Geometric analysis of Lorentzian distance function on spacelike hypersurfaces

Some analysis on the Lorentzian distance in a spacetime with controlled sectional (or Ricci) curvatures is done. In particular, we focus on the study of the restriction of such distance to a spacelike hypersurface satisfying the Omori-Yau maximum principle. As a consequence, and under appropriate hypotheses on the (sectional or Ricci) curvatures of the ambient spacetime, we obtain sharp estimates for the mean curvature of those hypersurfaces. Moreover, we also give a suficient condition for its hyperbolicity.Comment: Final version (January 2009). To appear in the Transactions of the American Mathematical Societ

Power and wavelength polarization bistability with very wide hysteresis cycles in a 1550nm-VCSEL subject to orthogonal optical injection

We have measured optical power and wavelength polarization bistability in a 1550nm-Vertical Cavity Surface-Emitting Laser (VCSEL) subject to orthogonally-polarized optical injection into the orthogonal polarization of the fundamental transverse mode. Optical bistability with very wide hysteresis cycles, up to four times wider than previously reported results has been measured for both the optical power and wavelength domain. We also report the experimental observation of three different shapes of polarization bistability, anticlockwise, clockwise and X-Shape bistability, all of them with wide hysteresis cycles. This rich variety of behaviour at the important wavelength of 1550 nm offers promise for the use of VCSELs for all-optical signal processing and optical switching/routing applications. ©2009 Optical Society of America

Aproximación a la inteligencia para la seguridad nacional

La inteligencia por ser una metodología en la que se desprenden valoración que permiten reconocer las amenazas que ponen en riesgo. Los Estados democrático requieren realizar dicha actividad, a fin de salvaguardar la seguridad nacional la producción de inteligencia se presenta como una tarea imperativa para todo estado, en especial en aquellos que muestran debilidades estructurales crónicas, este ya representa avance, ya que legitima el accionar de nuestros órganos de inteligencia. Existen algunos trabajos que analizan la importancia de la inteligencia para la seguridad nacional. La teoría democrática propone que el gobierno dispone el poder que reside originariamente en el pueblo, dentro de ciertos límites éticos y jurídicos. Se entiende por inteligencia el conocimiento obtenido a partir de la recolecció

Transnationalizing Mexican Legal Education: But, What About Students’ Expectations?

This article focuses on exploring the diversity of ways future students are exposed to law, as well as the multiple reasons that make the profession and degree attractive for them. It is based on the question “what experience or specific situation led to your interest in studying law?” that we asked almost 22,000 Mexican law students around the country at the beginning of the 2004-2005 academic year. This analysis is important because current efforts to transform legal education tend to consider only international components to incorporate into the law programs. But these reforms should also consider the regional or local needs of the participants of legal education which until now have not been taken into account. For example, as we describe in this article, one of five Mexican law students chose to study law because they or their relatives had been victims of violations to their rights, or as a result of perceiving their environment as marked by injustice, corruption and impunity. Law for them was a way to do something about it or, at least, be able to protect themselves and their families. This is a reality shared not only by other Latin American countries, but probably by most developing countries. Any reform to legal education should explore ways to incorporate the students’ ideas, interests and experiences into their studies not only to improve the program, but also to stimulate the students and increase their motivation

Transnationalizing Mexican Legal Education: But, What About Students’ Expectations?

This article focuses on exploring the diversity of ways future students are exposed to law, as well as the multiple reasons that make the profession and degree attractive for them. It is based on the question “what experience or specific situation led to your interest in studying law?” that we asked almost 22,000 Mexican law students around the country at the beginning of the 2004-2005 academic year. This analysis is important because current efforts to transform legal education tend to consider only international components to incorporate into the law programs. But these reforms should also consider the regional or local needs of the participants of legal education which until now have not been taken into account. For example, as we describe in this article, one of five Mexican law students chose to study law because they or their relatives had been victims of violations to their rights, or as a result of perceiving their environment as marked by injustice, corruption and impunity. Law for them was a way to do something about it or, at least, be able to protect themselves and their families. This is a reality shared not only by other Latin American countries, but probably by most developing countries. Any reform to legal education should explore ways to incorporate the students’ ideas, interests and experiences into their studies not only to improve the program, but also to stimulate the students and increase their motivation

Decision-Theoretic Planning with Person Trajectory Prediction for Social Navigation

Robots navigating in a social way should reason about people intentions when acting. For instance, in applications like robot guidance or meeting with a person, the robot has to consider the goals of the people. Intentions are inherently nonobservable, and thus we propose Partially Observable Markov Decision Processes (POMDPs) as a decision-making tool for these applications. One of the issues with POMDPs is that the prediction models are usually handcrafted. In this paper, we use machine learning techniques to build prediction models from observations. A novel technique is employed to discover points of interest (goals) in the environment, and a variant of Growing Hidden Markov Models (GHMMs) is used to learn the transition probabilities of the POMDP. The approach is applied to an autonomous telepresence robot

