576 research outputs found

    Generalised hyperbolicity in spacetimes with string-like singularities

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    In this paper we present well-posedness results of the wave equation in H1H^{1} for spacetimes that contain string-like singularities. These results extend a framework able to characterise gravitational singularities as obstruction to the dynamics of test fields rather than point particles. In particular, we discuss spacetimes with cosmic strings and the relation of our results to the Strong Cosmic Censorship Conjecture.Comment: Accepted for publication in Classical and Quantum Gravit

    Hawking's singularity theorem for C1,1C^{1,1}-metrics

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    We provide a detailed proof of Hawking's singularity theorem in the regularity class C1,1C^{1,1}, i.e., for spacetime metrics possessing locally Lipschitz continuous first derivatives. The proof uses recent results in C1,1C^{1,1}-causality theory and is based on regularisation techniques adapted to the causal structure.Comment: 19 pages, LaTeX; v2: corrected Lemma 4.2; v3: typos corrected, final versio

    Global Gronwall Estimates for Integral Curves on Riemannian Manifolds

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    We prove Gronwall-type estimates for the distance of integral curves of smooth vector fields on a Riemannian manifold. Such estimates are of central importance for all methods of solving ODEs in a verified way, i.e., with full control of roundoff errors. Our results may therefore be seen as a prerequisite for the generalization of such methods to the setting of Riemannian manifolds.Comment: 4 pages, 1 figure, correction of some misprint

    Feasibility study of a clinically-integrated randomized trial of modifications to radical prostatectomy

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    <p>Abstract</p> <p>Background</p> <p>Numerous technical modifications to radical prostatectomy have been proposed. Such modifications are likely to lead to only slight improvements in outcomes. Although small differences would be worthwhile, an appropriately powered randomized trial would need to be very large, and thus of doubtful feasibility given the expense, complexity and regulatory burden of contemporary clinical trials. We have proposed a novel methodology, the clinically-integrated randomized trial, which dramatically streamlines trial procedures in order to reduce the marginal cost of an additional patient towards zero. We aimed to determine the feasibility of implementing such a trial for radical prostatectomy.</p> <p>Methods</p> <p>Patients undergoing radical prostatectomy as initial treatment for prostate cancer were randomized in a factorial design to involvement of the fascia during placement of the anastomotic sutures, urethral irrigation, both or neither. Endpoint data were obtained from routine clinical documentation. Accrual and compliance rates were monitored to determine the feasibility of the trial.</p> <p>Results</p> <p>From a total of 260 eligible patients, 154 (59%) consented; 56 patients declined to participate, 20 were not approached on recommendation of the treating surgeon, and 30 were not approached for logistical reasons. Although recording by surgeons of the procedure used was incomplete (~80%), compliance with randomization was excellent when it was recorded, with only 6% of procedures inconsistent with allocation. Outcomes data was received from 71% of patients at one year. This improved to 83% as the trial progressed.</p> <p>Conclusions</p> <p>A clinically-integrated randomized trial was conducted at low cost, with excellent accrual, and acceptable compliance with treatment allocation and outcomes reporting. This demonstrates the feasibility of the methodology. Improved methods to ensure documentation of surgical procedures would be required before wider implementation.</p> <p>Trial registration</p> <p>ClinicalTrials.gov <a href="http://www.clinicaltrials.gov/ct2/show/NCT00928850">NCT00928850</a></p

    Temporal tensions: EU citizen migrants, asylum seekers and refugees navigating dominant temporalities of work in England

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    This article considers the role of temporality in the differential inclusion of migrants. In order to do this we draw on research which examined the working lives of a diverse group of new migrants in North East England: Eastern European migrants arriving from 2004 and asylum seekers and refugees arriving from 1999. In so doing we emphasise both distinct and shared experiences, related to immigration status but also a range of other dimensions of identity. We specifically consider how dominant temporalities regulate the lives of new migrants through degrees, periods and moments of acceleration/deceleration. The paper illustrates the ways in which dominant temporalities control access and non-access to particular, often precarious forms of work – but also how migrants attempt to navigate such restrictions through their own use and constructions of time. We explore this in relation to three 'phases' of time. Firstly, through experiences of the UK asylum system and work prohibition. Secondly for a broader group of participants we explore the speeding up and slowing down of transitions to and progression within work. Lastly, we consider how participants experience everyday temporal tensions between paid employment and unpaid care. Across these phases we suggest that dominant orderings of time and the narratives which make sense of these, represent non-simultaneous temporalities that do not neatly map onto each other

    A regularisation approach to causality theory for C^{1,1}Lorentzian metrics

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    We show that many standard results of Lorentzian causality theory remain valid if the regularity of the metric is reduced to C^{1,1}. Our approach is based on regularisations of the metric adapted to the causal structure
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