2,396 research outputs found
Globalization and its methodological discontents: Contextualizing globalization through the study of HIV/AIDS
There remains considerable discontent between globalization scholars about how to conceptualize its meaning and in regards to epistemological and methodological questions concerning how we can come to understand how these processes ultimately operate, intersect and transform our lives. This article argues that to better understand what globalization is and how it affects issues such as global health, we must take a differentiating approach, which focuses on how the multiple processes of globalization are encountered and informed by different social groups and with how these encounters are experienced within particular contexts. The article examines the heuristic properties of qualitative field research as a means to help better understand how the intersections of globalization are manifested within particular locations. To do so, the article focuses on three recent case studies conducted on globalization and HIV/AIDS and explores how these cases can help us to understand the contextual permutations involved within the processes of globalization
Dilaton black holes in grand canonical ensemble near the extreme state
Dilaton black holes with a pure electric charge are considered in a framework
of a grand canonical ensemble near the extreme state. It is shown that there
exists such a subset of boundary data that the Hawking temperature smoothly
goes to zero to an infinite value of a horizon radius but the horizon area and
entropy are finite and differ from zero. In string theory the existence of a
horizon in the extreme limit is due to the finiteness of a system only.Comment: 8 pages, RevTex 3.0. Presentation improved, discussion on metrics in
string theory simplified. To be published in Phys.Rev.
Long-term survival following traumatic brain injury: a population-based parametric survival analysis
<b><i>Background:</i></b> Long-term mortality may be increased following traumatic brain injury (TBI); however, the degree to which survival could be reduced is unknown. We aimed at modelling life expectancy following post-acute TBI to provide predictions of longevity and quantify differences in survivorship with the general population. <b><i>Methods:</i></b> A population-based retrospective cohort study using data from the Rochester Epidemiology Project (REP) was performed. A random sample of patients from Olmsted County, Minnesota with a confirmed TBI between 1987 and 2000 was identified and vital status determined in 2013. Parametric survival modelling was then used to develop a model to predict life expectancy following TBI conditional on age at injury. Survivorship following TBI was also compared with the general population and age- and gender-matched non-head injured REP controls. <b><i>Results:</i></b> Seven hundred and sixty nine patients were included in complete case analyses. The median follow-up time was 16.1 years (interquartile range 9.0-20.4) with 120 deaths occurring in the cohort during the study period. Survival after acute TBI was well represented by a Gompertz distribution. Victims of TBI surviving for at least 6 months post-injury demonstrated a much higher ongoing mortality rate compared to the US general population and non-TBI controls (hazard ratio 1.47, 95% CI 1.15-1.87). US general population cohort life table data was used to update the Gompertz model's shape and scale parameters to account for cohort effects and allow prediction of life expectancy in contemporary TBI. <b><i>Conclusions:</i></b> Survivors of TBI have decreased life expectancy compared to the general population. This may be secondary to the head injury itself or result from patient characteristics associated with both the propensity for TBI and increased early mortality. Post-TBI life expectancy estimates may be useful to guide prognosis, in public health planning, for actuarial applications and in the extrapolation of outcomes for TBI economic models
A comparison of Noether charge and Euclidean methods for Computing the Entropy of Stationary Black Holes
The entropy of stationary black holes has recently been calculated by a
number of different approaches. Here we compare the Noether charge approach
(defined for any diffeomorphism invariant Lagrangian theory) with various
Euclidean methods, specifically, (i) the microcanonical ensemble approach of
Brown and York, (ii) the closely related approach of Ba\~nados, Teitelboim, and
Zanelli which ultimately expresses black hole entropy in terms of the Hilbert
action surface term, (iii) another formula of Ba\~nados, Teitelboim and Zanelli
(also used by Susskind and Uglum) which views black hole entropy as conjugate
to a conical deficit angle, and (iv) the pair creation approach of Garfinkle,
Giddings, and Strominger. All of these approaches have a more restrictive
domain of applicability than the Noether charge approach. Specifically,
approaches (i) and (ii) appear to be restricted to a class of theories
satisfying certain properties listed in section 2; approach (iii) appears to
require the Lagrangian density to be linear in the curvature; and approach (iv)
requires the existence of suitable instanton solutions. However, we show that
within their domains of applicability, all of these approaches yield results in
agreement with the Noether charge approach. In the course of our analysis, we
generalize the definition of Brown and York's quasilocal energy to a much more
general class of diffeomorphism invariant, Lagrangian theories of gravity. In
an appendix, we show that in an arbitrary diffeomorphism invariant theory of
gravity, the ``volume term" in the ``off-shell" Hamiltonian associated with a
time evolution vector field always can be expressed as the spatial
integral of , where are the constraints
associated with the diffeomorphism invariance.Comment: 29 pages (double-spaced) late
Radiation Reaction: General approach and applications, especially to electrodynamics
Radiation reaction (but, more generally, fluctuations and dissipation) occurs
when a system interacts with a heat bath, a particular case being the
interaction of an electron with the radiation field. We have developed a
general theory for the case of a quantum particle in a general potential (but,
in more detail, an oscillator potential) coupled to an arbitrary heat bath at
