Double poles in Lattice QCD with mixed actions

TL;DR

This paper investigates the impact of mixed discretizations in lattice QCD, revealing a double pole in flavor-neutral meson propagators and assessing its effect on scaling violations, which may be minimal in practice.

Contribution

It demonstrates the presence of a double pole in flavor-neutral meson propagators in mixed-action lattice QCD and evaluates its practical significance.

Findings

Double pole exists in flavor-neutral Goldstone meson propagators.

Double-pole effects on scaling violations are likely small.

Mixed actions can introduce subtle effects in lattice QCD simulations.

Abstract

We consider effects resulting from the use of different discretizations for the valence and the sea quarks, considering Wilson and/or Ginsparg--Wilson fermions. We assume that such effects appear through scaling violations that can be studied using effective-lagrangian techniques. We show that a double pole is present in flavor-neutral Goldstone meson propagators, even if the flavor non-diagonal Goldstone mesons made out of valence or sea quark have equal masses. We then consider some observables known to be anomalously sensitive to the presence of a double pole. We find that the double-pole enhanced scaling violations may turn out to be rather small in practice.