162 research outputs found
Reversibility Violation in the Hybrid Monte Carlo Algorithm
We investigate reversibility violations in the Hybrid Monte Carlo algorithm.
Those violations are inevitable when computers with finite numerical precision
are being used. In SU(2) gauge theory, we study the dependence of observables
on the size of the reversibility violations. While we cannot find any
statistically significant deviation in observables related to the simulated
physical model, algorithmic specific observables signal an upper bound for
reversibility violations below which simulations appear unproblematic. This
empirically derived condition is independent of problem size and parameter
values, at least in the range of parameters studied here.Comment: 17 pages, 5 figures, typos corrected, comment added, matches
published versio
Flavor-singlet meson decay constants from twisted mass lattice QCD
We present an improved analysis of our lattice data for the --
system, including a correction of the relevant correlation functions for
residual topological finite size effects and employing consistent chiral and
continuum fits. From this analysis we update our physical results for the
masses and
, as well
as the mixing angle in the quark flavor basis
in excellent
agreement with other results from phenomenology. Similarly, we include an
analysis for the decay constant parameters, leading to
and
. The second error
reflects the uncertainty related to the chiral extrapolation. The data used for
this study has been generated on gauge ensembles provided by the European
Twisted Mass Collaboration with dynamical flavors of Wilson twisted
mass fermions. These ensembles cover a range of pion masses from
to and three values of the lattice
spacing. Combining our data with a prediction from chiral perturbation theory,
we give an estimate for the physical
decay widths and the singly-virtual
transition form factors in the limit of large momentum transfer.Comment: 22 pages, 8 figures, 12 tables; matching version accepted for
publicatio
A Mixed Action Analysis of and Mesons
We study and mesons and their mixing angle in a mixed action
approach with so-called Osterwalder-Seiler valence quarks on a Wilson twisted
mass sea. The gauge configurations have been generated by ETMC for
dynamical quark flavours and for three values of the lattice spacing. The main
results are that differences in between the mixed action and the unitary
approach vanish towards the continuum limit with the expected rate of
. The individual size of the lattice artifacts depends,
however, strongly on the observable used to match unitary and valence actions.
Moreover, we show that for the mass valence and valence plus sea quark
mass dependence differ significantly. Hence, in this case a re-tuning of the
simulation parameters in the valence sector only is not sufficient to
compensate for mismatches in the original quark masses.Comment: 30 pages, 8 figures, version accepted for publicatio
Digitizing lattice gauge theories in the magnetic basis: reducing the breaking of the fundamental commutation relations
We present a digitization scheme for the lattice gauge
theory Hamiltonian in the , where the gauge
links are unitary and diagonal. The digitization is obtained from a particular
partitioning of the group manifold, with the canonical momenta
constructed by an approximation of the Lie derivatives on this partitioning.
This construction, analogous to a discrete Fourier transform, preserves the
spectrum of the kinetic part of the Hamiltonian and the canonical commutation
relations exactly on a subspace of the truncated Hilbert space, while the
residual subspace can be projected above the cutoff of the theory
Testing the Witten-Veneziano Formula on the Lattice
In this proceeding contribution we report on a test of the famous
Witten-Veneziano formula using lattice techniques. We perform dedicated
quenched simulations and apply the spectral projector method to determine the
topological susceptibility in pure Yang-Mills theory. In order to compute the
relevant meson masses and the flavor singlet decay constant we employ lattice
QCD with dynamical Wilson twisted mass fermions. Taking the
continuum and the chiral limits we find good agreement within
uncertainties for both sides of the formula.Comment: 7 pages, 4 figures, presented at the 33rd International Symposium on
Lattice Field Theory, 14 -18 July 2015, Kobe International Conference Center,
Kobe, Japa
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