New Phases of SU(3) and SU(4) at Finite Temperature

The addition of an adjoint Polyakov loop term to the action of a pure gauge theory at finite temperature leads to new phases of SU(N) gauge theories. For SU(3), a new phase is found which breaks Z(3) symmetry in a novel way; for SU(4), the new phase exhibits spontaneous symmetry breaking of Z(4) to Z(2), representing a partially confined phase in which quarks are confined, but diquarks are not. The overall phase structure and thermodynamics is consistent with a theoretical model of the effective potential for the Polyakov loop based on perturbation theory.Comment: 18 pages, 17 figures, RevTeX

PT symmetry and large-N models

Recently developed methods for PT-symmetric models can be applied to quantum-mechanical matrix and vector models. In matrix models, the calculation of all singlet wave functions can be reduced to the solution a one-dimensional PT-symmetric model. The large-N limit of a wide class of matrix models exists, and properties of the lowest-lying singlet state can be computed using WKB. For models with cubic and quartic interactions, the ground state energy appears to show rapid convergence to the large-N limit. For the special case of a quartic model, we find explicitly an isospectral Hermitian matrix model. The Hermitian form for a vector model with O(N) symmetry can also be found, and shows many unusual features. The effective potential obtained in the large-N limit of the Hermitian form is shown to be identical to the form obtained from the original PT-symmetric model using familiar constraint field methods. The analogous constraint field prescription in four dimensions suggests that PT-symmetric scalar field theories are asymptotically free.Comment: 15 pages, to be published in J. Phys. A special issue on Pseudo Hermitian Hamiltonians in Quantum Physic

Reducing social inequalities in smoking: can evidence inform policy? A pilot study

Objective: To assess the potential contribution of evidence from existing systematic reviews of effectiveness to answering the question: what works in reducing social inequalities in smoking? Data source: The Cochrane Library (2002/4). Study selection: Systematic reviews of the effectiveness of community based tobacco control interventions, and all the primary studies included in one of these reviews. Data extraction: Reviews and primary studies were assessed for intent to assess the social distribution of intervention effects, information about the social inclusiveness or targeting of interventions, baseline sociodemographic data collected on participants, and estimates of effect size stratified by sociodemographic variables. Data synthesis: Only one review aimed to examine outcomes stratified by sex, age or socioeconomic status, and these aims were only achieved with respect to sex. Sociodemographic data about participants were frequently collected in primary studies, but not used to compare intervention effects between social groups. Conclusions: There may be scope for using existing research more effectively to contribute to evidence based policy to reduce social inequalities in smoking—by explicitly seeking stratified outcome data in new systematic reviews, by re-analysing original datasets, and/or by meta-analysis of individual participant data

Private politics in the garden of England: an atypical case of anti-wind farm contention

This article analyses an atypical case of anti-wind farm contention at Marden in south-east England. Anti-wind farm campaigns have typically sought to resist developments through planning institutions. Though focusing on planning, the Marden case successfully pursued a ‘private politics’ strategy, pressuring businesses (e.g. developer, investors and landowner) to withdraw their support and commitment. Drawing on 10 semi-structured interviews with stakeholders, and extensive documentary analysis, this article describes and explains this atypical case. It argues that Marden’s private politics involved strategic framing that aligned with businesses’ claims to corporate social and environmental responsibility. Though directly persuading companies on these terms failed, when the campaign ‘went public’, economic actors withdrew support. Marden’s trajectory and outcome are explained via resources and context particular to the case, and the potential reputational damage associated with its framing strategy. The article ends by noting interesting relationships and parallels between private politics and state focused local contention

Systematic reviews of health effects of social interventions: 1. Finding the evidence: how far should you go?

