"No-Scalar-Hair" Theorems for Nonminimally Coupled Fields with Quartic Self-Interaction

Self-gravitating scalar fields with nonminimal coupling to gravity and having a quartic self-interaction are considered in the domain of outer communications of a static black hole. It is shown that there is no value of the nonminimal coupling parameter $\zeta$ for which nontrivial static black hole solutions exist. This result establishes the correctness of Bekenstein ``no-scalar-hair'' conjecture for quartic self-interactions.Comment: 8 pages, RevTeX

Regular Magnetic Black Holes and Monopoles from Nonlinear Electrodynamics

It is shown that general relativity coupled to nonlinear electrodynamics (NED) with the Lagrangian $L(F)$, $F = F_mn F^mn$ having a correct weak field limit, leads to nontrivial static, spherically symmetric solutions with a globally regular metric if and only if the electric charge is zero and $L(F)$ tends to a finite limit as $F \to \infty$. Properties and examples of such solutions, which include magnetic black holes and soliton-like objects (monopoles), are discussed. Magnetic solutions are compared with their electric counterparts. A duality between solutions of different theories specified in two alternative formulations of NED (called $FP$ duality) is used as a tool for this comparison.Comment: 6 pages, Latex2e. One more theorem, some comments and two references have been added. Final journal versio

Dressing a black hole with non-minimally coupled scalar field hair

We investigate the possibility of dressing a four-dimensional black hole with classical scalar field hair which is non-minimally coupled to the space-time curvature. Our model includes a cosmological constant but no self-interaction potential for the scalar field. We are able to rule out black hole hair except when the cosmological constant is negative and the constant governing the coupling to the Ricci scalar curvature is positive. In this case, non-trivial hairy black hole solutions exist, at least some of which are linearly stable. However, when the coupling constant becomes too large, the black hole hair becomes unstable.Comment: 17 pages, 7 figures, uses iopart.cls. Minor changes, accepted for publication in Classical and Quantum Gravit

Chloride Ions in the Pore of Glycine and GABA Channels Shape the Time Course and Voltage Dependence of Agonist Currents

In the vertebrate CNS, fast synaptic inhibition is mediated by GABA and glycine receptors. We recently reported that the time course of these synaptic currents is slower when intracellular chloride is high. Here we extend these findings to measure the effects of both extracellular and intracellular chloride on the deactivation of glycine and GABA currents at both negative and positive holding potentials. Currents were elicited by fast agonist application to outside-out patches from HEK-293 cells expressing rat glycine or GABA receptors. The slowing effect of high extracellular chloride on current decay was detectable only in low intracellular chloride (4 mM). Our main finding is that glycine and GABA receptors "sense" chloride concentrations because of interactions between the M2 pore-lining domain and the permeating ions. This hypothesis is supported by the observation that the sensitivity of channel gating to intracellular chloride is abolished if the channel is engineered to become cation selective or if positive charges in the external pore vestibule are eliminated by mutagenesis. The appropriate interaction between permeating ions and channel pore is also necessary to maintain the channel voltage sensitivity of gating, which prolongs current decay at depolarized potentials. Voltage dependence is abolished by the same mutations that suppress the effect of intracellular chloride and also by replacing chloride with another permeant ion, thiocyanate. These observations suggest that permeant chloride affects gating by a foot-in-the-door effect, binding to a channel site with asymmetrical access from the intracellular and extracellular sides of the membrane

Renormalizability of Massive Gravity in Three Dimensions

We discuss renormalizability of a recently established, massive gravity theory with particular higher derivative terms in three space-time dimensions. It is shown that this massive gravity is certainly renormalizable as well as unitary, so it gives us a physically interesting toy model of perturbative quantum gravity in three dimensions.Comment: 13 pages, no figure

