Nonequilibrium Quantum Phase Transitions in the Dicke Model

We establish a set of nonequilibrium quantum phase transitions in the Dicke model by considering a monochromatic nonadiabatic modulation of the atom-field coupling. For weak driving the system exhibits a set of sidebands which allow the circumvention of the no-go theorem which otherwise forbids the occurence of superradiant phase transitions. At strong driving we show that the system exhibits a rich multistable structure and exhibits both first- and second-order nonequilibrium quantum phase transitions.Comment: 4 pages, 3 Figures, and supplementary material. This new version contains corrected typos, new references and new versions of the figures. Published by Physical Review Letter

An illuminative evaluation of an alcohol education project

This thesis is an illuminative evaluation of the Drinking Choices Project, a health education programme based in the North East of England. The data for the evaluation was gathered by using participant observation. The instructional system, the Drinking Choices Manual, is a five-day teaching plan which includes alcohol knowledge, health education skills and an examination of the attitudes appropriate for health educators in the alcohol field. It was written by Ina Simnett, Linda Wright and Martin Evans. All of the materials are presented in a framework of participatory learning. A pyramid model was designed for the dissemination of the programme; the first people trained were Health Education Officers (HEOs) from the District Health Authorities in the northern region. Courses were run throughout the region, in the first instance for HEOs to be trained to use the Drinking Choices Manual and then, following through the pyramid, the HEOs trained other professionals who trained other colleagues who then used the Drinking Choices materials with their clients. The Introduction to this report describes the initial development and background of the project and the Health Education Council, (which is the Funding body).The thesis is in three parts, the first of which consists of reviews of the literature in the three major aspects of the project: Research Methodology Alcohol use and abuse Participatory learning methods. The second part begins with a description of the culture of the HBO so as to understand the organisational system in which the innovation took place; then the progress through the pyramid of dissemination is described, along with a detailed examination of the Manual itself and an investigation into obstacles encountered in implementing the Project. Part III examines positive aspects of the project, including a variety of outcomes and spin-offs which resulted. In Chapters VIII and IX conclusions and recommendations are presented; in Chapter X, which was written six months after the project ended, the Steps to Successful Change are outlined, followed by an epilogue, appendices, and bibliography

Feedback Control of Quantum Transport

The current through nanostructures like quantum dots can be stabilized by a feedback loop that continuously adjusts system parameters as a function of the number of tunnelled particles $n$. At large times, the feedback loop freezes the fluctuations of $n$ which leads to highly accurate, continuous single particle transfers. For the simplest case of feedback acting simultaneously on all system parameters, we show how to reconstruct the original full counting statistics from the frozen distribution.Comment: 4 pages, 2 figure

Universal Conductance and Conductivity at Critical Points in Integer Quantum Hall Systems

The sample averaged longitudinal two-terminal conductance and the respective Kubo-conductivity are calculated at quantum critical points in the integer quantum Hall regime. In the limit of large system size, both transport quantities are found to be the same within numerical uncertainty in the lowest Landau band, $0.60\pm 0.02 e^2/h$ and $0.58\pm 0.03 e^2/h$, respectively. In the 2nd lowest Landau band, a critical conductance $0.61\pm 0.03 e^2/h$ is obtained which indeed supports the notion of universality. However, these numbers are significantly at variance with the hitherto commonly believed value $1/2 e^2/h$. We argue that this difference is due to the multifractal structure of critical wavefunctions, a property that should generically show up in the conductance at quantum critical points.Comment: 4 pages, 3 figure