QCD with rooted staggered fermions

TL;DR

This paper reviews the theoretical status of staggered lattice QCD with the fourth-root trick, discussing its nonlocality at finite lattice spacing and the arguments supporting its validity in the continuum limit, using effective field theories.

Contribution

It provides an overview of the theoretical justification and understanding of the rooted staggered fermion approach in lattice QCD, including effective field theory analysis.

Findings

Strong arguments support the continuum limit validity.

Effective field theories clarify the approach to the continuum.

Nonlocality at finite lattice spacing is addressed.

Abstract

In this talk, I will give an overview of the theoretical status of staggered Lattice QCD with the "fourth-root trick." In this regularization of QCD, a separate staggered quark field is used for each physical flavor, and the inherent four-fold multiplicity that comes with the use of staggered fermions is removed by taking the fourth root of the staggered determinant for each flavor. At nonzero lattice spacing, the resulting theory is nonlocal and not unitary, but there are now strong arguments that this disease is cured in the continuum limit. In addition, the approach to the continuum limit can be understood in detail in the framework of effective field theories such as staggered chiral perturbation theory.