Continuum Limit of Overlap Valence Quarks on a Twisted Mass Sea

TL;DR

This paper investigates the continuum limit of a mixed action lattice QCD setup with overlap valence quarks on a twisted mass sea, focusing on topological zero modes and their impact on physical observables.

Contribution

It introduces three matching conditions to relate overlap and twisted mass actions and analyzes the continuum limit behavior with respect to zero mode effects.

Findings

Zero mode effects can be controlled within certain parameter regions.

A continuum limit consistent with unitarity restoration is achievable.

Different matching conditions influence the approach to the continuum limit.

Abstract

We study a lattice QCD mixed action with overlap valence quarks on two flavours of Wilson maximally twisted mass sea quarks. Employing three different matching conditions to relate both actions to each other, we investigate the continuum limit by using three values of the lattice spacing ranging from 0.05 fm to 0.08 fm. A particular emphasis is put on the effect on physical observables of the topological zero modes appearing in the valence overlap operator. We estimate the region of parameter space where the contribution from these zero modes is sufficiently small such that their effects can be safely controlled and a restoration of unitarity of the mixed action in the continuum limit is reached.