1,284 research outputs found
Photon deflection and precession of the periastron in terms of spatial gravitational fields
We show that a Maxwell-like system of equations for spatial gravitational
fields and (latter being the analogy of a magnetic field),
modified to include an extra term for the field in the expression for
force, leads to the correct values for the photon deflection angle and for the
precession of the periastron
Electrodynamics with Lorentz-violating operators of arbitrary dimension
The behavior of photons in the presence of Lorentz and CPT violation is
studied. Allowing for operators of arbitrary mass dimension, we classify all
gauge-invariant Lorentz- and CPT-violating terms in the quadratic Lagrange
density associated with the effective photon propagator. The covariant
dispersion relation is obtained, and conditions for birefringence are
discussed. We provide a complete characterization of the coefficients for
Lorentz violation for all mass dimensions via a decomposition using
spin-weighted spherical harmonics. The resulting nine independent sets of
spherical coefficients control birefringence, dispersion, and anisotropy. We
discuss the restriction of the general theory to various special models,
including among others the minimal Standard-Model Extension, the isotropic
limit, the case of vacuum propagation, the nonbirefringent limit, and the
vacuum-orthogonal model. The transformation of the spherical coefficients for
Lorentz violation between the laboratory frame and the standard Sun-centered
frame is provided. We apply the results to various astrophysical observations
and laboratory experiments. Astrophysical searches of relevance include studies
of birefringence and of dispersion. We use polarimetric and dispersive data
from gamma-ray bursts to set constraints on coefficients for Lorentz violation
involving operators of dimensions four through nine, and we describe the mixing
of polarizations induced by Lorentz and CPT violation in the cosmic-microwave
background. Laboratory searches of interest include cavity experiments. We
present the theory for searches with cavities, derive the experiment-dependent
factors for coefficients in the vacuum-orthogonal model, and predict the
corresponding frequency shift for a circular-cylindrical cavity.Comment: 58 pages two-column REVTeX, accepted in Physical Review
Patient engagement with antibiotic messaging in secondary care: a qualitative feasibility study of the ‘review & revise’ experience
Background: We aimed to investigate and optimise the acceptability and usefulness of a patient leaflet about antibiotic prescribing decisions made during hospitalisation, and to explore individual patient experiences and preferences regarding the process of antibiotic prescription ‘review & revise’ which is a key strategy to minimise antibiotic overuse in hospitals.
Methods: In this qualitative study, run within the feasibility study of a large, cluster-randomised stepped wedge trial of 36 hospital organisations, a series of semi-structured, think-aloud telephone interviews were conducted and data were analysed using thematic analysis. Fifteen adult patients who had experienced a recent acute medical hospital admission during which they had been prescribed antimicrobials and offered a patient leaflet about antibiotic prescribing were recruited to the study.
Results: Participants reacted positively to the leaflet, reporting that it was both an accessible and important source of information which struck the appropriate balance between informing and reassuring. Participants all valued open communication with clinicians, and were keen to be involved in antibiotic prescribing decisions, with individuals reporting positive experiences regarding antibiotic prescription changes or stopping. Many participants had prior experience or knowledge of antibiotics and resistance, and generally welcomed efforts to reduce antibiotic usage. Overall, there was a feeling that healthcare professionals (HCPs) are trusted experts providing the most appropriate treatment for individual patient conditions.
