4,431 research outputs found
On the Bartnik extension problem for the static vacuum Einstein equations
We develop a framework for understanding the existence of asymptotically flat
solutions to the static vacuum Einstein equations with prescribed boundary data
consisting of the induced metric and mean curvature on a 2-sphere. A partial
existence result is obtained, giving a partial resolution of a conjecture of
Bartnik on such static vacuum extensions. The existence and uniqueness of such
extensions is closely related to Bartnik's definition of quasi-local mass.Comment: 33 pages, 1 figure. Minor revision of v2. Final version, to appear in
Class. Quantum Gravit
The shifting politics of patient activism: from bio-sociality to bio-digital citizenship
No embargo required.Digital media provide novel tools for patient activists from disease- and condition-specific communities. While those with debilitating conditions or disabilities have long recognised the value of collective action for advancing their interests, digital media offers activists unparalleled opportunities to fulfil their goals. This article explores the shifting politics of âactivismâ in the increasingly digitally mediated, commercialised context of healthcare, asking: what role have digital media played in the repertoire of activistsâ strategies? And, to what extent and how has the use of such media impacted the very concept of activism? Building on sociological ideas on emergent forms of âbiological citizenshipâ and drawing on findings from an analysis of available media, including television and print news reportage, online communications, published histories, and campaign material and other information produced by activists in HIV/AIDS and breast cancer communities, we argue that digital media have profoundly shaped how âactivismâ is enacted, both the goals pursued, and the strategies adopted, which serve to broadly align contemporary patient communitiesâ interests with those of science and business. This alignment, which we characterise as âbio-digital citizenshipâ, has involved a fundamental reorientation of âactivismâ from less of a struggle for rights to more of a striving to achieve a public profile and attract funding. We conclude by calling for a reconceptualisation of âactivismâ to more adequately reflect the workings of power in the digital age, whereby the agency and hopes of citizens are central to the workings of political rule
Peaks in the Hartle-Hawking Wave Function from Sums over Topologies
Recent developments in ``Einstein Dehn filling'' allow the construction of
infinitely many Einstein manifolds that have different topologies but are
geometrically close to each other. Using these results, we show that for many
spatial topologies, the Hartle-Hawking wave function for a spacetime with a
negative cosmological constant develops sharp peaks at certain calculable
geometries. The peaks we find are all centered on spatial metrics of constant
negative curvature, suggesting a new mechanism for obtaining local homogeneity
in quantum cosmology.Comment: 16 pages,LaTeX, no figures; v2: some changes coming from revision of
a math reference: wave function peaks sharp but not infinite; v3: added
paragraph in intro on interpretation of wave functio
Universality, limits and predictability of gold-medal performances at the Olympic Games
Inspired by the Games held in ancient Greece, modern Olympics represent the
world's largest pageant of athletic skill and competitive spirit. Performances
of athletes at the Olympic Games mirror, since 1896, human potentialities in
sports, and thus provide an optimal source of information for studying the
evolution of sport achievements and predicting the limits that athletes can
reach. Unfortunately, the models introduced so far for the description of
athlete performances at the Olympics are either sophisticated or unrealistic,
and more importantly, do not provide a unified theory for sport performances.
