Vector screening masses in the quark-gluon plasma and their physical significance

Static and non-static thermal screening states that couple to the conserved vector current are investigated in the high-temperature phase of QCD. Their masses and couplings to the current are determined at weak coupling, as well as using two-flavor lattice QCD simulations. A consistent picture emerges from the comparison, providing evidence that non-static Matsubara modes can indeed be treated perturbatively. We elaborate on the physical significance of the screening masses.Comment: 4 pages, 3 figures. Submitted as a contribution to the proceedings of the Quark Matter 2014 conference (talk given by H. Meyer

A relation between screening masses and real-time rates

Thermal screening masses related to the conserved vector current are determined for the case that the current carries a non-zero Matsubara frequency, both in a weak-coupling approach and through lattice QCD. We point out that such screening masses are sensitive to the same infrared physics as light-cone real-time rates. In particular, on the perturbative side, the inhomogeneous Schrodinger equation determining screening correlators is shown to have the same general form as the equation implementing LPM resummation for the soft-dilepton and photon production rates from a hot QCD plasma. The static potential appearing in the equation is identical to that whose soft part has been determined up to NLO and on the lattice in the context of jet quenching. Numerical results based on this potential suggest that screening masses overshoot the free results (multiples of 2piT) more strongly than at zero Matsubara frequency. Four-dimensional lattice simulations in two-flavour QCD at temperatures of 250 and 340 MeV confirm the non-static screening masses at the 10% level. Overall our results lend support to studies of jet quenching based on the same potential at T > 250 MeV.Comment: 32 pages. v2: clarifications added, typos corrected; published versio

A time dependent relation between EUV solar flare light-curves from lines with differing formation temperatures

Extreme ultraviolet (EUV) solar flare emissions evolve in time as the emitting plasma heats and then cools. Although accurately modeling this evolution has been historically difficult, especially for empirical relationships, it is important for understanding processes at the Sun, as well as for their influence on planetary atmospheres. With a goal to improve empirical flare models, a new simple empirical expression is derived to predict how cool emissions will evolve based on the evolution of a hotter emission. This technique is initially developed by studying 12 flares in detail observed by the EUV Variability Experiment (EVE) onboard the Solar Dynamics Observatory (SDO). Then, over 1100 flares observed by EVE are analyzed to validate these relationships. The Cargill and Enthalpy Based Thermal Evolution of Loops (EBTEL) flare cooling models are used to show that this empirical relationship implies the energy radiated by a population of hotter formed ions is approximately proportional to the energy exciting a population of cooler formed ions emitting when the peak formation temperatures of the two lines are up to 72% of each other and above 2 MK. These results have practical implications for improving flare irradiance empirical modeling and for identifying key emission lines for future monitoring of flares for space weather operations; and also provide insight into the cooling processes of flare plasma.Comment: Final version accepted for publication by the Journal of Space Weather and Space Climate on 23 November 201

Return-volatility linkages in the international equity and currency markets

This paper, which is motivated by the literature on international asset pricing and recent work on exchange rate determination, investigates dynamic relationshiops between major currency and equity markets. Using a multivariate GARCH framework, we examine conditional cross-autocorrelations between pairs of national equity markets and related exchange rates. This provides a parsimonious way of testing mean-volatility relationships in currency and equity markets and re-examining the robustness of relationships between equity markets, while controlling for exchange rate effects. We find that the relationship between currency and equity markets is bi-directional, significant, persistent, and independent of the relationship strictly between equity markets, and that it is better captured by the conditional second moments.international asset pricing; exchange rate determination; equity markets; relationships between currency and equity markets

Does hedging tell the full story? Reconciling differences in US aggregate and industry-level exchange rate risk premia

While the importance of currency movements to industry competitiveness is theoretically well established, there is little evidence that currency risk impacts US industries. Applying a conditional asset-pricing model to 36 US industries, we find that all industries have a significant currency premium that adds about 2.47 percentage points to the cost of equity and accounts for approximately 11.7% of the absolute value of total risk premia. Cross-industry variation in the currency premium is explained by foreign income, industry competitiveness, leverage, liquidity and other industry characteristics, while its time variation is explained by US aggregate foreign trade, monetary policy, growth opportunities and other macro variables. The results indicate that methodological weakness, not hedging, explains the insignificant industry currency risk premium found in previous work, thus resolving the conundrum that the currency risk premium is important at the aggregate stock market level, but not at industry level.exposure; currency risk premium; cost of equity; industry competition; international asset pricing

