Dynamical fermions as a global correction

Abstract

In the simplified setting of the Schwinger model we present a systematic study on the simulation of dynamical fermions by global accept/reject steps that take into account the fermion determinant. A family of exact algorithms is developed, which combine stochastic estimates of the determinant ratio with the exploitation of some exact extremal eigenvalues of the generalized problem defined by the `old' and the `new' Dirac operator. In this way an acceptable acceptance rate is achieved with large proposed steps and over a wide range of couplings and masses.

Comments: 39 pages, 9 figures, small changes in the text, Fig.5 and Tab.2 (incl. 1 corrected typo)