Dynamical fermions by global acceptance steps

A study of principle is conducted on the inclusion of the fermionic determinant as a Metropolis acceptance correction. It is carried out in the 2-D Schwinger model to prepare later applications to the Schr"odinger functional. A mixed stochastic/determistic acceptance step is found that allows to include some problematic modes in a way to avoid the collapse of the acceptance rate due to fluctuations.