A Complete Cosmological Solution to the Averaged Einstein Field Equations as found in Macroscopic Gravity

A formalism for analyzing the complete set of field equations describing Macroscopic Gravity is presented. Using this formalism, a cosmological solution to the Macroscopic Gravity equations is determined. It is found that if a particular segment of the connection correlation tensor is zero and if the macroscopic geometry is described by a flat Robertson-Walker metric, then the effective correction to the averaged Einstein Field equations of General Relativity i.e., the backreaction, is equivalent to a positive spatial curvature term. This investigation completes the analysis of [Phys. Rev. Lett., vol. 95, 151102, (2005)] and the formalism developed provides a possible basis for future studies.Comment: 11 page

Technologie verplicht

Overheidsorganisaties maken in toenemende mate gebruik van geavanceerde technologie. Hierdoor zijn zij in staat gebleken de kwaliteit én de snelheid van hun werkzaamheden aanzienlijk te verbeteren en het eind van de nieuwe mogelijkheden lijkt nog lang niet in zicht. Veel overheidsorganisaties volgen de technologische ontwikkelingen dan ook op de voet. Moderne technologie schept naast mogelijkheden echter ook verplichtingen. Immers, als overheidsorganisaties hun werk beter kunnen doen met behulp van technologie, moeten zij dat ook doen. Dit zou wel eens een belangrijke nieuwe verplichting in het recht kunnen worden: de verplichting om technologie te gebruiken. De stelling wordt, wat het openbaar ministerie betreft, ondersteund door arresten van het Hof Amsterdam en van de Hoge Raad

Averaging geometrical objects on a differentiable manifold

We construct a framework within which a mathematically precise, fully covariant, and exact averaging procedure for tensor fields on a manifold can be formulated. In particular, we introduce the Weitzenb\"ock connection for parallel transport and argue that, within the context of averaging, frames and connections are the natural geometrical objects on the manifold

Bianchi IX Brane-world Cosmologies

We shall investigate the asymptotic properties of the Bianchi type IX cosmological model in the Brane-world scenario. The matter content is assumed to be a combination of a perfect fluid and a minimimally coupled scalar field that is restricted to the Brane. A detailed qualitative analysis of the Bianchi type IX braneworld containing a scalar field having an exponential potential is undertaken. It is found that the Brane-Robertson Walker solution is a local source for the expanding Bianchi IX models, and if $k^2<2$ the expanding Bianchi IX models asymptote to the power-law inflationary solution. The only other local sink is the contracting Brane-Robertson Walker solution. An analysis of the Bianchi IX models with a scalar field with a general potential is discussed, and it is shown that in the case of expanding models, for physical scalar field potentials close to the initial singularity, the scalar field is effectively massless, and the solution is approximated by the Brane-Robertson Walker model.Comment: 28 pages, RevTe

Teleparallel Theories of Gravity: Illuminating a Fully Invariant Approach

Teleparallel gravity and its popular generalization $f(T)$ gravity can be formulated as fully invariant (under both coordinate transformations and local Lorentz transformations) theories of gravity. Several misconceptions about teleparallel gravity and its generalizations can be found in the literature, especially regarding their local Lorentz invariance. We describe how these misunderstandings may have arisen and attempt to clarify the situation. In particular, the central point of confusion in the literature appears to be related to the inertial spin connection in teleparallel gravity models. While inertial spin connections are commonplace in special relativity, and not something inherent to teleparallel gravity, the role of the inertial spin connection in removing the spurious inertial effects within a given frame of reference is emphasized here. The careful consideration of the inertial spin connection leads to the construction of a fully invariant theory of teleparallel gravity and its generalizations. Indeed, it is the nature of the spin connection that differentiates the relationship between what have been called good tetrads and bad tetrads and clearly shows that, in principle, any tetrad can be utilized. The field equations for the fully invariant formulation of teleparallel gravity and its generalizations are presented and a number of examples using different assumptions on the frame and spin connection are displayed to illustrate the covariant procedure. Various modified teleparallel gravity models are also briefly reviewed.Comment: v2: 72 pages, revised version, references added, matches published versio

Pressure at play:measuring player approach and avoidance behaviour through the keyboard

