Polyakov loop potential at finite density

The Polyakov loop potential serves to distinguish between the confined hadronic and the deconfined quark-gluon plasma phases of QCD. For Nf=2+1 quark flavors with physical masses we determine the Polyakov loop potential at finite temperature and density and extract the location of the deconfinement transition. We find a cross-over at small values of the chemical potential running into a critical end-point at mu/T > 1.Comment: 5 pages, 9 figure

Improved Upper Bounds to the Causal Quadratic Rate-Distortion Function for Gaussian Stationary Sources

We improve the existing achievable rate regions for causal and for zero-delay source coding of stationary Gaussian sources under an average mean squared error (MSE) distortion measure. To begin with, we find a closed-form expression for the information-theoretic causal rate-distortion function (RDF) under such distortion measure, denoted by $R_{c}^{it}(D)$, for first-order Gauss-Markov processes. Rc^{it}(D) is a lower bound to the optimal performance theoretically attainable (OPTA) by any causal source code, namely Rc^{op}(D). We show that, for Gaussian sources, the latter can also be upper bounded as Rc^{op}(D)\leq Rc^{it}(D) + 0.5 log_{2}(2\pi e) bits/sample. In order to analyze $R_{c}^{it}(D)$ for arbitrary zero-mean Gaussian stationary sources, we introduce \bar{Rc^{it}}(D), the information-theoretic causal RDF when the reconstruction error is jointly stationary with the source. Based upon \bar{Rc^{it}}(D), we derive three closed-form upper bounds to the additive rate loss defined as \bar{Rc^{it}}(D) - R(D), where R(D) denotes Shannon's RDF. Two of these bounds are strictly smaller than 0.5 bits/sample at all rates. These bounds differ from one another in their tightness and ease of evaluation; the tighter the bound, the more involved its evaluation. We then show that, for any source spectral density and any positive distortion D\leq \sigma_{x}^{2}, \bar{Rc^{it}}(D) can be realized by an AWGN channel surrounded by a unique set of causal pre-, post-, and feedback filters. We show that finding such filters constitutes a convex optimization problem. In order to solve the latter, we propose an iterative optimization procedure that yields the optimal filters and is guaranteed to converge to \bar{Rc^{it}}(D). Finally, by establishing a connection to feedback quantization we design a causal and a zero-delay coding scheme which, for Gaussian sources, achieves...Comment: 47 pages, revised version submitted to IEEE Trans. Information Theor

“Binge drinking? It’s good, it’s harmless fun”:a discourse analysis of accounts of female undergraduate drinking in Scotland

Binge drinking in young people, particularly females and students, is a source of some concern to those engaged in health education. The concept is usually defined in terms of quantities of alcohol consumed within a relatively short space of time. Research suggests that reasons for drinking are varied, and are likely to be influenced by culture and context. This study aimed to explore issues important to female undergraduate students in Scotland. Semi-structured interviews were carried out with 19 participants who were asked to describe what they understand by the term ‘binge drinking’, why they drink and what might trigger excessive consumption. Discourse analysis was used to explore the possible ‘functions’ of what was said, as well as the content. Participants showed sensitivity to how others might interpret their responses. They described binge drinking in terms of its behavioural effects rather than quantities consumed. Crucially, they positioned themselves outside the categories of ‘serious’ or ‘anti-social’ drinkers. These findings have important implications for our understanding of factors influencing drinking behaviour in this group of people, which in turn impacts on the potential design of health-enhancing interventions. The study also demonstrates the usefulness of a discourse analytic approach to accounts of drinking behaviour

Phenomenological Aspects of F-theory

Stabilizing a heterotic string vacuum with a large expectation value of the dilaton and simultaneously breaking low-energy supersymmetry is a long-standing problem of string phenomenology. We reconsider these issues in light of the recent developments in F-theory.Comment: 11 pages, phyzzx macro

Local discontinuous Galerkin methods for fractional ordinary differential equations

This paper discusses the upwinded local discontinuous Galerkin methods for the one-term/multi-term fractional ordinary differential equations (FODEs). The natural upwind choice of the numerical fluxes for the initial value problem for FODEs ensures stability of the methods. The solution can be computed element by element with optimal order of convergence $k+1$ in the $L^2$ norm and superconvergence of order $k+1+\min\{k,\alpha\}$ at the downwind point of each element. Here $k$ is the degree of the approximation polynomial used in an element and $\alpha$ ($\alpha\in (0,1]$) represents the order of the one-term FODEs. A generalization of this includes problems with classic $m$'th-term FODEs, yielding superconvergence order at downwind point as $k+1+\min\{k,\max\{\alpha,m\}\}$. The underlying mechanism of the superconvergence is discussed and the analysis confirmed through examples, including a discussion of how to use the scheme as an efficient way to evaluate the generalized Mittag-Leffler function and solutions to more generalized FODE's.Comment: 17 pages, 7 figure

The Hamiltonian Formulation of Higher Order Dynamical Systems

Using Dirac's approach to constrained dynamics, the Hamiltonian formulation of regular higher order Lagrangians is developed. The conventional description of such systems due to Ostrogradsky is recovered. However, unlike the latter, the present analysis yields in a transparent manner the local structure of the associated phase space and its local sympletic geometry, and is of direct application to {\em constrained\/} higher order Lagrangian systems which are beyond the scope of Ostrogradsky's approach.Comment: 17 pages. Revised: references adde

Critical Point and Deconfinement from Dyson-Schwinger Equations

We employ the Dyson-Schwinger equations for quark and gluon propagators in order to study QCD with 2+1 flavours at finite temperature and density. In a suitable truncation for these equations, we determine the position of the critical end-point as well as the deconfinement temperature at all chemical potentials. For the latter, the Polyakov-loop potential is obtained from the QCD propagators. This is possible for the first time at finite chemical potential, with implications for effective models.Comment: Proceedings for the 8th International Workshop on Critical Point and Onset of Deconfinement (CPOD 2013). 5 pages, 5 figure

Development of mercuric iodide uncooled x ray detectors and spectrometers

The results obtained in the development of miniature, lowpower, light weight mercuric iodide, HgI2, x ray spectrometers for future space missions are summarized. It was demonstrated that HgI2 detectors can be employed in a high resolution x ray spectrometer, operating in a scanning electron microscope. Also, the development of HgI2 x ray detectors to augment alpha backscattering spectrometers is discussed. These combination instruments allow for the identification of all chemical elements, with the possible exception of hydrogen, and their respective concentrations. Additionally, further investigations of questions regarding radiation damage effects in the HgI2 x ray detectors are reported