42 research outputs found
Topological susceptibility and the sampling of field space in lattice QCD simulations
We present a measurement of the topological susceptibility in two flavor QCD.
In this observable, large autocorrelations are present and also sizable cutoff
effects have to be faced in the continuum extrapolation. Within the statistical
accuracy of the computation, the result agrees with the expectation from
leading order chiral perturbation theory.Comment: 22 pages, 7 figures; References added, minor clarifications in the
text, results unchange
Status and challenges of simulations with dynamical fermions
An overview over the current state of algorithms for dynamical fermion
simulations is given. In particular some insight into the functioning of the
determinant spitting techniques is discussed. The critical slowing down of the
simulations towards the continuum limit and the role of the boundary conditions
is also reviewed.Comment: 20 pages, 9 figures, plenary talk presented at the 30th International
Symposium on Lattice Field Theory - Lattice 2012, June 24-29, 2012 Cairns,
Australi
Status and Future Perspectives for Lattice Gauge Theory Calculations to the Exascale and Beyond
In this and a set of companion whitepapers, the USQCD Collaboration lays out
a program of science and computing for lattice gauge theory. These whitepapers
describe how calculation using lattice QCD (and other gauge theories) can aid
the interpretation of ongoing and upcoming experiments in particle and nuclear
physics, as well as inspire new ones.Comment: 44 pages. 1 of USQCD whitepapers
Recommended from our members
Advances in Lattice Quantum Chromodynamics
In this thesis we make four contributions to the state of the art in numerical lattice simulations of quantum chromodynamics (QCD). First, we present the most detailed investigation yet of the autocorrelations of topological observations in hybrid Monte Carlo simulations of QCD and of the effects of the boundary conditions on these autocorrelations. This results in a numerical criterion for deciding when open boundary conditions are useful for reducing these autocorrelations, which are a major barrier to reliable calculations at fine lattice spacings. Second, we develop a dislocation-enhancing determinant, and demonstrate that it reduces the autocorrelation time of the topological charge. This alleviates problems with slow topological tunneling at fine lattice spacings, enabling simulations on fine lattices to be completed with much less computational effort. Third, we show how to apply the recently developed zMöbius technique to hybrid Monte Carlo evolutions with domain wall fermions, achieving nearly a factor of two speedup in the the light quark determinant, the single most expensive part of the calculation. The dislocation-enhancing determinant and the zMöbius technique have enabled us to begin simulations of fine ensembles with four flavors of dynamical domain wall quarks. Finally, we show how to include the previously-neglected G1 operator in nonperturbative renormalization of the ∆S = 1 effective weak Hamiltonian on the lattice. This removes an important systematic error in lattice calculations of weak matrix elements, in particular the important K → ππ decay