Dark energy as a kinematic effect

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A lógica matemática da arte ornamental: uma relação de equivalência a partir da estrutura atômica dos cristais

Based in aesthetic relationship between concepts of content and form intends to establish an relationship of analogy between ornaments and crystals. With the objective of building an theoretical investigation of relating the dynamics that happens in the crystals´ atoms to the symmetrical intervals of the ornamental patterns, it tries to draw a reasoning line that is going from the ‘Idea’ of Plato and ‘poiésis’ of Aristotle, until Hegel's philosophical enlargement, that admits the aesthetics as a science of the art integrated in a metaphysical process. Inherent to this question intends, in interrelation terms between aesthetics and metaphysics, content as being intelligent beginning, energy, and form as primitive element, matter, in order to evidence the possibility to calculate the same present symmetries in the ornamental arts like in the nature.

Quantisation of the bosonic string

In this work we review the basic principles of the theory of the relativistic bosonic string through the study of the action functionals of Nambu-Goto and Polyakov and the techniques required for their canonical, light-cone, and path-integral quantisation. For this purpose, we briefly review the main properties of the gauge symmetries and conformal field theory involved in the techniques studied.

A gauge theory for continuous spin particles

In this dissertation we explore the features of a Gauge Field Theory formulation for continuous spin particles (CSP). To make our discussion as self-contained as possible, we begin by introducing all the basics of Group Theory - and representation theory - which are necessary to understand where the CSP come from. We then apply what we learn from Group Theory to the study of the Lorentz and Poincaré groups, to the point where we are able to construct the CSP representation. Finally, after a brief review of the Higher-Spin formalism, through the Schwinger-Fronsdal actions, we enter the realm of CSP Field Theory. We study and explore all the local symmetries of the CSP action, as well as all of the nuances associated with the introduction of an enlarged spacetime, which is used to formulate the CSP action. We end our discussion by showing that the physical contents of the CSP action are precisely what we expected them to be, in comparison to our Group Theoretical approach.

O papel simbólico da língua na construção das identidades nacionais : o caráter identitário da discussão sobre o AO90 em Portugal

Tese de doutoramento, Estudos de Literatura e de Cultura (Cultura e Comunicação), Universidade de Lisboa, Faculdade de Letras, 2016

Anisotropia magnética em nanofilmes com assimetria cristalográfica

This Thesis comprises a theoretical study about the influence of the magnetocrystalline anisotropy on the static and dynamic magnetic properties of nanofilms: monolayers and trilayers coupled through the bilinear and biquadratic exchange fields, for situations in which the systems are grown in unusual [hkl] asymmetric directions. Using a theory based on a realistic phenomenological model for description of nanometric systems, we consider the total free magnetic energy including the Zeeman interaction, cubic and uniaxial anisotropies, demagnetizing and surface anysotropy energies, as well as the exchange terms. Numerical calculations are conducted by minimizing the total magnetic energy from the determination of equilibrium static configurations. We consider experimental parameters found in the literature to illustrate our results for Fe/Cr/Fe trilayer systems. In particular, a total of six different magnetic scenarios are analyzed for three regimens of exchange fields and the [211] and [321] asymmetric growth directions. After numerically minimize the total energy, we use the equilibrium configurations to calculate magnetization and magnetoresistance curves with the respective magnetic phases and corresponding critical fields. These results are also used to establish the boundary for occurrence of saturated states. Within the context of the spin waves, we solve the equation of motion for these systems in order to find the respective associated dispersion relations. The results show similar magnetization and magnetoresistance curves for both [211] and [321] growth scenarios, including an equivalent magnetic transition behavior. However, the combination of those peculiar symmetries and influence of the exchange energies results in attractive properties, including the generation of magnetic states as a function of the asymmetric degree imposed in the [hkl] growth orientations. There is also an increasing incompatibility between the values of saturation fields of magnetization and magnetoresistance for the cases in which a magnetic field acts along intermediate cubic anisotropic axes, particularly in the situations where the bilinear and biquadratic exchange fields are comparable. The dispersion relations and static results are consistent, the corresponding magnetic states are also present in both acoustic and optical modes. Furthermore, Goldstone excitations are also observed for that particular cases of a magnetic field acting in the intermediate axes, an effect related to transitions of second order and to the spontaneous symmetry breaking imposed by the combination of the biquadratic energy with the cubic and uniaxial anisotropies.

