Potential--density pairs for spherical galaxies and bulges: the influence of scalar fields

A family of potential--density pairs has been found for spherical halos and bulges of galaxies in the Newtonian limit of scalar--tensor theories of gravity. The scalar field is described by a Klein--Gordon equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. The net gravitational force is given by two contributions: the standard Newtonian potential plus a term stemming from massive scalar fields. General solutions have been found for spherical systems. In particular, we compute potential--density pairs of spherical galactic systems, and some other astrophysical quantities that are relevant to generating initial conditions for spherical galaxy simulations.Comment: Paper accepted for publication in MNRAS, with four figure

Salud laboral y fisioterapia preventiva en el dolor de espalda

[Resumen] El dolor de espalda es una de las quejas más antiguas del ser humano y su prevalencia en la población general de los países industrializados alcanza del 45 al 85%. En este artículo se abordan tanto los mecanismos de lesión implicados en el dolor de espalda como los factores de riesgo presentes durante la realización de trabajos dinámicos y trabajos estáticos. En el apartado de los mecanismos de lesión se analiza cómo se levantan las cargas y en el apartado de los factores de riesgo se discuten las ventajas y desventajas de mantener las posturas básicas. A partir de este análisis se describen medidas preventivas y se ofrecen recomendaciones ergonómicas para la prevención de este síntoma importante dentro del ámbito de la salud laboral. Se describe la labor preventiva de la Fisioterapia en este campo.[Abstract] The prevalence o/ the backache is one o/ the most ancient complaints o/ the human being, its prevalence among the general population o/ the industrialized countries is between the forty-five and the eighty-five per cent. In this descriptive article, both the injuring mechanisms of the backache and the risk factors during the dynamic and static work are included. In the first one, the lifting of loads is analyzed and in the second, the advantages and disadvantages o/ keeping the basic postures are described. Another two points will also be included; the preventive physioterapic measures and the most useful ergonomic recomendations to prevent one o/ the most important symptoms in any work field

Cosmological simulations using a static scalar-tensor theory

We present $\Lambda$CDM $N$-body cosmological simulations in the framework of a static general scalar-tensor theory of gravity. Due to the influence of the non-minimally coupled scalar field, the gravitational potential is modified by a Yukawa type term, yielding a new structure formation dynamics. We present some preliminary results and, in particular, we compute the density and velocity profiles of the most massive group.Comment: 4 pages, 6 figures, to appear in Journal of Physics: Conference Series: VII Mexican School on Gravitation and Mathematical Physics. 26 November to 1 December 2006, Playa del Carmen, Quintana Roo, Mexic

Evaluación de la asignatura Exploración Topográfica Manual

[Resumen] En este artículo exponemos los objetivos generales y específicos, los contenidos y la metodología de enseñanzas y evaluación de una asignatura de libre configuración ofertada por la Escuela Universitaria de Fisioterapia de la Universidad de A Coruña, cuyo título es Exploración Topográfica Manual[Abstract] A description is made o/ the general and specific aims, content, teaching method and evaluation of an optinal course offered at the University School o/ Physical Therapy o/ La Coruña, Spain, known as Manual Topographic Examination

Probing Yukawian gravitational potential by numerical simulations. I. Changing N-body codes

In the weak field limit general relativity reduces, as is well known, to the Newtonian gravitation. Alternative theories of gravity, however, do not necessarily reduce to Newtonian gravitation; some of them, for example, reduce to Yukawa-like potentials instead of the Newtonian potential. Since the Newtonian gravitation is largely used to model with success the structures of the universe, such as for example galaxies and clusters of galaxies, a way to probe and constrain alternative theories, in the weak field limit, is to apply them to model the structures of the universe. In the present study, we consider how to probe Yukawa-like potentials using N-body numerical simulations.Comment: 17 pages, 11 figures. To appear in General Relativity and Gravitatio

