Numerical simulation tests with light dynamical quarks

Two degenerate flavours of quarks are simulated with small masses down to about one fifth of the strange quark mass by using the two-step multi-boson (TSMB) algorithm. The lattice size is 8^3 x 16 with lattice spacing about 0.27fm which is not far from the N_t=4 thermodynamical cross-over line. Autocorrelations of different physical quantities are estimated as a function of the quark mass. The eigenvalue spectra of the Wilson-Dirac operator are investigated.Comment: 14 pages, 7 figures, uses svjour.cls; mistake in the autocorrelation of the pion mass corrected, version accepted for publication on Eur. Phys. J.

Unquenched simulations with N_f= 2 light quark flavours

The quark mass dependence of meson masses and decay constants in N_f = 2 QCD is studied at a fixed gauge coupling with different dynamical quark masses. Partially Quenched Wilson Chiral Perturbation Theory (PQW_#chi#PT) is applied to obtain the extrapolation to zero quark mass. It is shown, that in our analysis NNLO-terms play a more important role than O(a)-terms, which can be neglected. Also we compare our results with recent CP-PACS results. (orig.)Available from TIB Hannover: RA 2999(04-158) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Exploring the phase structure of lattice QCD with twisted mass quarks

The phase structure of zero temperature twisted mass lattice QCD is investigated. We find strong metastabilities in the plaquette observable when the untwisted quark mass sweeps across zero. (orig.)Available from TIB Hannover: RA2999(04-188) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman