Cosmic microwave background anisotropies: Nonlinear dynamics

We develop a new approach to local nonlinear effects in cosmic microwave background anisotropies, and discuss the qualitative features of these effects. New couplings of the baryonic velocity to radiation multipoles are found, arising from nonlinear Thomson scattering effects. We also find a new nonlinear shear effect on small angular scales. The full set of evolution and constraint equations is derived, including the nonlinear generalizations of the radiation multipole hierarchy, and of the dynamics of multi-fluids. These equations govern radiation anisotropies in any inhomogeneous spacetime, but their main application is to second-order effects in a universe that is close to the Friedmann models. Qualitative analysis is given here, and quantitative calculations are taken up in further papers.Comment: Revised version, with some important corrections and improved clarity, highlighting the new results on nonlinear Thomson scattering effects and nonlinear shear effects. To appear Phys Rev

Transitions to HE: CBL for non-traditional students

The aim of this paper is to describe the development of contextual based learning resources appropriate to Science Foundation students at the University of Huddersfield. In developing new resources the authors consulted with key stakeholders in the science community. A world class glass manufacturer and an industrially focused research and development unit based in the University of Huddersfield provided input into how industry based scenarios could be developed for use in the curriculum. Teachers from one of the country’s leading sixth form colleges provided examples of effective context based learning in an FE environment. This paper charts how an effective teaching and learning strategy has been tailored for use with Science Foundation students. It provides keyexamples of how context based learning (CBL) has been adapted for use with students of mixed abilities and backgrounds. The paper also highlights some of the problems encountered in developing appropriate resources and presents initial findings of the impact on students

Risk aversion in agricultural water management investments in Northern Ghana: Experimental evidence

Sub-Saharan Africa (SSA) is one of the regions in the world most affected by food price volatility and production variability. Poor small-scale farmers in this region are particularly vulnerable to this variability. As a result, households may be reluctant to adopt new agricultural water management (AWM) technologies when they involve more risk than what they mitigate. Despite risk’s role in agricultural water management investments, there have been few attempts to estimate the magnitude and nature of risk aversion in relation to this type of farm decisions. To partially close this gap, this paper uses an experimental approach applied to 137 households in Northern Ghana. We find that more than 70 percent of households are moderately or slightly risk averse. This contrasts with other studies in SSA, where most household decision-makers exhibit severe to extreme risk aversion. We also find that households that stand to lose as well as gain something from participation in games are less risk averse than households playing gains-only games. This result suggests that most farmers’ current wealth put them at risk of falling into a poverty trap. Thus, the losses from the riskiest investments on AWM technologies may fall more heavily on the poor, suggesting that additional efforts be given to the creation of viable insurance mechanisms

The ESO Spectroscopic facility

We present the concept of a novel facility dedicated to massively-multiplexed spectroscopy. The telescope has a very wide field Cassegrain focus optimised for fibre feeding. With a Field of View (FoV) of 2.5 degrees diameter and a 11.4m pupil, it will be the largest etendue telescope. The large focal plane can easily host up to 16.000 fibres. In addition, a gravity invariant focus for the central 10 arc-minutes is available to host a giant integral field unit (IFU). The 3 lenses corrector includes an ADC, and has good performance in the 360-1300 nm wavelength range. The top level science requirements were developed by a dedicated ESO working group, and one of the primary cases is high resolution spectroscopy of GAIA stars and, in general, how our Galaxy formed and evolves. The facility will therefore be equipped with both, high and low resolution spectrographs. We stress the importance of developing the telescope and instrument designs simultaneously. The most relevant R\&D aspect is also briefly discussed.Comment: 6 pages 4 figures , presented at IAU Symposium 334 "rediscovering our galaxy

Confidence based active learning for vehicle classification in urban traffic

This paper presents a framework for confidence based active learning for vehicle classification in an urban traffic environment. Vehicles are automatically detected using an improved background subtraction algorithm using a Gaussian mixture model. A vehicle observation vector is constructed from measurement-based features and an intensity-based pyramid HOG. The output scores of a linear SVM classifier are accurately calibrated to probabilities using an interpolated dynamic bin width histogram. The confidence value of each sample is measured by its probabilities. Thus, only a small number of low confidence samples need to be identified and annotated according to their confidence. Compared to passive learning, the number of annotated samples needed for the training dataset can be reduced significantly, yielding a high accuracy classifier with low computational complexity and high efficiency. The detected vehicles are classified into four main categories: car, van, bus and motorcycle. Experimental results demonstrate the effectiveness and efficiency of our approach. The method is general enough so that it can be used in other classification problems and domains, e.g. pedestrian detection

The fifty-year quest for universality in percolation theory in high dimensions

Although well described by mean-field theory in the thermodynamic limit, scaling has long been puzzling for finite systems in high dimensions. This raised questions about the efficacy of the renormalization group and foundational concepts such as universality, finite-size scaling and hyperscaling, until recently believed not to be applicable above the upper critical dimension. Significant theoretical progress has been made resolving these issues, and tested in numerous simulational studies of spin models. This progress rests upon superlinearity of correlation length, a notion that for a long time encountered resistance but is now broadly accepted. Percolation theory brings added complications such as proliferation of interpenetrating clusters in apparent conflict with suggestions coming from random-graph asymptotics and a dearth of reliable simulational guidance. Here we report on recent theoretical progress in percolation theory in the renormalization group framework in high dimensions that accommodates superlinear correlation and renders most of the above concepts mutually compatible under different boundary conditions. Results from numerical simulations for free and periodic boundary conditions which differentiate between previously competing theories are also presented. Although still fragmentary, these Monte Carlo results support the new framework which restores the renormalization group and foundational concepts on which it rests