Extended Ordered Paired Comparison Models with Application to Football Data from German Bundesliga

A general paired comparison model for the evaluation of sports competitions is proposed. It efficiently uses the available information by allowing for ordered response categories and team-specific home advantage effects. Penalized estimation techniques are used to identify clusters of teams that share the same ability. The model is extended to include team-specific explanatory variables. It is shown that regularization techniques allow to identify the contribution of explanatory variables to the success of teams. The usefulness of the methods is demonstrated by investigating the performance and its dependence on the budget for football teams of the German Bundesliga

Context-dependent motor skill and the role of practice

Research has shown that retrieval of learned information is better when the original learning context is reinstated during testing than when this context is changed. Recently, such contextual dependencies have also been found for perceptual-motor behavior. The current study investigated the nature of context-dependent learning in the discrete sequence production task, and in addition examined whether the amount of practice affects the extent to which sequences are sensitive to contextual alterations. It was found that changing contextual cues—but not the removal of such cues—had a detrimental effect on performance. Moreover, this effect was observed only after limited practice, but not after extensive practice. Our findings support the notion of a novel type of context-dependent learning during initial motor skill acquisition and demonstrate that this context-dependence reduces with practice. It is proposed that a gradual development with practice from stimulus-driven to representation-driven sequence execution underlies this practice effect

Effective-field-theory approach to persistent currents

Using an effective-field-theory (nonlinear sigma model) description of interacting electrons in a disordered metal ring enclosing magnetic flux, we calculate the moments of the persistent current distribution, in terms of interacting Goldstone modes (diffusons and cooperons). At the lowest or Gaussian order we reproduce well-known results for the average current and its variance that were originally obtained using diagrammatic perturbation theory. At this level of approximation the current distribution can be shown to be strictly Gaussian. The nonlinear sigma model provides a systematic way of calculating higher-order contributions to the current moments. An explicit calculation for the average current of the first term beyond Gaussian order shows that it is small compared to the Gaussian result; an order-of-magnitude estimation indicates that the same is true for all higher-order contributions to the average current and its variance. We therefore conclude that the experimentally observed magnitude of persistent currents cannot be explained in terms of interacting diffusons and cooperons.Comment: 12 pages, no figures, final version as publishe