Size and shape of Mott regions for fermionic atoms in a two-dimensional optical lattice

We investigate the harmonic-trap control of size and shape of Mott regions in the Fermi Hubbard model on a square optical lattice. The use of Lanczos diagonalization on clusters with twisted boundary conditions, followed by an average over 50-80 samples, drastically reduce finite-size effects in some ground state properties; calculations in the grand canonical ensemble together with a local-density approximation (LDA) allow us to simulate the radial density distribution. We have found that as the trap closes, the atomic cloud goes from a metallic state, to a Mott core, and to a Mott ring; the coverage of Mott atoms reaches a maximum at the core-ring transition. A `phase diagram' in terms of an effective density and the on-site repulsion is proposed, as a guide to maximize the Mott coverage. We also predict that the usual experimentally accessible quantities, the global compressibility and the average double occupancy (rather, its density derivative) display detectable signatures of the core-ring transition. Some spin correlation functions are also calculated, and predict the existence N\'eel ordering within Mott cores and rings.Comment: 5 pages, 6 figure

Self-Confidence and Timing of Entry

This paper analyzes the impact of overconfidence on the timing of entry in markets, profits, and welfare. To do that the paper uses an endogenous timing model where (i) players have private information about costs and (ii) one player is overconfident and the other is rational. The paper shows that for moderate levels of self-confidence there is a unique cost-dependent equilibrium where the overconfident player has a higher ex-ante probability of entering the market before the rational player. In this equilibrium self-confidence reduces the profits of the rational player but can increase the profits of the overconfident player provided that cost asymmetries are small. Finally, we show that overconfidence reduces welfare, except when cost asymmetries are very small.endogenous timing; entry; overconfidence

Lorentz-violating Yang-Mills theory: discussing the Chern-Simons-like term generation

We analyze the Chern-Simons-like term generation in the CPT-odd Lorentz-violating Yang-Mills theory interacting with fermions. Moreover, we study the anomalies of this model as well as its quantum stability. The whole analysis is performed within the algebraic renormalization theory, which is independent of the renormalization scheme. In addition, all results are valid to all orders in perturbation theory. We find that the Chern-Simons-like term is not generated by radiative corrections, just like its Abelian version. Additionally, the model is also free of gauge anomalies and quantum stable.Comment: 16 pages. No figures. Final version to appear in the Eur.Phys.J.

Metaversia: a mooc model for higher education

Globalization and economic interdependency of a post-modern society point toward an internationalization mission for the university. However, on a global scale, social, economic, and cultural circumstances have significant effects upon an individual’s ability to show the merit required in higher education. The growing open access movement reveals the early emergence of a meta-university that bring cost-efficiencies to institutions through the shared development of educational materials, which is particularly important to the developing world. But despite the huge success in the dissemination and democratization of knowledge provided by the open access movement, it has attached a severe financial downside, and configures a hamper in educational innovation due to its failure in harnessing Web 2.0 collaborative technologies. In order to find a model that better suits the needs of collaborative teaching and learning in a networked information economy, two approaches are followed in this dissertation. The first consists in the analysis and comparison of the open education ecosystem. On the other approach, based on the previous results, we propose a MOOC model, Metaversia, for a collaborative network that harness the capital exchange potential, and knowledge-building opportunities that rests on the connections between people, enabling citizen's full participation in the actual networked information economy.A globalização e interdependência económica de uma sociedade pós-moderna impelem a universidade para uma missão de internacionalização. Mas à escala global, circunstâncias sociais, económicas e culturais têm implicações significativas sobre a capacidade dos indivíduos em mostrar o mérito exigido no ensino superior. O movimento de acesso livre revela o surgimento precoce de uma meta universidade que traz mais valias do ponto de vista financeiro para as universidades através do desenvolvimento partilhado de materiais educativos. Mas, apesar do enorme sucesso na disseminação e democratização do conhecimento proporcionado pelo movimento de acesso livre, este possui severas desvantagens financeiras e configura um grande passo atrás na inovação pedagógica devido a sua falha no devido aproveitamento das tecnologias colaborativas da Web 2.0. A fim de encontrar um modelo que melhor se adeque às necessidades de ensino e aprendizagem colaborativa numa economia da informação em rede, duas abordagens são seguidas nesta tese. A primeira consiste na análise e comparação do ecossistema educação aberta. Na outra abordagem, com base nos resultados anteriores, propomos um modelo para um MOOC, Metaversia, para uma rede de colaboração que aproveita o potencial de troca de capital, e de construção de conhecimento que existe no relacionamento interpessoal, permitindo uma plena participação dos cidadãos numa economia da informação em rede

Use of Sociology Concepts as the Basis of a Model for Improving Accessibility in Smart Cities

AbstractThe use of mobile devices and their use for Internet access, for georeferentiation and services consumption had a huge increase.Today, these devices ability to establish cooperation networks and to interact intelligently and cooperatively with the surrounding environment has growing importance.In this paper, we propose a system, based on a model which uses the social paradigms in mobile ubiquitous interactions, capable to effectively connect and integrate these devices in order to improve the accessibility in the cities. The model is inspired in concepts from the theory of organizations and sociology, as the notions of “social role”, “ownership” and “responsibility”, to be incorporated in each device.We present an example for applying the model in the context of accessibility in smart cities for the pedestrian traffic light automatic management

Towards a taxonomy of innovation systems

The concept of National Innovation System (NIS) has been recently applied in the context of developing nations even tough it was originally developed in relation to the more developed economies (Japan, Scandinavian countries, US etc.). This raises the methodological problem of knowing whether what was learnt in the study of more advanced NISs is relevant for all sorts of economies regardless the maturity of their actual innovation systems. With this question in mind an exploratory exercise is implemented. First a technique for mapping different NIS is put forward and next based on such mapping a taxonomy of NISs is proposed. The technique although simple in the steps it requires shows analytical potential. The cartography it generates allows one to compare directly different countries, by visualizing in bi-dimensional space the graphic pattern of the relevant dimensions of their respective NISs. This technique is applied to 69 countries (87.4% of the world population) and a set of 29 indicators is used to examine these NISs along eight major dimensions. With the resulting data, and with the help of cluster analysis, a taxonomy of innovation systems is proposed. That taxonomy which contains 6 major types of NISs indicates that what differentiates most the individual systems is their performance in three critical dimensions: innovation, diffusion and basic and applied knowledge. Country size and the natural resources endowment of the economies also emerge as important contingency factors underlying the overall dynamics of different NISs.innovation; national innovation systems; economic development.