Evolution of magnetic fields through cosmological perturbation theory

The origin of galactic and extra-galactic magnetic fields is an unsolved problem in modern cosmology. A possible scenario comes from the idea of these fields emerged from a small field, a seed, which was produced in the early universe (phase transitions, inflation, ...) and it evolves in time. Cosmological perturbation theory offers a natural way to study the evolution of primordial magnetic fields. The dynamics for this field in the cosmological context is described by a cosmic dynamo like equation, through the dynamo term. In this paper we get the perturbed Maxwell's equations and compute the energy momentum tensor to second order in perturbation theory in terms of gauge invariant quantities. Two possible scenarios are discussed, first we consider a FLRW background without magnetic field and we study the perturbation theory introducing the magnetic field as a perturbation. The second scenario, we consider a magnetized FLRW and build up the perturbation theory from this background. We compare the cosmological dynamo like equation in both scenarios

Geodesic Deviation Equation in Bianchi Cosmologies

We present the Geodesic Deviation Equation (GDE) for the Friedmann-Robertson-Walker(FRW) universe and we compare it with the equation for Bianchi type I model. We justify consider this cosmological model due to the recent importance the Bianchi Models have as alternative models in cosmology. The main property of these models, solutions of Einstein Field Equations (EFE) is that they are homogeneous as the FRW model but they are not isotropic. We can see this because they have a non-null Weyl tensor in the GDE.Comment: Submitted to Journal of Physics: Conference Series (JPCS), ERE200

Brief Virtual Reality Mindfulness is More Effective than Audio Mindfulness and Colouring in Reducing Stress in University Students

Objectives: Although various multi-week mindfulness programs have been introduced for stress reduction over the past decades, there is still little evidence on the effectiveness of short, self-applied interventions. This study aims to compare the effectiveness of virtual reality mindfulness and audio mindfulness, as well as a simple colouring session. Method: Sixty-seven participants were initially enrolled, with 64 remaining after exclusions. They were randomly allocated to one of three face-to-face stress management interventions: virtual reality (VR) mindfulness, audio mindfulness or colouring. Before and after the 10-min intervention, questionnaires were administered to assess differences in perceived stress, psychological well-being, and engagement. Heart rate was also measured to indicate physiological stress. Results: VR mindfulness was the only intervention to significantly increase wellbeing. Both VR and colouring significantly reduced stress, with VR producing the largest reduction in heart rate, though this was not statistically significant when compared to baseline. The three conditions were perceived as highly engaging, with the highest scores corresponding to VR mindfulness and the lowest to audio mindfulness. Conclusions: This study shows that a single brief session of VR mindfulness can produce short-term beneficial effects in people at high risk of stress, greater than those achieved through colouring and audio mindfulness. This suggests promising direct implications for university mental health services, although future research is needed to explore long-term benefits as well as the relative efficacy of longer interventions. Preregistration: This study is not preregistered

El crecimiento de las exportaciones menores y el sistema de fomento de las exportaciones en Colombia

En este estudio se hará un intento de explicar el crecimiento de las exportaciones menores durante los últimos veinte años a la luz de las políticas colombianas de fomento de las exportaciones. El esfuerzo de fomento de las exportaciones menores se inició a base de aproximaciones sucesivas en las cuales varió con frecuencia la definición de las exportaciones menores y las políticas algunas veces cambiaron de un año a otro

Noncommutative Geometry Inspired Rotating Black Hole in Three Dimensions

We find a new rotating black hole in three-dimensional anti-de Sitter space using an anisotropic perfect fluid inspired by the noncommutative black hole. We deduce the thermodynamical quantities of this black hole and compare them with those of a rotating BTZ solution.Comment: 7 page

‘Let's be careful out there’: Maximization and core values predict action time in police decision making

This study tests the hypothesis that individual differences in trait maximization as well as in core personal values impact decision-making in dynamic and high-risk situations. 420 student-candidates at a Spanish police College (64.8 % male; 18 to 25 years) completed an online questionnaire that included maximization measures and core personal values. They then responded to three written vignettes that required dichotomous decisions (act vs. wait) under conditions of uncertainty. Multilevel modelling revealed that higher scores in maximization predicted a greater tendency to choose the action option later, but no differences were found in difficulty or perceived confidence. The tendency to wait was significantly higher among those who had wait-favouring core values; likewise, it was lower among those who had action-favouring core values. This study confirms the role of the trait maximization in the timeliness of decision-making, and illustrates the relationship between certain identified values, and decision making

Boundary Term in Metric f(R) Gravity: Field Equations in the Metric Formalism

The main goal of this paper is to get in a straightforward form the field equations in metric f(R) gravity, using elementary variational principles and adding a boundary term in the action, instead of the usual treatment in an equivalent scalar-tensor approach. We start with a brief review of the Einstein-Hilbert action, together with the Gibbons-York-Hawking boundary term, which is mentioned in some literature, but is generally missing. Next we present in detail the field equations in metric f(R) gravity, including the discussion about boundaries, and we compare with the Gibbons-York-Hawking term in General Relativity. We notice that this boundary term is necessary in order to have a well defined extremal action principle under metric variation.Comment: 12 pages, title changes by referee recommendation. Accepted for publication in General Relativity and Gravitation. Matches with the accepted versio

An Economic Evaluation of the Impact of Using Rapport-Based Interviewing Approaches With Child Sexual Abuse Suspects

Two studies examined whether rapport-based interviewing with child sexual abuse (CSA) suspects provides greater interview yield that could result in overall cost-savings to the investigation. First, multi-level modelling was applied to 35 naturalistic CSA suspect interviews to establish whether rapport-based interviewing techniques increase “yield” – defined as information of investigative value. The Observing Rapport Based Interviewing Technique (ORBIT coding manual was used to code interviews; it includes an assessment of both interpersonal adaptive and maladaptive rapport-based interviewer engagement as well as motivational interviewing (MI) strategies. The impact of these two strands (interpersonal and MI) on extracting information of investigative value (including strengthening a case for court and safeguarding) were examined. Adaptive interpersonal strategies increased case strengthening and safeguarding yield, with motivational interviewing having the largest impact on safeguarding yield. Both strategies increase the likelihood of gaining additional types of economic yield. Maladaptive interviewer strategies reduced case strengthening and different types of economic yield. In study two, literature-based economic estimates were applied to establish the potential cost benefits from following national ORBIT rapport training. Further training in adaptive and motivational interviewing could contribute cost savings between £19 and £78 million (annual unit costs) increasing to £238–£972 million (lifetime costs) for online CSA across England and Wales; and £157–£639 million (annual unit costs) increasing to £2–£8 billion (lifetime costs) for all CSA. Failure to commit training resource to this, or an alternative strategy, could mean the cost burden attributable to maladaptive interviewing (between £1 and £6 million for online CSA and £12 and £48 million for all CSA) is not successfully averted