Primordial non-Gaussianity from mixed inflaton-curvaton perturbations

We characterise the primordial perturbations produced due to both inflaton and curvaton fluctuations in models where the curvaton has a quadratic, cosine or hyperbolic potential, and the inflaton potential is characterised by the usual slow-roll parameters. Isocurvature curvaton field perturbations can produce significant non-Gaussianity in the primordial density field, in contrast with adiabatic inflaton field perturbations which produce negligible non-Gaussianity for canonical scalar fields. A non-self-interacting curvaton with quadratic potential produces a local-type non-Gaussianity that is well described by the non-linearity parameter fNL, which may be scale-dependent when the inflaton perturbations dominate the power spectrum. We show how observational bounds on non-linearity parameters and the tensor-scalar ratio can be used to constrain curvaton and inflaton parameters. We find a consistency relation between the bispectrum and trispectrum parameters in a mixed inflaton-curvaton model for a quadratic curvaton potential. Self-interaction terms in the curvaton potential can lead to both a large trispectrum parameter, gNL, and scale-dependence of the non-linearity parameters.Comment: 17 pages, 8 figures, (v2 references added

Tilted Ekpyrosis

We consider a simple model of cosmological collapse driven by canonical fields with exponential potentials. We generalise the two-field ekpyrotic collapse to consider non-orthogonal or tilted potentials and give the general condition for isocurvature field fluctuations to have a scale-invariant spectrum in this model. In particular we show that tilted potentials allow for a slightly red spectrum of perturbations as required by current observations. However a red spectrum of fluctuations implies that the two-field ekpyrotic phase must have a finite duration and requires a preceding phase which sets the initial conditions for what otherwise appears to be a fine-tuned trajectory in the phase space.Comment: 5 pages, references adde

Mixed-methods research: a new approach to evaluating the motivation and satisfaction of university students using advanced visual technologies

The final publication is available at link.springer.comA mixed-methods study evaluating the motivation and satisfaction of Architecture degree students using interactive visualization methods is presented in this paper. New technology implementations in the teaching field have been largely extended to all types of levels and educational frameworks. However, these innovations require approval validation and evaluation by the final users, the students. In this paper, the advantages and disadvantages of applying mixed evaluation technology are discussed in a case study of the use of interactive and collaborative tools for the visualization of 3D architectonical models. The main objective was to evaluate Architecture and Building Science students’ the motivation to use and satisfaction with this type of technology and to obtain adequate feedback that allows for the optimization of this type of experiment in future iterations.Postprint (author’s final draft

On the Combinatorial Complexity of Approximating Polytopes

Approximating convex bodies succinctly by convex polytopes is a fundamental problem in discrete geometry. A convex body $K$ of diameter $\mathrm{diam}(K)$ is given in Euclidean $d$-dimensional space, where $d$ is a constant. Given an error parameter $\varepsilon > 0$, the objective is to determine a polytope of minimum combinatorial complexity whose Hausdorff distance from $K$ is at most $\varepsilon \cdot \mathrm{diam}(K)$. By combinatorial complexity we mean the total number of faces of all dimensions of the polytope. A well-known result by Dudley implies that $O(1/\varepsilon^{(d-1)/2})$ facets suffice, and a dual result by Bronshteyn and Ivanov similarly bounds the number of vertices, but neither result bounds the total combinatorial complexity. We show that there exists an approximating polytope whose total combinatorial complexity is $\tilde{O}(1/\varepsilon^{(d-1)/2})$, where $\tilde{O}$ conceals a polylogarithmic factor in $1/\varepsilon$. This is a significant improvement upon the best known bound, which is roughly $O(1/\varepsilon^{d-2})$. Our result is based on a novel combination of both old and new ideas. First, we employ Macbeath regions, a classical structure from the theory of convexity. The construction of our approximating polytope employs a new stratified placement of these regions. Second, in order to analyze the combinatorial complexity of the approximating polytope, we present a tight analysis of a width-based variant of B\'{a}r\'{a}ny and Larman's economical cap covering. Finally, we use a deterministic adaptation of the witness-collector technique (developed recently by Devillers et al.) in the context of our stratified construction.Comment: In Proceedings of the 32nd International Symposium Computational Geometry (SoCG 2016) and accepted to SoCG 2016 special issue of Discrete and Computational Geometr

Hybridizing Non-dominated Sorting Algorithms: Divide-and-Conquer Meets Best Order Sort

Many production-grade algorithms benefit from combining an asymptotically efficient algorithm for solving big problem instances, by splitting them into smaller ones, and an asymptotically inefficient algorithm with a very small implementation constant for solving small subproblems. A well-known example is stable sorting, where mergesort is often combined with insertion sort to achieve a constant but noticeable speed-up. We apply this idea to non-dominated sorting. Namely, we combine the divide-and-conquer algorithm, which has the currently best known asymptotic runtime of $O(N (\log N)^{M - 1})$, with the Best Order Sort algorithm, which has the runtime of $O(N^2 M)$ but demonstrates the best practical performance out of quadratic algorithms. Empirical evaluation shows that the hybrid's running time is typically not worse than of both original algorithms, while for large numbers of points it outperforms them by at least 20%. For smaller numbers of objectives, the speedup can be as large as four times.Comment: A two-page abstract of this paper will appear in the proceedings companion of the 2017 Genetic and Evolutionary Computation Conference (GECCO 2017

