Chiral anomalies and rooted staggered fermions

TL;DR

The paper critically examines the validity of extrapolation methods in lattice gauge theory with staggered fermions, highlighting issues with continuum behavior and unitarity that challenge common resolutions.

Contribution

It demonstrates that the standard extrapolation approach distorts continuum holomorphic behavior and questions the effectiveness of adding extra states to cancel singularities.

Findings

Extrapolation distorts expected continuum holomorphic behavior.

Adding extra states introduces unitarity and locality issues.

Large cutoff effects are implied in the low-energy sector.

Abstract

A popular approximation in lattice gauge theory is an extrapolation in the number of fermion species away from the four fold degeneracy natural with the staggered fermion formulation. I show that the extrapolation procedure mutilates the expected continuum holomorphic behavior in the quark masses. The conventional resolution proposes canceling the unphysical singularities with a plethora of extra states appearing at finite lattice spacing. This unproven conjecture requires an explicit loss of unitarity and locality. Even if correct, the approach implies large cutoff effects in the low-energy flavor-neutral sector.