Computational Methods for UV-Suppressed Fermions

Lattice fermions with suppressed high momentum modes solve the ultraviolet slowing down problem in lattice QCD. This paper describes a stochastic evaluation of the effective action of such fermions. The method is a based on the Lanczos algorithm and it is shown to have the same complexity as in the case of standard fermions.Comment: 10 pages, 1 figur

Variants of L\"uscher's fermion algorithm

We study improved variants of L\"uscher's algorithm, including the cases of staggered fermions and finite density.Comment: 4 uuencoded PostScript pages, contribution to LAT95 (fig.1 removed to conserve space; available upon request

Creutz Fermions on an Orthogonal Lattice

In a recent paper, Creutz has given a new action describing two species of Dirac fermions with exact chiral symmetry on the lattice. This action depends on a parameter which may be fixed at a certain value in order to get the right continuum limit. In this letter, we elaborate more on this idea and present an action which is free of any other parameter except the fermion mass.Comment: 9 pages, version to be published in PR

Accurate hadron spectroscopy on blocked configurations by tadpole-renormalized, clover-improved Wilson quark action

We compare the quenched hadron spectrum on blocked and unblocked lattices for the Wilson quark action, the clover action and the tadpole-improved clover action. The latter gives a spectrum markedly closer to the original one, even though the cutoff is 1/a ~ 500 Mev.Comment: 3 pages (4 included figures), contribution to Lattice 94 conference, uuencoded compressed postscript fil

Systematic errors of L\"uscher's fermion method and its extensions

We study the systematic errors of L\"uscher's formulation of dynamical Wilson quarks and some of its variants, in the weak and strong coupling limits, and on a sample of small configurations at finite $\beta$. We confirm the existence of an optimal window in the cutoff parameter $\varepsilon$, and the exponential decrease of the error with the number of boson families. A non-hermitian variant improves the approximation further and allows for an odd number of flavors. A simple and economical Metropolis test is proposed, which makes the algorithm exact.Comment: 10 pages LaTeX, Comprehensive revision; figures adde

One-flavour QCD at finite temperature

We present results, for heavy to moderate quark masses, of a study of thermodynamic properties of 1-flavour QCD, using the multiboson algorithm. Finite-size scaling behaviour is studied on lattices of size $8^3\times 4$, $12^3\times 4$ and $16^3\times 4$. It is shown that, for heavy quarks, the peak of the Polyakov loop susceptibility grows linearly with the spatial volume, indicating a first order phase transition. The deconfinement ratio and the distribution of the norm of the Polyakov loop corroborate this result. For moderately heavy quarks the first-order transition weakens and becomes a crossover. We estimate the end point of the first-order phase transition to occur at a quark mass of about 1.6 GeV.Comment: 3 pages, 3 PostScript figures; Talk presented at LAT9