42 research outputs found
Simulations of Lattice Fermions with Chiral Symmetry in Quantum Chromodynamics
This thesis is dedicated to explore the feasibility of numerical calculations
in the --regime of QCD for the extraction of physical information. We
apply two formulations of the Ginsparg-Wilson fermions the Neuberger operator
and the hypercube overlap operator to compute the observables of interest. As a
main result we present the comparison of the distributions of the leading
individual eigenvalues of the Neuberger operator in QCD and the analytical
predictions of chiral random matrix theory. We observe a good agreement as long
as each side of the physical volume exceeds about L\approx 1.12\fm. It turns
out that this bound for is generic and sets the size of the physical volume
where the axial correlator behaves according to chiral perturbation theory.
This allows us to compute a value for the pion decay constant . As an
alternative procedure we only consider the contribution from the zero modes.
Here we are able to obtain an estimate for and . As a
theoretical development the L\"uscher topology conserving gauge action is
investigated. This enables us to sample the observables of interest in the
--regime without recomputing the index. We can report that a
promising gauge action has been identified.Comment: Ph.D. thesi
Meson correlation functions at high temperatures
We present preliminary results for the correlation- and spectral functions of
different meson channels on the lattice. The main focus lies on gaining control
over cut-off as well as on the finite-volume effects. Extrapolations of
screening masses above the deconfining temperature are guided by the result of
the free () case on the lattice and in the continuum. We study the
quenched non-perturbatively improved Wilson-clover fermion as well as the
hypercube fermion action which might show less cut-off effects.Comment: 6 pages, 8 figures (minor changes, citations added
Lattice Gauge Actions for Fixed Topology
We test a set of lattice gauge actions for QCD that suppress small plaquette
values and in this way also suppress transitions between topological sectors.
This is well suited for simulations in the epsilon-regime and it is expected to
help in numerical simulations with dynamical quarks.Comment: 3 pages. Talk presented at Quark Confinement and the Hadron Spectrum
VI, Villasimius, Sardinia, Italy, September 21-25, 2004. References adde
Meson Correlation Functions in the epsilon-Regime
We present a numerical pilot study of the meson correlation functions in the
epsilon-regime of chiral perturbation theory. Based on simulations with overlap
fermions we measured the axial and pseudo-scalar correlation functions, and we
discuss the implications for the leading low energy constants in the chiral
Lagrangian.Comment: 3 pages, 3 figures, talk presented at Lattice2003(chiral