Unstable horizons and singularity development in holography

In holographic applications one can encounter scenarios where a long-wavelength instability can arise. In such situations, it is often the case that the dynamical end point of the instability is a new equilibrium phase with a nonlinear scalar hair condensate outside the black hole horizon. We here review holographic setups where symmetric horizons suffer from long-wavelength instabilities where a suitable equilibrium condensate phase does not exist. We study the dynamics of the simplest model in this exotic class, and show that it uncovers arbitrarily large curvatures in the vicinity of the horizon which asymptotically turn such region singular, at finite time with respect to the boundary theory.Comment: 38 pages, 41 figure

A review on cultural landscape approach as a base for regeneration strategies on rural condition: Gran Canaria Island

The rural territory presents nowadays a complex situation with serial difficulties for the development of the traditional activities (agriculture, stockbreeding, etc). This leads to a decline of these environments, with consequences at very diverse levels. But in a particular way it is influencing in the abandonment of the settlements and in the deterioration of its tangible and untangible heritage. Thus, there is a need for planning tools that promote the sustainable development of the Rural Territory. The aim is to preserve the endogenous potential of these areas providing reactivation strategies that encourage the local development in its physical, social and cultural dimension. The case of Gran Canaria depicts how the Cultural Routes can configure an efficient tool for this. In this way, the touristic potential of these rural environments is not incompatible with the preservation of their heritage values. And the interpretation of the landscape and its memory can be a clue in this sense.Peer Reviewe

Propagation of a realistic magnetar jet through binary neutron star merger medium and implications for short gamma-ray bursts

The origin of short gamma-ray bursts (sGRBs) is associated with outflows powered by the remnant of a binary neutron star merger. This remnant can be either a black hole or a highly magnetized, fastly spinning neutron star, also known as a magnetar. Here, we present the results of two relativistic magnetohydrodynamical (RMHD) simulations aimed at investigating the large-scale dynamics and propagation of magnetar collimated outflows through the medium surrounding the remnant. The first simulation evolves a realistic jet by injecting external simulation data, while the second evolves an analytical model jet with similar properties for comparison. We find that both outflows remain collimated and successfully emerge through the static medium surrounding the remnant. However, they fail to attain relativistic velocities and only reach a mean maximum speed of ~0.7c for the realistic jet, and ~0.6c for the analytical jet. We also find that the realistic jet has a much more complex structure. The lack of highly relativistic speeds, that makes these jets unsuitable as short GRB sources, is due to numerical limitations and not general to all possible magnetar outflows. A jet like the one we study, however, could give rise to or augment a blue kilonova component. In addition, it would make the propagation of a relativistic jet easier, should one be launched after the neutron star collapses into a black hole.Comment: 11 pages, 7 figures, accepted to Ap

Nonlinear Behavior of Unstable Black Holes in Anti-de Sitter Spacetimes

The nonlinear dynamics of black holes is an increasingly relevant topic of which little is known. In this thesis, we study the full nonlinear dynamics of black holes, as well as their linear behavior, and combine them to find a comprehensive picture of the processes involved. In particular, we study the dynamics of unstable black holes in asymptotically anti-de Sitter spacetimes. We study their general behavior and approach to the final equilibrium state. In the first part of this work, we present linear studies of charged scalar field perturbations of Reissner-Nordstrom anti-de Sitter (RN-AdS) black holes in the small and large black hole regimes. We present their quasinormal mode spectra, identify the known mode families—superradiant modes, zero-damped modes, AdS modes, and the near-horizon mode— and track their migration under variation of the black hole and field parameters. We present results of the full nonlinear studies of perturbed small and large RN-AdS, showing the nonlinear development of the unstable superradiant modes. For generic initial conditions, charge and mass are transferred from the black hole to the scalar field, until an equilibrium solution with a scalar condensate is reached. Additionally, we use the results from the linear analysis to construct special initial data corresponding to an unstable overtone mode. We find that these special data evolve to produce a new equilibrium state, an excited hairy black hole with the scalar condensate in an overtone configuration. This state is, however, unstable, and the system eventually decays to the generic end state. This demonstrates the potential relevance of overtone modes as transients in black hole dynamics. In the second part of this work, we present linear and nonlinear studies of a planar Schwarzschild-AdS black hole and two massive scalar fields. Above the critical energy density the system reaches an equilibrium state where one of the scalars forms a condensate and the other vanishes. Below the critical energy density, how- ever, the system displays an instability at the linear regime. We present results of the full nonlinear development of this instability where a suitable equilibrium condensate does not exist. Indeed, we present compelling evidence that during the dynamics arbitrarily large curvatures are uncovered in the vicinity of the horizon, which turn such region singular in finite time with respect to the boundary observer

