Dispersion in the growth of matter perturbations

We consider the linear growth of matter perturbations on low redshifts in modified gravity Dark Energy (DE) models where G_eff(z,k) is explicitly scale-dependent. Dispersion in the growth today will only appear for scales of the order the critical scale ~ \lambda_{c,0}, the range of the fifth-force today. We generalize the constraint equation satisfied by the parameters \gamma_0(k) and \gamma'_0(k) \equiv \frac{d\gamma(z,k)}{dz}(z=0) to models with G_{eff,0}(k) \ne G. Measurement of \gamma_0(k) and \gamma'_0(k) on several scales can provide information about \lambda_{c,0}. In the absence of dispersion when \lambda_{c,0} is large compared to the probed scales, measurement of \gamma_0 and \gamma'_0 provides a consistency check independent of \lambda_{c,0}. This applies in particular to results obtained earlier for a viable f(R) model.Comment: 8 pages, 5 figure

The dispersion of growth of matter perturbations in f(R) gravity

We study the growth of matter density perturbations delta_m for a number of viable f(R) gravity models that satisfy both cosmological and local gravity constraints, where the Lagrangian density f is a function of the Ricci scalar R. If the parameter m=Rf_{,RR}/f_{,R} today is larger than the order of 10^{-6}, linear perturbations relevant to the matter power spectrum evolve with a growth rate s=d (ln delta_m)/d (ln a) (a is the scale factor) that is larger than in the LCDM model. We find the window in the free parameter space of our models for which spatial dispersion of the growth index gamma_0= gamma(z=0) (z is the redshift) appears in the range of values 0.40< gamma_0<0.55, as well as the region in parameter space for which there is essentially no dispersion and gamma_0 converges to values around 0.40<gamma_0<0.43. These latter values are much lower than in the LCDM model. We show that these unusual dispersed or converged spectra are present in most of the viable f(R) models with m(z=0) larger than the order of 10^{-6}. These properties will be essential in the quest for f(R) modified gravity models using future high-precision observations and they confirm the possibility to distinguish clearly most of these models from the LCDM model.Comment: 11 pages, 7 figure

Tratados Internacionais no Direito Interno Brasileiro: a Convenção de Viena sobre Direito dos Tratados e o Recurso Extraordinário 80.004/SE

TCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Jurídicas. Direito.Um dos maiores desafios do Direito Internacional sempre permaneceu sobre a eficácia de suas normas, seja no plano da sociedade de Estados, quanto no ordenamento jurídico interno das Nações. Dentro das tentativas de explicar a relação entre Direito Internacional e Direito Interno, destacam-se as teorias monista, liderada pelo jurista austríaco Hans Kelsen, e dualista, conduzida pelo alemão Heinrich Triepel e pelo italiano Dionisio Anzilotti. No primeiro caso, as normas advindas do Direito Internacional fazem parte do mesmo sistema jurídico que as provenientes do processo legislativo interno. De acordo com a teoria dualista, o sistema jurídico internacional não se confunde com o sistema jurídico interno, uma vez que o primeiro versa sobre relações entre Estados e o segundo entre Estado e indivíduos, direito público, ou somente entre indivíduos, direito privado. No direito brasileiro, a Constituição Federal de 1988, assim como suas antecessoras, não estabeleceu expressamente as relações entre normas internacionais e as de origens nacionais, tendo o Supremo Tribunal Federal apresentado diretrizes diferentes ao longo do século XX. Nas décadas de 40 e 50, existiu uma corrente predominante pela supremacia do Direito Internacional, modificada no ano de 1977 quando foi julgado o Recurso Extraordinário 80.004, cujo entendimento majoritário indicou a paridade na relação entre tratados e leis nacionais. Entretanto, com o desenvolvimento do Direito Internacional nos últimos tempos e as mudanças nos seus objetivos e finalidades, que passaram a incluir seus efeitos nos ordenamentos jurídicos internos, as doutrinas estrangeiras e brasileiras sugerem a aplicação de conceitos aparentemente incompatíveis com a decisão do Supremo Tribunal Federal em 1977. Nesse aspecto, a Convenção de Viena sobre o Direito dos Tratados de 1969, ratificada pelo Brasil em 2009, consagrou em seus artigos 26 e 27 o princípio do pacta sunt servanda e da impossibilidade de arguição do Direito Interno para se evadir de obrigações internacionais. Diante do compromisso assumido pelo Brasil no âmbito do Direito Internacional, questiona-se a manutenção do entendimento do Supremo Tribunal Federal, uma vez que em aparente desencontro com a Convenção de Viena