arbitrary temperature, and in an external time-dependent -number field. The
results may be applied to a large variety of problems in physics but we
concentrate by showing in detail the application to the blackbody radiation
heat bath, giving an exact result for radiation reaction problem which has no
unsatisfactory features such as the runaway solutions associated with the
Abraham-Lorentz theory. In addition, we show how atomic energy and free energy
shifts due to temperature may be calculated. Finally, we give a brief review of
applications to Josephson junctions, quantum statistical mechanics, mesoscopic
physics, quantum information, noise in gravitational wave detectors, Unruh
radiation and the violation of the quantum regression theore
Global Constitutionalism and the Responsibility to Protect
There is recent scholarship suggesting that the Responsibility to Protect (R2P) has now emerged as a master concept in relation to responding to mass atrocity crimes and that the R2P can further be seen as representative of an emerging global constitutional norm. In critical response, this article provides the first attempt to systematically investigate R2Pâs relationship with global constitutionalisation as well as to explore its wider implication with regard to global constitutionalism. In doing so, the article examines existing discussions of R2P and global constitutionalism, tracks the normative evolution of R2P in order to determine its current âstageâ of norm diffusion, and further attempts to locate the extent to which the R2P can be perceived as also part of a process of global constitutionalisation. From this analysis the article concludes that although the R2P could be labelled as, at best, a weak emerging norm, it fails to meet the more demanding signifier of an emerging constitutional norm and that there is further evidence to suggest that the R2P might be better understood as a stalled or degenerating norm
Supersymmetry of the 2+1 black holes
The supersymmetry properties of the asymptotically anti-de Sitter black holes
of Einstein theory in 2+1 dimensions are investigated. It is shown that (i) the
zero mass black hole has two exact super- symmetries; (ii) extreme
black holes with have only one; and (iii) generic black holes do
not have any. It is also argued that the zero mass hole is the ground state of
(1,1)-adS supergravity with periodic (``Ramond") boundary conditions on the
spinor fields.Comment: 9 pages LaTeX file, ULB-PMIF-93/0
A Note on Conserved Charges of Asymptotically Flat and Anti-de Sitter Spaces in Arbitrary Dimensions
The calculation of conserved charges of black holes is a rich problem, for
which many methods are known. Until recently, there was some controversy on the
proper definition of conserved charges in asymptotically anti-de Sitter (AdS)
spaces in arbitrary dimensions. This paper provides a systematic and explicit
Hamiltonian derivation of the energy and the angular momenta of both
asymptotically flat and asymptotically AdS spacetimes in any dimension D bigger
or equal to 4. This requires as a first step a precise determination of the
asymptotic conditions of the metric and of its conjugate momentum. These
conditions happen to be achieved in ellipsoidal coordinates adapted to the
rotating solutions.The asymptotic symmetry algebra is found to be isomorphic
either to the Poincare algebra or to the so(D-1, 2) algebra, as expected. In
the asymptotically flat case, the boundary conditions involve a generalization
of the parity conditions, introduced by Regge and Teitelboim, which are
necessary to make the angular momenta finite. The charges are explicitly
computed for Kerr and Kerr-AdS black holes for arbitrary D and they are shown
to be in agreement with thermodynamical arguments.Comment: 27 pages; v2 : references added, minor corrections; v3 : replaced to
match published version forthcoming in General Relativity and Gravitatio
Black Hole Entropy is Noether Charge
We consider a general, classical theory of gravity in dimensions, arising
from a diffeomorphism invariant Lagrangian. In any such theory, to each vector
field, , on spacetime one can associate a local symmetry and, hence, a
Noether current -form, , and (for solutions to the field
equations) a Noether charge -form, . Assuming only that the
theory admits stationary black hole solutions with a bifurcate Killing horizon,
and that the canonical mass and angular momentum of solutions are well defined
at infinity, we show that the first law of black hole mechanics always holds
for perturbations to nearby stationary black hole solutions. The quantity
playing the role of black hole entropy in this formula is simply times
the integral over of the Noether charge -form associated with
the horizon Killing field, normalized so as to have unit surface gravity.
Furthermore, we show that this black hole entropy always is given by a local
geometrical expression on the horizon of the black hole. We thereby obtain a
natural candidate for the entropy of a dynamical black hole in a general theory
of gravity. Our results show that the validity of the ``second law" of black
hole mechanics in dynamical evolution from an initially stationary black hole
to a final stationary state is equivalent to the positivity of a total Noether
flux, and thus may be intimately related to the positive energy properties of
the theory. The relationship between the derivation of our formula for black
hole entropy and the derivation via ``Euclidean methods" also is explained.Comment: 16 pages, EFI 93-4
An Effective Lagrangian with Broken Scale and Chiral Symmetry IV: Nucleons and Mesons at Finite Temperature
We study the finite temperature properties of an effective chiral Lagrangian
which describes nuclear matter. Thermal fluctuations in both the nucleon and
the meson fields are considered. The logarithmic and square root terms in the
effective potential are evaluated by expansion and resummation with the result
written in terms of the exponential integral and the error function,
respectively. In the absence of explicit chiral symmetry breaking a phase
transition restores the symmetry, but when the pion has a mass the transition
is smooth. The nucleon and meson masses as a functions of density and
temperature are discussed.Comment: 21 pages LaTeX + 11 postscript figures, uses epsf.st
- âŠ