Relaxation of isolated quantum systems beyond chaos

In classical statistical mechanics there is a clear correlation between relaxation to equilibrium and chaos. In contrast, for isolated quantum systems this relation is -- to say the least -- fuzzy. In this work we try to unveil the intricate relation between the relaxation process and the transition from integrability to chaos. We study the approach to equilibrium in two different many body quantum systems that can be parametrically tuned from regular to chaotic. We show that a universal relation between relaxation and delocalization of the initial state in the perturbed basis can be established regardless of the chaotic nature of system.Comment: 4+ pages, 4 figs. Closest to published versio

Weyl law for fat fractals

It has been conjectured that for a class of piecewise linear maps the closure of the set of images of the discontinuity has the structure of a fat fractal, that is, a fractal with positive measure. An example of such maps is the sawtooth map in the elliptic regime. In this work we analyze this problem quantum mechanically in the semiclassical regime. We find that the fraction of states localized on the unstable set satisfies a modified fractal Weyl law, where the exponent is given by the exterior dimension of the fat fractal.Comment: 8 pages, 4 figures, IOP forma

Two scenarios for quantum multifractality breakdown

We expose two scenarios for the breakdown of quantum multifractality under the effect of perturbations. In the first scenario, multifractality survives below a certain scale of the quantum fluctuations. In the other one, the fluctuations of the wave functions are changed at every scale and each multifractal dimension smoothly goes to the ergodic value. We use as generic examples a one-dimensional dynamical system and the three-dimensional Anderson model at the metal-insulator transition. Based on our results, we conjecture that the sensitivity of quantum multifractality to perturbation is universal in the sense that it follows one of these two scenarios depending on the perturbation. We also discuss the experimental implications.Comment: 5 pages, 4 figures, minor modifications, published versio

Multifractality of quantum wave functions in the presence of perturbations

We present a comprehensive study of the destruction of quantum multifractality in the presence of perturbations. We study diverse representative models displaying multifractality, including a pseudointegrable system, the Anderson model and a random matrix model. We apply several types of natural perturbations which can be relevant for experimental implementations. We construct an analytical theory for certain cases, and perform extensive large-scale numerical simulations in other cases. The data are analyzed through refined methods including double scaling analysis. Our results confirm the recent conjecture that multifractality breaks down following two scenarios. In the first one, multifractality is preserved unchanged below a certain characteristic length which decreases with perturbation strength. In the second one, multifractality is affected at all scales and disappears uniformly for a strong enough perturbation. Our refined analysis shows that subtle variants of these scenarios can be present in certain cases. This study could guide experimental implementations in order to observe quantum multifractality in real systems.Comment: 20 pages, 27 figure

Cultural identity and diversity management in education Immigrant children in portuguese school

A imigração, nas suas distintas dimensões de direitos, deveres, e responsabilidades transformou-se actualmente num desafio importante e estimulante para o sistema educativo de países democráticos e pluralistas, tal como é o caso de Portugal. Há que reconhecer que estamos a defrontar com interessantes e novos desafios de sustentabilidade social, baseada numa nova ordem de valores, tendo por pano de fundo uma sociedade que sofre uma vertiginosa mutação. Atualmente, esta é uma consolidação de imigrantes em muitos países europeus, como Portugal. Os imigrantes de segunda geração estão enchendo as salas de aula e de muitos que pretendem continuar seus estudos após a escolaridade obrigatória. Em nosso artigo apresentamos uma análise aprofundada da situação nas escolas portuguesas. É hoje consensual, entre os investigadores que se interessam pelas questões da educação, como mostramos neste documento resultado de uma pesquisa intensiva, o importante papel que a escola representa na construção do projecto de vida de todas as crianças e jovens nas sociedades contemporâneas.Immigration, in its different dimensions of rights, duties, and responsibilities now become a major and exciting challenge for the education system of pluralistic and democratic countries, as is the case of Portugal. It is clear that we are faced with new challenges and interesting social sustainability, based on a new order of values, with the backdrop of a society that suffers a precipitous change. Currently this is a consolidation of immigrants in many European countries, such as Portugal. The second-generation immigrants are filling the classrooms and many who intend to continue their studies after compulsory education. In our article we provide a deep analysis of the situation in Portuguese schools. It is now consensus among researchers who are interested in issues of education, as we show in this document result of intensive research, the important role that school plays in the construction of the project life of all children and young people in contemporary societies

