Quantum field theory on the Bertotti-Robinson space-time

We consider the problem of quantum field theory on the Bertotti-Robinson space-time, which arises naturally as the near horizon geometry of an extremal Reissner-Nordstrom black hole but can also arise in certain near-horizon limits of non-extremal Reissner Nordstrom space-time. The various vacuum states have been considered in the context of $AdS_{2}$ black holes by Spradlin and Strominger who showed that the Poincare vacuum, the Global vacuum and the Hartle-Hawking vacuum are all equivalent, while the Boulware vacuum and the Schwarzschild vacuum are equivalent. We verify this by explicitly computing the Green's functions in closed form for a massless scalar field corresponding to each of these vacua. Obtaining a closed form for the Green's function corresponding to the Boulware vacuum is non-trivial, we present it here for the first time by deriving a new summation formula for associated Legendre functions that allows us to perform the mode-sum. Having obtained the propagator for the Boulware vacuum, which is a zero-temperature Green's function, we can then consider the case of a scalar field at an arbitrary temperature by an infinite image imaginary-time sum, which yields the Hartle-Hawking propagator upon setting the temperature to the Hawking temperature. Finally, we compute the renormalized stress-energy tensor for a massless scalar field in the various quantum vacua.Comment: 15 pages, to be published in PR

Vacuum Polarization on the Schwarzschild Metric with a Cosmic String

We consider the problem of the renormalization of the vacuum polarization in a symmetry space-time with axial but not spherical symmetry, Schwarzschild space-time threaded by an infinite straight cosmic string. Unlike previous calculations, our framework to compute the renormalized vacuum polarization does not rely on special properties of Legendre functions, but rather has been developed in a way that we expect to be applicable to Kerr space-time

Determinants of physical activity promotion by smoking cessation advisors as an aid for quitting: Support for the Transtheoretical Model

Objectives: Physical activity (PA) can reduce cigarette cravings and aid quitting but little is known about its promotion by smoking cessation advisors. This study aimed to: (1) determine the extent to which smoking cessation advisors promote PA; and (2) examine the relationship between PA promotion as a cessation aid and advisor characteristics and cognitions, within the Transtheoretical Model (TM) framework. Methods: Self-report surveys assessing PA promotion, TM variables, advisors’ own PA levels and demographics were completed by 170 advisors in England and Scotland. Results: Advisors reported spending 29 minutes promoting PA over a 6/7-week clinic. Those in later stages of readiness for promoting PA as a cessation aid and those spending more time promoting PA held more positive beliefs regarding pros and cons, self-efficacy, outcome efficacy and importance of PA within smoking cessation. Time spent promoting PA and stage of readiness were strongly associated. There was a trend for the more physically active advisors to promote PA more often. Conclusions: About half the advisors promoted PA and TM variables predicted this variability. Practice Implications: PA promotion among smoking cessation advisors may be facilitated by enhancing self-efficacy, outcome efficacy and pro and con-beliefs related to PA promotion

A qualitative perspective on multiple health behaviour change: views of smoking cessation advisors who promote physical activity

There are mixed views on whether smoking cessation advisors should focus only on quitting smoking or also promote simultaneous health behaviour changes (e.g. diet, physical activity), but no studies have qualitatively examined the views and vicarious experiences of such health professionals. Semi-structured interviews were conducted with 11 trained smoking cessation advisors who promote physical activity to their clients. The data were categorised into themes using thematic analysis supported by qualitative data analysis software. We report themes that were related to why advisors promote multiple health behaviour change and issues in timing. Physical activity could be promoted as a cessation aid and also as part of a holistic lifestyle change consistent with a non-smoker identity, thereby increasing feelings of control and addressing fear of weight gain. Multiple changes were promoted pre-quit, simultaneously and post-quit, and advisors asserted that it is important to focus on the needs and capabilities of individual clients when deciding how to time multiple changes. Also, suggesting that PA was a useful and easily performed cessation aid rather than a new behaviour (i.e. structured exercise that may seem irrelevant) may help some clients to avoid a sense of overload

