Non-abelian Yang-Mills in Kundt spacetimes

We present new exact solutions of the Einstein-Yang-Mills system. The solutions are described by a null Yang-Mills field in a Kundt spacetime. They generalize a previously known solution for a metric of $pp$ wave type. The solutions are formally of Petrov type III.Comment: Talk presented at the XXVIII Spanish Relativity Meeting E.R.E. 2005, Oviedo, September 6-10, 2005, to be published by AIP Conference Proceedings, 5 page

Study of alternative geometries for fluidic oscillators by means of computational fluid mechanics

Se estudiará el fllujo en el interior de osciladores fluídicos mediante el uso de un código comercial de Mecánica de Fluidos Computacional.Se estudiarán diferentes diseños y se compararán sus rendimientos.1. Documentación y estudio del estado del arte. 2. Aprendizaje de los conceptos básicos de la Mecánica de Fluidos Computacional. 3. Aprendizaje de los programas ICEM CFD y ANSYS-FLUENT. 4. Selección de las geometrías y parámetros a estudiar.5. Mallado de dichas geometrías mediante ICEM CFD. 5. Simulación mediante ANSYS-FLUENT. 7. Extracción y análisis de resultados. 8. Conclusiones

Iterated nonexpansive mappings

We present a further study on fixed point theory for the so called iterated nonexpansive mappings, that is, mappings which are nonexpansive along the orbits. They are a direct generalization of the contraction type maps studied by Rheinboldt in the late sixties of the last century. This is a wide class of nonlinear mappings including several families of generalized nonexpansive mappings appearing in the recent litherature.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Higher dimensional VSI spacetimes and supergravity

We present the explicit form of higher dimensional VSI spacetimes in arbitrary number of dimensions. We discuss briefly the VSI's in the context of supergravity/strings.Comment: 3 pages, to be published in the Proceedings of the Eleventh Marcel Grossmann Meeting on General Relativit

Cross-border Access to E-Evidence: Framing the Evidence. CEPS in Liberty and Security in Europe No. 2020-02, February 2020

This paper aims at situating the policy discourse accompanying current European Union (EU) initiatives on facilitating access by public authorities to data held by private companies, including in scenarios regarded as crossing jurisdictional borders. More concretely, it contextualises these initiatives in light of the absence of publicly available statistical information on some of the issues which are at the very core of these matters. Firstly, the paper presents the three main current developments, that is, the proposed ‘E-evidence package’, the negotiation of an EU-United States (US) agreement facilitating access to e-evidence for the purpose of judicial cooperation in criminal matters, and the participation of the EU in the negotiations in the Council of Europe on a second additional protocol to the Cybercrime Convention, analysing some of the recurrent messages associated with defending the necessity of all these different measures. The Brief then reviews some of the information upon which are being constructed arguments used to purport the need for these developments, by granting particular attention to the Impact Assessment that accompanied the publication of the ‘E-evidence package’. Finally, it suggests that the absence of statistical data might have implications for the assessment of the proportionality of eventual legislative measures

Berwald spacetimes and very special relativity

In this work we study Berwald spacetimes and their vacuum dynamics, where the latter are based on a Finsler generalization of the Einstein's equations derived from an action on the unit tangent bundle. In particular, we consider a specific class of spacetimes which are non-flat generalizations of the very special relativity (VSR) line element, to which we refer as very general relativity (VGR). We derive necessary and sufficient conditions for the VGR line element to be of Berwald type. We present two novel examples with the corresponding vacuum field equations: a Finslerian generalization of vanishing scalar invariant (VSI) spacetimes in Einstein's gravity as well as the most general homogeneous and isotropic VGR spacetime.Comment: 17 pages, example section updated, journal references adde

Influence of the accommodation coefficient on nonlinear bubble oscillations

This paper numerically investigates the effect of mass transfer processes on spherical single bubble dynamics using the Hertz–Langmuir–Knudsen approximation for the mass flux across the interface. Bubble behavior, with and without mass transfer, is studied for different values of pressure wave amplitude and frequency, as well as initial bubble radius. Whereas mass transfer processes do not seem to play a significant role on the bubble response for pressure amplitudes smaller than 0.9 atm, they appear to have an important effect when the amplitude is greater than or equal to 1 atm. For the later case, where the minimum liquid pressure reaches values around its vapor pressure, the importance of mass transfer depends on frequency. For frequencies in the 10^3–10^5 Hz range and initial bubble radii of the order of tens of microns, bubble implosions with and with no mass transfer are significantly different; smaller radii display a lower sensitivity. In this regime, accurate model predictions must, therefore, carefully select the correct value of the accommodation coefficient. For frequencies greater than 10^5 Hz, as a first approximation mass transfer can be ignored

Supergravity solutions with constant scalar invariants

We study a class of constant scalar invariant (CSI) spacetimes, which belong to the higher-dimensional Kundt class, that are solutions of supergravity. We review the known CSI supergravity solutions in this class and we explicitly present a number of new exact CSI supergravity solutions, some of which are Einstein.Comment: 12 pages; to appear in IJMP