125 research outputs found
Polynomial Filtered HMC -- an algorithm for lattice QCD with dynamical quarks
Polynomial approximations to the inverse of the fermion matrix are used to
filter the dynamics of the upper energy scales in HMC simulations. The use of a
multiple time-scale integration scheme allows the filtered pseudofermions to be
evolved using a coarse step size. We introduce a novel generalisation of the
nested leapfrog which allows for far greater flexibility in the choice of time
scales. We observe a reduction in the computational expense of the molecular
dynamics integration of between 3--5 which improves as the quark mass
decreases.Comment: 10 pages, 7 figure
A Novel Multiple-Time Scale Integrator for the Hybrid Monte Carlo Algorithm
Hybrid Monte Carlo simulations that implement the fermion action using
multiple terms are commonly used. By the nature of their formulation they
involve multiple integration time scales in the evolution of the system through
simulation time. These different scales are usually dealt with by the
Sexton-Weingarten nested leapfrog integrator. In this scheme the choice of time
scales is somewhat restricted as each time step must be an exact multiple of
the next smallest scale in the sequence. A novel generalisation of the nested
leapfrog integrator is introduced which allows for far greater flexibility in
the choice of time scales, as each scale now must only be an exact multiple of
the smallest step size.Comment: Submitted to the proceedings of Tropical QCD II, held in Cairns,
Australia, 201
Scaling analysis of FLIC fermion actions
The Fat Link Irrelevant Clover (FLIC) fermion action is a variant of the
-improved Wilson action where the irrelevant operators are constructed
using smeared links. While the use of such smearing allows for the use of
highly improved definitions of the field strength tensor we show
that the standard 1-loop clover term with a mean field improved coefficient
is sufficient to remove the errors, avoiding the need for
non-perturbative tuning. This result enables efficient dynamical simulations in
QCD with the FLIC fermion action.Comment: 5 pages, 3 figure
Magnetic properties of the nucleon in a uniform background field
We present results for the magnetic moment and magnetic polarisability of the
neutron and the magnetic moment of the proton. These results are calculated
using the uniform background field method on 32^3 x 64 dynamical QCD lattices
provided by the PACS-CS collaboration as part of the ILDG. We use a uniform
background magnetic field quantised by the periodic spatial volume. We
investigate ways to improve the effective energy plots used to calculate
magnetic polarisabilities, including the use of correlation matrix techniques
with various source smearings.Comment: 9 pages, 14 figures, 2 table
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