Towards the topological susceptibility with overlap fermions

TL;DR

This paper estimates the QCD topological susceptibility using overlap fermions and a reweighting technique, revealing that current lattice spacings may require fermionic definitions of topological charge rather than the index theorem.

Contribution

It introduces a reweighting method with low-mode truncation for overlap fermions to study topological susceptibility, contrasting previous non-chiral fermion results.

Findings

Results align with continuum models, challenging the use of the index theorem at current lattice spacings.

Fermionic definitions of topological charge may be necessary for accurate lattice QCD calculations.

Abstract

Using a reweighting technique combined with a low-mode truncation of the fermionic determinant, we estimate the quark-mass dependence of the QCD topological susceptibility with overlap fermions. In contrast to previous lattice simulations which all used non-chiral fermions, our results appear to be consistent with the simple continuum model of D\"urr. This indicates that at current lattice spacings the use of the index theorem might not be justified and the fermionic definition of the charge might be needed.