The lifetime problem of evaporating black holes: mutiny or resignation

It is logically possible that regularly evaporating black holes exist in nature. In fact, the prevalent theoretical view is that these are indeed the real objects behind the curtain in astrophysical scenarios. There are several proposals for regularizing the classical singularity of black holes so that their formation and evaporation do not lead to information-loss problems. One characteristic is shared by most of these proposals: these regularly evaporating black holes present long-lived trapping horizons, with absolutely enormous evaporation lifetimes in whatever measure. Guided by the discomfort with these enormous and thus inaccessible lifetimes, we elaborate here on an alternative regularization of the classical singularity, previously proposed by the authors in an emergent gravity framework, which leads to a completely different scenario. In our scheme the collapse of a stellar object would result in a genuine time-symmetric bounce, which in geometrical terms amounts to the connection of a black-hole geometry with a white-hole geometry in a regular manner. The two most differential characteristics of this proposal are: i) the complete bouncing geometry is a solution of standard classical general relativity everywhere except in a transient region that necessarily extends beyond the gravitational radius associated with the total mass of the collapsing object; and ii) the duration of the bounce as seen by external observers is very brief (fractions of milliseconds for neutron-star-like collapses). This scenario motivates the search for new forms of stellar equilibrium different from black holes. In a brief epilogue we compare our proposal with a similar geometrical setting recently proposed by Haggard and Rovelli.Comment: 20 pages, 2 figures; v2: published version, references adde

Electromagnetism as an emergent phenomenon: a step-by-step guide

We give a detailed description of electrodynamics as an emergent theory from condensed-matter-like structures, not only {\it per se} but also as a warm-up for the study of the much more complex case of gravity. We will concentrate on two scenarios that, although qualitatively different, share some important features, with the idea of extracting the basic generic ingredients that give rise to emergent electrodynamics and, more generally, to gauge theories. We start with Maxwell's mechanical model for electrodynamics, where Maxwell's equations appear as dynamical consistency conditions. We next take a superfluid $^3$He-like system as representative of a broad class of fermionic quantum systems whose low-energy physics reproduces classical electrodynamics (Dirac and Maxwell equations as dynamical low-energy laws). An important lesson that can be derived from both analyses is that the vector potential has a microscopic physical reality and that it is only in the low-energy regime that this physical reality is blurred in favour of gauge invariance, which in addition turns out to be secondary to effective Lorentz invariance.Comment: 41 pages, 4 figures; v2: references added, version accepted for publicatio

A Rational Approach to Cryptographic Protocols

This work initiates an analysis of several cryptographic protocols from a rational point of view using a game-theoretical approach, which allows us to represent not only the protocols but also possible misbehaviours of parties. Concretely, several concepts of two-person games and of two-party cryptographic protocols are here combined in order to model the latters as the formers. One of the main advantages of analysing a cryptographic protocol in the game-theory setting is the possibility of describing improved and stronger cryptographic solutions because possible adversarial behaviours may be taken into account directly. With those tools, protocols can be studied in a malicious model in order to find equilibrium conditions that make possible to protect honest parties against all possible strategies of adversaries

Do transient white holes have a place in Nature?

The white-hole sector of Kruskal's solution is almost never used in physical applications. However, it can provide a radically different take on the gravitational collapse process, avoiding the problems appearing within the standard paradigm. In this contribution we will try to draw attention to some bouncing geometries that make a democratic usage of the black and white sectors of Kruskal's solution. We will argue that this type of behaviour could be perfectly natural in some approaches to the next physical level beyond classical General Relativity. © Published under licence by IOP Publishing Ltd.Peer Reviewe

Do stars die too long?

MG14, University of Rome "La Sapienza" - Rome, July 12-18, 2015; http://www.icra.it/mg/mg14/Current proposals for regularizing the classical singularity of black holes present longlived trapping horizons, with enormous inaccessible evaporation lifetimes. We propose an alternative regularization model, inspired in condensed matter gravitational analogues, in which the collapse of a stellar object would result in a genuine time-symmetric bounce. In geometrical terms this amounts to the connection of a black-hole geometry with a white-hole geometry in a regular manner. The complete bouncing geometry is a solution of standard classical general relativity everywhere except in a transient region that necessarily extends beyond the gravitational radius. The duration of the bounce as seen by external observers is very brief. This motivates the search for new forms of stellar equilibrium.Financial support was provided by the Spanish MICINN through Projects No. FIS2011-30145-C03-01 and FIS2011-30145-C03-02 (with FEDER contribution), and by the Junta de Andalucía through Project No. FQM219. R. C-R. acknowledges support from CSIC through the JAE-predoc program, cofunded by FSE.Peer Reviewe

The expansion of armed violence in the post-Cold War period: low intensity conflicts, international terrorism and transnational organized crime

El terrorismo se ha convertido en una forma preferente de ejercer la violencia en el sistema internacional. Varias causas han determinado esta transformación en el conflicto. La primera es la existencia de un poder hegemónico con capacidades militares sin posibilidad de oposición en un conflicto a gran escala. Esto ha llevado a que los conflictos que se generan se encauzan a través de los mecanismos establecidos de resolución de crisis en la búsqueda permanente de equilibrios frente a los intereses preponderantes de la potencia hegemónica. En cambio, los conflictos se expanden en los escalones inferiores entre actores carentes de los atributos del poder estatal, esto es, la territorialidad y la soberanía.Terrorism has turned into the preferable way of exercising violence in international system. Several causes have determined this transformation in the conflict. The first one is the existence of hegemonic Power with military capacities without comparison in the history. Consequently, the conflicts are channeled across the mechanism for pacific solution of crisis in permanent search of the balance opposite to interests of hegemonic. But the conflicts expand in the low between non state actors, lacking in the attributes of territoriality and sovereignty

