Broken scale invariance, massless dilaton and confinement in QCD

TL;DR

This paper explores how broken scale invariance in QCD leads to a massless dilaton-like excitation called the 'scalaron' and demonstrates that this effective theory can explain confinement and has implications for quark-gluon plasma and hadron spin structure.

Contribution

It introduces an effective low-energy theory of broken scale invariance in QCD that predicts a massless scalar excitation and provides a dual classical Yang-Mills formulation on curved spacetime.

Findings

Non-perturbative gluon interactions produce a massless dilaton ('scalaron') inside hadrons.

The effective theory predicts confinement through broken scale invariance.

Potential applications include modeling quark-gluon plasma and hadron spin structure.

Abstract

Classical conformal invariance of QCD in the chiral limit is broken explicitly by scale anomaly. As a result, the lightest scalar particle (scalar glueball, or dilaton) in QCD is not light, and cannot be described as a Goldstone boson. Nevertheless basing on an effective low-energy theory of broken scale invariance we argue that inside the hadrons the non-perturbative interactions of gluon fields result in the emergence of a massless dilaton excitation (which we call the "scalaron"). We demonstrate that our effective theory of broken scale invariance leads to confinement. This theory allows a dual formulation as a classical Yang-Mills theory on a curved conformal space-time background. Possible applications are discussed, including the description of strongly coupled quark-gluon plasma and the spin structure of hadrons.