Holographic studies of Einsteinian cubic gravity

Einsteinian cubic gravity provides a holographic toy model of a nonsupersymmetric CFT in three dimensions, analogous to the one defined by Quasi-topological gravity in four. The theory admits explicit non-hairy AdS$_4$ black holes and allows for numerous exact calculations, fully nonperturbative in the new coupling. We identify several entries of the AdS/CFT dictionary for this theory, and study its thermodynamic phase space, finding interesting new phenomena. We also analyze the dependence of R\'enyi entropies for disk regions on universal quantities characterizing the CFT. In addition, we show that $\eta/s$ is given by a non-analytic function of the ECG coupling, and that the existence of positive-energy black holes strictly forbids violations of the KSS bound. Along the way, we introduce a new method for evaluating Euclidean on-shell actions for general higher-order gravities possessing second-order linearized equations on AdS$_{(d+1)}$. Our generalized action involves the very same Gibbons-Hawking boundary term and counterterms valid for Einstein gravity, which now appear weighted by the universal charge $a^*$ controlling the entanglement entropy across a spherical region in the CFT dual to the corresponding higher-order theory.Comment: 59 pages, 7 figures, 1 table; v4: typos fixe

Regular Stringy Black Holes?

We study the first-order $\alpha'$ corrections to the singular 4-dimensional massless stringy black holes studied in the nineties in the context of the Heterotic Superstring. We show that the $\alpha'$ corrections not only induce a non-vanishing mass and give rise to an event horizon, but also eliminate the singularity giving rise to a regular spacetime whose global structure includes further asymptotically flat regions in which the spacetime's mass is positive or negative. We study the timelike and null geodesics and their effective potential, showing that the spacetime is geodesically complete. We discuss the validity of this solution, arguing that the very interesting and peculiar properties of the solution are associated to the negative energy contributions coming from the terms quadratic in the curvature. As a matter of fact, the 10-dimensional configuration is singular. We extract some general lessons on attempts to eliminate black-hole singularities by introducing terms of higher order in the curvature.Comment: 5 pages, 2 figure

The right to privacy and your personal agreement with the new law of intelligence

En el siguiente artículo se hace un análisis en el que se relacionan dos temáticas importantes: el derecho a la intimidad personal y los contenidos que incluye la nueva Ley de Inteligencia aprobada en Colombia, buscando revisar los posibles vacíos que a la luz de la protección de los Derechos Humanos se identifican en la Ley y cómo estos inciden para que los organismos con facultades para desarrollar actividades de inteligencia y contrainteligencia puedan cometer acciones inadecuadas con la justificación de los fines en cuanto a la seguridad nacional y la prevención de hechos que atenten contra ella.The existence of a legal framework for the activities of strategic intelligence enables preventing the realization of serious threats to national security and defense, but aimed primarily at compliance from those who are authorized to perform such duties, according to the established on the legal basis for the protection of rights and not infringe making in this sense, no right to those involved in the cases, in particular their right to privacy

Dimensionalización de la ideología en la Encuesta Social Europea: efecto de la no respuesta y testado

En las sociedades de tradición capitalista las posiciones de ideológicas de izquierdas en lo social se relacionan positivamente con las posiciones de izquierdas en lo económico. Sin embargo, investigaciones recientes señalan que esta relación se altera en los países postcomunistas, asociándose posiciones ideológicas de izquierdas en lo económico con posiciones de derechas en lo social. En esta investigación se analiza la citada relación con una muestra de países significativamente superior a las anteriores proveniente de la sexta ronda de la Encuesta Social Europea. Además, dado el alto nivel de no respuesta parcial de alguna las variables empleadas, se estudia la distribución de la misma en busca de estructuras respecto a las principales variables sociodemográficas (género, edad y nivel de estudios)

Leading higher-derivative corrections to Kerr geometry

We compute the most general leading-order correction to Kerr solution when the Einstein-Hilbert action is supplemented with higher-derivative terms, including the possibility of dynamical couplings controlled by scalars. The model we present depends on five parameters and it contains, as particular cases, Einstein-dilaton-Gauss-Bonnet gravity, dynamical Chern-Simons gravity and the effective action coming from Heterotic Superstring theory. By solving the corrected field equations, we find the modified Kerr metric that describes rotating black holes in these theories. We express the solution as a series in the spin parameter $\chi$, and we show that including enough terms in the expansion we are able to describe black holes with large spin. For the computations in the text we use an expansion up to order $\chi^{14}$, which is accurate for $\chi<0.7$, but we provide as well a Mathematica notebook that computes the solution at any given order. We study several properties of the corrected black holes, such as geometry of the horizon, ergosphere, light rings and scalar hair. Some of the corrections violate parity, and we highlight in those cases plots of horizons and ergospheres without $\mathbb{Z}_{2}$ symmetry.Comment: v3: The equations 4.41-4.43 for the lightring frequencies have been amended. These formulas were incorrect in the previous versions due to an error when translating the results to the LaTeX file (the error does not propagate to other results). For all the rest, this version matches the one published in JHE

Sistema distribuido para medida y procesado en tiempo real de sensores IoT

Internet of things (IoT) is a term we use today to describe all those technologies that enables interconnection of digital with physical world. IoT is present in our everyday life allowing to connect all kind of elements. They can be domestic devices, industrial or merchant ones, in such a way that the human can interact and modify them. In IoT, things are enabled to collect information from their surroundings, to later process it, analyze it and give it value and thus be able to create applications and offer innovative services. This services and applications are bit by bit changing the world, making it better and changing the concept of technology as we know it today. This project aims to implement an IoT application using a wireless sensor network (WSN). Each sensor collects some information, in our case, temperature, battery level and the values of two external sensors, chosen by the user, connected to the mote to proceed with its analysis and processing. The information will be presented to the user through two interfaces: a web page and an Android application. The user can view data in different formats for further analysis. To carry out the network implementation, a Raspberry Pi 3 Model B and four Zolertia Z1 motes were used. Z1 motes feature a low power microcontroller MSP430F2617. Contiki was used as operating system for motes. Raspberry Pi plays the role of a border router that allows the communication between the WSN and external IP network. To send the information from the nodes, we have developed a serie of programs that allow the sensor to send data using UDP as a transport protocol. On the other hand, to receive the information sent from the nodes, we have developed a UDP server. Finally, we have gone one step forward and we offer to the user to choose what kind of sensor want to work with

On the existence of a parent theory for General Relativity and Unimodular Gravity

General Relativity (GR) and Unimodular Gravity (UG) provide two equivalent descriptions of gravity that differ in the nature of the cosmological constant. While GR is based on the group of diffeomorphisms that permits the cosmological constant in the action, UG is based on the subgroup of volume-preserving diffeomorphisms together with Weyl transformations which forbid the presence of the cosmological constant. However, the cosmological constant reappears in UG as an integration constant so it arises as a global degree of freedom. Since gauge symmetries are simply redundancies in our description of physical systems, a natural question is whether there exists a "parent theory" with the full diffeomorphisms and Weyl transformations as gauge symmetries so that it reduces to GR and UG respectively by performing suitable (partial) gauge fixings. We will explore this question by introducing Stueckelberg fields both in GR and UG to complete the gauge symmetries in each theory to that of the would-be parent theory. Despite the dynamical equivalence of the two theories, we find that precisely the additional global degree of freedom provided by the cosmological constant in UG obstructs the construction of the parent theory.Comment: 29 pages, no figures, no table

Normas internacionales de información financiera

CD-T 657.32 C165; 76 pLo que se busca al elaborar este informe, es resumir los temas de mayor importancia referente a las Normas Internacionales de Contabilidad y a las Normas Internacionales de Información Financiera, especificando en cada una de ellas los principales aspectos de estas, incluyendo ejemplos en algunas con el fin de comprender con mayor facilidad su aplicación.Universidad Libre Seccional Pereir

Vector stability in quadratic metric-affine theories

In this work we study the stability of the four vector irreducible pieces of the torsion and the nonmetricity tensors in the general quadratic metric-affine Lagrangian in 4 dimensions. This highly constrains the theory reducing the parameter space of the quadratic curvature part from 16 to 5 parameters. We also study the sub-case of Weyl-Cartan gravity, proving that the stability of the vector sector completely fixes the dynamics of the full Lagrangian to just an Einstein-Proca theory or pure General Relativity.Comment: 21 pages, no figures, no table