3,455 research outputs found
Scalar Field Dark Matter: head-on interaction between two structures
In this manuscript we track the evolution of a system consisting of two
self-gravitating virialized objects made of a scalar field in the newtonian
limit. The Schr\"odinger-Poisson system contains a potential with
self-interaction of the Gross-Pitaevskii type for Bose Condensates. Our results
indicate that solitonic behavior is allowed in the scalar field dark matter
model when the total energy of the system is positive, that is, the two blobs
pass through each other as should happen for solitons; on the other hand, there
is a true collision of the two blobs when the total energy is negative.Comment: 8 revtex pages, 11 eps figures. v2 matches the published version.
v2=v1+ref+minor_change
Tras la recuperación de una millonaria deuda al Estado
Tras la recuperación de una millonaria deuda al Estad
Helico-conical optical beams self-heal
An optical beam is said to be self-healing when, distorted by an obstacle,
the beam corrects itself upon propagation. In this letter, we show through
experiments supported by numerical simulations, that Helico-conical optical
beams (HCOBs) self-heal. We observe the strong resilience of these beams with
different types of obstructions, and relate this to the characteristics of
their transverse energy flow.Comment: 4 pages, 5 figure
Measuring the translational and rotational velocity of particles in helical motion using structured light
We measure the rotational and translational velocity components of particles
moving in helical motion using the frequency shift they induced to the
structured light beam illuminating them. Under Laguerre-Gaussian mode
illumination, a particle with a helical motion reflects light that acquires an
additional frequency shift proportional to the angular velocity of rotation in
the transverse plane, on top of the usual frequency shift due to the
longitudinal motion. We determined both the translational and rotational
velocities of the particles by switching between two modes: by illuminating
with a Gaussian beam, we can isolate the longitudinal frequency shift; and by
using a Laguerre-Gaussian mode, the frequency shift due to the rotation can be
determined. Our technique can be used to characterize the motility of
microorganisms with a full three-dimensional movement.Comment: 5 pages,5 figure
Direction-sensitive transverse velocity measurement by phase-modulated structured light beams
The use of structured light beams to detect the velocity of targets moving
perpendicularly to the beam's propagation axis opens new avenues for remote
sensing of moving objects. However, determining the direction of motion is
still a challenge since detection is usually done by means of an
interferometric setup which only provides an absolute value of the frequency
shift. Here, we put forward a novel method that addresses this issue. It uses
dynamic control of the phase in the transverse plane of the structured light
beam so that the direction of the particles' movement can be deduced. This is
done by noting the change in the magnitude of the frequency shift as the
transverse phase of the structured light is moved appropriately. We demonstrate
our method with rotating micro-particles that are illuminated by a
Laguerre-Gaussian beam with a rotating phase about its propagation axis. Our
method, which only requires a dynamically configurable optical beam generator,
can easily be used with other types of motion by appropriate engineering and
dynamic modulation of the phase of the light beam.Comment: 5 pages, 4 figure
Effective shell model Hamiltonians from density functional theory: quadrupolar and pairing correlations
We describe a procedure for mapping a self-consistent mean-field theory (also
known as density functional theory) into a shell model Hamiltonian that
includes quadrupole-quadrupole and monopole pairing interactions in a truncated
space. We test our method in the deformed N=Z sd-shell nuclei Ne-20, Mg-24 and
Ar-36, starting from the Hartree-Fock plus BCS approximation of the USD shell
model interaction. A similar procedure is then followed using the SLy4 Skyrme
energy density functional in the particle-hole channel plus a zero-range
density-dependent force in the pairing channel. Using the ground-state solution
of this density functional theory at the Hartree-Fock plus BCS level, an
effective shell model Hamiltonian is constructed. We use this mapped
Hamiltonian to extract quadrupolar and pairing correlation energies beyond the
mean field approximation. The rescaling of the mass quadrupole operator in the
truncated shell model space is found to be almost independent of the coupling
