21,987 research outputs found
Lorentz-breaking effects in scalar-tensor theories of gravity
In this work, we study the effects of breaking Lorentz symmetry in
scalar-tensor theories of gravity taking torsion into account. We show that a
space-time with torsion interacting with a Maxwell field by means of a
Chern-Simons-like term is able to explain the optical activity in syncrotron
radiation emitted by cosmological distant radio sources. Without specifying the
source of the dilaton-gravity, we study the dilaton-solution. We analyse the
physical implications of this result in the Jordan-Fierz frame. We also analyse
the effects of the Lorentz breaking in the cosmic string formation process. We
obtain the solution corresponding to a cosmic string in the presence of torsion
by keeping track of the effects of the Chern-Simons coupling and calculate the
charge induced on this cosmic string in this framework. We also show that the
resulting charged cosmic string gives us important effects concerning the
background radiation.The optical activity in this case is also worked out and
discussed.Comment: 10 pages, no figures, ReVTex forma
How daily negative affect and emotional exhaustion correlates with work engagement and presenteeism-constrained productivity
Exploring productivity loss due to presenteeism and how it can have an influence on employees’ productivity has been an important concern for human resource managers. Using the conservation of resources theory and the job demands-resources model, this study investigated how work engagement could mediate the relationship between both emotional exhaustion and negative affect and productivity loss due to presenteeism in a country experiencing an economic downturn. A total of 42 employees from a health care institution completed a 10-day diary survey (420 diary tasks). Multilevel linear modeling results, including power analyses, showed that negative affect and emotional exhaustion predicted productivity loss due to presenteeism positively, whereas work engagement predicted productivity loss negatively. Furthermore, we found that at a day-level, work engagement mediated the effects of emotional exhaustion and negative affect on productivity loss due to presenteeism. This study highlights the importance of promoting work engagement to reduce the effects of negative affect and emotional exhaustion on productivity loss due to presenteeism through intervention.info:eu-repo/semantics/acceptedVersio
On the strategy frequency problem in batch Minority Games
Ergodic stationary states of Minority Games with S strategies per agent can
be characterised in terms of the asymptotic probabilities with which
an agent uses of his strategies. We propose here a simple and general
method to calculate these quantities in batch canonical and grand-canonical
models. Known analytic theories are easily recovered as limiting cases and, as
a further application, the strategy frequency problem for the batch
grand-canonical Minority Game with S=2 is solved. The generalization of these
ideas to multi-asset models is also presented. Though similarly based on
response function techniques, our approach is alternative to the one recently
employed by Shayeghi and Coolen for canonical batch Minority Games with
arbitrary number of strategies.Comment: 17 page
CFD code comparison for 2D airfoil flows
The current paper presents the effort, in the EU AVATAR project, to establish the necessary requirements to obtain consistent lift over drag ratios among seven CFD codes. The flow around a 2D airfoil case is studied, for both transitional and fully turbulent conditions at Reynolds numbers of 3 × 106 and 15 × 106. The necessary grid resolution, domain size, and iterative convergence criteria to have consistent results are discussed, and suggestions are given for best practice. For the fully turbulent results four out of seven codes provide consistent results. For the laminar-turbulent transitional results only three out of seven provided results, and the agreement is generally lower than for the fully turbulent case
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