La experiencia metodológica del proyecto cultural "Cambio de Sentido"

Exposición oral presentada en la sesión dedicada a Ámbitos, Innovación y Calidad, en las IV Jornadas Internacionales sobre Investigación en Arquitectura y Urbanismo."Cambio de sentido" es un proyecto cultural desarrollado transversalmente entre distintas disciplinas. El tema de investigación se refiere a la transformación del espacio público en la ciudad contemporánea. Pero esta reflexión se concreta dentro de la ciudad dispersa, una forma ocupar el territorio en la que el automóvil ha favorecido la aparición de nuevos espacios colectivos en torno a las infraestructuras viarias. En este ámbito se produce un amplio repertorio de situaciones cotidianas claramente representativas de la sociedad actual. Por otra parte, el proyecto se lleva a cabo con ciertas peculiaridades metodológicas, que incluyen diversas actividades en paralelo: una exposición, un curso y la publicación de un catálogo divulgativo. Así, el material generado va revelando otras maneras de cartografiar la ciudad, entendidas como una experiencia metodológica asociada al devenir de la cultura urbana.Ley Bosch, P. (2012). La experiencia metodológica del proyecto cultural "Cambio de Sentido". http://hdl.handle.net/10251/1490

A systematic review on multi-criteria group decision-making methods based on weights: analysis and classification scheme

Interest in group decision-making (GDM) has been increasing prominently over the last decade. Access to global databases, sophisticated sensors which can obtain multiple inputs or complex problems requiring opinions from several experts have driven interest in data aggregation. Consequently, the field has been widely studied from several viewpoints and multiple approaches have been proposed. Nevertheless, there is a lack of general framework. Moreover, this problem is exacerbated in the case of experts’ weighting methods, one of the most widely-used techniques to deal with multiple source aggregation. This lack of general classification scheme, or a guide to assist expert knowledge, leads to ambiguity or misreading for readers, who may be overwhelmed by the large amount of unclassified information currently available. To invert this situation, a general GDM framework is presented which divides and classifies all data aggregation techniques, focusing on and expanding the classification of experts’ weighting methods in terms of analysis type by carrying out an in-depth literature review. Results are not only classified but analysed and discussed regarding multiple characteristics, such as MCDMs in which they are applied, type of data used, ideal solutions considered or when they are applied. Furthermore, general requirements supplement this analysis such as initial influence, or component division considerations. As a result, this paper provides not only a general classification scheme and a detailed analysis of experts’ weighting methods but also a road map for researchers working on GDM topics or a guide for experts who use these methods. Furthermore, six significant contributions for future research pathways are provided in the conclusions.The first author acknowledges support from the Spanish Ministry of Universities [grant number FPU18/01471]. The second and third author wish to recognize their support from the Serra Hunter program. Finally, this work was supported by the Catalan agency AGAUR through its research group support program (2017SGR00227). This research is part of the R&D project IAQ4EDU, reference no. PID2020-117366RB-I00, funded by MCIN/AEI/10.13039/ 501100011033.Peer ReviewedPostprint (published version

A hierarchical integration method under social constraints to maximize satisfaction in multiple criteria group decision making systems

