Elucidating the Vacuum Structure of the Aoki Phase

TL;DR

This paper investigates the complex vacuum structure of two-flavor Wilson fermion QCD within the Aoki phase, providing numerical evidence that reveals new vacua with non-zero pseudoscalar condensates, challenging standard assumptions.

Contribution

It offers the first numerical evidence of a more intricate vacuum structure in the Aoki phase, identifying vacua not connected by symmetry transformations.

Findings

Discovery of new vacua with non-zero $iar
ext{ extbeta}
extbeta ext{ extbeta} ext{ extbeta}$ expectation values

Numerical simulations on lattices of sizes $4^4$, $6^4$, and $8^4$ support the complex vacuum structure

Challenging the standard wisdom about the vacuum structure in the Aoki phase

Abstract

In this paper, we discuss the vacuum structure of QCD with two flavors of Wilson fermions, inside the Aoki phase. We provide numerical evidence, coming from HMC simulations in $4^4$, $6^4$ and $8^4$ lattices, supporting a vacuum structure for this model at strong coupling more complex than the one assumed in the standard wisdom, with new vacua where the expectation value of $i\bar\psi\gamma_5\psi$ can take non-zero values, and which can not be connected with the Aoki vacua by parity-flavour symmetry transformations.