Asymptotically flat spacetimes in 3D bigravity

We report that a class of three-dimensional bimetric theories contain asymptotically flat solutions. These spacetimes can be cast in a set of asymptotic conditions at null infinity which are preserved under the infinite dimensional BMS group. Moreover, the algebra of the canonical generators exhibits a central extension. The possibility that these solutions describe regular black holes is also discussed.Comment: 6 page

Boundary dynamics of asymptotically flat 3D gravity coupled to higher spin fields

We construct a two-dimensional action principle invariant under a spin-three extension of BMS$_3$ group. Such a theory is obtained through a reduction of Chern-Simons action with a boundary. This procedure is carried out by imposing a set of boundary conditions obtained from asymptotically flat spacetimes in three dimensions. When implementing part of this set, we obtain an analog of chiral WZW model based on a contraction of $sl(3,\mathbb{R}) \times sl(3,\mathbb{R})$. The remaining part of the boundary conditions imposes constraints on the conserved currents of the model, which allows to further reduce the action principle. It is shown that a sector of this latter theory is related to a flat limit of Toda theory.Comment: 16 pages, no figure

Hunger and Meaning in the Novels of Cristina García

This thesis offers a novel interpretation of the relationship between food and cultural memory starting from the concept of Gothic food and its relationship to colonialism. This work evolves from anthropologist Fernando Ortiz’s contribution to Cuban cultural memory and his metaphor of transculturación through Cuba’s national dish, the ajiaco. The ajiaco, a soup, will be considered in connection to slavery and forced labour on the sugar plantations in Cuba. It symbolises the amalgamation of all the different cultures that interacted on the island because of the colonisation of the indigenous populations and the slave trade starting from the arrival of Christopher Columbus. The Cuban food metaphor provides an opportunity to compare the different ways in which cultural memory operates and specifically how the metaphor has been translated outside of Cuba, through the work of Cuban-American diasporic writer Cristina García in the U.S. The five García novels I have selected to be the focus of this study are: Dreaming in Cuban (1992), The Agüero Sisters (1997), Monkey Hunting (2003), The Lady Matador’s Hotel (2010) and King of Cuba (2013). I consider these works to be representative of an idea of hunger that highlights the paradox of its contemporary attitudes to consumption and globalisation in light of colonialism and its legacies. The five novels selected for analysis exemplify how, in the specific context of the 1959 Cuban Revolution and its aftermath, food and consumption are carriers of a notion of hunger which harbours the violence of colonialism revived by revolutionary upheaval. The thesis introduces the original idea of “dark food”, exemplified by sugar, as a concept able to provide an insight into the legacies of slavery and its relationship to capitalism. The aim of this project is to recentre food in relation to models of memory that shed light on the negative consequences of globalization and capitalism. There is an infinite Western hunger for excess portrayed in García’s texts in contrast with the hunger for basic commodities in Cuba that provides the opportunity to discuss the conflation between an insatiable appetite and the losses caused by historical upheavals. The idea of dark food is to provide a lens through which it is possible to observe contrasts from a middle ground, a place that encapsulates how consumption can both passively and actively shed light on complex identitarian issues that allow for alternative interpretations of the past

CSCWD technologies, applications and challenges [Editorial]

As CSCWD (Computer Supported Cooperative Work in Design) has involved the cooperation of multidisciplinary design teams, traditionally the communication among different design teams has been facilitated by the Intranet or Extranet, which makes the applications of CSCWD more expensive and hardly accessible to most organizations, especially small and medium enterprises. The Internet which can be accessed anywhere and at anytime has changed the whole world as well as CSCWD communities. The phenomenon of Internet has significantly reshaped the research of CSCWD. The universal and nearly free accessibility has made it much easier for people to coordinate and do collaborative design jobs without any physical location boundaries. The new technologies and applications from CSCWD have significantly contributed to the multidisciplinary design teams. Over the past thirteen years, CSCWD communities have been actively involved in the dynamic researches and practical developments from both academia and industry. In order to address the new challenges that CSCWD communities are facing, we carefully selected 15 manuscripts from 198 papers (from 360 original submissions) presented at the 12th International Conference on Computer Supported Cooperative Work in Design (CSCWD 2008), Xi�an, China on April 16-18, 2008, to forge this J.UCS special issue. It is intended for researchers and practitioners interested in CSCWD Technologies, Applications and Challenges. All selected papers have been revised and extended into current versions by three rigorous review rounds

On the Influence of Magnetic Fields on the Structure of Protostellar Jets

We here present the first results of fully three-dimensional (3-D) MHD simulations of radiative cooling pulsed (time-variable) jets for a set of parameters which are suitable for protostellar outflows. Considering different initial magnetic field topologies in approximate $equipartition$ with the thermal gas, i.e., (i) a longitudinal, and (ii) a helical field, both of which permeating the jet and the ambient medium; and (iii) a purely toroidal field permeating only the jet, we find that the overall morphology of the pulsed jet is not very much affected by the presence of the different magnetic field geometries in comparison to a nonmagnetic calculation. Instead, the magnetic fields tend to affect essentially the detailed structure and emission properties behind the shocks at the head and at the pulse-induced internal knots, particularly for the helical and toroidal geometries. In these cases, we find, for example, that the $H_\alpha$ emissivity behind the internal knots can be about three to four times larger than that of the purely hydrodynamical jet. We also find that some features, like the nose cones that often develop at the jet head in 2-D calculations involving toroidal magnetic fields, are smoothed out or absent in the 3-D calculations.Comment: 13 pages, 3 figures, Accepted by ApJ Letters after minor corrections (for high resolution figures, see http://www.iagusp.usp.br/~adriano/h.tar

Thermodynamics from a scaling Hamiltonian

There are problems with defining the thermodynamic limit of systems with long-range interactions; as a result, the thermodynamic behavior of these types of systems is anomalous. In the present work, we review some concepts from both extensive and nonextensive thermodynamic perspectives. We use a model, whose Hamiltonian takes into account spins ferromagnetically coupled in a chain via a power law that decays at large interparticle distance $r$ as $1/r^{\alpha}$ for $\alpha\geq0$. Here, we review old nonextensive scaling. In addition, we propose a new Hamiltonian scaled by $2\frac{(N/2)^{1-\alpha}-1}{1-\alpha}$ that explicitly includes symmetry of the lattice and dependence on the size, $N$, of the system. The new approach enabled us to improve upon previous results. A numerical test is conducted through Monte Carlo simulations. In the model, periodic boundary conditions are adopted to eliminate surface effects.Comment: 12 pages, 2 figures, submitted for publication to Phys. Rev.