Here, we address this issue by showing that relative performance improvements
of medal winners at the Olympics are normally distributed, implying that the
evolution of performance values can be described in good approximation as an
exponential approach to an a priori unknown limiting performance value. This
law holds for all specialties in athletics-including running, jumping, and
throwing-and swimming. We present a self-consistent method, based on normality
hypothesis testing, able to predict limiting performance values in all
specialties. We further quantify the most likely years in which athletes will
breach challenging performance walls in running, jumping, throwing, and
swimming events, as well as the probability that new world records will be
established at the next edition of the Olympic Games.Comment: 8 pages, 3 figures, 1 table. Supporting information files and data
are available at filrad.homelinux.or
Rotation-Measures across Parsec-scale Jets of FRI radio galaxies
We present the results of a parsec-scale polarization study of three FRI
radio galaxies - 3C66B, 3C78 and 3C264 - obtained with the Very Long Baseline
Array at 5, 8 and 15 GHz. Parsec-scale polarization has been detected in a
large number of beamed radio-loud active galactic nuclei, but in only a handful
of the relatively unbeamed radio galaxies. We report here the detection of
parsec-scale polarization at one or more frequencies in all three FRI galaxies
studied. We detect Faraday rotation measures of the order of a few hundred
rad/m^2 in the nuclear jet regions of 3C78 and 3C264. In 3C66B polarization was
detected at 8 GHz only. A transverse rotation measure gradient is observed
across the jet of 3C78. The inner-jet magnetic field, corrected for Faraday
rotation, is found to be aligned along the jet in both 3C78 and 3C264, although
the field becomes orthogonal further from the core in 3C78. The RM values in
3C78 and 3C264 are similar to those previously observed in nearby radio
galaxies. The transverse RM gradient in 3C78, the increase in the degree of
polarization at the jet edge, the large rotation in the polarization angles due
to Faraday rotation and the low depolarization between frequencies, suggests
that a layer surrounding the jet with a sufficient number of thermal electrons
and threaded by a toroidal or helical magnetic field is a good candidate for
the Faraday rotating medium. This suggestion is tentatively supported by Hubble
Space Telescope optical polarimetry but needs to be examined in a greater
number of sources.Comment: Accepted for publication in The Astrophysical Journal, March 2009 -
20 v694 issu
Ricci Solitons and Einstein-Scalar Field Theory
B List has recently studied a geometric flow whose fixed points correspond to
static Ricci flat spacetimes. It is now known that this flow is in fact Ricci
flow modulo pullback by a certain diffeomorphism. We use this observation to
associate to each static Ricci flat spacetime a local Ricci soliton in one
higher dimension. As well, solutions of Euclidean-signature Einstein gravity
coupled to a free massless scalar field with nonzero cosmological constant are
associated to shrinking or expanding Ricci solitons. We exhibit examples,
including an explicit family of complete expanding solitons which can be
thought of as a Ricci flow for a complete Lorentzian metric. The possible
generalization to Ricci-flat stationary metrics leads us to consider an
alternative to Ricci flow.Comment: 17 pages, 1 figure; Revised version (organizational changes, other
minor revisions and corrections, citations corrected and added), to appear in
CQ
Suited for Success? : Suits, Status, and Hybrid Masculinity
This document is the Accepted Manuscript version. The final, definitive version of this paper has been published in Men and Masculinities, March 2017, doi: https://doi.org/10.1177/1097184X17696193, published by SAGE Publishing, All rights reserved.This article analyzes the sartorial biographies of four Canadian men to explore how the suit is understood and embodied in everyday life. Each of these men varied in their subject positionsâbody shape, ethnicity, age, and gender identityâwhich allowed us to look at the influence of menâs intersectional identities on their relationship with their suits. The men in our research all understood the suit according to its most common representation in popular culture: a symbol of hegemonic masculinity. While they wore the suit to embody hegemonic masculine configurations of practiceâpower, status, and rationalityâmost of these men were simultaneously marginalized by the gender hierarchy. We explain this disjuncture by using the concept of hybrid masculinity and illustrate that changes in the style of hegemonic masculinity leave its substance intact. Our findings expand thinking about hybrid masculinity by revealing the ways subordinated masculinities appropriate and reinforce hegemonic masculinity.Peer reviewe
Comparison of tumour-based (Petersen Index) and inflammation-based (Glasgow Prognostic Score) scoring systems in patients undergoing curative resection for colon cancer
After resection, it is important to identify colon cancer patients, who are at a high risk of recurrence and who may benefit from adjuvant treatment. The Petersen Index (PI), a prognostic model based on pathological criteria is validated in Dukes' B and C disease. Similarly, the modified Glasgow Prognostic Score (mGPS) based on biochemical criteria has also been validated. This study compares both the scores in patients undergoing curative resection of colon cancer. A total of 244 patients underwent elective resection between 1997 and 2005. The PI was constructed from pathological reports; the mGPS was measured pre-operatively. The median follow-up was 67 months (minimum 36 months) during which 109 patients died; 68 of them from cancer. On multivariate analysis of age, Dukes' stage, PI and mGPS, age (hazard ratio, HR, 1.74, P=0.001), Dukes' stage (HR, 3.63, P<0.001), PI (HR, 2.05, P=0.010) and mGPS (HR, 2.34, P<0.001) were associated independently with cancer-specific survival. Three-year cancer-specific survival rates for Dukes' B patients with the low-risk PI were 98, 92 and 82% for the mGPS of 0, 1 and 2, respectively (P<0.05). The high-risk PI population is small, in particular for Dukes' B disease (9%). The mGPS further stratifies those patients classified as low risk by the PI. Combining both the scoring systems could identify patients who have undergone curative surgery but are at high-risk of cancer-related death, therefore guiding management and trial stratification
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