Return-volatility linkages in the international equity and currency markets

This paper, which is motivated by the literature on international asset pricing and recent work on exchange rate determination, investigates dynamic relationshiops between major currency and equity markets. Using a multivariate GARCH framework, we examine conditional cross- autocorrelations between pairs of national equity markets and related exchange rates. This provides a parsimonious way of testing mean- volatility relationships in currency and equity markets and re-examining the robustness of relationships between equity markets, while controlling for exchange rate effects. We find that the relationship between currency and equity markets is bi-directional, significant, persistent, and independent of the relationship strictly between equity markets, and that it is better captured by the conditional second momentsinternational asset pricing, exchange rate determination, equity markets, relationships between currency and equity markets

Growth or decline in the Church of England during the decade of Evangelism: did the Churchmanship of the Bishop matter?

The Decade of Evangelism occupied the attention of the Church of England throughout the 1990s. The present study employs the statistics routinely published by the Church of England in order to assess two matters: the extent to which these statistics suggest that the 43 individual dioceses finished the decade in a stronger or weaker position than they had entered it and the extent to which, according to these statistics, the performance of dioceses led by bishops shaped in the Evangelical tradition differed from the performance of dioceses led by bishops shaped in the Catholic tradition. The data demonstrated that the majority of dioceses were performing less effectively at the end of the decade than at the beginning, in terms of a range of membership statistics, and that the rate of decline varied considerably from one diocese to another. The only exception to the trend was provided by the diocese of London, which experienced some growth. The data also demonstrated that little depended on the churchmanship of the diocesan bishop in shaping diocesan outcomes on the performance indicators employed in the study

Observations of QSO J2233-606 in the Southern Hubble Deep Field

The Hubble Deep Field South (HDF-S) HST observations are expected to begin in October 1998. We present a composite spectrum of the QSO in the HDF-S field covering UV/optical/near IR wavelengths, obtained by combining data from the ANU 2.3m Telescope with STIS on the HST. This intermediate resolution spectrum covers the range 1600-10000A and allows us to derive some basic information on the intervening absorption systems which will be important in planning future higher resolution studies of this QSO.Comment: 9 pages and 2 figures, submitted to ApJ

Young people's attitudes to religious diversity : quantitative approaches from social psychology and empirical theology

This essay discusses the design of the quantitative component of the ‘Young People’s Attitudes to Religious Diversity’ project, conceived by Professor Robert Jackson within the Warwick Religions and Education Research Unit, and presents some preliminary findings from the data. The quantitative component followed and built on the qualitative component within a mixed method design. The argument is advanced in seven steps: introducing the major sources of theory on which the quantitative approach builds from the psychology of religion and from empirical theology; locating the empirical traditions of research among young people that have shaped the study; clarifying the notions and levels of measurement employed in the study anticipating the potential for various forms of data analysis; discussing some of the established measures incorporated in the survey; defining the ways in which the sample was structured to reflect the four nations of the UK, and London; illustrating the potential within largely descriptive cross-tabulation forms of analysis; and illustrating the potential within more sophisticated multivariate analytic models

Coordinate Confusion in Conformal Cosmology

A straight-forward interpretation of standard Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies is that objects move apart due to the expansion of space, and that sufficiently distant galaxies must be receding at velocities exceeding the speed of light. Recently, however, it has been suggested that a simple transformation into conformal coordinates can remove superluminal recession velocities, and hence the concept of the expansion of space should be abandoned. This work demonstrates that such conformal transformations do not eliminate superluminal recession velocities for open or flat matter-only FRLW cosmologies, and all possess superluminal expansion. Hence, the attack on the concept of the expansion of space based on this is poorly founded. This work concludes by emphasizing that the expansion of space is perfectly valid in the general relativistic framework, however, asking the question of whether space really expands is a futile exercise.Comment: 5 pages, accepted for publication in MNRAS Letter