1,948 research outputs found
Performance Analysis of the Multi-pass Transformation for Complex 3D-Stencils on GPUs
Artículo presentado al Congreso Español de Informática 2013Performance Analysis of the Multi-pass Transformation for Complex 3D-Stencils on GPU
Entanglement properties in the Inhomogeneous Tavis-Cummings model
In this work we study the properties of the atomic entanglement in the
eigenstates spectrum of the inhomogeneous Tavis-Cummings Model. The
inhomogeneity is present in the coupling among the atoms with quantum
electromagnetic field. We calculate analytical expressions for the concurrence
and we found that this exhibits a strong dependence on the inhomogeneity.Comment: 5 pages, 5 figure
On the origin of the jet-like radio/X-ray morphology of G290.1-0.8
The origin and evolution of supernova remnants of the mixed-morphology class
is not well understood. Several remnants present distorted radio or X-ray
shells with jet-like structures. G290.1-0.8 (MSH 11-61A) belongs to this class.
We aim to investigate the nature of this supernova remnant in order to unveil
the origin of its particular morphology. We based our work on the study of the
X-ray emitting plasma properties and the conditions imposed by the cold
interstellar medium where the remnant expanded. We use archival radio, HI line
data and X-ray observations from XMM-Newton and Chandra observatories, to study
G290.1-0.8 and its surrounding medium. Spatially resolved spectral analysis and
mean photon energy maps are used to obtain physical and geometrical parameters
of the source. Radio continuum and HI line maps give crucial information to
understand the radio/X-ray morphology. The X-ray images show that the remnant
presents two opposite symmetric bright spots on a symmetry axis running towards
the NW-SE direction. Spectral analysis and mean photon energy maps confirm that
the physical conditions of the emitting plasma are not homogeneous throughout
the remnant. In fact, both bright spots have higher temperatures than the rest
of the plasma and its constituents have not reached ionization equilibrium yet.
HI line data reveal low density tube-like structures aligned along the same
direction. This evidence supports the idea that the particular X-ray morphology
observed is a direct consequence of the structure of the interstellar medium
where the remnant evolved. However, the possibility that an undetected
point-like object, as a neutron star, exists within the remnant and contributes
to the X-ray emission cannot be discarded. Finally, we suggest that a supernova
explosion due to the collapse of a high-mass star with a strong bipolar wind
can explain the supernova remnant morphology.Comment: 8 pages, 6 figures. Accepted for publication in A&
Capacity Limits of Spectrum-Sharing in Hoyt (Nakagami-q) Fading Channels
A channel capacity analysis is presented in this work for a spectrum-sharing cognitive radio link in which the fading experienced by the signal is modeled with the Hoyt (Nakagami-q) distribution. Based on a novel formulation of the squared Hoyt distribution derived by the authors, simple expressions for the capacity of the secondary link in a number of scenarios of interest are derived, which are given in terms of easy-to-compute finite-range integrals of elementary functions. The effect of fading severity in the secondary transmitter-primary receiver (ST-PR) and secondary transmitter-secondary receiver (ST-SR) links, and the impact of different antenna gains on the system performance are analyzed. We show that in the presence of severe fading for the ST-PR link, the capacity of the ST-SR link is increased.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO. Fondos FEDER. European Union Marie-Curie COFUND U-mobility program
Abrupt Changes in the Dynamics of Quantum Disentanglement
Entanglement evolution in high dimensional bipartite systems under
dissipation is studied. Discontinuities for the time derivative of the lower
bound of entanglement of formation is found depending on the initial conditions
for entangled states. This abrupt changes along the evolution appears as
precursors of entanglement sudden death.Comment: 4 pages and 6 figures, submitted for publicatio
Large Nc scaling of meson masses and decay constants
We perform an ab initio calculation of the Nc scaling of the low-energy couplings of the chiral Lagrangian of low-energy strong interactions, extracted from the mass dependence of meson masses and decay constants. We compute these observables on the lattice with four degenerate fermions, Nf= 4 , and varying number of colours, Nc= 3 –6, at a lattice spacing of a≃ 0.075 fm. We find good agreement with the expected Nc scaling and measure the coefficients of the leading and subleading terms in the large Nc expansion. From the subleading Nc corrections, we can also infer the Nf dependence, that we use to extract the value of the low-energy couplings for different values of Nf. We find agreement with previous determinations at Nc= 3 and Nf= 2 , 3 and also, our results support a strong paramagnetic suppression of the chiral condensate in moving from Nf= 2 to Nf=
Plateau insulator transition in graphene
The quantum Hall effect in a single-layer graphene sample is studied in
strong magnetic fields up to 28 T. Our measurements reveal the existence of a
metal- insulator transition from filling factor to . The value
of the universal scaling exponent is found to be in graphene and
therefore in a truly two-dimensional system. This value of is in
agreement with the accepted universal value for the plateau-insulator
transitions in standard quasi two-dimensional electron and hole gases.Comment: 10 pages, 5 figure
El papel de la administración pública en el fomento y planificación del ecoturismo en la montaña española
En esta comunicación se presentan los primeros resultados de un estudio específico sobre el papel de las administraciones públicas en el fomento y planificación del ecoturismo en los destinos de montaña españoles. Los resultados permiten verificar la hipótesis sobre el protagonismo estructural de la gestión pública del turismo en la montaña española y, a su vez, refuerzan las evidencias que avalan la aportación del ecoturismo a los procesos de renovación turística de las áreas de montaña españolas en la última década. En relación con la metodología, dos referencias de interés: el estudio se ha centrado en el análisis de las características e implementación de los instrumentos de fomento y planificación en los últimos quince años, principalmente, con el propósito de constatar el cambio implícito en el planteamiento inicial del estudio; y, por otra parte, el análisis contempla los distintos niveles de gestión pública (administración central y administración regional)
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