A non-perturbative estimate of the heavy quark momentum diffusion coefficient

We estimate the momentum diffusion coefficient of a heavy quark within a pure SU(3) plasma at a temperature of about 1.5Tc. Large-scale Monte Carlo simulations on a series of lattices extending up to 192^3*48 permit us to carry out a continuum extrapolation of the so-called colour-electric imaginary-time correlator. The extrapolated correlator is analyzed with the help of theoretically motivated models for the corresponding spectral function. Evidence for a non-zero transport coefficient is found and, incorporating systematic uncertainties reflecting model assumptions, we obtain kappa = (1.8 - 3.4)T^3. This implies that the "drag coefficient", characterizing the time scale at which heavy quarks adjust to hydrodynamic flow, is (1.8 - 3.4) (Tc/T)^2 (M/1.5GeV) fm/c, where M is the heavy quark kinetic mass. The results apply to bottom and, with somewhat larger systematic uncertainties, to charm quarks.Comment: 18 pages. v2: clarifications adde

Critical point and scale setting in SU(3) plasma: An update

We explore a method developed in statistical physics which has been argued to have exponentially small finite-volume effects, in order to determine the critical temperature Tc of pure SU(3) gauge theory close to the continuum limit. The method allows us to estimate the critical coupling betac of the Wilson action for temporal extents up to Nt ~ 20 with < 0.1% uncertainties. Making use of the scale setting parameters r0 and sqrt{t0} in the same range of beta-values, these results lead to the independent continuum extrapolations Tc r0 = 0.7457(45) and Tc sqrt{t0} = 0.2489(14), with the latter originating from a more convincing fit. Inserting a conversion of r0 from literature (unfortunately with much larger errors) yields Tc / LambdaMSbar = 1.24(10).Comment: 12 pages. v2: clarifications and references added, published versio

Towards the continuum limit in transport coefficient computations

The analytic continuation needed for the extraction of transport coefficients necessitates in principle a continuous function of the Euclidean time variable. We report on progress towards achieving the continuum limit for 2-point correlator measurements in thermal SU(3) gauge theory, with specific attention paid to scale setting. In particular, we improve upon the determination of the critical lattice coupling and the critical temperature of pure SU(3) gauge theory, estimating r0*Tc ~ 0.7470(7) after a continuum extrapolation. As an application the determination of the heavy quark momentum diffusion coefficient from a correlator of colour-electric fields attached to a Polyakov loop is discussed.Comment: 7 pages. To appear in the Proceedings of the 31st International Symposium on Lattice Field Theory, July 29 - August 3, 2013, Mainz, German

Free energy density for mean field perturbation of states of a one-dimensional spin chain

Motivated by recent developments on large deviations in states of the spin chain, we reconsider the work of Petz, Raggio and Verbeure in 1989 on the variational expression of free energy density in the presence of a mean field type perturbation. We extend their results from the product state case to the Gibbs state case in the setting of translation-invariant interactions of finite range. In the special case of a locally faithful quantum Markov state, we clarify the relation between two different kinds of free energy densities (or pressure functions).Comment: 29 pages, Section 5 added, to appear in Rev. Math. Phy

Anisotropic Magnetoresistance in Ga1−x_{1-x}Mnx_xAs

We have measured the magnetoresistance in a series of Ga$_{1-x}$Mn$_x$As samples with 0.033$\le x \le$ 0.053 for three mutually orthogonal orientations of the applied magnetic field. The spontaneous resistivity anisotropy (SRA) in these materials is negative (i.e. the sample resistance is higher when its magnetization is perpendicular to the measuring current than when the two are parallel) and has a magnitude on the order of 5% at temperatures near 10K and below. This stands in contrast to the results for most conventional magnetic materials where the SRA is considerably smaller in magnitude for those few cases in which a negative sign is observed. The magnitude of the SRA drops from its maximum at low temperatures to zero at T$_C$ in a manner that is consistent with mean field theory. These results should provide a significant test for emerging theories of transport in this new class of materials.Comment: 4 pages with 4 figures. Submitted to Physical Review

Partial Kekule Ordering of Adatoms on Graphene

Electronic and transport properties of Graphene, a one-atom thick crystalline material, are sensitive to the presence of atoms adsorbed on its surface. An ensemble of randomly positioned adatoms, each serving as a scattering center, leads to the Bolzmann-Drude diffusion of charge determining the resistivity of the material. An important question, however, is whether the distribution of adatoms is always genuinely random. In this Article we demonstrate that a dilute adatoms on graphene may have a tendency towards a spatially correlated state with a hidden Kekule mosaic order. This effect emerges from the interaction between the adatoms mediated by the Friedel oscillations of the electron density in graphene. The onset of the ordered state, as the system is cooled below the critical temperature, is accompanied by the opening of a gap in the electronic spectrum of the material, dramatically changing its transport properties

Exploring Learning Problems of Filipino Nurse Candidates Working in Japan: Based on the Results of a Practice National Board Examination of Japan Given in English

This article investigates the status of the education and training of Filipino nurse candidates who have been working in Japan under the Japan-Philippine Economic Partnership Agreement (JPEPA). A survey was conducted among Filipino nurse candidates, using a practice examination based on the English version of Japan’s National Board Examination for Registered Nurses in 2009. Categorized by area, the mean correct answer rate for nursing-related questions ranged between 61% and 73%; the rate for questions concerning basic knowledge of body functions and diseases ranged between 55% and 57%. There was a large gap in terms of the results of the examination between those who had previously seen the exam questions and those who had never seen them. While 57.1% of those who had previously seen the questions satisfied the acceptance criteria, only 23.7%of those who had never viewed the test satisfied it. Based on these results, the factors which serve as obstacles that Filipino nurse candidates encounter in passing the national examination include not only difficulties in acquiring Japanese proficiency but also differences between Japan and the Philippines in respect to the nursing education curriculum and basic nursing policies

Exploring Learning Problems of Filipino Nurse Candidates Working in Japan: Based on the Results of a Practice National Board Examination of Japan Given in English

This article investigates the status of the education and training of Filipino nurse candidates who have been working in Japan under the Japan-Philippine Economic Partnership Agreement (JPEPA). A survey was conducted among Filipino nurse candidates, using a practice examination based on the English version of Japan’s National Board Examination for Registered Nurses in 2009. Categorized by area, the mean correct answer rate for nursing-related questions ranged between 61% and 73%; the rate for questions concerning basic knowledge of body functions and diseases ranged between 55% and 57%. There was a large gap in terms of the results of the examination between those who had previously seen the exam questions and those who had never seen them. While 57.1% of those who had previously seen the questions satisfied the acceptance criteria, only 23.7%of those who had never viewed the test satisfied it. Based on these results, the factors which serve as obstacles that Filipino nurse candidates encounter in passing the national examination include not only difficulties in acquiring Japanese proficiency but also differences between Japan and the Philippines in respect to the nursing education curriculum and basic nursing policies