Asymptotic symmetries and infrared phenomena in gauge theories and gravity

The objective of the following dissertation is to present the existent connection in the infrared regime behavior of both gauge theories and gravity. The first element in this picture analysis is the study of soft theorems, originally developed by Weinberg [1][2]. In a general sense, scattering processes are governed through constraints that control the way soft particles are produced. The second one shall be the asymptotic spacetime symmetries developed by Bondi, van der Burg, Metzner and Sachs [3] [4] of asymptotically flat spacetimes. They lead to the appearance of conserved charges associated to the behavior of the fields at null infinities. The third but not least, the existence of memory effects, like the ones studied by Christodolou [5][6] and Thorne [7] in the infrared limit. Again, in simple terms, they refer to the surgence of perturbations in the fabric of spacetime due to its propagation, leading to field shifts. We explore the connection in terms of the application of Fourier transforms and Ward identities. For simplicity we focus on the case of Quantum Electrodynamics and Quantum Gravity.O objetivo da seguinte dissertação é apresentar a conexão existente no comportamento do regime infravermelho em ambas as teorias de calibre e gravidade. O primeiro elemento desta análise é o estudo dos os teoremas soft , originalmente desenvolvidos por Weinberg [1][2]. Em um sentido geral, os processos de espalhamento são governados por meio de restrições que controlam a forma como as partículas soft são produzidas. O segundo elemento são as simetrias espaço-temporais assintóticas desenvolvidas por Bondi, van der Burg, Metzner e Sachs [3] [4] dos espaço-tempos assintoticamente planos. Eles fornecem o surgimento de cargas conservadas associadas ao comportamento dos campos através nos infinitos nulos. Terceiro, mas não menos importante, a existência de efeitos de memória, como os estudados por Christodolou [5][6] e Thorne [7] no limite infravermelho. Novamente, em termos simples, eles se referem ao surgimento de perturbações no tecido do espaço-tempo devido à sua propagação, levando a deslocamentos de campo. Nós exploramos a conexão em termos da aplicação de transformadas de Fourier e identidades de Ward. Por simplicidade, vamos-nos focar no caso da Eletrodinâmica Quântica e da Gravidade Quântica

Colombia and the Intelligence Cycle in the 21st Century, the Digital Age

Luuretsükkel on luureinfo analüüsimise ja kogumise peamine protsess, mida kasutatakse\n\rkogu maailmas. Kuna see süsteem on vananenud, siis ei saa see lahendada neid ülesandeid,\n\rmida tehnoloogia areng ja digiajastu on kaasa toonud. Info liigub küberruumis.\n\rLuuretsükkel kasutab erinevaid luureinfo vorme, tarvitades otsingus, kogumises, analüüsis\n\rja levitamises kaasaegseid tehnoloogilisi vahendeid. Luures on teada ebaõnnestumisi, mis\n\rtulenesid sellest, et ei suudetud jälgida luuretsüklit info muutumise kiiruse või\n\rolemasolevatest tehnoloogilistest süsteemidest puuduliku teadlikkuse tõttu.\n\rLuureprotsessi tuleb integreerida tehnoloogia ja küberruumiga, et 21. sajandil luurevõimet\n\rarendada. On vaja kasutada kõiki ressursse ja integreerida kõiki\n\rolemasolevaid tehnoloogilisi allikaid põhilistest protsessidest alates.\n\rTäielik protsess, mis ühendab luureinfo saamise protsessi küberruumi ja infotehnoloogia\n\rkasutamisega, on vajalik selleks, et olemasolevat informatsiooni kasutada ja kindlustada.\n\rSee uurimistöö pakub uut, luure läbiviimiseks mõeldut mikrotsüklite protsessi. See koosneb\n\rviiest mikrotsüklist ja selle eesmärk on luure protsesside ja tehnoloogiate integreerimine, et\n\rsaada paremaid tulemusi 21. sajandi luure arengutes.The intelligence cycle is the main process in developing and obtaining intelligence used worldwide. Currently, it has problems and is outdated because it was not created to face the challenges that technology and the digital age have brought about. Information moves and travels in cyberspace, which are current as well as the future land of conflicts. The intelligence cycle is using technology systems through different forms of intelligence taking advantage of current technological developments for the search, collection, analysis and dissemination, but is not being fully exploited. Cases have been observed, where intelligence failed because of not following the intelligence cycle due to the speed of information or lack of knowledge of technological systems at the service of intelligence. The intelligence process must be integrated and work hand in hand with technology and the cyberspace, developing intelligence for the 21st century. It is necessary to use all resources and integrate all existing technological sources starting from the core of the process. \n\rA complete process that integrates the process of obtaining intelligence with the use and exploitation of cyberspace and information technology is required for increasing, securing and exploiting all available information. In the development of this thesis, a new process of micro cycles for intelligence has been developed. It consists of five micro cycles and its purpose is to integrate intelligence processes and technology for better results in this new era of intelligence development in 21st century

Augmented reality applied in safety equipment inspections

The construction industry, and in particular a construction site, is a hazardous place for workers who are exposed to several risks. The dynamism and the complex interaction between the workers, machinery and the environment can lead to dangerous risks that need to be resolved. According to the European Union, the Architecture, Engineering, Construction and Operations (AECO) industry possess one of the highest accident rates among other industries, primarily due to the significant exposure to a construction site's risks compared to others. The accident rate is still relatively high despite the effort that the industry has made in terms of Occupational Risk Prevention (ORP) during the last years. The vision is to achieve the philosophy of zero accidents, which requires more effective methodologies that improve the capacity and the knowledge of the people involved in a construction site. These innovative solutions, consisting of building up risk-preventive data, training, and developing new technological tools to use on-site, are being studied and implemented by the industry. Nevertheless, there is still potential for enhancement on new methodologies that guarantees the safety of the workers