Searching for a continuum 4D field theory arising from a 5D non-abelian gauge theory

The anisotropic 5D SU(2) Yang-Mills model has been widely investigated on the lattice during the last decade. In the case where all dimensions are large in size, it was previously claimed that there is a new phase in the phase diagram, called the Layer phase. In this phase, the gauge fields would be localized on 4D layers. Previous works claim that the phase transition to the Layer phase is of second order, which would allow a continuum limit to be taken. We present the extension of the previous work to large lattices, for which we found a first order phase transition. This leaves the scenario that this 5D theory can be dimensionally reduced to a continuum 4D field theory, doubtful.Comment: 6 pages, 2 figures - talk presented at the 31st International Symposium on Lattice Field Theory - Lattice 2013, Mainz, German

An ``Improved" Lattice Study of Semi-leptonic Decays of D-Mesons

We present results of a lattice computation of the matrix elements of the vector and axial-vector currents which are relevant for the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$. The computations are performed in the quenched approximation to lattice QCD on a $24^3 \times 48$ lattice at $\beta=6.2$, using an $O(a)$-improved fermionic action. In the limit of zero lepton masses the semi-leptonic decays $D \rightarrow K$ and $D \rightarrow K^*$ are described by four form factors: $f^{+}_K,V,A_1$ and $A_2$, which are functions of $q^2$, where $q^{\mu}$ is the four-momentum transferred in the process. Our results for these form factors at $q^2=0$ are: f^+_K(0)=0.67 \er{7}{8} , V(0)=1.01 \err{30}{13} , A_1(0)=0.70 \err{7}{10} , A_2(0)=0.66 \err{10}{15} , which are consistent with the most recent experimental world average values. We have also determined the $q^2$ dependence of the form factors, which we find to be reasonably well described by a simple pole-dominance model. Results for other form factors, including those relevant to the decays \dpi and \drho, are also given.Comment: 41 pages, uuencoded compressed postscript file containing 14 figures, LaTeX, Edinburgh Preprint 94/546 and Southampton Preprint SHEP 93/94-3

Lattice QCD with mixed actions

We discuss some of the implications of simulating QCD when the action used for the sea quarks is different from that used for the valence quarks. We present exploratory results for the hadron mass spectrum and pseudoscalar meson decay constants using improved staggered sea quarks and HYP-smeared overlap valence quarks. We propose a method for matching the valence quark mass to the sea quark mass and demonstrate it on UKQCD clover data in the simpler case where the sea and valence actions are the same.Comment: 15 pages, 10 figures some minor modification to text and figures. Accepted for publicatio

Localization and chiral symmetry in 2+1 flavor domain wall QCD

We present results for the dependence of the residual mass of domain wall fermions (DWF) on the size of the fifth dimension and its relation to the density and localization properties of low-lying eigenvectors of the corresponding hermitian Wilson Dirac operator relevant to simulations of 2+1 flavor domain wall QCD. Using the DBW2 and Iwasaki gauge actions, we generate ensembles of configurations with a $16^3\times 32$ space-time volume and an extent of 8 in the fifth dimension for the sea quarks. We demonstrate the existence of a regime where the degree of locality, the size of chiral symmetry breaking and the rate of topology change can be acceptable for inverse lattice spacings $a^{-1} \ge 1.6$ GeV.Comment: 59 Pages, 23 figures, 1 MPG linke

The transition to a layered phase in the anisotropic five-dimensional SU(2) Yang-Mills theory

We extend to large lattices the work of a previous investigation of the phase diagram of the anisotropic five-dimensional SU(2) Yang-Mills model using Monte Carlo simulations in the regime where the lattice spacing in the fifth dimension is larger than in the other four dimensions. We find a first order phase transition between the confining and deconfining phase at the anisotropic parameter point $\beta_4=2.60$ which was previously claimed to be the critical point at which the order of the transition changes from first to second. We conclude that large lattices are required to establish the first order nature of this line of transitions and consequently that the scenario of dimensional reduction of the five-dimensional theory to a continuum four-dimensional theory via the existence of the so-called "layer phase" is unpromising.Comment: 5 pages, 1 table, 6 figure

