Odd-parity perturbations of self-similar Vaidya spacetime

We carry out an analytic study of odd-parity perturbations of the self-similar Vaidya space-times that admit a naked singularity. It is found that an initially finite perturbation remains finite at the Cauchy horizon. This holds not only for the gauge invariant metric and matter perturbation, but also for all the gauge invariant perturbed Weyl curvature scalars, including the gravitational radiation scalars. In each case, `finiteness' refers to Sobolev norms of scalar quantities on naturally occurring spacelike hypersurfaces, as well as pointwise values of these quantities.Comment: 28 page

The changing UV and X-ray properties of the Of?p star CPD -28 2561

The Of?p star CPD -28 2561 was monitored at high energies with XMM-Newton and HST. In X-rays, this magnetic oblique rotator displays bright and hard emission that varies by ~55% with rotational phase. These changes occur in phase with optical variations, as expected for magnetically confined winds; there are two maxima and two minima in X-rays during the 73d rotational period of CPD -28 2561. However, contrary to previously studied cases, no significant hardness variation is detected between minima and maxima, with the exception of the second minimum which is slightly distinct from the first one. In the UV domain, broad-band fluxes remain stable while line profiles display large variations. Stronger absorptions at low velocities are observed when the magnetic equator is seen edge-on, which can be reproduced by a detailed 3D model. However, a difference in absorption at high velocities in the CIV and NV lines is also detected for the two phases where the confined wind is seen nearly pole-on. This suggests the presence of strong asymmetries about the magnetic equator, mostly in the free-flowing wind (rather than in the confined dynamical magnetosphere).Comment: 14 pages, 11 figures, accepted for publication by MNRA

Research Report: Modifying Paradigms—Individual Differences, Creativity Techniques, and Exposure to Ideas in Group Idea Generation

In today's networked economy, ideas that challenge existing business models and paradigms are becoming more important. This study investigated how individual differences, groupware-based creativity techniques, and ideas from others influenced the type of ideas that individuals generated. While individual differences were important (in that some individuals were inherently more likely to generate ideas that followed the existing problem paradigm while others were more likely to generate paradigm-modifying ideas that attempted to change the problem paradigm), the exposure to paradigm-modifying ideas from others and the use of intuitive groupware-based creativity techniques rather than analytical groupware-based creativity techniques were found to increase the number of paradigm-modifying ideas produce

Legal liability of coaches: a UK perspective

Attracting more coaches is fundamental to achievement of the European dimension in sport and the further promotion of sport in the European Union. Given the emerging relationship between the law and sports coaching, recruitment of such volunteers may prove problematic. Accordingly, this article critically considers the legal liability of sports coaches. To inform this debate, the issue of negligent coaching is critically scrutinised from a UK perspective, uncovering a number of distinct legal vulnerabilities facing volunteer coaches. This includes the inherent limitations of ‘objective reasonableness’ when defining the standard of care required in the particular circumstances. More specifically, fuller analysis of the justification of customary practice, and the legal doctrine of in loco parentis, reveals important ramifications for all organisations providing training and support for coaches. In short, it is argued that proactively safeguarding coaches from professional liability should be a priority for national governing bodies, and, following the recently published EU Work Plan for Sport for 2014–2017, the Expert Group on Human Resource Management in Sport. Importantly, given the EU’s supporting, coordinating and supplementing competence in developing the European dimension in sport, a Commission funded project to address the implications of the ‘compensation culture’ in sport is also recommended