Blood in the Water: Salvadoran Rivers of Testimony and Resistance

From the 1970s to the early 1990s the dominant forms of literary production in El Salvador, Guatemala, and Nicaragua were testimonial literature and literature of resistance. During this time period, all three of these Central American countries were embroiled in bloody civil wars, and the written word was employed on the cultural front as a means of denouncing and resisting various forms of oppression. For both historical and artistic reasons, rivers frequently play an important role in cultural production from and about this era and have thus become embedded in the complex web of ideological signifiers that comprises the discursive practices of Central American literature

Time-varying price discovery in the eighteenth century: empirical evidence from the London and Amsterdam stock markets

This paper examines the time-varying nature of price discovery in eighteenth century cross-listed stocks. Specifically, we investigate how quickly news is reflected in prices for two of the great moneyed com- panies, the Bank of England and the East India Company, over the period 1723 to 1794. These British companies were cross-listed on the London and Amsterdam stock exchange and news between the capitals flowed mainly via the use of boats that transported mail. We examine in detail the historical context sur- rounding the defining events of the period, and use these as a guide to how the data should be analysed. We show that both trading venues contributed to price discovery, and although the London venue was more important for these stocks, its importance varies over time

Application of digital particle image velocimetry to insect aerodynamics: measurement of the leading-edge vortex and near wake of a Hawkmoth.

Some insects use leading-edge vortices to generate high lift forces, as has been inferred from qualitative smoke visualisations of the flow around their wings. Here we present the first Digital Particle Image Velocimetry (DPIV) data and quantitative analysis of an insect’s leading-edge vortex and near wake at two flight speeds. This allows us to describe objectively 2D slices through the flow field of a tethered Tobacco Hawkmoth (Manduca sexta). The near-field vortex wake appears to braodly resemble elliptical vortex loops. The presence of a leading-edge vortex towards the end of the downstroke is found to coincide with peak upward force production measured by a six-component force–moment balance. The topology of Manduca’s leading-edge vortex differs from that previously described because late in the downstroke, the structure extends continuously from wingtip across the thorax to the other wingtip

Readiness to use physical activity as a smoking cessation aid: a multiple behaviour change application of the Transtheoretical Model among quitters attending Stop Smoking Clinics

Objective: Physical activity (PA) reduces cigarette cravings during smoking abstinence. However, little is known about quitters’ use of PA. This study aimed to: (1) determine the extent of quitters’ past and current use of PA as a cessation aid, while attempting to quit; (2) examine the relationship between use of PA and quitter characteristics and cognitions, within the Transtheoretical Model framework. Methods: Self-report surveys were completed by 181 smokers attending Stop Smoking Services in England and Scotland. Results: Twenty-two percent of quitters reported currently using PA to control their smoking, and 35% had used it during a previous quit attempt. Those in a more advanced stage of readiness for using PA as a cessation aid, held more positive beliefs regarding self-efficacy and outcome efficacy. Conclusion: Quitters were more likely to use PA to help them quit when they had greater belief in their own ability to use PA and in the efficacy of PA to help them to quit, and were also meeting weekly PA targets for health. Practice implications: Strategies by stop smoking advisors that aim to enhance client self-efficacy and outcome efficacy beliefs regarding PA as a cessation aid may help to increase the use of this behavioural strategy, since it seems that most quitters do not use PA

Renormalized Vacuum Polarization and Stress Tensor on the Horizon of a Schwarzschild Black Hole Threaded by a Cosmic String

We calculate the renormalized vacuum polarization and stress tensor for a massless, arbitrarily coupled scalar field in the Hartle-Hawking vacuum state on the horizon of a Schwarzschild black hole threaded by an infinte straight cosmic string. This calculation relies on a generalized Heine identity for non-integer Legendre functions which we derive without using specific properties of the Legendre functions themselves.Comment: This is an expanded version of a previous submission, we have added the calculation of the stress tensor. 28 pages, 7 figure