Exploring the transition into the Chiral Regime of QCD using the Interacting Instanton Liquid Model

TL;DR

This paper uses the Interacting Instanton Liquid Model to study how non-perturbative QCD interactions depend on quark mass, revealing a transition into the chiral regime around 80 MeV where certain dynamical effects diminish.

Contribution

The study demonstrates the IILM's effectiveness in capturing quark mass dependence and identifies a natural scale (~80 MeV) marking the transition into the chiral regime of QCD.

Findings

Agreement of IILM with chiral perturbation theory and lattice results.

Identification of an 80 MeV quark mass scale for the transition.

Suppression of low-lying Dirac eigenmodes above this scale.

Abstract

The non-perturbative quark-gluon interaction depends significantly on the value of the quark mass. In particular, in the light quark mass regime, correlations are strongly influenced by dynamics associated to chiral symmetry breaking. We use the Interacting Instanton Liquid Model (IILM) as a tool to investigate the microscopic dynamical mechanisms which underly the dependence on the quark mass and drive the transition into the chiral regime of QCD. To ensure the validity of the model, we first verify that the dependence on the quark mass for several observables calculated in the IILM agrees well with the predictions of chiral perturbation theory and with lattice simulations. We then show that a quark mass m*~80 MeV emerging naturally from the model specifies the mass scale above which the dynamics associated with low-lying eigenmodes of the Direac operator becomes sub-leading and the contribution of the fermion determinant is suppressed.