An Efficient Implementation of Flux Formulae in Multidimensional Relativistic Hydrodynamical Codes

We derive and analyze a simplified formulation of the numerical viscosity terms appearing in the expression of the numerical fluxes associated to several High-Resolution Shock-Capturing schemes. After some algebraic pre-processing, we give explicit expressions for the numerical viscosity terms of two of the most widely used flux formulae, which implementation saves computational time in multidimensional simulations of relativistic flows. Additionally, such treatment explicitely cancells and factorizes a number of terms helping to amortiguate the growing of round-off errors. We have checked the performance of our formulation running a 3D relativistic hydrodynamical code to solve a standard test-bed problem and found that the improvement in efficiency is of high practical interest in numerical simulations of relativistic flows in Astrophysics.Comment: 10 pages, accepted for publication in Computer Physics Communication

A virtual laboratory designed for teaching diffractive lenses

[EN] We present a virtual laboratory generated in Matlab GuiQc (Graphical User Interface) for its use in Optics courses as an informatic tool for teaching the focusing properties of a diffractive lens. This Gui allows the students to learn easily and rapidly about the influence on the focal volume of the lens construction parameters. As an example in this work we analyze fractal diffractive lenses because we found that fractal geometry is a highly motivating topic for students since it is related to a wide range of scientific and technological phenomena.[ES] En este trabajo presentamos un laboratorio virtual desarrollado en Matlab GuiQc (Interfaz Gráfica con el Usuario) para su uso en los cursos de Óptica como herramienta informática para la enseñanza de las propiedades de focalización de las lentes difractivas. Esta interfaz GUI permite a los estudiantes aprender fácil y rápidamente la influencia de los parámetros constructivos de la lente en el volumen focal. A modo de ejemplo analizamos en este trabajo lentes difractivas fractales porque hemos encontrado que la geometría fractal es un tema muy motivador para los estudiantes ya que está relacionado con un gran número de fenómenos científicos y tecnológicos.Giménez, F.; Monsoriu, J.; Furlan, W.; Pons, A. (2010). A virtual laboratory designed for teaching diffractive lenses. Modelling in Science Education and Learning. 3:29-37. doi:10.4995/msel.2010.3108SWORD2937

Wearable Robots in Rehabilitation Engineering Tremor Suppression

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On the equivalence of the Einstein-Hilbert and the Einstein-Palatini formulations of general relativity for an arbitrary connection

In the framework of the Einstein-Palatini formalism, even though the projective transformation connecting the arbitrary connection with the Levi Civita connection has been floating in the literature for a long time and perhaps the result was implicitly known in the affine gravity community, yet as far as we know Julia and Silva were the first to realise its gauge character. We rederive this result by using the Rosenfeld-Dirac-Bergmann approach to constrained Hamiltonian systems and do a comprehensive self contained analysis establishing the equivalence of the Einstein-Palatini and the metric formulations without having to impose the gauge choice that the connection is symmetric. We also make contact with the the Einstein-Cartan theory when the matter Lagrangian has fermions.Comment: 18 pages. Slight change in the title and wording of some sections to emphasize the main results. References added. Matches published versio

Stability of the lattice formed in first-order phase transitions to matter containing strangeness in protoneutron stars

Well into the deleptonization phase of a core collapse supernova, a first-order phase transition to matter with macroscopic strangeness content is assumed to occur and lead to a structured lattice defined by negatively charged strange droplets. The lattice is shown to crystallize for expected droplet charges and separations at temperatures typically obtained during the protoneutronstar evolution. The melting curve of the lattice for small spherical droplets is presented. The one-component plasma model proves to be an adequate description for the lattice in its solid phase with deformation modes freezing out around the melting temperature. The mechanical stability against shear stresses is such that velocities predicted for convective phenomena and differential rotation during the Kelvin-Helmholtz cooling phase might prevent the crystallization of the phase transition lattice. A solid lattice might be fractured by transient convection, which could result in anisotropic neutrino transport. The melting curve of the lattice is relevant for the mechanical evolution of the protoneutronstar and therefore should be included in future hydrodynamics simulations.Comment: accepted for publication in Physical Review

Anàlisi espacio-temporal de la línia de costa i del foredune del sistema dunar de Sa Canova d’Artà (Mallorca)

[cat] Els sistemes platja-duna, són una de les morfologies sedimentàries més abundants a les Illes Balears. Aquests es troben composats per diferents subsistemes, els quals presenten diferents nivells de dinamisme. Des d’aquest punt de vista, la foredune és el sector més dinàmic de la part emergida del sistema i en la qual la vegetació té un paper clau per al desenvolupament de la resta del sistema. Tots i cada un dels sistemes existents a la comunitat autònoma i a la resta del món disposa d’una condicions/característiques que el fan peculiar i diferent a la resta; a part de les pròpies condicions físiques intrínseques al propi medi, a dia d’avui els sistemes han de fer front a tota una sèrie de pressions d’origen antròpic, destacant especialment l’activitat turística en el cas Balear. El cas d’estudi, és Sa Canova, situada al terme municipal d’Artà (NE de l’illa de Mallorca); aquest sistema tampoc n’és una excepció, al llarg del període d’estudi (1956-2012), ha sofert variacions, tant d’origen natural, com antròpic, les quals han tingut com a conseqüència el sistema dunar actualment existent.[eng] The beach-dune systems, are one of the most abundant sedimentary morphologies in the Balearic Islands. These are composed of different subsystems, which present different levels of dynamism. From this point of view, Foredune is the most dynamic sector of the emerging part of the system and in which vegetation plays a key role for the development of the rest of the system. Each and every one of the existing systems in the autonomous community and the rest of the world has conditions / characteristics that make it peculiar and different from the rest; Apart from the intrinsic physical conditions inherent in their own environment, today, systems have to deal with a whole series of pressures of anthropogenic origin, with special emphasis on tourism in the Balearic Islands. The case study is Sa Canova, located in the municipality of Artà (NE of the island of Mallorca); This system is not an exception either, during the period of study (1956-2012), it has undergone variations, both of natural origin and anthropic, which have resulted in the current dune system

Are Post-Newtonian templates faithful and effectual in detecting gravitational signals from neutron star binaries?

We compute the overlap function between Post-Newtonian (PN) templates and gravitational signals emitted by binary systems composed of one neutron star and one point mass, obtained by a perturbative approach. The calculations are performed for different stellar models and for different detectors, to estimate how effectual and faithful the PN templates are, and to establish whether effects related to the internal structure of neutron stars may possibly be extracted by the matched filtering technique.Comment: 14 pages, 3 figures, accepted for publication in Phys. Rev.