Accelerated motion and the self-force in Schwarzschild spacetime

We provide expansions of the Detweiler-Whiting singular field for motion along arbitrary, planar accelerated trajectories in Schwarzschild spacetime. We transcribe these results into mode-sum regularization parameters, computing previously unknown terms that increase the convergence rate of the mode-sum. We test our results by computing the self-force along a variety of accelerated trajectories. For non-uniformly accelerated circular orbits we present results from a new 1+1D discontinuous Galerkin time-domain code which employs an effective-source. We also present results for uniformly accelerated circular orbits and accelerated bound eccentric orbits computed within a frequency-domain treatment. Our regularization results will be useful for computing self-consistent self-force inspirals where the particle's worldline is accelerated with respect to the background spacetime.Comment: 19 pages, 6 figures (accepted CQG special issue article version

Thermal fluctuations in moderately damped Josephson junctions: Multiple escape and retrapping, switching- and return-current distributions and hysteresis

A crossover at a temperature T* in the temperature dependence of the width s of the distribution of switching currents of moderately damped Josephson junctions has been reported in a number of recent publications, with positive ds/dT and IV characteristics associated with underdamped behaviour for lower temperatures T<T*, and negative ds/dT and IV characteristics resembling overdamped behaviour for higher temperatures T>T*. We have investigated in detail the behaviour of Josephson junctions around the temperature T* by using Monte Carlo simulations including retrapping from the running state into the supercurrent state as given by the model of Ben-Jacob et al. We develop discussion of the important role of multiple escape and retrapping events in the moderate-damping regime, in particular considering the behaviour in the region close to T*. We show that the behaviour is more fully understood by considering two crossover temperatures, and that the shape of the distribution and s(T) around T*, as well as at lower T<T*, are largely determined by the shape of the conventional thermally activated switching distribution. We show that the characteristic temperatures T* are not unique for a particular Josephson junction, but have some dependence on the ramp rate of the applied bias current. We also consider hysteresis in moderately damped Josephson junctions and discuss the less commonly measured distribution of return currents for a decreasing current ramp. We find that some hysteresis should be expected to persist above T* and we highlight the importance, even well below T*, of accounting properly for thermal fluctuations when determining the damping parameter Q.Comment: Accepted for publication in PR

Change in physical self-perceptions across the transition to secondary school: relationships with perceived teacher-emphasised achievement goals in physical education

Objectives: This study aimed to examine the effects of change in perceived teacher achievement goal emphasis in physical education (PE) on physical self-perceptions and self-esteem across the transition to secondary school. Design & Methods: A longitudinal design was adopted with three time points, one at the end of primary school and two during the first year of secondary school. Participants (N = 491) were cross-classified by primary (N = 42) and secondary (N = 46) PE class in order to examine the association between perceived class-level teacher-emphasised goals and within-class student goals with self-beliefs. Results: Personal approach goals and class perceptions of teacher mastery approach goal promotion were all positively associated with ratings of co-ordination, sport competence, flexibility, and endurance in primary school. More favourable perceptions of coordination, sport competence, strength, flexibility, and endurance during the first year of secondary school were predicted by an increase in performance approach goal emphasis, whereas ratings of sport competence and flexibility were negatively associated with an increase in mastery approach goal emphasis. Conclusions: Although not entirely consonant with theoretical predictions, current findings suggest that teacher-emphasised performance approach goals in PE can promote development of several physical self-perceptions in the initial year of secondary school

Temporal relations among multidimensional perceptions of competence and trichotomous achievement goal adoption in physical education

This article was published in the journal Psychology of Sport and Exercise [© Elsevier Ltd]. The definitive version is available at: http://dx.doi.org/10.1016/j.psychsport.2011.04.007Objectives: The purpose of the present study was two-fold: (1) To empirically establish whether young people differentiate their perceived competence in physical education (PE) in terms of the self, mastery of tasks, and others, and (2) To examine longitudinal relations between these three ways of defining perceived competence and trichotomous achievement goals. Methods: At the start of the study, students (n = 227 males, n = 205 females; M age = 13.18, SD =.87 years) completed measures of mastery-approach, performance-approach- and performance-avoidance goals, along with other-, self- and mastery-referent forms of perceived competence. The same measures were subsequently recorded three, six and nine months later. Results: Analyses supported longitudinal factorial invariance for each goal and each type of perceived competence. Partial support was found for the positive influence of other-referent perceived competence on approach- and avoidance-performance goal adoption over time. Conclusion: Young people can construe their competence in PE in various ways. Relative to one’s classmates, increases in other-referenced perceptions of competence can subsequently lead to increased adoption of both performance goals