Implications of a "Fast Radio Burst" from a Galactic Magnetar

A luminous radio burst was recently detected in temporal coincidence with a hard X-ray flare from the Galactic magnetar SGR 1935+2154 with a time and frequency structure consistent with cosmological fast radio bursts (FRB) and a fluence within a factor of $\lesssim 10$ of the least energetic extragalactic FRB previously detected. Although active magnetars are commonly invoked FRB sources, several distinct mechanisms have been proposed for generating the radio emission which make different predictions for the accompanying higher frequency radiation. We show that the properties of the coincident radio and X-ray flares from SGR 1935+2154, including their approximate simultaneity and relative fluence $E_{\rm radio}/E_{\rm X} \sim 10^{-5}$, as well as the duration and spectrum of the X-ray emission, are consistent with extant predictions for the synchrotron maser shock model. Rather than arising from the inner magnetosphere, the X-rays are generated by (incoherent) synchrotron radiation from thermal electrons heated at the same shocks which produce the coherent maser emission. Although the rate of SGR 1935+2154-like bursts in the local universe is not sufficient to contribute appreciably to the extragalactic FRB rate, the inclusion of an additional population of more active magnetars with stronger magnetic fields than the Galactic population can explain both the FRB rate as well as the repeating fraction, however only if the population of active magnetars are born at a rate that is at least two-orders of magnitude lower than that of SGR 1935+2154-like magnetars. This may imply that the more active magnetar sources are not younger magnetars formed in a similar way to the Milky Way population (e.g. via ordinary supernovae), but instead through more exotic channels such as superluminous supernovae, accretion-induced collapse or neutron star mergers.Comment: 21 pages, 9 figures; submitted to ApJL; comments welcome

Decoherence and the Loschmidt echo

Environment--induced decoherence causes entropy increase. It can be quantified using, e.g., the purity $\varsigma={\rm Tr}\rho^2$. When the Hamiltonian of a quantum system is perturbed, its sensitivity to such perturbation can be measured by the Loschmidt echo $\bar M(t)$. It is given by the average squared overlap between the perturbed and unperturbed state. We describe the relation between the temporal behavior of $\varsigma(t)$ and $\bar M(t)$. In this way we show that the decay of the Loschmidt echo can be analyzed using tools developed in the study of decoherence. In particular, for systems with a classically chaotic Hamiltonian the decay of $\varsigma$ and $\bar M$ has a regime where it is dominated by the classical Lyapunov exponent

A 300 GHz "Always-in-Focus" Focusing System for Target Detection

A focusing system for a 300 GHz radar with 5 m target distance and 10 mm diameter spot size resolution is proposed. The focusing system is based on a Gaussian telescope scheme and its main parameters have been de¬signed using Gaussian beam quasi-optical propagation theory with an in-house developed MATLAB® based analysis tool. Then, this approach has been applied to a real focusing system based on two elliptical mirrors in order to reduce the distortion and cross-polar level and a plane mirror to provide scanning capabilities. The over¬all system has been simulated with a full-wave electromag¬netic simulator and its behavior is presented. With this approach, the focusing system always works "in-focus" since the only mirror that is rotated when scanning is the output plane mirror, so the beam is almost not distorted. The design process, although based in the well-known Gaussian beam quasi-optical propagation theory, provides a fast and accurate method and minimizes the overall size of the mirrors. As a consequence, the size of the focusing system is also reduced

Oportunidades y retos de la Estrategia Nacional de Formación y Acceso para la Apropiación Pedagógica de las TIC del programa Computadores para Educar

El gobierno nacional de Colombia a través del programa Computadores para Educar, en la actualidad adelanta en todo el país la “Estrategia Nacional de Formación y Acceso para la Apropiación Pedagógica de las TIC”, proceso mediante el cual dicha entidad ha logrado llegar a los rincones más apartados de Colombia llevando tecnología y formación en TIC a todas las comunidades educativas. En el marco de este proyecto, en la región 6 conformada por los departamentos de Cauca, Nariño y Putumayo, la Universidad de Nariño – como operador del programa –, dirige todo el proceso formativo a los docentes de 4.948 sedes educativas de la región; al mismo tiempo viene adelantando un proceso investigativo tendiente a analizar los beneficios, dificultades y retos que afronta el proceso formativo de los docentes de las instituciones educativas públicas de la región en el área de la apropiación pedagógica de las TIC, centrándose ante todo en la enorme posibilidad de mejorar la calidad educativa en dichas instituciones. La presente ponencia recoge las principales reflexiones en torno a la experiencia obtenida en este proceso formativo e investigativo adelantado por la Universidad, así como los hallazgos preliminares en torno al mejoramiento de estrategias didácticas, competencias investigativas y desarrollo de proyectos pedagógicos de aula que han hecho parte fundamental de la formación ofrecida hasta el momento