Spatial wave intensity correlations in quasi-one-dimensional wires

Spatial intensity correlations between waves transmitted through random media are analyzed within the framework of the random matrix theory of transport. Assuming that the statistical distribution of transfer matrices is isotropic, we found that the spatial correlation function can be expressed as the sum of three terms, with distinctive spatial dependences. This result coincides with the one obtained in the diffusive regime from perturbative calculations, but holds all the way from quasi-ballistic transport to localization. While correlations are positive in the diffusive regime, we predict a transition to negative correlations as the length of the system decreases.Comment: 10 pages, 3 figures. Submitted to Physical Review Letter

Broadband telecom transparency of semiconductor-coated metal nanowires: more transparent than glass

Metallic nanowires (NW) coated with a high permittivity dielectric are proposed as means to strongly reduce the light scattering of the conducting NW, rendering them transparent at infrared wavelengths of interest in telecommunications. Based on a simple, universal law derived from electrostatics arguments, we find appropriate parameters to reduce the scattering efficiency of hybrid metal-dielectric NW by up to three orders of magnitude as compared with the scattering efficiency of the homogeneous metallic NW. We show that metal@dielectric structures are much more robust against fabrication imperfections than analogous dielectric@metal ones. The bandwidth of the transparent region entirely covers the near IR telecommunications range. Although this effect is optimum at normal incidence and for a given polarization, rigorous theoretical and numerical calculations reveal that transparency is robust against changes in polarization and angle of incidence, and also holds for relatively dense periodic or random arrangements. A wealth of applications based on metal-NWs may benefit from such invisibility

Effect of long range spatial correlations on the lifetime statistics of an emitter in a two-dimensional disordered lattice

The effect of spatial correlations on the Purcell effect in a bidimensional dispersion of resonant nanoparticles is analyzed. We perform extensive calculations on the fluorescence decay rate of a point emitter embedded in a system of nanoparticles statistically distributed according to a simple 2D lattice-gas model near the critical point. For short-range correlations (high temperature thermalization) the Purcell factors present a long-tailed statistic which evolves towards a bimodal distribution when approaching the critical point where the spatial correlation length diverges. Our results suggest long-range correlations as a possible origin of the large fluctuations of experimental decay rates in disordered metal films.Comment: 6 pages, 5 figure

Computación cuántica : nuevas perspectivas en el tratamiento de la información

Peer Reviewe

Government, taxes and banking crises

This paper analyzes the effectiveness of different government policies to prevent the emergence of bank ing crises. In particular, we study the impact on welfare of using taxpayers money to recapitalize banks, government injection of money into the banking system through credit lines, the creation of a buffer and taxes on financial transactions (the Tobin tax). We illustrate the trade off between these policies and derive policy implications.Publicad

On the density of states and extinction mean free path of waves in random media: Dispersion relations and sum rules

We establish a fundamental relationship between the averaged density of states and the extinction mean free path of wave propagating in random media. From the principle of causality and the Kramers-Kronig relations, we show that both quantities are connected by dispersion relations and are constrained by a frequency sum rule. The results are valid under very general conditions and should be helpful in the analysis of measurements of wave transport through complex systems and in the design of randomly or periodically structured materials with specific transport properties.Comment: 2 (double) figures, 8 page

Impacto de las estrategias didácticas implementadas en lengua castellana a estudiantes de grado primero en tiempos de COVID-19

