Variations of the Lifshitz-van der Waals force between metals immersed in liquids

We present a theoretical calculation of the Lifshitz-van der Waals force between two metallic slabs embedded in a fluid, taking into account the change of the Drude parameters of the metals when in contact with liquids of different index of refraction. For the three liquids considered in this work, water, $CCl_3F$ and $CBr_3F$ the change in the Drude parameters of the metal imply a difference of up to 15% in the determination of the force at short separations. These variations in the force is bigger for liquids with a higher index of refraction.Comment: 2 figures, 1 tabl

Reduction of the Casimir force using aerogels

By using silicon oxide based aerogels we show numerically that the Casimir force can be reduced several orders of magnitude, making its effect negligible in nanodevices. This decrease in the Casimir force is also present even when the aerogels are deposited on metallic substrates. To calculate the Casimir force we model the dielectric function of silicon oxide aerogels using an effective medium dielectric function such as the Clausius-Mossotti approximation. The results show that both the porosity of the aerogel and its thickness can be use as control parameters to reduce the magnitude of the Casimir force.Comment: to appear J. Appl. Phy

The role of magnetoplasmons in Casimir force calculations

In this paper we review the role of magneto plasmon polaritons in the Casimir force calculations. By applying an external constant magnetic field a strong optical anisotropy is induced on two parallel slabs reducing the reflectivity and thus the Casimir force. As the external magnetic field increases, the Casimir force decreases. Thus, with an an external magnetic field the Casimir force can be controlled.The calculations are done in the Voigt configuration where the magnetic field is parallel to the slabs. In this configuration the reflection coefficients for TE and TM modes do not show mode conversion.Comment: contribution to QFEXT09, Norman, Oklahoma 200

Pull-in control due to Casimir forces using external magnetic fields

We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.Comment: accepted for publication in App. Phys. Let

Spatial dispersion in Casimir forces: A brief review

We present the basic principles of non-local optics in connection with the calculation of the Casimir force between half-spaces and thin films. At currently accessible distances $L$, non-local corrections amount to about half a percent, but they increase roughly as 1/L at smaller separations. Self consistent models lead to corrections with the opposite sign as models with abrupt surfaces.Comment: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 200

Frequency-dependent Drude damping in Casimir force calculations

The Casimir force is calculated between Au thin films that are described by a Drude model with a frequency dependent damping function. The model parameters are obtained from available experimental data for Au thin films. Two cases are considered; annealed and nonannealed films that have a different damping function. Compared with the calculations using a Drude model with a constant damping parameter, we observe changes in the Casimir force of a few percent. This behavior is only observed in films of no more than 300 $\AA$ thick.Comment: Proceedings of the meeting "60 years of Casimir effect", Brasilia, 200

MPI+OpenMP tasking scalability for the simulation of the human brain

The simulation of the behavior of the Human Brain is one of the most ambitious challenges today with a non-end of important applications. We can find many different initiatives in the USA, Europe and Japan which attempt to achieve such a challenging target. In this work we focus on the most important European initiative (Human Brain Project) and on one of the tools (Arbor). This tool simulates the spikes triggered in a neuronal network by computing the voltage capacitance on the neurons' morphology, being one of the most precise simulators today. In the present work, we have evaluated the use of MPI+OpenMP tasking on top of the Arbor simulator. In this paper, we present the main characteristics of the Arbor tool and how these can be efficiently managed by using MPI+OpenMP tasking. We prove that this approach is able to achieve a good scaling even when computing a relatively low workload (number of neurons) per node using up to 32 nodes. Our target consists of achieving not only a highly scalable implementation based on MPI, but also to develop a tool with a high degree of abstraction without losing control and performance by using MPI+OpenMP tasking.We would like to apreciate the valuable feedback and help provided by Benjamin Cumming and Alexander Peyser. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 720270 (HBP SGA1 and HBP SGA2), from the Spanish Ministry of Economy and Competitiveness under the project Computacion de Altas Prestaciones VII (TIN2015- ´ 65316-P) and the Departament d’Innovacio, Universitats i ´ Empresa de la Generalitat de Catalunya, under project MPEXPAR: Models de Programacio i Entorns d’Execuci ´ o Paral ´ ·lels (2014-SGR-1051). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska Curie grand agreement No.749516Peer ReviewedPostprint (author version