Study objective: There is little guidance on how to identify useful evidence about the health effects of social interventions. The aim of this study was to assess the value of different ways of finding this type of information. Design: Retrospective analysis of the sources of studies for one systematic review. Setting: Case study of a systematic review of the effectiveness of interventions in promoting a population shift from using cars towards walking and cycling. Main results: Only four of the 69 relevant studies were found in a "first-line" health database such as Medline. About half of all relevant studies were found through the specialist Transport database. Nine relevant studies were found through purposive internet searches and seven relevant studies were found by chance. The unique contribution of experts was not to identify additional studies, but to provide more information about those already found in the literature. Conclusions: Most of the evidence needed for this review was not found in studies indexed in familiar literature databases. Applying a sensitive search strategy across multiple databases and interfaces is very labour intensive. Retrospective analysis suggests that a more efficient method might have been to search a few key resources, then to ask authors and experts directly for the most robust reports of studies identified. However, internet publications and serendipitous discoveries did make a significant contribution to the total set of relevant evidence. Undertaking a comprehensive search may provide unique evidence and insights that would not be obtained using a more focused search

Promoting walking and cycling as an alternative to using cars: systematic review

Objectives: To assess what interventions are effective in promoting a population shift from using cars towards walking and cycling, and to assess the health and distributional effects of such interventions. Data sources: Published and unpublished reports in any language identified from electronic databases, bibliographies, websites and reference lists. Review methods: Systematic search and appraisal to identify experimental or observational studies with a prospective or controlled retrospective design that evaluated any intervention applied to an urban population or area by measuring outcomes in members of the local population. Results: 22 studies met the inclusion criteria. We found some evidence that targeted behaviour change programmes can change the behaviour of motivated subgroups, resulting (in the largest study) in a modal shift of around 5% of all trips at a population level. Single studies of commuter subsidies and a new railwy station have also shown modest effects. The balance of best available evidence about publicity campaigns, engineering measures and other interventions suggests that they have not been effective. Participants in trials of active commuting experienced short-term improvements in certain health and fitness measures, but we found no good evidence about the health effects of any effective population-level intervention. Conclusions: The best available evidence of effectiveness is for targeted behaviour change programmes, but the social distribution of their effects is unclear and some other types of intervention remain to be rigorously evaluated. We need a stronger evidence base for the health impacts of transport policies, preferably based on properly conducted prospective studies

Systematic reviews of health effects of social interventions: 2. Best available evidence: how low should you go?

Study objective: There is little guidance on how to select the best available evidence of health effects of social interventions. The aim of this paper was to assess the implications of setting particular inclusion criteria for evidence synthesis. Design: Analysis of all relevant studies for one systematic review, followed by sensitivity analysis of the effects of selecting studies based on a two dimensional hierarchy of study design and study population. Setting: Case study of a systematic review of the effectiveness of interventions in promoting a population shift from using cars towards walking and cycling. Main results: The distribution of available evidence was skewed. Population level interventions were less likely than individual level interventions to have been studied using the most rigorous study designs; nearly all of the population level evidence would have been missed if only randomised controlled trials had been included. Examining the studies that were excluded did not change the overall conclusions about effectiveness, but did identify additional categories of intervention such as health walks and parking charges that merit further research, and provided evidence to challenge assumptions about the actual effects of progressive urban transport policies. Conclusions: Unthinking adherence to a hierarchy of study design as a means of selecting studies may reduce the value of evidence synthesis and reinforce an "inverse evidence law" whereby the least is known about the effects of interventions most likely to influence whole populations. Producing generalisable estimates of effect sizes is only one possible objective of evidence synthesis. Mapping the available evidence and uncertainty about effects may also be important

Infrared upconversion for astronomical applications

The performance of an upconversion system is examined for observation of astronomical sources in the low to middle infrared spectral range. Theoretical values for the performance parameters of an upconversion system for astronomical observations are evaluated in view of the conversion efficiencies, spectral resolution, field of view, minimum detectable source brightness and source flux. Experimental results of blackbody measurements and molecular absorption spectrum measurements using a lithium niobate upconverter with an argon-ion laser as the pump are presented. Estimates of the expected optimum sensitivity of an upconversion device which may be built with the presently available components are given

A self-sustaining nonlinear dynamo process in Keplerian shear flows

A three-dimensional nonlinear dynamo process is identified in rotating plane Couette flow in the Keplerian regime. It is analogous to the hydrodynamic self-sustaining process in non-rotating shear flows and relies on the magneto-rotational instability of a toroidal magnetic field. Steady nonlinear solutions are computed numerically for a wide range of magnetic Reynolds numbers but are restricted to low Reynolds numbers. This process may be important to explain the sustenance of coherent fields and turbulent motions in Keplerian accretion disks, where all its basic ingredients are present.Comment: 4 pages, 7 figures, accepted for publication in Physical Review Letter