strength used in the pairing channel of the underlying mean-field theory.Comment: 15 pages, 5 figure
Un aporte a la transformación de la cultura de los empleadores a través del teletrabajo basado en las competencias digitales: una propuesta para la gamificación de la educación en el trabajo
El teletrabajo es un mecanismo de contratación que ofrece ventajas para el cumplimiento de los objetivos empresariales. Por un lado, favorece la competitividad en las organizaciones, y por el otro, aporta al mejoramiento de la eficiencia de los teletrabajadores, en el desempeño de sus actividades desde sitios fuera de la empresa. Por este motivo, se requiere el desarrollo de competencias a través de entornos lúdicos que favorezcan sus procesos de enseñanza-aprendizaje. En este artículo se presentan los resultados de una investigación realizada en la ciudad de Bucaramanga (Colombia) a empleadores del sector calzado (N=287), donde se indagó sobre las competencias que requiere el teletrabajador para desempeñarse con eficiencia en su trabajo. Se evidencia que en esta modalidad de contratación se requiere el desarrollo de las competencias digitales y que los entornos lúdicos favorecen el aprendizaje de los teletrabajadores, donde más que el uso de herramientas ofimáticas, se requiere ser responsable, comprometido y cumplir con los deberes, siendo la lectoescritura, la comunicación y la optimización del tiempo las habilidades que favorecen su desempeño laboral. Finalmente, se destaca la necesidad de crear escenarios lúdicos para capacitarlos en las TIC a través de estrategias de gamificación para mejorar sus procesos laborales en la comercialización de los productos de las empresas a través de los medios sociales
Water, land and carbon footprints of Chinese dairy in the past and future
Chinese food consumption shifts towards larger milk consumption. Traditional dairy systems depended on China's grasslands, but modern industrial systems using feed from croplands increase rapidly. The question is whether China can fulfill future milk demand using its natural resources and remain within greenhouse gas emission boundaries. To determine this, this study combines three footprint analyses - water footprint (WF), land footprint (LF) and carbon footprint (CF) - estimated via production chain approach. It compares WFs, LFs and CFs of milk, meat, and manure from six dairy systems in three categories: traditional grazing, traditional mixed, and modern industrial systems. It estimates future footprints for five production scenarios for low and high milk demand. Between 2000 and 2020, industrial systems increased, accounting for 79 % of production in 2020, while traditional production decreased. Traditional grazing systems have large green WFs per kg (17.2 m3), negligible blue WFs and large LFs (46 m2 low quality grassland). Traditional mixed systems have large CFs per kg (2.93 kg CO2) due to low efficiency. Modern industrial systems rely partly on irrigated croplands and have small green WFs, but large blue WFs per kg (0.54 m3), grey WFs (0.24 m3) and small LFs (1.80 m2 cropland). The findings indicate that with dominating industrial systems, milk production relies more on irrigation and limited croplands. In a realistic low demand situation, milk consumption stabilizes. However, consumption triples if the Chinese follow nutritional advice, resulting in 4 to 6 times larger WFs, LFs and CFs in 2035 depending on production scenarios. In 2035, population is largest, from 2035 to 2050 footprints decrease again. However, China cannot produce the milk for a high consumption situation limited by grassland and cropland availability. Alternatively, China could import feed or milk. However, it is questionable whether these huge quantities are available on the global market.</p
Interference pattern in the collision of structures in the BEC dark matter model: comparison with fluids
In order to explore nonlinear effects on the distribution of matter during
collisions within the Bose-Einstein condensate (BEC) dark matter model driven
by the Schr\"odinger-Poisson system of equations, we study the head-on
collision of structures and focus on the interference pattern formation in the
density of matter during the collision process. We explore the possibility that
the collision of two structures of fluid matter modeled with an ideal gas
equation of state also forms interference patterns and found a negative result.
Given that a fluid is the most common flavor of dark matter models, we conclude
that one fingerprint of the BEC dark matter model is the pattern formation in
the density during a collision of structures.Comment: 7 pages, 22 eps figure
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