Christian Hoelbling

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The speed, bandwidth and cost characteristics of today's PC graphics cards make them an attractive target as general purpose computational platforms. High performance can be achieved also for lattice simulations but the actual implementation can be cumbersome. This paper outlines the architecture and programming model of modern graphics cards for the(More)
We determine the topological susceptibility in the SU (3) pure gauge theory. We perform a series of high-statistics lattice studies and take the combined continuum and infinite volume limit. We find χ top r 4 0 = 0.0524(7)(6), which translates into χ 1/4 top = 193(1)(8) MeV with the second error exclusively due to the intrinsic scale ambiguity.
We study the scalar condensate and the topological susceptibility for a continuous range of quark masses in the Schwinger model with N f = 0, 1, 2 dynamical flavors, using both the overlap and the staggered discretization. At finite lattice spacing the differences between the two formulations become rather dramatic near the chiral limit, but they get(More)
We present a scaling analysis in the 1-flavor Schwinger model with the full overlap and the rooted staggered determinant. In the latter case the chiral and continuum limit of the scalar condensate do not commute, while for overlap fermions they do. For the topological susceptibility a universal continuum limit is suggested, as is for the partition function(More)
We propose new techniques for the numerical implementation of the overlap-Dirac operator, which exploit the physical properties of the underlying theory to avoid nested algorithms. We test these procedures in the two-dimensional Schwinger model and the results are very promising. These techniques can be directly applied to QCD simulations. We also present a(More)
We study the infrared part of the spectrum for UV-filtered staggered Dirac operators and compare them to the overlap counterpart. With sufficient filtering and at small enough lattice spacing the staggered spectra manage to " mimic " the overlap version. They show a 4-fold near-degeneracy, and a clear separation between would-be zero modes and non-zero(More)
We investigate the overlap operator with a UV filtered Wilson kernel. The filtering leads to a better localization of the operator even on coarse lattices and with the untuned choice ρ = 1. Furthermore, the axial-vector renormalization constant Z A is much closer to 1, reducing the mismatch with perturbation theory. We show that all these features persist(More)
We present evidence in the Schwinger model that rooted staggered fermions may correctly describe the m < 0 sector of a theory with an odd number of flavors. We point out that in QCD-type theories with a complex-valued quark mass every non-chiral action essentially " borrows " knowledge about the θ-transformation properties from the overlap action. The(More)