't Hooft Loops, Electric Flux Sectors and Confinement in SU(2) Yang-Mills Theory

We use 't Hooft loops of maximal size on finite lattices to calculate the free energy in the sectors of SU(2) Yang-Mills theory with fixed electric flux as a function of temperature and (spatial) volume. Our results provide evidence for the mass gap. The confinement of electric fluxes in the low temperature phase and their condensation in the high temperature phase are demonstrated. In a surprisingly large scaling window around criticality, the transition is quantitatively well described by universal exponents and amplitude ratios relating the properties of the two phases.Comment: 5 Pages, LaTeX 2.09 (uses revtex v3.1), 5 Figures (epsfig), revised version to appear in Phys. Rev.

Arrival Times, Complex Potentials and Decoherent Histories

We address a number of aspects of the arrival time problem defined using a complex potential of step function form. We concentrate on the limit of a weak potential, in which the resulting arrival time distribution function is closely related to the quantum-mechanical current. We first consider the analagous classical arrival time problem involving an absorbing potential, and this sheds some light on certain aspects of the quantum case. In the quantum case, we review the path decomposition expansion (PDX), in which the propagator is factored across a surface of constant time, so is very useful for potentials of step function form. We use the PDX to derive the usual scattering wave functions and the arrival time distribution function. This method gives a direct and geometrically appealing account of known results (but also points the way to how they can be extended to more general complex potentials). We use these results to carry out a decoherent histories analysis of the arrival time problem, taking advantage of a recently demonstrated connection between pulsed measurements and complex potentials. We obtain very simple and plausible expressions for the class operators (describing the amplitudes for crossing the origin during intervals of time) and show that decoherence of histories is obtained for a wide class of initial states (such as simple wave packets and superpositions of wave packets). We find that the decoherent histories approach gives results with a sensible classical limit that are fully compatible with standard results on the arrival time problem. We also find some interesting connections between backflow and decoherence.Comment: 43 page

The cost-effectiveness of increasing alcohol taxes: a modelling study

<p>Abstract</p> <p>Background</p> <p>Excessive alcohol use increases risks of chronic diseases such as coronary heart disease and several types of cancer, with associated losses of quality of life and life-years. Alcohol taxes can be considered as a public health instrument as they are known to be able to decrease alcohol consumption. In this paper, we estimate the cost-effectiveness of an alcohol tax increase for the entire Dutch population from a health-care perspective focusing on health benefits and health-care costs in alcohol users.</p> <p>Methods</p> <p>The chronic disease model of the National Institute for Public Health and the Environment was used to extrapolate from decreased alcohol consumption due to tax increases to effects on health-care costs, life-years gained and quality-adjusted life-years gained, A Dutch scenario in which tax increases for beer are planned, and a Swedish scenario representing one of the highest alcohol taxes in Europe, were compared with current practice in the Netherlands. To estimate cost-effectiveness ratios, yearly differences in model outcomes between intervention and current practice scenarios were discounted and added over the time horizon of 100 years to find net present values for incremental life-years gained, quality-adjusted life-years gained, and health-care costs.</p> <p>Results</p> <p>In the Swedish scenario, many more quality-adjusted life-years were gained than in the Dutch scenario, but both scenarios had almost equal incremental cost-effectiveness ratios: €5100 per quality-adjusted life-year and €5300 per quality-adjusted life-year, respectively.</p> <p>Conclusion</p> <p>Focusing on health-care costs and health consequences for drinkers, an alcohol tax increase is a cost-effective policy instrument.</p

Increasing Short-Stay Unplanned Hospital Admissions among Children in England; Time Trends Analysis '97-'06

BACKGROUND: Timely care by general practitioners in the community keeps children out of hospital and provides better continuity of care. Yet in the UK, access to primary care has diminished since 2004 when changes in general practitioners' contracts enabled them to 'opt out' of providing out-of-hours care and since then unplanned pediatric hospital admission rates have escalated, particularly through emergency departments. We hypothesised that any increase in isolated short stay admissions for childhood illness might reflect failure to manage these cases in the community over a 10 year period spanning these changes. METHODS AND FINDINGS: We conducted a population based time trends study of major causes of hospital admission in children 2 days. By 2006, 67.3% of all unplanned admissions were isolated short stays <2 days. The increases in admission rates were greater for common non-infectious than infectious causes of admissions. CONCLUSIONS: Short stay unplanned hospital admission rates in young children in England have increased substantially in recent years and are not accounted for by reductions in length of in-hospital stay. The majority are isolated short stay admissions for minor illness episodes that could be better managed by primary care in the community and may be evidence of a failure of primary care services

Cost-Effectiveness of an Opportunistic Screening Programme and Brief Intervention for Excessive Alcohol Use in Primary Care