A spherical scalar-tensor galaxy model

We build a spherical halo model for galaxies using a general scalar-tensor theory of gravity in its Newtonian limit. The scalar field is described by a time-independent Klein-Gordon equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. Our model, by construction, fits both the observed rotation velocities of stars in spirals and a typical luminosity profile. As a result, the form of the new Newtonian potential, the scalar field, and dark matter distribution in a galaxy are determined. Taking into account the constraints for the fundamental parameters of the theory (lambda,alpha), we analyze the influence of the scalar field in the dark matter distribution, resulting in shallow density profiles in galactic centers.Comment: 14 pages, 16 plots set in 7 figures, typos and references adde

Patrones de abundancia de los estadios tempranos de la sardina del Pacífico (Sardinops sagax) durante un periodo de enfriamiento en una laguna costera al sur de la corriente de California

Abundance patterns of eggs and larvae of the Pacific sardine, Sardinops sagax (Jenyns, 1842), in Bahía Magdalena, Baja California Sur, were analysed during a cooling period south of the California Current from 2005 to 2009. The thermohaline characteristics and zooplankton abundance were good descriptors of the potential spawning habitat. Individual quotient analyses showed a predominance of eggs and larvae within a SST range of 16 to 18°C, at low salinities (33.9-34.1) and at low density gradient variability (0.009-0.029), associated with deeper waters (25-40 m) near the main entrance, where the transparency was intermediate (6-8 m) and zooplankton abundance was relatively high ( > 316 ml/1000 m3). Increments within different class intervals meant that neither dissolved inorganic nitrogen (DIN), phosphates nor chlorophyll a predominated. The large interannual fluctuations in sardine spawning activity and preferential temperatures observed in historical and recent data suggest that two sardine stocks spawn in Bahia Magdalena: one stock spawned in the period 1981-1989 and one stock spawned in the period 1997-2009. The influence of cooling and warming periods as additional components of the regional environmental framework is analysed and discussed.Los patrones de abundancia de huevos y larvas de la sardina del Pacífico, Sardinops sagax, en Bahía Magdalena, Baja California Sur, fueron analizados durante un periodo de enfriamiento al sur de la Corriente de California de 2005 a 2009. La combinación de las características termohalinas y abundancia del zooplancton fueron buenos indicadores del hábitat potencial del desove. El análisis individual de cocientes mostró una predominancia de huevos y larvas en el intervalo de temperatura superficial del mar entre 16 y 18°C, a baja salinidad (33.9-34.1), y valores bajos de la diferencia del gradiente de densidad (0.009-0.029) asociados a las aguas profundas (25-40 m) cercanas a la entrada principal, donde la profundidad de transparencia fue intermedia (6-8 m), y la abundancia del zooplancton fue relativamente alta ( > 316 ml/1000 m3). El Nitrógeno Inorgánico Disuelto (DIN), fosfatos y clorofila a no revelan una clara predominancia, debido a incrementos en diferentes intervalos de clases. La amplia fluctuación interanual de la actividad reproductiva de la sardina y temperaturas preferenciales observadas en datos históricos y recientes sugiere la reproducción de dos poblaciones en Bahía Magdalena (1981-1989 y 1997-2009). La influencia de los periodos de enfriamiento y calentamiento como complemento de marco ambiental regional es analizada y discutida

Potential-density pairs for axisymmetric galaxies: the influence of scalar fields

We present a formulation for potential-density pairs to describe axisymmetric galaxies in the Newtonian limit of scalar-tensor theories of gravity. The scalar field is described by a modified Helmholtz equation with a source that is coupled to the standard Poisson equation of Newtonian gravity. The net gravitational force is given by two contributions: the standard Newtonian potential plus a term stemming from massive scalar fields. General solutions have been found for axisymmetric systems and the multipole expansion of the Yukawa potential is given. In particular, we have computed potential-density pairs of galactic disks for an exponential profile and their rotation curves.Comment: 8 pages, no figures, corrected version to the one that will appear in Gen. Relativ. Gravit., where a small typo in eq. (13) is presen