The locality of the square-root method for improved staggered quarks

TL;DR

This paper investigates whether improvements to staggered Dirac operators in lattice QCD affect their locality, concluding that such improvements do not alter the operators' localization properties even in the continuum limit.

Contribution

The study demonstrates that improved staggered Dirac operators maintain similar locality properties to unimproved ones, impacting the understanding of fermion determinant rooting in lattice QCD.

Findings

Improved operators have localization lengths comparable to one-link operators.

Improvement does not affect the locality of the square-rooted staggered operators.

Results have implications for fermion determinant rooting and valence quark formulations.

Abstract

We study the effects of improvement on the locality of square-rooted staggered Dirac operators in lattice QCD simulations. We find the localisation lengths of the improved operators (FAT7TAD and ASQTAD) to be very similar to that of the one-link operator studied by Bunk et al., being at least the Compton wavelength of the lightest particle in the theory, even in the continuum limit. We conclude that improvement has no effect. We discuss the implications of this result for the locality of the nth-rooted fermion determinant used to reduce the number of sea quark flavours, and for possible staggered valence quark formulations.