2,984 research outputs found
Entanglement entropy and macroscopic quantum states with dipolar bosons in a triple-well potential
We study interacting dipolar atomic bosons in a triple-well potential within
a ring geometry. This system is shown to be equivalent to a three-site
Bose-Hubbard model. We analyze the ground state of dipolar bosons by varying
the effective on-site interaction. This analysis is performed both numerically
and analytically by using suitable coherent-state representations of the ground
state. The latter exhibits a variety of forms ranging from the su(3) coherent
state in the delocalization regime to a macroscopic cat-like state with fully
localized populations, passing for a coexistence regime where the ground state
displays a mixed character. We characterize the quantum correlations of the
ground state from the bi-partition perspective. We calculate both numerically
and analytically (within the previous coherent-state representation) the
single-site entanglement entropy which, among various interesting properties,
exhibits a maximum value in correspondence to the transition from the cat-like
to the coexistence regime. In the latter case, we show that the ground-state
mixed form corresponds, semiclassically, to an energy exhibiting two
almost-degenerate minima.Comment: 9 pages, 2 figure
Spectral Statistics of the Triaxial Rigid Rotator: Semiclassical Origin of their Pathological Behavior
In this paper we investigate the local and global spectral properties of the
triaxial rigid rotator. We demonstrate that, for a fixed value of the total
angular momentum, the energy spectrum can be divided into two sets of energy
levels, whose classical analog are librational and rotational motions. By using
diagonalization, semiclassical and algebric methods, we show that the energy
levels follow the anomalous spectral statistics of the one-dimensional harmonic
oscillator.Comment: 14 pages with 5 figures, to be published in Int. J. Mod. Phys.
Colloidal hard-rod fluids near geometrically structured substrates
Density functional theory is used to study colloidal hard-rod fluids near an
individual right-angled wedge or edge as well as near a hard wall which is
periodically patterned with rectangular barriers. The Zwanzig model, in which
the orientations of the rods are restricted to three orthogonal orientations
but their positions can vary continuously, is analyzed by numerical
minimization of the grand potential. Density and orientational order profiles,
excess adsorptions, as well as surface and line tensions are determined. The
calculations exhibit an enrichment [depletion] of rods lying parallel and close
to the corner of the wedge [edge]. For the fluid near the geometrically
patterned wall, complete wetting of the wall -- isotropic liquid interface by a
nematic film occurs as a two-stage process in which first the nematic phase
fills the space between the barriers until an almost planar isotropic --
nematic liquid interface has formed separating the higher-density nematic fluid
in the space between the barriers from the lower-density isotropic bulk fluid.
In the second stage a nematic film of diverging film thickness develops upon
approaching bulk isotropic -- nematic coexistence.Comment: 9 pages, 9 figure
Spatial Distribution of Leprosy in the Amazon Region of Brazil
To detect areas with increased case-detection rates, we used spatial scan statistics to identify 5 of 10 clusters of leprosy in the Amazon region of Brazil. Despite increasing economic development, population growth, and road infrastructure, leprosy is endemic to this region, which is a source of case exportation to other parts of Brazil
A chargeless complex vector matter field in supersymmetric scenario
In this paper we construct and study a formulation of a chargeless complex
vector matter field in a supersymmetric framework. To this aim we combine two
no-chiral scalar superfields in order to take the vector component field to
build the chargeless complex vector superpartner where the respective field
strength transforms as matter fields by a global gauge symmetry. To the
aim to deal with consistent terms without breaking the global symmetry
it imposes a choice to the complex combination revealing a kind of symmetry
between the choices and eliminate the extra degrees of freedom consistently
with the supersymmetry. As the usual case the mass supersymmetric sector
contributes as a complement to dynamics of the model. We obtain the equations
of motion of the Proca's type field, for the chiral spinor fields and for the
scalar field on the mass-shell which show the same mass as expected. This work
establishes the firsts steps to extend the analysis of charged massive vector
field in a supersymmetric scenario.Comment: 8 page
Measuring the Spins of Stellar Black Holes: A Progress Report
We use the Novikov-Thorne thin disk model to fit the thermal continuum X-ray
spectra of black hole X-ray binaries, and thereby extract the dimensionless
spin parameter a* = a/M of the black hole as a parameter of the fit. We
summarize the results obtained to date for six systems and describe work in
progress on additional systems. We also describe recent methodological
advances, our current efforts to make our analysis software fully available to
others, and our theoretical efforts to validate the Novikov-Thorne model.Comment: 6 pages, conference proceedings, X-ray Astronomy 2009: Present
Status, Multi-Wavelength Approach and Future Perspectives, AIP, eds. A.
Comastri et al.; list of authors revise
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