Effects of non-perturbatively improved dynamical fermions in UKQCD simulations

We present results for QCD with 2 degenerate flavours of quark using a non-perturbatively improved action on a lattice volume of $16^3\times32$ where the bare gauge coupling and bare dynamical quark mass have been chosen to maintain a fixed physical lattice spacing and volume (1.71 fm). By comparing measurements from these matched ensembles, including quenched ones, we find evidence of dynamical quark effects on the short distance static potential, the scalar glueball mass and the topological susceptibility. There is little evidence of effects on the light hadron spectrum over the range of quark masses studied ($m_{\pi}/m_{\rho}\geq 0.60$).Comment: Lattice 2000 (Spectrum and quark masses), 4 pages, 5 figure

SenseCam intervention based on cognitive ctimulation therapy framework for early-stage dementia.

Estimates suggest that Ireland will have 50,000 people with dementia by 2016 and over 100,000 by 2036. Combined with European total costs estimated in 2005 at €130 billion. In the absence of a cure for dementia there is a real need to develop pervasive, user-centered technologies to enhance the well-being and quality of life of people with dementia. This study explores the use of Microsoft SenseCam images within the principles of Cognitive Stimulation Therapy (CST) to engage people with early stage dementia in meaningful discussion. The SenseCam intervention, like the CST approach, is aimed at general enhancement of quality of life and global cognitive and social functioning

Approximate actions for dynamical fermions

Recent developments and applications of approximate actions for full lattice QCD are described. We present first results based on the stochastic estimation of the fermion determinant on $12^3\times 24$ configurations at $\beta=5.2$.Comment: 3 pages, Latex, no figures, Contribution to Lattice 97, The XV International Symposium on Lattice Field Theory, Edinburgh 22-26 July 199

Unquenching the Schwinger Model (revised)

We study the quenched and unquenched lattice Schwinger model with Wilson fermions. The lowest non-trivial order of the systematic expansion recently proposed by Sexton and Weingarten is shown to allow good estimates of long distance physics from quenched configurations. Results for the static potential and the lowest bound state mass are presented.Comment: 4 pages, 2 figures, self-unpacking uuencoded compressed postscript Contribution to Lattice 95 [Revision: value corrected on p.3

Feasibility study of using the overlap-Dirac operator for hadron spectroscopy

We investigate a number of algorithms that calculate the quark propagators for the overlap-Dirac fermion operator. The QCD simulations were performed at beta = 5.9 with a lattice volume of 16**3*32.Comment: LATTICE99(Chiral Fermions) 3 pages, 2 figures. A problem with the incorrect definition of the overlap mass has been corrected. The results have changed, but not the conclusions of the pape

Case studies in SenseCam use for cognitive stimulation therapy in early-stage dementia.

Estimates suggest that Ireland will have 50,000 people with dementia by 2016 and over 100,000 by 2036. Combined with European total costs are estimated in 2005 at €130 billion. As dementia is incurable there is a real need to support the existing dementia health care practices and carers by innovative technology use. Using technology to improve mental health of the people with dementia is one way of such support. This research explores intervention which uses Microsoft SenseCam images within the principles of Cognitive Stimulation Therapy (CST) to engage people with early stage dementia in meaningful discussion. This SenseCam intervention, like the CST approach, aims at general enhancement of quality of life and global cognitive and social functioning

Pseudoscalar singlet physics with staggered fermions

We report on progress in measuring disconnected correlators associated with pseudoscalar flavor-singlet mesons. This will eventually allow us to compute the masses of the eta and eta' mesons. Flavor-singlet physics also presents an interesting test of the staggered fermion formulation, as disconnected correlators are sensitive to whether the same action governs both sea quarks and valence quarks. It can also help test the validity of the ``fourth-root trick'' used in unquenched lattice calculations where the number of flavors $N_f<4$.Comment: Talk presented at Lattice 2005 (Hadron spectrum and quark masses), 6 pages, 3 figure

Numerical Stability of Lanczos Methods

The Lanczos algorithm for matrix tridiagonalisation suffers from strong numerical instability in finite precision arithmetic when applied to evaluate matrix eigenvalues. The mechanism by which this instability arises is well documented in the literature. A recent application of the Lanczos algorithm proposed by Bai, Fahey and Golub allows quadrature evaluation of inner products of the form $\psi^\dagger g(A) \psi$. We show that this quadrature evaluation is numerically stable and explain how the numerical errors which are such a fundamental element of the finite precision Lanczos tridiagonalisation procedure are automatically and exactly compensated in the Bai, Fahey and Golub algorithm. In the process, we shed new light on the mechanism by which roundoff error corrupts the Lanczos procedureComment: 3 pages, Lattice 99 contributio

A study of the eta and eta' mesons with improved staggered fermions

We report on a high statistics lattice QCD calculation of the mass of the eta and eta' mesons using ASQTAD improved staggered fermions. The calculation used two ensembles with different lattice spacings and pion masses. We also report results for eta-eta' mixing. The results are in satisfactory agreement with other lattice calculations using other fermion formulations and with experiment, given the the unphysical quark masses used. We see no evidence of abnormal behaviour at the lattice spacings studied.Comment: 10 pages, 10 figures; replacing with published version (1 figure and some discussion added; typos corrected