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

TL;DR

This study uses numerical simulations to investigate the Aoki phase in lattice QCD with two Wilson fermions, confirming its existence at certain couplings and absence at others, thereby clarifying the phase structure.

Contribution

It provides a detailed numerical analysis of the Aoki phase with Wilson fermions, confirming its presence at specific parameters and refining the phase diagram.

Findings

Aoki phase exists at β=4.0 and 4.3.

No evidence of Aoki phase at β=4.6 and 5.0.

Used Hybrid Monte Carlo to compute order parameters.

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.