Decay of massless Dirac field around the Born-Infeld Black Hole

In this paper we investigate the perturbations by a massless Dirac spinor of a Born-Infeld black hole. The decay rates of the spinor field which is given by the quasinormal mode frequencies are computed using the sixth order WKB approximation. The behavior of the quasi normal modes with the non-linear parameter, temperature and charge of the black hole are analyzed in detail. We also compare the decay rates of the Born-Infeld black hole with its linear counter-part Reissner-Nordstrom black hole.Comment: Latex, 11 figures, references added, new data and new graphs adde

Friedmann Equations from Entropic Force

In this note by use of the holographic principle together with the equipartition law of energy and the Unruh temperature, we derive the Friedmann equations of a Friedmann-Robertson-Walker universe.Comment: latex, 8 pages, v2: minor modifications and to appear in PRD (Rapid Communication

On the emergence of Lorentzian signature and scalar gravity

In recent years, a growing momentum has been gained by the emergent gravity framework. Within the latter, the very concepts of geometry and gravitational interaction are not seen as elementary aspects of Nature but rather as collective phenomena associated to the dynamics of more fundamental objects. In this paper we want to further explore this possibility by proposing a model of emergent Lorentzian signature and scalar gravity. Assuming that the dynamics of the fundamental objects can give rise in first place to a Riemannian manifold and a set of scalar fields we show how time (in the sense of hyperbolic equations) can emerge as a property of perturbations dynamics around some specific class of solutions of the field equations. Moreover, we show that these perturbations can give rise to a spin-0 gravity via a suitable redefinition of the fields that identifies the relevant degrees of freedom. In particular, we find that our model gives rise to Nordstrom gravity. Since this theory is invariant under general coordinate transformations, this also shows how diffeomorphism invariance (albeit of a weaker form than the one of general relativity) can emerge from much simpler systems.Comment: 10 pages, revtex4. Replaced with the published versio

Medical students using the technique of 55-word stories to reflect on a 6-week rotation during the integrated primary care block

Background. Reflection and reflective practice are identified as a core competency for graduates in health professions education. Students are expected to be in a position to process experiences in a variety of ways through reflective learning. In doing so, they can explore the understanding of their actions and experiences, and the impact of these on themselves and others. Objectives. To draw on 5-weekly reflections by final-year medical students during the integrated primary care block placement. These reflections explore the learning that occurred during the rotation and the change in experiences during this period, and illustrate the use of reflection as a tool to support the development of professional practice. Methods. This descriptive qualitative study analysed students’ 55-word reflective stories during a 6-week preceptorship in either a rural or urban primary healthcare centre. The writing technique of short 55-word reflective stories was used to record student experiences. Inductive thematic analysis was conducted using MAXQDA software. This involved identifying the most commonly used words for each week through a word cloud, highlighting each week’s most notable focus for learning to generate themes and sub-themes. Results. Analysis of 127 logbook entries generated 464 stories on a range of experiences that had a significant impact on learning. Students’ reflections in the first 2 weeks were linked to personal experiences and views about the block. In subsequent weeks, reflections focused on the individual responses of students to the learning experiences regarding the curriculum, patient care, ethics, professionalism and the health system. Conclusions. The reflections highlighted the key learning experiences of the medical students and illustrated how meaning is constructed from these experiences. The 55-word stories as a reflection tool have potential to support reflection for students, and provide valuable insight into medical students’ learning journey during their clinical training

Entropy in Spin Foam Models: The Statistical Calculation

Recently an idea for computing the entropy of black holes in the spin foam formalism has been introduced. Particularly complete calculations for the three dimensional euclidean BTZ black hole were done. The whole calculation is based on observables living at the horizon of the black hole universe. Departing from this idea of observables living at the horizon, we now go further and compute the entropy of BTZ black hole in the spirit of statistical mechanics. We compare both calculations and show that they are very interrelated and equally valid. This latter behaviour is certainly due to the importance of the observables.Comment: 11 pages, 1 figur

A cohort study on the rate of progression of diabetic chronic kidney disease in different ethnic groups.

OBJECTIVE: To compare the rate of progression of diabetic chronic kidney disease in different ethnic groups. DESIGN: Prospective longitudinal observational study. PARTICIPANTS: All new patients attending a tertiary renal unit in east London with diabetic chronic kidney disease between 2000 and 2007 and followed up till 2009 were included. Patients presenting with acute end-stage kidney failure were excluded. MAIN OUTCOME MEASURES: The primary outcome was annual decline in the estimated glomerular filtration rate (eGFR) in different ethnic groups. Secondary end points were the number of patients developing end-stage kidney failure and total mortality during the study period. RESULTS: 329 patients (age 60±11.9 years, 208 men) were studied comprising 149 south Asian, 105 White and 75 Black patients. Mean follow-up was 6.0±2.3, 5.0±2.7 and 5.6±2.4 years for White, Black and south Asian patients, respectively. South Asian patients were younger and had a higher baseline eGFR, but both systolic and diastolic blood pressures were higher in Black patients (p<0.05). Baseline proteinuria was highest for the south Asian group followed by the White and Black groups. Adjusted linear regression analysis showed that an annual decline in eGFR was not significantly different between the three groups. The numbers of patients developing end-stage kidney failure and total mortality were also not significantly different between the three groups. ACE or angiotensin receptor blockers use, and glycated haemoglobin were similar at baseline and throughout the study period. CONCLUSIONS: We conclude that ethnicity is not an independent factor in the rate of progression renal failure in patients with diabetic chronic kidney disease

Compilation of extended recursion in call-by-value functional languages

This paper formalizes and proves correct a compilation scheme for mutually-recursive definitions in call-by-value functional languages. This scheme supports a wider range of recursive definitions than previous methods. We formalize our technique as a translation scheme to a lambda-calculus featuring in-place update of memory blocks, and prove the translation to be correct.Comment: 62 pages, uses pi

Supply Chain Control Principles in Local Food Production: A Norwegian Case Study

Based on an analysis of the supply chain of four producers of local specialty foods, we explore how planning and control principles can be applied to align supply chain capabilities and market requirements. It has been shown that local food struggles with market access, and that the supply chain is one of the obstacles preventing local food producers from gaining a solid market position. We identify a number of features of the local food chain, analyse the obstacles and develop generic designs and control principles for local food producers

On Quasinormal Modes, Black Hole Entropy, and Quantum Geometry

Loop quantum gravity can account for the Bekenstein-Hawking entropy of a black hole provided a free parameter is chosen appropriately. Recently, it was proposed that a new choice of the Immirzi parameter could predict both black hole entropy and the frequencies of quasinormal modes in the large $n$ limit, but at the price of changing the gauge group of the theory. In this note we use a simple physical argument within loop quantum gravity to arrive at the same value of the parameter. The argument uses strongly the necessity of having fermions satisfying basic symmetry and conservation principles, and therefore supports SU(2) as the relevant gauge group of the theory.Comment: 3 pages, revtex4, no figures, discussion expanded and references adde