The role of economic evaluation in the decision-making process of family physicians: design and methods of a qualitative embedded multiple-case study

<p>Abstract</p> <p>Background</p> <p>A considerable amount of resource allocation decisions take place daily at the point of the clinical encounter; especially in primary care, where 80 percent of health problems are managed. Ignoring economic evaluation evidence in individual clinical decision-making may have a broad impact on the efficiency of health services. To date, almost all studies on the use of economic evaluation in decision-making used a quantitative approach, and few investigated decision-making at the clinical level. An important question is whether economic evaluations affect clinical practice. The project is an intervention research study designed to understand the role of economic evaluation in the decision-making process of family physicians (FPs). The contributions of the project will be from the perspective of Pierre Bourdieu's sociological theory.</p> <p>Methods/design</p> <p>A qualitative research strategy is proposed. We will conduct an embedded multiple-case study design. Ten case studies will be performed. The FPs will be the unit of analysis. The sampling strategies will be directed towards theoretical generalization. The 10 selected cases will be intended to reflect a diversity of FPs. There will be two embedded units of analysis: FPs (micro-level of analysis) and field of family medicine (macro-level of analysis). The division of the determinants of practice/behaviour into two groups, corresponding to the macro-structural level and the micro-individual level, is the basis for Bourdieu's mode of analysis. The sources of data collection for the micro-level analysis will be 10 life history interviews with FPs, documents and observational evidence. The sources of data collection for the macro-level analysis will be documents and 9 open-ended, focused interviews with key informants from medical associations and academic institutions. The analytic induction approach to data analysis will be used. A list of codes will be generated based on both the original framework and new themes introduced by the participants. We will conduct within-case and cross-case analyses of the data.</p> <p>Discussion</p> <p>The question of the role of economic evaluation in FPs' decision-making is of great interest to scientists, health care practitioners, managers and policy-makers, as well as to consultants, industry, and society. It is believed that the proposed research approach will make an original contribution to the development of knowledge, both empirical and theoretical.</p

The particle spectra of confining field theories

Massive QED (Schwinger model) for one and two fermion species in 1+1 dimensions is studied using Hamiltonian lattice techniques. Bound-state masses are calculated as strong-coupling expansions in inverse powers of the dimensionless coupling constant. Various Pade approximant methods for extracting continuum predictions from these are compared. The non-relativistic limit of both lattice theories is the lattice linear potential model. This can be solved exactly. It is used to test convergence of the sequence of Pade approximants. The investigation is continued for the ordinary Schwinger model. At all coupling strengths, the best continuum estimates for bound-state masses come from values of the Pade approximants at non-zero lattice spacing. Two different lattice formulations of the two-species Schwinger model are studied. Both have a restoration of chiral SU(2) symmetry as the fermion mass vanishes. The corresponding symmetric vacuum is too complicated to do a perturbative calculation beyond second order, where the low-lying states are those of a Heisenberg antiferromagnetic chain, in qualitative agreement with the continuum theory. Strong-coupling expansions are carried out to high orders about the unsymmetric vacua of the massive theories. Continuum estimates for bound-state masses are compared. For weak coupling their convergence is understood in terms of the linear potential model. But for strong coupling convergence is slow; neither lattice can account for the whole particle spectrum, though each treats part of it well. Matrix methods are studied in an attempt to obtain better convergence from low-order calculations. Strong-coupling expansions for the Hamiltonian matrix in a non-degenerate subspace are extrapolated to zero lattice spacing using matrix Pade approximants. Improved continuum estimates ore obtained from the scalar mass matrix of the ordinary Schwinger model, but not from the pseudoscalar mass matrix.</p