Aggregating multiple opinions or assessments in a decision has always been a challenging field topic for researchers. Over the last decade, different approaches, mainly based on weighting data sources or decision-makers (DMs), have been proposed to resolve this issue, although social choice theory, focused on frameworks to combine individual opinions, is generally overlooked. To resolve this situation, a novel methodology is developed in this paper based on social choice theory and statistical mathematics. This method innovates by dividing the assessment into components which provides a multiple assessment analysis, assigning weights to each source regarding their position compared to the group for each considered criteria. This multiple-weighting process maximises individual and group satisfaction. Furthermore, the method makes it possible to manage previously assigned influence. An example is given to illustrate the proposed methodology. Additionally, sensitivity analysis is performed and comparisons with other methods are made. Finally, conclusions are presented.The first author acknowledges support from the Spanish Ministry of Education, Culture and Sports [grant number FPU18/01471]. The second and third author wish to recognise their support from the Serra Hunter programme. Finally, this work was supported by the Catalan agency AGAUR through its research group support program (2017SGR00227). This research is part of the R&D project IAQ4EDU, reference no. PID2020-117366RB-I00, funded by MCIN/AEI/10.13039/501100011033.Peer ReviewedPostprint (published version

Fetal Testosterone (2D:4D) as Predictor of Cognitive Reflection

The Cognitive Reflection Test (CRT) is a test introduced by S. Frederick (2005) Cognitive reflection and decision making, J Econ Perspect 19(4): 25-42. The task is designed to measure the tendency to override an intuitive response that is incorrect and to engage in further reflection that leads to the correct response. The consistent sex differences in CRT performance may suggest a role for gonadal hormones, particularly testosterone. A now widely studied putative marker for fetal testosterone is the second-to-fourth digit ratio (2D:4D). This paper tests to what extent 2D:4D, as a proxy for prenatal exposure to testosterone, can predict CRT scores in a sample of 623 students. After controlling for sex, we observe that a lower 2D:4D (reflecting a higher exposure to testosterone) is significantly associated with a higher number of correct answers. The result holds for both hands’ 2D:4Ds. In addition, the effect appears to be sharper for females than for males. We also control for patience and math proficiency, which are significantly related to performance in the CRT. But the effect of 2D:4D on performance in CRT is not reduced with these controls, implying that these variables are not mediating the relationship between digit ratio and CRT

Orbital X-Ray Variability of the Microquasar LS 5039

The properties of the orbit and the donor star in the high mass X-ray binary microquasar LS 5039 indicate that accretion processes should mainly occur via a radiatively driven wind. In such a scenario, significant X-ray variability would be expected due to the eccentricity of the orbit. The source has been observed at X-rays by several missions, although with a poor coverage that prevents to reach any conclusion about orbital variability. Therefore, we conducted RossiXTE observations of the microquasar system LS 5039 covering a full orbital period of 4 days. Individual observations are well fitted with an absorbed power-law plus a Gaussian at 6.7 keV, to account for iron line emission that is probably a diffuse background feature. In addition, we have taken into account that the continuum is also affected by significant diffuse background contamination. Our results show moderate power-law flux variations on timescales of days, as well as the presence of miniflares on shorter timescales. The new orbital ephemeris of the system recently obtained by Casares et al. have allowed us to show, for the first time, that an increase of emission is seen close to the periastron passage, as expected in an accretion scenario. Moreover, the detected orbital variability is a factor of ~4 smaller than the one expected by using a simple wind accretion model, and we suggest that an accretion disk around the compact object could be responsible for this discrepancy. On the other hand, significant changes in the photon index are also observed clearly anti-correlated with the flux variations. We interpret the overall X-ray spectral characteristics of LS 5039 in the context of X-ray radiation produced by inverse Compton and/or synchrotron processes in the jet of this microquasar.Comment: published in Astrophysical Journal, submission format (real number of pages: 7, 4 figures