Prácticas organizativas en las escuelas públicas de alto rendimiento en Brasil

This research aimed to point out and analyse the organizational practices of the principals in high performance public schools in Brazil, considering the Basic Education Development Index. A multiple case study was conducted in six schools in Volta Redonda, municipality of Rio de Janeiro, in a longitudinal research. It was concluded that in these schools the principals have worked in the same school for more than 20 years, and whose work is recognized by the community that elected him to the position. Principals act to ensure the best results for the students while assuming the responsibility for making critical management decisions. The principals are fully active in the management teams and encourage the participation of parents. The principal of the studied high performance schools unequivocally show that their focus is on the students and their learning, by following up academically all students and offering individualized attention to those with learning difficulties. Finally, it was found that in all the school units, there is a relationship of partnership, respect and cooperation with teachers. The results showed that the involvement and commitment of the school administrators is fundamental for high performance in learning and for the continuous improvement of school performanceEsta investigación busca identificar y analizar las prácticas organizativas de los directores de escuelas públicas de alto rendimiento en Brasil, considerando el Índice de Desarrollo de la Educación Básica. Se realizó un estudio de caso múltiple en seis escuelas en Volta Redonda (Río de Janeiro) en una investigación longitudinal. Se concluyó que en estas escuelas los directores han trabajado en la misma escuela más de 20 años, y su trabajo es reconocido por la comunidad. El director actúa para garantizar los mejores resultados para los estudiantes mientras asume la responsabilidad de la toma de decisiones de gestión críticas. Los directores participan activamente en los equipos de gestión y fomentan la participación de las familias. Los directores de las escuelas de alto rendimiento estudiadas muestran que se centran en los estudiantes y en su aprendizaje al realizar un seguimiento académico de todos los estudiantes y ofrecer atención individualizada a aquellos con dificultades de aprendizaje. En todas las escuelas existe una relación de respeto y cooperación con los maestros. Los resultados mostraron que la participación y el compromiso de los administradores de la escuela es fundamental para el alto rendimiento en el aprendizaje y para la mejora continua del rendimiento escola

Instructional experiment on Lenz's law

We present a visual manifestation of Lenz’s Law. The setup is composed of two coils connected by a central linear metal nucleus. Each of them has a LED plugged in parallel to its terminals. The primary is fed with a pulsating external voltage. We recorded a slow-motion video (960Hz) of the two blinking LEDs. It is possible to observe a complete out-of-phase fade-in/fade-out behavior of them, which is a direct consequence of the minus sign present in the electromagnetic induction equation. We also discuss how to introduce the apparatus in a classroom activity. The mathematical modeling and the numerical results are instructively derived along with the text. There is also a review of the technical features that must be taken into account to study the observation of high-frequency blinking LEDs

Chameleon dark energy models with characteristic signatures

In chameleon dark energy models, local gravity constraints tend to rule out parameters in which observable cosmological signatures can be found. We study viable chameleon potentials consistent with a number of recent observational and experimental bounds. A novel chameleon field potential, motivated by f(R) gravity, is constructed where observable cosmological signatures are present both at the background evolution and in the growth-rate of the perturbations. We study the evolution of matter density perturbations on low redshifts for this potential and show that the growth index today gamma_0 can have significant dispersion on scales relevant for large scale structures. The values of gamma_0 can be even smaller than 0.2 with large variations of gamma on very low redshifts for the model parameters constrained by local gravity tests. This gives a possibility to clearly distinguish these chameleon models from the Lambda-Cold-Dark-Matter model in future high-precision observations.Comment: 16 pages, 8 figure

A robust numerical strategy for finding surface waves in flows of non-Newtonian liquids

Gravity-driven flows of liquid films are frequent in nature and industry, such as in landslides, lava flow, cooling of nuclear reactors, and coating processes. In many of these cases, the liquid is non-Newtonian and has particular characteristics. In this paper, we analyze numerically the temporal stability of films of non-Newtonian liquids falling by gravity, on the onset of instability. The liquid flows over an incline, where surface waves appear under certain conditions, and we do not fix a priori its rheological behavior. For that, we made used of the Carreau-Yasuda model without assigning specific values to its constants, and we compute general stability solutions. The numerical strategy is based on expansions of Chebyshev polynomials for discretizing the Orr-Sommerfeld equation and boundary conditions, and a Galerkin method for solving the generalized eigenvalue problem. In addition, an Inverse Iteration method was implemented to increase accuracy and improve computational time. The result is a robust and light numerical tool capable of finding the critical conditions for different types of fluids, which we use to analyze some key fluids. We show that the outputs of the general code match previous solutions obtained for specific computations. Besides increasing our knowledge on surface-wave instabilities in non-Newtonian liquids, our findings provide a new tool for obtaining comprehensive solutions on the onset of instability.Comment: This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0