Numerical reinvestigation of the Aoki phase withNf=2Wilson fermions at zero temperature

We report on a numerical reinvestigation of the Aoki phase in lattice QCD with two flavors of Wilson fermions where the parity-flavor symmetry is spontaneously broken. For this purpose an explicitly symmetry-breaking source term $h\overline{\psi }i{\gamma }_5{\tau }^3\psi$ was added to the fermion action. The order parameter $〈\overline{\psi }i{\gamma }_5{\tau }^3\psi 〉$ was computed with the hybrid Monte Carlo algorithm at several values of $(\beta ,\kappa ,h)$ on lattices of sizes $4^4$ to ${12}^4$ and extrapolated to $h=0.\mathrm{}$ The existence of a parity-flavor breaking phase can be confirmed at $\beta =4.0\mathrm{}$ and 4.3, while we do not find parity-flavor breaking at $\beta =4.6\mathrm{}$ and 5.0.