A numerical reinvestigation of the Aoki phase with N_f=2 Wilson fermions at zero temperature

Abstract

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 $h\bar{\psi }i{\gamma }_5{\tau }^3\psi$ was added to the fermion action. The order parameter $<\bar{\psi }i{\gamma }_5{\tau }^3\psi >$ 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 $h=0$. The existence of a parity-flavor breaking phase can be confirmed at $\beta =4.0$ and 4.3, while we do not find parity-flavor breaking at $\beta =4.6$ and 5.0.

8 pages, 5 figures, Revised version as to be published in Phys.Rev.D