Dynamically Emergent Flavor in a Confining Theory with Unbroken Chiral Symmetry

TL;DR

This paper explores how truncation in QCD can lead to emergent flavor symmetries in a confining theory, suggesting new dynamical flavors may appear in the spectrum of particles with non-zero mass.

Contribution

It proposes that chiral symmetry restoration in truncated QCD can result in emergent dynamical flavors, demonstrated through a model with a single massive quark and spin-1 mesons.

Findings

Truncation restores full chiral symmetry in lattice QCD.

Emergent SU(2) flavor symmetry can appear for massive mesons.

Dynamical flavors may manifest in the spectrum of color-singlet particles.

Abstract

I discuss "truncated" QCD studied recently by Glozman et al. through numerical simulations. For two flavors it was observed that truncation restores the full chiral U(2)\times U(2) symmetry of the Lagrangian. Moreover, additional enhancement of the above symmetry connecting representations with distinct Lorentz spins was observed. I argue that the chiral symmetry restoration in a confining theory could entail emergent (extra) dynamical flavors which would show up in the spectrum of color-singlet particles provided their mass \neq 0. As an example, I consider truncated QCD with a single massless Dirac quark. Assuming the validity of the above observations,I demonstrate how a dynamical SU(2)_{fl} symmetry could emerge for massive spin-1 mesons without contradicting general principles.