"Vocales" by Mariano Etkin: Towards an Aesthetic Characterization of his Last Works

El presente trabajo se enmarca en el proyecto de investigación “El CLAEM en la escena musical argentina y latinoamericana de la segunda mitad del siglo XX” bajo la dirección del Dr. Edgardo Rodriguez en la FBA-UNLP. Trabajamos sobre la premisa de que el CLAEM fue un evento inédito en Latinoamerica y su presencia significó una bisagra en la escena musical latinoamericana ya que puso en contacto a los compositores locales con las vanguardias de Europa y de Estados Unidos. En este trabajo analizamos la obra Vocales (2013) para piano y barítono del compositor Mariano Etkin (1943-2016). Nuestra hipótesis es que esta obra tiene características que nos permiten hablar de un quiebre particular en la estética de la música del compositor que se ha caracterizado por poseer una concepción temporal no lineal. En Vocales hallamos un proceso de repetición mínimamente variada que se estructura de manera tal que, si bien a nivel microformal los materiales podrían parecer ser estáticos, en la macroforma de la obra ellos interactúan y se desarrollan de forma teleológica al presentar características direccionales a partir del ascenso paulatino del registro o el aumento en las duraciones entre otros procedimientos. A partir del análisis de esta obra, buscamos acercarnos a una caracterización estética de las últimas obras del compositor.This work is part of the research project "The CLAEM in the Argentine and Latin American music scene of the second half of the Twentieth Century" under the direction of Dr. Edgardo Rodriguez at the FBA-UNLP. We work on the premise that CLAEM was an unprecedented event in Latin America and its presence meant a hinge in the Latin American music scene by bringing the avant-garde of Europe and the United States into an institution located in Buenos Aires. In this work we analyze the piece Vocales (2013) for piano and baritone by Mariano Etkin (1943-2016). We argue that this piece has characteristics that show a break in the aesthetics of the composer's music previously signed by a non-linear temporal conception. In Vocales we find a minimally varied repetition process that is structured in such way that, although at a microform level the materials could appear to be static, in the macro-form they interact and develop teleologically by presenting directional characteristics to starting from the gradual ascent of the registry or the increase in durations among other procedures. From the analysis of this work, we seek to approach an aesthetic characterization of the composer's latest works.Asociación Argentina de MusicologíaFacultad de ArtesInstituto Nacional de Musicología "Carlos Vega

Computation of Casimir forces for dielectrics or intrinsic semiconductors based on the Boltzmann transport equation

The interaction between drifting carriers and traveling electromagnetic waves is considered within the context of the classical Boltzmann transport equation to compute the Casimir-Lifshitz force between media with small density of charge carriers, including dielectrics and intrinsic semiconductors. We expand upon our previous work [Phys. Rev. Lett. {\bf 101}, 163203 (2008)] and derive in some detail the frequency-dependent reflection amplitudes in this theory and compute the corresponding Casimir free energy for a parallel plate configuration. We critically discuss the the issue of verification of the Nernst theorem of thermodynamics in Casimir physics, and explicity show that our theory satisfies that theorem. Finally, we show how the theory of drifting carriers connects to previous computations of Casimir forces using spatial dispersion for the material boundaries.Comment: 9 pages, 2 figures; Contribution to Proceedings of "60 Years of the Casimir Effect", Brasilia, June 200

Casimir-like tunneling-induced electronic forces

We study the quantum forces that act between two nearby conductors due to electronic tunneling. We derive an expression for these forces by calculating the flux of momentum arising from the overlap of evanescent electronic fields. Our result is written in terms of the electronic reflection amplitudes of the conductors and it has the same structure as Lifshitz's formula for the electromagnetically mediated Casimir forces. We evaluate the tunneling force between two semiinfinite conductors and between two thin films separated by an insulating gap. We discuss some applications of our results.Comment: 8 pages, 3 figs, submitted to Proc. of QFEXT'05, to be published in J. Phys.