The chiral phase transition and the axial anomaly

TL;DR

This paper explores how restoring chiral symmetry in lattice QCD can reduce the axial anomaly's breaking, suggesting new experimental signals and testable predictions for different flavor numbers.

Contribution

It demonstrates the link between chiral symmetry restoration and the suppression of the axial anomaly in lattice QCD, providing a new perspective on phase transition behavior.

Findings

Restoration of chiral symmetry reduces $U_A(1)$ anomaly breaking.

Potential experimental signals from small $U_A(1)$ breaking in symmetric phase.

Testable lattice simulations for varying flavor numbers.

Abstract

To date numerical simulations of lattice QCD have not found a chiral phase transition of first order which is expected to occur for sufficiently light pions. We show how the restoration of an exact global chiral symmetry can strongly decrease the breaking of the approximate, anomalous $U_A(1)$ symmetry. This is testable on the lattice through simulations for one through four flavors. In QCD a small breaking of the $U_A(1)$ symmetry in the chirally symmetric phase generates novel experimental signals.