Locality and Scaling of Quenched Overlap Fermions

TL;DR

This paper demonstrates that overlap fermions maintain good localization and scaling properties on coarse lattices, making large-volume simulations feasible without sacrificing chiral symmetry, and contradicts recent concerns about localization at low inverse lattice spacing.

Contribution

The study provides direct evidence that overlap fermions are well localized and scale properly on coarse lattices, enabling efficient large-volume lattice QCD simulations.

Findings

Overlap Dirac operator's range is small in lattice units at various lattice spacings.

Hadronic masses scale well on coarser lattices.

Localization properties contradict recent speculation about low inverse lattice spacing.

Abstract

The overlap fermion offers the tremendous advantage of exact chiral symmetry on the lattice, but is numerically intensive. This can be made affordable while still providing large lattice volumes, by using coarse lattice spacing, given that good scaling and localization properties are established. Here, using overlap fermions on quenched Iwasaki gauge configurations, we demonstrate directly that the overlap Dirac operator's range is comfortably small in lattice units for each of the lattice spacings 0.20 fm, 0.17 fm, and 0.13 fm (and scales to zero in physical units in the continuum limit). In particular, our direct results contradict recent speculation that an inverse lattice spacing of $1 {\rm GeV}$ is too low to have satisfactory localization. Furthermore, hadronic masses (available on the two coarser lattices) scale very well.