O(a^2) improvement of the overlap-Dirac operator

TL;DR

This paper develops an $O(a^2)$-improved overlap-Dirac operator using Symanzik improvement, enhancing continuum behavior at low momentum and improving relativistic dispersion relations in full-QCD simulations.

Contribution

The paper introduces an $O(a^2)$-improved overlap-Dirac operator with an improved kernel and field rotations, advancing lattice fermion formulations.

Findings

Improved dispersion relations close to continuum at low momentum.

Relativistic dispersion relation satisfied within a few percent in full-QCD.

Enhanced off-shell amplitudes for both massless and massive fermions.

Abstract

We construct an $O(a^2)$-improved overlap-Dirac operator by designing an improved overlap kernel, based on the Symanzik improvement program. Field rotation terms are also identified to improve off-shell amplitudes for both massless and massive fermions. We check the free dispersion relation and propagator, and show that improved results become to close to the continuum ones at low momentum region. We test the effect of improvement on the full-QCD gauge configuration and find that the relativistic dispersion relation is satisfied within a few percent error up to $m_qa \approx 0.5$.