The topological susceptibility with dynamical overlap fermions

Using a reweighting technique combined with a low-mode truncation of the fermionic determinant, we perform the first computation of the quark-mass dependence of the QCD topological susceptibility with overlap fermions. In contrast to previous lattice simulations which all used non-chiral fermions, our results are in good agreement with the simple continuum model of Duerr. This demonstrates that chirality of the lattice fermion action is crucial for obtaining the expected suppression of the susceptibility. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(01-211) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Unquenching the topological susceptibility with an overlap action

We estimate the quark-mass dependence of the topological susceptibility with dynamical overlap and clover fermions. Unquenching effects on the susceptibility turn out to be well approximated by a reweighting of a quenched ensemble with a low-eigenmode truncation of the fermionic determinant. We find that it is most likely due to the explicit chiral symmetry breaking of the fermion action that present day dynamical simulations do not show the expected suppression of the topological susceptibility. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(01-209) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Low-lying fermion modes of N_f=2 improved Wilson fermions

We present preliminary results for the topological charge and susceptibility determined from the low-lying eigenmodes of the Wilson-Dirac operator. These modes have been computed on dynamical configurations with N_f=2 non-perturbatively improved Wilson fermions. We compare our results with the eigenmodes of fermions in the quenched approximation. (orig.)Available from TIB Hannover: RA 2999(01-167) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Low-lying Fermion modes: Dynamical versus quenched

We compare the low-lying eigenmodes of the O(a) improved Wilson-Dirac operator on quenched and dynamical configurations and investigate methods of probing the topological properties of gauge configurations. (orig.)SIGLEAvailable from TIB Hannover: RA 2999(02-173) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Vortex waistlines and long range fluctuations

We examine the manner in which a linear potential results from fluctuations due to vortices linked with the Wilson loop. Our discussion is based on exact relations and inequalities between the Wilson loop and the vortex and electric flux order parameters. We show that, contrary to the customary naive picture, only vortex fluctuations of thickness of the order of the spatial linear size of the loop are capable of producing a strictly linear potential. An effective theory of these long range fluctuations emerges naturally in the form of a strongly coupled Z(N) lattice gauge theory. We also point out that dynamical fermions introduced in this medium undergo chiral symmetry breaking. (orig.)Available from TIB Hannover: RA 2999(01-208) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Vortex waistlines and vortex gas

We investigate the manner in which a linear potential arises from fluctuations due to vortices linked with the Wilson loop. In particular, the customary naive picture is critically reexamined. (orig.)Available from TIB Hannover: RA 2999(01-210) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman