Gravitational entropy of Kerr black holes

Classical invariants of General Relativity can be used to approximate the entropy of the gravitational field. In this work, we study two proposed estimators based on scalars constructed out from the Weyl tensor, in Kerr spacetime. In order to evaluate Clifton, Ellis and Tavakol's proposal, we calculate the gravitational energy density, gravitational temperature, and gravitational entropy of the Kerr spacetime. We find that in the frame we consider, Clifton et al.'s estimator does not reproduce the Bekenstein-Hawking entropy of a Kerr black hole. The results are compared with previous estimates obtained by the authors using the Rudjord-Gr$\varnothing$n-Hervik approach. We conclude that the latter represents better the expected behaviour of the gravitational entropy of black holes.Comment: 12 pages, 7 figures, accepted for publication in General Relativity and Gravitatio

Gravitational entropy of black holes and wormholes

Pure thermodynamical considerations to describe the entropic evolution of the universe seem to violate the Second Law of Thermodynamics. This suggests that the gravitational field itself has entropy. In this paper we expand recent work done by Rudjord, Gr{\O}n and Sigbj{\O}rn where they suggested a method to calculate the gravitational entropy in black holes based on the so-called `Weyl curvature conjecture'. We study the formulation of an estimator for the gravitational entropy of Reissner-Nordstr\"om, Kerr, Kerr-Newman black holes, and a simple case of wormhole. We calculate in each case the entropy for both horizons and the interior entropy density. Then, we analyse whether the functions obtained have the expected behaviour for an appropriate description of the gravitational entropy density.Comment: 11 pages, 11 figures, accepted for publication in International Journal of Theoretical Physic

High-energy signatures of binary systems of supermassive black holes

Context. Binary systems of supermassive black holes are expected to be strong sources of long gravitational waves prior to merging. These systems are good candidates to be observed with forthcoming space-borne detectors. Only a few of these systems, however, have been firmly identified to date. Aims. We aim at providing a criterion for the identification of some supermassive black hole binaries based on the characteristics of the high-energy emission of a putative relativistic jet launched from the most massive of the two black holes. Methods. We study supermassive black hole binaries where the less massive black hole has carved an annular gap in the circumbinary disk, but nevertheless there is a steady mass flow across its orbit. Such a perturbed disk is hotter and more luminous than a standard thin disk in some regions. Assuming that the jet contains relativistic electrons, we calculate its broadband spectral energy distribution focusing on the inverse Compton up-scattering of the disk photons. We also compute the opacity to the gamma rays produced in the jet by photon annihilation with the disk radiation and take into account the effects of the anisotropy of the target photon field as seen from the jet. Results. We find that the excess of low-energy photons radiated by the perturbed disk causes an increment in the external Compton emission from the jet in the X-ray band, and a deep absorption feature at energies of tens of TeVs for some sets of parameters. According to our results, observations with Cherenkov telescopes might help in the identification of supermassive black hole binaries, especially those black hole binaries that host primaries from tens to hundreds of million of solar masses.Comment: 12 pages, 11 figures, accepted for publication in Astronomy & Astrophysic

Accretion disks around black holes in modified strong gravity

Stellar-mass black holes offer what is perhaps the best scenario to test theories of gravity in the strong-field regime. In particular, f(R) theories, which have been widely discuss in a cosmological context, can be constrained through realistic astrophysical models of phenomena around black holes. We aim at building radiative models of thin accretion disks for both Schwarzschild and Kerr black holes in f(R) gravity. We study particle motion in f(R)-Schwarzschild and Kerr space-times. We present the spectral energy distribution of the accretion disk around constant Ricci scalar f(R) black holes, and constrain specific f(R) prescriptions using features of these systems. A precise determination of both the spin and accretion rate onto black holes along with X-ray observations of their thermal spectrum might allow to identify deviations of gravity from General Relativity. We use recent data on the high-mass X-ray binary Cygnus X-1 to restrict the values of the parameters of a class of f(R) models.Comment: 16 pages, 20 figures, accepted for publication in Astronomy & Astrophysic

Cosmological black holes and the direction of time

Macroscopic irreversible processes emerge from fundamental physical laws of reversible character. The source of the local irreversibility seems to be not in the laws themselves but in the initial and boundary conditions of the equations that represent the laws. In this work we propose that the screening of currents by black hole event horizons determines, locally, a preferred direction for the flux of electromagnetic energy. We study the growth of black hole event horizons due to the cosmological expansion and accretion of cosmic microwave background radiation, for different cosmological models. We propose generalized McVittie co-moving metrics and integrate the rate of accretion of cosmic microwave background radiation onto a supermassive black hole over cosmic time. We find that for flat, open, and closed Friedmann cosmological models, the ratio of the total area of the black hole event horizons with respect to the area of a radial co-moving space-like hypersurface always increases. Since accretion of cosmic radiation sets an absolute lower limit to the total matter accreted by black holes, this implies that the causal past and future are not mirror symmetric for any spacetime event. The asymmetry causes a net Poynting flux in the global future direction; the latter is in turn related to the ever increasing thermodynamic entropy. Thus, we expose a connection between four different "time arrows": cosmological, electromagnetic, gravitational, and thermodynamic.Comment: 13 pages, 2 figures in Foundations of Science (2017

La transmisión intergeneracional de género en las prácticas cotidianas de las familias chilenas.

Tesis (Terapeuta Ocupacional)La siguiente tesis relaciona las prácticas intergeneracionales de género que se manifiestan con los procesos cotidianos de las familias chilenas, para conocer y entender cómo el concepto de ocupación se ha distorsionado con el tiempo, plasmando a su vez la reflexión y posterior discusión respecto a la dicotomía rol - género, invitando a problematizar cómo éstos conceptos que se conciben por separado, se determinan uno al otro mutuamente y socialmente se naturalizan y determinan la construcción de los seres humanos. El estudio investigativo llevado a cabo busca conocer lo que se invisibiliza socialmente, lo naturalizado, lo que no se cuestiona en el pasar del tiempo, que si bien la historia y cada ser ha sido parte de cada cambio ocurrido, no existe concientización al respecto de lo nacido. Despertar y reconocernos como seres construidos socialmente dará paso a un crecimiento de una sociedad más justa y consciente

Zonas de reserva campesina, proyectos políticos territoriales y pluralismo jurídico

Artículo de investigaciónEl trabajo de investigación pretende evidenciar la manera en que las organizaciones campesinas territoriales, al asumirse como actores sociales y trazarse proyectos políticos de carácter emancipatorio, construyen y consolidan sistemas normativos e institucionalidades comunitarias, los cuales dan cuenta de la existencia de paralelismos normativos frente a la administración de justicia del Estado colombiano y del pluralismo jurídico al interior del territorio nacional. De igual manera, la investigación desarrolla el papel de las Zonas de Reserva Campesina como figura de ordenamiento y producción de territorio que impulsa este fenómeno de pluralismo jurídico.PregradoAbogadoIntroducción 1. Genealogía de las Zonas de Reserva Campesina. 2. Las ZRC como Proyectos Políticos Territoriales Campesinos. 3. Sistemas normativos emergentes en las ZRC: una primera aproximacion desde el pluralismo jurídico. Conclusiones Bibliografí

Formas de participación de los campesinos en los proyectos en las Zonas de Interés de Desarrollo Rural, Económico y Social (Zidres) en la orinoquia colombiana: ¿una ruta hacia la equidad?

Artículo de reflexiónEl sector agrícola en Colombia ha sido de gran importancia en la historia del desarrollo del país, sin embargo, en los últimos años el sector rural se ha visto afectado en gran manera por los altos costos de insumos para cultivos, las condiciones climatológicas adversas y un mercado altamente restringido para pequeños campesinos (Arias, 2016). En esa medida y teniendo en cuenta los preceptos constitucionales sobre el Estado social de Derecho, se ha buscado mediante una serie de reformas agrarias generar mejores condiciones para los campesinos en Colombia (Torres, 2016), y que mediante el acceso equilibrado a ciertos terrenos o predios, los mismos puedan desarrollar actividades agrícolas que les generen una serie de ingresos y permitan su sostenibilidad en condiciones dignas. En razón de lo anterior, el desarrollo de artículo que se pretende realizar presenta una línea de Investigación documental de naturaleza documental descriptiva realizada a través de estudios casos, cuya finalidad es determinar las formas de participación de campesinos que tendrán en las asociaciones para el desarrollo de proyectos productivos en las Zonas de Interés de Desarrollo Rural y Económico (Zidres), con el fin de que se generen condiciones de equidad (Sepúlveda López & Solano de Jinete, 2008)INTRODUCCIÓN 1. Zonas de Desarrollo Rural Económico y Social 2. ZIDRES en la Orinoquia Colombiana 3. La participación de los campesinos como fundamento del desarrollo rural 4. CONCLUSIONES 5. REFERENCIASPregradoAbogad

An analysis of a regular black hole interior model

We analyze the thermodynamical properties of the regular static and spherically symmetric black hole interior model presented by Mboyne and Kazanas. Equations for the thermodynamical quantities valid for an arbitrary density profile are deduced, and from them we show that the model is thermodynamically unstable. Evidence is also presented pointing to its dynamical instability. The gravitational entropy of this solution based on the Weyl curvature conjecture is calculated, following the recipe given by Rudjord, Gr$\varnothing$n and Sigbj$\varnothing$rn, and it is shown to have the expected behavior.Comment: 22 pages, 17 figures, accepted for publication in International Journal of Theoretical Physic

The Relationship Between Religious/Spiritual Beliefs and Subjective Well-Being: A Case-Based Comparative Cross-National Study

The most unique aspect of religiosity/spirituality (R/S), supernatural beliefs, and their relationship with SWB has hardly been examined. This study explores the relationship between six R/S supernatural beliefs and SWB, in a case-based comparative cross-national design including two religious and two secular nations. Data were obtained from the International Social Survey Programme (ISSP) Religion IV module from the religious countries of the USA (n = 1060) and Turkey (n = 1353) and the secular countries of Denmark (n = 1281) and Czech Republic (n = 1112). SWB was measured as happiness and self-rated health. Statistical analyses were performed using binary logistic regression models replicated across countries. Results indicated that the American sample showed no evidence of relationships between R/S and SWB outcomes capable of improving the model over demographic and service attendance covariates. In Turkey, some R/S beliefs were found to be statistically significantly related to SWB, with positive and negative associations with happiness. No associations were found in the secular countries. Findings were discussed in the light of previous research and interpreted from a terror management theory perspective