Bound states for Overlap and Fixed Point Actions close to the chiral limit

We study the overlap and the fixed point Dirac operators for massive fermions in the two-flavor lattice Schwinger model. The masses of the triplet (pion) and singlet (eta) bound states are determined down to small fermion masses and the mass dependence is compared with various continuum model approximations. Near the chiral limit, at very small fermion masses the fixed point operator has stability problems, which in this study are dominated by finite size effects,Comment: 13 pages, 2 figure

Nucleon excited states on the lattice

We study the pion-nucleon system in s-wave in the framework of lattice QCD in order to gain new information on the nucleon excited states. We perform simulations for $n_f =2$ mass degenerate light quarks at a pion mass of 266 MeV. The results show that including the two-particle states drastically changes the energy levels. The variational analysis and the distillation approach play an important role in the extraction of the energy levels. The phase shift analysis allows to extract information on the resonance nature of the observed states.Comment: 6 pages, 2 figures, talk presented at Excited QCD 2013, Bjelasnica Mountain, Sarajev

Dirac zero-modes in compact U(1) gauge theory

We study properties of the zero and near-zero eigenmodes of the overlap Dirac operator in compact U(1) gauge theory. In the confinement phase the exact zero-modes are localized as found by studying the values of the inverse participation ratio and other features. Non-zero-eigenmodes are less localized in the confinement phase. In the Coulomb phase no zero-modes are observed and the eigenmodes show no localization at all.Comment: Minor corrections, 15 pages, 5 figures, LaTeX styl