Tricritical gravity waves in the four-dimensional generalized massive gravity

We construct a generalized massive gravity by combining quadratic curvature gravity with the Chern-Simons term in four dimensions. This may be a candidate for the parity-odd tricritical gravity theory. Considering the AdS$_4$ vacuum solution, we derive the linearized Einstein equation, which is not similar to that of the three dimensional (3D) generalized massive gravity. When a perturbed metric tensor is chosen to be the Kerr-Schild form, the linearized equation reduces to a single massive scalar equation. At the tricritical points where two masses are equal to -1 and 2, we obtain a log-square wave solution to the massive scalar equation. This is compared to the 3D tricritical generalized massive gravity whose dual is a rank-3 logarithmic conformal field theory.Comment: 17 pages, 1 figure, version to appear in EPJ

Desenvolupament d'un sistema d'informació geogràfica per a la lluita contra els incendis forestals. El Projecte SIGIF

L'objectiu del projecte és el desenvolupament d'un sistema d'informació geogràfica (SIG) per a la lluita contra els incendis forestals, que permeti avaluar el risc d'ignició, simular el procés de propagació i planificar la distribució dels recursos d'extinció en relació, d'una banda, amb els potencials d'ignició i propagació i, d'altra banda, en relació amb la vulnerabilitat dels assentaments humans. L'elecció d'aquests tres objectius com a prioritaris respon a la identificació del que ha de ser el cos fonamental d'un SIG per a la lluita contra els incendis forestals, ja que el coneixement de les àrees més vulnerables als incendis, com també dels factors desencadenants i sostenidors -per mitja de l'avaluació del risc d'ignició i la modelització del procés de propagació del foc- constitueix el punt de partida necessari per a qualsevol anàlisi posterior, ja sigui orientada a optimitzar la distribució dels recursos d'extinció o bé destinada a avaluar mesures i polítiques de prevenció.El objetivo del projecto es el desarrollo de un sistema de información geogrhfica (SIG) para la lucha contra los incendios forestales, que permita evaluar el riesgo de ignición, simular el proceso de propagación, planificar la distribución de los recursos de extinción en relación, por una parte, con los potenciales de ignición y de propagación y, por otra parte, en relación con la vulnerabilidad de los asentamientos humanos. La elección de estos tres objetivos como prioritarios responde a la identificación de lo que debe ser el núcleo fundamental de un SIG para la lucha contra los incendios forestales, ya que el conocimiento de las áreas vulnerables a los incendios, asi como de los factores desencadenantes y de sostén -mediante la evaluación del riesgo de ignición y la modelización del proceso de propagación del fuego- constituye el punto de partida necesario para cualquier análisis posterior, ya sea orientado a optimizar la distribución de los recursos o bien destinado a evaluar medidas y políticas de prevención

Creació automàtica de gràfics estadístics a partir de dades de soroll d'Europa amb tecnologies Open Source en el visor Noise Map Viewer de l'ETC-LUSI

El projecte ha consistit en la creació de gràfics estadístics de soroll d'Europa de forma automàtica amb tecnologies Open Source dins el visor Noise Map Viewer per Europa de l'ETC-LUSI. La llibreria utilitzada per fer aquest procés ha estat JFreeChart i el llenguatge de programació utilitzat ha estat Java (programació orientada a objectes) dins l'entorn de desenvolupament integrat Eclipse. La base de dades utilitzada ha estat PostgreSQL. Com a servidors s'han fet servir Apache (servidor HTTP) i Tomcat (servidor contenidor d'aplicacions). Un cop acabat el procés s'ha integrat dins de MapFish canviant el codi JavaScript corresponent de la web original

The family of regular interiors for non-rotating black holes with T00=T11T^0_0 = T^1_1

We find the general solution for the spacetimes describing the interior of static black holes with an equation of state of the type $T^0_0 = T^1_1$ ($T$ being the stress-energy tensor). This form is the one expected from taking into account different quantum effects associated with strong gravitational fields. We recover all the particular examples found in the literature. We remark that all the solutions found follow the natural scheme of an interior core linked smoothly with the exterior solution by a transient region. We also discuss their local energy properties and give the main ideas involved in a possible generalization of the scheme, in order to include other realistic types of sources.Comment: 31 pages, 1 figure, version to appear in Physical Review