The digital and multilingual competences. A good teaching practice for the EFL classroom of Secondary Education

In the context of modern education, the European Commission has recommended 8 key competences for lifelong learning. When considering the enhancement role played by the digital competence in the development of the all other ones, nurturing this competence becomes paramount. From the perspective of EFL education, the usage of ICTs in the classroom is directly linked to an improvement of communication skills. This is due to the fact that technology affords numerous opportunities in the form of digital resources and platforms available for educators to experiment with. On the other side, students seem more engaged and motivated to take part in class lessons. They want to actively interact in group activities and let their creative voices be heard. With that in mind, the paper presents a 10 session proposal, conceived as a good teaching practice directed at 4th of ESO EFL students.En el contexto de la educación moderna, la Comisión Europea ha recomendado 8 competencias clave para el aprendizaje permanente. Al considerar el papel potenciador que desempeña la competencia digital en el desarrollo de todas las demás, cultivar esta competencia se convierte en algo primordial. Con respecto a la enseñanza del inglés como lengua extranjera, el uso de las TIC en el aula está directamente relacionado con la mejora de las competencias comunicativas. La razón es que la tecnología ofrece numerosas oportunidades en forma de recursos y plataformas digitales disponibles para que los educadores experimenten. Por otro lado, los alumnos parecen más comprometidos y motivados para participar en las clases. Quieren interactuar activamente en las actividades de grupo y dejar oír su voz creativa. Así pues, se presenta una propuesta de 10 sesiones, concebidas como una buena práctica docente dirigida a alumnos de inglés de 4º de la ESO.Máster en Profesor de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanzas de Idioma

Plan para corrección de la cuenca de La Picacha ya cuenta con recursos

"Las obras de corrección de la cuenca de la quebrada La Picacha todavía no tienen una fecha fija de inicio. Mientras tanto, el Área Metropolitana del Valle de Aburrá informó que con tres mil millones de pesos apoyará la intervención de esta cuenca que tiene en riesgo a las familias de Belén Las Mercedes por las obras de canalización que hacen que el agua rompa en sus casas ante las crecientes. La docente y abogada de la Universidad de Medellín, Erika Castro Buitrago, explicó que ""cuando la quebrada, que es avenida torrencial, viene con mucha agua la curva le permite más velocidad y toda el agua se va encima de la gente, que está en el retiro permitido y tiene escritura pública"".

Habitantes de La Playita siguen a la espera de un traslado

Siempre que empieza la temporada invernal las noches son un suplicio para Leidy Lorena Rico. No es para más, pues su casa, en la que lleva más de quince años viviendo y donde ha tenido y levantado a tres hijos, está a escasos diez metros de la quebrada La Picacha, una de las avenidas torrenciales más riesgosas de Medellín.De esas 106 familias, 56 ya se encuentran reubicadas. 29 de ellas en la modalidad de vivienda definitiva, sea usada o nueva, y las otras 27 en arriendo subsidiado, según informó Genny Ocampo, subdirectora poblacional del Isvimed. El resto de viviendas, como el caso de Leidy, a quién le dijeron que la ubicarían en la Aurora, se encuentran o en trámites o iniciaron procesos y no pudieron continuar o simplemente porque se niegan a dejar atrás su hogar. Mención de Universidad de Medellín

Obtenção e caracterização de filmes poliméricos a partir de poli(vinilpiridina)/cloreto de ferro(III)

TCC (graduação) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Curso de Química.O presente trabalho descreve a preparação e o estudo de propriedades físicoquímicas de filmes poliméricos formados pela classe de polímeros poli(vinilpiridina) e cloreto de ferro(III). Para tanto foram preparados compostos com os polímeros poli(2-vinilpiridina) (P2VP) e poli(4-vinilpiridina) (P4VP) e sal FeCl3.6H2O, em diferentes proporções de polímero e sal: 1:1, 2:1 e 4:1 (mol de unidade monomérica/mol de sal). A formação do composto ocorre através da interação entre o par eletrônico disponível no nitrogênio piridínico da poli(vinilpiridina) e os orbitais d da camada de valência do íon metálico Fe(III), interação esta caracterizada através de estudos de espectros vibracionais na região do infravermelho, que mostram um deslocamento significativo da banda de estiramento C-N para o P2VP e P4VP com a formação dos complexos metálicos. Os filmes poliméricos também foram estudados e caracterizados por técnicas de análise termogravimétrica. As curvas de termogravimetria mostram que há uma diminuição na temperatura onde se inicia a degradação térmica dos complexos quando comparados com os polímeros puros. As curvas de calorimetria exploratória diferencial mostram que há um aumento na temperatura de transição vítrea dos complexos, o que sugere uma maior rigidez da cadeia polimérica com a complexação. Medidas de absorção de água indicam que os complexos absorvem quantidades significativas de água e dependem da quantidade de íons Fe(III) na amostra. Medidas de condutividade elétrica dos filmes mostram que há um aumento significativo em relação à condutividade dos polímeros, embora ainda sejam características de material não condutor