With the increased adoption of real-time objective measurements of player experience, advances have been made in characterising the dynamically changing aspects of the player experience during gameplay itself. A direct coupling to player action, however, is not without challenges. Many physiological responses, for instance, have an inherent delay, and often take some time to return to a baseline, providing challenges of interpretation when analysing rapidly changing gameplay on a micro level of interaction. The development of event-related, or phasic, measurements directly coupled to player actions provides additional insights, for instance through player modelling, but also through the use of behavioural characteristics of the human computer interaction itself. In this study, we focused on the latter, and measured keyboard pressure in a number of different, fast-paced action games. In this particular case, we related specific functional game actions (keyboard presses) to experiential player behaviour. We found keyboard pressure to be higher for avoidance as compared to approach-oriented actions. Additionally, the difference between avoidance and approach keyboard pressure related to levels of arousal. The findings illustrate the application potential of qualifying players’ functional actions at play (navigating in a game) and interpret player experience related to these actions through players’ real world behavioural characteristics like interface pressure

Устройства на основе фотонных кристаллов

Рассмотрены физико-технические особенности фотонных кристаллов. Представлен обзор конструкций и характеристик устройств на их основе

European neonatal intensive care nursing research priorities: an e-Delphi study.

OBJECTIVE: This study aimed to identify and prioritise neonatal intensive care nursing research topics across Europe using an e-Delphi technique. DESIGN: An e-Delphi technique with three questionnaire rounds was performed. Qualitative responses of round one were analysed by content analysis and research statements were generated to be ranged on importance on a scale of 1-6 (not important to most important). SETTING: Neonatal intensive care units (NICUs) in 17 European countries. POPULATION: NICU clinical nurses, managers, educators and researchers (n=75). INTERVENTION: None. MAIN OUTCOME MEASURES: A list of 43 research statements in eight domains. RESULTS: The six highest ranking statements (≥5.0 mean score) were related to prevention and reduction of pain (mean 5.49; SD 1.07), medication errors (mean 5.20; SD 1.13), end-of-life care (mean 5.05; SD 1.18), needs of parents and family (mean 5.04; SD 1.23), implementing evidence into nursing practice (mean 5.02; SD 1.03), and pain assessment (mean 5.02; SD 1.11). The research domains were prioritised and ranked: (1) pain and stress; (2) family centred care; (3) clinical nursing care practices; (4) quality and safety; (5) ethics; (6) respiratory and ventilation; (7) infection and inflammation; and (8) professional issues in neonatal intensive care nursing. CONCLUSIONS: The results of this study might support developing a nursing research strategy for the nursing section of the European Society of Paediatric and Neonatal Intensive Care. In addition, this may promote more European researcher collaboratives for neonatal nursing research

An Electronic Delphi Study to Establish Pediatric Intensive Care Nursing Research Priorities in Twenty European Countries*

OBJECTIVES:: To identify and to establish research priorities for pediatric intensive care nursing science across Europe. DESIGN:: A modified three-round electronic Delphi technique was applied. Questionnaires were translated into seven different languages. SETTING:: European PICUs. PARTICIPANTS:: The participants included pediatric intensive care clinical nurses, managers, educators, and researchers. In round 1, the qualitative responses were analyzed by content analysis and a list of research statements and domains was generated. In rounds 2 and 3, the statements were ranked on a scale of one to six (not important to most important). Mean scores and SDs were calculated for rounds 2 and 3. INTERVENTIONS:: None. MEASUREMENTS AND MAIN RESULTS:: Round 1 started with 90 participants, with round 3 completed by 64 (71%). The seven highest ranking statements ( 5.0 mean score) were related to end-of-life care, decision making around forgoing and sustaining treatment, prevention of pain, education and competencies for pediatric intensive care nurses, reducing healthcare-associated infections, identifying appropriate nurse staffing levels, and implementing evidence into nursing practice. Nine research domains were prioritized, and these were as follows: 1) clinical nursing care practices, 2) pain and sedation, 3) quality and safety, 4) respiratory and mechanical ventilation, 5) child- and family-centered care, 6) ethics, 7) professional issues in nursing, 8) hemodynamcis and resuscitation, and 9) trauma and neurocritical care. CONCLUSIONS:: The results of this study inform the European Society of Pediatric and Neonatal Intensive Care's nursing research agenda in the future. The results allow nurse researchers within Europe to encourage collaborative initiatives for nursing research