On the phase diagram of quenched QCD with Wilson fermions

In this talk, I reported on recent work on the Aoki phase diagram for quenched QCD with two flavors of Wilson fermions. Part of this work was done in collaboration with Yigal Shamir, and a shorter account of this part appeared recently. In this write-up, I will therefore limit myself to reporting on work done with Steve Sharpe and Robert Singleton, Jr., which has not been published yet. We discuss the symmetries of quenched QCD, paying careful attention to non-perturbative issues. This allows us to derive an effective lagrangian which agrees with standard quenched chiral perturbation theory, but which can also be used to address questions of a non-perturbative nature