Caracterización de parásitos en Columba livia (GMELIN 1789) y de su entorno próximo-Centro Poblado de Quebrada-Yanatile-Calca-Cusco

El objetivo del presente estudio, fue caracterizar parásitos de Columba livia (Gmelin 1789) y de su entorno próximo-centro poblado de Quebrada, Yanatile-Calca-Cusco. El lugar de estudio está ubicado a 1,357 m de altitud en la zona noreste del departamento del Cusco, con bosque húmedo premontano, con temperatura media de 23°C, el presente estudio se realizó desde agosto del 2019 a febrero del 2020, período en los cuales hubo intensas precipitaciónes donde se capturaron un total de 50 ejemplares de C. livia por trampas ideadas en base a la opinión de pobladores lugareños los que le denominan paqti (tapador). Cada uno de los ejemplares fueron sacrificados mediante dislocación cervical, seguido de una observación directa, de 6 partes del cuerpo de C. livia (cabeza, parte dorsal, parte ventral, ala derecha, ala izquierda y cola) llegándose a encontrar cuatro géneros de ectoparásitos tales como: Columbicola columbae 98% de prevalencia y una intensidad media de 45.33, Campanulotes bidentatus con 84% de prevalencia y 25.36 de intensidad media, Pseudolynchia canariensis 56% de prevalencia y 2.57 de intensidad media, se aislo un único ácaro quístico Laminosioptes cysticola primer reporte para Perú con 70% de prevalencia, no hallándose la intensidad media por ser extremadamente abundante. Para la obtención de endoparásitos del tracto digestivo se realizó las siguientes técnicas: Hisopado oral-faríngeo para la obtención de Trichomonas gallinae con 82% de prevalencia

Degradación enzimática de TRH y análogos en semen humano. Posible función en la fertilidad

Recientemente se ha descrito la presencia en semen humano de un péptido similar a la hormona liberadora de tirotropina (TRH) directamente implicado en la fertilidad, habiéndose denominado FPP (péptido promotor de la fertilidad). Se han determinado las actividades de las peptidasas más importantes en la degradación de estos péptidos en semen en distintos diagnósticos. Aunque se registran diferencias significativas en la actividad enzimática entre los distintos diagnósticos, dichas variaciones no son lo suficientemente claras como para aceptar estas peptidasas como marcadores válidos.Ugalkortasun arloan egindako azken aurkikuntzen artean tirotropinaren hormona askatzailearen (TRH) antzeko peptido baten aurkikuntza azpimarratzekoa da. Peptido honek ugalkortasunaren prozesuan eragin zuzena duela aurkitu da, izan ere ugalkortasuna errazten duen peptidoa izendatu diote (FPP). Haziko zatikietan ematen den peptido hauen apurketan peptidasa garrantzitsuenen funtzioa ezartzeko asmoz eta ugalkortasunarekin erlazionatutako diagnostiko adierazle bezala balio dezaketen frogatzeko asmoz, bere aktibitate entzimatikoak neurtu dira. Diagnostiko desberdinen artean aldaketa adierazgarriak badira ere, diferentziak ez dira nahiko argiak peptidasa hauek adierazle baliogarri bezala onartzeko.Parmi les derniers découvertes réalisées dans le champ de la fertilité il faut détacher la présence dans le liqueur seminale humain d'un peptide similaire à l'hormone libératrice de tirotropina (TRH) directèment impliqué dans ce procés qui a été nommé FPP (fertilization promoting peptide). A fin d'etablir le rol des peptidases les plus importants dans la dégradation de ses peptides dans les fractions seminales et de vérifier s'ils peuvent servir comme marqueurs des divers diagnostiques seminalesm rélationés avec la fertilité, les activités enzimatiques ant été déterminés. Malgré les differences significatives parmi les deux diagnostiques, ces variations ne sont pas suffisamment clairs pour accepterces peptidases comme des marqueurs valids.Recently it has been described the presence in human semen of a thyrotropin-releasing hormone (TRH) like peptide, directly implicated in the fertility and therefore it has been called fertilization promoting peptide (FPP). We have measured the activities of the most important peptidases in the degradation of these peptides in semen in different diagnostics. Although there are significative differences among the diagnostics, these variations are not clear enough to accept these peptidases like valid markers

Researchers' Seedbeds for the Development of Research Skills in Universities

The objective of this study is to demonstrate the effects of the application of the pedagogical strategy "researcher's seedbed" in the development of research skills in universities. This research is of quasi-experimental, longitudinal and prospective design, where 2 groups were formed: control and experimental, of 18 students each. A validated instrument was used to measure the research competences, as well as a rubric for the evaluation of the research projects. It began with a pre-test, and after 14 weeks of the development of the strategy, through different educational sessions, the post-test was administered. Likewise, the research projects carried out were evaluated. The results obtained showed that the pedagogical strategy had a positive effect on the development of research skills, with the highest evaluation being found in 40% of the students, with statistically significant differences between the control and experimental groups (Mann Whitney U, p=0.007), and between the pre-test and post-test (Wilcoxon, p=0.00). In the development of cognitive and procedural competence, an effect was also found in the strategy, but not in the attitudinal competence (Mann Whitney U, p=0.496). The application of this study is based on the fact that the formation of research groups in universities strengthens formative research in higher level students. This study shows the benefits of the implementation of strategies for the development of research competencies, since the product will be to train professionals with a scientific culture in favor of society