1,484 research outputs found
An MHD study of SN 1006 and determination of the ambient magnetic field direction
In this work we employ an MHD numerical code to reproduce the morphology
observed for SN 1006 in radio synchrotron and thermal X-ray emission. We
introduce a density discontinuity, in the form of a flat cloud parallel to the
Galactic Plane, in order to explain the NW filament observed in optical
wavelengths and in thermal X-rays. We compare our models with observations. We
also perform a test that contrasts the radio emitting bright limbs of the SNR
against the central region, finding additional support to our results. Our main
conclusion is that the most probable direction of the ambient magnetic field is
on average perpendicular to the Galactic Plane.Comment: 7 pages, 5 figures, accepted by MNRA
3D MHD simulation of polarized emission in SN 1006
We use three dimensional magnetohydrodynamic (MHD) simulations to model the
supernova remnant SN 1006. From our numerical results, we have carried out a
polarization study, obtaining synthetic maps of the polarized intensity, the
Stokes parameter , and the polar-referenced angle, which can be compared
with observational results. Synthetic maps were computed considering two
possible particle acceleration mechanisms: quasi-parallel and
quasi-perpendicular. The comparison of synthetic maps of the Stokes parameter
maps with observations proves to be a valuable tool to discern
unambiguously which mechanism is taking place in the remnant of SN 1006, giving
strong support to the quasi-parallel model.Comment: 6 pages, 4 figures, accepted by MNRA
International Evidence on Stochastic and Deterministic Monetary Neutrality.
We analyze the issue of the impact of multiple breaks on monetary neutrality results, using a long annual international data set. We empirically verify whether neutrality propositions remain addressable (and if so, whether they hold or not), when unit root tests are carried out allowing for multiple structural breaks in the long-run trend function of the variables. It is found that conclusions on neutrality are sensitive to the number and location of breaks. In order to interpret the evidence for structural breaks, we introduce a notion of deterministic monetary neutrality, which naturally arises in the absence of permanent stochastic shocks to the variables.Deterministic and Stochastic Neutrality and Superneutrality of Money, Unit Roots, Structural Breaks, Resampling Methods
On the sensitivity of extrasolar mass-loss rate ranges: HD 209458b a case study
We present a 3D hydrodynamic study of the effects that different stellar wind
conditions and planetary wind structures have on the calculated Ly-
absorptions produced during the transit of HD 209458b. Considering a range of
stellar wind speeds [350-800] km s, coronal temperature
[3-7] K and two values of the polytropic index
[1.01-1.13], while keeping fixed the stellar mass loss rate, we found a
that a range between [3-5] g s give
account for the observational absorption in Ly- measured for the
planetary system. Also, several models with anisotropic evaporation profiles
for the planetary escaping atmosphere were carried out, showing that both, the
escape through polar regions and through the night side yields larger
absorptions than an isotropic planetary wind
Numerical study of the effect of structure and geometry on van der Waals forces
We use multipolar expansions to find the force on a gold coated sphere above
a gold substrate; we study both an empty gold shell and a gold coated
polystyrene sphere. We find four characteristic separation ranges. In the first
region, which for the empty gold shell occurs for distances, d, smaller than
the thickness of the coating, the result agrees with that on a solid gold
sphere and varies as d^(-2); for larger separations there is a region where the
force behaves as if the coating is strictly two dimensional and varies as
d^(-5/2); in the third region the dependence is more unspecific; in the forth
region when d is larger than the radius, the force varies as d^(-4). For
homogeneous objects of more general shapes we introduce a numerical method
based on the solution of an integral equation for the electric field over a
system of objects with arbitrary shapes. We study the effect of shape and
orientation on the van der Waals interaction between an object and a substrate
and between two objects.Comment: 8 pages, presented in the QFEXT07 conference, submitted to Journal of
Physics
The role of geometry on dispersive forces
The role of geometry on dispersive forces is investigated by calculating the
energy between different spheroidal particles and planar surfaces, both with
arbitrary dielectric properties. The energy is obtained in the non-retarded
limit using a spectral representation formalism and calculating the interaction
between the surface plasmons of the two macroscopic bodies. The energy is a
power-law function of the separation of the bodies, where the exponent value
depends on the geometrical parameters of the system, like the separation
distance between bodies, and the aspect ratio among minor and major axes of the
spheroid.Comment: Presneted at QFEXT05, Barcelona 2005. Submitted to J. Phys.
Precio del agua y relocalización del recurso en la economía andaluza. Una aproximación desde un modelo de equilibrio general aplicado
El objetivo de este trabajo consiste en analizar los efectos que tendría un incremento en la tarifa del agua del sector agrario sobre la conservación del recurso, la eficiencia en el consumo y la posible relocalización del mismo entre los diferentes sectores productivos. La política tarifaria se aplicará sobre el sector agrario debido, por un lado, al excesivo consumo de agua realizado por dicho sector y, por otro, al bajo precio pagado por ella. La metodología que se utilizará para alcanzar el objetivo propuesto consistirá en un modelo de equilibrio general aplicado (MEGA), previamente diseñado para el análisis de impuestos directos de la economía andaluza (Cardenete y Sancho, 2003), mejorado y ampliado para incluir las emisiones contaminantes y la introducción de impuestos ambientales (André, Cardenete y Velázquez, 2005). Este modelo se modificará para introducir las variaciones en la tarifa del agua que trataremos de analizar mediante la introducción de un impuesto sobre la estructura de producción.reformas impositivas ambientales, equilibrio general aplicado, precio del agua.
Residual correlations in liquid drop mass calculations
A systematic study of correlations in the chart of calculated masses of
Moller and Nix is presented. It is shown that the differences between the
masses calculated by Moller at al and the measured ones have a well defined
oscillatory component as function of N and Z, which can be removed with an
appropriate fit, reducing significantly the error width, and concentrating the
error distribution on a single peak around zero. The residual correlations can
have important consequences in the errors as signaling the presence of chaos,
as was recently proposed.Comment: 23 pages, 18 figures. A more focused article with imporved figure
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