Space-Time Diffeomorphisms in Noncommutative Gauge Theories

In previous work [Rosenbaum M. et al., J. Phys. A: Math. Theor. 40 (2007), 10367-10382, hep-th/0611160] we have shown how for canonical parametrized field theories, where space-time is placed on the same footing as the other fields in the theory, the representation of space-time diffeomorphisms provides a very convenient scheme for analyzing the induced twisted deformation of these diffeomorphisms, as a result of the space-time noncommutativity. However, for gauge field theories (and of course also for canonical geometrodynamics) where the Poisson brackets of the constraints explicitely depend on the embedding variables, this Poisson algebra cannot be connected directly with a representation of the complete Lie algebra of space-time diffeomorphisms, because not all the field variables turn out to have a dynamical character [Isham C.J., Kuchar K.V., Ann. Physics 164 (1985), 288-315, 316-333]. Nonetheless, such an homomorphic mapping can be recuperated by first modifying the original action and then adding additional constraints in the formalism in order to retrieve the original theory, as shown by Kuchar and Stone for the case of the parametrized Maxwell field in [Kuchar K.V., Stone S.L., Classical Quantum Gravity 4 (1987), 319-328]. Making use of a combination of all of these ideas, we are therefore able to apply our canonical reparametrization approach in order to derive the deformed Lie algebra of the noncommutative space-time diffeomorphisms as well as to consider how gauge transformations act on the twisted algebras of gauge and particle fields. Thus, hopefully, adding clarification on some outstanding issues in the literature concerning the symmetries for gauge theories in noncommutative space-times.Comment: This is a contribution to the Special Issue on Deformation Quantization, published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA

Roman imperialism and local identities

REVELL, L. Roman imperialism and local identities. New York: Cambridge University Press, 2009. 236 pp. ISBN 978-0-521-88730-

Unexpected Density Fluctuations in Jammed Disordered Sphere Packings

We computationally study jammed disordered hard-sphere packings as large as a million particles. We show that the packings are saturated and hyperuniform, i.e., that local density fluctuations grow only as a logarithmically-augmented surface area rather than the volume of the window. The structure factor shows an unusual non-analytic linear dependence near the origin, $S(k)\sim|k|$. In addition to exponentially damped oscillations seen in liquids, this implies a weak power-law tail in the total correlation function, $h(r)\sim-r^{-4}$, and a long-ranged direct correlation function.Comment: Submitted for publicatio

Labour Standards And The “Race To The Bottom”: Rethinking Globalisation And Workers Rights From Developmental And Solidaristic Perspectives

There is a protracted stalemate between rich (the North) and poor (the South) countries over the question of minimum labour standards in developing economies. This paper is a sequel to Singh and Zammit (2000). It considers afresh key issues in the controversy. While fully recognizing the moral, political and philosophical dimension of this complex issue, the paper concentrates on the central economic question of the “race to the bottom”. It emphasizes the difficulties of establishing labour standards in the vast informal sectors in developing countries and suggests that the ILO conventions 87 and 98 should be amended to properly reflect these concerns. It also argues that ILO core conventions should be broadened to include the right to decent living. The overall conclusion is that labour standards are important indicators of economic development but their promotion is best achieved in a non-coercive and supportive international environment such as that provided by the ILO.Labour standards, Globalisation, Informal sector, Economic Development.

Distribution anisotropy: the influence of magnetic interactions on the anisotropy of magnetic remanence

The anisotropy of magnetic remanence (AMR) is often used as a tool for examining magnetic anisotropy of rocks. However, the influence of magnetostatic interactions on AMR has not been previously rigorously addressed either theoretically or experimentally, though it is widely thought to be highly significant. Using a three-dimensional micromagnetic algorithm, we have conducted a systematic numerical study of the role of magnetostatic interactions on AMR. We have considered both lineation and foliation, by modelling assemblages of ideal single domain grains and magnetically non-uniform magnetite-like cubic grains. We show that magnetostatic interactions strongly affect the measured AMR signal. It is found that depending on the orientation of the single-grain anisotropy and grain spacing it is possible for the AMR signal from a chain or grid of grains to be either oblate or prolate. For non-uniform grains, the degree of anisotropy generally increases with increasing interactions. In the modelling of AMR anisotropy, saturation isothermal remanence was chosen for numerical tractability. The influence of interactions on other types of more commonly measured AMR, are considered in light of the results in this paper. © The Geological Society of London 2004.Accepted versio

Categorical Comprehensions and Recursion

A new categorical setting is defined in order to characterize the subrecursive classes belonging to complexity hierarchies. This is achieved by means of coercion functors over a symmetric monoidal category endowed with certain recursion schemes that imitate the bounded recursion scheme. This gives a categorical counterpart of generalized safe composition and safe recursion.Comment: Comments are welcom

Spatiotemporal analysis of deforestation patterns and drivers reveals emergent threats to tropical forest landscapes

As deforestation breaches into new tropical frontiers, proactive conservation strategies require a trifecta of information on where deforestation is accelerating (emergent), how drivers of deforestation vary spatiotemporally, and where to focus limited conservation resources in protecting the most integral yet threatened forested landscapes. Here we introduce Emergent Threat Analysis, a process integrating Emerging Hot Spot Analysis of deforestation, visual classification of deforestation outcomes over time, and spatial quantification of contemporary forest condition. We applied Emergent Threat Analysis to tropical Southeast Asia, a global epicentre of biodiversity threatened by deforestation. We found that emergent hot spots (EHS)-a subset of hot spots characterized by strong, recent, and clustered patterns of deforestation-accounted for 26.1% of total forest loss from 1992 to 2018, with deforestation within EHS proceeding at 2.5 times the regional rate of gross loss. Oil palm and rubber plantation expansion were the principal drivers of deforestation within EHS of insular and mainland SE Asia, respectively. Over the study period, oil palm shifted in importance from Sumatra and Sarawak to Papua and Kalimantan, whereas rubber became prominent in Cambodia and Tanintharyi from 2006 to 2015. As of 2019, more than 170 000 km(2) of SE Asia's remaining forest occurred within EHS, of which 21.7% was protected. High and medium-integrity forest constituted 19.2% and 49.1% of remaining EHS forest, respectively, but of these, 35.0% of high-integrity and 23.9% of medium-integrity EHS forest were protected. Because we anticipate that tree plantation expansion will continue to drive deforestation in SE Asia, significantly heightened protection is needed to secure the long-term preservation of high and medium-integrity forest, especially in highly contested forest frontier regions. Finally, as a flexible, integrated process, Emergent Threat Analysis is applicable to deforestation fronts across the global tropics.Peer reviewe