O baralho de cartas das calçadas dos Açores : alguns exemplos da cidade da Horta

Na sequência do levantamento das simetrias das calçadas das 9 ilhas dos Açores, efetuado em 2013 (http://sites.uac.pt/rteixeira/simetrias/), foi desenvolvido um baralho de cartas que contempla exemplos em calçada de todas as ilhas. Este é um trabalho conjunto com Jorge Nuno Silva, Carlos Pereira dos Santos e Alda Carvalho, da Associação Ludus. Os exemplos escolhidos para o baralho servem para ilustrar diferentes tipos de rosáceas, frisos e padrões bidimensionais em Calçada Portuguesa (...) Vamos explorar em pormenor alguns exemplos de calçadas da cidade da Horta contemplados no baralho de cartas. (...)

À descoberta de padrões : Rosáceas em Calçada da Ilha Terceira

Prosseguimos a nossa viagem de descoberta de padrões nas calçadas dos Açores. Os padrões que encontramos no dia a dia podem ser classificados de acordo com as simetrias que apresentam. (...) Neste artigo, centramos a nossa atenção na classificação de figuras que apresentam simetrias de rotação e, em alguns casos, simetrias de reflexão. Essas figuras chamam-se rosáceas. (...) Passamos a analisar alguns exemplos de rosáceas em calçada da ilha Terceira. Começamos por uma borboleta com um eixo de simetria vertical e, portanto, com grupo de simetria D1, que pode ser apreciada no Jardim Duque da Terceira, em Angra do Heroísmo. (...)

Tradução parcial comentada do estudo Emigrantes Deportados nos Açores

Dissertação de Mestrado, Tradução e Assessoria Linguística, 13 de Junho de 2016, Universidade dos Açores.

A busca visual da cor, como medida avaliadora do funcionamento do sistema visual: um estudo exploratório a propósito da objetividade da felicidade em crianças

Este estudo, procura explicar a modularidade da mente humana, como um conjunto de módulos, permitindo desta forma contribuir para o estudo das ciências cognitivas. Estes módulos da arquitetura mental, permitem que a nossa mente interprete a cor resultante do sistema visual e das longitudes de ondas do espetro eletromagnético refratado dos objetos. Tendo por base o estudo do sistema visual, as células sensíveis, designadas por fotorrecetores percorrem o nervo ótico até atingir o encéfalo, localizando-se aí o sistema percetivo, permitindo desta forma realizar o estudo sobre busca visual da cor, como medida avaliadora do funcionamento do sistema visual, um estudo exploratório a propósito da objetividade da felicidade em crianças, que visa explorar a busca visual disjuntiva da cor como medida objetiva do bom funcionamento mental, do bem-estar subjetivo, como construto da felicidade. A amostra foi constituída por um grupo de 49 crianças não institucionalizadas e por um grupo de 16 crianças institucionalizadas, de ambos os sexos. Para a concretização deste estudo, foi necessária a utilização de uma tarefa de busca visual disjuntiva, que utilizou as simetrias de cores pertencentes ao mesmo par oponente e cores pertencentes a diferentes pares oponentes. Os resultados sugerem que não há qualquer interferência da institucionalização no funcionamento mental, logo no bem-estar subjetivo nas crianças; ABSTRACT: This study seeks to explain the modularity of the human mind, as a set of modules, giving this way a contribution to the study of the cognitive sciences. These modules of the mental architecture, allow our mind to interpret the resulting color of the visual system and the wavelengths of the electromagnetic spectrum refracted from the objects. Based on the study of our visual system, sensitive cells known as photoreceptors, which run along the optic nerve to the encephalon, being the perceptive system located there, allowing in this way to carry out the study on visual search of colour, as an assessment measure of the functioning of the visual system, an exploratory study concerning the objectivity of happiness in children, which aims to explore the disjunctive visual search of color as an objective measure of good mental functioning, of subjective well-being, as a construct of happiness. The sample consisted of a group of 49 non institutionalized children and of a group of 16 institutionalized children from both sexes. For the implementation of this study it was necessary to use a disjunctive visual search task, which used the Symmetry of colours belonging to the same opponent pair, and colours belonging to different opponent pairs. The results suggest that there is no interference from the institutionalization in mental functioning, therefore in the children’s subjective well being.