Lorentzian LQG vertex amplitude

We generalize a model recently proposed for Euclidean quantum gravity to the case of Lorentzian signature. The main features of the Euclidean model are preserved in the Lorentzian one. In particular, the boundary Hilbert space matches the one of SU(2) loop quantum gravity. As in the Euclidean case, the model can be obtained from the Lorentzian Barrett-Crane model from a flipping of the Poisson structure, or alternatively, by adding a topological term to the action and taking the small Barbero-Immirzi parameter limit.Comment: 9 pages; typos corrected and footnote adde

Culture-based artefacts to inform ICT design: foundations and practice

Cultural aspects frame our perception of the world and direct the many different ways people interact with things in it. For this reason, these aspects should be considered when designing technology with the purpose to positively impact people in a community. In this paper, we revisit the foundations of culture aiming to bring this concept in dialogue with design. To inform design with cultural aspects, we model reality in three levels of formality: informal, formal, and technical, and subscribe to a systemic vision that considers the technical solution as part of a more complex social system in which people live and interact. In this paper, we instantiate this theoretical and methodological view by presenting two case studies of technology design in which culture-based artefacts were employed to inform the design process. We claim that as important as including issues related to culture in the ICT design agenda—from the conception to the development, evaluation, and adoption of a technology—is the need to support the design process with adequate artefacts that help identifying cultural aspects within communities and translating them into sociotechnical requirements. We argue that a culturally informed perspective on design can go beyond an informative analysis, and can be integrated with the theoretical and methodological framework used to support design, throughout the entire design process

Coherent states in quantum gravity: a construction based on the flux representation of LQG

As part of a wider study of coherent states in (loop) quantum gravity, we introduce a modification to the standard construction, based on the recently introduced (non-commutative) flux representation. The resulting quantum states have some welcomed features, in particular concerning peakedness properties, when compared to other coherent states in the literature.Comment: 24 pages, 2 figures; Revised version to match the published one. Some references added. Discussion of the resolution of the identity include

Should voters be afraid of hard budget constraint legislation? fiscal responsibility law in brazilian municipalities

This manuscript demonstrates that voters have nothing to be afraid of when new hard budgetconstraint legislation is implemented. Our claim is that this kind of legislation reduces theasymmetry of information between voters and incumbents over the budget and, as aconsequence, the latter have incentives to increase the supply of public goods. As anationwide institutional innovation, the Fiscal Responsibility Law (FRL) is exogenous to allmunicipalities; therefore, there is no self-selection bias in its implementation. We show thatpublic goods expenditure increases after the FRL. Second, this increase occurs inmunicipalities located in the country’s poorest region. Third, our findings can be extended tothe supply of public goods because the higher the expenditure with health and education, thegreater the probability of incumbents being re-elected. Finally, there exists a “de facto”higher supply of public goods in education (number of per capita classrooms) after the FRL.

Application of the Ring Theory in the Segmentation of Digital Images

Ring theory is one of the branches of the abstract algebra that has been broadly used in images. However, ring theory has not been very related with image segmentation. In this paper, we propose a new index of similarity among images using Zn rings and the entropy function. This new index was applied as a new stopping criterion to the Mean Shift Iterative Algorithm with the goal to reach a better segmentation. An analysis on the performance of the algorithm with this new stopping criterion is carried out. The obtained results proved that the new index is a suitable tool to compare images.Comment: Very interesting new index to compute the similarity among images. arXiv admin note: substantial text overlap with arXiv:1306.262

Stopping Criterion for the Mean Shift Iterative Algorithm

Image segmentation is a critical step in computer vision tasks constituting an essential issue for pattern recognition and visual interpretation. In this paper, we propose a new stopping criterion for the mean shift iterative algorithm by using images defined in Zn ring, with the goal of reaching a better segmentation. We carried out also a study on the weak and strong of equivalence classes between two images. An analysis on the convergence with this new stopping criterion is carried out too.Comment: Have 8 pages. Is the first version of the more general pape