NIC Series Volume 43:   Towards the Confirmation of QCD on the Lattice Improved Actions and Algorithms Stefan F. Krieg   ISBN 978-3-9810843-9-9 October 2009, 89 pages   PDF

Lattice Quantum Chromodynamics has made tremendous progress over the last decade. New and improved simulation algorithms and lattice actions enable simulations of the theory with unprecedented accuracy.

In the first part of this thesis, novel simulation algorithms for dynamical overlap fermions are presented. The generic Hybrid Monte Carlo algorithm is adapted to treat the singularity in the Molecular Dynamics force, to increase the tunneling rate between different topological sectors and to improve the overall volume scaling of the combined algorithm. With this new method, simulations with dynamical overlap fermions can reach smaller lattice spacings, larger volumes, smaller quark masses, and therefore higher precision than had previously been possible.

The second part of this thesis is focused on a large scale simulation aiming to compute the light hadron mass spectrum. This simulation is based on a tree-level Symanzik improved gauge and tree-level improved stout-smeared Wilson clover action. The efficiency of the combination of this action and the improved simulation algorithms used allows to completely control all systematic errors. Therefore, this simulation provides a highly accurate ab initio calculation of the masses of the light hadrons, such as the proton, responsible for 95% of the mass of the visible universe, and confirms Lattice QCD in the light hadron sector.