Fully covariant and conformal formulation of the Z4 system in a reference-metric approach: comparison with the BSSN formulation in spherical symmetry

We adopt a reference-metric approach to generalize a covariant and conformal version of the Z4 system of the Einstein equations. We refer to the resulting system as ``fully covariant and conformal", or fCCZ4 for short, since it is well suited for curvilinear as well as Cartesian coordinates. We implement this fCCZ4 formalism in spherical polar coordinates under the assumption of spherical symmetry using a partially-implicit Runge-Kutta (PIRK) method and show that our code can evolve both vacuum and non-vacuum spacetimes without encountering instabilities. Our method does not require regularization of the equations to handle coordinate singularities, nor does it depend on constraint-preserving outer boundary conditions, nor does it need any modifications of the equations for evolutions of black holes. We perform several tests and compare the performance of the fCCZ4 system, for different choices of certain free parameters, with that of BSSN. Confirming earlier results we find that, for an optimal choice of these parameters, and for neutron-star spacetimes, the violations of the Hamiltonian constraint can be between 1 and 3 orders of magnitude smaller in the fCCZ4 system than in the BSSN formulation. For black-hole spacetimes, on the other hand, any advantages of fCCZ4 over BSSN are less evident.Comment: 13 pages, 10 figure

Recursos educativos en ciencias de la salud

Este artículo resume la presentación realizada el día 26 de enero de 2004, en el marco del curso de Formación en Metodología de la Investigación organizado por el Instituto de Salud Carlos III. En concreto se revisan los aspectos a tener en cuenta al elaborar un programa formativo como son el proceso de definición de competencias, la elaboración de un programa docente, la elección de las metodologías y estrategias docentes y el rol del profesor

Who receives treatment for alcohol use disorders in the European Union? A cross-sectional representative study in primary and specialized health care

Background Alcohol use disorders (AUDs) are highly prevalent in Europe, but only a minority of those affected receive treatment. It is therefore important to identify factors that predict treatment in order to reframe strategies aimed at improving treatment rates. Methods Representative cross-sectional study with patients aged 18\u201364 from primary health care (PC, six European countries, n = 8476, data collection 01/13\u201301/14) and from specialized health care (SC, eight European countries, n = 1762, data collection 01/13\u201303/14). For descriptive purposes, six groups were distinguished, based on type of DSM-IV AUD and treatment setting. Treatment status (yes/no) for any treatment (model 1), and for SC treatment (model 2) were main outcome measures in logistic regression models. Results AUDs were prevalent in PC (12-month prevalence: 11.8%, 95% confidence interval (CI): 11.2\u201312.5%), with 17.6% receiving current treatment (95%CI: 15.3\u201319.9%). There were clear differences between the six groups regarding key variables from all five predictor domains. Prediction of any treatment (model 1) or SC treatment (model 2) was successful with high overall accuracy (both models: 95%), sufficient sensitivity (model 1: 79%/model 2: 76%) and high specificity (both models: 98%). The most predictive single variables were daily drinking level, anxiety, severity of mental distress, and number of inpatient nights during the last 6 months. Conclusions Variables from four domains were highly predictive in identifying treatment for AUD, with SC treatment groups showing very high levels of social disintegration, drinking, comorbidity and functional losses. Earlier intervention and formal treatment for AUD in PC should be implemented to reduce these high levels of adverse outcomes

Confusing Head-On Collisions with Precessing Intermediate-Mass Binary Black Hole Mergers

We report a degeneracy between the gravitational-wave signals from quasi-circular precessing black-hole mergers and those from extremely eccentric mergers, namely head-on collisions. Performing model selection on numerically simulated signals of head-on collisions using models for quasi-circular binaries we find that, for signal-to-noise ratios of 15 and 25, typical of Advanced LIGO observations, head-on mergers with respective total masses of $M\in (125,300)M_\odot$ and $M\in (200,440)M_\odot$ would be identified as precessing quasi-circular intermediate-mass black hole binaries, located at a much larger distance. Ruling out the head-on scenario would require to perform model selection using currently nonexistent waveform models for head-on collisions, together with the application of astrophysically motivated priors on the (rare) occurrence of those events. We show that in situations where standard parameter inference of compact binaries may report component masses inside (outside) the pair-instability supernova gap, the true object may be a head-on merger with masses outside (inside) this gap. We briefly discuss the potential implications of these findings for the recent gravitational-wave detection GW190521, which we analyse in detail in [Phys. Rev. Lett. 126, 081101]

(Des)encuentros: La ficción televisiva a debate

Desde hace algún tiempo, y curiosamente coincidiendo con el centenario de su nacimiento, muchas voces vienen anunciando la inevitable muerte del cine. Las cifras del torrencial vaciado de las salas son irrebatibles, y múltiples las posibles razones que se congregan para dar con su explicación. El precio de las entradas, la comodidad del consumo doméstico, la piratería, e incluso la baja calidad de los productos que se estrenan en las salas comerciales, son motivos comúnmente defendidos. Sin embargo, todos aquellos que con premura ansiaban encontrar su cadáver no logran encontrarlo, y es que puede que el cine no haya muerto, sino que haya cambiado de aspecto. Así, las ideas del mercado hollywoodiense, al menos las más arriesgadas y diferentes —que casi por norma suelen resultar ser las más interesantes desde un punto de vista científico-crítico— debían buscar una plataforma a través de la cual poder manifestarse. Y esa plataforma la encontró el cine en su hermana pequeña —por edad—: la televisión.For some time, and curiously coinciding with the centenary of its birth, many voices have announced the inevitable death of cinema. Figures from the huge emptying of cinemas are irrefutable, and the possible reasons that explain this fact are numerous. The ticket prices, the comfort of home consumption, hacking, and even the low quality of the products that are shown in cinemas are commonly defended reasons. However, those who were anxious to find cinema’s deceased body can’t find it yet; and that is because maybe cinema is not already dead, but has changed in appearance instead. Thus, the ideas of the Hollywood market, at least the most daring and different, which almost as a rule tend to be the most interesting ones from a scientific and critical point of view, must find a platform through which they will be able to manifest themselves. And cinema has found this platform in its little sister (due to its age): televisio