Unphysical phases in staggered chiral perturbation theory

TL;DR

This paper investigates the phase structure of staggered quarks in lattice QCD using chiral perturbation theory, identifying unphysical phases at coarse lattice spacings and clarifying the number of broken phases.

Contribution

It demonstrates how chiral perturbation theory can interpret unphysical phases and establishes that only three broken phases exist for staggered quarks at small lattice spacings.

Findings

Unphysical phases appear at coarse lattice spacings in simulations with many staggered fermions.

Chiral perturbation theory can interpret one of these unphysical phases.

Only three broken phases are present at small lattice spacings.

Abstract

We study the phase diagram for staggered quarks using chiral perturbation theory. In beyond-the-standard-model simulations using a large number ($>8$) of staggered fermions, unphysical phases appear for coarse enough lattice spacing. We argue chiral perturbation theory can be used to interpret one of these phases. In addition, we show only three broken phases for staggered quarks exist, at least for lattice spacings in the regime $a^2\ll \Lambda^2_{\rm QCD}$.