Identity and inclusion in Portugal. Portuguese language and cultural diversity in school

Tras ya muchos años de inmigración, las escuelas portuguesas son fiel reflejo de la multiculturalidad social. Esta situación pone a prueba a los profesionales de la educación y a la sociedad en general. Desde las políticas educativas se está apostando por la interculturalidad y por la lengua portuguesa como elementos integradores; pero, como argumentamos, no son suficientes. La adecuada integración socioeducativa está muy influida por variables que analizamos en este trabajoAfter many years of immigration, Portuguese schools are a evident mirror of the multicultural society. This situation is a challenge for education professionals and society in general. From educational policy is betting on multiculturalism and the Portuguese language as integral elements, but that’s not enough, as we argue. Proper integration is strongly influenced by socio variables analyzed in this wor

Curriculum, family and others influential factors in second generation immigrants in Portugal

We realize a quantitative study based on an extensive questionnaire spent in all secondary schools in two large districts, such as Faro and Setubal, which have more than twenty five percent of total immigration to Portugal. For variables of sociological characterization of the students and their families were used frequencies to test the descriptive level and appropriated variables to inferential level. The other topics were subjected to several exploratory analysis factorial. The results presented here refer to the following factors: characteristics related to social and family environment of students, their academic routes, support and aid received by students and attributions of academic success. Finally, the data led us to discover relationships between factors influencing the improvement of the compulsory education of second generation immigrants in Portugal

Semiclassical approach to fidelity amplitude

The fidelity amplitude is a quantity of paramount importance in echo type experiments. We use semiclassical theory to study the average fidelity amplitude for quantum chaotic systems under external perturbation. We explain analytically two extreme cases: the random dynamics limit --attained approximately by strongly chaotic systems-- and the random perturbation limit, which shows a Lyapunov decay. Numerical simulations help us bridge the gap between both extreme cases.Comment: 10 pages, 9 figures. Version closest to published versio

Anomalía congénita del atlas asociada con fractura de la apófisis espinosa de C-7 : a propósito de 1 caso

Se presenta 1 paciente con un defecto congenita del arco posterior del atlas asociado con una fractura de la apólisis espinosa de C-7. La TAC, precedida de una correcta evaluación clínica, permiten diferenciar los traumatismos agudos de las anomalías congénitas en el atlas.A case of a congenital cleft of the posterior arch of the atlas associated with a fracture of the spinous process of C-7 is reported. Appropiate clinical evaluation and CT-scan study allow to differentiate acute trauma from a congenital abnormality in the atlas

Sulfonate-terminated carbosilane dendron-coated nanotubes: a greener point of view in protein sample preparation

Reduction or removal of solvents and reagents in protein sample preparation is a requirement. Dendrimers can strongly interact with proteins and have great potential as a greener alternative to conventional methods used in protein sample preparation. This work proposes the use of single-walled carbon nanotubes (SWCNTs) functionalized with carbosilane dendrons with sulfonate groups for protein sample preparation and shows the successful application of the proposed methodology to extract proteins from a complex matrix. SEM images of nanotubes and mixtures of nanotubes and proteins were taken. Moreover, intrinsic fluorescence intensity of proteins was monitored to observe the most significant interactions at increasing dendron generations under neutral and basic pHs. Different conditions for the disruption of interactions between proteins and nanotubes after protein extraction and different concentrations of the disrupting reagent and the nanotube were also tried. Compatibility of extraction and disrupting conditions with the enzymatic digestion of proteins for obtaining bioactive peptides was also studied. Finally, sulfonate-terminated carbosilane dendron-coated SWCNTs enabled the extraction of proteins from a complex sample without using non-environmentally friendly solvents that were required so far