Boundary terms in the Barrett-Crane spin foam model and consistent gluing

We extend the lattice gauge theory-type derivation of the Barrett-Crane spin foam model for quantum gravity to other choices of boundary conditions, resulting in different boundary terms, and re-analyze the gluing of 4-simplices in this context. This provides a consistency check of the previous derivation. Moreover we study and discuss some possible alternatives and variations that can be made to it and the resulting models.Comment: 10 pages, 2 figures, revtex; v2: typos in some formulas corrected, version appeared in journa

Contrasting the conceptualisation of victims of trafficking for sexual exploitation: a case study of Brazilians in Spain and Portugal

Despite the significant emphasis given to the trafficking of Brazilians to the sex industry of the Iberian Peninsula, the concepts of “victim of trafficking for sexual exploitation” used in these three countries vary. This article analyses the positions of Brazil, Spain and Portugal regarding the conceptualisation of “trafficking victim,” focusing on their legislation and policies, as well as on relevant narratives which show how these policies are being applied. It showcases how the incompatible definitions being used compromise genuine anti-trafficking actions and may be an indicator that stopping trafficking may not be the primary concern of the policies developed by these governments

A criminological reading of the concept of vulnerability: a case study of Brazilian trafficking victims

The United Nations Trafficking Protocol establishes the ‘abuse of a position of vulnerability’ as one of the means used to traffic persons. This term, however, was not properly defined, leaving it open for multiple interpretations, many of which do not focus on the well-being of the supposedly vulnerable victims. Through a case study of how (potential) Brazilian victims of trafficking are dealt with in Brazil and (to a lesser extent) outside the country, this article focuses on how ‘vulnerability’ is often interpreted as a synonym of strain which leads to deviant behavior. In this way, the concept is co-opted to enable the punishment or restraint of certain people (particularly women from developing countries) who are considered to be unsuitable to migrate

Light Cone Black Holes

When probed with conformally invariant matter fields, light cones in Minkowski spacetime satisfy thermodynamical relations which are the analog of those satisfied by stationary black holes coupled to standard matter fields. These properties stem from the fact that light cones are conformal Killing horizons stationary with respect to observers following the radial conformal Killing fields in flat spacetime. The four laws of light cone thermodynamics relate notions such as (conformal) temperature, (conformal) surface gravity, (conformal) energy and a conformally invariant notion related to area change. These quantities do not admit a direct physical interpretation in flat spacetime. However, they become the usual thermodynamical quantities when Minkowski is mapped, via a Weyl transformation, to a target spacetime where the conformal Killing field becomes a proper Killing field. In this paper we study the properties of such spacetimes. The simplest realisation turns out to be the Bertotti-Robinson solution, which is known to encode the near horizon geometry of near extremal and extremal charged black holes. The analogy between light cones in flat space and black hole horizons is therefore strengthened. The construction works in arbitrary dimensions; in two dimensions one recovers the Jackiv-Teitelboim black hole of dilaton gravity. Other interesting realisations are also presented.Comment: 23 pages, 7 figures; v2: typos corrected, matches published versio

Light Cone Thermodynamics

We show that null surfaces defined by the outgoing and infalling wave fronts emanating from and arriving at a sphere in Minkowski spacetime have thermodynamical properties that are in strict formal correspondence with those of black hole horizons in curved spacetimes. Such null surfaces, made of pieces of light cones, are bifurcate conformal Killing horizons for suitable conformally stationary observers. They can be extremal and non-extremal depending on the radius of the shining sphere. Such conformal Killing horizons have a constant light cone (conformal) temperature, given by the standard expression in terms of the generalisation of surface gravity for conformal Killing horizons. Exchanges of conformally invariant energy across the horizon are described by a first law where entropy changes are given by $1/(4\ell_p^2)$ of the changes of a geometric quantity with the meaning of horizon area in a suitable conformal frame. These conformal horizons satisfy the zeroth to the third laws of thermodynamics in an appropriate way. In the extremal case they become light cones associated with a single event; these have vanishing temperature as well as vanishing entropy.Comment: 30 pages, 5 pictures; V_2: a problem in the proof of the first law has been corrected. Results remain unchanged. Geometric interpretation and presentation improved; V_3: matches published versio

Considering the exploitation of migrants who sell sex: a case study of Brazilians in the Iberian sex industry

Although migrants who sell sex often go through a range of situations which might be considered exploitative, such situations are not always linked with trafficking. Most of the problems seem to be a result of three overlapping issues: problems which result from prostitution’s status as a forbidden or at best a grudgingly tolerated (yet still repressed) activity, problems that affect workers in low-status occupations and problems that affect (undocumented) migrants. The situation of Brazilian migrants who sell sex in the Iberian countries clearly illustrates this. While focusing almost exclusively on implementing (largely infective and potentially harmful) trafficking policies, Spain and Portugal have not addressed the issues which are considered by migrants as the most significant: police harassment and exploitation, unhygienic and unsafe working environments, lack of access to public services such as healthcare, lack of access to housing, as well as prejudice and stigmatization and the consequences thereof. By relying almost solely on a de jure and de facto law enforcement approach, comprehensive and well established international labour and migration instruments which could benefit all migrants who sell sex are ignored

DEBT LIMITS AND ENDOGENOUS GROWTH

This paper studies the consequences on growth and welfare of imposing limits to public borrowing. In the model economy, government spending may play two different roles, either as input in the production function, or providing services directly in the utility function. In these setups I study the effects of different fiscal policies with and without debt limits both in the balanced growth path and during the transitional dynamics. In the long run, if there is no limit, the growth effects of raising labor income taxes are negative, regardless of the role of government spending. However, the role public spending is crucial for the growth effects of changes in the ratio of public expenditures to output. In the presence of a limit to debt, higher labor tax rates have a positive effect on growth if government spending is productive. The opposite is true when private capital drives growth. Regarding welfare, raising labor income taxes imply a lower welfare cost of reducing debt than does cutting government spending, when this is productive.

Transcendental metagenre travelers: a background of the reception of Cervantes’ Don Quixote in Spain and France

No abstract available