Charging a Double Kerr Solution in 5D Einstein--Maxwell--Kalb--Ramond Theory

We consider the low-energy effective action of the 5D Einstein-Maxwell-Kalb-Ramond theory. After compactifying this truncated model on a two-torus and switching off the U(1) vector fields of this theory, we recall a formulation of the resulting three-dimensional action as a double Ernst system coupled to gravity. Further, by applying the so-called normalized Harrison transformation on a generic solution of this double Ernst system we recover the U(1) vector field sector of the theory. Afterward, we compute the field content of the generated charged configuration for the special case when the starting Ernst potentials correspond to a pair of interacting Kerr black holes, obtaining in this way an exact field configuration of the 5D Einstein-Maxwell-Kalb-Ramond theory endowed with effective Coulomb and dipole terms with momenta. Some physical properties of this object are analyzed as well as the effect of the normalized Harrison transformation on the double Kerr seed solution.Comment: 15 pages in latex, revised versio

Efficiency of Penrose process in spacetime of axially symmetric magnetized Reissner-Nordstr\"{o}m black hole

In this paper, we investigate the Penrose process in the purlieus of the axially symmetric magnetised Reissner-Nordstr\"{o}m black hole for both neutral and charged particles. We start with the study of the geometry of the black hole and find the regions where the $g_{tt}$ component of the metric tensor is positive (i.e. $g_{tt}>0$). It is interestingly found that the condition $g_{tt}>0$ is fulfilled not only close to the event horizon known as the ergosphere but also far away from the event horizon in the silhouette of potential wells. We also show that as the dimensionless magnetic field $B$ increases the silhouette of potential wells for which $g_{tt}>0$ grows correspondingly and eventually merges with ergoregion when $B\gtrsim 1.6$. Finally, we investigate the efficiency of the Penrose process for the axially symmetric magnetized black hole case and bring out the effect of the magnetic field on it. Further, we also compare our results with the one for Kerr black hole. We show that when the charge $Q$ of the black hole is kept constant, the efficiency of the energy extraction process for the case of {a neutral particle (i.e. $q/m=0$) first increases and then begins to decrease with rise in the value of $B$ field, in contrast to Kerr black hole where it always increases as the rotation parameter grows. However, for the case of a charged particle (i.e. $q\neq 0$) the efficiency always increases with the rise in the $B$ field and can go over $100\%$, when both $B$ and $q/m$ are large enough (say $B\approx1$ and $q/m>2.2$)}. It is worth noting that the existence of regions away from the horizon where $g_{tt}>0$ also favours the energy-extraction process away from the effect of the black hole. However, the energy extraction from these regions is pure consequence of the magnetic field.Comment: 10 pages, 6 captioned figures. Comments are welcom

La mediación de la memoria del terrorismo de ETA. Tratamiento del atentado contra la Casa Cuartel de Zaragoza en la prensa aragonesa (1987, 1997, 2007 y 2017).

El atentado contra la Casa Cuartel de Zaragoza (11/12/1987) fue el más sangriento que ETA perpetró en la Comunidad de Aragón y se saldó con un balance de 11 muertos, de los cuales 5 eran niños. El objetivo del presente trabajo es analizar cómo la prensa diaria aragonesa (Heraldo de Aragón, El Día y El Periódico de Aragón) cubrió esta masacre en su día y cómo lo ha hecho en su 10º, 20º y 30º aniversarios, coincidiendo estas fechas con diferentes etapas en la historia de la banda terrorista. Para ello, se ha recurrido a un análisis del contenido publicado de tipo cualitativo. La cobertura del atentado fue evolucionando desde una posición en segundo plano de las víctimas (1987) hasta el momento en que el dolor de las víctimas pasó a un primer plano a partir del 10o aniversario. La importancia fue decayendo con motivo del debilitamiento de la banda y los atentados del 11M, y en el 30o aniversario se puso encima de la mesa la cuestión del futuro de los etarras encarcelados.<br /

GUÍA PEDAGOGICA INGLÉS 7

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GUÍA PEDAGÓGICA INGLÉS 7

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