Abstract:

Noisy algorithms to update the quark determinant are usually formulated in terms of Gaussian measures or stochastic evaluations of the corresponding effective action. This talk describes a noisy algorithm of the second type which has no limitations on the size of the changes of the underlying gauge field. The method is attractive for the global update of the infrared degrees of freedom of the fermion determinant. It can be used also in all simulation algorithms of finite density QCD where the real part of the fermion measure is separated from the phase or in the imaginary chemical potential approach. At present the algorithm is illustrated by exmaples in QED2 and QCD4 on the lattice using ultraviolet suppressed quarks at zero chemical potential.