3 research outputs found
Spin chain simulations with a meron cluster algorithm
We apply a meron cluster algorithm to the XY spin chain, which describes a
quantum rotor. This is a multi-cluster simulation supplemented by an improved
estimator, which deals with objects of half-integer topological charge. This
method is powerful enough to provide precise results for the model with a
theta-term - it is therefore one of the rare examples, where a system with a
complex action can be solved numerically. In particular we measure the
correlation length, as well as the topological and magnetic susceptibility. We
discuss the algorithmic efficiency in view of the critical slowing down. Due to
the excellent performance that we observe, it is strongly motivated to work on
new applications of meron cluster algorithms in higher dimensions.Comment: 18 pages, 9 figures, published versio
Spectral properties of the Wilson Dirac operator in the -regime
We investigate the spectral properties of the Wilson Dirac operator in
quenched QCD in the microscopic regime. We distinguish the topological sectors
using the index as determined by the Wilson flow method. Consequently, the
distributions of the low-lying eigenvalues of the Wilson Dirac operator can be
compared in each of the topological sectors to predictions from random matrix
theory applied to the -regime of chiral perturbation theory. We find
rather good agreement for volumes as small as and
lattice spacings as coarse as , and demonstrate that it is
indeed possible to extract low-energy constants for Wilson fermions from the
spectral properties of the Wilson Dirac operator.Comment: Changed normalizations for some of the results, cosmetic updates to
several plots. Conclusions not affected. Version accepted for publication by
JHEP. 22 pages, 12 figure