Effective prevention of excessive alcohol use has the potential to reduce the public burden of disease considerably. We investigated the cost-effectiveness of Screening and Brief Intervention (SBI) for excessive alcohol use in primary care in the Netherlands, which is targeted at early detection and treatment of ‘at-risk’ drinkers.We compared a SBI scenario (opportunistic screening and brief intervention for ‘at-risk’ drinkers) in general practices with the current practice scenario (no SBI) in the Netherlands. We used the RIVM Chronic Disease Model (CDM) to extrapolate from decreased alcohol consumption to effects on health care costs and Quality Adjusted Life Years (QALYs) gained. Probabilistic sensitivity analysis was employed to study the effect of uncertainty in the model parameters. In total, 56,000 QALYs were gained at an additional cost of €298,000,000 due to providing alcohol SBI in the target population, resulting in a cost-effectiveness ratio of €5,400 per QALY gained.Prevention of excessive alcohol use by implementing SBI for excessive alcohol use in primary care settings appears to be cost-effective

On the Relationship Between Complex Potentials and Strings of Projection Operators

It is of interest in a variety of contexts, and in particular in the arrival time problem, to consider the quantum state obtained through unitary evolution of an initial state regularly interspersed with periodic projections onto the positive $x$-axis (pulsed measurements). Echanobe, del Campo and Muga have given a compelling but heuristic argument that the state thus obtained is approximately equivalent to the state obtained by evolving in the presence of a certain complex potential of step-function form. In this paper, with the help of the path decomposition expansion of the associated propagators, we give a detailed derivation of this approximate equivalence. The propagator for the complex potential is known so the bulk of the derivation consists of an approximate evaluation of the propagator for the free particle interspersed with periodic position projections. This approximate equivalence may be used to show that to produce significant reflection, the projections must act at time spacing less than 1/E, where E is the energy scale of the initial state.Comment: 29 pages, LaTex, 4 figures. Substantial revision

Quark zero modes in intersecting center vortex gauge fields

The zero modes of the Dirac operator in the background of center vortex gauge field configurations in $\R^2$ and $\R^4$ are examined. If the net flux in D=2 is larger than 1 we obtain normalizable zero modes which are mainly localized at the vortices. In D=4 quasi-normalizable zero modes exist for intersecting flat vortex sheets with the Pontryagin index equal to 2. These zero modes are mainly localized at the vortex intersection points, which carry a topological charge of $\pm 1/2$. To circumvent the problem of normalizability the space-time manifold is chosen to be the (compact) torus \T^2 and \T^4, respectively. According to the index theorem there are normalizable zero modes on \T^2 if the net flux is non-zero. These zero modes are localized at the vortices. On \T^4 zero modes exist for a non-vanishing Pontryagin index. As in $\R^4$ these zero modes are localized at the vortex intersection points.Comment: 20 pages, 4 figures, LaTeX2e, references added, treatment of ideal vortices on the torus shortene

The self-dual gauge fields and the domain wall fermion zero modes

A new type of gauge fixing of the Coulomb gauge domain wall fermion system that reduces the fluctuation of the effective running coupling and the effective mass of arbitrary momentum direction including the region outside the cylinder cut region is proposed and tested in the $16^3\times 32\times 16$ gauge configurations of RBC/UKQCD collaboration. The running coupling at the lowest momentum point does not show infrared suppression and compatible with the experimental data extracted from the JLab collaboration. The source of the fluctuation of the effective mass near momentum $p=$0.6GeV region is expected to be due to the domain wall fermion zero modes.Comment: 12 pages 2 figures, extended arguments and references adde

Probabilities in Quantum Cosmological Models: A Decoherent Histories Analysis Using a Complex Potential

In the quantization of simple cosmological models (minisuperspace models) described by the Wheeler-DeWitt equation, an important step is the construction, from the wave function, of a probability distribution answering various questions of physical interest, such as the probability of the system entering a given region of configuration space at any stage in its entire history. A standard but heuristic procedure is to use the flux of (components of) the wave function in a WKB approximation. This gives sensible semiclassical results but lacks an underlying operator formalism. In this paper, we address the issue of constructing probability distributions linked to the Wheeler-DeWitt equation using the decoherent histories approach to quantum theory. We show that the appropriate class operators (the generalization of strings of projectors) in quantum cosmology are readily constructed using a complex potential. We derive the class operator for entering or not entering one or more regions in configuration space. They commute with the Hamiltonian, have a sensible classical limit and are closely related to intersection number operators. We show that oscillatory WKB solutions to the Wheeler-DeWitt equation give approximate decoherence of histories, as do superpositions of WKB solutions, as long as the regions of configuration space are sufficiently large. The corresponding probabilities coincide, in a semiclassical approximation, with standard heuristic procedures. In brief, we exhibit the well-defined operator formalism underlying the usual heuristic interpretational methods in quantum cosmology.Comment: 49 pages, Latex, 8 figure

The Gluon Propagator without lattice Gribov copies

We study the gluon propagator in quenched lattice QCD using the Laplacian gauge which is free of lattice Gribov copies. We compare our results with those obtained in the Landau gauge on the lattice, as well as with various approximate solutions of the Dyson Schwinger equations. We find a finite value $\sim (445 \rm{MeV})^{-2}$ for the renormalized zero-momentum propagator (taking our renormalization point at 1.943 GeV), and a pole mass $\sim 640 \pm 140$ MeV.Comment: Discussion of the renormalized gluon propagator and of the Laplacian gauge fixing procedure extended. Version to appear in Phys. Rev. D. 15 pages, 8 figure