Conclusions: This study offers novel insights into how patients within secondary care are likely to respond to messages advocating a reduction in the use of antibiotics through the ‘review & revise’ approach. Due to the level of trust that patients place in their care provider, encouraging HCPs within secondary care to engage patients with greater communication and information provision could provide great advantages in the drive to reduce antibiotic use. It may also be beneficial for HCPs to view patient experiences as cumulative events that have the potential to impact future behaviour around antibiotic use. Finally, pre-testing messages about antibiotic prescribing and resistance is vital to dispelling any misconceptions either around effectiveness of treatment for patients, or perceptions of how messages may be received
Chaotic Properties of Dilute Two and Three Dimensional Random Lorentz Gases I: Equilibrium Systems
We compute the Lyapunov spectrum and the Kolmogorov-Sinai entropy for a
moving particle placed in a dilute, random array of hard disk or hard sphere
scatterers - i.e. the dilute Lorentz gas model. This is carried out in two
ways: First we use simple kinetic theory arguments to compute the Lyapunov
spectrum for both two and three dimensional systems. In order to provide a
method that can easily be generalized to non-uniform systems we then use a
method based upon extensions of the Lorentz-Boltzmann (LB) equation to include
variables that characterize the chaotic behavior of the system. The extended LB
equations depend upon the number of dimensions and on whether one is computing
positive or negative Lyapunov exponents. In the latter case the extended LB
equation is closely related to an "anti-Lorentz-Boltzmann equation" where the
collision operator has the opposite sign from the ordinary LB equation. Finally
we compare our results with computer simulations of Dellago and Posch and find
very good agreement.Comment: 48 pages, 3 ps fig
Height estimates for Killing graphs
The paper aims at proving global height estimates for Killing graphs defined
over a complete manifold with nonempty boundary. To this end, we first point
out how the geometric analysis on a Killing graph is naturally related to a
weighted manifold structure, where the weight is defined in terms of the length
of the Killing vector field. According to this viewpoint, we introduce some
potential theory on weighted manifolds with boundary and we prove a weighted
volume estimate for intrinsic balls on the Killing graph. Finally, using these
tools, we provide the desired estimate for the weighted height in the
assumption that the Killing graph has constant weighted mean curvature and the
weighted geometry of the ambient space is suitably controlled.Comment: 26 pages. Final version. To appear on Journal of Geometric Analysi
Cosmological quantum entanglement
We review recent literature on the connection between quantum entanglement
and cosmology, with an emphasis on the context of expanding universes. We
discuss recent theoretical results reporting on the production of entanglement
in quantum fields due to the expansion of the underlying spacetime. We explore
how these results are affected by the statistics of the field (bosonic or
fermionic), the type of expansion (de Sitter or asymptotically stationary), and
the coupling to spacetime curvature (conformal or minimal). We then consider
the extraction of entanglement from a quantum field by coupling to local
detectors and how this procedure can be used to distinguish curvature from
heating by their entanglement signature. We review the role played by quantum
fluctuations in the early universe in nucleating the formation of galaxies and
other cosmic structures through their conversion into classical density
anisotropies during and after inflation. We report on current literature
attempting to account for this transition in a rigorous way and discuss the
importance of entanglement and decoherence in this process. We conclude with
some prospects for further theoretical and experimental research in this area.
These include extensions of current theoretical efforts, possible future
observational pursuits, and experimental analogues that emulate these cosmic
effects in a laboratory setting.Comment: 23 pages, 2 figures. v2 Added journal reference and minor changes to
match the published versio
Dimensional dependence of the Stokes--Einstein relation and its violation
We generalize to higher spatial dimensions the Stokes--Einstein relation
(SER) and the leading correction to diffusivity in periodic systems, and
validate them using numerical simulations. Using these results, we investigate
the evolution of the SER violation with dimension in simple hard sphere glass
formers. The analysis suggests that the SER violation disappears around
dimension d=8, above which SER is not violated. The critical exponent
associated to the violation appears to evolve linearly in 8-d below d=8, as
predicted by Biroli and Bouchaud [J. Phys.: Cond. Mat. 19, 205101 (2007)], but
the linear coefficient is not consistent with their prediction. The SER
violation evolution with d establishes a new benchmark for theory, and a
complete description remains an open problem.Comment: 20 pages, 10 figure
The changing nature of labour regulation: the distinctiveness of the National Agreement for the Engineering Construction Industry
The article addresses the changing nature of labour regulation through analysis of the National Agreement for the Engineering Construction Industry, originating in 1981. It shows how multiple spatial regulatory scales, the changing coalitions of actors involved, employer and client engagement and labour agency have been critical to National Agreement for the Engineering Construction Industry's survival
British industrial relations pluralism in the era of neoliberalism
This article provides a broad overview of the pluralist tradition in UK industrial relations scholarship, identifying its defining characteristics and mapping its evolution in recent decades. It deals in turn with the following: the appreciation of the relative interests of workers and employers that lies at the heart of the pluralist frame of reference, the research agenda that flows from this understanding, pluralist conceptions of context and agency within industrial relations, the standards that pluralists habitually use when assessing the employment relationship, the targets and modes of critique that pluralists direct against intellectual opponents, and the prescriptions that pluralists offer for industrial relations reform. Throughout the article there is a focus on change within the pluralist tradition and the manner in which it has adapted to the hegemony of neoliberalism in the realms of both ideas and policy
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