The shape of hyperbolic Dehn surgery space

In this paper we develop a new theory of infinitesimal harmonic deformations for compact hyperbolic 3-manifolds with ``tubular boundary''. In particular, this applies to complements of tubes of radius at least R_0 = \arctanh(1/\sqrt{3}) \approx 0.65848 around the singular set of hyperbolic cone manifolds, removing the previous restrictions on cone angles. We then apply this to obtain a new quantitative version of Thurston's hyperbolic Dehn surgery theorem, showing that all generalized Dehn surgery coefficients outside a disc of ``uniform'' size yield hyperbolic structures. Here the size of a surgery coefficient is measured using the Euclidean metric on a horospherical cross section to a cusp in the complete hyperbolic metric, rescaled to have area 1. We also obtain good estimates on the change in geometry (e.g. volumes and core geodesic lengths) during hyperbolic Dehn filling. This new harmonic deformation theory has also been used by Bromberg and his coworkers in their proofs of the Bers Density Conjecture for Kleinian groups.Comment: 46 pages, 3 figure

Developing professional skills in journalism through blogs

The curriculum for journalism is being forced to change because the traditional print-based and broadcast modes are being challenged by wide and easy access to online mass communication. Primarily, students need to develop proficiency in writing, editing and publishing. However, they are also expected to be skilled in the Web medium as they venture into their careers, and weblogs offer a dynamic platform to develop these skills. Based on a statistical summary of student comments on the performance criteria for a blog project, a focus group interview and survey results, this paper will discuss the findings from the introduction of a course-based blog to an undergraduate course in Hong Kong, including: (1) the technical challenge of making Web features; (2) the perception of proficiency in online publishing; (3) the evaluative skills developed through a peer-review process; and (4) the development of a learning community through writing in blogs. © 2011 Taylor & Francis.postprin

Doing academic assignments: Whether to use a wiki or an alternative platform

Using a wiki in a group project can be a valuable experience, particularly when students are able to learn about collaboration between group members. Because they are not given a defined structure, students can flexibly design content with multimodality through the use of a wiki. However, students commonly experience some form of technical difficulty when using a wiki. A pilot study of two courses explored what preferred applications students used when preparing group wiki-based projects in one course, and it examined why some students preferred to use platforms other than a wiki in the other course. Results from the end-of-course survey suggest that while students were aware of features available in wikis, they preferred to use web tools that they were already familiar with to develop web-based products. Many students remarked that there was a lack of technical preparation for this learning platform, or they did not see the value in continuing to use wikis after completing the course. Also, some indicated that they favoured email applications such as Hotmail for collaboration and feedback purposes. Suggestions are offered to educators on how to improve student reception of wikis and other Web 2.0 e-learning tools. © 2010 IADIS.postprintThe 2010 IADIS International Conference on e-Learning, Freiburg, Germany, 26-30 July 2010. In Proceedings of the IADIS International Conference on e-Learning, 2010, v. 2, p. 209-21

Electron localisation in static and time-dependent one-dimensional model systems

Electron localization is the tendency of an electron in a many-body system to exclude other electrons from its vicinity. Using a new natural measure of localization based on the exact manyelectron wavefunction, we find that localization can vary considerably between different ground-state systems, and can also be strongly disrupted, as a function of time, when a system is driven by an applied electric field. We use our new measure to assess the well-known electron localization function (ELF), both in its approximate single-particle form (often applied within density-functional theory) and its full many-particle form. The full ELF always gives an excellent description of localization, but the approximate ELF fails in time-dependent situations, even when the exact Kohn-Sham orbitals are employed.Comment: 7 pages, 4 figure

Large NcN_c QCD at non-zero chemical potential

The general issue of large $N_c$ QCD at nonzero chemical potential is considered with a focus on understanding the difference between large $N_c$ QCD with an isospin chemical potential and large $N_c$ QCD with a baryon chemical potential. A simple diagrammatic analysis analogous to `t Hooft's analysis at $\mu=0$ implies that the free energy with a given baryon chemical potential is equal to the free energy with an isospin chemical potential of the same value plus $1/N_c$ corrections. Phenomenologically, these two systems behave quite differently. A scenario to explain this difference in light of the diagrammatic analysis is explored. This scenario is based on a phase transition associated with pion condensation when the isospin chemical potential exceeds $m_\pi/2$; associated with this transition there is breakdown of the $1/N_c$ expansion--in the pion condensed phase there is a distinct $1/N_c$ expansion including a larger set of diagrams. While this scenario is natural, there are a number of theoretical issues which at least superficially challenge it. Most of these can be accommodated. However, the behavior of quenched QCD which raises a number of apparently analogous issues cannot be easily understood completely in terms of an analogous scenario. Thus, the overall issue remains open

Managing the development of digital educational games

Based on the practical experience of developing webbased educational games in a joint universities project in Hong Kong, the authors discuss a 'seven-stage rapid game development model' with a 'dynamic fine tuning' of team composition. Reflection on lessons learned from the practical experience is described. © 2010 IEEE.published_or_final_versionThe 3rd IEEE International Conference on Digital Game and Intelligent Toy Enhanced Learning (DIGITEL), Kaohsiung, Taiwan, 12-16 April 2010. In Proceedings of the 3rd DIGITEL, 2010, p. 191-19

Orientational Ordering and Dynamics of Rodlike Polyelectrolytes

The interplay between electrostatic interactions and orientational correlations is studied for a model system of charged rods positioned on a chain, using Monte Carlo simulation techniques. It is shown that the coupling brings about the notion of {\em electrostatic frustration}, which in turn results in: (i) a rich variety of novel orientational orderings such as chiral phases, and (ii) an inherently slow dynamics characterized by stretched-exponential behavior in the relaxation functions of the system.Comment: 7 pages, 10 figure