116 research outputs found
Ground State Properties of an Asymmetric Hubbard Model for Unbalanced Ultracold Fermionic Quantum Gases
In order to describe unbalanced ultracold fermionic quantum gases on optical
lattices in a harmonic trap, we investigate an attractive () asymmetric
() Hubbard model with a Zeeman-like magnetic
field. In view of the model's spatial inhomogeneity, we focus in this paper on
the solution at Hartree-Fock level. The Hartree-Fock Hamiltonian is
diagonalized with particular emphasis on superfluid phases. For the special
case of spin-independent hopping we analytically determine the number of
solutions of the resulting self-consistency equations and the nature of the
possible ground states at weak coupling. Numerical results for unbalanced
Fermi-mixtures are presented within the local density approximation. In
particular, we find a fascinating shell structure, involving normal and
superfluid phases. For the general case of spin-dependent hopping we calculate
the density of states and the possible superfluid phases in the ground state.
In particular, we find a new magnetized superfluid phase.Comment: 9 pages, 5 figure
An Origin of CMR: Competing Phases and Disorder-Induced Insulator-to-Metal Transition in Manganites
We theoretically explore the mechanism of the colossal magnetoresistance in
manganese oxides by explicitly taking into account the phase competition
between the double-exchange ferromagnetism and the charge-ordered insulator. We
find that quenched disorder causes a drastic change of the multicritical phase
diagram by destroying the charge-ordered state selectively. As a result, there
appears a nontrivial phenomenon of the disorder-induced insulator-to-metal
transition in the multicritical regime. On the contrary, the disorder induces a
highly-insulating state above the transition temperature where charge-ordering
fluctuations are much enhanced. The contrasting effects provide an
understanding of the mechanism of the colossal magnetoresistance. The obtained
scenario is discussed in comparison with other theoretical proposals such as
the polaron theory, the Anderson localization, the multicritical-fluctuation
scenario, and the percolation scenario.Comment: 16 pages, 7 figures, submitted to Wandlitz Days on Magnetism:
Local-Moment Ferromagnets: Unique Properties for Modern Application
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
We report the first measurement of charged particle elliptic flow in Pb-Pb
collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurement is performed in the central pseudorapidity region
(||<0.8) and transverse momentum range 0.2< < 5.0 GeV/. The
elliptic flow signal v, measured using the 4-particle correlation method,
averaged over transverse momentum and pseudorapidity is 0.087 0.002
(stat) 0.004 (syst) in the 40-50% centrality class. The differential
elliptic flow v reaches a maximum of 0.2 near = 3
GeV/. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow
increases by about 30%. Some hydrodynamic model predictions which include
viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/389
ATLAS sensitivity to top quark and W boson polarization in events
Stringent tests on top quark production and decay mechanisms are provided by
the measurement of the top quark and W boson polarization. This paper presents
a detailed study of these two measurements with the ATLAS detector, in the
semileptonic (ttbar -> W W b bbar -> l nu j1 j2 b bbar) and dileptonic (ttbar
-> W W b bbar -> l nu l nu b bbar) ttbar channels. It is based on leading-order
Monte Carlo generators and on a fast simulation of the detector. A particular
attention is paid to the systematic uncertainties, which dominate the
statistical errors after one LHC year at low luminosity (10 fb^{-1}), and to
the background estimate. Combining results from both channel studies, the
longitudinal component of the W polarization (F\_0) can be measured with a 2%
accuracy and the right-handed component (F\_R) with a 1% precision with 10
fb^{-1}. Even though the top quarks in ttbar pairs are not polarized, a large
asymmetry is expected within the Standard Model in the like-spin versus
unlike-spin pair production. A 4% precision on this asymmetry measurement is
possible with 10 fb^{-1}, after combining results from both channel studies.
These promising results are converted in a sensitivity to new physics, such as
tWb anomalous couplings, top decay to charged Higgs boson, or new s-channels
(heavy resonance, gravitons) in ttbar production.Comment: 41+2 pages, 20 figures, ATLAS scientific note SN-ATLAS-2005-05
Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV
We report on the first measurement of the triangular , quadrangular
, and pentagonal charged particle flow in Pb-Pb collisions at 2.76
TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show
that the triangular flow can be described in terms of the initial spatial
anisotropy and its fluctuations, which provides strong constraints on its
origin. In the most central events, where the elliptic flow and
have similar magnitude, a double peaked structure in the two-particle azimuthal
correlations is observed, which is often interpreted as a Mach cone response to
fast partons. We show that this structure can be naturally explained from the
measured anisotropic flow Fourier coefficients.Comment: 10 pages, 4 figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/387
International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways
Pseudorapidity dependence of the anisotropic flow of charged particles in Pb–Pb collisions at sNN=2.76 TeV
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