critical value of
the optical potential depends on the interaction parameter.In general higher
the interaction parameter,lower the value of the optical potential required to
stabilize the vortex. The BEC with the singly quantized vortex is found to be
relatively more unstable in a 2-D optical lattice compared to a 1-D optical
lattice.Comment: Revised version with 11 pages including 1 figur
Atomic micromotion and geometric forces in a triaxial magnetic trap
Non-adiabatic motion of Bose-Einstein condensates of rubidium atoms arising
from the dynamical nature of a time-orbiting-potential (TOP) trap was observed
experimentally. The orbital micromotion of the condensate in velocity space at
the frequency of the rotating bias field of the TOP was detected by a
time-of-flight method. A dependence of the equilibrium position of the atoms on
the sense of rotation of the bias field was observed. We have compared our
experimental findings with numerical simulations. The nonadiabatic following of
the atomic spin in the trap rotating magnetic field produces geometric forces
acting on the trapped atoms.Comment: 4 pages, 4 figure
Facilities for the Energy Frontier of Nuclear Physics
The Relativistic Heavy Ion Collider at BNL has been exploring the energy
frontier of nuclear physics since 2001. Its performance, flexibility and
continued innovative upgrading can sustain its physics output for years to
come. Now, the Large Hadron Collider at CERN is about to extend the frontier
energy of laboratory nuclear collisions by more than an order of magnitude. In
the coming years, its physics reach will evolve towards still higher energy,
luminosity and varying collision species, within performance bounds set by
accelerator technology and by nuclear physics itself. Complementary high-energy
facilities will include fixed-target collisions at the CERN SPS, the FAIR
complex at GSI and possible electron-ion colliders based on CEBAF at JLAB, RHIC
at BNL or the LHC at CERN.Comment: Invited talk at the International Nuclear Physics Conference,
Vancouver, Canada, 4-9 July 2010, to be published in Journal of Physics:
Conference Series. http://inpc2010.triumf.ca
Ion detection in the photoionization of a Rb Bose-Einstein condensate
Two-photon ionization of Rubidium atoms in a magneto-optical trap and a
Bose-Einstein condensate (BEC) is experimentally investigated. Using 100 ns
laser pulses, we detect single ions photoionized from the condenstate with a
35(10)% efficiency. The measurements are performed using a quartz cell with
external electrodes, allowing large optical access for BECs and optical
lattices.Comment: 14 pages, 7 figure
STIRAP transport of Bose-Einstein condensate in triple-well trap
The irreversible transport of multi-component Bose-Einstein condensate (BEC)
is investigated within the Stimulated Adiabatic Raman Passage (STIRAP) scheme.
A general formalism for a single BEC in M-well trap is derived and analogy
between multi-photon and tunneling processes is demonstrated. STIRAP transport
of BEC in a cyclic triple-well trap is explored for various values of detuning
and interaction between BEC atoms. It is shown that STIRAP provides a complete
population transfer at zero detuning and interaction and persists at their
modest values. The detuning is found not to be obligatory. The possibility of
non-adiabatic transport with intuitive order of couplings is demonstrated.
Evolution of the condensate phases and generation of dynamical and geometric
phases are inspected. It is shown that STIRAP allows to generate the
unconventional geometrical phase which is now of a keen interest in quantum
computing.Comment: 9 pages, 6 figures. To be published in Laser Physics (v. 19, n.4,
2009
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