33,754 research outputs found
Accelerating Staggered Fermion Dynamics with the Rational Hybrid Monte Carlo (RHMC) Algorithm
Improved staggered fermion formulations are a popular choice for lattice QCD
calculations. Historically, the algorithm used for such calculations has been
the inexact R algorithm, which has systematic errors that only vanish as the
square of the integration step-size. We describe how the exact Rational Hybrid
Monte Carlo (RHMC) algorithm may be used in this context, and show that for
parameters corresponding to current state-of-the-art computations it leads to a
factor of approximately seven decrease in cost as well as having no step-size
errors.Comment: 4 pages, 2 figures, 1 tabl
Theology at the coal-face of hospitalisation - the development and evaluation of a postgraduate certificate in Healthcare Chaplaincy
Healthcare chaplaincy is working towards recognition as a registered health profession. An accredited programme of professional education is part of that process. The University of Glasgow supported by NHS Education for Scotland have developed a programme of professional education for healthcare chaplains that is integrated into an MSc. (MedSci) in healthcare. This article outlines the commissioning, development and evaluation of a postgraduate certificate in healthcare chaplaincy by students, clinical mentors and experienced healthcare chaplains. It also highlights an innovative approach to practice development in spiritual and religious care in healthcare
Effect of a Spin-1/2 Impurity on the Spin-1 Antiferromagnetic Heisenberg Chain
Low-lying excited states as well as the ground state of the spin-1 antiferro-
magnetic Heisenberg chain with a spin-1/2 impurity are investigated by means of
a variational method and a method of numerical diagonalization. It is shown
that 1) the impurity spin brings about massive modes in the Haldane gap, 2)
when the the impurity-host coupling is sufficiently weak, the phenomenological
Hamiltonian used by Hagiwara {\it et al.} in the analysis of ESR experimental
results for NENP containing a small amount of spin-1/2 Cu impurities is
equivalent to a more realistic Hamiltonian, as far as the energies of the
low-lying states are concerned, 3) the results obtained by the variational
method are in semi-quantitatively good agreement with those obtained by the
numerical diagonalization.Comment: 11 pages, plain TeX (Postscript figures are included), KU-CCS-93-00
Exact 2+1 flavour RHMC simulations
We consider the Rational Hybrid Monte Carlo algorithm for performing exact
2+1 flavour fermion simulations. The specific cases of ASQTAD and domain wall
fermions are considered. We find that in both cases the naive performance is
similar to conventional hybrid algorithms.Comment: 3 pages, no figure
Algorithm Shootout: R versus RHMC
We present initial results comparing the RHMC and R algorithms on large
lattices with small quark masses using chiral fermions. We also present results
concerning staggered fermions near the deconfinement/chiral phase transition.
We find that the RHMC algorithm not only eliminates the step-size error of the
R algorithm, but is also considerably more efficient. We discuss several
possibilities for further improvement to the RHMC algorithm.Comment: Proceedings from Lattice 2005 (Dublin
Constraining the orbits of sub-stellar companions imaged over short orbital arcs
Imaging a star's companion at multiple epochs over a short orbital arc
provides only four of the six coordinates required for a unique orbital
solution. Probability distributions of possible solutions are commonly
generated by Monte Carlo (MCMC) analysis, but these are biased by priors and
may not probe the full parameter space. We suggest alternative methods to
characterise possible orbits, which compliment the MCMC technique. Firstly the
allowed ranges of orbital elements are prior-independent, and we provide means
to calculate these ranges without numerical analyses. Hence several interesting
constraints (including whether a companion even can be bound, its minimum
possible semi-major axis and its minimum eccentricity) may be quickly computed
using our relations as soon as orbital motion is detected. We also suggest an
alternative to posterior probability distributions as a means to present
possible orbital elements, namely contour plots of elements as functions of
line of sight coordinates. These plots are prior-independent, readily show
degeneracies between elements and allow readers to extract orbital solutions
themselves. This approach is particularly useful when there are other
constraints on the geometry, for example if a companion's orbit is assumed to
be aligned with a disc. As examples we apply our methods to several imaged
sub-stellar companions including Fomalhaut b, and for the latter object we show
how different origin hypotheses affect its possible orbital solutions. We also
examine visual companions of A- and G-type main sequence stars in the
Washington Double Star Catalogue, and show that per cent must be
unbound.Comment: Accepted for publication in MNRA
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