Ante el cierre preventivo de instituciones escolares producto de la emergencia por COVID-19, cientos de países definieron un plan para que la educación no se detenga. Sin embargo, asegurar la continuidad en el proceso educativo no es simple y lleva implícito grandes desafíos para docentes, padres de familia, cuidadores y estudiantes; aunque existen recomendaciones el tema se reconoce como “abierto” y lejos aún de evidencias concluyentes que puedan orientar las acciones pedagógicas, (Pimentel, 2020) el panorama de las políticas educativas se describe como emergente y fluido, la evidencia y documentación es poca generalmente carece de detalles, lo que hace difícil determinar que funciona y que no en esta etapa (Jyones Gibbs, Sims, Rodnet y 2020). En este contexto la investigación recogió información sobre el impacto de las estrategias didácticas implementadas por los docentes de la Institución Educativa Cedid Ciudad Bolívar Sede C Jornada Tarde a los estudiantes de grado 102 durante el confinamiento por COVID-19 en el II y III periodo académico 2020. De los resultados surgió una descripción de las herramientas utilizadas para la enseñanza y el aprendizaje orientadas a dar continuidad a la educación para ello los docentes combinaron estrategias tradicionales y digitales de segunda y tercera generación. De otro lado se encontró que las principales problemáticas a las que se enfrentaron son logísticas, tecnológicas y socioafectivas. En cuanto al uso de la tecnología para la comunicación utilizaron WhatsApp, para su trabajo académico Google Classroom, Wixsite y la plataforma institucional, para trabajo sincrónico las plataformas Zoom, Teams y Meet. La mayoría de los docentes refieren requerir apoyo tecnológico y asesoría didáctica para continuar los procesos académicos. (apartes del texto)Facing the preventive closure of school institutions as a result of the COVID-19 emergency, hundreds of countries defined a plan so that education does not stop. However, ensuring continuity in the educational process is not that simple and it implies great challenges for teachers, parents, caregivers and students. Although there are some recommendations, the subject is recognized as "open" and still far from conclusive evidence that can guide pedagogical actions, the panorama of educational policies is described as emerging and fluid, the evidence and documentation is scarce, generally lacks details, which makes hard to determine what works and what doesn't at this point. Having this in mind, this research collected information on the impact of the didactic strategies implemented by the teachers of the “Institución Educativa Cedid Ciudad Bolívar Sede C Jornada Tarde” to the students of grade 102 during the confinement by COVID-19 in the II and III academic period of2020. As a result, a description of the tools used for teaching and learning surged and this aimed at providing continuity to education, this is why the teachers combined traditional and digital second and third generation strategies. On the other hand, it was found that the main problems the teachers faced are logistical, technological and socio-affective. Regarding the use of technology for communication, they used WhatsApp, for their academic work Google Classroom, Wixsite and the institutional platform, for synchronous work the Zoom, Teams and Meet platforms. Most of the teachers report requiring technological support and didactic advice to continue the academic processes.Fundación Universitaria Los Libertadore

Promoting sustainable consumption in Higher Education Institutions through integrative co-creative processes involving relevant stakeholders

The United Nations proposes to ensure a sustainable future for all through the Sustainable Development Goals, assigning a new role to each individual in all sectors of society. Higher Education Institutions are outstanding agents of change, introducing and implementing sustainability in a holistic way, connecting people, and including social and institutional considerations, with students being a key component of change. This study presents a co-creation model to incorporate sustainability in Higher Education Institutions, integrating all members of the university community with a multidisciplinary approach, seeking to address global needs with development tools for new products and services to facilitate the transition of consumers towards responsible consumption. The model aims to analyze the daily consumption pattern of the community at the university, to identify the degree of commitment to sustainability of its members, and to co-create in search of solutions related to responsible consumption and production. This is achieved through five phases of a model, each with specific tasks and objectives based on co-creation processes and tools. As a result, the model enables stakeholders to understand the needs of their community by actively participating within the five phases for developing more democratic solutions and social involvement regarding sustainability issues that can be solved through a co-creative process. The model combines the benefits through ethnographic techniques to discover habits, tools to involve participation, and co-creation to manage complex problems. Future research will focus on the application of the proposed model to more generalist contexts of society, addressing potential challenges due to vertical collaboration and barriers pre-established by society for the adoption of a sustainable lifestyle

Comments on the calculation of the specific growth rate in experiments with untagged individuals

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